Override system

Every default the engine picks can be redirected, but only from one place: the service-wide conventions block. There is no per-operation with clause. Each rule has the shape Target.property [qualifier] = value, where the target is an operation, an entity, a type alias, or an enum.

conventions {
  Shorten.http_method         = "POST"
  Shorten.http_path           = "/shorten"
  Shorten.http_status_success = 201

  Resolve.http_method            = "GET"
  Resolve.http_path              = "/{code}"
  Resolve.http_status_success    = 302
  Resolve.http_header "Location" = output.url

  UrlMapping.db_table      = "url_mappings"
  UrlMapping.db_timestamps = true
  UrlMapping.plural        = "url_mappings"

  ShortCode.strategy          = "tests.strategies_user:short_code"
  User.test_strategy.password = "tests.strategies_user:strong_password"
}

What you can set

On an operation: http_method, http_path, http_status_success, and http_header "Name", where the header name is the qualifier and the value is an output field. On an entity: db_table, db_timestamps, and plural. The last two control test-data generation: strategy names a generator for a type alias or enum, and test_strategy.field names one per entity field, with the field as the qualifier. The full property and target matrix is in the spec-language reference.

The set is deliberately small. It covers presentation, the method, path, status, headers, table and plural names, and the values a test harness invents, and it does not reach the parts of the output that carry the spec's guarantees.

Validation

Validate.scala checks each rule before anything is generated and reports a ConventionDiagnostic for a target that names no operation, entity, alias, or enum; an unknown property; a property that does not belong on its target, such as a db_table on an operation; a property that needs a qualifier and has none, such as http_header without a name; or a duplicate rule for the same target, property, and qualifier. A present override wins over the engine and profile default, and that is the whole of the precedence, since duplicates are rejected rather than ordered.

What stays fixed

Because the block exposes only presentation, no property removes a check or a constraint. The validation a requires clause compiles to, the CHECK or UNIQUE a field invariant compiles to, a table's surrogate primary key, and the foreign keys derived from state relations all stand, since dropping any of them would let the generated service diverge from the spec it was proven against. You can rename a column, change a status code, or rewrite an error message; you cannot remove the check underneath it.