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fix(web): math with an unescaped % typesets instead of showing raw TeX#29502

closed4
main
fix/issue-29493
opened10d agobyJJulius Marminge
2 files changed
View on GitHubTwo-way sync enabledPR last imported 2d ago

Problem

With Render math on, a formula that contains an unescaped % stays as raw TeX source permanently. TeX reads % as a comment even inside \text{}, so in \underbrace{…}_{\text{3.18% dividend yield}} the rest of the line, including the closing }}, is dropped and KaTeX throws Unexpected end of input in a macro argument. MathTypeset then shows the source fallback, which was meant for formulas that are still streaming.

Reproduced on main at 8657eecb in the web app, using an assistant reply with the issue's display equation. The equation stayed as raw source, while \[ y=3.18\% \] in the same message typeset. Inline \(p=\text{5% off}\) also stayed raw.

Change

MathTypeset keeps its first KaTeX parse unchanged. Only when that parse throws, it escapes every unescaped % (one not preceded by an odd run of backslashes) to \% and tries once more. If the escaping changed nothing, it skips the retry. The result, either markup or a parse failure, is cached under the original formula, so a remount does not parse it again. A formula whose % is a real comment already parses the first time, so it renders exactly as before. The copied source stays as the agent wrote it.

The escaping regex /\\[\s\S]|%/g has two fixed-width alternatives and no quantifiers, so it runs in linear time. It took 0.06–0.14 ms on 3000-character malformed inputs (all backslashes, all %, repeated {\text{%).

Scope and approval

Fixes pingdotgg/t3code#29493

This covers web and desktop, which share this renderer. Mobile renders math through the native Enriched Markdown renderer, a separate code path that this PR does not change.

Verification

  • vp test run src/components/chat/MarkdownMath.browser.test.tsx: 2 passed. The new test, typesets formulas with an unescaped percent sign inside \text, renders three formulas: the issue's display equation, inline p=\text{5% off}, and a+b % sum of the parts followed by =c, which contains a real comment. It also checks that the typeset output shows 3.18% dividend yield and 5% off. On main it fails with Expected element to match text content: /^R[\s\S]*3\.18%\sdividend yield/ Received: \[ R_e=\underbrace{…}_{\text{3.18% dividend yield}} … \]. The comment case passes on main and still passes.
  • vp run check:changed passed.
  • Manual reproduction on main 8657eecb in the web dev server, as described under Problem.
  • Not checked: before and after screenshots of the fixed rendering are not attached. Mobile was not checked; it uses a separate renderer.

Model and harness: Claude Opus 5.5 (Claude Code) leading in T3 Code, with Claude Opus 5.5 writing the test and the fix, and GPT-6.1 Sol (Codex) and Claude Opus 5.5 reviewing.

🤖 Generated with Claude Code

Checks

24 successful · 17 skipped
All checks passed
2243de2

Added 4 commits

  • Merge remote-tracking branch 'origin/main' into fix/issue-294932243de2
  • test(web): check the percent sign survives in typeset math98671fc
  • test(web): reproduce #29493 unescaped % in \text leaves math as raw sourceb63ce98
  • fix(web): typeset math with an unescaped percent signbe43b64
MmacroscopeappBot10d ago
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Approvability

Verdict: Approved at 2243de2

Macroscope's review found this PR approvable — Failed math expressions now get a second rendering attempt with unescaped percent signs treated literally. Existing KaTeX safety limits and raw-text fallback remain intact, keeping the change limited to presentation.

You can add or adjust custom eligibility rules. Learn more.

Ggithub-actionsBot10d ago
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Thread transfer impact

⚠️ The latest CI run did not produce a thread transfer result for 2243de2.

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Reviewing files that changed from the base of the PR and between 0847a448fdca5a688720050ca706cbbd37e6347e and 2243de2f58d263dc4ef2230be34323aa69ada338.

External image Files selected for processing: 2
  • apps/web/src/components/chat/MarkdownMath.browser.test.tsx
  • apps/web/src/components/chat/MathTypeset.tsx

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Walkthrough

The web math renderer retries formulas that fail KaTeX rendering after escaping percent signs. Browser tests cover display and inline formulas with percent signs in \text content.

Changes: Web math rendering

Layer / File(s)Summary
Retry failed formulas and test rendered output
apps/web/src/components/chat/MathTypeset.tsx, apps/web/src/components/chat/MarkdownMath.browser.test.tsx		The renderer retries failed formulas after escaping percent signs and caches the result under the original input. Browser tests check rendered text for display and inline formulas.

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: yash-singh1

Merge Risk: External image Low · up to 2243d

Some formulas mixing literal percent signs and TeX comments can display incorrect math. This is a bounded risk that should be addressed or accepted before merging.

