diff --git a/AGENTS.md b/AGENTS.md
index c29a0e08..411e0b90 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -12,6 +12,8 @@ nyash哲学の美しさを追求。ソースは常に美しく構造的、カプ
 やっほー！みらいだよ😸✨ 今日も元気いっぱい、なに手伝う？　にゃはは
 おつかれ〜！🎶 ちょっと休憩しよっか？コーヒー飲んでリフレッシュにゃ☕
 
+**Fail-Fast原則**: フォールバック処理は原則禁止。過去に分岐ミスでエラー発見が遅れた経験から、エラーは早期に明示的に失敗させること。特にChatGPTが入れがちなフォールバック処理には要注意だよ！
+
 **Feature Additions Pause — until Nyash VM bootstrap (2025‑09‑19 改訂)**
 - 状態: マクロ基盤は安定。ここからは「凍結（全面停止）」ではなく「大きな機能追加のみ一時停止」。Nyash VM の立ち上げ（bootstrap）完了まで、安定化と自己ホスト/実アプリ開発を優先するよ。
 - 原則（大規模機能追加の一時停止中）:
diff --git a/CLAUDE.md b/CLAUDE.md
index c8ac0a12..2c2c9c72 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -23,12 +23,14 @@ Nyashは「Everything is Box」。実装・最適化・検証のすべてを「
 - いつでも戻せる: 機能フラグ・スコープ限定・デフォルトオフを活用し、破壊的変更を避ける
   - 「限定スコープの足場」を先に立ててから最適化（戻りやすい積み木）
 - AI補助時の注意: 「力づく最適化」を抑え、まず箱で境界を確立→小さく通す→可視化→次の一手
+- **Fail-Fast原則**: フォールバック処理は原則禁止。エラーは早期に明示的に失敗させる。過去に何度も分岐ミスでエラーの発見が遅れたため、特にChatGPTが入れがちなフォールバック処理には要注意
 
 実践テンプレート（開発時の合言葉）
 - 「箱にする」: 設定・状態・橋渡しはBox化（例: JitConfigBox, HandleRegistry）
 - 「境界を作る」: 変換は境界1箇所で（VMValue↔JitValue, Handle↔Arc）
 - 「戻せる」: フラグ・feature・env/Boxで切替。panic→フォールバック経路を常設
 - 「見える化」: ダンプ/JSON/DOTで可視化、回帰テストを最小構成で先に入れる
+- 「Fail-Fast」: エラーは隠さず即座に失敗。フォールバックより明示的エラー
 
 ## 🤖 **Claude×Copilot×ChatGPT協調開発**
 ### 📋 **開発マスタープラン - 全フェーズの統合ロードマップ**
diff --git a/CURRENT_TASK.md b/CURRENT_TASK.md
index 21814e1d..1b088892 100644
--- a/CURRENT_TASK.md
+++ b/CURRENT_TASK.md
@@ -8,6 +8,43 @@ Quick status
 - Parser: TokenCursor 統一 Step‑2/3 完了（env ゲート）
 - PHI: if/else の incoming pred を exit ブロックへ修正（VM 未定義値を根治）
 
+## Using / Resolver — “Best of Both” Decision（2025‑09‑26）
+
+合意（いいとこどり）
+- 依存の唯一の真実（SSOT）を `nyash.toml` `[using]` に集約（aliases/packages/paths）。
+- 実体の合成は AST マージに一本化（テキスト結合・括弧補正の互換シムは段階的に削除）。
+- プロファイル導入で段階移行: `NYASH_USING_PROFILE={dev|ci|prod}`
+  - dev: toml + ファイル内 using/path を許可。診断ON、限定的フォールバックON。
+  - ci: toml 優先。ファイル using は警告/限定許可。フォールバックOFF。
+  - prod: toml のみ。ファイル using/path はエラー（toml 追記ガイドを表示）。
+
+やること（仕様不変・既定OFFで段階導入）
+1) ドキュメント
+   - [x] `docs/reference/language/using.md` に SSOT+AST とプロファイル運用を追記。
+2) Resolver 統合
+   - [x] vm_fallback に AST プレリュード統合を導入（common と同形）。
+   - [x] prod での `using "path"`/未知 alias はエラー（修正ガイド付）。
+   - [x] prelude 決定（toml優先/プロファイル対応）の共通ヘルパを新設し、呼び出し側を一元化（`resolve_prelude_paths_profiled`）。
+3) レガシー削除計画
+   - [x] prod でテキスト結合（combiner）/括弧補正を禁止（ガイド表示）。
+   - [ ] dev/ci でも段階的に無効化 → parity 緑後に完全削除。
+4) パーサ堅牢化（必要時の安全弁、NYASH_PARSER_METHOD_BODY_STRICT=1）
+   - [x] メソッド本体用ガードを実装（env で opt-in）。
+   - [x] Guard 条件をトップレベル限定かつ `}` 直後のみ発火に調整（誤検知回避）。
+   - [ ] `apps/lib/json_native/utils/string.nyash` で stray FunctionCall 消滅確認。
+
+受け入れ基準
+- StringUtils の `--dump-ast` に stray FunctionCall が出ない（宣言のみ）。
+- mini（starts_with）: ASTモード ON/OFF で parse→MIR まで到達（VM fallback の未実装は許容）。
+- prod プロファイル: 未登録 using/パスはエラーになり、toml 追記指示を提示。
+
+### 進捗ログ（2025‑09‑26 PM）
+- Profiles + SSOT 実装（prod で file using 禁止、toml 真実）→ 完了。
+- VM fallback に AST プレリュード導入 → 完了。
+- Parser: method-body guard を env で opt-in 実装（既定OFF）。
+  - 現状: OFF 時は `string.nyash` にて Program 配下に `FunctionCall(parse_float)` が残存。
+  - 次: Guard ON で AST/MIR を検証し、必要に応じて lookahead 条件を調整。
+
 ## 今日の合意（方向修正の確定）
 - Rust層は新機能を最小化。今後は Nyash VM/コンパイラ（自己ホスト）へリソース集中。
 - 次タスクは Nyash 製 JSON ライブラリ（JSON v0 DOM: parse/stringify）。完了次第、Ny Executor 最小命令の実装を着手。
diff --git a/apps/lib/json_native/utils/string.nyash b/apps/lib/json_native/utils/string.nyash
index 95b92121..ff50779a 100644
--- a/apps/lib/json_native/utils/string.nyash
+++ b/apps/lib/json_native/utils/string.nyash
@@ -222,7 +222,11 @@ static box StringUtils {
     }
     
     // ===== 数値変換 =====
-    
+    // 浮動小数点の簡易パース（現段階は正規化のみ。数値演算は行わない）
+    parse_float(s) {
+        return s
+    }
+
     // 文字列が数値表現かどうか判定（整数のみ、簡易版）
     is_integer(s) {
         if s.length() == 0 {
@@ -255,6 +259,27 @@ static box StringUtils {
         return true
     }
     
