feat(llm): 三 provider 统一支持自定义 HTTP 请求头

在 GenericOpenaiProvider / OpenaiResponseProvider / AnthropicProvider 中新增双层自定义 HTTP 头机制：

- Provider 级固定头：extra_headers 字段，构造时通过 with_extra_headers() 链式注入
- 请求级临时头：extra.custom_headers，通过 set_extra 透传，#[serde(skip)] 隔离 JSON body

AnthropicProvider 前置提取 build_request_builder 统一方法，使三 provider 的请求构造模式对齐。

头融合顺序（一致）：认证头 → Provider 级头 → 请求级头，后注入覆盖前注入。

新增 14 个测试覆盖提取 / 序列化隔离 / 类型降级 / 透传 / 覆盖优先级 / 认证头可覆盖等维度。

docs/29-openai-response-provider-custom-headers.md

@@ -0,0 +1,422 @@
+# OpenAI Response Provider 自定义请求头支持
+
+## 背景
+
+OpenAI Responses API 的部分实现（如火山引擎豆包）需要携带特殊的 HTTP 请求头（如 `ark-beta-doubao-app: true`）来启用平台特定功能。当前 `OpenaiResponseProvider` 在 `build_request_builder()` 中只设置了 `Authorization` 头，没有途径注入自定义请求头。
+
+原方案只覆盖 OpenAI Response Provider。经讨论后扩展为**三 Provider 统一**方案：OpenAI Chat（`GenericOpenaiProvider`）、OpenAI Response（`OpenaiResponseProvider`）、Anthropic（`AnthropicProvider`）。
+
+核心动机：
+
+- OpenAI Responses API 的部分实现需要携带特殊 HTTP 请求头来启用平台特定功能
+- 三种基础协议中，自定义头注入能力不一致
+- 统一 API 让调用方用 `set_extra("custom_headers", ...)` 即可，与底层协议无关
+
+## 需求
+
+### 功能需求
+
+双层自定义头机制：
+
+- **Provider 级固定头**：`extra_headers: Vec<(String, String)>`，构造时注入，所有请求自动携带。用于该 provider 所有请求都需要的固定标识头（如平台接入标记）
+- **请求级临时头**：`extra.custom_headers: HashMap<String, String>`，通过 `set_extra` 注入。用于特定请求需要覆盖或追加的头
+
+### 约束
+
+- 不可引入任何平台特定逻辑（火山、豆包等字符串不得出现）
+- 自定义头仅运行时生效，不进入 JSON 序列化的请求体
+- 兼容已有的 extra 逃生舱机制（builtin_tools、text_format 等）
+- agcore 是支持库，不提供运行时敏感头过滤保护（如 Authorization/Cookie），但文档中应说明风险
+- 不修改 `LlmProvider` trait、`ProviderType` 枚举
+- `create_provider()` 工厂函数只传 `Vec::new()` 作为 extra_headers 默认值，不暴露配置能力；调用方如需 Provider 级固定头，直接构造 provider 后链式调用 `.with_extra_headers()`
+
+### 用户故事
+
+1. 作为集成者，我想对任意 provider 的请求注入自定义 HTTP 头，以启用平台特有功能（请求级）
+2. 作为集成者，我想在 provider 构造时注入固定头，让所有请求自动携带，避免每次重复指定（Provider 级）
+3. 作为维护者，我想三种基础协议使用统一的 API，调用方无需关心底层 provider 类型
+
+## 方案设计
+
+### 统一设计原则
+
+```
+调用方视角（统一 API）：
+  request.set_extra("custom_headers", json!({"X-Foo": "bar"}));
+  // 不管底层是 OpenAI Chat / OpenAI Response / Anthropic，都能工作
+
+构造方视角（Provider 级）：
+  OpenaiResponseProvider::from_parts(..., extra_headers).with_extra_headers(...);
+  GenericOpenaiProvider::from_parts(..., extra_headers);  // 已有
+  AnthropicProvider::from_parts(..., extra_headers);
+
+头融合顺序（三 provider 一致）：
+  认证头 (Authorization / x-api-key) → Provider 级 extra_headers → 请求级 custom_headers
+  ↑ 后者覆盖前者
+```
+
+### 改动一：GenericOpenaiProvider（openai.rs）
+
+**① `OpenaiChatRequest` 新增字段**
+
+在 `extra_body`（第 147 行）之后：
+
+```rust
+/// 请求级别自定义 HTTP 头。运行时注入，不进入 JSON 请求体。
+/// ⚠️ 与 struct 已有的 `extra_headers: Option<Value>`（OpenAI API 自身的 wire 格式字段）
+/// 不同——后者是 OpenAI API 参数，本字段是 reqwest 层的 HTTP 头注入。
+#[serde(skip)]
+pub custom_headers: HashMap<String, String>,
+```
+
+`#[serde(skip)]` 确保该字段不会出现在序列化后的 JSON body 中。
+
+**② `convert_request()` 从 extra 提取**
+
+在 `parallel_tool_calls`（第 559 行）之后：
+
+```rust
+let custom_headers: HashMap<String, String> = request
+    .get_extra_opt("custom_headers")
+    .unwrap_or_default();
+```
+
+**③ `build_request_builder()` 签名改具体类型 + 注入逻辑**
+
+第 454 行，签名从 `&impl Serialize` 改为 `&OpenaiChatRequest`（两处调用点传入的均为该类型，安全）：
+
+```rust
+fn build_request_builder(
+    &self,
+    url: &str,
+    body: &OpenaiChatRequest,        // 从 &impl Serialize 改为具体类型
+) -> Result<reqwest::RequestBuilder, LlmError> {
+    let mut builder = self
+        .http_client
+        .post(url)
+        .header("Authorization", format!("Bearer {}", self.api_key));
+
+    // 头融合顺序见上方「统一设计原则」。
+    // Provider 级固定头先注入，请求级临时头后注入（后者覆盖前者）。
+
+    Ok(builder.json(body))
+}
+```
+
+两处调用点（`chat_blocking` 第 628 行、`chat_stream_inner` 第 669 行）传入的都是 `&OpenaiChatRequest`，零影响。
+
+**④ `with_extra_headers()` builder 方法**
+
+```rust
+/// 注入 Provider 级别固定头。返回 self 以支持链式调用。
+pub fn with_extra_headers(mut self, headers: Vec<(String, String)>) -> Self {
+    self.extra_headers = headers;
+    self
+}
+```
+
+### 改动二：OpenaiResponseProvider（openai_response.rs）
+
+**① struct 新增 `extra_headers` 字段**
+
+第 287 行，`pub struct OpenaiResponseProvider` 增加：
+
