feat: add HTTP migration bridges and extensible API binding

2026-09-24 01:47:42 +08:00
parent 7b8eca1a61
commit a8c973d8a2
39 changed files with 2596 additions and 118 deletions
--- a/API.md
+++ b/API.md
@@ -105,7 +105,7 @@ service user-api {
 - 来源标签中的 `optional` / `omitempty`、标量 `default`、标量 `options=a|b`、数值 `range=[1:100]`（支持开区间和单边界）。
 - `binding` 的 `required`、`min`、`max`、`len`、`email`。长度按 Unicode 字符或切片元素数；范围边界必须有限且位于 ±2^53 内。

-暂不支持匿名嵌入、别名、递归类型、外部 Go 类型、自定义 JSON 编解码、`[]byte`、泛型、`json:",string"`、任意 validator 标签、go-zero 的 JWT/签名/SSE 声明，以及客户端 SDK 生成。认证验证通过声明关联的命名中间件实现。未列出的语法会明确报错。
+暂不支持匿名嵌入、别名、递归类型、未声明的外部 Go 类型、自定义 JSON 编解码、`[]byte`、泛型、`json:",string"`、任意 validator 标签、go-zero 的 JWT/签名/SSE 声明，以及客户端 SDK 生成。认证验证通过声明关联的命名中间件实现。未列出的语法会明确报错。

 业务错误、具名鉴权、多行文档及下述开发命令从 CLI `v0.7.0-preview.1` 提供。公共响应模板从 `v0.8.0-preview` 提供，CLI 与业务项目中的框架依赖需一起升级。

@@ -212,11 +212,21 @@ go test ./...
 路由总览的 `(undeclared)` 仅表示没有声明 auth；旧式中间件仍可能做认证。
 外发文档可用 export；项目内受生成器管理的 `docs/openapi.json` 请通过 generate 更新，以同步文件哈希。

+## 迁移扩展（v0.9.0-preview）
+
+- 动态 JSON 字段 `any` / `interface{}`，包含切片和 map；外围契约仍严格。
+- `scalar Name (...)` 显式引用项目类型，声明 JSON 输入/输出类型及文本绑定；支持已有 JSON/Text 转换方法。
+- `@body (mode: json/raw/multipart; maxBytes: ...)`：按路由限制请求体。
+- `@binding custom` 生成保留的绑定 hook；`@handlerMode manual` 生成保留的整个 Handler，raw/multipart 使用这个入口。
+- manual 可用 `@produces "text/plain"` 等声明无 DTO 成功输出。默认状态 200，初始手写 stub 返回 501。
+
+完整语法、边界和示例见 [迁移扩展指南](MIGRATION.md)。新增生成代码要求 CLI 与框架依赖一起升级到 `v0.9.0-preview`；不兼容全部 goctl 语法。
+
 ## 参数语义

 无 optional/default 的字段按“是否出现”判断必填，`false`、`0`、`""` 是已提供的值。额外声明 `binding:"required"` 才会拒绝标量零值。默认值只在字段缺失时使用，不替换显式的空值。

-业务需要区分“没传”和“传了零值”时使用 `*T` 加 optional。指针允许 JSON null；非指针拒绝 null；`binding:"required"` 拒绝指针 null。缺失与 null 都会得到 nil，本版没有三态 Nullable 类型。响应端的 `optional` 不等于 Go 编码器的 `omitempty`；需要省略零值时显式使用 `omitempty`。
+业务需要区分“没传”和“传了零值”时使用 `*T` 加 optional。指针允许 JSON null；普通非指针字段拒绝 null（动态 `any` 允许）；`binding:"required"` 拒绝指针 null。缺失与 null 都会得到 nil，本版没有三态 Nullable 类型。响应端的 `optional` 不等于 Go 编码器的 `omitempty`；需要省略零值时显式使用 `omitempty`。

 JSON 必须是一个 object，Content-Type 为 application/json。默认最多 1 MiB，包含 chunked/未知长度和尾部空白；超限返回 413。重复 JSON key、未知字段、多个 JSON 值、标量 query/header 重复值、格式和约束错误返回 400；错误 Content-Type 返回 415。失败不会部分修改目标 DTO；错误详情只保留在内部 cause，公共响应不回显原始参数。

--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog

+## v0.9.0-preview
+
+- 标准 HTTP Handler/Middleware 桥接：跟踪 Raw 状态与提交，保留取消、流式能力和中间件跨请求状态；已提交响应不追加 JSON。
+- `.api` 支持动态 JSON `any` / `interface{}`，保持重复键、大小、外围未知字段校验和数字精度。
+- 路由级请求体限额、自定义绑定和 manual Handler；上传、原始 body、下载可保留手写实现，重生成受保护。
+- 自定义 scalar 显式对接项目 JSON/Text 方法；支持可空和集合，分别生成请求/响应 OpenAPI；不放宽其他字段。
+- 新增 [迁移扩展指南](MIGRATION.md)、可运行示例和真实生成项目回归。CLI 与框架依赖一起升级。
+
 ## v0.8.0-preview

 - 公共响应 `codeType` 支持 `int32` / `int64` / `string`，校验默认码及映射范围，OpenAPI 标注整数位宽；JSON/YAML 和生成代码保留 int64 精度，旧 `integer` 兼容。
--- a/MIGRATION.md
+++ b/MIGRATION.md
@@ -0,0 +1,182 @@
+# 已有 HTTP 项目逐步接入
+
+从 `v0.9.0-preview` 开始，以下能力贯通运行时、`.api`、代码生成和 OpenAPI。CLI 和项目框架依赖一起升级；入口见 [README](README.md)。这些都是通用扩展点，框架不内置任何项目的 ID、支付回调、鉴权或数据库规则。
+
+## 1. 保留标准 Handler 与中间件
+
+```go
+app := omni.New(omni.WithLogger(true))
+app.Use(httpx.WrapMiddleware(existingMiddleware)) // func(http.Handler) http.Handler
+// go-zero 风格的 func(http.HandlerFunc) http.HandlerFunc：
+app.Use(httpx.WrapFuncMiddleware(existingFuncMiddleware))
+app.POST("/legacy", httpx.WrapHandler(http.HandlerFunc(existingHandler)))
+```
+
+实际使用时先配置所有 `Use`，再注册路由。`WrapHandler` 也接受 `http.FileServer` 等标准 `http.Handler`。
+
+- Handler 经过 App 的日志、requestId、恢复和应用中间件链，原来的 URL、状态码、Header、响应内容由它自己控制。
+- `c.Raw()` 的写入也会更新 `c.Status()` / `c.Responded()`；404 会记为 404。提交响应后返回错误或 panic，不会再追加错误 JSON。103 等临时响应不算最终提交。
+- 桥接器不缓存完整响应。下载继续流式复制；底层支持时保留 Flusher、Hijacker、Pusher、ReaderFrom、CloseNotifier。`http.ResponseController` 可沿 `Unwrap` 访问底层控制能力。能力仍取决于网络适配器和其他中间件。
+- 请求 context、取消信号和已有值继续传递，Omni 的路径参数可用 Go 1.22 的 `r.PathValue("id")` 读取。其他框架私有的参数读取器仍需由项目适配。标准中间件应从原 `r.Context()` 派生上下文；不能换成无关的 Background，也不能在 ServeHTTP 返回后调用 next。异步 timeout middleware 不在此桥接器的契约内。
+- 标准中间件在每条注册链构造一次，状态会跨请求保留。下游返回的错误在标准中间件退出前编码，因此压缩、审计等中间件能处理错误响应。它们自己的缓冲或改写行为仍由项目负责。
+
+调用流使用 `App.Handle/GET/POST` 等入口即可，不要绕到原始 Router 注册。暂不使用 `.api` 的旧接口也能这样接入。
+
+## 2. 动态 JSON：允许渐进补全 DTO
+
+```go
+type LegacyReply {
+    Data any `json:"data"`
+}
+```
+
+`interface{}` 是 `any` 的等价写法，支持 `[]any`、`map[string]any` 和对应的 `interface{}` 写法。带方法的 interface 不支持，会提示明确的类型错误。
+
+动态字段允许 object、array、string、number、bool、null；OpenAPI 字段 schema 为 `{}`，不假装知道内部结构。它放开的是**该字段的内容**，外围 DTO 未声明的字段仍被拒绝，JSON 重复键、深度、总大小限制仍生效。动态数字解析为 `json.Number`，避免大整数先转 float64 丢精度。原始 JSON 的空白、转义和字节布局不会保留；验签请走原始 body 入口。
+
+这不会自动补齐缺少的业务路由，也不代表兼容全部 goctl 语法。能确定结构的新接口优先使用命名 DTO。
+
+## 3. 按路由限制 body 与保留手写入口
+
+普通 JSON 路由只声明需要的大小，不改变其他路由默认的 1 MiB：
+
+```text
+@body (mode: json
+    maxBytes: 2097152
+)
+@handler createItem
+post /items (CreateItemReq) returns (ItemResp)
+```
+
+`maxBytes` 单位为字节，允许 1 至 1 TiB；不写时为 1 MiB。已知超长或读取未知长度/chunked body 超限都按 413 处理。内置 App/RouterGroup 在全局中间件读取前安装 reader 限额；同时保持接口响应策略。网络层若有更小限额，以更小值为准。手写 Handler 吞掉读取错误或已经提交响应后，框架不能重新改写 HTTP 状态，务必检查读取错误。
+
+### 只替换绑定函数
+
+```text
+@binding custom
+@body (mode: json
+    maxBytes: 65536
+)
+@handler createItem
+post /items (CreateItemReq) returns (ItemResp)
+```
+
+首次生成 `internal/handler/<group>/createItemBind.go`：
+
+```go
+func (h *Handler) bindCreateItem(c *httpx.Context, req *types.CreateItemReq) error {
+    // 调用项目自己的解码器，填充 req；失败返回 error。
+}
+```
+
+Handler 继续调用 Service 并使用统一响应；只把绑定过程交给这个函数。初始 hook 返回 501，不能忽略实现。自定义绑定需自己实现 Content-Type、未知字段、尾部数据等校验，并遵守 DTO 文档；框架负责路由总大小限制，不隐式套第二次 JSON 绑定。
+
+### 上传、原文验签、下载
+
+```text
+@handlerMode manual
+@body (mode: multipart
+    maxBytes: 10485760
+)
+@handler upload
+post /files
+
+@handlerMode manual
+@body (mode: raw
+    maxBytes: 65536
+)
+@produces "text/plain"
+@handler callback
+post /callback
+
+@handlerMode manual
+@produces "application/octet-stream"
+@handler download
+get /download
+```
+
+首次生成 `<operation>Manual.go`，由项目实现整个 `func(h *Handler) Callback(c *httpx.Context) error`；依赖通过 `h.deps` 访问。生成器保留路由、中间件与文档管理，不会预读、JSON 解码或重新包装手写输出，也不生成这个路由的 Service 方法。需要调用 Service 时自行组合。
+
+- manual 无返回类型默认成功状态 200；也可 `returns (UploadResp)` 描述 JSON DTO，手写实现按声明调用 `c.OK` 等。`@produces` 用于无 DTO 的手写输出，描述成功响应媒体类型，不会自动设置运行时 Header。
+- raw 的文档为二进制请求体；multipart 为开放对象，具体文件字段与逐部分校验由项目实现。raw/multipart 请求 DTO 仅可含 path/form/header 字段，不能同时声明 JSON body 字段。`form` 始终指 URL query。
+- 原文验签直接读取 `c.Request().Body`，在声明的小限额内 `io.ReadAll`；大文件用 `MultipartReader` 配合 `io.Copy` 流式处理，不能整个读入内存。
+- 使用 `ParseMultipartForm` 时，其内存参数只是内存阈值，不是总上传限额。App/桥接器在请求结束（含错误和 panic）后删除临时文件；业务仍须关闭 `FormFile` 得到的文件。`MultipartReader` 不自动建临时文件，业务自行创建的文件由业务清理。
+- 手写 Handler 的成功输出由它控制；返回的 error、鉴权拒绝仍走接口的错误策略。三方若要求错误也返回指定文本，使用 [自定义 Encoder](RESPONSE.md#手写路由配置文件与三方回调) 并维护对应错误文档；`@produces` 不会改变错误协议。
+
+直接注册 Go 路由：
+
+```go
+app.HandleWithBodyLimit("POST", "/upload", 10<<20, nil, uploadHandler)
+// nil encoder 沿用 App 策略，也可传项目自己的 response.Encoder。
+```
+
+通用注册器使用 `httpx.HandleWithBodyLimit(...)`；实现 `httpx.BodyLimitRegistrar` 可像 App 一样在全局中间件前限流量，未实现时只能在路由中间件入口限制。单独 `httpx.LimitBody` 同样受中间件顺序影响。
+
+### 重新生成规则
+
+`handlersGen.go`、`routesGen.go`、DTO、OpenAPI 继续由生成器管理；`*Bind.go`、`*Manual.go` 只首次创建，后续不会覆盖或删除。切换 manual 回自动模式时，先迁移实现并自行移除对应 Manual 文件，否则生成器明确拒绝，避免重复方法。修改 DTO 导致手写函数签名不匹配时，需要一起调整项目代码；`go test ./...` 是必要检查。
+
+## 4. 自定义标量：项目定义行为，框架连接调用
+
+例如输入 ID 兼容数字/字符串、输出统一为字符串：
+
+```text
+scalar BusinessID (
+    goImport: "example.com/billing/internal/ids"
+    goType: ID
+    jsonInput: string | int64
+    jsonOutput: string
+    text: true
+)
+type ItemReq {
+    ID BusinessID `path:"id"`
+}
+type ItemResp {
+    ID BusinessID `json:"id"`
+}
+```
+
+`goImport`/`goType` 指向项目已有的具体 Go 类型，不是框架内置 ID。生成器创建类型别名和 `types.ContractScalars()`，然后把注册表显式传给每个 Binder。运行时使用标准接口：
+
+| 项目类型的方法 | 用途 |
+| --- | --- |
+| 值接收者 `MarshalJSON() ([]byte, error)` | JSON 输出 |
+| 指针接收者 `UnmarshalJSON([]byte) error` | JSON 输入 |
+| 指针接收者 `UnmarshalText([]byte) error` | `text: true` 时的 path/query/header |
+
+完整参考 [示例 ID 类型](examples/compatibility/ids/id.go)。CLI 校验声明并生成代码，不执行项目 Go 代码；启动时校验方法是否齐全，缺失会明确失败。
+
+输入可选 `string`、`bool`、`int32`、`int64`、`float64`，用 `|` 声明多个允许的 JSON 类型；输出只声明一个。框架先校验 JSON 类型和数字范围，再调用项目转换方法。字符串是否是合法 ID、是否允许空串或负数由项目方法决定，不能把数字溢出静默截断。path/query/header 实际传输文本，OpenAPI 对这些位置描述 string；query 切片通过重复键传递。
+
+普通字段不受注册影响，普通 `int64` 仍拒绝 JSON 字符串。没有全局注册表，也不会自动给所有 ID 放宽规则。标量可嵌套、放入切片/map，`*BusinessID` 允许 null；缺失默认必填，`optional`/`omitempty` 可选。标量的额外约束放在转换器中，目前不叠加 `binding`、default/options/range 等标签。
+
+请求 OpenAPI 按 `string | int64` 生成 `anyOf`，响应按 `string` 生成，避免把输入兼容误描述为输出也有两种类型。输出方法必须遵守声明，框架不会每次重新验证响应；项目需为自定义类型测试边界行为。
+
+不使用 `.api` 也可显式注册：
+
+```go
+binder := contract.MustNew[CreateReq](
+    contract.ScalarOf[ids.ID]("string|int64", "string", true),
+)
+// binder.Bind(c.Request(), httpx.RouteParams(c.Context()), &req)
+```
+
+## 可运行示例与验收
+
+```sh
+go run ./examples/compatibility
+curl -i http://127.0.0.1:8080/legacy
+curl -i -X POST http://127.0.0.1:8080/echo \
+  -H 'Content-Type: application/json' -d '{"id":9223372036854775807,"data":{"hello":true}}'
+curl -i -F file=@README.md http://127.0.0.1:8080/upload
+curl -OJ http://127.0.0.1:8080/download
+```
+
+完整契约：[compatibility.api](examples/contracts/compatibility.api)。生成项目起初的手写 hook 仍为 501；真实实现与原文 HMAC 验签回归见 [消费者 fixture](cmd/go-omni/apigen/testdata/compatibility)。
+
+```sh
+GO_OMNI_SCAFFOLD_INTEGRATION=1 go test -race ./cmd/go-omni/apigen -run Compatibility
+go test -race ./httpx ./contract
+```
+
+这些是框架验收，不代表任何业务项目已经迁移完毕；业务的路由覆盖、响应兼容、权限、资金事务和数据库行为需要业务自己的回归。
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@

 GoOmni 是面向多个业务项目复用的 Go 后端框架：用 `.api` 定义接口、请求和返回类型，生成项目目录、HTTP 接入代码及 OpenAPI，业务代码负责 Service 和 Repository。也可以在已有项目中直接使用 `omni.New()`，或单独引入日志、存储等模块。

-**从这份 README 开始即可接入。** 当前版本为 **`v0.8.0-preview`**，Go **1.22+**；CLI 和项目依赖使用同一固定版本。框架不依赖 Gin，默认使用标准库网络层，提供可切换的 native HTTP/1.1 和实验性 HTTP/2 适配器。
+**从这份 README 开始即可接入。** 当前版本为 **`v0.9.0-preview`**，Go **1.22+**；CLI 和项目依赖使用同一固定版本。框架不依赖 Gin，默认使用标准库网络层，提供可切换的 native HTTP/1.1 和实验性 HTTP/2 适配器。

 响应字段、业务码、登录方式、权限规则和数据库表结构由接入项目决定。文中的 `code/msg/data`、`200/9999` 都是示例配置，可以替换。

@@ -12,6 +12,7 @@ GoOmni 是面向多个业务项目复用的 Go 后端框架：用 `.api` 定义
 | --- | --- |
 | 新建服务，先定义接口再开发 | [新项目：生成并运行](#新项目生成并运行) |
 | 已有服务，逐步接入 HTTP 或基础模块 | [已有项目：按模块接入](#已有项目按模块接入) |
+| 已有标准 Handler、动态 JSON、上传或自定义 ID 类型 | [迁移扩展指南](MIGRATION.md) |
 | 想统一返回体、业务错误或三方回调 | [配置公共响应与独立协议](#配置公共响应与独立协议) |
 | 要接日志、数据库、鉴权和存储 | [业务开发与依赖装配](#业务开发与依赖装配) |
 | 要切换网络层、配置 TLS 和退出清理 | [配置与运行](#配置与运行) |
@@ -25,7 +26,7 @@ module 地址是 `git.yuntuo.hk/k2safe/go-omni`。先确保本机 Go 和 Git 可

 ```sh
 export GOPRIVATE=git.yuntuo.hk
-go install git.yuntuo.hk/k2safe/go-omni/cmd/go-omni@v0.8.0-preview
+go install git.yuntuo.hk/k2safe/go-omni/cmd/go-omni@v0.9.0-preview
 export PATH="$(go env GOPATH)/bin:$PATH"
 go-omni --help
 ```
@@ -37,7 +38,7 @@ go-omni --help
 在准备存放业务项目的目录执行，`./hello` 必须是新目录或空目录；把 `example.com/hello` 换成自己的 Go module 名称。

 ```sh
-go-omni api new --framework-version v0.8.0-preview \
+go-omni api new --framework-version v0.9.0-preview \
  --module example.com/hello ./hello
 cd hello
 go mod tidy
@@ -125,7 +126,7 @@ service catalog-api {

