## Summary
Adds syntax highlighting to the TUI for fenced code blocks in markdown
responses and file diffs, plus a `/theme` command with live preview and
persistent theme selection. Uses syntect (~250 grammars, 32 bundled
themes, ~1 MB binary cost) — the same engine behind `bat`, `delta`, and
`xi-editor`. Includes guardrails for large inputs, graceful fallback to
plain text, and SSH-aware clipboard integration for the `/copy` command.
<img width="1554" height="1014" alt="image"
src="https://github.com/user-attachments/assets/38737a79-8717-4715-b857-94cf1ba59b85"
/>
<img width="2354" height="1374" alt="image"
src="https://github.com/user-attachments/assets/25d30a00-c487-4af8-9cb6-63b0695a4be7"
/>
## Problem
Code blocks in the TUI (markdown responses and file diffs) render
without syntax highlighting, making it hard to scan code at a glance.
Users also have no way to pick a color theme that matches their terminal
aesthetic.
## Mental model
The highlighting system has three layers:
1. **Syntax engine** (`render::highlight`) -- a thin wrapper around
syntect + two-face. It owns a process-global `SyntaxSet` (~250 grammars)
and a `RwLock<Theme>` that can be swapped at runtime. All public entry
points accept `(code, lang)` and return ratatui `Span`/`Line` vectors or
`None` when the language is unrecognized or the input exceeds safety
guardrails.
2. **Rendering consumers** -- `markdown_render` feeds fenced code blocks
through the engine; `diff_render` highlights Add/Delete content as a
whole file and Update hunks per-hunk (preserving parser state across
hunk lines). Both callers fall back to plain unstyled text when the
engine returns `None`.
3. **Theme lifecycle** -- at startup the config's `tui.theme` is
resolved to a syntect `Theme` via `set_theme_override`. At runtime the
`/theme` picker calls `set_syntax_theme` to swap themes live; on cancel
it restores the snapshot taken at open. On confirm it persists `[tui]
theme = "..."` to config.toml.
## Non-goals
- Inline diff highlighting (word-level change detection within a line).
- Semantic / LSP-backed highlighting.
- Theme authoring tooling; users supply standard `.tmTheme` files.
## Tradeoffs
| Decision | Upside | Downside |
| ------------------------------------------------ |
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
-----------------------------------------------------------------------------------------------------------------------
|
| syntect over tree-sitter / arborium | ~1 MB binary increase for ~250
grammars + 32 themes; battle-tested crate powering widely-used tools
(`bat`, `delta`, `xi-editor`). tree-sitter would add ~12 MB for 20-30
languages or ~35 MB for full coverage. | Regex-based; less structurally
accurate than tree-sitter for some languages (e.g. language injections
like JS-in-HTML). |
| Global `RwLock<Theme>` | Enables live `/theme` preview without
threading Theme through every call site | Lock contention risk
(mitigated: reads vastly outnumber writes, single UI thread) |
| Skip background / italic / underline from themes | Terminal BG
preserved, avoids ugly rendering on some themes | Themes that rely on
these properties lose fidelity |
| Guardrails: 512 KB / 10k lines | Prevents pathological stalls on huge
diffs or pastes | Very large files render without color |
## Architecture
```
config.toml ─[tui.theme]─> set_theme_override() ─> THEME (RwLock)
│
┌───────────────────────────────────────────┘
│
markdown_render ─── highlight_code_to_lines(code, lang) ─> Vec<Line>
diff_render ─── highlight_code_to_styled_spans(code, lang) ─> Option<Vec<Vec<Span>>>
│
│ (None ⇒ plain text fallback)
│
/theme picker ─── set_syntax_theme(theme) // live preview swap
─── current_syntax_theme() // snapshot for cancel
─── resolve_theme_by_name(name) // lookup by kebab-case
```
Key files:
- `tui/src/render/highlight.rs` -- engine, theme management, guardrails
- `tui/src/diff_render.rs` -- syntax-aware diff line wrapping
- `tui/src/theme_picker.rs` -- `/theme` command builder
- `tui/src/bottom_pane/list_selection_view.rs` -- side content panel,
callbacks
- `core/src/config/types.rs` -- `Tui::theme` field
- `core/src/config/edit.rs` -- `syntax_theme_edit()` helper
## Observability
- `tracing::warn` when a configured theme name cannot be resolved.
- `Config::startup_warnings` surfaces the same message as a TUI banner.
- `tracing::error` when persisting theme selection fails.
## Tests
- Unit tests in `highlight.rs`: language coverage, fallback behavior,
CRLF stripping, style conversion, guardrail enforcement, theme name
mapping exhaustiveness.
- Unit tests in `diff_render.rs`: snapshot gallery at multiple terminal
sizes (80x24, 94x35, 120x40), syntax-highlighted wrapping, large-diff
guardrail, rename-to-different-extension highlighting, parser state
preservation across hunk lines.
