This repository implements a 'Repository Harness'—a Rust-based CLI framework designed to make software codebases legible and operable for AI agents. It functions as a control plane for agent-assisted development, managing project state (stories, decisions, traces) through a combination of Git-native documents and a durable SQLite layer. The system enforces architectural rules and invariants via mechanical validation rather than process bureaucracy, distinguishing between a generic 'Core' payload and product-specific 'Consumer' work (e.g., Symphony). Key capabilities include self-updating binaries, semantic changeset replay for auditability, and explicit agent skills for onboarding and auditing. Architecturally, the codebase follows a clean separation of concerns with a Rust workspace containing `harness` (core logic) and `harness-cli` (interface). It utilizes a repository pattern to decouple business logic from database access, implementing transactional logging via JSONL changesets that support idempotent replay. The tool manages its own lifecycle through a robust installer that supports cross-platform profiles (Core vs. Core+CLI) and handles file conflicts via deterministic three-way merges. Evidence capsules and epoch fencing ensure data integrity during agent interactions and state transitions. The project demonstrates a high level of engineering maturity through its focus on reproducibility and trust boundaries. It includes extensive documentation (ADRs, execution plans, stories) and a comprehensive test suite covering installer contracts, changeset rebuilds, and boundary checks. The separation of the 'Symphony' product into a distinct repository while retaining protocol primitives in the core highlights a mature approach to library vs. application boundaries.