DeepSeek V4.1 Flash Fast vs GPT OSS 120B
As of November 12, 2026, DeepSeek V4.1 Flash Fast costs 67% more per input token than GPT OSS 120B ($0.05 vs $0.03 per 1M) and has a 1M-token context window versus 131K.
DeepSeek V4.1 Flash Fast vs GPT OSS 120B side by side
| DeepSeek V4.1 Flash Fast | GPT OSS 120B | |
|---|---|---|
| Input, per 1M tokens | $0.05 | $0.03 |
| Output, per 1M tokens | $0.15 | $0.17 |
| Cache read, per 1M tokens | $0.003 | – |
| Cache write, per 1M tokens | – | – |
| Context window | 1,048,576 tokens | 131,000 tokens |
| Max output | 262,144 tokens | 131,072 tokens |
| Image input | No | – |
| Tool calling | Yes | Yes |
| Structured output (JSON) | Yes | Yes |
| Prompt caching | Yes | Yes |
| Reasoning | Yes | Yes |
| Providers on LiteLLM | 4 | 28 |
| Price shown is from | Refuseless | Weights & Biases |
| Added to LiteLLM | September 29, 2026 | August 2025 |
Cheapest provider for each
- DeepSeek V4.1 Flash Fast: Refuseless at $0.05 input and $0.15 output per 1M tokens (
refuseless/deepseek-v4.1-flash-fast) - GPT OSS 120B: Weights & Biases at $0.03 input and $0.17 output per 1M tokens (
wandb/openai/gpt-oss-120b)
When to pick which
Pick DeepSeek V4.1 Flash Fast for
- Costs 12% less per output token: $0.15 vs $0.17 per 1M.
- Larger context window: 1,048,576 vs 131,000 tokens.
Pick GPT OSS 120B for
- Costs 40% less per input token: $0.03 vs $0.05 per 1M.
- Available from 28 providers through LiteLLM, vs 4.
From differences in the data above only; where the data is equal, no reason is given.
Call DeepSeek V4.1 Flash Fast or GPT OSS 120B with LiteLLM
Both use the OpenAI format through LiteLLM, so switching is a model name change. Set each provider's API key in the environment first.
from litellm import completion
messages = [{"role": "user", "content": "Hello!"}]
# DeepSeek V4.1 Flash Fast
response = completion(model="refuseless/deepseek-v4.1-flash-fast", messages=messages)
# GPT OSS 120B
response = completion(model="wandb/openai/gpt-oss-120b", messages=messages)
# DeepSeek V4.1 Flash Fast, falling back to GPT OSS 120B if the call fails
response = completion(model="refuseless/deepseek-v4.1-flash-fast", messages=messages, fallbacks=["wandb/openai/gpt-oss-120b"])FAQ
Which is cheaper, DeepSeek V4.1 Flash Fast or GPT OSS 120B?
GPT OSS 120B is cheaper at 3 input tokens per output token: $0.065 per 1M tokens blended ($0.03 input, $0.17 output), versus $0.075 ($0.05 and $0.15) for DeepSeek V4.1 Flash Fast, as of November 12, 2026.
Which has the larger context window, DeepSeek V4.1 Flash Fast or GPT OSS 120B?
DeepSeek V4.1 Flash Fast has the larger context window: 1,048,576 tokens, versus 131,000 for GPT OSS 120B.
Can I switch from DeepSeek V4.1 Flash Fast to GPT OSS 120B without changing my code?
Yes. Through LiteLLM both use the OpenAI format, so switching means changing the model name from "refuseless/deepseek-v4.1-flash-fast" to "wandb/openai/gpt-oss-120b", or pointing a LiteLLM gateway model alias at the other model. You can also use one as a fallback for the other.