feat(core): preserve provider response body in session errors (anomal…

…yco#52136)
shuv1337 · Sep 30, 2026 · Sep 29, 2026 · Sep 29, 2026 · Sep 29, 2026 · Sep 29, 2026
commit c14a1f5acfa4d73ad15fb927e34810a329f0df57
diff --git a/packages/client/src/effect/api/api.ts b/packages/client/src/effect/api/api.ts
@@ -710,7 +710,12 @@ export type SessionLogOutput =
             | undefined
           readonly data: {
             readonly sessionID: Session.ID
-            readonly error: { readonly type: string; readonly message: string; readonly status?: number | undefined }
+            readonly error: {
+              readonly type: string
+              readonly message: string
+              readonly status?: number | undefined
+              readonly response?: { readonly body: string } | undefined
+            }
           }
         }
       | {
@@ -902,7 +907,12 @@ export type SessionLogOutput =
           readonly data: {
             readonly sessionID: Session.ID
             readonly assistantMessageID: SessionMessage.ID
-            readonly error: { readonly type: string; readonly message: string; readonly status?: number | undefined }
+            readonly error: {
+              readonly type: string
+              readonly message: string
+              readonly status?: number | undefined
+              readonly response?: { readonly body: string } | undefined
+            }
             readonly finish?: "content-filter" | undefined
             readonly rawFinish?: string | undefined
             readonly providerState?: SessionMessage.ProviderState | undefined
@@ -1112,7 +1122,12 @@ export type SessionLogOutput =
             readonly sessionID: Session.ID
             readonly assistantMessageID: SessionMessage.ID
             readonly id: string
-            readonly error: { readonly type: string; readonly message: string; readonly status?: number | undefined }
+            readonly error: {
+              readonly type: string
+              readonly message: string
+              readonly status?: number | undefined
+              readonly response?: { readonly body: string } | undefined
+            }
             readonly content?:
               | readonly [
                   (
@@ -1157,7 +1172,12 @@ export type SessionLogOutput =
             readonly assistantMessageID: SessionMessage.ID
             readonly attempt: number
             readonly at: number
-            readonly error: { readonly type: string; readonly message: string; readonly status?: number | undefined }
+            readonly error: {
+              readonly type: string
+              readonly message: string
+              readonly status?: number | undefined
+              readonly response?: { readonly body: string } | undefined
+            }
           }
         }
       | {
@@ -1238,7 +1258,12 @@ export type SessionLogOutput =
           readonly data: {
             readonly sessionID: Session.ID
             readonly reason: "auto" | "manual"
-            readonly error: { readonly type: string; readonly message: string; readonly status?: number | undefined }
+            readonly error: {
+              readonly type: string
+              readonly message: string
+              readonly status?: number | undefined
+              readonly response?: { readonly body: string } | undefined
+            }
             readonly inputID?: SessionMessage.ID | undefined
             readonly cost?: (number & Brand.Brand<"Money.USD">) | undefined
             readonly tokens?:

diff --git a/packages/client/src/promise/generated/types.ts b/packages/client/src/promise/generated/types.ts
@@ -133,7 +133,7 @@ export type ToolTextContent = { type: "text"; text: string }
 
 export type ToolFileContent = { type: "file"; uri: string; mime: string; name?: string | null }
 
-export type SessionStructuredError = { type: string; message: string; status?: number }
+export type SessionStructuredError = { type: string; message: string; status?: number; response?: { body: string } }
 
