Template Questions and Placeholders: inputs, when, sets and {{ }} Values

A question (inputs) is one step of the wizard, and a placeholder ({{...}}) is a value the platform fills in when it creates the template. Questions collect what only the user knows; placeholders connect the services and generate what nobody should type.

Questions

inputs is an ordered list. Each item becomes a step of the wizard, shown in that order.

Field	Required	Rule
`id`	yes	Lowercase letters, digits, `_` and `-`, up to 40 characters, unique in the template. Used as `{{inputs.<id>}}`.
`type`	yes	`text`, `secret`, `select`, `boolean`, `number`, `url` or `email`.
`label`	yes	Text per language, up to 128 characters.
`help`	no	Text per language, up to 512 characters.
`required`	no	Default `false`.
`default`	no	Text, number or boolean matching the type, up to 3,072 characters. For `select`, one of the option values.
`validation`	no	`regex`, `min`, `max`, `min_length`, `max_length`.
`generate`	no	`secret` only: `random:<n>` with `n` from 8 to 128, or `uuid`.
`editable`	no	With `false`, the value is always generated and the user cannot type one. Needs `generate`.
`when`	no	`{ input, equals }`: ask only when an earlier answer matches.
`options`	select	Up to 25 items `{ value, label?, sets? }`.

How each type is checked:

Type	Accepts	Validation that applies
`text`, `secret`	Text	`min_length`, `max_length`, `regex`
`url`	An `http` or `https` URL	`min_length`, `max_length`, `regex`
`email`	An e-mail address	`min_length`, `max_length`, `regex`
`number`	A number	`min`, `max`
`boolean`	`true` or `false`	None
`select`	One of the `options` values	None

A secret question is typed without echo. When generate is set and the user leaves it empty, the platform generates it on the server and shows it once in the outputs. A regex is limited to 200 characters and cannot use back-references, nested quantifiers or a repeated alternation, because it runs on the server; it only applies to text types. Token question, from the starter bot:

inputs:
  - id: discord_token
    type: secret
    required: true
    label: { pt-br: "Token do bot", en: "Bot token", es: "Token del bot" }
    help:
      en: "In the Discord Developer Portal: create the application, open Bot and use Reset Token."
      pt-br: "No Discord Developer Portal: crie a aplicação, abra Bot e use Reset Token."
    validation: { min_length: 50, max_length: 100 }

Conditions with `when`

when is an equality check against one earlier question, with no expression language. equals must fit the type of that question: a boolean for boolean, a number for number, one of the option values for select. A condition on a later question, on itself or on an unknown id is refused (invalid_when, unknown_input). A question whose condition is false is skipped, and its answer does not exist.

  - id: email
    type: select
    label: { pt-br: "Enviar e-mails do n8n?", en: "Send n8n emails?" }
    default: none
    options:
      - { value: none, label: { pt-br: "Não, configurar depois", en: "No, set it up later" } }
      - { value: smtp, label: { pt-br: "Sim, usar meu servidor SMTP", en: "Yes, use my SMTP server" } }
  - id: smtp_host
    type: text
    required: true
    label: { pt-br: "Servidor SMTP", en: "SMTP server" }
    when: { input: email, equals: smtp }

A database or Blob service accepts the same when to be created conditionally. An app service does not; use sets.services.

Options and `sets`

The effect of a choice lives in the option itself. sets can do three things. When several questions touch the same service or variable, the last one wins; memory from ram_extra adds up:

Key	Effect
`services`	`{ <service-id>: "on" \| "off" }` creates or skips a service.
`env`	`{ <app-service-id>: { NAME: value } }` adds variables to an app. Values accept placeholders.
`ram_extra`	`{ <service-id>: MB }` adds memory to the minimum and the recommended value of a service.

A template cannot end up without an app: if the chosen options turn every app off, the deploy is refused. Quote "on" and "off" in YAML so they stay text. This is how n8n offers Postgres, SQLite or workers without any expression:

inputs:
  - id: mode
    type: select
    label: { pt-br: "Como o n8n vai rodar?", en: "How will n8n run?", es: "¿Cómo va a correr n8n?" }
    default: postgres
    options:
      - value: postgres
        label: { pt-br: "Postgres gerenciado (recomendado)", en: "Managed Postgres (recommended)" }
        sets:
          services: { db: "on", queue: "off", worker: "off" }
          env: { app: { DB_TYPE: postgresdb } }
      - value: sqlite
        label: { pt-br: "SQLite interno (no disco do app)", en: "Built-in SQLite (on the app disk)" }
        sets:
          services: { db: "off", queue: "off", worker: "off" }
          env: { app: { DB_TYPE: sqlite } }

Placeholders

A placeholder is written {{ ... }}. The platform resolves it when it creates the template and again when a managed value changes (for example after a database password reset). It is never resolved in the browser. Placeholders work in env (and in sets.env) and in outputs. They do not work in main, build, start or healthcheck.path; there they give unknown_placeholder. Text outside {{ }} is never interpreted, and the value of a placeholder is never expanded again, so an answer that contains {{secrets.x}} stays as plain text.

