fix(shared-state): cap syncIds with FIFO eviction to stop memory growth

Bound createSharedState's syncIds Set to 1000 entries with oldest-first
eviction so long-lived, frequently-mutated shared state (e.g. the
terminals manager's 1s process poll) stops leaking memory for the life
of the process. Immediate duplicate-syncId de-dup is unaffected.

Implements plans/006; removes the plan file and marks it DONE in
plans/README.md.

Author: antfubot

packages/devframe/src/utils/shared-state.test.ts

@@ -304,6 +304,20 @@ describe('shared-state', () => {
       expect(state.syncIds.has('sync-2')).toBe(true)
     })
 
+    it('caps syncIds and evicts oldest-first (FIFO), keeping recent de-dup', () => {
+      const state = createSharedState({ initialValue: { count: 0 } })
+      for (let i = 0; i < 1500; i++) {
+        state.mutate((draft) => {
+          draft.count = i
+        }, `sync-${i}`)
+      }
+      expect(state.syncIds.size).toBeLessThanOrEqual(1000)
+      // The most recent id is retained (still de-duped)...
+      expect(state.syncIds.has('sync-1499')).toBe(true)
+      // ...the oldest was evicted.
+      expect(state.syncIds.has('sync-0')).toBe(false)
+    })
+
     it('should able to sync between two shared states', () => {
       const state1 = createSharedState({
         initialValue: { count: 0 },

packages/devframe/src/utils/shared-state.ts

@@ -71,6 +71,22 @@ export interface SharedStateOptions<T> {
   enablePatches?: boolean
 }
 
+/**
+ * Upper bound on retained syncIds. Loop echoes arrive near-immediately, so a
+ * generous window preserves de-dup while capping memory on long-lived,
+ * frequently-mutated states (e.g. a 1s terminal poll).
+ */
+const MAX_SYNC_IDS = 1000
+
+function rememberSyncId(syncIds: Set<string>, syncId: string): void {
+  syncIds.add(syncId)
+  if (syncIds.size > MAX_SYNC_IDS) {
+    const oldest = syncIds.values().next().value
+    if (oldest !== undefined)
+      syncIds.delete(oldest)
+  }
+}
+
 export function createSharedState<T extends object>(
   options: SharedStateOptions<T>,
 ): SharedState<T> {
@@ -91,15 +107,15 @@ export function createSharedState<T extends object>(
         return
       enableImmerPatches()
       state = applyPatches(state as unknown as Objectish, patches as unknown as Patch[]) as T
-      syncIds.add(syncId)
+      rememberSyncId(syncIds, syncId)
       events.emit('updated', state, undefined, syncId)
     },
     mutate: (fn, syncId = nanoid()) => {
       // Avoid loop syncs
       if (syncIds.has(syncId))
         return
 
-      syncIds.add(syncId)
+      rememberSyncId(syncIds, syncId)
       if (enablePatches) {
         const [newState, patches] = produceWithPatches(
           state as unknown as Objectish,

plans/006-bound-sharedstate-syncids.md

@@ -18,7 +18,7 @@ changes are allowed as long as they're marked).
 | 003 | Reject cross-origin WebSocket upgrades ⚠️ | security | P1 | S | — | DONE |
 | 004 | Stop git argument injection via `ref`/`hash` | security/bug | P1 | S | — | TODO |
 | 005 | Don't cache a rejected RPC `setup()` promise | bug | P1 | S | — | TODO |
-| 006 | Bound `SharedState.syncIds` (memory leak) | bug | P1 | S | — | TODO |
+| 006 | Bound `SharedState.syncIds` (memory leak) | bug | P1 | S | — | DONE |
 | 007 | Behavioral tests for the auth/OTP trust boundary | tests | P1 | S | — | TODO |
 | 008 | Cap hub terminal buffer + reject restart-after-terminate | bug | P2 | S | — | TODO |
 | 009 | Fix two server-side streaming lifecycle leaks | bug | P2 | S-M | — | TODO |