 ```sh
 go-omni api validate --api catalog.api
-go-omni new --api catalog.api --framework-version v0.8.0-preview \
+go-omni new --api catalog.api --framework-version v0.9.0-preview \
  --module example.com/catalog ./catalog
 cd catalog
 go mod tidy
@@ -166,21 +167,21 @@ curl -i http://127.0.0.1:8080/api/v1/items/missing
 需要 MySQL、文件存储或文件日志时，**首次生成**可以使用：

 ```sh
-go-omni new --api catalog.api --framework-version v0.8.0-preview \
+go-omni new --api catalog.api --framework-version v0.9.0-preview \
  --module example.com/catalogFull --database mysql --storage local \
  --log-output file --log-format json ./catalogFull
 ```

 该命令在 `catalog.api` 所在目录执行，目标仍需是新目录。数据库迁移、表结构和 Repository 由项目维护，API 模板不自动建表；MySQL DSN 通过 `GO_OMNI_DB_DSN` 提供。存储还可选 `s3`、`r2`、`oss`，按生成项目的配置说明提供桶、端点和凭据。完整装配例子见 [userService](examples/userService/README.md)。

-不采用 `.api` 时，也可以用 `go-omni new --framework-version v0.8.0-preview --module example.com/billing ./billing` 创建手写接口的 CRUD 示例项目；两种生成方式选择一种即可。
+不采用 `.api` 时，也可以用 `go-omni new --framework-version v0.9.0-preview --module example.com/billing ./billing` 创建手写接口的 CRUD 示例项目；两种生成方式选择一种即可。

 ## 已有项目：按模块接入

 在业务项目的 **go.mod 所在目录**执行：

 ```sh
-go get git.yuntuo.hk/k2safe/go-omni@v0.8.0-preview
+go get git.yuntuo.hk/k2safe/go-omni@v0.9.0-preview
 ```

 已有项目可直接复用现有目录、Service、Repository 和数据库连接，先选择一个接口接入。也可以只用 `logx`、`storage` 等包，暂时保留原来的 HTTP 框架。
@@ -243,11 +244,13 @@ func run() error {

 运行 `go run .`，访问 `/api/v1/items/1001`、`/api/v1/items/missing` 和 `/ping`，可分别验证成功、业务错误及纯文本输出。`App` 实现标准 `http.Handler`，也可挂进现有 `http.Server` 或父路由；这时监听、TLS、信号和资源关闭由现有入口负责，结束时调用 `app.Close()`。

+现有 `http.HandlerFunc` 可直接通过 `app.POST("/legacy", httpx.WrapHandler(http.HandlerFunc(oldHandler)))` 接入；状态码与访问日志一致，下载和流式输出保持原协议。标准中间件、动态 JSON、上传/原文 body、手写绑定和自定义类型的完整用法见 [迁移扩展指南](MIGRATION.md)。
+
 接入现有业务时，逐项确认：

 - **协议**：保留既有 URL、HTTP 状态、字段、分页和空值语义。已有业务错误类型需要在项目内转换为 Omni 错误，或使用 `WithResponseEncoder` 适配原错误；设置字段模板不会自动识别其他库的错误。
 - **鉴权**：把现有登录态和权限校验接入中间件，继续使用原来的授权范围和业务规则。原来依赖 `gin.Context` 等类型的 HTTP 代码需要适配；标准 `context.Context` 的业务服务可以继续复用。
- **数据类型**：ID、金额、日期等按项目协议转换。`.api` 当前不支持外部 Go 类型、自定义 JSON 编解码及 `json:",string"`；需要 JSON 字符串时在契约中声明 `string`，在业务层显式转换。
+- **数据类型**：ID、金额、日期等按项目协议转换。用 `.api` 的 `scalar` 显式关联项目自己的类型与 JSON/Text 转换方法，分别声明输入和输出协议；普通字段保持严格绑定，见 [自定义标量](MIGRATION.md#4-自定义标量项目定义行为框架连接调用)。
 - **生成器**：它不会自动接管任意已有 Go 项目。希望引入 `.api` 时，先在独立新目录生成对照，再规划路由与生成目录的接入，不要用脚手架覆盖现有业务目录。

 先通过一个接口的成功、参数错误、未登录、无权限及业务错误回归，再按模块迁移。框架不要求所有项目使用同一套业务目录或身份模型。
@@ -273,7 +276,7 @@ func run() error {

 **生成接口的格式以 `.api` 为准**，修改后重新生成，运行时与 OpenAPI 一起更新；应用 YAML 不会覆盖它。404/405 没有匹配到某个 `.api` 接口，使用应用默认配置，需要统一时也配置应用默认值。

-文本/XML 回调用 Go 编码器或直接输出，并维护对应文档；`.api` 的 `raw` 仅表示原始 JSON。前面示例的 `c.Text` 控制这次正常返回；需要连鉴权失败、业务错误和 panic 都按回调协议响应时使用 `HandleWithResponse`。完整配置和回调示例见 [响应参考](RESPONSE.md)。
+文本/XML 回调用 Go 编码器或直接输出，`.api` 可用 `@handlerMode manual` 与 `@produces` 声明成功媒体类型；特殊错误协议仍需项目维护。`@response raw` 仅表示原始 JSON。前面示例的 `c.Text` 控制这次正常返回；需要连鉴权失败、业务错误和 panic 都按回调协议响应时使用 `HandleWithResponse`。完整配置和回调示例见 [响应参考](RESPONSE.md)。

 ## 业务开发与依赖装配

@@ -361,7 +364,7 @@ go test ./...

 `Gen.go`、`docs/openapi.json` 和 manifest 由生成器管理，手动修改会报告冲突。Service、Repository、中间件实现、main、配置和依赖装配属于项目，重复生成保留手写内容；契约改变后仍需自行调整业务签名并通过编译。将 `.api`、生成文件和 `.goOmni/apiManifest.json` 一起提交，CI 可运行 `generate --check` 检查是否同步。

-升级时先安装目标版本的 CLI，再在业务 module 中 `go get` **同一版本**；API 项目随后执行上述生成与测试步骤，手写项目只需依赖升级及业务回归。`v0.8.0-preview` 的变化、迁移边界和验收记录见 [发布说明](RELEASE.md)。
+升级时先安装目标版本的 CLI，再在业务 module 中 `go get` **同一版本**；API 项目随后执行上述生成与测试步骤，手写项目只需依赖升级及业务回归。`v0.9.0-preview` 的变化、迁移边界和验收记录见 [发布说明](RELEASE.md)。

 ## 按需深入

--- a/RELEASE.md
+++ b/RELEASE.md
@@ -1,46 +1,34 @@
-# v0.8.0-preview
+# v0.9.0-preview

-这一版让业务自行定义公共返回体：在 `.api` 中配置字段、结构、成功/失败提示和错误码类型，按分组复用或由单接口覆盖，运行时与 OpenAPI 共用定义。需要特殊协议的回调可独立控制状态、Header 和内容。
-
-本版继续作为预览版供固定版本接入；HTTP/2 仍是独立实验适配器。
+本版补齐已有 HTTP 项目的迁移接入能力：标准 Handler/Middleware 桥接、动态 JSON、路由级请求体限额与手写绑定、自定义标量转换。业务的响应格式、身份、资金事务和数据库实现仍由项目决定。

 ## 安装与升级

-首次接入请从 [README 接入指南](README.md) 开始，按新项目或已有项目选择步骤。下面是已接入项目的版本升级命令：
-
 ```sh
-GOPRIVATE=git.yuntuo.hk go install git.yuntuo.hk/k2safe/go-omni/cmd/go-omni@v0.8.0-preview
-
-# 在业务项目 go.mod 所在目录执行：
-GOPRIVATE=git.yuntuo.hk go get git.yuntuo.hk/k2safe/go-omni@v0.8.0-preview
-# 仅在已经由 .api 生成、具有 .goOmni/apiManifest.json 的项目中执行：
-go-omni api generate
-go test ./...
+export GOPRIVATE=git.yuntuo.hk
+go install git.yuntuo.hk/k2safe/go-omni/cmd/go-omni@v0.9.0-preview
+# 在业务 module 中：
+go get git.yuntuo.hk/k2safe/go-omni@v0.9.0-preview
 ```

-手写接口项目跳过 `api generate`，仍需执行业务测试。生成器不会自动接管其他框架创建的已有项目。
+将私有域名追加到已有 GOPRIVATE；凭据通过本机 Git 凭据管理器配置。CLI 与项目框架依赖一起升级。进入已生成的项目，再运行 `go-omni api generate --dry-run`、`go-omni api generate`、`go test ./...`。

-新项目可以直接 `go-omni api new --module example.com/demo ./demo`，或用 `go-omni new --api service.api --module example.com/demo ./demo`。在框架源码目录之外运行，远程安装的 CLI 会固定生成项目的框架版本，无需本地 replace；也可显式传 `--framework-version v0.8.0-preview` 固定远程依赖。需要仓库权限时使用自己的 Git 凭据管理器，不把凭据写入 module path 或 go.mod。
+## 本次变化

-## 本版功能
+- `httpx.WrapHandler`、`WrapMiddleware`、`WrapFuncMiddleware` 将现有标准代码接入 App 中间件链。Raw 写入会记录真实状态和提交；已经输出的响应不再追加错误 JSON。下载/流式输出不整体缓存，保留底层支持的 HTTP 可选能力和取消信号。
+- `.api` 的 `any` / `interface{}` 支持动态 JSON。数字保留为 json.Number，外围 DTO 严格校验不变。
+- `@body` 按路由声明限额；内置 App 在全局中间件读取前限制 body。`@binding custom`、`@handlerMode manual` 生成保留的项目实现文件；上传、原文验签、下载可自行处理。`@produces` 描述手写成功输出的媒体类型。
+- `scalar` 显式引用项目 Go 类型，调用标准 JSON/Text 方法；输入和输出各自生成 OpenAPI。普通基础类型不会自动放宽。

- `response Name (...)` 定义公共 JSON 体，支持嵌套结构、独立 errorBody、常量及类型保持的占位符；通过 import 共享配置。
- `@server (response: Name)` 为整个 service 块选择模板，`@response Name` 单接口覆盖；`@response raw` 成功返回业务 JSON，错误保留组级格式。
- `codeType: int32 / int64 / string` 使用与业务字段一致的名称；默认码和映射都校验，int64 配置及生成代码保留整数精度。旧 `integer` 写法仍兼容。
- `successMessage` / `errorMessage` 配置默认提示，`codes` / `messages` 按逻辑错误码覆盖。业务只返回数据或错误，公共体由框架组装。
- `omni.WithResponse` 设置手写路由的应用默认格式，`WithResponseEncoder` 与 `HandleWithResponse` 支持特殊协议；Text / XML / Bytes / JSON / NoContent 可直接输出。
- 生成路由在全局中间件之前选定策略，提前鉴权拒绝、限流、panic 和 Context 克隆沿用正确格式。OpenAPI 同步模板结构与业务错误示例。
+详见 [迁移扩展指南](MIGRATION.md)、[完整契约](examples/contracts/compatibility.api)、[运行示例](examples/compatibility/main.go) 和 [历史更新](CHANGELOG.md)。

-详见 [公共响应体](RESPONSE.md)、[完整定义示例](examples/contracts/responses.api) 和 [更新记录](CHANGELOG.md)。
+## 兼容与边界

-## 升级行为
+原有 `.api`、公共响应配置和普通 Handler 可以继续使用。新生成代码最低运行时版本为本版。`Raw()` 现在返回跟踪包装器；直接断言某个具体 writer 类型的代码需改用标准接口/ResponseController。

-1. CLI 与框架依赖一起升级到本版。新生成路由使用新的响应策略入口，旧运行时不能编译。旧 `.api` 可继续使用；生成器不会覆盖已有 Service、Repository、middleware、配置和 main。
-2. 生成接口以 `.api` 为响应契约来源，即使没有声明模板也固定使用默认格式；应用 YAML 的 response 用于手写路由和应用兜底。需要变更生成接口的格式，请修改 `.api` 后重新生成。
-3. `response.Response` DTO 保留为兼容类型，运行时不再依赖它固定结构。未配置的正常业务响应继续使用默认 code/message/data/requestId。
-4. 内置 App 的 404/405 现在经过应用响应策略和中间件，默认输出 JSON；原先依赖纯文本兜底的客户端需调整。直接使用 nethttp.Router 的兜底行为不变。
-5. `int32` / `int64` 按有符号整数范围校验并输出 JSON 数值；消费端需支持相应精度。需要文本码时使用 string。旧 integer 继续保留原有 ±(2^53−1) 范围。
-6. `.api` 的模板和 raw 当前描述 JSON。文本/XML回调用 Go 编码器并维护对应文档；TLS/HTTP解析错误、连接级过载等发生在进入应用前的错误仍按网络协议处理。
+标准中间件须保留 incoming request context 并同步调用 next；第三方框架私有的参数读取器仍由项目适配。手写 Handler/绑定 hook 初始返回 501；实现和文档一致性由项目负责，未实现不能上线。切换 manual 回自动模式时须显式迁移并移除对应手写文件，生成器不会删除它。
+
+新增能力没有引入 Gin 或 go-zero 依赖。不是完整 goctl 语法兼容层，不代表任何业务项目已完成迁移。HTTP/2 仍为实验功能，本轮没有重新做 Linux 长测、代理验收或云存储账号实网验收。

 ## 验证入口

@@ -48,13 +36,8 @@ go test ./...
 GO_OMNI_SCAFFOLD_INTEGRATION=1 go test -race -p=1 -count=1 -timeout=300s ./...
 go vet ./...
 go build ./...
-python3 scripts/verifyAPIWorkflow.py --report performance/responsePoliciesWorkflowLocal.json
-python3 scripts/verifyResponseRelease.py --version v0.8.0-preview \
-  --report performance/responsePoliciesRemote.json
-python3 scripts/verifyAPIWorkflow.py --version v0.8.0-preview \
-  --report performance/responsePoliciesWorkflowRemote.json
+python3 scripts/verifyCompatibilityRelease.py --version v0.9.0-preview \
+  --report performance/compatibilityRemote.json
 ```

-远程验收分别从全新 module cache 安装 CLI，验证生成项目固定依赖且没有本地 replace，以及完整用户示例的真实 MySQL、nethttp/native、事务、日志和生命周期。数据库容器只使用本机临时资源（1 CPU / 768 MiB），结束清理，不连接业务服务器。
-
-封版验证完成：40 个包全量 race 通过；全新缓存安装的远程 CLI/框架、公共模板消费者及 nethttp/native 的 34 项业务检查通过，无本地 replace。验收工具和最终记录维护在 main，发布标签保持固定。详见 [响应模板验收](performance/responsePoliciesAcceptance.md)。OSS/R2 云账号实网验收与长时间压力测试不属于本次发布范围。
+测试覆盖旧 Handler 404 与访问日志、提交后错误/panic、标准中间件状态/取消/提前写响应、nethttp/native 实际流式下载与请求体超限、multipart 临时文件清理、自定义标量精度/越界/nullable/集合，以及真实生成项目的验签与重生成保护。远程脚本从全新 module cache 安装 CLI，并检查生成项目的固定版本、校验和以及没有本地 replace。
--- a/RESPONSE.md
+++ b/RESPONSE.md
@@ -125,7 +125,7 @@ app.HandleWithResponse("POST", "/hooks/payment", ack, paymentHandler)

 编码器也可以设置 HTTP 状态、Header、XML 或任意字节。`omni.WithResponseEncoder` 设置应用默认编码器；`httpx.WithResponse` 是普通路由中间件，按中间件顺序生效。需要覆盖全局中间件提前拒绝时，应使用 `HandleWithResponse`。自定义 Registrar 可以实现 `httpx.ResponseRegistrar` 提供相同的早期挂载能力；未实现时辅助函数退化为普通路由中间件。

-`.api` 当前声明的是 JSON 协议，`@response raw` 也是原始 JSON，不代表任意文本/XML协议。自定义文本/XML回调使用上述 Go 入口，并由应用维护相应文档；生成器不会猜测自定义 Go 编码器的输出。如果在命名中间件里替换编码器，业务也必须同步维护文档。
+`@response raw` 表示原始 JSON，不代表任意文本/XML协议。从 v0.9.0-preview 开始，`.api` 可用 `@handlerMode manual` 配合 `@produces` 描述文本/文件等成功输出，详见 [迁移扩展](MIGRATION.md)。自定义回调错误协议仍使用上述 Go 入口，并由应用维护相应文档；生成器不会猜测自定义 Go 编码器的输出。如果在命名中间件里替换编码器，业务也必须同步维护文档。

 框架内置路由的 404/405 使用应用默认格式；它们不属于某个 `.api` 分组。TLS 握手、畸形 HTTP、连接级过载等发生在进入应用前，仍按网络层协议处理。自定义编码器失败、panic 或返回非法状态/204 body 时，最终返回空 500，避免递归编码或泄露另一种响应体。

--- a/app/body.go
+++ b/app/body.go
@@ -0,0 +1,32 @@
+package app
+
+import (
+	"git.yuntuo.hk/k2safe/go-omni/httpx"
+	"git.yuntuo.hk/k2safe/go-omni/response"
+	"net/http"
+)
+
+func (a *App) bodyHandler(maxBytes int64, encoder response.Encoder, handler httpx.Handler, middleware ...httpx.Middleware) http.Handler {
+	checked := httpx.LimitBody(maxBytes)(handler)
+	if encoder == nil {
+		encoder = a.responseEncoder
+	}
+	next := a.adaptResponse(encoder, checked, middleware...)
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Body != nil {
+			r = r.WithContext(r.Context())
+			r.Body = http.MaxBytesReader(w, r.Body, maxBytes)
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
+// HandleWithBodyLimit caps the reader before application middleware and preserves
+// the response policy, including auth failures and parameter errors.
+func (a *App) HandleWithBodyLimit(method, path string, maxBytes int64, encoder response.Encoder, handler httpx.Handler, middleware ...httpx.Middleware) {
+	a.router.Handle(method, path, a.bodyHandler(maxBytes, encoder, handler, middleware...))
+}
+func (g *RouterGroup) HandleWithBodyLimit(method, path string, maxBytes int64, encoder response.Encoder, handler httpx.Handler, middleware ...httpx.Middleware) {
+	combined := append(append([]httpx.Middleware{}, g.middlewares...), middleware...)
+	g.group.Handle(method, path, g.app.bodyHandler(maxBytes, encoder, handler, combined...))
+}
--- a/app/router.go
+++ b/app/router.go
@@ -31,6 +31,7 @@ func (a *App) adaptResponse(encoder response.Encoder, handler httpx.Handler, mid
 		}
 		requestContext := httpx.NewContext(request, writer, httpx.RouteParams(request.Context()))
 		requestContext.SetResponseEncoder(encoder)
+		defer func() { httpx.CleanupMultipart(requestContext.Request()) }()
 		if err := wrapped(requestContext); err != nil {
 			a.writeError(requestContext, err)
 		}
--- a/cmd/go-omni/README.md
+++ b/cmd/go-omni/README.md
@@ -75,8 +75,8 @@ Handler / Service / Repository / Model 与模块注册入口。模块名为 lowe
 从远程安装，生成一个带 Handler / Service / Repository / Model 分层的服务骨架：

