libsoliton/soliton_capi/tests/capi_tests.rs

//! CAPI integration tests.
//!
//! Test categories:
//!
//! - **Error paths** — null pointer guards, zero-length guards, co-presence
//!   guards, and output-zeroing verification. MIRI-safe for all 51 CAPI
//!   functions; these are the primary target of this suite.
//!
//! - **PQ-free happy paths** — round-trips using zeroed/minimal key material.
//!   Relies on `xwing::from_bytes` and `IdentityPublicKey::from_bytes` being
//!   length-only (no structural validation), so zeroed bytes are accepted.
//!   Alice's first ratchet encrypt sends `kem_ct = None` (no PQ step).
//!   Bob's first decrypt matches `recv_ratchet_pk`, so no KEM decapsulation.
//!   All MIRI-safe.
//!
//! - **`mod pq`** — PQ-dependent happy paths (keygen, encap, decap, KEX).
//!   Excluded from the MIRI nextest profile via
//!   `- test(/^capi_tests::pq::/)`.

use std::ffi::CString;
use std::mem::{MaybeUninit, size_of};
use std::ptr;

use soliton_capi::*;

// ── Error code shorthands ────────────────────────────────────────────────────
const OK: i32 = SolitonError::Ok as i32;
const E_NULL: i32 = SolitonError::NullPointer as i32;
const E_LEN: i32 = SolitonError::InvalidLength as i32;
const E_DATA: i32 = SolitonError::InvalidData as i32;
const E_AEAD: i32 = SolitonError::AeadFailed as i32;
const E_VER: i32 = SolitonError::VerificationFailed as i32;
const E_BUNDLE: i32 = SolitonError::BundleVerificationFailed as i32;
const E_UNSUP_VER: i32 = SolitonError::UnsupportedVersion as i32;
const E_CONCURRENT: i32 = SolitonError::ConcurrentAccess as i32;

// ── Key / buffer size shorthands ─────────────────────────────────────────────
const PK: usize = SOLITON_PUBLIC_KEY_SIZE;
const SK: usize = SOLITON_SECRET_KEY_SIZE;
const XPKZ: usize = SOLITON_XWING_PK_SIZE;
const XSKZ: usize = SOLITON_XWING_SK_SIZE;
const XCTZ: usize = SOLITON_XWING_CT_SIZE;
const FP: usize = SOLITON_FINGERPRINT_SIZE;
const HSIG: usize = SOLITON_HYBRID_SIG_SIZE;
const NONCE: usize = SOLITON_AEAD_NONCE_SIZE;

// ── Test helpers ─────────────────────────────────────────────────────────────

/// Returns true iff every byte of the slice is zero.
fn is_zeroed(buf: &[u8]) -> bool {
    buf.iter().all(|&b| b == 0)
}

/// Fill a stack buffer with a known non-zero sentinel before passing to a
/// failing CAPI call, so we can assert the output was actually zeroed.
fn fill_nonzero<const N: usize>() -> [u8; N] {
    [0xAB; N]
}

/// Construct a valid (zeroed-bytes) Alice ratchet state for tests.
///
/// Uses `[0u8; XPKZ]` / `[0u8; XSKZ]` as the ephemeral X-Wing keys.
/// `from_bytes` is length-only, so no PQ keygen is needed.
/// Fingerprints: local=0x01, remote=0x02 (must differ to pass init guard).
unsafe fn make_alice() -> *mut SolitonRatchet {
    let rk = [0x11u8; 32];
    let ck = [0x22u8; 32];
    let local_fp = [0x01u8; 32];
    let remote_fp = [0x02u8; 32];
    let ek_pk = [0u8; XPKZ];
    // First 32 bytes are the X25519 secret key — must be non-zero to pass
    // the from_bytes zero-check on the send_ratchet_sk X25519 portion.
    let mut ek_sk = [0u8; XSKZ];
    ek_sk[..32].fill(0x33);
    let mut out: *mut SolitonRatchet = ptr::null_mut();
    let rc = unsafe {
        soliton_ratchet_init_alice(
            rk.as_ptr(),
            32,
            ck.as_ptr(),
            32,
            local_fp.as_ptr(),
            32,
            remote_fp.as_ptr(),
            32,
            ek_pk.as_ptr(),
            XPKZ,
            ek_sk.as_ptr(),
            XSKZ,
            &mut out,
        )
    };
    assert_eq!(rc, OK);
    assert!(!out.is_null());
    out
}

/// Construct a valid (zeroed-bytes) Bob ratchet state for tests.
///
/// `peer_ek` is the same zeroed 1216-byte blob used by Alice.
/// Fingerprints: local=0x02, remote=0x01 (mirrored from Alice).
unsafe fn make_bob() -> *mut SolitonRatchet {
    let rk = [0x11u8; 32];
    let ck = [0x22u8; 32];
    let local_fp = [0x02u8; 32];
    let remote_fp = [0x01u8; 32];
    let peer_ek = [0u8; XPKZ];
    let mut out: *mut SolitonRatchet = ptr::null_mut();
    let rc = unsafe {
        soliton_ratchet_init_bob(
            rk.as_ptr(),
            32,
            ck.as_ptr(),
            32,
            local_fp.as_ptr(),
            32,
            remote_fp.as_ptr(),
            32,
            peer_ek.as_ptr(),
            XPKZ,
            &mut out,
        )
    };
    assert_eq!(rc, OK);
    assert!(!out.is_null());
    out
}

/// Construct a valid storage keyring (version 1, non-zero 32-byte key).
unsafe fn make_keyring() -> *mut SolitonKeyRing {
    let key = [0x33u8; 32];
    let mut out: *mut SolitonKeyRing = ptr::null_mut();
    let rc = unsafe { soliton_keyring_new(key.as_ptr(), 32, 1, &mut out) };
    assert_eq!(rc, OK);
    assert!(!out.is_null());
    out
}

// ═══════════════════════════════════════════════════════════════════════════
// Version & buf_free
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn version_returns_nonnull_cstr() {
    let ptr = soliton_version();
    assert!(!ptr.is_null());
    // Must be a valid null-terminated string.
    let s = unsafe { std::ffi::CStr::from_ptr(ptr).to_str().unwrap() };
    assert!(!s.is_empty());
}

#[test]
fn buf_free_null_ptr_is_noop() {
    // Must not crash.
    unsafe {
        soliton_buf_free(ptr::null_mut());
    }
}

#[test]
fn buf_free_null_inner_ptr_is_noop() {
    // A SolitonBuf with ptr=null is safe to free.
    let mut buf = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    unsafe {
        soliton_buf_free(&mut buf);
    }
}

#[test]
fn buf_free_double_free_is_safe() {
    // After the first free, ptr is set to null — second call is a no-op.
    unsafe {
        let mut buf = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let data = b"test";
        // Construct a SolitonBuf wrapping an AEAD ciphertext for double-free test.
        let key = [0u8; 32];
        let nonce = [0u8; NONCE];
        let rc = soliton_aead_encrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            data.as_ptr(),
            data.len(),
            ptr::null(),
            0,
            &mut buf,
        );
        assert_eq!(rc, OK);
        assert!(!buf.ptr.is_null());
        soliton_buf_free(&mut buf);
        assert!(buf.ptr.is_null());
        soliton_buf_free(&mut buf); // second free must not crash
    }
}

#[test]
fn buf_free_corrupted_len_uses_internal_header() {
    // RT-70/RT-191: soliton_buf_free uses the internal allocation header
    // (stored at ptr-8, inaccessible to callers) for deallocation — not the
    // caller-visible `len`. Corrupting `len` must not cause heap corruption.
    unsafe {
        let key = [0u8; 32];
        let nonce = [0u8; NONCE];
        let data = b"test payload for internal header check";
        let mut buf = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_aead_encrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            data.as_ptr(),
            data.len(),
            ptr::null(),
            0,
            &mut buf,
        );
        assert_eq!(rc, OK);
        assert!(!buf.ptr.is_null());
        let original_len = buf.len;
        assert!(original_len > 0);

        // Corrupt the caller-visible len to a different value.
        buf.len = 1;

        // Free must use internal header for dealloc — no heap corruption.
        soliton_buf_free(&mut buf);
        assert!(buf.ptr.is_null(), "ptr must be nulled after free");
        assert_eq!(buf.len, 0, "len must be zeroed after free");
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// random_bytes
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn random_bytes_null_buf_returns_null_pointer() {
    let rc = unsafe { soliton_random_bytes(ptr::null_mut(), 16) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn random_bytes_zero_len_is_ok() {
    let mut buf = [0u8; 0];
    let rc = unsafe { soliton_random_bytes(buf.as_mut_ptr(), 0) };
    assert_eq!(rc, OK);
}

#[test]
fn random_bytes_fills_buffer() {
    let mut buf = [0u8; 32];
    let rc = unsafe { soliton_random_bytes(buf.as_mut_ptr(), 32) };
    assert_eq!(rc, OK);
    // With overwhelming probability, 32 random bytes are not all zero.
    // (Probability of failure: 1 in 2^256.)
    assert_ne!(buf, [0u8; 32]);
}

// ═══════════════════════════════════════════════════════════════════════════
// zeroize
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn zeroize_null_ptr_is_noop() {
    // Must not crash.
    unsafe { soliton_zeroize(ptr::null_mut(), 64) };
}

#[test]
fn zeroize_zero_len_is_noop() {
    let mut buf = [0xFFu8; 8];
    unsafe { soliton_zeroize(buf.as_mut_ptr(), 0) };
    assert_eq!(buf, [0xFF; 8]);
}

#[test]
fn zeroize_clears_buffer() {
    let mut buf = [0xABu8; 64];
    unsafe { soliton_zeroize(buf.as_mut_ptr(), buf.len()) };
    assert!(is_zeroed(&buf));
}

// ═══════════════════════════════════════════════════════════════════════════
// sha3_256
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn sha3_256_null_out_returns_null_pointer() {
    let data = b"hello";
    let rc = unsafe { soliton_sha3_256(data.as_ptr(), data.len(), ptr::null_mut(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn sha3_256_null_data_nonzero_len_returns_null_pointer() {
    // Output is zeroed before the data-null check fires.
    let mut out = fill_nonzero::<32>();
    let rc = unsafe { soliton_sha3_256(ptr::null(), 5, out.as_mut_ptr(), 32) };
    assert_eq!(rc, E_NULL);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn sha3_256_null_data_zero_len_hashes_empty() {
    // Null data with len=0 is allowed — hashes the empty string.
    let mut out = [0u8; 32];
    let rc = unsafe { soliton_sha3_256(ptr::null(), 0, out.as_mut_ptr(), 32) };
    assert_eq!(rc, OK);
    // SHA3-256("") = a7ffc6f8bf1ed76651c14756a061d662f580ff4de43b49fa82d80a4b80f8434a
    let expected: [u8; 32] = [
        0xa7, 0xff, 0xc6, 0xf8, 0xbf, 0x1e, 0xd7, 0x66, 0x51, 0xc1, 0x47, 0x56, 0xa0, 0x61, 0xd6,
        0x62, 0xf5, 0x80, 0xff, 0x4d, 0xe4, 0x3b, 0x49, 0xfa, 0x82, 0xd8, 0x0a, 0x4b, 0x80, 0xf8,
        0x43, 0x4a,
    ];
    assert_eq!(out, expected);
}

#[test]
fn sha3_256_known_hash() {
    let data = b"abc";
    let mut out = [0u8; 32];
    let rc = unsafe { soliton_sha3_256(data.as_ptr(), data.len(), out.as_mut_ptr(), 32) };
    assert_eq!(rc, OK);
    // SHA3-256("abc") from FIPS 202.
    let expected: [u8; 32] = [
        0x3a, 0x98, 0x5d, 0xa7, 0x4f, 0xe2, 0x25, 0xb2, 0x04, 0x5c, 0x17, 0x2d, 0x6b, 0xd3, 0x90,
        0xbd, 0x85, 0x5f, 0x08, 0x6e, 0x3e, 0x9d, 0x52, 0x5b, 0x46, 0xbf, 0xe2, 0x45, 0x11, 0x43,
        0x15, 0x32,
    ];
    assert_eq!(out, expected);
}

// ═══════════════════════════════════════════════════════════════════════════
// hmac_sha3_256
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn hmac_sha3_256_null_key_returns_null_pointer() {
    let mut out = [0u8; 32];
    let rc = unsafe { soliton_hmac_sha3_256(ptr::null(), 4, ptr::null(), 0, out.as_mut_ptr(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn hmac_sha3_256_null_out_returns_null_pointer() {
    let key = b"key";
    let rc = unsafe {
        soliton_hmac_sha3_256(key.as_ptr(), key.len(), ptr::null(), 0, ptr::null_mut(), 32)
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn hmac_sha3_256_null_data_nonzero_len_returns_null_pointer() {
    let key = b"key";
    let mut out = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_hmac_sha3_256(
            key.as_ptr(),
            key.len(),
            ptr::null(),
            5,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn hmac_sha3_256_empty_key_is_valid() {
    // RFC 2104 allows zero-length keys (unusual but not prohibited).
    let key = [0u8; 0];
    let data = b"message";
    let mut out = [0u8; 32];
    let rc = unsafe {
        soliton_hmac_sha3_256(
            key.as_ptr(),
            0,
            data.as_ptr(),
            data.len(),
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, OK);
    assert!(!is_zeroed(&out));
}

#[test]
fn hmac_sha3_256_known_mac() {
    // HMAC-SHA3-256 test vector (RFC 4231 inputs, SHA3-256 hash):
    //   Key  = 0x0b * 20
    //   Data = "Hi There"
    //   HMAC = ba85192310dffa96e2a3a40e69774351140bb7185e1202cdcc917589f95e16bb
    let key = [0x0bu8; 20];
    let data = b"Hi There";
    let mut out = [0u8; 32];
    let rc = unsafe {
        soliton_hmac_sha3_256(
            key.as_ptr(),
            key.len(),
            data.as_ptr(),
            data.len(),
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, OK);
    let expected: [u8; 32] = [
        0xba, 0x85, 0x19, 0x23, 0x10, 0xdf, 0xfa, 0x96, 0xe2, 0xa3, 0xa4, 0x0e, 0x69, 0x77, 0x43,
        0x51, 0x14, 0x0b, 0xb7, 0x18, 0x5e, 0x12, 0x02, 0xcd, 0xcc, 0x91, 0x75, 0x89, 0xf9, 0x5e,
        0x16, 0xbb,
    ];
    assert_eq!(out, expected);
}

// ═══════════════════════════════════════════════════════════════════════════
// hmac_sha3_256_verify
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn hmac_sha3_256_verify_null_tag_a_returns_null_pointer() {
    let tag = [0x42u8; 32];
    let rc = unsafe { soliton_hmac_sha3_256_verify(ptr::null(), 32, tag.as_ptr(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn hmac_sha3_256_verify_null_tag_b_returns_null_pointer() {
    let tag = [0x42u8; 32];
    let rc = unsafe { soliton_hmac_sha3_256_verify(tag.as_ptr(), 32, ptr::null(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn hmac_sha3_256_verify_matching_tags_returns_ok() {
    let key = [0x0bu8; 20];
    let data = b"Hi There";
    let mut tag = [0u8; 32];
    let rc = unsafe {
        soliton_hmac_sha3_256(
            key.as_ptr(),
            key.len(),
            data.as_ptr(),
            data.len(),
            tag.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, OK);
    let rc = unsafe { soliton_hmac_sha3_256_verify(tag.as_ptr(), 32, tag.as_ptr(), 32) };
    assert_eq!(rc, OK);
}

#[test]
fn hmac_sha3_256_verify_different_tags_returns_verification_failed() {
    let tag_a = [0x11u8; 32];
    let tag_b = [0x22u8; 32];
    let rc = unsafe { soliton_hmac_sha3_256_verify(tag_a.as_ptr(), 32, tag_b.as_ptr(), 32) };
    assert_eq!(rc, E_VER);
}

#[test]
fn hmac_sha3_256_verify_single_bit_difference_returns_verification_failed() {
    let tag_a = [0x00u8; 32];
    let mut tag_b = [0x00u8; 32];
    tag_b[31] = 0x01;
    let rc = unsafe { soliton_hmac_sha3_256_verify(tag_a.as_ptr(), 32, tag_b.as_ptr(), 32) };
    assert_eq!(rc, E_VER);
}

#[test]
fn hmac_sha3_256_verify_wrong_tag_a_len_returns_invalid_length() {
    let tag_a = [0x42u8; 32];
    let tag_b = [0x42u8; 32];
    let rc = unsafe { soliton_hmac_sha3_256_verify(tag_a.as_ptr(), 31, tag_b.as_ptr(), 32) };
    assert_eq!(rc, E_LEN);
}

#[test]
fn hmac_sha3_256_verify_wrong_tag_b_len_returns_invalid_length() {
    let tag_a = [0x42u8; 32];
    let tag_b = [0x42u8; 32];
    let rc = unsafe { soliton_hmac_sha3_256_verify(tag_a.as_ptr(), 32, tag_b.as_ptr(), 0) };
    assert_eq!(rc, E_LEN);
}

// ═══════════════════════════════════════════════════════════════════════════
// hkdf_sha3_256
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn hkdf_sha3_256_null_out_returns_null_pointer() {
    let rc = unsafe {
        soliton_hkdf_sha3_256(
            ptr::null(),
            0,
            ptr::null(),
            0,
            ptr::null(),
            0,
            ptr::null_mut(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn hkdf_sha3_256_zero_out_len_returns_invalid_length() {
    let mut out = [0u8; 32];
    let rc = unsafe {
        soliton_hkdf_sha3_256(
            ptr::null(),
            0,
            ptr::null(),
            0,
            ptr::null(),
            0,
            out.as_mut_ptr(),
            0,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn hkdf_sha3_256_out_len_too_large_returns_invalid_length() {
    let mut out = vec![0u8; 8161];
    let rc = unsafe {
        soliton_hkdf_sha3_256(
            ptr::null(),
            0,
            ptr::null(),
            0,
            ptr::null(),
            0,
            out.as_mut_ptr(),
            8161,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn hkdf_sha3_256_null_salt_nonzero_len_returns_null_pointer() {
    let mut out = fill_nonzero::<32>();
    let ikm = b"ikm";
    let rc = unsafe {
        soliton_hkdf_sha3_256(
            ptr::null(),
            5,
            ikm.as_ptr(),
            ikm.len(),
            ptr::null(),
            0,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn hkdf_sha3_256_null_ikm_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null ikm with nonzero ikm_len is invalid.
    let mut out = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_hkdf_sha3_256(
            ptr::null(),
            0,
            ptr::null(),
            1,
            ptr::null(),
            0,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn hkdf_sha3_256_null_info_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null info with nonzero info_len is invalid.
    let mut out = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_hkdf_sha3_256(
            ptr::null(),
            0,
            ptr::null(),
            0,
            ptr::null(),
            1,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn hkdf_sha3_256_empty_inputs_ok() {
    // All-null inputs with len=0 are valid (empty salt, empty IKM, empty info).
    let mut out = [0u8; 32];
    let rc = unsafe {
        soliton_hkdf_sha3_256(
            ptr::null(),
            0,
            ptr::null(),
            0,
            ptr::null(),
            0,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, OK);
    assert!(!is_zeroed(&out));
}

#[test]
fn hkdf_sha3_256_roundtrip_deterministic() {
    let salt = b"salt";
    let ikm = b"ikm";
    let info = b"info";
    let mut out1 = [0u8; 32];
    let mut out2 = [0u8; 32];
    unsafe {
        soliton_hkdf_sha3_256(
            salt.as_ptr(),
            salt.len(),
            ikm.as_ptr(),
            ikm.len(),
            info.as_ptr(),
            info.len(),
            out1.as_mut_ptr(),
            32,
        );
        soliton_hkdf_sha3_256(
            salt.as_ptr(),
            salt.len(),
            ikm.as_ptr(),
            ikm.len(),
            info.as_ptr(),
            info.len(),
            out2.as_mut_ptr(),
            32,
        );
    }
    assert_eq!(out1, out2);
    assert!(!is_zeroed(&out1));
}

// ═══════════════════════════════════════════════════════════════════════════
// aead_encrypt / aead_decrypt
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn aead_encrypt_null_key_returns_null_pointer() {
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_encrypt(
            ptr::null(),
            32,
            [0u8; NONCE].as_ptr(),
            NONCE,
            ptr::null(),
            0,
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn aead_encrypt_null_nonce_returns_null_pointer() {
    let key = [0u8; 32];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_encrypt(
            key.as_ptr(),
            32,
            ptr::null(),
            NONCE,
            ptr::null(),
            0,
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn aead_encrypt_null_plaintext_nonzero_len_returns_null_pointer() {
    let key = [0u8; 32];
    let nonce = [0u8; NONCE];
    // out is zeroed upfront; then null plaintext check fires.
    let mut nonzero = 0xABu8;
    let mut out = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let rc = unsafe {
        soliton_aead_encrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            ptr::null(),
            5,
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(out.ptr.is_null());
    assert_eq!(out.len, 0);
}

#[test]
fn aead_encrypt_null_aad_nonzero_len_returns_null_pointer() {
    // aad=null with aad_len>0 is a co-presence violation — caller logic bug.
    let key = [0u8; 32];
    let nonce = [0u8; NONCE];
    let plaintext = b"hello";
    let mut nonzero = 0xABu8;
    let mut out = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let rc = unsafe {
        soliton_aead_encrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            plaintext.as_ptr(),
            plaintext.len(),
            ptr::null(),
            5,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(out.ptr.is_null());
}