Pre-merge checks: Passed 4
Check nameStatusExplanation
Title checkPassedThe title names the fix and the affected area: web math with an unescaped % now typesets instead of showing raw TeX. The changeset adds an escape-and-retry path in MathTypeset.tsx and a browser test f…
Linked Issues checkPassedLinked issue #29493 has one active direct coding requirement: a formula with an unescaped % (including inside \text{}) must typeset with a literal percent sign instead of falling back to raw TeX. The …
Out of Scope Changes checkPassedThe whole-PR diff against merge base 0847a448 changes two files. apps/web/src/components/chat/MathTypeset.tsx adds the retry path. The existing parse logic moves into a new render() helper, which only…
Description checkPassedThe description follows the required structure and clearly explains the problem, implementation, scope, tests, observed results, and unchecked items. It identifies the missing screenshots and mobile v…
Full details: Title check

Explanation

The title names the fix and the affected area: web math with an unescaped % now typesets instead of showing raw TeX. The changeset adds an escape-and-retry path in MathTypeset.tsx and a browser test for unescaped % inside \text. The title is specific and follows conventional commit style. It is slightly long at 70 characters, but it is still clear.

Full details: Linked Issues check

Explanation

Linked issue #29493 has one active direct coding requirement: a formula with an unescaped % (including inside \text{}) must typeset with a literal percent sign instead of falling back to raw TeX. The reviewed head implements the suggested approach in apps/web/src/components/chat/MathTypeset.tsx. (1) render() keeps the first KaTeX call with the same options as before (throwOnError: true, trust: false, strict: "ignore", maxSize, maxExpand). (2) typeset() retries only when the first parse returns "" (failure). (3) The retry escapes each % not preceded by an odd run of backslashes, using the regex /\[\s\S]|%/g, which consumes backslash pairs first. (4) The retry runs only if the escaped string differs from the original. (5) The result, markup or empty failure, is stored in typesetCache under the original key, so remounts do not re-parse. Formulas with valid TeX comments parse on the first attempt and are unchanged. The copied source is not modified. The issue's mobile check is out of scope for this web renderer, and the PR states that it changes web only. The new test in MarkdownMath.browser.test.tsx covers the issue's display equation, inline \text{5% off}, and a real-comment case. The test run result was taken from the PR description; the test body was verified in the diff but not re-executed here.

Full details: Out of Scope Changes check

Explanation

The whole-PR diff against merge base 0847a448 changes two files. apps/web/src/components/chat/MathTypeset.tsx adds the retry path. The existing parse logic moves into a new render() helper, which only adds the return value and the empty-string failure result. The typesetCache key and set logic stay as before. apps/web/src/components/chat/MarkdownMath.browser.test.tsx adds one browser test for the reported cases. Both changes support the linked issue objective. No unrelated files or behavior changes were found. The new render() helper is a required refactor for the retry, not an unrelated change.

Full details: Description check

Explanation

The description follows the required structure and clearly explains the problem, implementation, scope, tests, observed results, and unchecked items. It identifies the missing screenshots and mobile verification, and it references the linked issue, although it does not include an explicit maintainer approval comment or explain an approval exemption.

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CcoderabbitaiBotreviewed · 1 inline thread10d ago
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Actionable comments posted: 1

  • Fix comments: Fix CodeRabbit comments on this PR
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6Inline comments:
7Review comments at @apps/web/src/components/chat/MathTypeset.tsx:
8- Line 36: Update the percent-escaping retry in MathTypeset so it does not
9escape percent signs that begin real TeX comments; when intent is ambiguous,
10retain the original-source fallback rather than changing the equation’s meaning.
11Add a test for the `\text{5% off} % +100` input followed by a newline and `+1`,
12verifying the comment remains excluded from the rendered equation.
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Reviewing files that changed from the base of the PR and between 0847a448fdca5a688720050ca706cbbd37e6347e and 2243de2f58d263dc4ef2230be34323aa69ada338.

External image Files selected for processing: 2
  • apps/web/src/components/chat/MarkdownMath.browser.test.tsx
  • apps/web/src/components/chat/MathTypeset.tsx

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apps/web/src/components/chat/MathTypeset.tsxline 36Resolved by Julius Marminge
Sshivam10d ago

[gpt-6.1-sol][Codex] on behalf of shivam.

Issue watch picked up https://github.com/pingdotgg/t3code/issues/29493 and found your fix here at head 2243de2f58d263dc4ef2230be34323aa69ada338. I read the report and confirmed that the original MathTypeset.tsx at 9bcf75335f9b2a8af877e1317c809b72a070b280 falls straight back to source when KaTeX throws. I did not run a reproduction or tests, and made no code changes. Handing the issue-watch work over to this PR under our Julius takeover rule.

JJulius Marminge2d ago

Thanks @juliusmarminge for the earlier fix and regression test. Closing this as a duplicate of #29511, where @meutex and contributors have continued the same fix. This PR has had no author push or reply in over a week.