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Title: feat(mcp): reuse warm connections for tool execution and discovery by waleedlatif1 · Pull Request #5760 · simstudioai/sim · GitHub

Open Graph Title: feat(mcp): reuse warm connections for tool execution and discovery by waleedlatif1 · Pull Request #5760 · simstudioai/sim

X Title: feat(mcp): reuse warm connections for tool execution and discovery by waleedlatif1 · Pull Request #5760 · simstudioai/sim

Description: Summary Adds a warm MCP connection pool so tool execution and discovery reuse a live connection per server instead of connecting, initializing, and tearing down on every call (the connect-per-operation pattern behind the systemic -32001 request timeouts) One warm connection per server, keyed by server id; concurrent requests multiplex over the single transport (verified against the MCP SDK, LibreChat, Cline, VS Code) Single-flight creation (concurrent misses share one connect), 60s liveness ping-cache, and eviction on config change, max age (re-resolves the pinned SSRF IP), idle timeout, transport close, and session error Wires all four connect-per-op sites through one withServerClient seam; calls carrying per-request headers bypass the pool (can't share a connection under different headers) Reconnect stays demand-driven via the callers' existing retry — no background reconnect loop. On by default, no flag Type of Change New feature Testing Added connection-pool.test.ts (12) and service-pool.test.ts (3); full MCP suite green (347 tests), tsc clean, boundary audit at baseline Not yet exercised against a live server under load — will watch pool-hit / timeout metrics after deploy Checklist Code follows project style guidelines Self-reviewed my changes Tests added/updated and passing No new warnings introduced I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

Open Graph Description: Summary Adds a warm MCP connection pool so tool execution and discovery reuse a live connection per server instead of connecting, initializing, and tearing down on every call (the connect-per-oper...

X Description: Summary Adds a warm MCP connection pool so tool execution and discovery reuse a live connection per server instead of connecting, initializing, and tearing down on every call (the connect-per-oper...

Opengraph URL: https://github.com/simstudioai/sim/pull/5760

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e55fff5 feat(mcp): reuse warm connections for tool execution and discovery waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/e55fff5d7a73db3a731fec96eadd60d04180c241
3b3bceb fix(mcp): make connection pool concurrency-safe and auth-scoped waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/3b3bceb0423517c15ffa69d755c601bf84b8b850
70bd09d fix(mcp): decouple pool validity from updatedAt, widen dead-connectio… waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/70bd09dcbf8436405f71ba770f48b544d16c7644
252a4a0 fix(mcp): retire pooled connections on auth failure and server delete waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/252a4a073908a151d786b64309fcdd5ad393d129
b86cfa3 improvement(mcp): defer bulk-discovery env resolution to the pool mis… waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/b86cfa321840b33ac4317a615701136c5a871efa
0362f9f fix(mcp): retire in-flight creates evicted mid-connect via server gen… waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/0362f9f20a0016010e154d623f9caec06c7a5b06
de3527f fix(mcp): use evicted-mid-create connections one-shot and decouple po… waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/de3527fe1de97b264217bdb3ecee34733b3aead4
fc2ee4c improvement(mcp): dedupe create thunks into buildClient, harden dispo… waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/fc2ee4c1ef51388b87f2d4e08347b472369f54b6
0edd043 fix(mcp): close acquire-gap races (re-resolve after stale ping, skip … waleedlatif1 Jul 18, 2026 https://github.com/simstudioai/sim/pull/5760/commits/0edd043d97dd00289d38f6a4add0bb8a277f02d4
3ac3d2d fix(mcp): retry auth failures in executeTool; simplify acquire re-che… waleedlatif1 Jul 19, 2026 https://github.com/simstudioai/sim/pull/5760/commits/3ac3d2d8d91711dfd0b178c2de33b8f36c3823d4
abd9848 fix(mcp): let bulk discovery reconnect a lost notification connection… waleedlatif1 Jul 19, 2026 https://github.com/simstudioai/sim/pull/5760/commits/abd98481f7bf22e3732a9bf16a3963682120b659
65bd1f3 fix(mcp): recover rotated credentials on discovery via shared fetchSe… waleedlatif1 Jul 19, 2026 https://github.com/simstudioai/sim/pull/5760/commits/65bd1f3e038fa7b5e5561b1ae01b8a99319921bc
d74d48d chore(mcp): add debug logging for pool hit/miss/eviction observability waleedlatif1 Jul 19, 2026 https://github.com/simstudioai/sim/pull/5760/commits/d74d48dfaf119d273137c6bfa51bdc5e6c55f296
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