Per-Attachment File Upload Behavior for Apps (#7451)

* Document attachment_size_limit

* changelog

* attachment_size_limit is MAX(default_limit, user_limit, guild_limit)

Author: colinloretz

docs/change-log/2025-04-03-per-attachment-file-upload-limit.md

@@ -0,0 +1,18 @@
+---
+title: "Per-Attachment File Upload Behavior for Apps"
+date: "2025-04-03"
+breaking: false
+topics:
+- "HTTP API"
+- "Interactions"
+---
+
+Starting today, file upload limits for apps are checked per-attachment rather than per-message. This change makes the app attachment behavior the same as when a user uploads multiple attachments on a single message.
+
+- File size limits now apply to each individual attachment
+- Previously, limits were applied to the combined size of all attachments in a message
+- This aligns app attachment handling with user attachment behavior
+
+The interaction payload will also include a new `attachment_size_limit` key that specifies the maximum allowed attachment size. This limit may be higher than the default attachment size limit, depending on the guild's boost status or the invoking user's Nitro status.
+
+For more information, check out [our documentation on file uploads](#DOCS_REFERENCE/uploading-files).

docs/interactions/receiving-and-responding.mdx

@@ -37,6 +37,7 @@ For [Message Components](#DOCS_INTERACTIONS_MESSAGE_COMPONENTS/) it includes ide
 | entitlements                   | array of [entitlement](#DOCS_RESOURCES_ENTITLEMENT/entitlement-object) objects                                                        | For [monetized apps](#DOCS_MONETIZATION_OVERVIEW), any entitlements for the invoking user, representing access to premium [SKUs](#DOCS_RESOURCES_SKU)                                                                                                                |
 | authorizing_integration_owners | dictionary with keys of [application integration types](#DOCS_RESOURCES_APPLICATION/application-object-application-integration-types) | Mapping of installation contexts that the interaction was authorized for to related user or guild IDs. See [Authorizing Integration Owners Object](#DOCS_INTERACTIONS_RECEIVING_AND_RESPONDING/interaction-object-authorizing-integration-owners-object) for details |
 | context?                       | [interaction context type](#DOCS_INTERACTIONS_RECEIVING_AND_RESPONDING/interaction-object-interaction-context-types)                  | Context where the interaction was triggered from                                                                                                                                                                                                                     |
+| attachment_size_limit          | integer                                                                                                                               | Attachment size limit in bytes                                                                                                                                                                                                                                       |
 
 \* This is always present on application command, message component, and modal submit interaction types. It is optional for future-proofing against new interaction types
 

docs/reference.mdx

@@ -397,7 +397,7 @@ https://cdn.discordapp.com/attachments/1012345678900020080/1234567891233211234/m
 ## Uploading Files
 
 > info
-> A file upload size limit applies to *all* files in a request (rather than each individual file). While the limit depends on the [**Boost Tier**](https://support.discord.com/hc/en-us/articles/360028038352-Server-Boosting-FAQ-#h_419c3bd5-addd-4989-b7cf-c7957ef92583) of a guild, it is `10 MiB` by default.
+> The file upload size limit applies to each file in a request. The default limit is `10 MiB` for all users, but may be higher for users depending on their [Nitro](https://support.discord.com/hc/en-us/articles/115000435108-What-are-Nitro-Nitro-Basic) status or by the server's [Boost Tier](https://support.discord.com/hc/en-us/articles/360028038352-Server-Boosting-FAQ-#h_419c3bd5-addd-4989-b7cf-c7957ef92583). The `attachment_size_limit` value provided [when working with interactions](#DOCS_INTERACTIONS_RECEIVING_AND_RESPONDING/interaction-object-interaction-structure) is calculated as the maximum of these values.
 
 Some endpoints support file attachments, indicated by the `files[n]` parameter. To add file(s), the standard `application/json` body must be replaced by a `multipart/form-data` body. The JSON message body can optionally be provided using the `payload_json` parameter.