diff --git a/.github/actions/cargo-cache/Dockerfile b/.github/actions/cargo-cache/Dockerfile
index 7306ad16e..0b4d14967 100644
--- a/.github/actions/cargo-cache/Dockerfile
+++ b/.github/actions/cargo-cache/Dockerfile
@@ -7,21 +7,18 @@ RUN --mount=type=bind,target=/cache \
     --mount=type=cache,target=/usr/local/cargo/git \
     --mount=type=cache,target=/app/backend/target \
     test -n "$CACHE_STAMP" \
-    && cp -a /cache/registry/. /usr/local/cargo/registry/ \
-    && cp -a /cache/git/. /usr/local/cargo/git/ \
-    && cp -a /cache/target/. /app/backend/target/
+    && tar -xzf /cache/registry.tar.gz -C /usr/local/cargo/registry \
+    && tar -xzf /cache/git.tar.gz -C /usr/local/cargo/git \
+    && tar -xzf /cache/target.tar.gz -C /app/backend/target
 
-FROM busybox:1.37.0-musl@sha256:5cec3fc171c87218698e85a52af7087de727372aae264a787b8112901a5b0092 AS collect
+FROM busybox:1.37.0-musl@sha256:5cec3fc171c87218698e85a52af7087de727372aae264a787b8112901a5b0092 AS snapshot
 ARG CACHE_STAMP
-# 一次导出三个 mount，避免逐目录创建镜像、载入 Docker 再复制文件。
+# 直接压缩 mount 内容，构建层和 runner 只保存归档，避免多份展开的编译产物占满磁盘
 RUN --mount=type=cache,target=/usr/local/cargo/registry \
     --mount=type=cache,target=/usr/local/cargo/git \
     --mount=type=cache,target=/app/backend/target \
     test -n "$CACHE_STAMP" \
-    && mkdir -p /cache/registry /cache/git /cache/target \
-    && cp -a /usr/local/cargo/registry/. /cache/registry/ \
-    && cp -a /usr/local/cargo/git/. /cache/git/ \
-    && cp -a /app/backend/target/. /cache/target/
-
-FROM scratch AS snapshot
-COPY --from=collect /cache/ /
+    && mkdir -p /cache \
+    && tar -czf /cache/registry.tar.gz -C /usr/local/cargo/registry . \
+    && tar -czf /cache/git.tar.gz -C /usr/local/cargo/git . \
+    && tar -czf /cache/target.tar.gz -C /app/backend/target .
diff --git a/.github/actions/cargo-cache/cargo-cache.sh b/.github/actions/cargo-cache/cargo-cache.sh
index 781112dc9..ff703e181 100644
--- a/.github/actions/cargo-cache/cargo-cache.sh
+++ b/.github/actions/cargo-cache/cargo-cache.sh
@@ -14,24 +14,42 @@ case "$architecture" in amd64|arm64) ;; *) exit 2 ;; esac
 dockerfile="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/Dockerfile"
 
 usable() {
-  local root="$1" path crates=false libraries=false
-  # 目录或 buildstamp 存在不代表编译发生过，必须同时有下载包与目标依赖。
-  for path in "$root"/registry/cache/*/*.crate; do
-    if [ -f "$path" ] && [ -s "$path" ]; then crates=true; break; fi
-  done
-  for path in "$root"/target/"$architecture"/release/deps/*.rlib; do
-    if [ -f "$path" ] && [ -s "$path" ]; then libraries=true; break; fi
-  done
-  [ "$crates" = true ] && [ "$libraries" = true ]
+  # 流式检查归档中的非空依赖文件，校验时不在 runner 展开编译产物
+  python3 - "$1" "$architecture" <<'PY'
+import pathlib
+import re
+import sys
+import tarfile
+
+root = pathlib.Path(sys.argv[1])
+architecture = sys.argv[2]
+
+def contains(filename, pattern):
+    with tarfile.open(root / filename, mode="r|gz") as archive:
+        return any(
+            member.isfile() and member.size > 0
+            and re.fullmatch(pattern, member.name.removeprefix("./"))
+            for member in archive
+        )
+
+try:
+    valid = (
+        (root / "git.tar.gz").stat().st_size > 0
+        and contains("registry.tar.gz", r"cache/[^/]+/[^/]+\.crate")
+        and contains("target.tar.gz", rf"{architecture}/release/deps/[^/]+\.rlib")
+    )
+except (OSError, tarfile.TarError):
+    valid = False
+sys.exit(0 if valid else 1)
+PY
 }
 
