Briefly. Anthropic released Claude Opus 5.5 on September 22, 2026. The model is designed for long-running agentic coding and professional work with documents and tools. Claude API pricing is $4 per 1M input tokens and $20 per 1M output tokens; cache reads cost $0.20. Anthropic estimates the typical task cost at roughly 40% lower than Opus 5 thanks to the pricing and lower token usage. This is the vendor’s claim, not a guarantee of savings in every workflow. Anthropic announcement, model documentation.
An article for engineering leaders, CTOs, and teams choosing a model for code, analytics, and AI agents. Facts and pricing were verified on September 22, 2026. It covers the published capabilities, pricing, and verification process; the comparison does not replace your own test on a real task set.
Contents
- What Claude Opus 5.5 is
- What changed versus Opus 5
- Claude Opus 5.5 pricing and budget planning
- What the benchmarks show
- Where to use the model
- Limitations and safety
- Availability and API
- Migrating from Opus 5
- How to test the model on your own tasks
- Frequently asked questions
- How AgentSunrise helps evaluate Opus 5.5
- Conclusion
What Claude Opus 5.5 is
Claude Opus 5.5 is Anthropic’s new model in the Claude 5.5 family, with API ID claude-opus-5-5. The company recommends it as a starting point for most workloads, especially long-running programming and analysis tasks. For more demanding scenarios, Anthropic suggests comparing it with Claude Fable 5.1 on your own tests. Model lineup overview.
An “agentic” task here means not a single chat reply, but a sequence of file reads, tool calls, edits, checks, and fixes. The quality of this work depends on both the model and the environment: permissions, tools, tests, context size, and stop conditions. So a strong result on a public leaderboard does not mean any agent can be immediately given access to production data.
Opus 5.5 has a context window of 1M tokens, a maximum standard output of 128K tokens, text and image input, and text output. Adaptive reasoning is always on; depth can be adjusted with the effort parameter, with the default set to medium. The documented knowledge cutoff is June 2026. The model should get fresh facts from trusted sources, not from parameter memory. Anthropic specification.
What changed versus Opus 5
| Parameter | Claude Opus 5 | Claude Opus 5.5 | What to verify in your environment |
|---|---|---|---|
| Input, $/1M tokens | 5 | 4 | Share of uncached context |
| Output, $/1M tokens | 25 | 20 | Response volume and reasoning |
| Cache read, $/1M tokens | 0.50 | 0.20 | System context repeatability |
| 5-minute cache write, $/1M tokens | 6.25 | 5 | Prompt refresh rate |
| Typical task cost | baseline | estimated by Anthropic to be about 40% lower | Actual tokens and repeat calls |
| Generation speed | baseline | Anthropic says more than 30% higher | End-to-end latency |
The prices, cache terms, and wording about typical cost are taken from the announcement and the model page. The savings percentage refers to Anthropic’s test workloads and includes changes in token count per task. It is not equal to a simple tariff difference: input and output pricing dropped by 20%, while cache read pricing dropped by 60%.
The improvement is also noticeable in scenarios where maintaining a long chain of work matters. Anthropic describes stronger results in agentic coding, computer use, and professional analytics. The company also notes clearer communication: the model more often puts conclusions before details and follows specified writing rules. This is useful for review, but the response style should be checked separately from action correctness. Anthropic announcement.
Claude Opus 5.5 Pricing and Budget Planning
Base API Pricing as of September 22, 2026: $4 per million input tokens, $20 per million output tokens, and $0.20 per million tokens read from cache. Cache writes for five minutes cost $5, and one-hour cache writes cost $8 per million tokens. Fast mode is priced separately: $8 per million input tokens and $40 per million output tokens; Anthropic says it is up to 2.5x faster than the standard mode. A 50% discount on input and output is available for batch processing. Model Page, announcement.
Example calculation, not the company’s bill: one call with 100,000 standard input tokens and 10,000 output tokens costs (100,000 / 1,000,000 × $4) + (10,000 / 1,000,000 × $20) = $0.60 without cache or paid tools. If 80,000 input tokens are actually read from cache and 20,000 are processed as standard input, that portion costs $0.016 + $0.08; with the same 10,000 output tokens, the total example is $0.296. The actual bill depends on caching policy, retention period, cache misses, and pricing for other calls.
