Best possible solution:

Use #102625 as the canonical landing path for this bug because it includes the same production fix plus regression coverage and accepted real behavior proof.

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

Yes from source inspection: current main renders Overview Event Log payload previews with raw .slice(0, 120), and the existing UTF-16 helper tests show surrogate-boundary truncation is a real string-level failure mode. I did not run live UI proof for this duplicate PR.

Is this the best way to solve the issue?

No for this branch as the best landing path: the code change is plausible, but #102625 is the better solution because it centralizes the preview formatter and adds regression proof.

Security review:

Security review cleared: The diff only imports an existing internal text-normalization helper and changes UI display truncation; no security or supply-chain surface is added.

AGENTS.md: found and applied where relevant.

What I checked:

• Current main behavior: Current main still renders Overview Event Log payload previews with formatEventPayload(entry.payload).slice(0, 120), which is the same bug both PRs target. (ui/src/pages/overview/event-log.ts:35, 6621ead871a9)
• Current PR diff: This PR changes only the Overview Event Log call site to use truncateUtf16Safe(formatEventPayload(entry.payload), 120) and does not add regression coverage or real behavior proof. (ui/src/pages/overview/event-log.ts:35, c9fea7031476)
• Canonical open PR: Live PR inspection shows fix(ui): keep event payload previews UTF-16 safe #102625 is open, targets the same Overview event payload preview UTF-16 boundary problem, and has proof: sufficient plus status: 👀 ready for maintainer look labels. (25a9f1109af6)
• Canonical diff scope: The canonical PR adds formatEventPayloadPreview, switches the same Overview Event Log call site to that formatter, and adds a focused jsdom regression test for a payload whose legacy 120-code-unit slice ends on a high surrogate. (ui/src/pages/overview/event-log.ts:35, 25a9f1109af6)
• History provenance: Local blame ties the current Event Log file and raw payload slice to commit 06b33f5, merged from improve(ui): remove the Roundness appearance setting #102641. (ui/src/pages/overview/event-log.ts:35, 06b33f54627c)
• Related search: Live GitHub search for surrogate-pair truncation found the proof-positive UI event-payload PR as the relevant overlapping open item.

Likely related people:

• steipete: Local blame ties the current Event Log file and raw preview slice to the recent overview UI cleanup merged through improve(ui): remove the Roundness appearance setting #102641. (role: recent area contributor; confidence: high; commits: 06b33f54627c; files: ui/src/pages/overview/event-log.ts, ui/src/pages/overview/view.ts)
• zhangguiping-xydt: Authored the stronger open canonical PR that covers the same Event Log truncation bug with a presenter helper, regression test, and real behavior proof. (role: canonical fix author; confidence: high; commits: 25a9f1109af6; files: ui/src/lib/presenter.ts, ui/src/pages/overview/event-log.ts, ui/src/pages/overview/event-log.test.ts)

Codex review notes: model internal, reasoning high; reviewed against 6621ead871a9.