diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cbe2809..94fa8eb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -40,13 +40,27 @@ jobs:
           git -C "${PY_FIXTURE_CHECKOUT}" checkout --detach FETCH_HEAD
           echo "Resolved fixture source: ${PY_FIXTURE_CHECKOUT}/tests/fixtures/conformance"
 
-      - name: Check fixture drift
+      - name: Check conformance fixture drift
         env:
           FIXTURES_SOURCE: /tmp/context-compiler-source/tests/fixtures/conformance
         run: |
           echo "Using FIXTURES_SOURCE=${FIXTURES_SOURCE}"
           npm run fixtures:check
 
+      - name: Check preprocessor fixture drift
+        env:
+          PREPROCESSOR_FIXTURES_SOURCE: /tmp/context-compiler-source/tests/fixtures/preprocessor
+        run: |
+          echo "Using PREPROCESSOR_FIXTURES_SOURCE=${PREPROCESSOR_FIXTURES_SOURCE}"
+          npm run fixtures:preprocessor:check
+
+      - name: Check structured fixture drift
+        env:
+          STRUCTURED_FIXTURES_SOURCE: /tmp/context-compiler-source/tests/fixtures/engine-regression/structured
+        run: |
+          echo "Using STRUCTURED_FIXTURES_SOURCE=${STRUCTURED_FIXTURES_SOURCE}"
+          npm run fixtures:structured:check
+
       - name: Build
         run: npm run build
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index aeb5e9d..415a8f4 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -98,8 +98,10 @@ Commands:
 
 - `FIXTURES_SOURCE=/path/to/context-compiler/tests/fixtures/conformance npm run fixtures:sync` to copy fixtures from Python into `tests/fixtures/conformance`
 - `FIXTURES_SOURCE=/path/to/context-compiler/tests/fixtures/conformance npm run fixtures:check` to detect drift between local fixtures and Python fixtures
+- `PREPROCESSOR_FIXTURES_SOURCE=/path/to/context-compiler/tests/fixtures/preprocessor npm run fixtures:preprocessor:check` to detect preprocessor fixture drift
+- `STRUCTURED_FIXTURES_SOURCE=/path/to/context-compiler/tests/fixtures/engine-regression/structured npm run fixtures:structured:check` to detect structured regression fixture drift
 
-`FIXTURES_SOURCE` is required for both commands.
+Each check command requires its matching `*_SOURCE` variable.
 
 ## Pull Requests