feat: add TTL-based cleanup worker

Phase 3: Background cleanup worker implementation
- Add module-level cleanupInterval variable for worker management
- Implement purgeExpiredMessages() with TTL-based logic:
  * Only purges messages beyond message_threshold
  * Checks lastViewed timestamp against min_ttl
  * Purges oldest->newest with configurable delay
  * Stops at first non-expired message (can't skip middle)
- Add startCleanupWorker() to begin periodic cleanup
  * Runs every cleanup_interval seconds
  * Only starts when config.enabled is true
- Add stopCleanupWorker() to halt cleanup and cleanup resources
- Worker removes message, parts, and view data for expired messages

Author: ryanwyler

packages/opencode/src/cli/cmd/tui/context/sync.tsx

@@ -29,6 +29,9 @@ import { batch, onMount } from "solid-js"
 import { Log } from "@/util/log"
 import type { Path } from "@opencode-ai/sdk"
 
+// Module-level cleanup worker state
+let cleanupInterval: Timer | null = null
+
 export const { use: useSync, provider: SyncProvider } = createSimpleContext({
   name: "Sync",
   init: () => {
@@ -387,6 +390,55 @@ export const { use: useSync, provider: SyncProvider } = createSimpleContext({
       bootstrap()
     })
 
+    // Cleanup worker functions
+    async function purgeExpiredMessages(
+      sessionID: string,
+      config: {
+        message_threshold?: number
+        min_ttl?: number
+        purge_delay?: number
+      },
+    ) {
+      const messages = store.message[sessionID]
+      const threshold = config.message_threshold ?? 100
+
+      if (!messages || messages.length <= threshold) return
+
+      const viewData = store.message_view[sessionID] || {}
+      const now = Date.now()
+      const minTTL = (config.min_ttl ?? 120) * 1000
+      const purgeDelay = (config.purge_delay ?? 0.1) * 1000
+
+      const candidatesForPurge = messages.slice(0, messages.length - threshold)
+
+      for (let i = 0; i < candidatesForPurge.length; i++) {
+        const msg = candidatesForPurge[i]
+        const viewInfo = viewData[msg.id]
+
+        const lastViewed = viewInfo?.lastViewed || msg.time.created
+        const timeSinceViewed = now - lastViewed
+
+        if (timeSinceViewed >= minTTL) {
+          setStore(
+            produce((draft) => {
+              const idx = draft.message[sessionID].findIndex((m) => m.id === msg.id)
+              if (idx !== -1) {
+                draft.message[sessionID].splice(idx, 1)
+                delete draft.part[msg.id]
+                if (draft.message_view[sessionID]) {
+                  delete draft.message_view[sessionID][msg.id]
+                }
+              }
+            }),
+          )
+
+          await new Promise((resolve) => setTimeout(resolve, purgeDelay))
+        } else {
+          break
+        }
+      }
+    }
+
     const fullSyncedSessions = new Set<string>()
     const result = {
       data: store,
@@ -501,6 +553,26 @@ export const { use: useSync, provider: SyncProvider } = createSimpleContext({
           }),
         )
       },
+      startCleanupWorker() {
+        if (cleanupInterval) return
+
+        const historyConfig = store.config.tui?.history_auto_scroll
+        if (!historyConfig?.enabled) return
+
+        const interval = (historyConfig.cleanup_interval ?? 30) * 1000
+
+        cleanupInterval = setInterval(() => {
+          for (const sessionID of Object.keys(store.message)) {
+            purgeExpiredMessages(sessionID, historyConfig)
+          }
+        }, interval)
+      },
+      stopCleanupWorker() {
+        if (cleanupInterval) {
+          clearInterval(cleanupInterval)
+          cleanupInterval = null
+        }
+      },
       bootstrap,
     }
     return result