fix(web): deduplicate subagent navigation

packages/host/apiproxy/src/api/events.schema.ts

@@ -65,7 +65,14 @@ export const muxFrameSchema = z.discriminatedUnion('type', [
 
 /** HostFrame union (payload slot of a host-stream ServerRequest). */
 export const hostFrameSchema = z.discriminatedUnion('type', [
-  z.object({ type: z.literal('host/session-added'), sessionId: sessionIdSchema, blank: z.boolean(), parentSessionId: sessionIdSchema.optional(), cwd: z.string().optional() }),
+  z.object({
+    type: z.literal('host/session-added'),
+    sessionId: sessionIdSchema,
+    blank: z.boolean(),
+    parentSessionId: sessionIdSchema.optional(),
+    origin: z.literal('subagent').optional(),
+    cwd: z.string().optional(),
+  }),
   z.object({ type: z.literal('host/session-removed'), sessionId: sessionIdSchema }),
   z.object({ type: z.literal('host/session-status'), sessionId: sessionIdSchema, running: z.boolean() }),
   z.object({ type: z.literal('host/agent-error'), sessionId: sessionIdSchema, message: z.string() }),

packages/host/apiproxy/src/api/events.ts

@@ -90,9 +90,9 @@ export type MuxFrame =
   | { type: 'stream/error'; error: RpcError }
 
 /**
- * Host stream frames. session-added carries the lineage anchor, the project
- * cwd, and the blank bit (the list-summary fields a client cannot wait for a
- * refresh to learn); the frame fires at session/created, so blank is
+ * Host stream frames. session-added carries the lineage anchor, product
+ * origin, project cwd, and blank bit (the list-summary fields a client cannot
+ * wait for a refresh to learn); the frame fires at session/created, so blank is
  * constantly true — clients flip it on the session's first
  * `host/session-status(running:true)` (a blank session never runs), and a
  * reconnecting client takes `session.list`'s summary.blank as authoritative.
@@ -106,7 +106,14 @@ export type MuxFrame =
  * workspace-changed — `workspace.list` re-baselines it on reconnect).
  */
 export type HostFrame =
-  | { type: 'host/session-added'; sessionId: SessionId; blank: boolean; parentSessionId?: SessionId; cwd?: string }
+  | {
+    type: 'host/session-added'
+    sessionId: SessionId
+    blank: boolean
+    parentSessionId?: SessionId
+    origin?: 'subagent'
+    cwd?: string
+  }
   | { type: 'host/session-removed'; sessionId: SessionId }
   | { type: 'host/session-status'; sessionId: SessionId; running: boolean }
   | { type: 'host/agent-error'; sessionId: SessionId; message: string }

packages/host/apiproxy/src/api/sessions.schema.ts

@@ -53,6 +53,7 @@ export const sessionSummarySchema = z.object({
   running: z.boolean(),
   blank: z.boolean(),
   parentSessionId: sessionIdSchema.optional(),
+  origin: z.literal('subagent').optional(),
   cwd: z.string().optional(),
   projections: z.lazy(() => sessionProjectionsBlockSchema).optional(),
 }) as unknown as z.ZodType<Wire<SessionSummary>>

packages/host/apiproxy/src/api/sessions.ts

@@ -153,6 +153,8 @@ export interface SessionSummary {
   blank: boolean
   /** fork/spawn lineage (session.header.parentSession passthrough); absent for root sessions. */
   parentSessionId?: SessionId
+  /** Coarse durable origin used by navigation surfaces; never proves resumability. */
+  origin?: 'subagent'
   /** Session working directory (header.cwd passthrough); absent when unrecorded. */
   cwd?: string
   /**