fix(core): preserve provider session failures

packages/schema/src/session-event.ts

@@ -50,6 +50,10 @@ const stepSettlementOptions = {
 
 export const UnknownError = SessionMessage.UnknownError
 export type UnknownError = SessionMessage.UnknownError
+export const ProviderError = SessionMessage.ProviderError
+export type ProviderError = SessionMessage.ProviderError
+export const Error = SessionMessage.Error
+export type Error = SessionMessage.Error
 
 export const AgentSwitched = Event.define({
   type: "session.next.agent.switched",
@@ -188,7 +192,7 @@ export namespace Step {
     schema: {
       ...Base,
       assistantMessageID: SessionMessageID.ID,
-      error: UnknownError,
+      error: Error,
     },
   })
   export type Failed = typeof Failed.Type

packages/schema/src/session-message.ts

@@ -17,6 +17,33 @@ export const UnknownError = Schema.Struct({
   message: Schema.String,
 }).annotate({ identifier: "Session.Error.Unknown" })
 
+export const ProviderErrorCategory = Schema.Literals([
+  "invalid-request",
+  "no-route",
+  "authentication",
+  "rate-limit",
+  "quota-exceeded",
+  "content-policy",
+  "provider-internal",
+  "transport",
+  "invalid-provider-output",
+  "unknown",
+])
+export type ProviderErrorCategory = typeof ProviderErrorCategory.Type
+
+export interface ProviderError extends Schema.Schema.Type<typeof ProviderError> {}
+export const ProviderError = Schema.Struct({
+  type: Schema.Literal("provider"),
+  category: ProviderErrorCategory,
+  message: Schema.String,
+  status: Schema.Finite.pipe(Schema.optional),
+  retryable: Schema.Boolean,
+  retryAfterMs: Schema.Finite.pipe(Schema.optional),
+}).annotate({ identifier: "Session.Error.Provider" })
+
+export const Error = Schema.Union([UnknownError, ProviderError]).pipe(Schema.toTaggedUnion("type"))
+export type Error = UnknownError | ProviderError
+
 const Base = {
   id: ID,
   metadata: Schema.Record(Schema.String, Schema.Unknown).pipe(Schema.optional),
@@ -173,7 +200,7 @@ export const Assistant = Schema.Struct({
     reasoning: Schema.Finite,
     cache: Schema.Struct({ read: Schema.Finite, write: Schema.Finite }),
   }).pipe(Schema.optional),
-  error: UnknownError.pipe(Schema.optional),
+  error: Error.pipe(Schema.optional),
   time: Schema.Struct({
     created: DateTimeUtcFromMillis,
     completed: DateTimeUtcFromMillis.pipe(Schema.optional),