diff --git a/tools/smokes/v2/lib/llvm_exe_runner.sh b/tools/smokes/v2/lib/llvm_exe_runner.sh
index bae66359..de341816 100644
--- a/tools/smokes/v2/lib/llvm_exe_runner.sh
+++ b/tools/smokes/v2/lib/llvm_exe_runner.sh
@@ -11,6 +11,98 @@
 
 set -uo pipefail
 
+# Source centralized environment configuration (SSOT)
+LIB_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+if [ -f "$LIB_DIR/env.sh" ]; then
+  source "$LIB_DIR/env.sh"
+fi
+
+# ============================================================================
+# Helper: require_joinir_dev
+# ============================================================================
+# Sets dev-only environment variables for JoinIR normalized shadow testing.
+# Must be called BEFORE build/run operations if the fixture requires dev-only features.
+#
+# Usage:
+#   require_joinir_dev
+#
+# NOTE: This now validates that env.sh has been sourced correctly.
+#
+require_joinir_dev() {
+  # Verify env.sh provided the defaults
+  if [ "${NYASH_JOINIR_DEV:-0}" != "1" ]; then
+    export NYASH_JOINIR_DEV=1
+  fi
+  if [ "${HAKO_JOINIR_STRICT:-0}" != "1" ]; then
+    export HAKO_JOINIR_STRICT=1
+  fi
+  echo "[INFO] JoinIR dev mode enabled (NYASH_JOINIR_DEV=1, HAKO_JOINIR_STRICT=1)"
+}
+
+# ============================================================================
+# Helper: check_output_contract
+# ============================================================================
+# Unified output validation interface for exit_code, numeric, and substring checks.
+#
+# Args:
+#   $1: contract_type - "exit_code" / "numeric" / "substring"
+#   $2: expected      - Expected value (string/number)
+#   $3: actual        - Actual value to compare
+#   $4: context       - (optional) Context description for error messages
+#
+# Returns:
+#   0 if contract satisfied, 1 otherwise
+#
+check_output_contract() {
+  local contract_type="${1:-}"
+  local expected="${2:-}"
+  local actual="${3:-}"
+  local context="${4:-output}"
+
+  if [ -z "$contract_type" ] || [ -z "$expected" ]; then
+    echo "[FAIL] check_output_contract: missing contract_type or expected value"
+    return 1
+  fi
+
+  case "$contract_type" in
+    exit_code)
+      if [ "$actual" -ne "$expected" ] 2>/dev/null; then
+        echo "[FAIL] OutputContract(exit_code): got $actual, expected $expected"
+        return 1
+      fi
+      echo "[PASS] OutputContract(exit_code): $actual == $expected"
+      return 0
+      ;;
+
+    numeric)
+      if [ "$actual" != "$expected" ]; then
+        echo "[FAIL] OutputContract(numeric): got '$actual', expected '$expected'"
+        echo "[INFO] Context: $context"
+        return 1
+      fi
+      echo "[PASS] OutputContract(numeric): $actual == $expected"
+      return 0
+      ;;
+
+    substring)
+      if ! printf "%s" "$actual" | grep -qF "$expected"; then
+        echo "[FAIL] OutputContract(substring): '$expected' not found in $context"
+        echo "[INFO] Actual output (first 200 chars):"
+        printf "%s" "$actual" | head -c 200
+        echo ""
+        return 1
+      fi
+      echo "[PASS] OutputContract(substring): '$expected' found in $context"
+      return 0
+      ;;
+
+    *)
+      echo "[FAIL] check_output_contract: unknown contract_type '$contract_type'"
+      return 1
+      ;;
+  esac
+}
+
 llvm_exe_cargo_target_dir() {
   # Use the workspace target dir by default so `NYASH_BIN` and plugin artifacts match local dev expectations.
   local target_dir="${LLVM_EXE_CARGO_TARGET_DIR:-$NYASH_ROOT/target}"
@@ -180,15 +272,12 @@ llvm_exe_build_and_run_numeric_smoke() {
   echo "[INFO] CLEAN output:"
   echo "$clean"
 
-  if [ "$clean" = "$EXPECTED" ]; then
+  if check_output_contract "numeric" "$EXPECTED" "$clean" "numeric stdout (first $EXPECTED_LINES lines)"; then
     return 0
   fi
 