#[test]
fn aead_decrypt_null_aad_nonzero_len_returns_null_pointer() {
    // aad=null with aad_len>0 is a co-presence violation — caller logic bug.
    let key = [0u8; 32];
    let nonce = [0u8; NONCE];
    let ct = [0u8; 32];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_decrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            ct.as_ptr(),
            ct.len(),
            ptr::null(),
            5,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn aead_decrypt_null_key_returns_null_pointer() {
    let ct = [0u8; 32];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_decrypt(
            ptr::null(),
            32,
            [0u8; NONCE].as_ptr(),
            NONCE,
            ct.as_ptr(),
            ct.len(),
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn aead_decrypt_zero_ciphertext_len_returns_invalid_length() {
    let key = [0u8; 32];
    let nonce = [0u8; NONCE];
    let ct = [0u8; 1];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_decrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            ct.as_ptr(),
            0,
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn aead_encrypt_wrong_key_len_returns_invalid_length() {
    let key = [0u8; 32];
    let nonce = [0u8; NONCE];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_encrypt(
            key.as_ptr(),
            16,
            nonce.as_ptr(),
            NONCE,
            ptr::null(),
            0,
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn aead_encrypt_wrong_nonce_len_returns_invalid_length() {
    let key = [0u8; 32];
    let nonce = [0u8; NONCE];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_encrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            12,
            ptr::null(),
            0,
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn aead_decrypt_wrong_key_len_returns_invalid_length() {
    let key = [0u8; 32];
    let nonce = [0u8; NONCE];
    let ct = [0u8; 32];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_decrypt(
            key.as_ptr(),
            33,
            nonce.as_ptr(),
            NONCE,
            ct.as_ptr(),
            ct.len(),
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn aead_decrypt_wrong_nonce_len_returns_invalid_length() {
    let key = [0u8; 32];
    let nonce = [0u8; NONCE];
    let ct = [0u8; 32];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_aead_decrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            0,
            ct.as_ptr(),
            ct.len(),
            ptr::null(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn aead_encrypt_decrypt_round_trip() {
    let key = [0x42u8; 32];
    let nonce = [0x01u8; NONCE];
    let plaintext = b"hello world";
    let aad = b"associated";
    unsafe {
        let mut ct_buf = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_aead_encrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            plaintext.as_ptr(),
            plaintext.len(),
            aad.as_ptr(),
            aad.len(),
            &mut ct_buf,
        );
        assert_eq!(rc, OK);
        assert!(!ct_buf.ptr.is_null());
        assert_eq!(ct_buf.len, plaintext.len() + 16); // plaintext + tag

        let mut pt_buf = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_aead_decrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            ct_buf.ptr,
            ct_buf.len,
            aad.as_ptr(),
            aad.len(),
            &mut pt_buf,
        );
        assert_eq!(rc, OK);
        assert!(!pt_buf.ptr.is_null());
        let pt = std::slice::from_raw_parts(pt_buf.ptr, pt_buf.len);
        assert_eq!(pt, plaintext);

        soliton_buf_free(&mut pt_buf);
        soliton_buf_free(&mut ct_buf);
    }
}

#[test]
fn aead_decrypt_tampered_ciphertext_returns_aead_failed() {
    let key = [0x42u8; 32];
    let nonce = [0x01u8; NONCE];
    let plaintext = b"hello";
    unsafe {
        let mut ct_buf = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_aead_encrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            plaintext.as_ptr(),
            plaintext.len(),
            ptr::null(),
            0,
            &mut ct_buf,
        );
        assert_eq!(rc, OK);
        // Flip one byte in the ciphertext.
        *ct_buf.ptr ^= 0xFF;

        let mut pt_buf = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_aead_decrypt(
            key.as_ptr(),
            32,
            nonce.as_ptr(),
            NONCE,
            ct_buf.ptr,
            ct_buf.len,
            ptr::null(),
            0,
            &mut pt_buf,
        );
        assert_eq!(rc, E_AEAD);
        // Output must be zeroed on failure.
        assert!(pt_buf.ptr.is_null());
        assert_eq!(pt_buf.len, 0);

        soliton_buf_free(&mut ct_buf);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// argon2id
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn argon2id_null_out_returns_null_pointer() {
    let rc = unsafe {
        soliton_argon2id(
            ptr::null(),
            0,
            [0u8; 8].as_ptr(),
            8,
            8,
            1,
            1,
            ptr::null_mut(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn argon2id_zero_out_len_returns_invalid_length() {
    let mut out = [0u8; 32];
    let rc = unsafe {
        soliton_argon2id(
            ptr::null(),
            0,
            [0u8; 8].as_ptr(),
            8,
            8,
            1,
            1,
            out.as_mut_ptr(),
            0,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn argon2id_null_password_nonzero_len_returns_null_pointer() {
    let mut out = fill_nonzero::<32>();
    let salt = [0u8; 8];
    let rc = unsafe {
        soliton_argon2id(
            ptr::null(),
            5,
            salt.as_ptr(),
            salt.len(),
            8,
            1,
            1,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn argon2id_null_salt_nonzero_len_returns_null_pointer() {
    let mut out = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_argon2id(
            ptr::null(),
            0,
            ptr::null(),
            5,
            8,
            1,
            1,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn argon2id_minimal_params_produces_output() {
    // m=8 KiB, t=1, p=1 — absolute minimum. Salt must be >= 8 bytes.
    let password = b"password";
    let salt = b"saltbytes";
    let mut out = [0u8; 32];
    let rc = unsafe {
        soliton_argon2id(
            password.as_ptr(),
            password.len(),
            salt.as_ptr(),
            salt.len(),
            8,
            1,
            1,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, OK);
    assert!(!is_zeroed(&out));
}

#[test]
fn argon2id_deterministic() {
    let password = b"pw";
    let salt = b"saltsalt";
    let mut out1 = [0u8; 32];
    let mut out2 = [0u8; 32];
    unsafe {
        soliton_argon2id(
            password.as_ptr(),
            password.len(),
            salt.as_ptr(),
            salt.len(),
            8,
            1,
            1,
            out1.as_mut_ptr(),
            32,
        );
        soliton_argon2id(
            password.as_ptr(),
            password.len(),
            salt.as_ptr(),
            salt.len(),
            8,
            1,
            1,
            out2.as_mut_ptr(),
            32,
        );
    }
    assert_eq!(out1, out2);
}

#[test]
fn argon2id_excessive_m_cost_returns_invalid_data() {
    let mut out = fill_nonzero::<32>();
    let salt = b"saltsalt";
    let rc = unsafe {
        soliton_argon2id(
            ptr::null(),
            0,
            salt.as_ptr(),
            salt.len(),
            4_194_305,
            1,
            1,
            out.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_DATA, "m_cost above 4 GiB cap must be rejected");
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

// ═══════════════════════════════════════════════════════════════════════════
// auth_verify (PQ-free: just HMAC comparison)
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn auth_verify_null_token_returns_null_pointer() {
    let proof = [0u8; 32];
    let rc = unsafe { soliton_auth_verify(ptr::null(), 32, proof.as_ptr(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn auth_verify_null_proof_returns_null_pointer() {
    let token = [0u8; 32];
    let rc = unsafe { soliton_auth_verify(token.as_ptr(), 32, ptr::null(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn auth_verify_matching_tokens() {
    let token = [0x42u8; 32];
    let rc = unsafe { soliton_auth_verify(token.as_ptr(), 32, token.as_ptr(), 32) };
    assert_eq!(rc, OK);
}

#[test]
fn auth_verify_mismatched_tokens() {
    let token = [0x42u8; 32];
    let proof = [0x43u8; 32];
    let rc = unsafe { soliton_auth_verify(token.as_ptr(), 32, proof.as_ptr(), 32) };
    assert_eq!(rc, E_VER);
}

#[test]
fn auth_verify_wrong_token_len_returns_invalid_length() {
    let token = [0x42u8; 32];
    let proof = [0x42u8; 32];
    let rc = unsafe { soliton_auth_verify(token.as_ptr(), 31, proof.as_ptr(), 32) };
    assert_eq!(rc, E_LEN);
}

#[test]
fn auth_verify_wrong_proof_len_returns_invalid_length() {
    let token = [0x42u8; 32];
    let proof = [0x42u8; 32];
    let rc = unsafe { soliton_auth_verify(token.as_ptr(), 32, proof.as_ptr(), 33) };
    assert_eq!(rc, E_LEN);
}

// ═══════════════════════════════════════════════════════════════════════════
// identity_generate (null-guard tests — no keygen, MIRI-safe)
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn identity_generate_null_pk_out_returns_null_pointer() {
    let mut sk_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut fp_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_identity_generate(ptr::null_mut(), &mut sk_out, &mut fp_out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_generate_null_sk_out_returns_null_pointer() {
    let mut pk_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut fp_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_identity_generate(&mut pk_out, ptr::null_mut(), &mut fp_out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_generate_null_fp_out_returns_null_pointer() {
    let mut pk_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut sk_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_identity_generate(&mut pk_out, &mut sk_out, ptr::null_mut()) };
    assert_eq!(rc, E_NULL);
}

// ═══════════════════════════════════════════════════════════════════════════
// identity_fingerprint (PQ-free: just SHA3-256 of key bytes)
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn identity_fingerprint_null_pk_returns_null_pointer() {
    let mut out = fill_nonzero::<32>();
    let rc = unsafe { soliton_identity_fingerprint(ptr::null(), PK, out.as_mut_ptr(), 32) };
    assert_eq!(rc, E_NULL);
    assert!(is_zeroed(&out), "out must be zeroed when pk is null");
}

#[test]
fn identity_fingerprint_null_out_returns_null_pointer() {
    let pk = [0u8; PK];
    let rc = unsafe { soliton_identity_fingerprint(pk.as_ptr(), PK, ptr::null_mut(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_fingerprint_zero_pk_len_returns_invalid_length() {
    let pk = [0u8; PK];
    let mut out = fill_nonzero::<32>();
    let rc = unsafe { soliton_identity_fingerprint(pk.as_ptr(), 0, out.as_mut_ptr(), 32) };
    assert_eq!(rc, E_LEN);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn identity_fingerprint_wrong_pk_len_returns_invalid_length() {
    let pk = [0u8; PK - 1];
    let mut out = fill_nonzero::<32>();
    let rc = unsafe { soliton_identity_fingerprint(pk.as_ptr(), PK - 1, out.as_mut_ptr(), 32) };
    assert_eq!(rc, E_LEN);
    assert!(is_zeroed(&out), "output must be zeroed on error");
}

#[test]
fn identity_fingerprint_zeroed_pk_produces_output() {
    // from_bytes is length-only — no keygen needed.
    let pk = [0u8; PK];
    let mut out = [0u8; 32];
    let rc = unsafe { soliton_identity_fingerprint(pk.as_ptr(), PK, out.as_mut_ptr(), 32) };
    assert_eq!(rc, OK);
    assert!(!is_zeroed(&out));
}

#[test]
fn identity_fingerprint_deterministic() {
    let pk = [0u8; PK];
    let mut fp1 = [0u8; FP];
    let mut fp2 = [0u8; FP];
    unsafe {
        soliton_identity_fingerprint(pk.as_ptr(), PK, fp1.as_mut_ptr(), 32);
        soliton_identity_fingerprint(pk.as_ptr(), PK, fp2.as_mut_ptr(), 32);
    }
    assert_eq!(fp1, fp2);
}

// ═══════════════════════════════════════════════════════════════════════════
// identity_sign / verify / encapsulate / decapsulate — error paths only
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn identity_sign_null_sk_returns_null_pointer() {
    let msg = b"message";
    let mut sig_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc =
        unsafe { soliton_identity_sign(ptr::null(), SK, msg.as_ptr(), msg.len(), &mut sig_out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_sign_zero_sk_len_returns_invalid_length() {
    let sk = [0u8; SK];
    let msg = b"message";
    let mut nonzero = 0xABu8;
    let mut sig = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let rc = unsafe { soliton_identity_sign(sk.as_ptr(), 0, msg.as_ptr(), msg.len(), &mut sig) };
    assert_eq!(rc, E_LEN);
    assert!(sig.ptr.is_null());
}

#[test]
fn identity_sign_null_message_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null message with nonzero message_len is invalid.
    // Use a non-null sentinel so that the zeroing step (which happens between
    // the null-pointer guard and the co-presence check) is observable.
    let sk = [0u8; SK];
    let mut sig_out = SolitonBuf {
        ptr: std::ptr::dangling_mut::<u8>(),
        len: 99,
    };
    let rc = unsafe { soliton_identity_sign(sk.as_ptr(), SK, ptr::null(), 1, &mut sig_out) };
    assert_eq!(rc, E_NULL);
    assert!(sig_out.ptr.is_null(), "sig_out.ptr must be zeroed on error");
    assert_eq!(sig_out.len, 0, "sig_out.len must be zeroed on error");
}

#[test]
fn identity_sign_null_sig_out_returns_null_pointer() {
    // sig_out is checked alongside sk in the combined null guard; passing null
    // sig_out returns E_NULL regardless of the other parameters.
    let sk = [0u8; SK];
    let rc = unsafe { soliton_identity_sign(sk.as_ptr(), SK, ptr::null(), 0, ptr::null_mut()) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_verify_null_pk_returns_null_pointer() {
    let msg = b"message";
    let sig = [0u8; HSIG];
    let rc = unsafe {
        soliton_identity_verify(ptr::null(), PK, msg.as_ptr(), msg.len(), sig.as_ptr(), HSIG)
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_verify_zero_pk_len_returns_invalid_length() {
    let pk = [0u8; PK];
    let msg = b"message";
    let sig = [0u8; HSIG];
    let rc = unsafe {
        soliton_identity_verify(pk.as_ptr(), 0, msg.as_ptr(), msg.len(), sig.as_ptr(), HSIG)
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn identity_verify_null_message_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null message with nonzero message_len is invalid.
    let pk = [0u8; PK];
    let sig = [0u8; HSIG];
    let rc =
        unsafe { soliton_identity_verify(pk.as_ptr(), PK, ptr::null(), 1, sig.as_ptr(), HSIG) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_verify_null_sig_nonzero_len_returns_null_pointer() {
    let pk = [0u8; PK];
    let msg = b"message";
    let rc = unsafe {
        soliton_identity_verify(pk.as_ptr(), PK, msg.as_ptr(), msg.len(), ptr::null(), HSIG)
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_encapsulate_null_pk_returns_null_pointer() {
    let mut ct_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut ss = [0u8; 32];
    let rc =
        unsafe { soliton_identity_encapsulate(ptr::null(), PK, &mut ct_out, ss.as_mut_ptr(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_encapsulate_zero_pk_len_zeroes_outputs() {
    let pk = [0u8; PK];
    let mut nonzero = 0xABu8;
    let mut ct = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let mut ss = fill_nonzero::<32>();
    let rc = unsafe { soliton_identity_encapsulate(pk.as_ptr(), 0, &mut ct, ss.as_mut_ptr(), 32) };
    assert_eq!(rc, E_LEN);
    assert!(ct.ptr.is_null());
    assert!(is_zeroed(&ss), "ss must be zeroed on error");
}

#[test]
fn identity_decapsulate_null_sk_returns_null_pointer() {
    let ct = [0u8; XCTZ];
    let mut ss = [0u8; 32];
    let rc = unsafe {
        soliton_identity_decapsulate(ptr::null(), SK, ct.as_ptr(), XCTZ, ss.as_mut_ptr(), 32)
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn identity_decapsulate_zero_sk_len_zeroes_ss() {
    let sk = [0u8; SK];
    let ct = [0u8; XCTZ];
    let mut ss = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_identity_decapsulate(sk.as_ptr(), 0, ct.as_ptr(), XCTZ, ss.as_mut_ptr(), 32)
    };
    assert_eq!(rc, E_LEN);
    assert!(is_zeroed(&ss), "ss must be zeroed on error");
}

// ═══════════════════════════════════════════════════════════════════════════
// auth_challenge / auth_respond — error paths only
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn auth_challenge_null_pk_returns_null_pointer() {
    let mut ct_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut token = [0u8; 32];
    let rc =
        unsafe { soliton_auth_challenge(ptr::null(), PK, &mut ct_out, token.as_mut_ptr(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn auth_challenge_zero_pk_len_zeroes_outputs() {
    let pk = [0u8; PK];
    let mut nonzero = 0xABu8;
    let mut ct = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let mut token = fill_nonzero::<32>();
    let rc = unsafe { soliton_auth_challenge(pk.as_ptr(), 0, &mut ct, token.as_mut_ptr(), 32) };
    assert_eq!(rc, E_LEN);
    assert!(ct.ptr.is_null());
    assert!(is_zeroed(&token), "token must be zeroed on error");
}

#[test]
fn auth_respond_null_sk_returns_null_pointer() {
    let ct = [0u8; XCTZ];
    let mut proof = [0u8; 32];
    let rc =
        unsafe { soliton_auth_respond(ptr::null(), SK, ct.as_ptr(), XCTZ, proof.as_mut_ptr(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn auth_respond_zero_sk_len_zeroes_proof() {
    let sk = [0u8; SK];
    let ct = [0u8; XCTZ];
    let mut proof = fill_nonzero::<32>();
    let rc =
        unsafe { soliton_auth_respond(sk.as_ptr(), 0, ct.as_ptr(), XCTZ, proof.as_mut_ptr(), 32) };
    assert_eq!(rc, E_LEN);
    assert!(is_zeroed(&proof), "proof must be zeroed on error");
}

// ═══════════════════════════════════════════════════════════════════════════
// ratchet_init_alice / init_bob
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn ratchet_init_alice_null_root_key_returns_null_pointer() {
    let ck = [0u8; 32];
    let fp = [0x01u8; 32];
    let fp2 = [0x02u8; 32];
    let ek_pk = [0u8; XPKZ];
    let ek_sk = [0u8; XSKZ];
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe {
        soliton_ratchet_init_alice(
            ptr::null(),
            32,
            ck.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            fp2.as_ptr(),
            32,
            ek_pk.as_ptr(),
            XPKZ,
            ek_sk.as_ptr(),
            XSKZ,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_init_alice_zero_ek_pk_len_sets_out_null() {
    let rk = [0u8; 32];
    let ck = [0u8; 32];
    let fp = [0x01u8; 32];
    let fp2 = [0x02u8; 32];
    let ek_pk = [0u8; XPKZ];
    let ek_sk = [0u8; XSKZ];
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe {
        soliton_ratchet_init_alice(
            rk.as_ptr(),
            32,
            ck.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            fp2.as_ptr(),
            32,
            ek_pk.as_ptr(),
            0,
            ek_sk.as_ptr(),
            XSKZ,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
    assert!(out.is_null(), "*out must be null on error");
}

#[test]
fn ratchet_init_alice_wrong_ek_pk_size_returns_invalid_length() {
    let rk = [0u8; 32];
    let ck = [0u8; 32];
    let fp = [0x01u8; 32];
    let fp2 = [0x02u8; 32];
    let ek_pk = [0u8; XPKZ - 1];
    let ek_sk = [0u8; XSKZ];
    let mut out: *mut SolitonRatchet = ptr::null_mut();
    let rc = unsafe {
        soliton_ratchet_init_alice(
            rk.as_ptr(),
            32,
            ck.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            fp2.as_ptr(),
            32,
            ek_pk.as_ptr(),
            XPKZ - 1,
            ek_sk.as_ptr(),
            XSKZ,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
    assert!(out.is_null());
}

#[test]
fn ratchet_init_bob_null_root_key_returns_null_pointer() {
    let ck = [0u8; 32];
    let fp = [0x02u8; 32];
    let fp2 = [0x01u8; 32];
    let peer_ek = [0u8; XPKZ];
    let mut out: *mut SolitonRatchet = ptr::null_mut();
    let rc = unsafe {
        soliton_ratchet_init_bob(
            ptr::null(),
            32,
            ck.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            fp2.as_ptr(),
            32,
            peer_ek.as_ptr(),
            XPKZ,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_init_bob_zero_peer_ek_len_sets_out_null() {
    let rk = [0u8; 32];
    let ck = [0u8; 32];
    let fp = [0x02u8; 32];
    let fp2 = [0x01u8; 32];
    let peer_ek = [0u8; XPKZ];
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe {
        soliton_ratchet_init_bob(
            rk.as_ptr(),
            32,
            ck.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            fp2.as_ptr(),
            32,
            peer_ek.as_ptr(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
    assert!(out.is_null(), "*out must be null on error");
}

#[test]
fn ratchet_init_alice_null_chain_key_returns_null_pointer() {
    let rk = [0u8; 32];
    let fp = [0x01u8; 32];
    let fp2 = [0x02u8; 32];
    let ek_pk = [0u8; XPKZ];
    let ek_sk = [0u8; XSKZ];
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe {
        soliton_ratchet_init_alice(
            rk.as_ptr(),
            32,
            ptr::null(),
            32,
            fp.as_ptr(),
            32,
            fp2.as_ptr(),
            32,
            ek_pk.as_ptr(),
            XPKZ,
            ek_sk.as_ptr(),
            XSKZ,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(out.is_null(), "*out must be null on error");
}

#[test]
fn ratchet_init_bob_null_chain_key_returns_null_pointer() {
    let rk = [0u8; 32];
    let fp = [0x02u8; 32];
    let fp2 = [0x01u8; 32];
    let peer_ek = [0u8; XPKZ];
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe {
        soliton_ratchet_init_bob(
            rk.as_ptr(),
            32,
            ptr::null(),
            32,
            fp.as_ptr(),
            32,
            fp2.as_ptr(),
            32,
            peer_ek.as_ptr(),
            XPKZ,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
    assert!(out.is_null(), "*out must be null on error");
}

#[test]
fn ratchet_init_alice_wrong_root_key_len_returns_invalid_length() {
    let rk = [0u8; 32];
    let ck = [0u8; 32];
    let fp = [0x01u8; 32];
    let fp2 = [0x02u8; 32];
    let ek_pk = [0u8; XPKZ];
    let ek_sk = [0u8; XSKZ];
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe {
        soliton_ratchet_init_alice(
            rk.as_ptr(),
            31,
            ck.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            fp2.as_ptr(),
            32,
            ek_pk.as_ptr(),
            XPKZ,
            ek_sk.as_ptr(),
            XSKZ,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
    assert!(out.is_null());
}

