# Claude Opus 4.8 vs GPT OSS 120B

Canonical HTML page: [Claude Opus 4.8 vs GPT OSS 120B](<https://impossibl.com/compare/anthropic/claude-opus-4-8/openai/gpt-oss-120b>)
Markdown alternative: [Claude Opus 4.8 vs GPT OSS 120B as Markdown](<https://impossibl.com/compare/anthropic/claude-opus-4-8/openai/gpt-oss-120b.md>)

Compare API pricing, context windows, and capabilities side by side. Prices are published API usage rates in USD; check billing units and context tiers alongside each price.

## Specifications and pricing

| Specification | Claude Opus 4.8 | GPT OSS 120B |
| --- | --- | --- |
| API identifier | anthropic/claude-opus-4-8 | openai/gpt-oss-120b |
| Creator | Anthropic | OpenAI |
| Model type | Text generation | Text generation |
| Inputs | text, image | text |
| Outputs | text | text |
| Base input price (USD) | $5.00 per million input tokens | $0.35 per million input tokens |
| Base output price (USD) | $25.00 per million output tokens | $0.75 per million output tokens |
| Cache read price (USD) | $0.50 per million cached input tokens | Not published |
| Cache write price (USD) | $6.25 per million tokens | Not published |
| One-hour cache write price (USD) | $10.00 per million tokens | Not published |
| Audio input token price (USD) | Not published | Not published |
| Context window | 1,000,000 tokens | 128,000 tokens |
| Tool calling | Not published | Not published |
| Endpoints | /v1/chat/completions | /v1/chat/completions |
| Context pricing tiers (USD per million tokens) | None published | None published |
| Retirement | Not announced in the public catalog | Not announced in the public catalog |

When total input, including cached input, strictly exceeds a context threshold, the highest qualifying tier applies to the whole request. Consult each model's complete Markdown for tier-specific cache rates; an unpublished tier cache price does not establish the base cache rate.

## Claude Opus 4.8 vs GPT OSS 120B: side-by-side summary

Claude Opus 4.8 and GPT OSS 120B are available through the Impossibl API.

They share the `/v1/chat/completions` endpoint. Set the model identifier to select the model for a supported request.

Claude Opus 4.8 is created by Anthropic. It has a 1,000,000-token context window. Base API pricing (USD): $5.00 per million input tokens; $25.00 per million output tokens.

GPT OSS 120B is created by OpenAI. It has a 128,000-token context window. Base API pricing (USD): $0.35 per million input tokens; $0.75 per million output tokens.

## Model details

- [Claude Opus 4.8: full model facts as Markdown](<https://impossibl.com/anthropic/claude-opus-4-8.md>); [HTML model page](<https://impossibl.com/anthropic/claude-opus-4-8>)
- [GPT OSS 120B: full model facts as Markdown](<https://impossibl.com/openai/gpt-oss-120b.md>); [HTML model page](<https://impossibl.com/openai/gpt-oss-120b>)

For compatible text or embedding models with token pricing, the HTML comparison page provides a shared workload calculator. It excludes cache creation, tool calls, taxes, balance-purchase fees, and workspace-specific adjustments.

## Sources and related links

Prices, capabilities, limits, and availability describe the public Impossibl API offering. An unpublished fact is unknown; a published zero price is zero. Compare matching billing units and check context tiers before estimating costs.

- [Public Impossibl model catalog](<https://api.impossibl.com/v1/models>)
- [Full model directory as JSON](<https://impossibl.com/models.json>)
- [Model directory as Markdown](<https://impossibl.com/models.md>)
- [API quickstart](<https://impossibl.com/docs/agent-quickstart>)
- [Model documentation](<https://impossibl.com/docs/models>)