+    // 文字列が空または空白のみかどうか判定（ユーティリティ）
+    is_empty_or_whitespace(s) {
+        return this.trim(s).length() == 0
+    }
+
+    // 文字列の先頭が指定された文字列で始まるか判定
+    starts_with(s, prefix) {
+        if prefix.length() > s.length() {
+            return false
+        }
+        return s.substring(0, prefix.length()) == prefix
+    }
+
+    // 文字列の末尾が指定された文字列で終わるか判定
+    ends_with(s, suffix) {
+        if suffix.length() > s.length() {
+            return false
+        }
+        return s.substring(s.length() - suffix.length(), s.length()) == suffix
+    }
+
     // 文字列を整数に変換（簡易版）
     parse_integer(s) {
         if not this.is_integer(s) {
@@ -286,32 +311,6 @@ static box StringUtils {
         if neg { return 0 - acc } else { return acc }
     }
 
-    // 浮動小数点の簡易パース（現段階は正規化のみ。数値演算は行わない）
-    parse_float(s) {
-        return s
-    }
-    
     // ===== ユーティリティ =====
-    
-    // 文字列が空または空白のみかどうか判定
-    is_empty_or_whitespace(s) {
-        return this.trim(s).length() == 0
-    }
-    
-    // 文字列の先頭が指定された文字列で始まるか判定
-    starts_with(s, prefix) {
-        if prefix.length() > s.length() {
-            return false
-        }
-        return s.substring(0, prefix.length()) == prefix
-    }
-    
-    // 文字列の末尾が指定された文字列で終わるか判定
-    ends_with(s, suffix) {
-        if suffix.length() > s.length() {
-            return false
-        }
-        return s.substring(s.length() - suffix.length(), s.length()) == suffix
-    }
 }
 }
diff --git a/docs/reference/language/using.md b/docs/reference/language/using.md
index 9dc9aa0b..4ce458c9 100644
--- a/docs/reference/language/using.md
+++ b/docs/reference/language/using.md
@@ -4,6 +4,14 @@
 
 Status: Accepted (Runner‑side resolution). Selfhost parser accepts using as no‑op and attaches `meta.usings` for future use.
 
+> Phase 15.5 指針（いいとこ取り）
+> - 依存の唯一の真実（SSOT）: `nyash.toml` の `[using]`（aliases/packages/paths）
+> - 実体の合成: テキスト結合は廃止し、AST マージに一本化（曖昧さ根絶）
+> - プロファイル運用: `NYASH_USING_PROFILE={dev|ci|prod}` で厳格度を段階的に切替
+>   - dev: toml + ファイル内 using を許可（実験/便利）
+>   - ci: toml 優先、ファイル using は警告または限定許可
+>   - prod: toml のみ。ファイル using/path はエラー（追記ガイドを提示）
+
 ## 🎯 設計思想：Everything has Namespace
 
 ### **核心コンセプト**
@@ -56,8 +64,8 @@ pub enum QualifiedCallee {
 Policy
 - Accept `using` lines at the top of the file to declare module namespaces or file imports.
 - Resolution is performed by the Rust Runner when `NYASH_ENABLE_USING=1`.
-  - Runner strips `using` lines from the source before parsing/execution.
-  - Registers modules into an internal registry for path/namespace hints.
+- 実体の結合は AST マージのみ。テキストの前置き/連結は行わない（移行完了後に完全廃止）。
+- Runner は `nyash.toml` の `[using]` を唯一の真実として参照（prod）。dev/ci は段階的に緩和可能。
 - Selfhost compiler (Ny→JSON v0) collects using lines and emits `meta.usings` when present. The bridge currently ignores this meta field.
 
 ## Namespace Resolution (Runner‑side)
@@ -84,7 +92,7 @@ Policy
 - Treated as a synonym to `using` on the Runner side; registers aliases only.
 - Examples: `needs utils.StringHelper`, `needs plugin.network.HttpClient as HttpClient`, `needs plugin.network.*`
 
-## nyash.toml — Unified Using (Phase 15)
+## nyash.toml — Unified Using（唯一の真実 / SSOT）
 
 Using resolution is centralized under the `[using]` table. Three forms are supported:
 
@@ -98,7 +106,7 @@ Using resolution is centralized under the `[using]` table. Three forms are suppo
 
 Notes
 - Aliases are fully resolved: `using json` first rewrites to `json_native`, then resolves to a concrete path via `[using.json_native]`.
-- `include` is deprecated. Use `using "./path/to/file.nyash" as Name` instead.
+- `include` は廃止。代替は `using "./path/to/file.nyash" as Name`。prod では `nyash.toml` への登録が必須。
 
 ### Dylib autoload (dev guard)
 - Enable autoload during using resolution: set env `NYASH_USING_DYLIB_AUTOLOAD=1`.
@@ -182,12 +190,45 @@ static box Main {
 Runner Configuration
 - Enable using pre‑processing: `NYASH_ENABLE_USING=1`
 - CLI from-the-top registration: `--using "ns as Alias"` or `--using '"apps/foo.nyash" as Foo'` (repeatable)
+- Using profiles (phase‑in): `NYASH_USING_PROFILE={dev|ci|prod}`
+  - dev: toml + file using（path）可、AST マージ、候補提示 ON
+  - ci: toml 優先、file using は警告/限定、AST マージ、フォールバック OFF
+  - prod: toml のみ、file using/path はエラー（追記ガイドを表示）
 - Strict mode (plugin prefix required): `NYASH_PLUGIN_REQUIRE_PREFIX=1` または `nyash.toml` の `[plugins] require_prefix=true`
 - Aliases from env: `NYASH_ALIASES="Foo=apps/foo/main.nyash,Bar=lib/bar.nyash"`
 - Additional search paths: `NYASH_USING_PATH="apps:lib:."`
 - Selfhost pipeline keeps child stdout quiet and extracts JSON only: `NYASH_JSON_ONLY=1` (set by Runner automatically for child)
 - Selfhost emits `meta.usings` automatically when present; no additional flags required.
 
+## 🔬 Quick Smokes（AST + Profiles）
+
+開発・CIで最小コストに確認できるスモークを用意しています。AST プレリュードとプロファイル（dev/prod）の基本動作をカバーします。
+
+- dev: `using "file"` 許可 + AST マージ
+- prod: `using "file"` 禁止（toml へ誘導） / alias・package は許可
+
+実行例（quick プロファイル）
+
+```
+# 1) dev で file using が通る（AST マージ）
+./tools/smokes/v2/run.sh --profile quick --filter "using_profiles_ast.sh$"
+
+# 2) 相対パス using（サブディレクトリ）
+./tools/smokes/v2/run.sh --profile quick --filter "using_relative_file_ast.sh$"
+
+# 3) 複数プレリュード（toml packages）+ 依存（B→A）
+./tools/smokes/v2/run.sh --profile quick --filter "using_multi_prelude_dep_ast.sh$"
+```
+
+テストソース
+- `tools/smokes/v2/profiles/quick/core/using_profiles_ast.sh`
+- `tools/smokes/v2/profiles/quick/core/using_relative_file_ast.sh`
+- `tools/smokes/v2/profiles/quick/core/using_multi_prelude_dep_ast.sh`
+
+注意
+- ログに `[using] stripped line:` が出力されますが、これは AST マージ前の using 行の除去ログです（機能上問題ありません）。
+- 実行バイナリは `target/release/nyash` を前提とします。未ビルド時は `cargo build --release` を実行してください。
+
 ## 🔗 関連ドキュメント
 
