Simon Willison's LLM 0.32a3 Adds Tool-Call Pause/Resume Primitives — Built Almost Entirely by Fable 5

Simon Willison / llm.datasette.io·medium signal

Driven by a human-in-the-loop ask_user() feature for Datasette Agent, LLM 0.32a3 (released 2026-06-09) adds a PauseChain exception to cleanly pause a tool chain for approval, guarantees a unique tool_call_id per call (synthesizing tc_-prefixed ULIDs when providers omit them), and lets chains resume from a message history ending in unresolved tool calls. Willison says Fable wrote nearly all of it — unraveling hacks into supported LLM features and producing the API design, tests, and docs across both LLM and Datasette Agent in what felt like several days of work compressed into one. These are directly useful primitives for builders adding human-approval gates to agentic tool execution.