Claude Fable 5.1 API TWD Cost 2026: AA Index Rank #1

Query date: 2026-09-20 (Taipei time). Benchmark data comes from the Artificial Analysis article published 2026-09-01. Pricing follows the USD unit prices shown on the BazaarLink models page, and the exchange rate is 1 USD = NT$ 31.5.

Anthropic has just launched Claude Fable 5.1, a full upgrade of Fable 5. Its Artificial Analysis Intelligence Index on the query date was 53.4. For relative ranking, check the leaderboard for the same day. BazaarLink listed it the same day, so you can call it directly with the model name claude-fable-5.1.

Bottom line up front: Fable 5.1 is priced at $10 per million input tokens and $50 per million output tokens. Its Artificial Analysis Intelligence Index on the query date was 53.4; for relative ranking, check the leaderboard for the same day. It suits tasks where correctness matters most and budget is not the top priority (complex agent workflows, long-running code refactoring). For general production tasks, Opus 5 or Sonnet 5 is usually better value, since Fable 5.1's input and output unit prices are 2x those of Opus 5.

Want to call Fable 5.1 and pay in TWD with a unified invoice that carries your tax ID? BazaarLink offers an OpenAI-compatible route with the same model unit prices, plus a 10% top-up service fee, addressing the expense-reporting pain point for Taiwan companies. See the complete guide to AI API expense reporting for Taiwan companies for details.

Third-party benchmark: Artificial Analysis Intelligence Index

On the Artificial Analysis leaderboard (query date 2026-09-20; data from the AA article published 2026-09-01):

Fable 5.1 scores 59.1% on HLE (Humanity's Last Exam), also beating the previous best of 55.5% held by Fable 5.

Scores across five thinking levels: Low 58, XHigh 65, Max 66 (Medium and High were not separately disclosed). Scores rise with thinking effort while the price stays the same. This means that with the same API call, you can use the reasoning_effort parameter to move directly between "quality" and "speed / output token volume," without switching models.

Price comparison (USD ↔ NT$)

Cache write $12.50/MTok (NT$ 394), cache-hit input $0.25/MTok (NT$ 7.9, only 2.5% of the base input price). For scenarios with repeated prefixes (system prompts, long documents, codebases), be sure to enable prompt caching, as the cost difference is very large.

The prices in this table match the BazaarLink models page, with no model markup. For the latest unit prices, see BazaarLink Models.

Scenario estimate: long-running agent refactoring tasks (NT$/month)

Assumptions: 20 codebase refactoring tasks per day, each with 15,000 input tokens (reading multi-file context) plus 4,000 output tokens (including thinking, Max effort).

• Monthly tasks: 20 × 30 = 600 calls
• Monthly input tokens: 600 × 15,000 = 9,000,000 (9 MTok)
• Monthly output tokens: 600 × 4,000 = 2,400,000 (2.4 MTok)

Cost:

• Input: 9 × NT$ 315 = NT$ 2,835
• Output: 2.4 × NT$ 1,575 = NT$ 3,780
• Total: NT$ 6,615/month (≈ USD 210)

→ The same workload on Opus 5: NT$ 3,308/month (half the cost). The extra NT$ 3,307/month is only worthwhile if the extra correctness from Fable 5.1 actually reduces manual review or rework. This is the question to ask when choosing a model, not "pick it because its score is higher."

Specs

• Context length: 1,000,000 tokens
• Input: text, images, files → output: text
• Deep reasoning: always on, default effort High, adjustable to Low / Medium / High / XHigh / Max
• Model ID: claude-fable-5.1 (compatibility alias: anthropic/claude-fable-5.1)

How to call it

curl https://bazaarlink.ai/api/v1/chat/completions \
  -H "Authorization: Bearer sk-bl-YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-fable-5.1",
    "messages": [{"role": "user", "content": "Hello"}],
    "reasoning_effort": "high"
  }'

OpenAI SDK compatible; just change base_url and model, no other code changes needed.

When to choose Fable 5.1, and when not to

Good fit:

• Models where correctness is the top priority, and where you have verified that the chosen model actually reduces rework on your tasks
• Long-running agent workflows (multi-step, refactoring that must stay consistent across files)
• Critical tasks where budget is not a constraint

Not a good fit:

• General production tasks (customer support, summarization, classification): Sonnet 5 or Opus 5 is usually better value
• High-frequency, low-error-tolerance calls: Fable 5.1's output runs long (thinking process), so each call costs 2x Opus 5
• Just wanting the "latest model": first run a small-scale test to verify whether the score gap translates into a noticeable quality improvement on your actual tasks

Sources and query log

• Artificial Analysis: Claude Fable 5.1 tops the Intelligence Index (query date 2026-09-20)
• BazaarLink Models: Claude Fable 5.1 (unit prices and specs; query date 2026-09-02)
• Further reading: How do I expense AI API costs in Taiwan? 2026 complete guide, Claude API TWD cost estimate 2026

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