fix: rehydrate state trees that expire during a background task

[FarhanAliRaza]

Summary

A background task releases the state lock while it runs. If the session expires in that time, async with self gets a recreated tree. The delta then carries only the handler's changes, and the browser keeps the values of the expired session (#7478).

A foreground event already recovers from this. When the rx.State root has empty router_data, _execute_event runs _rehydrate. This PR makes StateProxy.__aenter__ use the same signal:

• It restores the router from the event context.
• It calls BaseStateEventProcessor._rehydrate, now a staticmethod because it did not use self.

The hydrate snapshot carries is_hydrated=false, so the frontend does not write client storage. The router, the dynamic route args and rx.LocalStorage/rx.Cookie values stay correct. The result is the same as a foreground event on main today.

Supersedes #7543. That PR tracks recreated states in every manager and adds a Redis manifest key. This PR needs no new tracking state, and it also covers a Redis tree that expired completely.

Closes #7478

Test plan

• New unit test test_background_task_rehydrates_state_tree_expired_while_unlocked, for the memory and Redis managers. It fails on main and passes with this change.
• tests/units/istate, tests/units/reflex_base, test_state.py, test_event.py and test_app.py pass. The istate and event processor tests also pass against a live Redis.
• A manual run in a small app with a root state, a child state, a cross-state computed var, a ComponentState, an rx.LocalStorage var and a dynamic route. The background task sleeps longer than the token TTL.
  • Memory, full expiry: the expired values reset. pid, the router, is_hydrated and the browser's localStorage are kept.
  • Redis, full expiry and partial expiry: the expired values reset, and pid and localStorage are kept.
  • Control, no expiry: the background update sends no rehydrate snapshot.

Known limit, the same as the foreground path on main: on Redis, hydrate sends only the states loaded in the tree, so a sibling state that the task does not load keeps its old value.

[cubic-dev-ai]

All reported issues were addressed across 5 files

<sub>Reply with feedback, questions, or to request a fix.

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[greptile-apps]

Confidence Score: 4/5

[Medium impact] Fixes state rehydration when background tasks resume after session expiry.

The PR still needs the old-route recovery issue fixed before merging.

Findings

1.  Old page values return ▶

Summary

Background tasks now rehydrate loaded states when they re-enter an expired session.

• Background tasks restore expired state trees when they re-enter.

_{Reviews (3) · Last reviewed commit: "test: disable oplock when simulating Red..." · Reviewed by Greptile}

[greptile-apps]

Old page values return

ctx.router_data belongs to the event that started the background task, not necessarily the page the user is viewing now. If the task starts on /a, the user visits /b, and the session then expires before the task resumes, this code restores /a and sends its router values to the browser. _rehydrate also selects /a’s load handlers.

Recover the current browser route before rehydrating instead of treating the task’s old route as current.

[chatgpt-codex-connector]

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Reviewed commit: d0593158a5

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[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-16T19:43:28.539049Z	d059315	PR opened

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[codspeed]

Merging this PR will not alter performance

⚠️ 12 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• test_import_cli
• test_state_manager_memory_read_only_modify
• test_cli_startup[run_help]
• test_cli_startup[cloud_help]
• test_cli_startup[version]
• test_cli_startup[help]
• test_cli_startup[deploy_help]
• test_modify_state[disk]
• test_state_manager_memory_warm_get
• test_emit_update
• …and 2 more

✅ 148 untouched benchmarks

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_{Comparing FarhanAliRaza:farhan/7478-background-rehydrate (1792b36) with main (5ae5dcd)}