diff --git a/examples/server/beego/api/gen.go b/examples/server/beego/api/gen.go
index 139d25a0..a3163075 100644
--- a/examples/server/beego/api/gen.go
+++ b/examples/server/beego/api/gen.go
@@ -104,8 +104,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -114,7 +115,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -223,7 +224,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -357,8 +358,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []beego.MiddleWare
-	errHandler  OapiErrorHandler
+	middlewares     []beego.MiddleWare
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -376,6 +378,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // beegoHandler wraps an http.HandlerFunc for Beego with path param injection.
 func beegoHandler(h http.HandlerFunc, pathParams ...string) beego.HandleFunc {
 	return func(ctx *beecontext.Context) {
@@ -396,6 +406,9 @@ func RegisterRoutes(router *beego.ControllerRegister, svc ServiceInterface, opts
 	}
 
 	httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	router.Get("/health", beegoHandler(httpAdapter.HealthCheck))
 	router.Get("/users", beegoHandler(httpAdapter.ListUsers))
 	router.Post("/users", beegoHandler(httpAdapter.CreateUser))
diff --git a/examples/server/chi/api/gen.go b/examples/server/chi/api/gen.go
index 269632e1..8edcbe62 100644
--- a/examples/server/chi/api/gen.go
+++ b/examples/server/chi/api/gen.go
@@ -103,8 +103,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -113,7 +114,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -222,7 +223,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -356,8 +357,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -375,6 +377,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
@@ -388,6 +398,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.Method("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	r.Method("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	r.Method("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/config-variations/custom-service-name/types.gen.go b/examples/server/config-variations/custom-service-name/types.gen.go
index a81ce768..59930592 100644
--- a/examples/server/config-variations/custom-service-name/types.gen.go
+++ b/examples/server/config-variations/custom-service-name/types.gen.go
@@ -102,8 +102,9 @@ type CustomServiceNameInterface interface {
 // HTTPAdapter adapts the CustomServiceNameInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        CustomServiceNameInterface
-	errHandler OapiErrorHandler
+	svc             CustomServiceNameInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -112,7 +113,7 @@ func NewHTTPAdapter(svc CustomServiceNameInterface, errHandler OapiErrorHandler)
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -221,7 +222,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -355,8 +356,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -374,6 +376,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc CustomServiceNameInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
@@ -387,6 +397,9 @@ func NewRouter(svc CustomServiceNameInterface, opts ...RouterOption) chi.Router
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.Method("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	r.Method("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	r.Method("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/config-variations/diff-package-multiple-files/models/adapter.go b/examples/server/config-variations/diff-package-multiple-files/models/adapter.go
index dfc42a00..f69f1f5c 100644
--- a/examples/server/config-variations/diff-package-multiple-files/models/adapter.go
+++ b/examples/server/config-variations/diff-package-multiple-files/models/adapter.go
@@ -27,8 +27,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -37,7 +38,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -146,7 +147,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
diff --git a/examples/server/config-variations/diff-package-multiple-files/models/router.go b/examples/server/config-variations/diff-package-multiple-files/models/router.go
index 419da38f..77a86ce3 100644
--- a/examples/server/config-variations/diff-package-multiple-files/models/router.go
+++ b/examples/server/config-variations/diff-package-multiple-files/models/router.go
@@ -4,6 +4,7 @@ package models
 import (
 	"net/http"
 
+	"github.com/doordash-oss/oapi-codegen-dd/v3/pkg/runtime"
 	"github.com/go-chi/chi/v5"
 )
 
@@ -11,8 +12,9 @@ import (
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -30,6 +32,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
@@ -43,6 +53,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.Method("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	r.Method("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	r.Method("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/config-variations/diff-package-single-file/models/adapter.gen.go b/examples/server/config-variations/diff-package-single-file/models/adapter.gen.go
index 34df209b..8ec88f75 100644
--- a/examples/server/config-variations/diff-package-single-file/models/adapter.gen.go
+++ b/examples/server/config-variations/diff-package-single-file/models/adapter.gen.go
@@ -101,8 +101,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -111,7 +112,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -220,7 +221,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -354,8 +355,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -373,6 +375,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
@@ -386,6 +396,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.Method("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	r.Method("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	r.Method("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/config-variations/no-service/types.gen.go b/examples/server/config-variations/no-service/types.gen.go
index 96049467..374e9358 100644
--- a/examples/server/config-variations/no-service/types.gen.go
+++ b/examples/server/config-variations/no-service/types.gen.go
@@ -102,8 +102,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -112,7 +113,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -221,7 +222,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -355,8 +356,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -374,6 +376,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
@@ -387,6 +397,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.Method("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	r.Method("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	r.Method("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/config-variations/same-package-multiple-files/api/adapter.go b/examples/server/config-variations/same-package-multiple-files/api/adapter.go
index 9f8499fb..8dca4eea 100644
--- a/examples/server/config-variations/same-package-multiple-files/api/adapter.go
+++ b/examples/server/config-variations/same-package-multiple-files/api/adapter.go
@@ -27,8 +27,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -37,7 +38,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -146,7 +147,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewError(err.Error()))
 		return
 	}
diff --git a/examples/server/config-variations/same-package-multiple-files/api/router.go b/examples/server/config-variations/same-package-multiple-files/api/router.go
index 45f690dc..fc2bb5c7 100644
--- a/examples/server/config-variations/same-package-multiple-files/api/router.go
+++ b/examples/server/config-variations/same-package-multiple-files/api/router.go
@@ -4,6 +4,7 @@ package api
 import (
 	"net/http"
 
+	"github.com/doordash-oss/oapi-codegen-dd/v3/pkg/runtime"
 	"github.com/go-chi/chi/v5"
 )
 
@@ -11,8 +12,9 @@ import (
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -30,6 +32,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
@@ -43,6 +53,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.Method("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	r.Method("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	r.Method("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/config-variations/same-package-single-file/types.gen.go b/examples/server/config-variations/same-package-single-file/types.gen.go
index 96049467..374e9358 100644
--- a/examples/server/config-variations/same-package-single-file/types.gen.go
+++ b/examples/server/config-variations/same-package-single-file/types.gen.go
@@ -102,8 +102,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -112,7 +113,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -221,7 +222,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -355,8 +356,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -374,6 +376,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
@@ -387,6 +397,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.Method("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	r.Method("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	r.Method("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/config-variations/zero-endpoints/api/adapter.go b/examples/server/config-variations/zero-endpoints/api/adapter.go
index 78764b09..5d213ae5 100644
--- a/examples/server/config-variations/zero-endpoints/api/adapter.go
+++ b/examples/server/config-variations/zero-endpoints/api/adapter.go
@@ -1,6 +1,10 @@
 // Code generated by oapi-codegen. DO NOT EDIT.
 package api
 
