Writing Relayflows

Overview

Relayflows turns a coding-agent task into steps a journal can inspect, verify, and resume. A flow is data (YAML/JSON) or code (TypeScript) that compiles to the same journal-backed kernel spec. Every effect is journaled before it's treated as real — a journal write that fails fails the step, with no silent fallback.

Name collision warning. This repo also has skills for an older, unrelated engine that is also casually called "Relayflow" (singular) — @relayflows/core's WorkflowBuilder, a chained builder (workflow('name').pattern('dag').agent(...).step(...).run()). That's writing-agent-relay-workflows and migrating-persona-to-relayflow's territory. This skill is the v2 engine: @relayflows/surface's flow() function and the YAML/JSON dialect compiled by @relayflows/sdk. If you see .pattern(, .agent( as a chained builder call, or ctx.workflow.run(), you're in the other engine — stop and use one of those skills instead.

When to use this skill

• Writing a new .flow.ts or .flow.yaml/.flow.json for the flows CLI (package @relayflows/sdk, binary name flows).
• Deciding whether a step needs run (shell), llm (bare model call), or agent (harnessed coding agent in a workspace).
• Wiring up cli/model for an agent or llm step, in either language.
• Debugging a REFUSED [...] message from flows check or flows run.
• Choosing between TypeScript and YAML for a given flow.

The ladder

Three step verbs, one per rung — never more (packages/sdk/src/spec.ts, export type StepType = 'deterministic' | 'llm' | 'agent';):

1. run / deterministic — a shell command. No model. Implicit gate is exit_code == 0.
2. llm / llm — a bare model call. Prompt in, verified output out. No workspace, no tool use.
3. agent / agent — a harnessed coding agent in a workspace. Returns { summary, artifacts }, not raw text.

Plus four resident verbs that aren't ladder rungs: human (durable approval), dispatch (hand off to a child flow), done (typed finish), and in YAML, on/triggers (event entry points — out of scope for this skill).

Most flows only need run and llm. Climb to agent once a step needs hands on a real workspace.

Two ways to author the same thing

TypeScript

tsCopy code
import { flow } from '@relayflows/surface';

export default flow('hello', async (f) => {
  const greeting = await f.run('echo "Hello from Relayflows"');
  console.log(greeting.trim());

  const answer = await f.agent('greeter', {
    task: 'Reply with one short hello sentence. Do not use tools or modify files.',
    cli: 'claude',
    model: 'claude-sonnet-4-6',
  });
  console.log(answer.summary);

  f.done('success');
});

YAML

yamlCopy code
version: '0.1.0'
name: hello
steps:
  - id: greeting
    type: deterministic
    command: 'echo "Hello from Relayflows"'
  - id: greeter
    type: agent
    dependsOn: [greeting]
    instruction: 'Reply with one short hello sentence. Do not use tools or modify files.'
    cli: claude
    model: claude-sonnet-4-6

The real Ctx contract (TypeScript)

packages/surface/src/context.ts, current as of origin/main@86a2ec2:

tsCopy code
export interface AgentResult {
  summary: string;
  artifacts: string[];
}

export interface AgentOptions {
  task: string;
  workspace?: string;
  cli?: string;
  model?: string;
}

export interface Ctx {
  run(command: string): Step<string>;
  llm(strings: TemplateStringsArray, ...values: unknown[]): Step<string>;
  llm(
    prompt: string,
    options: { output: Record<string, unknown>; cli?: string; model?: string }
  ): Step<unknown>;
  agent(name: string, options: AgentOptions): Step<AgentResult>;
  human(question: string, options: { to: string }): Promise<boolean>;
  dispatch<T>(flow: string, input: unknown): Promise<T>;
  done(reason: RunCompletionReason): void;
  cloud: CloudHelper;
  slack: SlackHelper;
}

The real step shapes (YAML/JSON, packages/sdk/src/spec.ts)

```ts

tsCopy code
interface DeterministicStepSpec {
  type: 'deterministic';
  id: string;
  command: string;
  dependsOn?: string[];
  timeoutMs?: number;
  verification?: VerificationSpec; // omit for implicit exit_code
}

interface LlmStepSpec {
  type: 'llm';
  id: string;
  prompt: string;
  dependsOn?: string[];
  verification?: OutputVerificationSpec;
  model?: string;
  cli?: string;
}

interface AgentStepSpec {
  type: 'agent';
  id: string;
  instruction: string;
  dependsOn?: string[];
  verification?: OutputVerificationSpec;
  agent?: string; // selects a named FlowSpec.agents entry
  cli?: string;
  model?: string;
  surfaces?: { workspace?: { surface: string }[]; streams?: { stream: string }[]; external?: string[] };
  recoveryMode?: 'reset' | 'inspect' | 'manual'; // default 'reset'
  permissions?: {
    fileGlobs?: string[];
    networkAllowlist?: string[];
    accessPreset?: 'readonly' | 'readwrite';
  };
}

interface FlowSpec {
  version: string; // required, e.g. '0.1.0' — not optional
  name?: string;
  cli?: string; // flow-level CLI default
  agents?: Record<string, { cli: string; model: string }>; // both fields required
  steps: StepSpec[];
  budget?: { maxTokensIn?: number; maxTokensOut?: number; maxDollars?: string };
}

Verification gates

Verification is control flow, not decoration — a gate decides whether a step actually completed, not just whether the process exited cleanly (packages/sdk/src/spec.ts, VerificationGateType):

yamlCopy code
- id: classify
  type: llm
  prompt: 'Classify this ticket as bug, feature, or question: "the export button does nothing"'
  cli: claude
  model: claude-sonnet-4-6
  verification:
    type: output_contains
    value: bug

cli / model: what a step actually runs on

Both YAML and TypeScript agent/llm steps can set cli and model directly (TypeScript since flows#310, AgentOptions.cli?/.model?). Resolution order for cli — checked once per step by preflight.ts's resolveCli (packages/sdk/src/preflight.ts:265-282), identical regardless of authoring language because both compile to the same StepSpec:

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$ flows check hello.flow.yaml   # agent step, no cli anywhere
REFUSED [cli_unresolved] Step "greeter" has no CLI at step, flow, or project level. No flows.json was found from "..." to the filesystem root.

flows.json

jsonCopy code
{ "cli": "claude", "executors": ["cron"], "models": ["claude-sonnet-4-6"] }

Human approval and dispatch (TypeScript resident verbs)

