fix(bluetooth-sdk/ios): make ObservableStore thread-safe

[cedricshan]

Summary

ObservableStore (iOS) is annotated @MainActor, but it is reached from BLE background callbacks through the Obj-C / React Native bridge, which bypasses Swift actor isolation. The unsynchronized access races on the backing values dictionary and intermittently crashes the app with:

-[__NSTaggedDate countByEnumeratingWithState:objects:count:]: unrecognized selector sent to instance 0x8000000000000000

Crash backtrace (observed in Xcode, main thread aborts)

__pthread_kill
...
ObservableStore.getCategory(_:)
MentraBluetoothSDK.bluetoothStatus.getter      // DeviceStore.shared.store.getCategory(.bluetoothCategory)
MentraBluetoothSDK.state.getter
MentraBluetoothSDK.dispatchStoreUpdate(_:)
closure #1 in closure #2 in MentraBluetoothSDK...

The crash surfaces inside getCategory()'s for (key, value) in values enumeration once the dictionary reference has been corrupted by the data race (the corrupted pointer 0x8000000000000000 is a tagged NSDate). Because it is a race, it is intermittent — it typically fires after the BLE link has been up for a while and status updates are flowing.

Fix

Guard all reads/writes of values and listeners with an NSRecursiveLock:

• Recursive so a listener firing synchronously on the same thread can safely re-enter the store.
• In set(), listeners are snapshotted under the lock and the lock is released before emitting, so a cross-thread re-entrant listener cannot deadlock.
• Covers set, get, getCategory, wouldSkipSet, addListener, removeListener.

This makes the dictionary access safe regardless of the calling thread without changing the public API or the @MainActor annotation.

Notes / scope

• iOS only. The Android ObservableStore.kt is out of scope for this PR.
• No behavior change beyond serialization; the emit path and skip-if-unchanged semantics are preserved.

Test plan

• Builds.
• Ran on device (Mentra Live + iPhone, Expo 56 / RN 0.85, New Architecture). The __NSTaggedDate abort no longer reproduces over extended BLE status streaming where it previously crashed intermittently.

Made with Cursor

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Note

Medium Risk
Touches shared BLE state used on every status update; locking changes concurrency semantics but is narrowly scoped and preserves existing emit behavior.

Overview
Fixes intermittent iOS crashes from unsynchronized access to ObservableStore's backing dictionaries when BLE / RN bridge callbacks hit the store off the main thread despite @MainActor.

The change adds an NSRecursiveLock around all reads and writes to values and listeners (get, set, getCategory, wouldSkipSet, addListener, removeListener). In set(), listeners are snapshotted under the lock and notifications run after unlock so cross-thread re-entry cannot deadlock. Public API and emit / skip-if-unchanged behavior stay the same.

^{Reviewed by Cursor Bugbot for commit 0c0fbb5. Bugbot is set up for automated code reviews on this repo. Configure here.}

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Summary by cubic

Make the iOS ObservableStore thread-safe to stop intermittent crashes caused by BLE background callbacks bypassing @MainActor. Fixes the -[__NSTaggedDate …]: unrecognized selector crash during category enumeration.

• Bug Fixes
  • Guard all access to values and listeners with NSRecursiveLock.
  • In set, snapshot listeners under the lock and unlock before emitting to avoid re-entrant deadlocks.
  • Applies to set, get, getCategory, wouldSkipSet, addListener, removeListener; no API/behavior changes; iOS only.

^{Written for commit 0c0fbb5. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}