Writing 80-to-100 Validated Flows

Overview

Most agent workflows get a feature to ~80%: code written, types check, maybe a build passes. This skill covers the 80-to-100 gap — making a flow that fully validates a feature before it commits anything. The goal is that everything these flows produce is tested, verified and known-working, not just "an agent said it was done."

Everything here is written for Relayflows v2 — @relayflows/surface / @relayflows/sdk, CLI flows. For the authoring surface itself (the ladder, gates, cli/model resolution, flows.json, refusal shapes) see writing-relayflows. This skill is only about the validation shape you build on top of it.

Migrating from the old @relayflows/core WorkflowBuilder? v2 has no failOnError, no captureOutput, no {{steps.X.output}} templating and no .onError(). Every deterministic step is gated on exit code with no opt-out. The evidence recorder below is what replaces all four. Do not route new work back to the legacy engine.

When to use

• The deliverable must be production-ready, not just code-complete.
• The feature touches databases, APIs or infrastructure that can be exercised locally.
• "It compiles" is not sufficient proof of correctness.
• You want the commit at the end of the flow to represent code that is proven working.

Green gates are necessary and nowhere near sufficient