Show provider subagents in the subagents track (#2013)

* Add provider-owned subagent stream contract

* OpenCode provider: detect child sessions, attach adopted children to the hosting server, synthesize external turns

- Emit internal provider_child_session_detected / provider_session_deleted stream events from the global event stream (before the no-active-turn gate), including BFS hydration of existing descendants on subscribe
- Track child sessions in a registry mapping child session id -> hosting server url; resumeSession attaches via acquireExisting() so adopted children share the parent's server generation and keep receiving live events
- Synthesize external turns for adopted (externally driven) sessions so timeline, tool calls, and permission requests stream without a Paseo-initiated prompt
- Honor launchContext.env in resumeSession (acquireDedicated parity with createSession)
- Stop folding child tool parts into the parent's sub_agent action log; the parent row stays as a pointer

* Render provider subagents in workspace timelines

* fix provider subagent timeline reliability

* fix provider subagent lifecycle edge cases

* fix provider subagent event fidelity

* Fix provider subagent history fidelity

* Fix restored provider subagent state

* Fix provider subagent visibility edges

* Restore provider subagent timelines

* Page provider subagent history

* Forward subagent questions reliably

* fix(subagents): preserve OpenCode child context

* fix(subagents): harden provider timeline routing

* fix(subagents): preserve provider page continuity

* fix(subagents): retain live child prompts

---------

Co-authored-by: Omer <639682+omercnet@users.noreply.github.com>

packages/client/src/daemon-client.test.ts

@@ -555,6 +555,7 @@ test("advertises client capabilities in hello", async () => {
     protocolVersion: 1,
     capabilities: {
       custom_mode_icons: true,
+      provider_subagents: true,
       reasoning_merge_enum: true,
       terminal_reflowable_snapshot: true,
       browser_host: {

packages/client/src/daemon-client.ts

@@ -490,6 +490,22 @@ export interface FetchAgentTimelineOptions {
   timeout?: number;
 }
 
+export type ProviderSubagentListPayload = Extract<
+  SessionOutboundMessage,
+  { type: "agent.provider_subagents.list.response" }
+>["payload"];
+export type ProviderSubagentTimelinePayload = Extract<
+  SessionOutboundMessage,
+  { type: "agent.provider_subagents.timeline.get.response" }
+>["payload"];
+export interface FetchProviderSubagentTimelineOptions {
+  direction?: ProviderSubagentTimelinePayload["direction"];
+  cursor?: FetchAgentTimelineCursor;
+  limit?: number;
+  requestId?: string;
+  timeout?: number;
+}
+
 // COMPAT(daemon-client-object-options): added in v0.1.102; remove after
 // 2026-12-29 once SDK callers have migrated to object parameters.
 function normalizeFetchAgentOptions(
@@ -2429,6 +2445,65 @@ export class DaemonClient {
     return payload;
   }
 
+  async listProviderSubagents(
+    parentAgentId: string,
+    options: { requestId?: string; timeout?: number } = {},
+  ): Promise<ProviderSubagentListPayload> {
+    const requestId = this.createRequestId(options.requestId);
+    const message = SessionInboundMessageSchema.parse({
+      type: "agent.provider_subagents.list.request",
+      parentAgentId,
+      requestId,
+    });
+    const payload = await this.sendRequest({
+      requestId,
+      message,
+      timeout: options.timeout,
+      options: { skipQueue: true },
+      select: (response) =>
+        response.type === "agent.provider_subagents.list.response" &&
+        response.payload.requestId === requestId
+          ? response.payload
+          : null,
+    });
+    if (payload.error) {
+      throw new Error(payload.error);
+    }
+    return payload;
+  }
+
+  async fetchProviderSubagentTimeline(
+    parentAgentId: string,
+    subagentId: string,
+    options: FetchProviderSubagentTimelineOptions = {},
+  ): Promise<ProviderSubagentTimelinePayload> {
+    const requestId = this.createRequestId(options.requestId);
+    const message = SessionInboundMessageSchema.parse({
+      type: "agent.provider_subagents.timeline.get.request",
+      parentAgentId,
+      subagentId,
+      requestId,
+      ...(options.direction ? { direction: options.direction } : {}),
+      ...(options.cursor ? { cursor: options.cursor } : {}),
+      ...(typeof options.limit === "number" ? { limit: options.limit } : {}),
+    });
+    const payload = await this.sendRequest({
+      requestId,
+      message,
+      timeout: options.timeout,
+      options: { skipQueue: true },
+      select: (response) =>
+        response.type === "agent.provider_subagents.timeline.get.response" &&
+        response.payload.requestId === requestId
+          ? response.payload
+          : null,
+    });
+    if (payload.error) {
+      throw new Error(payload.error);
+    }
+    return payload;
+  }
+
   async buildAgentForkContext(
     agentId: string,
     options: AgentForkContextOptions = {},
@@ -4672,6 +4747,7 @@ export class DaemonClient {
             [CLIENT_CAPS.customModeIcons]: true,
             [CLIENT_CAPS.reasoningMergeEnum]: true,
             [CLIENT_CAPS.terminalReflowableSnapshot]: true,
+            [CLIENT_CAPS.providerSubagents]: true,
             ...this.config.capabilities,
           },
           ...(this.config.appVersion ? { appVersion: this.config.appVersion } : {}),