diff --git a/.changeset/fix-eve-update-vendored-types-for-modern-eve.md b/.changeset/fix-eve-update-vendored-types-for-modern-eve.md
new file mode 100644
index 000000000..3a4c0c92b
--- /dev/null
+++ b/.changeset/fix-eve-update-vendored-types-for-modern-eve.md
@@ -0,0 +1,5 @@
+---
+"braintrust": patch
+---
+
+fix(eve): update vendored types for modern Eve
diff --git a/js/src/instrumentation/plugins/eve-plugin.ts b/js/src/instrumentation/plugins/eve-plugin.ts
index 407d92d93..a740929b8 100644
--- a/js/src/instrumentation/plugins/eve-plugin.ts
+++ b/js/src/instrumentation/plugins/eve-plugin.ts
@@ -29,7 +29,7 @@ import type {
   EveRuntimeActionResult,
   EveRuntimeToolCallActionRequest,
   EveRuntimeToolResultActionResult,
-  EveSystemModelMessage,
+  EveStreamEvent,
 } from "../../vendor-sdk-types/eve";
 
 type SpanState = {
@@ -132,7 +132,9 @@ export function braintrustEveHook(options: {
   const bridge = new EveBridge(state);
   return {
     events: {
-      "*": async (event: EveHandleMessageStreamEvent, ctx: EveHookContext) => {
+      // Eve delivers every accepted stream event here, including ones newer
+      // than the union we model; `bridge.handle` narrows and ignores the rest.
+      "*": async (event: EveStreamEvent, ctx: EveHookContext) => {
         await bridge.handle(event, ctx, options.metadata);
       },
     },
@@ -153,6 +155,9 @@ export function createLegacyEveInstrumentation(options: {
         } catch (error) {
           debugLogger.warn("Error in Eve LLM input capture:", error);
         }
+        // We capture input for our own spans and contribute no runtime context
+        // to Eve's AI SDK telemetry spans.
+        return undefined;
       },
     },
     recordInputs: false,
@@ -167,6 +172,29 @@ function isEveHandleMessageStreamEvent(
   return isObject(event) && typeof event["type"] === "string";
 }
 
+/**
+ * Eve types model messages as the AI SDK's `ModelMessage`, whose shape moves
+ * between `ai` majors, so the boundary is untyped and asserted here instead.
+ * This checks only what the serializer relies on: a known role and a content
+ * value it can walk.
+ */
+function isEveModelMessage(message: unknown): message is EveModelMessage {
+  if (!isObject(message)) {
+    return false;
+  }
+  const role = message["role"];
+  if (
+    role !== "system" &&
+    role !== "user" &&
+    role !== "assistant" &&
+    role !== "tool"
+  ) {
+    return false;
+  }
+  const content = message["content"];
+  return typeof content === "string" || Array.isArray(content);
+}
+
 class ResumedEveSpan implements EveSpan {
   private endTime: number | undefined;
 
@@ -1965,11 +1993,15 @@ export function capturedModelInput(
   if (typeof instructions === "string") {
     value.push({ content: instructions, role: "system" });
   } else if (Array.isArray(instructions)) {
-    value.push(...instructions.map(capturedEveModelMessage));
-  } else if (instructions) {
-    value.push(capturedEveModelMessage(instructions as EveSystemModelMessage));
+    value.push(
+      ...instructions.filter(isEveModelMessage).map(capturedEveModelMessage),
+    );
+  } else if (isEveModelMessage(instructions)) {
+    value.push(capturedEveModelMessage(instructions));
   }
-  value.push(...messages.map(capturedEveModelMessage));
+  value.push(
+    ...messages.filter(isEveModelMessage).map(capturedEveModelMessage),
+  );
 
   try {
     const cloned: unknown = JSON.parse(JSON.stringify(value));
@@ -2110,6 +2142,13 @@ function capturedEveModelContentPart(
         providerReference: part.providerReference,
         type: part.type,
       };
+    default:
+      // Eve can deliver content parts newer than the ones we model. Record the
+      // discriminator so the message still round-trips instead of becoming a
+      // hole in the captured input.
+      return isObject(part) && typeof part["type"] === "string"
+        ? { type: part["type"] }
+        : {};
   }
 }
 
diff --git a/js/src/vendor-sdk-types/eve.ts b/js/src/vendor-sdk-types/eve.ts
index b8d535a88..8b08a136b 100644
--- a/js/src/vendor-sdk-types/eve.ts
+++ b/js/src/vendor-sdk-types/eve.ts
@@ -291,18 +291,29 @@ export type EveHandleMessageStreamEvent =
       readonly type: "session.completed";
     };
 
