mcp-opencode

An MCP server that lets an AI coding agent (Claude Code, Codex, or any MCP client) delegate implementation work to the OpenCode CLI — choosing an explicit provider + model on every call.

Use it to orchestrate with one model while offloading the actual code-writing to another: plan in Claude, implement with GLM 5.2, Kimi, DeepSeek, a local Ollama model, or anything else OpenCode can reach.

Provider-agnostic. This server contains no provider-specific logic. It passes your provider/model string straight to opencode run -m, so it works with every provider OpenCode supports (75+ via models.dev, plus local models). Whatever you've authenticated in OpenCode, you can use here.

Why

• Model per task. A cheap model for mechanical edits, a strong one for hard changes — decided per call, not baked into config.

• Real cost/token reporting returned with every run.

• Multi-turn. Continue a session to iterate on the same working tree.

• Safe by construction. cwd is confined to an allowlist; the child process tree is killed cleanly on timeout/abort/cost-cap; secrets are redacted from anything echoed back.

Related MCP server: AgentSpawnMCP

Prerequisites

• Node.js ≥ 20

• The OpenCode CLI installed and on PATH, with at least one provider authenticated (opencode auth login). Run opencode models to see what's available to you.

Register

No install step needed — npx fetches and runs the published package.

Claude Code:

claude mcp add -s user opencode \
  -e OPENCODE_MCP_ROOTS="$HOME/Projects" \
  -- npx -y mcp-opencode

Codex:

codex mcp add opencode \
  --env OPENCODE_MCP_ROOTS="$HOME/Projects" \
  -- npx -y mcp-opencode

Restart the client (or run claude mcp list / codex mcp list) to confirm it connects. The tools appear as opencode_run, opencode_reply, opencode_models.

Build from source (for development)

git clone https://github.com/shreeraman96/mcp-opencode.git
cd mcp-opencode
npm install
npm run build
npm test          # unit tests
npm run smoke     # optional: live test against a real free OpenCode model

Then register with node /absolute/path/to/mcp-opencode/dist/index.js instead of the npx command above.

Tools

opencode_run — start a new session

Returns status, sessionID, model, elapsed time, tokens/cost, a git-derived changed-files summary (when cwd is a repo), and the assistant output.

opencode_reply — continue a session

Takes a sessionID (ses_…) from a prior run plus a new prompt, model, cwd, and agent. model is required on every call — there is no silent inheritance from the original run, by design.

opencode_models

No input. Runs opencode models and returns the available list.

Example (Claude Code)

Delegate to OpenCode: call opencode_run with model fireworks-ai/accounts/fireworks/models/glm-5p2, cwd ~/Projects/myapp, agent build, and prompt "add input validation to routes/user.ts".

Swap the model string for anthropic/claude-sonnet-4-5, openai/gpt-oss-120b, opencode/big-pickle (free), or any local model — nothing else changes.

Configuration

cwd allowlist

cwd is resolved with fs.realpath (symlinks followed) and must land inside one of the OPENCODE_MCP_ROOTS directories. Requests outside the allowlist are rejected before opencode is ever spawned.

Permission model

OpenCode's build agent already runs edit/bash/webfetch non-interactively; the plan agent is read-only. This server relies on those built-in agent defaults and does not inject a custom permission config.

Note: passing a custom permission block via OPENCODE_CONFIG was found to hang opencode run in a non-TTY environment (an unanswerable ask prompt), so that path is deliberately avoided. See src/policy.ts.

--auto (OpenCode's "auto-approve anything not explicitly denied", which the CLI itself flags as dangerous) is off by default and only added when you set OPENCODE_MCP_ALLOW_AUTO=1 and the call uses agent: 'build'.

How it works

• src/run.ts spawns opencode detached in its own process group, so the whole subprocess tree is killed as a unit (SIGTERM → 5s grace → SIGKILL) on timeout, client abort, or a maxCostUsd breach. Process exit is treated as the authoritative completion signal.

• src/parse.ts streams the --format json output line-by-line without ever buffering the raw stream; assistant text is capped to head(40k)+tail(10k) chars past 50k total.

• src/queue.ts serializes runs that share the same resolved cwd; different working trees run concurrently.

• src/policy.ts holds the cwd allowlist, model/session validation, secret redaction, and error classification.

For long runs, the server emits MCP progress notifications every 15s (when the client supplies a progress token), which resets the client's idle timeout.

License

MIT