fix(memory): skip background-task-result blocks in the extraction window

[RowitZou]

Problem

Bug 3 from the 2026-05-20 dogfood had three parts. PR #8 (ce8ef67) fixed the transient-snapshot and role-name-filename symptoms via the memoryExtractor prompt. This PR closes the third — cross-layer duplication — which is a code issue, not a prompt one.

When a background dispatch completes, its deliverable is injected into the manager's prompt as a <background-task-result> block. The worker that produced it has already run its own extraction over its fork transcript (into its role-private L3). The manager's afterEndTurn extraction then sees the same block and re-extracts the finding into the user-level root (L1) — and cannot dedup it, because collectExistingMemoriesForRole(main) only covers L1 + _shared, not worker L3. The dogfood saw one "AI Agent PKM" research topic land 3 copies in the user root, on top of the worker's own L3 entries.

Fix

buildExtractPrompt now runs stripBackgroundResultBlocks over the rendered conversation text: each <background-task-result>…</background-task-result> span is replaced with a one-line marker. The manager's own assistant messages — its synthesis and reactions to the result — are untouched and still extracted; only the worker's raw deliverable is dropped.

It applies to every extraction (manager and worker), so a worker that itself received a sub-dispatch result also won't re-extract it.

Scope

The remaining same-topic copies across role-private L3 dirs (e.g. generalist/ + webSearcher/ both holding a PKM note) are by design — per-role extraction is intentional, and reconciling those is the curator's job. Bug 4's fix (536ba51) restored the curator's runtime + throttle so that path works again; the historical 113-file backlog will be consolidated once it runs.

This is the last of the Bug 3 / Bug 4 chain. No prompt strings changed.

Testing

• New extract.test.ts case: buildExtractPrompt strips a <background-task-result> block (inner finding gone, marker present) while keeping the manager's surrounding turn.
• The extract.test.ts JSON-ban regression guard is unaffected.
• pnpm typecheck clean; pnpm test 1463/1463 pass.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR fixes cross-layer memory duplication caused by <background-task-result>...</background-task-result> blocks being re-ingested by the manager’s extraction pass after a background dispatch completes. It prevents the manager (and any worker) from re-extracting the worker’s raw deliverable by stripping these blocks from the extraction window while keeping surrounding conversation context.

Changes:

• Add stripBackgroundResultBlocks() to replace <background-task-result>...</background-task-result> spans with a single-line omission marker.
• Apply the stripping step inside buildExtractPrompt() before truncating the extraction window.
• Add a regression test ensuring the block contents are removed while surrounding turns remain.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/memory/extract.ts	Strips <background-task-result> blocks from the conversation text used for memory extraction to avoid cross-layer duplication.
src/memory/extract.test.ts	Adds a test case asserting background-result blocks are removed from the extract prompt while adjacent user content remains.

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