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Model comparison · accepted catalogue facts 2026-10-21

Claude Fable 5 vs Claude Fable 5.1

Claude Fable 5.1 has an equal-or-higher measured score and an equal-or-lower estimated price. No known model-capability loss from Claude Fable 5; endpoint and task checks still apply. The reported score intervals do not overlap; this is not a task-specific success guarantee.

Editorial comparison: Anthropic generational trade-off: Claude Fable 5.1 vs Claude Fable 5 for capability versus token price Inclusion does not recommend either model.

Claude Fable 5

LMArena general · Elo · higher is better

Scale starts at 1040 Elo

1491.0

Balanced effective USD / 1M tokens · lower is better

$20.00/M

Claude Fable 5.1

LMArena general · Elo · higher is better

Scale starts at 1040 Elo

1509.9

Balanced effective USD / 1M tokens · lower is better

$20.00/M

In-Depth Analysis

Claude Fable 5 vs Claude Fable 5.1: Measured Technical Breakdown

Comprehensive comparison across measured human-preference evaluation, effective production token costs, architectural limits, and migration trade-offs.

Measured Capability (LMArena)
Claude Fable 5.1 leads by 18.9 Elo

Claude Fable 5: 1491 ±4.3 · Claude Fable 5.1: 1509.9 ±6.1 Statistically significant preference separation

Cost Comparison Across Canonical Production Workloads

Rates represent effective cost per 1M tokens under standard token blends. Cached prompt reads are factored according to workload context reuse.

Workload & RatioClaude Fable 5Claude Fable 5.1Cost DifferenceAdvantage
Balanced 3 tokens in per 1 out$20.00 /1M tokens$20.00 /1M tokens$0.0000 Same price
Summarise Huge input, tiny output$9.44 /1M tokens$9.22 /1M tokens$0.214 (2% diff)Claude Fable 5.1 costs less
Chat Long cached system prompt$23.30 /1M tokens$23.08 /1M tokens$0.225 (1% diff)Claude Fable 5.1 costs less
Code gen Output dominates$33.28 /1M tokens$33.22 /1M tokens$0.060 Claude Fable 5.1 costs less
Agentic Context replayed each turn$10.65 /1M tokens$10.20 /1M tokens$0.446 (4% diff)Claude Fable 5.1 costs less

Architectural & Operational Specifications

SpecificationClaude Fable 5Claude Fable 5.1Operational Note
Context window1,000,000 tokens1,000,000 tokens—
Max output generation128,000 tokens128,000 tokens—
Base input price$10.00 / 1M tokens$10.00 / 1M tokens—
Base output price$50.00 / 1M tokens$50.00 / 1M tokens—
Cached input price$1.00 / 1M tokens$0.250 / 1M tokensClaude Fable 5.1 offers lower cached prompt cost
Reasoning & thinking tokensSupported; standard ratesSupported; standard rates—
Input modalitiestext, image, filetext, image, file—
Tool calling / function useSupportedSupported—
Open weights & licenceProprietary (proprietary)Proprietary (API-only)—
Provider & reseller marketAnthropic · 6 provider offersAnthropic · 4 provider offers—

When to Choose Claude Fable 5

  • Direct integration with Anthropic tooling and API features.

When to Choose Claude Fable 5.1

  • Higher measured general capability (1509.9 Elo on human evaluation).
  • Direct integration with Anthropic tooling and API features.

Detailed Evidence Passports & Independent Audits

Claude Fable 5 Full model card, pricing ladder & provider offers → Claude Fable 5.1 Full model card, pricing ladder & provider offers → Alternatives to Claude Fable 5 Better-and-cheaper dominance audit → Alternatives to Claude Fable 5.1 Better-and-cheaper dominance audit →

Compare · model decision

Choose two or three models

Inspect the differences, estimate your workload and keep the evidence. All standard catalogue models are available, including unrated ones.

Catalogue facts
2026-10-21

2 / 3 selected · 0 requirements
Open public comparison link
Public workload and requirements

These settings are included in the share link. The fixed-request scenario and private evaluation data below are excluded.

