⚡ Developer Guide

Claude Mythos API

When Claude Mythos launches, it will be available via Anthropic's Messages API — the same endpoint you use today. Here's how to prepare, what model IDs to expect, and how to migrate from Opus.

Expected Model IDs

Based on Anthropic's existing naming convention (claude-{family}-{version}-{date}) and the leak data:

 # Expected model IDs (not yet available)
 claude-mythos-20260601    # Likely launch version
 claude-mythos-latest      # Alias (like "claude-opus-latest")

 # What's available NOW (use these today)
 claude-opus-4-6-20251101  # Current flagship 

API Structure (No Breaking Changes Expected)

The good news: Anthropic's Messages API is stable. You won't rewrite your integration. The request format stays identical — only the model ID changes:

 // Today (Opus)

const response = await anthropic.messages.create({

  model: "claude-opus-4-6-20251101",

  max_tokens: 4096,

  messages: [{ role: "user", content: "Hello" }]

});

 // After Mythos launch (change one line)

const response = await anthropic.messages.create({

  model: "claude-mythos-20260601",  // ← only this changes

  max_tokens: 4096,

  messages: [{ role: "user", content: "Hello" }]

});

New API Parameters for Mythos Features

Claude Mythos introduces new capabilities that require new API parameters:

New Feature	Parameter (est.)	Notes
Extended Thinking (32K)	`thinking.budget_tokens`	Same param, higher limit
Audio input	`content[].type: "audio"`	New content block type
Parallel tool calls	Automatic (no flag needed)	Returns multiple `tool_use` blocks
Computer Use GA	`tools[].type: "computer_20260601"`	Updated tool version
Context (400K)	`max_tokens` up to 400K	Check your contract tier

Migration Checklist

When Claude Mythos becomes available, run through this checklist:

Step 1 — Update model ID

Replace claude-opus-4-6-20251101 with claude-mythos-20260601. Test each model call individually before bulk migration.

Step 2 — Update max_tokens

Mythos's extended thinking outputs may be longer. For complex reasoning tasks, consider increasing max_tokens from 4096 to 8000–16000.

Step 3 — Re-test safety-sensitive prompts

Improved calibration means some prompts that Opus refused may now succeed. Conversely, Mythos may flag some edge cases Opus missed. Review your prompt library against the new model.

Step 4 — Update cost monitoring

Mythos is 1.5–2.5× more expensive than Opus. Update your cost dashboards. Consider model routing: use Mythos only for tasks where the capability jump is worth the premium.

Step 5 — Parallel tool calling audit

If you use tool use, Mythos may return multiple tool_use blocks in a single response. Update your tool handling loop to process arrays, not single items.

Expected Pricing

Model	Input ($/M tokens)	Output ($/M tokens)	Available
Claude Haiku 4.6	$0.25	$1.25	Now
Claude Sonnet 4.6	$3.00	$15.00	Now
Claude Opus 4.6	$15.00	$75.00	Now
Claude Mythos (est.)	$25–$40	$100–$150	Q2–Q3 2026

How to Get Early Access

Anthropic typically grants preview access in three waves:

Wave 1 (Private Preview)

Selected enterprise customers and API partners. Usually 4–8 weeks before public launch.

Wave 2 (Limited Beta)

Developers on the waitlist. Usually 1–2 weeks before public launch. Subscribe below to be in this group.

Wave 3 (Public GA)

All API users. Pricing and rate limits fully published. Enterprise contracts available.

The fastest path to Wave 2 access is to be on Anthropic's developer waitlist. We'll notify our subscribers immediately when that waitlist opens.

Cost Optimization Strategy

At 1.5–2.5× the price of Opus, model routing becomes essential:

Use Mythos for: Complex multi-step reasoning, large codebase analysis, audio tasks, tasks requiring the full 400K context window
Stick with Opus for: Standard generation tasks, 200K context is sufficient, cost-sensitive production workloads
Use Sonnet for: High-volume, latency-sensitive tasks where quality matters but cost is critical

Explore Claude Mythos →

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