fix(client): address conversation assembly review findings

packages/client/ui-conversation/src/client/conversation-nodes/turn-tail.ts

@@ -122,14 +122,26 @@ function tailData(context: ConversationNodeContext<TurnTailState>): TurnTailChat
     .filter((candidate): candidate is Readonly<FinalAssistantChatData> => candidate.finalNode !== undefined)
     .sort((left, right) => left.finalNode.seq - right.finalNode.seq)
   const closing = finalized.findLast(hasText) ?? null
-  const latest = finalized.at(-1)
+  let latestTranscriptSeq = finalized.at(-1)?.finalNode.seq
+  for (const match of context.matches) {
+    const event = match.event
+    const candidate = event.type === 'tool/call'
+      || (event.type === 'tool/result' && isAppendSurfaceEvent(event))
+      || (event.type === 'turn/end' && event.data.reason.kind === 'error')
+      || (event.type as string) === 'llm/retry'
+      ? event.seq
+      : undefined
+    if (candidate !== undefined && (latestTranscriptSeq === undefined || candidate > latestTranscriptSeq)) {
+      latestTranscriptSeq = candidate
+    }
+  }
   const metrics = deriveTurnMetrics(finalized.map(candidate => candidate.finalNode)).get(end.event.data.turn)
   return {
     turn: end.event.data.turn,
     seq: end.event.seq,
     time: end.event.time,
     closing,
-    branchUnavailable: closing === null || latest?.finalNode.seq !== closing.finalNode.seq,
+    branchUnavailable: closing === null || latestTranscriptSeq !== closing.finalNode.seq,
     ...metrics?.ttftMs === undefined ? {} : { ttftMs: metrics.ttftMs },
     ...metrics?.tokensPerSecond === undefined ? {} : { tokensPerSecond: metrics.tokensPerSecond },
   }
@@ -141,6 +153,9 @@ export const turnTailDefinition: ConversationNodeDefinition<TurnTailState> = {
   match: (event) => {
     if (event.type === 'turn/start') return { id: String(event.data.turn), role: 'start' }
     if (event.type === 'turn/end') return { id: String(event.data.turn), role: 'update' }
+    if (event.type === 'tool/call' || event.type === 'tool/result') {
+      return { id: String(event.data.turn), role: 'update' }
+    }
     const coordinates = turnCoordinates(event)
     if (coordinates !== undefined) return { id: String(coordinates.turn), role: 'update' }
     return null

packages/client/ui-conversation/src/client/index.ts

@@ -3,19 +3,18 @@
  * between the independently implemented skeleton and chat domains; `apply.ts`
  * owns their slot assembly.
  */
+export type {} from './conversation-nodes/assistant.ts'
+export type {} from './conversation-nodes/command.ts'
+export type {} from './conversation-nodes/compaction.ts'
+export type {} from './conversation-nodes/fallback.ts'
+export type {} from './conversation-nodes/message.ts'
+export type {} from './conversation-nodes/retry.ts'
+export type {} from './conversation-nodes/tool.ts'
+export type {} from './conversation-nodes/turn-error.ts'
+export type {} from './conversation-nodes/turn-tail.ts'
+
 export { apply, inject } from './apply.ts'
 export { ConversationService } from './service.ts'
-export { registerAssistantConversationNode } from './conversation-nodes/assistant.ts'
-export { registerChatConversationView } from './conversation-nodes/chat-snapshot-builder.ts'
-export { registerCommandConversationNode } from './conversation-nodes/command.ts'
-export { registerCompactionConversationNode } from './conversation-nodes/compaction.ts'
-export { registerUnknownConversationFallback } from './conversation-nodes/fallback.ts'
-export { registerInboxConversationNodes } from './conversation-nodes/inbox.ts'
-export { registerMessageConversationNode } from './conversation-nodes/message.ts'
-export { registerRetryConversationNode } from './conversation-nodes/retry.ts'
-export { registerToolConversationNode } from './conversation-nodes/tool.ts'
-export { registerTurnErrorConversationNode } from './conversation-nodes/turn-error.ts'
-export { registerTurnTailConversationNode } from './conversation-nodes/turn-tail.ts'
 export type { IConversation } from './service.ts'
 
 export type {

packages/client/ui-conversation/tests/conversation-node-definitions.spec.ts

@@ -16,7 +16,7 @@ import { toolDefinition } from '../src/client/conversation-nodes/tool.ts'
 import { turnErrorDefinition } from '../src/client/conversation-nodes/turn-error.ts'
 import { turnTailDefinition } from '../src/client/conversation-nodes/turn-tail.ts'
 import type {
-  AssistantChatData, ManualCompactionChatData, RetryChatData, ToolChatData,
+  AssistantChatData, ManualCompactionChatData, RetryChatData, ToolChatData, TurnTailChatData,
 } from '../src/client/contract/chat-nodes.ts'
 
 const DEFINITIONS: readonly ConversationNodeDefinition[] = [
@@ -413,6 +413,30 @@ describe('built-in conversation node Definitions', () => {
     ])
   })
 
+  it('keeps branching unavailable when a tool result follows the closing Assistant', () => {
+    const value = assembler([
+      at(1, 'turn/start', { turn: 1 }),
+      at(2, 'step/start', { turn: 1, step: 1 }),
+      at(3, 'assistant/message', {
+        turn: 1,
+        step: 1,
+        message: assistantMessage('assistant-before-tool', 'running a tool'),
+      }, { surfaceOp: 'append' }),
+      at(4, 'tool/call', { turn: 1, step: 1, callId: 'late-tool', name: 'read', arguments: '{}' }),
+      at(5, 'tool/result', {
+        turn: 1,
+        step: 1,
+        message: toolResult('late-tool', 'done'),
+      }, { surfaceOp: 'append' }),
+      at(6, 'step/end', { turn: 1, step: 1 }),
+      at(7, 'turn/end', { turn: 1, reason: { kind: 'completed' } }),
+    ])
+
+    const tail = node(snapshot(value), 'turn-tail')?.data as TurnTailChatData
+    expect(tail.closing?.finalNode.seq).toBe(3)
+    expect(tail.branchUnavailable).toBe(true)
+  })
+
   it('replays inbox predecessors after prepend and reclassifies the dependent message as steering', () => {
     const value = assembler([
       at(3, 'user/message', textMessage('steer-1', 'change direction'), { surfaceOp: 'append' }),