Cross-harness capability matrix

claude-agents is a multi-harness plugin marketplace. Source-of-truth lives under plugins/ as Claude Code markdown. Per-harness artifacts are generated by adapters under tools/adapters/.

This file mirrors the capability matrix in tools/adapters/capabilities.py. Edit there; regenerate via make docs.

Supported harnesses

Harness	Status	Generated paths
Claude Code	source-of-truth	plugins/, .claude-plugin/marketplace.json
OpenAI Codex CLI	supported	.codex/skills/, .codex/agents/, AGENTS.md
Cursor (2.5+)	supported	.cursor-plugin/, .cursor/rules/ (curated)
OpenCode (sst/opencode)	supported	.opencode/agents/, .opencode/commands/, opencode.json
Gemini CLI	supported	skills/, agents/, commands/ (at extension root)

Capability matrix

Capability	Claude Code	Codex	Cursor	OpenCode	Gemini
Skills (SKILL.md native)	✅	✅	✅ via .claude/	✅ via .claude/	✅ (auto-discovered)
Subagents (markdown native)	✅	TOML format	✅ via .claude/	✅ (different frontmatter)	✅ (April 2026 spec)
Slash commands	✅	converted to skills	✅	✅	TOML at commands/
Plugin marketplace	✅	—	✅ (2.5+)	—	— (direct URL install)
Parallel subagents	✅	✅	✅	✅	✅ (April 2026)
Per-agent tool allowlist	✅ (tools:)	only sandbox_mode	only readonly:	✅ (permission: block)	✅ (tools:)
TodoWrite tool	✅	—	—	✅	—
Task/Agent spawn tool	✅	name in prose	✅	✅ (task)	@agent syntax
MCP servers	✅	✅	✅	✅	✅
Lifecycle hooks	✅	—	—	✅ (TS plugins)	—
Context file	CLAUDE.md	AGENTS.md (32 KiB cap)	AGENTS.md	AGENTS.md / ~/.claude/CLAUDE.md	GEMINI.md
Context file recommended cap	150 lines / 500 tokens	150 lines / 500 tokens	150 lines / 500 tokens	150 lines / 500 tokens	150 lines / 500 tokens
Skill body hard cap	none	8 KB	none	none	none
Tool name case	CamelCase (Read)	action verbs (no tool vocab)	lowercase	lowercase (strict)	lowercase (Gemini names)
Bare model aliases	✅ (opus/sonnet/haiku)	mapped to GPT-5 family	use inherit	full provider/model-id	mapped to gemini-2.5-*

Graceful degradation

Each adapter handles incompatibilities mechanically — authors don't need to know the per-harness rules to write portable content.

Source pattern	Codex	Cursor	OpenCode	Gemini
tools: Read, Grep (agent allowlist)	dropped; sandbox_mode = "read-only" heuristic	dropped (Cursor doesn't honor)	converted to permission: deny block	passed through
color: blue (agent)	dropped	dropped	dropped	dropped
model: opus (agent)	mapped to gpt-5	rewritten to inherit	rewritten to anthropic/claude-opus-4-7	mapped to gemini-2.5-pro
TodoWrite in body	no equivalent — leave as-is	no equivalent — leave as-is	works as-is	no equivalent
Skill body > 8 KB	split into references/details.md	passed through	passed through	passed through
Agent named worker	namespaced to <plugin>__worker	passed through	passed through	passed through
Slash command (commands/<x>.md)	converted to skill	passed through	rewritten to .opencode/commands/	TOML at commands/<plugin>/<x>.toml

Output paths (all gitignored)

.claude-plugin/marketplace.json   # SOURCE OF TRUTH (committed)
plugins/                          # SOURCE OF TRUTH (committed)
GEMINI.md, AGENTS.md*             # context files (committed/generated)
.codex/skills/, .codex/agents/    # generated by Codex adapter
.cursor-plugin/, .cursor/rules/   # generated by Cursor adapter
.opencode/agents/, .opencode/commands/, opencode.json   # generated by OpenCode adapter
skills/, agents/, commands/       # generated by Gemini adapter (at extension root)

Regenerating

make generate HARNESS=codex
make generate HARNESS=cursor
make generate HARNESS=opencode
make generate HARNESS=gemini
# Or all at once:
make generate-all

See also

• authoring.md — portable-content style guide for plugin authors
• architecture.md — overall design principles
• plugin-eval.md — the harness_portability scoring dimension