feat(image): add GPT Image 2.5 and default to flare (#1562)

OpenAI shipped GPT Image 2.5 on 2026-09-08 as two model IDs rather than one:
flare is tuned for speed, sunburst for editing precision. Both accept text and
image input and run on /images/generations, /images/edits and the Responses
API, which is the path the native image_generation tool already uses.

Flare replaces gpt-image-2 as the default because OpenAI reports higher quality
at roughly half the latency, which suits create_image's one-shot call. Both
gpt-image-2 and gpt-image-1.5 stay on the whitelist, so a saved image_model
keeps working untouched.

Also in this change:

- The rejection message is now built from the whitelist itself instead of a
  hand-written string that drifts whenever a model is added.
- codex_build.go uses the DefaultImageModel constant instead of hardcoding
  "gpt-image-2", so the inline chat path cannot drift from the shared default.
- Both new models join the isEditModel branch so reference images route to
  /images/edits.
- ParamField gains an optional labelKey, letting the dropdown read its label
  from i18n instead of showing English inside a translated UI. It passes a
  defaultValue, so a missing key degrades to the literal rather than breaking.
- Locale keys added to all five catalogs; ko was missing the whole
  mediaChain.imageModel* group.

Surface parity: the desktop UI is unchanged because sortable-provider-card
renders no param form and passes params through as Record<string, unknown>.
The CLI is unchanged because cmd/ exposes no image-model flag. The API contract
is unchanged because image_model lives in the free-form params map; only the
backend whitelist widened.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

internal/providers/codex_build.go

@@ -118,7 +118,7 @@ func (p *CodexProvider) buildRequestBody(req ChatRequest, stream bool) map[strin
 				tools = append(tools, map[string]any{
 					"type":           "image_generation",
 					"action":         "generate",
-					"model":          "gpt-image-2",
+					"model":          DefaultImageModel,
 					"output_format":  "png",
 					"partial_images": 1,
 				})

internal/providers/codex_native_image_test.go

@@ -53,7 +53,7 @@ func mockImageServer(t *testing.T, captured *[]byte) *httptest.Server {
 // asserts each required field is present and well-formed.
 //
 // Sub-cases:
-//   - Default (empty ImageModel) → tools[0].model == "gpt-image-2"
+//   - Default (empty ImageModel) → tools[0].model == DefaultImageModel
 //   - Legacy (ImageModel: "gpt-image-1.5") → tools[0].model == "gpt-image-1.5"
 //   - Rejected (ImageModel: "dall-e-3") → GenerateImage returns error containing "unsupported image model"
 func TestCodexGenerateImage_BuildsNativeRequest(t *testing.T) {
@@ -163,7 +163,7 @@ func TestCodexGenerateImage_BuildsNativeRequest(t *testing.T) {
 }
 
 // TestCodexGenerateImage_ImageModelDefault verifies that an empty ImageModel results
-// in the default gpt-image-2 model in the outbound tools[0].model field.
+// in DefaultImageModel in the outbound tools[0].model field.
 func TestCodexGenerateImage_ImageModelDefault(t *testing.T) {
 	var captured []byte
 	server := mockImageServer(t, &captured)
@@ -174,7 +174,7 @@ func TestCodexGenerateImage_ImageModelDefault(t *testing.T) {
 
 	_, err := p.GenerateImage(context.Background(), NativeImageRequest{
 		Prompt:      "test",
-		ImageModel:  "", // explicitly empty — should default to gpt-image-2
+		ImageModel:  "", // explicitly empty - should fall back to DefaultImageModel
 		AspectRatio: "1:1",
 	})
 	if err != nil {
@@ -190,8 +190,8 @@ func TestCodexGenerateImage_ImageModelDefault(t *testing.T) {
 		t.Fatal("tools array is empty")
 	}
 	tool, _ := tools[0].(map[string]any)
-	if imgModel, _ := tool["model"].(string); imgModel != "gpt-image-2" {
-		t.Errorf("tools[0].model = %q, want gpt-image-2 (default)", imgModel)
+	if imgModel, _ := tool["model"].(string); imgModel != DefaultImageModel {
+		t.Errorf("tools[0].model = %q, want %q (default)", imgModel, DefaultImageModel)
 	}
 }
 

