Claude Mythos 5 vs Grok 4.5

Access is the headline difference here, and it runs one way. Claude Mythos 5 is the same underlying model as Claude Fable 5, offered without the dual-use safety measures to only approved organizations. Grok 4.5, released by xAI on July 8, 2026, is publicly available to any organization that signs up.

So the practical answer for nearly every buyer is this: Grok 4.5 is reachable today, and the realistic Anthropic option is Claude Fable 5, Mythos 5's generally available sibling. This page still compares Mythos 5 and Grok 4.5 on price and compliance for the businesses evaluating either path.

Grok 4.5 targets coding, agentic tasks, and knowledge work, with integrations including Databricks and Amazon Bedrock. Mythos 5 targets dual-use-sensitive research at approved organizations.

Claude Mythos 5 vs. Grok 4.5: Side-by-Side

Access: approved-only vs publicly available

Claude Mythos 5 is not open to the general public — it's the same underlying model as Claude Fable 5, offered without the dual-use safety measures, to a limited set of approved organizations.

Grok 4.5 has no such gate. Any organization can sign up and start using it following xAI's July 8, 2026 release.

For most businesses, that makes Grok 4.5 the practically available option between the two. If you're evaluating an Anthropic model and aren't approved for Mythos 5, look at Claude Fable 5 instead.

• Mythos 5: approved organizations only.
• Grok 4.5: publicly available now.
• Not approved for Mythos 5? Evaluate Claude Fable 5 instead.

Price: Mythos 5's cost is documented, Grok 4.5's isn't yet

Claude Mythos 5 shares Claude Fable 5's pricing: $10 per million input tokens and $50 per million output tokens.

xAI has not published official per-token pricing for Grok 4.5 as of this writing. Its predecessor, Grok 4.3, was priced at $1.25 input and $2.50 output per million tokens (xAI) — confirm current numbers directly with xAI.

• Claude Mythos 5: $10 / $50 per million tokens.
• Grok 4.5: pricing not yet published.
• Grok 4.3 (prior flagship): $1.25 / $2.50 per million tokens.

→ Compare per-token pricing for every AI model

Claude Mythos 5 vs Grok 4.5 benchmarks: what's actually published

Neither Claude Mythos 5's nor Grok 4.5's maker has published a same-day, apples-to-apples benchmark suite pitting these two exact versions against each other, so treat any comparison here as directional rather than a verified head-to-head.

Vendors have not published a directly comparable, head-to-head SWE-bench Verified score for these exact current-generation versions as of this writing. The most recent published reference points are Claude Opus 4.8 at about 88.6%, GPT-5 at about 74%, Grok 4 at about 75%, and Gemini 2.5 Pro at about 71% (Google) — treat these as directional, not a same-generation apples-to-apples test.

Until both vendors publish a matched benchmark run, the more reliable signal is a short pilot on your own tasks — coding, drafting, or analysis representative of your real workload.

• Claude Opus 4.8: ~88.6% on SWE-bench Verified.
• GPT-5: ~74% on SWE-bench Verified.
• Grok 4: ~75% on SWE-bench Verified.
• Gemini 2.5 Pro: ~71% on SWE-bench Verified.

Compliance: access control is itself a compliance factor

Claude Mythos 5's approval process functions as its own access-control gate, on top of Anthropic's standard compliance stack.

Grok 4.5's certification status was not detailed in public materials reviewed for this comparison. Confirm SOC 2 status and HIPAA BAA availability directly with xAI before sending regulated data.

• Mythos 5: gated by approval; inherits Anthropic's compliance stack.
• Grok 4.5: confirm current certifications directly with xAI.

How to choose for your business

If your organization is approved for Mythos 5 and your work involves the dual-use-sensitive research it's built for, it's worth evaluating directly. Otherwise, Grok 4.5 is reachable today for coding and agentic work, especially if your stack runs on Databricks or Amazon Bedrock.

For most buyers not approved for Mythos 5, the realistic comparison is Claude Fable 5 vs Grok 4.5, not this pairing.

• Approved for Mythos 5, dual-use-sensitive work: evaluate it directly.
• Not approved: compare Claude Fable 5 against Grok 4.5 instead.

The Verdict

For nearly every buyer, Grok 4.5 is the practically available option: it's public today, while Claude Mythos 5 requires organizational approval most businesses won't clear.

If you're evaluating Anthropic and don't have Mythos 5 approval, compare Claude Fable 5 against Grok 4.5 instead — that's the real-world decision most businesses face.