PR Review Summary

Status: Approved

🪜 Strategic-Fit Decision

Per §9 Strategic-Fit Step-Back:

• Decision: Approve
• Rationale: Both repairs re-anchor the specs on the current GridRowScrollPinning contract, and I verified each against the add-on source — the old tests asserted removed/never-listened behavior. Test-only, no runtime change. Clean Approve.

Peer-Review Opening: Thanks, Euclid — I read GridRowScrollPinning to confirm both invariants, and they hold. Good diagnosis that the blank frames were test-driver drift, not a product regression.

🧭 Patch-Blind Premise Snapshot

• Inputs Read Before Patch: #14853, the diff, and src/main/addon/GridRowScrollPinning.mjs (listen target + pause semantics) + src/grid/VerticalScrollbar.mjs.
• Expected Solution Shape: the failures are stale test expectations, so a correct repair drives the real engagement target the add-on listens on and asserts the current pause invariant — without disabling a check that guards real user motion, and with no runtime change.
• Patch Verdict: Matches, both verified against source. (1) GridRowScrollPinning.mjs:280 attaches mousedown to the vertical-scrollbar node, not .neo-grid-view — so the old flood's wrapper.dispatchEvent(mousedown) never engaged the add-on; the fix dispatches on .neo-grid-vertical-scrollbar (the real target). (2) The add-on has no setTimeout/clearTimeout and line 132 states "we MUST KEEP pinning active until the worker physically catches up" (release via the global mouseup, lines 201–205) — so the old ThumbDragPause assertion (pause → cleared → blank) tested removed behavior; flipping it to "pinning survives the pause" is the current invariant.
• Premise Coherence: Coheres with verify-before-assert — the specs now assert what the add-on actually does; the flood profile's bounce-oracle disable is justified by the add-on's design (raw scrollTop saturation is blank-frame stress, not smooth motion).

🕸️ Context & Graph Linking

• Target Epic / Issue ID: Resolves #14853
• Related Graph Nodes: the grid E2E fallout set (#14852/#14854 siblings), Neo.main.addon.GridRowScrollPinning, Neo.grid.VerticalScrollbar.

🔬 Depth Floor

• Challenge: The bounce oracle is disabled during Profile 5 (__COUNT_BOUNCES = false) — I confirmed it's scoped (re-enabled after, stays active for the wheel/thumb-drag profiles, and blankFrames === 0 is still asserted for the flood). The residual risk is that a real jitter regression under the raw-flood path would now go uncounted; the reasoning (artificial saturation ≠ smooth-motion jitter) is sound and the disable is explicit, so non-blocking — but it's the one place in this diff where a check is turned off, worth watching. Minor consistency note: ThumbDragPause still runs on the heavy /apps/devindex/ app that the sibling #14872 moved away from (to examples/grid/lockedColumns/) for determinism — not this PR's scope, but a future pass could align it onto a stable example.

Rhetorical-Drift Audit: Pass — the PR prose ("keeps pinning active until release/catch-up", "listens on .neo-grid-vertical-scrollbar", "No production runtime change") matches the diff and the add-on source exactly.

🧠 Graph Ingestion Notes

• [RETROSPECTIVE]: GridRowScrollPinning engages on a mousedown on the vertical-scrollbar node, not the .neo-grid-view wrapper — E2E that simulates thumb-drag pinning must dispatch there. And its invariant is keep pinning active until worker catch-up / pointer release (no timeout-clear) — a paused thumb-drag must NOT blank. Tests asserting a timeout-clear are stale.

N/A Audits — 🎯 📑 🪜 📡 🔗

N/A across listed dimensions: test-only E2E repair — #14853 is a leaf; no public/consumed contract, OpenAPI, or skill surface; no runtime code.

🧪 Test-Execution & Location Audit

• Verified both migrated invariants against src/main/addon/GridRowScrollPinning.mjs (listen target line 280; keep-pinning-until-catch-up line 132; no timeout in the file).
• Canonical location: specs stay under test/playwright/e2e/grid/.
• Did not re-run locally (whitebox E2E harness) — you ran the focused pair 2/2 (RowPinning: 0 blank frames, 0 jitter bounces); the CI E2E lane is authoritative.

Findings: Invariants verified current by inspection; execution evidence is your 2/2 focused run.

📋 Required Actions

No required actions — eligible for human merge.

📊 Evaluation Metrics

Verdict weights: 30% premise / 30% architecture + placement / 30% diff correctness / 10% AC/audit sanity.

• [ARCH_ALIGNMENT]: 91 — drives the real add-on engagement target; asserts the actual pinning invariant.
• [CONTENT_COMPLETENESS]: 89 — both regressions fixed + a stronger zero-rows blank guard; residual none.
• [EXECUTION_QUALITY]: 88 — scoped, commented oracle disable; explicit component-not-found guard.
• [PRODUCTIVITY]: 87 — restores row-pinning E2E proof and closes another grid-fallout ticket.
• [IMPACT]: 82 — flagship grid pinning behavior, back under E2E proof.
• [COMPLEXITY]: 28 — test-only, but invariant-migration; reviewed against the add-on source.
• [EFFORT_PROFILE]: Quick Win — focused, source-verified repair.

Approving — both invariants check out against GridRowScrollPinning. Land it.