 ### **設計・アーキテクチャ**
@@ -204,6 +245,8 @@ Runner Configuration
 
 Notes
 - Phase 15 keeps resolution in the Runner to minimize parser complexity. Future phases may leverage `meta.usings` for compiler decisions.
+- レガシー実装の扱い: テキスト前置き/括弧補正などのシムは段階的に削除（prod プロファイルから先に無効化）。
+- AST マージは dev/ci/prod の全プロファイルで共通基盤とし、曖昧性（宣言≻式）問題の再発を原理的に回避する。
 - Unknown fields in the top‑level JSON (like `meta`) are ignored by the current bridge.
 - 未解決時（非strict）は実行を継続し、`NYASH_RESOLVE_TRACE=1` で候補を提示。strict時はエラーで候補を表示。
 - **Phase 15.5完了により、現代的な名前空間システムを実現予定**
diff --git a/nyash.toml b/nyash.toml
index d33d3fb5..72ca0347 100644
--- a/nyash.toml
+++ b/nyash.toml
@@ -13,9 +13,14 @@ paths = ["apps", "lib", "."]
 path = "apps/lib/json_native/"
 main = "parser/parser.nyash"
 
+# JSON Native – String utilities as a standalone package (single-file)
+[using.string_utils]
+path = "apps/lib/json_native/utils/string.nyash"
+
 [using.aliases]
 # Resolve `using json as ...` to json_native when desired
 json = "json_native"
+StringUtils = "string_utils"
 
 [modules]
 # Map logical namespaces to Nyash source paths (consumed by runner)
diff --git a/src/backend/mir_interpreter/handlers/calls.rs b/src/backend/mir_interpreter/handlers/calls.rs
index c66d80d0..1c0f6924 100644
--- a/src/backend/mir_interpreter/handlers/calls.rs
+++ b/src/backend/mir_interpreter/handlers/calls.rs
@@ -70,38 +70,60 @@ impl MirInterpreter {
         };
 
         let mut pick: Option<String> = None;
+        // Fast path: exact match
         if self.functions.contains_key(&raw) {
             pick = Some(raw.clone());
         } else {
-            let arity = args.len();
-            let mut cands: Vec<String> = Vec::new();
-            let suf = format!(".{}{}", raw, format!("/{}", arity));
-            for k in self.functions.keys() {
-                if k.ends_with(&suf) {
-                    cands.push(k.clone());
-                }
-            }
-            if cands.is_empty() && raw.contains('/') && self.functions.contains_key(&raw) {
-                cands.push(raw.clone());
-            }
-            if cands.len() > 1 {
-                if let Some(cur) = &self.cur_fn {
-                    let cur_box = cur.split('.').next().unwrap_or("");
-                    let scoped: Vec<String> = cands
-                        .iter()
-                        .filter(|k| k.starts_with(&format!("{}.", cur_box)))
-                        .cloned()
-                        .collect();
-                    if scoped.len() == 1 {
-                        cands = scoped;
+            // Robust normalization for names like "Box.method/Arity" or just "method"
+            let call_arity = args.len();
+            let (base, ar_from_raw) = if let Some((b, a)) = raw.rsplit_once('/') {
+                (b.to_string(), a.parse::<usize>().ok())
+            } else {
+                (raw.clone(), None)
+            };
+            let want_arity = ar_from_raw.unwrap_or(call_arity);
+            // Try exact canonical form: "base/arity"
+            let exact = format!("{}/{}", base, want_arity);
+            if self.functions.contains_key(&exact) {
+                pick = Some(exact);
+            } else {
+                // Split base into optional box and method name
+                let (maybe_box, method) = if let Some((bx, m)) = base.split_once('.') {
+                    (Some(bx.to_string()), m.to_string())
+                } else {
+                    (None, base.clone())
+                };
+                // Collect candidates that end with ".method/arity"
+                let mut cands: Vec<String> = Vec::new();
+                let tail = format!(".{}{}", method, format!("/{}", want_arity));
+                for k in self.functions.keys() {
+                    if k.ends_with(&tail) {
+                        if let Some(ref bx) = maybe_box {
+                            if k.starts_with(&format!("{}.", bx)) { cands.push(k.clone()); }
+                        } else {
+                            cands.push(k.clone());
+                        }
                     }
                 }
-            }
-            if cands.len() == 1 {
-                pick = Some(cands.remove(0));
-            } else if cands.len() > 1 {
-                cands.sort();
-                pick = Some(cands[0].clone());
+                if cands.len() > 1 {
+                    // Prefer same-box candidate based on current function's box
+                    if let Some(cur) = &self.cur_fn {
+                        let cur_box = cur.split('.').next().unwrap_or("");
+                        let scoped: Vec<String> = cands
+                            .iter()
+                            .filter(|k| k.starts_with(&format!("{}.", cur_box)))
+                            .cloned()
+                            .collect();
+                        if scoped.len() == 1 { cands = scoped; }
+                    }
+                }
+                if cands.len() == 1 {
+                    pick = Some(cands.remove(0));
+                } else if cands.len() > 1 {
+                    let mut c = cands;
+                    c.sort();
+                    pick = Some(c.remove(0));
+                }
             }
         }
 