Apps and the stack

Placeholder	Value
`{{app.url}}`	Public URL of the app that owns the variable (empty if it has no web). In outputs, the main app.
`{{app.domain}}`	Public host name of that app, without the scheme.
`{{services.<id>.url}}`	Public URL of another app service.
`{{services.<id>.domain}}`	Public host name of another app service.
`{{stack.name}}`, `{{stack.id}}`	Name and id of the stack. Empty when the template creates a single app.

The URL and the host name follow the app: a variable whose value is exactly one of these placeholders is updated when the subdomain changes or when the user adds a custom domain. Inside a longer text (https://{{app.domain}}/x) the value is fixed at deploy time.

Databases

The app reaches the database through its public address, with client certificates. See Stacks.

Placeholder	Value
`{{services.<id>.url}}`	Complete connection URL of the database, password included.
`{{services.<id>.host}}`	Host of the database.
`{{services.<id>.port}}`	Port.
`{{services.<id>.user}}`	User (the `vertracloud` user for a new database).
`{{services.<id>.password}}`	Password.
`{{services.<id>.database}}`	Database name.
`{{services.<id>.ssl.ca_path}}`	Path of the CA certificate.
`{{services.<id>.ssl.cert_path}}`	Path of the client certificate.
`{{services.<id>.ssl.key_path}}`	Path of the client key.
`{{services.<id>.ssl.pem_path}}`	Path of the combined client PEM, used by MongoDB.
`{{services.<id>.ssl.p12_path}}`	Path of the client identity in PKCS#12 (`.p12`), used by Prisma 6. Its password is empty.
`{{services.<id>.ssl.p12_password}}`	Password of the `.p12`, empty.
`{{services.<id>.prisma_url}}`	Postgres URL in the shape Prisma 6 needs (`sslmode`, `sslcert` and `sslidentity` included). Empty for other engines.

The ssl.*_path values are absolute paths inside the app, in /app/.vertra/certs/<database_id>/ (ca.pem, client.crt, client.key, client.pem, client.p12). The platform writes them at every start, and your process (uid 1000) can read them. prisma_url carries the password, so it is sensitive and exists only when your manifest asks for it. Postgres from n8n, with certificates:

env:
  DB_POSTGRESDB_HOST: "{{services.db.host}}"
  DB_POSTGRESDB_PORT: "{{services.db.port}}"
  DB_POSTGRESDB_DATABASE: "{{services.db.database}}"
  DB_POSTGRESDB_USER: "{{services.db.user}}"
  DB_POSTGRESDB_PASSWORD: "{{services.db.password}}"
  DB_POSTGRESDB_SSL_CA_FILE: "{{services.db.ssl.ca_path}}"
  DB_POSTGRESDB_SSL_CERT_FILE: "{{services.db.ssl.cert_path}}"
  DB_POSTGRESDB_SSL_KEY_FILE: "{{services.db.ssl.key_path}}"

Blob folders

Placeholder	Value
`{{services.<id>.endpoint}}`	S3-compatible endpoint.
`{{services.<id>.bucket}}`	Bucket name.
`{{services.<id>.region}}`	Region.
`{{services.<id>.prefix}}`	The stack folder, `stacks/<stack-slug>/`.
`{{services.<id>.access_key_id}}`	Access key id of the managed key restricted to the folder.
`{{services.<id>.secret_access_key}}`	Secret key of that managed key.
`{{services.<id>.public_base_url}}`	Base URL for public files; empty when the folder is private.

Secrets and answers

Placeholder	Value
`{{secret:<n>}}`	A random secret of `n` characters (8 to 128), generated once and stored encrypted as the variable. Not allowed in outputs.
`{{secrets.<name>}}`	A secret declared in `secrets`, the same in every service that uses it.
`{{inputs.<id>}}`	The answer to a question.

Switched-off services

A placeholder that points to a service turned off by an answer resolves to an empty value, and a variable that ends up empty is not written. That is why the n8n template can list every DB_POSTGRESDB_* variable and still run on SQLite.

Managed variables

A variable whose value is a placeholder of a database, Blob folder or app is managed by the stack: it is updated on its own when the database changes password or certificate, or when the app’s address changes, and the dashboard shows a “managed by the stack” badge. Editing it by hand turns it into a regular variable.

What is refused

Mistake	Code
Unknown or malformed placeholder, or a field that does not exist for that kind of service	`unknown_placeholder`
A service id that is not in the manifest	`unknown_service`
`{{inputs.x}}` for a question that does not exist	`unknown_input`
`{{secrets.x}}` with `x` not declared in `secrets`	`unknown_placeholder`
Platform-controlled variable names such as `PORT`, `HOME` or `LD_PRELOAD`	`forbidden_env`
A literal value that looks like a credential	`secret_in_manifest`

See Validate and test for how to fix each one.

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Template Questions and Placeholders: inputs, when, sets and {{ }} Values

Questions

Conditions with `when`

Options and `sets`

Placeholders

Apps and the stack

Databases

Blob folders

Secrets and answers

Switched-off services

Managed variables

What is refused

​Questions

​Conditions with when

​Options and sets

​Placeholders

​Apps and the stack

​Databases

​Blob folders

​Secrets and answers

​Switched-off services

​Managed variables

​What is refused

Questions

Conditions with `when`

Options and `sets`

Placeholders

Apps and the stack

Databases

Blob folders

Secrets and answers

Switched-off services

Managed variables

What is refused