Three separate length levers on Opus 5: conversational verbosity, agentic narration, and files written to disk

Claude Platform Docs·medium signal

Opus 5's default responses, its per-message narration during agentic work, and the Markdown files it writes to disk all run longer than prior Opus models — and each needs its own instruction, because none of them respond to the effort parameter. Anthropic's pattern is a short conciseness instruction plus a `<tone_preference>` reminder near the end of long system prompts, a cadence description for narration ("before your first tool call, say in one sentence what you're about to do... when you finish, lead with the outcome"), and explicit calibration for deliverables ("do not pad with filler sections, redundant summaries, or boilerplate"). One useful meta-note for prompt authors: Anthropic states that "positive examples of the communication style you want tend to be more effective than instructions about what not to do."