diff --git a/Makefile b/Makefile
index 79de2fa421a5..14183d261028 100644
--- a/Makefile
+++ b/Makefile
@@ -47,7 +47,7 @@ endef
 # PHONY TARGETS - List every target that has a file/dir of the same name.
 #==============================================================================
 
-.PHONY: noir barretenberg noir-projects l1-contracts release-image boxes playground docs aztec-up spartan
+.PHONY: noir barretenberg noir-projects noir-projects-deps l1-contracts release-image boxes playground docs aztec-up spartan
 
 #==============================================================================
 # BOOTSTRAP TARGETS
@@ -284,19 +284,26 @@ claude-tests:
 # Noir Projects
 #==============================================================================
 
-noir-protocol-circuits: noir bb-cpp-native
+# Serial pre-step that caches the shared `noir-lang/*` git dependencies into
+# ~/.nargo/. Without this, the four noir-projects targets below race on the
+# same cache and one of the parallel `nargo` invocations can fail (e.g. with
+# a "Could not resolve host" git clone error) before the others populate it.
+noir-projects-deps: noir
+	$(call run_command,$@,$(ROOT)/noir-projects,$(ROOT)/ci3/denoise './bootstrap.sh prep')
+
+noir-protocol-circuits: noir bb-cpp-native noir-projects-deps
 	$(call build,$@,noir-projects/noir-protocol-circuits)
 
 noir-protocol-circuits-tests: noir noir-protocol-circuits
 	$(call test,$@,noir-projects/noir-protocol-circuits)
 
-mock-protocol-circuits: noir bb-cpp-native
+mock-protocol-circuits: noir bb-cpp-native noir-projects-deps
 	$(call build,$@,noir-projects/mock-protocol-circuits)
 
-noir-contracts: noir bb-cpp-native
+noir-contracts: noir bb-cpp-native noir-projects-deps
 	$(call build,$@,noir-projects/noir-contracts)
 
-aztec-nr: noir bb-cpp-native
+aztec-nr: noir bb-cpp-native noir-projects-deps
 	$(call build,$@,noir-projects/aztec-nr)
 
 # These tests are not included in the dep tree.
diff --git a/noir-projects/bootstrap.sh b/noir-projects/bootstrap.sh
index 006f75495900..098a8d7469c7 100755
--- a/noir-projects/bootstrap.sh
+++ b/noir-projects/bootstrap.sh
@@ -1,21 +1,23 @@
 #!/usr/bin/env bash
 source $(git rev-parse --show-toplevel)/ci3/source_bootstrap
 
+# Use fmt as a trick to download dependencies.
+# Otherwise parallel runs of nargo will trip over each other trying to download dependencies.
+# Also doubles up as our formatting check.
+# Exposed as a top-level command so the root Makefile can run it as a serial barrier
+# before the parallel noir-projects sub-builds.
+function prep {
+  set -eu
+  (cd noir-protocol-circuits && yarn && node ./scripts/generate_variants.js)
+  for dir in noir-contracts noir-protocol-circuits mock-protocol-circuits aztec-nr; do
+    (cd $dir && ../../noir/noir-repo/target/release/nargo fmt --check)
+  done
+}
+export -f prep
+
 function build {
   echo_header "noir-projects build"
 
-  # Use fmt as a trick to download dependencies.
-  # Otherwise parallel runs of nargo will trip over each other trying to download dependencies.
-  # Also doubles up as our formatting check.
-  function prep {
-    set -eu
-    (cd noir-protocol-circuits && yarn && node ./scripts/generate_variants.js)
-    for dir in noir-contracts noir-protocol-circuits mock-protocol-circuits aztec-nr; do
-      (cd $dir && ../../noir/noir-repo/target/release/nargo fmt --check)
-    done
-  }
-  export -f prep
-
   denoise prep
 
   parallel --tag --line-buffered --joblog joblog.txt --halt now,fail=1 denoise "'./{}/bootstrap.sh $cmd'" ::: \