# claudefable-5.ai

> Independent resource site covering Claude Fable 5 (`claude-fable-5`) and Claude Mythos 5 (`claude-mythos-5`) - the frontier AI models released by Anthropic on June 9, 2026. We publish verified specs, pricing, benchmarks, API guides, and launch news. Not affiliated with Anthropic, PBC.

Key facts about Claude Fable 5:
- Anthropic's most capable generally available model - "a Mythos-class model made safe for general use"
- Released June 9, 2026; API model ID `claude-fable-5`
- 1M-token context window (no long-context premium), 128K max output tokens, January 2026 knowledge cutoff
- Pricing: $10 per million input tokens / $50 per million output tokens (2x Claude Opus 4.8); Batch API $5/$25; cache hits $1/MTok
- Benchmarks: SWE-Bench Pro 80.3%, Terminal-Bench 2.1 88.0%, GDPval-AA Elo 1932, OSWorld-Verified 85.0%, Humanity's Last Exam (tools) 64.5%
- API: adaptive thinking always on (the only mode); `thinking: disabled`, `budget_tokens`, sampling params, and prefills all return 400; depth controlled by `output_config.effort` (low/medium/high/xhigh/max, default high)
- Safety: ASL-3, real-time classifiers (cyber, bio, reasoning-extraction), opt-in fallback to Opus 4.8 (<5% of sessions), 30-day mandatory data retention
- Claude Mythos 5 is the same model with cyber safeguards lifted, restricted to Project Glasswing partners
- Available on: Claude API, claude.ai paid plans (free until June 22, 2026), Claude Code (/model fable), Amazon Bedrock, Vertex AI, Microsoft Foundry, GitHub Copilot

## Core pages

- [Homepage](https://claudefable-5.ai/): Overview of Claude Fable 5 - specs, benchmarks, latest guides and news
- [Features](https://claudefable-5.ai/features/): Capabilities overview and supported API features
- [Model comparison](https://claudefable-5.ai/models/): Fable 5 vs Opus 4.8, Opus 4.7, Sonnet 4.6, Haiku 4.5, and Mythos 5
- [FAQ](https://claudefable-5.ai/faq/): Direct answers to the most common Fable 5 questions
- [About](https://claudefable-5.ai/about/): Site mission, sourcing policy, independence disclaimer

## Feature deep dives

- [Long-horizon agents](https://claudefable-5.ai/features/long-horizon-agents/): Multi-day autonomy, sub-agent delegation, the Stripe 50M-line migration
- [Adaptive thinking](https://claudefable-5.ai/features/adaptive-thinking/): Always-on reasoning and the effort parameter
- [1M context & memory](https://claudefable-5.ai/features/1m-context/): Context window, prompt caching (512-token minimum), file-based memory
- [Safety system](https://claudefable-5.ai/features/safety/): Classifiers, refusals, fallbacks, ASL-3, data retention
- [Claude Code agent workflows](https://claudefable-5.ai/features/claude-code-agent-workflows/): Planning, implementation checkpoints, tests, and review summaries with Fable 5

## Landing pages

- [Claude Code Fable](https://claudefable-5.ai/claude-code-fable/): What the phrase means and how to use `/model fable`
- [Fable Claude Code](https://claudefable-5.ai/fable-claude-code/): Team rollout and migration playbook
- [What is Fable?](https://claudefable-5.ai/what-is-fable/): Direct Fable 5 explainer
- [Claude Mythos](https://claudefable-5.ai/claude-mythos/): Mythos topic hub
- [Mythos](https://claudefable-5.ai/mythos/): Short definition page
- [Claude Code Fable 5](https://claudefable-5.ai/claude-code-fable-5/): Setup, command, and first-run workflow
- [Fable 5 Claude Code](https://claudefable-5.ai/fable-5-claude-code/): Cost and workflow guide
- [Claude Fable model](https://claudefable-5.ai/claude-fable-model/): Specs, model ID, pricing, and use cases
- [What is Fable 5 Claude?](https://claudefable-5.ai/what-is-fable-5-claude/): Direct answer for the Fable 5 Claude query variant
- [What is Fable 5?](https://claudefable-5.ai/what-is-fable-5/): Direct Claude Fable 5 explainer for search and AI answer engines

## Developer guides (blog)

- [API quickstart](https://claudefable-5.ai/blog/getting-started-claude-fable-5-api/): First request, breaking changes, code samples
- [Fable 5 vs Opus 4.8](https://claudefable-5.ai/blog/claude-fable-5-vs-opus-4-8/): Specs, benchmarks, and the real cost math
- [Effort parameter guide](https://claudefable-5.ai/blog/fable-5-effort-parameter-guide/): Tuning low/medium/high/xhigh/max
- [Migration guide](https://claudefable-5.ai/blog/migrating-to-claude-fable-5/): Step-by-step checklist from Opus 4.8 or older
- [What is Claude Mythos 5?](https://claudefable-5.ai/blog/what-is-claude-mythos-5/): The gated sibling model and Project Glasswing
- [Pricing explained](https://claudefable-5.ai/blog/fable-5-pricing-explained/): Full price tables and cost-control levers
- [Benchmarks](https://claudefable-5.ai/blog/claude-fable-5-benchmarks/): Complete results vs Opus 4.8, GPT-5.5, Gemini 3.1 Pro
- [Fable 5 in Claude Code](https://claudefable-5.ai/blog/fable-5-in-claude-code/): /model fable, usage multipliers, best practices
- [Claude Code Fable 5 prompts](https://claudefable-5.ai/blog/claude-code-fable-5-prompts/): Prompt patterns for long coding sessions

