Supersedes Claude 4 Haiku, positioning it as a step-up option rather than a true budget model. The 1M token context window is the headline feature. Output cost of $15/1M tokens is on the higher end for this tier — compare to Gemini 3.1 Pro at roughly $10/1M output before committing to high-volume use.
1M token context window enables processing entire codebases or lengthy document sets in a single pass
Anthropic's Constitutional AI training produces reliable, well-calibrated responses with lower hallucination rates than comparable-tier competitors
Strong instruction-following and structured output generation for production pipelines
Noticeably better nuanced prose and tone control than GPT-4.1 Mini or Gemini 3.1 Flash at similar price points
Weaknesses
At $15/1M output tokens, it's significantly more expensive than Gemini 3.1 Pro or GPT-4.1 for high-volume output workloads
No native image generation capability — purely a text-in/text-out model
Tends toward verbosity and over-qualification in responses, which can frustrate users wanting concise answers
Real-world use cases
What people actually use Claude Sonnet 4.5 for.
Ingesting and summarizing an entire legal contract repository (500k+ tokens) to identify clause inconsistencies
Writing and refining multi-chapter technical documentation with consistent voice and accurate code examples
Building an agentic coding assistant that maintains long conversation context across a full development session
How Claude Sonnet 4.5 compares
The nearest models people weigh against it, and what actually separates them.
vs Claude 3.5 Sonnet — Against Claude 3.5 Sonnet (Anthropic), Claude Sonnet 4.5 runs about 50% cheaper per token and takes 5x the context. Take Claude Sonnet 4.5 unless you specifically need what Claude 3.5 Sonnet does better.
vs Claude Fable 5 — Against Claude Fable 5 (Anthropic), Claude Sonnet 4.5 runs about 70% cheaper per token and answers faster. Take Claude Sonnet 4.5 unless you specifically need what Claude Fable 5 does better.
vs Claude Fable 5.1 — Against Claude Fable 5.1 (Anthropic), Claude Sonnet 4.5 runs about 70% cheaper per token and answers faster. Take Claude Sonnet 4.5 unless you specifically need what Claude Fable 5.1 does better.
Price History
Claude Sonnet 4.5 pricing over time
→0% since May 22
90 data points · tracked daily since May 22, 2026
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Start using Claude Sonnet 4.5
Production applications that need Claude's nuanced writing and reasoning without the latency or cost of Opus-class models.. Start free — no card required.
Claude 3.5 Sonnet is Anthropic's mid-cycle flagship model, balancing strong reasoning, coding, and instruction-following with a 200K context window. It sits between Haiku and Opus in Anthropic's lineup, offering near-flagship quality at a lower cost than top-tier models.
Verdict
One of the best models for coding and complex instruction-following, but its premium pricing demands premium use cases.
Quality score
81%
Pricing
$6.00/1M in
$30.00/1M out
Speed
Balanced
3/5 speed
Context
200k tokens
Pricing at $6 input / $30 output per million tokens is significantly higher than GPT-4o ($2.50/$10). Best accessed via Anthropic API or Amazon Bedrock. Claude 3.5 Sonnet (October 2024 version) supersedes the June 2024 release with improved performance.
Anthropic's new Mythos-class flagship and the most capable coding model anyone can use — 80.3% SWE-Bench Pro, an 11-point jump over Opus 4.8. 1M context, 128K output, native parallel subagents. Released June 9, 2026.
Verdict
New global #1 — 80.3% SWE-Bench Pro, the most capable model generally available.
Quality score
98%
Pricing
$10.00/1M in
$50.00/1M out
Speed
Deliberate
2/5 speed
Context
1M tokens
Launched June 9, 2026 as the public, Mythos-class release. Available on the Claude API, Microsoft Foundry, and Google Vertex AI. Free for all users until June 22, 2026. Same underlying model as Claude Mythos 5, with safeguards that block specific high-risk cyber responses.
