hanzo-mcp 0.15.8: require hanzoai>=2.2.1, never silence stderr

Floor hanzoai at 2.2.1 — the first release that actually ships
hanzoai.protocols, which permissions.py imports.

Drop the stderr→devnull redirect in stdio mode. The MCP stdio protocol
rides stdout alone; stderr is the channel clients log for diagnostics.
Silencing it turned the missing-module crash into a zero-byte mystery —
the client log literally suggests printing to stderr while the server
was throwing tracebacks into devnull. Run-loop failures also log with
exc_info so the traceback reaches the client log.

pkg/hanzo-mcp/hanzo_mcp/cli.py

@@ -83,10 +83,9 @@ def main() -> None:
             handlers=[],  # No handlers for stdio to prevent protocol corruption
         )
 
-        # Redirect stderr to devnull for stdio transport to prevent any output
-        # Store handles for proper cleanup to avoid resource leaks
-        _stderr_devnull = open(os.devnull, "w")
-        sys.stderr = _stderr_devnull
+        # stderr stays attached: the stdio protocol rides stdout only, and MCP
+        # clients capture stderr for diagnostics. Silencing it hides startup
+        # tracebacks and turns any crash into an undiagnosable failure.
 
         # Suppress stdout during potentially noisy imports unless user requested help/version
         _stdout_devnull = None
@@ -371,8 +370,8 @@ def main() -> None:
             pass
         sys.stdout = original_stdout
 
-    # Note: We intentionally keep stderr redirected to devnull for stdio transport
-    # to prevent any library noise from corrupting the protocol
+    # stderr is never redirected: it cannot corrupt the stdio protocol and is
+    # the only channel where startup failures are visible to MCP clients
 
     # Parse timeout arguments with human-readable format support
     command_timeout = _parse_timeout_arg(str(args.command_timeout))
@@ -556,7 +555,7 @@ def main() -> None:
             logger.info("\nShutting down...")
         sys.exit(0)
     except Exception as e:
-        logger.error(f"Server error: {e}")
+        logger.error(f"Server error: {e}", exc_info=True)
         sys.exit(1)
 
 

pkg/hanzo-mcp/pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "hanzo-mcp"
-version = "0.15.7"
+version = "0.15.8"
 description = "The Zen of Hanzo MCP: One server to rule them all. The ultimate MCP that orchestrates all others."
 readme = "README.md"
 requires-python = ">=3.12"
@@ -18,7 +18,8 @@ classifiers = [
 keywords = ["mcp", "claude", "hanzo", "code", "agent"]
 dependencies = [
     # Hanzo AI core SDK (canonical types, config, session, MCP client)
-    "hanzoai>=2.2.0",
+    # 2.2.1 is the first release shipping hanzoai.protocols (permissions.py imports it)
+    "hanzoai>=2.2.1",
     # Core MCP dependencies
     "mcp>=1.25.0",
     "fastmcp>=2.14.4",