internal/providers/codex_test.go

@@ -970,8 +970,8 @@ func TestCodexBuildRequestBodyImageGenerationTool(t *testing.T) {
 	if tool["action"] != "generate" {
 		t.Errorf("tool[action] = %v, want generate", tool["action"])
 	}
-	if tool["model"] != "gpt-image-2" {
-		t.Errorf("tool[model] = %v, want gpt-image-2", tool["model"])
+	if tool["model"] != DefaultImageModel {
+		t.Errorf("tool[model] = %v, want %v", tool["model"], DefaultImageModel)
 	}
 	if tool["output_format"] != "png" {
 		t.Errorf("tool[output_format] = %v, want png", tool["output_format"])
@@ -1039,8 +1039,8 @@ func TestCodexBuildRequestBodyMixedTools(t *testing.T) {
 	if img["action"] != "generate" {
 		t.Errorf("tools[1] action = %v, want generate", img["action"])
 	}
-	if img["model"] != "gpt-image-2" {
-		t.Errorf("tools[1] model = %v, want gpt-image-2", img["model"])
+	if img["model"] != DefaultImageModel {
+		t.Errorf("tools[1] model = %v, want %v", img["model"], DefaultImageModel)
 	}
 	// Function field must not bleed into image tool.
 	if _, has := img["name"]; has {

internal/providers/native_image.go

@@ -3,6 +3,7 @@ package providers
 import (
 	"context"
 	"fmt"
+	"strings"
 )
 
 // NativeImageProvider is implemented by OAuth-backed providers whose upstream
@@ -14,17 +15,29 @@ type NativeImageProvider interface {
 }
 
 // DefaultImageModel is the image model used by the Responses API image_generation
-// tool when the caller does not specify one. gpt-image-2 is the current (2026-Q2)
-// quality baseline; gpt-image-1.5 is available as a legacy fallback.
-const DefaultImageModel = "gpt-image-2"
+// tool when the caller does not specify one. GPT Image 2.5 (2026-09-08) ships as
+// two model IDs instead of one: "flare" tuned for speed, "sunburst" tuned for
+// editing precision. Flare is the default because it beats gpt-image-2 on quality
+// at roughly half the latency, which suits the one-shot create_image path.
+const DefaultImageModel = "gpt-image-2.5-flare"
 
 // allowedImageModels enumerates the image models the native ChatGPT Responses API
 // image_generation tool will accept. Constraining to this whitelist prevents
-// silent upstream rejections from arbitrary model names (e.g. "dall-e-3") and
-// keeps the PR's motivation — gpt-image-2 quality — as the default everywhere.
+// silent upstream rejections from arbitrary model names (e.g. "dall-e-3").
 var allowedImageModels = map[string]bool{
-	"gpt-image-2":   true, // default — latest quality
-	"gpt-image-1.5": true, // legacy fallback
+	"gpt-image-2.5-flare":    true, // default - fastest at high quality
+	"gpt-image-2.5-sunburst": true, // most capable at editing precision
+	"gpt-image-2":            true, // previous generation
+	"gpt-image-1.5":          true, // legacy fallback
+}
+
+// allowedImageModelList is the whitelist rendered for error messages, ordered
+// newest first so the suggestion a caller sees leads with the recommended model.
+var allowedImageModelList = []string{
+	"gpt-image-2.5-flare (default)",
+	"gpt-image-2.5-sunburst",
+	"gpt-image-2",
+	"gpt-image-1.5 (legacy)",
 }
 
 // ValidateImageModel returns the model to use, or an error if the caller
@@ -34,7 +47,7 @@ func ValidateImageModel(model string) (string, error) {
 		return DefaultImageModel, nil
 	}
 	if !allowedImageModels[model] {
-		return "", fmt.Errorf("unsupported image model %q; allowed: gpt-image-2 (default), gpt-image-1.5 (legacy)", model)
+		return "", fmt.Errorf("unsupported image model %q; allowed: %s", model, strings.Join(allowedImageModelList, ", "))
 	}
 	return model, nil
 }
@@ -47,7 +60,7 @@ type NativeImageRequest struct {
 	Model string
 
 	// ImageModel is the image-generation model attached to the image_generation
-	// tool (e.g. "gpt-image-2"). Must be a value accepted by ValidateImageModel;
+	// tool (e.g. "gpt-image-2.5-flare"). Must be a value accepted by ValidateImageModel;
 	// empty falls back to DefaultImageModel.
 	ImageModel string
 

