Ivy Pro School
Claude Opus 4.7 vs. Claude Mythos
“The gap between these two models is not about intelligence. It's about autonomy — and that distinction matters enormously for how you deploy AI.”
Anthropic released Claude Opus 4.7 on April 16, 2026 — a comprehensive upgrade touching nearly every area of the model's capabilities. At the same time, a more restricted and more powerful model sits in the background: Claude Mythos. Available only to select researchers and partners in a restricted preview, Mythos represents Anthropic's most capable model to date.
The central question for any professional or organization is simple: which model should you use, and why? The answer requires understanding a distinction that runs through every benchmark in this comparison — the difference between intelligence and autonomous execution.
Claude Opus 4.7
GA — Available NowGenerally available. Major vision, instruction, and memory upgrades. Best-in-class for supervised use.
Claude Mythos
Restricted PreviewRestricted preview. Leads the world on autonomous execution benchmarks. Held back due to cybersecurity capability.
What's New in Opus 4.7?
Released April 16, 2026, Opus 4.7 is not just a minor revision — it's a comprehensive upgrade. Here are the five biggest changes you'll actually notice.
Better Vision
Opus 4.7 now accepts images up to 2,576 pixels on the long edge — more than three times the resolution of earlier Claude models. This matters enormously for tasks like reading dense charts, processing high-quality screenshots, or extracting data from detailed diagrams.
Sharper Instruction Following
The model takes your instructions more literally than before. If you've been using Claude with prompts that were written for earlier models, you may need to re-tune them — Opus 4.7 will actually do what you said, including the parts you didn't fully intend.
Better Memory Across Sessions
In long agentic runs, Opus 4.7 is significantly better at using file-system memory to carry context between tasks, reducing the need to re-explain background every session.
New xhigh Effort Level
A new xhigh effort level gives fine-grained control over the reasoning-vs-latency tradeoff. In Claude Code, xhigh is now the default for all plans.
New Tokenizer
A new tokenizer processes text differently — the same input can map to 1.0–1.35× more tokens depending on content type, which affects cost. Anthropic recommends measuring real-traffic token usage before and after upgrading.
Benchmark Deep Dive
Benchmarks are split into two groups: knowledge benchmarks (can the model reason and answer questions?) and execution benchmarks (can the model autonomously complete complex tasks?). This distinction is the key to understanding the entire comparison.
Knowledge Benchmarks — Near Tie
Execution Benchmarks — Mythos Wins by 15–24 Points
The pattern is unmistakable. On tasks requiring pure intelligence, the two models are nearly identical — often within 1–3 percentage points. But on tasks requiring autonomous execution, Mythos pulls ahead by 15–24 points across the board.
Head-to-Head Comparison
The complete breakdown across every major category, in plain language.
| Category | Winner |
|---|---|
| Availability | Opus 4.7 |
| Pricing | Opus 4.7 |
| Answering Q&A | Tie |
| PhD-Level Science | Near Tie |
| Software Engineering | Mythos |
| Autonomous Coding | Mythos |
| Web Browsing Agent | Mythos |
| Multi-Tool Workflows | Mythos |
| Computer Use / OS Control | Mythos |
| Image / Vision Quality | Tie / Edge Opus 4.7 |
| Cybersecurity Capability | Mythos (restricted) |
| Financial Analysis | Near Tie |
| Safety Alignment | Mythos |
| Instruction Following | Opus 4.7 |
| Memory Across Sessions | Comparable |
Why is Mythos Restricted?
“Mythos isn't restricted because it's more powerful in a general sense. It's restricted primarily because of one capability: it is dramatically better at cybersecurity exploitation.”
On CyberGym — a benchmark that measures the ability to find and exploit software vulnerabilities — Mythos leads Opus 4.7 by roughly 15–19 percentage points. Anthropic explicitly states this was a key factor in keeping Mythos under restricted preview. The company launched Project Glasswing specifically to address the cybersecurity risks posed by advanced AI.
Opus 4.7 is the first model where Anthropic has deployed real-time safeguards that automatically detect and block cybersecurity misuse attempts. What they learn from Opus 4.7's deployment will inform whether and how Mythos-class models can ever be broadly released.
