Claude Code wrote a SPARQL extension for SQLite in Rust in 12 hours

Simon Willison gave Claude Code a single prompt in Ultracode mode, and in 12 hours the agent produced a full SPARQL 1.1 implementation in Rust inside SQLite, with multiple crates, docs and a tutorial. It passed 636 of 639 W3C tests, but Willison says he cannot feasibly review or maintain the code.

• The agent passed 636 of 639 W3C SPARQL 1.1 evaluation tests
• Code is split into crates for parsing, planning, execution, storage and FFI
• The orchestrator decided when to spawn new subagents
• Human review of code this size would take weeks