diff --git a/.changeset/esbuild-dependency-82f9a43d.md b/.changeset/esbuild-dependency-82f9a43d.md
new file mode 100644
index 000000000..2872ece74
--- /dev/null
+++ b/.changeset/esbuild-dependency-82f9a43d.md
@@ -0,0 +1,7 @@
+---
+"@opennextjs/cloudflare": patch
+---
+
+fix: declare esbuild as runtime dependency
+
+esbuild is imported at build time by the Cloudflare adapter but was only in devDependencies, so consumers relied on hoisting from @opennextjs/aws. Add it to dependencies so builds work under npm ci and with hoist conflicts.
diff --git a/packages/cloudflare/package.json b/packages/cloudflare/package.json
index b65c774c8..6a1049f21 100644
--- a/packages/cloudflare/package.json
+++ b/packages/cloudflare/package.json
@@ -59,6 +59,7 @@
 		"cloudflare": "^4.4.1",
 		"comment-json": "^4.5.1",
 		"enquirer": "^2.4.1",
+		"esbuild": "catalog:",
 		"glob": "catalog:",
 		"ts-tqdm": "^0.8.6",
 		"yargs": "catalog:"
@@ -73,7 +74,6 @@
 		"@types/rclone.js": "^0.6.1",
 		"@types/yargs": "catalog:",
 		"diff": "^8.0.2",
-		"esbuild": "catalog:",
 		"eslint": "catalog:",
 		"eslint-plugin-import": "catalog:",
 		"eslint-plugin-simple-import-sort": "catalog:",
diff --git a/packages/cloudflare/src/cli/build/build-deps.spec.ts b/packages/cloudflare/src/cli/build/build-deps.spec.ts
new file mode 100644
index 000000000..1b256e7b7
--- /dev/null
+++ b/packages/cloudflare/src/cli/build/build-deps.spec.ts
@@ -0,0 +1,26 @@
+import { readFileSync } from "node:fs";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+import { describe, expect, it } from "vitest";
+
+/**
+ * Regression test for https://github.com/opennextjs/opennextjs-cloudflare/issues/1339
+ *
+ * `esbuild` is imported at build time (see src/cli/build/bundle-server.ts and
+ * src/cli/build/open-next/*.ts) but used to be declared only in devDependencies,
+ * so consumers only got it by npm hoisting accident. It must be a real runtime
+ * `dependency` of the published package.
+ */
+const packageJsonPath = resolve(dirname(fileURLToPath(import.meta.url)), "../../../package.json");
+
+describe("build-time dependencies", () => {
+	it("declares esbuild as a runtime dependency", () => {
+		const { dependencies } = JSON.parse(readFileSync(packageJsonPath, "utf8")) as {
+			dependencies?: Record<string, string>;
+		};
+
+		expect(dependencies).toBeDefined();
+		expect(dependencies?.["esbuild"]).toBeDefined();
+	});
+});