Official: 'Sonnet 5' is now Claude Sonnet 4.6
claude-sonnet-4-6. Pricing confirmed at $3/$15. Users prefer it over Sonnet 4.5 ~70% of the time and over Opus 4.5 59% of the time. Computer use improvements with 60.4% on ARC-AGI-2.Opus 4.6 released: Agent Teams now available
Opus 4.6 gets 1M context + Finance Agent #1 ranking
Software stocks down 20%+ as 'vibe working' era begins
1M context, Dev Team mode, $3/$15 pricing confirmed
The "Opus Killer" Has Arrived
On February 3, a Vertex AI error log revealed what developers had been waiting for: a new Sonnet model, codenamed "Fennec." Leaked as "Sonnet 5," Anthropic officially released it as Claude Sonnet 4.6 on February 17, 2026, keeping the 4.x naming convention. Two weeks earlier, Opus 4.6 launched with Agent Teams. The real story is what testing reveals about both models.
Hands-on testing and official benchmarks confirm what the leaked data suggested: Sonnet 4.6 delivers Opus-tier coding performance at Sonnet-tier pricing. Users prefer it over Sonnet 4.5 approximately 70% of the time. For developers building with Claude, this changes the cost-capability equation entirely.
Background Reading
Claude Sonnet 5 Is Here. Opus 4.6 Just Dropped. What You Need to Know. →Full timeline from the Vertex AI leak to today's official releases.
What Testers Actually Found
Beyond the benchmark numbers, early access testing has revealed specific capabilities that matter for production development:
1. Superior UI Code Generation
Testers report Sonnet 4.6 produces "the most complete, detailed ASCII world map ever seen" from an AI model, an indicator of its improved spatial reasoning and structured output generation. For frontend developers, this translates to better component generation and more accurate UI implementations.
2. 1M Context Window (Confirmed)
Official sources confirm a 1 million token context window with "near-zero latency," a 5x increase from the 200K context of Sonnet 4.5. This enables processing entire codebases, lengthy documents, or extended conversation histories in a single context.
3. Stronger Coding Than Opus 4.5
The most significant finding: in coding workflows, Sonnet 4.6 outperforms Opus 4.5. Users prefer Sonnet 4.6 over Opus 4.5 59% of the time, particularly in structured generation tasks, API implementations, and complex refactoring operations.
The Benchmark Trajectory
Claude's SWE-Bench scores have improved dramatically in 18 months. Sonnet 4.6's 80.2% matches the 80% "human parity" threshold that many considered the ceiling for AI coding assistants:
SWE-Bench Verified scores for Claude models. Feb 2026 data is projected.
The trajectory tells the story: each Sonnet generation narrows the gap with Opus, and Sonnet 4.6 finally matches it at a fraction of the cost.
The Pricing Advantage
This is where it gets interesting for production workloads. Based on leaked pricing, here's the cost comparison:
| Model | Release | SWE-Bench | Price (In/Out) |
|---|---|---|---|
| Claude 3.5 Sonnet | June 2024 | 49.0% | $3 / $15 |
| Claude 3.7 Sonnet | Feb 2025 | 62.3% | $3 / $15 |
| Claude 4 Sonnet | May 2025 | 70.0% | $3 / $15 |
| Claude Opus 4.5 | Nov 2025 | 80.9% | $15 / $75 |
| Claude Opus 4.6 | Feb 5, 2026 | ~80%+ | $5 / $25 |
| Claude Sonnet 4.6 | Feb 17, 2026 | 80.2% | $3 / $15 |
At $3/$15 per million tokens vs. Opus 4.6's $5/$25, Sonnet 4.6 costs roughly 40% less for input and 40% less for output, while delivering comparable coding benchmarks.
When to Use Sonnet 4.6 vs. Opus 4.6
With both Opus 4.6 (Feb 5) and Sonnet 4.6 (Feb 17) now available, here's the decision framework for developers:
Choose Sonnet 4.6 For:
- Code generation and refactoring tasks
- High-volume API calls where cost matters
- UI component generation and frontend work
- Structured output generation (JSON, YAML, configs)
- Production workloads currently on Sonnet 4.5
Choose Opus 4.6 For:
- Complex multi-agent workflows using Agent Teams (parallel task coordination)
- Financial analysis, tops the Finance Agent benchmark
- Research and analysis requiring maximum capability with 1M context
- Enterprise workflows involving PowerPoint, document review, and cross-tool integration
- Mission-critical applications where cost is secondary to quality
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New Capabilities
Beyond the core benchmarks, both models ship with significant new features:
CONFIRMEDMulti-Agent Coding
Sonnet 4.6 supports multi-agent coding workflows where a Manager Agent analyzes your high-level goal and spawns specialized sub-agents (Backend, QA, Infrastructure) that work simultaneously on different files. This is separate from Opus 4.6's Agent Teams, which take a more general approach to parallel task coordination.
Computer Use Improvements
Sonnet 4.6 brings major improvements to computer use, scoring 60.4% on ARC-AGI-2 and showing substantial gains on OSWorld. Anthropic calls it their best model yet for operating computers autonomously.
Current Status
Both models are now officially released and widely available:
- Sonnet 4.6 officially released Feb 17: Available via API, claude.ai (default for Free and Pro plans), Amazon Bedrock, and Google Cloud Vertex AI. Model ID:
claude-sonnet-4-6 - Opus 4.6 released Feb 5: Agent Teams, 1M context, PowerPoint integration, and GitHub Copilot support
- Pricing confirmed: Sonnet 4.6 at $3/$15, Opus 4.6 at $5/$25 per million tokens
- 1M context on both: Both Sonnet 4.6 and Opus 4.6 offer 1M token context windows
- User preference data: Users prefer Sonnet 4.6 over Sonnet 4.5 ~70% of the time, over Opus 4.5 59% of the time
