Claude Haiku 5.5 vs Claude Mythos 5.1
Claude Haiku 5.5 and Claude Mythos 5.1 are closely matched at 49.9 and 44.3 on the LLM Stats Score. Claude Haiku 5.5 is 100.0x cheaper per token.
Anthropic · Anthropic · Updated for 2026
Which is better?
Claude Haiku 5.5 and Claude Mythos 5.1 are closely matched on the overall LLM Stats Score at 49.9 and 44.3.
In the 1 individual benchmarks reported for both models, Claude Mythos 5.1 wins 1; this is a narrower head-to-head signal than the composite indexes.
On price, Claude Haiku 5.5 is roughly 100.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Claude Haiku 5.5
- cost matters — it's about 100.0x cheaper per token
- you want the most recent training data — it shipped Oct 2026
Choose Claude Mythos 5.1
- you value its reported benchmark strengths — it wins 1 of 1 exact shared results
At a glance
The differences that matter most.
Individual benchmarks
36 reported for Claude Haiku 5.5 · 1 for Claude Mythos 5.1
Claude Haiku 5.5 outperforms in 0 benchmarks, while Claude Mythos 5.1 is better at 1 benchmark (Terminal-Bench 4.0).
Claude Mythos 5.1 significantly outperforms across most benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Haiku 5.5 ($0.10/1M tokens) is 100.0x cheaper than Claude Mythos 5.1 ($10.00/1M tokens).
For output processing, Claude Haiku 5.5 ($0.50/1M tokens) is 100.0x cheaper than Claude Mythos 5.1 ($50.00/1M tokens).
In conclusion, Claude Mythos 5.1 is more expensive than Claude Haiku 5.5.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Both models have the same input context window of 1,000,000 tokens. Both models can generate responses up to 128,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Claude Haiku 5.5 and Claude Mythos 5.1 support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Haiku 5.5
Claude Mythos 5.1
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Claude Haiku 5.5 was released on 2026-10-07, while Claude Mythos 5.1 was released on 2026-09-01.
Claude Haiku 5.5 is 1 month newer than Claude Mythos 5.1.
Oct 7, 2026
1 weeks ago
1mo newerSep 1, 2026
1 months ago
Knowledge Cutoff
When training data ends
Claude Haiku 5.5 has a documented knowledge cutoff of 2026-06-01, while Claude Mythos 5.1's cutoff date is not specified.
We can confirm Claude Haiku 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without Claude Mythos 5.1's cutoff date.
Jun 2026
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Provider Availability
Claude Haiku 5.5 is available from Anthropic. Claude Mythos 5.1 is available from Anthropic.
Claude Haiku 5.5
Claude Mythos 5.1
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Haiku 5.5 and Claude Mythos 5.1 side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Haiku 5.5 vs Claude Mythos 5.1.