new feature snippet

[Jaylon998]

What

This PR introduces a comprehensive snippet management system for Codex CLI, enabling developers to store, manage, and dynamically reference reusable code snippets within prompts.

Features Added

• Snippet Management Commands: snippet add, snippet show, snippet list, snippet remove, snippet help
• Inline Snippet References: Support for snippet: <label> syntax in prompts with automatic code expansion
• Error Handling: Graceful handling of missing snippets with user-friendly warnings
• Data Persistence: JSON-based storage in ~/.codex/snippets.json

Why

Developers frequently reuse common code patterns (debounce functions, API templates, utility functions) across different prompts. Currently, users must manually copy-paste or retype these patterns, leading to:

• Reduced productivity and increased friction
• Inconsistent code patterns across sessions
• Time wasted on repetitive typing
• Difficulty maintaining reusable code snippets

This feature addresses these pain points by providing a built-in snippet system similar to what developers expect in modern code editors.

How

Implementation Architecture

1. Storage Layer (snippet-storage.ts): JSON-based persistence with CRUD operations
2. Command Layer (snippet-commands.ts): CLI command parsing and user interaction
3. Resolution Layer (snippet-resolver.ts): Regex-based snippet detection and replacement
4. Integration Layer (input-utils.ts, cli.tsx): Seamless integration with existing input processing

Technical Details

• Pattern Recognition: Uses regex /snippet:\s*([a-zA-Z0-9_-]+)/g to detect references
• Replacement Strategy: Processes matches in reverse order to maintain string indices
• Error Resilience: Missing snippets trigger warnings but don't break the flow
• User Feedback: Real-time expansion notifications (✅ Expanded snippets: debounce)

Example Usage

# Add a snippet
codex snippet add debounce "function debounce(fn, delay) { ... }"

# Use in prompts
"Add resize handler using snippet: debounce"
# Expands to: "Add resize handler using function debounce(fn, delay) { ... }"

Testing

• ✅ All snippet management commands tested (add, show, list, remove)
• ✅ Inline replacement with single and multiple snippets
• ✅ Error handling for non-existent snippets
• ✅ Data persistence across sessions
• ✅ Integration with existing CLI workflows

Breaking Changes

None. This is a purely additive feature that doesn't modify existing functionality.

Files Changed

• codex-cli/src/utils/snippet-storage.ts - Core storage management
• codex-cli/src/utils/snippet-commands.ts - CLI command handlers
• codex-cli/src/utils/snippet-resolver.ts - Inline snippet resolution
• codex-cli/src/utils/input-utils.ts - Integration with input processing
• codex-cli/src/cli.tsx - CLI command routing

Related Issues

Addresses the need for code reusability and developer productivity enhancement in terminal-based AI coding workflows.

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Checklist:

• All tests pass locally
• Code follows project style guidelines
• Feature is documented with clear examples
• No breaking changes introduced
• Branch is up-to-date with main

[codex-maintainers]

Thanks for the contribution! We're primarily focused on the native/Rust implementation of Codex CLI and would love to see if this feature is still relevant on the latest version. If it is, we're happy to take a look at a PR to the codex-rs/ implementation.