fix: force kill MCP server processes on dispose to prevent orphan processes

[hendem]

Relates to #3013, #7261

Summary

• Track local MCP server transports to enable forceful process termination
• Add forceKillProcess() helper for cross-platform process termination
• Force kill remaining MCP processes on dispose after graceful close timeout
• Check if process is alive before attempting force kill

Problem

The MCP SDK's client.close() uses AbortController.abort() which may not work reliably for:

• Docker containers without --init flag
• Hung or unresponsive processes
• Processes that don't handle signals properly

Solution

Defensive fallback that only triggers if graceful close doesn't work:

1. Try graceful client.close() with 2 second timeout
2. Check if process is still alive
3. Force kill only if still running

Testing

Added tests in test/mcp/process-cleanup.test.ts.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[Copilot]

Pull request overview

This pull request introduces force-kill process cleanup for MCP (Model Context Protocol) server processes to prevent orphan processes from accumulating when graceful shutdown fails. The change tracks local MCP server transports and forcefully terminates their processes after attempting graceful closure, addressing a memory leak issue where ~300MB+ processes could persist after OpenCode exits.

Key changes:

• Added forceKillProcess() helper with platform-specific process termination (taskkill on Windows, SIGKILL on Unix)
• Introduced LocalTransportInfo type to track StdioClientTransport instances alongside MCP clients
• Modified dispose and disconnect logic to force-kill processes after 2-second graceful close timeout

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
packages/opencode/src/mcp/index.ts	Core implementation: adds LocalTransportInfo tracking, forceKillProcess helper, and force-kill logic in dispose/disconnect flows
packages/opencode/test/mcp/process-cleanup.test.ts	Unit tests verifying PID tracking for local transports and client.close() invocation during disconnect

Comments suppressed due to low confidence (1)

packages/opencode/src/mcp/index.ts:529

• When listTools fails during client creation, the code closes the MCP client but doesn't force kill the local process. If the graceful close fails (as described in the PR description), this could leave orphan processes. Consider adding force kill logic here as well, similar to the disconnect function, by checking if localTransport is defined and calling forceKillProcess after the failed close attempt.

    if (!result) {
      await mcpClient.close().catch((error) => {
        log.error("Failed to close MCP client", {
          error,
        })
      })
      status = {
        status: "failed",
        error: "Failed to get tools",
      }
      return {
        mcpClient: undefined,
        localTransport: undefined,
        status: {
          status: "failed" as const,
          error: "Failed to get tools",
        },
      }

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

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[github-actions]

Thanks for your contribution!

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