Chat markdown does not render TeX \(...\) / \[...\] or single-dollar math

[exAClior]

Before filing

• I searched open and closed issues for duplicates.
• I reproduced this on the latest release (v0.6.2).
• This is one bug, not several bundled together.

Closest existing issue

none found

Split from the same session as a second, independent display bug: when $$ / fenced math do parse, a garbled plaintext copy still appears. Filed separately.

What's broken

Chat markdown does not render TeX-style \(...\) / \[...\] or single-dollar $...$ as math. Those stay literal (and \( / \[ lose the backslash). Double-dollar and fenced math do parse; that path has a separate display bug.

Steps to reproduce

1. Launch Berd 0.6.2.
2. New chat. Goose, Grok 4.6 via xAI (xai_oauth). No prior history needed; this is renderer behavior.
3. Have the assistant emit (or otherwise display) these in one message:

   • inline TeX: \( \Omega \)

   • display TeX:

     \[
     \Omega = \sum_{n=1}^{\infty} \frac{1}{n^2}
     \]
     

   • spaced single-dollar: $ \Omega $

   • tight single-dollar: $\Omega$

4. Compare to $$\Omega$$, a $$ display block, and a fenced math block in the same message.

What you expected to happen

\(...\), \[...\], and $...$ render as math, the way common model output is written (Anthropic/TeX vs OpenAI-style delimiters).

What actually happened

From a screenshot of the live bubble:

1. \( \Omega \) rendered as ( Ω ) — backslash eaten, not math.
2. \[ ... \] rendered as [ Ω = \sum_{n=1}^{\infty} \frac{1}{n^2} ] — same, not math.
3. $ \Omega $ stayed literal $ Ω $.
4. $\Omega$ stayed literal $\Omega$.
5. $$\Omega$$, a $$ display block, and fenced math did become KaTeX (those still show a garbled duplicate; separate issue).

How often does it happen?

Every time — reliably reproducible

Berd version

0.6.2

Operating system

macOS (Apple Silicon)

Model and provider

Grok 4.6 via xAI (Goose / xai_oauth). Renderer-side; any model that emits these delimiters should hit it.

Relevant log output

no relevant log output

Looked at ~/Library/Logs/xyz.block.berd/berd.log around the turn. Nothing about KaTeX / math / Streamdown.

Screenshots, recordings, or other context

Screenshot of this session’s live delimiter matrix (same capture as the companion issue):

[exAClior]

Companion display bug when math does parse: #240