diff --git a/packages/bundler-plugin-core/src/index.ts b/packages/bundler-plugin-core/src/index.ts
index 2c38cac7..be2d24f9 100644
--- a/packages/bundler-plugin-core/src/index.ts
+++ b/packages/bundler-plugin-core/src/index.ts
@@ -269,6 +269,17 @@ export function createRollupDebugIdInjectionHooks(): {
           stripQueryAndHashFromPath(chunk.fileName).endsWith(ending)
         )
       ) {
+        // Check if a debug ID has already been injected to avoid duplicate injection (e.g. by another plugin or Sentry CLI)
+        const chunkStartSnippet = code.slice(0, 2000);
+        const chunkEndSnippet = code.slice(-500);
+
+        if (
+          chunkStartSnippet.includes("_sentryDebugIdIdentifier") ||
+          chunkEndSnippet.includes("//# debugId=")
+        ) {
+          return null; // Debug ID already present, skip injection
+        }
+
         const debugId = stringToUUID(code); // generate a deterministic debug ID
         const codeToInject = getDebugIdSnippet(debugId);
 
diff --git a/packages/bundler-plugin-core/test/index.test.ts b/packages/bundler-plugin-core/test/index.test.ts
index f6c60aa0..c3d5f5bb 100644
--- a/packages/bundler-plugin-core/test/index.test.ts
+++ b/packages/bundler-plugin-core/test/index.test.ts
@@ -1,5 +1,9 @@
 import { Compiler } from "webpack";
-import { getDebugIdSnippet, sentryUnpluginFactory } from "../src";
+import {
+  getDebugIdSnippet,
+  sentryUnpluginFactory,
+  createRollupDebugIdInjectionHooks,
+} from "../src";
 
 describe("getDebugIdSnippet", () => {
   it("returns the debugId injection snippet for a passed debugId", () => {
@@ -10,6 +14,88 @@ describe("getDebugIdSnippet", () => {
   });
 });
 
+describe("createRollupDebugIdInjectionHooks", () => {
+  const hooks = createRollupDebugIdInjectionHooks();
+
+  describe("renderChunk", () => {
+    it("should inject debug ID into clean JavaScript files", () => {
+      const code = 'console.log("Hello world");';
+      const result = hooks.renderChunk(code, { fileName: "bundle.js" });
+
+      expect(result).not.toBeNull();
+      expect(result?.code).toContain("_sentryDebugIdIdentifier");
+      expect(result?.code).toContain('console.log("Hello world");');
+    });
+
+    it("should inject debug ID after 'use strict'", () => {
+      const code = '"use strict";\nconsole.log("Hello world");';
+      const result = hooks.renderChunk(code, { fileName: "bundle.js" });
+
+      expect(result).not.toBeNull();
+      expect(result?.code).toMatch(/^"use strict";.*;{try/);
+    });
+
+    it.each([
+      ["bundle.js"],
+      ["bundle.mjs"],
+      ["bundle.cjs"],
+      ["bundle.js?foo=bar"],
+      ["bundle.js#hash"],
+    ])("should process file '%s': %s", (fileName) => {
+      const code = 'console.log("test");';
+      const result = hooks.renderChunk(code, { fileName });
+
+      expect(result).not.toBeNull();
+      expect(result?.code).toContain("_sentryDebugIdIdentifier");
+    });
+
+    it.each([["index.html"], ["styles.css"]])("should NOT process file '%s': %s", (fileName) => {
+      const code = 'console.log("test");';
+      const result = hooks.renderChunk(code, { fileName });
+
+      expect(result).toBeNull();
+    });
+
+    it.each([
+      [
+        "inline format at start",
+        ';{try{(function(){var e="undefined"!=typeof window?window:e._sentryDebugIdIdentifier="sentry-dbid-existing-id");})();}catch(e){}};console.log("test");',
+      ],
+      [
+        "comment format at end",
+        'console.log("test");\n//# debugId=f6ccd6f4-7ea0-4854-8384-1c9f8340af81\n//# sourceMappingURL=bundle.js.map',
+      ],
+      [
+        "inline format with large file",
+        '"use strict";\n' +
+          "// comment\n".repeat(10) +
+          ';{try{(function(){var e="undefined"!=typeof window?window:e._sentryDebugIdIdentifier="sentry-dbid-existing-id");})();}catch(e){}};' +
+          '\nconsole.log("line");\n'.repeat(100),
+      ],
+    ])("should NOT inject when debug ID already exists (%s)", (_description, code) => {
+      const result = hooks.renderChunk(code, { fileName: "bundle.js" });
+      expect(result).toBeNull();
+    });
+
+    it("should only check boundaries for performance (not entire file)", () => {
+      // Inline format beyond first 2KB boundary
+      const codeWithInlineBeyond2KB =
+        "a".repeat(2100) +
+        ';{try{(function(){var e="undefined"!=typeof window?window:e._sentryDebugIdIdentifier="sentry-dbid-existing-id");})();}catch(e){}};';
+
+      expect(hooks.renderChunk(codeWithInlineBeyond2KB, { fileName: "bundle.js" })).not.toBeNull();
+
+      // Comment format beyond last 500 bytes boundary
+      const codeWithCommentBeyond500B =
+        "//# debugId=f6ccd6f4-7ea0-4854-8384-1c9f8340af81\n" + "a".repeat(600);
+
+      expect(
+        hooks.renderChunk(codeWithCommentBeyond500B, { fileName: "bundle.js" })
+      ).not.toBeNull();
+    });
+  });
+});
+
 describe("sentryUnpluginFactory sourcemaps.disable behavior", () => {
   const mockReleaseInjectionPlugin = jest.fn((_injectionCode: string) => ({
     name: "mock-release-injection-plugin",