AnthropicProprietary

Claude Sonnet 5

Name: Claude Sonnet 5
Author: Anthropic

Anthropic's next-generation foundation model, achieving high performance with the latest training data and architecture.

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Parameters

Undisclosed

Context Window

License

Proprietary

Release Date

2026-06-30

Japanese Language Capability

✅High-Quality JP

Multilingual model with strong Japanese language processing capabilities.

API Pricing

Input Price (per 1M tokens)

Output Price (per 1M tokens)

Billing Mode: standard

Strengths

Weaknesses

Use Cases

Deep Analysis

Artificial Analysis Intelligence Index

#5 overall, 2-3 points behind GPT-5.5 (xhigh) and Opus 4.8 (max)

SWE-bench Pro

63.2%

vs Sonnet 4.6: 58.1%, Opus 4.8: 69.2%

Terminal-Bench 2.1

80.4%

Beats Opus 4.8 (74.6%); largest single improvement over 4.6

OSWorld-Verified

81.2%

vs Sonnet 4.6: 78.5%, Opus 4.8: 83.4%

Standard Input Price

$3/1M tokens

Intro $2/1M through Aug 31; vs Opus $5/1M

Standard Output Price

$15/1M tokens

Intro $10/1M through Aug 31; vs Opus $25/1M

Strengths

・Near-Opus agentic performance at roughly half the cost; beats Opus 4.8 on Terminal-Bench 2.1 and ties on knowledge work (GDPval-AA v2)
・Strongest prompt-injection robustness of any model tested (0.19% attack success rate), with lowest MASK lying rate (3.1%)
・Best-in-class agentic follow-through: runs tests, reads failures, patches code, and reruns without human prompting

Weaknesses

・Updated tokenizer inflates token counts 1.0-1.35x for identical text, making real-world costs higher than headline per-token pricing suggests
・Opus 4.8 retains clear leads on hardest tasks: +17.2 points on USAMO olympiad math, +6.0 on SWE-bench Pro, +6.6 on HLE no-tools
・Intentionally low cybersecurity capability; defaults to strong cyber safeguards unsuitable for legitimate security research without exemptions

Competitor Comparison

Model	Arena	Price
Claude Opus 4.8	N/A	$5/$25 per 1M
GPT-5.5	N/A	$5/$30 per 1M
Gemini 3.5 Flash	N/A	Per Google pricing

Overview

Claude Sonnet 5, released June 30, 2026, is Anthropic's most agentic mid-tier model to date, closing much of the performance gap to the flagship Opus 4.8 while costing roughly half as much per token. It scored 63.2% on SWE-bench Pro (up 5.1 points from Sonnet 4.6), 80.4% on Terminal-Bench 2.1 (actually beating Opus 4.8's 74.6%), and tied Opus 4.8 on knowledge work with a 1618 GDPval-AA v2 Elo. The model uses an updated tokenizer that can inflate token counts by up to 1.35x, which Anthropic offset with introductory pricing of $2/$10 per million tokens through August 31, 2026, after which standard pricing of $3/$15 applies. The model's defining characteristic is reliable agentic follow-through—early users report it finishing multi-step coding, debugging, and business automation tasks where previous Sonnets would stall or require human nudging. It ships with five effort levels (low through max), adaptive thinking that defaults to high, and a 1-million-token context window. Safety improvements are significant: the model achieved the lowest prompt-injection attack success rate (0.19%) and lowest sycophantic lying rate (3.1%) of any tested model. Sonnet 5 is now the default model on Claude's Free and Pro plans and is available across Claude Code, the Claude API, AWS Bedrock, Google Vertex AI, and Microsoft Foundry, plus third-party tools like Cursor, VS Code, and GitHub Copilot. For the vast majority of production agentic workloads, it represents the new best value in the Claude lineup, with Opus 4.8 now reserved for the hardest accuracy-critical tasks and cyber-research use cases.

