feat: add feature to monitor background agents (#125)

Also includes a fix to persist configuration across reconnects.

Reviewed-on: #125
Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Co-committed-by: Naomi Carrigan <commits@nhcarrigan.com>

src/lib/stores/agents.ts

@@ -0,0 +1,121 @@
+import { writable, derived } from "svelte/store";
+import type { AgentInfo } from "$lib/types/agents";
+
+// Map of conversation ID -> agents in that conversation
+const agentsByConversation = writable<Record<string, AgentInfo[]>>({});
+
+function createAgentStore() {
+  return {
+    subscribe: agentsByConversation.subscribe,
+
+    addAgent(conversationId: string, agent: AgentInfo) {
+      agentsByConversation.update((state) => {
+        const existing = state[conversationId] || [];
+        return {
+          ...state,
+          [conversationId]: [...existing, agent],
+        };
+      });
+    },
+
+    updateAgentId(conversationId: string, toolUseId: string, agentId: string) {
+      agentsByConversation.update((state) => {
+        const agents = state[conversationId];
+        if (!agents) return state;
+
+        const agentIndex = agents.findIndex((a) => a.toolUseId === toolUseId);
+        if (agentIndex === -1) return state;
+
+        const updated = [...agents];
+        updated[agentIndex] = {
+          ...updated[agentIndex],
+          agentId,
+        };
+
+        return {
+          ...state,
+          [conversationId]: updated,
+        };
+      });
+    },
+
+    endAgent(conversationId: string, toolUseId: string, endedAt: number, isError: boolean) {
+      agentsByConversation.update((state) => {
+        const agents = state[conversationId];
+        if (!agents) return state;
+
+        const agentIndex = agents.findIndex((a) => a.toolUseId === toolUseId);
+        if (agentIndex === -1) return state;
+
+        const updated = [...agents];
+        const agent = updated[agentIndex];
+        const durationMs = endedAt - agent.startedAt;
+
+        updated[agentIndex] = {
+          ...agent,
+          endedAt,
+          status: isError ? "errored" : "completed",
+          durationMs,
+        };
+
+        return {
+          ...state,
+          [conversationId]: updated,
+        };
+      });
+    },
+
+    markAllErrored(conversationId: string) {
+      agentsByConversation.update((state) => {
+        const agents = state[conversationId];
+        if (!agents) return state;
+
+        const now = Date.now();
+        const updated = agents.map((agent) =>
+          agent.status === "running"
+            ? { ...agent, endedAt: now, status: "errored" as const }
+            : agent
+        );
+
+        return {
+          ...state,
+          [conversationId]: updated,
+        };
+      });
+    },
+
+    clearCompleted(conversationId: string) {
+      agentsByConversation.update((state) => {
+        const agents = state[conversationId];
+        if (!agents) return state;
+
+        return {
+          ...state,
+          [conversationId]: agents.filter((a) => a.status === "running"),
+        };
+      });
+    },
+
+    clearConversation(conversationId: string) {
+      agentsByConversation.update((state) => {
+        // eslint-disable-next-line @typescript-eslint/no-unused-vars -- Unused destructured value
+        const { [conversationId]: _, ...rest } = state;
+        return rest;
+      });
+    },
+  };
+}
+
+export const agentStore = createAgentStore();
+
+export function getAgentsForConversation(conversationId: string) {
+  return derived(agentsByConversation, ($state) => $state[conversationId] || []);
+}
+
+export const runningAgentCount = derived(agentsByConversation, ($state) => {
+  let count = 0;
+  for (const agents of Object.values($state)) {
+    count += agents.filter((a) => a.status === "running").length;
+  }
+  return count;
+});

src/lib/stores/conversations.ts

@@ -435,7 +435,8 @@ function createConversationsStore() {
       type: TerminalLine["type"],
       content: string,
       toolName?: string,
-      cost?: TerminalLine["cost"]
+      cost?: TerminalLine["cost"],
+      parentToolUseId?: string
     ) => {
       ensureInitialized();
       const activeId = get(activeConversationId);
@@ -448,6 +449,7 @@ function createConversationsStore() {
         timestamp: new Date(),
         toolName,
         cost,
+        parentToolUseId,
       };
 
       conversations.update((convs) => {
@@ -469,7 +471,8 @@ function createConversationsStore() {
       type: TerminalLine["type"],
       content: string,
       toolName?: string,
-      cost?: TerminalLine["cost"]
+      cost?: TerminalLine["cost"],
+      parentToolUseId?: string
     ) => {
       ensureInitialized();
 
@@ -480,6 +483,7 @@ function createConversationsStore() {
         timestamp: new Date(),
         toolName,
         cost,
+        parentToolUseId,
       };
 
       conversations.update((convs) => {