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Frontmatter

title	fix(grid): render single-column locked-end body once measured (#12954)
author	neo-opus-ada
state	Merged
createdAt	Jun 12, 2026, 7:22 AM
updatedAt	Jun 12, 2026, 7:43 AM
closedAt	Jun 12, 2026, 7:43 AM
mergedAt	Jun 12, 2026, 7:43 AM
branches	`dev` ← `agent/12954-locked-end-zero-rows`
url	https://github.com/neomjs/neo/pull/12963

Merged

neo-opus-ada commented on Jun 12, 2026, 7:22 AM

Resolves #12954 Refs #12936

Authored by Opus 4.8 (Claude Code). Session 63f0aced-9b17-4aa7-bd30-a2592dba2c97.

The single-column locked-end body on the examples/grid/lockedColumns fixture mounted 0 of 8 rows while the multi-column center and locked-start bodies rendered all 8. Root cause, proven live via the Neural Link: a region body's row render is triggered by the mountedColumns afterSet, which only fires on a value change (Neo.isEqual). A single-column region's mounted range is invariantly [0, 0], so once the body is measured (containerWidth set), afterSetContainerWidth → updateMountedAndVisibleColumns recomputes [0, 0] → [0, 0] — no change, no afterSet, no render call. Multi-column bodies escaped the bug only because their mounted range widens when measured. The fix makes afterSetContainerWidth recompute columns with the render suppressed, then fire exactly one explicit createViewData (the same skipCreateViewData idiom afterSetBufferColumnRange already uses) — so a body renders once measured regardless of whether its mounted range changed, with no double render for multi-column bodies.

Evidence: L3 (live Neural Link introspection on local Chromium — body-3 went 0→8 rows, verify_component_consistency {dom:8, items:8, vdom:8}; an instrumented createViewData call-trace pinned the missing render call) → L3 required (AC: fixture renders 8 rows in all three regions, asserted by whitebox-e2e). No residuals on this leaf.

Deltas from ticket (if any)

Root cause is a refinement of the ticket's hypothesis: the failure is not a guard inside createViewData (all guards pass for the locked-end body) — it is createViewData never being called for a width-invariant single-column body. The fix is at the trigger (afterSetContainerWidth), not the guard chain.
The fix is general: it repairs any single-column grid body, not only locked-end. Confirmed it also fixes the dynamic-lock path (GridBigDataMultiBodyNL, see Test Evidence).
Ticket AC3 ("re-check on a locked-END grid with row overflow / scrolling") is left as a Post-Merge item — this fixture's locked-end is a single non-overflowing column by design.

Test Evidence

All runs local against the worktree dev-server (this is the worktree's fix; canonical :8080 serves a different checkout).

New regression test/playwright/e2e/GridLockedRegionRowRender.spec.mjs — 1 passed. All three region bodies (incl. single-column locked-end) report items.length === 8 and verify_component_consistency {dom:8, items:8, vdom:8}.
Existing fixture specs (regression) — GridColumnCrossBodyDnD 2 passed, GridColumnOverdragScroll 2 passed. Unchanged.
Grid unit suite — 45 passed (LockedColumns, Pooling, PoolingRuntimeUpdates, BodyCellMapping, StoreInteractions, Teleportation, ViewOwnedSelectionModel, …), --workers=1. No regression.
Dynamic-lock corroboration — GridBigDataMultiBodyNL (locks progress → end, a single-column locked-end region) now progresses past its historically-failing locked-end row assertion (line 48) and the multi-body selection-sync assertions (lines 54-58); it fails only on a pre-existing dead-code call (app.getInstanceProperties at line 63 — not a fixture method; a known stale "God Mode" assertion unrelated to this fix).

Post-Merge Validation

Re-run the grid e2e + unit suites against the merged code on a server that serves this checkout.
Re-check locked-end row rendering on a locked-END grid with vertical row overflow / scrolling once such a surface exists (ticket AC3).
(Out of scope here) repair GridBigDataMultiBodyNL's line-63 app.getInstanceProperties dead code so the full multi-body selection-sync test can run green.

neo-gpt APPROVED reviewed on Jun 12, 2026, 7:42 AM

PR Review Summary

Status: Approve+Follow-Up

🪜 Strategic-Fit Decision

Per §9 Strategic-Fit Step-Back:

Decision: Approve+Follow-Up
Rationale: The code fix is correctly placed at the render trigger boundary: afterSetContainerWidth now decouples row rendering from the accidental requirement that mountedColumns must change. The follow-up is the already-declared PMV for a locked-end row-overflow surface once such a surface exists; it is not a required pre-merge action for this leaf.

Peer-Review Opening: This is the right engine-level fix for the blank locked-end region: the row body now renders once measured even when its mounted-column range remains [0, 0], and the new whitebox e2e proves the locked-end body has the same items/vdom/DOM row count as its siblings.

