fix(web): preserve XML-like tags in user messages

[0utsights]

Summary

• display user-authored HTML/XML-like syntax literally in chat messages
• preserve sanitized raw HTML rendering for assistant messages
• add regression coverage for both behaviors

Root cause

ChatMarkdown always enabled raw HTML parsing and sanitization. Unknown XML-like elements in user input, such as <global-agent-instructions>, were therefore interpreted as HTML and removed from the rendered message.

User messages now opt out of raw HTML parsing, so their original text remains visible. Assistant messages keep the existing sanitized HTML behavior.

User impact

The rendered user message now matches what was typed instead of silently omitting XML-like tags. This only changes presentation; the message payload sent to the agent was already correct.

Fixes #4059.

Validation

• pnpm exec vp test apps/web/src/components/chat/MessagesTimeline.test.tsx (14 tests passed)
• pnpm exec vp check (0 errors; 10 existing warnings)
• pnpm exec vp run typecheck

Note

Preserve XML-like tags as text in user messages

• Adds a parseRawHtml prop (default true) to ChatMarkdown that controls whether HTML-like content is parsed into elements or rendered as inert source text.
• Sets parseRawHtml={false} for all user message rendering in UserMessageBody, so XML-like tags and comparison operators in user input appear as escaped text rather than HTML.
• Assistant messages continue to parse and sanitize raw HTML as before, supporting markup like <details>/<summary>.
• Behavioral Change: user messages that previously rendered HTML tags as elements will now display them as literal text.

^{Macroscope summarized f0da0f7.}

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Note

Low Risk
Presentation-only change for user bubbles with stricter display of user HTML; assistant markdown path is unchanged and tests lock in XSS-safe user rendering.

Overview
Fixes user chat bubbles silently dropping XML-like text (e.g. <global-agent-instructions>) because ChatMarkdown always ran raw HTML parsing and sanitization.

Adds a parseRawHtml flag (default true) that toggles the rehype-raw / rehype-sanitize pipeline. When false, HTML-like input is shown as escaped source text instead of being parsed or stripped. User message rendering in MessagesTimeline opts out with parseRawHtml={false} on every ChatMarkdown path; assistant messages keep the default so supported markup (e.g. <details>) still renders after sanitization.

Regression tests cover literal XML/comparisons in user text, inert handling of malicious user HTML, and unchanged sanitized assistant HTML behavior.

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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[macroscopeapp]

Approvability

Verdict: Approved

Simple, well-tested bug fix that adds a boolean prop to preserve XML-like tags as literal text in user messages. The change is self-contained with comprehensive test coverage including XSS protection verification.

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