Discover Claude Sonnet 4.5 benchmarks, Agent SDK, and pricing. Learn how its 30-hour autonomous coding run and new integrations transform real-world AI workflows.
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📊 Quick Stats: 77.2% SWE-bench accuracy • 30-hour autonomous run • $3/$15 per million tokens • Available in GitHub Copilot
When Claude Sonnet 4.5 launched on September 29, 2025, it instantly became the most talked-about model in developer circles. Not just because it broke benchmark records—but because it did something no other AI has shown in public: coding autonomously for 30 hours straight without losing focus or context.
This wasn't a lab stunt. It was a full, end-to-end project: database setup, app logic, UI, debugging, and deployment—all handled by Sonnet. For many engineers, it was the moment AI stopped being a "pair programmer" and started acting like a genuine AI colleague.
Benchmarks back that up:
Each of these results shows a new level of stability, reasoning, and endurance—the holy trinity of agentic AI. (Source: Anthropic, Leanware)
Here's the short list of what makes Sonnet 4.5 a milestone release:
30-Hour Run
Autonomous coding with zero context drop
Agent SDK
Virtual machines, memory, sub-agents
VS Code Extension
Checkpoints and rollbacks built-in
Memory System
Persistent context for long sessions
Chrome Extension
Automate browser workflows
Unchanged Pricing
$3/$15 per million tokens
The result: an AI that doesn't just "assist" you—it finishes the job.
SWE-bench Verified is the gold standard for software engineering benchmarks. It tests an AI's ability to fix real GitHub issues by reading code, interpreting logs, and proposing patches.
Sonnet 4.5 hit 77.2% accuracy—a new state-of-the-art—outperforming both GPT-5 Codex and Gemini Ultra. Under high-compute configurations (where multiple reasoning attempts are merged), it reached 82%, showing consistent precision across complex codebases.
Meanwhile, on OSWorld, a test that measures how well an AI can actually use a computer—switching tabs, editing spreadsheets, navigating VS Code—Sonnet scored 61.4%, up from 42% earlier this year. That's a jump rarely seen in this field and one that signals human-level digital fluency. (Source: Skywork.ai)
💡 What This Means:
These improvements translate to less rework, fewer crashes, and more usable code in real workflows.
Anthropic's public demo wasn't about endurance for its own sake—it was about coherence over time.
The model coded for 30 hours continuously, maintaining consistent logic and debugging its own work without intervention. Early testers reported:
This was made possible by two key breakthroughs:
(Source: PromptLayer Blog)
Together, these features push Sonnet 4.5 beyond the "chatbot" category and into a new realm: autonomous agentic intelligence.
Sonnet 4.5 comes with a redesigned developer experience built for real production work—not just prompt tinkering.
The new Claude Code extension turns VS Code into a full AI workspace. It lets developers:
This means no more lost work after a bad generation or context cutoff. For teams, it's like having a version-controlled AI teammate always available inside the editor.
Anthropic also rebuilt the Claude terminal for smoother feedback loops. The model can now run commands, interpret errors, and adjust code inline—mimicking a senior developer's workflow.
When paired with the memory and context editing APIs, this setup allows multi-hour sessions that stay consistent and performant—something no previous Claude release could do. (Source: TheNeuron.ai)
Long sessions have always been the Achilles' heel of LLMs. The further they go, the more they forget. Claude Sonnet 4.5 solves this with an entirely new memory and context system.
The Claude API now supports persistent memory modules—allowing the model to "recall" previous interactions across sessions. Developers can store context, prune old data, or inject new references mid-conversation without losing flow.
This makes a big difference for:
The ability to edit context dynamically also helps prevent runaway token usage and cost spikes—keeping projects scalable and cost-efficient.
If Claude 4.5's endurance is impressive, its Agent SDK is the real unlock for developers. For the first time, Anthropic is sharing the same infrastructure it uses internally to power Claude Code.
The Claude Agent SDK provides tools to build autonomous agents that can run for hours—or days—safely and predictably:
Managed Virtual Machines
Each agent runs in a controlled sandbox
Memory Modules
Persistent recall using memory_20250818
Context & Editing APIs
Dynamically manage what the agent "knows"
Sub-Agent Orchestration
Coordinate multiple specialized agents
Together, these pieces form a modular foundation for building systems that don't just respond—they work.
(Source: Anthropic Engineering Blog, DigitalApplied)
The SDK's refined memory management and permission controls give enterprises exactly what they need: autonomy with oversight.
Claude Sonnet 4.5 isn't just powerful in isolation—it's now integrated directly into the places where developers and teams already spend their time.
GitHub confirmed that Sonnet 4.5 is now live inside Copilot for Pro, Enterprise, and Business users. That means developers can select it directly in VS Code, the GitHub web interface, or even through the CLI.
Why does this matter?
Because Sonnet 4.5 brings deep reasoning and long-horizon context to Copilot's familiar workflow. It doesn't just autocomplete functions—it can now:
With its 1M-token context window and improved memory system, Sonnet can understand entire codebases at once—something no previous Copilot model could manage. (Source: Leanware)
Anthropic also partnered with Microsoft to bring Sonnet 4.5 into Office 365 Copilot, starting with Excel and Word. The new agent modes allow users to automate spreadsheet logic, analyze large datasets, and even draft technical documentation—all powered by the same model that dominates SWE-bench.
For example:
In Excel
Sonnet can trace errors across linked sheets and build macros autonomously.
