diff --git a/docs/wasm-runtime-architecture.md b/docs/wasm-runtime-architecture.md
index 78c8436..86c6a79 100644
--- a/docs/wasm-runtime-architecture.md
+++ b/docs/wasm-runtime-architecture.md
@@ -365,7 +365,10 @@ header free-functions are `inline`. The wasm backend exposes only declarations
   its permissions and proves the next CLI request compiles it, then sends 48
   requests and asserts the observed worker PID set does not exceed
   `WORKER_COUNT`, guarding against accidental reintroduction of request-count
-  recycling.
+  recycling. It also races a source edit against an active unit compile after
+  the generated C++ snapshot has been written. The compiler must either retry
+  and serve the post-edit source or fail closed; it must never stamp current
+  source metadata onto wasm produced from an older snapshot.
   `scripts/test_cold_component_deadline.sh` separately compiles a deliberately
   cold component that exceeds the development epoch window and proves the
   parent request still renders it. The dependency-invalidation gate also holds
diff --git a/scripts/test_dependency_invalidation.sh b/scripts/test_dependency_invalidation.sh
index a81fe4c..504228b 100755
--- a/scripts/test_dependency_invalidation.sh
+++ b/scripts/test_dependency_invalidation.sh
@@ -15,6 +15,9 @@ mutation_file="/tmp/uce-dependency-mutation-$$"
 post_body="/tmp/uce-dependency-post-body-$$"
 post_headers="/tmp/uce-dependency-post-headers-$$"
 lock_ready_file="/tmp/uce-dependency-lock-ready-$$"
+race_output="/tmp/uce-source-race-output-$$"
+race_error="/tmp/uce-source-race-error-$$"
+race_status="/tmp/uce-source-race-status-$$"
 http_host="${UCE_TEST_HTTP_HOST:-uce.openfu.com}"
 
 cleanup() {
@@ -22,7 +25,7 @@ cleanup() {
 	if [[ -n "$cache_dir" ]]; then
 		rm -rf "$cache_dir"
 	fi
-	rm -f "$mutation_file" "$post_body" "$post_headers" "$lock_ready_file"
+	rm -f "$mutation_file" "$post_body" "$post_headers" "$lock_ready_file" "$race_output" "$race_error" "$race_status"
 }
 trap cleanup EXIT
 mkdir -p "$source_dir"
@@ -179,6 +182,56 @@ touch -d "@$parent_mtime" "$parent_wasm"
 rm -f "$cache_dir/parent.uce.cwasm"
 for _ in {1..16}; do assert_marker parent dependency-marker-c; done
 
+race_unit="$source_dir/source-race.uce"
+race_cpp="$cache_dir/source-race.uce.cpp"
+{
+	printf '%s\n' 'String source_race_marker() { return("source-race-marker-a"); }'
+	for i in $(seq 1 3500); do
+		printf 'int source_race_padding_%s() { return(%s); }\n' "$i" "$i"
+	done
+	printf '%s\n' 'CLI(Request& context) { print(source_race_marker()); }'
+} >"$race_unit"
+rm -f "$cache_dir/source-race.uce.cpp" "$cache_dir/source-race.uce.wasm" "$cache_dir/source-race.uce.cwasm" "$cache_dir/source-race.uce.meta.txt"
+(
+	set +e
+	scripts/uce-cli "/$test_name/source-race.uce" >"$race_output" 2>"$race_error"
+	echo "$?" >"$race_status"
+) &
+race_pid=$!
+deadline=$((SECONDS + 10))
+while [[ ! -e "$race_cpp" && $SECONDS -lt $deadline ]]; do
+	if ! kill -0 "$race_pid" 2>/dev/null; then
+		echo "source-race compile finished before publishing generated C++" >&2
+		cat "$race_output" "$race_error" >&2 || true
+		exit 1
+	fi
+	sleep 0.02
+done
+if [[ ! -e "$race_cpp" ]]; then
+	echo "source-race compile did not publish generated C++ before deadline" >&2
+	exit 1
+fi
+if ! grep -q 'source-race-marker-a' "$race_cpp"; then
+	echo "source-race generated C++ did not contain the initial marker" >&2
+	exit 1
+fi
+if ! kill -0 "$race_pid" 2>/dev/null; then
+	echo "source-race compile finished before source mutation hook" >&2
+	cat "$race_output" "$race_error" >&2 || true
+	exit 1
+fi
+sed -i 's/source-race-marker-a/source-race-marker-b/' "$race_unit"
+wait "$race_pid"
+if [[ "$(cat "$race_status" 2>/dev/null || echo 1)" != "0" ]]; then
+	echo "source-race CLI request failed" >&2
+	cat "$race_output" "$race_error" >&2 || true
+	exit 1
+fi
+if [[ "$(cat "$race_output")" != *"source-race-marker-b"* ]]; then
+	echo "source changed during compile but UCE served stale wasm: $(cat "$race_output")" >&2
+	exit 1
+fi
+
 worker_count=$(awk -F= '/^[[:space:]]*WORKER_COUNT[[:space:]]*=/ {gsub(/^[[:space:]]+|[[:space:]]+$/, "", $2); print $2; exit}' /etc/uce/settings.cfg 2>/dev/null || true)
 worker_count="${worker_count:-4}"
 worker_pids=""
diff --git a/src/lib/compiler.cpp b/src/lib/compiler.cpp
index 35e6a34..ae9a3d7 100644
--- a/src/lib/compiler.cpp
+++ b/src/lib/compiler.cpp
@@ -215,16 +215,31 @@ String compiler_unit_build_token()
 	);
 }
 