+import (
+	"github.com/doordash-oss/oapi-codegen-dd/v3/pkg/runtime"
+)
+
 // ServiceInterface defines the service interface for business logic.
 type ServiceInterface interface {
 }
@@ -8,8 +12,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -18,5 +23,5 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
diff --git a/examples/server/config-variations/zero-endpoints/api/router.go b/examples/server/config-variations/zero-endpoints/api/router.go
index 523bfb3f..754e2f96 100644
--- a/examples/server/config-variations/zero-endpoints/api/router.go
+++ b/examples/server/config-variations/zero-endpoints/api/router.go
@@ -4,6 +4,7 @@ package api
 import (
 	"net/http"
 
+	"github.com/doordash-oss/oapi-codegen-dd/v3/pkg/runtime"
 	"github.com/go-chi/chi/v5"
 )
 
@@ -11,8 +12,9 @@ import (
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -30,6 +32,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
diff --git a/examples/server/echo/api/gen.go b/examples/server/echo/api/gen.go
index 177c94bc..674aa63e 100644
--- a/examples/server/echo/api/gen.go
+++ b/examples/server/echo/api/gen.go
@@ -102,8 +102,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -112,7 +113,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -221,7 +222,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -355,8 +356,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []echo.MiddlewareFunc
-	errHandler  OapiErrorHandler
+	middlewares     []echo.MiddlewareFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -374,6 +376,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given Echo instance with the service implementation.
 func NewRouter(e *echo.Echo, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -387,6 +397,9 @@ func NewRouter(e *echo.Echo, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	e.GET("/health", func(c echo.Context) error {
 		adapter.HealthCheck(c.Response(), c.Request())
 		return nil
diff --git a/examples/server/fasthttp/api/gen.go b/examples/server/fasthttp/api/gen.go
index 75bca3c8..ba068f55 100644
--- a/examples/server/fasthttp/api/gen.go
+++ b/examples/server/fasthttp/api/gen.go
@@ -105,8 +105,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -115,7 +116,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -224,7 +225,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -358,8 +359,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(fasthttp.RequestHandler) fasthttp.RequestHandler
-	errHandler  OapiErrorHandler
+	middlewares     []func(fasthttp.RequestHandler) fasthttp.RequestHandler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -377,6 +379,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // fasthttpHandler wraps an http.HandlerFunc with path param injection for fasthttp.
 func fasthttpHandler(h http.HandlerFunc, pathParams ...string) fasthttp.RequestHandler {
 	return func(ctx *fasthttp.RequestCtx) {
@@ -403,6 +413,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) *router.Router {
 	r := router.New()
 
 	httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.GET("/health", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.HealthCheck))
 	r.GET("/users", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.ListUsers))
 	r.POST("/users", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.CreateUser))
@@ -435,6 +448,9 @@ func Handler(svc ServiceInterface, opts ...RouterOption) fasthttp.RequestHandler
 	r := router.New()
 
