How OpenCode Works: A Go Agent Harness

OpenCode is a compact Go coding CLI — and almost everything interesting happens *around* the model call, in the harness layer. We trace one prompt end to end: a session-scoped model↔tool loop (three exits), bash and file tools that attach diffs + LSP diagnostics, every message and file mutation persisted to one SQLite db with versioned snapshots (the real rollback), and manual summary-anchor context truncation. In this video: - The session-scoped ReAct loop (no-tool finish / cancel / permission denied) - bash + edit tools (timeouts, truncation, diagnostics) - SQLite persistence + versioned file history (rollback) - Manual summary-anchor context truncation - The honest caveat: no sandbox — policy is not a boundary Grounded in the staged Go source. Subscribe for more agent-harness deep dives. #OpenCode #AgentHarness #Golang