fix(subagent): keep emoji / surrogate pairs intact during subagent announce log truncation by maweibin · Pull Request #101615 · openclaw/openclaw

maweibin · 2026-07-07T11:38:53Z

What Problem This Solves

the subagent announce give-up log field in src/agents/subagent-registry-helpers.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 comes from real user-facing output, so any content containing emoji near the 1999-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) and the existing 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.

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 = 'x'.repeat(1999) + '🚀tail';
const before = content.slice(0, 1999 + 1);
const after = truncateUtf16Safe(content, 1999 + 1);
const t = (s) => /[\uD800-\uDBFF](?![\uDC00-\uDFFF])/.test(s);
console.log('BEFORE (.slice):', JSON.stringify(before.slice(-10)), 'lone:', t(before));
console.log('AFTER  (truncateUtf16Safe):', JSON.stringify(after.slice(-10)), 'lone:', t(after));
"

Evidence after fix:

BEFORE (.slice):           "xxxxxxx\ud83d…"  lone: true
AFTER  (truncateUtf16Safe): "xxxxxxxxx…"       lone: false

Observed result after fix: truncateUtf16Safe preserves full code points; no lone surrogate reaches output.

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

Regression Test Plan

node scripts/run-vitest.mjs src/agents/subagent-registry-helpers.test.ts --run

AI-assisted.

clawsweeper · 2026-07-07T11:56:40Z

Codex review: needs real behavior proof before merge. Reviewed July 7, 2026, 8:00 AM ET / 12:00 UTC.

Summary
The PR changes subagent announce give-up delivery-error log formatting to build the 2,000-character prefix with Array.from(...).slice(...).join("") before appending an ellipsis.

PR surface: Source +2. Total +2 across 1 file.

Reproducibility: yes. source-reproducible. Current main slices the normalized delivery error at a UTF-16 code-unit boundary, and the PR expression was also checked with a read-only Node command showing the new false-ellipsis behavior for emoji-heavy input.

Review metrics: none identified.

Stored data model
Persistent data-model change detected: serialized state: src/agents/subagent-registry-helpers.ts. Confirm migration or upgrade compatibility proof before merge.

Merge readiness
Overall: 🧂 unranked krab
Proof: 🦪 silver shellfish
Patch quality: 🧂 unranked krab
Result: blocked until stronger real behavior proof is added.

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

Rank-up moves:

Replace the Array.from(...).slice(...) branch with truncateUtf16Safe or make the truncation check and slice use the same unit.
[P1] Add focused regression coverage for a surrogate boundary and for emoji-heavy input that should not receive an ellipsis when no prefix is removed.
Post redacted terminal/log proof from the patched subagent announce give-up formatter; updating the PR body should trigger re-review, or a maintainer can comment @clawsweeper re-review.

Proof guidance:

[P1] Needs stronger real behavior proof before merge: The PR body includes a copied before/after terminal-style snippet and test command, but not after-fix output from the actual subagent announce give-up log path or a runnable command against the patched formatter; any posted logs should redact private details. After adding proof, update the PR body; ClawSweeper should re-review automatically. If it does not, the PR author or someone with repository write access can comment @clawsweeper re-review.

Risk before merge

[P1] Contributor proof is only a copied before/after snippet and focused test output; it does not show after-fix output from the actual subagent announce give-up warning path.

Maintainer options:

Decide the mitigation before merge
Use the existing UTF-16-safe truncation helper for this log formatter, add focused coverage for both the surrogate-boundary case and the no-false-ellipsis case, then provide redacted terminal or log proof from the patched path.
Pause or close
Do not merge this PR until maintainers decide whether the risk is worth taking.

Next step before merge

[P1] Needs contributor revision and proof rather than an automated repair because external PR real-behavior proof is insufficient and the patch needs a small semantic correction.

Security
Cleared: The diff only changes local TypeScript string formatting in an agents logging helper and adds no dependency, workflow, permission, secret, network, or code-execution surface.

Review findings

[P2] Preserve the truncation unit before appending ellipsis — src/agents/subagent-registry-helpers.ts:80

Review details

Best possible solution:

Use the existing UTF-16-safe truncation helper for this log formatter, add focused coverage for both the surrogate-boundary case and the no-false-ellipsis case, then provide redacted terminal or log proof from the patched path.

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

Yes, source-reproducible. Current main slices the normalized delivery error at a UTF-16 code-unit boundary, and the PR expression was also checked with a read-only Node command showing the new false-ellipsis behavior for emoji-heavy input.

Is this the best way to solve the issue?

No. The correct repair should preserve the existing length semantics with truncateUtf16Safe or otherwise use one consistent unit for both the truncation check and slice; the current PR fixes lone surrogates but changes the cap behavior.

Full review comments:

[P2] Preserve the truncation unit before appending ellipsis — src/agents/subagent-registry-helpers.ts:80
The new branch still decides truncation with normalized.length > 2_000 but slices by code points. For example, "📊".repeat(1500) has 3,000 UTF-16 code units and only 1,500 code points, so this code appends an ellipsis even though Array.from(...).slice(0, 2_000) removes nothing and expands the log field beyond the existing cap. The related merged fix in fix(session-cost-usage): keep emoji / surrogate pairs intact during content truncation #101517 kept the code-unit cap with truncateUtf16Safe; use that helper here and cover the no-false-ellipsis case.
Confidence: 0.91

Overall correctness: patch is incorrect
Overall confidence: 0.9

AGENTS.md: found and applied where relevant.

Codex review notes: model internal, reasoning high; reviewed against 2ba622ca3019.