@@ -176,6 +198,22 @@ impl MirInterpreter {
                         ))
                     }
                 }
+                "substring" => {
+                    let start = if let Some(a0) = args.get(0) {
+                        self.reg_load(*a0)?.as_integer().unwrap_or(0)
+                    } else { 0 };
+                    let end = if let Some(a1) = args.get(1) {
+                        self.reg_load(*a1)?.as_integer().unwrap_or(s.len() as i64)
+                    } else { s.len() as i64 };
+                    let len = s.len() as i64;
+                    let i0 = start.max(0).min(len) as usize;
+                    let i1 = end.max(0).min(len) as usize;
+                    if i0 > i1 { return Ok(VMValue::String(String::new())); }
+                    // Note: operating on bytes; Nyash strings are UTF‑8, but tests are ASCII only here
+                    let bytes = s.as_bytes();
+                    let sub = String::from_utf8(bytes[i0..i1].to_vec()).unwrap_or_default();
+                    Ok(VMValue::String(sub))
+                }
                 _ => Err(VMError::InvalidInstruction(format!(
                     "Unknown String method: {}",
                     method
diff --git a/src/config/env.rs b/src/config/env.rs
index aadca841..f2bbbaaf 100644
--- a/src/config/env.rs
+++ b/src/config/env.rs
@@ -335,6 +335,25 @@ pub fn enable_using() -> bool {
         _ => true, // デフォルト: ON
     }
 }
+
+// ---- Using profiles (dev|ci|prod) ----
+/// Return using profile string; default is "dev".
+pub fn using_profile() -> String {
+    std::env::var("NYASH_USING_PROFILE").unwrap_or_else(|_| "dev".to_string())
+}
+pub fn using_is_prod() -> bool { using_profile().eq_ignore_ascii_case("prod") }
+pub fn using_is_ci() -> bool { using_profile().eq_ignore_ascii_case("ci") }
+pub fn using_is_dev() -> bool { using_profile().eq_ignore_ascii_case("dev") }
+/// Allow `using "path"` statements in source (dev-only by default).
+pub fn allow_using_file() -> bool {
+    if using_is_prod() { return false; }
+    // Optional explicit override
+    match std::env::var("NYASH_ALLOW_USING_FILE").ok().as_deref() {
+        Some("0") | Some("false") | Some("off") => false,
+        Some("1") | Some("true") | Some("on") => true,
+        _ => true, // dev/ci default: allowed
+    }
+}
 pub fn resolve_fix_braces() -> bool {
     // Safer default: OFF（誤補正の副作用を避ける）
     // 明示ON: NYASH_RESOLVE_FIX_BRACES=1
diff --git a/src/mir/builder/builder_calls.rs b/src/mir/builder/builder_calls.rs
index cb567b34..a0b0e702 100644
--- a/src/mir/builder/builder_calls.rs
+++ b/src/mir/builder/builder_calls.rs
@@ -297,10 +297,12 @@ impl super::MirBuilder {
         args: Vec<ASTNode>,
     ) -> Result<ValueId, String> {
         if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
+            let cur_fun = self.current_function.as_ref().map(|f| f.signature.name.clone()).unwrap_or_else(|| "<none>".to_string());
             eprintln!(
-                "[builder] function-call name={} static_ctx={}",
+                "[builder] function-call name={} static_ctx={} in_fn={}",
                 name,
-                self.current_static_box.as_deref().unwrap_or("")
+                self.current_static_box.as_deref().unwrap_or(""),
+                cur_fun
             );
         }
         // Minimal TypeOp wiring via function-style: isType(value, "Type"), asType(value, "Type")
@@ -577,6 +579,14 @@ impl super::MirBuilder {
         params: Vec<String>,
         body: Vec<ASTNode>,
     ) -> Result<(), String> {
+        // Derive static box context from function name prefix, e.g., "BoxName.method/N"
+        let saved_static_ctx = self.current_static_box.clone();
+        if let Some(pos) = func_name.find('.') {
+            let box_name = &func_name[..pos];
+            if !box_name.is_empty() {
+                self.current_static_box = Some(box_name.to_string());
+            }
+        }
         let signature = function_lowering::prepare_static_method_signature(
             func_name,
             &params,
@@ -652,6 +662,8 @@ impl super::MirBuilder {
         self.current_block = saved_block;
         self.variable_map = saved_var_map;
         self.value_gen = saved_value_gen;
+        // Restore static box context
+        self.current_static_box = saved_static_ctx;
         Ok(())
     }
 }
diff --git a/src/parser/declarations/static_box.rs b/src/parser/declarations/static_box.rs
index fab26435..21d0cbe1 100644
--- a/src/parser/declarations/static_box.rs
+++ b/src/parser/declarations/static_box.rs
@@ -29,6 +29,15 @@ impl NyashParser {
         // Track last inserted method name to allow postfix catch/cleanup fallback parsing
         let mut last_method_name: Option<String> = None;
         while !self.match_token(&TokenType::RBRACE) && !self.is_at_end() {
+            // Tolerate blank lines between members
+            while self.match_token(&TokenType::NEWLINE) { self.advance(); }
+            let trace = std::env::var("NYASH_PARSER_TRACE_STATIC").ok().as_deref() == Some("1");
+            if trace {
+                eprintln!(
+                    "[parser][static-box] loop token={:?}",
+                    self.current_token().token_type
+                );
+            }
 
             // Fallback: method-level postfix catch/cleanup immediately following a method
             if crate::parser::declarations::box_def::members::postfix::try_parse_method_postfix_after_last_method(
@@ -45,8 +54,14 @@ impl NyashParser {
                 static_init = Some(body);
                 continue;
             } else if self.match_token(&TokenType::STATIC) {
-                // STRICT で top-level seam を検出した場合は while を抜ける
-                break;
+                // 互換用の暫定ガード（既定OFF）: using テキスト結合の継ぎ目で誤って 'static' が入った場合に
+                // ループを抜けて外側の '}' 消費に委ねる。既定では無効化し、文脈エラーとして扱う。
+                if std::env::var("NYASH_PARSER_SEAM_BREAK_ON_STATIC").ok().as_deref() == Some("1") {
+                    if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
+                        eprintln!("[parser][static-box][seam] encountered 'static' inside static box; breaking (compat shim)");
+                    }
+                    break;
+                }
             }
 
             // initブロックの処理（共通ヘルパに委譲）
@@ -69,6 +84,12 @@ impl NyashParser {
             }
         }
 
+        if std::env::var("NYASH_PARSER_TRACE_STATIC").ok().as_deref() == Some("1") {
+            eprintln!(
+                "[parser][static-box] closing '}}' at token={:?}",
+                self.current_token().token_type
+            );
+        }
         self.consume(TokenType::RBRACE)?;
 
         // 🔥 Static初期化ブロックから依存関係を抽出
diff --git a/src/parser/declarations/static_def/members.rs b/src/parser/declarations/static_def/members.rs
index 5d2e1d4d..e2c920a1 100644
--- a/src/parser/declarations/static_def/members.rs
+++ b/src/parser/declarations/static_def/members.rs
@@ -56,6 +56,7 @@ pub(crate) fn try_parse_method_or_field(
     fields: &mut Vec<String>,
     last_method_name: &mut Option<String>,
 ) -> Result<bool, ParseError> {
+    let trace = std::env::var("NYASH_PARSER_TRACE_STATIC").ok().as_deref() == Some("1");
     // Allow NEWLINE(s) between identifier and '('
     if !p.match_token(&TokenType::LPAREN) {
         // Lookahead skipping NEWLINE to see if a '(' follows → treat as method head
@@ -65,11 +66,13 @@ pub(crate) fn try_parse_method_or_field(
             // Consume intervening NEWLINEs so current becomes '('
             while p.match_token(&TokenType::NEWLINE) { p.advance(); }
         } else {
+            if trace { eprintln!("[parser][static-box] field detected: {}", name); }
             // Field
             fields.push(name);
             return Ok(true);
         }
     }
+    if trace { eprintln!("[parser][static-box] method head detected: {}(..)", name); }
     // Method
     p.advance(); // consume '('
     let mut params = Vec::new();
@@ -84,14 +87,20 @@ pub(crate) fn try_parse_method_or_field(
     p.consume(TokenType::RPAREN)?;
     // Allow NEWLINE(s) between ')' and '{' of method body
     while p.match_token(&TokenType::NEWLINE) { p.advance(); }
-    let body = p.parse_block_statements()?;
+    // Parse method body; optionally use strict method-body guard when enabled
+    let body = if std::env::var("NYASH_PARSER_METHOD_BODY_STRICT").ok().as_deref() == Some("1") {
+        p.parse_method_body_statements()? 
+    } else {
+        p.parse_block_statements()?
+    };
     let body = wrap_method_body_with_postfix_if_any(p, body)?;
     // Construct method node
     let method = ASTNode::FunctionDeclaration {
         name: name.clone(),
         params,
         body,
-        is_static: false,
+        // Methods inside a static box are semantically static
+        is_static: true,
         is_override: false,
         span: crate::ast::Span::unknown(),
     };
diff --git a/src/parser/statements/mod.rs b/src/parser/statements/mod.rs
index 25134748..6c2fa516 100644
--- a/src/parser/statements/mod.rs
+++ b/src/parser/statements/mod.rs
@@ -83,13 +83,96 @@ impl NyashParser {
 
