Prompt reduction

shell/src/app/chat/chat-cleaner/chat-cleaner.spec.ts

@@ -17,6 +17,7 @@
 import {TestBed} from '@angular/core/testing';
 import {describe, it, expect, beforeEach} from 'vitest';
 import {ChatCleaner} from './chat-cleaner';
+import {MessageRole} from '../llm-client/llm-client';
 
 describe('ChatCleaner', () => {
   let service: ChatCleaner;
@@ -197,6 +198,73 @@ describe('ChatCleaner', () => {
     });
   });
 
+  describe('isUserLayoutSnapshot', () => {
+    it('returns true for unprompted USER messages with isSnapshot: true or JSON layout content', () => {
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.USER,
+          content: '[{"version":"v0.9"}]',
+          isSnapshot: true,
+        }),
+      ).toBe(true);
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.USER,
+          content: '[{"version":"v0.9"}]',
+        }),
+      ).toBe(true);
+    });
+
+    it('returns false for undefined, non-USER, prompted, attachment-bearing, or prose-prefixed messages', () => {
+      expect(service.isUserLayoutSnapshot(undefined)).toBe(false);
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.MODEL,
+          content: '[{"version":"v0.9"}]',
+        }),
+      ).toBe(false);
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.USER,
+          content: '[{"version":"v0.9"}]',
+          promptId: 'p1',
+        }),
+      ).toBe(false);
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.USER,
+          content: '[{"version":"v0.9"}]',
+          attachments: [{name: 'img.png', mimeType: 'image/png', data: 'abc'}],
+        }),
+      ).toBe(false);
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.USER,
+          content: '[{"version":"v0.9"}]',
+          isSnapshot: false,
+        }),
+      ).toBe(false);
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.USER,
+          content: 'Fix this: [{"version":"v0.9"}]',
+        }),
+      ).toBe(false);
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.USER,
+          content: undefined as unknown as string,
+        }),
+      ).toBe(false);
+      expect(
+        service.isUserLayoutSnapshot({
+          role: MessageRole.USER,
+          content: null as unknown as string,
+        }),
+      ).toBe(false);
+    });
+  });
+
   describe('Nullish and empty input resilience', () => {
     it('returns safe defaults when calling stripPulse on empty or nullish values', () => {
       expect(service.stripPulse('')).toBe('');

shell/src/app/chat/chat-cleaner/chat-cleaner.ts

@@ -16,6 +16,7 @@
 
 import {Injectable} from '@angular/core';
 import {tryParseJsonArray} from '../../utils/json';
+import {LlmMessage, MessageRole} from '../llm-client/llm-client';
 
 const MD_FENCE_REGEX = /```(?:jsonl?|jsonlines|a2ui|html|xml)?\s*([\s\S]*?)\s*```/gi;
 const TAG_REGEX = /<(thought|thinking|reasoning)>([\s\S]*?)(?:<\/\1>|$)/gi;
@@ -164,4 +165,19 @@ export class ChatCleaner {
     const parsedArray = tryParseJsonArray(trimmed);
     return parsedArray.success && isLayoutArray(parsedArray.data);
   }
+
+  /**
+   * Determines if a message is an unprompted USER canvas layout snapshot
+   * rather than a human prompt turn or a message with attachments.
+   */
+  isUserLayoutSnapshot(msg?: LlmMessage): boolean {
+    if (!msg || msg.role !== MessageRole.USER || msg.promptId || msg.attachments?.length) {
+      return false;
+    }
+    if (msg.isSnapshot !== undefined) {
+      return msg.isSnapshot;
+    }
+    const trimmed = typeof msg.content === 'string' ? msg.content.trim() : '';
+    return (trimmed.startsWith('[') || trimmed.startsWith('{')) && this.isLayoutSnapshot(trimmed);
+  }
 }