 	httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.GET("/health", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.HealthCheck))
 	r.GET("/users", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.ListUsers))
 	r.POST("/users", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.CreateUser))
diff --git a/examples/server/fiber/api/gen.go b/examples/server/fiber/api/gen.go
index 822d37fc..af815130 100644
--- a/examples/server/fiber/api/gen.go
+++ b/examples/server/fiber/api/gen.go
@@ -103,8 +103,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -113,7 +114,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -222,7 +223,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -356,8 +357,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []fiber.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []fiber.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -375,6 +377,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // fiberHTTPHandler wraps an http.HandlerFunc with path param injection for Fiber.
 func fiberHTTPHandler(h http.HandlerFunc, pathParams ...string) fiber.Handler {
 	return func(c fiber.Ctx) error {
@@ -401,6 +411,9 @@ func NewRouter(app *fiber.App, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	app.Get("/health", adaptor.HTTPHandlerFunc(httpAdapter.HealthCheck))
 	app.Get("/users", adaptor.HTTPHandlerFunc(httpAdapter.ListUsers))
 	app.Post("/users", adaptor.HTTPHandlerFunc(httpAdapter.CreateUser))
diff --git a/examples/server/gin/api/gen.go b/examples/server/gin/api/gen.go
index 06bc0f26..874e802e 100644
--- a/examples/server/gin/api/gen.go
+++ b/examples/server/gin/api/gen.go
@@ -102,8 +102,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -112,7 +113,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -221,7 +222,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -355,8 +356,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []gin.HandlerFunc
-	errHandler  OapiErrorHandler
+	middlewares     []gin.HandlerFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -374,6 +376,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given Gin engine with the service implementation.
 func NewRouter(r *gin.Engine, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -387,6 +397,9 @@ func NewRouter(r *gin.Engine, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.GET("/health", func(c *gin.Context) {
 		adapter.HealthCheck(c.Writer, c.Request)
 	})
diff --git a/examples/server/go-zero/api/gen.go b/examples/server/go-zero/api/gen.go
index ce36e66d..3b91cffa 100644
--- a/examples/server/go-zero/api/gen.go
+++ b/examples/server/go-zero/api/gen.go
@@ -105,8 +105,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -115,7 +116,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -224,7 +225,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -358,8 +359,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []rest.Middleware
-	errHandler  OapiErrorHandler
+	middlewares     []rest.Middleware
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -377,6 +379,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // RegisterRoutes registers all routes with the given go-zero server.
 func RegisterRoutes(server *rest.Server, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -385,6 +395,9 @@ func RegisterRoutes(server *rest.Server, svc ServiceInterface, opts ...RouterOpt
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 
 	routes := []rest.Route{
 		{
@@ -433,6 +446,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	r := router.NewRouter()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	_ = r.Handle("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	_ = r.Handle("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	_ = r.Handle("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/goframe/api/gen.go b/examples/server/goframe/api/gen.go
index 269c3cdf..bd352d9b 100644
--- a/examples/server/goframe/api/gen.go
+++ b/examples/server/goframe/api/gen.go
@@ -103,8 +103,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -113,7 +114,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -222,7 +223,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -356,8 +357,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []ghttp.HandlerFunc
-	errHandler  OapiErrorHandler
+	middlewares     []ghttp.HandlerFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -375,6 +377,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given GoFrame server with the service implementation.
 func NewRouter(s *ghttp.Server, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -388,6 +398,9 @@ func NewRouter(s *ghttp.Server, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	s.BindHandler("GET:/health", func(r *ghttp.Request) {
 		adapter.HealthCheck(r.Response.Writer, r.Request)
 	})
@@ -420,6 +433,9 @@ func Handler(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	mux := http.NewServeMux()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	mux.HandleFunc("GET /health", adapter.HealthCheck)
 	mux.HandleFunc("GET /users", adapter.ListUsers)
 	mux.HandleFunc("POST /users", adapter.CreateUser)
diff --git a/examples/server/gorilla-mux/api/gen.go b/examples/server/gorilla-mux/api/gen.go
index 052ba0e6..c73a6aa7 100644
--- a/examples/server/gorilla-mux/api/gen.go
+++ b/examples/server/gorilla-mux/api/gen.go
@@ -103,8 +103,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -113,7 +114,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -222,7 +223,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -356,8 +357,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []mux.MiddlewareFunc
-	errHandler  OapiErrorHandler
+	middlewares     []mux.MiddlewareFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -375,6 +377,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new mux.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) *mux.Router {
 	cfg := &routerConfig{}
@@ -388,6 +398,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) *mux.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.HandleFunc("/health", adapter.HealthCheck).Methods("GET")
 	r.HandleFunc("/users", adapter.ListUsers).Methods("GET")
 	r.HandleFunc("/users", adapter.CreateUser).Methods("POST")
diff --git a/examples/server/hertz/api/gen.go b/examples/server/hertz/api/gen.go
index ffcfec33..1493f15b 100644
--- a/examples/server/hertz/api/gen.go
+++ b/examples/server/hertz/api/gen.go
@@ -106,8 +106,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -116,7 +117,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -225,7 +226,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -359,8 +360,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []app.HandlerFunc
-	errHandler  OapiErrorHandler
+	middlewares     []app.HandlerFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -378,6 +380,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given Hertz server with the service implementation.
 func NewRouter(h *server.Hertz, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -391,6 +401,9 @@ func NewRouter(h *server.Hertz, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	h.Handle("GET", "/health", func(ctx context.Context, c *app.RequestContext) {
 		req, err := adaptor.GetCompatRequest(&c.Request)
 		if err != nil {
@@ -453,6 +466,9 @@ func Handler(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	mux := http.NewServeMux()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	mux.HandleFunc("GET /health", adapter.HealthCheck)
 	mux.HandleFunc("GET /users", adapter.ListUsers)
 	mux.HandleFunc("POST /users", adapter.CreateUser)
diff --git a/examples/server/iris/api/gen.go b/examples/server/iris/api/gen.go
index 1a42ba8c..a172eb6e 100644
--- a/examples/server/iris/api/gen.go
+++ b/examples/server/iris/api/gen.go
@@ -102,8 +102,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -112,7 +113,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -221,7 +222,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -355,8 +356,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []iris.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []iris.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -374,6 +376,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given Iris application with the service implementation.
 func NewRouter(app *iris.Application, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -387,6 +397,9 @@ func NewRouter(app *iris.Application, svc ServiceInterface, opts ...RouterOption
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	app.Handle("GET", "/health", func(ctx iris.Context) {
 		adapter.HealthCheck(ctx.ResponseWriter(), ctx.Request())
 	})
@@ -419,6 +432,9 @@ func Handler(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	mux := http.NewServeMux()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	mux.HandleFunc("GET /health", adapter.HealthCheck)
 	mux.HandleFunc("GET /users", adapter.ListUsers)
 	mux.HandleFunc("POST /users", adapter.CreateUser)
diff --git a/examples/server/kratos/api/gen.go b/examples/server/kratos/api/gen.go
index 63a5b7bd..d6cdb308 100644
--- a/examples/server/kratos/api/gen.go
+++ b/examples/server/kratos/api/gen.go
@@ -104,8 +104,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -114,7 +115,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -223,7 +224,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -357,8 +358,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -376,6 +378,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // RegisterRoutes registers all routes with the given Kratos HTTP server.
 // It creates a gorilla/mux router and mounts it using HandlePrefix.
 func RegisterRoutes(server *kratoshttp.Server, svc ServiceInterface, opts ...RouterOption) {
@@ -394,6 +404,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	r := mux.NewRouter()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.HandleFunc("/health", adapter.HealthCheck).Methods("GET")
 	r.HandleFunc("/users", adapter.ListUsers).Methods("GET")
 	r.HandleFunc("/users", adapter.CreateUser).Methods("POST")
diff --git a/examples/server/std-http/api/gen.go b/examples/server/std-http/api/gen.go
index 7778eb34..d0330c53 100644
--- a/examples/server/std-http/api/gen.go
+++ b/examples/server/std-http/api/gen.go
@@ -102,8 +102,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -112,7 +113,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -221,7 +222,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, 400, NewCreateUserErrorResponse(err.Error()))
 		return
 	}
@@ -355,8 +356,9 @@ func (a *HTTPAdapter) DeleteUser(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -374,6 +376,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new http.ServeMux with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) *http.ServeMux {
 	cfg := &routerConfig{}
@@ -384,6 +394,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) *http.ServeMux {
 	mux := http.NewServeMux()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	mux.HandleFunc("GET /health", applyMiddleware(http.HandlerFunc(adapter.HealthCheck), cfg.middlewares...))
 	mux.HandleFunc("GET /users", applyMiddleware(http.HandlerFunc(adapter.ListUsers), cfg.middlewares...))
 	mux.HandleFunc("POST /users", applyMiddleware(http.HandlerFunc(adapter.CreateUser), cfg.middlewares...))
diff --git a/examples/server/test/beego/testcase/adapter.gen.go b/examples/server/test/beego/testcase/adapter.gen.go
index 1e7fac14..3e60563e 100644
--- a/examples/server/test/beego/testcase/adapter.gen.go
+++ b/examples/server/test/beego/testcase/adapter.gen.go
@@ -141,8 +141,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -151,7 +152,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -269,7 +270,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1340,7 +1341,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1393,7 +1394,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1441,8 +1442,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []beego.MiddleWare
-	errHandler  OapiErrorHandler
+	middlewares     []beego.MiddleWare
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1460,6 +1462,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // beegoHandler wraps an http.HandlerFunc for Beego with path param injection.
 func beegoHandler(h http.HandlerFunc, pathParams ...string) beego.HandleFunc {
 	return func(ctx *beecontext.Context) {
@@ -1480,6 +1490,9 @@ func RegisterRoutes(router *beego.ControllerRegister, svc ServiceInterface, opts
 	}
 
