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
| Rate | Price | Unit |
|---|---|---|
| Input | — quoted on request | — |
| Output | — quoted on request | — |
Prompt caching is supported, so repeated prefixes bill below the listed input rate. This model is not provisioned yet; the rate is quoted on request.
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
Research synthesis
High-stakes drafting
Comparison
Compare against anything →| Attribute | Claude Opus 4.5 | o4 | Claude Sonnet 4.5 |
|---|---|---|---|
| Context window | 200K | 300K | 1M |
| Input price | R0.00 | R0.00 | R0.00 |
| 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. Blank cells are facts the supplier does not publish, not zeroes.
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 R0.00 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.
No. Claude Opus 4.5 is served through its provider's API only; the weights are not published, so self-hosting is not an option.
Prompt and response share one window: Claude Opus 4.5 accepts up to 200K tokens in total, so a long input leaves less room for the answer. The median across reasoning models is 200K. Recall is strongest well inside the limit. Test at your real prompt depth before relying on the ceiling.
o4 is the closest neighbour in the catalogue, with 300K of context at R0.00 per 1M tokens in. Put both in a comparison before wiring a fallback chain, so the trade-off is a decision rather than a default.