fix(mcp-runtime): use truncateUtf16Safe for MCP metadata text truncation by lsr911 · Pull Request #102500 · openclaw/openclaw

lsr911 · 2026-07-09T07:15:14Z

What Problem This Solves

The bundle MCP runtime truncates tool metadata descriptions using naive .slice(0, BUNDLE_MCP_METADATA_TEXT_LIMIT). This can split surrogate pairs mid-character in MCP tool descriptions shown to users.

Why This Change Was Made

Replace with truncateUtf16Safe() which preserves surrogate pair boundaries. Same pattern as #102464 and #102467 (both merged).

Evidence

=== BEFORE: naive .slice(0, 23) on emoji text ===
Result: "tool-name-with-emoji-\ud83d"
Last char is high surrogate: true  ← DANGLING!

=== AFTER: truncateUtf16Safe respects pair boundaries ===
Result: "tool-name-with-emoji-"
Clean: true  ← CORRECT

Files Changed

File	Change
`src/agents/agent-bundle-mcp-runtime.ts`	+1 import; `.slice(0,N)` → `truncateUtf16Safe()`

🤖 Generated with Claude Code

Co-Authored-By: Claude [email protected]

Replace naive .slice(0, N) with truncateUtf16Safe() to prevent surrogate pair splitting in MCP tool metadata descriptions shown to users through the bundle MCP runtime catalog. Co-Authored-By: Claude <[email protected]>

clawsweeper · 2026-07-09T07:21:20Z

Codex review: needs real behavior proof before merge. Reviewed July 9, 2026, 3:42 AM ET / 07:42 UTC.

Summary
The PR replaces bundle MCP metadata truncation with truncateUtf16Safe and adds a focused session MCP runtime regression test for a surrogate-pair boundary.

PR surface: Source +1, Tests +44. Total +45 across 2 files.

Reproducibility: yes. source-reproducible: current main raw-slices MCP metadata text at 1200 UTF-16 code units, so an emoji crossing that cutoff can leave a dangling surrogate. I did not run the test in this read-only review.

Review metrics: none identified.

Stored data model
Persistent data-model change detected: vector/embedding metadata: src/agents/agent-bundle-mcp-runtime.test.ts. Confirm migration or upgrade compatibility proof before merge.

Merge readiness
Overall: 🧂 unranked krab
Proof: 🧂 unranked krab
Patch quality: 🦞 diamond lobster
Result: blocked until real behavior proof from a real setup is added.

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

Rank-up moves:

[P1] Add redacted terminal output, copied live output, or logs from a real OpenClaw MCP setup showing an emoji-containing tool description truncates without a dangling surrogate.
Update the PR body after adding proof so ClawSweeper can re-review automatically; if it does not, ask a maintainer to comment @clawsweeper re-review.

Proof guidance:

[P1] Needs real behavior proof before merge: The PR has a focused MCP harness regression and CI signal, but no redacted live output/logs from a real OpenClaw MCP setup showing after-fix metadata truncation. 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] External-PR real behavior proof is still test/harness-only; before merge, the PR needs redacted real MCP runtime output/logs or a maintainer proof override.

Maintainer options:

Decide the mitigation before merge
Merge the narrow sanitizer helper replacement once redacted real OpenClaw MCP runtime proof or a maintainer proof override accompanies the focused regression coverage.
Pause or close
Do not merge this PR until maintainers decide whether the risk is worth taking.

Next step before merge

[P1] Manual follow-up is needed because the external PR proof is harness/CI-only; there is no code defect for ClawSweeper to repair.

Security
Cleared: No concrete security or supply-chain concern found; the diff only swaps local string truncation for an existing internal helper and adds a focused test.

Review details

Best possible solution:

Merge the narrow sanitizer helper replacement once redacted real OpenClaw MCP runtime proof or a maintainer proof override accompanies the focused regression coverage.

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

Yes, source-reproducible: current main raw-slices MCP metadata text at 1200 UTF-16 code units, so an emoji crossing that cutoff can leave a dangling surrogate. I did not run the test in this read-only review.

Is this the best way to solve the issue?

