fix: isolate visual tool failures from agent runs

session-reply-wait.test.mjs

@@ -2,6 +2,7 @@ import assert from 'node:assert/strict';
 import test from 'node:test';
 import { ReadableStream } from 'node:stream/web';
 import {
+  classifySessionProviderErrorMessage,
   consumeSessionEventsUntilFinish,
   eventMatchesRequest,
   parseSessionStreamEvent,
@@ -139,3 +140,45 @@ test('consumeSessionEventsUntilFinish surfaces provider tool history errors befo
     },
   );
 });
+
+test('consumeSessionEventsUntilFinish classifies unsupported visual history as degradable', async () => {
+  const message =
+    'Request failed: Bad request (400): Failed to deserialize the JSON body into the target type: messages[8]: unknown variant `image_url`, expected `text`';
+  assert.equal(
+    classifySessionProviderErrorMessage(message),
+    'SESSION_VISUAL_CONTEXT_UNSUPPORTED',
+  );
+
+  const frames = [
+    `data: ${JSON.stringify({
+      type: 'Message',
+      request_id: 'req-visual',
+      message: {
+        role: 'assistant',
+        content: [{
+          type: 'text',
+          text: `Ran into this error: ${message}\n\nPlease retry if you think this is a transient or recoverable error.`,
+        }],
+      },
+    })}\n\n`,
+    'data: {"type":"Finish","request_id":"req-visual"}\n\n',
+  ];
+  const stream = new ReadableStream({
+    start(controller) {
+      for (const frame of frames) controller.enqueue(new TextEncoder().encode(frame));
+      controller.close();
+    },
+  });
+
+  await assert.rejects(
+    consumeSessionEventsUntilFinish(stream, {
+      requestId: 'req-visual',
+      timeoutMs: 5000,
+    }),
+    (error) => {
+      assert.equal(error.code, 'SESSION_VISUAL_CONTEXT_UNSUPPORTED');
+      assert.equal(error.retryable, false);
+      return true;
+    },
+  );
+});