diff --git a/open-sse/handlers/imageGeneration.ts b/open-sse/handlers/imageGeneration.ts
index 98f5f32c19..bdd5943f88 100644
--- a/open-sse/handlers/imageGeneration.ts
+++ b/open-sse/handlers/imageGeneration.ts
@@ -87,6 +87,50 @@ const OPENAI_IMAGE_TO_IMAGE_MODELS = new Set([
 
 const IMAGE_ASPECT_RATIO_PATTERN = /^\d+:\d+$/;
 
+/**
+ * Resolve the upstream images endpoint for a custom (OpenAI-compatible) image
+ * provider node (#3205).
+ *
+ * Custom provider nodes store their base URL the same way the chat path does:
+ * in `credentials.providerSpecificData.baseUrl` (e.g. `https://example.com/v1`),
+ * NOT as a top-level `credentials.baseUrl`. Older callers may still pass a
+ * top-level `baseUrl`, so we honor that as a secondary source. When neither is
+ * present we fall back to `fallback` (the built-in Gemini OpenAI endpoint).
+ *
+ * Resolution order: providerSpecificData.baseUrl → credentials.baseUrl → fallback.
+ *
+ * A node base URL like `https://example.com/v1` is normalized and the
+ * OpenAI-compatible `/images/generations` path appended (mirroring
+ * `buildOpenAICompatibleUrl` in services/provider.ts). A node URL that already
+ * ends in `/images/generations` is returned as-is (no double-append). The
+ * `fallback` value is assumed to already be a complete URL and is returned
+ * verbatim.
+ */
+export function resolveImageBaseUrl(
+  credentials:
+    | { baseUrl?: unknown; providerSpecificData?: { baseUrl?: unknown } | null }
+    | null
+    | undefined,
+  fallback: string
+): string {
+  const psd = credentials?.providerSpecificData;
+  const psdBaseUrl =
+    psd && typeof psd === "object" && typeof psd.baseUrl === "string" && psd.baseUrl.trim()
+      ? psd.baseUrl.trim()
+      : null;
+  const topLevelBaseUrl =
+    typeof credentials?.baseUrl === "string" && credentials.baseUrl.trim()
+      ? credentials.baseUrl.trim()
+      : null;
+  const nodeBaseUrl = psdBaseUrl || topLevelBaseUrl;
+
+  if (!nodeBaseUrl) return fallback;
+
+  const normalized = nodeBaseUrl.replace(/\/+$/, "");
+  if (/\/images\/generations$/.test(normalized)) return normalized;
+  return `${normalized}/images/generations`;
+}
+
 function normalizeImageAspectRatio(value: unknown, fallbackSize: unknown): string {
   if (typeof value === "string") {
     const trimmedValue = value.trim();
@@ -257,9 +301,16 @@ export async function handleImageGeneration({
 
     const syntheticConfig = {
       id: provider,
-      baseUrl:
-        credentials?.baseUrl ||
-        `https://generativelanguage.googleapis.com/v1beta/openai/images/generations`,
+      // #3205: custom OpenAI-compatible nodes store their base URL in
+      // credentials.providerSpecificData.baseUrl (same as the chat path —
+      // see executors/default.ts:buildUrl / services/provider.ts:buildProviderUrl).
+      // Previously only the (always-absent) top-level credentials.baseUrl was
+      // read, so every custom image node fell back to the Gemini endpoint and
+      // returned "Please pass a valid API key".
+      baseUrl: resolveImageBaseUrl(
+        credentials,
+        `https://generativelanguage.googleapis.com/v1beta/openai/images/generations`
+      ),
       authType: "apikey",
       authHeader: "bearer",
       format: "openai",
diff --git a/src/app/api/v1/images/generations/route.ts b/src/app/api/v1/images/generations/route.ts
index 080248e8f6..2f4ad82c7a 100644
--- a/src/app/api/v1/images/generations/route.ts
+++ b/src/app/api/v1/images/generations/route.ts
@@ -20,6 +20,7 @@ import { v1ImageGenerationSchema } from "@/shared/validation/schemas";
 import { isValidationFailure, validateBody } from "@/shared/validation/helpers";
 
 import { getAllCustomModels, resolveProxyForConnection } from "@/lib/localDb";
+import { getProviderNodes } from "@/lib/db/providers";
 import { runWithProxyContext } from "@omniroute/open-sse/utils/proxyFetch.ts";
 
 /**
@@ -117,6 +118,43 @@ function publicBaseUrlHeaders(headers: Headers): Record<string, string> {
   return out;
 }
 