For budgeting, the more important metric is cost per accepted result, not the price per million tokens. Suppose an agent made ten attempts, and six passed tests and review. Then the total cost of all ten attempts should be divided by six, while also accounting for the human time spent on review and fixes. A cheap single call can turn into an expensive workflow if the agent repeats work often.
| Total Cost Component | What to Record in the Log |
|---|---|
| Tokens | input, output, cache read, cache write, retries |
| Tools | paid calls to search, computation, and external services |
| Time | latency to a verified result, not just the first response |
| Review | reviewer minutes, test runs, fixes |
| Risk | share of tasks that roll back, violate boundaries, or contain a factual error |
What the Benchmarks Show
Anthropic reports for Opus 5.5 66.4% on Terminal-Bench 4.0, 54.4% on FrontierCode v1.1 and 40.0% on AutomationBench under the company’s stated settings. In its table, Opus 5 scores 52.3%, 48.0%, and 26.9%, respectively. On GDPval-AA v2.1, Opus 5.5 reaches 1846 Elo versus 1708 for Opus 5. These numbers refer to different task sets and do not add up to a single “intelligence percentage.” Anthropic’s Methodology and Footnotes.
Three details matter for interpretation. First, the effort settings differ: most Opus 5.5 results are reported at max, while Terminal-Bench is at xhigh. Second, agent performance depends on tools and the test environment. Third, the vendor itself warns that small benchmark differences are less predictive of real-world performance. So the table is useful for choosing candidates to test, but a purchasing decision requires its own task set. Anthropic Announcement.
Early-user results provide another signal, but these are case studies selected by the vendor for publication, not an independent representative sample. Anthropic describes a large codebase migration and long work sessions. These results should not be turned into a timeline promise for every project: code complexity, test quality, tool access, and completion criteria all vary. Cases in the Announcement.
Where to Use the Model
Long-Horizon Coding
Opus 5.5 is a logical candidate for migrations, multi-repo refactoring, error analysis, and patch review. These tasks require reproducible tests and a clear definition of done. Give the agent a limited branch, a set of allowed commands, and a diff log. Acceptance should include tests, human review of the changed areas, and checks of third-party dependencies. The public FrontierCode result shows potential, but it does not confirm the quality for any specific repository. Anthropic.
Document and Knowledge Work
For analyzing reports, contracts, and mixed corporate files, the model can prepare a summary, a discrepancy table, and a list of questions. Each output should cite a passage from the source document. In financial and legal workflows, the reviewer must be able to trace the conclusion back to the source. A one-million-token context window helps load large materials, but it does not eliminate the need to verify search completeness and citation accuracy. Specification.
Cross-App Agent Workflows
The model can be evaluated on tasks where an agent reads incoming requests, checks a record in the system, and prepares a draft action. In the first stage, keep posting, payments, permission changes, and message sending under human control. Evaluation criteria include correct data selection, no unnecessary actions, time to completion, and the share of cases that require intervention. AutomationBench tests a similar class of scenarios, but a business process with your own data may produce a different picture. Test Description in the Announcement.
Limitations and Safety
Anthropic says Opus 5.5 is more resistant than Opus 5 to prompt injection under the published test conditions and performs better on its behavioral audit. At the same time, the company explicitly acknowledges the limitations of such evaluations. Prompt injection is an attacker’s instruction hidden inside external content that the agent mistakenly treats as a command. Model-level defenses reduce risk, but they do not replace tool isolation, least-privilege access, and confirmation of irreversible actions. Announcement and Protection Description.
Anthropic included the detailed test conditions and boundaries in the Opus 5.5 system card. For a practical defense framework for external content, see the separate analysis of multimodal prompt injection.
Because Anthropic considers the model comparable to Claude Mythos 5.1 in biology and cybersecurity, special organization verification programs apply to some research access. Do not assume that a capability shown in a public benchmark is automatically available to every account and in every environment. Anthropic announcement.
Operational limits are also significant. One million context tokens is maximum capacity, not proof of the same accuracy at every position in a long file. Higher effort can increase cost and latency. Models with the same name on different cloud platforms have different access, quotas, and settings. Before launch, check what data you can send to the provider, the processing region, and retention rules in your contract and console.
Availability and API
According to Anthropic, Claude Opus 5.5 is available in Claude and on Claude Platform, as well as through Amazon Web Services, Google Cloud, and Microsoft Azure. In the Claude API, the name used is claude-opus-5-5. The model page shows active status and a release date of September 22, 2026. Actual access, quotas, and region should be checked in the specific account. Announcement, documentation.
