# EP 40: What Is Claude Fable 5.2? Effort, Fast Mode and the Real Cost per Task - URL: https://www.agenticpod.net/episodes/ep40-claude-fable-5-2/ - Watch on YouTube: https://www.youtube.com/watch?v=UrRIgPdk9CI - Published: 2026-11-12 - Length: 6 min - Hosts: Stella (asks), Liam (answers). Both are AI hosts with AI-generated voices. ## Summary Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on November 9, 2026: the same underlying model at two safeguard levels, with Fable as the public one. ## Key takeaways - Fable 5.2 and Mythos 5.2 are the same underlying model at two safeguard levels: Fable is public, Mythos is for verified organizations. Context is 1,000,000 tokens in, max output 128,000. - Pricing dropped 20% from 5.1: $8 per million input tokens and $40 output, batch at $4 and $20, cache reads $0.20. Fast mode is up to 2.5x faster at double price, $16 and $80. - On FrontierCode 2.0, max effort is a trap: 45.7% at $44.70 per task, below xhigh at 49.1% and $14.19. High effort is the sweet spot at 45.3% and $6.72. - Migration gotchas return 400 errors: adaptive thinking cannot be disabled, forced tool_choice breaks, and temperature, top_p and top_k must be omitted. The model also requires 30 day data retention. ## Chapters - 0:00 Intro - 0:41 What Fable 5.2 and Mythos 5.2 actually are - 1:38 The price, the speed, and fast mode - 2:41 Effort levels and the real cost per task - 4:05 Migration gotchas and the honest verdict ## FAQ **What is Claude Fable 5.2?** Anthropic's public model released November 9, 2026, the same underlying model as Mythos 5.2 at a public safeguard level, with a 1,000,000 token context and 128,000 max output. The model ID is claude-fable-5-2. **How much does Claude Fable 5.2 cost?** $8 per million input tokens and $40 output, batch at $4 and $20, cache reads $0.20. Fast mode doubles it to $16 and $80 for up to 2.5x faster generation. **Which effort level should I use?** High for hard work: 45.3% on FrontierCode 2.0 at $6.72 per task. Max scored lower than xhigh (45.7% vs 49.1%) at $44.70 per task, so skip max until your own numbers prove otherwise. ## Resources - [Step-by-step guide](https://github.com/asly-97/ai-automation-workflows/tree/main/claude-fable-5-2-effort-fast-mode) - [What developers get with Fable 5.2 and Mythos 5.2](https://mer.vin/news/claude-fable-5-2-and-mythos-5-2-what-developers-get/) - [Fable 5.2 for agentic coding](https://blog.sandbase.ai/claude-fable-5-2-agentic-coding-try-today-2026/) ## Transcript ### Intro Liam: Hey hey hey, welcome to Agentic Pod! I'm Liam. Stella: And I'm Stella! Liam, Anthropic shipped Claude Fable 5.2 on November 9th, and the top effort level scores worse than the one below it? Liam: Worse, and it costs $44.70 a task against $14.19. That is real, from the FrontierCode 2.0 numbers. Stella: So the max button is a trap? Liam: Sometimes, yeah. By the end you will know the price, the 5 effort levels, fast mode, and when Fable is worth it. ### What Fable 5.2 and Mythos 5.2 actually are Stella: Okay, basics first. What did Anthropic actually release? Liam: Two models on November 9th, 2026. Claude Fable 5.2, and Claude Mythos 5.2. Stella: Two names, so two different models? Liam: Same underlying model, I mean, the exact same brain. The difference is the safeguard level. Stella: So Fable is the one I can use? Liam: Right. Fable is the public one. Mythos is only for verified organizations. Liam: Context is 1,000,000 tokens, max output is 128,000. The model ID is claude-fable-5-2. Stella: A million tokens in. A whole code base, plus your bad decisions from March. Liam: Especially those. It is up to 30% faster than 5.1, and its classifiers block about 55% fewer requests. Stella: Fewer false blocks is a real upgrade. Okay, what does it cost? ### The price, the speed, and fast mode Liam: Base price is $8 per million input tokens, and $40 per million output tokens. Stella: And that is cheaper than the last one? Liam: Down 20% from 5.1, which was $10 and $50. Batch halves it, to $4 and $20. Cache reads are $0.20. Stella: Okay. Now explain fast mode, because everyone will flip that switch. Liam: Fast mode makes generation up to 2.5x faster. Same model, same answers, just a higher serving rate. Stella: There is always a catch. Price? Liam: Double. $16 input and $80 output per million tokens. Stella: Double the price for speed. That is a taxi meter with a turbo button. Liam: That is exactly what it is. Fast mode lives in Claude Code, the Claude Platform, Google Cloud, and Microsoft Foundry. Stella: So speed is a choice, not a new model. Good. Now the part I actually care about. Effort. ### Effort levels and the real cost per task Stella: Five effort levels, right? Walk me through them. Liam: Low, medium, high, xhigh, and max. Effort is how hard the model thinks before it answers. Stella: And the defaults will trip people up? Liam: They will. The API defaults to high. Claude Code and the Claude apps default to medium. Stella: Same model, different default brainpower depending on the door you walk in. Sneaky. Liam: Now FrontierCode 2.0, 132 pull request tasks. Low scores 34.2% at $2.10 per task. Medium scores 37.6% at $2.48. Stella: Cheap so far. Keep going. Liam: High scores 45.3% at $6.72. Xhigh scores 49.1% at $14.19. Stella: And max, the one from the intro? Liam: Max scores 45.7% at $44.70. Lower than xhigh, and more than 3 times the price. Stella: So max is slower thinking that does worse and bills more. My favorite kind of upgrade. Liam: Be nice. One more anchor. High effort roughly matches Opus 5.5 at max effort, for about half the cost per task. Stella: That is the headline for me. But before anyone migrates, what breaks? ### Migration gotchas and the honest verdict Liam: 3 big ones. First, adaptive thinking cannot be disabled on this model. It thinks adaptively, period. Stella: Okay, what is number 2? Liam: Forced tool choice returns a 400 error. If your code forces tool_choice to any or tool, it breaks. And temperature, top_p, and top_k also return 400. You have to omit them. Stella: So old API code with sampling settings just falls over? Liam: It does. Number 3 is data. The model requires 30 day retention. No zero data retention, unless Anthropic authorizes it. Stella: And Claude Code needs an update, right? Liam: Version 2.1.321 or later. Fable is on the Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry, and paid Claude apps. Stella: Quick note for paid plan people, by the way. There was a launch promo week, November 9th to 16th. After that, Fable draws on usage credits on Pro. Liam: Good catch. Now the workflow I would actually run. Keep your current model as the daily driver. Stella: And Fable is the specialist you call in? Liam: Exactly. Route only your longest, hardest runs to Fable at high effort. Measure cost per finished task, not per token. Stella: And xhigh only where you measured a real gain. Not by vibes. Liam: Not by vibes. And Anthropic itself says start with Opus 5.5 for most coding and knowledge work. Move up to Fable only as needed. Stella: The maker telling you not to buy the big one. I respect that. Liam: My verdict: Fable 5.2 at high effort is the sweet spot. Max is a trap until your own numbers prove otherwise. Stella: Same. The step by step guide is in the description. Would you pay double for fast mode, or is high effort enough? Tell us in the comments. See you next time!