diff --git a/.github/workflows/sanity-check.yml b/.github/workflows/sanity-check.yml
new file mode 100644
index 00000000..4b45e99d
--- /dev/null
+++ b/.github/workflows/sanity-check.yml
@@ -0,0 +1,102 @@
+name: PR Sanity Check
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+permissions:
+  pull-requests: write
+  contents: read
+
+jobs:
+  sanity-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Fetch base branch
+        run: git fetch origin ${{ github.base_ref }}
+
+      - name: Block disallowed files by extension
+        run: |
+          echo "Checking for disallowed file extensions..."
+          CHANGED_FILES=$(git diff --name-only origin/${{ github.base_ref }}...HEAD)
+
+          # Block by extension
+          BLOCKED=$(echo "$CHANGED_FILES" | grep -E '\.(exe|dll|out|ezdb|db|sqlite|sqlite3)$' || true)
+          if [ -n "$BLOCKED" ]; then
+            echo "::error::Disallowed file extensions detected: $BLOCKED"
+            exit 1
+          fi
+
+          # Block IDE/OS junk folders
+          JUNK=$(echo "$CHANGED_FILES" | grep -E '^(\.idea/|\.vs/|__pycache__/)' || true)
+          if [ -n "$JUNK" ]; then
+            echo "::error::IDE/OS junk detected: $JUNK"
+            exit 1
+          fi
+
+          # Block OS junk files
+          OS_JUNK=$(echo "$CHANGED_FILES" | grep -E '(Thumbs\.db|Desktop\.ini|\.DS_Store)$' || true)
+          if [ -n "$OS_JUNK" ]; then
+            echo "::error::OS junk files detected: $OS_JUNK"
+            exit 1
+          fi
+
+          echo "No disallowed file extensions detected."
+
+      - name: Block meta/config files from other ecosystems
+        run: |
+          echo "Checking for ecosystem files..."
+          CHANGED_FILES=$(git diff --name-only origin/${{ github.base_ref }}...HEAD)
+
+          # Block meta/config files from other language ecosystems
+          SUSPICIOUS=$(echo "$CHANGED_FILES" | grep -E '^(package\.json|package-lock\.json|yarn\.lock|pnpm-lock\.yaml|bun\.lockb|bunfig\.toml|deno\.json|deno\.jsonc|tsconfig\.json|jsconfig\.json|requirements\.txt|Pipfile|Gemfile|Cargo\.toml|Cargo\.lock)$|node_modules/' || true)
+
+          if [ -n "$SUSPICIOUS" ]; then
+            echo "::error::Ecosystem config files detected: $SUSPICIOUS"
+            exit 1
+          fi
+          echo "No suspicious ecosystem files detected."
+
+      - name: Reject binary files except images
+        run: |
+          echo "Checking for binary files..."
+          CHANGED_FILES=$(git diff --name-only origin/${{ github.base_ref }}...HEAD)
+
+          for file in $CHANGED_FILES; do
+            if [ -f "$file" ]; then
+              MIME=$(file --mime-type -b "$file")
+
+              # Allow common image formats
+              if [[ "$MIME" =~ ^image/(jpeg|png|gif|svg\+xml|webp)$ ]]; then
+                echo "Allowed image file: $file ($MIME)"
+                continue
+              fi
+
+              # Reject executables and archives
+              if file "$file" | grep -qE "executable|binary|archive|compressed"; then
+                echo "::error::Binary/executable file detected: $file"
+                exit 1
+              fi
+
+              # Also check charset=binary for other binary types (but not images)
+              if file --mime "$file" | grep -q "charset=binary" && [[ ! "$MIME" =~ ^image/ ]]; then
+                echo "::error::Binary file detected: $file ($MIME)"
+                exit 1
+              fi
+            fi
+          done
+          echo "No disallowed binary files detected."
+
+      - name: Close PR if checks fail
+        if: failure()
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh pr close ${{ github.event.pull_request.number }} \
+            --repo ${{ github.repository }} \
+            --comment "This PR has been automatically closed because it contains disallowed files (binaries, executables, archives, or meta/config files from other ecosystems). Please remove these files and open a new PR."