A ↔ B

Claude Fable 5.1 has an equal-or-higher measured score and an equal-or-lower estimated price. No known model-capability loss from Claude Fable 5; endpoint and task checks still apply. The reported score intervals do not overlap; this is not a task-specific success guarantee.

Estimated blend: 75% input, 25% output; 0% cached input. Base context tier. Prompt length selects the billing tier. An unlisted cache-read rate uses that tier’s full input rate in this blend; missing required input or output rates prevent an estimate. The fixed-request estimate below validates actual context and output limits and requires a published cache-read rate when cache hits are assumed.

What changes between these models

Quality first, then estimated price. LMArena scores are human-preference measurements, not a benchmark of your application. A missing score is unrated.

  • Claude Fable 5 · Meets the stated model requirements
  • Claude Fable 5.1 · Meets the stated model requirements
Material differences and unknown evidence. Deltas compare each model with model A. Unknown facts remain visible.
Measured factA Claude Fable 5B Claude Fable 5.1
LMArena general score (Elo)1,4911,509.9Δ vs A: +18.9 Elo
Score interval half-width (± Elo)4.36.1Δ vs A: +1.8 Elo
Benchmark reasoning efforthighmax
LMArena document score (Elo)1,496.11,512.6Δ vs A: +16.5 Elo
Base cached-input USD / 1M tokens$1$0.25Δ vs A: -0.75 USD/M
Recorded licenceproprietaryUnknown
Distinct sellers in the catalogue54Δ vs A: -1
Recorded retirement dateUnknownUnknown
12 shared measured facts
Shared measured facts. Deltas compare each model with model A. Unknown facts remain visible.
Measured factA Claude Fable 5B Claude Fable 5.1
Estimated effective USD / 1M tokens$20$20Δ vs A: 0 USD/M
Base input USD / 1M tokens$10$10Δ vs A: 0 USD/M
Base output USD / 1M tokens$50$50Δ vs A: 0 USD/M
Context window (tokens)1,000,0001,000,000Δ vs A: 0 tokens
Output limit (tokens)128,000128,000Δ vs A: 0 tokens
Input modalitiestext, image, filetext, image, file
Tool useSupportedSupportedΔ vs A: 0
ReasoningSupportedSupportedΔ vs A: 0
Open weightsNot supportedNot supportedΔ vs A: 0
Model providerAnthropicAnthropic
Serving precision differs across offersNot supportedNot supportedΔ vs A: 0
Retirement evidenceNone announced; not a guaranteeNone announced; not a guarantee

Provider counts and precision flags describe catalogue offers. They do not establish the precision, availability, region, tool behaviour or limits of your chosen endpoint. Open each model’s provider table before switching.

Complete price ladders and billing conditions

Claude Fable 5

Rates below are USD per 1M tokens. A threshold selects that whole input/output rate pair.

Input-token thresholdInputOutputCached input
Base, up to and including first threshold$10$50$1

Claude Fable 5.1

Rates below are USD per 1M tokens. A threshold selects that whole input/output rate pair.

Input-token thresholdInputOutputCached input
Base, up to and including first threshold$10$50$0.25
Migration preflight · compare each candidate with model A

Keeping Claude Fable 5 is a valid decision. No pairwise comparison certifies a drop-in replacement.

Claude Fable 5 → Claude Fable 5.1

No known model-capability loss

  • Provider endpoint, serving precision, availability and task success need your own verification. Catalogue model capabilities do not certify an endpoint.
Check alternatives to Claude Fable 5

Estimate a fixed request shape

Private to this tab unless you save locally or explicitly export private details. These are estimates, not observed invoices. Cross-model token counts and task success are assumptions.

0.1 extra attempts means 10 extra full attempts per 100 requests. Cache writes, tool charges, taxes and unlisted charges are excluded.

  • Claude Fable 5Estimated total: $45 1,000 full attempts · base rates
  • Claude Fable 5.1Estimated total: $45 1,000 full attempts · base rates
Prompt and output sensitivity · sampled scenarios

Every point recalculates the entire request shape. Tier-boundary samples include one token below, at and above each threshold. Ordering between samples is not guaranteed. Lowest known cost excludes unknown estimates and is not a replacement recommendation.

