Paul BakausandClaude Opus 4.6
2d4c7899dd
Research each harness's official documentation to verify and correct
provider frontmatter configs. Remove Codex/Gemini body transforms that
targeted their commands systems, not skills.
- Add compatibility + metadata to Cursor and Agents (Copilot)
- Add allowed-tools to Pi
- Remove Codex $ARGNAME and Gemini {{args}} body transforms
- Add HARNESSES.md as source of truth for harness capabilities
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
4.3 KiB
Harness Skills Capabilities Reference
Source of truth for what each AI coding harness supports in terms of agent skills.
Used to inform provider configs in scripts/lib/transformers/providers.js.
Last verified: 2026-03-24
Official Documentation
| Harness | Docs URL |
|---|---|
| Claude Code | https://code.claude.com/docs/en/skills |
| Cursor | https://cursor.com/docs/context/skills |
| Gemini CLI | https://geminicli.com/docs/cli/skills/ |
| Codex CLI | https://developers.openai.com/codex/skills |
| GitHub Copilot (Agents) | https://code.visualstudio.com/docs/copilot/customization/agent-skills |
| Kiro | https://kiro.dev/docs/skills/ |
| OpenCode | https://opencode.ai/docs/skills/ |
| Pi | https://github.com/badlogic/pi-mono/blob/main/packages/coding-agent/docs/skills.md |
Spec Compliance
All harnesses follow the Agent Skills specification to varying degrees. The spec defines these frontmatter fields: name, description, license, compatibility, metadata, allowed-tools.
Provider-specific extensions beyond the spec: user-invocable, argument-hint, disable-model-invocation, allowed-tools (extended syntax), model, effort, context, agent, hooks, subtask, mcp.
Frontmatter Support
Fields marked with * are spec-standard. Others are provider extensions.
| Field | Claude Code | Cursor | Gemini | Codex | Copilot | Kiro | OpenCode | Pi |
|---|---|---|---|---|---|---|---|---|
name* |
Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
description* |
Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
license* |
Yes | Yes | Ignored | No | Yes | Yes | Yes | Yes |
compatibility* |
Yes | Yes | Ignored | No | Yes | Yes | Yes | Yes |
metadata* |
Yes | Yes | Ignored | No | Yes | Yes | Yes | Yes |
allowed-tools* |
Yes | No | Ignored | No | No | No | Yes | Yes |
user-invocable |
Yes | No | No | No | Yes | No | Yes | No |
argument-hint |
Yes | No | No | No | Yes | No | Yes | No |
disable-model-invocation |
Yes | Yes | No | No | Yes | No | Yes | Yes |
model |
Yes | No | No | No | No | No | Yes | No |
effort |
Yes | No | No | No | No | No | No | No |
context |
Yes | No | No | No | No | No | No | No |
agent |
Yes | No | No | No | No | No | Yes | No |
hooks |
Yes | No | No | No | No | No | No | No |
Notes:
- Gemini CLI validates only
nameanddescription; other spec fields are parsed but ignored. - Codex CLI uses a separate
agents/openai.yamlsidecar for extended metadata (icons, branding, MCP tools, invocation control). - Kiro recognizes
user-invocableanddisable-model-invocationper community reports but does not formally document them. - Unknown fields are silently ignored by all harnesses.
Skill Directory Structure
| Harness | Native directory | Also reads |
|---|---|---|
| Claude Code | .claude/skills/ |
- |
| Cursor | .cursor/skills/ |
.agents/skills/, .claude/skills/, .codex/skills/ |
| Gemini CLI | .gemini/skills/ |
.agents/skills/ |
| Codex CLI | .agents/skills/ (primary) |
- |
| GitHub Copilot | .github/skills/ |
.agents/skills/, .claude/skills/ |
| Kiro | .kiro/skills/ |
- |
| OpenCode | .opencode/skills/ |
.agents/skills/, .claude/skills/ |
| Pi | .pi/skills/ |
.agents/skills/ |
All harnesses support the {skill-name}/SKILL.md directory structure with optional reference/, scripts/, and assets/ subdirectories.
Placeholder / Variable Substitution
Claude Code supports runtime variable substitution directly in SKILL.md bodies: $ARGUMENTS, $0-$N, ${CLAUDE_SKILL_DIR}, ${CLAUDE_SESSION_ID}. No other harness supports substitution in skills.
Some harnesses have separate "custom commands" systems (distinct from skills) with their own substitution:
| Harness | Command system | Substitution syntax |
|---|---|---|
| Gemini CLI | .gemini/commands/ (TOML) |
{{args}}, !{shell}, @{file} |
| Codex CLI | .codex/prompts/ |
$ARGNAME |
| OpenCode | .opencode/commands/ |
$ARGUMENTS, $1-$N, !`shell` |
Our build system handles cross-provider placeholders at compile time via replacePlaceholders() for {{model}}, {{config_file}}, {{ask_instruction}}, and {{available_commands}}.