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Complete Config Reference

Verified status as of March 28, 2026.

This page is a practical reference for the config keys that show up across FastFN docs and examples.

Quick View

  • Complexity: Reference
  • Typical time: 10-20 minutes
  • Use this when: you want one place to look up both global and function-level config
  • Outcome: you can tell whether a setting belongs in fastfn.json, fn.config.json, or an environment variable

Global config: fastfn.json

Key Type What it controls
functions-dir string Default functions root
public-base-url string Canonical OpenAPI server URL
openapi-include-internal boolean Whether internal endpoints appear in OpenAPI
force-url boolean Global route override behavior
domains array Input for doctor domains checks
runtime-daemons object or string Per-runtime daemon counts
runtime-binaries object or string Host executables to use
hot-reload boolean Enable or disable hot reload

Function config: fn.config.json

Key Type What it controls
runtime string Explicit runtime for a function root
name string Function name shown in discovery and routes
entrypoint string Explicit handler file
assets object Static asset behavior for the root
home object Folder-level home alias behavior
invoke object Route methods, docs metadata, and invoke policy
schedule object Cron or interval style scheduling
worker_pool object Per-function queue and concurrency control
edge object Edge proxy forwarding rules
strict_fs boolean Function-level strict filesystem sandbox toggle
zero_config object Zero-config discovery knobs such as ignore dirs
zero_config_ignore_dirs array or string Compatibility alias for extra ignored directories

Nested blocks worth knowing

assets

Common fields:

  • directory
  • not_found_handling
  • run_worker_first

Typical use:

{
  "assets": {
    "directory": "public",
    "not_found_handling": "single-page-application",
    "run_worker_first": false
  }
}

invoke

Common fields:

  • methods
  • summary
  • query
  • body
  • force_url

Typical use:

{
  "invoke": {
    "methods": ["GET", "POST"],
    "summary": "Example handler"
  }
}

schedule

Common fields:

  • enabled — boolean, must be true for the schedule to fire
  • every_seconds — interval trigger (fires every N seconds, aligned to boundaries)
  • cron — cron expression (5 or 6 fields, plus macros like @daily)
  • timezone — timezone for cron expressions (e.g. "UTC", "-05:00")
  • method — HTTP method to use when invoking (default "GET")
  • query — query parameters passed to the handler
  • headers — headers passed to the handler
  • body — request body passed to the handler
  • context — context object passed to the handler
  • retry — retry config: max_attempts, base_delay_seconds, max_delay_seconds, jitter

Typical use:

{
  "schedule": {
    "every_seconds": 60,
    "enabled": true,
    "method": "GET",
    "query": {"action": "tick"}
  }
}

{
  "schedule": {
    "cron": "0 9 * * *",
    "timezone": "UTC",
    "enabled": true,
    "retry": {"max_attempts": 3, "base_delay_seconds": 5}
  }
}

Zero-config limitation

Schedules only work for functions in the runtime catalog. Pure zero-config file-based routes are not seen by the scheduler. Use runtime-scoped directories or explicit keys in fn.config.json.

shared_deps

A top-level array listing shared dependency packs to load:

{
  "shared_deps": ["qrcode_pack"]
}

Packs are resolved from <functions_root>/.fastfn/packs/<runtime>/<pack_name>/. Each pack is a directory with its own dependency files (requirements.txt, package.json, etc.) and is made available to the handler at invocation time.

worker_pool

Common fields:

  • enabled
  • max_workers
  • min_warm
  • idle_ttl_seconds

edge

Used for responses that proxy/forward upstream traffic instead of returning a normal function payload.

Practical precedence

  1. CLI flags and explicit command arguments
  2. Environment variables
  3. fastfn.json
  4. fn.config.json
  5. Runtime defaults

If you are unsure where a setting belongs, check the examples first and then the environment variable reference.

Last reviewed: March 28, 2026 · Docs on fastfn.dev