Steps

A flow runs a step from .chernabog/stages/ with step("name", input, { output }). Each runs in its own process, as one activity.

Kind	File	Contract
Effect	name.ts	default-exports defineStage({ name, input, output, run }); gets the SDK’s services
Shell	name, executable	reads { input, repo, run } as JSON on stdin; prints its output as JSON on the last line of stdout

Exit	Means
0	continue
78	skip the run
other	fail the run

A step that crashes partway runs again, so every step must be safe to repeat.

.chernabog/stages/find-work.ts

import { defineStage, GitHub, Skip } from "@chernabog/sdk";
import { Effect, Schema } from "effect";

export default defineStage({
  name: "find-work",
  input: Schema.Struct({}),
  output: Schema.Struct({ issue: Schema.Number }),
  run: () =>
    Effect.gen(function* () {
      const [issue] = yield* (yield* GitHub).queuedIssuesLabelled("auto:eligible");
      if (issue === undefined) return yield* new Skip({ reason: "nothing queued" });
      return { issue: issue.number };
    }),
});