HTTP MCP client gives up after ~15 s of connection-refused; session loses server until manual /mcp

Preflight

Searched existing issues. #55228 describes the same runtime behaviour but was auto-closed as stale and locked (not fixed); #90494 (open) covers the related startup-ordering case. Filing fresh per the bot's guidance.

What's Wrong?

For an HTTP (streamable-http) MCP server on localhost, Claude Code's MCP client gives up reconnecting after roughly 15 seconds of connection-refused. The log shows:

Max reconnection attempts (5) reached, giving up

After that the session has no access to that server until the user manually runs /mcp and reconnects. Nothing retries on the next tool use.

A session that starts while the port is refused behaves the same way: it retries only 3 times, then has no tools from that server for the rest of the session.

Fleet impact: with many concurrent Claude Code sessions sharing one local MCP server, a single server restart longer than ~15 s (deploy, container recreate, upgrade) strands every session at once. Each one needs a manual /mcp reconnect, and unattended or background sessions silently lose the server's tools for good.

What Should Happen?

Any of:

• a configurable reconnect budget (max attempts, initial delay, max delay) per server in .mcp.json / claude mcp add;
• retry with capped exponential backoff, indefinitely, for http transports;
• automatic reconnect attempt on the next tool call to a server that is marked failed.

Steps to Reproduce

1. Run any local HTTP MCP server, e.g. http://127.0.0.1:8080/mcp, and add it: claude mcp add --transport http example http://127.0.0.1:8080/mcp.
2. Start claude; confirm the server's tools work.
3. Stop the server (port now refuses connections) and wait about 20 s.
4. Restart the server on the same port.
5. Tools from the server remain unavailable. Only /mcp -> reconnect restores them.
6. Variant: stop the server first, start claude, start the server 20 s later. Tools never appear (3 retries only).

Error Messages/Logs

Max reconnection attempts (5) reached, giving up

Environment

• Claude Code 2.1.287
• macOS (Darwin 25.x)
• Transport: http / streamable-http, localhost
• Regression: unknown