feat(state): let delta coroutines drop their key via sentinel

[FarhanAliRaza]

A coroutine value in a delta can now resolve to _DROP_FROM_DELTA to omit its key, so inclusion that can only be decided asynchronously is deferred into the delta and resolved post-hoc by _resolve_delta. Emptied state subdicts are removed as well.

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Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

New Feature Submission:

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Changes To Core Features:

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[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing FarhanAliRaza:re-auth-state (95e64eb) with main (590711e)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[greptile-apps]

Greptile Summary

This PR introduces a _DROP_FROM_DELTA sentinel that delta-value coroutines can return to have their key omitted from the delta post-resolution, and rebinds EventContext to the target token inside modify_state so that fan-out tasks observe the correct session.

• _resolve_delta now checks each awaited coroutine result against the sentinel by identity and removes the key (and any resulting empty state subdict) before the delta is sent to the client.
• modify_state wraps the body in a contextlib.ExitStack that forks EventContext to the token under modification and restores the caller's context on exit, with a LookupError guard for call-sites that have no ambient event context.

Confidence Score: 5/5

Safe to merge; the sentinel drop logic is correct and the EventContext rebinding is properly scoped and restored.

Both changes are narrowly scoped: _resolve_delta only gains a sentinel identity-check with an empty-subdict cleanup, and modify_state's ExitStack pattern correctly restores context on both normal and exceptional exits.

reflex/state.py — Final should be added to the typing import block.

Important Files Changed

Filename	Overview
reflex/state.py	Adds _DROP_FROM_DELTA sentinel and updates _resolve_delta to drop sentinel-resolved keys and clean up empty subdicts. Logic is correct; Final is used in the annotation but not imported.
reflex/app.py	modify_state now forks and rebinds EventContext to the token being modified using contextlib.ExitStack; restoration on exit is correct and the LookupError path is properly guarded.
tests/units/test_state.py	Three new async tests cover coroutine resolution, sentinel-drop, and empty-subdict cleanup; all target the new _resolve_delta behaviour directly.
tests/units/test_app.py	New async test verifies EventContext token rebinding within modify_state and restoration after exit.

_{Reviews (3): Last reviewed commit: "Update reflex/state.py" | Re-trigger Greptile}

[greptile-apps]

Missing multi-drop-in-same-subdict test

The existing subdict-emptying test (test_resolve_delta_pops_subdict_emptied_by_drops) only exercises the case where a single coroutine empties the subdict. The more interesting ordering-sensitive path — where two coroutines in the same subdict both resolve to _DROP_FROM_DELTA — isn't covered. The empty-check logic (if not delta[state_name]) relies on the second coroutine's raw coroutine object still being in the dict when the first drop's check runs; while the logic is correct, adding a test case like {"s1": {"a": _coro(_DROP_FROM_DELTA), "b": _coro(_DROP_FROM_DELTA)}} would pin this invariant explicitly.