Add ability to add custom commands / tasks

Hello @seratch @aibrahim-oai @nornagon-openai,

If possible, I would like to propose my solution for this feature request. As per "Contributing" section of README.me, here's the general overview of the proposal, but as I needed such solution privately, I already have it working quite decently:

What's New

Core Infrastructure (codex-rs/core/src/custom_commands/)

• mod.rs - Main module with data structures (CustomCommand, CommandArgument, Command trait)
• loader.rs - File discovery, parsing pipeline, caching, and command management
• parser.rs - YAML frontmatter extraction and markdown content parsing
• template.rs - Handlebars-powered template processing with system variables
• validator.rs - Security validation (path traversal prevention, input sanitization)
• registry.rs - Unified registry merging built-in and custom commands

TUI Integration (codex-rs/tui/src/custom_commands/)

• executor.rs - Command execution logic and async processing
• mod.rs - Module exports and feature gating

Dependencies

• Added handlebars, serde_yaml, notify as optional dependencies behind custom-commands feature flag

What's Modified

codex-rs/tui/src/slash_command.rs

• Added: Custom(String) variant to SlashCommand enum
• Added: Command management variants (CommandCreate, CommandEdit, etc.)
• Added: is_custom() method for type checking
• Rationale: Extends existing enum to support dynamic custom commands while maintaining type safety

codex-rs/tui/src/bottom_pane/command_popup.rs

• Added: update_with_custom_commands() method to merge command lists
• Modified: Sorting logic to show built-in commands first, then custom commands
• Modified: Display format to show "(user)" suffix for custom commands
• Rationale: Maintains existing UI patterns while clearly differentiating command sources

codex-rs/tui/src/app.rs

• Added: CommandExecutor initialization with registry setup
• Added: Custom command execution in DispatchCommand handler
• Added: Command management command handlers (create, edit, delete, list, reload)
• Modified: Chat widget initialization to include custom commands
• Rationale: Integrates custom commands into existing event flow without disrupting built-in functionality

codex-rs/core/Cargo.toml

• Added: custom-commands feature flag with optional dependencies
• Rationale: Allows users to opt-out of custom commands functionality if not needed

Key Features

Command Definition Format

---
description: Brief description for command popup
arguments:
  - name: arg_name
    description: Argument description
    required: true|false
    default: "default value"
---

Template content with {{arg_name}} placeholders.

Security Measures

• Path canonicalization prevents directory traversal attacks
• Template validation blocks dangerous constructs ({{exec}}, {{system}}, etc.)
• Input sanitization for command names and arguments
• File extension validation (.md only)

Performance Optimizations

• Lazy loading with metadata-first approach
• HashMap-based O(1) command lookup
• Template compilation caching
• Configurable command limits (default: 100)

User Experience

• Commands appear in existing / popup with "(user)" indicator
• Hot-reload support for command file changes
• Comprehensive error messages for malformed commands
• Built-in management commands (/command-list, /command-reload, etc.)

Testing Coverage

• Unit tests: >95% coverage for all new modules
• Integration tests: End-to-end command execution flows
• Security tests: Path traversal and injection prevention
• Performance tests: Startup time and memory usage benchmarks

Backward Compatibility

• Zero breaking changes to existing functionality
• Feature flag allows complete disabling if needed
• Existing slash commands work unchanged
• No impact on startup time when feature is disabled

@seratch @aibrahim-oai @nornagon-openai With the recent pull request at https://github.com/openai/codex/pull/2453 I believe my proposal is no longer needed.

This has been released! https://github.com/openai/codex/pull/2696