 	httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	router.Get("/health", beegoHandler(httpAdapter.HealthCheck))
 	router.Get("/users", beegoHandler(httpAdapter.ListUsers))
 	router.Post("/users", beegoHandler(httpAdapter.CreateUser))
diff --git a/examples/server/test/chi/testcase/adapter.gen.go b/examples/server/test/chi/testcase/adapter.gen.go
index e50ad7d9..75302b1a 100644
--- a/examples/server/test/chi/testcase/adapter.gen.go
+++ b/examples/server/test/chi/testcase/adapter.gen.go
@@ -140,8 +140,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -150,7 +151,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -268,7 +269,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1339,7 +1340,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1392,7 +1393,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1440,8 +1441,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1459,6 +1461,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new chi.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	cfg := &routerConfig{}
@@ -1472,6 +1482,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) chi.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.Method("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	r.Method("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	r.Method("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/test/echo/testcase/adapter.gen.go b/examples/server/test/echo/testcase/adapter.gen.go
index 04c18efc..e2873420 100644
--- a/examples/server/test/echo/testcase/adapter.gen.go
+++ b/examples/server/test/echo/testcase/adapter.gen.go
@@ -140,8 +140,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -150,7 +151,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -268,7 +269,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1339,7 +1340,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1392,7 +1393,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1440,8 +1441,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []echo.MiddlewareFunc
-	errHandler  OapiErrorHandler
+	middlewares     []echo.MiddlewareFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1459,6 +1461,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given Echo instance with the service implementation.
 func NewRouter(e *echo.Echo, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -1472,6 +1482,9 @@ func NewRouter(e *echo.Echo, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	e.GET("/health", func(c echo.Context) error {
 		adapter.HealthCheck(c.Response(), c.Request())
 		return nil
diff --git a/examples/server/test/fasthttp/testcase/adapter.gen.go b/examples/server/test/fasthttp/testcase/adapter.gen.go
index 4fd4b815..90b97057 100644
--- a/examples/server/test/fasthttp/testcase/adapter.gen.go
+++ b/examples/server/test/fasthttp/testcase/adapter.gen.go
@@ -142,8 +142,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -152,7 +153,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -270,7 +271,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1341,7 +1342,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1394,7 +1395,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1442,8 +1443,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(fasthttp.RequestHandler) fasthttp.RequestHandler
-	errHandler  OapiErrorHandler
+	middlewares     []func(fasthttp.RequestHandler) fasthttp.RequestHandler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1461,6 +1463,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // fasthttpHandler wraps an http.HandlerFunc with path param injection for fasthttp.
 func fasthttpHandler(h http.HandlerFunc, pathParams ...string) fasthttp.RequestHandler {
 	return func(ctx *fasthttp.RequestCtx) {
@@ -1487,6 +1497,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) *router.Router {
 	r := router.New()
 
 	httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.GET("/health", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.HealthCheck))
 	r.GET("/users", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.ListUsers))
 	r.POST("/users", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.CreateUser))
@@ -1537,6 +1550,9 @@ func Handler(svc ServiceInterface, opts ...RouterOption) fasthttp.RequestHandler
 	r := router.New()
 