Vary input; hold output, requests, cache and retries fixed.
Input tokensClaude Fable 5Claude Fable 5.1Coverage
2,000$45Lowest known$45Lowest knownAll computed
4,096$65.96Lowest known$65.96Lowest knownAll computed
32,768$352.68Lowest known$352.68Lowest knownAll computed
131,072$1,335.72Lowest known$1,335.72Lowest knownAll computed
Vary output; hold input, requests, cache and retries fixed.
Output tokensClaude Fable 5Claude Fable 5.1
128$26.4$26.4
2,048$122.4$122.4
8,192$429.6$429.6

Bring your observed evaluation results

JSON is parsed locally. Prompts, filenames, individual responses and extra fields are not retained. Import only aggregate measurements for selected models. Task/version labels do not establish that two evaluations used the same dataset.

Expected format
[{"model":"provider/exact-model-id","task":"support-answer","version":"rubric-1","attempts":100,"successes":84,"costUsd":2.4,"latencyMs":950}]

Use the exact catalogue ID. Replace the example values with observed measurements. Omit costUsd or latencyMs when they are unknown. No public score is inferred from these observations.

Keep the decision and its evidence

A portable record retains selected facts, complete tier ladders, public requirements and the publication manifest. It also embeds the full permitted public catalogue to verify the input artifact checksum. Files are larger for this reason (up to 2 MB); local storage is limited to 12 records. Team review is local to this browser; there is no hosted collaboration.

Saving is opt-in and includes private review fields. Shared comparison links never include them. Version 1 Check references remain separate and are not overwritten or guessed into this format.

Saved local decisions · 0

No version 2 decision records are stored in this browser.

Questions this page answers

Is Claude Fable 5 a better-and-cheaper replacement for Claude Fable 5.1?

Claude Fable 5.1 has an equal-or-higher measured score and an equal-or-lower estimated price. No known model-capability loss from Claude Fable 5; endpoint and task checks still apply. The reported score intervals do not overlap; this is not a task-specific success guarantee.

Which model is higher rated: Claude Fable 5 or Claude Fable 5.1?

Claude Fable 5.1 scores higher on LMArena general (1509.9 ±6.1) compared to Claude Fable 5 (1491.0 ±4.3), a margin of 18.9 Elo points. The measured confidence intervals do not overlap, demonstrating a statistically significant preference lead on human evaluations.

Which model is more cost-effective: Claude Fable 5 or Claude Fable 5.1?

Both Claude Fable 5 and Claude Fable 5.1 share an identical effective price of $20.00 per 1M tokens on a balanced workload.

How do their context windows and generation limits compare?

Both Claude Fable 5 and Claude Fable 5.1 provide an identical 1,000,000-token context window. Maximum output generation limits are 128,000 tokens for Claude Fable 5 and 128,000 tokens for Claude Fable 5.1.

What capabilities are lost when switching between Claude Fable 5 and Claude Fable 5.1?

Neither model exhibits a confirmed loss in declared context or modalities when switching between them. However, differences in tokenizer efficiency, prompt alignment, and latency across providers should be benchmarked on task-specific test suites.

Can Claude Fable 5 or Claude Fable 5.1 be self-hosted or deployed privately?

Both Claude Fable 5 and Claude Fable 5.1 are proprietary cloud models offered via managed API endpoints. Claude Fable 5 is served by Anthropic and 6 catalogue offers, while Claude Fable 5.1 is served by Anthropic and 4 catalogue offers.

What is included in this comparison?

Accepted model capabilities, context and output limits, complete price-tier ladders, independent LMArena measurements and missing evidence. Provider endpoint precision and application success still need verification.

Can I compare a different workload or keep a decision record?

Yes. Change the public workload, prompt length and requirements in the comparison workspace. Fixed-request scenarios, aggregate evaluations and review notes stay local unless explicitly exported.

Evidence & Ask
Markdown for LLMs