c4f1af7a86
## 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. |
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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 | ||
| exec-server | ||
| 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 | ||
| skills | ||
| state | ||
| stdio-to-uds | ||
| 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.