opencode-subagent-mcp

Run Claude Code subagents on cheaper opencode models — for example opencode-go/deepseek-v4.1-flash (DeepSeek) from an opencode Go subscription — while Claude Code itself keeps talking to Anthropic directly. Delegate searches, refactors, bug fixes, tests and research to a model that costs a fraction of Opus or Sonnet, and keep the tools you already use: background agents, resume via send_message, worktree isolation, .claude/agents definitions, permission prompts and structured output.

It is a stdio MCP server. Your main Claude Code session is not proxied or routed anywhere; the server only runs the subagents you delegate to it, on a private opencode serve instance it starts itself.

Install

Requires Node 22+, git, and the opencode CLI logged in to the providers you want (opencode auth login).

As a Claude Code plugin (also adds a skill that tells Claude when to delegate to opencode):

claude plugin marketplace add sebstaq/opencode-subagent-mcp
claude plugin install opencode-subagent-mcp@sebstaq-opencode

Or as a plain MCP server:

claude mcp add -s user opencode -- npx -y [email protected]

What it runs and sends

• It starts a private opencode serve process on a random localhost port with a random password, and stops it when Claude Code exits. The password is generated for each run and only used between this server and that local process. The process inherits your environment so opencode can use the provider logins and API keys you already configured for it; this server never reads, stores or sends those credentials itself.
• The prompts you delegate, and the files and command output the subagent reads, go to the model provider you choose through opencode (by default opencode Go), under that provider's data retention terms. opencode keeps session history in its local database on your machine. Nothing else is sent anywhere; the server has no telemetry and makes no other network calls.
• It reads ~/.claude/settings.json, the project's .claude/settings.json and .claude/settings.local.json, and .claude/agents/*.md (user and project) to mirror your permission rules and agent definitions, and ~/.config/opencode-subagent-mcp/config.json if present.
• With isolation: "worktree" it creates git worktrees under the project's .claude/worktrees/ and removes them when they have no changes.

This is an independent project, not affiliated with Anthropic or the opencode team.

Tools

| Tool | Native equivalent | What it does | | -------------- | ---------------------------------- | --------------------------------------------------------------------- | | agent | Agent tool | Run a subagent; returns its final report, usage and worktree outcome | | send_message | SendMessage | Continue a finished agent with its full history; also after a restart | | wait | background completion notification | Collect a run_in_background agent (optionally with a timeout) | | stop | TaskStop | Abort a running agent and return what it produced | | list | /agents | This session's agents, Claude agent definitions and opencode agents |

An agent_id keeps working after the MCP server or Claude Code restarts: wait and stop return what happened to it, and send_message continues it. Agents from before a restart do not appear in list until their id is used again, but they still exist in opencode's local session store.

agent parameters: description, prompt, subagent_type, model, isolation: "worktree", permission_mode, tools, disallowed_tools, max_turns, effort, output_schema, run_in_background, cwd.

Parity with native subagents

| Native behaviour | Here | | ---------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | Fresh context, only the final message comes back | Same. Long output is truncated (maxResultChars) with the full text written to a file | | Runs in the project directory | Same (cwd from MCP roots, then CLAUDE_PROJECT_DIR, then the server's cwd) | | isolation: worktree | Same layout (.claude/worktrees/<name>, branch worktree-<name>, based on the default branch). Removed when unchanged, kept with commit/file summary otherwise. Outside paths are denied | | Permission prompts surface in the main session | opencode ask rules are shown as MCP elicitation dialogs (allow once / always / deny, with optional feedback) | | Permission modes | default, acceptEdits, auto, bypassPermissions, plan mapped to opencode rules; your Claude permissions.allow/ask/deny from user, project and local settings apply | | Background agents with completion notification | Claude Code moves long MCP calls to the background automatically and notifies when they finish; run_in_background + wait for explicit control | | Resume with full history | send_message (also works for agents from earlier sessions or after a restart, since opencode persists them) | | .claude/agents/*.md definitions | Used via subagent_type: prompt, tools, disallowedTools, permissionMode, maxTurns, effort, isolation. model applies only when it is an opencode provider/model | | maxTurns returns partial output | Same; status max_turns, resumable | | Progress in the UI | Tool calls are sent as MCP progress notifications | | Subagents cannot spawn subagents or ask the user questions | opencode's task and question tools are disabled | | Structured output | output_schema (JSON Schema) → opencode structured output, returned as structuredContent |

Known gaps: agents do not appear in Claude Code's /tasks agent view; there is no fork-with-parent-context; the Workflow tool's agent() cannot target them; auto mode has no safety classifier (it allows everything, including paths outside the project, except rules you configured and a fixed list of destructive commands that ask: rm -r/-rf, git push --force, git reset --hard, git clean -f, git restore/git checkout --, curl | sh, sudo, chmod -R/chown -R, dd, mkfs, npm/pnpm publish; opencode matches each command in a chain separately); the parent's permission mode is not visible to MCP servers, so the default comes from config; hooks, skills preloading, memory and per-agent MCP servers are not mapped.

Steering Claude

Claude Code picks between its native Agent tool and this one on its own, so routing is unpredictable. To make opencode the default for delegated work that is cheap to verify, paste the snippet from docs/claude-md-snippet.md into your global ~/.claude/CLAUDE.md.

Configuration

Optional ~/.config/opencode-subagent-mcp/config.json (or $OPENCODE_SUBAGENT_CONFIG):

{
  "defaultModel": "opencode-go/deepseek-v4.1-flash",
  "defaultPermissionMode": "auto",
  "pure": true,
  "opencodeBin": "opencode",
  "maxConcurrent": 8,
  "maxResultChars": 80000
}

OPENCODE_SUBAGENT_MODEL and OPENCODE_SUBAGENT_MODE override the first two. pure starts opencode without external plugins.

How it works

On first use the server starts opencode serve on a random loopback port with a random password, subscribes to its event stream, and drives one opencode session per agent (agent id = session id). Permission requests from opencode are answered through MCP elicitation. The opencode process is stopped with the MCP server; leftovers from crashed servers are reaped on the next start.

Development

pnpm check   # typecheck, lint, format check, unit tests
pnpm smoke [provider/model]   # end-to-end run against a real model in a temp repo

License

MIT