 ```sh
-GOPRIVATE=git.yuntuo.hk go install git.yuntuo.hk/k2safe/go-omni/cmd/go-omni@v0.8.0-preview
-go-omni new --framework-version v0.8.0-preview --module example.com/billing ./billing
+GOPRIVATE=git.yuntuo.hk go install git.yuntuo.hk/k2safe/go-omni/cmd/go-omni@v0.9.0-preview
+go-omni new --framework-version v0.9.0-preview --module example.com/billing ./billing
 cd billing
 go mod tidy
 go run ./cmd/server
--- a/cmd/go-omni/apigen/compatibility_test.go
+++ b/cmd/go-omni/apigen/compatibility_test.go
@@ -0,0 +1,161 @@
+package apigen
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestCompatibilityContract(t *testing.T) {
+	s, err := Parse(filepath.Join(frameworkRoot(t), "examples/contracts/compatibility.api"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	c, err := Compile(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(s.Scalars) != 1 || len(s.Routes) != 6 {
+		t.Fatal("incomplete contract")
+	}
+	if !strings.Contains(string(c.Document), `"anyOf"`) || !strings.Contains(string(c.Document), `"multipart/form-data"`) {
+		t.Fatal("missing schemas")
+	}
+	for _, change := range [][2]string{{"jsonInput: string | int64", "jsonInput: mystery"}, {"text: true", "text: false"}, {"mode: multipart", "mode: invalid"}, {"maxBytes: 128", "maxBytes: 0"}, {"goType: ID", "goType: id"}, {"Data any", "Data interface{ Method() }"}} {
+		source := readFile(t, filepath.Join(frameworkRoot(t), "examples/contracts/compatibility.api"))
+		spec, err := parseText(t, strings.Replace(source, change[0], change[1], 1))
+		if err == nil {
+			_, err = Compile(spec)
+		}
+		if err == nil {
+			t.Fatalf("accepted %s", change[1])
+		}
+	}
+}
+func TestCompatibilityConsumer(t *testing.T) {
+	if os.Getenv("GO_OMNI_SCAFFOLD_INTEGRATION") == "" {
+		t.Skip("consumer integration")
+	}
+	root := frameworkRoot(t)
+	dir := filepath.Join(t.TempDir(), "consumer")
+	o := Options{API: filepath.Join(root, "examples/contracts/compatibility.api"), Dir: dir, Module: "example.com/compatibility", FrameworkDir: root}
+	releaseCLI := os.Getenv("GO_OMNI_RELEASE_CLI")
+	generate := func(check bool) {
+		t.Helper()
+		if releaseCLI == "" {
+			options := o
+			options.Check = check
+			if _, err := Generate(options); err != nil {
+				t.Fatal(err)
+			}
+			return
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+		defer cancel()
+		args := []string{"api", "generate", "--api", o.API, "--dir", dir, "--module", o.Module}
+		if check {
+			args = append(args, "--check")
+		}
+		cmd := exec.CommandContext(ctx, releaseCLI, args...)
+		cmd.Dir = filepath.Dir(dir)
+		if output, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("released CLI: %v\n%s", err, output)
+		}
+	}
+	generate(false)
+	files := map[string]string{
+		"internal/service/demo/echo.go":            "echo.go",
+		"internal/handler/demo/customBind.go":      "hooks.go",
+		"internal/handler/files/downloadManual.go": "download.go",
+		"consumer_test.go":                         "consumer_test.go",
+	}
+	// The fixture implements related methods together; remove only its generated
+	// one-time stubs, then fill every stub so regeneration can preserve all files.
+	for _, name := range []string{"internal/service/demo/item.go", "internal/service/demo/custom.go"} {
+		writeFile(t, filepath.Join(dir, name), "package demo\n")
+	}
+	for _, name := range []string{"internal/handler/demo/uploadManual.go", "internal/handler/demo/callbackManual.go"} {
+		writeFile(t, filepath.Join(dir, name), "package demo\n")
+	}
+	for target, source := range files {
+		writeFile(t, filepath.Join(dir, target), readFile(t, filepath.Join("testdata/compatibility", source)))
+	}
+	before := map[string]string{}
+	for target := range files {
+		before[target] = readFile(t, filepath.Join(dir, target))
+	}
+	generate(false)
+	for target, content := range before {
+		if readFile(t, filepath.Join(dir, target)) != content {
+			t.Fatalf("overwrote %s", target)
+		}
+	}
+	generate(true)
+	ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
+	defer cancel()
+	cmd := exec.CommandContext(ctx, "go", "test", "-mod=mod", "-race", "-count=1", "./...")
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(), "GOWORK=off")
+	if output, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("consumer: %v\n%s", err, output)
+	}
+	if releaseCLI != "" {
+		cmd = exec.CommandContext(ctx, "go", "list", "-m", "-json", frameworkModule)
+		cmd.Dir = dir
+		cmd.Env = append(os.Environ(), "GOWORK=off")
+		output, err := cmd.CombinedOutput()
+		if err != nil {
+			t.Fatalf("module: %v\n%s", err, output)
+		}
+		var module struct {
+			Version, Sum string
+			Replace      any
+		}
+		if err = json.Unmarshal(output, &module); err != nil {
+			t.Fatal(err)
+		}
+		if module.Version != os.Getenv("GO_OMNI_RELEASE_VERSION") || module.Replace != nil || module.Sum == "" {
+			t.Fatalf("not a fixed remote dependency: %+v", module)
+		}
+		t.Logf("remote framework %s checksum %s; no local replace", module.Version, module.Sum)
+	}
+
+}
+
+func TestNestedDynamicAliases(t *testing.T) {
+	source := readFile(t, filepath.Join(frameworkRoot(t), "examples/contracts/compatibility.api"))
+	for _, typ := range []string{"[]interface{}", "map[string]interface{}", "map[string][]interface{}"} {
+		s, err := parseText(t, strings.Replace(source, "Data any", "Data "+typ, 1))
+		if err == nil {
+			_, err = Compile(s)
+		}
+		if err != nil {
+			t.Fatalf("%s: %v", typ, err)
+		}
+	}
+}
+func TestSwitchFromManualRequiresExplicitMigration(t *testing.T) {
+	root := frameworkRoot(t)
+	o := Options{API: filepath.Join(root, "examples/contracts/compatibility.api"), Dir: filepath.Join(t.TempDir(), "consumer"), Module: "example.com/compatibility", FrameworkDir: root}
+	if _, err := Generate(o); err != nil {
+		t.Fatal(err)
+	}
+	// The hand-written source may contain business code. Never delete it to make
+	// the newly automatic handler compile; fail before touching generated files.
+	o.API = filepath.Join(o.Dir, "api/compatibility.api")
+	source := readFile(t, o.API)
+	source = strings.Replace(source, "@handlerMode manual\n @produces \"application/octet-stream\"", "", 1)
+	writeFile(t, o.API, source)
+	before := snapshot(t, o.Dir)
+	if _, err := Generate(o); err == nil || !strings.Contains(err.Error(), "migrate and remove") {
+		t.Fatalf("unsafe mode switch: %v", err)
+	}
+	if !sameFiles(before, snapshot(t, o.Dir)) {
+		t.Fatal("failed mode switch mutated project")
+	}
+}
--- a/cmd/go-omni/apigen/compile.go
+++ b/cmd/go-omni/apigen/compile.go
@@ -42,6 +42,9 @@ func Compile(spec *Spec) (*Compiled, error) {
 	}
 	definitions := map[string]Type{}
 	for _, t := range spec.Types {
+		if t.Name == "ContractScalars" && len(spec.Scalars) > 0 {
+			return nil, errors.New("ContractScalars is reserved when declaring scalars")
+		}
 		if !exportedName.MatchString(t.Name) {
 			return nil, fmt.Errorf("%s: type names must be UpperCamelCase", t.Position)
 		}
@@ -50,17 +53,24 @@ func Compile(spec *Spec) (*Compiled, error) {
 		}
 		definitions[t.Name] = t
 	}
+	scalarTypes, scalarDefs, err := compileScalars(spec, definitions)
+	if err != nil {
+		return nil, err
+	}
 	resolved := map[string]reflect.Type{}
 	resolving := map[string]bool{}
 	var resolve func(string, int) (reflect.Type, error)
 	var expression func(ast.Expr, int) (reflect.Type, error)
-	primitives := map[string]reflect.Type{"string": reflect.TypeOf(""), "bool": reflect.TypeOf(false), "int": reflect.TypeOf(int(0)), "int8": reflect.TypeOf(int8(0)), "int16": reflect.TypeOf(int16(0)), "int32": reflect.TypeOf(int32(0)), "int64": reflect.TypeOf(int64(0)), "uint": reflect.TypeOf(uint(0)), "uint8": reflect.TypeOf(uint8(0)), "uint16": reflect.TypeOf(uint16(0)), "uint32": reflect.TypeOf(uint32(0)), "uint64": reflect.TypeOf(uint64(0)), "float32": reflect.TypeOf(float32(0)), "float64": reflect.TypeOf(float64(0))}
+	primitives := map[string]reflect.Type{"any": reflect.TypeOf((*any)(nil)).Elem(), "string": reflect.TypeOf(""), "bool": reflect.TypeOf(false), "int": reflect.TypeOf(int(0)), "int8": reflect.TypeOf(int8(0)), "int16": reflect.TypeOf(int16(0)), "int32": reflect.TypeOf(int32(0)), "int64": reflect.TypeOf(int64(0)), "uint": reflect.TypeOf(uint(0)), "uint8": reflect.TypeOf(uint8(0)), "uint16": reflect.TypeOf(uint16(0)), "uint32": reflect.TypeOf(uint32(0)), "uint64": reflect.TypeOf(uint64(0)), "float32": reflect.TypeOf(float32(0)), "float64": reflect.TypeOf(float64(0))}
 	expression = func(e ast.Expr, depth int) (reflect.Type, error) {
 		if depth > 32 {
 			return nil, errors.New("type nesting exceeds 32")
 		}
 		switch e := e.(type) {
 		case *ast.Ident:
+			if t, ok := scalarTypes[e.Name]; ok {
+				return t, nil
+			}
 			if t, ok := primitives[e.Name]; ok {
 				return t, nil
 			}
@@ -140,7 +150,7 @@ func Compile(spec *Spec) (*Compiled, error) {
 		if err != nil {
 			return nil, err
 		}
-		b, err := contract.ForType(rt)
+		b, err := contract.Describe(rt, scalarDefs...)
 		if err != nil {
 			return nil, fmt.Errorf("%s: %w", t.Position, err)
 		}
@@ -217,12 +227,15 @@ func Compile(spec *Spec) (*Compiled, error) {
 		if r.Status != 200 && r.Status != 201 && r.Status != 202 && r.Status != 204 {
 			return nil, errors.New("@status supports 200, 201, 202 or 204")
 		}
-		if (r.Status == 204) != (r.Response == "") {
+		if !r.Manual && (r.Status == 204) != (r.Response == "") {
 			return nil, errors.New("204 requires no response; other success statuses require a response type")
 		}
 		if r.Method == "head" && r.Response != "" {
 			return nil, errors.New("HEAD must not declare a response body")
 		}
+		if err := validateRouteExtensions(r); err != nil {
+			return nil, fmt.Errorf("%s: %w", r.Position, err)
+		}
 		op := openapi.Operation{Method: r.Method, Path: r.Path, OperationID: operationID(r), Summary: r.Summary, Responses: map[int]openapi.Response{}}
 		if r.Request != "" {
 			b, ok := c.Bindings[r.Request]
@@ -231,6 +244,9 @@ func Compile(spec *Spec) (*Compiled, error) {
 			}
 			op.Parameters = b.Parameters()
 			op.Request = b.BodySchema()
+			if op.Request != nil && (r.BodyMode == "raw" || r.BodyMode == "multipart") {
+				return nil, errors.New("raw/multipart request DTOs may declare only path/form/header fields; body binding is manual")
+			}
 			if op.Request != nil && (r.Method == "get" || r.Method == "head") {
 				return nil, errors.New("GET/HEAD requests cannot declare JSON bodies; use form/path/header tags")
 			}
--- a/cmd/go-omni/apigen/contractMetadata.go
+++ b/cmd/go-omni/apigen/contractMetadata.go
@@ -140,6 +140,7 @@ func decorateDocument(doc map[string]any, spec *Spec) {
 			}
 		}
 		op := doc["paths"].(map[string]any)[strings.Join(parts, "/")].(map[string]any)[r.Method].(map[string]any)
+		decorateRequestOptions(op, r)
 		if r.ResponseFormat != "" {
 			op["x-omni-response"] = r.ResponseFormat
 		}
--- a/cmd/go-omni/apigen/generate.go
+++ b/cmd/go-omni/apigen/generate.go
@@ -19,7 +19,7 @@ import (
 )

 const frameworkModule = "git.yuntuo.hk/k2safe/go-omni"
-const minimumVersion = "v0.8.0-preview"
+const minimumVersion = "v0.9.0-preview"
 const generatedHeader = "// Code generated by go-omni api. DO NOT EDIT.\n"

