Choosing a Claude API Model
Choose a model using the workload you need to pass, not a family name alone. The Chinese source includes earlier Sonnet, Opus and Haiku identifiers; treat those examples as historical rather than a current availability list.
#Compare on your own tasks
| Workload | Measure before choosing |
|---|---|
| Extraction and routing | Field accuracy, latency, invalid-output rate |
| Coding and analysis | Correctness, test results, tool-call reliability |
| Long documents | Retrieval of relevant details, omissions, total context cost |
| Interactive chat | Time to first useful output and full response time |
| Image input | Supported formats and accuracy on your actual images |
A more capable model may reduce retries, but a larger model is not automatically the cheapest or most reliable choice for every stage. Test lighter routing separately from difficult reasoning.
#Record the exact configuration
Store the model identifier, SDK version, prompt revision, enabled features and evaluation dataset version. An alias may change behavior over time; a pinned version helps reproduce a result but still needs a retirement plan.
Use ANTHROPIC_MODEL as application configuration. Verify that the identifier is available to your account and supports the features used by the request. Context size, output limits, pricing and regional availability vary; do not apply an old table to every model.
#Make a change measurable
Run the same fixed cases before and after a model change. Include malformed input, a missing answer, long context and a tool failure. Compare task success, unsupported claims, usage and latency. Keep a rollback configuration if the new model regresses.
