# Claude Fable 5.2 vs GPT-6 Astra

> Markdown mirror of https://router.one/models/compare/claude-fable-5-2-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 58% less on a 1M-input + 1M-output mix. Both carry a 1.05M context window. Claude Fable 5.2 answers on /v1/chat/completions and /v1/messages (Claude Code); GPT-6 Astra on /v1/chat/completions and /v1/responses (Codex CLI). Claude Fable 5.2 is in no plan and bills the wallet; GPT-6 Astra counts against the Flagship models allowance on Max and Ultra.

Claude Fable 5.2 and GPT-6 Astra compared on current per-token rates, context window, and capabilities — both callable through one OpenAI-compatible endpoint that logs each request it forwards.

## Claude Fable 5.2 vs GPT-6 Astra: rates, context window, and capabilities

| Spec | Claude Fable 5.2 | GPT-6 Astra |
| --- | --- | --- |
| Input / 1M tokens | $4.80 | $2.00 |
| Output / 1M tokens | $24.00 | $10.00 |
| Cached input / 1M tokens | $0.12 | $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 Fable 5.2](https://router.one/models/claude-fable-5-2) | [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 Fable 5.2 vs GPT-6 Astra?

Base-tier rates: For a workload of 1M input plus 1M output tokens at current rates: Claude Fable 5.2 comes to $28.80, GPT-6 Astra comes to $12.00 — GPT-6 Astra is about 58% 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 Fable 5.2 and GPT-6 Astra

The API key and base URL stay the same, but this is not a one-string switch for every client or request. Router One serves Claude Fable 5.2 on /v1/messages and /v1/chat/completions and GPT-6 Astra on the OpenAI-format endpoints /v1/chat/completions and /v1/responses, so /v1/chat/completions is the one endpoint both share: Claude Code (/v1/messages) runs only the Claude side, Codex CLI (/v1/responses) only the GPT side, and Router One answers a model sent to an endpoint it does not serve with HTTP 400 invalid_request_error (code INVALID_REQUEST). Per Anthropic's Claude Fable 5.2 overview and what's new pages and its effort docs (checked 2026-11-12), Claude Fable 5.2 always thinks adaptively and its thinking cannot be turned off; effort is set with output_config.effort, from low, medium, high (the API default), xhigh and max; Anthropic says to omit temperature, top_p and top_k; and on Anthropic's own API disabled thinking, a manual thinking budget and forced tool use (tool_choice any or tool) each return a 400 error. Per OpenAI's GPT-6 Astra model page and GPT-6 guide (checked 2026-11-12), effort is set with reasoning.effort on the Responses API and reasoning_effort on Chat Completions; GPT-6 Astra accepts low, medium, high, xhigh and max but not none (OpenAI suggests low instead) and takes tool calls only on the Responses API; OpenAI says to remove temperature, top_p and top_logprobs; and its pages do not state a default effort for GPT-6 Astra. So code that sends tools has to change path as well as model, neither model has a none level, and a request written for both leaves out the sampling parameters named above. On a Max or Ultra plan the billing differs: as of the 2026-11-12 plan response, GPT-6 Astra counts against the Flagship models allowance, while Claude Fable 5.2, in no plan tier, 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-fable-5.2", "messages": [{"role": "user", "content": "Hello"}]}'

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

## FAQ

### Is Claude Fable 5.2 cheaper than GPT-6 Astra?

Compared at base-tier rates (GPT-6 Astra: request input ≤ 272,000 tokens). Input: Claude Fable 5.2 $4.80 vs GPT-6 Astra $2.00 / 1M tokens; GPT-6 Astra has the lower rate. Output: Claude Fable 5.2 $24.00 vs GPT-6 Astra $10.00 / 1M tokens; GPT-6 Astra has the lower rate. 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 Fable 5.2 or GPT-6 Astra included in a Router One subscription?

Claude Fable 5.2 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 Fable 5.2 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 client or request. Router One serves Claude Fable 5.2 on /v1/messages and /v1/chat/completions and GPT-6 Astra on the OpenAI-format endpoints /v1/chat/completions and /v1/responses, so /v1/chat/completions is the one endpoint both share: Claude Code (/v1/messages) runs only the Claude side, Codex CLI (/v1/responses) only the GPT side, and Router One answers a model sent to an endpoint it does not serve with HTTP 400 invalid_request_error (code INVALID_REQUEST). Per Anthropic's Claude Fable 5.2 overview and what's new pages and its effort docs (checked 2026-11-12), Claude Fable 5.2 always thinks adaptively and its thinking cannot be turned off; effort is set with output_config.effort, from low, medium, high (the API default), xhigh and max; Anthropic says to omit temperature, top_p and top_k; and on Anthropic's own API disabled thinking, a manual thinking budget and forced tool use (tool_choice any or tool) each return a 400 error. Per OpenAI's GPT-6 Astra model page and GPT-6 guide (checked 2026-11-12), effort is set with reasoning.effort on the Responses API and reasoning_effort on Chat Completions; GPT-6 Astra accepts low, medium, high, xhigh and max but not none (OpenAI suggests low instead) and takes tool calls only on the Responses API; OpenAI says to remove temperature, top_p and top_logprobs; and its pages do not state a default effort for GPT-6 Astra. So code that sends tools has to change path as well as model, neither model has a none level, and a request written for both leaves out the sampling parameters named above. On a Max or Ultra plan the billing differs: as of the 2026-11-12 plan response, GPT-6 Astra counts against the Flagship models allowance, while Claude Fable 5.2, in no plan tier, 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 2026-11-13 (UTC) and refresh within the hour.

## More comparisons

- [Claude Fable 5.2 vs Claude Opus 5.5](https://router.one/models/compare/claude-fable-5-2-vs-claude-opus-5-5)
- [GPT-6 Astra vs Claude Opus 5](https://router.one/models/compare/gpt-6-astra-vs-claude-opus-5)
- [GPT-6 Astra vs GPT-5.6 Sol](https://router.one/models/compare/gpt-6-astra-vs-gpt-5-6-sol)
- [Claude Fable 5 vs GPT-6 Astra](https://router.one/models/compare/claude-fable-5-vs-gpt-6-astra)

## See also

- Canonical page: https://router.one/models/compare/claude-fable-5-2-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 Fable 5.2 API guide: https://router.one/blog/claude-fable-5-2-api-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