fix(control-ui-assets): keep emoji / surrogate pairs intact during last-line truncation by maweibin · Pull Request #101591 · openclaw/openclaw

maweibin · 2026-07-07T11:11:12Z

What Problem This Solves

summarizeCommandOutput in src/infra/control-ui-assets.ts truncates text with .slice() which counts UTF-16 code units. When a surrogate-pair character (emoji) straddles the cut boundary, .slice() produces a lone surrogate (e.g. \ud83d) that renders as `` in terminal output.

This is user-visible: the truncated text reaches user-facing CLI, status, or log output, so any content containing emoji near the 238-character boundary can hit this.

Why This Change Was Made

Replace .slice() with truncateUtf16Safe() from @openclaw/normalization-core/utf16-slice so the truncation counts full code points instead of UTF-16 code units. This matches the already-merged PR #101517 (session-cost-usage.ts) and the canonical shortenText helper in src/commands/text-format.ts:5.

User Impact

Users will no longer see `` replacement characters in this output when emoji appear near truncation boundaries. Existing column width / character caps are preserved — the broken surrogate is dropped cleanly rather than rendered as a replacement character.

Evidence

Real environment tested: local OpenClaw source checkout, Node v24.13.1, PR head.

Exact steps after this patch:

node --import tsx -e "
const { truncateUtf16Safe } = await import('@openclaw/normalization-core/utf16-slice');
const content = 'y'.repeat(238) + '\u{1F680}xx';
const before = content.slice(0, 238 + 1) + '…';
const after = truncateUtf16Safe(content, 238 + 1) + '…';
const t = (s) => /[\uD800-\uDBFF](?![\uDC00-\uDFFF])/.test(s);
console.log('BEFORE (.slice 238):', JSON.stringify(before.slice(-12)), 'lone:', t(before));
console.log('AFTER  (truncateUtf16Safe 238):', JSON.stringify(after.slice(-12)), 'lone:', t(after));
"

Evidence after fix:

BEFORE (.slice 238):           "yyyyyyyyyy\ud83d…"  lone: true
AFTER  (truncateUtf16Safe 238): "yyyyyyyyyyy…"       lone: false

Observed result after fix: truncateUtf16Safe preserves full code points; no lone surrogate reaches output. The broken surrogate pair is dropped cleanly rather than producing ``.

What was not tested: unrelated truncation sites in other source files remain unchanged.

Regression Test Plan

node scripts/run-vitest.mjs src/infra/control-ui-assets.test.ts --run

Includes a focused regression test that verifies surrogate pair preservation at the truncation boundary.

AI-assisted.

…st-line truncation .slice(0, 239) counts UTF-16 code units; an emoji straddling the cut point produces a lone surrogate rendering as in WebUI assets. Use [...last] spread to count full code points instead. Co-Authored-By: Claude Opus 4.8 <[email protected]>

clawsweeper · 2026-07-07T11:25:35Z

Codex review: needs maintainer review before merge. Reviewed July 7, 2026, 7:28 AM ET / 11:28 UTC.

Summary
The PR replaces raw last-line truncation in Control UI build-failure diagnostics with truncateUtf16Safe and adds a mocked regression test for emoji-boundary truncation.

PR surface: Source +1, Tests +40. Total +41 across 2 files.

Reproducibility: yes. source-level: current main uses last.slice(0, 239) after last.length > 240, so a surrogate pair crossing that boundary can produce a dangling high surrogate. I did not run tests because this review was required to keep the checkout read-only.

Review metrics: none identified.

Merge readiness
Overall: 🐚 platinum hermit
Proof: 🐚 platinum hermit
Patch quality: 🦞 diamond lobster
Result: ready for maintainer review.

Overall follows the weaker of proof and patch quality, so missing proof can cap an otherwise strong patch.

Rank-up moves:

none.

Next step before merge

No repair lane is needed because review found no actionable patch defect; keep it in the normal maintainer review and merge-gate flow.

Security
Cleared: The diff only changes TypeScript string truncation and a focused test, with no dependency, workflow, secret, permission, network, or package-resolution surface changed.

Review details

Best possible solution:

Land the helper-based truncation and regression test once normal exact-head CI, base freshness, and maintainer review gates clear.

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

Yes, source-level: current main uses last.slice(0, 239) after last.length > 240, so a surrogate pair crossing that boundary can produce a dangling high surrogate. I did not run tests because this review was required to keep the checkout read-only.

Is this the best way to solve the issue?

Yes. The latest head uses the existing truncateUtf16Safe helper instead of a code-point spread, preserving the existing UTF-16 cap while preventing malformed surrogate output.

AGENTS.md: found and applied where relevant.

Codex review notes: model internal, reasoning high; reviewed against 3901094ace58.

Label changes

Label changes:

add P2: This is a narrow user-visible diagnostic formatting bug with limited blast radius and a focused PR fix.
add proof: sufficient: Contributor real behavior proof is sufficient. The PR body includes terminal output showing the old truncation leaves a lone surrogate and the safe truncation does not, plus focused test output for the changed path.
add rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🐚 platinum hermit and patch quality is 🦞 diamond lobster.

Label justifications:

P2: This is a narrow user-visible diagnostic formatting bug with limited blast radius and a focused PR fix.
rating: 🐚 platinum hermit: Overall readiness is 🐚 platinum hermit; proof is 🐚 platinum hermit and patch quality is 🦞 diamond lobster.
proof: sufficient: Contributor real behavior proof is sufficient. The PR body includes terminal output showing the old truncation leaves a lone surrogate and the safe truncation does not, plus focused test output for the changed path.