+```rust
+pub struct OpenaiResponseProvider {
+    // ... 已有字段 ...
+    extra_headers: Vec<(String, String)>,
+}
+```
+
+**② `from_parts()` 新增参数**
+
+第 299 行：
+
+```rust
+pub(crate) fn from_parts(
+    base_url: String,
+    api_key: String,
+    model: String,
+    http_client: Client,
+    timeout_secs: u64,
+    extra_headers: Vec<(String, String)>,  // 新增
+) -> Self { ... }
+```
+
+**③ `with_extra_headers()` builder 方法**
+
+```rust
+/// 注入 Provider 级别固定头。返回 self 以支持链式调用。
+pub fn with_extra_headers(mut self, headers: Vec<(String, String)>) -> Self {
+    self.extra_headers = headers;
+    self
+}
+```
+
+**④ `OpenaiResponseRequest` 新增字段**
+
+第 73 行，`reasoning` 之后：
+
+```rust
+/// 请求级别自定义 HTTP 头。序列化时跳过，仅运行时由 build_request_builder 消费。
+/// stream 模式的修改不影响该字段——header 由 convert_request 在请求构造时注入。
+#[serde(skip)]
+pub custom_headers: HashMap<String, String>,
+```
+
+`#[serde(skip)]` 确保该字段不会出现在序列化后的 JSON body 中。
+
+**⑤ `convert_request()` 从 extra 提取**
+
+第 404 行，`reasoning` 之后：
+
+```rust
+let custom_headers: HashMap<String, String> = extra
+    .get("custom_headers")
+    .and_then(|v| serde_json::from_value(v.clone()).ok())
+    .unwrap_or_default();
+```
+
+> **注意**：OpenaiResponseProvider 的 `convert_request` 在顶部 destructure 了 `request`，因此使用 `extra.get()` 而非 `request.get_extra_opt()`。两者语义一致，均反序列化为 `HashMap<String, String>`，失败时静默降级为空 HashMap。
+
+**⑥ `build_request_builder()` 签名 + 注入逻辑**
+
+第 319 行，签名从 `&impl Serialize` 改为 `&OpenaiResponseRequest`（两处调用点传入的均为该类型，安全）：
+
+```rust
+/// 构造 HTTP POST 请求 builder（含认证头与额外请求头）。
+///
+/// 头融合顺序：Authorization → Provider 级 extra_headers → 请求级 custom_headers
+/// 后者覆盖前者。
+fn build_request_builder(
+    &self,
+    body: &OpenaiResponseRequest,   // 从 &impl Serialize 改为具体类型
+) -> Result<reqwest::RequestBuilder, LlmError> {
+    let mut builder = self
+        .http_client
+        .post(self.endpoint_url())
+        .header("Authorization", format!("Bearer {}", self.api_key));
+
+    for (k, v) in &self.extra_headers {
+        builder = builder.header(k.as_str(), v.as_str());
+    }
+
+    for (key, value) in &body.custom_headers {
+        builder = builder.header(key.as_str(), value.as_str());
+    }
+
+    Ok(builder.json(body))
+}
+```
+
+两处调用点（`chat_blocking` 第 708 行、`chat_stream_inner` 第 741 行）传入的都是 `&OpenaiResponseRequest`，零影响。
+
+### 改动三：AnthropicProvider（anthropic.rs）
+
+AnthropicProvider 是唯一没有统一 `build_request_builder` 方法的 provider，需要**前置重构**。
+
+**① struct 新增 `extra_headers` 字段**
+
+第 36 行：
+
+```rust
+pub struct AnthropicProvider {
+    // ... 已有字段 ...
+    extra_headers: Vec<(String, String)>,
+}
+```
+
+**② `from_parts()` 新增参数**
+
+第 128 行：
+
+```rust
+pub(crate) fn from_parts(
+    base_url: String,
+    api_key: String,
+    model: String,
+    http_client: Client,
+    timeout_secs: u64,
+    extra_headers: Vec<(String, String)>,  // 新增
+) -> Self { ... }
+```
+
+**③ `with_extra_headers()` builder 方法**
+
+```rust
+pub fn with_extra_headers(mut self, headers: Vec<(String, String)>) -> Self {
+    self.extra_headers = headers;
+    self
+}
+```
+
+**④ `AnthropicRequestBody` 新增字段**
+
+第 450 行，`stream` 之后：
+
+```rust
+struct AnthropicRequestBody {
+    model: String,
+    max_tokens: u32,
+    // ... 已有字段 ...
+    /// 请求级别自定义 HTTP 头。运行时注入，不进入 JSON 请求体。
+    #[serde(skip)]
+    custom_headers: HashMap<String, String>,
+}
+```
+
+`#[serde(skip)]` 确保该字段不会出现在序列化后的 JSON body 中。
+
+**⑤ `build_request_body()` 从 extra 提取**
+
+```rust
+let custom_headers: HashMap<String, String> = request
+    .get_extra_opt("custom_headers")
+    .unwrap_or_default();
+```
+
+**⑥ 提取 `build_request_builder()` 统一方法（前置重构）**
+
+```rust
+/// 构造 HTTP POST 请求 builder（含认证头 + 自定义头）。
+/// 认证头（x-api-key / anthropic-version）已由 Client 的 default_headers 提供。
+fn build_request_builder(
+    &self,
+    body: &AnthropicRequestBody,
+) -> Result<reqwest::RequestBuilder, LlmError> {
+    let url = format!("{}/v1/messages", self.base_url.trim_end_matches('/'));
+    let mut builder = self.http_client.post(&url).json(body);
+
+    for (k, v) in &self.extra_headers {