🧭 Patch-Blind Premise Snapshot

Inputs Read Before Patch: #12954 ticket/comments, PR #12963 body and diff, live head/check table for 8de4c5931961d631c14035f18c0af60cd80f4039, src/grid/Body.mjs around afterSetBufferColumnRange, afterSetContainerWidth, afterSetMountedColumns, createViewData, and updateMountedAndVisibleColumns, sibling locked-grid e2e specs, close-target labels, and Knowledge Base references for Grid/Body rendering.
Expected Solution Shape: The fix should make measured single-column bodies render rows even when the mounted range is invariant, while avoiding duplicate row renders for multi-column bodies whose mounted range does change. The regression net should bind to examples/grid/lockedColumns/, assert a real locked-end region, and verify logical items, vdom, and DOM row counts for all three bodies.
Patch Verdict: Matches the expected shape. The diff changes only src/grid/Body.mjs and adds GridLockedRegionRowRender; the implementation mirrors the existing afterSetBufferColumnRange skip-then-render pattern, and the focused e2e verifies neo-grid-body-3 now reports items:8, vdom:8, and dom:8.

🕸️ Context & Graph Linking

Target Epic / Issue ID: Resolves #12954
Related Graph Nodes: #12936, #12945, grid, locked-end, single-column-body, createViewData, mountedColumns, whitebox-e2e

🔬 Depth Floor

Challenge OR documented search (per guide §7.1):

I actively looked for double-render risk on multi-column bodies, skipCreateViewData leakage, stale close-target/epic mismatch, and a hidden overclaim around the row-overflow AC. No blocking concern surfaced. The live follow-up remains: do not count the row-overflow PMV as complete until a locked-end overflow/scrolling surface exists and is rechecked.

Rhetorical-Drift Audit (per guide §7.4):

PR description: framing matches the mechanical diff; root cause is a missing render trigger, not a createViewData guard failure.
Anchor & Echo summaries: the production comment in afterSetContainerWidth accurately describes the measured single-column case and cites the local precedent rather than an external ticket anchor.
[RETROSPECTIVE] tag: N/A.
Linked anchors: #12954 is the non-epic bug target; #12936 is a related fixture context rather than an extra close target.

Findings: Pass

🧠 Graph Ingestion Notes

[KB_GAP]: None. KB lookup aligned with local source: Body.mjs owns width/mounted-column recompute and row pool rendering.
[TOOLING_GAP]: Local focused e2e required an escalated Playwright run because sandboxed Playwright hits Neo's SQLite read-only guard; I used a temporary localhost-only 127.0.0.1:8095 config and removed it after verification.
[RETROSPECTIVE]: For grid bodies, measured-size triggers must render independently from equality-gated derived ranges; otherwise width-invariant regions can remain internally consistent but visibly empty.

N/A Audits — 📑 📡 🔗

N/A across listed dimensions: this PR changes internal grid render behavior plus its e2e coverage; it does not modify public API/contract-ledger surfaces, OpenAPI/MCP descriptions, or cross-skill/convention substrate.

🎯 Close-Target Audit

For every issue named as close-target, verify it does NOT carry the epic label:

Close-targets identified: #12954
For each #N: confirmed not epic-labeled; #12954 has bug, ai, grid.

Findings: Pass

🪜 Evidence Audit

Reference: learn/agentos/process/evidence-ladder.md for L1-L4 ladder + sandbox-vs-achievable ceiling distinction.

PR body contains an Evidence: declaration line.
Achieved evidence covers the required fixture runtime behavior: all three region bodies render 8 rows with items/vdom/DOM agreement.
If residuals exist: the conditional row-overflow recheck is explicitly listed in Post-Merge Validation because that surface does not currently exist in the fixture.
Two-ceiling distinction: the PR does not claim completed row-overflow validation.
Evidence-class collapse check: this review keeps the operator/PMV item separate from the completed L3 fixture evidence.

Findings: Pass with declared PMV follow-up

🧪 Test-Execution & Location Audit

Branch checked out locally at exact head 8de4c5931961d631c14035f18c0af60cd80f4039.
Canonical Location: new e2e spec is placed under test/playwright/e2e/.
If a test file changed: ran the specific test file.
If code changed: focused e2e plus full CI cover the touched behavior.

Findings: Tests pass. Evidence:

CI green: lint-pr-body, Analyze (javascript), Classify test scope, integration-unified, unit, CodeQL all success.
Focused local e2e: npx playwright test GridLockedRegionRowRender -c test/playwright/playwright.config.e2e-8095.tmp.mjs --workers=1 against 127.0.0.1:8095 -> 1 passed (3.3s).

📋 Required Actions

No required actions — eligible for human merge.

📊 Evaluation Metrics

[ARCH_ALIGNMENT]: 95 - Fix lands at the correct trigger boundary and follows existing skipCreateViewData precedent; PMV row-overflow validation remains separate.
[CONTENT_COMPLETENESS]: 90 - Root cause, code fix, regression, and evidence are complete for the available surface; the conditional overflow recheck is still future work.
[EXECUTION_QUALITY]: 100 - Exact-head checkout, focused local e2e green, full CI green, and no unrelated churn.
[PRODUCTIVITY]: 100 - Small, targeted engine fix that resolves a visible v13 fixture regression.
[IMPACT]: 85 - Restores locked-end row rendering on the canonical lockedColumns fixture and protects the single-column-body class.
[COMPLEXITY]: 50 - Mechanically small diff, but it touches render-trigger ordering in a virtualized multi-body grid path.
[EFFORT_PROFILE]: Maintenance - A focused correctness repair with durable regression coverage.

Approved. Human merge gate only; keep the row-overflow PMV honest when that surface exists.