Claude Fable 5.2 API: Model ID, Price ($8 / $40), Breaking Changes and Claude Code Setup

Short answer

Claude Fable 5.2 is out. Anthropic released it on November 9, 2026 (release notes), and it's priced lower than Fable 5.1.

• Model ID: claude-fable-5-2
• Price: $8 per million input tokens and $40 per million output tokens (Fable 5.1: $10 / $50)
• Limits: 1M-token context, up to 128k output tokens
• Thinking: adaptive thinking is always on

It's on the Claude API, Claude Platform on AWS and Google Cloud, and Anthropic's announcement adds all paid Claude plans and all major cloud platforms. Anthropic says it beats Opus 5.5 on almost every capability it evaluated and writes output up to 30% faster than Fable 5.1. Claude Fable 5.2 is live on Moyi API: call claude-fable-5-2 with your existing key; Claude Fable 5.1 (claude-fable-5-1) and Claude Opus 5.5 (claude-opus-5-5) work with the same key. Details: Claude Fable 5.2 page.

New accounts start with a $0 balance — top up before your first request. Top up from $5. If a request returns 402 (400 on the OpenAI format) with "wallet balance is insufficient", your balance is empty — your base URL and key are fine. Top up and retry.

Get an API key and use Claude Fable 5.2 today

Specs

From Anthropic's What's new in Claude Fable 5.2:

Claude Mythos 5.2 (claude-mythos-5-2) has the same capabilities but is only for organizations verified through Anthropic's verification programs. Anthropic still suggests starting most work on the latest Claude Opus and moving to Fable 5.2 when Opus at higher effort isn't enough.

Four breaking changes from Fable 5.1

1. Editing earlier turns invalidates thinking blocks on every account. If your code changes the system prompt, tools or an earlier message and then sends back a Fable 5.2 thinking block, the request returns a 400 error ("The block is bound to a different conversation"). On Fable 5.1 this only applied to accounts created on or after August 31, 2026.
2. Only Fable 5.2 and Mythos 5.2 read Fable 5.2 thinking blocks. Switching a conversation from Fable 5.2 to another model drops that reasoning; the request still succeeds.
3. The older computer_20251124 computer-use tool returns an error. Use the computer_toolset_20260801 toolset.
4. With the advisor tool (beta), a Fable 5.2 executor needs a Fable 5.2 or Mythos 5.2 advisor.

Anthropic says nothing changes if Claude Code, claude.ai, Claude Managed Agents or the Claude Agent SDK builds your requests, or if your code keeps system and tools fixed and only appends messages.

How to call it

Python with the Anthropic SDK, on Anthropic's API:

import anthropic

client = anthropic.Anthropic(api_key="sk-ant-your-key")

message = client.messages.create(
    model="claude-fable-5-2",
    max_tokens=4096,
    messages=[{"role": "user", "content": "Review this function for race conditions."}],
)
print(message.content[0].text)

On Moyi API, the same code runs with claude-fable-5-2; only the base URL and key change:

client = anthropic.Anthropic(
    base_url="https://api.moyi-api.com",
    api_key="sk-your-key",
)
# then call client.messages.create(model="claude-fable-5-2", ...) as above

Claude Code

Claude Code picks the Fable model from ANTHROPIC_DEFAULT_FABLE_MODEL. Through Moyi API:

export ANTHROPIC_BASE_URL=https://api.moyi-api.com
export ANTHROPIC_AUTH_TOKEN=sk-your-key
export ANTHROPIC_DEFAULT_FABLE_MODEL=claude-fable-5-2

Full setup: Claude Code CLI setup.

FAQ

Is Claude Fable 5.2 cheaper than Fable 5.1?

Yes, at list price: $8 / $40 per million tokens versus $10 / $50.

Can I use Claude Fable 5.2 on Moyi API?

Yes. Use the model ID claude-fable-5-2 with your Moyi API key; the base URL and key are the same as for Fable 5.1.

Do I need to change my code to switch from Fable 5.1?

Only if your code edits earlier turns, system or tools mid-conversation, uses computer_20251124, or pairs the advisor tool with an older model. Otherwise, change the model ID.

Read next

• Claude Fable 5.2 vs Fable 5.1 vs Opus 5.5: price and which to pick
• How to use Claude Fable 5.2 without an Anthropic account
• Claude Fable 5.1 API guide