principle-files-are-the-contractlisted

# Files Are the Contract The conversation is ephemeral; the artifact on disk is durable. Work that matters is written to a file that declares what it is — and, where a gate governs it, whether the gate passed — and steps communicate through those files, never through shared chat memory. Trusting the model to remember fails often enough to plan for. **Why:** A file survives a truncated context, a compaction, a crash, a new session, and a handoff to a different agent. The state lives on disk, not in memory. The file is the value passed between steps, and it revises only by explicit rule — a design is overwritten on revision, a verdict record is appended and never overwritten — so nothing is silently lost. **Pattern:** - A step that produced no artifact did not happen. Write the file before reporting the step done. - Pass a path, not a paraphrase: the consumer reads the artifact itself, never the producer's summary of it. - Rebuild in-session state (ledgers, phase tables) by scanning the artifacts; after any interruption the files are authoritative. - Long procedures checkpoint to an append-only log, so a fresh context can resume from disk instead of from recollection. - Record decisions, approvals, and pre-images in the artifact directory, so a later turn — or a later run — can audit what happened.