Do not mix up API pricing and a Claude subscription. The subscription is limited by plan rules and usage periods, while the API is billed by tokens and separate modes. Anthropic has announced higher five-hour limits for Pro, Max, Team, and some Enterprise plans, but that does not mean unlimited access. Anthropic announcement.
Migration from Opus 5
Simply replacing the model string can break an existing agent. Anthropic guide lists four changes: thinking cannot be turned off; forced tool use returns an error; thinking blocks are tied to the model and the conversation; the early computer use tool version computer_20251124 is not accepted in the Claude API and Google Cloud. The appearance of intermediate responses between tool calls also changes: user text may end up in a thinking block, empty when the default display value is used.
Migration steps:
- Set a baseline. Save a set of real, anonymized prompts, Opus 5 responses, tokens, time, errors, and accepted results.
- Check the parameters. Find in the code where thinking is disabled, forced tool use, block transfer between conversations, and the older version of computer use are used.
- Run a paired test. Run the same tasks in the same environment on the old and new model, recording
effort. - Test streaming interfaces. If the application shows intermediate progress to the user, make sure the block change does not leave a blank screen.
- Roll out gradually. Start with a small share of reversible tasks and define the rollback condition for Opus 5 in advance.
How to test the model on your own tasks
A practical test set should include more than just successful examples. Take typical tasks, difficult cases, incomplete inputs, and attempts to override instructions inside documents. Group them by impact: low-cost high-volume operations, complex research, and actions with high damage if they fail. For each case, record the expected artifact, acceptance criteria, and prohibited actions.
If the team is choosing a model for multiple processes, use unified criteria and a model router for business as an additional architecture plan. Having a router does not, by itself, reduce the bill: savings must be shown by measuring the full chain.
Minimum evaluation protocol: the same input and tools for both models; at least one blind review where the evaluation is subjective; automated tests for code; source links for analytics; full accounting of tokens and human time. The number of cases depends on process diversity, not a magic threshold. If the set is small, publish that as a limitation rather than a confident generalization.
| Question | Acceptance metric |
|---|---|
| Does the agent do the right work? | share of accepted results based on pre-recorded criteria |
| How much does the final result cost? | cost of all attempts / number of accepted results |
| Does it fit the process? | time to an accepted result, including review |
| Is the risk manageable? | extra tool calls, rollbacks, permission violations |
| Does the quality hold up? | repeat runs across different input types |
The method of this article is a comparison of Anthropic's announcement, official specifications and published benchmark conditions as of the verification date. We did not conduct our own model comparison and do not present the vendor's figures as a client result. This matters because agent settings, task mix, and the cost of evaluation change the conclusion.
Frequently asked questions
When was Claude Opus 5.5 released?
Anthropic lists the release date as September 22, 2026. Availability in a specific cloud and account is checked separately. Source.
How much does the Claude Opus 5.5 API cost?
The base price is $4 per million input tokens and $20 per million output tokens; cache reads cost $0.20 per million. Fast mode and long-term cache writes are priced differently. Source.
What is the model name in the API?
The Claude API identifier is claude-opus-5-5. Check its support and quotas in your project. Source.
Is Opus 5.5 really 40% cheaper than Opus 5?
This is Anthropic’s estimate for typical tasks, based on token counts and the new pricing. Standard input and output pricing has been reduced by 20%; the actual savings for a specific team depend on cache usage, retries, and effort mode. Source.
Do everyone need to switch from Opus 5?
There is no one-size-fits-all answer. Before migrating, check for API incompatibilities and compare accepted-result rates, cost, and latency on your own tasks. API Changes.
Is the model suitable for an autonomous agent?
It is a good candidate for testing, but agent authority is determined by the system. Limit permissions, verify external data, log actions, and require human approval for irreversible operations.
How AgentSunrise helps evaluate Opus 5.5
AgentSunrise can connect model selection to a verifiable company process:
- describe one process, its current cost, data sources, and acceptance criteria;
- prepare a limited agentic or RAG setup for working with code and internal knowledge;
- test the model on typical and complex tasks, accounting for tokens, review time, and errors;
- set up the integration, controlled launch, team training, and support for the chosen process.
The first step is to choose one reversible scenario and document its baseline, data, constraints, and acceptance criteria. Discuss the task.
Conclusion
Claude Opus 5.5 combines lower API pricing with strong published results in agentic coding and professional work. For businesses, the decision to switch depends on whether the model delivers more accepted results on your own tasks at an acceptable cost, latency, and risk. Start with a side-by-side test against your current model, check API incompatibilities, and expand the agent’s permissions gradually.