diff --git a/docs/project-memory/shared-memory/decision-log.md b/docs/project-memory/shared-memory/decision-log.md
index 29d29c4f3..c2b9f4ad4 100644
--- a/docs/project-memory/shared-memory/decision-log.md
+++ b/docs/project-memory/shared-memory/decision-log.md
@@ -16,6 +16,16 @@
 
 ---
 
+## 2026-07-29 像素规整降级必须复用交付尺寸守卫
+
+- 背景：像素模式接入「角色带背景原图与透明图统一交付尺寸」后，删除了原先像素路径末尾的后置尺寸恢复。但像素规整的 best-effort 降级分支（预算耗尽、回读 provider 原图失败或超时、CPU permit 获取失败、worker 内 deadline、join 异常、worker 超时）都直接返回 BgFilter 原始输出并把尺寸错误置为 `None`，跳过了非像素路径已有的尺寸比对与 alpha 回贴。BgFilter 回图尺寸漂移是已知现象，叠加并发上限 2 导致的 permit 超时后，角色会绕过「改用已保存的同尺寸原图完成画布」的安全降级，角色和图标都可能持久化尺寸漂移的低分辨率透明图。
+- 决策：像素路径的每一条降级都必须经 `degrade_editor_pixel_art_to_postprocessed_with_dimension_guard` 收口，该守卫复用非像素路径的 `apply_editor_postprocessed_alpha_from_persisted_provider_source_or_original`：先做纯内存尺寸比对，与交付尺寸一致就原样返回且不产生额外 OSS GET；漂移才回读原图重贴 alpha；修复失败返回尺寸错误交由调用方降级。由 provider 原图逐像素合成的 `rgba_source` fallback 尺寸天然正确，不再经守卫。像素路径函数因此需要显式接收交付宽高。
+- 影响范围：`server-rs/crates/api-server/src/editor_project.rs` 的角色与图标像素规整降级路径；不改变成功路径、OSS PUT 次数、资源类型、画布项或前端契约，OSS GET 仍只在尺寸漂移时发生。
+- 验证方式：`pixel_art_degrade_paths_guard_postprocessed_delivery_dimensions` 结构断言固定"降级分支不得返回 `(postprocessed, None, …)`"与守卫的委托实现；运行 `cargo test -p api-server editor_project --manifest-path server-rs/Cargo.toml`、`npm run check:rustfmt`、`npm run check:encoding` 和 `git diff --check`。
+- 关联文档：本文件「2026-07-29 角色带背景原图与透明图统一交付尺寸」与「2026-07-28 图片生成风格使用可扩展字段并以纯内存像素规整首发」。
+
+---
+
 ## 2026-07-29 角色带背景原图与透明图统一交付尺寸
 
 - 背景：图片画布已将模型原生回图归一到统一业务像素矩阵，但角色分支为了保留 provider 原生分辨率，先持久化带背景原图，只在扣背后归一透明主图。因此同一个 1K 角色任务会同时给出模型原生大图和长边 `1024` 的透明图。
diff --git a/server-rs/crates/api-server/src/editor_project.rs b/server-rs/crates/api-server/src/editor_project.rs
index f36f40205..05a692290 100644
--- a/server-rs/crates/api-server/src/editor_project.rs
+++ b/server-rs/crates/api-server/src/editor_project.rs
@@ -2028,6 +2028,8 @@ pub(crate) async fn generate_editor_image_for_owner(
             apply_editor_postprocessed_alpha_and_pixel_art_from_persisted_provider_source_or_original(
                 state,
                 source_object_key.as_str(),
+                delivery_width,
+                delivery_height,
                 removal.image,
                 request_context.external_call_deadline(),
             )
@@ -3204,9 +3206,35 @@ fn resolve_editor_pixel_art_processing_deadline(
         .unwrap_or(local_deadline)
 }
 
+// 中文注释：像素规整的每一条 best-effort 降级都不能直接把 BgFilter 原始输出当作
+// 最终结果——它的尺寸可能相对交付尺寸漂移。这里复用非像素路径的同一套守卫：先做
+// 纯内存尺寸比对，一致就原样返回且不产生 OSS GET；只有真的漂移才回读原图重贴
+// alpha，修不好则返回尺寸错误，由调用方走原图安全降级。
+async fn degrade_editor_pixel_art_to_postprocessed_with_dimension_guard(
+    state: &AppState,
+    provider_source_object_key: &str,
+    delivery_width: u32,
+    delivery_height: u32,
+    postprocessed: DownloadedOpenAiImage,
+    reason: String,
+) -> (DownloadedOpenAiImage, Option<AppError>, Option<String>) {
+    let (image, dimension_error) =
+        apply_editor_postprocessed_alpha_from_persisted_provider_source_or_original(
+            state,
+            provider_source_object_key,
+            delivery_width,
+            delivery_height,
+            postprocessed,
+        )
+        .await;
+    (image, dimension_error, Some(reason))
+}
+
 async fn apply_editor_postprocessed_alpha_and_pixel_art_from_persisted_provider_source_or_original(
     state: &AppState,
     provider_source_object_key: &str,
+    delivery_width: u32,
+    delivery_height: u32,
     postprocessed: DownloadedOpenAiImage,
     request_deadline: Option<Instant>,
 ) -> (DownloadedOpenAiImage, Option<AppError>, Option<String>) {
@@ -3216,11 +3244,15 @@ async fn apply_editor_postprocessed_alpha_and_pixel_art_from_persisted_provider_
     // BgFilter 前持久化并释放，因此这里只回读既有对象一次；这次回读同时承担
     // 尺寸漂移时的 alpha 回贴，禁止为两个步骤分别发起 OSS GET。
     if Instant::now() >= processing_deadline {
-        return (
+        return degrade_editor_pixel_art_to_postprocessed_with_dimension_guard(
+            state,
+            provider_source_object_key,
+            delivery_width,
+            delivery_height,
             postprocessed,
-            None,
-            Some("像素规整处理预算已耗尽，已保留透明后处理图。".to_string()),
-        );
+            "像素规整处理预算已耗尽，已保留透明后处理图。".to_string(),
+        )
+        .await;
     }
     let provider_source = match tokio::time::timeout_at(
         tokio::time::Instant::from_std(processing_deadline),
@@ -3231,19 +3263,41 @@ async fn apply_editor_postprocessed_alpha_and_pixel_art_from_persisted_provider_
         Ok(Ok(provider_source)) => provider_source,
         Ok(Err(error)) => {
             let reason = error.body_text();
-            return (postprocessed, None, Some(reason));
+            return degrade_editor_pixel_art_to_postprocessed_with_dimension_guard(
+                state,
+                provider_source_object_key,
+                delivery_width,
+                delivery_height,
+                postprocessed,
+                reason,
+            )
+            .await;
         }
         Err(_) => {
-            return (
+            return degrade_editor_pixel_art_to_postprocessed_with_dimension_guard(
+                state,
+                provider_source_object_key,
+                delivery_width,
+                delivery_height,
                 postprocessed,
-                None,
-                Some("像素规整读取 provider 原图超时，已保留透明后处理图。".to_string()),
-            );
+                "像素规整读取 provider 原图超时，已保留透明后处理图。".to_string(),
+            )
+            .await;
         }
     };
     let permit = match acquire_editor_pixel_art_cpu_permit(processing_deadline).await {
         Ok(permit) => permit,
-        Err(error) => return (postprocessed, None, Some(error)),
+        Err(error) => {
+            return degrade_editor_pixel_art_to_postprocessed_with_dimension_guard(
+                state,
+                provider_source_object_key,
+                delivery_width,
+                delivery_height,
+                postprocessed,
+                error,
+            )
+            .await;
+        }
     };
 