 command=(docker buildx build --builder "$builder" --file "$dockerfile" --progress plain)
-# mount 的内容不参与层指纹，用时间戳重跑复制；--no-cache 会重置 cache mount。
+# mount 的内容不参与层指纹，用时间戳重跑归档操作；--no-cache 会重置 cache mount
 command+=(--build-arg "CACHE_STAMP=$(date +%s%N)" --target "$operation")
 valid=false
 if [ "$operation" = restore ]; then
   if usable "$directory"; then
-    mkdir -p "$directory"/{registry,git,target}
     "${command[@]}" --output type=cacheonly "$directory"
     valid=true
   else
@@ -43,10 +61,11 @@ else
   temporary="$(mktemp -d "${directory}.XXXXXX")"
   trap 'rm -rf "$temporary"' EXIT
   mkdir "$temporary"/{context,snapshot}
-  # tar 流避开 local exporter 的逐文件同步阻塞，直接解包以免额外落盘整份归档。
+  # tar 流避开 local exporter 的逐文件同步阻塞，只接收 /cache 下的压缩归档
+  # 直接导出打包阶段，避免再创建一层归档副本
   # https://github.com/moby/buildkit/issues/2950
   "${command[@]}" --output type=tar,dest=- "$temporary/context" \
-    | tar -xf - -C "$temporary/snapshot"
+    | tar -xf - -C "$temporary/snapshot" --strip-components=1 cache/
   if usable "$temporary/snapshot"; then
     rm -rf "$directory"
     mv "$temporary/snapshot" "$directory"
diff --git a/.github/workflows/_container.yml b/.github/workflows/_container.yml
index 43fe91568..e41bb61f8 100644
--- a/.github/workflows/_container.yml
+++ b/.github/workflows/_container.yml
@@ -36,10 +36,9 @@ jobs:
         with:
           path: ${{ runner.temp }}/container-cargo
           # 同一平台和依赖复用快照，源码变化由 Cargo 指纹判定是否重编译
-          key: container-cargo-v3-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('backend/Cargo.lock', 'backend/rust-toolchain.toml', 'backend/**/Cargo.toml', 'backend/.cargo/config.toml', 'deploy/Dockerfile', '.github/actions/cargo-cache/Dockerfile') }}
+          key: container-cargo-v4-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('backend/Cargo.lock', 'backend/rust-toolchain.toml', 'backend/**/Cargo.toml', 'backend/.cargo/config.toml', 'deploy/Dockerfile', '.github/actions/cargo-cache/Dockerfile') }}
           restore-keys: |
-            container-cargo-v3-${{ runner.os }}-${{ runner.arch }}-
-            container-cargo-v2-${{ runner.os }}-${{ runner.arch }}-
+            container-cargo-v4-${{ runner.os }}-${{ runner.arch }}-
 
       - name: Restore Cargo mounts to BuildKit
         id: cargo-restore
@@ -50,6 +49,9 @@ jobs:
           path: ${{ runner.temp }}/container-cargo
           architecture: amd64
 
+      - name: Release restored Cargo snapshot
+        run: rm -rf "$RUNNER_TEMP/container-cargo"
+
       - name: Build runtime image
         uses: docker/build-push-action@c3c9e263c25d99ce0380d002d59b67737d91b0dc # v7.4.0
         with: