Best possible solution:

Land the shared helper and focused handler tests after dropping the CHANGELOG.md hunk; keep release-note context in the PR body or squash message.

Do we have a high-confidence way to reproduce the issue?

Yes. Source inspection shows current main runs the cleanup after final compaction and unconditionally zeroes every assistant usage snapshot; I did not run a live TUI/gateway reproduction in this read-only review.

Is this the best way to solve the issue?

Mostly yes. The runtime change targets the live compaction handler and shares the replay sanitizer invariant, but the release-owned changelog edit is not part of the correct fix.

Full review comments:

• [P3] Remove the release-owned changelog edit — CHANGELOG.md:28
CHANGELOG.md is release-owned in this repo, and normal fix PRs should keep release-note context in the PR body or squash message instead. Please drop this hunk before merge.
  Confidence: 0.91

Overall correctness: patch is correct
Overall confidence: 0.86

AGENTS.md: found and applied where relevant.

Codex review notes: model internal, reasoning high; reviewed against f1b8827d20c8.

Label justifications:

• P2: This fixes a normal-priority agent session accounting bug where post-compaction context usage can be reported as zero.
• rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🌊 off-meta tidepool and patch quality is 🐚 platinum hermit.
• status: 👀 ready for maintainer look: ClawSweeper has no concrete contributor-facing blocker left for this PR. Not applicable: The author is an OpenClaw automation bot, so the external contributor real-behavior proof gate does not apply; the PR body and CI provide supplemental validation signal.

PR surface:

Source +11, Tests +213, Docs 0. Total +224 across 5 files.

Acceptance criteria:

• [P1] git diff --check.

What I checked:

• Current-main bug path: On current main, non-retry handleCompactionEnd calls clearStaleAssistantUsageOnSessionMessages, and that helper assigns makeZeroUsageSnapshot() to every assistant message without checking a compaction boundary. (src/agents/embedded-agent-subscribe.handlers.compaction.ts:138, f1b8827d20c8)
• PR helper boundary: The PR-head helper finds the latest compaction summary, uses timestamp or legacy index boundaries, and keeps marker-free zero-all behavior opt-in for the live handler. (src/agents/compaction-usage.ts:21, 0f3740507ecb)
• PR live handler use: The PR live compaction handler calls the shared helper with mutate: true and whenMissingCompactionSummary: "zeroAssistantUsage", preserving the old marker-free final compaction behavior. (src/agents/embedded-agent-subscribe.handlers.compaction.ts:195, 0f3740507ecb)
• Regression coverage: The PR adds handler coverage for stale-before/fresh-after usage, summary-first transcripts, legacy no-timestamp ordering, marker-free compaction, and timestamp-fresh usage before delayed summaries. (src/agents/embedded-agent-subscribe.handlers.compaction.test.ts:370, 0f3740507ecb)
• Dependency contract inside repo: Agent core compaction summaries carry numeric or string timestamps, and context usage derives from the last assistant usage snapshot, so stale zeroing and fresh preservation directly affect the context counter. (packages/agent-core/src/types.ts:360, f1b8827d20c8)
• Release-owned changelog policy: Root repository policy says CHANGELOG.md is release-only and normal PRs should not edit it; this PR still modifies line 28 in that file. (AGENTS.md:230, f1b8827d20c8)

Likely related people:

• steipete: Commit 7e0b3f16e3bd changed the old subscribe compaction cleanup to preserve assistant usage shape by zeroing snapshots, which is the behavior this PR narrows. (role: introduced behavior; confidence: high; commits: 7e0b3f16e3bd; files: src/agents/pi-embedded-subscribe.handlers.compaction.ts, src/agents/pi-embedded-subscribe.subscribe-embedded-pi-session.splits-long-single-line-fenced-blocks-reopen.test.ts, src/agents/embedded-agent-subscribe.handlers.compaction.ts)
• vignesh07: Commit 6bf5e76be666 added the replay-side stale pre-compaction usage snapshot pattern that this PR promotes into a shared helper. (role: adjacent boundary-pattern contributor; confidence: high; commits: 6bf5e76be666; files: src/agents/pi-embedded-runner.sanitize-session-history.test.ts, src/agents/embedded-agent-runner/replay-history.ts)
• ragesaq: Current-main blame attributes the renamed compaction handler, replay sanitizer, and agent-core compaction timestamp/usage paths to a15427d605. (role: recent current-main area contributor; confidence: medium; commits: a15427d605fe; files: src/agents/embedded-agent-subscribe.handlers.compaction.ts, src/agents/embedded-agent-runner/replay-history.ts, packages/agent-core/src/harness/messages.ts)

• 🦀 challenger crab: rare, exceptional readiness with strong proof, clean implementation, and convincing validation.
• 🦞 diamond lobster: very strong readiness with only minor maintainer review expected.
• 🐚 platinum hermit: good normal PR, likely mergeable with ordinary maintainer review.
• 🦐 gold shrimp: useful signal, but proof or patch confidence is still limited.
• 🦪 silver shellfish: thin signal; proof, validation, or implementation needs work.
• 🧂 unranked krab: not merge-ready because proof is missing/unusable or there are serious correctness or safety concerns.
• 🌊 off-meta tidepool: rating does not apply to this item.

Shiny media proof means a screenshot, video, or linked artifact directly shows the changed behavior. Runtime, network, CSP, and security claims still need visible diagnostics.

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