Claude Code MCP First-Round Cold Start Issue
Top-Gas-1422 · reddit · 2026-07-15
While debugging MCP testing tools, the author discovered that Claude Code gives MCP servers a startup window of only about 1–2 seconds.
Observed Behavior
- initialize completes in about 0.72 seconds, but tools aren't fully dispatched until around 2.3 seconds.
- The first conversation turn is constructed without any MCP tools available, leaving the server marked as pending.
- There are no errors or warnings during this process; the model simply falls back to a standard response.
Impact
- Any server with a slow cold start is affected, such as those using Python virtual environments, Docker, heavy dependencies, or TypeScript dev compilation chains.
- This results in the initial request effectively being a "tool-less response," which is hard for both users and developers to notice.
Recommendations
- Make initialize return as quickly as possible, ideally in under 1 second.
- Optimize packaging and deployment, or delay loading heavy dependencies until after the handshake.
- The author notes that MCPTIMEOUT doesn't seem to extend this specific window and plans to file an issue in the repository.
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