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Messaging providers represent files and voice recordings differently. Aion normalizes each inbound item into provider-neutral A2A parts while preserving the provider event for integrations that need native details. Provider support varies. Check Messaging feature support before assuming that an integration supplies attachment metadata, accessible content, or voice transcription.

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Media model

Each retained media item has one URL-backed file part. Its Event metadata is a complete MessageMediaPayload, and its mediaId associates that file with an optional transcript part in the same A2A message. Adapters and agents must inspect all parts. They must not assume that the first text part is the complete request. Provider-authored caption text appears before transcript text, and each transcript is linked to its source item by mediaId. For the complete schemas, see the Distribution/Messaging extension.

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File identity and immutable history

An accessible media file carries two Aion identifiers:
  • fileId is the stable File Recording identifier.
  • fileVersionId is the exact immutable File Recordable identifier represented by the part.
The file URL and its timestamps are historical task facts. Aion does not rewrite a saved task when a grant or object expires, and a historical URL never drifts to a newer File version. An authorized client may receive a new grant for the same fileVersionId only while those exact bytes are retained and access remains authorized. File-part metadata includes accessExpiresAt for the exact URL and may include retentionExpiresAt for the bytes. After the URL expires, the Files API returns an authorization or expiry response as appropriate. After the retained bytes expire, the historical URL returns 410 Gone. If its exact file version no longer exists, clients should treat the content as expired. The task and its metadata remain unchanged until normal A2A task cleanup.

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Availability and transcription

MessageMediaPayload.availability records the file’s dispatch-time access facts. The payload appears only on an accessible file part, so its status is available. Availability does not imply that a later client can refresh an expired grant; the refreshable field records that dispatch-time capability. Automatic transcription has an independent terminal status: Only completed has a transcript text part. Other statuses must not fabricate transcript text. Provider pages state whether no-speech suppresses agent dispatch or whether another terminal status still delivers the file.

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Access, safety, and retention

Aion file URLs route through the authenticated Files API rather than exposing provider credentials or object-store addresses. Access checks use the File’s organization and owner association. File egress is measured asynchronously so authorized downloads can start streaming without waiting for usage publication. Ingest applies bounded size, MIME/signature, executable-type, and attachment-disposition checks. These controls reduce obvious type confusion; they are not an Aion-owned malware-scanning service. Agents and downstream applications remain responsible for deciding whether and how to process untrusted content. Retention is purpose-specific. Supported Telegram Bot media and Slack native-audio bytes are retained for one hour after the file becomes ready. Profile images remain until replacement or explicit deletion. Other attachment categories require an explicit retention policy before content storage is enabled. When A2A task cleanup encounters retained media, it requests best-effort logical File deletion. Task cleanup continues if deletion fails; deadline and later orphan reconciliation remain able to remove leftover bytes. File tombstones and billing facts remain available for audit.

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Provider differences

See the Email, Slack, and Telegram Bot pages for provider-specific request behavior.