diff --git a/test/harness/replayingCapiProxy.test.ts b/test/harness/replayingCapiProxy.test.ts
index 062fe89ae9..2eb022ac13 100644
--- a/test/harness/replayingCapiProxy.test.ts
+++ b/test/harness/replayingCapiProxy.test.ts
@@ -1661,6 +1661,21 @@ Always include PINEAPPLE_COCONUT_42.
             data: Array<{ id: string }>;
           };
           expect(parsed.data.map((model) => model.id)).toEqual(["claude-sonnet-5"]);
+          expect(parsed.data[0]).toMatchObject({
+            capabilities: {
+              supports: { vision: true },
+              limits: {
+                vision: {
+                  max_prompt_images: 2,
+                  max_prompt_image_size: expect.any(Number),
+                  supported_media_types: expect.arrayContaining([
+                    "image/png",
+                    "image/jpeg",
+                  ]),
+                },
+              },
+            },
+          });
         } finally {
           await proxy.stop();
         }
@@ -1694,6 +1709,23 @@ Always include PINEAPPLE_COCONUT_42.
         expect(parsed.data).toHaveLength(2);
         expect(parsed.data[0].id).toBe("gpt-4o");
         expect(parsed.data[1].id).toBe("claude-sonnet-4");
+        for (const model of parsed.data) {
+          expect(model).toMatchObject({
+            capabilities: {
+              supports: { vision: true },
+              limits: {
+                vision: {
+                  max_prompt_images: 2,
+                  max_prompt_image_size: expect.any(Number),
+                  supported_media_types: expect.arrayContaining([
+                    "image/png",
+                    "image/jpeg",
+                  ]),
+                },
+              },
+            },
+          });
+        }
       } finally {
         await proxy.stop();
       }
diff --git a/test/harness/replayingCapiProxy.ts b/test/harness/replayingCapiProxy.ts
index 9bcafcdad4..ef4fadb9d4 100644
--- a/test/harness/replayingCapiProxy.ts
+++ b/test/harness/replayingCapiProxy.ts
@@ -14,6 +14,7 @@ import type {
 import { ChatCompletionStream } from "openai/resources/chat/completions";
 import path from "path";
 import yaml from "yaml";
+import type { ModelCapabilitiesLimitsVision } from "../../nodejs/src/generated/rpc";
 import {
   CapturedExchange,
   CapturingHttpProxy,
@@ -2018,7 +2019,15 @@ function createGetModelsResponse(modelIds: string[]) {
       name: id,
       capabilities: {
         supports: { vision: true },
-        limits: { max_context_window_tokens: 128000 },
+        limits: {
+          max_context_window_tokens: 128000,
+          // Replay fixtures contain two image-bearing messages.
+          vision: {
+            max_prompt_images: 2,
+            max_prompt_image_size: 20 * 1024 * 1024,
+            supported_media_types: ["image/png", "image/jpeg"],
+          } satisfies ModelCapabilitiesLimitsVision,
+        },
       },
     })),
   };