---
phase: quick
plan: 260329-ton
subsystem: utils/companion-ui
tags: [markdown, rendering, xss, companion-texts]
dependency_graph:
  requires: []
  provides: [renderInlineMarkdown utility]
  affects: [src/app.ts, src/ui/screens.ts, src/forest/reward.ts]
tech_stack:
  added: []
  patterns: [inline-markdown-rendering, XSS-safe innerHTML]
key_files:
  created:
    - src/utils/markdown.ts
    - src/utils/markdown.test.ts
  modified:
    - src/app.ts
    - src/ui/screens.ts
    - src/forest/reward.ts
decisions:
  - Bold must be processed before italic so ** is not consumed as two separate *
  - HTML escaping happens before markdown processing (prevents XSS injection)
  - Italic regex requires non-space characters at asterisk boundaries to avoid false positives on math-like expressions
metrics:
  duration: ~5 minutes
  completed: "2026-03-29"
  tasks_completed: 2
  files_changed: 5
---

# Quick Task 260329-ton: Markdown in Companion Texts Summary

**One-liner:** Safe inline markdown renderer (`renderInlineMarkdown`) wired to all 3 AI-generated text insertion points so *italic* and **bold** display as styled HTML instead of raw asterisks.

## Tasks Completed

| # | Task | Commit | Files |
|---|------|--------|-------|
| 1 | Create renderInlineMarkdown utility with tests (TDD) | e10bdf8 | src/utils/markdown.ts, src/utils/markdown.test.ts |
| 2 | Replace .textContent with .innerHTML + renderInlineMarkdown at all AI-text insertion points | d038cc3 | src/app.ts, src/ui/screens.ts, src/forest/reward.ts |

## What Was Built

A `renderInlineMarkdown(text: string): string` pure utility function that:
1. Escapes HTML special characters (`& < > " '`) first to prevent XSS
2. Converts `**bold**` to `<strong>bold</strong>`
3. Converts `*italic*` to `<em>italic</em>`
4. Leaves standalone asterisks surrounded by spaces untouched

Used via `innerHTML = renderInlineMarkdown(text)` at:
- `/src/app.ts` line 228: greeting text from `getGreeting()`
- `/src/ui/screens.ts` line 423: letter intro text from `getLetterIntro()`
- `/src/forest/reward.ts` line 208: forest comment from `getForestComment()`

## Verification

- `npx vitest run` — 92 tests pass (7 new markdown tests + 85 existing)
- `npx tsc --noEmit` — no type errors
- `grep renderInlineMarkdown` — exactly 3 usage sites (plus imports) across the 3 target files

## Decisions Made

1. **Bold before italic in processing order** — `**` must be matched before `*` so double-asterisk isn't consumed as two single asterisks first.
2. **HTML escape before markdown** — ensures any `<`, `>` in AI-generated text is neutralized before regex transforms it to valid HTML. No injection risk even if Gemini outputs HTML tags.
3. **Italic regex boundary rule** — pattern `/\*(\S[^*]*?\S|\S)\*/g` requires non-whitespace at the asterisk boundary, preventing `2 * 3 * 4` from becoming `2 <em>3</em> 4`.

## Deviations from Plan

None — plan executed exactly as written.

## Known Stubs

None.

## Self-Check: PASSED

Files created:
- /home/dev/workspace/zauberwald/src/utils/markdown.ts — FOUND
- /home/dev/workspace/zauberwald/src/utils/markdown.test.ts — FOUND

Commits:
- 860d671 (test RED)
- e10bdf8 (feat GREEN)
- d038cc3 (feat wiring)