fix: write-ahead audit entry so calls stop when the audit log stops accepting writes (SEC-03)

src/aegis_gitea_mcp/audit.py

@@ -162,6 +162,21 @@ class AuditLogger:
             payload["error"] = error
         return self._append_entry("tool_invocation", payload)
 
+    def log_tool_call_started(
+        self, tool_name: str, correlation_id: str, domain: str | None = None
+    ) -> str:
+        """Write the write-ahead entry of a call that is about to run.
+
+        The dispatcher writes it before executing a known tool and refuses the call
+        when it cannot be written, so an audit log that stopped accepting writes
+        after startup (full disk, revoked mount) stops the calls instead of letting
+        them run unrecorded. The final ``tool_invocation`` entry carries the result.
+        """
+        payload: dict[str, Any] = {"correlation_id": correlation_id, "tool_name": tool_name}
+        if domain is not None:
+            payload["domain"] = domain
+        return self._append_entry("tool_call_started", payload)
+
     def log_access_denied(
         self,
         tool_name: str,

src/aegis_gitea_mcp/server.py

@@ -430,6 +430,19 @@ class _Dispatcher:
                 record.outcome = "unknown_tool"
                 raise MCPError(types.INVALID_PARAMS, f"Unknown tool: {record.tool}")
             record.domain = entry.domain
+            # Write-ahead entry: a call whose start cannot be recorded does not run.
+            try:
+                audit.log_tool_call_started(entry.tool.name, request_id, entry.domain)
+            except Exception as exc:
+                logger.error("audit log write failed, refusing the call: %s", type(exc).__name__)
+                record.outcome = "audit_unavailable"
+                return _result(
+                    _error_payload(
+                        "audit_unavailable",
+                        "The audit log is not writable, so the call was not executed",
+                    ),
+                    is_error=True,
+                )
             try:
                 return await self._dispatch(entry, arguments, record)
             except Exception as exc: