Claude Opus 5.5: Testing Long-Running Coding and Agent Work
RouterHub Team · Updated 2026-09-23

Claude Opus 5.5 is now available on RouterHub as anthropic/claude-opus-5-5. Anthropic’s latest Opus model is designed for demanding coding, agent workflows, and professional knowledge work. Teams can evaluate it through RouterHub using the same model access path as their other AI workloads.
What changed with Claude Opus 5.5?
Anthropic positions Opus 5.5 as a step forward for long-running work across large codebases. Its release highlights codebase-wide migrations, debugging, code review, and tasks that require an agent to plan, use tools, check its work, and keep going through multiple steps. Anthropic also reports clearer writing and stronger performance on document-heavy research and analysis.
For an engineering team, the interesting question is whether those gains survive a real repository: one with existing interfaces, partial documentation, test failures, and changes that can have effects outside the file being edited. Opus 5.5 is worth testing on work where a plausible patch is only the beginning and a reviewable, tested result is the actual goal.
Claude Opus 5.5 on RouterHub at a glance
| Item | Detail |
|---|---|
| Provider | Anthropic |
| RouterHub model ID | anthropic/claude-opus-5-5 |
| Inputs and output | Text and image inputs; text output |
| Context window | 1,000,000 tokens |
| Maximum output | 128,000 tokens |
The published RouterHub model page shows the current route and calling details. Check the parameters supported by your integration before moving an existing workflow to the new model.
What do the published evaluations show?
Anthropic reports a 52.5% score on CursorBench 4.0 for Opus 5.5 at medium effort, its default setting. Its reported Opus 5 result is 46.6% at maximum effort. The 52.5% figure is the medium-effort result, not the maximum-effort score in Anthropic’s overview. CursorBench tests coding agents on ambiguous tasks that span multiple files. These are Anthropic-published results with different effort settings, not tests run by RouterHub or a guarantee for a particular codebase.
The result points to a useful evaluation target: multi-file changes where the agent must gather context, make a focused edit, and verify that the surrounding system still works. Benchmark scores help identify candidates; your own acceptance tests determine whether a model belongs in production.
Where should teams try it first?
A repository-level repair. Give the model a reproducible bug, the affected code, and the interfaces the fix must preserve. Review the proposed cause, run the tests, and check adjacent behavior.
A migration across files. Use a bounded change with a clear completion standard, such as updating a shared API or replacing a dependency. Compare the number of corrections and the quality of the final diff, not just whether the first edit compiles.
A document-heavy technical brief. Provide specifications, incident notes, and decisions that may conflict. Ask for an actionable brief that identifies open questions and traces conclusions to the supplied material.
For each task, hold the inputs, tools, and acceptance criteria steady against your current model. Record completed-task quality, review effort, elapsed time, and total usage. That gives you a practical basis for deciding where Opus 5.5 adds value and where a lighter model remains sufficient.