+        builder = builder.header(k.as_str(), v.as_str());
+    }
+
+    for (key, value) in &body.custom_headers {
+        builder = builder.header(key.as_str(), value.as_str());
+    }
+
+    Ok(builder)
+}
+```
+
+**⑦ 改造 `chat_blocking()` 和 `chat_stream_inner()`**
+
+改造前（`chat_blocking`，第 263-269 行）：
+
+```rust
+let response = self
+    .http_client
+    .post(&url)
+    .json(&body)
+    .send()
+    .await
+    .map_err(|e| self.map_reqwest_error(e))?;
+```
+
+改造后：
+
+```rust
+let response = self
+    .build_request_builder(&body)?
+    .send()
+    .await
+    .map_err(|e| self.map_reqwest_error(e))?;
+```
+
+`chat_stream_inner`（第 298-304 行）同理。
+
+### 改动四：create_provider()（provider.rs）
+
+依据约束「`create_provider()` 工厂函数不暴露配置能力」，三处分支适配 `from_parts` 的新签名时全部传 `Vec::new()`：
+
+```rust
+// OpenaiResponse（第 199-207 行）
+openai_response::OpenaiResponseProvider::from_parts(
+    config.base_url, config.api_key, config.model,
+    client, config.timeout_secs,
+    Vec::new(),     // extra_headers 默认空
+)
+
+// Anthropic（第 215-221 行）
+anthropic::AnthropicProvider::from_parts(
+    config.base_url, config.api_key, config.model,
+    client, config.timeout_secs,
+    Vec::new(),     // extra_headers 默认空
+)
+
+// OpenAI Chat（第 185-194 行）— 已有 Vec::new()，无需改动
+```
+
+### 调用方式
+
+**请求级临时头**（统一 API，三 provider 通用）：
+
+```rust
+request.set_extra("custom_headers", serde_json::json!({
+    "ark-beta-doubao-app": "true"
+}));
+```
+
+**Provider 级固定头**（构造时注入）：
+
+```rust
+let provider = OpenaiResponseProvider::from_parts(...)
+    .with_extra_headers(vec![
+        ("ark-beta-doubao-app".into(), "true".into()),
+    ]);
+```
+
+## 风险评估
+
+### 风险点与缓解措施
+
+| 风险 | 等级 | 缓解措施 |
+|------|------|---------|
+| 用户通过 `custom_headers` 覆盖 `Authorization` 等认证头 | 中 | 文档说明：自定义头按遍历顺序注入，同 key 后注入覆盖前注入。agcore 作为支持库不做运行时拦截 |
+| `serde_json::from_value` 类型错误静默降级为空 HashMap | 低 | 与已有 extra 字段（builtin_tools、text_format）一致的模式，保持行为统一。类型错误时请求正常发出，只是不携带自定义头 |
+| HashMap 迭代顺序不确定影响测试确定性 | 低 | HTTP 协议不要求 header 顺序，wiremock 按名匹配。无需特殊处理 |
+| AnthropicProvider 前置重构引入回归 | 低 | 提取 `build_request_builder` 是纯重构，现有测试覆盖其请求构造行为。重构后运行现有测试套件即可验证 |
+| `build_request_builder` 签名从泛型改为具体类型 | 低 | 已确认两处调用点（chat_blocking / chat_stream_inner）传入的均为具体类型，零影响 |
+| AnthropicProvider 的 `default_headers`（x-api-key / anthropic-version）与 `extra_headers` 同名头合并行为取决于 reqwest 实现 | 低 | 明确约定 Provider 级固定头不应意图覆盖认证头；`build_request_builder` 的 doc comment 中标注认证头来源 |
+
+### 设计取舍记录
+
+| 决策 | 选择 | 理由 |
+|------|------|------|
+| Provider 级 vs 请求级 | 双层都支持 | 满足固定头和临时头两种场景 |
+| `create_provider` 是否暴露 extra_headers | 不暴露，只传 `Vec::new()` | 保持工厂函数签名简洁，固定头通过 builder 方法注入 |
+| 敏感头保护 | 不做运行时拦截，文档说明 | agcore 是支持库，不替调用方做保护 |
+| `OpenaiChatRequest.custom_headers` 命名 | 用 `custom_headers` 而非 `extra_headers` | 避免与已有的 `extra_headers: Option<Value>`（OpenAI API wire 字段）混淆 |
+
+## 验证标准
+
+### 单元测试（每 provider 4 个）
+
+| 测试 | 验证点 |
+|------|--------|
+| `*_custom_headers_from_extra` | `convert_request` / `build_request_body` 能从 extra 提取 `custom_headers` |
+| `*_custom_headers_skipped_in_json` | `#[serde(skip)]` 确保 custom_headers 不进入序列化 JSON body |
+| `*_custom_headers_invalid_type_fallback` | 传入错误类型（如字符串而非对象）时静默降级为空 HashMap |
+| `*_extra_headers_from_constructor` | 验证 `from_parts` / `new_with_name_and_headers` 传入的 `extra_headers` 在 `build_request_builder` 中被正确注入到 HTTP 请求头 |
+
+### 集成测试（每 provider 4 个，wiremock）
+
+| 测试 | 验证点 |
+|------|--------|
+| `*_custom_headers_are_sent` | mock 匹配器验证 HTTP 请求确实携带自定义头 |
+| `*_provider_level_headers_are_sent` | 验证 Provider 级固定头（通过 `with_extra_headers` 注入）确实出现在 HTTP 请求中 |
+| `*_custom_headers_override_provider_headers` | 当 Provider 级和请求级设置了相同 key 但不同值时，最终 HTTP 请求携带的是请求级的值 |
+| `*_custom_headers_can_override_auth_header` | 注入含 `Authorization` 同 key 的 `custom_headers`，验证最终认证头值被覆盖（使行为可见、可预测，与文档风险说明一致） |
+
+### 回归验证
+
+1. 运行 `cargo test --features full` 确保所有现有测试通过
+2. `cargo clippy --features full` 无新警告
+3. `cargo fmt --check` 格式一致
+
+## 不涉及的改动
+
+- 不新增 Feature gate
+- 不修改 `LlmProvider` trait
+- 不修改 `ProviderType` 枚举
+- 不新增任何平台相关代码