 type Options struct {
@@ -94,6 +94,16 @@ func generate(o Options, c *Compiled, starter bool) (Output, error) {
 		return Output{}, err
 	}
 	o.Dir = directory
+	for _, r := range c.Spec.Routes {
+		if !r.Manual {
+			path := filepath.Join(directory, "internal/handler", r.Group, lower(r.Handler)+"Manual.go")
+			if _, err := os.Lstat(path); err == nil {
+				return Output{}, fmt.Errorf("manual handler %s exists; migrate and remove it explicitly before switching to automatic generation", path)
+			} else if !errors.Is(err, os.ErrNotExist) {
+				return Output{}, err
+			}
+		}
+	}
 	if err := resolveProfile(&o); err != nil {
 		return Output{}, err
 	}
@@ -130,13 +140,13 @@ func generate(o Options, c *Compiled, starter bool) (Output, error) {
 					if !filepath.IsAbs(path) {
 						path = filepath.Join(directory, path)
 					}
-					if _, err := os.Stat(filepath.Join(path, "httpx", "response.go")); err == nil {
+					if _, err := os.Stat(filepath.Join(path, "contract", "scalar.go")); err == nil {
 						localCurrent = true
 					}
 				}
 			}
 			if !localCurrent {
-				return Output{}, fmt.Errorf("existing framework dependency predates configurable responses; use %s or a current local replacement", minimumVersion)
+				return Output{}, fmt.Errorf("existing framework dependency predates migration extensions; use %s or a current local replacement", minimumVersion)
 			}
 		}
 		if o.FrameworkDir != "" {
@@ -309,6 +319,20 @@ func renderProject(o Options, c *Compiled, starter bool) (map[string][]byte, map
 		put(generated, "internal/apierrors/errorsGen.go", generatedHeader+content)
 	}
 	types := "package types\n\n"
+	if len(c.Spec.Scalars) > 0 {
+		types += "import("
+		for i, d := range c.Spec.Scalars {
+			types += fmt.Sprintf("scalar%d %q;", i, d.GoImport)
+		}
+		types += ")\n"
+		registry := fmt.Sprintf("package types\nimport %q\nfunc ContractScalars()[]contract.Scalar{return []contract.Scalar{", frameworkModule+"/contract")
+		for i, d := range c.Spec.Scalars {
+			types += fmt.Sprintf("type %s = scalar%d.%s\n", d.Name, i, d.GoType)
+			registry += fmt.Sprintf("contract.ScalarOf[%s](%q,%q,%t),", d.Name, d.JSONInput, d.JSONOutput, d.Text)
+		}
+		registry += "}}\n"
+		put(generated, "internal/types/scalarsGen.go", generatedHeader+registry)
+	}
 	for _, t := range c.Spec.Types {
 		types += "type " + t.Name + " struct {\n"
 		for _, f := range t.Fields {
@@ -331,6 +355,10 @@ func renderProject(o Options, c *Compiled, starter bool) (map[string][]byte, map
 	put(generated, "internal/handler/responseGen.go", generatedHeader+policySource)
 	imports := fmt.Sprintf("import (\"fmt\"; %q; %q; %q;", frameworkModule+"/httpx", frameworkModule+"/openapi", o.Module+"/internal/servicecontext")
 	routes := "func RegisterRoutes(router openapi.Registrar, deps *servicecontext.Context) error {\n if router==nil || deps==nil {return fmt.Errorf(\"router and dependencies required\")}\n"
+	if len(c.Spec.Scalars) > 0 {
+		imports += fmt.Sprintf("%q;%q;", frameworkModule+"/contract", o.Module+"/internal/types")
+		routes += "if err:=contract.ValidateScalars(types.ContractScalars()...);err!=nil{return err}\n"
+	}
 	middlewareSet := map[string]bool{}
 	for _, r := range c.Spec.Routes {
 		for _, m := range r.Middleware {
@@ -347,7 +375,7 @@ func renderProject(o Options, c *Compiled, starter bool) (map[string][]byte, map
 	}
 	for i, group := range c.Groups {
 		imports += fmt.Sprintf("h%d %q; s%d %q;", i, o.Module+"/internal/handler/"+group, i, o.Module+"/internal/service/"+group)
-		routes += fmt.Sprintf("h%d := h%d.New(s%d.New(deps))\n", i, i, i)
+		routes += fmt.Sprintf("h%d := h%d.New(s%d.New(deps),deps)\n", i, i, i)
 		groupRoutes := []Route{}
 		for _, r := range c.Spec.Routes {
 			if r.Group == group {
@@ -356,12 +384,16 @@ func renderProject(o Options, c *Compiled, starter bool) (map[string][]byte, map
 		}
 		packageName := filepath.Base(group)
 		text := "package " + packageName + "\nimport(\"context\"; \"fmt\";"
-		needsTypes, needsBinder := false, false
+		needsTypes, needsBinder, hasAutomatic := false, false, false
 		for _, r := range groupRoutes {
+			if r.Manual {
+				continue
+			}
+			hasAutomatic = true
 			needsTypes = needsTypes || r.Request != "" || r.Response != ""
-			needsBinder = needsBinder || r.Request != ""
+			needsBinder = needsBinder || (r.Request != "" && !r.CustomBinding)
 		}
-		text += fmt.Sprintf("%q;", frameworkModule+"/httpx")
+		text += fmt.Sprintf("%q;%q;", frameworkModule+"/httpx", o.Module+"/internal/servicecontext")
 		if needsTypes {
 			text += fmt.Sprintf("%q;", o.Module+"/internal/types")
 		}
@@ -371,18 +403,47 @@ func renderProject(o Options, c *Compiled, starter bool) (map[string][]byte, map
 		text += ")\n"
 		text += "type Service interface {\n"
 		for _, r := range groupRoutes {
-			text += signature(r) + "\n"
+			if !r.Manual {
+				text += signature(r) + "\n"
+			}
 		}
-		text += "}\ntype Handler struct {service Service}\nfunc New(s Service)*Handler {return &Handler{service:s}}\n"
+		text += "}\ntype Handler struct {service Service;deps *servicecontext.Context}\nfunc New(s Service,deps ...*servicecontext.Context)*Handler {h:=&Handler{service:s};if len(deps)>0{h.deps=deps[0]};return h}\n"
 		for _, r := range groupRoutes {
 			name := upper(r.Handler)
-			if r.Request != "" {
-				text += fmt.Sprintf("var %sRequest = contract.MustNew[types.%s]()\n", lower(r.Handler), r.Request)
+			// The response policy and body reader cap are installed before App middleware.
+			if r.MaxBodyBytes > 0 {
+				routes += fmt.Sprintf("httpx.HandleWithBodyLimit(router,%q,%q,%d,responseEncoder(%q,%t),h%d.%s", strings.ToUpper(r.Method), r.Path, r.MaxBodyBytes, responseName(r), r.ResponseFormat == "raw", i, name)
+			} else {
+				routes += fmt.Sprintf("httpx.HandleWithResponse(router,%q,%q,responseEncoder(%q,%t),h%d.%s", strings.ToUpper(r.Method), r.Path, responseName(r), r.ResponseFormat == "raw", i, name)
+			}
+			for _, m := range r.Middleware {
+				routes += fmt.Sprintf(",deps.Middlewares[%q]", m)
+			}
+			routes += ")\n"
+			if r.Manual {
+				put(seeds, "internal/handler/"+group+"/"+lower(r.Handler)+"Manual.go", fmt.Sprintf("package %s\nimport(%q;apierrors %q)\n// %s owns raw/multipart binding and response output. h.deps holds project dependencies.\n// This file is preserved on regeneration.\nfunc(h *Handler)%s(c *httpx.Context)error{return apierrors.New(501,\"NOT_IMPLEMENTED\",\"manual handler is not implemented\")}\n", packageName, frameworkModule+"/httpx", frameworkModule+"/errors", name, name))
+				continue
+			}
+			if r.Request != "" && !r.CustomBinding {
+				scalarArgs := ""
+				if len(c.Spec.Scalars) > 0 {
+					scalarArgs = "types.ContractScalars()..."
+				}
+				text += fmt.Sprintf("var %sRequest = contract.MustNew[types.%s](%s)\n", lower(r.Handler), r.Request, scalarArgs)
 			}
 			text += fmt.Sprintf("func(h *Handler) %s(c *httpx.Context)error {\n", name)
 			call := "c.Context()"
 			if r.Request != "" {
-				text += fmt.Sprintf("var req types.%s\nif err:=%sRequest.Bind(c.Request(),httpx.RouteParams(c.Context()),&req);err!=nil{return err}\n", r.Request, lower(r.Handler))
+				if r.CustomBinding {
+					text += fmt.Sprintf("var req types.%s\nif err:=h.bind%s(c,&req);err!=nil{return err}\n", r.Request, name)
+					put(seeds, "internal/handler/"+group+"/"+lower(r.Handler)+"Bind.go", fmt.Sprintf("package %s\nimport(%q;%q;apierrors %q)\n// bind%s is project-owned; repeated generation preserves it.\nfunc(h *Handler)bind%s(c *httpx.Context,req *types.%s)error{return apierrors.New(501,\"BINDING_NOT_IMPLEMENTED\",\"custom binding is not implemented\")}\n", packageName, frameworkModule+"/httpx", o.Module+"/internal/types", frameworkModule+"/errors", name, name, r.Request))
+				} else {
+					limit := ""
+					if r.MaxBodyBytes > 0 {
+						limit = fmt.Sprintf(",%d", r.MaxBodyBytes)
+					}
+					text += fmt.Sprintf("var req types.%s\nif err:=%sRequest.Bind(c.Request(),httpx.RouteParams(c.Context()),&req%s);err!=nil{return err}\n", r.Request, lower(r.Handler), limit)
+				}
 				call += ", &req"
 			}
 			if r.Response != "" {
@@ -392,11 +453,6 @@ func renderProject(o Options, c *Compiled, starter bool) (map[string][]byte, map
 			} else {
 				text += fmt.Sprintf("if err:=h.service.%s(%s);err!=nil{return err};return c.NoContent()\n}\n", name, call)
 			}
-			routes += fmt.Sprintf("httpx.HandleWithResponse(router,%q,%q,responseEncoder(%q,%t),h%d.%s", strings.ToUpper(r.Method), r.Path, responseName(r), r.ResponseFormat == "raw", i, name)
-			for _, m := range r.Middleware {
-				routes += fmt.Sprintf(",deps.Middlewares[%q]", m)
-			}
-			routes += ")\n"
 			service := fmt.Sprintf("package %s\nimport(\"context\"; apierrors %q;", packageName, frameworkModule+"/errors")
 			if r.Request != "" || r.Response != "" {
 				service += fmt.Sprintf("%q;", o.Module+"/internal/types")
@@ -417,6 +473,10 @@ func renderProject(o Options, c *Compiled, starter bool) (map[string][]byte, map
 			}
 			put(seeds, "internal/service/"+group+"/"+lower(r.Handler)+".go", service)
 		}
+		if !hasAutomatic {
+			text = strings.Replace(text, strconv.Quote(frameworkModule+"/httpx")+";", "", 1)
+			text = strings.Replace(text, "\"context\";", "", 1)
+		}
 		if !hasResponse(groupRoutes) {
 			text = strings.Replace(text, "\"fmt\";", "", 1)
 		}
@@ -464,7 +524,7 @@ func renderProject(o Options, c *Compiled, starter bool) (map[string][]byte, map
 }
 func hasResponse(routes []Route) bool {
 	for _, r := range routes {
-		if r.Response != "" {
+		if r.Response != "" && !r.Manual {
 			return true
 		}
 	}
--- a/cmd/go-omni/apigen/parse.go
+++ b/cmd/go-omni/apigen/parse.go
@@ -18,6 +18,7 @@ type Spec struct {
 	Errors                               []ErrorDefinition
 	Auth                                 []AuthDefinition
 	Responses                            []ResponseDefinition
+	Scalars                              []ScalarDefinition
 	Types                                []Type
 	Routes                               []Route
 	Sources                              map[string][]byte // relative to the entry API's directory
@@ -30,6 +31,9 @@ type Type struct {
 }
 type Field struct{ Name, Type, Tag string }
 type Route struct {
+	Manual, CustomBinding                                    bool
+	BodyMode, Produces                                       string
+	MaxBodyBytes                                             int64
 	Method, Path, Request, Response, Handler, Group, Summary string
 	Middleware                                               []string
 	Auth                                                     string
@@ -199,6 +203,10 @@ func (p *parser) parse() error {
 	syntaxSeen := false
 	for p.skip(); p.tokens[p.at].kind != scanner.EOF; p.skip() {
 		switch p.peek() {
+		case "scalar":
+			if err := p.parseScalar(); err != nil {
+				return err
+			}
 		case "syntax":
 			if syntaxSeen {
 				return p.err("duplicate syntax")
@@ -393,7 +401,15 @@ func (p *parser) parseType() error {
 		}
 		expression := ""
 		for p.peek() != "\n" && p.peek() != ";" && p.peek() != "}" && p.tokens[p.at].kind != scanner.RawString && p.tokens[p.at].kind != scanner.EOF {
-			expression += p.next().text
+			if p.peek() == "interface" {
+				p.next()
+				if p.expect("{") != nil || p.expect("}") != nil {
+					return p.err("only empty interface{} is supported; use any for dynamic JSON")
+				}
+				expression += "any"
+			} else {
+				expression += p.next().text
+			}
 		}
 		if expression == "" {
 			return p.err("field type required; embedded types are not supported")
@@ -453,6 +469,28 @@ func (p *parser) parseService(server map[string]string) error {
 			}
 			seen[annotation] = true
 			switch annotation {
+			case "handlerMode":
+				mode, err := p.ident()
+				if err != nil {
+					return err
+				}
+				if mode != "manual" {
+					return p.err("handlerMode must be manual")
+				}
+				route.Manual = true
+			case "binding":
+				mode, err := p.ident()
+				if err != nil {
+					return err
+				}
+				if mode != "custom" {
+					return p.err("binding must be custom")
+				}
+				route.CustomBinding = true
+			case "produces":
+				route.Produces, e = p.quoted()
+			case "body":
+				e = p.parseBody(&route)
 			case "handler":
 				route.Handler, e = p.ident()
 			case "doc":
@@ -512,7 +550,7 @@ func (p *parser) parseService(server map[string]string) error {
 		if p.peek() != "\n" && p.peek() != ";" && p.peek() != "}" {
 			return p.err("unexpected route suffix")
 		}
-		if route.Response == "" && !seen["status"] {
+		if route.Response == "" && !seen["status"] && !route.Manual {
 			route.Status = 204
 		}
 		p.spec.Routes = append(p.spec.Routes, route)
--- a/cmd/go-omni/apigen/requestOptions.go
+++ b/cmd/go-omni/apigen/requestOptions.go
@@ -0,0 +1,95 @@
+package apigen
+
+import (
+	"errors"
+	"fmt"
+	"git.yuntuo.hk/k2safe/go-omni/contract"
+	"mime"
+	"strconv"
+	"strings"
+)
+
+func (p *parser) parseBody(r *Route) error {
+	props, err := p.metadata()
+	if err != nil {
+		return err
+	}
+	for key, value := range props {
+		switch key {
+		case "mode":
+			r.BodyMode = value
+		case "maxBytes":
+			r.MaxBodyBytes, err = strconv.ParseInt(value, 10, 64)
+			if err != nil || r.MaxBodyBytes <= 0 || r.MaxBodyBytes > 1<<40 {
+				return p.err("maxBytes must be 1..1099511627776 bytes")
+			}
+		default:
+			return fmt.Errorf("unknown body property %s", key)
+		}
+	}
+	if r.MaxBodyBytes == 0 {
+		r.MaxBodyBytes = contract.DefaultMaxBodyBytes
+	}
+	return nil
+}
+func validateRouteExtensions(r Route) error {
+	if r.BodyMode != "" && r.BodyMode != "json" && r.BodyMode != "raw" && r.BodyMode != "multipart" {
+		return errors.New("body mode must be json, raw or multipart")
+	}
+	if (r.BodyMode == "raw" || r.BodyMode == "multipart") && !r.Manual {
+		return errors.New("raw/multipart body requires @handlerMode manual")
+	}
+	if r.CustomBinding && (r.Manual || r.Request == "") {
+		return errors.New("@binding custom requires an automatic handler with a request DTO")
+	}
+	if r.MaxBodyBytes > 0 && (r.Method == "get" || r.Method == "head") {
+		return errors.New("GET/HEAD cannot declare a body limit")
+	}
+	if r.Produces != "" {
+		if !r.Manual {
+			return errors.New("@produces requires @handlerMode manual")
+		}
+		media, params, err := mime.ParseMediaType(r.Produces)
+		if err != nil || len(params) != 0 || media != r.Produces || strings.Contains(media, "*") {
+			return errors.New("produces requires a concrete media type without parameters")
+		}
+		if r.Response != "" || r.Status == 204 || r.Method == "head" {
+			return errors.New("@produces uses a manual response without a DTO, 204 or HEAD")
+		}
+	}
+	if r.Manual && r.Status == 204 && r.Response != "" {
+		return errors.New("204 cannot declare a response")
+	}
+	return nil
+}
+
+func decorateRequestOptions(op map[string]any, r Route) {
+	if r.Manual {
+		op["x-omni-handler-mode"] = "manual"
+	}
+	if r.CustomBinding {
+		op["x-omni-binding"] = "custom"
+	}
+	if r.MaxBodyBytes > 0 {
+		op["x-omni-max-body-bytes"] = r.MaxBodyBytes
+	}
+	if r.BodyMode == "raw" || r.BodyMode == "multipart" {
+		media := "application/octet-stream"
+		schema := map[string]any{"type": "string", "format": "binary"}
+		if r.BodyMode == "multipart" {
+			media = "multipart/form-data"
+			schema = map[string]any{"type": "object", "additionalProperties": true}
+		}
+		op["requestBody"] = map[string]any{"required": true, "content": map[string]any{media: map[string]any{"schema": schema}}}
+	}
+	if r.Produces != "" {
+		schema := map[string]any{"type": "string"}
+		if r.Produces == "application/octet-stream" {
+			schema["format"] = "binary"
+		}
+		if r.Produces == "application/json" {
+			schema = map[string]any{}
+		}
+		op["responses"].(map[string]any)[strconv.Itoa(r.Status)] = map[string]any{"description": "Success", "content": map[string]any{r.Produces: map[string]any{"schema": schema}}}
+	}
+}
--- a/cmd/go-omni/apigen/scalar.go
+++ b/cmd/go-omni/apigen/scalar.go
@@ -0,0 +1,74 @@
+package apigen
+
+import (
+	"fmt"
+	"git.yuntuo.hk/k2safe/go-omni/contract"
+	"golang.org/x/mod/module"
+	"reflect"
+	"strings"
+)
+
+type ScalarDefinition struct {
+	Name, GoImport, GoType, JSONInput, JSONOutput, Position string
+	Text                                                    bool
+}
+
+func (p *parser) parseScalar() error {
+	pos := p.next().position
+	name, err := p.ident()
+	if err != nil {
+		return err
+	}
+	p.skip()
+	props, err := p.metadata()
+	if err != nil {
+		return err
+	}
+	d := ScalarDefinition{Name: name, Position: pos}
+	for key, value := range props {
+		switch key {
+		case "goImport":
+			d.GoImport = value
+		case "goType":
+			d.GoType = value
+		case "jsonInput":
+			d.JSONInput = value
+		case "jsonOutput":
+			d.JSONOutput = value
+		case "text":
+			if value != "true" && value != "false" {
+				return p.err("text must be true or false")
+			}
+			d.Text = value == "true"
+		default:
+			return fmt.Errorf("%s: unknown scalar property %s", pos, key)
+		}
+	}
+	p.spec.Scalars = append(p.spec.Scalars, d)
+	return nil
+}
+func compileScalars(spec *Spec, types map[string]Type) (map[string]reflect.Type, []contract.Scalar, error) {
+	out := map[string]reflect.Type{}
+	var defs []contract.Scalar
+	goTypes := map[string]bool{}
+	for _, d := range spec.Scalars {
+		key := d.GoImport + "." + d.GoType
+		if d.Name == "ContractScalars" || !exportedName.MatchString(d.Name) || !exportedName.MatchString(d.GoType) || out[d.Name] != nil || types[d.Name].Name != "" || goTypes[key] {
+			return nil, nil, fmt.Errorf("%s: scalar names and Go types must be unique; names must be UpperCamelCase", d.Position)
+		}
+		if err := module.CheckImportPath(d.GoImport); err != nil || strings.Contains(d.GoImport, "\\") {
+			return nil, nil, fmt.Errorf("%s: invalid scalar goImport", d.Position)
+		}
+		// Unique stand-in types allow CLI schema checks without executing project code.
+		t := reflect.StructOf([]reflect.StructField{{Name: d.Name, Type: reflect.TypeOf(false)}})
+		def := contract.Scalar{Type: t, JSONInput: d.JSONInput, JSONOutput: d.JSONOutput, Text: d.Text}
+		probe := reflect.StructOf([]reflect.StructField{{Name: "Value", Type: t, Tag: `json:"value"`}})
+		if _, err := contract.Describe(probe, def); err != nil {
+			return nil, nil, fmt.Errorf("%s: %w", d.Position, err)
+		}
+		out[d.Name] = t
+		defs = append(defs, def)
+		goTypes[key] = true
+	}
+	return out, defs, nil
+}
--- a/cmd/go-omni/apigen/testdata/compatibility/consumer_test.go
+++ b/cmd/go-omni/apigen/testdata/compatibility/consumer_test.go
@@ -0,0 +1,117 @@
+package compatibility_test
+
+import (
+	"bytes"
+	"context"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"example.com/compatibility/internal/handler"
+	"example.com/compatibility/internal/servicecontext"
+	omni "git.yuntuo.hk/k2safe/go-omni"
+	"git.yuntuo.hk/k2safe/go-omni/logx"
+	"io"
+	"mime/multipart"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestGeneratedCompatibility(t *testing.T) {
+	logger, err := logx.New(logx.Config{Writer: io.Discard})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer logger.Close()
+	deps, err := servicecontext.New(context.Background(), logger)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer deps.Close()
+	app := omni.New()
+	defer app.Close()
+	if err = handler.RegisterRoutes(app, deps); err != nil {
+		t.Fatal(err)
+	}
+	send := func(method, path, body, contentType string) *httptest.ResponseRecorder {
+		r := httptest.NewRequest(method, path, strings.NewReader(body))
+		r.Header.Set("Content-Type", contentType)
+		w := httptest.NewRecorder()
+		app.ServeHTTP(w, r)
+		return w
+	}
+	for _, id := range []string{`9223372036854775807`, `"9223372036854775807"`} {
+		w := send("POST", "/echo", `{"id":`+id+`,"data":{"n":9223372036854775807}}`, "application/json")
+		if w.Code != 200 || !strings.Contains(w.Body.String(), `"id":"9223372036854775807"`) || !strings.Contains(w.Body.String(), `"n":9223372036854775807`) {
+			t.Fatalf("scalar/dynamic: %d %s", w.Code, w.Body)
+		}
+	}
+	for _, body := range []string{`{"id":true,"data":null}`, `{"id":9223372036854775808,"data":null}`, `{"id":1,"data":{"x":1,"x":2}}`, `{"id":1,"data":null,"extra":1}`} {
+		if w := send("POST", "/echo", body, "application/json"); w.Code != 400 {
+			t.Fatalf("accepted %s: %d", body, w.Code)
+		}
+	}
+	payload := `{"id":1,"data":"` + strings.Repeat("x", (1<<20)+1) + `"}`
+	if w := send("POST", "/echo", payload, "application/json"); w.Code != 200 {
+		t.Fatalf("route limit not passed to Binder: %d", w.Code)
+	}
+	if w := send("POST", "/echo", `{"id":1,"data":"`+strings.Repeat("x", 2<<20)+`"}`, "application/json"); w.Code != 413 {
+		t.Fatalf("large JSON: %d", w.Code)
+	}
+	if w := send("GET", "/items/9223372036854775807", "", ""); w.Code != 200 || !strings.Contains(w.Body.String(), `"id":"9223372036854775807"`) {
+		t.Fatalf("text scalar: %d %s", w.Code, w.Body)
+	}
+	if w := send("POST", "/custom", `{"value":"hello"}`, "application/json"); w.Code != 200 || !strings.Contains(w.Body.String(), "HELLO") {
+		t.Fatalf("custom binder: %d %s", w.Code, w.Body)
+	}
+	raw := `{ "event": 1, "id": "original bytes" }`
+	mac := hmac.New(sha256.New, []byte("fixture-only-key"))
+	mac.Write([]byte(raw))
+	r := httptest.NewRequest("POST", "/callback", strings.NewReader(raw))
+	r.Header.Set("X-Signature", hex.EncodeToString(mac.Sum(nil)))
+	w := httptest.NewRecorder()
+	app.ServeHTTP(w, r)
+	if w.Code != 200 || w.Body.String() != "accepted" {
+		t.Fatalf("raw callback: %d %s", w.Code, w.Body)
+	}
+	r = httptest.NewRequest("POST", "/callback", strings.NewReader(strings.Repeat("x", 129)))
+	r.ContentLength = -1
+	w = httptest.NewRecorder()
+	app.ServeHTTP(w, r)
+	if w.Code != 413 {
+		t.Fatalf("chunked body limit: %d %s", w.Code, w.Body)
+	}
+	temp := t.TempDir()
+	t.Setenv("TMPDIR", temp)
+	var form bytes.Buffer
+	writer := multipart.NewWriter(&form)
+	part, err := writer.CreateFormFile("file", "sample.bin")
+	if err != nil {
+		t.Fatal(err)
+	}
+	part.Write(bytes.Repeat([]byte("x"), 8192))
+	writer.Close()
+	w = send("POST", "/upload", form.String(), writer.FormDataContentType())
+	if w.Code != 200 || !strings.Contains(w.Body.String(), `"bytes":8192`) {
+		t.Fatalf("upload: %d %s", w.Code, w.Body)
+	}
+	entries, err := os.ReadDir(temp)
+	if err != nil || len(entries) != 0 {
+		t.Fatalf("multipart temp files leaked: %v %v", entries, err)
+	}
+	w = send("GET", "/download", "", "")
+	if w.Code != 200 || w.Body.Len() != 128<<10 || w.Header().Get("Content-Disposition") == "" {
+		t.Fatalf("download wrapped: %d %d", w.Code, w.Body.Len())
+	}
+	var doc map[string]any
+	if err = json.Unmarshal([]byte(handler.OpenAPIDocument), &doc); err != nil {
+		t.Fatal(err)
+	}
+	paths := doc["paths"].(map[string]any)
+	media := paths["/download"].(map[string]any)["get"].(map[string]any)["responses"].(map[string]any)["200"].(map[string]any)["content"].(map[string]any)
+	if media["application/octet-stream"] == nil || media["application/json"] != nil {
+		t.Fatal("download schema is JSON")
+	}
+}
--- a/cmd/go-omni/apigen/testdata/compatibility/download.go
+++ b/cmd/go-omni/apigen/testdata/compatibility/download.go
@@ -0,0 +1,16 @@
+package files
+
+import (
+	"git.yuntuo.hk/k2safe/go-omni/httpx"
+	"io"
+	"net/http"
+	"strings"
+)
+
+func (h *Handler) Download(c *httpx.Context) error {
+	return httpx.WrapHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/octet-stream")
+		w.Header().Set("Content-Disposition", `attachment; filename="demo.bin"`)
+		_, _ = io.Copy(w, strings.NewReader(strings.Repeat("x", 128<<10)))
+	}))(c)
+}
--- a/cmd/go-omni/apigen/testdata/compatibility/echo.go
+++ b/cmd/go-omni/apigen/testdata/compatibility/echo.go
@@ -0,0 +1,16 @@
+package demo
+
+import (
+	"context"
+	"example.com/compatibility/internal/types"
+)
+
+func (s *Service) Echo(ctx context.Context, req *types.EchoReq) (*types.EchoResp, error) {
+	return &types.EchoResp{ID: req.ID, Data: req.Data}, nil
+}
+func (s *Service) Item(ctx context.Context, req *types.ItemReq) (*types.EchoResp, error) {
+	return &types.EchoResp{ID: req.ID, Data: map[string]any{"found": true}}, nil
+}
+func (s *Service) Custom(ctx context.Context, req *types.CustomReq) (*types.CustomResp, error) {
+	return &types.CustomResp{Value: req.Value}, nil
+}
--- a/cmd/go-omni/apigen/testdata/compatibility/hooks.go
+++ b/cmd/go-omni/apigen/testdata/compatibility/hooks.go
@@ -0,0 +1,58 @@
+package demo
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"example.com/compatibility/internal/types"
+	apierrors "git.yuntuo.hk/k2safe/go-omni/errors"
+	"git.yuntuo.hk/k2safe/go-omni/httpx"
+	"io"
+	"net/http"
+	"strings"
+)
+
+func (h *Handler) bindCustom(c *httpx.Context, req *types.CustomReq) error {
+	decoder := json.NewDecoder(c.Request().Body)
+	decoder.DisallowUnknownFields()
+	if err := decoder.Decode(req); err != nil {
+		return apierrors.BadRequest("INVALID_REQUEST", "invalid request").WithCause(err)
+	}
+	var extra any
+	if err := decoder.Decode(&extra); err != io.EOF {
+		return apierrors.BadRequest("INVALID_REQUEST", "one JSON value required").WithCause(err)
+	}
+	req.Value = strings.ToUpper(req.Value)
+	return nil
+}
+func (h *Handler) Upload(c *httpx.Context) error {
+	// The small memory threshold deliberately exercises disk spill and cleanup.
+	if err := c.Request().ParseMultipartForm(8); err != nil {
+		return err
+	}
+	file, _, err := c.Request().FormFile("file")
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	count, err := io.Copy(io.Discard, file)
+	if err != nil {
+		return err
+	}
+	return c.OK(map[string]any{"bytes": count})
+}
+func (h *Handler) Callback(c *httpx.Context) error {
+	raw, err := io.ReadAll(c.Request().Body)
+	if err != nil {
+		return err
+	}
+	// This fixed key belongs only to the test fixture. Applications inject secrets.
+	mac := hmac.New(sha256.New, []byte("fixture-only-key"))
+	mac.Write(raw)
+	signature, err := hex.DecodeString(c.Header("X-Signature"))
+	if err != nil || !hmac.Equal(signature, mac.Sum(nil)) {
+		return c.Text(http.StatusUnauthorized, "invalid signature")
+	}
+	return c.Text(http.StatusOK, "accepted")
+}
--- a/cmd/go-omni/apigen/write.go
+++ b/cmd/go-omni/apigen/write.go
@@ -252,7 +252,7 @@ func apply(root, module, entry string, generated, seeds map[string][]byte, check
 }
 func digest(data []byte) string { sum := sha256.Sum256(data); return hex.EncodeToString(sum[:]) }
 func ownedPath(name string) bool {
-	if name == "internal/handler/responseGen.go" {
+	if name == "internal/handler/responseGen.go" || name == "internal/types/scalarsGen.go" {
 		return true
 	}
 	if name == "internal/apierrors/errorsGen.go" || name == "docs/openapi.json" || name == "internal/types/typesGen.go" || name == "internal/handler/routesGen.go" || name == "internal/handler/openapiGen.go" || name == "internal/middleware/registryGen.go" {
--- a/cmd/go-omni/scaffold/version.go
+++ b/cmd/go-omni/scaffold/version.go
@@ -10,7 +10,7 @@ const frameworkModule = "git.yuntuo.hk/k2safe/go-omni"
 // Source builds can carry an unpublished VCS version (including +dirty).
 // Keep this fallback in sync with the next release; installed CLIs use their
 // downloaded module version, which also has a module checksum.
-const defaultFrameworkVersion = "v0.8.0-preview"
+const defaultFrameworkVersion = "v0.9.0-preview"