 	httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.GET("/health", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.HealthCheck))
 	r.GET("/users", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.ListUsers))
 	r.POST("/users", fasthttpadaptor.NewFastHTTPHandlerFunc(httpAdapter.CreateUser))
diff --git a/examples/server/test/fiber/testcase/adapter.gen.go b/examples/server/test/fiber/testcase/adapter.gen.go
index 38884f36..bdff3a9e 100644
--- a/examples/server/test/fiber/testcase/adapter.gen.go
+++ b/examples/server/test/fiber/testcase/adapter.gen.go
@@ -141,8 +141,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -151,7 +152,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -269,7 +270,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1340,7 +1341,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1393,7 +1394,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1441,8 +1442,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []fiber.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []fiber.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1460,6 +1462,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // fiberHTTPHandler wraps an http.HandlerFunc with path param injection for Fiber.
 func fiberHTTPHandler(h http.HandlerFunc, pathParams ...string) fiber.Handler {
 	return func(c fiber.Ctx) error {
@@ -1486,6 +1496,9 @@ func NewRouter(app *fiber.App, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	app.Get("/health", adaptor.HTTPHandlerFunc(httpAdapter.HealthCheck))
 	app.Get("/users", adaptor.HTTPHandlerFunc(httpAdapter.ListUsers))
 	app.Post("/users", adaptor.HTTPHandlerFunc(httpAdapter.CreateUser))
diff --git a/examples/server/test/gin/testcase/adapter.gen.go b/examples/server/test/gin/testcase/adapter.gen.go
index 72eebad9..e1c2d18d 100644
--- a/examples/server/test/gin/testcase/adapter.gen.go
+++ b/examples/server/test/gin/testcase/adapter.gen.go
@@ -140,8 +140,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -150,7 +151,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -268,7 +269,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1339,7 +1340,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1392,7 +1393,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1440,8 +1441,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []gin.HandlerFunc
-	errHandler  OapiErrorHandler
+	middlewares     []gin.HandlerFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1459,6 +1461,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given Gin engine with the service implementation.
 func NewRouter(r *gin.Engine, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -1472,6 +1482,9 @@ func NewRouter(r *gin.Engine, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.GET("/health", func(c *gin.Context) {
 		adapter.HealthCheck(c.Writer, c.Request)
 	})
diff --git a/examples/server/test/go-zero/testcase/adapter.gen.go b/examples/server/test/go-zero/testcase/adapter.gen.go
index ea8a8044..4e14c5ea 100644
--- a/examples/server/test/go-zero/testcase/adapter.gen.go
+++ b/examples/server/test/go-zero/testcase/adapter.gen.go
@@ -142,8 +142,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -152,7 +153,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -270,7 +271,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1341,7 +1342,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1394,7 +1395,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1442,8 +1443,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []rest.Middleware
-	errHandler  OapiErrorHandler
+	middlewares     []rest.Middleware
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1461,6 +1463,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // RegisterRoutes registers all routes with the given go-zero server.
 func RegisterRoutes(server *rest.Server, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -1469,6 +1479,9 @@ func RegisterRoutes(server *rest.Server, svc ServiceInterface, opts ...RouterOpt
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 
 	routes := []rest.Route{
 		{
@@ -1607,6 +1620,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	r := router.NewRouter()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	_ = r.Handle("GET", "/health", http.HandlerFunc(adapter.HealthCheck))
 	_ = r.Handle("GET", "/users", http.HandlerFunc(adapter.ListUsers))
 	_ = r.Handle("POST", "/users", http.HandlerFunc(adapter.CreateUser))
diff --git a/examples/server/test/goframe/testcase/adapter.gen.go b/examples/server/test/goframe/testcase/adapter.gen.go
index 215dc78b..3a586d09 100644
--- a/examples/server/test/goframe/testcase/adapter.gen.go
+++ b/examples/server/test/goframe/testcase/adapter.gen.go
@@ -140,8 +140,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -150,7 +151,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -268,7 +269,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1339,7 +1340,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1392,7 +1393,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1440,8 +1441,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []ghttp.HandlerFunc
-	errHandler  OapiErrorHandler
+	middlewares     []ghttp.HandlerFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1459,6 +1461,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given GoFrame server with the service implementation.
 func NewRouter(s *ghttp.Server, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -1472,6 +1482,9 @@ func NewRouter(s *ghttp.Server, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	s.BindHandler("GET:/health", func(r *ghttp.Request) {
 		adapter.HealthCheck(r.Response.Writer, r.Request)
 	})
@@ -1572,6 +1585,9 @@ func Handler(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	mux := http.NewServeMux()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	mux.HandleFunc("GET /health", adapter.HealthCheck)
 	mux.HandleFunc("GET /users", adapter.ListUsers)
 	mux.HandleFunc("POST /users", adapter.CreateUser)
diff --git a/examples/server/test/gorilla-mux/testcase/adapter.gen.go b/examples/server/test/gorilla-mux/testcase/adapter.gen.go
index 09dcbd8a..94dcd9d6 100644
--- a/examples/server/test/gorilla-mux/testcase/adapter.gen.go
+++ b/examples/server/test/gorilla-mux/testcase/adapter.gen.go
@@ -140,8 +140,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -150,7 +151,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -268,7 +269,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1339,7 +1340,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1392,7 +1393,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1440,8 +1441,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []mux.MiddlewareFunc
-	errHandler  OapiErrorHandler
+	middlewares     []mux.MiddlewareFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1459,6 +1461,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new mux.Router with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) *mux.Router {
 	cfg := &routerConfig{}
@@ -1472,6 +1482,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) *mux.Router {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.HandleFunc("/health", adapter.HealthCheck).Methods("GET")
 	r.HandleFunc("/users", adapter.ListUsers).Methods("GET")
 	r.HandleFunc("/users", adapter.CreateUser).Methods("POST")
diff --git a/examples/server/test/hertz/testcase/adapter.gen.go b/examples/server/test/hertz/testcase/adapter.gen.go
index dce514ed..9180d524 100644
--- a/examples/server/test/hertz/testcase/adapter.gen.go
+++ b/examples/server/test/hertz/testcase/adapter.gen.go
@@ -143,8 +143,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -153,7 +154,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -271,7 +272,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1342,7 +1343,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1395,7 +1396,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1443,8 +1444,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []app.HandlerFunc
-	errHandler  OapiErrorHandler
+	middlewares     []app.HandlerFunc
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1462,6 +1464,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given Hertz server with the service implementation.
 func NewRouter(h *server.Hertz, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -1475,6 +1485,9 @@ func NewRouter(h *server.Hertz, svc ServiceInterface, opts ...RouterOption) {
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	h.Handle("GET", "/health", func(ctx context.Context, c *app.RequestContext) {
 		req, err := adaptor.GetCompatRequest(&c.Request)
 		if err != nil {
@@ -1713,6 +1726,9 @@ func Handler(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	mux := http.NewServeMux()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	mux.HandleFunc("GET /health", adapter.HealthCheck)
 	mux.HandleFunc("GET /users", adapter.ListUsers)
 	mux.HandleFunc("POST /users", adapter.CreateUser)
diff --git a/examples/server/test/iris/testcase/adapter.gen.go b/examples/server/test/iris/testcase/adapter.gen.go
index ac6a61ff..1b987d70 100644
--- a/examples/server/test/iris/testcase/adapter.gen.go
+++ b/examples/server/test/iris/testcase/adapter.gen.go
@@ -140,8 +140,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -150,7 +151,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -268,7 +269,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1339,7 +1340,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1392,7 +1393,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1440,8 +1441,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []iris.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []iris.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1459,6 +1461,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter registers routes on the given Iris application with the service implementation.
 func NewRouter(app *iris.Application, svc ServiceInterface, opts ...RouterOption) {
 	cfg := &routerConfig{}
@@ -1472,6 +1482,9 @@ func NewRouter(app *iris.Application, svc ServiceInterface, opts ...RouterOption
 	}
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	app.Handle("GET", "/health", func(ctx iris.Context) {
 		adapter.HealthCheck(ctx.ResponseWriter(), ctx.Request())
 	})
@@ -1572,6 +1585,9 @@ func Handler(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	mux := http.NewServeMux()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	mux.HandleFunc("GET /health", adapter.HealthCheck)
 	mux.HandleFunc("GET /users", adapter.ListUsers)
 	mux.HandleFunc("POST /users", adapter.CreateUser)
diff --git a/examples/server/test/kratos/testcase/adapter.gen.go b/examples/server/test/kratos/testcase/adapter.gen.go
index 177843f4..79a48ec9 100644
--- a/examples/server/test/kratos/testcase/adapter.gen.go
+++ b/examples/server/test/kratos/testcase/adapter.gen.go
@@ -141,8 +141,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -151,7 +152,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -269,7 +270,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1340,7 +1341,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1393,7 +1394,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1441,8 +1442,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1460,6 +1462,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // RegisterRoutes registers all routes with the given Kratos HTTP server.
 // It creates a gorilla/mux router and mounts it using HandlePrefix.
 func RegisterRoutes(server *kratoshttp.Server, svc ServiceInterface, opts ...RouterOption) {
@@ -1478,6 +1488,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) http.Handler {
 	r := mux.NewRouter()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	r.HandleFunc("/health", adapter.HealthCheck).Methods("GET")
 	r.HandleFunc("/users", adapter.ListUsers).Methods("GET")
 	r.HandleFunc("/users", adapter.CreateUser).Methods("POST")
diff --git a/examples/server/test/server_test.go b/examples/server/test/server_test.go
index 48267b7c..da677263 100644
--- a/examples/server/test/server_test.go
+++ b/examples/server/test/server_test.go
@@ -24,6 +24,7 @@ import (
 	irisapi "github.com/doordash-oss/oapi-codegen-dd/v3/examples/server/test/iris/testcase"
 	kratosapi "github.com/doordash-oss/oapi-codegen-dd/v3/examples/server/test/kratos/testcase"
 	stdhttpapi "github.com/doordash-oss/oapi-codegen-dd/v3/examples/server/test/std-http/testcase"
+	"github.com/doordash-oss/oapi-codegen-dd/v3/pkg/runtime"
 	"github.com/gin-gonic/gin"
 	"github.com/gofiber/fiber/v3"
 	iris "github.com/kataras/iris/v12"
@@ -458,3 +459,52 @@ func TestGetItemsByStatus_TypeAndRatingPathParams(t *testing.T) {
 		})
 	}
 }
+
+func TestWithJSONBodyDecoder(t *testing.T) {
+	t.Run("custom decoder is called for JSON body", func(t *testing.T) {
+		var called bool
+		mux := stdhttpapi.NewRouter(stdhttpapi.NewService(),
+			stdhttpapi.WithJSONBodyDecoder(func(body io.Reader, target any) error {
+				called = true
+				return runtime.DecodeJSONBody(body, target)
+			}),
+		)
+
+		reqBody := `{"name": "Alice", "email": "alice@example.com"}`
+		req := httptest.NewRequest("POST", "/users", strings.NewReader(reqBody))
+		req.Header.Set("Content-Type", "application/json")
+		resp, err := httpHandler{mux}.Do(req)
+		require.NoError(t, err)
+		defer func() { _ = resp.Body.Close() }()
+
+		assert.True(t, called, "custom body decoder should have been called")
+		assert.Equal(t, http.StatusCreated, resp.StatusCode)
+	})
+
+	t.Run("custom decoder can transform the body", func(t *testing.T) {
+		mux := stdhttpapi.NewRouter(stdhttpapi.NewService(),
+			stdhttpapi.WithJSONBodyDecoder(func(body io.Reader, target any) error {
+				data, err := io.ReadAll(body)
+				if err != nil {
+					return err
+				}
+				modified := strings.Replace(string(data), "Original", "Transformed", 1)
+				return runtime.DecodeJSONBody(strings.NewReader(modified), target)
+			}),
+		)
+
+		reqBody := `{"name": "Original", "email": "test@example.com"}`
+		req := httptest.NewRequest("POST", "/users", strings.NewReader(reqBody))
+		req.Header.Set("Content-Type", "application/json")
+		resp, err := httpHandler{mux}.Do(req)
+		require.NoError(t, err)
+		defer func() { _ = resp.Body.Close() }()
+
+		assert.Equal(t, http.StatusCreated, resp.StatusCode)
+
+		var user map[string]any
+		err = json.NewDecoder(resp.Body).Decode(&user)
+		require.NoError(t, err)
+		assert.Equal(t, "Transformed", user["name"])
+	})
+}
diff --git a/examples/server/test/std-http/testcase/adapter.gen.go b/examples/server/test/std-http/testcase/adapter.gen.go
index 1a10ad99..6d149268 100644
--- a/examples/server/test/std-http/testcase/adapter.gen.go
+++ b/examples/server/test/std-http/testcase/adapter.gen.go
@@ -139,8 +139,9 @@ type ServiceInterface interface {
 // HTTPAdapter adapts the ServiceInterface to HTTP handlers.
 // This struct is generated and should not be modified.
 type HTTPAdapter struct {
-	svc        ServiceInterface
-	errHandler OapiErrorHandler
+	svc             ServiceInterface
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -149,7 +150,7 @@ func NewHTTPAdapter(svc ServiceInterface, errHandler OapiErrorHandler) *HTTPAdap
 	if errHandler == nil {
 		errHandler = &OapiDefaultErrorHandler{}
 	}
-	return &HTTPAdapter{svc: svc, errHandler: errHandler}
+	return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 // HealthCheck handles GET /health
@@ -267,7 +268,7 @@ func (a *HTTPAdapter) CreateUser(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateUserBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateUser",
@@ -1338,7 +1339,7 @@ func (a *HTTPAdapter) CreateOrder(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateOrderBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateOrder",
@@ -1391,7 +1392,7 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 	// Parse request body
 	defer r.Body.Close()
 	var body CreateCompanyBody
-	if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+	if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
 		a.errHandler.HandleError(w, r, http.StatusBadRequest, OapiHandlerError{
 			Kind:        OapiErrorKindDecode,
 			OperationID: "CreateCompany",
@@ -1439,8 +1440,9 @@ func (a *HTTPAdapter) CreateCompany(w http.ResponseWriter, r *http.Request) {
 type RouterOption func(*routerConfig)
 