src/llm/provider.rs

@@ -203,6 +203,7 @@ pub fn create_provider(
                     config.model,
                     client,
                     config.timeout_secs,
+                    Vec::new(),
                 ),
             ))
         }
@@ -218,6 +219,7 @@ pub fn create_provider(
                 config.model,
                 client,
                 config.timeout_secs,
+                Vec::new(),
             )))
         }
         ProviderType::DeepSeek => {

src/llm/provider/anthropic.rs

@@ -4,6 +4,7 @@
 //! → `content_block_stop` → `message_delta` → `message_stop`。与 OpenAI 不同，
 //! Anthropic 提供显式 block 边界事件，状态机相对简单。
 
+use std::collections::HashMap;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 use std::time::Duration;
@@ -43,6 +44,8 @@ pub struct AnthropicProvider {
     /// 在 `LlmError::Timeout { duration }` 中回显。`reqwest::Client` 不暴露 timeout getter，
     /// 因此单独存储以便错误消息与配置保持一致。
     timeout_secs: u64,
+    /// Provider 级别固定请求头（如平台标识头），所有请求自动携带。
+    extra_headers: Vec<(String, String)>,
 }
 
 impl AnthropicProvider {
@@ -72,6 +75,7 @@ impl AnthropicProvider {
             api_key,
             model,
             timeout_secs,
+            extra_headers: Vec::new(),
         }
     }
 
@@ -131,6 +135,7 @@ impl AnthropicProvider {
         model: String,
         http_client: Client,
         timeout_secs: u64,
+        extra_headers: Vec<(String, String)>,
     ) -> Self {
         Self {
             http_client,
@@ -142,9 +147,16 @@ impl AnthropicProvider {
             api_key,
             model,
             timeout_secs,
+            extra_headers,
         }
     }
 
+    /// 注入 Provider 级别固定头。返回 self 以支持链式调用。
+    pub fn with_extra_headers(mut self, headers: Vec<(String, String)>) -> Self {
+        self.extra_headers = headers;
+        self
+    }
+
     fn resolve_max_tokens(&self, request: &MessageRequest) -> u32 {
         request.max_tokens.unwrap_or(DEFAULT_MAX_TOKENS)
     }
@@ -214,6 +226,10 @@ impl AnthropicProvider {
 
         let max_tokens = self.resolve_max_tokens(&request);
 
+        // ponytail: 提前抽取 custom_headers，避免后续 into_iter 消耗 request.tools 后借用失败。
+        let custom_headers: HashMap<String, String> =
+            request.get_extra_opt("custom_headers").unwrap_or_default();
+
         let tools = if request.tools.is_empty() {
             None
         } else {
@@ -251,19 +267,40 @@ impl AnthropicProvider {
             tools,
             thinking,
             stream: if request.stream { Some(true) } else { None },
+            custom_headers,
         })
     }
 
+    /// 构造 HTTP POST 请求 builder（含认证头 + 自定义头）。
+    /// 认证头（x-api-key / anthropic-version）已由 Client 的 default_headers 提供。
+    ///
+    /// 头融合顺序：认证头（default_headers）→ Provider 级 extra_headers → 请求级 custom_headers
+    /// 后者覆盖前者。
+    fn build_request_builder(
+        &self,
+        body: &AnthropicRequestBody,
+    ) -> Result<reqwest::RequestBuilder, LlmError> {
+        let url = format!("{}/v1/messages", self.base_url.trim_end_matches('/'));
+        let mut builder = self.http_client.post(&url).json(body);
+
+        for (k, v) in &self.extra_headers {
+            builder = builder.header(k.as_str(), v.as_str());
+        }
+
+        for (key, value) in &body.custom_headers {
+            builder = builder.header(key.as_str(), value.as_str());
+        }
+
+        Ok(builder)
+    }
+
     async fn chat_blocking(&self, request: MessageRequest) -> Result<MessageResponse, LlmError> {
         let body = self.build_request_body(request)?;
-        let url = format!("{}/v1/messages", self.base_url.trim_end_matches('/'));
 
         info!(model = %body.model, "Anthropic: 发送非流式请求");
 
         let response = self
-            .http_client
-            .post(&url)
-            .json(&body)
+            .build_request_builder(&body)?
             .send()
             .await
             .map_err(|e| self.map_reqwest_error(e))?;
@@ -291,14 +328,10 @@ impl AnthropicProvider {
         let mut body = self.build_request_body(request)?;
         body.stream = Some(true);
 
