diff --git a/src/mir/builder/control_flow/joinir/parity_checker.rs b/src/mir/builder/control_flow/joinir/parity_checker.rs
index a79c4f7e..34e6cdd6 100644
--- a/src/mir/builder/control_flow/joinir/parity_checker.rs
+++ b/src/mir/builder/control_flow/joinir/parity_checker.rs
@@ -45,9 +45,9 @@ impl MirBuilder {
                     func_name, canonical_pattern, actual_pattern
                 );
 
-                // Check strict mode (NOTE: Will be replaced with SSOT in Phase 138-P2-B)
-                let is_strict = std::env::var("HAKO_JOINIR_STRICT").is_ok()
-                    || std::env::var("NYASH_JOINIR_STRICT").is_ok();
+                // Phase 138-P2-B: Use SSOT for environment variable check
+                use crate::config::env::joinir_dev;
+                let is_strict = joinir_dev::strict_enabled();
 
                 if is_strict {
                     // Strict mode: fail fast