- Unit tests in `theme_picker.rs`: preview rendering (wide + narrow),
dim overlay on deletions, subtitle truncation, cancel-restore, fallback
for unavailable configured theme.
- Unit tests in `list_selection_view.rs`: side layout geometry, stacked
fallback, buffer clearing, cancel/selection-changed callbacks.
- Integration test in `lib.rs`: theme warning uses the final
(post-resume) config.
## Cargo Deny: Unmaintained Dependency Exceptions
This PR adds two `cargo deny` advisory exceptions for transitive
dependencies pulled in by `syntect v5.3.0`:
| Advisory | Crate | Status |
|----------|-------|--------|
| RUSTSEC-2024-0320 | `yaml-rust` | Unmaintained (maintainer
unreachable) |
| RUSTSEC-2025-0141 | `bincode` | Unmaintained (development ceased;
v1.3.3 considered complete) |
**Why this is safe in our usage:**
- Neither advisory describes a known security vulnerability. Both are
"unmaintained" notices only.
- `bincode` is used by syntect to deserialize pre-compiled syntax sets.
Again, these are **static vendored artifacts** baked into the binary at
build time. No user-supplied bincode data is ever deserialized. - Attack
surface is zero for both crates; exploitation would require a
supply-chain compromise of our own build artifacts.
- These exceptions can be removed when syntect migrates to `yaml-rust2`
and drops `bincode`, or when alternative crates are available upstream.
- introduce RenderableItem to support both owned and borrowed children
in composite Renderables
- refactor some of our gnarlier manual layouts, BottomPane and
ChatWidget, to use ColumnRenderable
- Renderable and friends now handle cursor_pos()
Refactor trust_directory to use ColumnRenderable & friends, thus
correcting wrapping behavior at small widths. Also introduce
RowRenderable with fixed-width rows.
- fixed wrapping in trust_directory
- changed selector cursor to match other list item selections
- allow y/n to work as well as 1/2
- fixed key_hint to be standard
before:
<img width="661" height="550" alt="Screenshot 2025-10-09 at 9 50 36 AM"
src="https://github.com/user-attachments/assets/e01627aa-bee4-4e25-8eca-5575c43f05bf"
/>
after:
<img width="661" height="550" alt="Screenshot 2025-10-09 at 9 51 31 AM"
src="https://github.com/user-attachments/assets/cb816cbd-7609-4c83-b62f-b4dba392d79a"
/>
Also, simplify the streaming behavior.
This fixes a number of display issues with streaming markdown, and paves
the way for better markdown features (e.g. customizable styles, syntax
highlighting, markdown-aware wrapping).
Not currently supported:
- footnotes
- tables
- reference-style links
i'm not yet convinced i have the best heuristics for what to highlight,
but this feels like a useful step towards something a bit easier to
read, esp. when the model is producing large commands.
<img width="669" height="589" alt="Screenshot 2025-09-03 at 8 21 56 PM"
src="https://github.com/user-attachments/assets/b9cbcc43-80e8-4d41-93c8-daa74b84b331"
/>
also a fairly significant refactor of our line wrapping logic.
#### Summary
- Emit a “Proposed Command” history cell when an ExecApprovalRequest
arrives (parity with proposed patches).
- Simplify the approval dialog: show only the reason/instructions; move
the command preview into history.
- Make approval/abort decision history concise:
- Single line snippet; if multiline, show first line + " ...".
- Truncate to 80 graphemes with ellipsis for very long commands.
#### Details
- History
- Add `new_proposed_command` to render a header and indented command
preview.
- Use shared `prefix_lines` helper for first/subsequent line prefixes.
- Approval UI
- `UserApprovalWidget` no longer renders the command in the modal; shows
optional `reason` text only.
- Decision history renders an inline, dimmed snippet per rules above.
- Tests (snapshot-based)
- Proposed/decision flow for short command.
- Proposed multi-line + aborted decision snippet with “ ...”.
- Very long one-line command -> truncated snippet with “…”.
- Updated existing exec approval snapshots and test reasons.
<img width="1053" height="704" alt="Screenshot 2025-09-03 at 11 57
35 AM"
src="https://github.com/user-attachments/assets/9ed4c316-9daf-4ac1-80ff-7ae1f481dd10"
/>
after approving:
<img width="1053" height="704" alt="Screenshot 2025-09-03 at 11 58
18 AM"
src="https://github.com/user-attachments/assets/a44e243f-eb9d-42ea-87f4-171b3fb481e7"
/>
rejection:
<img width="1053" height="207" alt="Screenshot 2025-09-03 at 11 58
45 AM"
src="https://github.com/user-attachments/assets/a022664b-ae0e-4b70-a388-509208707934"
/>
big command:
https://github.com/user-attachments/assets/2dd976e5-799f-4af7-9682-a046e66cc494
Wait for newlines, then render markdown on a line by line basis. Word wrap it for the current terminal size and then spit it out line by line into the UI. Also adds tests and fixes some UI regressions.
Felipe Coury ·
viyatb-oai ·
Jeremy Rose ·
easong-openai ·