GPT-5.1 Codex vs GLM 5.1 for coding
GPT-5.1 Codex is the stronger coder of the two on benchmarks, but GLM 5.1 can be the better pick when cost, speed, or context window matter more. Below: a side-by-side spec table and exactly when to pick each.
At a glance
| Spec | GPT-5.1 Codex | GLM 5.1 |
|---|---|---|
| Provider | OpenAI | Z.ai (Tsinghua) |
| Released | Nov 2025 | 2026 |
| SWE-bench Verified | 75% | 58% |
| HumanEval | 95% | — |
| MMLU | 88% | 87% |
| Context window | 400K | 128K |
| Max output | 128K | 32K |
| Input price (per 1M) | $1.25 | Free (self-hosted) |
| Output price (per 1M) | $10 | Free (self-hosted) |
| Price tier | Mid | Free |
| Speed | Medium | Standard |
| Hosting | Closed/API | Open-weights |
| Modality | Text + Vision | Text-only |
| Knowledge cutoff | Oct 2025 | 2026 |
Pick GPT-5.1 Codex if…
- It scores higher on SWE-bench Verified (75% vs 58%), the best proxy for real-world coding.
- It has a larger context window (400K vs 128K).
- It's tuned for codex CLI and long-horizon coding agents; engineered for terminal-driven workflows.
Pick GLM 5.1 if…
- It's cheaper (Free tier vs Mid).
- It's tuned for top-tier agentic engineering, complex multi-step workflows, sustained long-horizon coding, self-improving agent loops.
GPT-5.1 Codex vs GLM 5.1: which is better for coding?
GPT-5.1 Codex is the stronger coder of the two on benchmarks, but GLM 5.1 can be the better pick when cost, speed, or context window matter more. See the full spec table for SWE-bench, HumanEval, MMLU, context window, and pricing on both. Benchmarks are a directional signal, not a guarantee for your codebase — the most reliable test is running both on a real task you care about.
Compare these head-to-head with live data, or build a full stack around your pick — Flowpicker shows compatibility and monthly cost.
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See the full model leaderboard ranked by SWE-bench, HumanEval, and MMLU.