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/protocol/src/messages.ts

@@ -1295,6 +1295,22 @@ export const FetchAgentTimelineRequestMessageSchema = z.object({
   projection: z.enum(["projected", "canonical"]).optional(),
 });
 
+export const ProviderSubagentListRequestMessageSchema = z.object({
+  type: z.literal("agent.provider_subagents.list.request"),
+  parentAgentId: z.string(),
+  requestId: z.string(),
+});
+
+export const ProviderSubagentTimelineRequestMessageSchema = z.object({
+  type: z.literal("agent.provider_subagents.timeline.get.request"),
+  parentAgentId: z.string(),
+  subagentId: z.string(),
+  requestId: z.string(),
+  direction: z.enum(["tail", "before", "after"]).optional(),
+  cursor: AgentTimelineCursorSchema.optional(),
+  limit: z.number().int().nonnegative().optional(),
+});
+
 export const AgentForkContextRequestMessageSchema = z.object({
   type: z.literal("agent.fork_context.request"),
   agentId: z.string(),
@@ -2089,6 +2105,8 @@ export const SessionInboundMessageSchema = z.discriminatedUnion("type", [
   RestartServerRequestMessageSchema,
   DaemonUpdateRequestMessageSchema,
   FetchAgentTimelineRequestMessageSchema,
+  ProviderSubagentListRequestMessageSchema,
+  ProviderSubagentTimelineRequestMessageSchema,
   AgentForkContextRequestMessageSchema,
   SetAgentModeRequestMessageSchema,
   SetAgentModelRequestMessageSchema,
@@ -2367,6 +2385,8 @@ export const ServerInfoStatusPayloadSchema = z
         daemonSelfUpdate: z.boolean().optional(),
         // COMPAT(agentForkContext): added in v0.1.102, remove gate after 2026-12-28.
         agentForkContext: z.boolean().optional(),
+        // COMPAT(providerSubagents): added in v0.1.107, remove gate after 2027-01-12.
+        providerSubagents: z.boolean().optional(),
       })
       .optional(),
   })
@@ -2958,6 +2978,88 @@ export const FetchAgentTimelineResponseMessageSchema = z.object({
   }),
 });
 
+export const ProviderSubagentDescriptorPayloadSchema = z.object({
+  id: z.string(),
+  parentAgentId: z.string(),
+  provider: AgentProviderSchema,
+  title: z.string().nullable(),
+  description: z.string().nullable(),
+  status: z.enum(["running", "completed", "failed", "canceled"]),
+  createdAt: z.string(),
+  updatedAt: z.string(),
+  toolCallId: z.string().nullable(),
+  cwd: z.string().nullable().optional(),
+});
+
+export type ProviderSubagentDescriptorPayload = z.infer<
+  typeof ProviderSubagentDescriptorPayloadSchema
+>;
+
+export const ProviderSubagentListResponseMessageSchema = z.object({
+  type: z.literal("agent.provider_subagents.list.response"),
+  payload: z.object({
+    requestId: z.string(),
+    parentAgentId: z.string(),
+    subagents: z.array(ProviderSubagentDescriptorPayloadSchema),
+    error: z.string().nullable(),
+  }),
+});
+
+export const ProviderSubagentTimelineResponseMessageSchema = z.object({
+  type: z.literal("agent.provider_subagents.timeline.get.response"),
+  payload: z.object({
+    requestId: z.string(),
+    parentAgentId: z.string(),
+    subagentId: z.string(),
+    provider: AgentProviderSchema.nullable(),
+    direction: z.enum(["tail", "before", "after"]),
+    epoch: z.string(),
+    reset: z.boolean(),
+    staleCursor: z.boolean(),
+    gap: z.boolean(),
+    window: z.object({
+      minSeq: z.number().int().nonnegative(),
+      maxSeq: z.number().int().nonnegative(),
+      nextSeq: z.number().int().nonnegative(),
+    }),
+    hasOlder: z.boolean(),
+    hasNewer: z.boolean(),
+    rows: z.array(
+      z.object({
+        item: AgentTimelineItemPayloadSchema,
+        timestamp: z.string(),
+        seq: z.number().int().nonnegative(),
+      }),
+    ),
+    error: z.string().nullable(),
+  }),
+});
+
+export const ProviderSubagentUpdateMessageSchema = z.object({
+  type: z.literal("agent.provider_subagents.update"),
+  payload: z.discriminatedUnion("kind", [
+    z.object({
+      kind: z.literal("upsert"),
+      subagent: ProviderSubagentDescriptorPayloadSchema,
+    }),
+    z.object({
+      kind: z.literal("timeline"),
+      parentAgentId: z.string(),
+      subagentId: z.string(),
+      provider: AgentProviderSchema,
+      item: AgentTimelineItemPayloadSchema,
+      timestamp: z.string(),
+      seq: z.number().int().nonnegative(),
+      epoch: z.string(),
+    }),
+    z.object({
+      kind: z.literal("remove"),
+      parentAgentId: z.string(),
+      subagentId: z.string(),
+    }),
+  ]),
+});
+
 export const AgentForkContextResponseMessageSchema = z.object({
   type: z.literal("agent.fork_context.response"),
   payload: z.object({
@@ -4207,6 +4309,9 @@ export const SessionOutboundMessageSchema = z.discriminatedUnion("type", [
   ArchiveWorkspaceResponseMessageSchema,
   FetchAgentResponseMessageSchema,
   FetchAgentTimelineResponseMessageSchema,
+  ProviderSubagentListResponseMessageSchema,
+  ProviderSubagentTimelineResponseMessageSchema,
+  ProviderSubagentUpdateMessageSchema,
   AgentForkContextResponseMessageSchema,
   CancelAgentResponseMessageSchema,
   ClearAgentAttentionResponseMessageSchema,
@@ -4679,6 +4784,7 @@ export const WSHelloMessageSchema = z.object({
       [CLIENT_CAPS.reasoningMergeEnum]: z.boolean().optional(),
       [CLIENT_CAPS.customModeIcons]: z.boolean().optional(),
       [CLIENT_CAPS.terminalReflowableSnapshot]: z.boolean().optional(),
+      [CLIENT_CAPS.providerSubagents]: z.boolean().optional(),
       [CLIENT_CAPS.browserHost]: BrowserAutomationHostCapabilitySchema.optional(),
     })
     .passthrough()