Environment Variables

Variable	Purpose
`DOWNCITY_FEDERATION_TOKEN_SIGNING_KEY`	Lets Federation issue and validate `user_token` internally
`DOWNCITY_CITY_DATABASE_URL`	Optional. Specifies the database URL used by Federation
`OPENAI_API_KEY`	Example provider key; recommended to write it into the Federation database through Admin env
`OPENAI_BASE_URL`	Example provider base URL; recommended to write it into the Federation database through Admin env

fed deploy interactively provisions the administrator ID and password. The password is stored as a PBKDF2 digest and administrator sessions are stored server-side; there is no administrator key environment variable. DOWNCITY_FEDERATION_TOKEN_SIGNING_KEY and BETTER_AUTH_SECRET are generated automatically on first boot and stored in Federation's env table.

If DOWNCITY_CITY_DATABASE_URL is omitted, the default database path is:

.base/downcity.sqlite

How provider env is used

The model handler reads directly from input.env:

import { createDeepSeek } from "@ai-sdk/deepseek";
import {
  AIChannel,
  read_required_env,
  type AIChannelStreamInput,
  type LanguageModelV3StreamResult,
} from "@downcity/federation";

class DeepSeekChannel extends AIChannel {
  constructor() {
    super({
      id: "deepseek",
      env: { DEEPSEEK_API_KEY: "DeepSeek API Key" },
      env_key: "DEEPSEEK_API_KEY",
      base_url: "https://api.deepseek.com",
      ai_sdk_provider_id: "deepseek",
    });
  }

  protected async stream(
    input: AIChannelStreamInput,
  ): Promise<LanguageModelV3StreamResult> {
    const deepseek = createDeepSeek({
      apiKey: read_required_env(input, this.env_key ?? ""),
      baseURL: this.base_url,
    });
    const model = deepseek(input.model.upstream_model);
    return model.doStream(input.call);
  }
}

const deepseek = new DeepSeekChannel();

So the practical rules are simple:

you choose the env key names yourself
uppercase snake case is recommended
read values through input.env(key) or read_required_env() inside stream()

Write values into the database

A trusted backend can write provider keys through FederationAdmin:

await admin.env.upsert({
  key: "DEEPSEEK_API_KEY",
  value: "sk-xxx",
});

These values are stored in the env table inside the Federation database. Business runtime reads only from that Federation-managed env table and no longer falls back to .env or process environment variables.

How provider env is used

Write values into the database

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