[jeffdupont]

Fixes AIC-3574.

Why

init_client is async, but it built the LaunchDarkly LDClient right inside the coroutine. That constructor blocks for up to start_wait=10 seconds while it connects. In an asyncio app, the whole event loop froze for that time: no other requests, timers or tasks ran. This also happened on the lazy init behind the first config()/inspect_config() call. The JS SDK awaits waitForInitialization(), so it never blocks the loop.

Fix

• packages/client/src/launchdarkly_ai_server/lifecycle.py: build the client with await asyncio.to_thread(client_cls, ld_config, start_wait=10), following the existing to_thread use in evaluations/module.py and evaluations/tools.py.
• Race guard: two first calls can now both be connecting at once. After the await, if another call already set the singleton, this call closes its own client (sync or awaitable close, errors ignored, as on the failure path) and returns the existing one. No lock was added: the guard runs between the await and the assignment, with no other await point in between.
• Cancellation: to_thread can't stop the thread, so a call cancelled mid-build (e.g. a request timeout around the lazy first init) would leave the finished client's streaming connection open. The build runs behind asyncio.shield, and a cancelled call closes that client when the thread finishes (found by Bugbot).
• packages/client/tests/test_lifecycle.py: (a) a ticker task keeps running while a slow LDClient constructor (time.sleep(0.3)) runs; (b) asyncio.gather(init_client(), init_client()) returns one client, and the extra one is closed; (c) a call cancelled mid-build ends with that client closed and no singleton set.

Testing

• make test: 2547 passed, 14 skipped
• make typecheck: no issues in 75 source files
• make lint: all checks passed. make format-check: 161 files already formatted.
• Without the fix, both new tests fail: (a) assert 0 >= 5 (the loop never ticked); (b) Expected close to have been awaited once. Awaited 0 times. Without the cancellation fix, (c) fails: Expected close to have been awaited once. Awaited 0 times. The three new tests passed 5 runs in a row.

Related: https://github.com/launchdarkly/ai-sdks-monorepo/pull/70

🤖 Generated with Claude Code

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Note

Overview
init_client no longer blocks the event loop while the LaunchDarkly LDClient connects (up to 10s). Construction runs via asyncio.to_thread instead of calling the SDK constructor directly in the coroutine, matching the pattern used in evaluations code and the TS SDK’s non-blocking init.

Concurrency and cancellation are handled so stray clients don’t keep streaming connections open: if two first-time init_client calls race, the loser closes its client and returns the singleton winner; if the caller is cancelled mid-build, asyncio.shield plus _close_abandoned_client closes the client when the background thread finishes (with a small _closing_tasks set so async close() isn’t dropped).

Tests add coverage for loop responsiveness during slow LDClient construction, single-client behavior under asyncio.gather, and cleanup after cancel.

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