Model comparison
GPT-5.1-Codex vs Mistral Medium 3.5 128B
Head-to-head evidence from 13 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.1-Codex #105 (Estimated); Mistral Medium 3.5 128B unranked (Not scored). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.1-Codex and Mistral Medium 3.5 128B share 13 comparable benchmark results. 0 of 8 categories are comparable. 3 results are unique to GPT-5.1-Codex; 12 to Mistral Medium 3.5 128B.
Updated July 27, 2026- Shared results
- 13
- GPT-5.1-Codex only
- 3
- Mistral Medium 3.5 128B only
- 12
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.1-Codex and Mistral Medium 3.5 128B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 13 shared benchmark results across 6 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 256K for Mistral Medium 3.5 128B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.1-Codex | Δ | Mistral Medium 3.5 128B |
|---|---|---|---|
| Coding | GPT-5.1-CodexNot measured | MarginNo overlap | Mistral Medium 3.5 128B77.6 |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.1-Codex | Mistral Medium 3.5 128B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1-CodexNot available | Mistral Medium 3.5 128B$1.5 input / $7.5 output | A complete price comparison is not available. |
| Generation speedtokens per second | GPT-5.1-CodexNot available | Mistral Medium 3.5 128BNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.1-CodexNot available | Mistral Medium 3.5 128BNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1-Codex400K | Mistral Medium 3.5 128B256K | GPT-5.1-Codex lists the larger context window. |
Benchmark Deep Dive
Agentic12 benchmarks
| Benchmark | GPT-5.1-Codex | Mistral Medium 3.5 128B | Result |
|---|---|---|---|
| τ²-bench resultsSource | 83% | 94.2% | Mistral Medium 3.5 128B leads |
| Gert LabsSource | 49.68% | 39.10% | GPT-5.1-Codex leads |
| JobBenchSource | 26.2% | — | Not comparable |
| τ³-bench resultsSource | — | 91.4% | Not comparable |
| AA Agentic IndexSource | — | 19.0% | Not comparable |
| GDPval-AASource | — | 21.6% | Not comparable |
| GDPval-AASource | — | 933 | Not comparable |
| AA EnterpriseOps-GymSource | — | 33.7% | Not comparable |
| AA Harvey LABSource | — | 69.1% | Not comparable |
| terminalBenchHardSource | — | 33.3% | Not comparable |
| AA BriefcaseSource | — | 516 | Not comparable |
| AA Tau3 BankingSource | — | 14.4% | Not comparable |
Coding4 benchmarks
Reasoning2 benchmarks
Knowledge7 benchmarks
| Benchmark | GPT-5.1-Codex | Mistral Medium 3.5 128B | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 34.7% | 29.9% | GPT-5.1-Codex leads |
| AA-GPQA DiamondSource | 86.0% | 74.8% | GPT-5.1-Codex leads |
| AA-HLESource | 23.4% | 12.8% | GPT-5.1-Codex leads |
| AA-Omniscience IndexSource | -6.0% | -36.3% | GPT-5.1-Codex leads |
| AA-Omniscience AccuracySource | 39.2% | 25.1% | GPT-5.1-Codex leads |
| AA-Omniscience Hallucination RateSource | 74.4% | 82.0% | GPT-5.1-Codex leads |
| AA Openness IndexSource | — | 33.3% | Not comparable |
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-5.1-Codex | Mistral Medium 3.5 128B | Result |
|---|---|---|---|
| AA-IFBenchSource | 70.0% | 68.8% | GPT-5.1-Codex leads |
Frequently Asked Questions (3)
Can I compare GPT-5.1-Codex and Mistral Medium 3.5 128B 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.
What data is available for GPT-5.1-Codex and Mistral Medium 3.5 128B today?
Mistral Medium 3.5 128B: $1.50 input / $7.50 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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