diff --git a/examples/plugin/jshandler/Makefile b/examples/plugin/jshandler/Makefile
new file mode 100644
index 00000000..f1db3a3c
--- /dev/null
+++ b/examples/plugin/jshandler/Makefile
@@ -0,0 +1,23 @@
+PLUGIN_NAME ?= jshandler
+BUILD_DIR ?= .
+GOOS ?= $(shell go env GOOS)
+GOARCH ?= $(shell go env GOARCH)
+
+EXT_linux = so
+EXT_freebsd = so
+EXT_darwin = dylib
+EXT_windows = dll
+PLUGIN_EXT = $(or $(EXT_$(GOOS)),so)
+PLUGIN_OUTPUT ?= $(BUILD_DIR)/$(PLUGIN_NAME).$(PLUGIN_EXT)
+PLUGIN_HEADER = $(basename $(PLUGIN_OUTPUT)).h
+
+.PHONY: build clean
+
+build:
+	CGO_ENABLED=1 GOOS=$(GOOS) GOARCH=$(GOARCH) go build -buildmode=c-shared -o $(PLUGIN_OUTPUT) .
+
+clean:
+	rm -f $(BUILD_DIR)/$(PLUGIN_NAME).so
+	rm -f $(BUILD_DIR)/$(PLUGIN_NAME).dylib
+	rm -f $(BUILD_DIR)/$(PLUGIN_NAME).dll
+	rm -f $(PLUGIN_HEADER)
diff --git a/examples/plugin/jshandler/README.md b/examples/plugin/jshandler/README.md
new file mode 100644
index 00000000..e9b5aca4
--- /dev/null
+++ b/examples/plugin/jshandler/README.md
@@ -0,0 +1,119 @@
+# JS Handler Plugin
+
+A CLIProxyAPI plugin that executes external JavaScript scripts to intercept and modify requests, responses, and streaming chunks using the Goja VM engine.
+
+## Features
+
+- **Request Interception** (`on_before_request`): Modify request payloads and headers before upstream delivery.
+- **Response Interception** (`on_after_nonstream_response`): Modify non-streaming response bodies and headers.
+- **Stream Chunk Interception** (`on_after_stream_response`): Modify individual streaming chunks with read-only `history_chunks` context.
+- **Hot Reload**: Scripts are automatically reloaded when modified on disk.
+- **Execution Timeout**: Configurable timeout prevents infinite loops.
+- **Graceful Degradation**: Original data is preserved on JS execution errors.
+
+## Configuration
+
+```yaml
+plugins:
+  enabled: true
+  dir: "plugins-dir"
+  configs:
+    jshandler:
+      enabled: true
+      script_paths:
+        - /path/to/custom_handler.js
+        - ./relative_handler.js
+      timeout: 1s
+```
+
+### Fields
+
+| Field | Type | Default | Description |
+|-------|------|---------|-------------|
+| `enabled` | boolean | `true` | Enable or disable the plugin |
+| `script_paths` | array | `[]` | JS script file paths (absolute or relative to plugin directory) |
+| `timeout` | string | `1s` | Execution timeout per JS hook call |
+
+## JS Script API
+
+Scripts can export these global functions:
+
+### `on_before_request(ctx)`
+
+Called before the request is sent upstream.
+
+**ctx structure:**
+```javascript
+{
+    "id": "request-id",
+    "body": "...",        // Request body string
+    "headers": {},        // Request headers
+    "url": "",
+    "model": "gpt-4",
+    "protocol": "openai"
+}
+```
+
+### `on_after_nonstream_response(ctx)`
+
+Called after a non-streaming response is received from upstream.
+
+**ctx structure (non-streaming):**
+```javascript
+{
+    "id": "request-id",
+    "body": "...",        // Full response body
+    "req": { "body": "...", "headers": {}, "url": "" },
+    "protocol": "openai",
+    "headers": {},
+    "chunk": null,
+    "history_chunks": null
+}
+```
+
+### `on_after_stream_response(ctx)`
+
+Called after each streaming response chunk is received from upstream.
+
+**ctx structure:**
+```javascript
+{
+    "id": "request-id",
+    "body": null,
+    "req": { "body": "...", "headers": {}, "url": "" },
+    "protocol": "openai",
+    "headers": {},
+    "chunk": "...",              // Current writable chunk
+    "history_chunks": ["..."]    // Read-only frozen array
+}
+```
+
+### Return Value
+
+Return the modified `ctx` object, or a plain string to replace the body/chunk.
+
+## Built-in Scripts
+
+The `scripts/` directory contains built-in scripts loaded automatically:
+
+- `copilot_handler.js`: Fixes tool-call `finish_reason` for GitHub Copilot compatibility.
+
+## Building
+
+```bash
+make build
+```
+
+The Makefile chooses the plugin extension from the target platform:
+
+| GOOS | Output |
+|------|--------|
+| `linux` / `freebsd` | `jshandler.so` |
+| `darwin` | `jshandler.dylib` |
+| `windows` | `jshandler.dll` |
+
+You can override the target and output directory:
+
+```bash
+make build GOOS=darwin GOARCH=arm64 BUILD_DIR=/path/to/plugins/darwin/arm64
+```
diff --git a/examples/plugin/jshandler/abi.go b/examples/plugin/jshandler/abi.go
new file mode 100644
index 00000000..d4e3b39e
--- /dev/null
+++ b/examples/plugin/jshandler/abi.go
@@ -0,0 +1,291 @@
+package main
+
+/*
+#define _GNU_SOURCE
+#include <dlfcn.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct {
+	void* ptr;
+	size_t len;
+} cliproxy_buffer;
+
+typedef int (*cliproxy_host_call_fn)(void*, const char*, const uint8_t*, size_t, cliproxy_buffer*);
+typedef void (*cliproxy_host_free_fn)(void*, size_t);
+
+typedef struct {
+	uint32_t abi_version;
+	void* host_ctx;
+	cliproxy_host_call_fn call;
+	cliproxy_host_free_fn free_buffer;
+} cliproxy_host_api;
+
+typedef int (*cliproxy_plugin_call_fn)(char*, uint8_t*, size_t, cliproxy_buffer*);
+typedef void (*cliproxy_plugin_free_fn)(void*, size_t);
+typedef void (*cliproxy_plugin_shutdown_fn)(void);
+
+typedef struct {
+	uint32_t abi_version;
+	cliproxy_plugin_call_fn call;
+	cliproxy_plugin_free_fn free_buffer;
+	cliproxy_plugin_shutdown_fn shutdown;
+} cliproxy_plugin_api;
+
+extern int JSHandlerPluginCall(char*, uint8_t*, size_t, cliproxy_buffer*);
+extern void JSHandlerPluginFree(void*, size_t);
+extern void JSHandlerPluginShutdown(void);
+
+static const char* jshandler_shared_object_path() {
+	Dl_info info;
+	if (dladdr((void*)&JSHandlerPluginCall, &info) == 0 || info.dli_fname == NULL) {
+		return NULL;
+	}
+	return info.dli_fname;
+}
+
+static int jshandler_call_host(cliproxy_host_api* api, const char* method, const uint8_t* request, size_t request_len, cliproxy_buffer* response) {
+	return api->call(api->host_ctx, method, request, request_len, response);
+}
+
+static void jshandler_free_host_buffer(cliproxy_host_api* api, void* ptr, size_t len) {
+	api->free_buffer(ptr, len);
