fix(daemon): isolate parallel subAgent text streams in transcript reducer

packages/cli/src/acp-integration/session/SubAgentTracker.test.ts

@@ -719,6 +719,10 @@ describe('SubAgentTracker', () => {
             type: 'text',
             text: 'Hello, this is a response from the model.',
           },
+          _meta: expect.objectContaining({
+            parentToolCallId: 'parent-call-123',
+            subagentType: 'test-subagent',
+          }),
         }),
       );
     });

packages/cli/src/acp-integration/session/SubAgentTracker.ts

@@ -276,6 +276,8 @@ export class SubAgentTracker {
         event.text,
         'assistant',
         event.thought ?? false,
+        undefined,
+        this.getSubagentMeta(),
       );
     };
   }

packages/cli/src/acp-integration/session/emitters/MessageEmitter.ts

@@ -69,12 +69,16 @@ export class MessageEmitter extends BaseEmitter {
   async emitAgentThought(
     text: string,
     timestamp?: string | number,
+    subagentMeta?: SubagentMeta,
   ): Promise<void> {
-    const epochMs = BaseEmitter.toEpochMs(timestamp);
+    const _meta = this.buildChunkMeta(
+      BaseEmitter.toEpochMs(timestamp),
+      subagentMeta,
+    );
     await this.sendUpdate({
       sessionUpdate: 'agent_thought_chunk',
       content: { type: 'text', text },
-      ...(epochMs != null && { _meta: { timestamp: epochMs } }),
+      ...(_meta ? { _meta } : {}),
     });
   }
 
@@ -87,12 +91,16 @@ export class MessageEmitter extends BaseEmitter {
   async emitAgentMessage(
     text: string,
     timestamp?: string | number,
+    subagentMeta?: SubagentMeta,
   ): Promise<void> {
-    const epochMs = BaseEmitter.toEpochMs(timestamp);
+    const _meta = this.buildChunkMeta(
+      BaseEmitter.toEpochMs(timestamp),
+      subagentMeta,
+    );
     await this.sendUpdate({
       sessionUpdate: 'agent_message_chunk',
       content: { type: 'text', text },
-      ...(epochMs != null && { _meta: { timestamp: epochMs } }),
+      ...(_meta ? { _meta } : {}),
     });
   }
 
@@ -139,12 +147,28 @@ export class MessageEmitter extends BaseEmitter {
     role: 'user' | 'assistant',
     isThought: boolean = false,
     timestamp?: string | number,
+    subagentMeta?: SubagentMeta,
   ): Promise<void> {
     if (role === 'user') {
       return this.emitUserMessage(text, timestamp);
     }
     return isThought
-      ? this.emitAgentThought(text, timestamp)
-      : this.emitAgentMessage(text, timestamp);
+      ? this.emitAgentThought(text, timestamp, subagentMeta)
+      : this.emitAgentMessage(text, timestamp, subagentMeta);
+  }
+
+  private buildChunkMeta(
+    epochMs: number | undefined,
+    subagentMeta?: SubagentMeta,
+  ): Record<string, unknown> | undefined {
+    const meta: Record<string, unknown> = {};
+    if (subagentMeta?.parentToolCallId) {
+      meta['parentToolCallId'] = subagentMeta.parentToolCallId;
+    }
+    if (subagentMeta?.subagentType) {
+      meta['subagentType'] = subagentMeta.subagentType;
+    }
+    if (epochMs != null) meta['timestamp'] = epochMs;
+    return Object.keys(meta).length > 0 ? meta : undefined;
   }
 }

packages/sdk-typescript/src/daemon/ui/normalizer.ts

@@ -408,11 +408,29 @@ function normalizeSessionUpdate(
     }
     case 'agent_message_chunk': {
       const text = getTextContent(update['content']);
-      return text ? [{ ...base, type: 'assistant.text.delta', text }] : [];
+      if (!text) return [];
+      const parentToolCallId = extractParentToolCallId(update);
+      return [
+        {
+          ...base,
+          type: 'assistant.text.delta' as const,
+          text,
+          ...(parentToolCallId ? { parentToolCallId } : {}),
+        },
+      ];
     }
     case 'agent_thought_chunk': {
       const text = getTextContent(update['content']);
-      return text ? [{ ...base, type: 'thought.text.delta', text }] : [];
+      if (!text) return [];
+      const parentToolCallId = extractParentToolCallId(update);
+      return [
+        {
+          ...base,
+          type: 'thought.text.delta' as const,
+          text,
+          ...(parentToolCallId ? { parentToolCallId } : {}),
+        },
+      ];
     }
     case 'tool_call':
     case 'tool_call_update':
@@ -465,6 +483,13 @@ function normalizeSessionUpdate(
   }
 }
 
