Claude Fable 5 vs Claude Mythos 5.1

Both list a base rate of $10 per million input tokens. Actual cost can differ with context tiers, caching, tools and other charges. Claude Fable 5: Standard USD/MTok input/output $10/$50 with no long-context surcharge; cache reads $1, 5-minute writes $12.50, 1-hour writes $20. Batch $5/$25. US-only inference adds 10% to input/output and cache reads/writes on Anthropic-operated routes where supported; Foundry uses US Data Zone Standard. Bedrock and Google-managed Google Cloud have independent regional prices. Adaptive thinking is always on; default effort high. Knowledge cutoff January 2026; retirement not sooner than June 9, 2027. Historical access suspension June 12 and restoration July 1, 2026 remain separate events. Server-side tools can add usage fees; tool schemas/results and thinking consume billable tokens. Claude Mythos 5.1: Standard USD/MTok input/output $10/$50, matching Fable 5.1; cache reads $0.25, 5-minute writes $12.50, 1-hour writes $20. Batch $5/$25. US-only inference adds 10% to input/output and cache reads/writes on Anthropic-operated routes where supported; Foundry uses US Data Zone Standard. Bedrock and Google-managed Google Cloud have independent regional prices. Access requires verification; the public API ID does not grant entitlement. Retirement not sooner than September 1, 2027 is a minimum commitment, not an announced shutdown. Server-side tools can add usage fees; tool schemas/results and thinking consume billable tokens.

Both list a base rate of $50 per million output tokens. Actual cost can differ with context tiers, caching, tools and other charges. Claude Fable 5: Standard USD/MTok input/output $10/$50 with no long-context surcharge; cache reads $1, 5-minute writes $12.50, 1-hour writes $20. Batch $5/$25. US-only inference adds 10% to input/output and cache reads/writes on Anthropic-operated routes where supported; Foundry uses US Data Zone Standard. Bedrock and Google-managed Google Cloud have independent regional prices. Adaptive thinking is always on; default effort high. Knowledge cutoff January 2026; retirement not sooner than June 9, 2027. Historical access suspension June 12 and restoration July 1, 2026 remain separate events. Server-side tools can add usage fees; tool schemas/results and thinking consume billable tokens. Claude Mythos 5.1: Standard USD/MTok input/output $10/$50, matching Fable 5.1; cache reads $0.25, 5-minute writes $12.50, 1-hour writes $20. Batch $5/$25. US-only inference adds 10% to input/output and cache reads/writes on Anthropic-operated routes where supported; Foundry uses US Data Zone Standard. Bedrock and Google-managed Google Cloud have independent regional prices. Access requires verification; the public API ID does not grant entitlement. Retirement not sooner than September 1, 2027 is a minimum commitment, not an announced shutdown. Server-side tools can add usage fees; tool schemas/results and thinking consume billable tokens.

Both accept about 1M tokens of context, so document length will not decide between them.

Both expose these named effort settings: "low", "medium", "high", "xhigh", "max". The same labels do not guarantee equal compute budgets or behavior across providers. Compare quality, latency and cost on your own tasks.

Both are classified in our frontier tier; this editorial grouping does not imply equal capability. Claude Fable 5 is a candidate for long-running agents; Claude Mythos 5.1 is a candidate for cyber-defence research. Compare accuracy, tool reliability, latency and cost on representative tasks.