 type routerConfig struct {
-	middlewares []func(http.Handler) http.Handler
-	errHandler  OapiErrorHandler
+	middlewares     []func(http.Handler) http.Handler
+	errHandler      OapiErrorHandler
+	jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -1458,6 +1460,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
 	}
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+	return func(cfg *routerConfig) {
+		cfg.jsonBodyDecoder = fn
+	}
+}
+
 // NewRouter creates a new http.ServeMux with the given service implementation.
 func NewRouter(svc ServiceInterface, opts ...RouterOption) *http.ServeMux {
 	cfg := &routerConfig{}
@@ -1468,6 +1478,9 @@ func NewRouter(svc ServiceInterface, opts ...RouterOption) *http.ServeMux {
 	mux := http.NewServeMux()
 
 	adapter := NewHTTPAdapter(svc, cfg.errHandler)
+	if cfg.jsonBodyDecoder != nil {
+		adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+	}
 	mux.HandleFunc("GET /health", applyMiddleware(http.HandlerFunc(adapter.HealthCheck), cfg.middlewares...))
 	mux.HandleFunc("GET /users", applyMiddleware(http.HandlerFunc(adapter.ListUsers), cfg.middlewares...))
 	mux.HandleFunc("POST /users", applyMiddleware(http.HandlerFunc(adapter.CreateUser), cfg.middlewares...))
diff --git a/pkg/codegen/templates/handler/adapter.tmpl b/pkg/codegen/templates/handler/adapter.tmpl
index e32a3844..3f731822 100644
--- a/pkg/codegen/templates/handler/adapter.tmpl
+++ b/pkg/codegen/templates/handler/adapter.tmpl
@@ -39,6 +39,7 @@ type {{ $serviceName }}Interface interface {
 type HTTPAdapter struct {
     svc {{ $serviceName }}Interface
     errHandler OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // NewHTTPAdapter creates a new HTTPAdapter wrapping the given service.
@@ -47,7 +48,7 @@ func NewHTTPAdapter(svc {{ $serviceName }}Interface, errHandler OapiErrorHandler
     if errHandler == nil {
         errHandler = &OapiDefaultErrorHandler{}
     }
-    return &HTTPAdapter{svc: svc, errHandler: errHandler}
+    return &HTTPAdapter{svc: svc, errHandler: errHandler, jsonBodyDecoder: runtime.DecodeJSONBody}
 }
 
 {{define "handle-validation-error"}}
@@ -331,7 +332,7 @@ func (a *HTTPAdapter) {{ $op.ID | ucFirst }}(w http.ResponseWriter, r *http.Requ
     defer r.Body.Close()
     {{- if or (eq $op.Body.ContentType "application/json") (hasSuffix $op.Body.ContentType "+json") }}
     var body {{ $op.Body.Name }}
-    if err := runtime.DecodeJSONBody(r.Body, &body); err != nil {
+    if err := a.jsonBodyDecoder(r.Body, &body); err != nil {
         {{- if $hasTypedError }}
         a.errHandler.HandleError(w, r, {{ $op.Response.Error.StatusCode }}, New{{ $errorTypeName }}(err.Error()))
         {{- else }}
diff --git a/pkg/codegen/templates/handler/beego/handler.tmpl b/pkg/codegen/templates/handler/beego/handler.tmpl
index b8b25c6b..32c917c0 100644
--- a/pkg/codegen/templates/handler/beego/handler.tmpl
+++ b/pkg/codegen/templates/handler/beego/handler.tmpl
@@ -28,6 +28,7 @@ beecontext "github.com/beego/beego/v2/server/web/context"{{end}}
 type routerConfig struct {
     middlewares []beego.MiddleWare
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -45,6 +46,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
     }
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
+
 // beegoHandler wraps an http.HandlerFunc for Beego with path param injection.
 func beegoHandler(h http.HandlerFunc, pathParams ...string) beego.HandleFunc {
     return func(ctx *beecontext.Context) {
@@ -72,6 +81,9 @@ func RegisterRoutes(router *beego.ControllerRegister, svc {{ $serviceName }}Inte
     {{- if $operations }}
 
     httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         router.{{ $op.Method | lower | ucFirst }}("{{template "router-path" $op.Path}}", beegoHandler(httpAdapter.{{ $op.ID | ucFirst }}{{ if $op.PathParams }}{{ range $op.PathParams.Schema.Properties }}, "{{ .JsonFieldName }}"{{ end }}{{ end }}))
     {{- end }}
diff --git a/pkg/codegen/templates/handler/chi/handler.tmpl b/pkg/codegen/templates/handler/chi/handler.tmpl
index eb4f2f1d..09eca8d1 100644
--- a/pkg/codegen/templates/handler/chi/handler.tmpl
+++ b/pkg/codegen/templates/handler/chi/handler.tmpl
@@ -26,6 +26,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []func(http.Handler) http.Handler
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -42,6 +43,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -63,6 +72,9 @@ func NewRouter(svc {{ $serviceName }}Interface, opts ...RouterOption) chi.Router
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         r.Method("{{ $op.Method }}", "{{template "router-path" $op.Path}}", http.HandlerFunc(adapter.{{ $op.ID | ucFirst }}))
     {{- end }}
diff --git a/pkg/codegen/templates/handler/echo/handler.tmpl b/pkg/codegen/templates/handler/echo/handler.tmpl
index b99fc97e..56c59d31 100644
--- a/pkg/codegen/templates/handler/echo/handler.tmpl
+++ b/pkg/codegen/templates/handler/echo/handler.tmpl
@@ -27,6 +27,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []echo.MiddlewareFunc
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -43,6 +44,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -64,6 +73,9 @@ func NewRouter(e *echo.Echo, svc {{ $serviceName }}Interface, opts ...RouterOpti
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         e.{{ $op.Method | caps }}("{{template "router-path" $op.Path}}", func(c echo.Context) error {
             {{- if $op.PathParams }}
diff --git a/pkg/codegen/templates/handler/fasthttp/handler.tmpl b/pkg/codegen/templates/handler/fasthttp/handler.tmpl
index 6b53b773..100068a4 100644
--- a/pkg/codegen/templates/handler/fasthttp/handler.tmpl
+++ b/pkg/codegen/templates/handler/fasthttp/handler.tmpl
@@ -29,6 +29,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []func(fasthttp.RequestHandler) fasthttp.RequestHandler
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -46,6 +47,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
     }
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
+
 // fasthttpHandler wraps an http.HandlerFunc with path param injection for fasthttp.
 func fasthttpHandler(h http.HandlerFunc, pathParams ...string) fasthttp.RequestHandler {
     return func(ctx *fasthttp.RequestCtx) {
@@ -79,6 +88,9 @@ func NewRouter(svc {{ $serviceName }}Interface, opts ...RouterOption) *router.Ro
     {{- if $operations }}
 
     httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         {{- if $op.PathParams }}
         r.{{ $op.Method }}("{{template "router-path" $op.Path}}", fasthttpHandler(httpAdapter.{{ $op.ID | ucFirst }}{{ range $op.PathParams.Schema.Properties }}, "{{ .JsonFieldName }}"{{ end }}))
@@ -118,6 +130,9 @@ func Handler(svc {{ $serviceName }}Interface, opts ...RouterOption) fasthttp.Req
     {{- if $operations }}
 
     httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         {{- if $op.PathParams }}
         r.{{ $op.Method }}("{{ $op.Path }}", fasthttpHandler(httpAdapter.{{ $op.ID | ucFirst }}{{ range $op.PathParams.Schema.Properties }}, "{{ .JsonFieldName }}"{{ end }}))
diff --git a/pkg/codegen/templates/handler/fiber/handler.tmpl b/pkg/codegen/templates/handler/fiber/handler.tmpl
index fac503be..accf48f2 100644
--- a/pkg/codegen/templates/handler/fiber/handler.tmpl
+++ b/pkg/codegen/templates/handler/fiber/handler.tmpl
@@ -28,6 +28,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []fiber.Handler
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -45,6 +46,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
     }
 }
 
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
+
 // fiberHTTPHandler wraps an http.HandlerFunc with path param injection for Fiber.
 func fiberHTTPHandler(h http.HandlerFunc, pathParams ...string) fiber.Handler {
     return func(c fiber.Ctx) error {
@@ -78,6 +87,9 @@ func NewRouter(app *fiber.App, svc {{ $serviceName }}Interface, opts ...RouterOp
     {{- if $operations }}
 
     httpAdapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        httpAdapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         {{- if $op.PathParams }}
         app.{{ $op.Method | lower | ucFirst }}("{{template "router-path" $op.Path}}", fiberHTTPHandler(httpAdapter.{{ $op.ID | ucFirst }}{{ range $op.PathParams.Schema.Properties }}, "{{ .JsonFieldName }}"{{ end }}))
diff --git a/pkg/codegen/templates/handler/gin/handler.tmpl b/pkg/codegen/templates/handler/gin/handler.tmpl
index 4fc6bbd6..a651c6e2 100644
--- a/pkg/codegen/templates/handler/gin/handler.tmpl
+++ b/pkg/codegen/templates/handler/gin/handler.tmpl
@@ -27,6 +27,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []gin.HandlerFunc
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -43,6 +44,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -64,6 +73,9 @@ func NewRouter(r *gin.Engine, svc {{ $serviceName }}Interface, opts ...RouterOpt
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         r.{{ $op.Method | caps }}("{{template "router-path" $op.Path}}", func(c *gin.Context) {
             {{- if $op.PathParams }}
diff --git a/pkg/codegen/templates/handler/go-zero/handler.tmpl b/pkg/codegen/templates/handler/go-zero/handler.tmpl
index 43bc8143..bef65221 100644
--- a/pkg/codegen/templates/handler/go-zero/handler.tmpl
+++ b/pkg/codegen/templates/handler/go-zero/handler.tmpl
@@ -28,6 +28,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []rest.Middleware
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -44,6 +45,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -60,6 +69,9 @@ func RegisterRoutes(server *rest.Server, svc {{ $serviceName }}Interface, opts .
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
 
