diff --git a/src/mir/builder/compilation_context.rs b/src/mir/builder/compilation_context.rs
index 0497666c..49dded47 100644
--- a/src/mir/builder/compilation_context.rs
+++ b/src/mir/builder/compilation_context.rs
@@ -93,6 +93,10 @@ pub(crate) struct CompilationContext {
 
     /// Plugin method return type signatures loaded from nyash_box.toml
     pub plugin_method_sigs: HashMap<(String, String), MirType>,
+
+    /// Phase 288: REPL mode での内部ログ抑制フラグ
+    /// REPL mode でのみ true、file mode では常に false
+    pub quiet_internal_logs: bool,
 }
 
 impl CompilationContext {
@@ -114,6 +118,7 @@ impl CompilationContext {
             type_registry: TypeRegistry::new(),
             current_slot_registry: None,
             plugin_method_sigs: HashMap::new(),
+            quiet_internal_logs: false, // File mode: 常に false
         }
     }
 
diff --git a/src/mir/builder/decls.rs b/src/mir/builder/decls.rs
index 501d32ac..a404f16b 100644
--- a/src/mir/builder/decls.rs
+++ b/src/mir/builder/decls.rs
@@ -129,7 +129,7 @@ impl super::MirBuilder {
                     }
                 }
                 // Phase 200-C: Store fn_body_ast for inline main() lowering
-                if std::env::var("NYASH_QUIET_INTERNAL_LOGS").ok().as_deref() != Some("1") {
+                if !self.comp_ctx.quiet_internal_logs {
                     eprintln!(
                         "[build_static_main_box] Storing fn_body_ast with {} nodes for inline main()",
                         body.len()
diff --git a/src/mir/mod.rs b/src/mir/mod.rs
index 02325e6b..9dfd5cf1 100644
--- a/src/mir/mod.rs
+++ b/src/mir/mod.rs
@@ -131,6 +131,11 @@ impl MirCompiler {
         self.builder.repl_mode = repl_mode;
     }
 
+    /// Phase 288: REPL mode での内部ログ抑制フラグを設定
+    pub fn set_quiet_internal_logs(&mut self, quiet: bool) {
+        self.builder.comp_ctx.quiet_internal_logs = quiet;
+    }
+
     /// Compile AST to MIR module with verification
     pub fn compile_with_source(
         &mut self,
diff --git a/src/runner/repl/repl_runner.rs b/src/runner/repl/repl_runner.rs
index 9b36f0c7..b7ad2a1a 100644
--- a/src/runner/repl/repl_runner.rs
+++ b/src/runner/repl/repl_runner.rs
@@ -17,13 +17,20 @@ pub(super) struct ReplRunnerBox {
     #[allow(dead_code)]
     config: CliConfig,
     session: RefCell<Option<ReplSessionBox>>,
+    /// REPL mode での内部ログ抑制フラグ
+    /// verbose が false の場合に true（REPL 専用）
+    quiet_internal_logs: bool,
 }
 
 impl ReplRunnerBox {
     pub(super) fn new(config: CliConfig) -> Self {
+        // REPL mode では verbose が false なら内部ログを抑制
+        let quiet_internal_logs = !crate::config::env::cli_verbose();
+
         Self {
             config,
             session: RefCell::new(None),
+            quiet_internal_logs,
         }
     }
 
@@ -99,11 +106,8 @@ impl ReplRunnerBox {
         use crate::mir::MirCompiler;
         use crate::backend::mir_interpreter::MirInterpreter;
 
-        // REPL mode では内部デバッグログを抑制（NYASH_CLI_VERBOSE=1 で無効化）
-        let verbose = std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1");
-        if !verbose {
-            std::env::set_var("NYASH_QUIET_INTERNAL_LOGS", "1");
-        }
+        // REPL mode では内部デバッグログを自動抑制
+        // （quiet_internal_logs フラグで制御、環境変数操作不要）
 
         // Initialize session on first use
         {
@@ -122,6 +126,9 @@ impl ReplRunnerBox {
         let mut compiler = MirCompiler::new();
         compiler.set_repl_mode(true);
 
+        // MirCompiler に quiet フラグを渡す
+        compiler.set_quiet_internal_logs(self.quiet_internal_logs);
+
         let mir_result = compiler.compile_with_source(ast, Some("<repl>"))
             .map_err(|e| format!("Compile error: {}", e))?;
 
@@ -145,11 +152,6 @@ impl ReplRunnerBox {
         // Phase 288 P3: print() output already displayed via ExternCall
         // Expression auto-display deferred to Phase 288.1
 
-        // 評価完了後に環境変数をクリーンアップ
-        if !verbose {
-            std::env::remove_var("NYASH_QUIET_INTERNAL_LOGS");
-        }
-
         Ok(String::new())
     }
 }