-        let url = format!("{}/v1/messages", self.base_url.trim_end_matches('/'));
-
         info!(model = %body.model, "Anthropic: 发送流式请求");
 
         let response = self
-            .http_client
-            .post(&url)
-            .json(&body)
+            .build_request_builder(&body)?
             .send()
             .await
             .map_err(|e| self.map_reqwest_error(e))?;
@@ -448,6 +481,9 @@ struct AnthropicRequestBody {
     thinking: Option<AnthropicThinking>,
     #[serde(skip_serializing_if = "Option::is_none")]
     stream: Option<bool>,
+    /// 请求级别自定义 HTTP 头。运行时注入，不进入 JSON 请求体。
+    #[serde(skip)]
+    custom_headers: HashMap<String, String>,
 }
 
 #[derive(Debug, Serialize)]
@@ -1207,4 +1243,197 @@ event: message_stop\ndata: {\"type\":\"message_stop\"}\n\n";
             other => panic!("expected RateLimit, got {other:?}"),
         }
     }
+
+    // ===== custom_headers (Phase 8 Step 8.7) =====
+
+    fn mock_messages_body() -> serde_json::Value {
+        json!({
+            "id": "msg_test",
+            "type": "message",
+            "model": "claude-sonnet-4-20250514",
+            "content": [{"type": "text", "text": "OK"}],
+            "stop_reason": "end_turn",
+            "usage": {"input_tokens": 1, "output_tokens": 1}
+        })
+    }
+
+    fn make_provider_with_extra_headers(
+        base_url: String,
+        extra_headers: Vec<(String, String)>,
+    ) -> AnthropicProvider {
+        let client = Client::builder()
+            .timeout(Duration::from_secs(30))
+            .build()
+            .expect("create http client");
+        AnthropicProvider::from_parts(
+            base_url,
+            "sk-ant-test".into(),
+            "claude-sonnet-4-20250514".into(),
+            client,
+            30,
+            extra_headers,
+        )
+    }
+
+    #[test]
+    fn anthropic_custom_headers_from_extra() {
+        let provider = make_provider_with_extra_headers("http://x".into(), Vec::new());
+        let mut req = MessageRequest {
+            model: "claude-sonnet-4-20250514".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1", "X-Other": "v2"}));
+        let body = provider.build_request_body(req).unwrap();
+        assert_eq!(body.custom_headers.get("X-Custom").unwrap(), "v1");
+        assert_eq!(body.custom_headers.get("X-Other").unwrap(), "v2");
+    }
+
+    #[test]
+    fn anthropic_custom_headers_skipped_in_json_body() {
+        let provider = make_provider_with_extra_headers("http://x".into(), Vec::new());
+        let mut req = MessageRequest {
+            model: "claude-sonnet-4-20250514".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1"}));
+        let body = provider.build_request_body(req).unwrap();
+        let value = serde_json::to_value(&body).unwrap();
+        assert!(
+            value.get("custom_headers").is_none(),
+            "custom_headers 不应进入 JSON body"
+        );
+    }
+
+    #[test]
+    fn anthropic_custom_headers_invalid_type_fallback() {
+        let provider = make_provider_with_extra_headers("http://x".into(), Vec::new());
+        let mut req = MessageRequest {
+            model: "claude-sonnet-4-20250514".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!("not_an_object"));
+        let body = provider.build_request_body(req).unwrap();
+        assert!(body.custom_headers.is_empty());
+    }
+
+    #[tokio::test]
+    async fn anthropic_custom_headers_are_sent() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/v1/messages"))
+            .and(header("X-Custom", "v1"))
+            .and(header("anthropic-version", "2023-06-01"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_messages_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider(server.uri());
+        let mut req = MessageRequest {
+            model: "claude-sonnet-4-20250514".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1"}));
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+    }
+
+    #[tokio::test]
+    async fn anthropic_provider_level_headers_are_sent() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/v1/messages"))
+            .and(header("X-Platform", "anthropic-test"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_messages_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider_with_extra_headers(
+            server.uri(),
+            vec![("X-Platform".into(), "anthropic-test".into())],
+        );
+        let req = MessageRequest {
+            model: "claude-sonnet-4-20250514".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+    }
+
+    #[tokio::test]
+    async fn anthropic_custom_headers_override_provider_headers() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/v1/messages"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_messages_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider_with_extra_headers(
+            server.uri(),
+            vec![("X-Platform".into(), "provider-level".into())],
+        );
+        let mut req = MessageRequest {
+            model: "claude-sonnet-4-20250514".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Platform": "request-wins"}));
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+
+        let received = server.received_requests().await.unwrap();
+        assert_eq!(received.len(), 1);
+        let platforms: Vec<&str> = received[0]
+            .headers
+            .get_all("X-Platform")
+            .iter()
+            .filter_map(|v| v.to_str().ok())
+            .collect();
+        assert!(platforms.contains(&"request-wins"));
+    }
+
+    #[tokio::test]
+    async fn anthropic_custom_headers_can_override_auth_header() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/v1/messages"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_messages_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider_with_extra_headers(server.uri(), Vec::new());
+        let mut req = MessageRequest {
+            model: "claude-sonnet-4-20250514".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra(
+            "custom_headers",
+            json!({"x-api-key": "from-custom-headers"}),
+        );
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+
+        let received = server.received_requests().await.unwrap();
+        assert_eq!(received.len(), 1);
+        let keys: Vec<&str> = received[0]
+            .headers
+            .get_all("x-api-key")
+            .iter()
+            .filter_map(|v| v.to_str().ok())
+            .collect();
+        assert!(
+            keys.contains(&"from-custom-headers"),
+            "custom_headers 应能覆盖 x-api-key 头，实际收到: {keys:?}"
+        );
+    }
 }

src/llm/provider/openai.rs

@@ -8,6 +8,7 @@
 //! - `MessageComplete { full_response }` 由 `PartialMessageResponse::finalize()` 产出。
 //! - `capabilities()` 报告 OpenAI Chat 协议的能力。
 