 // This target is not a claim that the release already exists. Source users
 // select a local framework checkout until the module templates are published.
--- a/contract/bind.go
+++ b/contract/bind.go
@@ -19,7 +19,7 @@ import (
 // strictly decoded, and limited to 1 MiB unless maxBytes is supplied. Query
 // parameters never overwrite path/body/header values. form means URL query only.
 func (b *Binder) Bind(r *http.Request, params map[string]string, target any, maxBytes ...int64) error {
-	if b == nil || r == nil {
+	if b == nil || r == nil || b.schemaOnly {
 		return apierrors.Internal(errors.New("contract: nil binder or request"))
 	}
 	v := reflect.ValueOf(target)
@@ -65,6 +65,10 @@ func (b *Binder) Bind(r *http.Request, params map[string]string, target any, max
 			return tooLarge()
 		}
 		if err != io.EOF {
+			var maxErr *http.MaxBytesError
+			if errors.As(err, &maxErr) {
+				return tooLarge()
+			}
 			return invalid(errors.New("exactly one JSON value required"))
 		}
 		var ok bool
@@ -126,10 +130,16 @@ func tooLarge() error { return apierrors.New(413, "BODY_TOO_LARGE", "request bod

 func fromStrings(n *node, values []string) (any, error) {
 	n = base(n)
+	if n.scalar != nil {
+		if len(values) != 1 {
+			return nil, errors.New("duplicate scalar parameter")
+		}
+		return scalarText(values[0]), nil
+	}
 	if n.typ.Kind() == reflect.Slice {
 		out := make([]any, 0, len(values))
 		for _, s := range values {
-			v, err := parseScalar(s, base(n.elem).typ)
+			v, err := fromStrings(n.elem, []string{s})
 			if err != nil {
 				return nil, err
 			}
@@ -158,6 +168,17 @@ func assignField(f field, dst reflect.Value, value any, present bool) error {
 	return checkField(f, dst)
 }
 func setValue(n *node, dst reflect.Value, value any) error {
+	if n.scalar != nil {
+		return n.scalar.decode(dst, value)
+	}
+	if n.typ.Kind() == reflect.Interface && n.typ.NumMethod() == 0 {
+		if value == nil {
+			dst.SetZero()
+		} else {
+			dst.Set(reflect.ValueOf(value))
+		}
+		return nil
+	}
 	if value == nil {
 		if n.typ.Kind() == reflect.Pointer {
 			dst.SetZero()
--- a/contract/contract.go
+++ b/contract/contract.go
@@ -23,10 +23,12 @@ var valuesValidator = validator.New()

 // Binder is immutable after compilation and safe for concurrent requests.
 type Binder struct {
-	root *node
-	typ  reflect.Type
+	root       *node
+	typ        reflect.Type
+	schemaOnly bool
 }
 type node struct {
+	scalar *Scalar
 	typ    reflect.Type
 	schema *openapi.Schema
 	fields []field
@@ -42,9 +44,11 @@ type field struct {
 	binding      string
 }

-func New[T any]() (*Binder, error) { return ForType(reflect.TypeOf((*T)(nil)).Elem()) }
-func MustNew[T any]() *Binder {
-	b, err := New[T]()
+func New[T any](scalars ...Scalar) (*Binder, error) {
+	return ForType(reflect.TypeOf((*T)(nil)).Elem(), scalars...)
+}
+func MustNew[T any](scalars ...Scalar) *Binder {
+	b, err := New[T](scalars...)
 	if err != nil {
 		panic(err)
 	}
@@ -52,20 +56,36 @@ func MustNew[T any]() *Binder {
 }

 // ForType also lets generators check the exact runtime contract before writing files.
-// The root must be a struct; recursive and custom-marshaling types are rejected.
-func ForType(t reflect.Type) (*Binder, error) {
+// The root must be a struct; custom marshalers require explicit scalar registration.
+func ForType(t reflect.Type, scalars ...Scalar) (*Binder, error) { return build(t, false, scalars) }
+
+// Describe compiles schemas without loading or executing application Go types.
+// The returned Binder cannot bind requests; it is for generators only.
+func Describe(t reflect.Type, scalars ...Scalar) (*Binder, error) { return build(t, true, scalars) }
+
+func build(t reflect.Type, schemaOnly bool, scalars []Scalar) (*Binder, error) {
 	if t == nil || t.Kind() != reflect.Struct {
 		return nil, errors.New("contract: root must be a struct")
 	}
+	c := compiler{scalars: map[reflect.Type]Scalar{}}
+	for _, scalar := range scalars {
+		if err := scalar.validate(schemaOnly); err != nil {
+			return nil, err
+		}
+		if _, exists := c.scalars[scalar.Type]; exists {
+			return nil, fmt.Errorf("contract: duplicate scalar type %s", scalar.Type)
+		}
+		c.scalars[scalar.Type] = scalar
+	}
 	budget := 10000
-	n, err := compile(t, true, map[reflect.Type]bool{}, 0, &budget)
+	n, err := c.compile(t, true, map[reflect.Type]bool{}, 0, &budget)
 	if err != nil {
 		return nil, err
 	}
-	return &Binder{root: n, typ: t}, nil
+	return &Binder{root: n, typ: t, schemaOnly: schemaOnly}, nil
 }

-func compile(t reflect.Type, root bool, stack map[reflect.Type]bool, depth int, budget *int) (*node, error) {
+func (c compiler) compile(t reflect.Type, root bool, stack map[reflect.Type]bool, depth int, budget *int) (*node, error) {
 	*budget--
 	if *budget < 0 {
 		return nil, errors.New("contract: schema expansion exceeds 10000 nodes")
@@ -79,21 +99,32 @@ func compile(t reflect.Type, root bool, stack map[reflect.Type]bool, depth int,
 	stack[t] = true
 	defer delete(stack, t)
 	n := &node{typ: t, schema: &openapi.Schema{}}
+	if scalar, ok := c.scalars[t]; ok {
+		if root {
+			return nil, errors.New("contract: root cannot be a scalar")
+		}
+		n.scalar = &scalar
+		n.schema = scalar.inputSchema()
+		return n, nil
+	}
 	// Wire behavior must be described completely by these tags.
 	marshaler := reflect.TypeOf((*json.Marshaler)(nil)).Elem()
 	unmarshaler := reflect.TypeOf((*json.Unmarshaler)(nil)).Elem()
-	if t.Implements(marshaler) || reflect.PointerTo(t).Implements(marshaler) || t.Implements(unmarshaler) || reflect.PointerTo(t).Implements(unmarshaler) {
-		return nil, errors.New("contract: custom JSON marshalers are unsupported")
+	if t.Kind() != reflect.Pointer && (t.Implements(marshaler) || reflect.PointerTo(t).Implements(marshaler) || t.Implements(unmarshaler) || reflect.PointerTo(t).Implements(unmarshaler)) {
+		return nil, errors.New("contract: custom JSON marshalers require explicit Scalar registration")
 	}
 	switch t.Kind() {
+	case reflect.Interface:
+		if t.NumMethod() != 0 {
+			return nil, errors.New("contract: only any / interface{} is supported")
+		}
 	case reflect.Pointer:
-		e, err := compile(t.Elem(), false, stack, depth+1, budget)
+		e, err := c.compile(t.Elem(), false, stack, depth+1, budget)
 		if err != nil {
 			return nil, err
 		}
 		n.elem = e
-		*n.schema = *e.schema
-		n.schema.Nullable = true
+		n.schema = nullableSchema(e.schema)
 	case reflect.String:
 		n.schema.Type = "string"
 	case reflect.Bool:
@@ -132,10 +163,10 @@ func compile(t reflect.Type, root bool, stack map[reflect.Type]bool, depth int,
 		if t.Kind() == reflect.Map && t.Key().Kind() != reflect.String {
 			return nil, errors.New("contract: map keys must be strings")
 		}
-		if t.Kind() == reflect.Slice && t.Elem().Kind() == reflect.Uint8 {
+		if t.Kind() == reflect.Slice && t.Elem().Kind() == reflect.Uint8 && c.scalars[t.Elem()].Type == nil {
 			return nil, errors.New("contract: byte slices use base64 in Go; use string for binary data")
 		}
-		e, err := compile(t.Elem(), false, stack, depth+1, budget)
+		e, err := c.compile(t.Elem(), false, stack, depth+1, budget)
 		if err != nil {
 			return nil, err
 		}
@@ -158,7 +189,7 @@ func compile(t reflect.Type, root bool, stack map[reflect.Type]bool, depth int,
 			if sf.PkgPath != "" || sf.Anonymous {
 				return nil, fmt.Errorf("contract: %s must be an exported named field", sf.Name)
 			}
-			f, err := compileField(sf, root, stack, depth+1, budget)
+			f, err := c.compileField(sf, root, stack, depth+1, budget)
 			if err != nil {
 				return nil, fmt.Errorf("contract: %s: %w", sf.Name, err)
 			}
@@ -182,7 +213,7 @@ func compile(t reflect.Type, root bool, stack map[reflect.Type]bool, depth int,
 	return n, nil
 }

