diff --git a/genkit-tools/common/src/manager/manager.ts b/genkit-tools/common/src/manager/manager.ts
index 0f664301fb..0eb86973cb 100644
--- a/genkit-tools/common/src/manager/manager.ts
+++ b/genkit-tools/common/src/manager/manager.ts
@@ -17,6 +17,7 @@
 import axios, { type AxiosError } from 'axios';
 import chokidar from 'chokidar';
 import EventEmitter from 'events';
+import * as fsSync from 'fs';
 import fs from 'fs/promises';
 import path from 'path';
 import {
@@ -390,6 +391,10 @@ export class RuntimeManager {
    */
   private async handleNewDevUi(filePath: string) {
     try {
+      if (!fsSync.existsSync(filePath)) {
+        // file already got deleted, ignore...
+        return;
+      }
       const { content, toolsInfo } = await retriable(
         async () => {
           const content = await fs.readFile(filePath, 'utf-8');
@@ -433,6 +438,10 @@ export class RuntimeManager {
    */
   private async handleNewRuntime(filePath: string) {
     try {
+      if (!fsSync.existsSync(filePath)) {
+        // file already got deleted, ignore...
+        return;
+      }
       const { content, runtimeInfo } = await retriable(
         async () => {
           const content = await fs.readFile(filePath, 'utf-8');
@@ -448,7 +457,12 @@ export class RuntimeManager {
           runtimeInfo.name = runtimeInfo.id;
         }
         const fileName = path.basename(filePath);
-        if (await checkServerHealth(runtimeInfo.reflectionServerUrl)) {
+        if (
+          await checkServerHealth(
+            runtimeInfo.reflectionServerUrl,
+            runtimeInfo.id
+          )
+        ) {
           if (
             runtimeInfo.reflectionApiSpecVersion !=
             GENKIT_REFLECTION_API_SPEC_VERSION
@@ -529,7 +543,9 @@ export class RuntimeManager {
   private async performHealthChecks() {
     const healthCheckPromises = Object.entries(this.filenameToRuntimeMap).map(
       async ([fileName, runtime]) => {
-        if (!(await checkServerHealth(runtime.reflectionServerUrl))) {
+        if (
+          !(await checkServerHealth(runtime.reflectionServerUrl, runtime.id))
+        ) {
           await this.removeRuntime(fileName);
         }
       }
@@ -541,19 +557,14 @@ export class RuntimeManager {
    * Removes the runtime file which will trigger the removal watcher.
    */
   private async removeRuntime(fileName: string) {
-    const runtime = this.filenameToRuntimeMap[fileName];
-    if (runtime) {
-      try {
-        const runtimesDir = await findRuntimesDir(this.projectRoot);
-        const runtimeFilePath = path.join(runtimesDir, fileName);
-        await fs.unlink(runtimeFilePath);
-      } catch (error) {
-        logger.debug(`Failed to delete runtime file: ${error}`);
-      }
-      logger.debug(
-        `Removed unhealthy runtime with ID ${runtime.id} from manager.`
-      );
+    try {
+      const runtimesDir = await findRuntimesDir(this.projectRoot);
+      const runtimeFilePath = path.join(runtimesDir, fileName);
+      await fs.unlink(runtimeFilePath);
+    } catch (error) {
+      logger.debug(`Failed to delete runtime file: ${error}`);
     }
+    logger.debug(`Removed unhealthy runtime ${fileName} from manager.`);
   }
 }
 
diff --git a/genkit-tools/common/src/utils/utils.ts b/genkit-tools/common/src/utils/utils.ts
index aeab3fb57e..d2a404a834 100644
--- a/genkit-tools/common/src/utils/utils.ts
+++ b/genkit-tools/common/src/utils/utils.ts
@@ -139,9 +139,12 @@ export async function detectRuntime(directory: string): Promise<Runtime> {
 /**
  * Checks the health of a server with a /api/__health endpoint.
  */
-export async function checkServerHealth(url: string): Promise<boolean> {
+export async function checkServerHealth(
+  url: string,
+  id?: string
+): Promise<boolean> {
   try {
-    const response = await fetch(`${url}/api/__health`);
+    const response = await fetch(`${url}/api/__health${id ? `?id=${id}` : ''}`);
     return response.status === 200;
   } catch (error) {
     if (isConnectionRefusedError(error)) {
diff --git a/go/genkit/reflection.go b/go/genkit/reflection.go
index afa24a3159..bb32c79bff 100644
--- a/go/genkit/reflection.go
+++ b/go/genkit/reflection.go
@@ -55,6 +55,15 @@ type reflectionServer struct {
 	RuntimeFilePath string // Path to the runtime file that was written at startup.
 }
 
+func (s *reflectionServer) runtimeID() string {
+	_, port, err := net.SplitHostPort(s.Addr)
+	if err != nil {
+		// This should not happen with a valid address.
+		return strconv.Itoa(os.Getpid())
+	}
+	return fmt.Sprintf("%d-%s", os.Getpid(), port)
+}
+
 // findAvailablePort finds the next available port starting from the given port number.
 func findAvailablePort(startPort int) (string, error) {
 	for port := startPort; port < startPort+100; port++ {
@@ -91,10 +100,10 @@ func startReflectionServer(ctx context.Context, g *Genkit, errCh chan<- error, s
 
 	s := &reflectionServer{
 		Server: &http.Server{
-			Addr:    addr,
-			Handler: serveMux(g),
+			Addr: addr,
 		},
 	}
+	s.Handler = serveMux(g, s)
 
 	slog.Debug("starting reflection server", "addr", s.Addr)
 
