unicity-aos/aos-ce · warning

aos-mcp: could not audit rejected hook message

Error message

aos-mcp: could not audit rejected hook message: {error}

What it means

When capsule-mcp rejects a host hook message, it attempts to write an audit record (host, event, reason) via a logging/audit sink. If that audit write fails, it logs this warning; the message is still rejected. The warning exists so rejections remain auditable — losing the audit trail is the real concern, not the rejection itself.

Solutions

  1. Inspect the {error} in the log to identify the failing audit sink and fix its availability/configuration.
  2. Verify the audit sink credentials/permissions allow writes.
  3. Fall back to a secondary audit channel (stdout log capture) until the sink recovers.
  4. Re-audit manually if compliance requires a record of the rejection.

Example fix

// before
if let Err(error) = audit::record(&serde_json::json!({
    "host": bounded_audit(host), "event": bounded_audit(event), "reason": reason,
})) {
    log::warn(format!("aos-mcp: could not audit rejected hook message: {error}"));
}
// after
if let Err(error) = audit::record(&serde_json::json!({
    "host": bounded_audit(host), "event": bounded_audit(event), "reason": reason,
})) {
    log::warn(format!("aos-mcp: could not audit rejected hook message: {error}"));
    log::info("AUDIT-FALLBACK host={host} event={event} reason={reason}");
}
Defensive patterns

Strategy: fallback

Validate before calling

// verify audit sink writability before processing hooks
let audit_ok = audit::health_check().is_ok();

Try / catch

if let Err(e) = audit::record(&payload) {
    log::warn("audit write failed: {e}");
    // emit to secondary log channel
}

Prevention

When it happens

Trigger: The audit sink call in reject() (invoked from handle and relay_response paths) returns Err after building the json!({host, event, reason}) payload — e.g., audit KV/log store unavailable or write rejected.

Common situations: Audit storage outage or quota exhaustion while hook messages are being rejected; misconfigured audit sink; host/event strings rejected by the sink.

Related errors

AI-assisted analysis of unicity-aos/aos-ce@f6f22024fb (2026-09-13). Data as JSON: /api/errors/b5c93cbe58cfed8a. Report an issue: GitHub.

Appendix: source

Thrown at capsules/capsule-mcp/src/host_hooks.rs:377

}

fn is_lower_hex(value: &str, expected_len: usize) -> bool {
    value.len() == expected_len
        && value
            .bytes()
            .all(|byte| byte.is_ascii_digit() || (b'a'..=b'f').contains(&byte))
}

fn reject(host: &str, event: &str, reason: &str) {
    if let Err(error) = ipc::publish_json(
        "astrid.v1.audit.hook_ingress_rejected",
        &serde_json::json!({
            "host": bounded_audit(host),
            "event": bounded_audit(event),
            "reason": reason,
        }),
    ) {
        log::warn(format!(
            "aos-mcp: could not audit rejected hook message: {error}"
        ));
    }
}

fn bounded_audit(value: &str) -> &str {
    let end = value.floor_char_boundary(value.len().min(128));
    &value[..end]
}

#[cfg(test)]
mod tests {
    use super::*;

    fn request() -> HostHookRequest {
        let token = "a".repeat(64);
        let route_id = derive_route_id("codex", "codex-session", &token);
        let correlation_id = "b".repeat(32);

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