Six breakthrough capabilities distinguish Claude Mythos from every model in Anthropic's lineup. Here's the technical breakdown of what makes it different.
Claude Opus 4.6 supports 200K tokens — already among the longest context windows in production. Claude Mythos is estimated to double this to ~400K tokens based on architectural hints in the leak.
In practical terms, 400K tokens means:
Source: Reference to MAX_CONTEXT_TOKENS: 409600 found in deobfuscated Claude Code VS Code extension (Feb 2026). 409,600 = 400K, aligned with power-of-2 architecture choices.
Unlike Claude Opus which handles only text and images, Claude Mythos natively processes audio input — speech, recorded meetings, audio files. This is a first for the Claude family.
Capabilities implied by the leak:
Claude Opus already supports "Extended Thinking" — an internal chain-of-thought that can run up to 16K tokens before responding. Claude Mythos extends this to an estimated 32K reasoning tokens.
This deeper thinking budget explains the +39% SWE-bench score improvement — longer internal reasoning allows the model to explore more solution paths, catch edge cases, and verify its own code before responding.
Computer Use shipped as a beta feature in Claude Opus. With Mythos, it moves to GA (General Availability) — meaning:
For developers: Computer Use GA is the foundation of true software agents — models that can autonomously operate macOS/Windows/Linux desktops to complete multi-step tasks.
Claude Opus can call tools sequentially — one after another. Claude Mythos introduces parallel tool calling: multiple tool invocations dispatched simultaneously, then results merged.
| Scenario | Opus 4.6 (Sequential) | Mythos (Parallel) |
|---|---|---|
| 3-source web research | ~9 seconds | ~3.5 seconds |
| DB + API + file read | ~6 seconds | ~2.2 seconds |
| Multi-repo code review | ~45 seconds | ~16 seconds |
Timing estimates based on architectural analysis. Actual performance will depend on tool latency, not just model speed.
Anthropic's biggest challenge with Opus has been over-refusal — the model declining legitimate requests due to false positive safety triggers. Claude Mythos is designed to be better calibrated: more helpful on benign requests, more reliably cautious on genuinely harmful ones.
This matters for enterprise developers who've struggled with Opus refusing to write code involving encryption, security research, or competitive intelligence — topics that are professionally legitimate but pattern-match to Opus's training.
Leaked evaluation internal metric: "Calibration score" — balancing false positive refusals vs. false negative harmful outputs. Mythos reportedly achieves 2.3× better calibration than Opus 4.6 on Anthropic's internal eval suite.
| Capability | Opus 4.6 | Claude Mythos |
|---|---|---|
| Context Window | 200K | ~400K |
| Audio Input | ✗ | ✓ |
| Extended Thinking | 16K tokens | ~32K tokens |
| Computer Use | Beta | GA |
| Parallel Tools | ✗ | ✓ |
| Safety Calibration | Good | 2.3× Better (est.) |
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