fix(images): forward Antigravity image size (#11952)

Boarded with #11954/#11953/#11951/#11948 in one combined worktree: typecheck:core, check:file-size, check:changelog-integrity, check:complexity, check:cognitive-complexity, check:cycles all green; 85/85 focused tests pass. Confirmed the Antigravity Gemini path only forwarded aspectRatio into generationConfig, dropping the requested size tier entirely. Thanks for the fix and the 3:4/2K regression coverage.

open-sse/handlers/imageGeneration.ts

@@ -175,6 +175,7 @@ const OPENAI_IMAGE_TO_IMAGE_MODELS = new Set([
 ]);
 
 const IMAGE_ASPECT_RATIO_PATTERN = /^\d+:\d+$/;
+const IMAGE_SIZE_PATTERN = /^(?:1K|2K|4K)$/;
 
 /**
  * Resolve the upstream images endpoint for a custom (OpenAI-compatible) image
@@ -235,6 +236,13 @@ function normalizeImageAspectRatio(value: unknown, fallbackSize: unknown): strin
   return mapImageSize(typeof fallbackSize === "string" ? fallbackSize : null);
 }
 
+function normalizeImageGenerationSize(snakeCaseValue: unknown, camelCaseValue: unknown): string {
+  const value = snakeCaseValue ?? camelCaseValue;
+  if (typeof value !== "string") return "1K";
+  const normalized = value.trim().toUpperCase();
+  return IMAGE_SIZE_PATTERN.test(normalized) ? normalized : "1K";
+}
+
 function parseJsonOrNull(value: string): unknown | null {
   try {
     return JSON.parse(value);
@@ -996,12 +1004,16 @@ async function handleGeminiImageGeneration({ model, providerConfig, body, creden
   const candidateCount =
     typeof body.n === "number" && Number.isFinite(body.n) && body.n > 0 ? Math.floor(body.n) : 1;
   const promptText = typeof body.prompt === "string" ? body.prompt : String(body.prompt ?? "");
+  const aspectRatio = normalizeImageAspectRatio(body.aspect_ratio, body.size);
+  const imageSize = normalizeImageGenerationSize(body.image_size, body.imageSize);
 
   // Summarized request for call log
   const logRequestBody = {
     model: body.model,
     prompt: promptText.slice(0, 200),
     size: body.size || "default",
+    aspect_ratio: aspectRatio,
+    image_size: imageSize,
     n: candidateCount,
   };
 
@@ -1030,7 +1042,8 @@ async function handleGeminiImageGeneration({ model, providerConfig, body, creden
       generationConfig: {
         candidateCount,
         imageConfig: {
-          aspectRatio: normalizeImageAspectRatio(body.aspect_ratio, body.size),
+          aspectRatio,
+          imageSize,
         },
       },
     },
@@ -1050,7 +1063,7 @@ async function handleGeminiImageGeneration({ model, providerConfig, body, creden
     const promptPreview = promptText.slice(0, 60);
     log.info(
       "IMAGE",
-      `antigravity/${model} (gemini) | prompt: "${promptPreview}..." | format: gemini-image`
+      `antigravity/${model} (gemini) | prompt: "${promptPreview}..." | ${aspectRatio} ${imageSize}`
     );
   }
 

tests/unit/image-generation-handler.test.ts

@@ -752,7 +752,8 @@ test("handleImageGeneration sends Antigravity image requests with native image_g
         model: "antigravity/gemini-3.1-flash-image-preview",
         prompt: "painted beach",
         size: "1024x1024",
-        aspect_ratio: "not-a-ratio",
+        aspect_ratio: "3:4",
+        image_size: "2K",
       },
       credentials: { accessToken: "ag-token", projectId: "project-123" },
       log: null,
@@ -777,7 +778,7 @@ test("handleImageGeneration sends Antigravity image requests with native image_g
       contents: [{ role: "user", parts: [{ text: "painted beach" }] }],
       generationConfig: {
         candidateCount: 1,
-        imageConfig: { aspectRatio: "1:1" },
+        imageConfig: { aspectRatio: "3:4", imageSize: "2K" },
       },
     });
     assert.deepEqual(result.data.data, [