Claude Opus 5.5 vs Opus 5: What Changed, What It Costs

Anthropic released Claude Opus 5.5 on September 22, 2026. The short version: it costs less than Opus 5 and scores higher than Opus 5 on every benchmark Anthropic published for both models.

That combination is unusual. Most frontier releases ask you to trade cost for capability. This one moves both in the same direction, which makes the decision simpler than the last few launches did.

Every figure below was read from Anthropic's pricing page and Anthropic's launch announcement on September 22, 2026, the day of release.

The short answer

What Anthropic shipped

The model string is claude-opus-5-5. It is available through the Anthropic API and on AWS, Google Cloud, and Microsoft Azure.

Two behavioral notes worth knowing before you swap the string:

• Extended thinking is always on for this model. It cannot be disabled, so plan for thinking tokens in your output budget.
• Anthropic says Opus 5.5 produces output more than 30% faster than Opus 5, and that it costs around 40% less to run for the same work once speed and pricing are combined.

Anthropic also says Claude Sonnet 5.5 and Claude Haiku 5.5 are coming in the next few weeks. If you are mid-way through a model evaluation, that is worth factoring into the timing.

Pricing, side by side

List prices per million tokens, read from Anthropic's pricing page on September 22, 2026.

Anthropic also lists a fast mode for Opus 5.5 at 2x standard pricing, returning output up to 2.5x faster.

The cost math

Take a workload of 10 million input tokens and 2 million output tokens in a month, which is a realistic monthly footprint for a content pipeline doing summarization, tagging, and draft review.

• Opus 5: $50 input plus $50 output = $100
• Opus 5.5: $40 input plus $40 output = $80

A flat 20% saving before caching. The cache read rate is where it widens: $0.20 against $0.50 per million is 60% cheaper, so anything that replays a large system prompt or a big content payload on every call saves considerably more than 20%.

One caveat that cuts the other way. Thinking cannot be disabled on Opus 5.5, and thinking tokens are billed as output. Measure billed tokens on your own workload before you assume the full 20%.

Benchmarks

Anthropic's published scores for the three models most teams are choosing between. Read from the launch announcement on September 22, 2026.

The pattern is consistent: the widest margins are on agentic and terminal work, and the narrowest are on knowledge benchmarks. Terminal-Bench-Science moves from 29.0% to 58.7%, which is the single largest jump in the table. Chat-shaped evaluations move by a few points.

Read those numbers with care

Anthropic itself notes in the announcement that benchmark margins have become a less reliable guide to real-world quality, and that the gap between Opus 5.5 and Fable 5.1 is narrower in practice than the scores suggest. That is an unusual thing for a vendor to publish about its own launch, and it is worth taking at face value.

The practical read: a 10 point gap on an agentic benchmark is a reason to test, not a guarantee your workload improves. Run your own evaluation on your own tasks.

What changes in production

For most teams the migration is a one-line change from claude-opus-5 to claude-opus-5-5. The things that actually need attention:

1. Output token budgets. Always-on thinking means your output token count per request will likely rise. If you have hard caps or per-request cost alarms, recalibrate them before you switch.
2. Latency assumptions. Faster output changes timeout tuning and any streaming UI that was built around Opus 5's pacing.
3. Prompts tuned to Opus 5. Prompts that were heavily shaped around one model's quirks rarely transfer cleanly. Re-run your evaluation set rather than assuming parity.
4. Opus 5 is now legacy. It still runs at its original rate, so nothing breaks today, but legacy status is a signal about where the roadmap is going.

Using Opus 5.5 in Cosmic

Opus 5.5 is available in Cosmic, so you can point content generation at it without standing up a separate integration. Pass claude-opus-5-5 as the model to cosmic.ai.generateText(), and generation runs through the same REST API and TypeScript SDK as the rest of your content:

import { createBucketClient } from '@cosmicjs/sdk'

const cosmic = createBucketClient({
  bucketSlug: 'BUCKET_SLUG',
  readKey: 'BUCKET_READ_KEY',
  writeKey: 'BUCKET_WRITE_KEY'
})

const response = await cosmic.ai.generateText({
  prompt: 'Write a launch announcement for our September release',
  model: 'claude-opus-5-5',
  max_tokens: 1000
})

console.log(response.text)

Cosmic's model list describes Opus 5.5 as the recommended Opus for long-running agentic coding and knowledge work, with adaptive thinking always on. That matches Anthropic's own note that thinking cannot be disabled on this model, so plan for reasoning tokens on every call rather than treating them as opt-in.

One thing to plan for on any frontier model: Cosmic bills AI text generation in tokens drawn from your plan allocation, and the deduction is multiplied by the model's tier, so a frontier model draws down faster than a budget one for the same number of tokens. The current model IDs and tier multipliers are listed in the AI API reference.

Keep model config out of your source code

Anthropic has now shipped two frontier models inside a month, with two more announced for the coming weeks. If the model name is a string literal in your application code, every one of those releases becomes a pull request, a review, and a deploy.

A better shape: store the model identifier as content, read it at runtime, and change it from a dashboard.

import { createBucketClient } from '@cosmicjs/sdk';

const cosmic = createBucketClient({
  bucketSlug: process.env.COSMIC_BUCKET_SLUG!,
  readKey: process.env.COSMIC_READ_KEY!,
});

// Model routing lives in Cosmic, not in this file.
const { object: config } = await cosmic.objects
  .findOne({ type: 'ai-settings', slug: 'model-routing' })
  .props(['metadata']);

const model =
  task.needsJudgment
    ? config.metadata.escalation_model // 'claude-opus-5-5'
    : config.metadata.default_model;   // 'claude-sonnet-5'

When Sonnet 5.5 lands, someone updates a field and the change is live on the next request. No deploy, no engineering ticket, no waiting for a release window.

This is how Cosmic's AI features are built, and it is the same pattern behind the Cosmic MCP server, which lets Claude read and write your content through scoped keys rather than through your application code.

FAQ

Is Opus 5.5 cheaper than Opus 5?
Yes. $4 per million input tokens and $20 per million output tokens, against $5 and $25 for Opus 5. Cache reads are $0.20 against $0.50. Read from Anthropic's pricing page on September 22, 2026.

Is Opus 5 being retired?
Anthropic now lists Opus 5 among its legacy models, still available at its original rate. No shutdown date was announced in the release.

Should I move from Sonnet 5 to Opus 5.5?
Not by default. Sonnet 5 is $2 and $10 per million tokens, half the Opus 5.5 rate. The case for escalating is judgment-heavy and long-horizon agentic work, which is where the published margins are widest.

Can I turn off extended thinking on Opus 5.5?
No. Anthropic states that thinking cannot be disabled on this model.

What about Sonnet 5.5 and Haiku 5.5?
Anthropic says both are coming in the next few weeks. Neither has published pricing yet.

Build on infrastructure that outlives the model

The model tier you pick today has a shelf life measured in weeks. The content layer underneath it does not.

Cosmic is an AI-powered headless CMS with a REST API and a TypeScript SDK, so your content, your prompts, and your model configuration can all be edited by the people who own them rather than shipped through a deploy pipeline. See how the AI features work, or read the model comparison this post extends.

Start free on the Free plan: 1 Bucket, 2 team members, 1,000 Objects, no credit card required. If you want to talk through a specific setup, book time with our CEO.