#[test]
fn ratchet_init_bob_wrong_fp_len_returns_invalid_length() {
    let rk = [0u8; 32];
    let ck = [0u8; 32];
    let fp = [0x02u8; 32];
    let fp2 = [0x01u8; 32];
    let peer_ek = [0u8; XPKZ];
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe {
        soliton_ratchet_init_bob(
            rk.as_ptr(),
            32,
            ck.as_ptr(),
            32,
            fp.as_ptr(),
            33,
            fp2.as_ptr(),
            32,
            peer_ek.as_ptr(),
            XPKZ,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
    assert!(out.is_null());
}

#[test]
fn ratchet_free_null_is_noop() {
    unsafe {
        soliton_ratchet_free(ptr::null_mut());
    }
}

#[test]
fn ratchet_free_double_is_noop() {
    unsafe {
        let mut alice = make_alice();
        soliton_ratchet_free(&mut alice);
        assert!(alice.is_null(), "pointer must be nulled after free");
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn encrypted_message_free_null_is_noop() {
    // Must not crash — consistent with ratchet_free_null_is_noop.
    unsafe {
        soliton_encrypted_message_free(ptr::null_mut());
    }
}

#[test]
fn encrypted_message_free_double_is_noop() {
    // Inner SolitonBuf fields are nulled by soliton_buf_free on first call;
    // second call sees null ptrs and no-ops.
    unsafe {
        let mut alice = make_alice();
        let plaintext = b"double-free test";
        let mut msg = MaybeUninit::<SolitonEncryptedMessage>::zeroed();
        let rc =
            soliton_ratchet_encrypt(alice, plaintext.as_ptr(), plaintext.len(), msg.as_mut_ptr());
        assert_eq!(rc, OK);
        let mut msg = msg.assume_init();
        soliton_encrypted_message_free(&mut msg);
        soliton_encrypted_message_free(&mut msg); // second free must not crash
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn initiated_session_free_double_is_noop() {
    // Inner SolitonBuf fields are nulled on first free; second is a no-op.
    unsafe {
        let mut session = std::mem::zeroed::<SolitonInitiatedSession>();
        // Zero-init is valid for this type (all ptrs null, all bufs empty).
        soliton_kex_initiated_session_free(&mut session);
        soliton_kex_initiated_session_free(&mut session); // must not crash
    }
}

#[test]
fn received_session_free_double_is_noop() {
    unsafe {
        let mut session = SolitonReceivedSession {
            root_key: [0u8; 32],
            chain_key: [0u8; 32],
            peer_ek: SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            },
        };
        soliton_kex_received_session_free(&mut session);
        soliton_kex_received_session_free(&mut session); // must not crash
    }
}

#[test]
fn decoded_session_init_free_double_is_noop() {
    // Decode a valid session init, then free twice.
    let encoded = make_encoded_session_init(false);
    let mut out: SolitonDecodedSessionInit = unsafe { MaybeUninit::zeroed().assume_init() };
    let rc = unsafe { soliton_kex_decode_session_init(encoded.as_ptr(), encoded.len(), &mut out) };
    assert_eq!(rc, OK);
    unsafe {
        soliton_decoded_session_init_free(&mut out);
        soliton_decoded_session_init_free(&mut out); // must not crash
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// ratchet_encrypt
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn ratchet_encrypt_null_ratchet_returns_null_pointer() {
    // Use a sentinel-filled output buffer to verify that *out is zeroed before
    // the ratchet-null check fires. The out-null and ratchet-null guards are
    // separate so that zeroing always occurs when out is non-null.
    unsafe {
        let mut out = MaybeUninit::<SolitonEncryptedMessage>::uninit();
        std::ptr::write_bytes(out.as_mut_ptr(), 0xAB, 1);
        let rc = soliton_ratchet_encrypt(ptr::null_mut(), ptr::null(), 0, out.as_mut_ptr());
        assert_eq!(rc, E_NULL);
        let out_bytes = std::slice::from_raw_parts(
            out.as_ptr() as *const u8,
            size_of::<SolitonEncryptedMessage>(),
        );
        assert!(
            is_zeroed(out_bytes),
            "out must be zeroed when ratchet is null"
        );
    }
}

#[test]
fn ratchet_encrypt_null_plaintext_zero_len_succeeds() {
    // null plaintext with zero len is valid — encrypts an empty message.
    unsafe {
        let mut alice = make_alice();
        let mut out = MaybeUninit::<SolitonEncryptedMessage>::zeroed();
        let rc = soliton_ratchet_encrypt(alice, ptr::null(), 0, out.as_mut_ptr());
        assert_eq!(rc, OK);
        let mut msg = out.assume_init();
        soliton_encrypted_message_free(&mut msg);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_encrypt_null_plaintext_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null plaintext with nonzero plaintext_len is invalid.
    unsafe {
        let mut alice = make_alice();
        let mut out = MaybeUninit::<SolitonEncryptedMessage>::zeroed();
        let rc = soliton_ratchet_encrypt(alice, ptr::null(), 1, out.as_mut_ptr());
        assert_eq!(rc, E_NULL);
        soliton_ratchet_free(&mut alice);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// ratchet_decrypt — including co-presence guards
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn ratchet_decrypt_null_ratchet_returns_null_pointer() {
    let rpk = [0u8; XPKZ];
    let ct = [0u8; 1];
    let mut pt_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_ratchet_decrypt(
            ptr::null_mut(),
            rpk.as_ptr(),
            XPKZ,
            ptr::null(),
            0,
            0,
            0,
            ct.as_ptr(),
            ct.len(),
            &mut pt_out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_decrypt_zero_ciphertext_len_returns_invalid_length() {
    unsafe {
        let mut bob = make_bob();
        let rpk = [0u8; XPKZ];
        let ct = [0u8; 1];
        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_ratchet_decrypt(
            bob,
            rpk.as_ptr(),
            XPKZ,
            ptr::null(),
            0,
            0,
            0,
            ct.as_ptr(),
            0,
            &mut pt_out,
        );
        assert_eq!(rc, E_LEN);
        soliton_ratchet_free(&mut bob);
    }
}

#[test]
fn ratchet_decrypt_copresence_null_ptr_nonzero_len() {
    // kem_ct=null but kem_ct_len=5 → NullPointer (co-presence guard).
    unsafe {
        let mut bob = make_bob();
        let rpk = [0u8; XPKZ];
        let ct = [0u8; 32];
        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_ratchet_decrypt(
            bob,
            rpk.as_ptr(),
            XPKZ,
            ptr::null(),
            5,
            0,
            0,
            ct.as_ptr(),
            ct.len(),
            &mut pt_out,
        );
        assert_eq!(rc, E_NULL);
        soliton_ratchet_free(&mut bob);
    }
}

#[test]
fn ratchet_decrypt_copresence_nonnull_ptr_zero_len() {
    // kem_ct=non-null but kem_ct_len=0 → NullPointer (co-presence guard).
    unsafe {
        let mut bob = make_bob();
        let rpk = [0u8; XPKZ];
        let kem_ct = [0u8; XCTZ];
        let ct = [0u8; 32];
        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_ratchet_decrypt(
            bob,
            rpk.as_ptr(),
            XPKZ,
            kem_ct.as_ptr(),
            0,
            0,
            0,
            ct.as_ptr(),
            ct.len(),
            &mut pt_out,
        );
        assert_eq!(rc, E_NULL);
        soliton_ratchet_free(&mut bob);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// ratchet_encrypt_first / decrypt_first
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn ratchet_encrypt_first_null_chain_key_returns_null_pointer() {
    let mut payload = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut next_ck = [0u8; 32];
    let rc = unsafe {
        soliton_ratchet_encrypt_first(
            ptr::null(),
            0,
            ptr::null(),
            0,
            ptr::null(),
            0,
            &mut payload,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_encrypt_first_null_plaintext_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null plaintext with nonzero plaintext_len is invalid.
    // Outputs are zeroed after the null guard and before co-presence checks.
    let chain_key = [0u8; 32];
    let mut payload = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 99,
    };
    let mut next_ck = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_ratchet_encrypt_first(
            chain_key.as_ptr(),
            32,
            ptr::null(),
            1,
            ptr::null(),
            0,
            &mut payload,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert_eq!(
        payload.len, 0,
        "payload.len must be zeroed after co-presence error"
    );
    assert_eq!(
        next_ck, [0u8; 32],
        "next_ck must be zeroed after co-presence error"
    );
}

#[test]
fn ratchet_encrypt_first_null_aad_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null aad with nonzero aad_len is invalid.
    // Outputs are zeroed after the null guard and before co-presence checks.
    let chain_key = [0u8; 32];
    let plaintext = b"msg";
    let mut payload = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 99,
    };
    let mut next_ck = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_ratchet_encrypt_first(
            chain_key.as_ptr(),
            32,
            plaintext.as_ptr(),
            plaintext.len(),
            ptr::null(),
            1,
            &mut payload,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert_eq!(
        payload.len, 0,
        "payload.len must be zeroed after co-presence error"
    );
    assert_eq!(
        next_ck, [0u8; 32],
        "next_ck must be zeroed after co-presence error"
    );
}

#[test]
fn ratchet_encrypt_first_null_payload_out_returns_null_pointer() {
    let chain_key = [0u8; 32];
    let mut next_ck = [0u8; 32];
    let rc = unsafe {
        soliton_ratchet_encrypt_first(
            chain_key.as_ptr(),
            32,
            ptr::null(),
            0,
            ptr::null(),
            0,
            ptr::null_mut(),
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_encrypt_first_null_ratchet_init_key_out_returns_null_pointer() {
    let chain_key = [0u8; 32];
    let mut payload = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_ratchet_encrypt_first(
            chain_key.as_ptr(),
            32,
            ptr::null(),
            0,
            ptr::null(),
            0,
            &mut payload,
            ptr::null_mut(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_decrypt_first_null_chain_key_returns_null_pointer() {
    let payload = [0u8; 1];
    let mut pt_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut next_ck = [0u8; 32];
    let rc = unsafe {
        soliton_ratchet_decrypt_first(
            ptr::null(),
            0,
            payload.as_ptr(),
            payload.len(),
            ptr::null(),
            0,
            &mut pt_out,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_decrypt_first_null_encrypted_payload_returns_null_pointer() {
    let chain_key = [0u8; 32];
    let mut pt_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut next_ck = [0u8; 32];
    let rc = unsafe {
        soliton_ratchet_decrypt_first(
            chain_key.as_ptr(),
            32,
            ptr::null(),
            1,
            ptr::null(),
            0,
            &mut pt_out,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_decrypt_first_null_plaintext_out_returns_null_pointer() {
    let chain_key = [0u8; 32];
    let payload = [0u8; 1];
    let mut next_ck = [0u8; 32];
    let rc = unsafe {
        soliton_ratchet_decrypt_first(
            chain_key.as_ptr(),
            32,
            payload.as_ptr(),
            payload.len(),
            ptr::null(),
            0,
            ptr::null_mut(),
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_decrypt_first_null_ratchet_init_key_out_returns_null_pointer() {
    let chain_key = [0u8; 32];
    let payload = [0u8; 1];
    let mut pt_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_ratchet_decrypt_first(
            chain_key.as_ptr(),
            32,
            payload.as_ptr(),
            payload.len(),
            ptr::null(),
            0,
            &mut pt_out,
            ptr::null_mut(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_decrypt_first_null_aad_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null aad with nonzero aad_len is invalid.
    // Outputs are zeroed after the null guard and before co-presence checks.
    let chain_key = [0u8; 32];
    let payload = [0u8; 1];
    let mut pt_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 99,
    };
    let mut next_ck = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_ratchet_decrypt_first(
            chain_key.as_ptr(),
            32,
            payload.as_ptr(),
            payload.len(),
            ptr::null(),
            1,
            &mut pt_out,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_NULL);
    assert_eq!(
        pt_out.len, 0,
        "pt_out.len must be zeroed after co-presence error"
    );
    assert_eq!(
        next_ck, [0u8; 32],
        "next_ck must be zeroed after co-presence error"
    );
}

#[test]
fn ratchet_decrypt_first_zero_payload_len_returns_invalid_length() {
    // encrypted_payload_len == 0 is rejected after the null and co-presence
    // guards: a zero-length encrypted payload cannot contain a valid GCM tag.
    // Pass aad = null, aad_len = 0 to ensure the aad co-presence guard is not
    // the first error (null aad with aad_len == 0 is a valid empty AAD).
    let chain_key = [0u8; 32];
    let dummy_payload = [0u8; 1]; // non-null pointer, but encrypted_payload_len = 0
    let mut pt_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut next_ck = [0u8; 32];
    let rc = unsafe {
        soliton_ratchet_decrypt_first(
            chain_key.as_ptr(),
            32,
            dummy_payload.as_ptr(),
            0,
            ptr::null(),
            0,
            &mut pt_out,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn ratchet_encrypt_first_decrypt_first_round_trip() {
    let chain_key = [0x11u8; 32];
    let plaintext = b"session init payload";
    let aad = b"session aad";
    unsafe {
        let mut payload_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut next_ck_enc = [0u8; 32];
        let rc = soliton_ratchet_encrypt_first(
            chain_key.as_ptr(),
            32,
            plaintext.as_ptr(),
            plaintext.len(),
            aad.as_ptr(),
            aad.len(),
            &mut payload_out,
            next_ck_enc.as_mut_ptr(),
            32,
        );
        assert_eq!(rc, OK);
        assert!(!payload_out.ptr.is_null());
        assert!(!is_zeroed(&next_ck_enc));

        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut next_ck_dec = [0u8; 32];
        let rc = soliton_ratchet_decrypt_first(
            chain_key.as_ptr(),
            32,
            payload_out.ptr,
            payload_out.len,
            aad.as_ptr(),
            aad.len(),
            &mut pt_out,
            next_ck_dec.as_mut_ptr(),
            32,
        );
        assert_eq!(rc, OK);
        assert!(!pt_out.ptr.is_null());
        let pt = std::slice::from_raw_parts(pt_out.ptr, pt_out.len);
        assert_eq!(pt, plaintext);
        // Both sides derive the same ratchet-init key.
        assert_eq!(next_ck_enc, next_ck_dec);

        soliton_buf_free(&mut pt_out);
        soliton_buf_free(&mut payload_out);
    }
}

#[test]
fn ratchet_decrypt_first_tampered_returns_aead_failed() {
    let chain_key = [0x22u8; 32];
    let plaintext = b"payload";
    unsafe {
        let mut payload_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut next_ck = [0u8; 32];
        let rc = soliton_ratchet_encrypt_first(
            chain_key.as_ptr(),
            32,
            plaintext.as_ptr(),
            plaintext.len(),
            ptr::null(),
            0,
            &mut payload_out,
            next_ck.as_mut_ptr(),
            32,
        );
        assert_eq!(rc, OK);
        // Flip one byte.
        *payload_out.ptr ^= 0xFF;
        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut next_ck_dec = [0u8; 32];
        let rc = soliton_ratchet_decrypt_first(
            chain_key.as_ptr(),
            32,
            payload_out.ptr,
            payload_out.len,
            ptr::null(),
            0,
            &mut pt_out,
            next_ck_dec.as_mut_ptr(),
            32,
        );
        assert_eq!(rc, E_AEAD);
        soliton_buf_free(&mut payload_out);
    }
}

#[test]
fn ratchet_encrypt_first_wrong_chain_key_len_returns_invalid_length() {
    let chain_key = [0u8; 32];
    let mut payload = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut next_ck = [0u8; 32];
    let rc = unsafe {
        soliton_ratchet_encrypt_first(
            chain_key.as_ptr(),
            31,
            ptr::null(),
            0,
            ptr::null(),
            0,
            &mut payload,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn ratchet_decrypt_first_wrong_chain_key_len_returns_invalid_length() {
    let chain_key = [0u8; 32];
    let payload = [0u8; 41];
    let mut pt_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut next_ck = [0u8; 32];
    let rc = unsafe {
        soliton_ratchet_decrypt_first(
            chain_key.as_ptr(),
            33,
            payload.as_ptr(),
            payload.len(),
            ptr::null(),
            0,
            &mut pt_out,
            next_ck.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_LEN);
}

// ═══════════════════════════════════════════════════════════════════════════
// ratchet_reset, ratchet_to_bytes, ratchet_from_bytes
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn ratchet_reset_null_returns_null_pointer() {
    let rc = unsafe { soliton_ratchet_reset(ptr::null_mut()) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_reset_zeroes_state() {
    unsafe {
        let mut alice = make_alice();
        let rc = soliton_ratchet_reset(alice);
        assert_eq!(rc, OK);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_to_bytes_null_ratchet_returns_null_pointer() {
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_ratchet_to_bytes(ptr::null_mut(), &mut out, ptr::null_mut()) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_to_bytes_null_inner_ratchet_returns_null_pointer() {
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut ratchet: *mut SolitonRatchet = ptr::null_mut();
    let rc = unsafe { soliton_ratchet_to_bytes(&mut ratchet, &mut out, ptr::null_mut()) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_to_bytes_null_out_returns_null_pointer() {
    unsafe {
        let mut alice = make_alice();
        // data_out null → early return, ratchet NOT consumed.
        let rc = soliton_ratchet_to_bytes(&mut alice, ptr::null_mut(), ptr::null_mut());
        assert_eq!(rc, E_NULL);
        assert!(
            !alice.is_null(),
            "ratchet must not be consumed on early error"
        );
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_from_bytes_null_data_returns_null_pointer() {
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe { soliton_ratchet_from_bytes(ptr::null(), 1, &mut out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_from_bytes_null_out_returns_null_pointer() {
    let data = [0u8; 1];
    let rc = unsafe { soliton_ratchet_from_bytes(data.as_ptr(), data.len(), ptr::null_mut()) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_from_bytes_zero_len_returns_invalid_length() {
    let data = [0u8; 1];
    let mut out: *mut SolitonRatchet = 0xDEAD as *mut _;
    let rc = unsafe { soliton_ratchet_from_bytes(data.as_ptr(), 0, &mut out) };
    assert_eq!(rc, E_LEN);
    assert!(out.is_null());
}

#[test]
fn ratchet_serialize_deserialize_round_trip() {
    unsafe {
        let mut alice = make_alice();
        let mut bytes_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut epoch1_out: u64 = 0;
        // to_bytes consumes alice — *alice is set to null on success.
        let rc = soliton_ratchet_to_bytes(&mut alice, &mut bytes_out, &mut epoch1_out);
        assert_eq!(rc, OK);
        assert!(!bytes_out.ptr.is_null());
        assert!(alice.is_null(), "ratchet must be consumed after to_bytes");
        assert!(epoch1_out > 0, "epoch_out must be populated");

        let mut alice2: *mut SolitonRatchet = ptr::null_mut();
        let rc = soliton_ratchet_from_bytes(bytes_out.ptr, bytes_out.len, &mut alice2);
        assert_eq!(rc, OK);
        assert!(!alice2.is_null());

        // Serialize alice2 and compare: both serializations should match
        // (excluding the epoch field at bytes 1..9, which advances on each to_bytes call).
        let mut bytes_out2 = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut epoch2_out: u64 = 0;
        let rc = soliton_ratchet_to_bytes(&mut alice2, &mut bytes_out2, &mut epoch2_out);
        assert_eq!(rc, OK);
        assert!(alice2.is_null(), "ratchet must be consumed after to_bytes");
        let b1 = std::slice::from_raw_parts(bytes_out.ptr, bytes_out.len);
        let b2 = std::slice::from_raw_parts(bytes_out2.ptr, bytes_out2.len);
        assert_eq!(b1[0], b2[0], "version must match");
        assert_eq!(b1[9..], b2[9..], "all fields after epoch must match");
        // Epoch must advance by exactly 1.
        let epoch1 = u64::from_be_bytes(b1[1..9].try_into().unwrap());
        let epoch2 = u64::from_be_bytes(b2[1..9].try_into().unwrap());
        assert_eq!(epoch2, epoch1 + 1);
        // epoch_out must match the epoch embedded in the blob.
        assert_eq!(epoch1_out, epoch1, "epoch_out must match blob epoch");
        assert_eq!(epoch2_out, epoch2, "epoch_out must match blob epoch");

        soliton_buf_free(&mut bytes_out);
        soliton_buf_free(&mut bytes_out2);
        // alice and alice2 already consumed by to_bytes — no ratchet_free needed.
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// Ratchet round-trip (PQ-free: Alice's first encrypt has no KEM step)
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn ratchet_pq_free_round_trip_alice_to_bob() {
    // Alice and Bob both initialized with zeroed keys on the same root_key/chain_key.
    // Alice's first encrypt: kem_ct=None (send_ratchet_pk=Some, ratchet_pending=false).
    // Bob's first decrypt: recv_ratchet_pk=[0;1216] == header.ratchet_pk=[0;1216] → no KEM.
    unsafe {
        let mut alice = make_alice();
        let mut bob = make_bob();

        let plaintext = b"hello ratchet";

        // Alice encrypts.
        let mut msg: MaybeUninit<SolitonEncryptedMessage> = MaybeUninit::zeroed();
        let rc =
            soliton_ratchet_encrypt(alice, plaintext.as_ptr(), plaintext.len(), msg.as_mut_ptr());
        assert_eq!(rc, OK);
        let msg = msg.assume_init();

        // Verify kem_ct is absent (no PQ ratchet step on first message).
        assert!(
            msg.header.kem_ct.ptr.is_null() || msg.header.kem_ct.len == 0,
            "first message must not contain kem_ct"
        );