```ts

tsCopy code
import { flow } from '@relayflows/surface';

export default flow('ship-feature', async (f) => {
  const plan = await f.agent('planner', {
    task: 'Research and plan: add OAuth2 support',
    workspace: 'acme/api: readonly', // compiles to relayauth path scopes
  });

  const ok = await f.human(`Ship this?\n${plan.summary}`, { to: 'khaliq' });
  if (!ok) return f.done('canceled');

  const pr = await f.dispatch('garden/implement', plan); // hands off to a child flow
  f.done('success');
});

Running it: flows check / run / resume

Real usage (packages/sdk/src/cli.ts):

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flows check [--json] <flow.yaml|spec.json>
flows run [--json] [--no-spawn] [--no-observer-link] [--data-dir <dir>] [--local-agent] <flow.yaml|spec.json>
flows run [--json] [--no-spawn] [--no-observer-link] [--data-dir <dir>] [--local-agent] <flow.ts> --input <inline-json-or-file>
flows resume [--json] [--no-spawn] [--no-observer-link] [--data-dir <dir>] <run-id>

Common mistakes

• Forgetting version in a YAML/JSON FlowSpec. It's required, not optional — flows check refuses a spec without it.
• Adding agents: to a TypeScript flow() header. FlowHeader has no such field; it throws TypeError: flow header has unknown fields: agents at authoring time. Named-agent maps + agent: selector are YAML/JSON-only (flows#300 tracks TypeScript composition via use:, not yet shipped).
• Assuming flows.json's models sets a default model. It only validates models already declared elsewhere; it never selects one.
• Not awaiting a step, or manually .then()-chaining one. Both are refused (unawaited_step / unsupported_verb) rather than silently ignored — the executor closes every root operation's lifecycle explicitly.
• Running a .flow.ts without --input. Required even for flows that don't use their input argument.
• Expecting a fifth done() reason. The set is closed: success | step_failed | canceled | budget_exceeded. Don't invent partial or skipped.

What this skill does NOT cover

• Named-agent maps in TypeScript (agents: { reviewer: { cli, model } } + reuse across steps by name) — YAML/JSON only today. Tracked for TS composition via use: at flows#300.
• recoveryMode, permissions, surfaces, budget, memory on agent steps — real YAML/JSON fields with no TypeScript equivalent. Author that step in YAML and reach it from TypeScript with f.dispatch if you need them.
• Cloud execution (flows run --cloud), triggers/webhooks, memory retrieval, and the f.mcp/f.slack helper namespaces — each is its own surface with its own gotchas; see the Relayflows product docs for what's shipped versus designed-but-not-yet-implemented.
• The older @relayflows/core WorkflowBuilder engine — see writing-agent-relay-workflows and migrating-persona-to-relayflow in this repo.

Quick reference

Verified against

AgentWorkforce/flows@86a2ec2 (origin/main). Built packages/surface and packages/sdk from source in a clean worktree (published npm @relayflows/surface@2.0.8 is stale — it predates flows#310 and lacks cli/model on AgentOptions; local build was symlinked in instead), then ran the real CLI:

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$ flows check hello.flow.yaml         # this skill's YAML example, cli/model added, flows.json models allowlist set
CHECK PASSED hello.flow.yaml            # exit 0

$ flows check hello.flow.ts            # this skill's TypeScript example
CHECK PASSED hello.flow.ts              # exit 0

$ flows check extract.flow.yaml        # this skill's output_contains example
CHECK PASSED extract.flow.yaml          # exit 0

$ flows check hello.flow.yaml           # same YAML, no flows.json anywhere
REFUSED [cli_unresolved] Step "greeter" has no CLI at step, flow, or project level. ...   # exit 2

$ flows check hello.flow.yaml           # step model not in flows.json's models[]
REFUSED [model_unknown] Step "greeter" declares model "claude-sonnet-4-6" ... not listed in project model registry ...   # exit 2