internal/providers/native_image_test.go

@@ -0,0 +1,53 @@
+package providers
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestValidateImageModel(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   string
+		want    string
+		wantErr bool
+	}{
+		{name: "empty falls back to default", input: "", want: DefaultImageModel},
+		{name: "flare", input: "gpt-image-2.5-flare", want: "gpt-image-2.5-flare"},
+		{name: "sunburst", input: "gpt-image-2.5-sunburst", want: "gpt-image-2.5-sunburst"},
+		{name: "previous generation", input: "gpt-image-2", want: "gpt-image-2"},
+		{name: "legacy", input: "gpt-image-1.5", want: "gpt-image-1.5"},
+		{name: "unversioned 2.5 is not a real model id", input: "gpt-image-2.5", wantErr: true},
+		{name: "unrelated model", input: "dall-e-3", wantErr: true},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := ValidateImageModel(tc.input)
+			if tc.wantErr {
+				if err == nil {
+					t.Fatalf("ValidateImageModel(%q) = %q, want error", tc.input, got)
+				}
+				// The error must list the allowed models so the caller can self-correct.
+				if !strings.Contains(err.Error(), DefaultImageModel) {
+					t.Errorf("error %q does not mention the default model %q", err, DefaultImageModel)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("ValidateImageModel(%q) returned error: %v", tc.input, err)
+			}
+			if got != tc.want {
+				t.Errorf("ValidateImageModel(%q) = %q, want %q", tc.input, got, tc.want)
+			}
+		})
+	}
+}
+
+// TestDefaultImageModelIsAllowed guards against the default drifting out of the
+// whitelist, which would make every create_image call with no explicit model fail.
+func TestDefaultImageModelIsAllowed(t *testing.T) {
+	if !allowedImageModels[DefaultImageModel] {
+		t.Fatalf("DefaultImageModel %q is missing from allowedImageModels", DefaultImageModel)
+	}
+}

internal/tools/create_image.go

@@ -395,7 +395,9 @@ func (t *CreateImageTool) callProvider(ctx context.Context, cp credentialProvide
 
 	// OpenAI image-to-image (Edits)
 	if len(refImgs) > 0 && (ptype == "openai" || providerName == "openai" || ptype == "openai_compat") {
-		isEditModel := model == "gpt-image-2" ||
+		isEditModel := model == "gpt-image-2.5-flare" ||
+			model == "gpt-image-2.5-sunburst" ||
+			model == "gpt-image-2" ||
 			model == "gpt-image-1.5" ||
 			model == "gpt-image-1" ||
 			model == "gpt-image-1-mini" ||

internal/tools/create_image_native_path_test.go

@@ -201,7 +201,7 @@ func TestCreateImageTool_ThreadsImageModel(t *testing.T) {
 		{
 			name:            "default (empty params.image_model)",
 			chainImageModel: "",
-			wantImageModel:  "", // provider validator defaults to gpt-image-2
+			wantImageModel:  "", // passed through empty; the provider validator applies the default
 		},
 		{
 			name:            "legacy gpt-image-1.5",

ui/web/src/i18n/locales/en/tools.json

@@ -246,7 +246,9 @@
       "save": "Save",
       "saving": "Saving...",
       "imageModelLabel": "Image model",
-      "imageModelDefaultOption": "Default · gpt-image-2 (recommended)",
+      "imageModelFlareOption": "Default · gpt-image-2.5-flare (recommended)",
+      "imageModelSunburstOption": "Precise · gpt-image-2.5-sunburst",
+      "imageModelPreviousOption": "Previous · gpt-image-2",
       "imageModelLegacyOption": "Legacy · gpt-image-1.5"
     },
     "toast": {

ui/web/src/i18n/locales/ko/tools.json

@@ -171,7 +171,12 @@
       "addProvider": "공급자 추가",
       "cancel": "취소",
       "save": "저장",
-      "saving": "저장 중..."
+      "saving": "저장 중...",
+      "imageModelLabel": "이미지 모델",
+      "imageModelFlareOption": "기본 · gpt-image-2.5-flare (권장)",
+      "imageModelSunburstOption": "정밀 · gpt-image-2.5-sunburst",
+      "imageModelPreviousOption": "이전 · gpt-image-2",
+      "imageModelLegacyOption": "레거시 · gpt-image-1.5"
     },
     "toast": {
       "toggled": "도구 업데이트됨",

ui/web/src/i18n/locales/ru/tools.json

@@ -245,7 +245,9 @@
       "save": "Сохранить",
       "saving": "Сохранение...",
       "imageModelLabel": "Модель изображений",
-      "imageModelDefaultOption": "По умолчанию · gpt-image-2 (рекомендуется)",
+      "imageModelFlareOption": "По умолчанию · gpt-image-2.5-flare (рекомендуется)",
+      "imageModelSunburstOption": "Точная · gpt-image-2.5-sunburst",
+      "imageModelPreviousOption": "Предыдущая · gpt-image-2",
       "imageModelLegacyOption": "Устаревшая · gpt-image-1.5"
     },
     "toast": {

