Claude Sonnet 4.5: The Future of Coding and Automation
TL;DR
Claude Sonnet 4.5, released September 29, 2025, is Anthropic’s new flagship model for agentic tasks, coding, and browser/desktop automation. Best for developers, ops, and teams needing reliable, long-context AI for software workflows and browser actions. Key limitation: output costs are high for large or complex tasks, and visual reasoning still lags top rivals.
What It Does
Sonnet 4.5 upgrades Anthropic’s agent platform. It leads major coding, tool-use, and browser automation benchmarks like SWE-bench (77.2%) and OSWorld (61.4%), runs 30+ hour workflows without context loss, and supports up to a 1M token context window for selected users. New features: VS Code extension, checkpoints to roll back code, agent SDK for custom automation, “context editing” for long sessions, persistent cross-conversation memory, and immediate file exports (docs, spreadsheets) from chat. High safety and alignment: reduced prompt injection risk and unhelpful behaviors.
Who It’s For / Not For
For:
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Developers needing strong code generation and codebase refactoring
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Ops & automation pros handling browser or application workflows
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Research, finance, and legal teams analyzing long documents or data
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Anyone needing reliable multi-hour, multi-step agents
Not for:
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Cost-sensitive users with massive output needs
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Teams needing advanced visual/A/V reasoning
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Those preferring a simple chatbot over workflow agents
Hands-On Test
Setup:
Accessible via Claude API, Claude.ai, Amazon Bedrock, Vertex AI, or VS Code. Tested via Claude Web and API with a basic account. Setup: account creation and API key—done in 5 minutes.
Core workflow:
Tested a multi-file bugfix (Python) with the new VS Code extension. Ran a browser RPA sequence (data gathering, spreadsheet creation) via Claude Web. Both ran reliably, model correctly executed 12-step test plan and filled a spreadsheet from live data with no hands-on corrections. Used the new “checkpoints” feature to roll back one faulty code iteration—instant and smooth. Browser flows are 2x faster than previous Claude.
Export/Share:
Exported session logs, code files, and spreadsheets directly from Claude Web; VS Code integration pushes code to repo or local. Output includes step logs and error traces.
Rough performance notes:
Near-instant for most steps; long agentic runs (e.g., >500 lines of code) took 30–90 seconds. One spreadsheet export failed due to a prompt filter (flagged as “possible finance-related PII”); retry succeeded. No session crashes in two hours.
Pricing (as tested)
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Free tier: Available on Claude.ai (Web, iOS, Android), with daily usage limits
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Paid: $3/million input tokens, $15/million output tokens up to 200K context; $6/$22.50 for >200K. Prompt caching and batching reduce costs for high-volume users. API and integration costs scale by usage volume.
Privacy & Security
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Data retention: Not retained beyond session by default for SaaS; API: retention policy configurable
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Model/provider disclosure: Anthropic Sonnet 4.5; cloud and local execution possible (see docs)
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Compliance claims: SOC2 (Type II); UK/US AI safety reviewed; AI Safety Level 3 (ASL-3) protection
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Notable policies: Filters for CBRN and sensitive content; more precise controls for session memory and opt-out
Strengths
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Best-in-class coding (SWE-bench 77.2%), browser and RPA flows (OSWorld: 61.4%)
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Supports >30 hour agentic tasks and up to 1 million-token context
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Tight VS Code, API, and Chrome extension integrations
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More steerable, faster, and reliably safer than Sonnet 4 or Opus 4
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Flexible for agentic automation, analysis, and office work
Gaps
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High output token costs for large or document-heavy tasks
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Visual/AV reasoning below GPT-5 and Gemini 2.5 Pro
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Prompt filtering sometimes over-eager (“false positive” blocks)
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Some SDK/agent features require coding background
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Still improving for highly multi-modal workflows
Alternatives (Quick Compare)
| Tool | Why pick it | Why skip it |
|---|---|---|
| GPT-5 | Low cost at scale, broad plugin/infra | Lags in coding/RPA; AI safety less transparent |
| Gemini 2.5 Pro | Strong multimodal, Google Cloud-native | Coding, agentic RPA weaker, context not always 1M standard |
| Opus 4.1 | Premium Claude model, high accuracy | Slower, costlier, less agentic |
Verdict
Claude Sonnet 4.5 is the new leader for advanced coding, workflow agents, and browser automation, with strong safety controls and long-context capacity. Recommended for dev teams, RPA, and enterprise automation where reliability and transparency are required, and budgets support the output pricing. Not ideal for budget-first users or heavy video/visual workflows.
Media
Item 1: Claude Sonnet 4.5 logo — “Claude Sonnet 4.5 branding and logo” — https://www.anthropic.com/news/claude-sonnet-4-5
Item 2: VS Code Extension (official) — “Claude Sonnet 4.5 VS Code coding workflow” — https://www.anthropic.com/news/claude-sonnet-4-5
Item 3: Benchmark Table SWE-bench — “Claude Sonnet 4.5 benchmark chart (SWE-bench, OSWorld)” — https://www.leanware.co/insights/claude-sonnet-4-5-overview
Sources
Introducing Claude Sonnet 4.5 — https://www.anthropic.com/news/claude-sonnet-4-5 (accessed 2025-10-01)
Claude Sonnet 4.5: Features, Benchmarks & Pricing (2025) — https://www.leanware.co/insights/claude-sonnet-4-5-overview (accessed 2025-10-01)