        // Bob decrypts.
        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_ratchet_decrypt(
            bob,
            msg.header.ratchet_pk.ptr,
            msg.header.ratchet_pk.len,
            ptr::null(),
            0, // kem_ct absent
            msg.header.n,
            msg.header.pn,
            msg.ciphertext.ptr,
            msg.ciphertext.len,
            &mut pt_out,
        );
        assert_eq!(rc, OK, "Bob should decrypt Alice's first message");
        assert!(!pt_out.ptr.is_null());
        let pt = std::slice::from_raw_parts(pt_out.ptr, pt_out.len);
        assert_eq!(pt, plaintext);

        soliton_buf_free(&mut pt_out);
        // Free SolitonEncryptedMessage buffers.
        let mut msg_owned = msg;
        soliton_encrypted_message_free(&mut msg_owned);
        soliton_ratchet_free(&mut alice);
        soliton_ratchet_free(&mut bob);
    }
}

#[test]
fn ratchet_pq_free_decrypt_tampered_returns_aead_failed() {
    unsafe {
        let mut alice = make_alice();
        let mut bob = make_bob();

        let mut msg: MaybeUninit<SolitonEncryptedMessage> = MaybeUninit::zeroed();
        let rc = soliton_ratchet_encrypt(alice, b"secret".as_ptr(), 6, msg.as_mut_ptr());
        assert_eq!(rc, OK);
        let msg = msg.assume_init();

        // Tamper with the ciphertext.
        let ct_copy = std::slice::from_raw_parts(msg.ciphertext.ptr, msg.ciphertext.len).to_vec();
        let mut bad_ct = ct_copy.clone();
        bad_ct[0] ^= 0xFF;

        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_ratchet_decrypt(
            bob,
            msg.header.ratchet_pk.ptr,
            msg.header.ratchet_pk.len,
            ptr::null(),
            0,
            msg.header.n,
            msg.header.pn,
            bad_ct.as_ptr(),
            bad_ct.len(),
            &mut pt_out,
        );
        assert_eq!(rc, E_AEAD);

        soliton_buf_free(&mut pt_out);
        let mut msg_owned = msg;
        soliton_encrypted_message_free(&mut msg_owned);
        soliton_ratchet_free(&mut alice);
        soliton_ratchet_free(&mut bob);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// ratchet_derive_call_keys + call_keys_*
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn ratchet_derive_call_keys_null_ratchet_returns_null_pointer() {
    let kem_ss = [0u8; 32];
    let call_id = [0u8; 16];
    let mut out: *mut SolitonCallKeys = 0xDEAD as *mut _;
    let rc = unsafe {
        soliton_ratchet_derive_call_keys(
            ptr::null(),
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn ratchet_derive_call_keys_null_kem_ss_returns_null_pointer() {
    unsafe {
        let mut alice = make_alice();
        let call_id = [0u8; 16];
        let mut out: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            ptr::null(),
            32,
            call_id.as_ptr(),
            16,
            &mut out,
        );
        assert_eq!(rc, E_NULL);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_derive_call_keys_null_call_id_returns_null_pointer() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0u8; 32];
        let mut out: *mut SolitonCallKeys = ptr::null_mut();
        let rc =
            soliton_ratchet_derive_call_keys(alice, kem_ss.as_ptr(), 32, ptr::null(), 16, &mut out);
        assert_eq!(rc, E_NULL);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_derive_call_keys_null_out_returns_null_pointer() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0u8; 32];
        let call_id = [0u8; 16];
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            ptr::null_mut(),
        );
        assert_eq!(rc, E_NULL);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_derive_call_keys_wrong_kem_ss_len_returns_invalid_length() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0x55u8; 32];
        let call_id = [0xAAu8; 16];
        let mut ck_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            16,
            call_id.as_ptr(),
            16,
            &mut ck_ptr,
        );
        assert_eq!(rc, E_LEN);
        assert!(ck_ptr.is_null());
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_derive_call_keys_wrong_call_id_len_returns_invalid_length() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0x55u8; 32];
        let call_id = [0xAAu8; 16];
        let mut ck_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            32,
            &mut ck_ptr,
        );
        assert_eq!(rc, E_LEN);
        assert!(ck_ptr.is_null());
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_derive_call_keys_zero_kem_ss_returns_invalid_data() {
    // All-zero kem_ss indicates a KEM failure or uninitialized buffer; the
    // call would derive keys from only root_key + call_id, losing ephemeral FS.
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0u8; 32];
        let call_id = [0xAAu8; 16];
        let mut ck_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut ck_ptr,
        );
        assert_eq!(rc, E_DATA);
        assert!(ck_ptr.is_null());
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn ratchet_derive_call_keys_equal_fingerprints_returns_invalid_data() {
    // Equal fingerprints collapse send/recv role assignment: both parties
    // would compute the same key assignment, defeating the role split.
    // This is caught at init_alice/init_bob time. With the test helpers
    // using distinct fps (0x01 vs 0x02), derive_call_keys should succeed.
    // To test this guard, we'd need to construct a ratchet with equal fps,
    // which init_alice/init_bob now rejects. This test verifies that
    // derive_call_keys propagates the error if the state somehow has equal fps.
    unsafe {
        // make_alice uses 0x01/0x02 fps, so derive_call_keys will succeed.
        // The equal-fingerprint guard is now in init_alice/init_bob instead.
        let mut alice = make_alice();
        let kem_ss = [0x55u8; 32];
        let call_id = [0xAAu8; 16];
        let mut ck_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut ck_ptr,
        );
        assert_eq!(rc, OK);
        soliton_call_keys_free(&mut ck_ptr);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn call_keys_null_keys_returns_null_pointer() {
    let mut out = [0u8; 32];
    assert_eq!(
        unsafe { soliton_call_keys_send_key(ptr::null(), out.as_mut_ptr(), 32) },
        E_NULL
    );
    assert_eq!(
        unsafe { soliton_call_keys_recv_key(ptr::null(), out.as_mut_ptr(), 32) },
        E_NULL
    );
    assert_eq!(
        unsafe { soliton_call_keys_advance(ptr::null_mut()) },
        E_NULL
    );
}

#[test]
fn call_keys_send_key_null_out_returns_null_pointer() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0x01u8; 32];
        let call_id = [0xAAu8; 16];
        let mut keys_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut keys_ptr,
        );
        assert_eq!(rc, OK);
        assert_eq!(
            soliton_call_keys_send_key(keys_ptr, ptr::null_mut(), 32),
            E_NULL
        );
        soliton_call_keys_free(&mut keys_ptr);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn call_keys_recv_key_null_out_returns_null_pointer() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0x01u8; 32];
        let call_id = [0xAAu8; 16];
        let mut keys_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut keys_ptr,
        );
        assert_eq!(rc, OK);
        assert_eq!(
            soliton_call_keys_recv_key(keys_ptr, ptr::null_mut(), 32),
            E_NULL
        );
        soliton_call_keys_free(&mut keys_ptr);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn call_keys_send_key_wrong_out_len_returns_invalid_length() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0x01u8; 32];
        let call_id = [0xAAu8; 16];
        let mut keys_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut keys_ptr,
        );
        assert_eq!(rc, OK);
        let mut out = [0u8; 32];
        assert_eq!(
            soliton_call_keys_send_key(keys_ptr, out.as_mut_ptr(), 16),
            E_LEN
        );
        soliton_call_keys_free(&mut keys_ptr);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn call_keys_recv_key_wrong_out_len_returns_invalid_length() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0x01u8; 32];
        let call_id = [0xAAu8; 16];
        let mut keys_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut keys_ptr,
        );
        assert_eq!(rc, OK);
        let mut out = [0u8; 32];
        assert_eq!(
            soliton_call_keys_recv_key(keys_ptr, out.as_mut_ptr(), 16),
            E_LEN
        );
        soliton_call_keys_free(&mut keys_ptr);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn call_keys_free_null_is_noop() {
    unsafe {
        soliton_call_keys_free(ptr::null_mut());
    }
}

#[test]
fn call_keys_free_double_is_noop() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0xCCu8; 32];
        let call_id = [0xDDu8; 32];
        let mut keys_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut keys_ptr,
        );
        assert_eq!(rc, 0);
        soliton_call_keys_free(&mut keys_ptr);
        assert!(keys_ptr.is_null(), "pointer must be nulled after free");
        soliton_call_keys_free(&mut keys_ptr);
        soliton_ratchet_free(&mut alice);
    }
}

#[test]
fn call_keys_derive_and_advance() {
    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0x55u8; 32];
        let call_id = [0xAAu8; 16];
        let mut ck_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut ck_ptr,
        );
        assert_eq!(rc, OK);
        assert!(!ck_ptr.is_null());

        let mut send_key1 = [0u8; 32];
        let mut recv_key1 = [0u8; 32];
        soliton_call_keys_send_key(ck_ptr, send_key1.as_mut_ptr(), 32);
        soliton_call_keys_recv_key(ck_ptr, recv_key1.as_mut_ptr(), 32);
        assert!(!is_zeroed(&send_key1));
        assert!(!is_zeroed(&recv_key1));
        assert_ne!(send_key1, recv_key1, "send and recv keys must differ");

        // Advance ratchets keys.
        soliton_call_keys_advance(ck_ptr);
        let mut send_key2 = [0u8; 32];
        soliton_call_keys_send_key(ck_ptr, send_key2.as_mut_ptr(), 32);
        assert_ne!(send_key1, send_key2, "keys must change after advance");

        soliton_call_keys_free(&mut ck_ptr);
        soliton_ratchet_free(&mut alice);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// keyring_new / add_key / remove_key
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn keyring_new_null_key_returns_null_pointer() {
    let mut out: *mut SolitonKeyRing = ptr::null_mut();
    let rc = unsafe { soliton_keyring_new(ptr::null(), 32, 1, &mut out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn keyring_new_version_zero_rejected() {
    let key = [0u8; 32];
    let mut out: *mut SolitonKeyRing = 0xDEAD as *mut _;
    let rc = unsafe { soliton_keyring_new(key.as_ptr(), 32, 0, &mut out) };
    assert_eq!(rc, E_UNSUP_VER, "version 0 must return UnsupportedVersion");
    assert!(out.is_null());
}

#[test]
fn keyring_new_wrong_key_len_returns_invalid_length() {
    let key = [0u8; 32];
    let mut out: *mut SolitonKeyRing = ptr::null_mut();
    let rc = unsafe { soliton_keyring_new(key.as_ptr(), 16, 1, &mut out) };
    assert_eq!(rc, E_LEN);
    assert!(out.is_null());
}

#[test]
fn keyring_add_key_wrong_key_len_returns_invalid_length() {
    unsafe {
        let mut kr = make_keyring();
        let key = [0u8; 32];
        let rc = soliton_keyring_add_key(kr, key.as_ptr(), 0, 2, 0);
        assert_eq!(rc, E_LEN);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn keyring_add_key_null_keyring_returns_null_pointer() {
    let key = [0u8; 32];
    let rc = unsafe { soliton_keyring_add_key(ptr::null_mut(), key.as_ptr(), 32, 2, 0) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn keyring_add_key_version_zero_rejected() {
    unsafe {
        let mut kr = make_keyring();
        let key = [0u8; 32];
        let rc = soliton_keyring_add_key(kr, key.as_ptr(), 32, 0, 0);
        assert_eq!(rc, E_UNSUP_VER, "version 0 must return UnsupportedVersion");
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn keyring_remove_key_null_keyring_returns_null_pointer() {
    let rc = unsafe { soliton_keyring_remove_key(ptr::null_mut(), 1) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn keyring_remove_key_version_zero_rejected() {
    unsafe {
        let mut kr = make_keyring();
        let rc = soliton_keyring_remove_key(kr, 0);
        assert_eq!(rc, E_UNSUP_VER, "version 0 must return UnsupportedVersion");
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn keyring_remove_active_key_rejected() {
    // Removing the active key (version 1) must fail.
    unsafe {
        let mut kr = make_keyring();
        let rc = soliton_keyring_remove_key(kr, 1);
        assert_eq!(
            rc, E_DATA,
            "removing the active key must return InvalidData"
        );
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn keyring_free_null_is_noop() {
    unsafe {
        soliton_keyring_free(ptr::null_mut());
    }
}

#[test]
fn keyring_free_double_is_noop() {
    unsafe {
        let key = [0x42u8; 32];
        let mut kr: *mut SolitonKeyRing = ptr::null_mut();
        soliton_keyring_new(key.as_ptr(), 32, 1, &mut kr);
        assert!(!kr.is_null());
        soliton_keyring_free(&mut kr);
        assert!(kr.is_null(), "pointer must be nulled after free");
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn keyring_add_rotate_remove() {
    unsafe {
        let mut kr = make_keyring();
        let key2 = [0x22u8; 32];
        // Add key 2, make it active.
        let rc = soliton_keyring_add_key(kr, key2.as_ptr(), 32, 2, 1);
        assert_eq!(rc, OK);
        // Now key 1 is no longer active — it can be removed.
        let rc = soliton_keyring_remove_key(kr, 1);
        assert_eq!(rc, OK);
        soliton_keyring_free(&mut kr);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// storage_encrypt / storage_decrypt
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn storage_encrypt_null_keyring_returns_null_pointer() {
    let ch = CString::new("ch").unwrap();
    let seg = CString::new("seg").unwrap();
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_storage_encrypt(
            ptr::null(),
            ptr::null(),
            0,
            ch.as_ptr(),
            seg.as_ptr(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn storage_encrypt_null_channel_id_returns_null_pointer() {
    unsafe {
        let mut kr = make_keyring();
        let seg = CString::new("seg").unwrap();
        let mut out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc =
            soliton_storage_encrypt(kr, ptr::null(), 0, ptr::null(), seg.as_ptr(), 0, &mut out);
        assert_eq!(rc, E_NULL);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn storage_encrypt_null_plaintext_nonzero_len_returns_null_pointer() {
    // Co-presence guard: null plaintext with nonzero plaintext_len is invalid.
    unsafe {
        let mut kr = make_keyring();
        let ch = CString::new("ch").unwrap();
        let seg = CString::new("seg").unwrap();
        let mut out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc =
            soliton_storage_encrypt(kr, ptr::null(), 1, ch.as_ptr(), seg.as_ptr(), 0, &mut out);
        assert_eq!(rc, E_NULL);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn storage_decrypt_null_keyring_returns_null_pointer() {
    let blob = [0u8; 64];
    let ch = CString::new("ch").unwrap();
    let seg = CString::new("seg").unwrap();
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_storage_decrypt(
            ptr::null(),
            blob.as_ptr(),
            blob.len(),
            ch.as_ptr(),
            seg.as_ptr(),
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn storage_decrypt_zero_blob_len_returns_invalid_length() {
    unsafe {
        let mut kr = make_keyring();
        let blob = [0u8; 1];
        let ch = CString::new("ch").unwrap();
        let seg = CString::new("seg").unwrap();
        let mut out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_storage_decrypt(kr, blob.as_ptr(), 0, ch.as_ptr(), seg.as_ptr(), &mut out);
        assert_eq!(rc, E_LEN);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn storage_encrypt_decrypt_round_trip() {
    unsafe {
        let mut kr = make_keyring();
        let plaintext = b"sensitive channel message";
        let ch = CString::new("channel-1").unwrap();
        let seg = CString::new("segment-0").unwrap();

        let mut blob_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_storage_encrypt(
            kr,
            plaintext.as_ptr(),
            plaintext.len(),
            ch.as_ptr(),
            seg.as_ptr(),
            0,
            &mut blob_out,
        );
        assert_eq!(rc, OK);
        assert!(!blob_out.ptr.is_null());

        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_storage_decrypt(
            kr,
            blob_out.ptr,
            blob_out.len,
            ch.as_ptr(),
            seg.as_ptr(),
            &mut pt_out,
        );
        assert_eq!(rc, OK);
        let pt = std::slice::from_raw_parts(pt_out.ptr, pt_out.len);
        assert_eq!(pt, plaintext);

        soliton_buf_free(&mut pt_out);
        soliton_buf_free(&mut blob_out);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn storage_decrypt_wrong_aad_returns_aead_failed() {
    // Decrypting with wrong channel_id must fail authentication.
    unsafe {
        let mut kr = make_keyring();
        let plaintext = b"data";
        let ch = CString::new("channel-right").unwrap();
        let ch_wrong = CString::new("channel-wrong").unwrap();
        let seg = CString::new("seg").unwrap();

        let mut blob_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_storage_encrypt(
            kr,
            plaintext.as_ptr(),
            plaintext.len(),
            ch.as_ptr(),
            seg.as_ptr(),
            0,
            &mut blob_out,
        );
        assert_eq!(rc, OK);

        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_storage_decrypt(
            kr,
            blob_out.ptr,
            blob_out.len,
            ch_wrong.as_ptr(),
            seg.as_ptr(),
            &mut pt_out,
        );
        assert_eq!(rc, E_AEAD);

        soliton_buf_free(&mut blob_out);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn storage_encrypt_empty_plaintext_round_trip() {
    unsafe {
        let mut kr = make_keyring();
        let ch = CString::new("channel-1").unwrap();
        let seg = CString::new("segment-0").unwrap();

        let mut blob_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_storage_encrypt(
            kr,
            ptr::null(),
            0,
            ch.as_ptr(),
            seg.as_ptr(),
            0,
            &mut blob_out,
        );
        assert_eq!(rc, OK);
        assert!(!blob_out.ptr.is_null());

        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_storage_decrypt(
            kr,
            blob_out.ptr,
            blob_out.len,
            ch.as_ptr(),
            seg.as_ptr(),
            &mut pt_out,
        );
        assert_eq!(rc, OK);
        assert_eq!(pt_out.len, 0);

        soliton_buf_free(&mut pt_out);
        soliton_buf_free(&mut blob_out);
        soliton_keyring_free(&mut kr);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// dm_queue_encrypt / dm_queue_decrypt
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn dm_queue_encrypt_null_keyring_returns_null_pointer() {
    let fp = [0xABu8; 32];
    let bid = CString::new("batch-0").unwrap();
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_dm_queue_encrypt(
            ptr::null(),
            ptr::null(),
            0,
            fp.as_ptr(),
            32,
            bid.as_ptr(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn dm_queue_encrypt_null_recipient_fp_returns_null_pointer() {
    unsafe {
        let mut kr = make_keyring();
        let bid = CString::new("batch-0").unwrap();
        let mut out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_encrypt(
            kr,
            ptr::null(),
            0,
            ptr::null(),
            0,
            bid.as_ptr(),
            0,
            &mut out,
        );
        assert_eq!(rc, E_NULL);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn dm_queue_encrypt_null_batch_id_returns_null_pointer() {
    unsafe {
        let mut kr = make_keyring();
        let fp = [0xABu8; 32];
        let mut out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_encrypt(
            kr,
            ptr::null(),
            0,
            fp.as_ptr(),
            32,
            ptr::null(),
            0,
            &mut out,
        );
        assert_eq!(rc, E_NULL);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn dm_queue_encrypt_wrong_fp_len_returns_invalid_length() {
    unsafe {
        let mut kr = make_keyring();
        let fp = [0xABu8; 32];
        let bid = CString::new("batch-0").unwrap();
        let mut out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_encrypt(
            kr,
            ptr::null(),
            0,
            fp.as_ptr(),
            16,
            bid.as_ptr(),
            0,
            &mut out,
        );
        assert_eq!(rc, E_LEN);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn dm_queue_decrypt_wrong_fp_len_returns_invalid_length() {
    unsafe {
        let mut kr = make_keyring();
        let fp = [0xABu8; 32];
        let bid = CString::new("batch-0").unwrap();
        let blob = [0u8; 64];
        let mut out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_decrypt(
            kr,
            blob.as_ptr(),
            blob.len(),
            fp.as_ptr(),
            16,
            bid.as_ptr(),
            &mut out,
        );
        assert_eq!(rc, E_LEN);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn dm_queue_decrypt_null_keyring_returns_null_pointer() {
    let fp = [0xABu8; 32];
    let bid = CString::new("batch-0").unwrap();
    let blob = [0u8; 64];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_dm_queue_decrypt(
            ptr::null(),
            blob.as_ptr(),
            blob.len(),
            fp.as_ptr(),
            32,
            bid.as_ptr(),
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn dm_queue_decrypt_zero_blob_len_returns_invalid_length() {
    unsafe {
        let mut kr = make_keyring();
        let fp = [0xABu8; 32];
        let bid = CString::new("batch-0").unwrap();
        let mut out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_decrypt(
            kr,
            [0u8; 1].as_ptr(),
            0,
            fp.as_ptr(),
            32,
            bid.as_ptr(),
            &mut out,
        );
        assert_eq!(rc, E_LEN);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn dm_queue_encrypt_decrypt_round_trip() {
    unsafe {
        let mut kr = make_keyring();
        let plaintext = b"dm queue payload";
        let fp = [0xABu8; 32];
        let bid = CString::new("batch-42").unwrap();

        let mut blob_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_encrypt(
            kr,
            plaintext.as_ptr(),
            plaintext.len(),
            fp.as_ptr(),
            32,
            bid.as_ptr(),
            0,
            &mut blob_out,
        );
        assert_eq!(rc, OK);
        assert!(!blob_out.ptr.is_null());

        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_decrypt(
            kr,
            blob_out.ptr,
            blob_out.len,
            fp.as_ptr(),
            32,
            bid.as_ptr(),
            &mut pt_out,
        );
        assert_eq!(rc, OK);
        let pt = std::slice::from_raw_parts(pt_out.ptr, pt_out.len);
        assert_eq!(pt, plaintext);

        soliton_buf_free(&mut pt_out);
        soliton_buf_free(&mut blob_out);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn dm_queue_decrypt_wrong_fp_returns_aead_failed() {
    unsafe {
        let mut kr = make_keyring();
        let plaintext = b"data";
        let fp = [0xABu8; 32];
        let fp_wrong = [0xCDu8; 32];
        let bid = CString::new("batch-0").unwrap();

        let mut blob_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_encrypt(
            kr,
            plaintext.as_ptr(),
            plaintext.len(),
            fp.as_ptr(),
            32,
            bid.as_ptr(),
            0,
            &mut blob_out,
        );
        assert_eq!(rc, OK);