+function extractParentToolCallId(
+  update: Record<string, unknown>,
+): string | undefined {
+  const meta = isRecord(update['_meta']) ? update['_meta'] : undefined;
+  return meta ? getString(meta, 'parentToolCallId') : undefined;
+}
+
 function normalizeToolUpdate(
   update: Record<string, unknown>,
   base: NormalizedEventBase,

packages/sdk-typescript/src/daemon/ui/store.ts

@@ -142,6 +142,12 @@ function createState(
       ...(seed.permissionBlockByRequestId ?? {}),
     },
     toolProgress: { ...(seed.toolProgress ?? {}) },
+    activeAssistantBlockByParent: {
+      ...(seed.activeAssistantBlockByParent ?? {}),
+    },
+    activeThoughtBlockByParent: {
+      ...(seed.activeThoughtBlockByParent ?? {}),
+    },
     lastResyncRequired:
       seed.lastResyncRequired !== undefined
         ? { ...seed.lastResyncRequired }

packages/sdk-typescript/src/daemon/ui/transcript.ts

@@ -13,6 +13,7 @@ import type {
   DaemonTranscriptReducerOptions,
   DaemonTranscriptState,
   DaemonUiEvent,
+  DaemonUiTextEvent,
   DaemonUserShellTranscriptBlock,
 } from './types.js';
 import { DAEMON_PLAN_TOOL_CALL_ID } from './types.js';
@@ -42,6 +43,8 @@ export function createDaemonTranscriptState(
     toolBlockByCallId: {},
     trimmedToolNotificationByCallId: {},
     permissionBlockByRequestId: {},
+    activeAssistantBlockByParent: {},
+    activeThoughtBlockByParent: {},
     // PR-E sidechannel: track current tool / approval mode / progress
     toolProgress: {},
     awaitingResync: false,
@@ -98,6 +101,8 @@ export function appendLocalUserTranscriptMessage(
   next.activeUserBlockId = block.id;
   next.activeAssistantBlockId = undefined;
   next.activeThoughtBlockId = undefined;
+  next.activeAssistantBlockByParent = {};
+  next.activeThoughtBlockByParent = {};
   return trimTranscriptState(next);
 }
 
@@ -364,6 +369,10 @@ export function selectPendingPermissionBlocks(
   );
 }
 
+// Keyed (parentToolCallId) and scalar (activeAssistantBlockId) paths are
+// fully independent. Neither clears nor finalizes the other's blocks.
+// Only finishAssistant() or clearActiveText() with matching parentToolCallId
+// can finalize keyed-path blocks.
 function appendTextDelta(
   state: DaemonTranscriptState,
   kind: 'user' | 'assistant' | 'thought',
@@ -374,7 +383,24 @@ function appendTextDelta(
   text: string,
   event: DaemonUiEvent,
 ): void {
-  const existing = getWritableBlockById(state, state[activeKey]);
+  const parentId =
+    kind !== 'user' && 'parentToolCallId' in event
+      ? (event as DaemonUiTextEvent).parentToolCallId
+      : undefined;
+
+  const parentMap =
+    parentId != null
+      ? kind === 'assistant'
+        ? state.activeAssistantBlockByParent
+        : kind === 'thought'
+          ? state.activeThoughtBlockByParent
+          : undefined
+      : undefined;
+
+  const effectiveId =
+    parentMap && parentId != null ? parentMap[parentId] : state[activeKey];
+
+  const existing = getWritableBlockById(state, effectiveId);
   if (existing && existing.kind === kind) {
     existing.text = appendBoundedText(existing.text, text);
     existing.updatedAt = state.now;
@@ -392,11 +418,37 @@ function appendTextDelta(
   );
   if (kind === 'assistant') block.streaming = true;
   if (kind === 'thought') block.collapsed = true;
+  if (parentId != null) {
+    (block as DaemonTextTranscriptBlock).parentToolCallId = parentId;
+  }
   appendBlock(state, block);
-  state[activeKey] = block.id;
-  if (kind !== 'user') state.activeUserBlockId = undefined;
-  if (kind !== 'assistant') state.activeAssistantBlockId = undefined;
-  if (kind !== 'thought') state.activeThoughtBlockId = undefined;
+
+  if (parentMap && parentId != null) {
+    parentMap[parentId] = block.id;
+  } else {
+    state[activeKey] = block.id;
+  }
+
+  if (parentId != null) {
+    if (kind === 'assistant') {
+      delete state.activeThoughtBlockByParent[parentId];
+    }
+    if (kind === 'thought') {
+      const evictedAssistId = state.activeAssistantBlockByParent[parentId];
+      if (evictedAssistId) {
+        const evicted = getWritableBlockById(state, evictedAssistId);
+        if (evicted?.kind === 'assistant') {
+          evicted.streaming = false;
+          evicted.updatedAt = state.now;
+        }
+      }
+      delete state.activeAssistantBlockByParent[parentId];
+    }
+  } else {
+    if (kind !== 'user') state.activeUserBlockId = undefined;
+    if (kind !== 'assistant') state.activeAssistantBlockId = undefined;
+    if (kind !== 'thought') state.activeThoughtBlockId = undefined;
+  }
 }
 
