The predecessor of forge: a stop-hook-driven autonomous coding loop for Claude Code, built February–March 2026.
BTL ran as a Claude Code Stop hook: at the end of each agent turn it re-injected the next backlog item, ran the project's build and tests, parsed numeric error counts, and made an explicit keep-or-revert decision — improvement keeps, regression reverts, three identical non-zero metrics flags stagnation. v4 replaced the original binary pass/fail gate with numeric metric tracking (ESLint, tsc, pytest, ruff, jest parsers).
This repo holds the technical reference (BTL.md), the v4 spec and redesign research
(docs/), and the test backlog it worked from. The hook scripts themselves lived in
the operator's ~/.claude/ config.
BTL was retired in favour of forge, which moved the loop out of stop-hooks into a standalone event-driven orchestrator with the same backpressure philosophy.
Archived; published as a historical artifact. No support, no roadmap.