Pick gpt-oss-120b for self-hostable on a single 80gb h100 gpu via mxfp4 or configurable reasoning depth (low/medium/high). Pick Grok Code Fast 1 for fast, cheap agentic coding at $0.20/$1.50 or low-latency code generation and terminal tasks. Choose gpt-oss-120b if you need self-hosting or data privacy; Grok Code Fast 1 if you want a managed API.
gpt-oss-120b (OpenAI) and Grok Code Fast 1 (xAI) are two of the models people most often weigh against each other in 2026. gpt-oss-120b is openAI's open-weight 117B-parameter MoE reasoning model (5.1B active) that runs on a single 80GB GPU and approaches o4-mini on reasoning, coding, and tool use. Grok Code Fast 1 is xAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. They diverge most on price, context window and open vs. closed weights — each quantified below from the models' real specs.
Key differences
Cost model: gpt-oss-120b ships open weights you can self-host (hardware cost only, no per-token fee), while Grok Code Fast 1 is API-metered at $0.2/$1.5 per 1M tokens. Your choice depends on whether you want zero marginal cost at the price of running infrastructure.
Context window: Grok Code Fast 1 holds 2× more — 256K (~384 pages) vs 131K (~197 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: Grok Code Fast 1 is the newer model by about 23 days (released August 28, 2025), usually meaning fresher training data and capabilities.
Specifications
Spec
gpt-oss-120b
Grok Code Fast 1
Provider
OpenAI (US)
xAI (US)
Released
August 5, 2025
August 28, 2025
Context window
131K (~197 pages)
256K (~384 pages)
Price (in/out)
Open weight (self-host / free)
$0.2/$1.5 per 1M tokens
Open weight?
Yes — self-hostable
No — API only
Modalities
text, code
text, code
SWE-Bench Verified
62.4%
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Self-hostable on a single 80GB H100 GPU via MXFP4: gpt-oss-120b — Open weights make this possible at all — Grok Code Fast 1 is API-only, so it cannot leave the vendor's servers.
Configurable reasoning depth (low/medium/high): gpt-oss-120b — OpenAI's open-weight 117B-parameter MoE reasoning model (5.1B active) that runs on a single 80GB GPU and approaches o4-mini on reasoning, coding, and tool use — and its weights are open while Grok Code Fast 1 is API-only.
Agentic tool use, function calling, and code execution: gpt-oss-120b — gpt-oss-120b lists agentic tool use, function calling, and code execution among its strengths; Grok Code Fast 1 does not.
Fast, cheap agentic coding at $0.20/$1.50: Grok Code Fast 1 — XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality — and it carries the larger 256K context.
Low-latency code generation and terminal tasks: Grok Code Fast 1 — XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality — and it is the newer of the two.
High-volume coding pipelines where speed beats peak quality: Grok Code Fast 1 — Grok Code Fast 1 lists high-volume coding pipelines where speed beats peak quality among its strengths; gpt-oss-120b does not.
Lowest cost at scale: gpt-oss-120b — Its weights are open, so at volume you pay for your own hardware instead of Grok Code Fast 1's $0.2/$1.5 per 1M tokens.
Largest single-prompt input: Grok Code Fast 1 — Its 256K window is about 2× larger than gpt-oss-120b's 131K, fitting roughly 384 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: gpt-oss-120b — At Open weight (self-host / free) it undercuts Grok Code Fast 1, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: Grok Code Fast 1 — Larger 256K window fits more in one prompt.
A team with data-privacy or self-hosting needs: gpt-oss-120b — Open weights let you run it on your own hardware; Grok Code Fast 1 is API-only.
Anyone whose priority is self-hostable on a single 80gb h100 gpu via mxfp4: gpt-oss-120b — It is specifically built for that.
Anyone whose priority is fast, cheap agentic coding at $0.20/$1.50: Grok Code Fast 1 — That is its strongest area.
gpt-oss-120b: where it fits
OpenAI's open-weight 117B-parameter MoE reasoning model (5.1B active) that runs on a single 80GB GPU and approaches o4-mini on reasoning, coding, and tool use. Released August 5, 2025 by OpenAI, it is built for self-hostable on a single 80GB H100 GPU via MXFP4, configurable reasoning depth (low/medium/high), agentic tool use, function calling, and code execution, and full chain-of-thought visibility for debugging.
Its trade-offs are real: text-only, no image, audio, or video input, and 131K context and 5.1B active params trail the largest frontier closed models. As an open-weight model, its running cost is your own hardware rather than a per-token fee.
