Tmux MCP Server

A Bun/Node-compatible TypeScript toolkit that exposes tmux pane context and logs through the Model Context Protocol (MCP). It lets MCP-compatible assistants inspect and troubleshoot your live tmux session.

Requirements

• Node.js 20+
• Bun 1.2+
• tmux installed on the host machine

Configure MCP Agents

MCP-capable tools should launch the server themselves. Configure each agent to run bunx @yuki-yano/tmux-mcp@latest (or npx @yuki-yano/tmux-mcp@latest) as a command provider; there is no need to start the server manually.

MCP Tool Reference

All tools live under the tmux namespace. Validation is handled with Zod; requests outside these shapes are rejected and surface as tool call failed errors.

tmux.describe-context

• Purpose: identify the most relevant tmux pane and provide ranked alternatives.
• Request fields (optional):
  • paneHint: string matched against pane id/title/session/window/command.
  • tags: string[] placeholder for future tagged panes (accepted but unused).
• Response: { primaryPane, candidates } where each pane includes { id, title, session, window, command? }.

tmux.fetch-log

• Purpose: take a one-off log snapshot from a tmux pane or file.
• Required field: mode must be "capture" or "file".
• When to use: choose mode: "capture" for panes, mode: "file" for local log files. Use tmux.stream-log for anything that needs to keep streaming.

Capture mode (pane snapshot)

• paneId — tmux pane id (for example "%305").
• lines — positive integer ≤ 10_000; defaults to TMUX_CONTEXT_CAPTURE_LINES (2000 if unset).
• filters — optional timeRange, keywords, levels filters.
• maskPatterns — strings or regex fragments replaced with ***.
• summary — include { totalLines, errorCount, firstErrorLine? }.

{ "mode": "capture", "paneId": "%305", "lines": 400 }

File mode (log tail)

• filePath — absolute path to the log file; response exposes a readable stream.

{ "mode": "file", "filePath": "/var/log/app.log" }

Info: Passing mode: "tail" or mode: "stream" triggers a validation error. For live streaming call tmux.stream-log.

tmux.stream-log

• Purpose: manage a live pipe-pane stream.
• Start: { "mode": "stream", "paneId": "%1" } (the optional action: "start" is ignored).
• Stop: { "mode": "stream", "action": "stop", "streamId": "...", "stopToken": "..." } using the id and stopToken returned when you started the stream.
• Responses: { id, stopToken } for both start and stop.
• Errors: paneId is required, Stream not found: ..., Invalid stop token.

Typical Failure Scenarios

• Missing required fields (paneId is required, filePath is required).
• Unsupported mode strings supplied to fetch-log (the error message includes the valid options).
• Using a stale or incorrect stopToken when stopping a stream.

Example Calls

tmux.describe-context { "paneHint": "%3" }

// Start then stop a live stream (generic MCP JSON-RPC)
{
  "name": "tmux.stream-log",
  "arguments": { "mode": "stream", "paneId": "%1" }
}
{
  "name": "tmux.stream-log",
  "arguments": { "mode": "stream", "action": "stop", "streamId": "…", "stopToken": "…" }
}

Optional Local Installation

If you need to bundle the server with other tooling:

npm install @yuki-yano/tmux-mcp
# or
bun add @yuki-yano/tmux-mcp

Once installed locally, the executable name is tmux-mcp, so npx tmux-mcp or bunx tmux-mcp will resolve to the same CLI.

Configuration

Environment variables tweak runtime behaviour:

| Variable | Description | | --- | --- | | TMUX_CONTEXT_TMUX_PATH | Absolute path to the tmux binary (falls back to $TMUX or tmux). | | TMUX_CONTEXT_CAPTURE_LINES | Default capture-pane line count (defaults to 2000). | | TMUX_CONTEXT_AUDIT_PATH | File destination for JSON Lines audit logs (defaults to STDOUT). | | NODE_ENV | When test, suppresses info logs for cleaner test output. |

Developer Notes (for contributors)

• Source lives in src/ and follows a functional style (no classes or interfaces).
• src/index.ts wires dependencies; src/sdk-server.ts registers MCP tools via @modelcontextprotocol/sdk.
• Supporting modules handle tmux integration, log formatting, file tailing, configuration, and auditing.
• Tests in tests/ mock external processes/files so they run without tmux.
• bun run ci executes formatting, type checks, lint, and tests before publishing.