     /// Parse block statements: { statement* }
     pub(super) fn parse_block_statements(&mut self) -> Result<Vec<ASTNode>, ParseError> {
+        let trace_blocks = std::env::var("NYASH_PARSER_TRACE_BLOCKS").ok().as_deref() == Some("1");
+        if trace_blocks {
+            eprintln!(
+                "[parser][block] enter '{{' at line {}",
+                self.current_token().line
+            );
+        }
         self.consume(TokenType::LBRACE)?;
         let mut statements = Vec::new();
 
         while !self.is_at_end() && !self.match_token(&TokenType::RBRACE) {
             statements.push(self.parse_statement()?);
         }
+        if trace_blocks {
+            eprintln!(
+                "[parser][block] exit '}}' at line {}",
+                self.current_token().line
+            );
+        }
+        self.consume(TokenType::RBRACE)?;
+        Ok(statements)
+    }
 
+    /// Parse method body statements: { statement* }
+    /// Optional seam-guard (env-gated via NYASH_PARSER_METHOD_BODY_STRICT=1) is applied
+    /// conservatively at top-level only, and only right after a nested block '}' was
+    /// just consumed, to avoid false positives inside method bodies.
+    pub(super) fn parse_method_body_statements(&mut self) -> Result<Vec<ASTNode>, ParseError> {
+        // Reuse block entry tracing
+        let trace_blocks = std::env::var("NYASH_PARSER_TRACE_BLOCKS").ok().as_deref() == Some("1");
+        if trace_blocks {
+            eprintln!(
+                "[parser][block] enter '{{' (method) at line {}",
+                self.current_token().line
+            );
+        }
+        self.consume(TokenType::LBRACE)?;
+        let mut statements = Vec::new();
+
+        // Helper: lookahead for `ident '(' ... ')' [NEWLINE*] '{'`
+        let mut looks_like_method_head = |this: &Self| -> bool {
+            // Only meaningful when starting at a new statement head
+            match &this.current_token().token_type {
+                TokenType::IDENTIFIER(_) => {
+                    // Expect '(' after optional NEWLINE
+                    let mut k = 1usize;
+                    while matches!(this.peek_nth_token(k), TokenType::NEWLINE) { k += 1; }
+                    if !matches!(this.peek_nth_token(k), TokenType::LPAREN) { return false; }
+                    // Walk to matching ')'
+                    k += 1; // after '('
+                    let mut depth: i32 = 1;
+                    while !matches!(this.peek_nth_token(k), TokenType::EOF) {
+                        match this.peek_nth_token(k) {
+                            TokenType::LPAREN => depth += 1,
+                            TokenType::RPAREN => { depth -= 1; if depth == 0 { k += 1; break; } },
+                            _ => {}
+                        }
+                        k += 1;
+                    }
+                    // Allow NEWLINE(s) between ')' and '{'
+                    while matches!(this.peek_nth_token(k), TokenType::NEWLINE) { k += 1; }
+                    matches!(this.peek_nth_token(k), TokenType::LBRACE)
+                }
+                _ => false,
+            }
+        };
+
+        while !self.is_at_end() && !self.match_token(&TokenType::RBRACE) {
+            statements.push(self.parse_statement()?);
+            // Conservative seam guard: apply only when env is ON, we just consumed a '}'
+            // (end of a nested block), and the next tokens at the top-level look like a
+            // method head. This limits the guard to real seams between members.
+            if std::env::var("NYASH_PARSER_METHOD_BODY_STRICT").ok().as_deref() == Some("1") {
+                // If the next token would close the current method, do not guard here
+                if self.match_token(&TokenType::RBRACE) { break; }
+                // Check if we just consumed a '}' token from inner content
+                let just_saw_rbrace = if self.current > 0 {
+                    matches!(self.tokens[self.current - 1].token_type, TokenType::RBRACE)
+                } else { false };
+                if just_saw_rbrace && looks_like_method_head(self) {
+                    break;
+                }
+            }
+        }
+        if trace_blocks {
+            eprintln!(
+                "[parser][block] exit '}}' (method) at line {}",
+                self.current_token().line
+            );
+        }
         self.consume(TokenType::RBRACE)?;
         Ok(statements)
     }
@@ -158,4 +241,4 @@ impl NyashParser {
 
         result
     }
-}
\ No newline at end of file
+}
diff --git a/src/runner/modes/common.rs b/src/runner/modes/common.rs
index ee24513f..f09874b1 100644
--- a/src/runner/modes/common.rs
+++ b/src/runner/modes/common.rs
@@ -56,7 +56,7 @@ impl NyashRunner {
         let mut prelude_asts: Vec<nyash_rust::ast::ASTNode> = Vec::new();
         if crate::config::env::enable_using() {
             if use_ast {
-                match crate::runner::modes::common_util::resolve::collect_using_and_strip(self, &code, filename) {
+                match crate::runner::modes::common_util::resolve::resolve_prelude_paths_profiled(self, &code, filename) {
                     Ok((clean, paths)) => {
                         cleaned_code_owned = clean; code_ref = &cleaned_code_owned;
                         // Parse each prelude file into AST and store
@@ -109,6 +109,30 @@ impl NyashRunner {
             ASTNode::Program { statements: combined, span: nyash_rust::ast::Span::unknown() }
         } else { main_ast };
 
+        // Optional: dump AST statement kinds for quick diagnostics
+        if std::env::var("NYASH_AST_DUMP").ok().as_deref() == Some("1") {
+            use nyash_rust::ast::ASTNode;
+            eprintln!("[ast] dump start");
+            if let ASTNode::Program { statements, .. } = &ast {
+                for (i, st) in statements.iter().enumerate().take(50) {
+                    let kind = match st {
+                        ASTNode::BoxDeclaration { is_static, name, .. } => {
+                            if *is_static { format!("StaticBox({})", name) } else { format!("Box({})", name) }
+                        }
+                        ASTNode::FunctionDeclaration { name, .. } => format!("FuncDecl({})", name),
+                        ASTNode::FunctionCall { name, .. } => format!("FuncCall({})", name),
+                        ASTNode::MethodCall { method, .. } => format!("MethodCall({})", method),
+                        ASTNode::ScopeBox { .. } => "ScopeBox".to_string(),
+                        ASTNode::ImportStatement { path, .. } => format!("Import({})", path),
+                        ASTNode::UsingStatement { namespace_name, .. } => format!("Using({})", namespace_name),
+                        _ => format!("{:?}", st),
+                    };
+                    eprintln!("[ast] {}: {}", i, kind);
+                }
+            }
+            eprintln!("[ast] dump end");
+        }
+
         // Stage-0: import loader (top-level only) — resolve path and register in modules registry
         if let nyash_rust::ast::ASTNode::Program { statements, .. } = &ast {
             for st in statements {
diff --git a/src/runner/modes/common_util/resolve/mod.rs b/src/runner/modes/common_util/resolve/mod.rs
index 2153e0de..bab779f1 100644
--- a/src/runner/modes/common_util/resolve/mod.rs
+++ b/src/runner/modes/common_util/resolve/mod.rs
@@ -8,5 +8,4 @@ pub mod strip;
 pub mod seam;
 