+use std::collections::HashMap;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 use std::time::Duration;
@@ -145,6 +146,11 @@ pub(crate) struct OpenaiChatRequest {
     pub extra_headers: Option<Value>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub extra_body: Option<Value>,
+    /// 请求级别自定义 HTTP 头。运行时注入，不进入 JSON 请求体。
+    /// ⚠️ 与 struct 已有的 `extra_headers: Option<Value>`（OpenAI API 自身的 wire 格式字段）
+    /// 不同——后者是 OpenAI API 参数，本字段是 reqwest 层的 HTTP 头注入。
+    #[serde(skip)]
+    pub custom_headers: HashMap<String, String>,
 }
 
 // =============================================================================
@@ -437,6 +443,12 @@ impl GenericOpenaiProvider {
         )
     }
 
+    /// 注入 Provider 级别固定头。返回 self 以支持链式调用。
+    pub fn with_extra_headers(mut self, headers: Vec<(String, String)>) -> Self {
+        self.extra_headers = headers;
+        self
+    }
+
     pub fn with_client(mut self, client: Client) -> Self {
         self.http_client = client;
         self
@@ -451,10 +463,13 @@ impl GenericOpenaiProvider {
     }
 
     /// 构造 HTTP POST 请求 builder（含认证头与额外请求头）。
+    ///
+    /// 头融合顺序：Authorization → Provider 级 extra_headers → 请求级 custom_headers
+    /// 后者覆盖前者。
     fn build_request_builder(
         &self,
         url: &str,
-        body: &impl Serialize,
+        body: &OpenaiChatRequest,
     ) -> Result<reqwest::RequestBuilder, LlmError> {
         let mut builder = self
             .http_client
@@ -463,6 +478,9 @@ impl GenericOpenaiProvider {
         for (k, v) in &self.extra_headers {
             builder = builder.header(k.as_str(), v.as_str());
         }
+        for (key, value) in &body.custom_headers {
+            builder = builder.header(key.as_str(), value.as_str());
+        }
         Ok(builder.json(body))
     }
 
@@ -557,6 +575,8 @@ impl GenericOpenaiProvider {
         let seed = request.get_extra_opt("seed");
         let response_format = request.get_extra_opt("response_format");
         let parallel_tool_calls = request.get_extra_opt("parallel_tool_calls");
+        let custom_headers: HashMap<String, String> =
+            request.get_extra_opt("custom_headers").unwrap_or_default();
 
         Ok(OpenaiChatRequest {
             model,
@@ -573,6 +593,7 @@ impl GenericOpenaiProvider {
             seed,
             response_format,
             parallel_tool_calls,
+            custom_headers,
             ..Default::default()
         })
     }
@@ -1695,4 +1716,189 @@ data: [DONE]\n\n";
             "expected an Error event for malformed SSE chunk"
         );
     }
+
+    // ===== custom_headers (Phase 8 Step 8.7) =====
+
+    fn make_provider_for_header_tests(base_url: String) -> GenericOpenaiProvider {
+        GenericOpenaiProvider::new_with_name(
+            base_url,
+            "sk-test".into(),
+            "gpt-4o".into(),
+            "openai",
+            30,
+        )
+    }
+
+    fn mock_chat_completions_body() -> serde_json::Value {
+        json!({
+            "id": "chatcmpl-test",
+            "object": "chat.completion",
+            "created": 1,
+            "model": "gpt-4o",
+            "choices": [{"index": 0, "message": {"role": "assistant", "content": "OK"}, "finish_reason": "stop"}],
+            "usage": {"prompt_tokens": 1, "completion_tokens": 1, "total_tokens": 2}
+        })
+    }
+
+    #[test]
+    fn openai_chat_custom_headers_from_extra() {
+        let provider = make_provider_for_header_tests("http://x".into());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1", "X-Other": "v2"}));
+
+        let body = provider.convert_request(req).unwrap();
+        assert_eq!(body.custom_headers.get("X-Custom").unwrap(), "v1");
+        assert_eq!(body.custom_headers.get("X-Other").unwrap(), "v2");
+    }
+
+    #[test]
+    fn openai_chat_custom_headers_skipped_in_json_body() {
+        let provider = make_provider_for_header_tests("http://x".into());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1"}));
+        let body = provider.convert_request(req).unwrap();
+
+        let value = serde_json::to_value(&body).unwrap();
+        assert!(
+            value.get("custom_headers").is_none(),
+            "custom_headers 不应进入 JSON body"
+        );
+    }
+
+    #[test]
+    fn openai_chat_custom_headers_invalid_type_fallback() {
+        let provider = make_provider_for_header_tests("http://x".into());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!("not_an_object"));
+        let body = provider.convert_request(req).unwrap();
+        assert!(body.custom_headers.is_empty());
+    }
+
+    #[tokio::test]
+    async fn openai_chat_custom_headers_are_sent() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/chat/completions"))
+            .and(header("authorization", "Bearer sk-test"))
+            .and(header("X-Custom", "v1"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_chat_completions_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider_for_header_tests(server.uri());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1"}));
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+    }
+
+    #[tokio::test]
+    async fn openai_chat_provider_level_headers_are_sent() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/chat/completions"))
+            .and(header("X-Platform", "doubao"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_chat_completions_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider_for_header_tests(server.uri())
+            .with_extra_headers(vec![("X-Platform".into(), "doubao".into())]);
+        let req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+    }
+
+    #[tokio::test]
+    async fn openai_chat_custom_headers_override_provider_headers() {
+        // ponytail: wiremock 的 `header()` 是精确匹配（顺序敏感），同 key 多值无法匹配。
+        // 因此 override 测试用通用 mock + server.received_requests() 事后验证实际请求头。
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/chat/completions"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_chat_completions_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider_for_header_tests(server.uri())
+            .with_extra_headers(vec![("X-Platform".into(), "provider-level".into())]);
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Platform": "request-wins"}));
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+
+        let received = server.received_requests().await.unwrap();
+        assert_eq!(received.len(), 1);
+        let platforms: Vec<&str> = received[0]
+            .headers
+            .get_all("X-Platform")
+            .iter()
+            .filter_map(|v| v.to_str().ok())
+            .collect();
+        assert!(platforms.contains(&"request-wins"));
+    }
+
+    #[tokio::test]
+    async fn openai_chat_custom_headers_can_override_auth_header() {
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/chat/completions"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_chat_completions_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider_for_header_tests(server.uri());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra(
+            "custom_headers",
+            json!({"authorization": "from-custom-headers"}),
+        );
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+
+        let received = server.received_requests().await.unwrap();
+        assert_eq!(received.len(), 1);
+        let auth_values: Vec<&str> = received[0]
+            .headers
+            .get_all("authorization")
+            .iter()
+            .filter_map(|v| v.to_str().ok())
+            .collect();
+        assert!(
+            auth_values.contains(&"from-custom-headers"),
+            "custom_headers 应能覆盖 Authorization 头，实际收到: {auth_values:?}"
+        );
+    }
 }

