Anthropic wants developers to use Claude and its family of tools to handle complete coding tasks. The company introduced Claude Opus 5.5 on Tuesday to span more of the software application development lifecycle: from design specification creation through debugging to code generation and testing.As the first release in a new family of Claude 5.5 models, Anthropic says that Claude Opus 5.5 performs at the level of Claude Fable 5.1 on “most work” tasks and costs around 40% less to run than Opus 5. GitHub chief product officer Mario Rodriguez is quoted in Anthropic’s launch announcement on exactly where software engineers sit today with frontier models for code automation. He said that developers want agents.“In our testing [of Claude Opus 5.5] across GitHub Copilot CLI and VS Code, Claude Opus 5.5 used among the fewest tokens and steps we measured. In VS Code, it solved more terminal tasks than Opus 5 in less than half the steps. More than making individual tasks more efficient, it’s making developers’ bigger projects more achievable,” says Rodriguez.Where does Claude Opus 5.5 get its power from?Anthropic explains that the Claude 5.5 family’s expanded full-lifecycle capabilities were developed under an established set of practices.These practice elements include extensive alignment testing (model evaluation processes put in place to make sure actions and outputs closely match human values and intended goals), pre-release evaluation by outside organizations, and safeguards for high-risk areas such as cybersecurity and biology.The organization says that on its most comprehensive alignment test, Opus 5.5 is the strongest-performing model tested to date, with particular improvements in several behaviors that contributed to recent cybersecurity incidents (e.g., biased reasoning, attempting to escape a sandbox, and others).Independent SRE & AI reliability architect Akash Thakur tells The New Stack that Anthropic’s work getting its model to complete whole coding tasks is impressive, but “getting it to know when it hasn’t” is the harder problem developers need to think about.“Models working at the level of Claude Opus 5.5 are genuinely good at breaking a project into small, finishable pieces — and that’s the real unlock, because momentum on software comes from finishing things, not starting them,” Thakur says. “…But ‘completed’ and ‘correct’ aren’t the same thing. The task that looks done and completed is exactly the one that often costs the team later, so the win isn’t removing the human — it’s moving them from writing the code to verifying it.”“Models working at the level of Claude Opus 5.5 are genuinely good at breaking a project into small, finishable pieces …but ‘completed’ and ‘correct’ aren’t the same thing.”Suggesting that we are now witnessing a “higher bar for more capable models”, Anthropic said that models that could fully automate AI research itself should meet a higher safety standard. The company noted that as AI becomes more capable, public policy should play a larger role in making sure these systems are safe. Its recent work with Accenture is offered as an example of how Anthropic is building the infrastructure to support this.Sprawling jobs: codebase-wide migrations & auditsGetting more specific, Anthropic has claimed Opus 5.5 is “particularly good” at long, sprawling jobs like codebase-wide migrations and audits. An early tester said it audited and fixed a 200,000-line codebase in under three hours, while Opus 5 took over 20 hours and used 2.5x as many tokens. “In an internal test, we asked Opus 5.5 and Fable 5.1 to translate HAProxy, widely used software that balances web traffic loads across servers, from C into Rust. Both rewrites passed nearly all of HAProxy’s own regression tests, but Opus 5.5 finished in 9.5 hours compared to 12 for Fable 5.1, and cost 51% less,” said Anthropic in a press statement.Field CTO for the EMEA region at Coder, Eric Paulsen, tells The New Stack that he is happy to hear Claude Opus 5.5 is becoming more holistically capable, but he’s “not surprised” because AI is “eating the software delivery chain end to end” today.“Despite the efficiencies showcased in Opus 5.5, the moment an agent can reliably finish real work, the question stops being whether the model is good enough and becomes where you’re letting it run,” Paulsen says. “Kicking off a Claude Code session on a laptop that can be compromised, stolen, or simply run out of compute is not an engineering environment; capable agents need dedicated, governed infrastructure with the same guardrails, secrets handling, and observability a developer would demand of any other production workload. As we’ve seen here with Anthropic’s own work, firms need to underline testing and safeguard procedures for launches of this kind,” he added. Anthropic assures users that external testing has been conducted and that the model was tested before release by Frontier Design and METR. When established safeguards for Opus 5.5 intervene, requests “fall back to another model transparently,” meaning developers may not see which model actually handled a given call.In cybersecurity, users can identify and fix bugs in their code, but most cybersecurity tasks will be re-routed to Opus 4.8. Requests flagged by biology and frontier LLM development classifiers will be re-routed to Opus 5. Vetted organizations can apply to Anthropic’s Life Sciences Verification Program to use Opus 5.5 for biology research, and the company says it will expand its Cyber Verification Program in the coming weeks.The developer’s terminal prompt has fundamentally changedHasData co-founder, Sergey Ermakovich, tells The New Stack that his work as a web scraping specialist for data pipelines and AI means he sees zen-like, one-brick-at-a-time logic in what Anthropic has done. “The biggest change — and it’s a trend that will have driven Anthropic’s design and development aspirations for Claude Opus 5.5 — is that the terminal is no longer just a place where a developer pastes generated code,” Ermakovich says. “The terminal now becomes part of the model’s workspace.”Because a model can run commands, inspect failures, modify files, and verify the result, Ermakovich suggests it can “close the loop” instead of handing unfinished work back to an engineer. “That makes small complete tasks much more valuable. Fix one failing test, update one dependency, migrate one endpoint, verify it, then move to the next task,” he adds.“The terminal is no longer just a place where a developer pastes generated code — the terminal now becomes part of the model’s workspace.”Commenting on the development of this model as part of Anthropic’s approved corporate messaging, John Ruelas, staff software engineer at Ramp, said that verbose, hard-to-follow output has been his “biggest frustration” with frontier models, but “Claude Opus 5.5 fixes it” for him.He noted that it writes like a good colleague and follows his company’s writing rules. A design spec came out usable with very minimal edits, and when it rewrote one of his prompts, he preferred its version to his own. When it optimized the team’s test suite, he could follow its reasoning easily and “shipped the change with confidence.”We’re so done with the autocomplete eraVice president of AI strategy at Abbyy, Maxime Vermeir, tells The New Stack that the more lifecycle-wide Claude Opus 5.5 features on offer show that “we’re done with the autocomplete era” for basic code automation tools.“Anthropic’s elevation here reflects the fact that it used to be thought of as marvelous if AI could complete a developer’s next line of code, but today the expectation is that you hand it a whole Jira ticket and that it gets done,” Vermeir says. “But despite the power on show with Claude Opus 5.5, the question remains as to how much these newer models will actually understand what ‘done’ means, as often it seems they have a desire to keep burning tokens by offering you yet another thing it didn’t quite do right.”Opus 5.5 also “communicates more naturally” than prior models, with early testers finding its writing clearer and easier to follow, making it a better work partner over long sessions.Costed out lower than Opus 5, Opus 5.5 is priced at $4 per million input tokens and $20 per million output tokens (20% less than Opus 5), and Anthropic has cut cache read prices by 60% for token-billed usage. Opus 5.5 also needs fewer tokens for higher-quality work and generates output more than 30% faster than Opus 5.The post Claude Opus 5.5 wants to finish your coding tasks, not just start them appeared first on The New Stack.