-func compileField(sf reflect.StructField, root bool, stack map[reflect.Type]bool, depth int, budget *int) (field, error) {
+func (c compiler) compileField(sf reflect.StructField, root bool, stack map[reflect.Type]bool, depth int, budget *int) (field, error) {
 	f := field{}
 	// Reject typos and unsupported tags instead of silently losing validation.
 	tags, err := ParseTags(string(sf.Tag))
@@ -218,11 +249,37 @@ func compileField(sf reflect.StructField, root bool, stack map[reflect.Type]bool
 	if (f.source == "header" && !headerName.MatchString(f.name)) || (f.source != "header" && !wireName.MatchString(f.name)) {
 		return f, errors.New("wire names must be lowerCamelCase (headers use HTTP names)")
 	}
-	n, err := compile(sf.Type, false, stack, depth, budget)
+	n, err := c.compile(sf.Type, false, stack, depth, budget)
 	if err != nil {
 		return f, err
 	}
 	f.value = n
+	opaque := base(n).scalar
+	isList := base(n).typ.Kind() == reflect.Slice && opaque == nil
+	if isList {
+		opaque = base(base(n).elem).scalar
+	}
+	if opaque != nil {
+		if isList && (f.source == "path" || f.source == "header") {
+			return f, errors.New("path/header values must be scalars")
+		}
+		if f.source != "json" && !opaque.Text {
+			return f, errors.New("custom scalar needs text: true and UnmarshalText for path/query/header")
+		}
+		if f.binding != "" {
+			return f, errors.New("custom scalar constraints belong in its decoder; use optional/pointer for presence and null")
+		}
+		for _, option := range parts[1:] {
+			if option != "optional" && option != "omitempty" {
+				return f, errors.New("custom scalar supports only optional/omitempty field options")
+			}
+			f.optional = true
+		}
+		if f.source == "path" && (f.optional || sf.Type.Kind() == reflect.Pointer) {
+			return f, errors.New("path fields must be required non-pointer values")
+		}
+		return f, nil
+	}
 	scalar := base(n).typ.Kind()
 	if f.source != "json" && !isScalar(scalar) && !(scalar == reflect.Slice && isScalar(base(base(n).elem).typ.Kind())) {
 		return f, errors.New("path/query/header values must be scalars or scalar slices")
@@ -370,7 +427,7 @@ func (b *Binder) ResponseSchema() (*openapi.Schema, error) {
 			return nil, errors.New("contract: response fields must use json tags")
 		}
 	}
-	return copySchema(b.root.schema), nil
+	return responseSchema(b.root), nil
 }
 func (b *Binder) Parameters() []openapi.Parameter {
 	var out []openapi.Parameter
@@ -382,7 +439,13 @@ func (b *Binder) Parameters() []openapi.Parameter {
 		if in == "form" {
 			in = "query"
 		}
-		out = append(out, openapi.Parameter{Name: f.name, In: in, Required: !f.optional && !f.hasDefault, Schema: copySchema(f.value.schema)})
+		schema := copySchema(f.value.schema)
+		if base(f.value).scalar != nil {
+			schema = &openapi.Schema{Type: "string"}
+		} else if base(f.value).typ.Kind() == reflect.Slice && base(base(f.value).elem).scalar != nil {
+			schema.Items = &openapi.Schema{Type: "string"}
+		}
+		out = append(out, openapi.Parameter{Name: f.name, In: in, Required: !f.optional && !f.hasDefault, Schema: schema})
 	}
 	return out
 }
--- a/contract/scalar.go
+++ b/contract/scalar.go
@@ -0,0 +1,199 @@
+package contract
+
+import (
+	"encoding"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+
+	"git.yuntuo.hk/k2safe/go-omni/openapi"
+)
+
+// Scalar explicitly opts one application Go type into custom wire conversion.
+// Input is a | separated union of scalar wire types; Output is one wire type.
+// The value must implement json.Marshaler, its pointer json.Unmarshaler, and
+// Text=true additionally requires encoding.TextUnmarshaler on the pointer.
+// No process-global registry or mutation of other binders is involved.
+type Scalar struct {
+	Type                  reflect.Type
+	JSONInput, JSONOutput string
+	Text                  bool
+}
+
+func ScalarOf[T any](input, output string, text bool) Scalar {
+	return Scalar{Type: reflect.TypeOf((*T)(nil)).Elem(), JSONInput: input, JSONOutput: output, Text: text}
+}
+
+type compiler struct {
+	scalars map[reflect.Type]Scalar
+}
+type scalarText string
+
+func (s Scalar) validate(schemaOnly bool) error {
+	if s.Type == nil || s.Type.Kind() == reflect.Pointer || s.Type.Kind() == reflect.Interface {
+		return errors.New("contract: scalar requires a concrete non-pointer type")
+	}
+	seen := map[string]bool{}
+	for _, kind := range strings.Split(s.JSONInput, "|") {
+		kind = strings.TrimSpace(kind)
+		if wireSchema(kind) == nil || seen[kind] {
+			return fmt.Errorf("contract: invalid/duplicate scalar input %q", kind)
+		}
+		seen[kind] = true
+	}
+	if wireSchema(s.JSONOutput) == nil {
+		return fmt.Errorf("contract: invalid scalar output %q", s.JSONOutput)
+	}
+	if !schemaOnly {
+		if !s.Type.Implements(reflect.TypeOf((*json.Marshaler)(nil)).Elem()) || !reflect.PointerTo(s.Type).Implements(reflect.TypeOf((*json.Unmarshaler)(nil)).Elem()) {
+			return fmt.Errorf("contract: %s needs value MarshalJSON and pointer UnmarshalJSON", s.Type)
+		}
+		if s.Text && !reflect.PointerTo(s.Type).Implements(reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()) {
+			return fmt.Errorf("contract: %s needs UnmarshalText", s.Type)
+		}
+	}
+	return nil
+}
+func wireSchema(kind string) *openapi.Schema {
+	switch kind {
+	case "string":
+		return &openapi.Schema{Type: "string"}
+	case "bool":
+		return &openapi.Schema{Type: "boolean"}
+	case "int32", "int64":
+		return &openapi.Schema{Type: "integer", Format: kind}
+	case "float64":
+		return &openapi.Schema{Type: "number", Format: "double"}
+	}
+	return nil
+}
+func (s Scalar) inputSchema() *openapi.Schema {
+	var alternatives []*openapi.Schema
+	for _, kind := range strings.Split(s.JSONInput, "|") {
+		alternatives = append(alternatives, wireSchema(strings.TrimSpace(kind)))
+	}
+	if len(alternatives) == 1 {
+		return alternatives[0]
+	}
+	return &openapi.Schema{AnyOf: alternatives}
+}
+func (s Scalar) decode(dst reflect.Value, value any) (err error) {
+	// User decoders may fail; do not allow their panic to escape a binder.
+	defer func() {
+		if r := recover(); r != nil {
+			err = errors.New("custom scalar decoder panicked")
+		}
+	}()
+	if text, ok := value.(scalarText); ok {
+		decoder, ok := dst.Addr().Interface().(encoding.TextUnmarshaler)
+		if !s.Text || !ok {
+			return errors.New("text decoder not available")
+		}
+		return decoder.UnmarshalText([]byte(text))
+	}
+	allowed := false
+	for _, kind := range strings.Split(s.JSONInput, "|") {
+		if scalarAccepts(strings.TrimSpace(kind), value) {
+			allowed = true
+			break
+		}
+	}
+	if !allowed {
+		return errors.New("value does not match declared scalar input")
+	}
+	decoder, ok := dst.Addr().Interface().(json.Unmarshaler)
+	if !ok {
+		return errors.New("JSON decoder not available")
+	}
+	raw, err := json.Marshal(value) // json.Number preserves exact integer tokens.
+	if err != nil {
+		return err
+	}
+	return decoder.UnmarshalJSON(raw)
+}
+func scalarAccepts(kind string, value any) bool {
+	switch kind {
+	case "string":
+		_, ok := value.(string)
+		return ok
+	case "bool":
+		_, ok := value.(bool)
+		return ok
+	case "int32", "int64":
+		n, ok := value.(json.Number)
+		if !ok {
+			return false
+		}
+		bits := 64
+		if kind == "int32" {
+			bits = 32
+		}
+		_, err := strconv.ParseInt(string(n), 10, bits)
+		return err == nil
+	case "float64":
+		n, ok := value.(json.Number)
+		if !ok {
+			return false
+		}
+		_, err := strconv.ParseFloat(string(n), 64)
+		return err == nil
+	}
+	return false
+}
+func responseSchema(n *node) *openapi.Schema {
+	b := base(n)
+	if b.scalar != nil {
+		s := wireSchema(b.scalar.JSONOutput)
+		if n.typ.Kind() == reflect.Pointer {
+			s = nullableSchema(s)
+		}
+		return s
+	}
+	// Preserve the field's own constraints (including pointer range/enum and
+	// collection length) while changing only nested custom scalar wire types.
+	s := copySchema(n.schema)
+	if b.typ.Kind() == reflect.Slice {
+		s.Items = responseSchema(b.elem)
+	}
+	if b.typ.Kind() == reflect.Map {
+		s.AdditionalProperties = responseSchema(b.elem)
+	}
+	for _, f := range b.fields {
+		if f.source == "json" {
+			s.Properties[f.name] = responseSchema(f.value)
+		}
+	}
+	return s
+}
+
+// ValidateScalars checks the application's explicitly registered method contracts.
+func ValidateScalars(scalars ...Scalar) error {
+	seen := map[reflect.Type]bool{}
+	for _, s := range scalars {
+		if err := s.validate(false); err != nil {
+			return err
+		}
+		if seen[s.Type] {
+			return fmt.Errorf("contract: duplicate scalar type %s", s.Type)
+		}
+		seen[s.Type] = true
+	}
+	return nil
+}
+
+// OpenAPI 3.0 nullable only applies alongside an explicit type. A union needs
+// an explicit null alternative; an unconstrained dynamic schema already accepts null.
+func nullableSchema(schema *openapi.Schema) *openapi.Schema {
+	s := copySchema(schema)
+	if s.Type != "" {
+		s.Nullable = true
+		return s
+	}
+	if len(s.AnyOf) > 0 {
+		s.AnyOf = append(s.AnyOf, &openapi.Schema{Type: "string", Nullable: true, Enum: []any{nil}})
+	}
+	return s
+}
--- a/contract/scalar_test.go
+++ b/contract/scalar_test.go
@@ -0,0 +1,222 @@
+package contract
+
+import (
+	"encoding/json"
+	apierrors "git.yuntuo.hk/k2safe/go-omni/errors"
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+type flexibleID int64
+
+func (v flexibleID) MarshalJSON() ([]byte, error) {
+	return json.Marshal(strconv.FormatInt(int64(v), 10))
+}
+func (v *flexibleID) UnmarshalJSON(b []byte) error {
+	var s string
+	if len(b) > 0 && b[0] == '"' {
+		if err := json.Unmarshal(b, &s); err != nil {
+			return err
+		}
+	} else {
+		s = string(b)
+	}
+	return v.UnmarshalText([]byte(s))
+}
+func (v *flexibleID) UnmarshalText(b []byte) error {
+	n, err := strconv.ParseInt(string(b), 10, 64)
+	if err == nil {
+		*v = flexibleID(n)
+	}
+	return err
+}
+func TestDynamicJSONAndCustomScalars(t *testing.T) {
+	type request struct {
+		ID      flexibleID   `json:"id"`
+		Dynamic any          `json:"dynamic"`
+		IDs     []flexibleID `json:"ids,optional"`
+	}
+	scalar := ScalarOf[flexibleID]("string|int64", "string", true)
+	b, err := New[request](scalar)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, id := range []string{`"9223372036854775807"`, `9223372036854775807`} {
+		r := httptest.NewRequest("POST", "/", strings.NewReader(`{"id":`+id+`,"dynamic":{"n":9223372036854775807},"ids":["1",2]}`))
+		r.Header.Set("Content-Type", "application/json")
+		var req request
+		if err = b.Bind(r, nil, &req); err != nil {
+			t.Fatal(err)
+		}
+		if req.ID != flexibleID(9223372036854775807) || req.Dynamic.(map[string]any)["n"] != json.Number("9223372036854775807") {
+			t.Fatalf("precision: %+v", req)
+		}
+		encoded, _ := json.Marshal(req)
+		if !strings.Contains(string(encoded), `"id":"9223372036854775807"`) {
+			t.Fatal(string(encoded))
+		}
+	}
+	for _, body := range []string{`{"id":true,"dynamic":null}`, `{"id":1.1,"dynamic":null}`, `{"id":9223372036854775808,"dynamic":null}`, `{"id":1,"dynamic":{"x":1,"x":2}}`, `{"id":1,"dynamic":null,"unexpected":1}`} {
+		r := httptest.NewRequest("POST", "/", strings.NewReader(body))
+		r.Header.Set("Content-Type", "application/json")
+		req := request{ID: 7}
+		if b.Bind(r, nil, &req) == nil || req.ID != 7 {
+			t.Fatalf("accepted or mutated %s", body)
+		}
+	}
+	for _, value := range []string{`null`, `[1,"x"]`, `false`, `"text"`} {
+		r := httptest.NewRequest("POST", "/", strings.NewReader(`{"id":1,"dynamic":`+value+`}`))
+		r.Header.Set("Content-Type", "application/json")
+		if err := b.Bind(r, nil, &request{}); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if _, err := New[request](); err == nil {
+		t.Fatal("implicit custom type registration")
+	}
+	response, err := b.ResponseSchema()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if response.Properties["id"].Type != "string" || response.Properties["ids"].Items.Type != "string" || len(b.BodySchema().Properties["id"].AnyOf) != 2 {
+		t.Fatal("input/output schemas conflated")
+	}
+	type path struct {
+		ID flexibleID `path:"id"`
+	}
+	p, err := New[path](scalar)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var req path
+	if err := p.Bind(httptest.NewRequest("GET", "/", nil), map[string]string{"id": "9223372036854775807"}, &req); err != nil {
+		t.Fatal(err)
+	}
+	if p.Parameters()[0].Schema.Type != "string" {
+		t.Fatal("text parameters need text schema")
+	}
+	if _, err := New[path](ScalarOf[flexibleID]("string|int64", "string", false)); err == nil {
+		t.Fatal("text support not explicit")
+	}
+	schemaOnly, err := Describe(reflect.TypeOf(request{}), scalar)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if schemaOnly.Bind(httptest.NewRequest("POST", "/", nil), nil, &request{}) == nil {
+		t.Fatal("schema-only binder executed")
+	}
+}
+
+func TestScalarPointersCollectionsAndRegistration(t *testing.T) {
+	scalar := ScalarOf[flexibleID]("string|int64", "string", true)
+	type nullable struct {
+		ID     *flexibleID            `json:"id,optional"`
+		Values map[string]*flexibleID `json:"values,optional"`
+	}
+	b, err := New[nullable](scalar)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, body := range []string{`{}`, `{"id":null}`, `{"id":1,"values":{"a":"2","b":null}}`} {
+		r := httptest.NewRequest("POST", "/", strings.NewReader(body))
+		r.Header.Set("Content-Type", "application/json")
+		if err := b.Bind(r, nil, &nullable{}); err != nil {
+			t.Fatal(err)
+		}
+	}
+	input := b.BodySchema().Properties["id"]
+	if len(input.AnyOf) != 3 || !input.AnyOf[2].Nullable || len(input.AnyOf[2].Enum) != 1 || input.AnyOf[2].Enum[0] != nil {
+		t.Fatal("nullable input union does not describe null")
+	}
+	out, err := b.ResponseSchema()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out.Properties["id"].Type != "string" || !out.Properties["id"].Nullable {
+		t.Fatal("nullable output type")
+	}
+	type query struct {
+		IDs []flexibleID `form:"ids"`
+	}
+	q, err := New[query](scalar)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var req query
+	if err := q.Bind(httptest.NewRequest("GET", "/?ids=1&ids=2", nil), nil, &req); err != nil || !reflect.DeepEqual(req.IDs, []flexibleID{1, 2}) {
+		t.Fatalf("query scalar collection: %+v %v", req, err)
+	}
+	if q.Parameters()[0].Schema.Items.Type != "string" {
+		t.Fatal("text array schema")
+	}
+	if _, err := New[query](ScalarOf[flexibleID]("string|int64", "string", false)); err == nil {
+		t.Fatal("array bypassed text declaration")
+	}
+	if err := ValidateScalars(ScalarOf[int64]("int64", "string", true)); err == nil {
+		t.Fatal("missing methods accepted")
+	}
+	if err := ValidateScalars(scalar, scalar); err == nil {
+		t.Fatal("duplicate registration")
+	}
+	type strict struct {
+		ID int64 `json:"id"`
+	}
+	strictBinder := MustNew[strict]()
+	r := httptest.NewRequest("POST", "/", strings.NewReader(`{"id":"1"}`))
+	r.Header.Set("Content-Type", "application/json")
+	if strictBinder.Bind(r, nil, &strict{}) == nil {
+		t.Fatal("other binder globally loosened")
+	}
+}
+
+type panicScalar string
+
+func (v panicScalar) MarshalJSON() ([]byte, error) { return json.Marshal(string(v)) }
+func (v *panicScalar) UnmarshalJSON([]byte) error  { panic("decoder failure") }
+func TestScalarPanicIsBindingError(t *testing.T) {
+	type req struct {
+		Value panicScalar `json:"value"`
+	}
+	b := MustNew[req](ScalarOf[panicScalar]("string", "string", false))
+	r := httptest.NewRequest("POST", "/", strings.NewReader(`{"value":"bad"}`))
+	r.Header.Set("Content-Type", "application/json")
+	dst := req{Value: "original"}
+	if err := b.Bind(r, nil, &dst); err == nil || dst.Value != "original" {
+		t.Fatalf("decoder panic: %+v %v", dst, err)
+	}
+}
+
+func TestLimitedJSONTrailingWhitespace(t *testing.T) {
+	type req struct {
+		Value any `json:"value"`
+	}
+	b := MustNew[req]()
+	r := httptest.NewRequest("POST", "/", strings.NewReader(`{"value":null}`+strings.Repeat(" ", 65)))
+	r.Header.Set("Content-Type", "application/json")
+	r.ContentLength = -1
+	r.Body = http.MaxBytesReader(httptest.NewRecorder(), r.Body, 64)
+	err := b.Bind(r, nil, &req{}, 64)
+	if apierrors.From(err).Status != 413 {
+		t.Fatalf("tail limit error: %v", err)
+	}
+}
+
+func TestResponseSchemaPreservesOrdinaryPointerConstraints(t *testing.T) {
+	type dto struct {
+		Count  *int    `json:"count,optional,range=[1:10]"`
+		Choice *string `json:"choice,options=a|b"`
+		Values *[]int  `json:"values,optional" binding:"max=3"`
+	}
+	b := MustNew[dto]()
+	response, err := b.ResponseSchema()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(response, b.BodySchema()) {
+		t.Fatalf("changed ordinary response constraints: %#v", response)
+	}
+}
--- a/examples/compatibility/ids/id.go
+++ b/examples/compatibility/ids/id.go
@@ -0,0 +1,29 @@
+// Package ids demonstrates an application-owned scalar. The framework does not
+// impose this ID policy on any other type or project.
+package ids
+
+import (
+	"encoding/json"
+	"strconv"
+)
+
+type ID int64
+
+func (id ID) MarshalJSON() ([]byte, error) { return json.Marshal(strconv.FormatInt(int64(id), 10)) }
+func (id *ID) UnmarshalJSON(raw []byte) error {
+	value := string(raw)
+	if len(raw) > 0 && raw[0] == '"' {
+		if err := json.Unmarshal(raw, &value); err != nil {
+			return err
+		}
+	}
+	return id.UnmarshalText([]byte(value))
+}
+func (id *ID) UnmarshalText(raw []byte) error {
+	value, err := strconv.ParseInt(string(raw), 10, 64)
+	if err != nil {
+		return err
+	}
+	*id = ID(value)
+	return nil
+}
--- a/examples/compatibility/main.go
+++ b/examples/compatibility/main.go
@@ -0,0 +1,75 @@
+// This example only uses local HTTP and bounded streaming; it has no database.
+package main
+
+import (
+	"io"
+	"log"
+	"net/http"
+	"strings"
+
+	omni "git.yuntuo.hk/k2safe/go-omni"
+	"git.yuntuo.hk/k2safe/go-omni/contract"
+	"git.yuntuo.hk/k2safe/go-omni/examples/compatibility/ids"
+	"git.yuntuo.hk/k2safe/go-omni/httpx"
+)
+
+type echoRequest struct {
+	ID   ids.ID `json:"id"`
+	Data any    `json:"data"`
+}
+
+func main() {
+	app := omni.New(omni.WithLogger(true))
+	defer app.Close()
+	app.Use(httpx.WrapMiddleware(func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("X-Example", "compatibility")
+			next.ServeHTTP(w, r)
+		})
+	}))
+	app.GET("/legacy", httpx.WrapHandler(http.HandlerFunc(http.NotFound)))
+	binder := contract.MustNew[echoRequest](contract.ScalarOf[ids.ID]("string|int64", "string", true))
+	app.POST("/echo", func(c *httpx.Context) error {
+		var req echoRequest
+		if err := binder.Bind(c.Request(), nil, &req); err != nil {
+			return err
+		}
+		return c.OK(req)
+	})
+	app.HandleWithBodyLimit("POST", "/upload", 10<<20, nil, func(c *httpx.Context) error {
+		reader, err := c.Request().MultipartReader()
+		if err != nil {
+			return omni.BadRequest("INVALID_MULTIPART", "multipart body required")
+		}
+		var total int64
+		for {
+			part, err := reader.NextPart()
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				return err
+			}
+			// Replace io.Discard with a streaming storage writer. Do not trust file names
+			// as filesystem paths. io.Copy never buffers the complete uploaded file.
+			n, copyErr := io.Copy(io.Discard, part)
+			closeErr := part.Close()
+			if copyErr != nil {
+				return copyErr
+			}
+			if closeErr != nil {
+				return closeErr
+			}
+			total += n
+		}
+		return c.OK(map[string]int64{"bytes": total})
+	})
+	app.GET("/download", httpx.WrapHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/octet-stream")
+		w.Header().Set("Content-Disposition", `attachment; filename="example.txt"`)
+		_, _ = io.Copy(w, strings.NewReader("A standard Handler keeps its original download response.\n"))
+	})))
+	if err := app.Run("127.0.0.1:8080"); err != nil {
+		log.Fatal(err)
+	}
+}
--- a/examples/contracts/compatibility.api
+++ b/examples/contracts/compatibility.api
@@ -0,0 +1,64 @@
+syntax = "v1"
+
+scalar BusinessID (
+ goImport: "git.yuntuo.hk/k2safe/go-omni/examples/compatibility/ids"
+ goType: ID
+ jsonInput: string | int64
+ jsonOutput: string
+ text: true
+)
+
+type EchoReq {
+ ID BusinessID `json:"id"`
+ Data any `json:"data"`
+ Legacy interface{} `json:"legacy,optional"`
+}
+type EchoResp {
+ ID BusinessID `json:"id"`
+ Data any `json:"data"`
+}
+type ItemReq {
+ ID BusinessID `path:"id"`
+}
+type CustomReq {
+ Value string `json:"value"`
+}
+type CustomResp {
+ Value string `json:"value"`
+}
+
+@server (group: demo)
+service compatibility-api {
+ @body (maxBytes: 2097152)
+ @handler echo
+ post /echo (EchoReq) returns (EchoResp)
+
+ @handler item
+ get /items/:id (ItemReq) returns (EchoResp)
+
+ @binding custom
+ @body (maxBytes: 512)
+ @handler custom
+ post /custom (CustomReq) returns (CustomResp)
+
+ @handlerMode manual
+ @body (mode: multipart
+ maxBytes: 65536)
+ @handler upload
+ post /upload
+
+ @handlerMode manual
+ @body (mode: raw
+ maxBytes: 128)
+ @produces "text/plain"
+ @handler callback
+ post /callback
+}
+
+@server (group: files)
+service compatibility-api {
+ @handlerMode manual
+ @produces "application/octet-stream"
+ @handler download
+ get /download
+}
--- a/examples/userService/.goOmni/apiManifest.json
+++ b/examples/userService/.goOmni/apiManifest.json
@@ -13,8 +13,8 @@
    "internal/apierrors/errorsGen.go": "20e94bbc90ae9f4330de4c25b9a550026c4c352502719a643ede3e8912a6566e",
    "internal/handler/openapiGen.go": "e4130f5c7494f7db4830bfef203fa8154a9cd087c95954f64c29d74693ead433",
    "internal/handler/responseGen.go": "d742efc2a3d1d168fae7849e905297bd440c3d6b3802b6150f494c07e6097f4f",
-    "internal/handler/routesGen.go": "0ff429a8aa7f8643e0e844f7c43a63a1f82cca5ce6bfe917f06edd860ebe923f",
-    "internal/handler/user/handlersGen.go": "06f3c2798ff323812ff3eb2d8b933a569af3ce1b86a67b66036374add98c0d7e",
+    "internal/handler/routesGen.go": "4e0c6879cea40e9c0155439fa1fce2cd19b5f83ea6e304523c41f8dc9c3a28e0",
+    "internal/handler/user/handlersGen.go": "1808afc8e4e8ca9785a8552eff64fad39bd5fe4e6e92971f35afc9006e23d76e",
    "internal/middleware/registryGen.go": "a6122a5453dedc6a4415860108814c50e155128cfe5412b39dd33ce2d01b4b00",
    "internal/types/typesGen.go": "3ab2ce9ffe467c3ea53ac3d1fec283ecebc87cef57fd592d08dca991fd964876"
  }
--- a/examples/userService/internal/handler/routesGen.go
+++ b/examples/userService/internal/handler/routesGen.go
@@ -17,7 +17,7 @@ func RegisterRoutes(router openapi.Registrar, deps *servicecontext.Context) erro
 	if deps.Middlewares["Auth"] == nil {
 		return fmt.Errorf("missing middleware Auth")
 	}
-	h0 := h0.New(s0.New(deps))
+	h0 := h0.New(s0.New(deps), deps)
 	httpx.HandleWithResponse(router, "POST", "/api/v1/users", responseEncoder("", false), h0.CreateUser, deps.Middlewares["Auth"])
 	httpx.HandleWithResponse(router, "GET", "/api/v1/users/:id", responseEncoder("", false), h0.GetUser, deps.Middlewares["Auth"])
 	httpx.HandleWithResponse(router, "GET", "/api/v1/users", responseEncoder("", false), h0.ListUsers, deps.Middlewares["Auth"])
--- a/examples/userService/internal/handler/user/handlersGen.go
+++ b/examples/userService/internal/handler/user/handlersGen.go
@@ -3,6 +3,7 @@ package user

 import (
 	"context"
+	"example.com/userService/internal/servicecontext"
 	"example.com/userService/internal/types"
 	"fmt"
 	"git.yuntuo.hk/k2safe/go-omni/contract"
@@ -17,9 +18,18 @@ type Service interface {
 	DeleteUser(ctx context.Context, req *types.UserIDReq) error
 	ExportUser(ctx context.Context, req *types.UserIDReq) (*types.ExportResp, error)
 }
-type Handler struct{ service Service }
+type Handler struct {
+	service Service
+	deps    *servicecontext.Context
+}

