GPT-5.4 Mini vs gpt-oss-120b
OpenAI · US | OpenAI · US · Updated June 2026
Quick verdict
Both are OpenAI models. GPT-5.4 Mini is the newer, generally stronger default; reach for gpt-oss-120b when its lower price or a specific cost or latency profile matters more than the latest capabilities.
GPT-5.4 Mini and gpt-oss-120b are both OpenAI models, so the real question is not which lab to trust but which tier fits your workload and budget. GPT-5.4 Mini is openAI's free, fast workhorse — capable general AI with no subscription needed. 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. Since both come from the same lab, the comparison below focuses on the tier-and-cost trade-offs that actually separate them.
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 GPT-5.4 Mini is API-metered at $0.75/$4.5 per 1M tokens. Your choice depends on whether you want zero marginal cost at the price of running infrastructure.
- ▸Context window: GPT-5.4 Mini holds 3.1× more — 400K (~600 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: GPT-5.4 Mini is the newer model by about 7 months (released March 17, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
| Spec | GPT-5.4 Mini | gpt-oss-120b |
|---|---|---|
| Provider | OpenAI (US) | OpenAI (US) |
| Released | March 17, 2026 | August 5, 2025 |
| Context window | 400K (~600 pages) | 131K (~197 pages) |
| Price (in/out) | $0.75/$4.5 per 1M tokens | Open weight (self-host / free) |
| Open weight? | No — API only | Yes — self-hostable |
| Modalities | text, image, code | text, code |
| SWE-Bench Verified | Not published | 62.4% |
| MRCR v2 @ 1M | Not published | Not published |
Who wins what
Free for every ChatGPT user
GPT-5.4 Mini
OpenAI's free, fast workhorse — capable general AI with no subscription needed — and it carries the larger 400K context.
Fast, low-cost general tasks
GPT-5.4 Mini
OpenAI's free, fast workhorse — capable general AI with no subscription needed — and it is the newer of the two.
Subagent capabilities
GPT-5.4 Mini
GPT-5.4 Mini lists subagent capabilities among its strengths; gpt-oss-120b does not.
Self-hostable on a single 80GB H100 GPU via MXFP4
gpt-oss-120b
Open weights make this possible at all — GPT-5.4 Mini is API-only, so it cannot leave the vendor's servers.
Configurable reasoning depth (low/medium/high)
gpt-oss-120b
GPT-5.4 Mini is comparatively weak here — not for the hardest reasoning
Agentic tool use, function calling, and code execution
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 GPT-5.4 Mini is API-only.
Lowest cost at scale
gpt-oss-120b
Its weights are open, so at volume you pay for your own hardware instead of GPT-5.4 Mini's $0.75/$4.5 per 1M tokens.
Largest single-prompt input
GPT-5.4 Mini
Its 400K window is about 3.1× larger than gpt-oss-120b's 131K, fitting roughly 600 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 GPT-5.4 Mini, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ GPT-5.4 Mini
Larger 400K 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; GPT-5.4 Mini is API-only.
Anyone whose priority is free for every chatgpt user
→ GPT-5.4 Mini
It is specifically built for that.
Anyone whose priority is self-hostable on a single 80gb h100 gpu via mxfp4
→ gpt-oss-120b
That is its strongest area.
GPT-5.4 Mini: where it fits
OpenAI's free, fast workhorse — capable general AI with no subscription needed. Released March 17, 2026 by OpenAI, it is built for free for every ChatGPT user, fast, low-cost general tasks, subagent capabilities, and native multimodal reasoning.
Its trade-offs are real: smaller context than flagship models, and not for the hardest reasoning. At $0.75 in / $4.5 out per million tokens, it sits in the budget price band.
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: 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.
The bottom line for this matchup
Because GPT-5.4 Mini and gpt-oss-120b come from the same lab (OpenAI), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. GPT-5.4 Mini is the more capable, more recent option; the other earns its place only when its price or latency profile fits a specific job better. Most teams should default to GPT-5.4 Mini and drop down only with a concrete reason.
Want both GPT-5.4 Mini and gpt-oss-120b 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.
See pricingFrequently asked questions
Is GPT-5.4 Mini or gpt-oss-120b better for coding?
Public SWE-Bench figures are not available for GPT-5.4 Mini, so the honest test is your own repository — run an identical real bug through both. By design, GPT-5.4 Mini leans toward free for every chatgpt user while gpt-oss-120b leans toward self-hostable on a single 80gb h100 gpu via mxfp4, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.4 Mini or gpt-oss-120b?
gpt-oss-120b is open-weight, so self-hosting means no per-token fee (you pay for hardware instead), while GPT-5.4 Mini is API-metered at $0.75/$4.5 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?
GPT-5.4 Mini — 400K vs 131K, about 3.1× larger. Useful only if the model actually reasons over the full window, which not all do.
Should I upgrade from gpt-oss-120b to GPT-5.4 Mini?
Since both are OpenAI models, the newer one (GPT-5.4 Mini) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, GPT-5.4 Mini or gpt-oss-120b?
GPT-5.4 Mini — released March 17, 2026, about 7 months after gpt-oss-120b.
Related comparisons
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.