## News

- [Launch announcement coverage](https://claudefable-5.ai/news/anthropic-announces-claude-fable-5/): The June 9, 2026 launch story
- [Free in paid plans until June 22](https://claudefable-5.ai/news/fable-5-free-paid-plans-june-22/): Subscription availability window
- [Day-one platform GA](https://claudefable-5.ai/news/fable-5-github-copilot-bedrock-vertex/): GitHub Copilot, Bedrock, Vertex AI, Foundry
- [Community reaction](https://claudefable-5.ai/news/community-reaction-fable-5/): Simon Willison, Hacker News, Ethan Mollick, the classifier debate
- [Project Glasswing](https://claudefable-5.ai/news/project-glasswing-mythos-5/): Why Mythos 5 stays behind closed doors

## Optional

- [Full machine-readable content](https://claudefable-5.ai/llms-full.txt): Expanded fact sheet for AI assistants
- [Official Anthropic announcement](https://www.anthropic.com/news/claude-fable-5-mythos-5): Primary source

## Expanded SEO and GEO cluster

- [what is claude fable 5](https://claudefable-5.ai/what-is-claude-fable-5/): Claude Fable 5 is the public Claude Fable model for advanced coding, long-context research, and agentic work. On this site, the term maps to the API model ID claude-fable-5, a 1M-token context window, 128K maximum output, always-on adaptive thinking, and public pricing of $10 per million input tokens and $50 per million output tokens.
- [fable 5 model](https://claudefable-5.ai/fable-5-model/): The Fable 5 model is Claude Fable 5, a high-capability Claude model designed for hard coding tasks, research synthesis, and long-running agent workflows. The model is best used when accuracy, planning depth, and long context matter more than lowest token cost.
- [reddit claude](https://claudefable-5.ai/reddit-claude/): People searching Reddit Claude topics usually want practical signals: whether Fable 5 is worth the cost, whether Claude Code improves with Fable, how the model behaves on real codebases, and what limits or refusals to expect. This page organizes those questions without quoting unsourced Reddit posts.
- [claude fable reddit](https://claudefable-5.ai/claude-fable-reddit/): The most useful Claude Fable Reddit questions are not hype questions. They are implementation questions: how much does Fable cost, when should it replace Opus or Sonnet, what does it add in Claude Code, and how should teams evaluate results before paying for higher token prices.
- [claude fable pricing](https://claudefable-5.ai/claude-fable-pricing/): Claude Fable pricing is $10 per million input tokens and $50 per million output tokens on the Claude API. Batch API usage is listed at half that rate, and prompt caching can reduce repeated-context costs when long prefixes are reused.
- [fable pricing](https://claudefable-5.ai/fable-pricing/): Fable pricing normally refers to Claude Fable 5 token pricing. The public API rate is $10 per million input tokens and $50 per million output tokens, with lower effective costs possible through batch jobs, prompt caching, and routing routine work to cheaper models.
- [claude fable 5 pricing](https://claudefable-5.ai/claude-fable-5-pricing/): Claude Fable 5 pricing should be evaluated at workflow level, not just token level. A hard migration or repository-wide debugging run can justify a premium model if it reduces retries, review cycles, and engineer time.
- [claude fable 5 model](https://claudefable-5.ai/claude-fable-5-model/): The Claude Fable 5 model is a frontier Claude model for difficult knowledge work. It is strongest when a task needs planning, codebase context, tool use, and careful self-checking across a large amount of information.
- [reddit claude fable 5](https://claudefable-5.ai/reddit-claude-fable-5/): Reddit Claude Fable 5 searches usually come from users who want practical evidence before switching models. The best approach is to test the model against your own codebase, measure retries and review time, and compare total workflow cost rather than one prompt price.
- [claude fable 5 reddit](https://claudefable-5.ai/claude-fable-5-reddit/): Use Claude Fable 5 Reddit discussion as a source of questions, not as final evidence. Convert anecdotes into tests: run the same issue on your repository, record cost, count failed attempts, and compare the quality of final patches.

