feat(tui): fire-and-forget async subagent tasks

packages/opencode/src/agent/agent.ts

@@ -83,7 +83,7 @@ export namespace Agent {
       },
       general: {
         name: "general",
-        description: `General-purpose agent for researching complex questions and executing multi-step tasks. Use this agent to execute multiple units of work in parallel.`,
+        description: `General-purpose agent for researching complex questions and executing multi-step tasks. Use this agent to execute multiple units of work in parallel. Ideal for async execution when work can proceed concurrently.`,
         permission: PermissionNext.merge(
           defaults,
           PermissionNext.fromConfig({
@@ -113,7 +113,7 @@ export namespace Agent {
           }),
           user,
         ),
-        description: `Fast agent specialized for exploring codebases. Use this when you need to quickly find files by patterns (eg. "src/components/**/*.tsx"), search code for keywords (eg. "API endpoints"), or answer questions about the codebase (eg. "how do API endpoints work?"). When calling this agent, specify the desired thoroughness level: "quick" for basic searches, "medium" for moderate exploration, or "very thorough" for comprehensive analysis across multiple locations and naming conventions.`,
+        description: `Fast agent specialized for exploring codebases. Use this when you need to quickly find files by patterns (eg. "src/components/**/*.tsx"), search code for keywords (eg. "API endpoints"), or answer questions about the codebase (eg. "how do API endpoints work?"). When calling this agent, specify the desired thoroughness level: "quick" for basic searches, "medium" for moderate exploration, or "very thorough" for comprehensive analysis across multiple locations and naming conventions. Ideal for async execution when running multiple independent explorations.`,
         prompt: PROMPT_EXPLORE,
         options: {},
         mode: "subagent",

packages/opencode/src/cli/cmd/tui/app.tsx

@@ -290,6 +290,21 @@ function App() {
       keybind: "session_new",
       category: "Session",
       onSelect: () => {
+        if (route.data.type === "session") {
+          const currentSessionID = route.data.sessionID
+          const children = sync.data.session.filter((s) => s.parentID === currentSessionID)
+          for (const child of children) {
+            const status = sync.data.session_status[child.id]
+            if (status?.type === "busy" || status?.type === "retry") {
+              toast.show({
+                variant: "warning",
+                message: `Cannot start new session: background task "${child.title}" is still running`,
+              })
+              return
+            }
+          }
+        }
+
         const current = promptRef.current
         // Don't require focus - if there's any text, preserve it
         const currentPrompt = current?.current?.input ? current.current : undefined
@@ -562,7 +577,11 @@ function App() {
 
   sdk.event.on(SessionApi.Event.Deleted.type, (evt) => {
     if (route.data.type === "session" && route.data.sessionID === evt.properties.info.id) {
-      route.navigate({ type: "home" })
+      if (evt.properties.info.parentID) {
+        route.navigate({ type: "session", sessionID: evt.properties.info.parentID })
+      } else {
+        route.navigate({ type: "home" })
+      }
       toast.show({
         variant: "info",
         message: "The current session was deleted",

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

@@ -218,21 +218,22 @@ export const { use: useSync, provider: SyncProvider } = createSimpleContext({
           break
         }
         case "message.part.updated": {
-          const parts = store.part[event.properties.part.messageID]
+          const part = event.properties.part
+          const parts = store.part[part.messageID]
           if (!parts) {
-            setStore("part", event.properties.part.messageID, [event.properties.part])
+            setStore("part", part.messageID, [part])
             break
           }
-          const result = Binary.search(parts, event.properties.part.id, (p) => p.id)
+          const result = Binary.search(parts, part.id, (p) => p.id)
           if (result.found) {
-            setStore("part", event.properties.part.messageID, result.index, reconcile(event.properties.part))
+            setStore("part", part.messageID, result.index, reconcile(part))
             break
           }
           setStore(
             "part",
-            event.properties.part.messageID,
+            part.messageID,
             produce((draft) => {
-              draft.splice(result.index, 0, event.properties.part)
+              draft.splice(result.index, 0, part)
             }),
           )
           break