diff --git a/apps/dokploy/__test__/compose/domain/merge-key.test.ts b/apps/dokploy/__test__/compose/domain/merge-key.test.ts
new file mode 100644
index 000000000..0da3c8513
--- /dev/null
+++ b/apps/dokploy/__test__/compose/domain/merge-key.test.ts
@@ -0,0 +1,149 @@
+import type { Compose } from "@dokploy/server/services/compose";
+import type { Domain } from "@dokploy/server/services/domain";
+import { addDomainToCompose } from "@dokploy/server/utils/docker/domain";
+import { describe, expect, it } from "vitest";
+
+const listAnchorYaml = `
+x-common: &common
+  restart: unless-stopped
+  labels:
+    - com.example.team=platform
+  networks: [default, dokploy-network]
+
+services:
+  api:
+    <<: *common
+    image: nginx
+  worker:
+    <<: *common
+    image: busybox
+`;
+
+const mapAnchorYaml = `
+x-common: &common
+  networks:
+    default: {}
+    shared:
+      aliases: [shared-api]
+
+services:
+  api:
+    <<: *common
+    image: nginx
+`;
+
+const defaultOnlyAnchorYaml = `
+x-common: &common
+  networks: [default]
+
+services:
+  api:
+    <<: *common
+    image: nginx
+  worker:
+    <<: *common
+    image: busybox
+`;
+
+const buildCompose = (composeFile: string, isolatedDeployment = false) =>
+	({
+		appName: "merge-app",
+		composeType: "docker-compose",
+		composePath: "docker-compose.yml",
+		sourceType: "raw",
+		serverId: null,
+		isolatedDeployment,
+		isolatedDeploymentsVolume: false,
+		randomize: false,
+		suffix: "",
+		composeFile,
+	}) as unknown as Compose;
+
+const domain: Domain = {
+	host: "api.example.com",
+	port: 80,
+	customEntrypoint: null,
+	https: false,
+	uniqueConfigKey: 1,
+	customCertResolver: null,
+	certificateType: "none",
+	applicationId: "",
+	composeId: "compose-id",
+	domainType: "compose",
+	serviceName: "api",
+	domainId: "domain-id",
+	path: "/",
+	createdAt: "",
+	previewDeploymentId: "",
+	internalPath: "/",
+	stripPath: false,
+	middlewares: null,
+	forwardAuthEnabled: false,
+	enabled: true,
+};
+
+describe("compose services using YAML merge keys (#5625)", () => {
+	it("keeps anchor networks when a domain is attached", async () => {
+		const result = await addDomainToCompose(buildCompose(listAnchorYaml), [
+			domain,
+		]);
+
+		expect(result?.services?.api).not.toHaveProperty("<<");
+		expect(result?.services?.api?.networks).toEqual(
+			expect.arrayContaining(["default", "dokploy-network"]),
+		);
+		expect(result?.services?.api?.restart).toBe("unless-stopped");
+	});
+
+	it("keeps anchor networks on isolated deployments", async () => {
+		const result = await addDomainToCompose(
+			buildCompose(listAnchorYaml, true),
+			[],
+		);
+
+		expect(result?.services?.api?.networks).toEqual(
+			expect.arrayContaining(["default", "dokploy-network", "merge-app"]),
+		);
+		expect(result?.services?.worker?.networks).toEqual(
+			expect.arrayContaining(["default", "dokploy-network", "merge-app"]),
+		);
+	});
+
+	it("keeps anchor labels next to the Dokploy labels", async () => {
+		const result = await addDomainToCompose(buildCompose(listAnchorYaml), [
+			domain,
+		]);
+
+		expect(result?.services?.api?.labels).toEqual(
+			expect.arrayContaining([
+				"com.example.team=platform",
+				"traefik.enable=true",
+				"traefik.docker.network=dokploy-network",
+			]),
+		);
+	});
+
+	it("keeps map-form anchor networks", async () => {
+		const result = await addDomainToCompose(buildCompose(mapAnchorYaml), [
+			domain,
+		]);
+
+		expect(result?.services?.api?.networks).toMatchObject({
+			default: {},
+			shared: { aliases: ["shared-api"] },
+			"dokploy-network": {},
+		});
+	});
+
+	it("does not leak injected networks into sibling services", async () => {
+		const result = await addDomainToCompose(
+			buildCompose(defaultOnlyAnchorYaml),
+			[domain],
+		);
+
+		expect(result?.services?.api?.networks).toEqual(
+			expect.arrayContaining(["default", "dokploy-network"]),
+		);
+		expect(result?.services?.worker?.networks).toEqual(["default"]);
+	});
+});
diff --git a/packages/server/src/utils/docker/compose.ts b/packages/server/src/utils/docker/compose.ts
index 2e2011b03..7beb1e55b 100644
--- a/packages/server/src/utils/docker/compose.ts
+++ b/packages/server/src/utils/docker/compose.ts
@@ -20,6 +20,7 @@ export const randomizeComposeFile = async (
 	const composeFile = compose.composeFile;
 	const composeData = parse(composeFile, {
 		maxAliasCount: 10000,
+		merge: true,
 	}) as ComposeSpecification;
 
 	const randomSuffix = suffix || generateRandomHash();
diff --git a/packages/server/src/utils/docker/domain.ts b/packages/server/src/utils/docker/domain.ts
index e9fd373ae..bee1513d2 100644
--- a/packages/server/src/utils/docker/domain.ts
+++ b/packages/server/src/utils/docker/domain.ts
@@ -70,6 +70,7 @@ export const loadDockerCompose = async (
 		const yamlStr = readFileSync(path, "utf8");
 		const parsedConfig = parse(yamlStr, {
 			maxAliasCount: 10000,
+			merge: true,
 		}) as ComposeSpecification;
 		return parsedConfig;
 	}
@@ -95,6 +96,7 @@ export const loadDockerComposeRemote = async (
 		if (!stdout) return null;
 		const parsedConfig = parse(stdout, {
 			maxAliasCount: 10000,
+			merge: true,
 		}) as ComposeSpecification;
 		return parsedConfig;
 	} catch {
@@ -164,6 +166,7 @@ export const applyComposeFilePatch = async (
 	try {
 		const parsed = parse(composeFilePatch.content, {
 			maxAliasCount: 10000,
+			merge: true,
 		}) as ComposeSpecification;
 		return parsed ?? null;
 	} catch {
@@ -273,6 +276,7 @@ export const addDomainToCompose = async (
 	if (compose.sourceType === "raw") {
 		result = parse(compose.composeFile, {
 			maxAliasCount: 10000,
+			merge: true,
 		}) as ComposeSpecification;
 	} else if (compose.serverId) {
 		result = await loadDockerComposeRemote(compose);