diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 58c3fe2ab01..2f9ba8e95c6 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -33,6 +33,24 @@ jobs:
           echo "has_firmware=$(echo "$FILES" | grep -qE '^(omi|omiGlass)/.*\.(c|cpp|cc|cxx|h|hpp)$' && echo true || echo false)" >> $GITHUB_OUTPUT
           echo "has_frontend=$(echo "$FILES" | grep -q '^web/frontend/' && echo true || echo false)" >> $GITHUB_OUTPUT
           echo "has_personas=$(echo "$FILES" | grep -q '^web/personas-open-source/' && echo true || echo false)" >> $GITHUB_OUTPUT
+          # Also run the Rust check when this workflow changes so CI PRs dogfood
+          # the new guard instead of only validating YAML syntax.
+          echo "has_desktop_rust=$(echo "$FILES" | grep -qE '^desktop/macos/Backend-Rust/|^\.github/workflows/lint\.yml$' && echo true || echo false)" >> $GITHUB_OUTPUT
+
+      # -- Universal source hygiene --
+      - name: Check merge conflict markers
+        run: |
+          failed=0
+          while IFS= read -r file; do
+            if [ -f "$file" ] && grep -I -nE '^(<<<<<<<|>>>>>>>)' "$file"; then
+              failed=1
+            fi
+          done < /tmp/changed-files.txt
+
+          if [ "$failed" -eq 1 ]; then
+            echo "FAIL: unresolved merge conflict markers found in changed files"
+            exit 1
+          fi
 
       # -- Dart --
       - name: Setup Flutter
@@ -103,6 +121,29 @@ jobs:
             echo "$FILES" | xargs clang-format --dry-run --Werror
           fi
 
+      # -- Desktop Rust backend --
+      - name: Cache desktop Rust backend build
+        if: steps.changed.outputs.has_desktop_rust == 'true'
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            desktop/macos/Backend-Rust/target
+          key: ${{ runner.os }}-desktop-rust-${{ hashFiles('desktop/macos/Backend-Rust/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-desktop-rust-
+
+      - name: Check desktop Rust backend
+        if: steps.changed.outputs.has_desktop_rust == 'true'
+        run: |
+          FILES=$(grep -E '^desktop/macos/Backend-Rust/.*\.rs$' /tmp/changed-files.txt || true)
+          if [ -n "$FILES" ]; then
+            echo "$FILES" | xargs rustfmt --edition 2021 --check
+          fi
+          cd desktop/macos/Backend-Rust
+          cargo check --locked
+
       # -- Frontend --
       - name: Setup Node.js
         if: steps.changed.outputs.has_frontend == 'true' || steps.changed.outputs.has_personas == 'true'
diff --git a/scripts/pre-commit b/scripts/pre-commit
index fc7011f1c00..eaef5dfdcd1 100755
--- a/scripts/pre-commit
+++ b/scripts/pre-commit
@@ -1,5 +1,25 @@
 #!/bin/sh
 
+# Universal source hygiene: fail fast on unresolved merge conflict markers.
+STAGED_FILES=$(git diff --cached --name-only --diff-filter=ACM)
+
+if [ -n "$STAGED_FILES" ]; then
+  conflict_found=0
+  while IFS= read -r file; do
+    [ -n "$file" ] || continue
+    if git grep --cached -n -I -E '^(<<<<<<<|>>>>>>>)' -- "$file"; then
+      conflict_found=1
+    fi
+  done <<EOF
+$STAGED_FILES
+EOF
+
+  if [ "$conflict_found" -eq 1 ]; then
+    echo "Unresolved merge conflict markers found in staged files" >&2
+    exit 1
+  fi
+fi
+
 # Dart formatting for app/
 STAGED_DART_FILES=$(git diff --cached --name-only --diff-filter=ACM "app/**.dart" | grep -v -e '\.gen\.dart$' -e '\.g\.dart$')
 
@@ -79,4 +99,34 @@ if [ -n "$STAGED_C_FILES" ]; then
   echo "$STAGED_C_FILES" | xargs git add
 fi
 
+# Rust formatting/checking for desktop backend.
+STAGED_DESKTOP_RUST_INPUTS=$(git diff --cached --name-only --diff-filter=ACM | grep -E '^desktop/macos/Backend-Rust/' || true)
+STAGED_DESKTOP_RUST_FILES=$(printf '%s\n' "$STAGED_DESKTOP_RUST_INPUTS" | grep -E '\.rs$' || true)
+
+if [ -n "$STAGED_DESKTOP_RUST_INPUTS" ]; then
+  echo "Checking desktop Rust backend..."
+  if ! command -v cargo >/dev/null 2>&1; then
+    echo "cargo is not installed. Please install Rust/Cargo first" >&2
+    exit 1
+  fi
+  if [ -n "$STAGED_DESKTOP_RUST_FILES" ]; then
+    while IFS= read -r file; do
+      [ -n "$file" ] || continue
+      if ! rustfmt --edition 2021 "$file"; then
+        echo "rustfmt failed for $file" >&2
+        exit 1
+      fi
+      git add "$file"
+    done <<EOF
+$STAGED_DESKTOP_RUST_FILES
+EOF
+  fi
+  if ! (
+    cd desktop/macos/Backend-Rust && \
+      cargo check --locked
+  ); then
+    exit 1
+  fi
+fi
+
 exit 0