fix(hooks): address Copilot review feedback on #1021

- _output(): use sys.modules.get() instead of unconditional import to
  avoid triggering mcp_server's stdout redirect as a side effect
- _output(): write-all loop for os.write() to handle partial writes and
  EINTR; fall back to sys.stdout.buffer on OSError
- _output() docstring: remove inaccurate _save_diary_direct reference
- stop_hook_active guard: narrow except to ImportError/AttributeError,
  default silent_guard=False (safe: preserves block-mode loop prevention
  when config load fails) and log a warning instead of silently changing
  behavior
- tests: two new regression tests covering the real-stdout-fd path and
  the fd-1 fallback path

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mempalace/hooks_cli.py

@@ -134,24 +134,35 @@ def _log(message: str):
 
 
 def _output(data: dict):
-    """Print JSON to the real stdout, even if mcp_server has hijacked sys.stdout.
+    """Print JSON to stdout without importing modules that may redirect streams.
 
-    mempalace.mcp_server redirects stdout → stderr at module import (fd and
+    If mempalace.mcp_server is already loaded, reuse its saved real stdout fd.
-    sys-level) to protect the MCP stdio protocol from ChromaDB's C-level
+    Otherwise, write directly to fd 1 so hook responses still go to stdout even
-    prints. Silent-save imports it transitively via _save_diary_direct, so
+    if sys.stdout has been redirected elsewhere.
-    sys.stdout is stderr by the time we get here. Claude Code reads hook
-    output from fd 1, so we write there directly using the saved fd.
     """
-    payload = json.dumps(data, indent=2, ensure_ascii=False) + "\n"
+    payload = (json.dumps(data, indent=2, ensure_ascii=False) + "\n").encode("utf-8")
+
+    real_stdout_fd: int | None = None
+    mcp_mod = sys.modules.get("mempalace.mcp_server") or sys.modules.get(
+        f"{__package__}.mcp_server" if __package__ else "mcp_server"
+    )
+    if mcp_mod is not None:
+        real_stdout_fd = getattr(mcp_mod, "_REAL_STDOUT_FD", None)
+
+    fd = real_stdout_fd if real_stdout_fd is not None else 1
+    offset = 0
     try:
-        from .mcp_server import _REAL_STDOUT_FD
+        while offset < len(payload):
-        if _REAL_STDOUT_FD is not None:
+            try:
-            os.write(_REAL_STDOUT_FD, payload.encode("utf-8"))
+                offset += os.write(fd, payload[offset:])
-            return
+            except InterruptedError:
-    except Exception:
+                continue
+        return
+    except OSError:
         pass
-    sys.stdout.write(payload)
+
-    sys.stdout.flush()
+    sys.stdout.buffer.write(payload)
+    sys.stdout.buffer.flush()
 
 
 def _get_mine_dir(transcript_path: str = "") -> str:
@@ -230,11 +241,16 @@ def hook_stop(data: dict, harness: str):
     # no loop to prevent — and Claude Code's plugin dispatch sets this flag on every
     # fire after the first, which would otherwise suppress all subsequent auto-saves.
     if str(stop_hook_active).lower() in ("true", "1", "yes"):
+        silent_guard = False
         try:
             from .config import MempalaceConfig
-            silent_guard = MempalaceConfig().hook_silent_save
+        except ImportError as exc:
-        except Exception:
+            _log(f"WARNING: could not import MempalaceConfig for stop guard: {exc}; preserving block-mode guard")
-            silent_guard = True
+        else:
+            try:
+                silent_guard = MempalaceConfig().hook_silent_save
+            except AttributeError as exc:
+                _log(f"WARNING: could not read hook_silent_save: {exc}; preserving block-mode guard")
         if not silent_guard:
             _output({})
             return

tests/test_hooks_cli.py

@@ -218,6 +218,66 @@ def test_precompact_allows(tmp_path):
 # --- _log ---
 
 
+def test_output_writes_to_real_stdout_fd_when_mcp_server_loaded():
+    """_output() must reach fd 1 even when mcp_server has redirected sys.stdout."""
+    import types
+
+    fake_module = types.ModuleType("mempalace.mcp_server")
+
+    read_fd, write_fd = os.pipe()
+    try:
+        fake_module._REAL_STDOUT_FD = write_fd
+        with patch.dict("sys.modules", {"mempalace.mcp_server": fake_module}):
+            from mempalace.hooks_cli import _output
+
+            _output({"systemMessage": "test"})
+
+        os.close(write_fd)
+        written = b""
+        while True:
+            chunk = os.read(read_fd, 4096)
+            if not chunk:
+                break
+            written += chunk
+    finally:
+        os.close(read_fd)
+
+    data = json.loads(written.decode())
+    assert data["systemMessage"] == "test"
+
+
+def test_output_falls_back_to_fd1_when_mcp_server_absent():
+    """_output() writes to fd 1 directly when mcp_server is not loaded."""
+    read_fd, write_fd = os.pipe()
+    try:
+        orig_fd1 = os.dup(1)
+        os.dup2(write_fd, 1)
+        os.close(write_fd)
+        try:
+            modules_without_mcp = {k: v for k, v in __import__("sys").modules.items()
+                                    if "mcp_server" not in k}
+            with patch.dict("sys.modules", modules_without_mcp, clear=True):
+                from mempalace.hooks_cli import _output
+                _output({"continue": True})
+        finally:
+            os.dup2(orig_fd1, 1)
+            os.close(orig_fd1)
+    except Exception:
+        os.close(read_fd)
+        raise
+
+    written = b""
+    while True:
+        chunk = os.read(read_fd, 4096)
+        if not chunk:
+            break
+        written += chunk
+    os.close(read_fd)
+
+    data = json.loads(written.decode())
+    assert data["continue"] is True
+
+
 def test_log_writes_to_hook_log(tmp_path):
     with patch("mempalace.hooks_cli.STATE_DIR", tmp_path):
         _log("test message")