diff --git a/packages/runtime/src/__tests__/model-adapter.test.ts b/packages/runtime/src/__tests__/model-adapter.test.ts
index 0697f0d9b0..7941d1a3f9 100644
--- a/packages/runtime/src/__tests__/model-adapter.test.ts
+++ b/packages/runtime/src/__tests__/model-adapter.test.ts
@@ -214,6 +214,41 @@ describe('ModelAdapter stream and error normalization', () => {
     assert.equal(adapter.mapFinishReason('provider-new-reason'), 'end_turn');
   });
 
+  test('projects a structured network error to a consistent reason and safe message', () => {
+    const event = newAdapter().makeErrorEvent('turn-1', {
+      message: 'fetch failed',
+      detail: 'token=sk-live-secret-token-value',
+    });
+
+    assert.equal(event.reason, 'network');
+    assert.equal(event.message, 'Network error');
+    assert.equal(JSON.stringify(event).includes('sk-live-secret-token-value'), false);
+  });
+
+  test('retains Node connection copy without promoting retry classification', () => {
+    const adapter = newAdapter();
+    const error = new Error('connect ECONNREFUSED 127.0.0.1:443');
+    const event = adapter.makeErrorEvent('turn-1', error);
+
+    assert.equal(adapter.classifyError(error), 'Error');
+    assert.equal(event.reason, undefined);
+    assert.equal(event.message, 'Network error');
+  });
+
+  test('projects string provider errors through the same classification', () => {
+    const event = newAdapter().makeErrorEvent('turn-1', 'fetch failed');
+
+    assert.equal(event.reason, 'network');
+    assert.equal(event.message, 'Network error');
+  });
+
+  test('keeps an unknown structured provider error generic', () => {
+    const event = newAdapter().makeErrorEvent('turn-1', { message: 'provider exploded' });
+
+    assert.equal(event.reason, undefined);
+    assert.equal(event.message, 'Operation failed');
+  });
+
   test('classifies provider context-length overflow errors as ContextLength', () => {
     const adapter = newAdapter();
     const overflow = (message: string, extra: Record<string, unknown> = {}) =>
diff --git a/packages/runtime/src/model-adapter.ts b/packages/runtime/src/model-adapter.ts
index 533c454a3a..383e17d8ba 100644
--- a/packages/runtime/src/model-adapter.ts
+++ b/packages/runtime/src/model-adapter.ts
@@ -12,7 +12,7 @@ import type { ModelMessage } from 'ai';
 
 import type { AsyncEventQueue } from './async-queue.js';
 import { resolveModelRuntime } from './model-runtime.js';
-import { classifyError, errorReasonFromClass } from './tool-runtime.js';
+import { classifyError, errorPresentationFromClass } from './tool-runtime.js';
 
 /**
  * Build an ai-sdk LanguageModel from a single input object.
@@ -301,8 +301,9 @@ export class ModelAdapter {
   }
 
   makeErrorEvent(turnId: string, err: unknown): ErrorEvent {
-    const message = generalizedErrorMessage(err);
-    const reason = errorReasonFromClass(classifyError(err));
+    const errorClass = classifyError(err);
+    const presentation = errorPresentationFromClass(errorClass);
+    const message = presentation.message ?? generalizedErrorMessage(err);
     const code = err instanceof Error && 'code' in err
       ? String((err as { code?: unknown }).code)
       : undefined;
@@ -313,7 +314,7 @@ export class ModelAdapter {
       ts: this.input.now(),
       recoverable: false,
       ...(code !== undefined ? { code } : {}),
-      ...(reason !== undefined ? { reason } : {}),
+      ...(presentation.reason !== undefined ? { reason: presentation.reason } : {}),
       message,
     };
   }
diff --git a/packages/runtime/src/tool-runtime.ts b/packages/runtime/src/tool-runtime.ts
index 01231bf270..e3f6f678f0 100644
--- a/packages/runtime/src/tool-runtime.ts
+++ b/packages/runtime/src/tool-runtime.ts
@@ -1647,24 +1647,27 @@ export function classifyError(error: unknown): string {
   return error instanceof Error ? (error.name || 'Other') : 'Other';
 }
 
-export function errorReasonFromClass(errorClass: string): string | undefined {
+export function errorPresentationFromClass(errorClass: string): {
+  reason?: string;
+  message?: string;
+} {
   switch (errorClass) {
     case 'ContextLength':
-      return 'context_overflow';
+      return { reason: 'context_overflow', message: 'Context window exceeded' };
     case 'Timeout':
-      return 'timeout';
+      return { reason: 'timeout', message: 'Request timed out' };
     case 'Auth':
-      return 'auth';
+      return { reason: 'auth', message: 'Authentication failed' };
     case 'ProviderBilling':
-      return 'provider_billing';
+      return { reason: 'provider_billing', message: 'Provider billing required' };
     case 'ProviderUnavailable':
-      return 'provider_unavailable';
+      return { reason: 'provider_unavailable', message: 'Provider returned an error' };
     case 'RateLimit':
-      return 'rate_limit';
+      return { reason: 'rate_limit', message: 'Rate limit exceeded' };
     case 'Network':
-      return 'network';
+      return { reason: 'network', message: 'Network error' };
     default:
-      return undefined;
+      return {};
   }
 }