Grok Code Fast 1: where it fits
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. Released August 28, 2025 by xAI, it is built for fast, cheap agentic coding at $0.20/$1.50, low-latency code generation and terminal tasks, high-volume coding pipelines where speed beats peak quality, and a 256K window sized for real codebases.
Its trade-offs: text and code only — no image, audio or video input, xAI did not publish a SWE-Bench Verified score, a speed-tier coding model, not a frontier reasoner, and narrow focus — built for code, not general knowledge work. At $0.2 in / $1.5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
The defining split here is open vs. closed. gpt-oss-120b gives you weights you control — self-host it, fine-tune it, keep data in-house, pay only for hardware. Grok Code Fast 1 gives you a managed, always-updated API with no infrastructure to run. Teams with GPUs, privacy requirements, or huge volume often favour the open model; teams that want zero ops and the latest capabilities favour the closed one. Capability is close enough that this operational question, not the benchmark, usually decides it.
Frequently asked questions
Is gpt-oss-120b or Grok Code Fast 1 better for coding?
Public SWE-Bench figures are not available for Grok Code Fast 1, so the honest test is your own repository — run an identical real bug through both. By design, gpt-oss-120b leans toward self-hostable on a single 80gb h100 gpu via mxfp4 while Grok Code Fast 1 leans toward fast, cheap agentic coding at $0.20/$1.50, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, gpt-oss-120b or Grok Code Fast 1?
gpt-oss-120b is open-weight, so self-hosting means no per-token fee (you pay for hardware instead), while Grok Code Fast 1 is API-metered at $0.2/$1.5 per 1M tokens. For most teams without GPUs, the API model is cheaper to start; at very high volume, self-hosting can win.
Which has the bigger context window?
Grok Code Fast 1 — 256K vs 131K, about 2× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both gpt-oss-120b and Grok Code Fast 1 together?
Yes — a multi-model platform like LumiChats gives you gpt-oss-120b, Grok Code Fast 1 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, gpt-oss-120b or Grok Code Fast 1?
Grok Code Fast 1 — released August 28, 2025, about 23 days after gpt-oss-120b.
gpt-oss-120b vs Grok Code Fast 1
OpenAI · US | xAI · US · Updated June 2026
Quick verdict
Pick gpt-oss-120b for self-hostable on a single 80gb h100 gpu via mxfp4 or configurable reasoning depth (low/medium/high). Pick Grok Code Fast 1 for fast, cheap agentic coding at $0.20/$1.50 or low-latency code generation and terminal tasks. Choose gpt-oss-120b if you need self-hosting or data privacy; Grok Code Fast 1 if you want a managed API.
gpt-oss-120b (OpenAI) and Grok Code Fast 1 (xAI) are two of the models people most often weigh against each other in 2026. gpt-oss-120b is openAI's open-weight 117B-parameter MoE reasoning model (5.1B active) that runs on a single 80GB GPU and approaches o4-mini on reasoning, coding, and tool use. Grok Code Fast 1 is xAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. They diverge most on price, context window and open vs. closed weights — each quantified below from the models' real specs.
Key differences at a glance
▸Cost model: gpt-oss-120b ships open weights you can self-host (hardware cost only, no per-token fee), while Grok Code Fast 1 is API-metered at $0.2/$1.5 per 1M tokens. Your choice depends on whether you want zero marginal cost at the price of running infrastructure.
▸Context window: Grok Code Fast 1 holds 2× more — 256K (~384 pages) vs 131K (~197 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: Grok Code Fast 1 is the newer model by about 23 days (released August 28, 2025), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
gpt-oss-120b
Grok Code Fast 1
Provider
OpenAI (US)
xAI (US)
Released
August 5, 2025
August 28, 2025
Context window
131K (~197 pages)
256K (~384 pages)
Price (in/out)
Open weight (self-host / free)
$0.2/$1.5 per 1M tokens
Open weight?
Yes — self-hostable
No — API only
Modalities
text, code
text, code
SWE-Bench Verified
62.4%
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Self-hostable on a single 80GB H100 GPU via MXFP4
gpt-oss-120b
Open weights make this possible at all — Grok Code Fast 1 is API-only, so it cannot leave the vendor's servers.
Configurable reasoning depth (low/medium/high)
gpt-oss-120b
OpenAI's open-weight 117B-parameter MoE reasoning model (5.1B active) that runs on a single 80GB GPU and approaches o4-mini on reasoning, coding, and tool use — and its weights are open while Grok Code Fast 1 is API-only.
