Anthropic publishes Claude Fable 5.1 prompting guide covering tool batching, compaction, safeguards

alex_verem · x · 2026-09-09

Anthropic's platform docs detail behavioral differences and prompting patterns for Claude Fable 5.1 (5 prompts carry over unchanged). Highlights: choosing effort levels when latency/cost overshoot; batching independent tool calls in agent loops; requesting progress updates between calls; keeping conversation history append-only to avoid "bound to a different conversation" errors; fixing over-dense prose and under-structured chat replies; marking retrieved-source quoting; preserving constraints in compaction summaries; keeping fixes and tests to task scope; plus sections on search triggering, safeguard false positives, file edits, long outputs, subagents, and vision.

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