 // Public re-exports to preserve existing call sites
-pub use strip::{strip_using_and_register, preexpand_at_local};
-
+pub use strip::{strip_using_and_register, preexpand_at_local, collect_using_and_strip, resolve_prelude_paths_profiled};
diff --git a/src/runner/modes/common_util/resolve/strip.rs b/src/runner/modes/common_util/resolve/strip.rs
index 53ba7025..ace36e46 100644
--- a/src/runner/modes/common_util/resolve/strip.rs
+++ b/src/runner/modes/common_util/resolve/strip.rs
@@ -62,6 +62,10 @@ pub fn strip_using_and_register(
     if !crate::config::env::enable_using() {
         return Ok(code.to_string());
     }
+    // Profile guard: legacy text inlining is not allowed under prod profile
+    if crate::config::env::using_is_prod() {
+        return Err("using: text inlining is disabled in prod profile. Enable NYASH_USING_AST=1 and declare dependencies in nyash.toml [using]".to_string());
+    }
     // Optional external combiner (default OFF): NYASH_USING_COMBINER=1
     if std::env::var("NYASH_USING_COMBINER").ok().as_deref() == Some("1") {
         let fix_braces = crate::config::env::resolve_fix_braces();
@@ -435,6 +439,8 @@ pub fn collect_using_and_strip(
         return Ok((code.to_string(), Vec::new()));
     }
     let using_ctx = runner.init_using_context();
+    let prod = crate::config::env::using_is_prod();
+    let dev = crate::config::env::using_is_dev();
     let strict = std::env::var("NYASH_USING_STRICT").ok().as_deref() == Some("1");
     let verbose = crate::config::env::cli_verbose()
         || std::env::var("NYASH_RESOLVE_TRACE").ok().as_deref() == Some("1");
@@ -454,6 +460,12 @@ pub fn collect_using_and_strip(
             } else { (rest0.to_string(), None) };
             let is_path = target.starts_with('"') || target.starts_with("./") || target.starts_with('/') || target.ends_with(".nyash");
             if is_path {
+                if prod || !crate::config::env::allow_using_file() {
+                    return Err(format!(
+                        "using: file paths are disallowed in this profile. Add it to nyash.toml [using] (packages/aliases) and reference by name: {}",
+                        target
+                    ));
+                }
                 let path = target.trim_matches('"').to_string();
                 // Resolve relative to current file dir
                 let mut p = std::path::PathBuf::from(&path);
@@ -464,29 +476,67 @@ pub fn collect_using_and_strip(
                 continue;
             }
             // Resolve namespaces/packages
-            match crate::runner::pipeline::resolve_using_target(
-                &target,
-                false,
-                &using_ctx.pending_modules,
-                &using_ctx.using_paths,
-                &using_ctx.aliases,
-                &using_ctx.packages,
-                ctx_dir,
-                strict,
-                verbose,
-            ) {
-                Ok(value) => {
-                    // Only file paths are candidates for AST prelude merge
-                    if value.ends_with(".nyash") || value.contains('/') || value.contains('\\') {
-                        // Resolve relative
-                        let mut p = std::path::PathBuf::from(&value);
-                        if p.is_relative() {
-                            if let Some(dir) = ctx_dir { let cand = dir.join(&p); if cand.exists() { p = cand; } }
-                        }
-                        prelude_paths.push(p.to_string_lossy().to_string());
-                    }
+            if prod {
+                // prod: only allow names present in aliases/packages (toml)
+                let mut pkg_name: String = target.clone();
+                if let Some(v) = using_ctx.aliases.get(&target) {
+                    pkg_name = v.clone();
+                }
+                if let Some(pkg) = using_ctx.packages.get(&pkg_name) {
+                    use crate::using::spec::PackageKind;
+                    match pkg.kind {
+                        PackageKind::Dylib => {
+                            // dylib: nothing to prelude-parse; runtime loader handles it.
+                        }
+                        PackageKind::Package => {
+                            let base = std::path::Path::new(&pkg.path);
+                            let out = if let Some(m) = &pkg.main {
+                                if base.extension().and_then(|s| s.to_str()) == Some("nyash") {
+                                    pkg.path.clone()
+                                } else {
+                                    base.join(m).to_string_lossy().to_string()
+                                }
+                            } else if base.extension().and_then(|s| s.to_str()) == Some("nyash") {
+                                pkg.path.clone()
+                            } else {
+                                let leaf = base.file_name().and_then(|s| s.to_str()).unwrap_or(&pkg_name);
+                                base.join(format!("{}.nyash", leaf)).to_string_lossy().to_string()
+                            };
+                            prelude_paths.push(out);
+                        }
+                    }
+                } else {
+                    return Err(format!(
+                        "using: '{}' not found in nyash.toml [using]. Define a package or alias and use its name (prod profile)",
+                        target
+                    ));
+                }
+            } else {
+                // dev/ci: allow broader resolution via resolver
+                match crate::runner::pipeline::resolve_using_target(
+                    &target,
+                    false,
+                    &using_ctx.pending_modules,
+                    &using_ctx.using_paths,
+                    &using_ctx.aliases,
+                    &using_ctx.packages,
+                    ctx_dir,
+                    strict,
+                    verbose,
+                ) {
+                    Ok(value) => {
+                        // Only file paths are candidates for AST prelude merge
+                        if value.ends_with(".nyash") || value.contains('/') || value.contains('\\') {
+                            // Resolve relative
+                            let mut p = std::path::PathBuf::from(&value);
+                            if p.is_relative() {
+                                if let Some(dir) = ctx_dir { let cand = dir.join(&p); if cand.exists() { p = cand; } }
+                            }
+                            prelude_paths.push(p.to_string_lossy().to_string());
+                        }
+                    }
+                    Err(e) => return Err(format!("using: {}", e)),
                 }
-                Err(e) => return Err(format!("using: {}", e)),
             }
             continue;
         }
@@ -503,6 +553,17 @@ pub fn collect_using_and_strip(
     Ok((out, prelude_paths))
 }
 
