cast

cast hosts private RSS feeds and podcast episodes. Publish audio into a feed and cast returns a public RSS 2.0 + iTunes XML URL that any podcast client can subscribe to. No object store, no RSS host, no separate accounts. It is dvmkit's first stateful-resource DVM: feeds are owned by a caller pubkey, and every capability is signed with that key.

Canonical endpoint: https://cast.dvmkit.ai. Six capabilities under one descriptor, all owner-signed with secp256k1 + BIP-340 Schnorr requests.

Published reference. This page is the source of truth for cast's documented inputs, outputs, prices, and errors. The running service publishes its current capability schemas and advertised prices in its live descriptor. Full output envelope shapes are in the dvm CLI reference.

Capabilities

The SDK dispatches on the wire capability field. The first add-episode against a feed_slug creates the feed; every later call requires the calling pubkey to match the feed owner.

Capability	Pricing	Idempotent	What it does
add-episode	Paid	No	Publish an episode (creates the feed on first call)
update-feed	Free	Yes	Edit feed-level metadata + cover art (post-publish)
update-episode	Free	Yes	Patch an episode in place, preserving its GUID
delete-episode	Free	Yes	Remove one episode by episode_id
delete-feed	Free	Yes	Remove a feed and cascade-delete its episodes
list-feeds	Free	Yes	List feeds owned by the calling pubkey (recovery path)

add-episode

Submit a signed AddEpisodeInput with one of two mutually-exclusive audio sources:

• audio_url: cast HEAD-fetches the URL during the quote, prices on size × TTL, then streams it into storage after payment.
• audio_upload_handle: UUID from a prior POST /v1/ingest/audio (bytes-upload); the quote prices from the recorded byte count.

ttl_days is required (no default): it sets the retention window and drives storage cost. At expiry the cleanup cron auto-deletes the episode; restoring means re-publishing (and paying again). Because it's consequential and hard to reverse, an agent acting for a human should confirm the retention window before publishing.

Result: { feed_url, episode_id, ttl_days, expires_at }.

Feed-level title, description, author, category, explicit flag, and cover art are not set here: use update-feed. Only per-episode artwork (episode_image_url / episode_image_upload_handle), chapters, and transcript belong on the episode. Caps: 200 MB per episode, 50 episodes per feed, ttl_days ∈ [1, 3650].

Free capabilities

• update-feed: edit any feed metadata field post-publish (title, description, language, author, category, explicit, owner name/email, copyright, iTunes type, cover image). Feed identity/URL is preserved.
• update-episode: patch an episode's title, description, artwork, transcript, or chapters in place. Preserves GUID, pub_date, feed position, and audio enclosure (podcast clients see an edit, not a re-download). Replace-only: swapping audio is delete-episode + re-add.
• delete-episode / delete-feed: idempotent removes; a missing target returns { deleted: false }.
• list-feeds: the recovery path for a restarted agent. Returns every feed owned by the calling pubkey with canonical feed_url values, episode counts, and an empty_feed warning when a feed has no episodes (Apple rejects those).

CLI example

Every capability is invoked the same way: dvm request -d dvmkit--cast/<capability> with a signed identity.

dvm request -d dvmkit--cast/add-episode --as my-identity --data '{
  "feed_slug":"my-show","feed_title":"My Show",
  "episode":{"title":"Ep 1","audio_url":"https://example.com/ep1.mp3","ttl_days":365}
}'
dvm request -d dvmkit--cast/list-feeds     --as my-identity --data '{}'
dvm request -d dvmkit--cast/update-feed    --as my-identity --data '{"feed_slug":"my-show","feed":{"author":"Jane Smith"}}'
dvm request -d dvmkit--cast/delete-episode --as my-identity --data '{"feed_slug":"my-show","episode_id":"<uuid>"}'

Pricing

Only add-episode is paid:

Component	Cost
Per-add fee	$0.02 USD
Storage	ceil(audio_bytes / 1MB) × ttl_days × $0.000005 USD

Storage scales with the retention window, so a longer ttl_days costs more. Sats binding is derived at the 402 handshake using the SDK FX fetcher; both the /v1/quote description and the add-episode result name the retention window and expiry instant explicitly.

Public surfaces

• GET https://cast.dvmkit.ai/feeds/{owner_short}/{feed_slug}: the public RSS 2.0 + iTunes feed. owner_short is the first 12 hex chars of sha256(pubkey).
• POST /v1/ingest/audio: stage raw audio bytes (signed claim), returns a 15-min upload_handle.
• POST /v1/ingest/image: stage cover / episode artwork (JPEG/PNG/WebP, square, ≥ 1400×1400).

Auth

Per-request secp256k1 + BIP-340 Schnorr signature over the canonical-JSON body, at the descriptor level so all six capabilities share one auth slot. Drift window ±5 minutes; replay window 10 minutes (Postgres-backed, survives restarts). An unsigned, stale or replayed request rejects with a structured 401 auth_error before payment is taken.

The CLI handles this for you: dvm init creates a default signing identity and dvm quote / dvm request sign with it automatically. Pass --as <identity> only when you want to sign as a different one. For cast that also selects which owner's feeds you are operating on, since the verified pubkey is the ownership key.

Prepaid credit

cast offers a prepaid balance, so an agent publishing a run of episodes funds once instead of paying per job. The funding menu rides on every quote and every 402.

Field	Value
Minimum funding	$0.10
Maximum residual balance	$5.00
Credit lifetime	30 days from the most recent funding

dvm credit fund dvmkit--cast --amount 2.00
dvm credit balance dvmkit--cast
dvm credit drain dvmkit--cast     # reclaim it, works after expiry too

A job priced above the maximum still clears: the ceiling binds how much balance you may hold, not what you may spend. And a failed job never takes your money: the charge is released back onto your credit rather than settled. See Prepaid credit for the full model. (This is about job payments; deleting a feed or episode does not refund the storage you already used.)

Error codes

Failures throw a typed error rendered as code (+ sub_reason). payment_failed comes from the SDK's 402 handshake before any cast handler runs.

Code	Representative sub-reasons	Trigger
auth_error	signature_invalid, timestamp_drift, replay_detected	Request signature, clock, or nonce invalid
invalid_input	ssrf_blocked, wrong_content_type, oversize, probe_failed, cover_invalid, audio_source_required, upload-handle not_found / expired / not_owner / kind_mismatch	Bad source URL, bad asset, or a bad/expired upload handle
feed_full	—	Feed already at 50 episodes. Delete one or use a new feed_slug
provider_error	upstream_status, upstream_timeout, upstream_network, upload_failed	The upstream source or storage host failed, not cast itself. Transient, retry
rate_limited	upstream, ingest_concurrency, ingest_ip_concurrency, ingest_global_concurrency	Upstream 429 or a concurrent-upload cap. Back off per Retry-After
not_found	feed_not_found, episode_not_found, path_not_found	Operating on a feed/episode the caller doesn't own or that doesn't exist
internal_error	unexpected	An unexpected DVM-side fault

See also

• Explore the catalog · dvm CLI reference · Caller quickstart
• Other first-party DVMs: scrape · scribe · narrate · discover