 export type SessionMessageCompactionRunning = {
   type: "compaction"
@@ -3183,7 +3183,12 @@ export type SessionImportInput = {
                   | {
                       readonly status: "error"
                       readonly input: { readonly [x: string]: JsonValue }
-                      readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+                      readonly error: {
+                        readonly type: string
+                        readonly message: string
+                        readonly status?: number
+                        readonly response?: { readonly body: string }
+                      }
                       readonly content?: readonly [
                         (
                           | { readonly type: "text"; readonly text: string }
@@ -3220,11 +3225,21 @@ export type SessionImportInput = {
             readonly reasoning: number
             readonly cache: { readonly read: number; readonly write: number }
           }
-          readonly error?: { readonly type: string; readonly message: string; readonly status?: number }
+          readonly error?: {
+            readonly type: string
+            readonly message: string
+            readonly status?: number
+            readonly response?: { readonly body: string }
+          }
           readonly retry?: {
             readonly attempt: number
             readonly at: number
-            readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+            readonly error: {
+              readonly type: string
+              readonly message: string
+              readonly status?: number
+              readonly response?: { readonly body: string }
+            }
           }
         }
       | (
@@ -3276,7 +3291,12 @@ export type SessionImportInput = {
               readonly time: { readonly created: number }
               readonly status: "failed"
               readonly reason: "auto" | "manual"
-              readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+              readonly error: {
+                readonly type: string
+                readonly message: string
+                readonly status?: number
+                readonly response?: { readonly body: string }
+              }
               readonly cost?: number
               readonly tokens?: {
                 readonly input: number
@@ -3500,7 +3520,12 @@ export type SessionImportInput = {
                   | {
                       readonly status: "error"
                       readonly input: { readonly [x: string]: JsonValue }
-                      readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+                      readonly error: {
+                        readonly type: string
+                        readonly message: string
+                        readonly status?: number
+                        readonly response?: { readonly body: string }
+                      }
                       readonly content?: readonly [
                         (
                           | { readonly type: "text"; readonly text: string }
@@ -3537,11 +3562,21 @@ export type SessionImportInput = {
             readonly reasoning: number
             readonly cache: { readonly read: number; readonly write: number }
           }
-          readonly error?: { readonly type: string; readonly message: string; readonly status?: number }
+          readonly error?: {
+            readonly type: string
+            readonly message: string
+            readonly status?: number
+            readonly response?: { readonly body: string }
+          }
           readonly retry?: {
             readonly attempt: number
             readonly at: number
-            readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+            readonly error: {
+              readonly type: string
+              readonly message: string
+              readonly status?: number
+              readonly response?: { readonly body: string }
+            }
           }
         }
       | (
@@ -3593,7 +3628,12 @@ export type SessionImportInput = {
               readonly time: { readonly created: number }
               readonly status: "failed"
               readonly reason: "auto" | "manual"
-              readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+              readonly error: {
+                readonly type: string
+                readonly message: string
+                readonly status?: number
+                readonly response?: { readonly body: string }
+              }
               readonly cost?: number
               readonly tokens?: {
                 readonly input: number
@@ -3817,7 +3857,12 @@ export type SessionImportInput = {
                   | {
                       readonly status: "error"
                       readonly input: { readonly [x: string]: JsonValue }
-                      readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+                      readonly error: {
+                        readonly type: string
+                        readonly message: string
+                        readonly status?: number
+                        readonly response?: { readonly body: string }
+                      }
                       readonly content?: readonly [
                         (
                           | { readonly type: "text"; readonly text: string }
@@ -3854,11 +3899,21 @@ export type SessionImportInput = {
             readonly reasoning: number
             readonly cache: { readonly read: number; readonly write: number }
           }
-          readonly error?: { readonly type: string; readonly message: string; readonly status?: number }
+          readonly error?: {
+            readonly type: string
+            readonly message: string
+            readonly status?: number
+            readonly response?: { readonly body: string }
+          }
           readonly retry?: {
             readonly attempt: number
             readonly at: number
-            readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+            readonly error: {
+              readonly type: string
+              readonly message: string
+              readonly status?: number
+              readonly response?: { readonly body: string }
+            }
           }
         }
       | (
@@ -3910,7 +3965,12 @@ export type SessionImportInput = {
               readonly time: { readonly created: number }
               readonly status: "failed"
               readonly reason: "auto" | "manual"
-              readonly error: { readonly type: string; readonly message: string; readonly status?: number }
+              readonly error: {
+                readonly type: string
+                readonly message: string
+                readonly status?: number
+                readonly response?: { readonly body: string }
+              }
               readonly cost?: number
               readonly tokens?: {
                 readonly input: number

diff --git a/packages/core/src/session/to-session-error.ts b/packages/core/src/session/to-session-error.ts
@@ -69,5 +69,10 @@ export function toSessionError(cause: unknown): SessionError.Error {
 
 function providerError(type: string, reason: AIError["reason"]): SessionError.Error {
   const status = reason.http?.status
-  return { type, message: reason.message, ...(status === undefined ? {} : { status }) }
+  return {
+    type,
+    message: reason.message,
+    ...(status === undefined ? {} : { status }),
+    ...(reason.body === undefined ? {} : { response: { body: reason.body } }),
+  }
 }
diff --git a/packages/core/test/session-error.test.ts b/packages/core/test/session-error.test.ts
@@ -110,6 +110,7 @@ describe("toSessionError", () => {
       type: "provider.invalid-request",
       message: "too large",
       status: 413,
+      response: { body: '{"error":"context limit"}' },
     })
     expect(
       toSessionError(
@@ -127,6 +128,14 @@ describe("toSessionError", () => {
     })
   })
 
+  test("preserves provider response body without HTTP status", () => {
+    expect(toSessionError(llm(new RateLimitError({ message: "Slow down", body: '{"error":"rate limit"}' })))).toEqual({
+      type: "provider.rate-limit",
+      message: "Slow down",
+      response: { body: '{"error":"rate limit"}' },
+    })
+  })
+
   test("preserves unresolved provider endpoint errors", () => {
     const error = new ModelResolver.UnresolvedProviderVariablesError({
       providerID: Provider.ID.make("cloudflare-workers-ai"),

diff --git a/packages/schema/src/session-error.ts b/packages/schema/src/session-error.ts
@@ -8,4 +8,5 @@ export const Error = Schema.Struct({
   type: Schema.String,
   message: Schema.String,
   status: Schema.Int.check(Schema.isBetween({ minimum: 100, maximum: 599 })).pipe(optional),
+  response: Schema.Struct({ body: Schema.String }).pipe(optional),
 }).annotate({ identifier: "Session.StructuredError" })
diff --git a/packages/schema/test/session-error.test.ts b/packages/schema/test/session-error.test.ts
@@ -11,6 +11,7 @@ describe("SessionError", () => {
   test("round trips current and future error types through JSON", () => {
     const values: SessionError.Error[] = [
       { type: "provider.rate-limit", message: "Slow down" },
+      { type: "provider.rate-limit", message: "Slow down", status: 429, response: { body: '{"error":{}}' } },
       { type: "provider.auth", message: "Authentication failed" },
       { type: "provider.future-condition", message: "A future provider failure" },
       { type: "unknown", message: "Unexpected" },
@@ -36,6 +37,9 @@ describe("SessionError", () => {
   test("rejects missing envelope fields", () => {
     expect(() => Schema.decodeUnknownSync(SessionError.Error)({ type: "provider.auth" })).toThrow()
     expect(() => Schema.decodeUnknownSync(SessionError.Error)({ message: "Missing type" })).toThrow()
+    expect(() =>
+      Schema.decodeUnknownSync(SessionError.Error)({ type: "provider.auth", message: "Failed", response: {} }),
+    ).toThrow()
   })
 })