Claude Opus 4.5
anthropic/claude-opus-4.5Anthropic's deepest model: frontier reasoning with the judgment for genuinely hard, open-ended work.
Model overview
Context window
200K
tokens
Input price
—
quoted on request
Output price
—
quoted on request
Weekly volume
—
tokens / week
Open weights
No
API only
Capabilities
6
of 11 tags
Description
Claude Opus 4.5 is a reasoning model from Anthropic. Webparam does not stock this model yet and can source it on request — tell us what you need it for and we will come back with availability and a price. Anthropic’s stated focus is frontier models with a safety-first identity. The weights are not published, so it is API-only.
Capabilities
- Reasoning
- Spends extra billed tokens thinking before it answers, trading latency and cost for accuracy.
- Tool calling
- Calls functions you define and returns their arguments as structured data, the basis of agents.
- JSON mode
- Constrains the response to valid JSON matching a schema you supply.
- Streaming
- Emits tokens as they are generated, so answers appear progressively rather than all at once.
- Caching
- Reuses already-processed prompt prefixes across requests, cutting input cost for repeated context.
- Vision input
- Accepts images alongside text in the prompt.
Strengths & weaknesses
Strengths
- Frontier judgment on open-ended problems
- Top-tier agentic coding
- Extended thinking with tools
Weaknesses
- Highest output price in the catalogue
- 200K context trails Sonnet's 1M
Pricing
Free| Rate | Price | Unit |
|---|---|---|
| Input | $0.00 | per 1M tokens |
| Output | — not charged | — |
Prompt caching is supported, so repeated prefixes bill below the listed input rate. Free at the point of use; fair-use rate limits apply to the free tier. Illustrative placeholder pricing.
Context window
200Ktokens
covers prompt and response together, so a long input leaves less room for the answer.
Supported features
| Feature | Support |
|---|---|
| Tool calling | Supported |
| JSON mode | Supported |
| Streaming | Supported |
| Vision input | Supported |
| Audio input | Not supported |
| Long context | Not supported |
| Open weights | Not supported |
| Reasoning | Supported |
| Fine-tunable | Not supported |
| Batch | Not supported |
| Caching | Supported |
Example use cases
Hardest agentic work
Frontier judgment on open-ended problems
Research synthesis
Top-tier agentic coding
High-stakes drafting
Extended thinking with tools
Comparison
| Attribute | Claude Opus 4.5 | o4 | Claude Sonnet 4.5 |
|---|---|---|---|
| Context window | 200K | 300K | 1M |
| Input price | $0.00 | $0.00 | $0.00 |
| Output price | — not charged | — not charged | — not charged |
| Tool calling | Supported | Supported | Supported |
| JSON mode | Supported | Supported | Supported |
| Vision input | Supported | Not supported | Supported |
| Open weights | Not supported | Not supported | Not supported |
| Prompt caching | Supported | Not supported | Supported |
Best value in each row is highlighted. Illustrative placeholder data.
Provider information
View Anthropic →Anthropic · San Francisco, United States · est. 2021
Founded by former OpenAI researchers, Anthropic pairs frontier capability with an explicit safety research agenda. 5's million-token context a favourite for repository-scale tasks.
Recent releases
Documentation
Frequently asked questions
Input is billed at $0.00 per 1M tokens, and there is no separate output charge. Prompt caching bills repeated prefixes below the listed input rate. Every figure on this page is an illustrative placeholder.