Merging this PR will degrade performance by 3.27%

❌ 1 regressed benchmark
✅ 25 untouched benchmarks
⏩ 8 skipped benchmarks¹

Performance Changes

_{Comparing FarhanAliRaza:re-auth-state (dccb4e5) with main (d6324cf)}

Greptile Summary

This PR introduces two related changes: a _DROP_FROM_DELTA sentinel that lets async coroutine values in a state delta signal their own omission (resolved post-hoc in _resolve_delta), and a fix to modify_state that rebinds EventContext.token to the token being modified so that shared-state fan-out tasks observe the correct client token rather than the actor's inherited context.

• reflex/state.py: Adds _DROP_FROM_DELTA: Final = object() and updates _resolve_delta to delete any delta key whose coroutine resolves to the sentinel, pruning any state subdict left empty as a result. The two-pass approach (create all tasks first, then await sequentially) preserves existing parallelism and correctly handles mixed dropped/kept/plain-value subdicts.
• reflex/app.py: modify_state now forks EventContext to the target token inside a contextlib.ExitStack, silently skipping the rebind when no EventContext is active (LookupError), and restores the original context on exit.
• Tests: Four new async tests in test_state.py cover plain pass-through, partial drops, and full-subdict pruning; test_app.py adds a test verifying the token rebinding round-trip.

Confidence Score: 5/5

Safe to merge — both changes are well-scoped, the sentinel logic handles all mixed-value cases correctly, and the EventContext rebinding properly restores caller state on exit.

The _resolve_delta two-pass design keeps raw coroutine objects in the delta dict until explicitly deleted, so the if not delta[state_name] empty-check is always accurate even when multiple keys for the same state resolve to the sentinel. The ExitStack-based rebinding in modify_state uses try/except LookupError to no-op safely when no EventContext exists, and the callback correctly restores the original token. Test coverage addresses all relevant combinations.

No files require special attention.

Important Files Changed

_{Reviews (4): Last reviewed commit: "chore(state): add Final to typing import..." | Re-trigger Greptile}