# Claude Opus 5.5 vs GPT-6 Astra

> Markdown mirror of https://router.one/models/compare/claude-opus-5-5-vs-gpt-6-astra for AI assistants and crawlers. Router One is a unified, OpenAI-compatible LLM API gateway.

GPT-6 Astra is the lower-priced of the two on Router One at base-tier rates (GPT-6 Astra: request input ≤ 272,000 tokens) — about 17% less on a 1M-input + 1M-output mix. GPT-6 Astra's lower 1M-input + 1M-output total holds only for requests of up to 272,000 input tokens; above that the ordering reverses: Claude Opus 5.5 comes to $14.40 vs $19.00 for GPT-6 Astra. Both carry a 1.05M context window. Claude Opus 5.5 answers on /v1/chat/completions and /v1/messages (Claude Code); GPT-6 Astra on /v1/chat/completions and /v1/responses (Codex CLI). Claude Opus 5.5 is in no plan and bills the wallet; GPT-6 Astra counts against the Flagship models allowance on Max and Ultra.

Claude Opus 5.5 and GPT-6 Astra compared on current per-token rates, context window, and capabilities — both callable through one OpenAI-compatible endpoint with per-request cost traces.

## Claude Opus 5.5 vs GPT-6 Astra: rates, context window, and capabilities

| Spec | Claude Opus 5.5 | GPT-6 Astra |
| --- | --- | --- |
| Input / 1M tokens | $2.40 | $2.00 |
| Output / 1M tokens | $12.00 | $10.00 |
| Cached input / 1M tokens | $0.40 | $0.20 |
| Context window | 1.05M | 1.05M |
| Capabilities | Chat, Streaming, Tool calling, Vision | Chat, Streaming, Tool calling, Vision |
| Subscription plans | Not in any plan — wallet | Flagship models — Max, Ultra |
| Detail page | [Claude Opus 5.5](https://router.one/models/claude-opus-5-5) | [GPT-6 Astra](https://router.one/models/gpt-6-astra) |

GPT-6 Astra: request input ≤ 272,000 tokens: Input $2.00 / 1M tokens, Output $10.00 / 1M tokens, Cache write $2.50 / 1M tokens, Cached input $0.20 / 1M tokens; request input > 272,000 tokens: Input $4.00 / 1M tokens, Output $15.00 / 1M tokens, Cache write $5.00 / 1M tokens, Cached input $0.40 / 1M tokens. The total input tokens in each request select the tier; its rates apply to the whole request, not only tokens above the threshold.

## What does 1M tokens cost on Claude Opus 5.5 vs GPT-6 Astra?

Base-tier rates: For a workload of 1M input plus 1M output tokens at current rates: Claude Opus 5.5 comes to $14.40, GPT-6 Astra comes to $12.00 — GPT-6 Astra is about 17% cheaper on this mix. Real workloads skew heavily toward input tokens, so weigh the input rate by your own ratio; the cached-input row above is the posted catalog rate for that model.

## Switch between Claude Opus 5.5 and GPT-6 Astra

The API key and base URL stay the same, but this is not a one-string switch for every request. Per OpenAI's GPT-6 guide (checked 2026-10-03), GPT-6 Astra takes tool calls only on the Responses API, does not accept the none reasoning effort (OpenAI suggests low) and takes no temperature, top_p or logprobs settings. Router One serves Claude Opus 5.5 on /v1/messages and /v1/chat/completions, not on /v1/responses. So tool-using code has to change path as well as model: Claude Code (/v1/messages) runs only the Claude side and Codex CLI (/v1/responses) only the GPT side. On a Max or Ultra plan the billing changes too: GPT-6 Astra counts against the Flagship models allowance, while Claude Opus 5.5, in no plan tier as of the 2026-10-03 plan response, bills the wallet per token.

