Olmo 3 (AI2) vs Codex (OpenAI)
Which one should you pick? Here's the full breakdown.
Olmo 3 (AI2)
Allen Institute for AI's fully-open frontier reasoning models -- Olmo 3 family (2025-11-20) includes 7B and 32B sizes, four variants (Base, Think, Instruct, RLZero). Apache 2.0 with fully open data + checkpoints + training logs. Olmo 3-Think 32B matches Qwen3-32B-Thinking at 6x fewer training tokens
Codex (OpenAI)
OpenAI's cloud-based coding agent -- runs parallel tasks, proposes PRs, and lives inside ChatGPT
Powered by GPT-5.3-Codex / GPT-5.4
| Category | Olmo 3 (AI2) | Codex (OpenAI) |
|---|---|---|
| Ease of Use | 6.0 | 8.0 |
| Output Quality | 8.0 | 8.0 |
| Value | 9.5 | 8.0 |
| Features | 8.0 | 9.0 |
| Overall | 7.9 | 8.3 |
Pricing Comparison
| Feature | Olmo 3 (AI2) | Codex (OpenAI) |
|---|---|---|
| Free Tier | Yes | Yes |
| Starting Price | $0 | $0 |
Benchmark Head-to-Head
GPT-5.3-Codex benchmarks — Olmo 3 (AI2) has no published benchmarks
| Benchmark | Description | Score |
|---|---|---|
| SWE-bench | Real GitHub issue fixing | 72% |
| HumanEval | Python code generation | 95% |
Which Should You Pick?
Pick Olmo 3 (AI2) if...
- ✓Better value for money (9.5/10)
AI researchers doing reproducibility work, training-data studies, instruction-tuning research, or RLHF-free (RLZero) experimentation. Also valuable for academic institutions and non-profits that want to use an open-weight model whose provenance is fully auditable. Good as a teaching / learning model where inspecting checkpoints matters.
Visit Olmo 3 (AI2)Pick Codex (OpenAI) if...
- ✓Easier to use (8 vs 6)
- ✓More features (9 vs 8)
Developers already paying for ChatGPT Plus who want a coding agent at no extra cost. Especially good for parallel task execution -- assign multiple bug fixes or feature branches and let Codex work them simultaneously.
Visit Codex (OpenAI)Our Verdict
Codex (OpenAI) edges out Olmo 3 (AI2) with a 8.3 vs 7.9 overall score. Both are solid picks, but Codex (OpenAI) has the advantage in features.