-  echo "[FAIL] Output mismatch"
   echo "[INFO] Raw output (tail):"
   echo "$output" | tail -n 80
-  echo "[INFO] Expected:"
-  printf "%s\n" "$EXPECTED"
   return 1
 }
 
@@ -241,12 +330,11 @@ llvm_exe_build_and_run_expect_exit_code() {
   local exit_code=$?
   set -e
 
-  if [ "$exit_code" -ne "$EXPECTED_EXIT_CODE" ]; then
-    echo "[FAIL] Execution exit code mismatch: got $exit_code, expected $EXPECTED_EXIT_CODE"
-    echo "[INFO] Raw output (tail):"
-    echo "$output" | tail -n 80
-    return 1
+  if check_output_contract "exit_code" "$EXPECTED_EXIT_CODE" "$exit_code" "executable exit code"; then
+    return 0
   fi
 
-  return 0
+  echo "[INFO] Raw output (tail):"
+  echo "$output" | tail -n 80
+  return 1
 }
diff --git a/tools/smokes/v2/lib/test_runner.sh b/tools/smokes/v2/lib/test_runner.sh
index aee87465..5733b947 100644
--- a/tools/smokes/v2/lib/test_runner.sh
+++ b/tools/smokes/v2/lib/test_runner.sh
@@ -9,6 +9,12 @@ set -uo pipefail
 if [ -z "${NYASH_ROOT:-}" ]; then
   export NYASH_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../../../.." && pwd)"
 fi
+
+# Source centralized environment configuration (SSOT)
+LIB_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+if [ -f "$LIB_DIR/env.sh" ]; then
+  source "$LIB_DIR/env.sh"
+fi
 # Prefer hakorune binary if exists; fallback to nyash for compatibility
 if [ -z "${NYASH_BIN:-}" ]; then
   if [ -x "$NYASH_ROOT/target/release/hakorune" ]; then
@@ -842,6 +848,27 @@ verify_v1_inline_file() {
     fi
     return 1
 }
+# ============================================================================
+# Helper: require_joinir_dev
+# ============================================================================
+# Sets dev-only environment variables for JoinIR normalized shadow testing.
+# Must be called BEFORE build/run operations if the fixture requires dev-only features.
+#
+# Usage:
+#   require_joinir_dev
+#
+require_joinir_dev() {
+  # JoinIR dev mode now controlled by env.sh (SSOT)
+  # Verify it's enabled (should be default=1 from env.sh)
+  if [ "${NYASH_JOINIR_DEV:-0}" != "1" ]; then
+    export NYASH_JOINIR_DEV=1
+  fi
+  if [ "${HAKO_JOINIR_STRICT:-0}" != "1" ]; then
+    export HAKO_JOINIR_STRICT=1
+  fi
+  echo "[INFO] JoinIR dev mode enabled (NYASH_JOINIR_DEV=1, HAKO_JOINIR_STRICT=1)"
+}
+
 # Dev profile helpers (centralize bring-up toggles for MirBuilder)
 # Usage: call enable_mirbuilder_dev_env in canaries that need it.
 enable_mirbuilder_dev_env() {
@@ -849,12 +876,12 @@ enable_mirbuilder_dev_env() {
     export NYASH_USE_NY_COMPILER=0
     # Allow FileBox provider fallback (dev only)
     export NYASH_FAIL_FAST=${NYASH_FAIL_FAST:-0}
-    # Enable using resolution in VM
-    export NYASH_ENABLE_USING=1
-    export HAKO_ENABLE_USING=1
-    # Allow file-based using in dev (e.g., using "hako.mir.builder")
-    export NYASH_ALLOW_USING_FILE=1
-    export HAKO_ALLOW_USING_FILE=1
+    # Using system already configured by env.sh (SSOT), but ensure enabled
+    export NYASH_ENABLE_USING="${NYASH_ENABLE_USING:-1}"
+    export HAKO_ENABLE_USING="${HAKO_ENABLE_USING:-1}"
+    # File-based using also from env.sh, but ensure enabled for dev
+    export NYASH_ALLOW_USING_FILE="${NYASH_ALLOW_USING_FILE:-1}"
+    export HAKO_ALLOW_USING_FILE="${HAKO_ALLOW_USING_FILE:-1}"
     # Optional: preinclude heavy using segments for legacy/prelude-heavy paths (default OFF)
     if [ "${SMOKES_DEV_PREINCLUDE:-0}" = "1" ]; then
         export HAKO_PREINCLUDE=1
@@ -875,13 +902,13 @@ enable_mirbuilder_dev_env() {
 # Sets environment defaults for LLVM crate backend and EXE link paths.
 # Usage: call enable_exe_dev_env in EXE canaries.
 enable_exe_dev_env() {
-    # Prefer crate backend when available
-    export NYASH_LLVM_BACKEND=${NYASH_LLVM_BACKEND:-crate}
+    # LLVM backend already configured by env.sh (SSOT), fallback to crate
+    export NYASH_LLVM_BACKEND="${NYASH_LLVM_BACKEND:-crate}"
     # Tool locations (override when cross)
-    export NYASH_NY_LLVM_COMPILER=${NYASH_NY_LLVM_COMPILER:-"$NYASH_ROOT/target/release/ny-llvmc"}
+    export NYASH_NY_LLVM_COMPILER="${NYASH_NY_LLVM_COMPILER:-$NYASH_ROOT/target/release/ny-llvmc}"
     # NyRT (kernel) lib search path for linking EXEs
-    export NYASH_EMIT_EXE_NYRT=${NYASH_EMIT_EXE_NYRT:-"$NYASH_ROOT/target/release"}
-    # Optional verification toggles (kept ON by default only for canaries that opt-in)
-    export NYASH_LLVM_VERIFY=${NYASH_LLVM_VERIFY:-0}
-    export NYASH_LLVM_VERIFY_IR=${NYASH_LLVM_VERIFY_IR:-0}
+    export NYASH_EMIT_EXE_NYRT="${NYASH_EMIT_EXE_NYRT:-$NYASH_ROOT/target/release}"
+    # Verification toggles from env.sh (SSOT)
+    export NYASH_LLVM_VERIFY="${NYASH_LLVM_VERIFY:-0}"
+    export NYASH_LLVM_VERIFY_IR="${NYASH_LLVM_VERIFY_IR:-0}"
 }
diff --git a/tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_llvm_exe.sh b/tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_llvm_exe.sh
index 965dd67d..113f4d54 100644
--- a/tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_llvm_exe.sh
+++ b/tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_llvm_exe.sh
@@ -11,8 +11,7 @@ llvm_exe_preflight_or_skip || exit 0
 
