diff --git a/content/docs/data-modeling/field-types.mdx b/content/docs/data-modeling/field-types.mdx
index 2a9438337b..d5eb9f9182 100644
--- a/content/docs/data-modeling/field-types.mdx
+++ b/content/docs/data-modeling/field-types.mdx
@@ -483,6 +483,21 @@ Auto-incrementing number with format template.
 { name: 'ticket_number', label: 'Ticket #', type: 'autonumber', autonumberFormat: 'TKT-{0000}' }
 ```
 
+<Callout type="warn">
+**An autonumber is unique and monotonic per scope — it is not gapless.** Any
+write that gets rejected after the number was reserved — a unique violation on
+another field, a failed validation rule, a `beforeInsert` hook that throws —
+still consumes that number, and it is never reissued. `TKT-0001` succeeding and
+`TKT-0002` failing means the next row is `TKT-0003`; `TKT-0002` will not exist.
+
+This is a decided property of the counter, not a bug to work around. If you are
+building an invoice, contract, or receipt sequence on an `autonumber` field,
+design for gaps: an autonumber guarantees a unique, ever-increasing business
+identifier, but it is **not** a legally gapless document number. Treat that
+guarantee as a separate requirement to satisfy explicitly, not something
+`autonumber` already gives you.
+</Callout>
+
 ---
 
 ## Embedded Structured Types
diff --git a/content/docs/data-modeling/schema-design.mdx b/content/docs/data-modeling/schema-design.mdx
index 9ad5025117..15b333f210 100644
--- a/content/docs/data-modeling/schema-design.mdx
+++ b/content/docs/data-modeling/schema-design.mdx
@@ -218,6 +218,13 @@ Field.autonumber({
 // no separate reset config. A fixed prefix like 'INV-{000}' keeps one global counter.
 ```
 
+The counter is unique and monotonic per scope, **not gapless** — a rejected
+write (a unique violation on another field, a failed validation rule, a
+throwing `beforeInsert`) still consumes the number it reserved. Before wiring
+an `autonumber` field to an invoice, contract, or receipt sequence, see the
+[full contract](/docs/data-modeling/field-types#autonumber) in the Field Type
+Gallery.
+
 ### User Fields
 
 Pick a person — the equivalent of Airtable's *Collaborator* or Salesforce's