diff --git a/docs/technical/【技术方案】Raw GPT Image 2图片编辑代理-2026-09-07.md b/docs/technical/【技术方案】Raw GPT Image 2图片编辑代理-2026-09-07.md
index c5dd38c37..4c319b003 100644
--- a/docs/technical/【技术方案】Raw GPT Image 2图片编辑代理-2026-09-07.md	
+++ b/docs/technical/【技术方案】Raw GPT Image 2图片编辑代理-2026-09-07.md	
@@ -35,7 +35,7 @@ POST /api/raw/v1/images/edit
 }
 ```
 
-`image` 是必填的单图结构 `{ data, mimeType }`；`mask` 可选并使用相同结构。`image` 和 `mask` 的 `mimeType` 必须为 `image/png`，base64 解码后必须是可完整解码的有效 PNG 文件，提供 mask 时其宽高必须与 image 完全一致；空数据、非 PNG 字节、MIME 不匹配或尺寸不一致均在扣费前返回 400。服务端不把输入格式另建成请求参数。`prompt` 必填。`quality`、`background` 和 `output_format` 采用 GPT Image 模型支持的值。
+`image` 是必填的单图结构 `{ data, mimeType }`；`mask` 可选并使用相同结构。`image` 和 `mask` 的 `mimeType` 必须为 `image/png`，base64 解码后必须是可完整解码的有效 PNG 文件，提供 mask 时其宽高必须与 image 完全一致；空数据、非 PNG 字节、MIME 不匹配或尺寸不一致均在扣费前返回 400。服务端不把输入格式另建成请求参数。`prompt` 必填，UTF-8 原始字节长度不得超过 `16 KiB`；超限在扣费前返回 400。`quality`、`background` 和 `output_format` 采用 GPT Image 模型支持的值。
 
 `width`、`height` 使用严格输出尺寸规则，均在扣费前校验：
 
diff --git a/server-rs/crates/api-server/src/raw_image.rs b/server-rs/crates/api-server/src/raw_image.rs
index e0e88a876..1c46e7fbc 100644
--- a/server-rs/crates/api-server/src/raw_image.rs
+++ b/server-rs/crates/api-server/src/raw_image.rs
@@ -59,6 +59,8 @@ pub(crate) struct RawImageEditResponse {
     pub(crate) data: Vec<RawImageEditItem>,
 }
 
+const RAW_IMAGE_MAX_PROMPT_BYTES: usize = 16 * 1024;
+
 pub(crate) async fn edit_raw_image(
     State(state): State<AppState>,
     Extension(request_context): Extension<RequestContext>,
@@ -156,6 +158,11 @@ fn prepare_request(payload: RawImageEditRequest) -> Result<PreparedRawImageEdit,
     if payload.prompt.trim().is_empty() {
         return Err(bad_request("prompt 不能为空"));
     }
+    if payload.prompt.len() > RAW_IMAGE_MAX_PROMPT_BYTES {
+        return Err(bad_request(format!(
+            "prompt 不能超过 {RAW_IMAGE_MAX_PROMPT_BYTES} 字节"
+        )));
+    }
     validate_raw_image_edit_dimensions(payload.width, payload.height)
         .map_err(|error| bad_request(error.to_string()))?;
     validate_optional_value(
@@ -430,4 +437,21 @@ mod tests {
 
         assert!(format!("{error:?}").contains("mask 尺寸必须与 image 一致"));
     }
+
+    #[test]
+    fn prompt_uses_raw_utf8_byte_limit() {
+        let payload = serde_json::json!({
+            "image": {"data": encoded_png(1, 1), "mimeType": "image/png"},
+            "prompt": "a".repeat(RAW_IMAGE_MAX_PROMPT_BYTES + 1),
+            "width": 1024,
+            "height": 1024
+        });
+        let parsed: RawImageEditRequest = serde_json::from_value(payload).expect("request");
+        let error = match prepare_request(parsed) {
+            Ok(_) => panic!("oversized prompt should fail before image decode and billing"),
+            Err(error) => error,
+        };
+
+        assert!(format!("{error:?}").contains("prompt 不能超过 16384 字节"));
+    }
 }
diff --git a/server-rs/crates/platform-image/Cargo.toml b/server-rs/crates/platform-image/Cargo.toml
index 9da088343..2030dab06 100644
--- a/server-rs/crates/platform-image/Cargo.toml
+++ b/server-rs/crates/platform-image/Cargo.toml
@@ -9,6 +9,7 @@ base64 = { workspace = true }
 curl = { workspace = true }
 image = { workspace = true, features = ["jpeg", "png", "webp"] }
 reqwest = { workspace = true, features = ["json", "multipart", "rustls-tls"] }
+serde = { workspace = true }
 serde_json = { workspace = true }
 tokio = { workspace = true, features = ["io-util", "macros", "net", "time"] }
 tracing = { workspace = true }