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Anthropic model°

Claude Sonnet 4.5

Claude Sonnet 4.5 is Anthropic's most advanced Sonnet model, built for real-world agents and coding workflows and positioned as the mid-tier workhorse in the Claude line.

AnthropicVerified 24/09/2026Released 29/09/2025

01 / decision

Decision snapshot

Each figure sits next to the middle of the field, so it can be read as dear or cheap, wide or narrow, rather than floating on its own. Compared against the 126 models we track, not against an absolute standard.

Capability

Not measured

No published benchmark scores yet

Input / 1M tokens

$3.00

field median $0.30

Output / 1M tokens

$15.00

field median $1.25

Context

1,000K

field median 524K

02 / overview

What Claude Sonnet 4.5 is, and when to reach for it

Four questions, answered separately, because somebody arrives at one of them rather than at the top of the page.

What it is

The job it was built for, and the job it is not for.

Claude Sonnet 4.5 is a general-purpose text model tuned towards agentic work: long-running coding tasks, tool use, and multi-step workflows that have to hold together without a human checking each turn. Anthropic points to state-of-the-art results on coding benchmarks such as SWE-bench Verified. It is not a specialist retrieval or embedding model, and it is not the cheapest option if the job is bulk classification or short summarisation.

When it arrived, and when to use it

Where it sits in its line, and when a sibling is the better pick.

Claude Sonnet 4.5 first appeared on 29 September 2025, sitting in the middle of Anthropic's range between the small Haiku models and the larger Opus tier. It is the right pick when you want strong coding and agent behaviour at Sonnet economics rather than Opus economics. It is the wrong pick for high-volume, low-difficulty calls where a smaller Claude will do the same job for less.

How you reach it

The API, the apps it powers, and what its limits let you do.

Claude Sonnet 4.5 is reached through the Anthropic API and powers the Claude consumer apps and Claude Code. It takes text, images and files in the same request, so you can hand it a screenshot, a PDF and a prompt together. The context window runs to a million tokens, which is enough to hold an entire codebase or a long document set in one pass, and output can stretch to tens of thousands of tokens for large refactors or full drafts.

Why it matters

What changes because this exists, or why it does not.

Claude Sonnet 4.5 makes long-context agent work practical at a mid-tier price: tasks that previously meant chunking a repository, or reaching for the top-tier model, now fit in a single call. For teams building coding agents or document-heavy workflows, that removes a lot of orchestration code. If your workload is short prompts and short answers, nothing here changes much.

Follows Claude Sonnet 4, and is the newest in its line. See the whole line.

03 / evidence

How much of this is verified

Split by category, so a strong number never hides a thin evidence base. Verified means we read it on the benchmark's own published results; a provider's claim about its own model is shown and labelled rather than dropped.

No published benchmark scores for this model yet.

We publish a score only where we can link the result to where it was published. Until a benchmark result for this model exists in a source we read, this section stays empty rather than being filled with a provider's marketing figure.

How we decide what counts as evidence

04 / ledger

Benchmark ledger

Every published row, grouped by category, each compared with the best published score on the same benchmark. 'Is 64% good' is a question nobody can answer; '26 points behind the leader' is one anybody can.

Nothing in the ledger yet.

Each row here carries a score, the benchmark it came from, what the leading model scored on the same test, and a link to the published result. Rows appear as results are published and read.

How we decide what counts as evidence

05 / capability

Capability shape

Where this model is strong, and against how many peers. Ranks are against models with evidence in that category, not against everything we track: ranking against models nobody tested would rank who published, not who is better.

No category scores to shape yet.

A category score is the weighted mean of the benchmarks published for it. With no published rows there is nothing to average, and an empty chart drawn at zero would say something false.

How we decide what counts as evidence

06 / cost

What it costs

List API rates as last read from the provider, with the source on every row, plus every change we have recorded since we started tracking it.

Claude Sonnet 4.5 API pricingSurge45°
ChargePriceUnitRead onSource
Input$3.00per 1M tokens2026-09-24Check
Output$15.00per 1M tokens2026-09-24Check

Claude Sonnet 4.5 sits in the mid band of the market: clearly more than the small, fast models from any provider, clearly less than the frontier tier including Anthropic's own Opus models. For most agent and coding workloads it is the sensible default, and you would only move up when a task genuinely fails at this level.

What a month costsSurge45°
WorkloadInput / monthOutput / monthCost
A small product team20M tokens5M tokens$135.00
A busy support assistant200M tokens40M tokens$1,200.00
A document pipeline1000M tokens100M tokens$4,500.00

List API rates, no caching and no batch discount, which both providers offer and which change the answer a great deal. Treat these as the ceiling, not the bill.

07 / specs

Specifications

As listed by the provider's own catalogue and re-read every few hours. Anything absent is absent there too.

SpecificationSurge45°
Context window1,000,000 tokens
Maximum output64,000 tokens
Modalitiestext, image, file
Released29/09/2025
StatusCurrent
Catalogue identifieranthropic/claude-sonnet-4.5

08 / lineage

Lineage

What this model replaced, what replaced it, and what else its provider has in the field.

Also from Anthropic

09 / line

The line

Every model in this family in release order, so a page from eight months ago says in one glance that two newer ones exist.

Came before

← Claude Sonnet 4

Came after

Nothing newer in this line yet.

  1. 01Claude Sonnet 422/05/2025
  2. 02Claude Sonnet 4.529/09/2025

Ordered by release date and worked out from the naming, so a new member slots in as soon as its page exists. A retired model keeps its page and its place in the line.

10 / notes

Our notes

What this model changes for a brand trying to be cited in AI answers, and every change we have logged since it launched.

What it changes for you

Claude Sonnet 4.5 is the model behind most Claude conversations, so it is doing a large share of the work when a buyer asks Claude to compare tools in your category. Its very large context window means it can pull in and weigh long source documents, so depth and structure in your public material matter more than keyword density. If your product pages, docs and comparison content read cleanly as evidence, you are more likely to be the vendor it names.

Where buyers meet this model

Buyers meet Claude Sonnet 4.5 in the Claude apps on web, desktop and mobile, where it is the default model most people talk to, and in Claude Code when their engineers are working. Developers meet it through the Anthropic API and the cloud marketplaces that resell it. Any answer a prospect gets in Claude about your category is likely coming from this model.

Change log

Nothing published here yet. Changes appear within hours of a provider announcing them.

11 / questions

Questions

The things people ask about this model, answered from what is on this page rather than from anywhere else.

What is Claude Sonnet 4.5 best at?
Real-world agents and coding workflows. Anthropic positions it as its most advanced Sonnet model, with state-of-the-art performance on coding benchmarks such as SWE-bench Verified.
Can Claude Sonnet 4.5 read images and files?
Yes. It accepts text, images and files, so you can combine a document, a screenshot and a written instruction in a single request.
When should I use a different Claude model?
Use a smaller Haiku model for high-volume, low-difficulty calls where cost per request dominates, and step up to Opus only when a task genuinely fails at the Sonnet level.
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Is Claude Sonnet 4.5 recommending you?

Models change what gets cited. We measure whether AI answers name your brand or your competitors across every assistant, and show you what to change.

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