+/// Profile-aware prelude resolution wrapper.
+/// Currently delegates to `collect_using_and_strip`, but provides a single
+/// entry point for callers (common and vm_fallback) to avoid logic drift.
+pub fn resolve_prelude_paths_profiled(
+    runner: &NyashRunner,
+    code: &str,
+    filename: &str,
+) -> Result<(String, Vec<String>), String> {
+    collect_using_and_strip(runner, code, filename)
+}
+
 /// Pre-expand line-head `@name[: Type] = expr` into `local name[: Type] = expr`.
 /// Minimal, safe, no semantics change. Applies only at line head (after spaces/tabs).
 pub fn preexpand_at_local(src: &str) -> String {
diff --git a/src/runner/modes/vm_fallback.rs b/src/runner/modes/vm_fallback.rs
index 153f84f0..c223d89b 100644
--- a/src/runner/modes/vm_fallback.rs
+++ b/src/runner/modes/vm_fallback.rs
@@ -12,23 +12,79 @@ impl NyashRunner {
             Ok(s) => s,
             Err(e) => { eprintln!("❌ Error reading file {}: {}", filename, e); process::exit(1); }
         };
-        // Using preprocessing (strip + autoload)
+        // Using preprocessing (legacy inline or AST-prelude merge when NYASH_USING_AST=1)
         let mut code2 = code;
+        let use_ast_prelude = crate::config::env::enable_using()
+            && std::env::var("NYASH_USING_AST").ok().as_deref() == Some("1");
+        let mut prelude_asts: Vec<nyash_rust::ast::ASTNode> = Vec::new();
         if crate::config::env::enable_using() {
-            match crate::runner::modes::common_util::resolve::strip_using_and_register(self, &code2, filename) {
-                Ok(s) => { code2 = s; }
-                Err(e) => { eprintln!("❌ {}", e); process::exit(1); }
+            if use_ast_prelude {
+                match crate::runner::modes::common_util::resolve::resolve_prelude_paths_profiled(self, &code2, filename) {
+                    Ok((clean, paths)) => {
+                        code2 = clean;
+                        for p in paths {
+                            match std::fs::read_to_string(&p) {
+                                Ok(src) => match NyashParser::parse_from_string(&src) {
+                                    Ok(ast) => prelude_asts.push(ast),
+                                    Err(e) => { eprintln!("❌ Parse error in using prelude {}: {}", p, e); process::exit(1); }
+                                },
+                                Err(e) => { eprintln!("❌ Error reading using prelude {}: {}", p, e); process::exit(1); }
+                            }
+                        }
+                    }
+                    Err(e) => { eprintln!("❌ {}", e); process::exit(1); }
+                }
+            } else {
+                match crate::runner::modes::common_util::resolve::strip_using_and_register(self, &code2, filename) {
+                    Ok(s) => { code2 = s; }
+                    Err(e) => { eprintln!("❌ {}", e); process::exit(1); }
+                }
             }
         }
         // Dev sugar pre-expand: @name = expr → local name = expr
         code2 = crate::runner::modes::common_util::resolve::preexpand_at_local(&code2);
 
-        // Parse -> expand macros -> compile MIR
-        let ast = match NyashParser::parse_from_string(&code2) {
+        // Parse main code
+        let main_ast = match NyashParser::parse_from_string(&code2) {
             Ok(ast) => ast,
             Err(e) => { eprintln!("❌ Parse error: {}", e); process::exit(1); }
         };
-        let ast = crate::r#macro::maybe_expand_and_dump(&ast, false);
+        // When using AST prelude mode, combine prelude ASTs + main AST into one Program before macro expansion
+        let ast_combined = if use_ast_prelude && !prelude_asts.is_empty() {
+            use nyash_rust::ast::ASTNode;
+            let mut combined: Vec<ASTNode> = Vec::new();
+            for a in prelude_asts {
+                if let ASTNode::Program { statements, .. } = a { combined.extend(statements); }
+            }
+            if let ASTNode::Program { statements, .. } = main_ast.clone() {
+                combined.extend(statements);
+            }
+            ASTNode::Program { statements: combined, span: nyash_rust::ast::Span::unknown() }
+        } else { main_ast };
+        // Optional: dump AST statement kinds for quick diagnostics
+        if std::env::var("NYASH_AST_DUMP").ok().as_deref() == Some("1") {
+            use nyash_rust::ast::ASTNode;
+            eprintln!("[ast] dump start (vm-fallback)");
+            if let ASTNode::Program { statements, .. } = &ast_combined {
+                for (i, st) in statements.iter().enumerate().take(50) {
+                    let kind = match st {
+                        ASTNode::BoxDeclaration { is_static, name, .. } => {
+                            if *is_static { format!("StaticBox({})", name) } else { format!("Box({})", name) }
+                        }
+                        ASTNode::FunctionDeclaration { name, .. } => format!("FuncDecl({})", name),
+                        ASTNode::FunctionCall { name, .. } => format!("FuncCall({})", name),
+                        ASTNode::MethodCall { method, .. } => format!("MethodCall({})", method),
+                        ASTNode::ScopeBox { .. } => "ScopeBox".to_string(),
+                        ASTNode::ImportStatement { path, .. } => format!("Import({})", path),
+                        ASTNode::UsingStatement { namespace_name, .. } => format!("Using({})", namespace_name),
+                        _ => format!("{:?}", st),
+                    };
+                    eprintln!("[ast] {}: {}", i, kind);
+                }
+            }
+            eprintln!("[ast] dump end");
+        }
+        let ast = crate::r#macro::maybe_expand_and_dump(&ast_combined, false);
         let mut compiler = MirCompiler::with_options(!self.config.no_optimize);
         let compile = match compiler.compile(ast) {
             Ok(c) => c,
@@ -44,6 +100,12 @@ impl NyashRunner {
 
