Open conformance suite · v0.1
Tested facts about
AI coding agents.
What does your coding agent actually support? Small, reproducible tests for Codex, Antigravity CLI, OpenCode and more.
No rankings. No synthetic scores.
Just documented and observed behavior.
$ harnessfacts run codex instructions.nested
01 Create a temporary fixture
02 Run the agent
03 Check the exact output
04 Save the evidence
A fact you can inspect. A test you can repeat.
$ harnessfacts compare codex opencode
6Agent adapters
12Executable tests
70Completed observations
100%Open methodology
The compatibility notebook
Every observation has a version, an environment, and evidence.
| Capability | OpenAI Codex | Antigravity CLI | OpenCode | Claude Code |
|---|---|---|---|---|
| Root instructions | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: unknown |
| Nested instructions | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: unknown |
| Instruction precedence | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: unknown |
| MCP stdio | ✓ OBSERVEDv0.153.4 · linux x64Documented: yes ↗ | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: unknown |
| MCP HTTP | ✓ OBSERVEDv0.153.4 · linux x64Documented: yes ↗ | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: unknown |
| Headless execution | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: yes ↗ | ? UNKNOWNDocumented: yes ↗ |
| Exit semantics | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: unknown |
| Structured output | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: yes ↗ |
| Skill discovery | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: yes ↗ | ? UNKNOWNDocumented: unknown |
| Hook execution | ? UNKNOWNDocumented: unknown | ? UNKNOWNDocumented: unknown | ? UNKNOWNDocumented: unknown | ? UNKNOWNDocumented: unknown |
| Git worktrees | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: unknown |
| Repository boundary | ✓ OBSERVEDv0.153.4 · linux x64Documented: unknown | ✓ OBSERVEDv1.1.27 · linux x64Documented: unknown | ✓ OBSERVEDv1.18.29 · linux x64Documented: unknown | ? UNKNOWNDocumented: unknown |
✓ Observed in a completed run× Expected behavior not observed? Insufficient evidenceHow to read these results →
Small tests. Inspectable results.
See the fixture, prompt, and exact condition behind every capability.
Browse the suite →02 / UNDERSTANDKeep uncertainty visible.
A documented feature is a claim. An observed result records one execution.
Read the methodology →03 / CONTRIBUTEOne result makes a difference.
Run a test on your machine, add an adapter, or help verify another platform.
Contribute a result →