ui/web/src/i18n/locales/vi/tools.json

@@ -246,7 +246,9 @@
       "save": "Lưu",
       "saving": "Đang lưu...",
       "imageModelLabel": "Mô hình ảnh",
-      "imageModelDefaultOption": "Mặc định · gpt-image-2 (khuyến nghị)",
+      "imageModelFlareOption": "Mặc định · gpt-image-2.5-flare (khuyến nghị)",
+      "imageModelSunburstOption": "Chính xác · gpt-image-2.5-sunburst",
+      "imageModelPreviousOption": "Đời trước · gpt-image-2",
       "imageModelLegacyOption": "Cũ · gpt-image-1.5"
     },
     "toast": {

ui/web/src/i18n/locales/zh/tools.json

@@ -160,7 +160,9 @@
       "settings": "设置",
       "timeout": "超时",
       "imageModelLabel": "图像模型",
-      "imageModelDefaultOption": "默认 · gpt-image-2（推荐）",
+      "imageModelFlareOption": "默认 · gpt-image-2.5-flare（推荐）",
+      "imageModelSunburstOption": "精细 · gpt-image-2.5-sunburst",
+      "imageModelPreviousOption": "上一代 · gpt-image-2",
       "imageModelLegacyOption": "旧版 · gpt-image-1.5"
     },
     "noMatchDescription": "请尝试其他搜索词。",

ui/web/src/pages/builtin-tools/media-param-field-control.tsx

@@ -1,3 +1,4 @@
+import { useTranslation } from "react-i18next";
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
 import { Switch } from "@/components/ui/switch";
@@ -20,9 +21,14 @@ export function ParamFieldControl({
   value: unknown;
   onChange: (v: unknown) => void;
 }) {
+  const { t } = useTranslation("tools");
+  // Schema labels are English literals; labelKey opts a field into i18n.
+  const label = (f: { label: string; labelKey?: string }) =>
+    f.labelKey ? t(f.labelKey, { defaultValue: f.label }) : f.label;
+
   return (
     <div className="space-y-1">
-      <Label className="text-xs">{field.label}</Label>
+      <Label className="text-xs">{label(field)}</Label>
       {field.type === "select" && field.options && (
         <Select value={String(value ?? "")} onValueChange={onChange}>
           <SelectTrigger className="h-8 text-sm">
@@ -31,7 +37,7 @@ export function ParamFieldControl({
           <SelectContent>
             {field.options.map((opt) => (
               <SelectItem key={opt.value} value={opt.value}>
-                {opt.label}
+                {label(opt)}
               </SelectItem>
             ))}
           </SelectContent>

ui/web/src/pages/builtin-tools/media-provider-params-schema.ts

@@ -1,8 +1,10 @@
 export type ParamField = {
   key: string;
   label: string;
+  /** i18n key in the "tools" namespace; falls back to `label` when absent. */
+  labelKey?: string;
   type: "select" | "toggle" | "number" | "text";
-  options?: { value: string; label: string }[];
+  options?: { value: string; label: string; labelKey?: string }[];
   default?: unknown;
   min?: number;
   max?: number;
@@ -16,11 +18,31 @@ export const MEDIA_PARAMS_SCHEMA: Record<string, Record<string, ParamField[]>> =
       {
         key: "image_model",
         label: "Image model",
+        labelKey: "builtin.mediaChain.imageModelLabel",
         type: "select",
-        default: "gpt-image-2",
+        // Keep in sync with allowedImageModels in internal/providers/native_image.go.
+        default: "gpt-image-2.5-flare",
         options: [
-          { value: "gpt-image-2", label: "Default · gpt-image-2 (recommended)" },
-          { value: "gpt-image-1.5", label: "Legacy · gpt-image-1.5" },
+          {
+            value: "gpt-image-2.5-flare",
+            label: "Default · gpt-image-2.5-flare (recommended)",
+            labelKey: "builtin.mediaChain.imageModelFlareOption",
+          },
+          {
+            value: "gpt-image-2.5-sunburst",
+            label: "Precise · gpt-image-2.5-sunburst",
+            labelKey: "builtin.mediaChain.imageModelSunburstOption",
+          },
+          {
+            value: "gpt-image-2",
+            label: "Previous · gpt-image-2",
+            labelKey: "builtin.mediaChain.imageModelPreviousOption",
+          },
+          {
+            value: "gpt-image-1.5",
+            label: "Legacy · gpt-image-1.5",
+            labelKey: "builtin.mediaChain.imageModelLegacyOption",
+          },
         ],
       },
     ],