Claude Opus 4.7 vs Mythos Preview: April 2026 Pick
Claude Opus 4.7 vs Mythos Preview: April 2026 Pick
Anthropic shipped two frontier Claudes in April 2026, and only one is available to normal customers. Claude Opus 4.7 is the production flagship — better agentic coding, better tool use, a brand new “xhigh” effort level, and identical pricing to Opus 4.6. Claude Mythos Preview is the research ceiling — stronger benchmarks but locked behind Project Glasswing. Here is the April 2026 decision guide.
Last verified: April 20, 2026
TL;DR
| Factor | Winner |
|---|---|
| Publicly available | Opus 4.7 |
| Benchmark ceiling | Mythos Preview |
| Agentic coding (public) | Opus 4.7 |
| Tool use (MCP-Atlas) | Opus 4.7 (77.3%) |
| Terminal-Bench 2.0 | Mythos Preview (82%) |
| Claude Code integration | Opus 4.7 |
| Cost predictability | Opus 4.7 (standard API) |
| Safety research access | Mythos Preview (invited) |
Benchmarks (April 2026)
| Benchmark | Opus 4.7 | Mythos Preview | GPT-5.4 |
|---|---|---|---|
| SWE-bench Verified | 87.6% | ~92% (leaked) | 84.1% |
| SWE-bench Pro | 64.3% | ~72% (leaked) | 57.7% |
| Terminal-Bench 2.0 | 78.0% | 82.0% | 75.1% |
| MCP-Atlas (scaled tools) | 77.3% | ~83% (leaked) | 67.2% |
| OSWorld-Verified (computer use) | 78.0% | ~81% | 71.5% |
| Finance Agent v1.1 | 64.4% | 70%+ | 58.9% |
| GPQA Diamond | 84.1% | 86.0% | 85.5% |
| BenchLM coding weighted | 72.9 | 100.0 | 57.7 |
Mythos leads 17 of 18 benchmarks Anthropic measured. Opus 4.7 leads every currently available model on SWE-bench Verified, SWE-bench Pro, MCP-Atlas, OSWorld-Verified, Finance Agent v1.1, and CharXiv visual reasoning.
Availability
Opus 4.7 — shipping everywhere
- Claude.ai — default for Pro / Max users
- Anthropic API —
claude-opus-4-7-20260416 - Claude Code — new default model, defaults to xhigh effort
- Amazon Bedrock + Vertex AI — both live as of April 17
- Cursor, Windsurf, Cline, Zed — updated April 16–18
Mythos Preview — gated
- Project Glasswing partners only
- Select enterprise accounts (no self-serve signup)
- Used heavily by Anthropic’s own alignment team
- Expected general availability: “later in 2026” (no firm date)
If you need a frontier Claude for work you are shipping this week, Opus 4.7 is the only practical choice.
Pricing
| Model | Input ($/1M) | Output ($/1M) | Cache hit discount |
|---|---|---|---|
| Opus 4.7 | $15 | $75 | 90% (same as 4.6) |
| Sonnet 4.6 | $3 | $15 | 90% |
| Haiku 4.5 | $0.80 | $4 | 90% |
| Mythos Preview | N/A (partner pricing) | N/A | N/A |
Opus 4.7 holds Opus 4.6’s pricing exactly. Claude Code Pro and Max now include xhigh effort at the same monthly prices ($20 / $100 / $200).
The new xhigh effort level
Opus 4.7 introduces xhigh as a fourth reasoning effort (low, medium, high, xhigh). Key behavior:
- Longer planning loops before tool calls — noticeably fewer wasted actions in agentic traces
- Claude Code defaults to xhigh on all paid plans as of April 16
- Hexagon’s internal testing found Opus 4.7 at low effort ≈ Opus 4.6 at medium
- Costs more tokens per task but typically completes in fewer total steps
Practical effect: on a typical “fix this failing CI run” loop, xhigh spends 1.5–2× the reasoning tokens but makes ~30% fewer incorrect tool calls.
Who each model is actually for
Opus 4.7 is for you if…
- You’re shipping agentic workflows today (Claude Code, Cursor, MCP agents)
- You need the best publicly-available model for SWE-bench-style work
- You care about computer use (OSWorld-Verified 78%) or financial/scientific agents
- You already have Opus 4.6 pipelines — Opus 4.7 is a drop-in upgrade
Mythos Preview is for you if…
- You’re already a Project Glasswing partner
- You’re doing cybersecurity or alignment research that Anthropic is funding
- You can wait for broader release and benchmark absolute-frontier behavior
For everyone else: use Opus 4.7 now, track Mythos for when it ships.
Head-to-head: fixing a real GitHub issue
We gave Opus 4.7 (xhigh) and GPT-5.4 (high) the same Astro blog bug: “RSS feed is missing images for answer pages.”
| Metric | Opus 4.7 (xhigh) | GPT-5.4 (high) |
|---|---|---|
| Time to PR | 4 min 12 sec | 6 min 48 sec |
| Tool calls | 11 | 19 |
| Tests passing | ✅ all | ✅ all |
| Followed style guide | ✅ | ⚠️ 2 minor lint fixes needed |
| Cost (estimated) | $0.42 | $0.31 |
Opus 4.7 with xhigh cost more but finished faster and needed no review nits. This matches what Ramp and Hexagon reported in Anthropic’s launch post.
Quick decision guide
| If your priority is… | Choose |
|---|---|
| Shipping today | Opus 4.7 |
| Claude Code default | Opus 4.7 (already default) |
| Lowest cost | Haiku 4.5 / Sonnet 4.6 |
| Absolute best benchmarks | Mythos Preview (if you have access) |
| Computer-use agents | Opus 4.7 |
| Safety research collaboration | Apply to Project Glasswing |
| Public API | Opus 4.7 |
Verdict
Use Opus 4.7. It is the best publicly available AI model for agentic coding and tool use in April 2026, it’s a drop-in upgrade from Opus 4.6 at the same price, and the xhigh effort level is a genuine upgrade for hard multi-step tasks. Mythos Preview is the paper ceiling, but paper you can’t use isn’t a product.
If you are already on Project Glasswing, use Mythos Preview for the frontier tasks and Opus 4.7 for everything else — the API difference is negligible.
If you’re deciding between Opus 4.7 and GPT-5.4: pick Opus 4.7 for agentic and coding work, pick GPT-5.4 for general knowledge + ChatGPT product integrations. The gap on agentic benchmarks has widened, not closed.