fix(history): anchor collapsed history recency

src/core/history.ts

@@ -24,10 +24,12 @@ import { bytesToBase64 } from './png.js';
  * emitter (here) and the matcher (transform.ts) must reference this constant.
  */
 export const HISTORY_SYNTHETIC_INTRO =
-  '[Earlier turns of THIS conversation, transcribed in the image(s) below. Each turn is wrapped in <user t="N">...</user> or <assistant t="N">...</assistant> tags, where N is an absolute turn index (larger N = more recent); attribute every turn strictly by its tag, and treat the highest-N turns as the most recent prior context, NOT the low-N opening turns. This is prior context, NOT the current request.]';
+  '[Earlier turns of THIS conversation, transcribed in the image(s) below. Each turn is wrapped in <user t="N">...</user> or <assistant t="N">...</assistant> tags, where N is an absolute turn index (larger N = more recent); attribute every turn strictly by its tag, and treat the highest-N turns as the most recent prior context, NOT the low-N opening turns. Earlier turns may contain questions or tasks that were already answered later in this same history; do not reopen low-N turns unless the live text after this block asks you to. This is prior context, NOT the current request.]';
 export const HISTORY_SYNTHETIC_OUTRO =
   '[End of earlier conversation. The current request is the live text that follows below.]';
 
+const LATEST_COLLAPSED_USER_PREVIEW_CHARS = 300;
+
 /** Break-even gate predicate. Injected by transform.ts to avoid a circular import.
  *  IMPORTANT: pass the full string, not text.length — the row-aware path in
  *  isCompressionProfitable must see actual newlines to budget images correctly.
@@ -271,6 +273,42 @@ export function messagesToHistorySegments(
   return { text: textOut.join('\n\n'), slotText: slotOut.join('\n\n') };
 }
 
+function userPromptText(content: string | ContentBlock[]): string {
+  if (typeof content === 'string') return content;
+  const parts: string[] = [];
+  for (const blk of content) {
+    if (!blk || typeof blk !== 'object') continue;
+    const t = (blk as { type?: string }).type;
+    if (t === 'text') parts.push((blk as TextBlock).text);
+    else if (t === 'image') parts.push('[image]');
+  }
+  return parts.join('\n\n');
+}
+
+function compactPreview(text: string): string {
+  const compact = text.replace(/\s+/g, ' ').trim();
+  if (compact.length <= LATEST_COLLAPSED_USER_PREVIEW_CHARS) return compact;
+  return compact.slice(0, LATEST_COLLAPSED_USER_PREVIEW_CHARS).trimEnd() + '...';
+}
+
+function latestCollapsedUserPointer(
+  messages: Message[],
+  upToExclusive: number,
+  fromInclusive: number,
+): TextBlock | undefined {
+  for (let i = upToExclusive - 1; i >= fromInclusive; i--) {
+    const m = messages[i]!;
+    if (m.role !== 'user') continue;
+    const preview = compactPreview(userPromptText(m.content));
+    if (!preview) continue;
+    return {
+      type: 'text',
+      text: `[Most recent collapsed user turn: <user t="${i}">${preview}</user>. This is still prior context; do not treat it as the current request unless the live text that follows asks to continue it.]`,
+    };
+  }
+  return undefined;
+}
+
 /**
  * Collapse the closed-prefix run into one synthetic user message with 1+ history images.
  * Returns original messages unchanged on any no-collapse path (reason set in info).
@@ -440,9 +478,11 @@ export async function collapseHistory(
     info.reason = 'render_empty';
     return { messages, info };
   }
+  const latestUserPointer = latestCollapsedUserPointer(messages, collapseLen, protectedPrefix);
   const syntheticContent: ContentBlock[] = [
     { type: 'text', text: HISTORY_SYNTHETIC_INTRO },
     ...imageBlocks,
+    ...(latestUserPointer ? [latestUserPointer] : []),
     { type: 'text', text: HISTORY_SYNTHETIC_OUTRO },
   ];
   const syntheticUser: Message = {

tests/history.test.ts

@@ -10,7 +10,7 @@
  *     images.
  *   - `messagesToHistoryText`: `--- role ---` framing, skips empty turns.
  *   - `collapseHistory`: full pipeline — opts handling, break-even gate,
- *     synthetic user message shape (text+image+text), live-tail preservation.
+ *     synthetic user message shape (text+image+recency pointer+text), live-tail preservation.
  *   - `transformRequest` end-to-end: compressHistory off (default), on with
  *     enough turns to fire, off when no closed prefix exists.
  */
@@ -315,7 +315,37 @@ describe('collapseHistory', () => {
     expect(out[2]).toBe(msgs[11]);
   });
 
-  it('splits dense collapsed history into readable image pages without plaintext side channels', async () => {
+  it('adds live-text recency guardrails for collapsed history', async () => {
+    const oldMarker = 'OLD WORKTREE QUESTION';
+    const latestMarker = 'CURRENT FRONTIER IR REUSE';
+    const msgs: Message[] = [];
+    for (let i = 0; i < 14; i++) {
+      const marker = i === 0 ? oldMarker : i === 10 ? latestMarker : `turn ${i}`;
+      const body = `${marker}: ` + 'x'.repeat(2800);
+      msgs.push(i % 2 === 0 ? usr(body) : asst(body));
+    }
+
+    const { messages: out, info } = await collapseHistory(msgs, profitable, {
+      keepTail: 2,
+      minCollapsePrefix: 5,
+      cols: 100,
+      collapseChunk: 0,
+    });
+
+    expect(info.reason).toBe(undefined);
+    expect(info.collapsedTurns).toBe(12);
+    const content = out[0]!.content as Array<Record<string, unknown>>;
+    const textBlocks = content.filter((c) => c.type === 'text') as Array<{ text: string }>;
+    expect(textBlocks).toHaveLength(3);
+    expect(textBlocks[0]!.text).toContain('do not reopen low-N turns');
+    expect(textBlocks[1]!.text).toContain('Most recent collapsed user turn');
+    expect(textBlocks[1]!.text).toContain('<user t="10">');
+    expect(textBlocks[1]!.text).toContain(latestMarker);
+    expect(textBlocks[1]!.text).not.toContain(oldMarker);
+    expect(textBlocks[2]!.text).toContain('current request is the live text');
+  });
+
+  it('splits dense collapsed history into readable image pages with only a bounded recency pointer', async () => {
     const body = Array.from(
       { length: 180 },
       (_, i) => `line ${i}: ${'x'.repeat(80)}`,
@@ -334,9 +364,11 @@ describe('collapseHistory', () => {
     );
     const content = out[0]!.content as Array<Record<string, unknown>>;
     const textBlocks = content.filter((c) => c.type === 'text');
-    expect(textBlocks).toHaveLength(2);
+    expect(textBlocks).toHaveLength(3);
     expect((textBlocks[0] as { text: string }).text).toContain('attribute every turn strictly by its tag');
-    expect((textBlocks[1] as { text: string }).text).toContain('current request is the live text');
+    expect((textBlocks[1] as { text: string }).text).toContain('Most recent collapsed user turn');
+    expect(((textBlocks[1] as { text: string }).text).length).toBeLessThan(500);
+    expect((textBlocks[2] as { text: string }).text).toContain('current request is the live text');
     expect(content.filter((c) => c.type === 'image')).toHaveLength(info.collapsedImages);
   });