BlaBla: executable project memory cuts coding agent handoff cost by 63% vs prose context
KiborgikDEV · reddit · 2026-09-15
A developer open-sourced BlaBla, an MIT-licensed Rust CLI that moves project intent out of agent chat context into executable contracts. behavior.bla captures observable state, actions, postconditions and invariants — the verifier generates action sequences, tracks semantic coverage, and shrinks failures into reproducible counterexamples; structure.bla encodes static constraints like required/forbidden symbols and dependencies. A finish gate only exits successfully when the project is OVERALL GREEN, and a dedicated YELLOW state exists because "no failure observed" proved unreliable after thousands of executed actions still missed reachable states. In a 4-stage handoff experiment with fresh Haiku sessions on the same Python project, BlaBla matched full prose on behavior (106/106) and passed architecture checks where human summaries failed, using 2.51M input tokens ($0.62, 91 turns) vs 8.55M ($1.78, 181 turns) for prose — a 63% cost cut. The author stresses it's a single-model synthetic observation, not a general claim, and invites reproductions and false-GREEN reports. Limits: heuristic verification, Python-only structure provider.
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