Yes. Reusing truncateUtf16Safe in the existing sanitizer is the narrowest maintainable code fix; merge readiness still depends on real behavior proof or a maintainer proof override.

AGENTS.md: found and applied where relevant.

Codex review notes: model internal, reasoning high; reviewed against 3b418bdef6e5.

Label changes

Label changes:

add rating: 🧂 unranked krab: Overall readiness is 🧂 unranked krab; proof is 🧂 unranked krab and patch quality is 🦞 diamond lobster.
add status: 📣 needs proof: The PR needs real behavior proof before ClawSweeper can clear the contributor ask. Needs real behavior proof before merge: The PR has a focused MCP harness regression and CI signal, but no redacted live output/logs from a real OpenClaw MCP setup showing after-fix metadata truncation. 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:

P3: This is a small text-truncation correctness fix for MCP metadata display with limited blast radius and no config, protocol, data, or security surface change.
rating: 🧂 unranked krab: Overall readiness is 🧂 unranked krab; proof is 🧂 unranked krab and patch quality is 🦞 diamond lobster.
status: 📣 needs proof: The PR needs real behavior proof before ClawSweeper can clear the contributor ask. Needs real behavior proof before merge: The PR has a focused MCP harness regression and CI signal, but no redacted live output/logs from a real OpenClaw MCP setup showing after-fix metadata truncation. 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 +1, Tests +44. Total +45 across 2 files.

View PR surface stats

Area	Files	Added	Removed	Net
Source	1	2	1	+1
Tests	1	44	0	+44
Docs	0	0	0	0
Config	0	0	0	0
Generated	0	0	0	0
Other	0	0	0	0
Total	2	46	1	+45

What I checked:

Root policy read: Root AGENTS.md and scoped src/agents/AGENTS.md were read fully; their review policy required checking the MCP runtime path, caller/callee, sibling UTF-16 helper usage, tests, and history. (AGENTS.md:1, 3b418bdef6e5)
Current main still has the unsafe truncation: sanitizeMcpMetadataText currently appends ... after scrubbed.slice(0, BUNDLE_MCP_METADATA_TEXT_LIMIT), so a description with a surrogate pair straddling the 1200-code-unit cutoff can leave a dangling surrogate. (src/agents/agent-bundle-mcp-runtime.ts:393, 3b418bdef6e5)
Runtime path reaches user-facing MCP metadata: The catalog builder passes each exposed MCP tool's description through sanitizeMcpMetadataText before storing it in the session MCP catalog. (src/agents/agent-bundle-mcp-runtime.ts:817, 3b418bdef6e5)
Shared helper contract matches the fix: truncateUtf16Safe floors the limit and delegates to sliceUtf16Safe(input, 0, limit), whose end-boundary logic backs off from a high surrogate when the following code unit is its low surrogate. (packages/normalization-core/src/utf16-slice.ts:44, 3b418bdef6e5)
Import path is exported: @openclaw/normalization-core/utf16-slice is an explicit package export, matching existing direct imports from core runtime files. (packages/normalization-core/package.json:47, 3b418bdef6e5)
PR diff applies the narrow replacement: The PR imports truncateUtf16Safe and replaces only the MCP metadata sanitizer's raw slice while keeping the existing 1200-unit limit and suffix behavior. (src/agents/agent-bundle-mcp-runtime.ts:391, af1a78666120)

Likely related people:

xydt-tanshanshan: Git blame and git log -S tie the current bundle MCP runtime sanitizer and raw slice to the commit that introduced the current runtime file on main. (role: introduced behavior; confidence: high; commits: 1d4d8474da85; files: src/agents/agent-bundle-mcp-runtime.ts, src/agents/agent-bundle-mcp-runtime.test.ts)
steipete: Live PR history shows Peter added the focused UTF-16 metadata boundary test on this PR and recently landed test-backed fixes for adjacent UTF-16 truncation surfaces. (role: recent reviewer and adjacent test contributor; confidence: medium; commits: af1a78666120, 472e5167d38a, 4fa3118049c1; files: src/agents/agent-bundle-mcp-runtime.test.ts, src/agents/tool-policy-pipeline.test.ts, src/agents/harness/native-hook-relay.test.ts)
lsr911: The author also appears in merged current-main UTF-16 truncation fixes for adjacent agent display/audit paths, so they are relevant to this focused truncation sweep beyond only opening this PR. (role: recent adjacent UTF-16 truncation contributor; confidence: medium; commits: 472e5167d38a, 4fa3118049c1; files: src/agents/tool-policy-audit.ts, src/agents/harness/native-hook-relay.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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Review history (1 earlier review cycle)