        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_decrypt(
            kr,
            blob_out.ptr,
            blob_out.len,
            fp_wrong.as_ptr(),
            32,
            bid.as_ptr(),
            &mut pt_out,
        );
        assert_eq!(rc, E_AEAD);

        soliton_buf_free(&mut blob_out);
        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn dm_queue_encrypt_empty_plaintext_round_trip() {
    unsafe {
        let mut kr = make_keyring();
        let fp = [0xABu8; 32];
        let bid = CString::new("batch-0").unwrap();

        let mut blob_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_encrypt(
            kr,
            ptr::null(),
            0,
            fp.as_ptr(),
            32,
            bid.as_ptr(),
            0,
            &mut blob_out,
        );
        assert_eq!(rc, OK);
        assert!(!blob_out.ptr.is_null());

        let mut pt_out = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_dm_queue_decrypt(
            kr,
            blob_out.ptr,
            blob_out.len,
            fp.as_ptr(),
            32,
            bid.as_ptr(),
            &mut pt_out,
        );
        assert_eq!(rc, OK);
        assert_eq!(pt_out.len, 0);

        soliton_buf_free(&mut pt_out);
        soliton_buf_free(&mut blob_out);
        soliton_keyring_free(&mut kr);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// kex_sign_prekey / kex_verify_bundle / kex_initiate / kex_receive — error paths
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn kex_sign_prekey_null_sk_returns_null_pointer() {
    let spk = [0u8; XPKZ];
    let mut sig_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_kex_sign_prekey(ptr::null(), SK, spk.as_ptr(), XPKZ, &mut sig_out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_sign_prekey_zero_sk_len_returns_invalid_length() {
    let sk = [0u8; SK];
    let spk = [0u8; XPKZ];
    let mut nonzero = 0xABu8;
    let mut sig = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let rc = unsafe { soliton_kex_sign_prekey(sk.as_ptr(), 0, spk.as_ptr(), XPKZ, &mut sig) };
    assert_eq!(rc, E_LEN);
    assert!(sig.ptr.is_null());
}

#[test]
fn kex_sign_prekey_null_spk_pub_nonzero_len_returns_null_pointer() {
    // spk_pub is always null-checked (not co-presence); nonzero len still triggers E_NULL.
    let sk = [0u8; SK];
    let mut sig_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_kex_sign_prekey(sk.as_ptr(), SK, ptr::null(), XPKZ, &mut sig_out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_verify_bundle_null_pk_returns_null_pointer() {
    let pk = [0u8; PK];
    let spk = [0u8; XPKZ];
    let sig = [0u8; HSIG];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let rc = unsafe {
        soliton_kex_verify_bundle(
            ptr::null(),
            PK,
            pk.as_ptr(),
            PK,
            spk.as_ptr(),
            XPKZ,
            sig.as_ptr(),
            HSIG,
            cv.as_ptr(),
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_verify_bundle_zero_len_returns_invalid_length() {
    let pk = [0u8; PK];
    let spk = [0u8; XPKZ];
    let sig = [0u8; HSIG];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let rc = unsafe {
        soliton_kex_verify_bundle(
            pk.as_ptr(),
            0,
            pk.as_ptr(),
            PK,
            spk.as_ptr(),
            XPKZ,
            sig.as_ptr(),
            HSIG,
            cv.as_ptr(),
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn kex_verify_bundle_null_known_ik_pk_returns_null_pointer() {
    let pk = [0u8; PK];
    let spk = [0u8; XPKZ];
    let sig = [0u8; HSIG];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let rc = unsafe {
        soliton_kex_verify_bundle(
            pk.as_ptr(),
            PK,
            ptr::null(),
            PK,
            spk.as_ptr(),
            XPKZ,
            sig.as_ptr(),
            HSIG,
            cv.as_ptr(),
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_initiate_null_alice_pk_returns_null_pointer() {
    let pk = [0u8; PK];
    let sk = [0u8; SK];
    let spk = [0u8; XPKZ];
    let sig = [0u8; HSIG];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let mut out_storage = MaybeUninit::<SolitonInitiatedSession>::uninit();
    let out = out_storage.as_mut_ptr();
    let rc = unsafe {
        soliton_kex_initiate(
            ptr::null(),
            PK,
            sk.as_ptr(),
            SK,
            pk.as_ptr(),
            PK,
            spk.as_ptr(),
            XPKZ,
            1,
            sig.as_ptr(),
            HSIG,
            ptr::null(),
            0,
            0,
            cv.as_ptr(),
            out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_receive_null_bob_pk_returns_null_pointer() {
    let pk = [0u8; PK];
    let _sk = [0u8; SK]; // declared for symmetry; null check fires before it's needed
    let spk_sk = [0u8; XSKZ];
    let sig = [0u8; HSIG];
    let ek = [0u8; XPKZ];
    let ct = [0u8; XCTZ];
    let fp = [0u8; 32];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let wire = SolitonSessionInitWire {
        sender_sig: sig.as_ptr(),
        sender_sig_len: HSIG,
        sender_ik_fingerprint: fp.as_ptr(),
        sender_ik_fingerprint_len: 32,
        recipient_ik_fingerprint: fp.as_ptr(),
        recipient_ik_fingerprint_len: 32,
        sender_ek: ek.as_ptr(),
        sender_ek_len: XPKZ,
        ct_ik: ct.as_ptr(),
        ct_ik_len: XCTZ,
        ct_spk: ct.as_ptr(),
        ct_spk_len: XCTZ,
        spk_id: 1,
        ct_opk: ptr::null(),
        ct_opk_len: 0,
        opk_id: 0,
        crypto_version: cv.as_ptr(),
    };
    let decap_keys = SolitonSessionDecapKeys {
        spk_sk: spk_sk.as_ptr(),
        spk_sk_len: XSKZ,
        opk_sk: ptr::null(),
        opk_sk_len: 0,
    };
    let mut out = SolitonReceivedSession {
        root_key: [0u8; 32],
        chain_key: [0u8; 32],
        peer_ek: SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        },
    };
    let rc = unsafe {
        soliton_kex_receive(
            ptr::null(),
            PK,
            pk.as_ptr(),
            SK,
            pk.as_ptr(),
            PK,
            &wire,
            &decap_keys,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_received_session_free_null_is_noop() {
    unsafe {
        soliton_kex_received_session_free(ptr::null_mut());
    }
}

#[test]
fn kex_initiated_session_free_null_is_noop() {
    unsafe {
        soliton_kex_initiated_session_free(ptr::null_mut());
    }
}

#[test]
fn kex_receive_null_sender_sig_returns_null_pointer() {
    let pk = [0u8; PK];
    let spk_sk = [0u8; XSKZ];
    let ek = [0u8; XPKZ];
    let ct = [0u8; XCTZ];
    let fp = [0u8; 32];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let wire = SolitonSessionInitWire {
        sender_sig: ptr::null(), // null — triggers NullPointer
        sender_sig_len: HSIG,
        sender_ik_fingerprint: fp.as_ptr(),
        sender_ik_fingerprint_len: 32,
        recipient_ik_fingerprint: fp.as_ptr(),
        recipient_ik_fingerprint_len: 32,
        sender_ek: ek.as_ptr(),
        sender_ek_len: XPKZ,
        ct_ik: ct.as_ptr(),
        ct_ik_len: XCTZ,
        ct_spk: ct.as_ptr(),
        ct_spk_len: XCTZ,
        spk_id: 1,
        ct_opk: ptr::null(),
        ct_opk_len: 0,
        opk_id: 0,
        crypto_version: cv.as_ptr(),
    };
    let decap_keys = SolitonSessionDecapKeys {
        spk_sk: spk_sk.as_ptr(),
        spk_sk_len: XSKZ,
        opk_sk: ptr::null(),
        opk_sk_len: 0,
    };
    let mut out = SolitonReceivedSession {
        root_key: [0u8; 32],
        chain_key: [0u8; 32],
        peer_ek: SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        },
    };
    let rc = unsafe {
        soliton_kex_receive(
            pk.as_ptr(),
            PK,
            pk.as_ptr(),
            PK,
            pk.as_ptr(),
            PK,
            &wire,
            &decap_keys,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_receive_null_crypto_version_returns_null_pointer() {
    let pk = [0u8; PK];
    let spk_sk = [0u8; XSKZ];
    let sig = [0u8; HSIG];
    let ek = [0u8; XPKZ];
    let ct = [0u8; XCTZ];
    let fp = [0u8; 32];
    let wire = SolitonSessionInitWire {
        sender_sig: sig.as_ptr(),
        sender_sig_len: HSIG,
        sender_ik_fingerprint: fp.as_ptr(),
        sender_ik_fingerprint_len: 32,
        recipient_ik_fingerprint: fp.as_ptr(),
        recipient_ik_fingerprint_len: 32,
        sender_ek: ek.as_ptr(),
        sender_ek_len: XPKZ,
        ct_ik: ct.as_ptr(),
        ct_ik_len: XCTZ,
        ct_spk: ct.as_ptr(),
        ct_spk_len: XCTZ,
        spk_id: 1,
        ct_opk: ptr::null(),
        ct_opk_len: 0,
        opk_id: 0,
        crypto_version: ptr::null(), // null — triggers NullPointer
    };
    let decap_keys = SolitonSessionDecapKeys {
        spk_sk: spk_sk.as_ptr(),
        spk_sk_len: XSKZ,
        opk_sk: ptr::null(),
        opk_sk_len: 0,
    };
    let mut out = SolitonReceivedSession {
        root_key: [0u8; 32],
        chain_key: [0u8; 32],
        peer_ek: SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        },
    };
    let rc = unsafe {
        soliton_kex_receive(
            pk.as_ptr(),
            PK,
            pk.as_ptr(),
            PK,
            pk.as_ptr(),
            PK,
            &wire,
            &decap_keys,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

// ═══════════════════════════════════════════════════════════════════════════
// kex_build_first_message_aad / kex_encode_session_init
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn kex_build_aad_null_sender_fp_returns_null_pointer() {
    let fp = [0u8; 32];
    let encoded = b"data";
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_build_first_message_aad(
            ptr::null(),
            32,
            fp.as_ptr(),
            32,
            encoded.as_ptr(),
            encoded.len(),
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_build_aad_null_recipient_fp_returns_null_pointer() {
    let fp = [0u8; 32];
    let encoded = b"data";
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_build_first_message_aad(
            fp.as_ptr(),
            32,
            ptr::null(),
            32,
            encoded.as_ptr(),
            encoded.len(),
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_build_aad_null_session_init_encoded_returns_null_pointer() {
    let fp = [0u8; 32];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_build_first_message_aad(
            fp.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            ptr::null(),
            1,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_build_aad_null_aad_out_returns_null_pointer() {
    let fp = [0u8; 32];
    let encoded = b"data";
    let rc = unsafe {
        soliton_kex_build_first_message_aad(
            fp.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            encoded.as_ptr(),
            encoded.len(),
            ptr::null_mut(),
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_build_aad_zero_encoded_len_returns_invalid_length() {
    let fp = [0u8; 32];
    let encoded = b"data";
    let mut nonzero = 0xABu8;
    let mut out = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let rc = unsafe {
        soliton_kex_build_first_message_aad(
            fp.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            encoded.as_ptr(),
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
    assert!(out.ptr.is_null());
}

#[test]
fn kex_build_aad_oversized_encoded_returns_invalid_length() {
    // encoded_len > 8192 → InvalidLength.
    let fp = [0u8; 32];
    let encoded = vec![0u8; 8193];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_build_first_message_aad(
            fp.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            encoded.as_ptr(),
            encoded.len(),
            &mut out,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn kex_build_aad_valid_inputs_returns_aad() {
    let fp_a = [0x01u8; 32];
    let fp_b = [0x02u8; 32];
    let encoded = b"minimal_encoded_session_init";
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_build_first_message_aad(
            fp_a.as_ptr(),
            32,
            fp_b.as_ptr(),
            32,
            encoded.as_ptr(),
            encoded.len(),
            &mut out,
        )
    };
    assert_eq!(rc, OK);
    assert!(!out.ptr.is_null());
    unsafe { soliton_buf_free(&mut out) };
}

#[test]
fn kex_encode_session_init_null_crypto_version_returns_null_pointer() {
    let fp = [0u8; 32];
    let ek = [0u8; XPKZ];
    let ct = [0u8; XCTZ];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_encode_session_init(
            ptr::null(),
            fp.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            ek.as_ptr(),
            XPKZ,
            ct.as_ptr(),
            XCTZ,
            ct.as_ptr(),
            XCTZ,
            1,
            ptr::null(),
            0,
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_encode_session_init_copresence_ct_opk_null_nonzero_len() {
    // ct_opk=null but ct_opk_len=5 → NullPointer.
    let fp = [0u8; 32];
    let ek = [0u8; XPKZ];
    let ct = [0u8; XCTZ];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_encode_session_init(
            cv.as_ptr(),
            fp.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            ek.as_ptr(),
            XPKZ,
            ct.as_ptr(),
            XCTZ,
            ct.as_ptr(),
            XCTZ,
            1,
            ptr::null(),
            5,
            0,
            &mut out,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_encode_session_init_nonzero_opk_id_without_ct_opk_returns_invalid_data() {
    // ct_opk=null but opk_id=5 → InvalidData.
    let fp = [0u8; 32];
    let ek = [0u8; XPKZ];
    let ct = [0u8; XCTZ];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_encode_session_init(
            cv.as_ptr(),
            fp.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            ek.as_ptr(),
            XPKZ,
            ct.as_ptr(),
            XCTZ,
            ct.as_ptr(),
            XCTZ,
            1,
            ptr::null(),
            0,
            5,
            &mut out,
        )
    };
    assert_eq!(rc, E_DATA);
}

#[test]
fn kex_encode_session_init_zeroed_keys_succeeds() {
    // With zeroed X-Wing keys (length-only validation), encoding must succeed.
    let fp = [0u8; 32];
    let ek = [0u8; XPKZ];
    let ct = [0u8; XCTZ];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        soliton_kex_encode_session_init(
            cv.as_ptr(),
            fp.as_ptr(),
            32,
            fp.as_ptr(),
            32,
            ek.as_ptr(),
            XPKZ,
            ct.as_ptr(),
            XCTZ,
            ct.as_ptr(),
            XCTZ,
            1,
            ptr::null(),
            0,
            0,
            &mut out,
        )
    };
    assert_eq!(rc, OK);
    assert!(!out.ptr.is_null());
    unsafe { soliton_buf_free(&mut out) };
}

// ── kex_decode_session_init ──────────────────────────────────────────────────

/// Produce valid encoded SessionInit bytes via encode, for use in decode tests.
///
/// Uses zeroed key bytes — length-only validation, no keygen, MIRI-safe.
fn make_encoded_session_init(with_opk: bool) -> Vec<u8> {
    let fp = [0x01u8; 32];
    let rfp = [0x02u8; 32];
    let ek = [0x03u8; XPKZ];
    let ct = [0x04u8; XCTZ];
    let ct2 = [0x05u8; XCTZ];
    let ct_opk = [0x06u8; XCTZ];
    let cv = CString::new("lo-crypto-v1").unwrap();
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe {
        if with_opk {
            soliton_kex_encode_session_init(
                cv.as_ptr(),
                fp.as_ptr(),
                32,
                rfp.as_ptr(),
                32,
                ek.as_ptr(),
                XPKZ,
                ct.as_ptr(),
                XCTZ,
                ct2.as_ptr(),
                XCTZ,
                42,
                ct_opk.as_ptr(),
                XCTZ,
                99,
                &mut out,
            )
        } else {
            soliton_kex_encode_session_init(
                cv.as_ptr(),
                fp.as_ptr(),
                32,
                rfp.as_ptr(),
                32,
                ek.as_ptr(),
                XPKZ,
                ct.as_ptr(),
                XCTZ,
                ct2.as_ptr(),
                XCTZ,
                42,
                ptr::null(),
                0,
                0,
                &mut out,
            )
        }
    };
    assert_eq!(rc, OK, "encode must succeed for decode tests");
    let bytes = unsafe { std::slice::from_raw_parts(out.ptr, out.len) }.to_vec();
    unsafe { soliton_buf_free(&mut out) };
    bytes
}

#[test]
fn kex_decode_session_init_null_encoded_returns_null_pointer() {
    let mut out: SolitonDecodedSessionInit = unsafe { MaybeUninit::zeroed().assume_init() };
    let rc = unsafe { soliton_kex_decode_session_init(ptr::null(), 10, &mut out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_decode_session_init_null_out_returns_null_pointer() {
    let encoded = [0u8; 10];
    let rc = unsafe {
        soliton_kex_decode_session_init(encoded.as_ptr(), encoded.len(), ptr::null_mut())
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn kex_decode_session_init_zero_len_returns_invalid_length() {
    let encoded = [0u8; 10];
    let mut out: SolitonDecodedSessionInit = unsafe { MaybeUninit::zeroed().assume_init() };
    let rc = unsafe { soliton_kex_decode_session_init(encoded.as_ptr(), 0, &mut out) };
    assert_eq!(rc, E_LEN);
}

#[test]
fn kex_decode_session_init_truncated_returns_invalid_data() {
    let encoded = make_encoded_session_init(false);
    // Truncate by 1 byte — parser can't reach the end.
    let truncated = &encoded[..encoded.len() - 1];
    let mut out: SolitonDecodedSessionInit = unsafe { MaybeUninit::zeroed().assume_init() };
    let rc =
        unsafe { soliton_kex_decode_session_init(truncated.as_ptr(), truncated.len(), &mut out) };
    assert_eq!(rc, E_DATA);
    // Output must be zeroed on error.
    assert!(out.crypto_version.ptr.is_null());
}

#[test]
fn kex_decode_session_init_trailing_byte_returns_invalid_data() {
    let mut encoded = make_encoded_session_init(false);
    encoded.push(0x00);
    let mut out: SolitonDecodedSessionInit = unsafe { MaybeUninit::zeroed().assume_init() };
    let rc = unsafe { soliton_kex_decode_session_init(encoded.as_ptr(), encoded.len(), &mut out) };
    assert_eq!(rc, E_DATA);
    assert!(out.crypto_version.ptr.is_null());
}

#[test]
fn kex_decode_session_init_roundtrip_without_opk() {
    let encoded = make_encoded_session_init(false);
    let mut out: SolitonDecodedSessionInit = unsafe { MaybeUninit::zeroed().assume_init() };
    let rc = unsafe { soliton_kex_decode_session_init(encoded.as_ptr(), encoded.len(), &mut out) };
    assert_eq!(rc, OK);
    // crypto_version must be "lo-crypto-v1" with null terminator
    assert!(!out.crypto_version.ptr.is_null());
    let cv_bytes =
        unsafe { std::slice::from_raw_parts(out.crypto_version.ptr, out.crypto_version.len) };
    assert_eq!(cv_bytes, b"lo-crypto-v1\0");
    // Fixed fields
    assert_eq!(out.sender_fp, [0x01u8; 32]);
    assert_eq!(out.recipient_fp, [0x02u8; 32]);
    assert_eq!(out.sender_ek, [0x03u8; XPKZ]);
    assert_eq!(out.ct_ik, [0x04u8; XCTZ]);
    assert_eq!(out.ct_spk, [0x05u8; XCTZ]);
    assert_eq!(out.spk_id, 42);
    assert_eq!(out.has_opk, 0x00);
    // ct_opk / opk_id not valid — no assertion on their values
    unsafe { soliton_decoded_session_init_free(&mut out) };
}

#[test]
fn kex_decode_session_init_roundtrip_with_opk() {
    let encoded = make_encoded_session_init(true);
    let mut out: SolitonDecodedSessionInit = unsafe { MaybeUninit::zeroed().assume_init() };
    let rc = unsafe { soliton_kex_decode_session_init(encoded.as_ptr(), encoded.len(), &mut out) };
    assert_eq!(rc, OK);
    // crypto_version must be "lo-crypto-v1" with null terminator
    assert!(!out.crypto_version.ptr.is_null());
    let cv_bytes =
        unsafe { std::slice::from_raw_parts(out.crypto_version.ptr, out.crypto_version.len) };
    assert_eq!(cv_bytes, b"lo-crypto-v1\0");
    assert_eq!(out.sender_fp, [0x01u8; 32]);
    assert_eq!(out.recipient_fp, [0x02u8; 32]);
    assert_eq!(out.sender_ek, [0x03u8; XPKZ]);
    assert_eq!(out.ct_ik, [0x04u8; XCTZ]);
    assert_eq!(out.ct_spk, [0x05u8; XCTZ]);
    assert_eq!(out.spk_id, 42);
    assert_eq!(out.has_opk, 0x01);
    assert_eq!(out.ct_opk, [0x06u8; XCTZ]);
    assert_eq!(out.opk_id, 99);
    unsafe { soliton_decoded_session_init_free(&mut out) };
}

// ═══════════════════════════════════════════════════════════════════════════
// verification_phrase
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn verification_phrase_null_pk_a_returns_null_pointer() {
    let pk = [0u8; PK];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_verification_phrase(ptr::null(), PK, pk.as_ptr(), PK, &mut out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn verification_phrase_null_pk_b_returns_null_pointer() {
    let pk = [0u8; PK];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_verification_phrase(pk.as_ptr(), PK, ptr::null(), PK, &mut out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn verification_phrase_wrong_pk_len_returns_invalid_length() {
    let pk = [0u8; PK];
    let mut nonzero = 0xABu8;
    let mut out = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let rc = unsafe { soliton_verification_phrase(pk.as_ptr(), PK - 1, pk.as_ptr(), PK, &mut out) };
    assert_eq!(rc, E_LEN);
    assert!(out.ptr.is_null());
}

