diff --git a/.gitea/workflows/pr-check.yaml b/.gitea/workflows/pr-check.yaml
index f5fe2b3..0e66a5c 100644
--- a/.gitea/workflows/pr-check.yaml
+++ b/.gitea/workflows/pr-check.yaml
@@ -21,19 +21,26 @@ jobs:
           SERVER_URL="${GITHUB_SERVER_URL:-${GITEA_SERVER_URL:-}}"
           REPO_NAME="${GITHUB_REPOSITORY:-${GITEA_REPOSITORY:-}}"
           COMMIT_SHA="${GITHUB_SHA:-${GITEA_SHA:-}}"
-          
-          # Try to get URL from git remote if env vars are missing
-          if [ -z "$SERVER_URL" ] || [ -z "$REPO_NAME" ]; then
-             echo "Warning: Env vars missing, attempting to detect from remote..."
-          fi
+
+          : "${SERVER_URL:?Could not determine SERVER_URL}"
+          : "${REPO_NAME:?Could not determine REPO_NAME}"
+          : "${COMMIT_SHA:?Could not determine COMMIT_SHA}"
 
           echo "Using SERVER_URL=$SERVER_URL"
           echo "Using REPO_NAME=$REPO_NAME"
           echo "Using COMMIT_SHA=$COMMIT_SHA"
 
-          git clone "$SERVER_URL/$REPO_NAME.git" .
-          git fetch origin main:main
-          git checkout "$COMMIT_SHA"
+          if [ -d ".git" ]; then
+            echo "Repo already initialized in workspace; using fetch"
+            git remote set-url origin "$SERVER_URL/$REPO_NAME.git"
+          else
+            git clone "$SERVER_URL/$REPO_NAME.git" .
+          fi
+
+          # 关键：不要把 main fetch 到本地分支 main（会冲突）
+          git fetch origin main:refs/remotes/origin/main
+          git fetch --depth=1 origin "$COMMIT_SHA"
+          git checkout -f "$COMMIT_SHA"
 
       - name: 1. OpenAPI Contract Level Check
         env:
diff --git a/scripts/check-openapi-diff.sh b/scripts/check-openapi-diff.sh
index 3a01c99..b8de879 100644
--- a/scripts/check-openapi-diff.sh
+++ b/scripts/check-openapi-diff.sh
@@ -7,7 +7,7 @@ set -eu
 # 3. Fail if breaking changes are found without explicit developer acknowledgement.
 
 # Base branch to compare against
-BASE_BRANCH="main"
+BASE_BRANCH="refs/remotes/origin/main"
 
 die() {
   echo "ERROR: $*" >&2