+}
+*/
+import "C"
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"path/filepath"
+	"sync"
+	"unsafe"
+
+	"github.com/router-for-me/CLIProxyAPI/v7/sdk/pluginabi"
+	"github.com/router-for-me/CLIProxyAPI/v7/sdk/pluginapi"
+)
+
+var jsHandlerABIState = struct {
+	sync.RWMutex
+	host         *C.cliproxy_host_api
+	plugin       *jsHandlerPlugin
+	shuttingDown bool
+	inFlight     sync.WaitGroup
+}{}
+
+const maxCGoBytesLen = C.size_t(1<<31 - 1)
+
+type abiEnvelope struct {
+	OK     bool            `json:"ok"`
+	Result json.RawMessage `json:"result,omitempty"`
+	Error  *abiError       `json:"error,omitempty"`
+}
+
+type abiError struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+type abiLifecycleRequest struct {
+	ConfigYAML []byte `json:"config_yaml"`
+	PluginDir  string `json:"plugin_dir,omitempty"`
+}
+
+type abiRegistration struct {
+	SchemaVersion uint32             `json:"schema_version"`
+	Metadata      pluginapi.Metadata `json:"metadata"`
+	Capabilities  abiCapabilities    `json:"capabilities"`
+}
+
+type abiCapabilities struct {
+	RequestInterceptor     bool `json:"request_interceptor"`
+	ResponseInterceptor    bool `json:"response_interceptor"`
+	StreamChunkInterceptor bool `json:"response_stream_interceptor"`
+}
+
+type abiIdentifierResponse struct {
+	Identifier string `json:"identifier"`
+}
+
+func main() {}
+
+func inferPluginDir() string {
+	sharedObjectPath := C.jshandler_shared_object_path()
+	if sharedObjectPath == nil {
+		return ""
+	}
+	return filepath.Dir(C.GoString(sharedObjectPath))
+}
+
+//export cliproxy_plugin_init
+func cliproxy_plugin_init(host *C.cliproxy_host_api, plugin *C.cliproxy_plugin_api) C.int {
+	if host == nil || plugin == nil {
+		return 1
+	}
+	jsHandlerABIState.Lock()
+	jsHandlerABIState.host = host
+	jsHandlerABIState.shuttingDown = false
+	jsHandlerABIState.Unlock()
+
+	plugin.abi_version = C.uint32_t(pluginabi.ABIVersion)
+	plugin.call = C.cliproxy_plugin_call_fn(C.JSHandlerPluginCall)
+	plugin.free_buffer = C.cliproxy_plugin_free_fn(C.JSHandlerPluginFree)
+	plugin.shutdown = C.cliproxy_plugin_shutdown_fn(C.JSHandlerPluginShutdown)
+	return 0
+}
+
+//export JSHandlerPluginCall
+func JSHandlerPluginCall(method *C.char, request *C.uint8_t, requestLen C.size_t, response *C.cliproxy_buffer) C.int {
+	if response != nil {
+		response.ptr = nil
+		response.len = 0
+	}
+	if method == nil {
+		writeABIResponse(response, abiErrorEnvelope("invalid_method", "method is required"))
+		return 0
+	}
+	var requestBytes []byte
+	if request != nil && requestLen > 0 {
+		if requestLen > maxCGoBytesLen {
+			writeABIResponse(response, abiErrorEnvelope("request_too_large", "request payload is too large"))
+			return 0
+		}
+		requestBytes = C.GoBytes(unsafe.Pointer(request), C.int(requestLen))
+	}
+	raw, errHandle := handleJSHandlerABIMethod(context.Background(), C.GoString(method), requestBytes)
+	if errHandle != nil {
+		writeABIResponse(response, abiErrorEnvelope("plugin_error", errHandle.Error()))
+		return 0
+	}
+	writeABIResponse(response, raw)
+	return 0
+}
+
+//export JSHandlerPluginFree
+func JSHandlerPluginFree(ptr unsafe.Pointer, len C.size_t) {
+	if ptr != nil {
+		C.free(ptr)
+	}
+}
+
+//export JSHandlerPluginShutdown
+func JSHandlerPluginShutdown() {
+	jsHandlerABIState.Lock()
+	jsHandlerABIState.shuttingDown = true
+	jsHandlerABIState.plugin = nil
+	jsHandlerABIState.host = nil
+	jsHandlerABIState.Unlock()
+	jsHandlerABIState.inFlight.Wait()
+}
+
+func handleJSHandlerABIMethod(ctx context.Context, method string, request []byte) ([]byte, error) {
+	switch method {
+	case pluginabi.MethodPluginRegister, pluginabi.MethodPluginReconfigure:
+		return handleJSHandlerRegister(request)
+	}
+
+	p, done, errPlugin := beginJSHandlerPluginCall()
+	if errPlugin != nil {
+		return nil, errPlugin
+	}
+	defer done()
+	switch method {
+	case pluginabi.MethodRequestInterceptBefore:
+		var req pluginapi.RequestInterceptRequest
+		if errDecode := json.Unmarshal(request, &req); errDecode != nil {
+			return nil, errDecode
+		}
+		resp, errCall := p.InterceptRequest(ctx, req)
+		return abiOKEnvelopeWithError(resp, errCall)
+	case pluginabi.MethodResponseInterceptAfter:
+		var req pluginapi.ResponseInterceptRequest
+		if errDecode := json.Unmarshal(request, &req); errDecode != nil {
+			return nil, errDecode
+		}
+		resp, errCall := p.InterceptResponse(ctx, req)
+		return abiOKEnvelopeWithError(resp, errCall)
+	case pluginabi.MethodResponseInterceptStreamChunk:
+		var req pluginapi.StreamChunkInterceptRequest
+		if errDecode := json.Unmarshal(request, &req); errDecode != nil {
+			return nil, errDecode
+		}
+		resp, errCall := p.InterceptStreamChunk(ctx, req)
+		return abiOKEnvelopeWithError(resp, errCall)
+	default:
+		return abiErrorEnvelope("unknown_method", "unknown method: "+method), nil
+	}
+}
+
+func handleJSHandlerRegister(request []byte) ([]byte, error) {
+	var req abiLifecycleRequest
+	if errDecode := json.Unmarshal(request, &req); errDecode != nil {
+		return nil, errDecode
+	}
+	plugin, errBuild := buildPlugin(req.ConfigYAML, req.PluginDir)
+	if errBuild != nil {
+		return nil, errBuild
+	}
+	p, ok := plugin.Capabilities.RequestInterceptor.(*jsHandlerPlugin)
+	if !ok || p == nil {
+		return nil, fmt.Errorf("jshandler plugin registration returned invalid interceptor")
+	}
+	jsHandlerABIState.Lock()
+	jsHandlerABIState.plugin = p
+	jsHandlerABIState.shuttingDown = false
+	jsHandlerABIState.Unlock()
+	return abiOKEnvelope(abiRegistration{
+		SchemaVersion: pluginabi.SchemaVersion,
+		Metadata:      plugin.Metadata,
+		Capabilities: abiCapabilities{
+			RequestInterceptor:     plugin.Capabilities.RequestInterceptor != nil,
+			ResponseInterceptor:    plugin.Capabilities.ResponseInterceptor != nil,
+			StreamChunkInterceptor: plugin.Capabilities.StreamChunkInterceptor != nil,
+		},
+	})
+}
+
+func beginJSHandlerPluginCall() (*jsHandlerPlugin, func(), error) {
+	jsHandlerABIState.Lock()
+	defer jsHandlerABIState.Unlock()
+	if jsHandlerABIState.shuttingDown {
+		return nil, nil, fmt.Errorf("jshandler plugin is shutting down")
+	}
+	if jsHandlerABIState.plugin == nil {
+		return nil, nil, fmt.Errorf("jshandler plugin is not registered")
+	}
+	jsHandlerABIState.inFlight.Add(1)
+	return jsHandlerABIState.plugin, jsHandlerABIState.inFlight.Done, nil
+}
+
+func abiOKEnvelopeWithError(v any, err error) ([]byte, error) {
+	if err != nil {
+		return nil, err
+	}
+	return abiOKEnvelope(v)
+}
+
+func abiOKEnvelope(v any) ([]byte, error) {
+	raw, errMarshal := json.Marshal(v)
+	if errMarshal != nil {
+		return nil, errMarshal
+	}
+	return json.Marshal(abiEnvelope{OK: true, Result: raw})
+}
+
+func abiErrorEnvelope(code, message string) []byte {
+	raw, _ := json.Marshal(abiEnvelope{OK: false, Error: &abiError{Code: code, Message: message}})
+	return raw
+}
+
+func writeABIResponse(response *C.cliproxy_buffer, raw []byte) {
+	if response == nil || len(raw) == 0 {
+		return
+	}
+	ptr := C.CBytes(raw)
+	if ptr == nil {
+		return
+	}
+	response.ptr = ptr
+	response.len = C.size_t(len(raw))
+}
diff --git a/examples/plugin/jshandler/abi_test.go b/examples/plugin/jshandler/abi_test.go
new file mode 100644
index 00000000..c46eb1f5
--- /dev/null
+++ b/examples/plugin/jshandler/abi_test.go
@@ -0,0 +1,36 @@
+package main
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestABIRegistrationUsesHostStreamCapabilityField(t *testing.T) {
+	raw, errMarshal := abiOKEnvelope(abiRegistration{
+		Capabilities: abiCapabilities{
+			RequestInterceptor:     true,
+			ResponseInterceptor:    true,
+			StreamChunkInterceptor: true,
+		},
+	})
+	if errMarshal != nil {
+		t.Fatalf("abiOKEnvelope() error = %v", errMarshal)
+	}
+
+	var envelope abiEnvelope
+	if errUnmarshal := json.Unmarshal(raw, &envelope); errUnmarshal != nil {
+		t.Fatalf("json.Unmarshal(envelope) error = %v", errUnmarshal)
+	}
+	var result struct {
+		Capabilities map[string]bool `json:"capabilities"`
+	}
+	if errUnmarshal := json.Unmarshal(envelope.Result, &result); errUnmarshal != nil {
+		t.Fatalf("json.Unmarshal(result) error = %v", errUnmarshal)
+	}
+	if !result.Capabilities["response_stream_interceptor"] {
+		t.Fatalf("response_stream_interceptor capability was not advertised: %v", result.Capabilities)
+	}
+	if _, exists := result.Capabilities["stream_chunk_interceptor"]; exists {
+		t.Fatalf("legacy stream_chunk_interceptor field should not be advertised: %v", result.Capabilities)
+	}
+}
diff --git a/examples/plugin/jshandler/config.go b/examples/plugin/jshandler/config.go
new file mode 100644
index 00000000..9a6c24f2
--- /dev/null
+++ b/examples/plugin/jshandler/config.go
@@ -0,0 +1,140 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"gopkg.in/yaml.v3"
+)
+
+const jsHandlerProvider = "jshandler"
+const pluginName = "jshandler"
+
+type jsHandlerConfig struct {
+	Enabled     bool          `yaml:"enabled"`
+	ScriptPaths []string      `yaml:"script_paths"`
+	TimeoutRaw  string        `yaml:"timeout"`
+	Timeout     time.Duration `yaml:"-"`
+}
+
+func defaultJSHandlerConfig() jsHandlerConfig {
+	return jsHandlerConfig{
+		Enabled: true,
+		Timeout: 1 * time.Second,
+	}
+}
+
+func parseJSHandlerConfig(raw []byte) (jsHandlerConfig, error) {
+	cfg := defaultJSHandlerConfig()
+	if len(strings.TrimSpace(string(raw))) > 0 {
+		if errUnmarshal := yaml.Unmarshal(raw, &cfg); errUnmarshal != nil {
+			return cfg, fmt.Errorf("invalid jshandler config: %w", errUnmarshal)
+		}
+	}
+	if strings.TrimSpace(cfg.TimeoutRaw) != "" {
+		parsed, errParse := time.ParseDuration(strings.TrimSpace(cfg.TimeoutRaw))
+		if errParse != nil || parsed <= 0 {
+			return cfg, fmt.Errorf("invalid jshandler timeout %q", cfg.TimeoutRaw)
+		}
+		cfg.Timeout = parsed
+	}
+	if cfg.Timeout <= 0 {
+		cfg.Timeout = 1 * time.Second
+	}
+	return cfg, nil
+}
+
+func (cfg *jsHandlerConfig) resolvedScriptPaths(pluginDir string) ([]string, error) {
+	var paths []string
+	for _, p := range cfg.ScriptPaths {
+		p = strings.TrimSpace(p)
+		if p == "" {
+			continue
+		}
+		originalPath := p
+		relativePath := !filepath.IsAbs(p)
+		if !filepath.IsAbs(p) {
+			if pluginDir == "" {
+				return nil, fmt.Errorf("relative script path %q requires plugin_dir", originalPath)
+			}
+			p = filepath.Join(pluginDir, p)
+			if !isPathWithinDir(p, pluginDir) {
+				return nil, fmt.Errorf("relative script path %q escapes plugin_dir", originalPath)
+			}
+		}
+		cleanPath, errClean := filepath.Abs(filepath.Clean(p))
+		if errClean != nil {
+			return nil, errClean
+		}
+		if relativePath {
+			resolvedPath, errEval := filepath.EvalSymlinks(cleanPath)
+			if errEval != nil {
+				return nil, errEval
+			}
+			if !isResolvedPathWithinDir(resolvedPath, pluginDir) {
+				return nil, fmt.Errorf("relative script path %q escapes plugin_dir through symlink", originalPath)
+			}
+			cleanPath = resolvedPath
+		}
+		paths = append(paths, cleanPath)
+	}
+	return paths, nil
+}
+
+func builtinScriptPaths(pluginDir string) []string {
+	if pluginDir == "" {
+		return nil
+	}
+	scriptsDir := filepath.Join(pluginDir, "scripts")
+	cleanScriptsDir, errClean := filepath.Abs(filepath.Clean(scriptsDir))
+	if errClean != nil {
+		return nil
+	}
+	entries, errRead := os.ReadDir(scriptsDir)
+	if errRead != nil {
+		return nil
+	}
+	var paths []string
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+		name := entry.Name()
+		if strings.HasSuffix(strings.ToLower(name), ".js") {
+			candidate := filepath.Join(cleanScriptsDir, name)
+			resolved, errEval := filepath.EvalSymlinks(candidate)
+			if errEval != nil || !isResolvedPathWithinDir(resolved, cleanScriptsDir) {
+				continue
+			}
+			paths = append(paths, resolved)
+		}
+	}
+	return paths
+}
+
+func isPathWithinDir(path, dir string) bool {
+	cleanPath, errPath := filepath.Abs(filepath.Clean(path))
+	if errPath != nil {
+		return false
+	}
+	cleanDir, errDir := filepath.Abs(filepath.Clean(dir))
+	if errDir != nil {
+		return false
+	}
+	rel, errRel := filepath.Rel(cleanDir, cleanPath)
+	if errRel != nil {
+		return false
+	}
+	return rel == "." || (rel != "" && !strings.HasPrefix(rel, ".."+string(filepath.Separator)) && rel != "..")
+}
+
+func isResolvedPathWithinDir(path, dir string) bool {
+	resolvedDir, errEval := filepath.EvalSymlinks(dir)
+	if errEval != nil {
+		return false
+	}
+	return isPathWithinDir(path, resolvedDir)
+}
diff --git a/examples/plugin/jshandler/config_test.go b/examples/plugin/jshandler/config_test.go
new file mode 100644
index 00000000..8ff3abb1
--- /dev/null
+++ b/examples/plugin/jshandler/config_test.go
@@ -0,0 +1,64 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestResolvedScriptPathsRejectsRelativeSymlinkEscapingPluginDir(t *testing.T) {
+	pluginDir := t.TempDir()
+	outsideDir := t.TempDir()
+	outsideScript := filepath.Join(outsideDir, "handler.js")
+	if errWrite := os.WriteFile(outsideScript, []byte("function on_before_request(ctx) { return ctx; }\n"), 0600); errWrite != nil {
+		t.Fatalf("os.WriteFile() error = %v", errWrite)
+	}
+
+	linkPath := filepath.Join(pluginDir, "handler.js")
+	if errSymlink := os.Symlink(outsideScript, linkPath); errSymlink != nil {
+		t.Skipf("os.Symlink() is not available: %v", errSymlink)
+	}
+
+	cfg := jsHandlerConfig{ScriptPaths: []string{"handler.js"}}
+	_, errResolve := cfg.resolvedScriptPaths(pluginDir)
+	if errResolve == nil {
+		t.Fatal("resolvedScriptPaths() expected error for escaping symlink")
+	}
+	if !strings.Contains(errResolve.Error(), "escapes plugin_dir") {
+		t.Fatalf("resolvedScriptPaths() error = %v, want escapes plugin_dir", errResolve)
+	}
+}
+
+func TestResolvedScriptPathsAllowsRelativeSymlinkInsidePluginDir(t *testing.T) {
+	pluginDir := t.TempDir()
+	scriptsDir := filepath.Join(pluginDir, "scripts")
+	if errMkdir := os.Mkdir(scriptsDir, 0700); errMkdir != nil {
+		t.Fatalf("os.Mkdir() error = %v", errMkdir)
+	}
+	realScript := filepath.Join(scriptsDir, "handler.js")
+	if errWrite := os.WriteFile(realScript, []byte("function on_before_request(ctx) { return ctx; }\n"), 0600); errWrite != nil {
+		t.Fatalf("os.WriteFile() error = %v", errWrite)
+	}
+
+	linkPath := filepath.Join(pluginDir, "handler.js")
+	if errSymlink := os.Symlink(realScript, linkPath); errSymlink != nil {
+		t.Skipf("os.Symlink() is not available: %v", errSymlink)
+	}
+
+	cfg := jsHandlerConfig{ScriptPaths: []string{"handler.js"}}
+	paths, errResolve := cfg.resolvedScriptPaths(pluginDir)
+	if errResolve != nil {
+		t.Fatalf("resolvedScriptPaths() error = %v", errResolve)
+	}
+	if len(paths) != 1 {
+		t.Fatalf("resolvedScriptPaths() returned %d paths, want 1", len(paths))
+	}
+	resolvedRealScript, errEval := filepath.EvalSymlinks(realScript)
+	if errEval != nil {
+		t.Fatalf("filepath.EvalSymlinks() error = %v", errEval)
+	}
+	if paths[0] != resolvedRealScript {
+		t.Fatalf("resolvedScriptPaths()[0] = %q, want %q", paths[0], resolvedRealScript)
+	}
+}
diff --git a/examples/plugin/jshandler/engine.go b/examples/plugin/jshandler/engine.go
new file mode 100644
index 00000000..8da181ff
--- /dev/null
+++ b/examples/plugin/jshandler/engine.go
@@ -0,0 +1,183 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+
+	"github.com/dop251/goja"
+	log "github.com/sirupsen/logrus"
+)
+
+type jsEngine struct {
+	vm *goja.Runtime
+}
+
+const maxJSScriptBytes = 8 * 1024 * 1024
+
+func newJSEngine() *jsEngine {
+	engine := &jsEngine{
+		vm: goja.New(),
+	}
+	engine.initConsole()
+	return engine
+}
+
+func (engine *jsEngine) initConsole() {
+	console := engine.vm.NewObject()
+	consoleLogWrapper := func(call goja.FunctionCall) goja.Value {
+		args := make([]interface{}, len(call.Arguments))
+		for i, arg := range call.Arguments {
+			args[i] = arg.Export()
+		}
+		log.Info("JS console log: ", fmt.Sprint(args...))
+		return goja.Undefined()
+	}
+	_ = console.Set("log", consoleLogWrapper)
+	_ = engine.vm.Set("console", console)
+}
+
+func (engine *jsEngine) runProgram(program *goja.Program, timeout time.Duration) error {
+	if program == nil {
+		return errors.New("program is nil")
+	}
+	timer, done := engine.startInterruptTimer(timeout)
+	defer engine.stopInterruptTimer(timer, done)
+
+	_, err := engine.vm.RunProgram(program)
+	if err != nil {
+		return fmt.Errorf("failed to run JS program: %w", err)
+	}
+	return nil
+}
+
+var ErrFunctionNotFound = errors.New("function not found")
+var errJSTimeout = errors.New("javascript execution timeout")
+
+func (engine *jsEngine) startInterruptTimer(timeout time.Duration) (*time.Timer, <-chan struct{}) {
+	done := make(chan struct{})
+	timer := time.AfterFunc(timeout, func() {
+		defer close(done)
+		engine.vm.Interrupt(errJSTimeout)
+	})
+	return timer, done
+}
+
+func (engine *jsEngine) stopInterruptTimer(timer *time.Timer, done <-chan struct{}) {
+	if timer == nil {
+		return
+	}
+	if timer.Stop() {
+		return
+	}
+	<-done
+	engine.vm.ClearInterrupt()
+}
+
+func (engine *jsEngine) frozenStringArray(values []string) (goja.Value, error) {
+	items := make([]interface{}, len(values))
+	for i, value := range values {
+		items[i] = value
+	}
+	array := engine.vm.NewArray(items...)
+	objectValue := engine.vm.Get("Object")
+	if objectValue == nil || goja.IsUndefined(objectValue) {
+		return nil, errors.New("Object constructor is unavailable")
+	}
+	freezeValue := objectValue.ToObject(engine.vm).Get("freeze")
+	freezeFunc, ok := goja.AssertFunction(freezeValue)
+	if !ok {
+		return nil, errors.New("Object.freeze is unavailable")
+	}
+	if _, errFreeze := freezeFunc(goja.Undefined(), array); errFreeze != nil {
+		return nil, errFreeze
+	}
+	return array, nil
+}
+
+func (engine *jsEngine) callFunction(name string, timeout time.Duration, args ...interface{}) (goja.Value, error) {
+	jsVal := engine.vm.Get(name)
+	if jsVal == nil || goja.IsUndefined(jsVal) {
+		return nil, fmt.Errorf("%w: function '%s' does not exist", ErrFunctionNotFound, name)
+	}
+	jsFunc, ok := goja.AssertFunction(jsVal)
+	if !ok {
+		return nil, fmt.Errorf("function '%s' is invalid", name)
+	}
+
+	jsArgs := make([]goja.Value, len(args))
+	for i, arg := range args {
+		jsArgs[i] = engine.vm.ToValue(arg)
+	}
+
+	timer, done := engine.startInterruptTimer(timeout)
+	defer engine.stopInterruptTimer(timer, done)
+
+	result, err := jsFunc(goja.Undefined(), jsArgs...)
+	if err != nil {
+		return nil, err
+	}
+
+	return result, nil
+}
+
+type jsCachedProgram struct {
+	program *goja.Program
+	modTime time.Time
+}
+
+var (
+	jsProgramsMU    sync.RWMutex
+	jsProgramsCache = make(map[string]jsCachedProgram)
+)
+
+func getJSProgram(path string) (*goja.Program, error) {
+	cleanPath, errClean := filepath.Abs(filepath.Clean(path))
+	if errClean != nil {
+		return nil, errClean
+	}
+	resolvedPath, errEval := filepath.EvalSymlinks(cleanPath)
+	if errEval != nil {
+		return nil, errEval
+	}
+	info, err := os.Stat(resolvedPath)
+	if err != nil {
+		return nil, err
+	}
+	if info.Size() > maxJSScriptBytes {
+		return nil, fmt.Errorf("JS script %s is too large: %d bytes", resolvedPath, info.Size())
+	}
+	modTime := info.ModTime()
+
+	jsProgramsMU.RLock()
+	cached, exists := jsProgramsCache[resolvedPath]
+	jsProgramsMU.RUnlock()
+	if exists && cached.modTime.Equal(modTime) {
+		return cached.program, nil
+	}
+
+	data, errRead := os.ReadFile(resolvedPath)
+	if errRead != nil {
+		return nil, errRead
+	}
+
+	compiled, errCompile := goja.Compile(resolvedPath, string(data), false)
+	if errCompile != nil {
+		return nil, fmt.Errorf("failed to compile JS script %s: %w", resolvedPath, errCompile)
+	}
+
+	jsProgramsMU.Lock()
+	defer jsProgramsMU.Unlock()
+	if cached, exists = jsProgramsCache[resolvedPath]; exists && cached.modTime.Equal(modTime) {
+		return cached.program, nil
+	}
+
+	jsProgramsCache[resolvedPath] = jsCachedProgram{
+		program: compiled,
+		modTime: modTime,
+	}
+	return compiled, nil
+}
diff --git a/examples/plugin/jshandler/engine_test.go b/examples/plugin/jshandler/engine_test.go
new file mode 100644
index 00000000..33bbd8c3
--- /dev/null
+++ b/examples/plugin/jshandler/engine_test.go
@@ -0,0 +1,25 @@
+package main
+
+import (
+	"testing"
+	"time"
+)
+
+func TestStopInterruptTimerClearsExpiredInterrupt(t *testing.T) {
+	engine := newJSEngine()
+	timer, done := engine.startInterruptTimer(time.Nanosecond)
+	select {
+	case <-done:
+	case <-time.After(time.Second):
+		t.Fatal("interrupt timer did not fire")
+	}
+
+	engine.stopInterruptTimer(timer, done)
+	value, errRun := engine.vm.RunString("1 + 1")
+	if errRun != nil {
+		t.Fatalf("RunString() error after clearing interrupt = %v", errRun)
+	}
+	if got := value.ToInteger(); got != 2 {
+		t.Fatalf("RunString() = %d, want 2", got)
+	}
+}
diff --git a/examples/plugin/jshandler/go.mod b/examples/plugin/jshandler/go.mod
new file mode 100644
index 00000000..1cd5f78d
--- /dev/null
+++ b/examples/plugin/jshandler/go.mod
@@ -0,0 +1,18 @@
+module github.com/router-for-me/CLIProxyAPIPlugins/jshandler
+
+go 1.26.0
+
+require (
+	github.com/dop251/goja v0.0.0-20260607120635-348e6bea910d
+	github.com/router-for-me/CLIProxyAPI/v7 v7.1.55
+	github.com/sirupsen/logrus v1.9.4
+	gopkg.in/yaml.v3 v3.0.1
+)
+
+require (
+	github.com/dlclark/regexp2/v2 v2.2.1 // indirect
+	github.com/go-sourcemap/sourcemap v2.1.3+incompatible // indirect
+	github.com/google/pprof v0.0.0-20230207041349-798e818bf904 // indirect
+	golang.org/x/sys v0.38.0 // indirect
+	golang.org/x/text v0.31.0 // indirect
+)
diff --git a/examples/plugin/jshandler/go.sum b/examples/plugin/jshandler/go.sum
new file mode 100644
index 00000000..7654f0cc
--- /dev/null
+++ b/examples/plugin/jshandler/go.sum
@@ -0,0 +1,30 @@
+github.com/Masterminds/semver/v3 v3.5.0 h1:kQceYJfbupGfZOKZQg0kou0DgAKhzDg2NZPAwZ/2OOE=
+github.com/Masterminds/semver/v3 v3.5.0/go.mod h1:4V+yj/TJE1HU9XfppCwVMZq3I84lprf4nC11bSS5beM=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dlclark/regexp2/v2 v2.2.1 h1:mf4KkFUj0gJuarK8P+LgiS+Lit7m9N1yAwEfPbee7R0=
+github.com/dlclark/regexp2/v2 v2.2.1/go.mod h1:avUrQvPaLz2DrFNHJF0taWAFFX2C1GMSSoeiqFjcBmU=
+github.com/dop251/goja v0.0.0-20260607120635-348e6bea910d h1:xbM5U2EvWKkHxzEQJ2DEn20FwolWZahuTnVHr6WL3Q4=
+github.com/dop251/goja v0.0.0-20260607120635-348e6bea910d/go.mod h1:Sc+QOu1WruvaaeT/cxFez/pXHpI9ZDjg/E8QNfSVveI=
+github.com/go-sourcemap/sourcemap v2.1.3+incompatible h1:W1iEw64niKVGogNgBN3ePyLFfuisuzeidWPMPWmECqU=
+github.com/go-sourcemap/sourcemap v2.1.3+incompatible/go.mod h1:F8jJfvm2KbVjc5NqelyYJmf/v5J0dwNLS2mL4sNA1Jg=
+github.com/goccy/go-yaml v1.19.2 h1:PmFC1S6h8ljIz6gMRBopkjP1TVT7xuwrButHID66PoM=
+github.com/goccy/go-yaml v1.19.2/go.mod h1:XBurs7gK8ATbW4ZPGKgcbrY1Br56PdM69F7LkFRi1kA=
+github.com/google/pprof v0.0.0-20230207041349-798e818bf904 h1:4/hN5RUoecvl+RmJRE2YxKWtnnQls6rQjjW5oV7qg2U=
+github.com/google/pprof v0.0.0-20230207041349-798e818bf904/go.mod h1:uglQLonpP8qtYCYyzA+8c/9qtqgA3qsXGYqCPKARAFg=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/router-for-me/CLIProxyAPI/v7 v7.1.55 h1:gaZc8W025JV/CpTBpFH16af8yenC/IYuK/nBa+Age4k=
+github.com/router-for-me/CLIProxyAPI/v7 v7.1.55/go.mod h1:5LQLwZuB03QHP2jsRo4Kl7pJBgsu9w0O/v1F6Ze+d4U=
+github.com/sirupsen/logrus v1.9.4 h1:TsZE7l11zFCLZnZ+teH4Umoq5BhEIfIzfRDZ1Uzql2w=
+github.com/sirupsen/logrus v1.9.4/go.mod h1:ftWc9WdOfJ0a92nsE2jF5u5ZwH8Bv2zdeOC42RjbV2g=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
+golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.31.0 h1:aC8ghyu4JhP8VojJ2lEHBnochRno1sgL6nEi9WGFGMM=
+golang.org/x/text v0.31.0/go.mod h1:tKRAlv61yKIjGGHX/4tP1LTbc13YSec1pxVEWXzfoeM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/examples/plugin/jshandler/interceptor.go b/examples/plugin/jshandler/interceptor.go
new file mode 100644
index 00000000..347a59ee
--- /dev/null
+++ b/examples/plugin/jshandler/interceptor.go
@@ -0,0 +1,477 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"reflect"
+	"strings"
+	"time"
+
+	"github.com/dop251/goja"
+	"github.com/router-for-me/CLIProxyAPI/v7/sdk/pluginapi"
+	log "github.com/sirupsen/logrus"
+)
+
+type jsHandlerPlugin struct {
+	cfg        jsHandlerConfig
+	configYAML []byte
+	pluginDir  string
+}
+
+type processedHeaders struct {
+	headers      http.Header
+	clearHeaders []string
+}
+
+var _ pluginapi.RequestInterceptor = (*jsHandlerPlugin)(nil)
+var _ pluginapi.ResponseInterceptor = (*jsHandlerPlugin)(nil)
+var _ pluginapi.StreamChunkInterceptor = (*jsHandlerPlugin)(nil)
+
+func (p *jsHandlerPlugin) Identifier() string {
+	return jsHandlerProvider
+}
+
+func (p *jsHandlerPlugin) allScriptPaths() []string {
+	paths := builtinScriptPaths(p.pluginDir)
+	configuredPaths, errPaths := p.cfg.resolvedScriptPaths(p.pluginDir)
+	if errPaths != nil {
+		log.Warnf("failed to resolve JS handler script paths: %v", errPaths)
+		return paths
+	}
+	paths = append(paths, configuredPaths...)
+	return paths
+}
+
+func (p *jsHandlerPlugin) InterceptRequest(ctx context.Context, req pluginapi.RequestInterceptRequest) (pluginapi.RequestInterceptResponse, error) {
+	resp := pluginapi.RequestInterceptResponse{}
+	scriptPaths := p.allScriptPaths()
+	if len(scriptPaths) == 0 {
+		return resp, nil
+	}
+
+	body := string(req.Body)
+	headers := cloneHeader(req.Headers)
+	var clearHeaders []string
+
+	for _, scriptPath := range scriptPaths {
+		scriptPath = strings.TrimSpace(scriptPath)
+		if scriptPath == "" {
+			continue
+		}
+		processed, cleared, errJS := p.applyJSBeforeRequest(scriptPath, []byte(body), req.Model, req.SourceFormat, headers)
+		if errJS != nil {
+			log.Warnf("failed to execute JS request interceptor [%s]: %v", scriptPath, errJS)
+			continue
+		}
+		body = string(processed)
+		clearHeaders = append(clearHeaders, cleared...)