Agentic tool use, function calling, and code execution
gpt-oss-120b
gpt-oss-120b lists agentic tool use, function calling, and code execution among its strengths; Grok Code Fast 1 does not.
Fast, cheap agentic coding at $0.20/$1.50
Grok Code Fast 1
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality — and it carries the larger 256K context.
Low-latency code generation and terminal tasks
Grok Code Fast 1
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality — and it is the newer of the two.
High-volume coding pipelines where speed beats peak quality
Grok Code Fast 1
Grok Code Fast 1 lists high-volume coding pipelines where speed beats peak quality among its strengths; gpt-oss-120b does not.
Lowest cost at scale
gpt-oss-120b
Its weights are open, so at volume you pay for your own hardware instead of Grok Code Fast 1's $0.2/$1.5 per 1M tokens.
Largest single-prompt input
Grok Code Fast 1
Its 256K window is about 2× larger than gpt-oss-120b's 131K, fitting roughly 384 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ gpt-oss-120b
At Open weight (self-host / free) it undercuts Grok Code Fast 1, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ Grok Code Fast 1
Larger 256K window fits more in one prompt.
A team with data-privacy or self-hosting needs
→ gpt-oss-120b
Open weights let you run it on your own hardware; Grok Code Fast 1 is API-only.
Anyone whose priority is self-hostable on a single 80gb h100 gpu via mxfp4
→ gpt-oss-120b
It is specifically built for that.
Anyone whose priority is fast, cheap agentic coding at $0.20/$1.50
→ Grok Code Fast 1
That is its strongest area.
gpt-oss-120b: where it fits
OpenAI's open-weight 117B-parameter MoE reasoning model (5.1B active) that runs on a single 80GB GPU and approaches o4-mini on reasoning, coding, and tool use. Released August 5, 2025 by OpenAI, it is built for self-hostable on a single 80GB H100 GPU via MXFP4, configurable reasoning depth (low/medium/high), agentic tool use, function calling, and code execution, and full chain-of-thought visibility for debugging.
Its trade-offs are real: text-only, no image, audio, or video input, and 131K context and 5.1B active params trail the largest frontier closed models. As an open-weight model, its running cost is your own hardware rather than a per-token fee.
Grok Code Fast 1: where it fits
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. Released August 28, 2025 by xAI, it is built for fast, cheap agentic coding at $0.20/$1.50, low-latency code generation and terminal tasks, high-volume coding pipelines where speed beats peak quality, and a 256K window sized for real codebases.
Its trade-offs: text and code only — no image, audio or video input, xAI did not publish a SWE-Bench Verified score, a speed-tier coding model, not a frontier reasoner, and narrow focus — built for code, not general knowledge work. At $0.2 in / $1.5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
The defining split here is open vs. closed. gpt-oss-120b gives you weights you control — self-host it, fine-tune it, keep data in-house, pay only for hardware. Grok Code Fast 1 gives you a managed, always-updated API with no infrastructure to run. Teams with GPUs, privacy requirements, or huge volume often favour the open model; teams that want zero ops and the latest capabilities favour the closed one. Capability is close enough that this operational question, not the benchmark, usually decides it.
Want both gpt-oss-120b and Grok Code Fast 1 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Is gpt-oss-120b or Grok Code Fast 1 better for coding?
Public SWE-Bench figures are not available for Grok Code Fast 1, so the honest test is your own repository — run an identical real bug through both. By design, gpt-oss-120b leans toward self-hostable on a single 80gb h100 gpu via mxfp4 while Grok Code Fast 1 leans toward fast, cheap agentic coding at $0.20/$1.50, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, gpt-oss-120b or Grok Code Fast 1?
gpt-oss-120b is open-weight, so self-hosting means no per-token fee (you pay for hardware instead), while Grok Code Fast 1 is API-metered at $0.2/$1.5 per 1M tokens. For most teams without GPUs, the API model is cheaper to start; at very high volume, self-hosting can win.
Which has the bigger context window?
Grok Code Fast 1 — 256K vs 131K, about 2× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both gpt-oss-120b and Grok Code Fast 1 together?
Yes — a multi-model platform like LumiChats gives you gpt-oss-120b, Grok Code Fast 1 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, gpt-oss-120b or Grok Code Fast 1?
Grok Code Fast 1 — released August 28, 2025, about 23 days after gpt-oss-120b.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.