     let provider_source = Arc::new(provider_source);
@@ -3287,21 +3341,49 @@ async fn apply_editor_postprocessed_alpha_and_pixel_art_from_persisted_provider_
         tokio::time::timeout_at(tokio::time::Instant::from_std(processing_deadline), worker).await;
     match result {
         Ok(Ok(Ok(image))) => (image, None, None),
-        Ok(Ok(Err((fallback, preparation_error, error)))) => (
-            fallback.unwrap_or_else(|| take_arc_downloaded_image(postprocessed)),
-            preparation_error,
+        // 中文注释：fallback 由 provider 原图逐像素合成，尺寸天然等于交付尺寸，
+        // 不需要再走守卫；准备阶段已产出尺寸错误时同样直接交回调用方降级。
+        Ok(Ok(Err((Some(rgba_source), preparation_error, error)))) => {
+            (rgba_source, preparation_error, Some(error))
+        }
+        Ok(Ok(Err((None, Some(preparation_error), error)))) => (
+            take_arc_downloaded_image(postprocessed),
+            Some(preparation_error),
             Some(error),
         ),
-        Ok(Err(error)) => (
-            take_arc_downloaded_image(postprocessed),
-            None,
-            Some(format!("像素规整工作线程异常：{error}")),
-        ),
-        Err(_) => (
-            take_arc_downloaded_image(postprocessed),
-            None,
-            Some("像素规整处理超时，已保留透明后处理图。".to_string()),
-        ),
+        Ok(Ok(Err((None, None, error)))) => {
+            degrade_editor_pixel_art_to_postprocessed_with_dimension_guard(
+                state,
+                provider_source_object_key,
+                delivery_width,
+                delivery_height,
+                take_arc_downloaded_image(postprocessed),
+                error,
+            )
+            .await
+        }
+        Ok(Err(error)) => {
+            degrade_editor_pixel_art_to_postprocessed_with_dimension_guard(
+                state,
+                provider_source_object_key,
+                delivery_width,
+                delivery_height,
+                take_arc_downloaded_image(postprocessed),
+                format!("像素规整工作线程异常：{error}"),
+            )
+            .await
+        }
+        Err(_) => {
+            degrade_editor_pixel_art_to_postprocessed_with_dimension_guard(
+                state,
+                provider_source_object_key,
+                delivery_width,
+                delivery_height,
+                take_arc_downloaded_image(postprocessed),
+                "像素规整处理超时，已保留透明后处理图。".to_string(),
+            )
+            .await
+        }
     }
 }
 
@@ -4630,6 +4712,8 @@ pub(crate) async fn generate_editor_icon_spritesheet_for_owner(
         apply_editor_postprocessed_alpha_and_pixel_art_from_persisted_provider_source_or_original(
             state,
             source_object_key.as_str(),
+            source_width,
+            source_height,
             removal.image,
             request_context.external_call_deadline(),
         )
@@ -9201,6 +9285,39 @@ mod tests {
         );
     }
 
+    #[test]
+    fn pixel_art_degrade_paths_guard_postprocessed_delivery_dimensions() {
+        let source = include_str!("editor_project.rs");
+        // 中文注释：像素规整的每一条 best-effort 降级（预算耗尽、回读原图失败或超时、
+        // permit 获取失败、worker 内 deadline、join 异常、worker 超时）都不能把 BgFilter
+        // 原始输出连同 None 尺寸错误直接交回调用方，否则角色会绕过原图安全降级、
+        // 角色和图标都可能持久化尺寸漂移的低分辨率透明图。
+        assert_function_not_contains(
+            source,
+            "async fn apply_editor_postprocessed_alpha_and_pixel_art_from_persisted_provider_source_or_original",
+            "fn restore_editor_generated_image_output_dimensions",
+            &[
+                "return (postprocessed, None,",
+                "(postprocessed, None, Some(reason))",
+                "take_arc_downloaded_image(postprocessed),\n            None,",
+                "fallback.unwrap_or_else(",
+            ],
+        );
+        // 守卫必须复用非像素路径的同一套尺寸比对与 alpha 回贴，保证尺寸一致时
+        // 不产生额外 OSS GET，漂移修不好时返回尺寸错误。
+        assert_function_contains_in_order(
+            source,
+            "async fn degrade_editor_pixel_art_to_postprocessed_with_dimension_guard",
+            "async fn apply_editor_postprocessed_alpha_and_pixel_art_from_persisted_provider_source_or_original",
+            &[
+                "apply_editor_postprocessed_alpha_from_persisted_provider_source_or_original",
+                "delivery_width",
+                "delivery_height",
+                "(image, dimension_error, Some(reason))",
+            ],
+        );
+    }
+
     #[test]
     fn pixel_art_provider_input_prep_shares_deadline_and_cpu_permit() {
         let source = include_str!("editor_project.rs");