 function finishAssistant(state: DaemonTranscriptState): void {
@@ -406,6 +458,16 @@ function finishAssistant(state: DaemonTranscriptState): void {
     existing.updatedAt = state.now;
   }
   state.activeAssistantBlockId = undefined;
+
+  for (const blockId of Object.values(state.activeAssistantBlockByParent)) {
+    const block = getWritableBlockById(state, blockId);
+    if (block?.kind === 'assistant') {
+      block.streaming = false;
+      block.updatedAt = state.now;
+    }
+  }
+  state.activeAssistantBlockByParent = {};
+  state.activeThoughtBlockByParent = {};
 }
 
 function upsertToolBlock(
@@ -542,7 +604,7 @@ function upsertToolBlock(
   // never points at it. Effective-status keeps the pointer in sync
   // with what was actually written to the block.
   updateCurrentToolPointer(state, event.toolCallId, event.status ?? 'pending');
-  clearActiveText(state);
+  clearActiveText(state, event.parentToolCallId);
 }
 
 /**
@@ -842,6 +904,8 @@ function cloneTranscriptState(
     blocks: state.blocks,
     blockIndexById: state.blockIndexById,
     toolBlockByCallId: { ...state.toolBlockByCallId },
+    activeAssistantBlockByParent: { ...state.activeAssistantBlockByParent },
+    activeThoughtBlockByParent: { ...state.activeThoughtBlockByParent },
     trimmedToolNotificationByCallId: {
       ...state.trimmedToolNotificationByCallId,
     },
@@ -926,6 +990,20 @@ function trimTranscriptState(
   if (!keptIds.has(state.activeThoughtBlockId ?? '')) {
     state.activeThoughtBlockId = undefined;
   }
+  for (const [parentId, blockId] of Object.entries(
+    state.activeAssistantBlockByParent,
+  )) {
+    if (!keptIds.has(blockId)) {
+      delete state.activeAssistantBlockByParent[parentId];
+    }
+  }
+  for (const [parentId, blockId] of Object.entries(
+    state.activeThoughtBlockByParent,
+  )) {
+    if (!keptIds.has(blockId)) {
+      delete state.activeThoughtBlockByParent[parentId];
+    }
+  }
   return state;
 }
 
@@ -1021,10 +1099,26 @@ function allocateBlockId(state: DaemonTranscriptState, prefix: string): string {
   return id;
 }
 
-function clearActiveText(state: DaemonTranscriptState): void {
-  finishAssistant(state);
-  state.activeUserBlockId = undefined;
-  state.activeThoughtBlockId = undefined;
+function clearActiveText(
+  state: DaemonTranscriptState,
+  parentToolCallId?: string,
+): void {
+  if (parentToolCallId) {
+    const assistId = state.activeAssistantBlockByParent[parentToolCallId];
+    if (assistId) {
+      const block = getWritableBlockById(state, assistId);
+      if (block?.kind === 'assistant') {
+        block.streaming = false;
+        block.updatedAt = state.now;
+      }
+      delete state.activeAssistantBlockByParent[parentToolCallId];
+    }
+    delete state.activeThoughtBlockByParent[parentToolCallId];
+  } else {
+    finishAssistant(state);
+    state.activeUserBlockId = undefined;
+    state.activeThoughtBlockId = undefined;
+  }
 }
 
 function appendBoundedText(existing: string, text: string): string {

packages/sdk-typescript/src/daemon/ui/types.ts

@@ -82,6 +82,7 @@ export interface DaemonUiEventBase {
 export interface DaemonUiTextEvent extends DaemonUiEventBase {
   type: 'user.text.delta' | 'assistant.text.delta' | 'thought.text.delta';
   text: string;
+  parentToolCallId?: string;
 }
 
 export interface DaemonUiUserShellCommandEvent extends DaemonUiEventBase {
@@ -647,6 +648,8 @@ export interface DaemonTextTranscriptBlock extends DaemonTranscriptBlockBase {
   text: string;
   streaming?: boolean;
   collapsed?: boolean;
+  /** Used by the reducer for per-subAgent block routing; renderers may use it for nesting. */
+  parentToolCallId?: string;
 }
 
 export interface DaemonToolTranscriptBlock extends DaemonTranscriptBlockBase {
@@ -793,6 +796,8 @@ export interface DaemonTranscriptState
   activeUserBlockId?: string;
   activeAssistantBlockId?: string;
   activeThoughtBlockId?: string;
+  activeAssistantBlockByParent: Record<string, string>;
+  activeThoughtBlockByParent: Record<string, string>;
   blockIndexById: Record<string, number>;
   toolBlockByCallId: Record<string, string>;
   trimmedToolNotificationByCallId: Record<string, true>;