fix(agents): RPC calls no longer hang during connection churn#1746
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usePartySocket replaces the underlying socket object whenever connection
options change (async query refresh, enabled toggle, path change). The
RPC layer didn't account for that:
- a call issued against a stale `agent` reference (e.g. captured by a
mount-time effect) was buffered inside the permanently-closed old
socket and its promise never settled
- a call transmitted just before replacement lost its response — RPC
responses are connection-bound — with no rejection either
- the old socket's close event was unobservable after the swap, so
"connection closed" cleanup never ran for it
useAgent:
- call(), agent.stub, and agent.setState now route through a ref to the
live socket, so stale references keep working after a replacement.
- RPC requests are only handed to a socket once it's OPEN. Until then
they're queued by the hook and flushed on the next open — including on
a replacement socket. Queued requests were never transmitted, so
flushing can't double-execute anything server-side.
- Pending calls are tagged with the socket they were transmitted on.
When a socket closes or is replaced, only calls sent on *that* socket
are rejected ("Connection closed"); queued calls survive, and calls in
flight on a newer socket are no longer spuriously rejected by a stale
close event from an old one.
- Destination guard: queued calls only follow the connection to the same
agent instance. If the hook is re-pointed at a different address
(agent, name, basePath, or path props change) before a queued call was
transmitted, the call is rejected instead of executing against an
instance it wasn't composed for.
- Non-streaming calls get a default 30s timeout as a backstop so lost
responses reject instead of hanging. Configurable via the new
`defaultCallTimeout` option (0 disables); an explicit per-call
`timeout` always wins (`timeout: 0` opts out). Streaming calls are
exempt.
AgentClient:
- Pending calls track whether their request was actually transmitted.
On a transient disconnect, transmitted calls are rejected (their
response can never arrive) while buffered calls stay pending —
PartySocket re-sends them on reconnect. A permanent close rejects
everything.
- Same `defaultCallTimeout` backstop as the hook.
Both now log a console.warn when an RPC response arrives with no
matching pending call (e.g. after a timeout) instead of silently
discarding it.
New rpc-robustness react test suite covers mount-time calls, stale
references after replacement, queued-call flush, in-flight rejection on
replacement, the destination guard, default-timeout behavior (including
timeout: 0 and streaming exemption), and the dropped-response warning;
client.test.ts gains the AgentClient equivalents.
Fixes #1738
Co-authored-by: Cursor <cursoragent@cursor.com>
🦋 Changeset detectedLatest commit: 0238e3e The changes in this PR will be included in the next version bump. This PR includes changesets to release 1 package
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Summary
Fixes #1738.
usePartySocketreplaces the underlying socket object whenever connection options change (async query refresh,enabledtoggle, path change). The RPC layer didn't account for that, producing three ways for acall()promise to never settle:agentreference (e.g. captured by a mount-time effect — the exact pattern in the issue) was buffered inside the permanently-closed old socket and never transmitteduseAgentcall(),agent.stub, andagent.setStateroute through a ref to the live socket, so stale references keep working after a replacement.Connection closed; queued calls survive, and calls in flight on a newer socket are no longer spuriously rejected by a stale close event from an old one.agent,name,basePath, or path props change) before a queued call was transmitted, the call rejects instead of executing against an instance it wasn't composed for. Credential-only changes (query refresh) still flush normally.defaultCallTimeoutoption (0disables); an explicit per-calltimeoutalways wins (timeout: 0opts out). Streaming calls are exempt — long-lived streams are legitimate.AgentClientdefaultCallTimeoutbackstop.Both now
console.warnwhen an RPC response arrives with no matching pending call (e.g. after a timeout) instead of silently discarding it.Upstream
Companion partysocket PR (cloudflare/partykit#403) fixes the underlying buffered-message loss and unobservable close at the library level — synchronous close events,
send()returning transmit status,drainQueuedMessages(), and destination-guarded buffer transfer in the hooks. This PR is self-contained and doesn't depend on it: the hook-level queue here never relies on PartySocket's internal buffer. The agents react suite was also smoke-tested against the new partysocket build (96/96 passing), so the future dependency bump is safe.Test plan
rpc-robustness.test.tsxsuite (9 tests): mount-time call resolves; staleagentreference works after socket replacement; queued calls flush onto a replacement socket; in-flight calls on a replaced socket reject promptly; destination guard rejects queued calls when the agent address changes; default timeout fires;timeout: 0opts out; streaming calls exempt from the backstop; dropped-response warningAgentClienttests inclient.test.ts(6 tests): transmitted vs. buffered rejection on transient disconnect, buffered calls surviving reconnect, default timeout,timeout: 0, streaming exemption, dropped-response warningpnpm run checkandnx affected -t test(9 projects) greenChangeset included (
agentsminor).Made with Cursor