A practical recommended max_tokens setting for Claude Opus 4.5 depends on what kind of workload you’re running, but there are reliable ranges that work well for most production applications. In general, Opus 4.5 benefits from giving the model enough room to finish its reasoning without letting responses balloon unnecessarily. For typical tasks—analysis, coding assistance, planning, document processing—a starting point of 1024–4096 output tokens is a safe and effective baseline. This range allows Opus 4.5 to produce well-structured, complete answers while keeping cost and latency predictable. If you frequently see truncated responses, you can increase the ceiling gradually.
For heavier tasks, such as multi-file code generation, long technical summaries, or agent workflows requiring extended reasoning, it’s reasonable to increase the ceiling to 8192–16384 output tokens. These higher ceilings give Opus 4.5 the space it needs to produce multi-section reports, large code diffs, or multi-step plans in one pass. You should still monitor response length in production since not every call needs the full allowance, and unnecessarily high settings can inflate your total output-token bill. In long-running agent loops, it’s often better to issue several smaller steps, each with a modest max_tokens, rather than request one giant output.
If your architecture includes retrieval—such as feeding Opus 4.5 context from a vector database like Milvus or Zilliz Cloud—that context will already occupy a significant portion of your input token budget. In these cases, many teams purposefully lower max_tokens per call (e.g., 512–2048) and rely on iterative refinement instead of a single long answer. This approach keeps latency and cost stable, while allowing the agent to run multiple reasoning steps using fresh RAG results. Over time, the best max_tokens value will come from measurements: log truncation events, average output size, and latency per route, then tune the ceiling per endpoint based on actual usage and cost objectives.