ModelSpec is an analysis of alternatives for AI models: it decides which models fit a job from your requirements, sourced benchmarks and real cost, and shows its work.

Claude Fable 5 vs Claude Opus 5.5 for Regulated data (best available), as of 2026-09-23

Find the strongest assistant among offerings with the data-handling commitments regulated workloads need.

Worked example as of 2026-09-23, from the public data image.

What the evidence says

The evidence separates them: Claude Opus 5.5 leads for Regulated data (best available), with a 75% chance of being the best model in the full lineup for this job, as of 2026-09-23.

Claude Fable 5 has a 25% chance of matching or beating Claude Opus 5.5 on this job's objective.

probability bands: a model joins the leader when P(its score >= the leader's) >= 0.25 under the score posteriors; a weighted capability with an 80% interval wider than 2.8 is not enough evidence

Decision status: answered. P(best) and score intervals retain the full ranked lineup for this job, including models beyond this pair and models with thin evidence. Models with unknown objective values remain unranked and are outside this probability. P(best) is not a head-to-head probability. Separation from this challenger need not mean a unique best model across that lineup.

Scores and score intervals use the objective's dimensionless normalised units. Cost per task is in USD for the selected offering and the applied spec's task size. When task size is omitted, the engine uses its documented default. Unavailable means the engine returned no value.

HIPAA-ready offerings; strongest assistant, cost no object.

Requirements

• offering.data.trains_on_customer_data = No: Customer prompts and outputs must not be available for model training.
• offering.data.zero_retention = Yes: The provider must offer a mode that stores neither prompts nor outputs.
• offering.attestation.baa = Yes: The provider must offer a HIPAA business associate agreement for the service.

Preferences

• chat_preference: Rank only by assistant quality among compliant offerings.

Evidence for Claude Fable 5

Missing facts for Claude Fable 5

• model.hardware_fit_indeterminate: unknown
• model.languages: unknown
• model.parameters_total: unknown
• origin.base_lineage: not_disclosed
• origin.weights_hosting: not_disclosed
• offering.api_model_id: unknown
• offering.attestation.soc2: not_disclosed
• offering.private_deployment: unknown
• offering.router_slug: unknown
• offering.speed.throughput: unknown
• offering.speed.time_to_first_token: unknown

Evidence for Claude Opus 5.5

Missing facts for Claude Opus 5.5

• model.hardware_fit_indeterminate: unknown
• model.languages: unknown
• model.parameters_total: unknown
• origin.base_lineage: not_disclosed
• origin.weights_hosting: not_disclosed
• offering.api_model_id: unknown
• offering.attestation.soc2: not_disclosed
• offering.router_slug: unknown
• offering.speed.throughput: unknown
• offering.speed.time_to_first_token: unknown

What this template teaches

Governance promises are Musts; with no cost term, quality alone ranks what passes.

Decision dec_deeb0e6f23ab984de448de39 on public snapshot snap_05a963d2477ac2fb.

Read the full dated job answer.

The live board uses current data. This link applies the template to its full lineup.

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