-String compiler_unit_metadata_text(Request* context, SharedUnit* su)
+String compiler_unit_metadata_text(Request* context, SharedUnit* su, String input_signature = "")
 {
+	if(input_signature == "")
+		input_signature = compiler_unit_input_signature(context, su);
 	return(
 		"format=uce-unit-metadata-v1\n"
 		"unit_abi_version=" + std::to_string(UCE_UNIT_ABI_VERSION) + "\n"
-		"input_signature=" + compiler_unit_input_signature(context, su) + "\n"
+		"input_signature=" + input_signature + "\n"
 		"build_token=" + compiler_unit_build_token() + "\n"
 	);
 }
 
+String compiler_cached_wasm_path(String wasm_path)
+{
+	if(wasm_path.size() >= 5 && wasm_path.rfind(".wasm", wasm_path.size() - 5) == wasm_path.size() - 5)
+		return(wasm_path.substr(0, wasm_path.size() - 5) + ".cwasm");
+	return(wasm_path + ".cwasm");
+}
+
+void compiler_unlink_unit_wasm_artifacts(SharedUnit* su)
+{
+	file_unlink(su->wasm_name);
+	file_unlink(compiler_cached_wasm_path(su->wasm_name));
+}
+
 String compiler_wasm_compile_script(Request* context)
 {
 	String script = "scripts/compile_wasm_unit";
@@ -832,33 +847,48 @@ void compile_shared_unit(Request* context, SharedUnit* su)
 	}
 
 	shell_exec("mkdir -p " + shell_escape(su->pre_path));
-	file_put_contents(su->pre_path + "/" + su->pre_file_name, preprocess_shared_unit(context, su));
-	file_put_contents(su->api_file_name, join(su->api_declarations, "\n"));
+	String compiled_input_signature;
+	for(u64 attempt = 0; attempt < 2; attempt++)
+	{
+		su->api_declarations.clear();
+		compiled_input_signature = compiler_unit_input_signature(context, su);
+		file_put_contents(su->pre_path + "/" + su->pre_file_name, preprocess_shared_unit(context, su));
+		file_put_contents(su->api_file_name, join(su->api_declarations, "\n"));
 
-	su->compiler_messages = trim(shell_exec(shell_escape(compiler_wasm_compile_script(context))+" "+
-		shell_escape(su->src_path)+" "+
-		shell_escape(su->bin_path)+" "+
-		shell_escape(su->file_name)+" "+
-		shell_escape(su->pre_file_name)+" "+
-		shell_escape(su->wasm_file_name)
-	));
+		su->compiler_messages = trim(shell_exec(shell_escape(compiler_wasm_compile_script(context))+" "+
+			shell_escape(su->src_path)+" "+
+			shell_escape(su->bin_path)+" "+
+			shell_escape(su->file_name)+" "+
+			shell_escape(su->pre_file_name)+" "+
+			shell_escape(su->wasm_file_name)
+		));
 
-	if(su->compiler_messages.length() == 0 && !file_exists(su->wasm_name))
-		su->compiler_messages = "wasm compile script completed without creating " + su->wasm_name;
+		if(su->compiler_messages.length() == 0 && !file_exists(su->wasm_name))
+			su->compiler_messages = "wasm compile script completed without creating " + su->wasm_name;
+		if(su->compiler_messages.length() > 0)
+			break;
+		String current_input_signature = compiler_unit_input_signature(context, su);
+		if(current_input_signature == compiled_input_signature)
+			break;
+		compiler_unlink_unit_wasm_artifacts(su);
+		if(attempt == 1)
+			su->compiler_messages = "source changed during wasm compile; retry required";
+	}
 
 	if(su->compiler_messages.length() > 0)
 	{
 		String raw_messages = su->compiler_messages;
 		file_put_contents(su->compile_output_file_name, raw_messages + "\n");
 		file_put_contents(su->wasm_check_file_name, raw_messages + "\n");
-		file_unlink(su->wasm_name);
+		compiler_unlink_unit_wasm_artifacts(su);
 		compiler_record_compile_result(su, time_precise() - comp_start, false, "compile_error", raw_messages);
 		printf("%s \n", compiler_format_compile_failure(su, raw_messages).c_str());
 	}
 	else
 	{
 		su->last_compiled = file_mtime(su->wasm_name);
-		file_put_contents(su->meta_file_name, compiler_unit_metadata_text(context, su));
+		file_unlink(compiler_cached_wasm_path(su->wasm_name));
+		file_put_contents(su->meta_file_name, compiler_unit_metadata_text(context, su, compiled_input_signature));
 		file_unlink(su->compile_output_file_name);
 		file_unlink(su->wasm_check_file_name);
 		compiler_record_compile_result(