c3c75878e8
## 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. |
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| .. | ||
| .cargo | ||
| .config | ||
| .github/workflows | ||
| ansi-escape | ||
| app-server | ||
| app-server-protocol | ||
| app-server-test-client | ||
| apply-patch | ||
| arg0 | ||
| async-utils | ||
| backend-client | ||
| chatgpt | ||
| cli | ||
| cloud-requirements | ||
| cloud-tasks | ||
| cloud-tasks-client | ||
| codex-api | ||
| codex-backend-openapi-models | ||
| codex-client | ||
| codex-experimental-api-macros | ||
| config | ||
| core | ||
| debug-client | ||
| docs | ||
| exec | ||
| execpolicy | ||
| execpolicy-legacy | ||
| feedback | ||
| file-search | ||
| hooks | ||
| keyring-store | ||
| linux-sandbox | ||
| lmstudio | ||
| login | ||
| mcp-server | ||
| network-proxy | ||
| ollama | ||
| otel | ||
| process-hardening | ||
| protocol | ||
| responses-api-proxy | ||
| rmcp-client | ||
| scripts | ||
| secrets | ||
| shell-command | ||
| shell-escalation | ||
| skills | ||
| state | ||
| stdio-to-uds | ||
| test-macros | ||
| tui | ||
| utils | ||
| vendor | ||
| windows-sandbox-rs | ||
| .gitignore | ||
| BUILD.bazel | ||
| Cargo.lock | ||
| Cargo.toml | ||
| clippy.toml | ||
| config.md | ||
| default.nix | ||
| deny.toml | ||
| node-version.txt | ||
| README.md | ||
| rust-toolchain.toml | ||
| rustfmt.toml | ||
Codex CLI (Rust Implementation)
We provide Codex CLI as a standalone, native executable to ensure a zero-dependency install.
Installing Codex
Today, the easiest way to install Codex is via npm:
npm i -g @openai/codex
codex
You can also install via Homebrew (brew install --cask codex) or download a platform-specific release directly from our GitHub Releases.
Documentation quickstart
- First run with Codex? Start with
docs/getting-started.md(links to the walkthrough for prompts, keyboard shortcuts, and session management). - Want deeper control? See
docs/config.mdanddocs/install.md.
What's new in the Rust CLI
The Rust implementation is now the maintained Codex CLI and serves as the default experience. It includes a number of features that the legacy TypeScript CLI never supported.
Config
Codex supports a rich set of configuration options. Note that the Rust CLI uses config.toml instead of config.json. See docs/config.md for details.
Model Context Protocol Support
MCP client
Codex CLI functions as an MCP client that allows the Codex CLI and IDE extension to connect to MCP servers on startup. See the configuration documentation for details.
MCP server (experimental)
Codex can be launched as an MCP server by running codex mcp-server. This allows other MCP clients to use Codex as a tool for another agent.
Use the @modelcontextprotocol/inspector to try it out:
npx @modelcontextprotocol/inspector codex mcp-server
Use codex mcp to add/list/get/remove MCP server launchers defined in config.toml, and codex mcp-server to run the MCP server directly.
Notifications
You can enable notifications by configuring a script that is run whenever the agent finishes a turn. The notify documentation includes a detailed example that explains how to get desktop notifications via terminal-notifier on macOS. When Codex detects that it is running under WSL 2 inside Windows Terminal (WT_SESSION is set), the TUI automatically falls back to native Windows toast notifications so approval prompts and completed turns surface even though Windows Terminal does not implement OSC 9.
codex exec to run Codex programmatically/non-interactively
To run Codex non-interactively, run codex exec PROMPT (you can also pass the prompt via stdin) and Codex will work on your task until it decides that it is done and exits. Output is printed to the terminal directly. You can set the RUST_LOG environment variable to see more about what's going on.
Use codex exec --ephemeral ... to run without persisting session rollout files to disk.
Experimenting with the Codex Sandbox
To test to see what happens when a command is run under the sandbox provided by Codex, we provide the following subcommands in Codex CLI:
# macOS
codex sandbox macos [--full-auto] [--log-denials] [COMMAND]...
# Linux
codex sandbox linux [--full-auto] [COMMAND]...
# Windows
codex sandbox windows [--full-auto] [COMMAND]...
# Legacy aliases
codex debug seatbelt [--full-auto] [--log-denials] [COMMAND]...
codex debug landlock [--full-auto] [COMMAND]...
Selecting a sandbox policy via --sandbox
The Rust CLI exposes a dedicated --sandbox (-s) flag that lets you pick the sandbox policy without having to reach for the generic -c/--config option:
# Run Codex with the default, read-only sandbox
codex --sandbox read-only
# Allow the agent to write within the current workspace while still blocking network access
codex --sandbox workspace-write
# Danger! Disable sandboxing entirely (only do this if you are already running in a container or other isolated env)
codex --sandbox danger-full-access
The same setting can be persisted in ~/.codex/config.toml via the top-level sandbox_mode = "MODE" key, e.g. sandbox_mode = "workspace-write".
Code Organization
This folder is the root of a Cargo workspace. It contains quite a bit of experimental code, but here are the key crates:
core/contains the business logic for Codex. Ultimately, we hope this to be a library crate that is generally useful for building other Rust/native applications that use Codex.exec/"headless" CLI for use in automation.tui/CLI that launches a fullscreen TUI built with Ratatui.cli/CLI multitool that provides the aforementioned CLIs via subcommands.
If you want to contribute or inspect behavior in detail, start by reading the module-level README.md files under each crate and run the project workspace from the top-level codex-rs directory so shared config, features, and build scripts stay aligned.