+	}
+
+	if len(body) > 0 {
+		resp.Body = []byte(body)
+	}
+	resp.Headers = headers
+	resp.ClearHeaders = dedupeStrings(clearHeaders)
+	return resp, nil
+}
+
+func (p *jsHandlerPlugin) InterceptResponse(ctx context.Context, req pluginapi.ResponseInterceptRequest) (pluginapi.ResponseInterceptResponse, error) {
+	resp := pluginapi.ResponseInterceptResponse{}
+	scriptPaths := p.allScriptPaths()
+	if len(scriptPaths) == 0 {
+		return resp, nil
+	}
+
+	bodyStr := string(req.Body)
+	reqHeadersMap := headerToAnyMap(req.RequestHeaders)
+	respHeaders := cloneHeader(req.ResponseHeaders)
+	var clearHeaders []string
+
+	for _, scriptPath := range scriptPaths {
+		scriptPath = strings.TrimSpace(scriptPath)
+		if scriptPath == "" {
+			continue
+		}
+		processedBody, processedHeaders, bodyModified, errJS := p.applyJSAfterResponse(
+			scriptPath, req.Model, req.SourceFormat,
+			reqHeadersMap, req.RequestBody,
+			bodyStr, nil, respHeaders, false, nil,
+		)
+		if errJS != nil {
+			log.Warnf("failed to execute JS response interceptor [%s]: %v", scriptPath, errJS)
+			continue
+		}
+		if bodyModified {
+			bodyStr = processedBody
+		}
+		if processedHeaders != nil {
+			respHeaders = processedHeaders.headers
+			clearHeaders = append(clearHeaders, processedHeaders.clearHeaders...)
+		}
+	}
+
+	if len(bodyStr) > 0 {
+		resp.Body = []byte(bodyStr)
+	}
+	resp.Headers = respHeaders
+	resp.ClearHeaders = dedupeStrings(clearHeaders)
+	return resp, nil
+}
+
+func (p *jsHandlerPlugin) InterceptStreamChunk(ctx context.Context, req pluginapi.StreamChunkInterceptRequest) (pluginapi.StreamChunkInterceptResponse, error) {
+	resp := pluginapi.StreamChunkInterceptResponse{}
+	scriptPaths := p.allScriptPaths()
+	if len(scriptPaths) == 0 {
+		return resp, nil
+	}
+
+	reqHeadersMap := headerToAnyMap(req.RequestHeaders)
+	respHeaders := cloneHeader(req.ResponseHeaders)
+	var clearHeaders []string
+	historyStrings := make([]string, 0, len(req.HistoryChunks))
+	for _, hc := range req.HistoryChunks {
+		historyStrings = append(historyStrings, string(hc))
+	}
+
+	isHeaderInit := req.ChunkIndex == pluginapi.StreamChunkHeaderInitIndex
+	chunkStr := ""
+	if !isHeaderInit && len(req.Body) > 0 {
+		chunkStr = string(req.Body)
+	}
+
+	var chunkPtr *string
+	chunkModified := false
+	if !isHeaderInit {
+		chunkPtr = &chunkStr
+	}
+
+	for _, scriptPath := range scriptPaths {
+		scriptPath = strings.TrimSpace(scriptPath)
+		if scriptPath == "" {
+			continue
+		}
+		processedBody, processedHeaders, chunkChanged, errJS := p.applyJSAfterResponse(
+			scriptPath, req.Model, req.SourceFormat,
+			reqHeadersMap, req.RequestBody,
+			"", chunkPtr, respHeaders, !isHeaderInit, historyStrings,
+		)
+		if errJS != nil {
+			log.Warnf("failed to execute JS stream chunk interceptor [%s]: %v", scriptPath, errJS)
+			continue
+		}
+		if processedHeaders != nil {
+			respHeaders = processedHeaders.headers
+			clearHeaders = append(clearHeaders, processedHeaders.clearHeaders...)
+		}
+		if chunkPtr != nil && chunkChanged {
+			*chunkPtr = processedBody
+			chunkModified = true
+		}
+	}
+
+	resp.Headers = respHeaders
+	resp.ClearHeaders = dedupeStrings(clearHeaders)
+	if chunkPtr != nil && *chunkPtr != "" {
+		resp.Body = []byte(*chunkPtr)
+	} else if isHeaderInit {
+		// header-only init, no body to return
+	} else if chunkModified || len(req.Body) == 0 {
+		resp.DropChunk = true
+	}
+	return resp, nil
+}
+
+func (p *jsHandlerPlugin) applyJSBeforeRequest(scriptPath string, payloadBytes []byte, model, protocol string, headers http.Header) ([]byte, []string, error) {
+	program, err := getJSProgram(scriptPath)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	engine := newJSEngine()
+	if errRun := engine.runProgram(program, p.cfg.Timeout); errRun != nil {
+		return nil, nil, errRun
+	}
+
+	headersMap := headerToAnyMap(headers)
+
+	jsCtx := map[string]any{
+		"id":       generateRequestID(),
+		"body":     string(payloadBytes),
+		"headers":  headersMap,
+		"url":      "",
+		"model":    model,
+		"protocol": protocol,
+	}
+
+	jsVal, errCall := engine.callFunction("on_before_request", p.cfg.Timeout, jsCtx)
+	if errCall != nil {
+		if errors.Is(errCall, ErrFunctionNotFound) {
+			return payloadBytes, nil, nil
+		}
+		return nil, nil, fmt.Errorf("on_before_request failed for %s: %w", scriptPath, errCall)
+	}
+
+	if jsVal == nil || goja.IsUndefined(jsVal) || goja.IsNull(jsVal) {
+		return payloadBytes, nil, nil
+	}
+
+	exported := jsVal.Export()
+	if exported == nil {
+		return payloadBytes, nil, nil
+	}
+
+	var clearHeaders []string
+	if objMap, ok := exported.(map[string]any); ok {
+		if headersVal, exists := objMap["headers"]; exists {
+			clearHeaders = append(clearHeaders, updateHeaderFromAny(headers, headersVal)...)
+		}
+		if bodyVal, exists := objMap["body"]; exists {
+			if bodyStr, okStr := bodyVal.(string); okStr {
+				return []byte(bodyStr), clearHeaders, nil
+			}
+		}
+	}
+
+	if bodyStr, ok := exported.(string); ok {
+		return []byte(bodyStr), clearHeaders, nil
+	}
+
+	return payloadBytes, clearHeaders, nil
+}
+
+func (p *jsHandlerPlugin) applyJSAfterResponse(
+	scriptPath, model, protocol string,
+	reqHeadersMap map[string]any, reqBody []byte,
+	bodyStr string, chunkStr *string,
+	respHeaders http.Header, isStream bool, historyChunks []string,
+) (string, *processedHeaders, bool, error) {
+	program, err := getJSProgram(scriptPath)
+	if err != nil {
+		return bodyStr, nil, false, err
+	}
+
+	engine := newJSEngine()
+	if errRun := engine.runProgram(program, p.cfg.Timeout); errRun != nil {
+		return bodyStr, nil, false, errRun
+	}
+
+	var bodyVal any = bodyStr
+	if isStream {
+		bodyVal = nil
+	}
+
+	reqCtx := engine.vm.NewObject()
+	if errSet := reqCtx.Set("body", string(reqBody)); errSet != nil {
+		return bodyStr, nil, false, errSet
+	}
+	if errSet := reqCtx.Set("headers", reqHeadersMap); errSet != nil {
+		return bodyStr, nil, false, errSet
+	}
+	if errSet := reqCtx.Set("url", ""); errSet != nil {
+		return bodyStr, nil, false, errSet
+	}
+
+	jsCtx := engine.vm.NewObject()
+	if errSet := jsCtx.Set("id", generateRequestID()); errSet != nil {
+		return bodyStr, nil, false, errSet
+	}
+	if errSet := jsCtx.Set("body", bodyVal); errSet != nil {
+		return bodyStr, nil, false, errSet
+	}
+	if errSet := jsCtx.Set("req", reqCtx); errSet != nil {
+		return bodyStr, nil, false, errSet
+	}
+	if errSet := jsCtx.Set("protocol", protocol); errSet != nil {
+		return bodyStr, nil, false, errSet
+	}
+	if errSet := jsCtx.Set("headers", headerToAnyMap(respHeaders)); errSet != nil {
+		return bodyStr, nil, false, errSet
+	}
+	if isStream {
+		if chunkStr != nil {
+			if errSet := jsCtx.Set("chunk", *chunkStr); errSet != nil {
+				return bodyStr, nil, false, errSet
+			}
+		} else {
+			if errSet := jsCtx.Set("chunk", ""); errSet != nil {
+				return bodyStr, nil, false, errSet
+			}
+		}
+		historyChunksValue, errHistory := engine.frozenStringArray(historyChunks)
+		if errHistory != nil {
+			return bodyStr, nil, false, fmt.Errorf("failed to freeze history_chunks: %w", errHistory)
