Anthropic's model for the most demanding reasoning and long-horizon agentic work. 1M-token context window, up to 128K output tokens, adaptive thinking that is always on.
The most capable model of Anthropic's Opus 4 series. State of the art on long-horizon agentic work, coding and knowledge tasks, with a 1M-token context window at standard pricing.
Anthropic's current Opus model for long-running agentic coding and knowledge work. 1M-token context window, up to 128K output tokens, adaptive thinking that is always on.
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About Claude Opus 4
TL;DRAs of September 23, 2026
Claude Opus 4 is a model by Anthropic in the Text & chat category. Claude Opus 4 is currently not available on Railwail. The context window holds 200,000 tokens, and one response can be up to 32,000 tokens long. Newer version: Claude Opus 4.8.
Background
About Anthropic
Founded 2021 · San Francisco, USA
Anthropic was founded in 2021 by Dario Amodei (CEO) and Daniela Amodei (President) after both left OpenAI together with several senior researchers including Tom Brown, Sam McCandlish and Jared Kaplan. The company is structured as a Public Benefit Corporation focused on AI safety research and the deployment of reliable, interpretable, and steerable AI systems. Anthropic's foundational research includes Constitutional AI (2022), Sparse Autoencoders for interpretability, and the influential paper 'Scaling Laws for Neural Language Models'. The Claude model family launched in March 2023, with major releases including Claude 2 (2023), Claude 3 family (Haiku, Sonnet, Opus in March 2024), Claude 3.5 Sonnet (June 2024), Claude 3.7 Sonnet with extended thinking (February 2025) and Claude 4 family (May 2025). Investors include Google ($3B+), Amazon (committed up to $8B), Spark Capital and Lightspeed, with total funding exceeding $15 billion and a 2025 valuation above $60 billion. Anthropic also publishes Responsible Scaling Policies and is a leading voice in ASL safety levels.
Claude Opus 4 is Anthropic's flagship reasoning model released in May 2025, optimized for agentic coding, multi-hour autonomous tasks and deep research. It uses a decoder-only Transformer architecture trained on a diverse multilingual corpus including curated web data, code repositories, books and licensed datasets, with an explicit data cutoff of March 2025. The model is post-trained with a combination of Reinforcement Learning from Human Feedback (RLHF), Constitutional AI (CAI) and Reinforcement Learning from AI Feedback (RLAIF), where a constitution of principles guides self-critique and revision. Opus 4 supports two operating modes: standard fast responses and extended thinking mode in which the model produces an internal reasoning trace before its final answer. Tool use, parallel tool calling and long-running agent loops are first-class behaviours, with native support for Anthropic's computer use API (screen control, mouse, keyboard). Vision grounding was trained jointly with text so that images, charts and PDFs can be reasoned about within the same context window. The model was evaluated against ASL-3 safeguards under Anthropic's Responsible Scaling Policy and shipped with classifier-based safety filters covering CBRN, cyberweapons, and child safety.
State-of-the-art coding performance on SWE-bench Verified (~72% on agentic eval at launch)
Extended thinking mode for chain-of-thought reasoning on hard math and science problems
Sustained multi-hour autonomous coding sessions with tool use and self-correction
Native computer use: screenshots, mouse and keyboard control of a virtual desktop
200K token context window with strong needle-in-haystack recall across the full window
Multimodal input: text, images, PDFs, charts and diagrams in a single prompt
Parallel tool calling and stable multi-turn agent loops
Constitutional-AI alignment with low refusal rate on benign questions
Strong instruction following including XML tags, schemas and strict JSON output
Multilingual fluency across English, German, French, Spanish, Japanese, Chinese and more
Best for: complex coding agents, research synthesis from large document sets, regulated-industry copilots, autonomous workflows.
Training & license
Pretrained on a curated mix of publicly available internet text, licensed third-party data, code from public repositories and human-generated conversations. Anthropic does not disclose exact token counts but the corpus is multi-trillion tokens with heavy filtering for quality, deduplication and copyright. The data cutoff is March 2025. Post-training uses RLHF, Constitutional AI and RLAIF on a much smaller, high-quality set of human-rated comparisons and synthetic constitutional critiques.
License: Proprietary commercial license via Anthropic API, Amazon Bedrock and Google Vertex AI. Commercial use permitted under Anthropic's Usage Policy.
Safety testing: Deployed under Responsible Scaling Policy ASL-3 safeguards with constitutional classifiers, automated red-teaming, third-party evaluations by METR and Apollo Research, and a Bug Bounty programme.
Known limitations
No native audio or video input
Knowledge cutoff March 2025; lacks real-time information without tool use
Higher latency and cost than Sonnet/Haiku tiers
Will refuse some legitimate red-team and security research prompts
Proprietary commercial license via Anthropic API, Amazon Bedrock and Google Vertex AI. Commercial use permitted under Anthropic's Usage Policy.
Catalog entry updated
September 23, 2026
Tags
flagship
reasoning
agentic
07
Example prompts
Examples from the Railwail catalog. They were not generated live on this page.
Deep Research
Analyze the economic implications of universal basic income. Consider arguments from both proponents and critics, citing specific pilot programs.
Show example answer
UBI has been tested in several notable pilot programs with mixed but informative results. Finland's 2017-2018 experiment gave 2,000 unemployed citizens €560/month and found improved well-being and modest employment gains, though critics noted the small sample size. Stockton, California's SEED program ($500/month to 125 residents) showed recipients were more likely to find full-time employment than the control group, challenging the 'laziness' argument. Proponents argue UBI provides a safety net that encourages entrepreneurship and addresses job displacement from automation. Critics counter that large-scale funding—estimated at $3+ trillion annually for the US—would require massive tax restructuring, and inflationary pressures could erode the benefit's purchasing power.
Agentic Planning
I need to migrate a monolithic Django app to microservices. Create a step-by-step migration plan with risk mitigation strategies.
Show example answer
Phase 1 (Weeks 1-4): Audit and map all domain boundaries in your monolith. Identify bounded contexts using domain-driven design principles. Document all inter-module dependencies and shared database tables.
Phase 2 (Weeks 5-8): Implement the Strangler Fig pattern—deploy an API gateway that routes traffic to either the monolith or new services. Extract the least-coupled domain first (often authentication or notifications) as a proof of concept.
Phase 3 (Weeks 9-16): Gradually extract remaining services. For each: create a dedicated database, implement an anti-corruption layer for data sync, and use event-driven communication (Kafka/RabbitMQ) instead of synchronous calls.
Risk mitigation: Run services in parallel with the monolith ('dark launching') before cutting over. Implement distributed tracing (Jaeger/Zipkin) from day one. Keep rollback paths open by maintaining the monolith until each service proves stable in production for at least 2 sprint cycles.
Claude Opus 4 is a model by Anthropic in the Text & chat category. It is listed on Railwail but cannot be run at the moment.
How much does Claude Opus 4 cost on Railwail?
Claude Opus 4 cannot be run on Railwail at the moment, so there is no current price. Available alternatives with prices are listed further down this page.
What is the context window of Claude Opus 4?
The context window of Claude Opus 4 holds 200,000 tokens. One response can be up to 32,000 tokens long.
How fast is Claude Opus 4?
There are not enough measured runs of Claude Opus 4 on Railwail yet to state a run time. It depends on the input, the settings and the load at the provider.
Is Claude Opus 4 better than Claude Opus 4.8?
That depends on the task. Claude Opus 4 (Anthropic) and Claude Opus 4.8 (Anthropic) are both models in the Text & chat category. The comparison page shows their prices and specifications side by side.