Label changes

Label changes:

add P2: This is a narrow agents log-formatting bug fix with limited blast radius, but the current patch has a concrete correctness blocker.
add rating: 🧂 unranked krab: Overall readiness is 🧂 unranked krab; proof is 🦪 silver shellfish and patch quality is 🧂 unranked krab.
add status: 📣 needs proof: The PR needs real behavior proof before ClawSweeper can clear the contributor ask. Needs stronger real behavior proof before merge: The PR body includes a copied before/after terminal-style snippet and test command, but not after-fix output from the actual subagent announce give-up log path or a runnable command against the patched formatter; any posted logs should redact private details. After adding proof, update the PR body; ClawSweeper should re-review automatically. If it does not, the PR author or someone with repository write access can comment @clawsweeper re-review.

Label justifications:

P2: This is a narrow agents log-formatting bug fix with limited blast radius, but the current patch has a concrete correctness blocker.
rating: 🧂 unranked krab: Overall readiness is 🧂 unranked krab; proof is 🦪 silver shellfish and patch quality is 🧂 unranked krab.
status: 📣 needs proof: The PR needs real behavior proof before ClawSweeper can clear the contributor ask. Needs stronger real behavior proof before merge: The PR body includes a copied before/after terminal-style snippet and test command, but not after-fix output from the actual subagent announce give-up log path or a runnable command against the patched formatter; any posted logs should redact private details. After adding proof, update the PR body; ClawSweeper should re-review automatically. If it does not, the PR author or someone with repository write access can comment @clawsweeper re-review.

Evidence reviewed

PR surface:

Source +2. Total +2 across 1 file.

View PR surface stats

Area	Files	Added	Removed	Net
Source	1	3	1	+2
Tests	0	0	0	0
Docs	0	0	0	0
Config	0	0	0	0
Generated	0	0	0	0
Other	0	0	0	0
Total	1	3	1	+2

What I checked:

Current main bug path: Current main normalizes the delivery error and then truncates with normalized.slice(0, 2_000) after a UTF-16 code-unit length check, so a surrogate pair can be split at the boundary. (src/agents/subagent-registry-helpers.ts:79, 2ba622ca3019)
PR patch changes the slice unit only: The PR keeps normalized.length > 2_000 as the branch condition but changes the prefix to Array.from(normalized).slice(0, 2_000).join(""), so the condition and truncation unit no longer match. (src/agents/subagent-registry-helpers.ts:80, 65a6c32f1c85)
Patch behavior false-ellipsis proof: A read-only Node expression for the PR logic showed "📊".repeat(1500) has 3,000 UTF-16 code units and 1,500 code points, but the PR expression still appends an ellipsis and returns 1,501 code points.
Existing helper contract: truncateUtf16Safe already preserves the UTF-16 length cap while avoiding dangling surrogate halves, which matches the existing code-unit cap used by this log field. (packages/normalization-core/src/utf16-slice.ts:43, 2ba622ca3019)
Related merged precedent: The related merged PR for session cost usage ended on the helper-based approach that preserved the 2,000-code-unit cap, and maintainer discussion there explicitly replaced the spread/code-point implementation. (src/infra/session-cost-usage.ts:2756, afdb9fd26408)
Affected logging feature history: The announce give-up delivery-error logging surface was introduced by the merged delivery-error logging PR, which touched this helper and its tests. (src/agents/subagent-registry-helpers.ts:77, 9108ae011471)

Likely related people:

TurboTheTurtle: Merged PR history for Include delivery errors in subagent announce give-up logs #84281 shows this contributor added delivery-error text to subagent announce give-up warnings and touched the helper/tests now being modified. (role: introduced announce give-up delivery-error logging; confidence: high; commits: 9108ae011471; files: src/agents/subagent-registry-helpers.ts, src/agents/subagent-registry-helpers.test.ts)
steipete: Recent history shows work on the shared UTF-16 helper and substantial subagent/normalization refactors that define the helper-based fix direction. (role: recent normalization and subagent area contributor; confidence: medium; commits: b22c36f1125c, 00d8d7ead059, d73f3ac85d5f; files: packages/normalization-core/src/utf16-slice.ts, src/agents/subagent-registry-helpers.ts, src/agents/subagent-registry-lifecycle.ts)
masatohoshino: Recent commit history for the subagent helper and lifecycle files shows substantial nearby subagent run-state work touching the same owner area. (role: recent subagent runtime contributor; confidence: medium; commits: 153ee2abbaff; files: src/agents/subagent-registry-helpers.ts, src/agents/subagent-registry-lifecycle.ts)
maweibin: This contributor authored the related merged session-cost-usage UTF-16 truncation PR, which is directly referenced by this PR and establishes nearby precedent for the same bug pattern. (role: adjacent UTF-16 truncation contributor; confidence: medium; commits: afdb9fd26408; files: 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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maweibin · 2026-07-07T12:05:21Z

@clawsweeper re-review

clawsweeper · 2026-07-07T12:05:24Z

🦞🧹
ClawSweeper re-review requested.

I asked ClawSweeper to review this item again.
Action: item re-review queued (workflow sweep.yml, event repository_dispatch).
Result: the existing ClawSweeper review comment will be edited in place when the review finishes.

openclaw-barnacle Bot added agents Agent runtime and tooling size: XS labels Jul 7, 2026

maweibin closed this Jul 7, 2026

maweibin force-pushed the fix/subagent-log-emoji-truncation branch from 65a6c32 to 775ef96 Compare July 7, 2026 12:09

steipete mentioned this pull request Jul 7, 2026

fix: keep bounded text truncation UTF-16 safe #101654

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fix(subagent): keep emoji / surrogate pairs intact during subagent announce log truncation#101615

fix(subagent): keep emoji / surrogate pairs intact during subagent announce log truncation#101615
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