fix(tui): isolate turn state from app render

ui-tui/src/__tests__/stateIsolation.test.ts

@@ -0,0 +1,46 @@
+import { beforeEach, describe, expect, it } from 'vitest'
+
+import { patchTurnState, resetTurnState } from '../app/turnStore.js'
+import { $uiState, resetUiState } from '../app/uiStore.js'
+
+const shallowEqual = <T extends Record<string, unknown>>(a: T, b: T) =>
+  Object.keys(a).length === Object.keys(b).length && Object.keys(a).every(key => Object.is(a[key], b[key]))
+
+const subscribeSelected = <T extends Record<string, unknown>>(selector: () => T) => {
+  let current = selector()
+  let calls = 0
+
+  const unsubscribe = $uiState.listen(() => {
+    const next = selector()
+
+    if (shallowEqual(next, current)) {
+      return
+    }
+
+    current = next
+    calls++
+  })
+
+  return { calls: () => calls, unsubscribe }
+}
+
+describe('TUI state isolation', () => {
+  beforeEach(() => {
+    resetUiState()
+    resetTurnState()
+  })
+
+  it('does not notify ui/composer subscribers for high-frequency turn updates', () => {
+    const composerRelevant = subscribeSelected(() => ({ busy: $uiState.get().busy, sid: $uiState.get().sid }))
+
+    try {
+      for (let i = 0; i < 50; i++) {
+        patchTurnState({ streaming: `token ${i}` })
+      }
+    } finally {
+      composerRelevant.unsubscribe()
+    }
+
+    expect(composerRelevant.calls()).toBe(0)
+  })
+})