chore(main): release 2.4.0

.release-please-manifest.json

@@ -1,3 +1,3 @@
 {
-  ".": "2.3.1"
+  ".": "2.4.0"
 } 

CHANGELOG.md

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 # Changelog
 
+## [2.4.0](https://github.com/growthbook/growthbook-python/compare/v2.3.1...v2.4.0) (2026-08-18)
+
+
+### Features
+
+* Async sticky bucketing for `GrowthBookClient` ([#128](https://github.com/growthbook/growthbook-python/pull/128), [#129](https://github.com/growthbook/growthbook-python/pull/129)):
+  * New `AbstractAsyncStickyBucketService` base class with `async` `get_assignments` / `save_assignments`; override `get_all_assignments` to batch all lookups for a user into one round trip (e.g. a single Redis `MGET`). Existing synchronous `AbstractStickyBucketService` implementations keep working with both clients — the async client offloads their blocking calls to a thread pool.
+  * Sticky bucket reads no longer block the event loop. Assignments are fetched per evaluation for the supplied `UserContext`, matching the JavaScript SDK's multi-user client; concurrent evaluations for the same user share a single cancellation-safe in-flight lookup.
+  * Sticky bucket writes are fire-and-forget: evaluation never waits on persistence. New assignments are immediately visible to later evaluations in the same process, and the client keeps an authoritative in-process copy of every document it has written, so a slow or stale store read can never roll back an assignment. Saves are serialized per document key so completion order cannot regress the stored document.
+  * New `GrowthBookClient.flush_sticky_bucket_saves()` waits for all pending writes to persist (useful for serverless and short-lived processes); `close()` flushes automatically.
+  * Optional bounded read cache for hot users via `Options(sticky_bucket_cache_ttl=..., sticky_bucket_cache_size=...)`; disabled by default.
+* Async user callbacks in `GrowthBookClient` ([#128](https://github.com/growthbook/growthbook-python/pull/128), [#129](https://github.com/growthbook/growthbook-python/pull/129)): `on_experiment_viewed`, `on_feature_usage`, and `subscribe()` callbacks may now be coroutines. They are scheduled on the event loop without blocking evaluation, and a tracking callback that raises is retried on the next evaluation of the same experiment/user pair.
+* Added `customFields` property to `Experiment` ([#125](https://github.com/growthbook/growthbook-python/pull/125))
+
+
+### Performance Improvements
+
+* Lock-free evaluation in `GrowthBookClient`: feature updates now swap an immutable snapshot instead of taking a per-evaluation lock ([#129](https://github.com/growthbook/growthbook-python/pull/129))
+* `stop_refresh()` no longer blocks the event loop during shutdown ([#128](https://github.com/growthbook/growthbook-python/pull/128))
+* In the included benchmark (`tests/scripts/benchmark_async_client.py`: 100 concurrent requests, 1 ms simulated service latency), distinct-user throughput with a network-backed sticky bucket service goes from ~350 evaluations/second with multi-second event-loop stalls on 2.3.x to ~20,000 evaluations/second with sub-2 ms loop lag.
+
+
+### Bug Fixes
+
+* Sticky bucket refresh no longer triggers a redundant feature reload per identifier attribute in the synchronous client ([#124](https://github.com/growthbook/growthbook-python/pull/124))
+* The shared sticky bucket assignment-docs dict is now mutated in place instead of replaced when initially empty, preserving in-process read-your-writes ([#128](https://github.com/growthbook/growthbook-python/pull/128))
+* The synchronous `GrowthBook` class now raises `ValueError` at construction if given an async sticky bucket service, instead of failing silently at runtime ([#128](https://github.com/growthbook/growthbook-python/pull/128))
+
+
+### Tests and CI
+
+* Synced the conformance corpus with the JavaScript SDK 0.8.0 cases, with documented skips for unsupported contextual-bandit cases ([#130](https://github.com/growthbook/growthbook-python/pull/130))
+* Consumer-facing typing is now checked in CI via a mypy probe; public callback annotations accept both plain functions and coroutines ([#128](https://github.com/growthbook/growthbook-python/pull/128))
+* Replaced sleep-based concurrency tests with deterministic event-gated tests and added a high-concurrency benchmark harness for the async client ([#128](https://github.com/growthbook/growthbook-python/pull/128))
+
+
+### Compatibility notes
+
+* Sticky bucket writes from `GrowthBookClient` are now eventual rather than synchronous with evaluation. Read-your-writes is preserved in-process; short-lived processes should `await client.flush_sticky_bucket_saves()` (or `close()`) before exit to guarantee persistence.
+* `GrowthBookClient` now fetches sticky bucket assignments per evaluation instead of caching them for the lifetime of the process. This matches the JavaScript SDK and picks up cross-process assignment changes promptly, but increases service lookups; opt into bounded caching with `sticky_bucket_cache_ttl` / `sticky_bucket_cache_size` if needed.
+
 ## [2.3.1](https://github.com/growthbook/growthbook-python/compare/v2.3.0...v2.3.1) (2026-06-18)
 
 

growthbook/__init__.py

@@ -20,5 +20,5 @@
 )
 
 # x-release-please-start-version
-__version__ = "2.3.1"
+__version__ = "2.4.0"
 # x-release-please-end

setup.cfg

@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 2.3.1
+current_version = 2.4.0
 commit = True
 tag = True