bug: MCP server - SSE connection from Claude Code CLI drops after ≈ 5 min idle – “Body Timeout Error”

[mulyoved]

Provide environment information

System:
OS: Linux 6.1 Debian GNU/Linux 12 (bookworm) 12 (bookworm)
CPU: (8) x64 Intel(R) Xeon(R) CPU @ 2.80GHz
Memory: 28.92 GB / 31.35 GB
Container: Yes
Shell: 5.2.15 - /bin/bash
Binaries:
Node: 22.13.0 - ~/miniforge3/bin/node
Yarn: 1.22.22 - /usr/bin/yarn
npm: 10.9.2 - ~/miniforge3/bin/npm

Describe the bug

When Claude Code CLI connects to a local Trigger.dev MCP server, the Server-Sent Events (SSE) stream is closed after ~5 minutes of inactivity.
Once closed, every MCP call fails until the Claude CLI process is restarted (Trigger.dev server itself does not need a restart).

MCP server "triggerdev" Error: SSE error: TypeError: terminated: Body Timeout Error

Expected
The SSE control channel should stay open indefinitely so the CLI can send tasks even after long idle periods.

Likely cause
Most HTTP servers/proxies close an SSE response that stays silent for several minutes. Because the Trigger.dev MCP endpoint sends no keep-alive heartbeat while idle, the connection hits this idle “body timeout” and terminates.

Reproduction repo

None

To reproduce

Start Trigger.dev MCP server locally

trigger dev --mcp # or equivalent command

In another terminal, run

claude --mcp-debug

Execute any MCP command → it succeeds.

Leave the session idle for ~5 minutes.

Run another MCP command.
Actual: CLI logs the error above and the command fails.
Work-around: Restarting claude --mcp-debug restores functionality.

Additional information

Proposed fix: Send a periodic SSE heartbeat/keep-alive (e.g. : keepalive\n\n) every ≤ 30 s so the stream never appears idle.

Related discussions & bugs

Source | Note -- | -- anthropics/claude-code #424 | Long MCP tasks hit timeout; mentions same Body Timeout and need for heartbeats modelcontextprotocol/typescript-sdk #270 | SSE closed after 300 s idle; fixed by adding keep-alive ping Cursor Community thread (Apr 2025) | Users report identical error; resolved by sending : keepalive comments Figma MCP Server issue #41 | Maintainers confirm adding SSE ping prevents Body Timeout disconnects