Which Claude Fable 5.1 conclusions hold up?

OpenRouter: Provider Performance and Benchmark Snapshot for Claude Fable 5.1

The September 2, 2026 OpenRouter snapshot shows P50 latency of 3.76–7.34 seconds and throughput of 26–48 tok/s across four providers, plus GPQA Diamond, TAU-Bench, structured-output errors, and availability; it is routing-layer telemetry.

Source-specific observation

The page is for `anthropic/claude-fable-5.1`, released September 1, 2026; Azure, Anthropic, Bedrock BYOK, and Vertex P50 latency/throughput use different windows from the one-week averages.

Published conditions

AutoExacto reports GPQA Diamond at 87.4%–90.0% and TAU-Bench at 76.8%–79.4% by provider; full item sets, repeats, effort, and sampling are not published, and auto-routing fails over on provider errors.

Claude Fable 5.1 Official Release: Multiple Benchmarks, Cost Tiers, and Safety Boundaries

Anthropic’s September 2026 release separates Fable 5.1’s coding, knowledge-work, and long-running-task claims from production-safeguard boundaries; Browserbase reports 82% browser-agent completion, while Rogo reports equal Finance accuracy with 20% fewer tokens.

Source-specific observation

September 2026 official release page; Browserbase reports 82% completion on its hardest browser-agent benchmark, about ten minutes per task, versus 74% for Opus 5 and 57% for Fable 5.

Published conditions

Rogo’s internal Finance benchmark reports equal accuracy with 20% fewer tokens; Anthropic notes that production-safeguard interventions can score zero or route some cybersecurity and biology work to Opus 4.8 or Opus 5.

Artificial Analysis: Claude Fable 5.1 Intelligence Index, Task Breakdowns, and Cost

Artificial Analysis’s September 1, 2026 pre-release evaluation gives Fable 5.1 max an Intelligence Index of 66, HLE 59.1%, Terminal-Bench v2.1 91.4%, and SciCode 62.0%; its default server-side fallback supplied about 4% of output tokens from Opus 4.8 or Opus 5.

Unverified: the original source could not be rechecked.

Source-specific observation

September 1, 2026 article; the pre-release evaluation uses max effort and the Artificial Analysis Intelligence Index, with about $3.76 per max task and 65 at xhigh for about $2.72.

Published conditions

Anthropic’s default fallback routes safety-flagged requests to Opus 4.8 or Opus 5 and supplied about 4% of Index output tokens; the GDPval-AA v2 gap versus Opus 5 is within the confidence interval.

SimpleBench: Claude Fable 5.1's Everyday Reasoning and Human Baseline

The SimpleBench snapshot collected on 2026-09-08 records Fable 5.1 at 86.6% on AVG@5, above the 83.7% average of nine non-expert participants; the set has 200+ multiple-choice questions on spatial, temporal, social, and language-trap reasoning.

Unverified: the original source could not be rechecked.

Source-specific observation

The source page gives no separate publication date for the Fable 5.1 row; the collected snapshot uses 200+ six-option text questions, an AVG@5 aggregate, and a leaderboard that can change.

Published conditions

The human baseline has nine English-native participants with at least high-school mathematics, each answering 25 random questions; the model row does not disclose effort, temperature, snapshot, or seed.

OpenRouter: Provider Performance and Benchmark Snapshot for Claude Fable 5.1

The September 2, 2026 OpenRouter snapshot shows P50 latency of 3.76–7.34 seconds and throughput of 26–48 tok/s across four providers, plus GPQA Diamond, TAU-Bench, structured-output errors, and availability; it is routing-layer telemetry.

Source-specific observation

The page is for `anthropic/claude-fable-5.1`, released September 1, 2026; Azure, Anthropic, Bedrock BYOK, and Vertex P50 latency/throughput use different windows from the one-week averages.

Published conditions

AutoExacto reports GPQA Diamond at 87.4%–90.0% and TAU-Bench at 76.8%–79.4% by provider; full item sets, repeats, effort, and sampling are not published, and auto-routing fails over on provider errors.

Claude Fable 5.1 Official Release: Multiple Benchmarks, Cost Tiers, and Safety Boundaries

Anthropic’s September 2026 release separates Fable 5.1’s coding, knowledge-work, and long-running-task claims from production-safeguard boundaries; Browserbase reports 82% browser-agent completion, while Rogo reports equal Finance accuracy with 20% fewer tokens.

Source-specific observation

September 2026 official release page; Browserbase reports 82% completion on its hardest browser-agent benchmark, about ten minutes per task, versus 74% for Opus 5 and 57% for Fable 5.

Published conditions

Rogo’s internal Finance benchmark reports equal accuracy with 20% fewer tokens; Anthropic notes that production-safeguard interventions can score zero or route some cybersecurity and biology work to Opus 4.8 or Opus 5.

Artificial Analysis: Claude Fable 5.1 Intelligence Index, Task Breakdowns, and Cost

Artificial Analysis’s September 1, 2026 pre-release evaluation gives Fable 5.1 max an Intelligence Index of 66, HLE 59.1%, Terminal-Bench v2.1 91.4%, and SciCode 62.0%; its default server-side fallback supplied about 4% of output tokens from Opus 4.8 or Opus 5.

Unverified: the original source could not be rechecked.

Source-specific observation

September 1, 2026 article; the pre-release evaluation uses max effort and the Artificial Analysis Intelligence Index, with about $3.76 per max task and 65 at xhigh for about $2.72.

Published conditions

Anthropic’s default fallback routes safety-flagged requests to Opus 4.8 or Opus 5 and supplied about 4% of Index output tokens; the GDPval-AA v2 gap versus Opus 5 is within the confidence interval.

SimpleBench: Claude Fable 5.1's Everyday Reasoning and Human Baseline

The SimpleBench snapshot collected on 2026-09-08 records Fable 5.1 at 86.6% on AVG@5, above the 83.7% average of nine non-expert participants; the set has 200+ multiple-choice questions on spatial, temporal, social, and language-trap reasoning.

Unverified: the original source could not be rechecked.

Source-specific observation

The source page gives no separate publication date for the Fable 5.1 row; the collected snapshot uses 200+ six-option text questions, an AVG@5 aggregate, and a leaderboard that can change.

Published conditions

The human baseline has nine English-native participants with at least high-school mathematics, each answering 25 random questions; the model row does not disclose effort, temperature, snapshot, or seed.

Reddit community: Skepticism about Fable 5.1 benchmarks and task-tiered experience

A September 2, 2026 Reddit discussion combines reactions to the official chart with quota and safety-guardrail anecdotes, warning that benchmarks may diverge from daily coding; comments share no common task, version, client, or logs.

Unverified: the original source could not be rechecked.

Source-specific observation

The post mainly relays an official chart; comments highlight a 52.6% versus 29.0% Terminal-Bench-Science gap without rerunning the benchmark.

Published conditions

Some users report roughly 20% quota use for two short tasks or exhausting a five-hour allowance in 20 minutes, while others report benign safety triggers; account, tokens, effort, and full inputs are unknown.