fix(composio): answer MCP initialize locally so OpenCode can mount tools

[santhiprakash]

What changed

The connected-apps stdio bridge now answers MCP initialize itself (same shape as computer-proxy / permission-proxy) instead of forwarding that handshake as the only reply. It still POSTs initialize upstream so Composio can issue an mcp-session-id. Non-call relay failures now return a JSON-RPC error instead of a tools/call result.

Fixes #481.

Why

OpenCode/ACP mounts session/new stdio servers as type: "local". The client treats the server as failed unless initialize returns capabilities + serverInfo.

connector-proxy relayed that handshake to Composio. When the upstream URL was missing from the child env, the relay timed out, or Composio answered with a newer protocolVersion, the catch path replied:

{ "result": { "content": [{ "type": "text", "text": "connected apps are unavailable" }], "isError": true } }

That is a tools result, not an initialize result. OpenCode then logs server unavailable key=composio type=local status=failed and never exposes COMPOSIO_SEARCH_TOOLS / COMPOSIO_GET_TOOL_SCHEMAS / COMPOSIO_MULTI_EXECUTE_TOOL, even though the UI still shows Google Sheets as connected.

How it was verified

On Node 24.19.0:

pnpm exec vitest run server/connector-proxy.test.ts
# Test Files  1 passed (1)
# Tests  5 passed (5)

pnpm typecheck
# tsc -b && tsc -p tsconfig.server.json  (exit 0)

New coverage:

• initialize with no OMB_CONNECTOR_UPSTREAM_URL returns protocolVersion / capabilities / serverInfo, not {content,isError}.
• initialize with upstream still POSTs the handshake (session id + auth header) and does not echo the secret on stdout.
• tools/list still relays.
• A failed tools/list relay returns {error:{code:-32000,...}} rather than a tools result.

Deterministic before/after for the no-upstream initialize path (the old catch used textResult):

before: { result: { content: [{ type: "text", text: "connected apps are unavailable" }], isError: true } }
after:  { result: { protocolVersion: "2024-11-05", capabilities: { tools: {} }, serverInfo: { name: "openmausbot-connectors", version: "1" } } }

Screenshots (UI changes)

n/a — stdio MCP bridge only.

Checklist

• pnpm typecheck and pnpm test pass locally
• Server behavior changes come with tests (see CONTRIBUTING.md → Tests)
• No dist-server/ edits (it's build output)
• macOS-only code is platform-gated; no shell: true / cmd.exe string-building
• No secrets in logs, responses, events, or argv

The focused suite is server/connector-proxy.test.ts (5/5) plus pnpm typecheck. Full pnpm test was not rerun; this diff is confined to the connector proxy.

Problem

Connect Google Sheets through Composio, restart OpenMausBot, switch the bot to Codex/OpenCode, ask it to read the sheet. Composio tools are not mounted. Logs: WARN: server unavailable key=composio type=local status=failed.

Triage / Root cause

server/connector-proxy.ts handle() sent every method including initialize through relay(). A throw (missing OMB_CONNECTOR_UPSTREAM_URL, HTTP error, timeout) was answered with textResult(..., true) — valid for tools/call, invalid for initialize. OpenCode's local MCP client then marked composio failed and skipped tool listing.

Fix

• Answer initialize locally with the stdio-server handshake (capabilities, serverInfo), echoing the client's protocolVersion.
• Still relay initialize upstream when OMB_CONNECTOR_UPSTREAM_URL is set, so the Composio transport session is created.
• Ignore notifications/initialized.
• Use a JSON-RPC error for non-call relay failures; keep textResult for tools/call.

Verification

pnpm exec vitest run server/connector-proxy.test.ts — 5 passed. pnpm typecheck — pass. Node 24.19.0.

Notes / Risks

tools/list and tools/call still require a reachable harness/Composio upstream; this only stops a broken initialize handshake from hiding the whole server. Independent of #500 (iOS failover) and of open #498/#499. Does not change the ACP mcpServers wire shape (OpenCode's ACP adapter treats a type field as remote).

Summary by CodeRabbit

• New Features

  • Added local handling for initialization requests and notifications.
  • Added server capability and metadata information to initialization responses.
  • Added support for relaying tool listings from upstream services.
  • Added bounded fallback behavior when upstream initialization is delayed.
  • Added clearer JSON-RPC error responses when request relaying is unavailable.
  • Improved error handling while preserving readable tool-call errors and suppressing secrets.

• Tests

  • Expanded coverage for initialization, session setup, tool listing, fallback behavior, and relay failures.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📝 Walkthrough

Walkthrough

The connector proxy now returns a local MCP handshake, attempts upstream initialization for one second, relays initialized notifications and tool requests, suppresses upstream secrets, and returns method-specific errors when upstream relays fail.

Changes

MCP connector proxy

Layer / File(s)	Summary
Local MCP initialization server/connector-proxy.ts, server/connector-proxy.test.ts	The proxy builds a local MCP handshake, bounds upstream initialization to one second, forwards initialized notifications, and preserves session-header behavior without exposing secrets.
Method-specific relay errors server/connector-proxy.ts, server/connector-proxy.test.ts	Successful tools/list responses remain relayed. Tool-call failures return text error results. Other identified requests return JSON-RPC errors with code -32000. Notifications remain silent.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to cfa9c

The change makes the local MCP handshake valid while preserving upstream session setup and returns appropriate JSON-RPC errors for relay failures; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: milind-soni

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 8 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the primary change: answering MCP initialize locally so OpenCode can mount Composio tools.
Description check	✅ Passed	The description is complete and relevant. It documents the change, rationale, verification, tests, checklist status, scope, risks, and issue reference.
Linked Issues check	✅ Passed	The changes address issue #481 by returning a valid local MCP initialize response, preserving upstream session establishment, relaying tools/list and tools/call requests, and returning valid JSON-RPC …
Out of Scope Changes check	✅ Passed	The code and test changes remain within scope. They target connector-proxy MCP initialization, upstream session handling, relay error behavior, and related test coverage required by issue #481.

Full details: Linked Issues check

Explanation

The changes address issue #481 by returning a valid local MCP initialize response, preserving upstream session establishment, relaying tools/list and tools/call requests, and returning valid JSON-RPC errors for non-call relay failures. These changes support successful Composio tool mounting for Codex/OpenCode bots.

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Actionable comments posted: 1

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Inline comments:
In `@server/connector-proxy.ts`:
- Around line 155-161: Update the initialize handling around relay so a stalled
configured upstream cannot delay the local initializeResult beyond a short
initialization budget; preserve ordering by completing or abandoning upstream
initialization before relaying notifications/initialized. Add coverage for an
upstream whose POST never completes and verify the local handshake still
succeeds promptly.

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[lightcloud00]

Contributor follow-up published

The timeout repair is now available as santhiprakash/OpenMausBot#1, targeting the exact contributor branch behind upstream PR #501.

• exact head: cfa9c8286ba5fdb54fdbae7648107a47251daa94
• remote SHA readback matches
• full Node 24 fleet gate passed
• CodeRabbit is green and the contributor PR is mergeable

This bounds a stalled configured upstream MCP initialize handshake to one second while preserving initialized ordering. The merge attempt was made once and GitHub correctly denied it because lightcloud00 has read-only access to the contributor fork. The remaining action is for santhiprakash to merge the one-commit follow-up; that updates the source branch of upstream PR #501 without replacing its history.