diff --git a/infra/k8s/argo/lob-backtest-sweep-template.yaml b/infra/k8s/argo/lob-backtest-sweep-template.yaml
index b571b2cb0..71573053f 100644
--- a/infra/k8s/argo/lob-backtest-sweep-template.yaml
+++ b/infra/k8s/argo/lob-backtest-sweep-template.yaml
@@ -216,7 +216,13 @@ spec:
 
             echo "=== Cache MISS: compiling fxt-backtest for $SHORT_SHA ==="
             if [ -d "$BUILD/.git" ]; then
-              cd "$BUILD"; git fetch origin; git checkout "$SHA"
+              # Same pattern as alpha-perception-template.yaml: prior
+              # cargo build mutates Cargo.lock (and sometimes other
+              # generated files); --force checkout overwrites them,
+              # `git clean -fd` drops untracked. Without this, the
+              # second SHA's checkout fails on dirty working tree.
+              cd "$BUILD"; git fetch origin
+              git checkout --force "$SHA"; git clean -fd
             else
               git clone --filter=blob:none "$REPO" "$BUILD"
               cd "$BUILD"; git checkout "$SHA"