+		}
+		if errDefine := jsCtx.DefineDataProperty("history_chunks", historyChunksValue, goja.FLAG_FALSE, goja.FLAG_FALSE, goja.FLAG_TRUE); errDefine != nil {
+			return bodyStr, nil, false, fmt.Errorf("failed to define history_chunks: %w", errDefine)
+		}
+	} else {
+		if errSet := jsCtx.Set("chunk", nil); errSet != nil {
+			return bodyStr, nil, false, errSet
+		}
+		if errSet := jsCtx.Set("history_chunks", nil); errSet != nil {
+			return bodyStr, nil, false, errSet
+		}
+	}
+
+	hookName := "on_after_nonstream_response"
+	if isStream {
+		hookName = "on_after_stream_response"
+	}
+	jsVal, errCall := engine.callFunction(hookName, p.cfg.Timeout, jsCtx)
+	if errCall != nil {
+		if errors.Is(errCall, ErrFunctionNotFound) {
+			return bodyStr, nil, false, nil
+		}
+		return bodyStr, nil, false, fmt.Errorf("%s failed for %s: %w", hookName, scriptPath, errCall)
+	}
+
+	if jsVal == nil || goja.IsUndefined(jsVal) || goja.IsNull(jsVal) {
+		return bodyStr, nil, false, nil
+	}
+
+	exported := jsVal.Export()
+	if exported == nil {
+		return bodyStr, nil, false, nil
+	}
+
+	var headersResult *processedHeaders
+	if objMap, ok := exported.(map[string]any); ok {
+		if headersVal, exists := objMap["headers"]; exists {
+			cleared := updateHeaderFromAny(respHeaders, headersVal)
+			headersResult = &processedHeaders{headers: respHeaders, clearHeaders: cleared}
+		}
+		if !isStream {
+			if bodyVal, exists := objMap["body"]; exists {
+				if bStr, okStr := bodyVal.(string); okStr {
+					return bStr, headersResult, true, nil
+				}
+			}
+		} else {
+			if chunkVal, exists := objMap["chunk"]; exists {
+				if cStr, okStr := chunkVal.(string); okStr {
+					return cStr, headersResult, true, nil
+				}
+			}
+		}
+	}
+
+	if strVal, ok := exported.(string); ok {
+		return strVal, headersResult, true, nil
+	}
+
+	return bodyStr, headersResult, false, nil
+}
+
+func headerToAnyMap(h http.Header) map[string]any {
+	m := make(map[string]any)
+	if h == nil {
+		return m
+	}
+	for k, v := range h {
+		switch len(v) {
+		case 0:
+			continue
+		case 1:
+			m[k] = v[0]
+		default:
+			m[k] = append([]string(nil), v...)
+		}
+	}
+	return m
+}
+
+func updateHeaderFromAny(h http.Header, val interface{}) []string {
+	var clearHeaders []string
+	if h == nil || val == nil {
+		return clearHeaders
+	}
+	rv := reflect.ValueOf(val)
+	if rv.Kind() != reflect.Map {
+		return clearHeaders
+	}
+	for _, key := range rv.MapKeys() {
+		kStr := key.String()
+		vVal := rv.MapIndex(key).Interface()
+		if vVal == nil {
+			h.Del(kStr)
+			clearHeaders = append(clearHeaders, kStr)
+		} else if valStr, ok := vVal.(string); ok {
+			h.Set(kStr, valStr)
+		} else {
+			values, okValues := stringSliceFromAny(vVal)
+			if !okValues {
+				h.Set(kStr, fmt.Sprintf("%v", vVal))
+				continue
+			}
+			if len(values) == 0 {
+				h.Del(kStr)
+				clearHeaders = append(clearHeaders, kStr)
+			} else {
+				h[http.CanonicalHeaderKey(kStr)] = values
+			}
+		}
+	}
+	return clearHeaders
+}
+
+func cloneHeader(h http.Header) http.Header {
+	cloned := make(http.Header, len(h))
+	for key, values := range h {
+		cloned[key] = append([]string(nil), values...)
+	}
+	return cloned
+}
+
+func stringSliceFromAny(val any) ([]string, bool) {
+	switch typed := val.(type) {
+	case []string:
+		return append([]string(nil), typed...), true
+	case []any:
+		values := make([]string, 0, len(typed))
+		for _, item := range typed {
+			itemStr, okItem := item.(string)
+			if !okItem {
+				return nil, false
+			}
+			values = append(values, itemStr)
+		}
+		return values, true
+	}
+
+	rv := reflect.ValueOf(val)
+	if rv.Kind() != reflect.Slice && rv.Kind() != reflect.Array {
+		return nil, false
+	}
+	values := make([]string, 0, rv.Len())
+	for i := 0; i < rv.Len(); i++ {
+		item, okItem := rv.Index(i).Interface().(string)
+		if !okItem {
+			return nil, false
+		}
+		values = append(values, item)
+	}
+	return values, true
+}
+
+func dedupeStrings(values []string) []string {
+	if len(values) == 0 {
+		return nil
+	}
+	seen := make(map[string]struct{}, len(values))
+	deduped := make([]string, 0, len(values))
+	for _, value := range values {
+		canonical := http.CanonicalHeaderKey(value)
+		if _, exists := seen[canonical]; exists {
+			continue
+		}
+		seen[canonical] = struct{}{}
+		deduped = append(deduped, canonical)
+	}
+	return deduped
+}
+
+func generateRequestID() string {
+	return fmt.Sprintf("%s-%x", time.Now().Format("20060102150405"), time.Now().UnixNano()&0xffffffff)
+}
diff --git a/examples/plugin/jshandler/interceptor_test.go b/examples/plugin/jshandler/interceptor_test.go
new file mode 100644
index 00000000..8a310812
--- /dev/null
+++ b/examples/plugin/jshandler/interceptor_test.go
@@ -0,0 +1,100 @@
+package main
+
+import (
+	"net/http"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestApplyJSAfterResponseUsesFrozenNativeHistoryChunks(t *testing.T) {
+	scriptPath := filepath.Join(t.TempDir(), "stream.js")
+	script := `
+function on_after_stream_response(ctx) {
+    if (!Object.isFrozen(ctx.history_chunks)) {
+        throw new Error("history_chunks is not frozen");
+    }
+    var original = ctx.history_chunks[0];
+    try {
+        ctx.history_chunks[0] = "changed";
+    } catch (e) {
+    }
+    if (ctx.history_chunks[0] !== original) {
+        throw new Error("history_chunks item was changed");
+    }
+    try {
+        ctx.history_chunks = ["changed"];
+    } catch (e) {
+    }
+    if (ctx.history_chunks[0] !== original) {
+        throw new Error("history_chunks property was replaced");
+    }
+    return { chunk: ctx.chunk + "|ok" };
+}
+`
+	if errWrite := os.WriteFile(scriptPath, []byte(script), 0600); errWrite != nil {
+		t.Fatalf("os.WriteFile() error = %v", errWrite)
+	}
+
+	plugin := &jsHandlerPlugin{cfg: defaultJSHandlerConfig()}
+	chunk := `data: {"choices":[{"delta":{},"finish_reason":null}]}`
+	processedBody, _, changed, errApply := plugin.applyJSAfterResponse(
+		scriptPath,
+		"gpt-test",
+		"openai",
+		nil,
+		nil,
+		"",
+		&chunk,
+		http.Header{},
+		true,
+		[]string{`data: {"choices":[{"delta":{"tool_calls":[{"index":0}]}}]}`},
+	)
+	if errApply != nil {
+		t.Fatalf("applyJSAfterResponse() error = %v", errApply)
+	}
+	if !changed {
+		t.Fatal("applyJSAfterResponse() changed = false, want true")
+	}
+	if processedBody != chunk+"|ok" {
+		t.Fatalf("applyJSAfterResponse() body = %q, want %q", processedBody, chunk+"|ok")
+	}
+}
+
+func TestApplyJSAfterResponseDispatchesNonStreamHook(t *testing.T) {
+	scriptPath := filepath.Join(t.TempDir(), "nonstream.js")
+	script := `
+function on_after_stream_response(ctx) {
+    throw new Error("stream hook should not run");
+}
+function on_after_nonstream_response(ctx) {
+    return { body: ctx.body + "|nonstream" };
+}
+`
+	if errWrite := os.WriteFile(scriptPath, []byte(script), 0600); errWrite != nil {
+		t.Fatalf("os.WriteFile() error = %v", errWrite)
+	}
+
+	plugin := &jsHandlerPlugin{cfg: defaultJSHandlerConfig()}
+	processedBody, _, changed, errApply := plugin.applyJSAfterResponse(