#[test]
fn verification_phrase_zeroed_pks_produces_phrase() {
    // from_bytes is length-only — no keygen needed.
    let pk_a = [0x11u8; PK];
    let pk_b = [0x22u8; PK];
    let mut out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_verification_phrase(pk_a.as_ptr(), PK, pk_b.as_ptr(), PK, &mut out) };
    assert_eq!(rc, OK);
    assert!(!out.ptr.is_null());
    assert!(out.len > 0);
    // Phrase is null-terminated; the null byte is at index len-1.
    let phrase_bytes = unsafe { std::slice::from_raw_parts(out.ptr, out.len) };
    assert_eq!(
        *phrase_bytes.last().unwrap(),
        0,
        "phrase must be null-terminated"
    );
    unsafe { soliton_buf_free(&mut out) };
}

#[test]
fn verification_phrase_deterministic() {
    let pk_a = [0x11u8; PK];
    let pk_b = [0x22u8; PK];
    unsafe {
        let mut out1 = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut out2 = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_verification_phrase(pk_a.as_ptr(), PK, pk_b.as_ptr(), PK, &mut out1);
        assert_eq!(rc, OK);
        let rc = soliton_verification_phrase(pk_a.as_ptr(), PK, pk_b.as_ptr(), PK, &mut out2);
        assert_eq!(rc, OK);
        let p1 = std::slice::from_raw_parts(out1.ptr, out1.len);
        let p2 = std::slice::from_raw_parts(out2.ptr, out2.len);
        assert_eq!(p1, p2);
        soliton_buf_free(&mut out1);
        soliton_buf_free(&mut out2);
    }
}

#[test]
fn verification_phrase_commutative() {
    // verification_phrase sorts keys before hashing, so phrase(A, B) == phrase(B, A).
    let pk_a = [0x11u8; PK];
    let pk_b = [0x22u8; PK];
    unsafe {
        let mut out_ab = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut out_ba = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = soliton_verification_phrase(pk_a.as_ptr(), PK, pk_b.as_ptr(), PK, &mut out_ab);
        assert_eq!(rc, OK);
        let rc = soliton_verification_phrase(pk_b.as_ptr(), PK, pk_a.as_ptr(), PK, &mut out_ba);
        assert_eq!(rc, OK);
        let p_ab = std::slice::from_raw_parts(out_ab.ptr, out_ab.len);
        let p_ba = std::slice::from_raw_parts(out_ba.ptr, out_ba.len);
        assert_eq!(p_ab, p_ba, "verification_phrase must be commutative");
        soliton_buf_free(&mut out_ab);
        soliton_buf_free(&mut out_ba);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// xwing_keygen / encapsulate / decapsulate — error paths only
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn xwing_keygen_null_pk_out_returns_null_pointer() {
    let mut sk_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_xwing_keygen(ptr::null_mut(), &mut sk_out) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn xwing_keygen_null_sk_out_zeroes_pk_out() {
    let mut pk_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let rc = unsafe { soliton_xwing_keygen(&mut pk_out, ptr::null_mut()) };
    assert_eq!(rc, E_NULL);
    // Null check fires before zeroing for xwing_keygen — only the return code matters here.
}

#[test]
fn xwing_encapsulate_null_pk_returns_null_pointer() {
    let mut ct_out = SolitonBuf {
        ptr: ptr::null_mut(),
        len: 0,
    };
    let mut ss = [0u8; 32];
    let rc =
        unsafe { soliton_xwing_encapsulate(ptr::null(), XPKZ, &mut ct_out, ss.as_mut_ptr(), 32) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn xwing_encapsulate_zero_pk_len_zeroes_outputs() {
    let pk = [0u8; XPKZ];
    let mut nonzero = 0xABu8;
    let mut ct = SolitonBuf {
        ptr: &mut nonzero as *mut u8,
        len: 42,
    };
    let mut ss = fill_nonzero::<32>();
    let rc = unsafe { soliton_xwing_encapsulate(pk.as_ptr(), 0, &mut ct, ss.as_mut_ptr(), 32) };
    assert_eq!(rc, E_LEN);
    assert!(ct.ptr.is_null());
    assert!(is_zeroed(&ss), "ss must be zeroed on error");
}

#[test]
fn xwing_decapsulate_null_sk_returns_null_pointer() {
    let ct = [0u8; XCTZ];
    let mut ss = [0u8; 32];
    let rc = unsafe {
        soliton_xwing_decapsulate(ptr::null(), XSKZ, ct.as_ptr(), XCTZ, ss.as_mut_ptr(), 32)
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn xwing_decapsulate_zero_sk_len_zeroes_ss() {
    let sk = [0u8; XSKZ];
    let ct = [0u8; XCTZ];
    let mut ss = fill_nonzero::<32>();
    let rc = unsafe {
        soliton_xwing_decapsulate(sk.as_ptr(), 0, ct.as_ptr(), XCTZ, ss.as_mut_ptr(), 32)
    };
    assert_eq!(rc, E_LEN);
    assert!(is_zeroed(&ss), "ss must be zeroed on error");
}

#[test]
fn xwing_decapsulate_wrong_ct_len_zeroes_ss() {
    let sk = [0u8; XSKZ];
    let ct = [0u8; XCTZ];
    let mut ss = fill_nonzero::<32>();
    // ct_len != SOLITON_XWING_CT_SIZE → InvalidLength; ss must be zeroed.
    let rc = unsafe {
        soliton_xwing_decapsulate(
            sk.as_ptr(),
            XSKZ,
            ct.as_ptr(),
            XCTZ - 1,
            ss.as_mut_ptr(),
            32,
        )
    };
    assert_eq!(rc, E_LEN);
    assert!(is_zeroed(&ss), "ss must be zeroed on wrong-length ct");
}

// ═══════════════════════════════════════════════════════════════════════════
// Concurrent access detection — excluded from MIRI (multi-threaded)
// ═══════════════════════════════════════════════════════════════════════════

#[test]
fn ratchet_concurrent_access_detected() {
    use std::sync::{Arc, Barrier};
    use std::thread;

    unsafe {
        let ratchet = make_alice();
        let ptr_val = ratchet as usize;
        let barrier = Arc::new(Barrier::new(2));
        let plaintext = [0u8; 64];

        let b = barrier.clone();
        let t = thread::spawn(move || {
            b.wait();
            let ptr = ptr_val as *mut SolitonRatchet;
            let mut concurrent_seen = false;
            // Use encrypt (holds the guard for HMAC + AEAD, ~microseconds)
            // instead of reset (nanoseconds) to widen the collision window.
            for _ in 0..1_000 {
                let mut msg = std::mem::zeroed::<SolitonEncryptedMessage>();
                let rc =
                    soliton_ratchet_encrypt(ptr, plaintext.as_ptr(), plaintext.len(), &mut msg);
                if rc == E_CONCURRENT {
                    concurrent_seen = true;
                }
                if rc == OK {
                    soliton_encrypted_message_free(&mut msg);
                }
            }
            concurrent_seen
        });

        barrier.wait();
        let mut concurrent_seen = false;
        for _ in 0..1_000 {
            let mut msg = std::mem::zeroed::<SolitonEncryptedMessage>();
            let rc =
                soliton_ratchet_encrypt(ratchet, plaintext.as_ptr(), plaintext.len(), &mut msg);
            if rc == E_CONCURRENT {
                concurrent_seen = true;
            }
            if rc == OK {
                soliton_encrypted_message_free(&mut msg);
            }
        }

        let thread_saw = t.join().unwrap();
        assert!(
            concurrent_seen || thread_saw,
            "expected at least one ConcurrentAccess across 2000 encrypt calls"
        );

        let mut ratchet = ratchet;
        soliton_ratchet_free(&mut ratchet);
    }
}

#[test]
fn keyring_concurrent_access_detected() {
    use std::sync::{Arc, Barrier};
    use std::thread;

    unsafe {
        let key = [0x42u8; 32];
        let mut kr: *mut SolitonKeyRing = ptr::null_mut();
        soliton_keyring_new(key.as_ptr(), 32, 1, &mut kr);
        assert!(!kr.is_null());

        let ptr_val = kr as usize;
        let barrier = Arc::new(Barrier::new(2));
        let plaintext = [0xAAu8; 256];
        let channel = c"concurrent-ch";
        let segment = c"concurrent-seg";

        let b = barrier.clone();
        let t = thread::spawn(move || {
            b.wait();
            let ptr = ptr_val as *const SolitonKeyRing;
            let mut concurrent_seen = false;
            // Use storage_encrypt (holds the guard for AEAD, ~microseconds)
            // instead of remove_key (nanoseconds) to widen the collision window.
            for _ in 0..1_000 {
                let mut blob = SolitonBuf {
                    ptr: ptr::null_mut(),
                    len: 0,
                };
                let rc = soliton_storage_encrypt(
                    ptr,
                    plaintext.as_ptr(),
                    plaintext.len(),
                    channel.as_ptr(),
                    segment.as_ptr(),
                    0,
                    &mut blob,
                );
                if rc == E_CONCURRENT {
                    concurrent_seen = true;
                }
                if rc == OK && !blob.ptr.is_null() {
                    soliton_buf_free(&mut blob);
                }
            }
            concurrent_seen
        });

        barrier.wait();
        let mut concurrent_seen = false;
        for _ in 0..1_000 {
            let mut blob = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_storage_encrypt(
                kr,
                plaintext.as_ptr(),
                plaintext.len(),
                channel.as_ptr(),
                segment.as_ptr(),
                0,
                &mut blob,
            );
            if rc == E_CONCURRENT {
                concurrent_seen = true;
            }
            if rc == OK && !blob.ptr.is_null() {
                soliton_buf_free(&mut blob);
            }
        }

        let thread_saw = t.join().unwrap();
        assert!(
            concurrent_seen || thread_saw,
            "expected at least one ConcurrentAccess across 2000 encrypt calls"
        );

        soliton_keyring_free(&mut kr);
    }
}

#[test]
fn call_keys_concurrent_access_detected() {
    use std::sync::{Arc, Barrier};
    use std::thread;

    unsafe {
        let mut alice = make_alice();
        let kem_ss = [0xCCu8; 32];
        let call_id = [0xDDu8; 32];
        let mut keys_ptr: *mut SolitonCallKeys = ptr::null_mut();
        let rc = soliton_ratchet_derive_call_keys(
            alice,
            kem_ss.as_ptr(),
            32,
            call_id.as_ptr(),
            16,
            &mut keys_ptr,
        );
        assert_eq!(rc, OK);

        let ptr_val = keys_ptr as usize;
        let barrier = Arc::new(Barrier::new(2));

        let b = barrier.clone();
        let t = thread::spawn(move || {
            b.wait();
            let ptr = ptr_val as *mut SolitonCallKeys;
            let mut concurrent_seen = false;
            for _ in 0..10_000 {
                let rc = soliton_call_keys_advance(ptr);
                assert!(
                    rc == OK || rc == E_CONCURRENT,
                    "expected OK or ConcurrentAccess, got {rc}"
                );
                if rc == E_CONCURRENT {
                    concurrent_seen = true;
                }
                thread::yield_now();
            }
            concurrent_seen
        });

        barrier.wait();
        let mut concurrent_seen = false;
        for _ in 0..10_000 {
            let rc = soliton_call_keys_advance(keys_ptr);
            assert!(
                rc == OK || rc == E_CONCURRENT,
                "expected OK, ConcurrentAccess, or ChainExhausted, got {rc}"
            );
            if rc == E_CONCURRENT {
                concurrent_seen = true;
            }
            thread::yield_now();
        }

        let thread_saw = t.join().unwrap();
        assert!(
            concurrent_seen || thread_saw,
            "expected at least one ConcurrentAccess across 20000 calls"
        );

        soliton_call_keys_free(&mut keys_ptr);
        soliton_ratchet_free(&mut alice);
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// PQ round-trips — excluded from MIRI via nextest profile filter
// ═══════════════════════════════════════════════════════════════════════════
pub mod pq {
    use super::*;

    #[test]
    fn xwing_keygen_encap_decap_round_trip() {
        unsafe {
            let mut pk_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut sk_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_xwing_keygen(&mut pk_out, &mut sk_out);
            assert_eq!(rc, OK);
            assert_eq!(pk_out.len, XPKZ);
            assert_eq!(sk_out.len, XSKZ);

            let mut ct_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut ss_enc = [0u8; 32];
            let rc = soliton_xwing_encapsulate(
                pk_out.ptr,
                pk_out.len,
                &mut ct_out,
                ss_enc.as_mut_ptr(),
                32,
            );
            assert_eq!(rc, OK);
            assert_eq!(ct_out.len, XCTZ);

            let mut ss_dec = [0u8; 32];
            let rc = soliton_xwing_decapsulate(
                sk_out.ptr,
                sk_out.len,
                ct_out.ptr,
                ct_out.len,
                ss_dec.as_mut_ptr(),
                32,
            );
            assert_eq!(rc, OK);
            assert_eq!(ss_enc, ss_dec, "shared secrets must match");
            assert!(!is_zeroed(&ss_enc));

            soliton_buf_free(&mut ct_out);
            soliton_buf_free(&mut sk_out);
            soliton_buf_free(&mut pk_out);
        }
    }

    #[test]
    fn identity_generate_sign_verify_round_trip() {
        unsafe {
            let mut pk_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut sk_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut fp_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_identity_generate(&mut pk_out, &mut sk_out, &mut fp_out);
            assert_eq!(rc, OK);
            assert_eq!(pk_out.len, PK);
            assert_eq!(sk_out.len, SK);
            assert!(fp_out.len > 0); // hex string + null terminator

            let msg = b"test message";
            let mut sig_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_identity_sign(
                sk_out.ptr,
                sk_out.len,
                msg.as_ptr(),
                msg.len(),
                &mut sig_out,
            );
            assert_eq!(rc, OK);
            assert_eq!(sig_out.len, HSIG);

            let rc = soliton_identity_verify(
                pk_out.ptr,
                pk_out.len,
                msg.as_ptr(),
                msg.len(),
                sig_out.ptr,
                sig_out.len,
            );
            assert_eq!(rc, OK);

            // Wrong message must fail.
            let bad_msg = b"wrong message";
            let rc = soliton_identity_verify(
                pk_out.ptr,
                pk_out.len,
                bad_msg.as_ptr(),
                bad_msg.len(),
                sig_out.ptr,
                sig_out.len,
            );
            assert_eq!(rc, E_VER);

            soliton_buf_free(&mut sig_out);
            soliton_buf_free(&mut fp_out);
            soliton_buf_free(&mut sk_out);
            soliton_buf_free(&mut pk_out);
        }
    }

    #[test]
    fn identity_sign_verify_empty_message() {
        unsafe {
            let mut pk_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut sk_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut fp_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_identity_generate(&mut pk_out, &mut sk_out, &mut fp_out);

            let mut sig_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            // Sign empty message (null + len=0 is allowed).
            let rc = soliton_identity_sign(sk_out.ptr, sk_out.len, ptr::null(), 0, &mut sig_out);
            assert_eq!(rc, OK);
            let rc = soliton_identity_verify(
                pk_out.ptr,
                pk_out.len,
                ptr::null(),
                0,
                sig_out.ptr,
                sig_out.len,
            );
            assert_eq!(rc, OK);

            soliton_buf_free(&mut sig_out);
            soliton_buf_free(&mut fp_out);
            soliton_buf_free(&mut sk_out);
            soliton_buf_free(&mut pk_out);
        }
    }

    #[test]
    fn identity_encapsulate_decapsulate_round_trip() {
        unsafe {
            let mut pk_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut sk_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut fp_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_identity_generate(&mut pk_out, &mut sk_out, &mut fp_out);

            let mut ct_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut ss_enc = [0u8; 32];
            let rc = soliton_identity_encapsulate(
                pk_out.ptr,
                pk_out.len,
                &mut ct_out,
                ss_enc.as_mut_ptr(),
                32,
            );
            assert_eq!(rc, OK);

            let mut ss_dec = [0u8; 32];
            let rc = soliton_identity_decapsulate(
                sk_out.ptr,
                sk_out.len,
                ct_out.ptr,
                ct_out.len,
                ss_dec.as_mut_ptr(),
                32,
            );
            assert_eq!(rc, OK);
            assert_eq!(ss_enc, ss_dec);
            assert!(!is_zeroed(&ss_enc));

            soliton_buf_free(&mut ct_out);
            soliton_buf_free(&mut fp_out);
            soliton_buf_free(&mut sk_out);
            soliton_buf_free(&mut pk_out);
        }
    }

    #[test]
    fn auth_challenge_respond_verify_round_trip() {
        unsafe {
            // Generate client keypair.
            let mut client_pk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut client_sk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut fp = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_identity_generate(&mut client_pk, &mut client_sk, &mut fp);

            // Server: challenge.
            let mut ct_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut token = [0u8; 32];
            let rc = soliton_auth_challenge(
                client_pk.ptr,
                client_pk.len,
                &mut ct_out,
                token.as_mut_ptr(),
                32,
            );
            assert_eq!(rc, OK);

            // Client: respond.
            let mut proof = [0u8; 32];
            let rc = soliton_auth_respond(
                client_sk.ptr,
                client_sk.len,
                ct_out.ptr,
                ct_out.len,
                proof.as_mut_ptr(),
                32,
            );
            assert_eq!(rc, OK);

            // Server: verify.
            let rc = soliton_auth_verify(token.as_ptr(), 32, proof.as_ptr(), 32);
            assert_eq!(rc, OK);

            // Wrong proof must fail.
            let bad_proof = [0u8; 32];
            let rc = soliton_auth_verify(token.as_ptr(), 32, bad_proof.as_ptr(), 32);
            assert_eq!(rc, E_VER);

            soliton_buf_free(&mut ct_out);
            soliton_buf_free(&mut fp);
            soliton_buf_free(&mut client_sk);
            soliton_buf_free(&mut client_pk);
        }
    }

    #[test]
    fn kex_sign_prekey_and_verify_bundle() {
        unsafe {
            // Generate Bob's identity keypair.
            let mut bob_pk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut bob_sk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut bob_fp = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_identity_generate(&mut bob_pk, &mut bob_sk, &mut bob_fp);

            // Generate Bob's SPK (X-Wing keypair).
            let mut spk_pub = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut spk_sk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_xwing_keygen(&mut spk_pub, &mut spk_sk);

            // Bob signs the SPK.
            let mut sig_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_kex_sign_prekey(
                bob_sk.ptr,
                bob_sk.len,
                spk_pub.ptr,
                spk_pub.len,
                &mut sig_out,
            );
            assert_eq!(rc, OK);

            // Verify bundle.
            let cv = CString::new("lo-crypto-v1").unwrap();
            let rc = soliton_kex_verify_bundle(
                bob_pk.ptr,
                bob_pk.len,
                bob_pk.ptr,
                bob_pk.len,
                spk_pub.ptr,
                spk_pub.len,
                sig_out.ptr,
                sig_out.len,
                cv.as_ptr(),
            );
            assert_eq!(rc, OK);

            // Bundle with tampered IK must fail.
            let mut diff_pk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut diff_sk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut diff_fp = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_identity_generate(&mut diff_pk, &mut diff_sk, &mut diff_fp);
            let rc = soliton_kex_verify_bundle(
                bob_pk.ptr,
                bob_pk.len,
                diff_pk.ptr,
                diff_pk.len, // known_ik_pk differs from bundle_ik_pk
                spk_pub.ptr,
                spk_pub.len,
                sig_out.ptr,
                sig_out.len,
                cv.as_ptr(),
            );
            assert_eq!(
                rc, E_BUNDLE,
                "mismatched IK must return BundleVerificationFailed"
            );

            soliton_buf_free(&mut diff_fp);
            soliton_buf_free(&mut diff_sk);
            soliton_buf_free(&mut diff_pk);
            soliton_buf_free(&mut sig_out);
            soliton_buf_free(&mut spk_sk);
            soliton_buf_free(&mut spk_pub);
            soliton_buf_free(&mut bob_fp);
            soliton_buf_free(&mut bob_sk);
            soliton_buf_free(&mut bob_pk);
        }
    }

    #[test]
    fn kex_full_initiate_receive_round_trip() {
        unsafe {
            // Alice and Bob keypairs.
            let (alice_pk, alice_sk) = generate_identity_keypair();
            let (bob_pk, bob_sk) = generate_identity_keypair();

            // Bob's signed pre-key.
            let mut spk_pub = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut spk_sk_buf = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_xwing_keygen(&mut spk_pub, &mut spk_sk_buf);
            let mut spk_sig = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_kex_sign_prekey(
                bob_sk.ptr,
                bob_sk.len,
                spk_pub.ptr,
                spk_pub.len,
                &mut spk_sig,
            );

            let cv = CString::new("lo-crypto-v1").unwrap();

            // Alice initiates.
            let mut session_out = std::mem::zeroed::<SolitonInitiatedSession>();
            let rc = soliton_kex_initiate(
                alice_pk.ptr,
                alice_pk.len,
                alice_sk.ptr,
                alice_sk.len,
                bob_pk.ptr,
                bob_pk.len,
                spk_pub.ptr,
                spk_pub.len,
                1,
                spk_sig.ptr,
                spk_sig.len,
                ptr::null(),
                0,
                0, // no OPK
                cv.as_ptr(),
                &mut session_out,
            );
            assert_eq!(rc, OK, "kex_initiate must succeed");
            assert!(
                !session_out.root_key.iter().all(|&b| b == 0),
                "root key must be non-zero"
            );

