Model comparison
Composer 2 Fast vs GPT-5.1-Codex
Head-to-head evidence from 0 shared benchmark results across 0 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Composer 2 Fast unranked (Not scored); GPT-5.1-Codex #105 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Composer 2 Fast and GPT-5.1-Codex share 0 comparable benchmark results. 0 of 8 categories are comparable. 1 result is unique to Composer 2 Fast; 16 to GPT-5.1-Codex.
Updated July 28, 2026- Shared results
- 0
- Composer 2 Fast only
- 1
- GPT-5.1-Codex only
- 16
- Comparable categories
- 0 / 8
Benchmark data for Composer 2 Fast and GPT-5.1-Codex is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 0 shared benchmark results across 0 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
GPT-5.1-Codex has the larger context window at 400K, compared with 200K for Composer 2 Fast.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Composer 2 Fast | GPT-5.1-Codex | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Composer 2 FastNot available | GPT-5.1-CodexNot available | A complete price comparison is not available. |
| Generation speedtokens per second | Composer 2 FastNot available | GPT-5.1-CodexNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Composer 2 FastNot available | GPT-5.1-CodexNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Composer 2 Fast200K | GPT-5.1-Codex400K | GPT-5.1-Codex lists the larger context window. |
Benchmark Deep Dive
Agentic3 benchmarks
Coding3 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | Composer 2 Fast | GPT-5.1-Codex | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | — | 34.7% | Not comparable |
| AA-GPQA DiamondSource | — | 86.0% | Not comparable |
| AA-HLESource | — | 23.4% | Not comparable |
| AA-Omniscience IndexSource | — | -6.0% | Not comparable |
| AA-Omniscience AccuracySource | — | 39.2% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 74.4% | Not comparable |
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | Composer 2 Fast | GPT-5.1-Codex | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 70.0% | Not comparable |
Frequently Asked Questions (2)
Can I compare Composer 2 Fast and GPT-5.1-Codex on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
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Know when it’s worth switching models
The model to choose, the cheaper alternative, and the release we would wait on.
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