+/**
+ * Resolve a `prefix/model` image request to the internal `<nodeId>/<model>`
+ * form (#3205).
+ *
+ * The custom-model lookup below only matches the full internal id
+ * (`<nodeId>/<modelId>`), so a request that uses the user-defined provider
+ * prefix (e.g. `myImg/gpt-image-2`) never matched and fell through to
+ * "Invalid image model". This mirrors how chat resolves prefixes in
+ * `src/sse/services/model.ts` (match on `node.prefix` OR `node.id`).
+ *
+ * Returns the rewritten model string, or the original string when no node
+ * prefix matches (so built-in and already-internal ids are untouched).
+ */
+async function resolveImageModelPrefix(modelStr: string): Promise<string> {
+  if (typeof modelStr !== "string") return modelStr;
+  const slash = modelStr.indexOf("/");
+  if (slash <= 0) return modelStr;
+
+  const prefixPart = modelStr.slice(0, slash);
+  const rest = modelStr.slice(slash + 1);
+  if (!rest) return modelStr;
+
+  try {
+    const nodes = await getProviderNodes({ type: "openai-compatible" });
+    // Prefer an explicit user-defined prefix match; node.id (internal UUID) is
+    // already handled by the exact-id loop, so only rewrite when the prefix
+    // differs from the node id.
+    const matched = nodes.find((node: any) => node.prefix === prefixPart);
+    if (matched && matched.id && matched.id !== prefixPart) {
+      return `${matched.id}/${rest}`;
+    }
+  } catch {
+    // DB unavailable (pre-migration / tests) — leave the model untouched.
+  }
+  return modelStr;
+}
+
 export async function POST(request) {
   let rawBody;
   try {
@@ -136,6 +174,14 @@ export async function POST(request) {
   const policy = await enforceApiKeyPolicy(request, body.model);
   if (policy.rejection) return policy.rejection;
 
+  // #3205: rewrite a user-prefixed custom image model (`myImg/gpt-image-2`) to
+  // its internal `<nodeId>/<model>` form so the custom-model lookup and
+  // handler's resolvedProvider extraction resolve correctly. Built-in and
+  // already-internal ids pass through unchanged.
+  if (!parseImageModel(body.model).provider) {
+    body.model = await resolveImageModelPrefix(body.model);
+  }
+
   // Parse model to get provider
   let { provider } = parseImageModel(body.model);
   let isCustomModel = false;
diff --git a/tests/unit/image-generation-baseurl-3205.test.ts b/tests/unit/image-generation-baseurl-3205.test.ts
new file mode 100644
index 0000000000..de12ad5416
--- /dev/null
+++ b/tests/unit/image-generation-baseurl-3205.test.ts
@@ -0,0 +1,60 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { resolveImageBaseUrl } from "@omniroute/open-sse/handlers/imageGeneration.ts";
+
+const GEMINI_FALLBACK =
+  "https://generativelanguage.googleapis.com/v1beta/openai/images/generations";
+
+test("#3205: custom node baseUrl from providerSpecificData is used (not Gemini fallback)", () => {
+  const credentials = { providerSpecificData: { baseUrl: "https://example.com/v1" } };
+  const resolved = resolveImageBaseUrl(credentials, GEMINI_FALLBACK);
+
+  assert.ok(
+    resolved.startsWith("https://example.com/"),
+    `expected resolved URL to point to example.com, got: ${resolved}`
+  );
+  assert.ok(
+    !resolved.includes("generativelanguage.googleapis.com"),
+    `resolved URL must not fall back to the Gemini endpoint, got: ${resolved}`
+  );
+  // A node configured as https://example.com/v1 should yield the OpenAI-compatible
+  // images path appended.
+  assert.equal(resolved, "https://example.com/v1/images/generations");
+});
+
+test("#3205: providerSpecificData.baseUrl wins over top-level credentials.baseUrl", () => {
+  const credentials = {
+    baseUrl: "https://toplevel.example/v1",
+    providerSpecificData: { baseUrl: "https://psd.example/v1" },
+  };
+  const resolved = resolveImageBaseUrl(credentials, GEMINI_FALLBACK);
+  assert.equal(resolved, "https://psd.example/v1/images/generations");
+});
+
+test("#3205: trailing slash on node baseUrl is normalized (no double slash)", () => {
+  const credentials = { providerSpecificData: { baseUrl: "https://example.com/v1/" } };
+  const resolved = resolveImageBaseUrl(credentials, GEMINI_FALLBACK);
+  assert.equal(resolved, "https://example.com/v1/images/generations");
+});
+
+test("#3205: an already-complete images URL is not double-appended", () => {
+  const credentials = {
+    providerSpecificData: { baseUrl: "https://example.com/v1/images/generations" },
+  };
+  const resolved = resolveImageBaseUrl(credentials, GEMINI_FALLBACK);
+  assert.equal(resolved, "https://example.com/v1/images/generations");
+});
+
+test("#3205: top-level credentials.baseUrl is honored when no providerSpecificData", () => {
+  const credentials = { baseUrl: "https://legacy.example/v1" };
+  const resolved = resolveImageBaseUrl(credentials, GEMINI_FALLBACK);
+  assert.equal(resolved, "https://legacy.example/v1/images/generations");
+});
+
+test("#3205: falls back to provided default when no node baseUrl present", () => {
+  const resolved = resolveImageBaseUrl({}, GEMINI_FALLBACK);
+  assert.equal(resolved, GEMINI_FALLBACK);
+  const resolvedNull = resolveImageBaseUrl(null, GEMINI_FALLBACK);
+  assert.equal(resolvedNull, GEMINI_FALLBACK);
+});