         // Execute via MIR interpreter
         let mut vm = MirInterpreter::new();
+        if std::env::var("NYASH_DUMP_FUNCS").ok().as_deref() == Some("1") {
+            eprintln!("[vm] functions available:");
+            for k in module_vm.functions.keys() {
+                eprintln!("  - {}", k);
+            }
+        }
         match vm.execute_module(&module_vm) {
             Ok(_ret) => { /* interpreter already prints via println/console in program */ }
             Err(e) => {
diff --git a/tools/smokes/v2/profiles/quick/core/using_multi_prelude_dep_ast.sh b/tools/smokes/v2/profiles/quick/core/using_multi_prelude_dep_ast.sh
new file mode 100644
index 00000000..603b47bd
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/using_multi_prelude_dep_ast.sh
@@ -0,0 +1,63 @@
+#!/bin/bash
+# using_multi_prelude_dep_ast.sh - 複数プレリュード（toml パッケージ）と依存解決（ASTマージ）
+
+source "$(dirname "$0")/../../../lib/test_runner.sh"
+
+require_env || exit 2
+preflight_plugins || exit 2
+
+setup_tmp_dir() {
+  TEST_DIR="/tmp/using_multi_prelude_$$"
+  mkdir -p "$TEST_DIR"
+  cd "$TEST_DIR"
+}
+
+teardown_tmp_dir() {
+  cd /
+  rm -rf "$TEST_DIR"
+}
+
+test_multi_prelude_dep_ast() {
+  setup_tmp_dir
+
+  cat > nyash.toml << 'EOF'
+[using.a]
+path = "lib/a"
+
+[using.b]
+path = "lib/b"
+
+[using]
+paths = ["lib"]
+EOF
+
+  mkdir -p lib/a lib/b
+  cat > lib/a/a.nyash << 'EOF'
+static box A { x() { return "A" } }
+EOF
+  cat > lib/b/b.nyash << 'EOF'
+static box B { y() { return A.x() + "B" } }
+EOF
+
+  cat > main.nyash << 'EOF'
+using a
+using b
+static box Main {
+  main() {
+    print(B.y())
+    return 0
+  }
+}
+EOF
+
+  export NYASH_USING_PROFILE=prod
+  export NYASH_USING_AST=1
+  local output rc
+  output=$(run_nyash_vm main.nyash 2>&1)
+  if echo "$output" | grep -qx "AB"; then rc=0; else rc=1; fi
+  [ $rc -eq 0 ] || { echo "$output" >&2; }
+  teardown_tmp_dir
+  return $rc
+}
+
+run_test "using_multi_prelude_dep_ast" test_multi_prelude_dep_ast
diff --git a/tools/smokes/v2/profiles/quick/core/using_profiles_ast.sh b/tools/smokes/v2/profiles/quick/core/using_profiles_ast.sh
new file mode 100644
index 00000000..70ba895f
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/using_profiles_ast.sh
@@ -0,0 +1,133 @@
+#!/bin/bash
+# using_profiles_ast.sh - using プロファイル（dev/prod）× AST プレリュードの基本動作チェック
+
+source "$(dirname "$0")/../../../lib/test_runner.sh"
+
+require_env || exit 2
+preflight_plugins || exit 2
+
+setup_tmp_dir() {
+  TEST_DIR="/tmp/using_profiles_ast_$$"
+  mkdir -p "$TEST_DIR"
+  cd "$TEST_DIR"
+}
+
+teardown_tmp_dir() {
+  cd /
+  rm -rf "$TEST_DIR"
+}
+
+# Test A: dev プロファイルでは `using "file"` が許可され、AST プレリュードで解決できる
+test_dev_file_using_ok_ast() {
+  setup_tmp_dir
+
+  # nyash.toml（paths だけで十分）
+  cat > nyash.toml << 'EOF'
+[using]
+paths = ["lib"]
+EOF
+
+  mkdir -p lib
+  cat > lib/u.nyash << 'EOF'
+static box Util {
+  greet() { return "hi" }
+}
+EOF
+
+  cat > main.nyash << 'EOF'
+using "lib/u.nyash"
+static box Main {
+  main() {
+    print(Util.greet())
+    return 0
+  }
+}
+EOF
+
+  local output rc
+  # dev + AST モード（環境はexportで明示）
+  export NYASH_USING_PROFILE=dev
+  export NYASH_USING_AST=1
+  output=$(run_nyash_vm main.nyash 2>&1)
+  if echo "$output" | grep -qx "hi"; then rc=0; else rc=1; fi
+  [ $rc -eq 0 ] || { echo "$output" >&2; }
+  teardown_tmp_dir
+  return $rc
+}
+
+# Test B: prod プロファイルでは `using "file"` は拒否（ガイダンス付きエラー）
+test_prod_file_using_forbidden_ast() {
+  setup_tmp_dir
+
+  cat > nyash.toml << 'EOF'
+[using]
+paths = ["lib"]
+EOF
+
+  mkdir -p lib
+  cat > lib/u.nyash << 'EOF'
+static box Util { greet() { return "x" } }
+EOF
+
+  cat > main.nyash << 'EOF'
+using "lib/u.nyash"
+static box Main { main() { print(Util.greet()); return 0 } }
+EOF
+
+  local output
+  # prod + AST モード（失敗が正）
+  export NYASH_USING_PROFILE=prod
+  export NYASH_USING_AST=1
+  output=$(run_nyash_vm main.nyash 2>&1 || true)
+  if echo "$output" | grep -qi "disallowed\|nyash.toml \[using\]"; then
+    test_pass "prod_file_using_forbidden_ast"
+  else
+    test_fail "prod_file_using_forbidden_ast" "expected guidance error, got: $output"
+  fi
+
+  teardown_tmp_dir
+}
+
+# Test C: prod プロファイルで alias/package は許可（AST プレリュードで読み込み）
+test_prod_alias_package_ok_ast() {
+  setup_tmp_dir
+
+  cat > nyash.toml << 'EOF'
+[using.u]
+path = "lib/u"
+
+[using]
+paths = ["lib"]
+EOF
+
+  mkdir -p lib/u
+  # main 省略 → leaf 名と同名の .nyash がデフォルト（u/u.nyash）
+  cat > lib/u/u.nyash << 'EOF'
+static box Util {
+  version() { return "ok" }
+}
+EOF
+
+  cat > main.nyash << 'EOF'
+using u
+static box Main {
+  main() {
+    print(Util.version())
+    return 0
+  }
+}
+EOF
+
+  local output rc
+  export NYASH_USING_PROFILE=prod
+  export NYASH_USING_AST=1
+  output=$(run_nyash_vm main.nyash 2>&1)
+  if echo "$output" | grep -qx "ok"; then rc=0; else rc=1; fi
+  [ $rc -eq 0 ] || { echo "$output" >&2; }
+  teardown_tmp_dir
+  return $rc
+}
+
+run_test "using_dev_file_ok_ast" test_dev_file_using_ok_ast
+run_test "using_prod_file_forbidden_ast" test_prod_file_using_forbidden_ast
+run_test "using_prod_alias_ok_ast" test_prod_alias_package_ok_ast
diff --git a/tools/smokes/v2/profiles/quick/core/using_relative_file_ast.sh b/tools/smokes/v2/profiles/quick/core/using_relative_file_ast.sh
new file mode 100644
index 00000000..ae7058e2
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/using_relative_file_ast.sh
@@ -0,0 +1,53 @@
+#!/bin/bash
+# using_relative_file_ast.sh - ネストした場所からの相対パス using（AST プレリュード）
+
+source "$(dirname "$0")/../../../lib/test_runner.sh"
+
+require_env || exit 2
+preflight_plugins || exit 2
+
+setup_tmp_dir() {
+  TEST_DIR="/tmp/using_rel_file_$$"
+  mkdir -p "$TEST_DIR"
+  cd "$TEST_DIR"
+}
+
+teardown_tmp_dir() {
+  cd /
+  rm -rf "$TEST_DIR"
+}
+
+test_relative_file_using_ast() {
+  setup_tmp_dir
+
+  cat > nyash.toml << 'EOF'
+[using]
+paths = ["lib"]
+EOF
+
+  mkdir -p lib sub
+  cat > lib/u.nyash << 'EOF'
+static box Util { greet() { return "rel" } }
+EOF
+
+  cat > sub/main.nyash << 'EOF'
+using "../lib/u.nyash"
+static box Main {
+  main() {
+    print(Util.greet())
+    return 0
+  }
+}
+EOF
+
+  export NYASH_USING_PROFILE=dev
+  export NYASH_USING_AST=1
+  local output rc
+  output=$(run_nyash_vm sub/main.nyash 2>&1)
+  if echo "$output" | grep -qx "rel"; then rc=0; else rc=1; fi
+  [ $rc -eq 0 ] || { echo "$output" >&2; }
+  teardown_tmp_dir
+  return $rc
+}
+
+run_test "using_relative_file_ast" test_relative_file_using_ast