Hold MCP connections only while work runs (fix DO hibernation / free-tier burn) - #13
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A Durable Object holding live MCP client connections never hibernates:
it stays resident — and billed — around the clock even with zero
traffic, while an identical object without connections sleeps at once.
Measured on production: ~109,000 active seconds/day from a few hundred
requests, tripping the free tier's 13,000 GB-s daily cap every day
(each object ~7h/day); a controlled experiment showed 0s active for an
idle object whose connection had been removed vs 170–900s+ for ones
that kept it.
Connections are now opened just before a turn (setup(..., {connect}) —
called by the client before send/retry) or on demand for direct tool
calls, released when the turn ends (onChatResponse/onChatError, and
after callAppTool), and swept on every wake (onStart) to clear leftovers
restored from a previous isolate. A Google connection mid-consent is
kept, since its OAuth state rides on the connection row. My apps shows
"on" for engine apps (no live-connection claim) and "connected" for
Google once tokens exist.
Claude-Session: https://claude.ai/code/session_01MKLJUWk6biNAKXupHTTWn5
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Live MCP client connections prevent Durable Object hibernation — objects stayed resident ~7h/day each with near-zero traffic, exhausting the free tier's 13,000 GB-s daily cap every day (verified by per-object analytics and a controlled experiment: removed connection → 0s active). Connections now open right before a turn or tool call, release when it ends, and are swept on wake.
https://claude.ai/code/session_01MKLJUWk6biNAKXupHTTWn5