 # Phase 131 is a dev-only Normalized shadow loop case.
 # LLVM EXE emission must run with JoinIR dev/strict enabled, otherwise it will freeze.
-export NYASH_JOINIR_DEV=1
-export HAKO_JOINIR_STRICT=1
+require_joinir_dev
 
 # Phase 131: minimal plugin set (StringBox, ConsoleBox, IntegerBox only)
 STRINGBOX_SO="$NYASH_ROOT/plugins/nyash-string-plugin/libnyash_string_plugin.so"
diff --git a/tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_vm.sh b/tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_vm.sh
index c52f0f98..9e5909d7 100644
--- a/tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_vm.sh
+++ b/tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_vm.sh
@@ -9,6 +9,9 @@ source "$(dirname "$0")/../../../lib/test_runner.sh"
 export SMOKES_USE_PYVM=0
 require_env || exit 2
 
+# Phase 131 is a dev-only Normalized shadow loop case.
+require_joinir_dev
+
 PASS_COUNT=0
 FAIL_COUNT=0
 RUN_TIMEOUT_SECS=${RUN_TIMEOUT_SECS:-10}
@@ -22,8 +25,6 @@ INPUT="$NYASH_ROOT/apps/tests/phase131_loop_true_break_once_min.hako"
 set +e
 OUTPUT=$(timeout "$RUN_TIMEOUT_SECS" env \
   NYASH_DISABLE_PLUGINS=1 \
-  HAKO_JOINIR_STRICT=1 \
-  NYASH_JOINIR_DEV=1 \
   "$NYASH_BIN" --backend vm "$INPUT" 2>&1)
 EXIT_CODE=$?
 set -e