Claude Fable 5.1
Save 72%Officialanthropic/claude-fable-5-1
Anthropic's most powerful model — Mythos-class, cache reads at 2.5%.
- Context window
- 1M
- Max output
- 8K
- Input modalities
- text · image
- Output modalities
- text
- Capabilities
- Vision · Reasoning · Tool Calling · Coding · Cache
- Upstream release
- 2026-09-01
- RouteMux name
- anthropic/claude-fable-5-1
Try Claude Fable 5.1 here
Tune the request, see the current price ceiling, and inspect the real response without leaving this model page.
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What is Claude Fable 5.1
Claude Fable 5.1 is the current top of Anthropic's generally available lineup, succeeding Fable 5. It is built for autonomous coding, long-horizon agents, and the kind of analysis where a half-right answer is worth nothing. 1M-token context window, native prompt caching, vision input.
Through RouteMux it is $2.80 per 1M input tokens against Anthropic's $10, and $14 against $50 on output — the same per-token price as Fable 5. Same model, same Anthropic Messages API, billed from a prepaid wallet instead of an Anthropic account, with failed and timed-out requests not charged.
What actually changed is caching. Anthropic prices cache reads on Fable 5.1 at 2.5% of the base input rate rather than the usual 10%, which lands at $0.07 per 1M tokens here — a quarter of what Fable 5 costs. Long sessions, large system prompts, and agents that re-read the same codebase are where that shows up.
It still sits above Opus 5 and still costs twice as much per token, so the honest way to choose has not changed: try Opus 5 first, and move up only when it is demonstrably not enough.
Claude Fable 5.1 API pricing
Source: anthropic_x0.28 · Verified 2026-09-02
Cache read $0.07/M · Cache write $3.5/M
Estimate cost
Limited time20% extra Credits on your first top-up — up to 200 bonus Credits
Applies to your first top-up within 72 hours of signing up. Minimum $20, once per account.
Key capabilities
Top of the generally available lineup
Anthropic positions it as its most capable GA model for autonomous coding and long-horizon work, succeeding Fable 5.
Cache reads at a quarter the price
Anthropic bills cache reads at 2.5% of base input on this model instead of the usual 10% — $0.07 per 1M tokens here. The more you hit cache, the wider the gap with Fable 5.
Thinking is always on
No thinking budget to set — and none accepted. Depth is controlled by the effort level instead.
Anthropic Messages native
No translation layer; the request is the same one you would send to Anthropic directly.
Interface and protocols
Use any of these IDs to call this model via the API.
anthropic/claude-fable-5-1Replace the ROUTEMUX_KEY placeholder with your API key. Create one →
from anthropic import Anthropic
client = Anthropic(
base_url="https://api.routemux.com/anthropic",
api_key="<ROUTEMUX_KEY>",
)
message = client.messages.create(
model="anthropic/claude-fable-5-1",
max_tokens=1024,
messages=[{"role": "user", "content": "What is the meaning of life?"}],
)
print(message.content[0].text)Performance (last 30 days)
Claude Fable 5.1 FAQ
›What is Claude Fable 5.1?
Anthropic's most powerful model — Mythos-class, cache reads at 2.5%.
›How large is the context window of Claude Fable 5.1?
Claude Fable 5.1 supports a context window of up to 1M tokens, with up to 8K output tokens per request.
›How much does the Claude Fable 5.1 API cost?
Through RouteMux, Claude Fable 5.1 costs $2.8 for input and $14 for output (USD per 1M tokens), below the official list price.
›How do I call Claude Fable 5.1 via API?
Claude Fable 5.1 is OpenAI-compatible: point your base URL at RouteMux and set the model field to anthropic/claude-fable-5-1 — no code changes needed.
›Which input and output modalities does Claude Fable 5.1 support?
Claude Fable 5.1 accepts text, image as input and produces text as output.
›When was Claude Fable 5.1 released?
Claude Fable 5.1 was released on September 1, 2026.
›How is Fable 5.1 different from Fable 5?
Input and output cost exactly the same per token ($2.80 / $14). The differences are the model itself and cache reads, which drop from $0.28 to $0.07 — Anthropic gives 5.1 a 2.5% cache multiplier where Fable 5 gets the standard 10%. If your workload hits cache at all, there is no reason to stay on 5.
›Fable 5.1 or Opus 5?
Fable sits above Opus in Anthropic's lineup and costs twice as much per token here ($2.80 vs $1.40 input). Both have a 1M context and the same capability set, so the difference is answer quality on hard tasks, not capacity. Start with Opus 5 and move up if it falls short.
›Is this the same Fable 5.1 as Anthropic's?
Yes — same model and same Messages API surface. RouteMux forwards the request and bills your prepaid wallet.
Sources
Reviewed by Jerry Fan on 2026-09-02