fix(acp): load global MCP config in kimi acp server

[nankingjing]

Summary

kimi acp (the multi-session ACP server) never loads the user's globally-configured MCP servers, so ACP clients (Zed, JetBrains AI Assistant, orchestrators) only ever see the built-in tools — a parity gap with interactive kimi, which does load them. Fixes #2464.

Root cause

Interactive kimi seeds its MCP configs from the global config file (<share>/mcp.json) when no --mcp-config-file is passed (cli/__init__.py):

if not file_configs:
    default_mcp_file = get_global_mcp_config_file()
    if default_mcp_file.exists():
        file_configs.append(default_mcp_file)

The ACP server path (ACPServer.new_session / _setup_session) only ever built its config from the servers the ACP client passed in the request:

mcp_config = acp_mcp_servers_to_mcp_config(mcp_servers or [])
cli_instance = await KimiCLI.create(session, mcp_configs=[mcp_config], ui_mode="acp")

When the client sends no mcp_servers (the common case), acp_mcp_servers_to_mcp_config([]) returns an empty MCPConfig, so no MCP servers are ever connected. The globally-configured servers were never consulted, and the callback-level --mcp-config-file option is skipped once the acp subcommand is invoked.

Fix

Introduce _build_mcp_configs(), which merges the global MCP config (via the same get_global_mcp_config_file() used by interactive mode) with any servers the ACP client supplied, and use it in both new_session and _setup_session. KimiToolset.load_mcp_tools already iterates over a list of configs, so passing multiple MCPConfigs merges their servers; client-provided servers take precedence on name conflicts (registered last).

A malformed/unreadable global config is logged and skipped (_load_global_mcp_config returns None) so a broken file cannot abort ACP session creation.

Tests

Added tests/acp/test_server_mcp_config.py covering:

• missing global config file -> None
• malformed global config -> ignored, no raise
• global servers appear in the assembled configs
• no global config + no client servers -> no MCP servers

Verification

Verified by reading the interactive vs. ACP code paths, KimiCLI.create / load_agent / KimiToolset.load_mcp_tools signatures and merge behavior, and MCPConfig usage across the codebase. Syntax-checked both files locally with py_compile. Not executed (no test run available in this environment).

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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