`compare.sh`

```bash
curl https://api.router.one/v1/chat/completions \
  -H "Authorization: Bearer sk-your-router-one-key" \
  -H "Content-Type: application/json" \
  -d '{"model": "anthropic/claude-opus-5.5", "messages": [{"role": "user", "content": "Hello"}]}'

# Same request, other model — change one string:
#   "model": "openai/gpt-6-astra"
```

## FAQ

### Is Claude Opus 5.5 cheaper than GPT-6 Astra?

Compared at base-tier rates (GPT-6 Astra: request input ≤ 272,000 tokens). Input: Claude Opus 5.5 $2.40 vs GPT-6 Astra $2.00 / 1M tokens; GPT-6 Astra has the lower rate. Output: Claude Opus 5.5 $12.00 vs GPT-6 Astra $10.00 / 1M tokens; GPT-6 Astra has the lower rate. GPT-6 Astra's lower 1M-input + 1M-output total holds only for requests of up to 272,000 input tokens; above that the ordering reverses: Claude Opus 5.5 comes to $14.40 vs $19.00 for GPT-6 Astra. Total cost depends on the workload's input, output and cache usage. GPT-6 Astra: request input ≤ 272,000 tokens: Input $2.00 / 1M tokens, Output $10.00 / 1M tokens, Cache write $2.50 / 1M tokens, Cached input $0.20 / 1M tokens; request input > 272,000 tokens: Input $4.00 / 1M tokens, Output $15.00 / 1M tokens, Cache write $5.00 / 1M tokens, Cached input $0.40 / 1M tokens. The total input tokens in each request select the tier; its rates apply to the whole request, not only tokens above the threshold. Rates change; the /models page is the live source of truth.

### Is Claude Opus 5.5 or GPT-6 Astra included in a Router One subscription?

Claude Opus 5.5 is in no Router One plan, so every call bills the wallet per token. GPT-6 Astra counts against the Flagship models allowance on Max and Ultra: Max 150 and Ultra 450 requests per 30-day cycle, shared by every model in that tier. GPT-6 Astra requests above its long-context threshold count as more than one quota request. Requests beyond a plan's allowance bill the wallet per token.

### Can I switch between Claude Opus 5.5 and GPT-6 Astra without changing code?

The API key and base URL stay the same, but this is not a one-string switch for every request. Per OpenAI's GPT-6 guide (checked 2026-10-03), GPT-6 Astra takes tool calls only on the Responses API, does not accept the none reasoning effort (OpenAI suggests low) and takes no temperature, top_p or logprobs settings. Router One serves Claude Opus 5.5 on /v1/messages and /v1/chat/completions, not on /v1/responses. So tool-using code has to change path as well as model: Claude Code (/v1/messages) runs only the Claude side and Codex CLI (/v1/responses) only the GPT side. On a Max or Ultra plan the billing changes too: GPT-6 Astra counts against the Flagship models allowance, while Claude Opus 5.5, in no plan tier as of the 2026-10-03 plan response, bills the wallet per token.

### Where do these numbers come from?

Specs and prices on this page render from the live Router One catalog — the same data as the /models page — and refresh with it. Pricing methodology is documented on /pricing-methodology. Rates on this page were read from the live catalog on 2026-10-03 (UTC) and refresh within the hour.

## More comparisons

- [Claude Opus 5.5 vs GPT-6 Sol](https://router.one/models/compare/claude-opus-5-5-vs-gpt-6-sol)
- [Claude Opus 5.5 vs Claude Sonnet 5](https://router.one/models/compare/claude-opus-5-5-vs-claude-sonnet-5)
- [Grok 4.7 vs GPT-6 Astra](https://router.one/models/compare/grok-4-7-vs-gpt-6-astra)
- [GPT-6.1 Sol vs Claude Sonnet 5.5](https://router.one/models/compare/gpt-6-1-sol-vs-claude-sonnet-5-5)

## See also

- Canonical page: https://router.one/models/compare/claude-opus-5-5-vs-gpt-6-astra
- All model comparisons: https://router.one/models/compare
- All models & prices: https://router.one/models (markdown: https://router.one/models.md)
- Pricing: https://router.one/pricing
- Claude API access: https://router.one/cheap-claude-api
- GPT API access: https://router.one/cheap-gpt-api
- Claude Opus 5.5 API guide: https://router.one/blog/claude-opus-5-5-api-guide
- Claude Code on Opus 5.5: https://router.one/blog/claude-code-opus-5-5-setup
- Migrating to Claude Opus 5.5: https://router.one/blog/claude-opus-5-5-migration-guide
- GPT-6 Astra API guide: https://router.one/blog/gpt-6-astra-api-guide
- Cost calculator: https://router.one/llm-cost-calculator
- Pricing methodology: https://router.one/pricing-methodology