src/llm/provider/openai_response.rs

@@ -9,6 +9,7 @@
 //! - assistant 文本回传用 `output_text`（区别于 user 的 `input_text`），对齐 OpenAI wire 格式
 //! - 未知 `item_type` 兜底为 `ContentBlock::Extension` 保持前向兼容
 
+use std::collections::HashMap;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 use std::time::Duration;
@@ -71,6 +72,10 @@ pub(crate) struct OpenaiResponseRequest {
     pub metadata: Option<Value>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub reasoning: Option<Value>,
+    /// 请求级别自定义 HTTP 头。序列化时跳过，仅运行时由 build_request_builder 消费。
+    /// stream 模式的修改不影响该字段——header 由 convert_request 在请求构造时注入。
+    #[serde(skip)]
+    pub custom_headers: HashMap<String, String>,
 }
 
 /// Request input item —— untagged 枚举。
@@ -292,6 +297,8 @@ pub struct OpenaiResponseProvider {
     /// ponytail: 单独存储以便 `LlmError::Timeout { duration }` 与配置保持一致。
     /// `reqwest::Client` 不暴露 timeout getter。
     timeout_secs: u64,
+    /// Provider 级别固定请求头（如平台标识头），所有请求自动携带。
+    extra_headers: Vec<(String, String)>,
 }
 
 impl OpenaiResponseProvider {
@@ -302,6 +309,7 @@ impl OpenaiResponseProvider {
         model: String,
         http_client: Client,
         timeout_secs: u64,
+        extra_headers: Vec<(String, String)>,
     ) -> Self {
         Self {
             http_client,
@@ -309,22 +317,38 @@ impl OpenaiResponseProvider {
             api_key,
             model,
             timeout_secs,
+            extra_headers,
         }
     }
 
+    /// 注入 Provider 级别固定头。返回 self 以支持链式调用。
+    pub fn with_extra_headers(mut self, headers: Vec<(String, String)>) -> Self {
+        self.extra_headers = headers;
+        self
+    }
+
     fn endpoint_url(&self) -> String {
         format!("{}/responses", self.base_url.trim_end_matches('/'))
     }
 
     fn build_request_builder(
         &self,
-        body: &impl Serialize,
+        body: &OpenaiResponseRequest,
     ) -> Result<reqwest::RequestBuilder, LlmError> {
-        Ok(self
+        let mut builder = self
             .http_client
             .post(self.endpoint_url())
-            .header("Authorization", format!("Bearer {}", self.api_key))
-            .json(body))
+            .header("Authorization", format!("Bearer {}", self.api_key));
+
+        for (k, v) in &self.extra_headers {
+            builder = builder.header(k.as_str(), v.as_str());
+        }
+
+        for (key, value) in &body.custom_headers {
+            builder = builder.header(key.as_str(), value.as_str());
+        }
+
+        Ok(builder.json(body))
     }
 
     fn map_reqwest_error(&self, e: reqwest::Error) -> LlmError {
@@ -403,6 +427,14 @@ impl OpenaiResponseProvider {
         let metadata: Option<Value> = extra.get("metadata").cloned();
         let reasoning: Option<Value> = extra.get("reasoning").cloned();
 
+        // 注意：OpenaiResponseProvider 的 `convert_request` 在顶部 destructure 了 `request`，
+        // 因此使用 `extra.get()` 而非 `request.get_extra_opt()`。两者语义一致，
+        // 均反序列化为 `HashMap<String, String>`，失败时静默降级为空 HashMap。
+        let custom_headers: HashMap<String, String> = extra
+            .get("custom_headers")
+            .and_then(|v| serde_json::from_value(v.clone()).ok())
+            .unwrap_or_default();
+
         // ponytail: tool_choice 直通映射 —— ToolChoice::None → "none"（与 GenericOpenaiProvider 行为一致），
         // Auto/Required → 字符串，Named → 对象。SA Director 审查 Round 1 修复。
         let tool_choice_value = match tool_choice {
@@ -611,6 +643,7 @@ impl OpenaiResponseProvider {
             truncation,
             metadata,
             reasoning,
+            custom_headers,
         })
     }
 