            // Bob receives.
            // Reconstruct SessionInit wire fields from Alice's session_out.
            let wire = SolitonSessionInitWire {
                sender_sig: session_out.sender_sig.ptr,
                sender_sig_len: session_out.sender_sig.len,
                sender_ik_fingerprint: session_out.sender_ik_fingerprint.as_ptr(),
                sender_ik_fingerprint_len: 32,
                recipient_ik_fingerprint: session_out.recipient_ik_fingerprint.as_ptr(),
                recipient_ik_fingerprint_len: 32,
                sender_ek: session_out.ek_pk.ptr,
                sender_ek_len: session_out.ek_pk.len,
                ct_ik: session_out.ct_ik.ptr,
                ct_ik_len: session_out.ct_ik.len,
                ct_spk: session_out.ct_spk.ptr,
                ct_spk_len: session_out.ct_spk.len,
                spk_id: session_out.spk_id,
                ct_opk: ptr::null(),
                ct_opk_len: 0,
                opk_id: 0,
                crypto_version: cv.as_ptr(),
            };
            let decap_keys = SolitonSessionDecapKeys {
                spk_sk: spk_sk_buf.ptr,
                spk_sk_len: spk_sk_buf.len,
                opk_sk: ptr::null(),
                opk_sk_len: 0,
            };
            let mut received_out = SolitonReceivedSession {
                root_key: [0u8; 32],
                chain_key: [0u8; 32],
                peer_ek: SolitonBuf {
                    ptr: ptr::null_mut(),
                    len: 0,
                },
            };
            let rc = soliton_kex_receive(
                bob_pk.ptr,
                bob_pk.len,
                bob_sk.ptr,
                bob_sk.len,
                alice_pk.ptr,
                alice_pk.len,
                &wire,
                &decap_keys,
                &mut received_out,
            );
            assert_eq!(rc, OK, "kex_receive must succeed");

            // Both sides must derive the same root key and the same initial chain key.
            assert_eq!(
                session_out.root_key, received_out.root_key,
                "root keys must match"
            );
            assert_ne!(
                received_out.root_key, [0u8; 32],
                "root key must be non-zero"
            );
            // initial_chain_key (Alice's side) feeds ratchet_encrypt_first;
            // chain_key (Bob's side) feeds ratchet_decrypt_first. They must match
            // for the first application-message AEAD to succeed.
            assert_eq!(
                session_out.initial_chain_key, received_out.chain_key,
                "initial chain keys must match between Alice and Bob"
            );
            assert_ne!(
                received_out.chain_key, [0u8; 32],
                "chain key must be non-zero"
            );

            soliton_kex_received_session_free(&mut received_out);
            soliton_kex_initiated_session_free(&mut session_out);
            soliton_buf_free(&mut spk_sig);
            soliton_buf_free(&mut spk_sk_buf);
            soliton_buf_free(&mut spk_pub);
            free_identity_keypair(bob_pk, bob_sk);
            free_identity_keypair(alice_pk, alice_sk);
        }
    }

    /// Full PQ ratchet round-trip with direction change (RT-383).
    ///
    /// Unlike the PQ-free round-trip, this test uses real X-Wing keygen so that
    /// when Bob replies to Alice, the ratchet step triggers an actual KEM
    /// encapsulation/decapsulation through the CAPI.
    #[test]
    fn ratchet_pq_round_trip_with_direction_change() {
        unsafe {
            // Generate real X-Wing keypairs for Alice's ephemeral key.
            let mut ek_pk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut ek_sk = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_xwing_keygen(&mut ek_pk, &mut ek_sk);

            // Shared root key and chain key (synthetic — in real use these come from KEX).
            let rk = [0x41u8; 32];
            let ck = [0x42u8; 32];
            let alice_fp = [0x01u8; 32];
            let bob_fp = [0x02u8; 32];

            // Initialize Alice (has EK secret key for KEM decapsulation on receive).
            let mut alice: *mut SolitonRatchet = ptr::null_mut();
            let rc = soliton_ratchet_init_alice(
                rk.as_ptr(),
                32,
                ck.as_ptr(),
                32,
                alice_fp.as_ptr(),
                32,
                bob_fp.as_ptr(),
                32,
                ek_pk.ptr,
                ek_pk.len,
                ek_sk.ptr,
                ek_sk.len,
                &mut alice,
            );
            assert_eq!(rc, OK, "init_alice must succeed");

            // Initialize Bob (has Alice's EK public key for KEM encapsulation on send).
            let mut bob: *mut SolitonRatchet = ptr::null_mut();
            let rc = soliton_ratchet_init_bob(
                rk.as_ptr(),
                32,
                ck.as_ptr(),
                32,
                bob_fp.as_ptr(),
                32,
                alice_fp.as_ptr(),
                32,
                ek_pk.ptr,
                ek_pk.len,
                &mut bob,
            );
            assert_eq!(rc, OK, "init_bob must succeed");

            // Alice → Bob (first message: no KEM step, same as PQ-free).
            let msg1_pt = b"alice to bob";
            let mut msg1: MaybeUninit<SolitonEncryptedMessage> = MaybeUninit::zeroed();
            let rc =
                soliton_ratchet_encrypt(alice, msg1_pt.as_ptr(), msg1_pt.len(), msg1.as_mut_ptr());
            assert_eq!(rc, OK);
            let msg1 = msg1.assume_init();
            // First message has no KEM ciphertext.
            assert!(msg1.header.kem_ct.ptr.is_null() || msg1.header.kem_ct.len == 0);

            let mut pt1_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_ratchet_decrypt(
                bob,
                msg1.header.ratchet_pk.ptr,
                msg1.header.ratchet_pk.len,
                ptr::null(),
                0,
                msg1.header.n,
                msg1.header.pn,
                msg1.ciphertext.ptr,
                msg1.ciphertext.len,
                &mut pt1_out,
            );
            assert_eq!(rc, OK, "Bob must decrypt Alice's first message");
            assert_eq!(
                std::slice::from_raw_parts(pt1_out.ptr, pt1_out.len),
                msg1_pt
            );

            // Bob → Alice (direction change: triggers KEM encap with a new ratchet key).
            let msg2_pt = b"bob to alice";
            let mut msg2: MaybeUninit<SolitonEncryptedMessage> = MaybeUninit::zeroed();
            let rc =
                soliton_ratchet_encrypt(bob, msg2_pt.as_ptr(), msg2_pt.len(), msg2.as_mut_ptr());
            assert_eq!(rc, OK);
            let msg2 = msg2.assume_init();
            // Direction change produces a KEM ciphertext.
            assert!(
                !msg2.header.kem_ct.ptr.is_null() && msg2.header.kem_ct.len > 0,
                "direction change must produce kem_ct"
            );

            let mut pt2_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_ratchet_decrypt(
                alice,
                msg2.header.ratchet_pk.ptr,
                msg2.header.ratchet_pk.len,
                msg2.header.kem_ct.ptr,
                msg2.header.kem_ct.len,
                msg2.header.n,
                msg2.header.pn,
                msg2.ciphertext.ptr,
                msg2.ciphertext.len,
                &mut pt2_out,
            );
            assert_eq!(rc, OK, "Alice must decrypt Bob's reply (KEM decap path)");
            assert_eq!(
                std::slice::from_raw_parts(pt2_out.ptr, pt2_out.len),
                msg2_pt
            );

            // Cleanup.
            soliton_buf_free(&mut pt1_out);
            soliton_buf_free(&mut pt2_out);
            let mut msg1 = msg1;
            let mut msg2 = msg2;
            soliton_encrypted_message_free(&mut msg1);
            soliton_encrypted_message_free(&mut msg2);
            soliton_ratchet_free(&mut alice);
            soliton_ratchet_free(&mut bob);
            soliton_buf_free(&mut ek_sk);
            soliton_buf_free(&mut ek_pk);
        }
    }

    /// Full KEX → first-message → ratchet integration test (RT-385).
    ///
    /// Exercises the complete handshake lifecycle through the CAPI:
    /// 1. KEX initiate (Alice) + receive (Bob) → shared root_key + chain_key
    /// 2. encrypt_first / decrypt_first → first application message + next_ck
    /// 3. ratchet_init_alice / ratchet_init_bob → steady-state ratchet
    /// 4. ratchet_encrypt / ratchet_decrypt → bidirectional messaging
    #[test]
    fn kex_to_ratchet_full_integration() {
        unsafe {
            // ── Step 0: Generate identity keypairs ──
            let (alice_pk, alice_sk) = generate_identity_keypair();
            let (bob_pk, bob_sk) = generate_identity_keypair();

            // Bob's signed pre-key.
            let mut spk_pub = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut spk_sk_buf = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_xwing_keygen(&mut spk_pub, &mut spk_sk_buf);
            let mut spk_sig = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            soliton_kex_sign_prekey(
                bob_sk.ptr,
                bob_sk.len,
                spk_pub.ptr,
                spk_pub.len,
                &mut spk_sig,
            );

            let cv = CString::new("lo-crypto-v1").unwrap();

            // ── Step 1: KEX ──
            let mut session_out = std::mem::zeroed::<SolitonInitiatedSession>();
            let rc = soliton_kex_initiate(
                alice_pk.ptr,
                alice_pk.len,
                alice_sk.ptr,
                alice_sk.len,
                bob_pk.ptr,
                bob_pk.len,
                spk_pub.ptr,
                spk_pub.len,
                1,
                spk_sig.ptr,
                spk_sig.len,
                ptr::null(),
                0,
                0,
                cv.as_ptr(),
                &mut session_out,
            );
            assert_eq!(rc, OK, "kex_initiate must succeed");

            let wire = SolitonSessionInitWire {
                sender_sig: session_out.sender_sig.ptr,
                sender_sig_len: session_out.sender_sig.len,
                sender_ik_fingerprint: session_out.sender_ik_fingerprint.as_ptr(),
                sender_ik_fingerprint_len: 32,
                recipient_ik_fingerprint: session_out.recipient_ik_fingerprint.as_ptr(),
                recipient_ik_fingerprint_len: 32,
                sender_ek: session_out.ek_pk.ptr,
                sender_ek_len: session_out.ek_pk.len,
                ct_ik: session_out.ct_ik.ptr,
                ct_ik_len: session_out.ct_ik.len,
                ct_spk: session_out.ct_spk.ptr,
                ct_spk_len: session_out.ct_spk.len,
                spk_id: session_out.spk_id,
                ct_opk: ptr::null(),
                ct_opk_len: 0,
                opk_id: 0,
                crypto_version: cv.as_ptr(),
            };
            let decap_keys = SolitonSessionDecapKeys {
                spk_sk: spk_sk_buf.ptr,
                spk_sk_len: spk_sk_buf.len,
                opk_sk: ptr::null(),
                opk_sk_len: 0,
            };
            let mut received_out = SolitonReceivedSession {
                root_key: [0u8; 32],
                chain_key: [0u8; 32],
                peer_ek: SolitonBuf {
                    ptr: ptr::null_mut(),
                    len: 0,
                },
            };
            let rc = soliton_kex_receive(
                bob_pk.ptr,
                bob_pk.len,
                bob_sk.ptr,
                bob_sk.len,
                alice_pk.ptr,
                alice_pk.len,
                &wire,
                &decap_keys,
                &mut received_out,
            );
            assert_eq!(rc, OK, "kex_receive must succeed");
            assert_eq!(session_out.root_key, received_out.root_key);
            assert_eq!(session_out.initial_chain_key, received_out.chain_key);

            // ── Step 2: First message (encrypt_first / decrypt_first) ──
            let first_msg = b"hello from alice";
            let first_aad = b"session-aad";
            let mut first_payload = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut next_ck_alice = [0u8; 32];
            let rc = soliton_ratchet_encrypt_first(
                session_out.initial_chain_key.as_ptr(),
                32,
                first_msg.as_ptr(),
                first_msg.len(),
                first_aad.as_ptr(),
                first_aad.len(),
                &mut first_payload,
                next_ck_alice.as_mut_ptr(),
                32,
            );
            assert_eq!(rc, OK, "encrypt_first must succeed");

            let mut first_pt_out = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let mut next_ck_bob = [0u8; 32];
            let rc = soliton_ratchet_decrypt_first(
                received_out.chain_key.as_ptr(),
                32,
                first_payload.ptr,
                first_payload.len,
                first_aad.as_ptr(),
                first_aad.len(),
                &mut first_pt_out,
                next_ck_bob.as_mut_ptr(),
                32,
            );
            assert_eq!(rc, OK, "decrypt_first must succeed");
            assert_eq!(
                std::slice::from_raw_parts(first_pt_out.ptr, first_pt_out.len),
                first_msg
            );
            assert_eq!(next_ck_alice, next_ck_bob, "next chain keys must match");

            // ── Step 3: Initialize ratchets ──
            // Compute fingerprints for ratchet init.
            let mut alice_fp = [0u8; 32];
            let mut bob_fp = [0u8; 32];
            let rc =
                soliton_identity_fingerprint(alice_pk.ptr, alice_pk.len, alice_fp.as_mut_ptr(), 32);
            assert_eq!(rc, OK);
            let rc = soliton_identity_fingerprint(bob_pk.ptr, bob_pk.len, bob_fp.as_mut_ptr(), 32);
            assert_eq!(rc, OK);

            let mut alice_ratchet: *mut SolitonRatchet = ptr::null_mut();
            let rc = soliton_ratchet_init_alice(
                session_out.root_key.as_ptr(),
                32,
                next_ck_alice.as_ptr(),
                32,
                alice_fp.as_ptr(),
                32,
                bob_fp.as_ptr(),
                32,
                session_out.ek_pk.ptr,
                session_out.ek_pk.len,
                session_out.ek_sk.ptr,
                session_out.ek_sk.len,
                &mut alice_ratchet,
            );
            assert_eq!(rc, OK, "ratchet_init_alice must succeed");

            let mut bob_ratchet: *mut SolitonRatchet = ptr::null_mut();
            let rc = soliton_ratchet_init_bob(
                received_out.root_key.as_ptr(),
                32,
                next_ck_bob.as_ptr(),
                32,
                bob_fp.as_ptr(),
                32,
                alice_fp.as_ptr(),
                32,
                received_out.peer_ek.ptr,
                received_out.peer_ek.len,
                &mut bob_ratchet,
            );
            assert_eq!(rc, OK, "ratchet_init_bob must succeed");

            // ── Step 4: Bidirectional ratchet messaging ──
            // Alice → Bob
            let msg_a2b = b"steady-state alice to bob";
            let mut enc_a2b: MaybeUninit<SolitonEncryptedMessage> = MaybeUninit::zeroed();
            let rc = soliton_ratchet_encrypt(
                alice_ratchet,
                msg_a2b.as_ptr(),
                msg_a2b.len(),
                enc_a2b.as_mut_ptr(),
            );
            assert_eq!(rc, OK);
            let enc_a2b = enc_a2b.assume_init();

            let mut pt_a2b = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_ratchet_decrypt(
                bob_ratchet,
                enc_a2b.header.ratchet_pk.ptr,
                enc_a2b.header.ratchet_pk.len,
                if enc_a2b.header.kem_ct.ptr.is_null() {
                    ptr::null()
                } else {
                    enc_a2b.header.kem_ct.ptr
                },
                enc_a2b.header.kem_ct.len,
                enc_a2b.header.n,
                enc_a2b.header.pn,
                enc_a2b.ciphertext.ptr,
                enc_a2b.ciphertext.len,
                &mut pt_a2b,
            );
            assert_eq!(rc, OK, "Bob must decrypt ratchet message from Alice");
            assert_eq!(std::slice::from_raw_parts(pt_a2b.ptr, pt_a2b.len), msg_a2b);

            // Bob → Alice (direction change, triggers KEM)
            let msg_b2a = b"steady-state bob to alice";
            let mut enc_b2a: MaybeUninit<SolitonEncryptedMessage> = MaybeUninit::zeroed();
            let rc = soliton_ratchet_encrypt(
                bob_ratchet,
                msg_b2a.as_ptr(),
                msg_b2a.len(),
                enc_b2a.as_mut_ptr(),
            );
            assert_eq!(rc, OK);
            let enc_b2a = enc_b2a.assume_init();
            assert!(
                !enc_b2a.header.kem_ct.ptr.is_null() && enc_b2a.header.kem_ct.len > 0,
                "direction change must produce kem_ct"
            );

            let mut pt_b2a = SolitonBuf {
                ptr: ptr::null_mut(),
                len: 0,
            };
            let rc = soliton_ratchet_decrypt(
                alice_ratchet,
                enc_b2a.header.ratchet_pk.ptr,
                enc_b2a.header.ratchet_pk.len,
                enc_b2a.header.kem_ct.ptr,
                enc_b2a.header.kem_ct.len,
                enc_b2a.header.n,
                enc_b2a.header.pn,
                enc_b2a.ciphertext.ptr,
                enc_b2a.ciphertext.len,
                &mut pt_b2a,
            );
            assert_eq!(
                rc, OK,
                "Alice must decrypt ratchet message from Bob (KEM path)"
            );
            assert_eq!(std::slice::from_raw_parts(pt_b2a.ptr, pt_b2a.len), msg_b2a);

            // ── Cleanup ──
            soliton_buf_free(&mut pt_a2b);
            soliton_buf_free(&mut pt_b2a);
            let mut enc_a2b = enc_a2b;
            let mut enc_b2a = enc_b2a;
            soliton_encrypted_message_free(&mut enc_a2b);
            soliton_encrypted_message_free(&mut enc_b2a);
            soliton_buf_free(&mut first_pt_out);
            soliton_buf_free(&mut first_payload);
            soliton_ratchet_free(&mut alice_ratchet);
            soliton_ratchet_free(&mut bob_ratchet);
            soliton_kex_received_session_free(&mut received_out);
            soliton_kex_initiated_session_free(&mut session_out);
            soliton_buf_free(&mut spk_sig);
            soliton_buf_free(&mut spk_sk_buf);
            soliton_buf_free(&mut spk_pub);
            free_identity_keypair(bob_pk, bob_sk);
            free_identity_keypair(alice_pk, alice_sk);
        }
    }

    // Helpers for the KEX test.
    unsafe fn generate_identity_keypair() -> (SolitonBuf, SolitonBuf) {
        let mut pk = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut sk = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let mut fp = SolitonBuf {
            ptr: ptr::null_mut(),
            len: 0,
        };
        let rc = unsafe { soliton_identity_generate(&mut pk, &mut sk, &mut fp) };
        assert_eq!(rc, OK);
        unsafe { soliton_buf_free(&mut fp) };
        (pk, sk)
    }

    unsafe fn free_identity_keypair(mut pk: SolitonBuf, mut sk: SolitonBuf) {
        unsafe {
            soliton_buf_free(&mut pk);
            soliton_buf_free(&mut sk);
        }
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// Streaming AEAD
// ═══════════════════════════════════════════════════════════════════════════

const CHUNK_SZ: usize = soliton::constants::STREAM_CHUNK_SIZE;
const HDR_SZ: usize = soliton::constants::STREAM_HEADER_SIZE;
const ENC_MAX: usize = soliton::constants::STREAM_ENCRYPT_MAX;

/// Helper: create an encryptor, return (handle, header).
unsafe fn stream_enc_setup(
    key: &[u8; 32],
    aad: &[u8],
    compress: bool,
) -> (*mut SolitonStreamEncryptor, [u8; HDR_SZ]) {
    let mut enc: *mut SolitonStreamEncryptor = ptr::null_mut();
    let rc = unsafe {
        soliton_stream_encrypt_init(
            key.as_ptr(),
            32,
            if aad.is_empty() {
                ptr::null()
            } else {
                aad.as_ptr()
            },
            aad.len(),
            compress,
            &mut enc,
        )
    };
    assert_eq!(rc, OK);
    assert!(!enc.is_null());

    let mut hdr = [0u8; HDR_SZ];
    let rc = unsafe { soliton_stream_encrypt_header(enc, hdr.as_mut_ptr(), HDR_SZ) };
    assert_eq!(rc, OK);
    (enc, hdr)
}

/// Helper: create a decryptor from key + header.
unsafe fn stream_dec_setup(
    key: &[u8; 32],
    header: &[u8; HDR_SZ],
    aad: &[u8],
) -> *mut SolitonStreamDecryptor {
    let mut dec: *mut SolitonStreamDecryptor = ptr::null_mut();
    let rc = unsafe {
        soliton_stream_decrypt_init(
            key.as_ptr(),
            32,
            header.as_ptr(),
            HDR_SZ,
            if aad.is_empty() {
                ptr::null()
            } else {
                aad.as_ptr()
            },
            aad.len(),
            &mut dec,
        )
    };
    assert_eq!(rc, OK);
    assert!(!dec.is_null());
    dec
}

// ── Null-pointer guards ──────────────────────────────────────────────────

#[test]
fn stream_encrypt_init_null_key() {
    let mut enc: *mut SolitonStreamEncryptor = ptr::null_mut();
    let rc =
        unsafe { soliton_stream_encrypt_init(ptr::null(), 32, ptr::null(), 0, false, &mut enc) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn stream_encrypt_init_null_out() {
    let key = [0x42u8; 32];
    let rc = unsafe {
        soliton_stream_encrypt_init(key.as_ptr(), 32, ptr::null(), 0, false, ptr::null_mut())
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn stream_encrypt_init_null_aad_nonzero_len() {
    let key = [0x42u8; 32];
    let mut enc: *mut SolitonStreamEncryptor = ptr::null_mut();
    let rc =
        unsafe { soliton_stream_encrypt_init(key.as_ptr(), 32, ptr::null(), 10, false, &mut enc) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn stream_encrypt_header_null_enc() {
    let mut hdr = [0u8; HDR_SZ];
    let rc = unsafe { soliton_stream_encrypt_header(ptr::null(), hdr.as_mut_ptr(), HDR_SZ) };
    assert_eq!(rc, E_NULL);
}

