GLM-5.1 vs gpt-oss-120b
GLM-5.1 (2026) and gpt-oss-120b (2025) are frontier reasoning models from Zhipu AI and OpenAI. GLM-5.1 ships a 200k-token context window, while gpt-oss-120b ships a 131k-token context window. On Google-Proof Q&A, GLM-5.1 leads by 8 pts. On pricing, gpt-oss-120b costs $0.04/1M input tokens versus $0.98/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
gpt-oss-120b is ~2413% cheaper at $0.04/1M; pay for GLM-5.1 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | GLM-5.1 | gpt-oss-120b |
|---|---|---|
| Best for | reasoning-heavy apps, tool-calling agents, and provider-routed production | tool-calling agents and provider-routed production |
| Decision fit | Coding, RAG, and Agents | RAG, Agents, and Long context |
| Context window | 200k | 131k |
| Cheapest output | $3.08/1M tokens | $0.18/1M tokens |
| Provider routes | 5 tracked | 10 tracked |
| Shared benchmarks | Google-Proof Q&A leader | 1 rows |
Decision tradeoffs
- GLM-5.1 leads the largest shared benchmark signal on Google-Proof Q&A by 8 points.
- GLM-5.1 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GLM-5.1 uniquely exposes Reasoning and Code execution in local model data.
- Local decision data tags GLM-5.1 for Coding, RAG, and Agents.
- gpt-oss-120b has the lower cheapest tracked output price at $0.18/1M tokens.
- gpt-oss-120b has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags gpt-oss-120b for RAG, Agents, and Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GLM-5.1
$1,554
Cheapest tracked route/tier: Z.ai
gpt-oss-120b
$76.20
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $1,478. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter, Fireworks AI, and Vercel AI Gateway; start route-level A/B tests there.
- gpt-oss-120b is $2.90/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning and Code execution before moving production traffic.
- Provider overlap exists on OpenRouter, Fireworks AI, and Vercel AI Gateway; start route-level A/B tests there.
- GLM-5.1 is $2.90/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GLM-5.1 adds Reasoning and Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-07 | 2025-08-05 |
| Context window | 200k | 131k |
| Parameters | 754B total, 40B active | 120B |
| Architecture | mixture of experts | decoder only |
| License | MIT | Open Weights |
| Knowledge cutoff | 2025-11 | 2025-08 |
Pricing and availability
| Pricing attribute | GLM-5.1 | gpt-oss-120b |
|---|---|---|
| Input price | $0.98/1M tokens | $0.04/1M tokens |
| Output price | $3.08/1M tokens | $0.18/1M tokens |
| Providers |
Capabilities
| Capability | GLM-5.1 | gpt-oss-120b |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | Yes | No |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | GLM-5.1 | gpt-oss-120b |
|---|---|---|
| Google-Proof Q&A | 86.2 | 78.2 |
Deep dive
On shared benchmark coverage, Google-Proof Q&A has GLM-5.1 at 86.2 and gpt-oss-120b at 78.2, with GLM-5.1 ahead by 8 points. The largest visible gap is 8 points on Google-Proof Q&A, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on reasoning mode: GLM-5.1 and code execution: GLM-5.1. Both models share function calling, tool use, and structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, GLM-5.1 lists $0.98/1M input and $3.08/1M output tokens on the cheapest tracked provider, while gpt-oss-120b lists $0.04/1M input and $0.18/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts gpt-oss-120b lower by about $1.53 per million blended tokens. Availability is 5 providers versus 10, so concentration risk also matters.
Choose GLM-5.1 when coding workflow support and larger context windows are central to the workload. Choose gpt-oss-120b when provider fit, lower input-token cost, and broader provider choice are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, GLM-5.1 or gpt-oss-120b?
GLM-5.1 supports 200k tokens, while gpt-oss-120b supports 131k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is cheaper, GLM-5.1 or gpt-oss-120b?
gpt-oss-120b is cheaper on tracked token pricing. GLM-5.1 costs $0.98/1M input and $3.08/1M output tokens. gpt-oss-120b costs $0.04/1M input and $0.18/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GLM-5.1 or gpt-oss-120b open source?
GLM-5.1 is listed under MIT. gpt-oss-120b is listed under Open Weights. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for reasoning mode, GLM-5.1 or gpt-oss-120b?
GLM-5.1 has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for function calling, GLM-5.1 or gpt-oss-120b?
Both GLM-5.1 and gpt-oss-120b expose function calling. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Where can I run GLM-5.1 and gpt-oss-120b?
GLM-5.1 is available on Z.ai, OpenRouter, Fireworks AI, Vercel AI Gateway, and Novita AI. gpt-oss-120b is available on Cloudflare Workers AI, OpenRouter, Together AI, Fireworks AI, and GCP Vertex AI. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-25. Data sourced from public model cards and provider documentation.