     routes := []rest.Route{
     {{- range $operations }}{{ $op := . }}
@@ -95,6 +107,9 @@ func NewRouter(svc {{ $serviceName }}Interface, opts ...RouterOption) http.Handl
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
     _ = r.Handle("{{ $op.Method }}", "{{template "router-path" $op.Path}}", http.HandlerFunc(adapter.{{ $op.ID | ucFirst }}))
     {{- end }}
diff --git a/pkg/codegen/templates/handler/goframe/handler.tmpl b/pkg/codegen/templates/handler/goframe/handler.tmpl
index 813fa39e..1c9374ab 100644
--- a/pkg/codegen/templates/handler/goframe/handler.tmpl
+++ b/pkg/codegen/templates/handler/goframe/handler.tmpl
@@ -27,6 +27,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []ghttp.HandlerFunc
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -43,6 +44,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -64,6 +73,9 @@ func NewRouter(s *ghttp.Server, svc {{ $serviceName }}Interface, opts ...RouterO
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         s.BindHandler("{{ $op.Method | caps }}:{{template "router-path" $op.Path}}", func(r *ghttp.Request) {
             {{- if $op.PathParams }}
@@ -93,6 +105,9 @@ func Handler(svc {{ $serviceName }}Interface, opts ...RouterOption) http.Handler
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         mux.HandleFunc("{{ $op.Method | caps }} {{ $op.Path }}", adapter.{{ $op.ID | ucFirst }})
     {{- end }}
diff --git a/pkg/codegen/templates/handler/gorilla-mux/handler.tmpl b/pkg/codegen/templates/handler/gorilla-mux/handler.tmpl
index 8fae91ba..f60172bd 100644
--- a/pkg/codegen/templates/handler/gorilla-mux/handler.tmpl
+++ b/pkg/codegen/templates/handler/gorilla-mux/handler.tmpl
@@ -26,6 +26,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []mux.MiddlewareFunc
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -42,6 +43,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -63,6 +72,9 @@ func NewRouter(svc {{ $serviceName }}Interface, opts ...RouterOption) *mux.Route
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         r.HandleFunc("{{template "router-path" $op.Path}}", adapter.{{ $op.ID | ucFirst }}).Methods("{{ $op.Method }}")
     {{- end }}
diff --git a/pkg/codegen/templates/handler/hertz/handler.tmpl b/pkg/codegen/templates/handler/hertz/handler.tmpl
index 43a059a5..ae74818f 100644
--- a/pkg/codegen/templates/handler/hertz/handler.tmpl
+++ b/pkg/codegen/templates/handler/hertz/handler.tmpl
@@ -31,6 +31,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []app.HandlerFunc
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -47,6 +48,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -68,6 +77,9 @@ func NewRouter(h *server.Hertz, svc {{ $serviceName }}Interface, opts ...RouterO
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         h.Handle("{{ $op.Method | caps }}", "{{template "router-path" $op.Path}}", func(ctx context.Context, c *app.RequestContext) {
             req, err := adaptor.GetCompatRequest(&c.Request)
@@ -103,6 +115,9 @@ func Handler(svc {{ $serviceName }}Interface, opts ...RouterOption) http.Handler
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         mux.HandleFunc("{{ $op.Method | caps }} {{ $op.Path }}", adapter.{{ $op.ID | ucFirst }})
     {{- end }}
diff --git a/pkg/codegen/templates/handler/iris/handler.tmpl b/pkg/codegen/templates/handler/iris/handler.tmpl
index fa363a82..66cb090c 100644
--- a/pkg/codegen/templates/handler/iris/handler.tmpl
+++ b/pkg/codegen/templates/handler/iris/handler.tmpl
@@ -27,6 +27,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []iris.Handler
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -43,6 +44,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -64,6 +73,9 @@ func NewRouter(app *iris.Application, svc {{ $serviceName }}Interface, opts ...R
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         app.Handle("{{ $op.Method | caps }}", "{{template "router-path" $op.Path}}", func(ctx iris.Context) {
             {{- if $op.PathParams }}
@@ -93,6 +105,9 @@ func Handler(svc {{ $serviceName }}Interface, opts ...RouterOption) http.Handler
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
     mux.HandleFunc("{{ $op.Method | caps }} {{ escapeGoString $op.Path }}", adapter.{{ $op.ID | ucFirst }})
     {{- end }}
diff --git a/pkg/codegen/templates/handler/kratos/handler.tmpl b/pkg/codegen/templates/handler/kratos/handler.tmpl
index 7d2a5dc4..724d3475 100644
--- a/pkg/codegen/templates/handler/kratos/handler.tmpl
+++ b/pkg/codegen/templates/handler/kratos/handler.tmpl
@@ -27,6 +27,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []func(http.Handler) http.Handler
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -43,6 +44,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -69,6 +78,9 @@ func NewRouter(svc {{ $serviceName }}Interface, opts ...RouterOption) http.Handl
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
     r.HandleFunc("{{template "router-path" $op.Path}}", adapter.{{ $op.ID | ucFirst }}).Methods("{{ $op.Method }}")
     {{- end }}
diff --git a/pkg/codegen/templates/handler/std-http/handler.tmpl b/pkg/codegen/templates/handler/std-http/handler.tmpl
index 38c8f9e1..a1337227 100644
--- a/pkg/codegen/templates/handler/std-http/handler.tmpl
+++ b/pkg/codegen/templates/handler/std-http/handler.tmpl
@@ -26,6 +26,7 @@ limitations under the License.
 type routerConfig struct {
     middlewares []func(http.Handler) http.Handler
     errHandler  OapiErrorHandler
+    jsonBodyDecoder runtime.JSONBodyDecoderFunc
 }
 
 // WithMiddleware adds middleware to the router.
@@ -42,6 +43,14 @@ func WithErrorHandler(h OapiErrorHandler) RouterOption {
         cfg.errHandler = h
     }
 }
+
+// WithJSONBodyDecoder sets a custom function for decoding JSON request bodies.
+// If not set, runtime.DecodeJSONBody is used.
+func WithJSONBodyDecoder(fn runtime.JSONBodyDecoderFunc) RouterOption {
+    return func(cfg *routerConfig) {
+        cfg.jsonBodyDecoder = fn
+    }
+}
 {{end}}
 
 {{define "new-router"}}
@@ -60,6 +69,9 @@ func NewRouter(svc {{ $serviceName }}Interface, opts ...RouterOption) *http.Serv
     {{- if $operations }}
 
     adapter := NewHTTPAdapter(svc, cfg.errHandler)
+    if cfg.jsonBodyDecoder != nil {
+        adapter.jsonBodyDecoder = cfg.jsonBodyDecoder
+    }
     {{- range $operations }}{{ $op := . }}
         mux.HandleFunc("{{ $op.Method }} {{template "router-path" $op.Path}}", applyMiddleware(http.HandlerFunc(adapter.{{ $op.ID | ucFirst }}), cfg.middlewares...))
     {{- end }}
diff --git a/pkg/runtime/json.go b/pkg/runtime/json.go
index e0ae4e3b..4b2739f7 100644
--- a/pkg/runtime/json.go
+++ b/pkg/runtime/json.go
@@ -213,6 +213,10 @@ func UnmarshalAs[T any](v json.RawMessage) (T, error) {
 	return res, err
 }
 
+// JSONBodyDecoderFunc decodes a request body into the target value.
+// The default implementation is DecodeJSONBody.
+type JSONBodyDecoderFunc func(body io.Reader, target any) error
+
 // DecodeJSONBody decodes a JSON request body into the target value.
 // It wraps common JSON decoding errors with user-friendly messages:
 //   - io.EOF or empty body -> "request body is empty"