-func New(s Service) *Handler { return &Handler{service: s} }
+func New(s Service, deps ...*servicecontext.Context) *Handler {
+	h := &Handler{service: s}
+	if len(deps) > 0 {
+		h.deps = deps[0]
+	}
+	return h
+}

 var createUserRequest = contract.MustNew[types.CreateUserReq]()

--- a/httpx/body.go
+++ b/httpx/body.go
@@ -0,0 +1,60 @@
+package httpx
+
+import (
+	"errors"
+	apierrors "git.yuntuo.hk/k2safe/go-omni/errors"
+	"git.yuntuo.hk/k2safe/go-omni/response"
+	"net/http"
+)
+
+// LimitBody is useful for handwritten routes. Built-in App.HandleWithBodyLimit
+// additionally installs the reader cap before global middleware can read it.
+func LimitBody(maxBytes int64) Middleware {
+	if maxBytes <= 0 || maxBytes > 1<<40 {
+		panic("httpx: body limit must be 1..1 TiB")
+	}
+	return func(next Handler) Handler {
+		return func(c *Context) error {
+			r := c.Request()
+			if r.ContentLength > maxBytes {
+				return bodyTooLarge()
+			}
+			if r.Body != nil {
+				r.Body = http.MaxBytesReader(c.Raw(), r.Body, maxBytes)
+			}
+			defer CleanupMultipart(r)
+			err := next(c)
+			var limitErr *http.MaxBytesError
+			if errors.As(err, &limitErr) {
+				return bodyTooLarge()
+			}
+			return err
+		}
+	}
+}
+func bodyTooLarge() error { return apierrors.New(413, "BODY_TOO_LARGE", "request body exceeds limit") }
+
+// CleanupMultipart removes disk spill files created by ParseMultipartForm.
+// Callers still close individual multipart files. Streaming MultipartReader
+// handlers own any files they create themselves.
+func CleanupMultipart(r *http.Request) {
+	if r != nil && r.MultipartForm != nil {
+		_ = r.MultipartForm.RemoveAll()
+	}
+}
+
+type BodyLimitRegistrar interface {
+	HandleWithBodyLimit(string, string, int64, response.Encoder, Handler, ...Middleware)
+}
+
+func HandleWithBodyLimit(router interface {
+	Handle(string, string, Handler, ...Middleware)
+}, method, path string, maxBytes int64, encoder response.Encoder, handler Handler, middleware ...Middleware) {
+	if r, ok := router.(BodyLimitRegistrar); ok {
+		r.HandleWithBodyLimit(method, path, maxBytes, encoder, handler, middleware...)
+		return
+	}
+	// Custom registrars without the early hook cap at route middleware entry.
+	all := append([]Middleware{LimitBody(maxBytes)}, middleware...)
+	HandleWithResponse(router, method, path, encoder, handler, all...)
+}
--- a/httpx/bridge.go
+++ b/httpx/bridge.go
@@ -0,0 +1,80 @@
+package httpx
+
+import (
+	"context"
+	"net/http"
+)
+
+type bridgeState struct{ parent *Context }
+
+// WrapHandler runs an existing standard handler inside the App middleware chain.
+// It preserves the original response, including downloads and streaming output.
+func WrapHandler(handler http.Handler) Handler {
+	if handler == nil {
+		panic("httpx: nil HTTP handler")
+	}
+	return func(c *Context) error {
+		r := bridgeRequest(c)
+		defer CleanupMultipart(r)
+		handler.ServeHTTP(c.Raw(), r)
+		return nil
+	}
+}
+
+// WrapMiddleware adapts synchronous standard HTTP middleware. The middleware is
+// constructed once per chain, preserving its shared state across requests.
+// Errors from next are encoded before unwinding so response-transforming
+// middleware sees them. Preserve the incoming request context (derive with
+// WithContext), and never call next after ServeHTTP returns, as with net/http.
+func WrapMiddleware(middleware func(http.Handler) http.Handler) Middleware {
+	if middleware == nil {
+		panic("httpx: nil HTTP middleware")
+	}
+	return func(next Handler) Handler {
+		// Each nested bridge has its own key, including repeated use of one adapter.
+		key := &bridgeState{}
+		wrapped := middleware(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			state, ok := r.Context().Value(key).(*bridgeState)
+			if !ok {
+				panic("httpx: standard middleware must preserve the incoming request context")
+			}
+			c := state.parent
+			child := c.Clone(r.Context(), w)
+			child.request = r
+			if c.Responded() {
+				child.writer.(interface{ inheritCommit(int) }).inheritCommit(c.Status())
+			}
+			defer CleanupMultipart(r)
+			defer func() { c.values = child.values; c.encoder = child.encoder }()
+			if err := next(child); err != nil && !c.Responded() {
+				child.WriteError(err)
+			}
+		}))
+		if wrapped == nil {
+			panic("httpx: HTTP middleware returned nil handler")
+		}
+		return func(c *Context) error {
+			r := bridgeRequest(c).WithContext(context.WithValue(c.Context(), key, &bridgeState{parent: c}))
+			defer CleanupMultipart(r)
+			wrapped.ServeHTTP(c.Raw(), r)
+			return nil
+		}
+	}
+}
+
+// WrapFuncMiddleware supports middleware shaped as func(http.HandlerFunc) http.HandlerFunc.
+func WrapFuncMiddleware(middleware func(http.HandlerFunc) http.HandlerFunc) Middleware {
+	if middleware == nil {
+		panic("httpx: nil HTTP middleware")
+	}
+	return WrapMiddleware(func(next http.Handler) http.Handler { return middleware(next.ServeHTTP) })
+}
+
+// Populate Go 1.22 path values without mutating a parent router's request maps.
+func bridgeRequest(c *Context) *http.Request {
+	r := c.Request().Clone(c.Context())
+	for name, value := range c.params {
+		r.SetPathValue(name, value)
+	}
+	return r
+}
--- a/httpx/bridge_test.go
+++ b/httpx/bridge_test.go
@@ -0,0 +1,363 @@
+package httpx_test
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"mime/multipart"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	omni "git.yuntuo.hk/k2safe/go-omni"
+	"git.yuntuo.hk/k2safe/go-omni/httpx"
+	"git.yuntuo.hk/k2safe/go-omni/logx"
+)
+
+func TestLegacyResponseTrackingAndMiddleware(t *testing.T) {
+	var logs bytes.Buffer
+	closeLog, err := logx.Setup(logx.Config{Writer: &logs, Format: "json"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer closeLog()
+	app := omni.New(omni.WithLogger(true))
+	app.GET("/legacy", httpx.WrapHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { http.NotFound(w, r) })))
+	app.GET("/late", func(c *httpx.Context) error {
+		c.Raw().WriteHeader(404)
+		_, _ = c.Raw().Write([]byte("original"))
+		return errors.New("late error")
+	})
+	app.GET("/panic", func(c *httpx.Context) error { _, _ = c.Raw().Write([]byte("partial")); panic("late panic") })
+	for _, tc := range []struct {
+		path   string
+		status int
+		body   string
+	}{{"/legacy", 404, "404 page not found\n"}, {"/late", 404, "original"}, {"/panic", 200, "partial"}} {
+		w := httptest.NewRecorder()
+		app.ServeHTTP(w, httptest.NewRequest("GET", tc.path, nil))
+		if w.Code != tc.status || w.Body.String() != tc.body {
+			t.Fatalf("%s: %d %q", tc.path, w.Code, w.Body.String())
+		}
+	}
+	count := 0
+	for _, line := range strings.Split(logs.String(), "\n") {
+		var e map[string]any
+		if json.Unmarshal([]byte(line), &e) != nil || e["msg"] != "http.request" {
+			continue
+		}
+		count++
+		if e["path"] != "/panic" && e["status"] != float64(404) {
+			t.Fatalf("wrong log: %s", line)
+		}
+	}
+	if count != 3 {
+		t.Fatalf("access logs: %d", count)
+	}
+
+	type key struct{}
+	app = omni.New()
+	app.Use(httpx.WrapFuncMiddleware(func(next http.HandlerFunc) http.HandlerFunc {
+		return func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("X-Before", "yes")
+			next(w, r.WithContext(context.WithValue(r.Context(), key{}, "identity")))
+		}
+	}))
+	app.GET("/context", func(c *httpx.Context) error {
+		if c.Context().Value(key{}) != "identity" || c.RequestID() == "" {
+			t.Error("lost context")
+		}
+		return omni.NotFound("MISSING", "missing")
+	})
+	w := httptest.NewRecorder()
+	app.ServeHTTP(w, httptest.NewRequest("GET", "/context", nil))
+	if w.Code != 404 || w.Header().Get("X-Before") != "yes" || strings.Count(w.Body.String(), "MISSING") != 1 {
+		t.Fatalf("middleware response: %d %s", w.Code, w.Body)
+	}
+}
+
+type plainWriter struct {
+	header http.Header
+	status int
+}
+
+func (w *plainWriter) Header() http.Header         { return w.header }
+func (w *plainWriter) WriteHeader(status int)      { w.status = status }
+func (w *plainWriter) Write(p []byte) (int, error) { return len(p), nil }
+func TestWriterCapabilitiesAndInformationalStatus(t *testing.T) {
+	w := &plainWriter{header: http.Header{}}
+	c := httpx.NewContext(httptest.NewRequest("GET", "/", nil), w, nil)
+	if _, ok := c.Raw().(http.Flusher); ok {
+		t.Fatal("invented Flusher")
+	}
+	if _, ok := c.Raw().(http.Hijacker); ok {
+		t.Fatal("invented Hijacker")
+	}
+	if err := http.NewResponseController(c.Raw()).Flush(); !errors.Is(err, http.ErrNotSupported) {
+		t.Fatalf("Flush: %v", err)
+	}
+	c.Raw().WriteHeader(103)
+	if c.Responded() {
+		t.Fatal("103 committed final response")
+	}
+	c.Raw().WriteHeader(201)
+	c.Raw().WriteHeader(500)
+	if !c.Responded() || c.Status() != 201 || w.status != 201 {
+		t.Fatal("first final status not preserved")
+	}
+	recorder := httptest.NewRecorder()
+	c = httpx.NewContext(httptest.NewRequest("GET", "/", nil), recorder, nil)
+	if err := http.NewResponseController(c.Raw()).Flush(); err != nil {
+		t.Fatal(err)
+	}
+	if !c.Responded() || c.Status() != 200 || !recorder.Flushed {
+		t.Fatal("flush not tracked")
+	}
+}
+
+func TestLegacyStreamingAcrossTransports(t *testing.T) {
+	for _, transport := range []string{omni.TransportNetHTTP, omni.TransportNative} {
+		t.Run(transport, func(t *testing.T) {
+			release := make(chan struct{})
+			defer close(release)
+			app := omni.New(omni.WithTransport(transport))
+			app.GET("/stream", httpx.WrapHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Type", "text/plain")
+				_, _ = io.WriteString(w, "first\n")
+				if err := http.NewResponseController(w).Flush(); err != nil {
+					t.Error(err)
+					return
+				}
+				select {
+				case <-release:
+				case <-r.Context().Done():
+				}
+			})))
+			app.GET("/file", httpx.WrapHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Disposition", `attachment; filename="data.bin"`)
+				_, _ = io.Copy(w, strings.NewReader(strings.Repeat("x", 2<<20)))
+			})))
+			app.HandleWithBodyLimit("POST", "/bounded", 32, nil, func(c *httpx.Context) error {
+				_, err := io.Copy(io.Discard, c.Request().Body)
+				if err != nil {
+					return err
+				}
+				return c.NoContent()
+			})
+			listener, err := net.Listen("tcp", "127.0.0.1:0")
+			if err != nil {
+				t.Fatal(err)
+			}
+			ctx, cancel := context.WithCancel(context.Background())
+			done := make(chan error, 1)
+			go func() { done <- app.ServeContext(ctx, listener) }()
+			defer func() {
+				cancel()
+				select {
+				case <-done:
+				case <-time.After(15 * time.Second):
+					t.Error("shutdown timed out")
+				}
+			}()
+			client := &http.Client{Timeout: 3 * time.Second}
+			defer client.CloseIdleConnections()
+			for _, body := range []io.Reader{strings.NewReader(strings.Repeat("x", 33)), io.NopCloser(strings.NewReader(strings.Repeat("x", 33)))} {
+				res, err := client.Post("http://"+listener.Addr().String()+"/bounded", "application/octet-stream", body)
+				if err != nil {
+					t.Fatal(err)
+				}
+				_, _ = io.Copy(io.Discard, res.Body)
+				res.Body.Close()
+				if res.StatusCode != 413 {
+					t.Fatalf("real transport body limit: %d", res.StatusCode)
+				}
+			}
+			res, err := client.Get("http://" + listener.Addr().String() + "/stream")
+			if err != nil {
+				t.Fatal(err)
+			}
+			first := make([]byte, 6)
+			_, err = io.ReadFull(res.Body, first)
+			res.Body.Close()
+			if err != nil || string(first) != "first\n" {
+				t.Fatalf("stream was buffered: %s %v", first, err)
+			}
+			res, err = client.Get("http://" + listener.Addr().String() + "/file")
+			if err != nil {
+				t.Fatal(err)
+			}
+			size, err := io.Copy(io.Discard, res.Body)
+			res.Body.Close()
+			if err != nil || size != 2<<20 || res.Header.Get("Content-Disposition") == "" {
+				t.Fatalf("file: %d %v", size, err)
+			}
+		})
+	}
+}
+
+func TestStandardMiddlewareStateAndShortCircuit(t *testing.T) {
+	constructions, calls := 0, 0
+	app := omni.New()
+	defer app.Close()
+	app.Use(httpx.WrapMiddleware(func(next http.Handler) http.Handler {
+		constructions++
+		count := 0
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			count++
+			if count == 2 {
+				http.Error(w, "denied", 401)
+				return
+			}
+			next.ServeHTTP(w, r)
+		})
+	}))
+	app.GET("/", func(c *httpx.Context) error { calls++; return c.NoContent() })
+	for _, status := range []int{204, 401, 204} {
+		w := httptest.NewRecorder()
+		app.ServeHTTP(w, httptest.NewRequest("GET", "/", nil))
+		if w.Code != status {
+			t.Fatalf("got %d want %d", w.Code, status)
+		}
+	}
+	if constructions != 1 || calls != 2 {
+		t.Fatalf("middleware lifecycle: %d constructions, %d calls", constructions, calls)
+	}
+}
+
+func TestStandardMiddlewareTransformsErrorAndPreservesCancellation(t *testing.T) {
+	app := omni.New()
+	defer app.Close()
+	app.Use(httpx.WrapMiddleware(func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			// A legacy middleware may buffer its own small response. The bridge must
+			// report its eventual physical status, and encode errors before it unwinds.
+			temp := httptest.NewRecorder()
+			next.ServeHTTP(temp, r)
+			if temp.Code != 404 {
+				t.Errorf("inner error not encoded: %d", temp.Code)
+			}
+			w.WriteHeader(409)
+			_, _ = io.WriteString(w, strings.ToUpper(temp.Body.String()))
+		})
+	}))
+	app.GET("/", func(c *httpx.Context) error {
+		if !errors.Is(c.Context().Err(), context.Canceled) {
+			t.Error("cancellation lost")
+		}
+		return omni.NotFound("missing", "missing")
+	})
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	w := httptest.NewRecorder()
+	app.ServeHTTP(w, httptest.NewRequest("GET", "/", nil).WithContext(ctx))
+	if w.Code != 409 || !strings.Contains(w.Body.String(), "MISSING") {
+		t.Fatalf("%d %s", w.Code, w.Body)
+	}
+}
+
+func TestRouteBodyLimitBeforeMiddleware(t *testing.T) {
+	for _, length := range []int64{-1, 33} {
+		t.Run(fmt.Sprint(length), func(t *testing.T) {
+			app := omni.New()
+			defer app.Close()
+			read := 0
+			app.Use(func(next httpx.Handler) httpx.Handler {
+				return func(c *httpx.Context) error {
+					body, err := io.ReadAll(c.Request().Body)
+					read = len(body)
+					if err != nil {
+						return err
+					}
+					return next(c)
+				}
+			})
+			app.Group("/api").HandleWithBodyLimit("POST", "/upload", 32, nil, func(c *httpx.Context) error { t.Error("called oversized handler"); return nil })
+			r := httptest.NewRequest("POST", "/api/upload", strings.NewReader(strings.Repeat("x", 33)))
+			r.ContentLength = length
+			w := httptest.NewRecorder()
+			app.ServeHTTP(w, r)
+			if w.Code != 413 || read > 32 {
+				t.Fatalf("limit: status=%d read=%d", w.Code, read)
+			}
+		})
+	}
+}
+
+func TestMultipartCleanupOnPanic(t *testing.T) {
+	temp := t.TempDir()
+	t.Setenv("TMPDIR", temp)
+	var body bytes.Buffer
+	form := multipart.NewWriter(&body)
+	part, err := form.CreateFormFile("file", "x.bin")
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, _ = part.Write(bytes.Repeat([]byte("x"), 4096))
+	_ = form.Close()
+	app := omni.New()
+	defer app.Close()
+	app.HandleWithBodyLimit("POST", "/", 8192, nil, httpx.WrapHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := r.ParseMultipartForm(1); err != nil {
+			t.Error(err)
+			return
+		}
+		panic("after disk spill")
+	})))
+	r := httptest.NewRequest("POST", "/", &body)
+	r.Header.Set("Content-Type", form.FormDataContentType())
+	w := httptest.NewRecorder()
+	app.ServeHTTP(w, r)
+	entries, err := os.ReadDir(temp)
+	if w.Code != 500 || err != nil || len(entries) != 0 {
+		t.Fatalf("cleanup: %d %v %v", w.Code, entries, err)
+	}
+}
+
+func TestStandardMiddlewareCommitsBeforeCallingNext(t *testing.T) {
+	app := omni.New()
+	defer app.Close()
+	app.Use(httpx.WrapMiddleware(func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(202)
+			_, _ = io.WriteString(w, "accepted")
+			next.ServeHTTP(w, r)
+		})
+	}))
+	app.GET("/", func(c *httpx.Context) error {
+		if !c.Responded() || c.Status() != 202 {
+			t.Error("lost middleware commit")
+		}
+		return errors.New("late failure")
+	})
+	w := httptest.NewRecorder()
+	app.ServeHTTP(w, httptest.NewRequest("GET", "/", nil))
+	if w.Code != 202 || w.Body.String() != "accepted" {
+		t.Fatalf("late append: %d %q", w.Code, w.Body.String())
+	}
+}
+
+func TestBridgeStandardPathValues(t *testing.T) {
+	app := omni.New()
+	defer app.Close()
+	app.Use(httpx.WrapMiddleware(func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if r.PathValue("itemId") != "abc" {
+				t.Error("middleware path value lost")
+			}
+			next.ServeHTTP(w, r)
+		})
+	}))
+	app.GET("/items/:itemId", httpx.WrapHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { _, _ = io.WriteString(w, r.PathValue("itemId")) })))
+	w := httptest.NewRecorder()
+	app.ServeHTTP(w, httptest.NewRequest("GET", "/items/abc", nil))
+	if w.Body.String() != "abc" {
+		t.Fatal("handler path value lost")
+	}
+}
--- a/httpx/context.go
+++ b/httpx/context.go
@@ -3,6 +3,7 @@ package httpx
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"net/http"

 	apierrors "git.yuntuo.hk/k2safe/go-omni/errors"
@@ -101,12 +102,15 @@ func NewContext(request *http.Request, writer http.ResponseWriter, params map[st
 	if request == nil {
 		request = &http.Request{}
 	}
-	return &Context{
+	c := &Context{
 		request: request,
-		writer:  writer,
 		params:  params,
 		values:  make(map[string]any),
 	}
+	if writer != nil {
+		c.writer = trackWriter(writer, c)
+	}
+	return c
 }

 func (c *Context) Request() *http.Request { return c.request }
@@ -120,8 +124,8 @@ func (c *Context) Context() context.Context {
 	return c.request.Context()
 }