+		scriptPath,
+		"gpt-test",
+		"openai",
+		nil,
+		nil,
+		`{"ok":true}`,
+		nil,
+		http.Header{},
+		false,
+		nil,
+	)
+	if errApply != nil {
+		t.Fatalf("applyJSAfterResponse() error = %v", errApply)
+	}
+	if !changed {
+		t.Fatal("applyJSAfterResponse() changed = false, want true")
+	}
+	if processedBody != `{"ok":true}|nonstream` {
+		t.Fatalf("applyJSAfterResponse() body = %q", processedBody)
+	}
+}
diff --git a/examples/plugin/jshandler/main.go b/examples/plugin/jshandler/main.go
new file mode 100644
index 00000000..06358a7a
--- /dev/null
+++ b/examples/plugin/jshandler/main.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+	"github.com/router-for-me/CLIProxyAPI/v7/sdk/pluginapi"
+)
+
+func buildPlugin(configYAML []byte, pluginDir string) (pluginapi.Plugin, error) {
+	cfg, errParse := parseJSHandlerConfig(configYAML)
+	if errParse != nil {
+		return pluginapi.Plugin{}, errParse
+	}
+	if pluginDir == "" {
+		pluginDir = inferPluginDir()
+	}
+	p := &jsHandlerPlugin{
+		cfg:        cfg,
+		configYAML: append([]byte(nil), configYAML...),
+		pluginDir:  pluginDir,
+	}
+	return pluginapi.Plugin{
+		Metadata: pluginapi.Metadata{
+			Name:             pluginName,
+			Version:          "0.1.0",
+			Author:           "router-for-me",
+			GitHubRepository: "https://github.com/router-for-me/CLIProxyAPI",
+			ConfigFields: []pluginapi.ConfigField{
+				{
+					Name:        "enabled",
+					Type:        pluginapi.ConfigFieldTypeBoolean,
+					Description: "Enable or disable the JS handler plugin.",
+				},
+				{
+					Name:        "script_paths",
+					Type:        pluginapi.ConfigFieldTypeArray,
+					Description: "List of JS script file paths to load (absolute or relative to plugin directory).",
+				},
+				{
+					Name:        "timeout",
+					Type:        pluginapi.ConfigFieldTypeString,
+					Description: "Execution timeout per JS hook call as a Go duration, such as 1s.",
+				},
+			},
+		},
+		Capabilities: pluginapi.Capabilities{
+			RequestInterceptor:     p,
+			ResponseInterceptor:    p,
+			StreamChunkInterceptor: p,
+		},
+	}, nil
+}
diff --git a/examples/plugin/jshandler/scripts/copilot_handler.js b/examples/plugin/jshandler/scripts/copilot_handler.js
new file mode 100644
index 00000000..6d50fff2
--- /dev/null
+++ b/examples/plugin/jshandler/scripts/copilot_handler.js
@@ -0,0 +1,116 @@
+function on_before_request(ctx) {
+    try {
+        var req = JSON.parse(ctx.body);
+        console.log("[" + ctx.id + "] message: " + ctx.body);
+        if (req.messages) {
+            for (var i = 0; i < req.messages.length; i++) {
+                if (typeof req.messages[i].content === "string") {
+                    req.messages[i].content = req.messages[i].content.replace("sensitive_word", "safe_word");
+                }
+            }
+        }
+        ctx.body = JSON.stringify(req);
+        console.log("[" + ctx.id + "] message: " + ctx.body);
+    } catch (e) {
+        console.log("[" + ctx.id + "] Failed to parse request JSON, skipping payload modification: " + e.message);
+    }
+    return ctx;
+}
+
+function parse_stream_chunk(chunk) {
+    var leading = "";
+    var payload = chunk.trim();
+    var trailing = "";
+
+    var dataIndex = chunk.indexOf("data:");
+    if (dataIndex >= 0) {
+        leading = chunk.substring(0, dataIndex) + "data:";
+        var afterData = chunk.substring(dataIndex + 5);
+        var newlineIndex = afterData.indexOf("\n");
+        if (newlineIndex >= 0) {
+            payload = afterData.substring(0, newlineIndex).trim();
+            trailing = afterData.substring(newlineIndex);
+        } else {
+            payload = afterData.trim();
+        }
+    }
+
+    if (payload === "" || payload === "[DONE]") {
+        return null;
+    }
+
+    return {
+        obj: JSON.parse(payload),
+        leading: leading,
+        trailing: trailing
+    };
+}
+
+function stringify_stream_chunk(parsed) {
+    if (parsed.leading !== "") {
+        return parsed.leading + " " + JSON.stringify(parsed.obj) + parsed.trailing;
+    }
+    return JSON.stringify(parsed.obj);
+}
+
+function on_after_stream_response(ctx) {
+    console.log("[" + ctx.id + "] Received response with status: " + ctx.status);
+    if (ctx.chunk === undefined || ctx.chunk === null || ctx.chunk === "") {
+        return ctx;
+    }
+
+    try {
+        var parsed = parse_stream_chunk(ctx.chunk);
+        if (parsed === null) {
+            return ctx;
+        }
+        var obj = parsed.obj;
+        if (obj.choices && obj.choices.length > 0) {
+            var choice = obj.choices[0];
+            var has_tool_calls = choice.delta && choice.delta.tool_calls && choice.delta.tool_calls.length > 0;
+
+            if (has_tool_calls) {
+                if (choice.finish_reason !== null) {
+                    console.log("[" + ctx.id + "] Tool call chunk has finish_reason = [" + choice.finish_reason + "], forcing reset to null, tool index: " + choice.delta.tool_calls[0].index);
+                    choice.finish_reason = null;
+                    ctx.chunk = stringify_stream_chunk(parsed);
+                }
+            } else {
+                var history_had_tool_calls = false;
+                if (ctx.history_chunks && ctx.history_chunks.length > 0) {
+                    for (var i = 0; i < ctx.history_chunks.length; i++) {
+                        try {
+                            var h_parsed = parse_stream_chunk(ctx.history_chunks[i]);
+                            if (h_parsed === null) {
+                                continue;
+                            }
+                            var hist_obj = h_parsed.obj;
+                            if (hist_obj.choices && hist_obj.choices.length > 0) {
+                                var h_choice = hist_obj.choices[0];
+                                if (h_choice.delta && h_choice.delta.tool_calls && h_choice.delta.tool_calls.length > 0) {
+                                    history_had_tool_calls = true;
+                                    break;
+                                }
+                            }
+                        } catch (err) {
+                        }
+                    }
+                }
+
+                if (history_had_tool_calls && choice.finish_reason !== null && choice.finish_reason !== "tool_calls") {
+                    console.log("[" + ctx.id + "] Detected history contains tool calls, modifying finish_reason from [" + choice.finish_reason + "] to [tool_calls]");
+                    choice.finish_reason = "tool_calls";
+                    ctx.chunk = stringify_stream_chunk(parsed);
+                }
+            }
+        }
+    } catch (e) {
+        console.log("[" + ctx.id + "] Failed to parse streaming response JSON chunk: " + e.message + " | chunk content: " + ctx.chunk);
+    }
+    return ctx;
+}
+
+function on_after_nonstream_response(ctx) {
+    console.log("[" + ctx.id + "] Received non-streaming response. Response content: " + ctx.body);
+    return ctx;
+}