Benchmarks & Performance

Claude Sonnet 5 shows clear improvement over Sonnet 4.6 across virtually every evaluation, while narrowing (but not eliminating) the gap to Opus 4.8 on most benchmarks. **Key Benchmark Results (max effort, averaged over 5 trials):** | Benchmark | Sonnet 5 | Sonnet 4.6 | Opus 4.8 | GPT-5.5 | Gemini 3.5 Flash | |---|---|---|---|---|---| | SWE-bench Verified | 85.2% | — | 88.6% | — | — | | SWE-bench Pro | 63.2% | 58.1% | 69.2% | 58.6% | 55.1% | | Terminal-Bench 2.1 | 80.4% | 67.0% | 74.6% | 83.4% | — | | OSWorld-Verified | 81.2% | 78.5% | 83.4% | 78.7% | 78.4% | | Humanity's Last Exam (no tools) | 43.2% | 34.6% | 49.8% | 41.4% | 40.2% | | Humanity's Last Exam (tools) | 57.4% | 46.8% | 57.9% | 52.2% | — | | BrowseComp (single agent) | 84.7% | 76.2% | — | 84.4% | — | | GDPval-AA v2 (Elo) | 1618 | 1395 | 1615 | 1509 | 1357 | | FrontierCode v1 | 38.8% | 15.1% | — | 25.5% | — | | USAMO 2026 | 79.5% | 55.0% | 96.7% | — | — | | AutomationBench | 13.5% | 5.3% | — | 12.9% | 14.5% | | HealthBench Professional | 57.8% | 44.2% | 56.9% | 51.8% | — | | CursorBench | 61.2% | 49.0% | 63.8% | — | — | | ProgramBench | 76-86% | 52-74% | 80-90% | — | — | **Independent Evaluation (Artificial Analysis):** - Intelligence Index: 53 (#5 overall, 6 points above Sonnet 4.6, 2-3 points behind Opus 4.8) - Per-task cost on Intelligence Index: $2.29 (roughly 15% more than Opus 4.8 at standard pricing due to higher token usage) **Notable highlights:** - Terminal-Bench 2.1 is the biggest single gain (+13.4 points) and the one benchmark where Sonnet 5 beats Opus 4.8 - GDPval-AA v2 is the only headline metric where Sonnet 5 edges Opus 4.8 (1618 vs 1615 Elo) - FrontierCode more than doubled from 15.1% to 38.8%, indicating structural improvement in sustained agentic work - The model burns ~40% more output tokens per task than Sonnet 4.6 at max effort

Detailed Comparison

**Claude Sonnet 5 vs Claude Opus 4.8:** The central comparison in the Claude lineup. Sonnet 5 costs 40% less per token ($3/$15 vs $5/$25) and delivers faster latency. It wins or ties Opus 4.8 on Terminal-Bench 2.1 (80.4 vs 74.6), knowledge work GDPval-AA v2 (1618 vs 1615 Elo), HLE with tools (57.4 vs 57.9%), and prompt-injection robustness (tied at 0.19%). Opus 4.8 retains clear leads on SWE-bench Pro (69.2 vs 63.2%), USAMO olympiad math (96.7 vs 79.5%), OSWorld-Verified (83.4 vs 81.2%), and deeper reasoning tasks. The 1M context window and 128K output cap are identical. Anthropic's own system card positions them as a single cost-performance curve where effort level lets developers choose their sweet spot. Recommendation: use Sonnet 5 as default; reserve Opus 4.8 for hardest accuracy-critical tasks and cyber research. **Claude Sonnet 5 vs GPT-5.5:** Sonnet 5 leads on SWE-bench Pro (63.2 vs 58.6%), BrowseComp (84.7 vs 84.4%), and AutomationBench (13.5 vs 12.9%). GPT-5.5 leads on Terminal-Bench 2.1 (83.4 vs 80.4%) and HLE with tools (52.2 vs 57.4% — though Sonnet 5 leads here). Sonnet 5 has stronger prompt-injection robustness (0.19 vs 3.08% attack success). Both are priced in the same general tier. No direct comparison exists yet with GPT-5.6. **Claude Sonnet 5 vs Gemini 3.5 Flash:** Sonnet 5 outperforms on SWE-bench Pro (63.2 vs 55.1%), OSWorld-Verified (81.2 vs 78.4%), AutomationBench (13.5 vs 14.5%), and prompt-injection robustness (0.19 vs 6.66% attack success). Gemini 3.5 Flash focuses on speed and multimodal versatility. Sonnet 5 is priced similarly but offers superior agentic coding and safety. No direct comparison exists yet with Gemini 3.5 Pro.

Community Feedback

Developer and researcher reactions on launch day (June 30, 2026) were mixed-to-positive, with praise concentrated on the price-to-performance ratio and skepticism about value at full standard pricing. **Positive sentiment:** The official @ClaudeDevs account highlighted 'top-tier performance on coding and tool use at Sonnet pricing.' @kimmonismus on X called it 'near Opus 4.8-level performance, but cheaper.' Hacker News user phillipcarter described it as 'another great incremental update to the workhorse,' noting they use Sonnet over Opus for most coding. Multiple early-access partners in Anthropic's launch post praised the model's ability to finish multi-step tasks autonomously — one reported it writing a reproducing test, implementing a fix, and stashing it to confirm the bug returned, all in a single pass. **Mixed/critical sentiment:** Hacker News user mchusma noted the model is 'far more compelling at the $2/$10 launch price than at full standard pricing.' conradkay questioned whether it 'seems worse even on price/performance than GLM 5.2' at 744B parameters. andai argued 'if you're doing something hard, just use a bigger model.' mag7269 asked 'when can we get a new Haiku?' reflecting developer fatigue with mid-tier refreshes while the budget tier ages. bredren saw clear value at low and medium effort but less so at high effort versus Opus 4.8. **Adoption patterns:** The model's immediate placement as the default on Free and Pro plans means most Claude users are now running Sonnet 5 without actively choosing it. Early reports from partners like Zapier, Pace (insurance), ClickHouse, Eve (legal), and Lovable confirm adoption in production automation, computer-use agents, and professional knowledge work. Reddit threads on r/ClaudeAI and r/LocalLLaMA saw active benchmark discussion and GLM-5.2/K2.7 comparisons on day one.

