diff --git a/packages/ai/src/decision.ts b/packages/ai/src/decision.ts
index 83009bd2c0b..ffd5f28feff 100644
--- a/packages/ai/src/decision.ts
+++ b/packages/ai/src/decision.ts
@@ -155,10 +155,11 @@ export interface DecisionModelRoute<Options extends DecisionOptions = DecisionOp
 export class DecisionModelCompatibility extends Schema.Class<DecisionModelCompatibility>("Decision.ModelCompatibility")(
   {
     /**
-     * Where a System One host reads media, from models.dev `[api.systemone] compatibility.image_input`:
-     * `assets` (TypeSafe's assets map), `images` (top-level lists) or `state` (items inside a state list).
+     * Where a System One host reads media, from models.dev `[api.systemone] compatibility.media_input`, named after
+     * where the media goes in the body: `assets` (TypeSafe's assets map, referenced from the state), `state` (items
+     * inside a state list) or `root` (one top-level list per kind: `images`, `audio`, `videos`).
      */
-    imageInput: Schema.optional(Schema.Literals(["assets", "images", "state"])),
+    mediaInput: Schema.optional(Schema.Literals(["assets", "state", "root"])),
   },
 ) {}
 
diff --git a/packages/ai/src/protocols/cloudflare-run-decisions.ts b/packages/ai/src/protocols/cloudflare-run-decisions.ts
index 2d1a93cbf96..c806029ac4f 100644
--- a/packages/ai/src/protocols/cloudflare-run-decisions.ts
+++ b/packages/ai/src/protocols/cloudflare-run-decisions.ts
@@ -27,7 +27,7 @@ export const protocol = DecisionRoute.protocol({
   inlineMedia: true,
   body: {
     from: (request) =>
-      SystemOne.encodeBody(request, "images").pipe(Effect.map((input) => ({ model: request.model.id, input }))),
+      SystemOne.encodeBody(request, "root").pipe(Effect.map((input) => ({ model: request.model.id, input }))),
   },
   response: {
     decode: (response, context) =>
diff --git a/packages/ai/src/protocols/system-one.ts b/packages/ai/src/protocols/system-one.ts
index da9000be9cc..fd4b9382bbc 100644
--- a/packages/ai/src/protocols/system-one.ts
+++ b/packages/ai/src/protocols/system-one.ts
@@ -19,8 +19,8 @@ export const DEFAULT_PATH = "/systemone"
 
 export const DEFAULT_BASE_URL = "https://api.typesafe.ai/v1"
 
-/** `messages` is Baseten's own placement (parts in a user message inside `state.messages`), set by its provider. */
-type ImageInput = NonNullable<DecisionModelCompatibility["imageInput"]> | "messages"
+/** `state.messages` is Baseten's own placement (parts in a user message inside `state.messages`), set by its provider. */
+type MediaInput = NonNullable<DecisionModelCompatibility["mediaInput"]> | "state.messages"
 
 const Probability = Schema.Number.check(Schema.isBetween({ minimum: 0, maximum: 1 }))
 const Answer = Schema.Union([
@@ -58,13 +58,13 @@ export type Response = Schema.Schema.Type<typeof Response>
 const ID = "system-one"
 const NAME = "System One"
 
-/** The System One body without `model`; media goes where the model's `imageInput` says, else `fallback`. */
+/** The System One body without `model`; media goes where the model's `mediaInput` says, else `fallback`. */
 export const encodeBody = Effect.fn("SystemOne.encodeBody")(function* (
   request: DecisionRequestFor,
-  fallback: ImageInput,
+  fallback: MediaInput,
 ) {
   const questions = yield* encodeQuestions(request.questions)
-  const placed = yield* placeMedia(request, request.model.compatibility?.imageInput ?? fallback)
+  const placed = yield* placeMedia(request, request.model.compatibility?.mediaInput ?? fallback)
   return { ...mergeJsonRecords(request.providerOptions, request.http?.body), ...placed, questions }
 })
 
@@ -103,7 +103,7 @@ const encodeQuestions = (questions: ReadonlyArray<DecisionQuestion>) =>
     ] as const)
   }).pipe(Effect.map(Object.fromEntries))
 
-const placeMedia = Effect.fnUntraced(function* (request: DecisionRequestFor, imageInput: ImageInput) {
+const placeMedia = Effect.fnUntraced(function* (request: DecisionRequestFor, mediaInput: MediaInput) {
   const parts = request.input
   const unsupported = (asset: Media.Asset, accepted: string) =>
     new AIError({
@@ -116,9 +116,9 @@ const placeMedia = Effect.fnUntraced(function* (request: DecisionRequestFor, ima
     })
   const media = parts.flatMap((part) => (part.type === "media" ? [part.media] : []))
   if (media.length === 0) return { state: state(parts.map(plain)) }
-  if (imageInput === "state") return { state: yield* Effect.forEach(parts, (part) => stateItem(part, unsupported)) }
+  if (mediaInput === "state") return { state: yield* Effect.forEach(parts, (part) => stateItem(part, unsupported)) }
   // Chat-style content in one user message: text and JSON as text parts, media as in `state`.
-  if (imageInput === "messages")
+  if (mediaInput === "state.messages")
     return {
       state: {
         messages: [
@@ -133,7 +133,7 @@ const placeMedia = Effect.fnUntraced(function* (request: DecisionRequestFor, ima
         ],
       },
     }
-  if (imageInput === "images") {
+  if (mediaInput === "root") {
     const lists = { image: "images", audio: "audio", video: "videos" } as const
     const unplaced = media.find((asset) => !Object.hasOwn(lists, asset.kind))
     if (unplaced !== undefined) return yield* unsupported(unplaced, "images, audio and video")
diff --git a/packages/ai/src/providers/baseten.ts b/packages/ai/src/providers/baseten.ts
index e5a80243976..77d6f4fade9 100644
--- a/packages/ai/src/providers/baseten.ts
+++ b/packages/ai/src/providers/baseten.ts
@@ -47,7 +47,7 @@ const decisionProtocol = DecisionRoute.protocol({
   id: "baseten-system-one",
   body: {
     from: (request) =>
-      SystemOne.encodeBody(request, "messages").pipe(Effect.map((body) => ({ ...body, model: request.model.id }))),
+      SystemOne.encodeBody(request, "state.messages").pipe(Effect.map((body) => ({ ...body, model: request.model.id }))),
   },
 })
 
diff --git a/packages/ai/src/providers/openrouter.ts b/packages/ai/src/providers/openrouter.ts
index f0972ac7ec5..1ef52754f2f 100644
--- a/packages/ai/src/providers/openrouter.ts
+++ b/packages/ai/src/providers/openrouter.ts
@@ -203,7 +203,7 @@ export const configure = (input: LanguageModelOptions = {}) => {
     http: input.http,
   })
   const decision = (modelID: string | ModelID) =>
-    decisionRoute.model<OpenRouterDecisionOptions>({ id: modelID, compatibility: { imageInput: "state" } })
+    decisionRoute.model<OpenRouterDecisionOptions>({ id: modelID, compatibility: { mediaInput: "state" } })
   return {
     id,
     model: (modelID: string | ModelID) =>