Coding leaderSWE-Bench Pro #1Mythos-classParallel subagentsAgenticLong contextPremiumNew
Best for
The hardest coding tasks, autonomous multi-step agents, and frontier-grade reasoning
Anthropic's September 1, 2026 frontier release and the new capability ceiling for coding, agents, and scientific work. Base pricing is unchanged at $10/$50, but cache reads dropped 75% to $0.25/1M — roughly 25% cheaper on typical workloads and up to 45% cheaper on agentic ones. 1M context, 128K output, adaptive thinking always on.
Verdict
New frontier leader — better than Fable 5 on every published benchmark, and cheaper to run.
Quality score
98%
Pricing
$10.00/1M in
$50.00/1M out
Speed
Deliberate
2/5 speed
Context
1M tokens
Released September 1, 2026 alongside Claude Mythos 5.1, the first update to the Mythos-class line since Fable 5 on June 9. API ID claude-fable-5-1; generally available on the Claude API, Amazon Bedrock, Google Cloud, and Microsoft Foundry. Published launch numbers (Fable 5.1 / Fable 5 / Opus 5 / GPT-5.6 Sol): Terminal-Bench-Science 0.1 52.6 / 24.7 / 29.0 / 22.4; Terminal-Bench 4.0 55.8 / 42.0 / 52.3 / 37.3; CursorBench 3.2.0 73.4 / 70.5 / 70.0 / 67.2; AutomationBench 31.4 / 17.1 / 26.9 / 19.6; OSWorld 2.0 strict 41.7 / 36.1 / 39.6; Humanity's Last Exam (no tools) 60.9 / 57.8 / 56.6; GDPval-AA v2 1853 / 1723 / 1824 / 1711. GDPval-AA v2 is rescaled from the v1 numbers quoted on the Fable 5 page and is not directly comparable to them.
Pricing moves, ranking shifts, and capability updates.
New ModelMar 27, 2026
Anthropic: Claude Sonnet 4.5 — added to UseRightAI
Anthropic: Claude Sonnet 4.5 (Anthropic) is now indexed. It supersedes Claude 4 Haiku. A dependable mid-tier Claude model with a best-in-class context window, but output pricing limits its appeal for scale.
Claude Sonnet 4.5 costs $3 per million input tokens and $15 per million output tokens on the API, with cached input at $0.3 per million. A month of 10M input and 2M output tokens runs about $60.00 at list price, before any batch or caching discounts.
What is the context window of Claude Sonnet 4.5?
Claude Sonnet 4.5 has a 1M tokens context window, with up to 64k tokens of output per response. That is the total of prompt plus response the model can hold in one request.
What is the knowledge cutoff of Claude Sonnet 4.5?
Claude Sonnet 4.5's training data runs through July 31, 2025, and the model was released on September 29, 2025. For anything after that date it needs web search or documents in the prompt.
What is Claude Sonnet 4.5 best for?
Claude Sonnet 4.5 is best for production applications that need claude's nuanced writing and reasoning without the latency or cost of opus-class models.. It is a strong fit when that workflow matters more than the tradeoffs around balanced pricing and balanced speed.
When should I avoid Claude Sonnet 4.5?
You need high-volume text generation on a tight budget, or require native image generation or multimodal output capabilities.
What is a cheaper alternative to Claude Sonnet 4.5?
GPT-5.1-Codex-Max (OpenAI) at $1.25/1M/1M input against Claude Sonnet 4.5's $3.00/1M/1M — roughly 38% less per token all in. The strongest choice for serious software engineering work, provided you can absorb the output-side pricing. Compare it first if Claude Sonnet 4.5's pricing is the thing stopping you.
What is a faster alternative to Claude Sonnet 4.5?
Claude 3.5 Sonnet — balanced against Claude Sonnet 4.5's balanced, with 200k tokens of context. Worth the swap when response time is what your users notice rather than the last few points of reasoning depth.
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