Claude Fable 5

by Anthropic

Released 12 days after Claude Opus 4.8 · All Anthropic releases

Claude Fable 5 is Anthropic's most capable widely released model, with exceptional performance across software engineering, vision, knowledge work, and scientific research. It maintains focus across millions of tokens and improves its own outputs using persistent, file-based memory, compressing long-running work into far fewer sessions. The model achieves state-of-the-art vision performance, extracting precise numbers from detailed scientific figures and rebuilding a web app's source code from screenshots alone. Fable 5 posts top scores on senior-level reasoning benchmarks and, in its research-grade form, consistently produces novel, compelling scientific hypotheses when paired with domain expertise. With a 1M token context window, the model excels at extensive codebases, lengthy contracts, and comprehensive research documentation. Built-in classifiers detect a narrow set of high-risk requests and hand them off to a more constrained model, a path that on average affects fewer than 5% of sessions.

Call Claude Fable 5 on Opper with the OpenAI SDK. Sign up without a credit card. Get started

Key info

Input
Output
Features
Context window
1M
Max output
128K
Input price
$10.00 /1M$1.00 cache read · $12.50 write
Output price
$50.00 /1M
Released
  • US residency available
  • Zero data retention with abuse monitoring
  • No training by default
  • GDPR DPA available

Available routes

Claude Fable 5 runs on 3 different routes through the Opper gateway. Compare residency, zero data retention and training posture at a glance, with full data-handling detail per route below.

ProviderRegionZero data retentionTrainingInputOutputCache read
USNo$10.00$50.00$1.00$12.50 write
MultiNo$10.00$50.00$1.00$12.50 write
MultiNo$10.00$50.00$1.00$12.50 write

Uptime and availability

Claude Fable 5 runs on 3 independently monitored routes through the Opper gateway. A direct integration leaves you on one of them, the gateway serves whichever is healthy.

100%effective uptime, last 30 days
Averaged across these routes on their own, a single provider reached 94.36% over the same window.
Daily status through the gateway, which serves each request from whichever route is healthy.
3 monitored providers serve Claude Fable 5.

Measured over the last 30 days from each provider's official status feed via StatusGator. Refreshed hourly. See uptime for every provider Opper monitors.

Data handling per route

Each route hosting Claude Fable 5 has its own privacy posture, residency, and GDPR terms. Postures are maintained by Opper with a last-verification timestamp.

Anthropic United States🇺🇸

Zero data retention with abuse monitoring: prompts and outputs are kept for abuse monitoring only, for a window the provider does not state, and are not used for training. No training on customer data. US; SCCs; DPA available.

Zero data retention
With abuse monitoring, window not stated.
Training
No training on customer data.
Logging
Abuse monitoring
Abuse monitoring
On by default, holds flagged content, 730 days, a person can view samples
Caching
Content cached for replay
GDPR DPA
DPA available
Transfer mechanism
SCCs

Azure Multi-region

Zero data retention with abuse monitoring: nothing is logged or used for training; content flagged by abuse monitoring is held for review. No training on customer data. GLOBAL; SCCs; DPA available.

Zero data retention
With abuse monitoring, flagged content held.
Training
No training on customer data.
Logging
None
Abuse monitoring
On by default, holds flagged content, 730 days, a person can view samples
Caching
Content cached for replay
GDPR DPA
DPA available
Transfer mechanism
SCCs

Google Cloud Multi-region

Zero data retention with abuse monitoring: prompts and outputs are kept for abuse monitoring only, for a window the provider does not state, and are not used for training. No training on customer data. GLOBAL; SCCs; DPA available.

Zero data retention
With abuse monitoring, window not stated.
Training
No training on customer data.
Logging
Abuse monitoring
Abuse monitoring
On by default, holds flagged content, 90 days, a person can view samples
GDPR DPA
DPA available
Transfer mechanism
SCCs

Benchmarks

Independent benchmark scores — composite indices for reasoning, coding, and math, plus individual eval scores where available.

Intelligence Index49.6
Coding Index76.5
Reasoning & knowledge
GPQA Diamond
93%
Humanity's Last Exam
56%
Long-context reasoning
82%
Coding
SciCode
61%
Agentic & tool use
Terminal-Bench Hard
63%
τ²-Bench Telecom
99%
Math & instruction following
IFBench
63%

Get started

Call Claude Fable 5 through the Opper gateway with one API key. Opper is drop-in compatible with the OpenAI, Anthropic and Google AI SDKs.

Claude Fable 5 is a premium model on Opper. Sign up needs no credit card: you get an API key straight away and the free models work in the playground and the API. Add a card to use premium models, pay-as-you-go with no minimum.

Set it up with your agent

Copy this and paste it into a coding agent like Claude Code, Cursor or Codex and it'll wire up Opper for you.

Or call it directly

import OpenAI from "openai";
const client = new OpenAI({
apiKey: process.env.OPPER_API_KEY,
baseURL: "https://api.opper.ai/v3/compat",
});
const completion = await client.chat.completions.create({
model: "claude-fable-5",
messages: [{ role: "user", content: "Hello" }],
});
console.log(completion.choices[0].message.content);

Compare Claude Fable 5 with…

Side-by-side on privacy, EU hosting, pricing, and benchmarks.

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