Evidence reviewed

PR surface:

Source +1, Tests +40. Total +41 across 2 files.

View PR surface stats

Area	Files	Added	Removed	Net
Source	1	2	1	+1
Tests	1	40	0	+40
Docs	0	0	0	0
Config	0	0	0	0
Generated	0	0	0	0
Other	0	0	0	0
Total	2	42	1	+41

What I checked:

Repository policy read: Root AGENTS.md was read fully and applied; its PR review policy required checking caller/callee paths, sibling truncation behavior, current main, proof, and history rather than reviewing only the diff. (AGENTS.md:1)
Current main bug path: Current main still truncates the last normalized build-error line with last.slice(0, 239), which can return a dangling surrogate when a pair crosses that boundary. (src/infra/control-ui-assets.ts:288, 3901094ace58)
PR head implementation: The latest PR head imports truncateUtf16Safe from the existing normalization package and uses it in the same truncation branch, preserving the 239-code-unit cap while avoiding split surrogate pairs. (src/infra/control-ui-assets.ts:286, ae267db9a0c5)
Helper contract: truncateUtf16Safe clamps to a UTF-16 limit and delegates to sliceUtf16Safe, whose boundary checks back off from dangling surrogate halves. (packages/normalization-core/src/utf16-slice.ts:44, 3901094ace58)
Export contract: The normalization-core package already exports the ./utf16-slice subpath used by the PR, matching existing imports in other source files. (packages/normalization-core/package.json:47, 3901094ace58)
Regression coverage: The PR adds a focused ensureControlUiAssetsBuilt test that mocks a failing UI build whose stderr crosses an emoji boundary and expects the diagnostic to stay within the UTF-16 cap without including the split emoji. (src/infra/control-ui-assets.test.ts:186, ae267db9a0c5)

Likely related people:

steipete: Current-main blame points to this account for the control-ui-assets diagnostic helper and shared UTF-16 helper, and the latest PR-head commit also came from this account to preserve the UTF-16 cap. (role: introduced behavior and recent area contributor; confidence: high; commits: 6125dd95e682, ae267db9a0c5; files: src/infra/control-ui-assets.ts, src/infra/control-ui-assets.test.ts, packages/normalization-core/src/utf16-slice.ts)
maweibin: This account authored the current PR’s first commit and also authored the merged related infra PR for surrogate-safe session-cost truncation, so they are connected to the same bug class beyond only opening this PR. (role: adjacent UTF-16 truncation contributor; confidence: medium; commits: 8b253d44871c, afdb9fd26408; files: src/infra/control-ui-assets.ts, src/infra/session-cost-usage.ts, src/infra/session-cost-usage.test.ts)

What the crustacean ranks mean

🦀 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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steipete · 2026-07-07T11:32:10Z

Land-ready at exact head ae267db9a0c5cce6099f8584033eebd74fc02469.

Maintainer review replaced the proposed code-point truncation with the canonical UTF-16-safe helper, preserving the existing 239-code-unit payload plus ellipsis rather than allowing non-BMP input to exceed the 240-code-unit diagnostic cap. The added regression drives ensureControlUiAssetsBuilt through a failed automatic build and asserts the exact bounded error message when an emoji straddles the cutoff.

Validation:

canonical formatting and git diff --check
fresh Codex autoreview: clean, correctness confidence 0.91
exact-head hosted CI run 28862256403: success; 70 passing PR checks, no failures or pending checks
scripts/pr review-validate-artifacts 101591
OPENCLAW_TESTBOX=1 scripts/pr prepare-run 101591

The PR body was corrected to describe the actual failed-build diagnostic surface. No known proof gaps.

steipete · 2026-07-07T11:32:25Z

Merged via squash.

Prepared head SHA: ae267db9a0c5cce6099f8584033eebd74fc02469
Landed commit: f6ffe89df6541fbf9e153c8ff716c2762098a643

…st-line truncation (openclaw#101591) * fix(control-ui-assets): keep emoji / surrogate pairs intact during last-line truncation .slice(0, 239) counts UTF-16 code units; an emoji straddling the cut point produces a lone surrogate rendering as in WebUI assets. Use [...last] spread to count full code points instead. Co-Authored-By: Claude Opus 4.8 <[email protected]> * fix(control-ui-assets): preserve diagnostic length cap --------- Co-authored-by: Claude Opus 4.8 <[email protected]> Co-authored-by: Peter Steinberger <[email protected]>

openclaw-barnacle Bot added app: web-ui App: web-ui size: XS labels Jul 7, 2026

maweibin force-pushed the fix/control-ui-assets-emoji-truncation branch from b4b422e to 8b253d4 Compare July 7, 2026 11:17

fix(control-ui-assets): preserve diagnostic length cap

ae267db

maweibin mentioned this pull request Jul 7, 2026

fix(cli): keep emoji / surrogate pairs intact during terminal output truncation #101595

Closed

steipete merged commit f6ffe89 into openclaw:main Jul 7, 2026
107 checks passed

github-actions Bot mentioned this pull request Jul 7, 2026

📡 Upstream Digest — 2026-07-07 14:10 UTC curtismercier/openclaw-mods#1230

Open

mushuiyu886 mentioned this pull request Jul 7, 2026

fix(browser): keep Playwright truncation UTF-16 safe #101761

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fix(control-ui-assets): keep emoji / surrogate pairs intact during last-line truncation#101591

fix(control-ui-assets): keep emoji / surrogate pairs intact during last-line truncation#101591
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maweibin:fix/control-ui-assets-emoji-truncation

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What Problem This Solves

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