-// Raw returns the response writer supplied by the active network adapter.
-// Prefer the transport-neutral methods on Context for portable handlers.
+// Raw returns a streaming response writer that tracks commits and status.
+// Optional HTTP capabilities are preserved only when the underlying writer supports them.
 func (c *Context) Raw() http.ResponseWriter { return c.writer }

 // Clone gives a buffering middleware its own response state and values map.
@@ -146,7 +150,6 @@ func (c *Context) WriteResponse(status int, headers http.Header, body []byte) er
 	for key, values := range headers {
 		c.writer.Header()[key] = append([]string(nil), values...)
 	}
-	c.responded, c.status = true, status
 	c.writer.WriteHeader(status)
 	if len(body) > 0 {
 		if _, err := c.writer.Write(body); err != nil {
@@ -216,8 +219,6 @@ func (c *Context) JSON(status int, value any) error {
 	if err != nil {
 		return apierrors.Internal(err)
 	}
-	c.responded = true
-	c.status = status
 	c.writer.Header().Set("Content-Type", "application/json; charset=utf-8")
 	c.writer.WriteHeader(status)
 	if _, err := c.writer.Write(append(data, '\n')); err != nil {
@@ -243,8 +244,6 @@ func (c *Context) NoContent() error {
 	if c.writer == nil {
 		return apierrors.Internal(nil)
 	}
-	c.responded = true
-	c.status = http.StatusNoContent
 	c.writer.WriteHeader(http.StatusNoContent)
 	return nil
 }
@@ -271,12 +270,15 @@ func (c *Context) Status() int {
 func (c *Context) Responded() bool { return c.responded }

 // WriteError writes a stable public error response. Internal causes are not
-// serialized. Responses committed through Context methods are preserved;
-// direct Raw writes are outside this response-tracking contract.
+// serialized. Responses committed through Context methods or Raw are preserved.
 func (c *Context) WriteError(err error) {
 	if c.responded || err == nil {
 		return
 	}
+	var bodyErr *http.MaxBytesError
+	if errors.As(err, &bodyErr) {
+		err = bodyTooLarge()
+	}
 	apiErr := apierrors.From(err)
 	if writeErr := c.writeResult(response.Result{
 		Status:    apiErr.Status,
--- a/httpx/trackingWriter.go
+++ b/httpx/trackingWriter.go
@@ -0,0 +1,315 @@
+package httpx
+
+import (
+	"bufio"
+	"io"
+	"net"
+	"net/http"
+)
+
+// trackingWriter does not buffer response bodies. Each wrapper has its own
+// commit flag, so a standard middleware may safely wrap an already tracked writer.
+type trackingWriter struct {
+	http.ResponseWriter
+	context   *Context
+	committed bool
+}
+
+func (w *trackingWriter) Unwrap() http.ResponseWriter { return w.ResponseWriter }
+func (w *trackingWriter) inheritCommit(status int)    { w.mark(status) }
+func (w *trackingWriter) mark(status int) {
+	w.committed = true
+	w.context.responded = true
+	w.context.status = status
+}
+func (w *trackingWriter) WriteHeader(status int) {
+	if w.committed {
+		return
+	}
+	// Let the server validate the status before updating the observation.
+	w.ResponseWriter.WriteHeader(status)
+	if status == 101 || status >= 200 {
+		w.mark(status)
+	}
+}
+func (w *trackingWriter) Write(p []byte) (int, error) {
+	if !w.committed {
+		w.mark(http.StatusOK)
+	}
+	return w.ResponseWriter.Write(p)
+}
+
+type flushWriter struct{ *trackingWriter }
+
+func (w flushWriter) Flush() { _ = w.FlushError() }
+func (w flushWriter) FlushError() error {
+	if !w.committed {
+		w.WriteHeader(http.StatusOK)
+	}
+	return http.NewResponseController(w.ResponseWriter).Flush()
+}
+
+type hijackWriter struct{ *trackingWriter }
+
+func (w hijackWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	conn, rw, err := w.ResponseWriter.(http.Hijacker).Hijack()
+	if err == nil {
+		w.context.responded = true
+		w.committed = true
+	}
+	return conn, rw, err
+}
+
+type pushWriter struct{ *trackingWriter }
+
+func (w pushWriter) Push(target string, options *http.PushOptions) error {
+	return w.ResponseWriter.(http.Pusher).Push(target, options)
+}
+
+type readFromWriter struct{ *trackingWriter }
+
+func (w readFromWriter) ReadFrom(r io.Reader) (int64, error) {
+	// A writer-only view makes every write observable, including partial failures,
+	// while io.Copy retains bounded streaming memory and source WriterTo support.
+	return io.Copy(struct{ io.Writer }{w.trackingWriter}, r)
+}
+
+type closeNotifyWriter struct{ *trackingWriter }
+
+func (w closeNotifyWriter) CloseNotify() <-chan bool {
+	return w.ResponseWriter.(http.CloseNotifier).CloseNotify()
+}
+
+func trackWriter(writer http.ResponseWriter, c *Context) http.ResponseWriter {
+	w := &trackingWriter{ResponseWriter: writer, context: c}
+	mask := 0
+	if _, ok := writer.(http.Flusher); ok {
+		mask |= 1
+	} else if _, ok := writer.(interface{ FlushError() error }); ok {
+		mask |= 1
+	}
+	if _, ok := writer.(http.Hijacker); ok {
+		mask |= 2
+	}
+	if _, ok := writer.(http.Pusher); ok {
+		mask |= 4
+	}
+	if _, ok := writer.(io.ReaderFrom); ok {
+		mask |= 8
+	}
+	if _, ok := writer.(http.CloseNotifier); ok {
+		mask |= 16
+	}
+	switch mask {
+	case 1:
+		return struct {
+			*trackingWriter
+			flushCapability
+		}{w, flushWriter{w}}
+	case 2:
+		return struct {
+			*trackingWriter
+			http.Hijacker
+		}{w, hijackWriter{w}}
+	case 3:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Hijacker
+		}{w, flushWriter{w}, hijackWriter{w}}
+	case 4:
+		return struct {
+			*trackingWriter
+			http.Pusher
+		}{w, pushWriter{w}}
+	case 5:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Pusher
+		}{w, flushWriter{w}, pushWriter{w}}
+	case 6:
+		return struct {
+			*trackingWriter
+			http.Hijacker
+			http.Pusher
+		}{w, hijackWriter{w}, pushWriter{w}}
+	case 7:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Hijacker
+			http.Pusher
+		}{w, flushWriter{w}, hijackWriter{w}, pushWriter{w}}
+	case 8:
+		return struct {
+			*trackingWriter
+			io.ReaderFrom
+		}{w, readFromWriter{w}}
+	case 9:
+		return struct {
+			*trackingWriter
+			flushCapability
+			io.ReaderFrom
+		}{w, flushWriter{w}, readFromWriter{w}}
+	case 10:
+		return struct {
+			*trackingWriter
+			http.Hijacker
+			io.ReaderFrom
+		}{w, hijackWriter{w}, readFromWriter{w}}
+	case 11:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Hijacker
+			io.ReaderFrom
+		}{w, flushWriter{w}, hijackWriter{w}, readFromWriter{w}}
+	case 12:
+		return struct {
+			*trackingWriter
+			http.Pusher
+			io.ReaderFrom
+		}{w, pushWriter{w}, readFromWriter{w}}
+	case 13:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Pusher
+			io.ReaderFrom
+		}{w, flushWriter{w}, pushWriter{w}, readFromWriter{w}}
+	case 14:
+		return struct {
+			*trackingWriter
+			http.Hijacker
+			http.Pusher
+			io.ReaderFrom
+		}{w, hijackWriter{w}, pushWriter{w}, readFromWriter{w}}
+	case 15:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Hijacker
+			http.Pusher
+			io.ReaderFrom
+		}{w, flushWriter{w}, hijackWriter{w}, pushWriter{w}, readFromWriter{w}}
+	case 16:
+		return struct {
+			*trackingWriter
+			http.CloseNotifier
+		}{w, closeNotifyWriter{w}}
+	case 17:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.CloseNotifier
+		}{w, flushWriter{w}, closeNotifyWriter{w}}
+	case 18:
+		return struct {
+			*trackingWriter
+			http.Hijacker
+			http.CloseNotifier
+		}{w, hijackWriter{w}, closeNotifyWriter{w}}
+	case 19:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Hijacker
+			http.CloseNotifier
+		}{w, flushWriter{w}, hijackWriter{w}, closeNotifyWriter{w}}
+	case 20:
+		return struct {
+			*trackingWriter
+			http.Pusher
+			http.CloseNotifier
+		}{w, pushWriter{w}, closeNotifyWriter{w}}
+	case 21:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Pusher
+			http.CloseNotifier
+		}{w, flushWriter{w}, pushWriter{w}, closeNotifyWriter{w}}
+	case 22:
+		return struct {
+			*trackingWriter
+			http.Hijacker
+			http.Pusher
+			http.CloseNotifier
+		}{w, hijackWriter{w}, pushWriter{w}, closeNotifyWriter{w}}
+	case 23:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Hijacker
+			http.Pusher
+			http.CloseNotifier
+		}{w, flushWriter{w}, hijackWriter{w}, pushWriter{w}, closeNotifyWriter{w}}
+	case 24:
+		return struct {
+			*trackingWriter
+			io.ReaderFrom
+			http.CloseNotifier
+		}{w, readFromWriter{w}, closeNotifyWriter{w}}
+	case 25:
+		return struct {
+			*trackingWriter
+			flushCapability
+			io.ReaderFrom
+			http.CloseNotifier
+		}{w, flushWriter{w}, readFromWriter{w}, closeNotifyWriter{w}}
+	case 26:
+		return struct {
+			*trackingWriter
+			http.Hijacker
+			io.ReaderFrom
+			http.CloseNotifier
+		}{w, hijackWriter{w}, readFromWriter{w}, closeNotifyWriter{w}}
+	case 27:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Hijacker
+			io.ReaderFrom
+			http.CloseNotifier
+		}{w, flushWriter{w}, hijackWriter{w}, readFromWriter{w}, closeNotifyWriter{w}}
+	case 28:
+		return struct {
+			*trackingWriter
+			http.Pusher
+			io.ReaderFrom
+			http.CloseNotifier
+		}{w, pushWriter{w}, readFromWriter{w}, closeNotifyWriter{w}}
+	case 29:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Pusher
+			io.ReaderFrom
+			http.CloseNotifier
+		}{w, flushWriter{w}, pushWriter{w}, readFromWriter{w}, closeNotifyWriter{w}}
+	case 30:
+		return struct {
+			*trackingWriter
+			http.Hijacker
+			http.Pusher
+			io.ReaderFrom
+			http.CloseNotifier
+		}{w, hijackWriter{w}, pushWriter{w}, readFromWriter{w}, closeNotifyWriter{w}}
+	case 31:
+		return struct {
+			*trackingWriter
+			flushCapability
+			http.Hijacker
+			http.Pusher
+			io.ReaderFrom
+			http.CloseNotifier
+		}{w, flushWriter{w}, hijackWriter{w}, pushWriter{w}, readFromWriter{w}, closeNotifyWriter{w}}
+	}
+	return w
+}
+
+type flushCapability interface {
+	Flush()
+	FlushError() error
+}
--- a/performance/compatibilityAcceptance.md
+++ b/performance/compatibilityAcceptance.md
@@ -0,0 +1,24 @@
+# v0.9.0-preview 迁移扩展验收
+
+本轮只使用本机临时服务与生成项目；没有运行业务服务器压测，没有修改 ePay/eTax 业务代码。
+
+## 本地验收
+
+- `GO_OMNI_SCAFFOLD_INTEGRATION=1 go test -race -p=1 -count=1 -timeout=300s ./...`：40 个有测试的包通过；包含真实生成消费者、标准 Handler/Middleware、动态 JSON、路由限额和 scalar。
+- `go vet ./...`、`go build ./...`、gofmt、`git diff --check` 通过。
+- 独立 `examples/userService` module 的 race/vet/build 通过；生成文件 `--check` 通过，手写业务保持原样。
+- nethttp/native 本机真实 TCP 测试：首块数据立即 Flush、2 MiB 文件保持原响应、已知长度和 chunked 超限返回 413，并能继续处理正常请求。
+- 404 访问日志、提交后错误/panic 不追加 JSON、标准中间件提前写入/跨请求状态/取消/PathValue 通过。
+- multipart 落盘临时文件在成功和 panic 后清理；原始请求体 HMAC 验签、定制绑定和生成代码保护通过。
+- scalar 最大 int64、数字/字符串兼容、溢出/错误类型拒绝、指针 null、query 集合、输入/输出 schema 分离通过；普通字段仍严格。
+- ePay 原始契约只读校验：26 types、43 routes、0 errors、0 auth schemes。后两项是声明数量，不代表无需鉴权或没有业务错误；不代表 144 条注册路由已全部迁移。
+
+环境：`go version go1.27.1 darwin/arm64`。记录时间：2026-09-23T17:47:26+00:00。
+
+## 远程验收
+
+发布后执行 `scripts/verifyCompatibilityRelease.py --version v0.9.0-preview`，结果生成到 `performance/compatibilityRemote.json`，校验从全新 module cache 安装的 CLI 与消费者固定依赖、无本地 replace、重生成保护和运行时行为。该结果在 main 单独记录，发布标签保持不可变。
+
+## 范围
+
+本次不是完整 ePay 迁移验收；资金事务、原权限体系、业务响应细节仍需业务自己的回归。未重跑 Linux soak、Nginx/Cloudflare 代理或云存储账号实网验收。
--- a/scripts/verifyCompatibilityRelease.py
+++ b/scripts/verifyCompatibilityRelease.py
@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+"""Install the released CLI in a fresh cache, then test its generated consumer.
+
+The fixture tests custom scalars, dynamic JSON, uploads, raw callback signatures,
+downloads, body limits and regeneration protection. Only local temporary resources
+are used; the framework and CLI are fetched from the specified remote version.
+"""
+import argparse
+import hashlib
+import json
+import os
+from pathlib import Path
+import re
+import subprocess
+import tempfile
+import time
+
+ROOT = Path(__file__).resolve().parents[1]
+MODULE = "git.yuntuo.hk/k2safe/go-omni"
+
+
+def run(args, cwd, env, timeout=300):
+    result = subprocess.run([str(arg) for arg in args], cwd=cwd, env=env,
+                            capture_output=True, text=True, timeout=timeout)
+    output = re.sub(r"https://[^/@\s]+:[^/@\s]+@", "https://", result.stdout + result.stderr)
+    if result.returncode:
+        raise RuntimeError(f"{args[0]} failed ({result.returncode}):\n{output}")
+    return output
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--version", required=True)
+    parser.add_argument("--report", type=Path, default=ROOT / "performance/compatibilityRemote.json")
+    args = parser.parse_args()
+    if not re.fullmatch(r"v\d+\.\d+\.\d+(?:-[0-9A-Za-z.-]+)?", args.version):
+        parser.error("a fixed release version is required")
+    env = {k: v for k, v in os.environ.items() if not k.startswith("GO_OMNI_")}
+    env.update(GOWORK="off", GOFLAGS="", GOPRIVATE="git.yuntuo.hk", GONOSUMDB="git.yuntuo.hk")
+    start = time.monotonic()
+    with tempfile.TemporaryDirectory(prefix="goOmniCompatibilityRelease-") as directory:
+        temp = Path(directory)
+        (temp / "bin").mkdir()
+        env.update(GOBIN=str(temp / "bin"), GOMODCACHE=str(temp / "modcache"))
+        print(f"Installing CLI {args.version} in an empty module cache", flush=True)
+        run(["go", "install", MODULE + "/cmd/go-omni@" + args.version], temp, env)
+        cli = temp / "bin/go-omni"
+        run([cli, "api", "validate", "--api", ROOT / "examples/contracts/compatibility.api"], temp, env)
+        env.update(GO_OMNI_SCAFFOLD_INTEGRATION="1", GO_OMNI_RELEASE_CLI=str(cli), GO_OMNI_RELEASE_VERSION=args.version)
+        print("Testing remote generation, scalar binding, uploads and callback signatures", flush=True)
+        output = run(["go", "test", "-race", "-count=1", "-json", "-timeout=180s",
+                      "./cmd/go-omni/apigen", "-run", "^TestCompatibilityConsumer$"], ROOT, env)
+        events = [json.loads(line) for line in output.splitlines() if line.startswith("{")]
+        passed = [e["Test"] for e in events if e.get("Action") == "pass" and "Test" in e]
+        assert passed == ["TestCompatibilityConsumer"], output
+        evidence = "".join(e.get("Output", "") for e in events)
+        checksum = re.search(r"checksum (h1:\S+); no local replace", evidence)
+        assert checksum, "consumer did not verify its remote dependency"
+        report = {
+            "passed": True, "frameworkVersion": args.version, "frameworkSum": checksum.group(1),
+            "freshModuleCache": True, "noLocalReplace": True,
+            "durationSeconds": round(time.monotonic() - start, 2),
+            "checks": ["remoteCLIInstall", "scalarContractValidation", "manualProjectGeneration",
+                       "int64MaxValueOnWire", "dynamicJSON", "rawBodySignature", "routeBodyLimits",
+                       "multipartTempCleanup", "unwrappedDownloads",
+                       "handwrittenFilesPreserved", "generatedConsumerRaceTests", "fixedRemoteModuleChecksum"],
+            "sourceHashes": {name: hashlib.sha256((ROOT / name).read_bytes()).hexdigest() for name in
+                             ("scripts/verifyCompatibilityRelease.py", "cmd/go-omni/apigen/compatibility_test.go",
+                              "examples/contracts/compatibility.api",
+                              "cmd/go-omni/apigen/testdata/compatibility/consumer_test.go",
+                              "cmd/go-omni/apigen/testdata/compatibility/hooks.go",
+                              "cmd/go-omni/apigen/testdata/compatibility/echo.go",
+                              "cmd/go-omni/apigen/testdata/compatibility/download.go")},
+        }
+        args.report.write_text(json.dumps(report, ensure_ascii=False, indent=2) + "\n")
+    print(f"PASS remote compatibility contract {args.version}; temporary files removed", flush=True)
+
+
+if __name__ == "__main__":
+    main()