Use Cases

**1. Multi-step software engineering and debugging:** Sonnet 5 excels at sustained coding workflows — writing changes, running tests, reading failures, patching, and rerunning without human prompting. Its 80.4% on Terminal-Bench 2.1 (beating Opus) and 63.2% on SWE-bench Pro make it the best value for daily coding. Early users report it finishing complex PRs end-to-end, tracing bugs to root causes rather than patching symptoms. Choose Sonnet 5 over Opus for most coding; escalate to Opus only for deeply ambiguous, multi-file refactors requiring sophisticated backtracking. **2. Agentic business automation:** For workflows like Zapier-style task chains (updating Salesforce, sending emails, processing insurance claims), Sonnet 5's autonomous follow-through at $3/$15 per million tokens makes multi-step automation economically viable. Pace reported it consistently taking correct actions quickly on real insurance systems. Choose Sonnet 5 over cheaper models for complex chains requiring planning and tool use; choose over Opus when cost per task matters more than the last few points of accuracy. **3. Professional knowledge work (legal, finance, research):** Sonnet 5 tied or beat Opus 4.8 on GDPval-AA v2 (1618 vs 1615 Elo), AA-Briefcase (1393 vs 1352), and HealthBench Professional (57.8 vs 56.9%). It runs longer trajectories (183 avg turns on AA-Briefcase vs 55 for Opus), suggesting it compensates for lower per-turn intelligence with more thorough exploration. Eve reported it sitting on the Pareto frontier for legal tasks. Choose Sonnet 5 for routine professional deliverables; escalate to Opus for high-stakes analysis where a single error has outsized consequences. **4. Agentic web research and information retrieval:** On BrowseComp, Sonnet 5 scored 84.7% (single agent, 10M-token budget), comparable to GPT-5.5's 84.4% and matching Opus 4.8's cost-accuracy profile. Its prompt-injection robustness (0.19% attack success) makes it particularly safe for agents that read untrusted web content. Choose Sonnet 5 over all competitors for research agents that encounter adversarial content; the safety profile is a genuine differentiator.

Latest News

**June 30, 2026 — Launch:** Anthropic released Claude Sonnet 5 as the default model for Free and Pro plans on claude.ai, with immediate availability across Claude Code, Claude Platform/API (model ID: claude-sonnet-5), AWS Bedrock, Google Vertex AI, and Microsoft Foundry. Third-party tools including Cursor, VS Code, GitHub Copilot, and OpenRouter added support the same day. **Pricing:** Introductory pricing of $2/MTok input, $10/MTok output runs through August 31, 2026, after which standard pricing of $3/$15 applies. The model uses an updated tokenizer (shared with Opus 4.7) that inflates token counts 1.0-1.35x for the same text. Anthropic calibrated intro pricing to make migration from Sonnet 4.6 roughly cost-neutral. **Safety:** Real-time cyber safeguards are enabled by default, using the same classifiers as Opus 4.7/4.8 (lighter than Fable 5's stricter safeguards). Cyber Verification Program participants have automatic access. Prompt-injection robustness matches Opus 4.8 at 0.19% attack success rate. **Rate limits:** Anthropic raised rate limits across Chat, Cowork, Claude Code, and the Claude Platform (following the April 26, 2026 simplification to Start/Build/Scale tiers) to accommodate higher token usage at higher effort levels. **Anthropic also corrected** a BrowseComp cost-performance chart in the launch post, updating it to match the methodology documented in the system card (10M token budget with compaction and programmatic tool calling).

The model's defining characteristic is reliable agentic follow-through—early users report it finishing multi-step coding, debugging, and business automation tasks where previous Sonnets would stall or require human nudging. It ships with five effort levels (low through max), adaptive thinking that defaults to high, and a 1-million-token context window. Safety improvements are significant: the model achieved the lowest prompt-injection attack success rate (0.19%) and lowest sycophantic lying rate (3.1%) of any tested model.

Sonnet 5 is now the default model on Claude's Free and Pro plans and is available across Claude Code, the Claude API, AWS Bedrock, Google Vertex AI, and Microsoft Foundry, plus third-party tools like Cursor, VS Code, and GitHub Copilot. For the vast majority of production agentic workloads, it represents the new best value in the Claude lineup, with Opus 4.8 now reserved for the hardest accuracy-critical tasks and cyber-research use cases.

Sources

Analysis generated: 2026-07-17