perf(sdk): make CopilotClient.start() single-flight - #2561
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Concurrent createSession()/resumeSession() on a fresh client each auto-start the CLI; without an in-flight guard the second spawn overwrote this.cliProcess and orphaned the first, which stop() never terminates. Guard start() with a shared startPromise so concurrent callers join one spawn; clear it on completion so a failed start can retry. Adds regression tests (single-flight + retry-after-failure). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Summary
CopilotClient.start()was not single-flight: concurrent first calls (includingauto-start from
createSession()/resumeSession()) could each spawn aseparate CLI process. The client only tracked the last
this.cliProcess, sostop()could not terminate the earlier ones — a duplicate cold-start cost and areal process leak.
This guards
start()with a shared in-flightstartPromise: concurrent callersawait one startup, and the guard is cleared on completion so a failed start can
be retried. The original start sequence moved into a private
doStart(); startuporder is unchanged and no public API changed.
Closes #2560
Changes
nodejs/src/client.ts: addstartPromise;start()returns the in-flightstart when one is running;
doStart()holds the original startup sequence.nodejs/test/client.test.ts: regression tests for single-flight andretry-after-failure.
Verification
npm test -- test/client.test.ts -t 'single-flight'→ 2 passed.tsc --noEmit→ clean.createSession()on a fresh client):3 → 1 CLI process spawned; 2 → 0 orphaned after
stop().Notes
main; a rebase may be needed before merge.