@@ -159,7 +168,7 @@ func (s *reflectionServer) writeRuntimeFile(url string) error {
 
 	runtimeID := os.Getenv("GENKIT_RUNTIME_ID")
 	if runtimeID == "" {
-		runtimeID = strconv.Itoa(os.Getpid())
+		runtimeID = s.runtimeID()
 	}
 
 	timestamp := time.Now().UTC().Format(time.RFC3339)
@@ -238,10 +247,14 @@ func findProjectRoot() (string, error) {
 }
 
 // serveMux returns a new ServeMux configured for the required Reflection API endpoints.
-func serveMux(g *Genkit) *http.ServeMux {
+func serveMux(g *Genkit, s *reflectionServer) *http.ServeMux {
 	mux := http.NewServeMux()
 	// Skip wrapHandler here to avoid logging constant polling requests.
-	mux.HandleFunc("GET /api/__health", func(w http.ResponseWriter, _ *http.Request) {
+	mux.HandleFunc("GET /api/__health", func(w http.ResponseWriter, r *http.Request) {
+		if id := r.URL.Query().Get("id"); id != "" && id != s.runtimeID() {
+			http.Error(w, "Invalid runtime ID", http.StatusServiceUnavailable)
+			return
+		}
 		w.WriteHeader(http.StatusOK)
 	})
 	mux.HandleFunc("GET /api/actions", wrapReflectionHandler(handleListActions(g)))
diff --git a/go/genkit/reflection_test.go b/go/genkit/reflection_test.go
index 75d2278f5a..d47a10a027 100644
--- a/go/genkit/reflection_test.go
+++ b/go/genkit/reflection_test.go
@@ -90,7 +90,11 @@ func TestServeMux(t *testing.T) {
 	core.DefineAction(g.reg, "test/inc", api.ActionTypeCustom, nil, nil, inc)
 	core.DefineAction(g.reg, "test/dec", api.ActionTypeCustom, nil, nil, dec)
 
-	ts := httptest.NewServer(serveMux(g))
+	s := &reflectionServer{
+		Server: &http.Server{},
+	}
+	ts := httptest.NewServer(serveMux(g, s))
+	s.Addr = strings.TrimPrefix(ts.URL, "http://")
 	defer ts.Close()
 
 	t.Parallel()
@@ -104,6 +108,26 @@ func TestServeMux(t *testing.T) {
 		if res.StatusCode != http.StatusOK {
 			t.Errorf("health check failed: got status %d, want %d", res.StatusCode, http.StatusOK)
 		}
+
+		// Test with correct runtime ID
+		res, err = http.Get(ts.URL + "/api/__health?id=" + s.runtimeID())
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer res.Body.Close()
+		if res.StatusCode != http.StatusOK {
+			t.Errorf("health check with correct id failed: got status %d, want %d", res.StatusCode, http.StatusOK)
+		}
+
+		// Test with incorrect runtime ID
+		res, err = http.Get(ts.URL + "/api/__health?id=invalid-id")
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer res.Body.Close()
+		if res.StatusCode != http.StatusServiceUnavailable {
+			t.Errorf("health check with incorrect id failed: got status %d, want %d", res.StatusCode, http.StatusServiceUnavailable)
+		}
 	})
 
 	t.Run("list actions", func(t *testing.T) {
diff --git a/js/core/src/reflection.ts b/js/core/src/reflection.ts
index 659bd40b30..f5f01ee34b 100644
--- a/js/core/src/reflection.ts
+++ b/js/core/src/reflection.ts
@@ -82,6 +82,10 @@ export class ReflectionServer {
     };
   }
 
+  get runtimeId() {
+    return `${process.pid}${this.port !== null ? `-${this.port}` : ''}`;
+  }
+
   /**
    * Finds a free port to run the server on based on the original chosen port and environment.
    */
@@ -112,7 +116,11 @@ export class ReflectionServer {
       next();
     });
 
-    server.get('/api/__health', async (_, response) => {
+    server.get('/api/__health', async (req, response) => {
+      if (req.query['id'] && req.query['id'] !== this.runtimeId) {
+        response.status(503).send('Invalid runtime ID');
+        return;
+      }
       await this.registry.listActions();
       response.status(200).send('OK');
     });
@@ -322,16 +330,13 @@ export class ReflectionServer {
       const date = new Date();
       const time = date.getTime();
       const timestamp = date.toISOString();
-      const runtimeId = `${process.pid}${
-        this.port !== null ? `-${this.port}` : ''
-      }`;
       this.runtimeFilePath = path.join(
         runtimesDir,
-        `${runtimeId}-${time}.json`
+        `${this.runtimeId}-${time}.json`
       );
       const fileContent = JSON.stringify(
         {
-          id: process.env.GENKIT_RUNTIME_ID || runtimeId,
+          id: process.env.GENKIT_RUNTIME_ID || this.runtimeId,
           pid: process.pid,
           name: this.options.name,
           reflectionServerUrl: `http://localhost:${this.port}`,
diff --git a/js/plugins/vertexai/src/rerankers/v2/index.ts b/js/plugins/vertexai/src/rerankers/v2/index.ts
index bc27f4db25..8597878e6d 100644
--- a/js/plugins/vertexai/src/rerankers/v2/index.ts
+++ b/js/plugins/vertexai/src/rerankers/v2/index.ts
@@ -24,8 +24,8 @@ import { ActionType } from 'genkit/registry';
 import { RerankerReference, z } from 'genkit';
 import { getDerivedOptions } from '../../common/utils.js';
 import * as reranker from './reranker.js';
-import { VertexRerankerPluginOptions } from './types.js';
-export { VertexRerankerPluginOptions };
+import { type VertexRerankerPluginOptions } from './types.js';
+export { type VertexRerankerPluginOptions };
 
 async function initializer(pluginOptions: VertexRerankerPluginOptions) {
   const clientOptions = await getDerivedOptions(