CPU profile (Apr 2026, real-user scroll on 11k-line session) showed three
hot loops in the per-frame render path:
Output.get() per-frame walk: 24% total
└─ sliceAnsi(line, from, to) per write: 18% total
stringWidth(line) chain (cached + JS): 14% total
All three were re-doing identical work every frame: same string → same
clipped slice → same width.
Fixes:
1. Memoize stringWidth (8k-entry LRU) for non-ASCII strings; ASCII fast-path
skips the cache (inline scan beats Map.get for short ASCII, the >90%
case). String.charCodeAt scan up to 64 chars is cheaper than the regex
fallback.
2. Memoize wrapText (4k-entry LRU keyed by maxWidth|wrapType|text) — wrapAnsi
is pure and the same content reflows identically every frame.
3. Memoize sliceAnsi (4k-entry LRU keyed by start|end|str) for the
end-defined hot path used by Output.get().
4. Skip the slice entirely in Output.get() when the line already fits the
clip box (startsBefore=false && endsAfter=false). Most transcript lines
never exceed their container width, and tokenizing them just to slice
(line, 0, width) was pure overhead. This single fast-path drops
sliceAnsi from 18% → ~0% in the profile.
Also tighten virtualization constants (MAX_MOUNTED 260→120, OVERSCAN 40→20,
SLIDE_STEP 25→12) and cap historical-message render at 800 chars / 16
lines via HISTORY_RENDER_MAX_*; messages inside the FULL_RENDER_TAIL_ITEMS
window still render in full so reading-zone behavior is unchanged.
Validation, real-user CPU profile, page-up scroll on 11k-line session:
Output.get() self-time: 24% → 0.3%
sliceAnsi total: 18% → not in top 25
stringWidth family: 14% → ~3%
idle: 60.7% → 77.3%
Frame timings (synthetic page-up profile harness):
dur p95: ~10ms → 4.87ms
dur p99: 25ms+ → 12.80ms
yoga p99: ~20ms → 1.87ms
The remaining CPU in the profile is Yoga layoutNode + React commit,
which is the irreducible work for this UI tree size.
- Drop the outer no-op capture group from INLINE_RE and restructure the
source as an ordered list of patterns-with-index-comments so each
alternative is individually greppable. Shift group indices in MdInline
down by one accordingly.
- Inline single-use helpers (parseFence, isFenceClose, isMarkdownFence,
trimBareUrl) and intermediate variables (path, lang, raw, prefix, body,
depth, task body, setext match, etc.).
- Hoist block-level regexes used inside MdImpl (FENCE_CLOSE_RE, SETEXT_RE,
BULLET_RE, TASK_RE, NUMBERED_RE, QUOTE_RE) to top-level consts so
they're compiled once instead of per-line.
- Collapse the duplicate compact-vs-normal blank-line branches into one
if/!compact gap call.
- Move Fence and MdProps types to the bottom per house style.
- Shorten splitTableRow → splitRow and use optional chaining in a few
match sites.
No behavior change; 162/162 tests pass. Net -22 LoC.
The inline markdown regex had `~([^~\s][^~]*?)~` for Pandoc-style subscript
(H~2~O, CO~2~). On models that decorate prose with kaomoji like `thing ~!`
and `cool ~?` — Kimi especially — the opener `~!` paired with the next
stray `~` on the line and dim-formatted everything between them with a
leading `_` character, mangling markdown output.
Tighten the pattern to short alphanumeric-only content (`~[A-Za-z0-9]{1,8}~`)
since real subscript never contains punctuation, spaces, or long runs.
Same tightening applied to stripInlineMarkup so width measurement stays
consistent. Classic CLI was unaffected because it renders these literally.
Models frequently emit bare codepoints like U+26A0 (⚠), U+2139 (ℹ),
U+2764 (❤), U+2714 (✔), U+2600 (☀), U+263A (☺) which, per Unicode, have
Emoji_Presentation=No and render as monochrome text-style glyphs in
terminals unless followed by VS16 (U+FE0F). Agent output leaked through
the TUI like `⚠ careful` instead of `⚠️ careful`.
Added `ensureEmojiPresentation` (lib/emoji.ts): scans for the curated
set of text-default codepoints and appends VS16 when the next char is
not already VS16, ZWJ, or a keycap-enclosing mark. Idempotent and
fast-pathed by a Unicode-range regex so ASCII-heavy text is untouched.
Applied once at the top of `Md`'s line parse. Hermes-ink's stringWidth
already accounts for VS16, so cursor/layout stays correct.
The agent emits `MEDIA:<path>` to signal file delivery to the gateway,
and `[[audio_as_voice]]` as a voice-delivery hint. The gateway strips
both before sending to Telegram/Discord/Slack, but the TUI was rendering
them raw through markdown — which is also how the intraword underscore
bug originally surfaced (`browser_screenshot_ecc…`).
At the `Md` layer, detect both sentinels on their own line:
- `MEDIA:<path>` → `▸ <path>` with the path rendered literal and wrapped
in a `Link` for OSC 8 hyperlink support (absolute paths get a
`file://` URL, so modern terminals make them click-to-open).
- `[[audio_as_voice]]` → dropped silently; it has no meaning in TUI.
Covers tests for quoted/backticked MEDIA variants, Windows drive paths,
whitespace, and the inline-in-prose case (left untouched — still
protected by the intraword-underscore guard).
renderLink was discarding the URL entirely — it rendered the label as amber
underlined text and dropped the href. Result: Cmd+Click / Ctrl+Click did
nothing in any terminal, including Ghostty.
Now both markdown links `[label](url)` and bare `https://…` URLs are wrapped
in @hermes/ink's Link component, which emits OSC 8 (\\x1b]8;;url\\x07label\\x1b]8;;\\x07)
when supportsHyperlinks() returns true. ADDITIONAL_HYPERLINK_TERMINALS already
includes ghostty, iTerm2, kitty, alacritty, Hyper.
Autolinks that look like bare emails (foo@bar.com) now prepend mailto: in the
href so they open the mail client correctly.
Also adds a typed declaration for Link in hermes-ink.d.ts.
Adds a minimal hand-rolled highlighter for ts/js/jsx/tsx, py, sh/bash, go, rust,
json, yaml, sql. Recognizes whole-line comments, single/double/backtick strings,
numbers, and per-language keyword sets. Unknown langs fall through to the current
plain rendering; the existing diff-specific colorization is preserved.
Closes the §8 "Markdown syntax highlighting is missing (only diff gets colored)"
finding from the TUI v2 audit without pulling in a highlighter library.