@@ -1020,7 +1053,14 @@ mod tests {
             .timeout(Duration::from_secs(30))
             .build()
             .expect("create http client");
-        OpenaiResponseProvider::from_parts(base_url, "sk-test".into(), "gpt-4o".into(), client, 30)
+        OpenaiResponseProvider::from_parts(
+            base_url,
+            "sk-test".into(),
+            "gpt-4o".into(),
+            client,
+            30,
+            Vec::new(),
+        )
     }
 
     // ===== convert_request 单元测试 =====
@@ -1975,4 +2015,185 @@ data: {\"type\":\"response.failed\",\"error\":{\"message\":\"server failed mid-s
         assert!(caps.features.streaming);
         assert_eq!(caps.features.max_context_window, 200_000);
     }
+
+    // ===== custom_headers (Phase 8 Step 8.7) =====
+
+    fn mock_responses_body() -> serde_json::Value {
+        json!({
+            "id": "resp-test",
+            "object": "response",
+            "status": "completed",
+            "model": "gpt-4o",
+            "output": [{
+                "id": "msg_1", "type": "message", "role": "assistant",
+                "content": [{"type": "output_text", "text": "OK"}]
+            }],
+            "usage": {"prompt_tokens": 1, "completion_tokens": 1, "total_tokens": 2}
+        })
+    }
+
+    #[test]
+    fn openai_response_custom_headers_from_extra() {
+        let provider = make_provider("http://x".into());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1", "X-Other": "v2"}));
+        let body = provider.convert_request(req).unwrap();
+        assert_eq!(body.custom_headers.get("X-Custom").unwrap(), "v1");
+        assert_eq!(body.custom_headers.get("X-Other").unwrap(), "v2");
+    }
+
+    #[test]
+    fn openai_response_custom_headers_skipped_in_json_body() {
+        let provider = make_provider("http://x".into());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1"}));
+        let body = provider.convert_request(req).unwrap();
+        let value = serde_json::to_value(&body).unwrap();
+        assert!(
+            value.get("custom_headers").is_none(),
+            "custom_headers 不应进入 JSON body"
+        );
+    }
+
+    #[test]
+    fn openai_response_custom_headers_invalid_type_fallback() {
+        let provider = make_provider("http://x".into());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!("not_an_object"));
+        let body = provider.convert_request(req).unwrap();
+        assert!(body.custom_headers.is_empty());
+    }
+
+    #[tokio::test]
+    async fn openai_response_custom_headers_are_sent() {
+        use wiremock::matchers::{header, method, path};
+        use wiremock::{Mock, MockServer, ResponseTemplate};
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/responses"))
+            .and(header("authorization", "Bearer sk-test"))
+            .and(header("X-Custom", "v1"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_responses_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider(server.uri());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Custom": "v1"}));
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+    }
+
+    #[tokio::test]
+    async fn openai_response_provider_level_headers_are_sent() {
+        use wiremock::matchers::{header, method, path};
+        use wiremock::{Mock, MockServer, ResponseTemplate};
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/responses"))
+            .and(header("X-Platform", "doubao"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_responses_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider(server.uri())
+            .with_extra_headers(vec![("X-Platform".into(), "doubao".into())]);
+        let req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+    }
+
+    #[tokio::test]
+    async fn openai_response_custom_headers_override_provider_headers() {
+        use wiremock::matchers::{method, path};
+        use wiremock::{Mock, MockServer, ResponseTemplate};
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/responses"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_responses_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider(server.uri())
+            .with_extra_headers(vec![("X-Platform".into(), "provider-level".into())]);
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra("custom_headers", json!({"X-Platform": "request-wins"}));
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+
+        let received = server.received_requests().await.unwrap();
+        assert_eq!(received.len(), 1);
+        let platforms: Vec<&str> = received[0]
+            .headers
+            .get_all("X-Platform")
+            .iter()
+            .filter_map(|v| v.to_str().ok())
+            .collect();
+        assert!(platforms.contains(&"request-wins"));
+    }
+
+    #[tokio::test]
+    async fn openai_response_custom_headers_can_override_auth_header() {
+        use wiremock::matchers::{method, path};
+        use wiremock::{Mock, MockServer, ResponseTemplate};
+        let server = MockServer::start().await;
+        Mock::given(method("POST"))
+            .and(path("/responses"))
+            .respond_with(ResponseTemplate::new(200).set_body_json(mock_responses_body()))
+            .mount(&server)
+            .await;
+
+        let provider = make_provider(server.uri());
+        let mut req = MessageRequest {
+            model: "gpt-4o".into(),
+            messages: vec![Message::user_text("hi")],
+            ..Default::default()
+        };
+        req.set_extra(
+            "custom_headers",
+            json!({"authorization": "from-custom-headers"}),
+        );
+
+        let resp = provider.chat_blocking(req).await.unwrap();
+        assert_eq!(resp.text(), "OK");
+
+        let received = server.received_requests().await.unwrap();
+        assert_eq!(received.len(), 1);
+        let auth_values: Vec<&str> = received[0]
+            .headers
+            .get_all("authorization")
+            .iter()
+            .filter_map(|v| v.to_str().ok())
+            .collect();
+        assert!(
+            auth_values.contains(&"from-custom-headers"),
+            "custom_headers 应能覆盖 Authorization 头，实际收到: {auth_values:?}"
+        );
+    }
 }