CyberGym Score
+19pt gap — key restriction trigger
Anthropic's Response
- Real-time safeguards in Opus 4.7 that block misuse
- Project Glasswing — dedicated cybersecurity risk program
- Cyber Verification Program for legitimate security researchers
- Learnings from Opus 4.7 deployment will shape Mythos release path
The Key Insight: Knowledge vs. Execution
If you walk away with one idea from this article, make it this: the gap between Opus 4.7 and Mythos is not really about intelligence. Both models can think at roughly the same level. The gap is about autonomous execution.
Intelligence (Near Tie)
- GPQA Diamond — near tie (94.2% vs 94.6%)
- MMLU Pro — near tie
- Humanity's Last Exam — near tie
- MATH reasoning — near tie
Autonomous Execution (Mythos Wins)
- BrowseComp — +24pts
- Terminal-Bench — +15pts
- MCP Atlas — +21pts
- OS World — +16pts
Think of it this way: Opus 4.7 is an incredibly smart person who follows your instructions brilliantly. Mythos is that same smart person, except they can also independently plan a multi-week project, book their own flights, and manage the whole thing without checking in every hour. The intelligence is similar. The autonomy is not.
Opus 4.7 vs. Opus 4.6
For users upgrading from Opus 4.6, the differences are significant and practical. Here's what changes and what to watch for.
Vision
Major upgrade — up to 2,576px images (3× previous resolution)
Instruction Following
Significantly more literal — re-tune prompts written for 4.6
Memory Across Sessions
Substantially improved in long agentic runs
Tokenizer
New tokenizer: 1.0–1.35× more tokens per input, affects cost
Effort Control
New xhigh effort level; Claude Code default raised to xhigh
Output Tokens
Reasons more at higher effort — produces more output tokens
Migration Tip
Anthropic recommends measuring real-traffic token usage before and after upgrading — the new tokenizer's 1.0–1.35× token expansion can meaningfully affect costs at scale.
Who Should Use What?
A practical decision guide in plain English. For most use cases, Opus 4.7 is the right answer — Mythos only wins when autonomous execution is the critical requirement.
| Your Use Case | Best Choice |
|---|---|
Writing, research, Q&A, analysis | Opus 4.7 |
Coding with your supervision | Opus 4.7 |
Long autonomous coding runs | Mythos (if available) |
Building AI agents that browse the web | Mythos (if available) |
Finance, legal, professional documents | Opus 4.7 |
Computer use / desktop automation | Mythos (if available) |
Processing high-res images / charts | Opus 4.7 |
Security research (legitimate uses) | Opus 4.7 + Cyber Program |
The Bigger Picture
Anthropic has, for the first time, clearly separated two different types of AI capability: raw intelligence and autonomous execution. Opus 4.7 is among the best in the world at the former. Mythos leads the world at the latter.
The fact that the knowledge gap is so small — 1–3% on most reasoning benchmarks — suggests that raw intelligence is becoming a commodity. What differentiates frontier models in 2026 is no longer “can it answer this question correctly?” but “can it complete this 20-step task without me babysitting it?”
Mythos is Anthropic's answer to that second question. But because autonomous execution at that level comes with serious risks — especially in cybersecurity — Anthropic has chosen to keep it under tight wraps while using Opus 4.7 as a testbed for the safety safeguards that might eventually make a broad Mythos release possible.
Key Takeaway
For most people, most of the time, Opus 4.7 is the right tool. It's excellent, it's available, and it's getting better. Mythos is a glimpse of what agentic AI looks like when all the guardrails are off — but for now, that future is still on a waiting list.
Benchmark figures are sourced from Anthropic's official Opus 4.7 announcement (April 16, 2026) and the model system card. Some figures are approximate based on published charts. All comparisons reflect API-accessible model versions as of publication date.
The Bottom Line
Raw intelligence is becoming a commodity. The frontier of AI in 2026 is not about answering questions better — it's about completing multi-step tasks autonomously, reliably, and safely.
Opus 4.7 is a major upgrade for any professional who interacts with AI directly — better vision, better instruction following, better memory. It is the right model for the vast majority of real-world use cases.
Mythos represents the next level: autonomous execution that surpasses anything currently publicly available. The reason it's restricted is the reason it matters — it can do things that require very careful handling.
Use Opus 4.7 if you…
- Need a model available to you today
- Work on writing, research, analysis, or coding
- Want improved vision for charts and screenshots
- Need literal instruction following
Wait for Mythos if you…
- Need fully autonomous multi-step task execution
- Are building web agents or computer-use systems
- Require unsupervised long-horizon coding runs
- Can wait for restricted access to clear