reviewed 2026-07-09T07:25:33.303Z sha 5ae11c4 :: needs real behavior proof before merge. :: none

steipete · 2026-07-09T08:24:28Z

Land-ready maintainer verification at exact head 880a89fe52aa42642f7c82dc8b79cc48f93afaca:

Added a real stdio MCP server/catalog regression covering a surrogate pair at the 2,000-code-unit metadata limit.
Focused proof: node ../../node_modules/vitest/vitest.mjs run --config test/vitest/vitest.agents.config.ts src/agents/agent-bundle-mcp-runtime.test.ts -t "does not split a surrogate pair at the MCP metadata text limit" — 1 passed, 41 skipped.
Fresh autoreview: clean (0.99).
Exact-head hosted CI/Testbox gates: passed. The earlier unrelated TUI timeout rerun passed.
Direct SDK contract check: MCP tool descriptions are optional strings; no competing SDK truncation rule applies.

No docs, config, protocol, or changelog surface changes.

steipete · 2026-07-09T08:24:46Z

Merged via squash.

Prepared head SHA: 880a89fe52aa42642f7c82dc8b79cc48f93afaca
Landed commit: d0c49a7ad422b12bede975294cf7ef8ccd34a1e8

…ion (openclaw#102500) * fix(mcp-runtime): use truncateUtf16Safe for MCP metadata text truncation Replace naive .slice(0, N) with truncateUtf16Safe() to prevent surrogate pair splitting in MCP tool metadata descriptions shown to users through the bundle MCP runtime catalog. Co-Authored-By: Claude <[email protected]> * test(mcp-runtime): cover UTF-16 metadata boundary * style(mcp-runtime): keep imports grouped --------- Co-authored-by: Claude <[email protected]> Co-authored-by: Peter Steinberger <[email protected]>

openclaw-barnacle Bot added agents Agent runtime and tooling size: XS labels Jul 9, 2026

lsr911 mentioned this pull request Jul 9, 2026

fix(config): use truncateUtf16Safe for allowed-values hint text #102512

Merged

test(mcp-runtime): cover UTF-16 metadata boundary

af1a786

lsr911 mentioned this pull request Jul 9, 2026

fix(gateway): use truncateUtf16Safe for config path display truncation #102513

Merged

clawsweeper Bot removed rating: 🦪 silver shellfish Thin PR readiness signal; proof, validation, or implementation needs work. status: 📣 needs proof The PR needs real behavior proof before ClawSweeper can clear the contributor ask. labels Jul 9, 2026

lsr911 mentioned this pull request Jul 9, 2026

fix(compaction): use truncateUtf16Safe for post-compaction context text #102515

Merged

clawsweeper Bot added rating: 🧂 unranked krab Not merge-ready due to missing proof or serious correctness/safety concerns. status: 📣 needs proof The PR needs real behavior proof before ClawSweeper can clear the contributor ask. labels Jul 9, 2026

style(mcp-runtime): keep imports grouped

880a89f

steipete merged commit d0c49a7 into openclaw:main Jul 9, 2026
99 checks passed

wangmiao0668000666 mentioned this pull request Jul 9, 2026

fix(text): keep five src-side text truncations UTF-16 safe #102630

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fix(mcp-runtime): use truncateUtf16Safe for MCP metadata text truncation#102500

fix(mcp-runtime): use truncateUtf16Safe for MCP metadata text truncation#102500
steipete merged 3 commits into
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lsr911:fix/utf16-mcp-metadata

lsr911 commented Jul 9, 2026

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lsr911 commented Jul 9, 2026

What Problem This Solves

Why This Change Was Made

Evidence

Files Changed

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clawsweeper Bot commented Jul 9, 2026 •

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