+/**
+ * Loose shape of any runtime stream event delivered to the wildcard hook.
+ *
+ * Eve's `HookEventMap` is a closed map that grows over time (eve@0.48 exposes
+ * 33 events to authored hooks). Our handler must accept every one of them, so
+ * the boundary is typed loosely here and narrowed to
+ * {@link EveHandleMessageStreamEvent} inside the plugin. Keeping the two apart
+ * is what lets the event union above stay a discriminated union: folding a
+ * catch-all member into it would widen `data` to `unknown` after every
+ * `type` narrowing.
+ */
+export interface EveStreamEvent {
+  readonly data?: unknown;
+  readonly meta?: unknown;
+  readonly type: string;
+}
+
 export interface EveHookDefinition {
   readonly events?: {
     readonly "*"?: (
-      event: EveHandleMessageStreamEvent,
+      event: EveStreamEvent,
       ctx: EveHookContext,
     ) => void | Promise<void>;
-    readonly [eventType: string]:
-      | ((
-          event: EveHandleMessageStreamEvent,
-          ctx: EveHookContext,
-        ) => void | Promise<void>)
-      | undefined;
   };
 }
 
@@ -475,12 +486,19 @@ export type EveModelMessage =
       readonly role: "tool";
     };
 
+/**
+ * Model input snapshot handed to `step.started`.
+ *
+ * Eve types `messages` as the AI SDK's `ModelMessage` and `instructions` as
+ * `SystemModelMessage`, both of which change shape between `ai` majors. We only
+ * read these to serialize them, so the boundary stays untyped and the parts we
+ * capture are narrowed defensively by `capturedModelInput`. The capture
+ * contract itself lives in {@link EveModelMessage} and
+ * {@link EveModelMessageContentPart}.
+ */
 export interface EveInstrumentationModelInput {
-  readonly instructions?:
-    | string
-    | EveSystemModelMessage
-    | readonly EveSystemModelMessage[];
-  readonly messages: readonly EveModelMessage[];
+  readonly instructions?: unknown;
+  readonly messages: readonly unknown[];
 }
 
 export interface EveInstrumentationStepStartedEventInput {
@@ -499,14 +517,14 @@ export interface EveInstrumentationStepStartedEventInput {
 
 export interface EveInstrumentationDefinition {
   readonly events?: {
+    /**
+     * Eve requires this to return the runtime context to merge into the AI SDK
+     * telemetry span, or `undefined` to contribute none. `void` is not an
+     * accepted return type, so handlers must return explicitly.
+     */
     readonly "step.started"?: (
       input: EveInstrumentationStepStartedEventInput,
-    ) => void | { readonly runtimeContext?: EveJsonObject };
-    readonly [eventType: string]:
-      | ((
-          input: EveInstrumentationStepStartedEventInput,
-        ) => void | { readonly runtimeContext?: EveJsonObject })
-      | undefined;
+    ) => { readonly runtimeContext: EveJsonObject } | undefined;
   };
   readonly recordInputs?: boolean;
   readonly recordOutputs?: boolean;
@@ -526,7 +544,12 @@ export interface EveProviderSetupContext {
 }
 
 export interface EveProviderState {
-  get(): EveJsonValue | undefined;
+  /**
+   * Read as `unknown` rather than `EveJsonValue`: eve declares its JSON value
+   * as an interface-based union that is not structurally assignable to ours,
+   * and we narrow the stored value defensively at every read anyway.
+   */
+  get(): unknown;
   set(value: EveJsonValue | undefined): void;
 }