#[test]
fn stream_encrypt_header_null_out() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let rc = unsafe { soliton_stream_encrypt_header(enc, ptr::null_mut(), HDR_SZ) };
    assert_eq!(rc, E_NULL);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_encrypt_chunk_null_enc() {
    let pt = vec![0u8; CHUNK_SZ];
    let mut out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            ptr::null_mut(),
            pt.as_ptr(),
            pt.len(),
            true,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn stream_encrypt_chunk_null_out() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let pt = vec![0u8; CHUNK_SZ];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            ptr::null_mut(),
            ENC_MAX,
            &mut written,
        )
    };
    assert_eq!(rc, E_NULL);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_encrypt_chunk_null_out_written() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let pt = vec![0u8; CHUNK_SZ];
    let mut out = vec![0u8; ENC_MAX];
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            out.as_mut_ptr(),
            out.len(),
            ptr::null_mut(),
        )
    };
    assert_eq!(rc, E_NULL);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_encrypt_chunk_null_plaintext_nonzero_len() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let mut out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            ptr::null(),
            1,
            true,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, E_NULL);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_encrypt_chunk_null_plaintext_zero_len_final() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let mut out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            ptr::null(),
            0,
            true,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);
    assert!(written > 0); // tag_byte + AEAD tag
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_encrypt_is_finalized_null() {
    let mut out = false;
    assert_eq!(
        unsafe { soliton_stream_encrypt_is_finalized(ptr::null(), &mut out) },
        E_NULL
    );
    assert_eq!(
        unsafe { soliton_stream_encrypt_is_finalized(ptr::null(), ptr::null_mut()) },
        E_NULL
    );
}

#[test]
fn stream_encrypt_free_null() {
    // Outer null is a no-op (returns 0), matching ratchet_free/keyring_free/call_keys_free.
    assert_eq!(unsafe { soliton_stream_encrypt_free(ptr::null_mut()) }, OK);
    let mut null: *mut SolitonStreamEncryptor = ptr::null_mut();
    assert_eq!(unsafe { soliton_stream_encrypt_free(&mut null) }, OK);
}

#[test]
fn stream_decrypt_init_null_key() {
    let hdr = [0u8; HDR_SZ];
    let mut dec: *mut SolitonStreamDecryptor = ptr::null_mut();
    let rc = unsafe {
        soliton_stream_decrypt_init(
            ptr::null(),
            32,
            hdr.as_ptr(),
            HDR_SZ,
            ptr::null(),
            0,
            &mut dec,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn stream_decrypt_init_null_header() {
    let key = [0x42u8; 32];
    let mut dec: *mut SolitonStreamDecryptor = ptr::null_mut();
    let rc = unsafe {
        soliton_stream_decrypt_init(
            key.as_ptr(),
            32,
            ptr::null(),
            HDR_SZ,
            ptr::null(),
            0,
            &mut dec,
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn stream_decrypt_init_null_out() {
    let key = [0x42u8; 32];
    let hdr = [0u8; HDR_SZ];
    let rc = unsafe {
        soliton_stream_decrypt_init(
            key.as_ptr(),
            32,
            hdr.as_ptr(),
            HDR_SZ,
            ptr::null(),
            0,
            ptr::null_mut(),
        )
    };
    assert_eq!(rc, E_NULL);
}

#[test]
fn stream_decrypt_chunk_nulls() {
    let mut out = vec![0u8; CHUNK_SZ];
    let mut written = 0usize;
    let mut last = false;
    let chunk = [0u8; 17];

    assert_eq!(
        unsafe {
            soliton_stream_decrypt_chunk(
                ptr::null_mut(),
                chunk.as_ptr(),
                17,
                out.as_mut_ptr(),
                CHUNK_SZ,
                &mut written,
                &mut last,
            )
        },
        E_NULL
    );
}

#[test]
fn stream_encrypt_chunk_at_null_enc() {
    let pt = b"data";
    let mut out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    assert_eq!(
        unsafe {
            soliton_stream_encrypt_chunk_at(
                ptr::null(),
                0,
                pt.as_ptr(),
                pt.len(),
                true,
                out.as_mut_ptr(),
                out.len(),
                &mut written,
            )
        },
        E_NULL
    );
}

#[test]
fn stream_encrypt_chunk_at_null_out() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let pt = b"data";
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk_at(
            enc,
            0,
            pt.as_ptr(),
            pt.len(),
            true,
            ptr::null_mut(),
            ENC_MAX,
            &mut written,
        )
    };
    assert_eq!(rc, E_NULL);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_encrypt_chunk_at_null_out_written() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let pt = b"data";
    let mut out = vec![0u8; ENC_MAX];
    let rc = unsafe {
        soliton_stream_encrypt_chunk_at(
            enc,
            0,
            pt.as_ptr(),
            pt.len(),
            true,
            out.as_mut_ptr(),
            out.len(),
            ptr::null_mut(),
        )
    };
    assert_eq!(rc, E_NULL);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_encrypt_chunk_at_round_trip() {
    // Encrypt a chunk via encrypt_chunk_at, decrypt via sequential decrypt_chunk.
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let pt = b"encrypt_chunk_at round trip";
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk_at(
            enc,
            0,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);
    assert!(written > 0);

    // finalized must NOT be set — encrypt_chunk_at does not seal the stream.
    let mut fin = true;
    let rc = unsafe { soliton_stream_encrypt_is_finalized(enc, &mut fin) };
    assert_eq!(rc, OK);
    assert!(!fin);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);
    assert_eq!(&dec_out[..dec_written], pt);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn stream_encrypt_chunk_at_wrong_index_aead_fails() {
    // Ciphertext produced at index 0 cannot be decrypted at index 1.
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let pt = b"index mismatch";
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk_at(
            enc,
            0,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    // Feed chunk encrypted at index 0 to decrypt_chunk_at with index 1.
    let rc = unsafe {
        soliton_stream_decrypt_chunk_at(
            dec,
            1,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, E_AEAD);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn stream_encrypt_chunk_at_out_too_small() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let pt = b"x";
    let mut out = vec![0u8; ENC_MAX - 1];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk_at(
            enc,
            0,
            pt.as_ptr(),
            pt.len(),
            true,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, E_LEN);
    assert_eq!(written, 0);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn miri_capi_stream_encrypt_chunk_at_small() {
    // MIRI-friendly: small plaintext, exercises the full encrypt_chunk_at →
    // decrypt_chunk_at round-trip through the FFI boundary.
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let pt = b"miri encrypt_chunk_at";
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk_at(
            enc,
            0,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk_at(
            dec,
            0,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);
    assert_eq!(&dec_out[..dec_written], pt);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn stream_decrypt_chunk_at_nulls() {
    let mut out = vec![0u8; CHUNK_SZ];
    let mut written = 0usize;
    let mut last = false;
    let chunk = [0u8; 17];

    assert_eq!(
        unsafe {
            soliton_stream_decrypt_chunk_at(
                ptr::null(),
                0,
                chunk.as_ptr(),
                17,
                out.as_mut_ptr(),
                CHUNK_SZ,
                &mut written,
                &mut last,
            )
        },
        E_NULL
    );
}

#[test]
fn stream_decrypt_is_finalized_null() {
    let mut out = false;
    assert_eq!(
        unsafe { soliton_stream_decrypt_is_finalized(ptr::null(), &mut out) },
        E_NULL
    );
}

#[test]
fn stream_decrypt_expected_index_null() {
    let mut out = 0u64;
    assert_eq!(
        unsafe { soliton_stream_decrypt_expected_index(ptr::null(), &mut out) },
        E_NULL
    );
}

#[test]
fn stream_decrypt_free_null() {
    // Outer null is a no-op (returns 0), matching ratchet_free/keyring_free/call_keys_free.
    assert_eq!(unsafe { soliton_stream_decrypt_free(ptr::null_mut()) }, OK);
    let mut null: *mut SolitonStreamDecryptor = ptr::null_mut();
    assert_eq!(unsafe { soliton_stream_decrypt_free(&mut null) }, OK);
}

// ── Length validation ────────────────────────────────────────────────────

#[test]
fn stream_encrypt_init_wrong_key_len() {
    let key = [0x42u8; 31];
    let mut enc: *mut SolitonStreamEncryptor = ptr::null_mut();
    let rc =
        unsafe { soliton_stream_encrypt_init(key.as_ptr(), 31, ptr::null(), 0, false, &mut enc) };
    assert_eq!(rc, E_LEN);
}

#[test]
fn stream_decrypt_init_wrong_key_len() {
    let key = [0x42u8; 31];
    let hdr = [0u8; HDR_SZ];
    let mut dec: *mut SolitonStreamDecryptor = ptr::null_mut();
    let rc = unsafe {
        soliton_stream_decrypt_init(
            key.as_ptr(),
            31,
            hdr.as_ptr(),
            HDR_SZ,
            ptr::null(),
            0,
            &mut dec,
        )
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn stream_decrypt_init_wrong_header_len() {
    let key = [0x42u8; 32];
    let hdr = [0u8; 25];
    let mut dec: *mut SolitonStreamDecryptor = ptr::null_mut();
    let rc = unsafe {
        soliton_stream_decrypt_init(key.as_ptr(), 32, hdr.as_ptr(), 25, ptr::null(), 0, &mut dec)
    };
    assert_eq!(rc, E_LEN);
}

#[test]
fn stream_encrypt_init_aad_too_large() {
    // AAD exceeding 256 MiB cap returns InvalidLength.
    // Pass a non-null pointer with an oversized length — the function checks
    // aad_len before dereferencing, so we use a 1-byte dummy pointer.
    let key = [0x42u8; 32];
    let dummy_aad: u8 = 0;
    let mut enc: *mut SolitonStreamEncryptor = ptr::null_mut();
    let rc = unsafe {
        soliton_stream_encrypt_init(
            key.as_ptr(),
            32,
            &dummy_aad as *const u8,
            256 * 1024 * 1024 + 1,
            false,
            &mut enc,
        )
    };
    assert_eq!(rc, E_LEN);
    assert!(enc.is_null());
}

#[test]
fn stream_encrypt_chunk_out_too_small() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let pt = vec![0xAAu8; CHUNK_SZ];
    let mut out = vec![0u8; ENC_MAX - 1];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, E_LEN);
    assert_eq!(written, 0);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_decrypt_chunk_out_too_small() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };
    let pt = vec![0xBBu8; CHUNK_SZ];
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0u8; CHUNK_SZ - 1]; // too small
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, E_LEN);
    assert_eq!(dec_written, 0);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

// ── Output zeroing ───────────────────────────────────────────────────────

#[test]
fn stream_decrypt_chunk_zeros_output_on_failure() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };
    let pt = vec![0xAAu8; CHUNK_SZ];
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        );
    }

    // Corrupt the chunk.
    enc_out[5] ^= 0xFF;

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0xABu8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, E_AEAD);
    assert_eq!(dec_written, 0);
    assert!(!last);
    assert!(is_zeroed(&dec_out));

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn stream_encrypt_chunk_zeros_output_on_failure() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    // Oversized non-final chunk → InvalidData.
    let bad_pt = vec![0u8; CHUNK_SZ + 1];
    let mut out = vec![0xABu8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            bad_pt.as_ptr(),
            bad_pt.len(),
            false,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, E_DATA);
    assert_eq!(written, 0);
    assert!(is_zeroed(&out));

    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

// ── Round-trip ───────────────────────────────────────────────────────────

#[test]
fn capi_stream_round_trip_uncompressed() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    // Encrypt 2 non-final + 1 final.
    let pt0 = vec![0x01u8; CHUNK_SZ];
    let pt1 = vec![0x02u8; CHUNK_SZ];
    let pt2 = vec![0x03u8; 500];

    let mut enc_bufs: Vec<(Vec<u8>, usize)> = Vec::new();
    for (pt, is_last) in [(&pt0, false), (&pt1, false), (&pt2, true)] {
        let mut out = vec![0u8; ENC_MAX];
        let mut written = 0usize;
        let rc = unsafe {
            soliton_stream_encrypt_chunk(
                enc,
                pt.as_ptr(),
                pt.len(),
                is_last,
                out.as_mut_ptr(),
                out.len(),
                &mut written,
            )
        };
        assert_eq!(rc, OK);
        assert!(written > 0);
        enc_bufs.push((out, written));
    }

    // Decrypt sequentially.
    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    for (i, (pt, _is_last_expected)) in [(&pt0, false), (&pt1, false), (&pt2, true)]
        .iter()
        .enumerate()
    {
        let (ref enc_buf, enc_written) = enc_bufs[i];
        let mut dec_out = vec![0u8; CHUNK_SZ];
        let mut written = 0usize;
        let mut last = false;
        let rc = unsafe {
            soliton_stream_decrypt_chunk(
                dec,
                enc_buf.as_ptr(),
                enc_written,
                dec_out.as_mut_ptr(),
                dec_out.len(),
                &mut written,
                &mut last,
            )
        };
        assert_eq!(rc, OK);
        assert_eq!(&dec_out[..written], pt.as_slice());
        assert_eq!(last, *_is_last_expected);
    }

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn capi_stream_round_trip_compressed() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], true) };

    let pt = vec![0xCCu8; CHUNK_SZ]; // compressible
    let mut out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);
    assert_eq!(&dec_out[..dec_written], &pt);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn capi_stream_round_trip_empty_file() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let mut out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            ptr::null(),
            0,
            true,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);
    assert_eq!(written, 17); // tag_byte + AEAD tag

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);
    assert_eq!(dec_written, 0);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn capi_stream_random_access() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let pt0 = vec![0x10u8; CHUNK_SZ];
    let pt1 = vec![0x20u8; CHUNK_SZ];
    let pt2 = vec![0x30u8; CHUNK_SZ];
    let pt3 = vec![0x40u8; 200];

    let mut chunks: Vec<(Vec<u8>, usize)> = Vec::new();
    for (pt, is_last) in [(&pt0, false), (&pt1, false), (&pt2, false), (&pt3, true)] {
        let mut out = vec![0u8; ENC_MAX];
        let mut written = 0usize;
        let rc = unsafe {
            soliton_stream_encrypt_chunk(
                enc,
                pt.as_ptr(),
                pt.len(),
                is_last,
                out.as_mut_ptr(),
                out.len(),
                &mut written,
            )
        };
        assert_eq!(rc, OK);
        chunks.push((out, written));
    }

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };

    // Random-access decrypt chunk 2.
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk_at(
            dec,
            2,
            chunks[2].0.as_ptr(),
            chunks[2].1,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(!last);
    assert_eq!(&dec_out[..written], &pt2);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

// ── Getters ──────────────────────────────────────────────────────────────

#[test]
fn stream_encrypt_is_finalized_lifecycle() {
    let key = [0x42u8; 32];
    let (enc, _) = unsafe { stream_enc_setup(&key, &[], false) };

    let mut fin = true;
    let rc = unsafe { soliton_stream_encrypt_is_finalized(enc, &mut fin) };
    assert_eq!(rc, OK);
    assert!(!fin);

    let mut out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            ptr::null(),
            0,
            true,
            out.as_mut_ptr(),
            out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let rc = unsafe { soliton_stream_encrypt_is_finalized(enc, &mut fin) };
    assert_eq!(rc, OK);
    assert!(fin);

    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_decrypt_is_finalized_lifecycle() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            ptr::null(),
            0,
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };

    let mut fin = true;
    let rc = unsafe { soliton_stream_decrypt_is_finalized(dec, &mut fin) };
    assert_eq!(rc, OK);
    assert!(!fin);

    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);

    let rc = unsafe { soliton_stream_decrypt_is_finalized(dec, &mut fin) };
    assert_eq!(rc, OK);
    assert!(fin);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn stream_decrypt_expected_index_increments() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let pt0 = vec![0x01u8; CHUNK_SZ];
    let pt1 = [0x02u8; 100];
    let mut c0 = vec![0u8; ENC_MAX];
    let mut c1 = vec![0u8; ENC_MAX];
    let mut w0 = 0usize;
    let mut w1 = 0usize;
    unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt0.as_ptr(),
            pt0.len(),
            false,
            c0.as_mut_ptr(),
            c0.len(),
            &mut w0,
        );
        soliton_stream_encrypt_chunk(
            enc,
            pt1.as_ptr(),
            pt1.len(),
            true,
            c1.as_mut_ptr(),
            c1.len(),
            &mut w1,
        );
    }

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };

    let mut idx = 99u64;
    let rc = unsafe { soliton_stream_decrypt_expected_index(dec, &mut idx) };
    assert_eq!(rc, OK);
    assert_eq!(idx, 0);

    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut written = 0usize;
    let mut last = false;
    unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            c0.as_ptr(),
            w0,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut written,
            &mut last,
        );
    }

    let rc = unsafe { soliton_stream_decrypt_expected_index(dec, &mut idx) };
    assert_eq!(rc, OK);
    assert_eq!(idx, 1);

    unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            c1.as_ptr(),
            w1,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut written,
            &mut last,
        );
    }

    let rc = unsafe { soliton_stream_decrypt_expected_index(dec, &mut idx) };
    assert_eq!(rc, OK);
    assert_eq!(idx, 2);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

// ── Handle safety ────────────────────────────────────────────────────────

#[test]
fn stream_encrypt_free_nullifies_pointer() {
    let key = [0x42u8; 32];
    let (mut enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    let rc = unsafe { soliton_stream_encrypt_free(&mut enc) };
    assert_eq!(rc, OK);
    assert!(enc.is_null());
}

#[test]
fn stream_decrypt_free_nullifies_pointer() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };
    let mut dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let rc = unsafe { soliton_stream_decrypt_free(&mut dec) };
    assert_eq!(rc, OK);
    assert!(dec.is_null());
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

#[test]
fn stream_encrypt_double_free_noop() {
    let key = [0x42u8; 32];
    let (mut enc, _) = unsafe { stream_enc_setup(&key, &[], false) };
    assert_eq!(unsafe { soliton_stream_encrypt_free(&mut enc) }, OK);
    assert_eq!(unsafe { soliton_stream_encrypt_free(&mut enc) }, OK); // null → no-op
}

#[test]
fn stream_decrypt_double_free_noop() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };
    let mut dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    assert_eq!(unsafe { soliton_stream_decrypt_free(&mut dec) }, OK);
    assert_eq!(unsafe { soliton_stream_decrypt_free(&mut dec) }, OK);
    unsafe { soliton_stream_encrypt_free(&mut (enc as *mut _)) };
}

// ═══════════════════════════════════════════════════════════════════════════
// Small-data MIRI-friendly streaming tests
// ═══════════════════════════════════════════════════════════════════════════
//
// The full-chunk streaming tests (capi_stream_round_trip_*, random_access,
// expected_index_increments) use 1 MiB AEAD and time out under MIRI. These
// variants exercise the same CAPI paths with tiny plaintext.

#[test]
fn miri_capi_stream_round_trip_small() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, b"ctx", false) };

    let pt = b"small miri test";
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);
    assert!(written > 0);

    let dec = unsafe { stream_dec_setup(&key, &hdr, b"ctx") };
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);
    assert_eq!(&dec_out[..dec_written], pt);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn miri_capi_stream_round_trip_compressed_small() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], true) };

    let pt = b"compressible data for miri";
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);
    assert_eq!(&dec_out[..dec_written], pt);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn miri_capi_stream_random_access_small() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let pt = b"random access miri";
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk_at(
            dec,
            0,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);
    assert_eq!(&dec_out[..dec_written], pt);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

#[test]
fn miri_capi_stream_expected_index_small() {
    let key = [0x42u8; 32];
    let (enc, hdr) = unsafe { stream_enc_setup(&key, &[], false) };

    let pt = b"index test";
    let mut enc_out = vec![0u8; ENC_MAX];
    let mut written = 0usize;
    let rc = unsafe {
        soliton_stream_encrypt_chunk(
            enc,
            pt.as_ptr(),
            pt.len(),
            true,
            enc_out.as_mut_ptr(),
            enc_out.len(),
            &mut written,
        )
    };
    assert_eq!(rc, OK);

    let dec = unsafe { stream_dec_setup(&key, &hdr, &[]) };
    let mut idx: u64 = 99;
    let rc = unsafe { soliton_stream_decrypt_expected_index(dec, &mut idx) };
    assert_eq!(rc, OK);
    assert_eq!(idx, 0);

    let mut dec_out = vec![0u8; CHUNK_SZ];
    let mut dec_written = 0usize;
    let mut last = false;
    let rc = unsafe {
        soliton_stream_decrypt_chunk(
            dec,
            enc_out.as_ptr(),
            written,
            dec_out.as_mut_ptr(),
            dec_out.len(),
            &mut dec_written,
            &mut last,
        )
    };
    assert_eq!(rc, OK);
    assert!(last);

    let rc = unsafe { soliton_stream_decrypt_expected_index(dec, &mut idx) };
    assert_eq!(rc, OK);
    assert_eq!(idx, 1);

    unsafe {
        soliton_stream_encrypt_free(&mut (enc as *mut _));
        soliton_stream_decrypt_free(&mut (dec as *mut _));
    }
}

// ═══════════════════════════════════════════════════════════════════════════
// Header freshness verification
// ═══════════════════════════════════════════════════════════════════════════

/// Verify that the checked-in `soliton.h` matches what cbindgen would
/// generate from the current source. Run `cargo test -p libsoliton_capi`
/// after changing any `extern "C"` function or `#[repr(C)]` type to
/// regenerate the header.
#[test]
fn header_up_to_date() {
    let crate_dir = env!("CARGO_MANIFEST_DIR");
    let config_path = format!("{crate_dir}/cbindgen.toml");
    let header_path = format!("{crate_dir}/soliton.h");

    let config = cbindgen::Config::from_file(&config_path).expect("failed to read cbindgen.toml");

    // cbindgen::Bindings has no Display impl — write to a temp file and
    // read back for comparison.
    let tmp = std::env::temp_dir().join("soliton_header_check.h");

    cbindgen::Builder::new()
        .with_crate(crate_dir)
        .with_config(config)
        .generate()
        .expect("cbindgen failed to generate bindings")
        .write_to_file(&tmp);

    let generated =
        std::fs::read_to_string(&tmp).expect("failed to read generated header from temp file");
    let _ = std::fs::remove_file(&tmp);

    let checked_in = std::fs::read_to_string(&header_path)
        .expect("soliton.h not found — run `cargo test -p libsoliton_capi` to generate it");

    if generated != checked_in {
        // Overwrite the stale header so the next test run passes.
        std::fs::write(&header_path, &generated).expect("failed to write soliton.h");
        panic!(
            "soliton.h was out of date and has been regenerated. \
             Please review the diff and commit the updated header."
        );
    }
}