diff --git a/cli/bash/commands/basectl/subcommands/setup_common.sh b/cli/bash/commands/basectl/subcommands/setup_common.sh
index 8dc46e8..741ff10 100644
--- a/cli/bash/commands/basectl/subcommands/setup_common.sh
+++ b/cli/bash/commands/basectl/subcommands/setup_common.sh
@@ -2069,7 +2069,9 @@ setup_run_check_json() {
 
     if setup_profiles_enabled; then
         if ! profile_json="$(setup_run_base_dev_layer check --format json)"; then
-            [[ -n "$profile_json" ]] || profile_json='{"schema_version":1,"status":"error","profiles":[],"checks":[]}'
+            if [[ -z "$profile_json" ]]; then
+                return 1
+            fi
         fi
         profile_status="$(setup_json_payload_status "$profile_json")"
         status="$(setup_merge_diagnostic_status "$status" "$profile_status")"
@@ -2077,7 +2079,9 @@ setup_run_check_json() {
 
     if [[ -n "$project" ]]; then
         if ! project_json="$(setup_run_project_artifact_check_json "$remote_network")"; then
-            [[ -n "$project_json" ]] || project_json='{"schema_version":1,"status":"error","checks":[]}'
+            if [[ -z "$project_json" ]]; then
+                return 1
+            fi
         fi
         project_status="$(setup_json_payload_status "$project_json")"
         status="$(setup_merge_diagnostic_status "$status" "$project_status")"
diff --git a/cli/bash/commands/basectl/tests/check.bats b/cli/bash/commands/basectl/tests/check.bats
index 9cc646e..73929ac 100644
--- a/cli/bash/commands/basectl/tests/check.bats
+++ b/cli/bash/commands/basectl/tests/check.bats
@@ -524,6 +524,33 @@ load ./setup_helpers.bash
     [ "${stderr:-}" = "" ]
 }
 
+@test "basectl check project --format json fails fast on runtime directory errors" {
+    local venv_dir="$TEST_HOME/.base.d/base/.venv"
+    local workspace="$TEST_TMPDIR/workspace"
+
+    create_brew_stub
+    create_xcode_stubs
+    touch "$TEST_STATE_DIR/xcode-installed"
+    mkdir -p "$TEST_TMPDIR/CommandLineTools" "$workspace/demo"
+    touch "$TEST_STATE_DIR/python-installed"
+    touch "$TEST_STATE_DIR/bats-installed"
+    touch "$TEST_STATE_DIR/pyyaml-installed"
+    touch "$TEST_STATE_DIR/click-installed"
+    printf 'project:\n  name: demo\nartifacts: []\n' > "$workspace/demo/base_manifest.yaml"
+    BASE_SETUP_TEST_WORKSPACE="$workspace" create_project_setup_venv_stub "$venv_dir"
+    BASE_SETUP_TEST_WORKSPACE="$workspace" create_project_setup_venv_stub "$TEST_HOME/.base.d/demo/.venv" 1
+    touch "$TEST_STATE_DIR/project-setup-fail-before-output"
+    printf "Error: Unable to create Base runtime directory '%s'.\n" "$TEST_TMPDIR/unwritable-cache/cli/base_setup/logs" > "$TEST_STATE_DIR/project-setup-stderr"
+
+    run_base_command_separate_stderr BASE_SETUP_TEST_WORKSPACE="$workspace" check demo --format json
+
+    [ "$status" -eq 1 ]
+    [ "$output" = "" ]
+    [[ "$stderr" == *"Error: Unable to create Base runtime directory"* ]]
+    [[ "$stderr" != *'"project_checks"'* ]]
+    [[ "$stderr" != *"Project artifact check passed."* ]]
+}
+
 @test "basectl check project --format json reports broken project virtualenv integrity" {
     local missing_home="$TEST_TMPDIR/missing-project-python-home"
     local venv_dir="$TEST_HOME/.base.d/base/.venv"
diff --git a/cli/bash/commands/basectl/tests/setup_helpers.bash b/cli/bash/commands/basectl/tests/setup_helpers.bash
index 71ed50e..93c5609 100644
--- a/cli/bash/commands/basectl/tests/setup_helpers.bash
+++ b/cli/bash/commands/basectl/tests/setup_helpers.bash
@@ -559,6 +559,12 @@ if [[ "${1:-}" == "-m" && "${2:-}" == "base_setup" ]]; then
     if [[ "$action" == "bootstrap" ]]; then
         printf '%s\n' "${BASE_SETUP_RECREATE_PROJECT_VENV:-}" > "$BASE_SETUP_TEST_STATE_DIR/project-bootstrap-recreate-venv"
     fi
+    if [[ -f "$BASE_SETUP_TEST_STATE_DIR/project-setup-fail-before-output" ]]; then
+        if [[ -f "$BASE_SETUP_TEST_STATE_DIR/project-setup-stderr" ]]; then
+            cat "$BASE_SETUP_TEST_STATE_DIR/project-setup-stderr" >&2
+        fi
+        exit "$(cat "$BASE_SETUP_TEST_STATE_DIR/project-setup-exit-code")"
+    fi
     if [[ "$action" == "precheck" && "$output_format" == "json" ]]; then
         if [[ "$remote_network" == true ]]; then
             printf '[{"id":"BASE-P080","status":"ok","name":"git_repository","message":"Project is inside a Git repository.","fix":""},{"id":"BASE-P083","status":"ok","name":"git_origin_reachability","message":"Project Git origin remote is reachable.","fix":""}]\n'