diff --git a/.github/workflows/pr_main.yaml b/.github/workflows/pr_main.yaml
index 34cac9dc0..cb10ec72a 100644
--- a/.github/workflows/pr_main.yaml
+++ b/.github/workflows/pr_main.yaml
@@ -99,9 +99,18 @@ jobs:
 
       - name: Run ignored executor tests
         run: |
-          cargo test --release -p executor test_ethrex -- --ignored
           cargo test --release -p executor test_ckzg -- --ignored
 
+      # ethrex host-reference tests live in the detached `tooling/ethrex-tests`
+      # workspace (ethrex pins rkyv's `unaligned` feature, which must not
+      # feature-unify with the main workspace's aligned proof format), so run
+      # them from that directory to use its isolated Cargo.lock. The guest ELF
+      # and committed fixtures are already present from the steps above.
+      # --include-ignored also runs the heavier synthetic-block test.
+      - name: Run ethrex host-reference tests (detached workspace)
+        run: |
+          cd tooling/ethrex-tests && cargo test --release -- --include-ignored
+
   test-cli:
     name: CLI tests
     runs-on: ubuntu-latest
diff --git a/Makefile b/Makefile
index bf39496b9..110c2d31f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 .PHONY: deps deps-linux deps-macos compile-programs-asm compile-programs-rust compile-bench \
 compile-programs compile-recursion-elfs clean-asm clean-rust clean-bench clean-shared \
 clean-recursion-elfs clean test test-asm \
-test-rust test-executor test-flamegraph flamegraph-prover test-profile-recursion test-profile-recursion-single test-profile-recursion-multi \
+test-rust test-ethrex test-executor test-flamegraph flamegraph-prover test-profile-recursion test-profile-recursion-single test-profile-recursion-multi \
 test-fast test-prover test-prover-all test-prover-debug test-disk-spill test-math-cuda test-cuda-integration test-cuda-fallback \
 test-prover-cuda test-prover-comprehensive-cuda \
 bench-math-cuda bench-prover bench-prover-cuda build check clippy fmt lint regen-ethrex-fixtures \
@@ -262,6 +262,11 @@ test-asm: compile-programs-asm
 test-rust: compile-programs-rust
 	cargo test -p executor --test rust
 
+# ethrex host-reference tests live in the detached `tooling/ethrex-tests`
+# workspace (ethrex pins rkyv's `unaligned` feature; isolated Cargo.lock).
+test-ethrex: compile-programs-rust
+	cd tooling/ethrex-tests && cargo test --release -- --include-ignored
+
 test-flamegraph:
 	cargo test -p executor --test flamegraph