fix(ui-trajectory): consume prompt changes once

packages/client/ui-trajectory/tests/snapshot-builder.spec.ts

@@ -0,0 +1,62 @@
+import { describe, expect, it } from 'vitest'
+import type { RequestView } from '@deepseek-ai/dsh-client-runtime/client'
+import type { TrajectoryConversationViewNode } from '../src/client/trajectory-contract.ts'
+import { TrajectorySnapshotBuilder } from '../src/client/trajectory-snapshot-builder.ts'
+
+function assistantRequest(startSeq: number, step: number): Extract<RequestView, { purpose: 'assistant' }> {
+  return {
+    purpose: 'assistant',
+    startSeq,
+    turn: 1,
+    step,
+    startedAt: startSeq,
+    completedAt: startSeq + 1,
+    status: 'complete',
+  }
+}
+
+describe('TrajectorySnapshotBuilder', () => {
+  it('inherits one request header across requests without repeating its prompt change', () => {
+    const prompt = {
+      config: { provider: 'test', model: 'test' },
+      system: 'one initial prompt',
+      tools: [],
+    }
+    const nodes: TrajectoryConversationViewNode[] = [
+      {
+        key: 'header',
+        kind: 'trajectory-request-header',
+        id: '2',
+        target: 'trajectory',
+        anchorSeq: 2,
+        data: {
+          kind: 'request-header',
+          header: {
+            seq: 2,
+            time: 2,
+            prompt,
+            change: { seq: 2, time: 2, kind: 'initial' },
+            location: { kind: 'session' },
+          },
+        },
+      },
+      ...[assistantRequest(3, 1), assistantRequest(5, 2)].map(request => ({
+        key: `assistant:${request.step}`,
+        kind: 'trajectory-assistant-step',
+        id: `1:${request.step}`,
+        target: 'trajectory' as const,
+        anchorSeq: request.startSeq,
+        data: { kind: 'assistant' as const, partial: null, request },
+      })),
+    ]
+
+    const snapshot = new TrajectorySnapshotBuilder().replace({ nodes })
+
+    expect(snapshot.requests.map(request => request.purpose === 'assistant'
+      ? request.prompt?.system
+      : undefined)).toEqual(['one initial prompt', 'one initial prompt'])
+    expect(snapshot.requests.map(request => request.purpose === 'assistant'
+      ? request.promptChange?.kind
+      : undefined)).toEqual(['initial', undefined])
+  })
+})