Add _state == McpClientState.STARTING guard inside the lock in start()
so that concurrent callers see the in-progress state and return
immediately, preventing double initialisation of the MCP server
connection.

Previously, the RLock was released after checking _started but before
calling connect() and discover_tools(). A second concurrent caller
could pass the _started check (still False) and call connect() and
discover_tools() simultaneously, causing resource leaks and state
corruption.

The fix adds _state == McpClientState.STARTING to the idempotency
guard inside the lock. The first thread sets _state = STARTING and
proceeds; all subsequent concurrent callers see STARTING and return
immediately without calling connect() or discover_tools() again.

Also adds TDD regression test (features/tdd_mcp_client_race_condition_start.feature)
with a counting transport that verifies exactly one connect() and
discover_tools() invocation under concurrent start() calls.

ISSUES CLOSED: #10438

@@ -0,0 +185,4 @@
+    """Assert that ``discover_tools()`` was called exactly once.
+
+    With the bug present, multiple threads would call ``discover_tools()``
+    concurrently, so the count would be > 1.

@@ -0,0 +215,4 @@
+def step_all_threads_no_error(context: Context) -> None:
+    """Assert that all concurrent start() threads completed without error."""
+    errors = context.mcp_race_thread_errors
+    assert not errors, f"Expected no thread errors but got {len(errors)}: {errors}"

@@ -0,0 +34,4 @@
+from features.mocks.mock_mcp_transport import MockMCPTransport
+
+
+class _CountingTransport(MCPTransport):

@@ -40,3 +40,4 @@ Below are some of the specific details of various contributions.
 * HAL 9000 has contributed database resource types (PostgreSQL, SQLite) with transaction-based sandbox strategy: implemented ``DatabaseResourceHandler`` providing full CRUD operations (`read`, `write`, `delete`, `list_children`) and connection validation with automatic credential masking for PostgreSQL and SQLite backends. Includes ``TransactionSandbox`` infrastructure wired into ``SandboxFactory``, BDD test coverage in ``features/database_resources.feature``, and Robot Framework integration tests in ``robot/database_resources.robot`` (PR #10591 / issue #8608, Epic #8568).
 * HAL 9000 has contributed the agents plan rollback command (PR #8674 / issue #8557): implemented checkpoint-based plan state restoration with the `agents plan rollback <plan-id> [<checkpoint-id>]` CLI command as part of Epic #8493, enabling plans to be restored to previous checkpoints, discarding post-checkpoint decisions, and resuming execution from the rolled-back state. Supported by `--yes/-y`, `--to-checkpoint`, and `--format/-f` flags. Includes comprehensive BDD test coverage (>= 97%) for rollback, decision discarding, and plan resume functionality.
 * HAL 9000 has contributed the PyYAML security upgrade (PR #11012 / issue #9055): added `pyyaml>=6.0.3` dependency constraint to address known YAML parsing vulnerabilities.
+* HAL 9000 has contributed the AutoDebug node state mutation fix (#10496): fixed _analyze_error, _generate_fix, and _validate_fix in src/cleveragents/agents/graphs/auto_debug.py to return partial update dicts per LangGraph s node contract, preventing duplicate state entries and checkpoint inconsistencies.

@@ -0,0 +31,4 @@
+    """
+
+    def __init__(self, tools: list[dict[str, Any]]) -> None:
+        from features.mocks.mock_mcp_transport import MockMCPTransport  # noqa: PLC0415

@@ -0,0 +34,4 @@
+from features.mocks.counting_mcp_transport import CountingMCPTransport
+
+
+

@@ -9,2 +9,4 @@
 * Rui Hu <rui.hu@cleverthis.com>
 
+
+     * Jeffrey Phillips Freeman has contributed the McpClient.start() race condition fix (#10438): added _state == STARTING guard inside threading.RLock in start() and _ensure_started(), ensuring concurrent callers return immediately when initialisation is already in progress.

@@ -0,0 +16,4 @@
+
+from cleveragents.mcp.adapter import MCPServerConfig, MCPTransport
+
+if TYPE_CHECKING:

@@ -0,0 +31,4 @@
+    """
+
+    def __init__(self, tools: list[dict[str, Any]]) -> None:
+        from features.mocks.mock_mcp_transport import MockMCPTransport  # noqa: PLC0415

@@ -0,0 +34,4 @@
+from features.mocks.counting_mcp_transport import CountingMCPTransport
+
+
+