## Additional blog guides

- [What Is Claude Fable 5? The Short Answer for Developers](https://claudefable-5.ai/blog/what-is-claude-fable-5/): A practical explanation of Claude Fable 5, the Fable 5 model, pricing, Claude Code use cases, and the questions searchers ask before trying it.
- [Fable 5 Model Guide: Specs, Strengths, and Tradeoffs](https://claudefable-5.ai/blog/fable-5-model-guide/): A model guide for Fable 5 covering specs, strengths, pricing tradeoffs, Claude Code usage, and when teams should route work to cheaper models.
- [Reddit Claude Fable 5 Reactions: How to Read the Signal](https://claudefable-5.ai/blog/reddit-claude-fable-5-reactions/): A practical guide to reading Reddit-style Claude Fable 5 reactions without over-trusting anecdotes, hype, or isolated benchmark claims.
- [Claude Fable Reddit Sentiment: What Buyers Should Watch](https://claudefable-5.ai/blog/claude-fable-reddit-sentiment/): How buyers should interpret Claude Fable Reddit discussion around pricing, model quality, coding workflows, latency, refusals, and plan limits.
- [Claude Fable Pricing Guide for Developers](https://claudefable-5.ai/blog/claude-fable-pricing-guide/): Claude Fable pricing explained for developers: token rates, batch jobs, prompt caching, Claude Code usage, and cost-control decisions.
- [Fable Pricing Cost Breakdown: Inputs, Outputs, and Cache Hits](https://claudefable-5.ai/blog/fable-pricing-cost-breakdown/): A Fable pricing cost breakdown for Claude Fable 5, including input tokens, output tokens, batch discounts, prompt caching, and practical budgeting.
- [Claude Fable 5 Model vs Opus: When the Upgrade Makes Sense](https://claudefable-5.ai/blog/claude-fable-5-model-vs-opus/): Claude Fable 5 model vs Opus comparison focused on coding workflows, research quality, price, retries, and practical model routing.
- [How to Evaluate Fable 5 Pricing Before a Team Rollout](https://claudefable-5.ai/blog/how-to-evaluate-fable-5-pricing/): A rollout checklist for evaluating Fable 5 pricing, including pilot tasks, cost tracking, acceptance criteria, and model-routing policy.
- [Reddit Claude Code Fable Workflows: Questions Worth Testing](https://claudefable-5.ai/blog/reddit-claude-code-fable-workflows/): A Claude Code Fable workflow guide inspired by common community questions around model switching, prompt setup, testing, and pricing.
- [Fable 5 Model Selection Checklist](https://claudefable-5.ai/blog/fable-5-model-selection-checklist/): A checklist for deciding when to choose the Fable 5 model, when to use a cheaper Claude model, and how to measure the result.

## Additional news analysis

- [Claude Fable 5 Search Interest Rises Around Model and Pricing Questions](https://claudefable-5.ai/news/claude-fable-5-search-interest-rises/): Search demand around Claude Fable 5 is clustering around definition, model capability, pricing, and Claude Code evaluation queries.
- [Fable 5 Model Queries Spike as Developers Compare Premium AI Options](https://claudefable-5.ai/news/fable-5-model-queries-spike/): Fable 5 model queries are increasing as developers compare premium Claude options for coding, research, and agent workflows.
- [Reddit Claude Discussion Roundup: Pricing and Coding Questions Lead](https://claudefable-5.ai/news/reddit-claude-discussion-roundup/): A roundup-style news brief on the main Reddit Claude question types: pricing, coding workflow, model switching, and evaluation.
- [Claude Fable Reddit Reaction Roundup Focuses on Cost and Model Fit](https://claudefable-5.ai/news/claude-fable-reddit-reaction-roundup/): Claude Fable Reddit-style discussion is centered on whether the model improves difficult workflows enough to justify higher usage cost.
- [Claude Fable Pricing Search Demand Moves Toward Workflow Cost](https://claudefable-5.ai/news/claude-fable-pricing-search-demand/): Claude Fable pricing searches increasingly focus on total workflow cost rather than only the headline token rate.
- [Fable Pricing Comparison Interest Grows Among Team Buyers](https://claudefable-5.ai/news/fable-pricing-comparison-interest/): Fable pricing comparison queries show teams looking for model-routing rules, budget controls, and Claude Code rollout guidance.
- [Developers Compare Fable 5 Model Costs Against Review Time](https://claudefable-5.ai/news/developers-compare-fable-5-model-costs/): Developers are evaluating Fable 5 model costs against review cycles, failed attempts, test repair, and engineering time.
- [Claude Code Users Test Fable 5 for Repository-Wide Tasks](https://claudefable-5.ai/news/claude-code-users-test-fable-5/): Claude Code users are testing Fable 5 on repository-wide refactors, migrations, debugging chains, and long implementation plans.
- [Community Searchers Ask: What Is Claude Fable 5?](https://claudefable-5.ai/news/community-asks-what-is-claude-fable-5/): Definition searches around what is Claude Fable 5 show that many users still need a concise answer before comparing pricing or workflows.
- [Fable 5 Pricing Questions Center on API Rates, Cache, and Batch Use](https://claudefable-5.ai/news/fable-5-pricing-questions-after-launch/): Fable 5 pricing questions after launch center on input/output token rates, prompt caching, Batch API discounts, and when to escalate tasks.