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## Problem The TUI diff renderer uses hardcoded background palettes for insert/delete lines that don't respect the user's chosen syntax theme. When a theme defines `markup.inserted` / `markup.deleted` scope backgrounds (the convention used by GitHub, Solarized, Monokai, and most VS Code themes), those colors are ignored — the diff always renders with the same green/red tints regardless of theme selection. Separately, ANSI-16 terminals (and Windows Terminal sessions misreported as ANSI-16) rendered diff backgrounds as full-saturation blocks that obliterated syntax token colors, making highlighted diffs unreadable. ## Mental model Diff backgrounds are resolved in three layers: 1. **Color level detection** — `diff_color_level_for_terminal()` maps the raw `supports-color` probe + Windows Terminal heuristics to a `DiffColorLevel` (TrueColor / Ansi256 / Ansi16). Windows Terminal gets promoted from Ansi16 to TrueColor when `WT_SESSION` is present. 2. **Background resolution** — `resolve_diff_backgrounds()` queries the active syntax theme for `markup.inserted`/`markup.deleted` (falling back to `diff.inserted`/`diff.deleted`), then overlays those on top of the hardcoded palette. For ANSI-256, theme RGB values are quantized to the nearest xterm-256 index. For ANSI-16, backgrounds are `None` (foreground-only). 3. **Style composition** — The resolved `ResolvedDiffBackgrounds` is threaded through every call to `style_add`, `style_del`, `style_sign_*`, and `style_line_bg_for`, which decide how to compose foreground+background for each line kind and theme variant. A new `RichDiffColorLevel` type (a subset of `DiffColorLevel` without Ansi16) encodes the invariant "we have enough depth for tinted backgrounds" at the type level, so background-producing functions have exhaustive matches without unreachable arms. ## Non-goals - No change to gutter (line number column) styling — gutter backgrounds still use the hardcoded palette. - No per-token scope background resolution — this is line-level background only; syntax token colors come from the existing `highlight_code_to_styled_spans` path. - No dark/light theme auto-switching from scope backgrounds — `DiffTheme` is still determined by querying the terminal's background color. ## Tradeoffs - **Theme trust vs. visual safety:** When a theme defines scope backgrounds, we trust them unconditionally for rich color levels. A badly authored theme could produce illegible combinations. The fallback for `None` backgrounds (foreground-only) is intentionally conservative. - **Quantization quality:** ANSI-256 quantization uses perceptual distance across indices 16–255, skipping system colors. The result is approximate — a subtle theme tint may land on a noticeably different xterm index. - **Single-query caching:** `resolve_diff_backgrounds` is called once per `render_change` invocation (i.e., once per file in a diff). If the theme changes mid-render (live preview), the next file picks up the new backgrounds. ## Architecture Files changed: | File | Role | |---|---| | `tui/src/render/highlight.rs` | New: `DiffScopeBackgroundRgbs`, `diff_scope_background_rgbs()`, scope extraction helpers | | `tui/src/diff_render.rs` | New: `RichDiffColorLevel`, `ResolvedDiffBackgrounds`, `resolve_diff_backgrounds*`, `quantize_rgb_to_ansi256`, Windows Terminal promotion; modified: all style helpers to accept/thread `ResolvedDiffBackgrounds` | The scope-extraction code lives in `highlight.rs` because it uses `syntect::highlighting::Highlighter` and the theme singleton. The resolution and quantization logic lives in `diff_render.rs` because it depends on diff-specific types (`DiffTheme`, `DiffColorLevel`, ratatui `Color`). ## Observability No runtime logging was added. The most useful debugging aid is the `diff_color_level_for_terminal` function, which is pure and fully unit-tested — to diagnose a color-depth mismatch, log its four inputs (`StdoutColorLevel`, `TerminalName`, `WT_SESSION` presence, `FORCE_COLOR` presence). Scope resolution can be tested by loading a custom `.tmTheme` with known `markup.inserted` / `markup.deleted` backgrounds and checking the diff output in a truecolor terminal. ## Tests - **Windows Terminal promotion:** 7 unit tests cover every branch of `diff_color_level_for_terminal` (ANSI-16 promotion, `WT_SESSION` unconditional promotion, `FORCE_COLOR` suppression, conservative `Unknown` level). - **ANSI-16 foreground-only:** Tests verify that `style_add`, `style_del`, `style_sign_*`, `style_line_bg_for`, and `style_gutter_for` all return `None` backgrounds on ANSI-16. - **Scope resolution:** Tests verify `markup.*` preference over `diff.*`, `None` when no scope matches, bundled theme resolution, and custom `.tmTheme` round-trip. - **Quantization:** Test verifies ANSI-256 quantization of a known RGB triple. - **Insta snapshots:** 2 new snapshot tests (`ansi16_insert_delete_no_background`, `theme_scope_background_resolution`) lock visual output.
npm i -g @openai/codex
or brew install --cask codex
Codex CLI is a coding agent from OpenAI that runs locally on your computer.
If you want Codex in your code editor (VS Code, Cursor, Windsurf), install in your IDE.
If you want the desktop app experience, run
codex app or visit the Codex App page.
If you are looking for the cloud-based agent from OpenAI, Codex Web, go to chatgpt.com/codex.
Quickstart
Installing and running Codex CLI
Install globally with your preferred package manager:
# Install using npm
npm install -g @openai/codex
# Install using Homebrew
brew install --cask codex
Then simply run codex to get started.
You can also go to the latest GitHub Release and download the appropriate binary for your platform.
Each GitHub Release contains many executables, but in practice, you likely want one of these:
- macOS
- Apple Silicon/arm64:
codex-aarch64-apple-darwin.tar.gz - x86_64 (older Mac hardware):
codex-x86_64-apple-darwin.tar.gz
- Apple Silicon/arm64:
- Linux
- x86_64:
codex-x86_64-unknown-linux-musl.tar.gz - arm64:
codex-aarch64-unknown-linux-musl.tar.gz
- x86_64:
Each archive contains a single entry with the platform baked into the name (e.g., codex-x86_64-unknown-linux-musl), so you likely want to rename it to codex after extracting it.
Using Codex with your ChatGPT plan
Run codex and select Sign in with ChatGPT. We recommend signing into your ChatGPT account to use Codex as part of your Plus, Pro, Team, Edu, or Enterprise plan. Learn more about what's included in your ChatGPT plan.
You can also use Codex with an API key, but this requires additional setup.
Docs
This repository is licensed under the Apache-2.0 License.