Set in the workflow's components (Components): workflow-wide fields in @Workflow, limits and model providers in its settings(), agent fields in each @Agent, router fields in each @Router. Assembled and validated at startup; profiles override them without code. Secrets are never there — model provider keys are process variables (OPENROUTER_API_KEY in .env), the app's own settings live in environments.

@Workflow({
  name: "job-scout", // lowercase, digits, dashes — the key of the daily spend ledger
  version: "2.0.0", // labels every run; profiles set their own
  flow: [chain(ChatWorkflowStart, ScoutAgent, ChatWorkflowFinish)],
  defaults: {
    models: { temperature: 0 }, // every chat model (agents, LLM routers)
    router: { kind: "jev", model: "typesafe/jev-1.13" }, // guards, tools' decisions
    tools: { maxToolCalls: 8 },
    history: { limit: 5 },
  },
  guards: {
    input: { prompt_injection: { threshold: 0.7, refusal: "I can't help with that request." } },
  },
  compaction: { every: 5, keep: 10, model: { model: "moonshotai/kimi-k2.6", thinking: "none" } },
  mcp: [ShortlistServer],
  promptVariables: { boards: "acme (Acme)" },
})
export class JobScout implements WorkflowDefinition {
  settings(): WorkflowSettings {
    return WorkflowSettings.builder()
      .limits({ perRun: { steps: 12, cost: usd(0.1) }, perDay: { cost: usd(1) } })
      .modelProviders([OpenRouterModelProvider, DecisionsModelProvider])
      .build();
  }
}

Timeouts, retries, circuit breakers, request fields (e.g. OpenRouter's provider: { ignore: [...] }) and costs belong to the model provider — see Model providers; price on an agent is an optional override of the provider's price table. Every setting is checked against its model at startup and by agboss check --models.

Per agent: @Agent({ historyLimit, historySummaries }), or a memoryStrategy (Memory Management).

{ kind: "jev", model: "typesafe/jev-1.13" } or { kind: "llm", model, … }. Flow routers (@Router) name their own model — see Routers.

perRun: { steps, cost } and perDay: { cost } (values with units: usd() from agboss/units). Steps = visits of agents and routers (default (agents + routers) × 3). Hitting one fails the run with LimitExceededError naming the key (limits.perRun.steps, limits.perRun.cost, limits.perDay.cost, routers.<name>.maxVisits). perDay.cost requires perRun.cost ([limits.per-run-required]). Details: FinOps.

A used server that is missing, unreachable, lacks an env variable or has a drifted contract stops startup. See Mcp.

From @Agent classes: model, description (shown to routers), prompt / promptUrls / promptVariables, tools (class references — a missing one does not compile), maxToolCalls, historyLimit, historySummaries, judges + maxRetries, rag, memoryStrategy, compensate, price, and any defaults.models field as an override.

Input and output guards: threshold, refusal, optional model per guard. See Guards.

every turns per summary (≥ 2), keep summaries readers see by default (the queue drops the oldest), model — the model that writes them. Readers: defaults.history.summaries, per agent historySummaries (0 = none); historyLimit caps the raw turns since the last compaction. A workflow may override the prompt (compactionPrompt). See Terns and evaluation.

The app's settings live in environments/ next to the workflow file — the workflow itself says nothing about them. The contract is a module augmentation:

// src/environments/environment.ts — which fields every environment has
declare module "agboss" {
  interface Environment {
    readonly apiUrl: string;
    readonly apiKey: string;
  }
}
export {};

// src/environments/dev.environment.ts — one file per environment: dev, staging, test, …
import { defineEnvironment, fromEnv } from "agboss";

export default defineEnvironment({
  apiUrl: "https://api.example.com", // a value in the file
  apiKey: fromEnv("API_KEY", { secret: true }), // a process variable, masked when printed
});

Services inject the values with the ENV token, never process.env:

import { ENV, Injectable, type Environment } from "agboss";

@Injectable({ deps: [ENV] })
export class Api {
  constructor(private readonly env: Environment) {}
}

--env <name> (every workflow command), createApp(W, { env }) and testWith(W, { env | environment }) pick one (default dev); an unknown name or a fromEnv variable without a value or default fails at start, naming it. agboss check validates the selected environment, agboss describe shows it with secrets masked.