In Word
It can summarize entire compliance documents or convert tech notes into executive briefs.
This closes the gap between technical teams and business units, letting both collaborate on the same AI infrastructure.
Finally, the Claude for Chrome extension brings Sonnet 4.5's agentic capabilities into the browser. It can:
For researchers, analysts, and data engineers, this turns the browser itself into an AI automation surface—ideal for repetitive online workflows. (Source: TheNeuron.ai)
When a model gains this much autonomy, safety becomes the central question. Anthropic designed Claude Sonnet 4.5 to be its most aligned frontier model yet—built under its AI Safety Level 3 framework.
This framework introduces a new layer of protection with filters for:
Internal audits showed major reductions in problematic behaviors like deception, sycophancy, and power-seeking tendencies—all signs of improved alignment in agentic systems.
Compared to Opus 4, false-positive content flags were cut by a factor of 10, reducing interruptions in normal enterprise workflows. (Source: Anthropic)
For the first time, Anthropic used mechanistic interpretability tools to visualize how Sonnet 4.5 reasons internally. These tools help engineers trace the model's decision pathways—turning "black box" reasoning into observable structure.
This transparency is key for regulated industries like finance, healthcare, and defense, where explainability is non-negotiable. Sonnet 4.5 doesn't just produce results—it shows why it made them.
One of the biggest surprises in this release is what didn't change: the price.
Input tokens
$3
per million
Output tokens
$15
per million
Those rates match Sonnet 4.0 exactly, despite the leap in capability and context size. All paid Claude plans now include code execution and file creation, making it possible to run full development loops directly in chat or through the API. (Source: Claude.com)
For developers running agent workloads, this predictability matters. A single enterprise workflow might involve:
With Sonnet's token efficiency and context editing, teams can now forecast usage with near-linear cost scaling. It's the balance between high performance and budget control that makes Sonnet 4.5 an easy API upgrade.
The AI landscape is fierce. GPT-5, Gemini Ultra, and Grok 4 all push in similar directions—but Sonnet 4.5 carved its own lane: sustained focus and agentic reliability.
| Model | SWE-bench Verified | OSWorld | Max Context | Strength |
|---|---|---|---|---|
| Claude Sonnet 4.5 | 77.2% | 61.4% | 1M tokens | Long-horizon reasoning |
| GPT-5 | 77.0% | 58.9% | 512K tokens | Tool diversity |
| Gemini Ultra | 74.5% | 59.0% | 1M tokens | Multimodal tasks |
| Grok 4 | 70.3% | 55.2% | 256K tokens | Conversational tone |
(Source: Skywork.ai)
While GPT-5 and Gemini excel in flexibility, Sonnet's strength lies in unbroken flow. Its 30-hour autonomous coding run remains unmatched in any public test. That endurance is what enterprises are paying attention to.
Anthropic didn't just publish benchmarks—they shared real-world case studies from early partners.
Cognition (AI Dev Platform)
+18% boost in code planning speed and +12% improvement in end-to-end evaluations compared to Sonnet 3.6.
Finance Sector
Firms described Sonnet's insights as "investment-grade," meaning its screening and analysis passed human audit thresholds.
Cybersecurity
Vulnerability triage time dropped by 44%, even as accuracy improved.
Together, these results show measurable ROI—less time lost to debugging, faster iteration cycles, and safer automation across industries. (Source: Leanware)
For teams ready to deploy, Anthropic designed Sonnet 4.5's ecosystem to feel plug-and-play.
/checkpoint to save a state./rollback to revert instantly—ideal for collaborative debugging.pip install claude-agent-sdk.For 30-hour or longer agent sessions, Anthropic recommends:
With these frameworks, developers can safely scale Sonnet's autonomy without sacrificing oversight. (Source: DigitalApplied)
Even a top-tier model has trade-offs.
While token prices are low, long autonomous runs can rack up costs. Teams should design pipelines that checkpoint work, summarize context periodically, and reuse prior outputs to minimize redundant token use.
As with any large model, subtle logic or arithmetic bugs can slip through. Anthropic suggests using redundant verification loops—Sonnet checking its own code with second-pass reviews—to catch edge cases early.
Enterprise-grade safety depends on consistent performance over long sessions. Using memory editing and sandboxed environments prevents context poisoning or tool misfires in multi-agent systems.
Yes. The SDK includes APIs for sub-agent orchestration and persistent memory modules, allowing multiple agents to share context safely.
They reflect fewer regressions, faster debugging, and higher-quality commits, directly cutting dev hours on complex fixes.
For most workflows, yes. It's designed to complement GitHub Copilot but can also operate independently for autonomous code completion and refactoring.
They provide traceable reasoning and regulatory alignment, giving enterprises confidence to use Claude in sensitive environments.
A 100,000-token interaction—about a large app feature—costs roughly $1.80. Predictable, linear, and scalable for multi-hour agent tasks.
When projects demand endurance, contextual continuity, and full-agent autonomy—not just quick responses. Sonnet 4.5 excels where long, complex reasoning chains are critical.
Claude Sonnet 4.5 isn't just another benchmark win—it's proof that autonomous, context-durable AI is ready for production.
With its 30-hour coding run, Agent SDK, and Safety Level 3 architecture, it delivers what developers and enterprises have wanted for years: an AI colleague that stays focused, accountable, and reliable.
For teams exploring long-running agents or enterprise-scale automation, Claude Sonnet 4.5 is more than a model—it's the foundation of the next generation of AI-driven work.
(Source: Anthropic)
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