fix: route MCP server log notifications to loguru instead of TUI

[he-yufeng]

Problem

MCP servers (e.g. SearXNG) send log notifications on each request. fastmcp.Client defaults to default_log_handler, which uses RichHandler(stderr=True) — these messages end up dumped into the TUI:

[03/28/26 08:29:23] INFO     Server log: meta=None level='info' logger=None data={'message': 'MCP SearXNG Server v0.10.0 connected via STDIO'}

Root Cause

fastmcp/client/logging.py has a default_log_handler that routes MCP LoggingMessageNotification through Python's standard logging module with a RichHandler targeting stderr. When kimi-cli creates fastmcp.Client(MCPConfig(...)) without specifying log_handler, this default kicks in and the messages bypass loguru entirely.

Fix

Pass a custom log_handler to fastmcp.Client that routes MCP server log notifications through kimi-cli's loguru logger at DEBUG level. The messages still go to kimi.log for debugging, but no longer pollute the TUI.

The handler also properly extracts the message field from the notification data (SearXNG uses data.message, not data.msg), avoiding the raw str(message) fallback that produced the ugly meta=None level='info' ... output.

Fixes #1624

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[devin-ai-integration]

Devin Review found 1 potential issue.

View 2 additional findings in Devin Review.

[devin-ai-integration]

🔴 AttributeError when MCP server sends non-dict log data

The _mcp_log_handler calls data.get("message") on message.data, but per the MCP spec, data is typed as Any and can be any JSON-serializable value — including a plain string, number, or list. If an MCP server sends a log notification with a string data (e.g. "Server started"), calling .get() on it raises AttributeError: 'str' object has no attribute 'get'. This exception propagates up from mcp.client.session:_received_notification (line 431 of mcp/client/session.py) and can crash the MCP session, potentially disconnecting the server.

Suggested fix

Check if data is a dict before calling .get():

data = message.data
if isinstance(data, dict):
    msg = data.get("message") or data.get("msg") or str(data)
else:
    msg = str(data)

Suggested change

	data = message.data
	msg = data.get("message") or data.get("msg") or str(data)
	data = message.data
	msg = data.get("message") or data.get("msg") or str(data) if isinstance(data, dict) else str(data)

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Handle non-object MCP log payloads safely

The new _mcp_log_handler assumes message.data is a mapping and calls .get(...), but MCP log notification payloads can be arbitrary JSON values (for example a plain string or null). In those cases this line raises AttributeError, which can propagate out of the notification callback and disrupt MCP client handling for servers that emit non-object log payloads. Add a type guard (e.g., isinstance(data, dict)) before using .get, and fall back to str(data) otherwise.

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