diff --git a/docs/development/current/main/investigations/phase-259-block-parameterized-cfg-consult.md b/docs/development/current/main/investigations/phase-259-block-parameterized-cfg-consult.md
new file mode 100644
index 00000000..1bdb78fc
--- /dev/null
+++ b/docs/development/current/main/investigations/phase-259-block-parameterized-cfg-consult.md
@@ -0,0 +1,167 @@
+# Phase 259: Block-Parameterized CFG / Join-Explicit CFG — ChatGPT Pro 相談パケット
+
+目的: ChatGPT Pro に「正規化（normalized）をどう設計し、小さい強い箱（Box）で結び、block-parameterized CFG へ段階移行するか」を相談するためのコピペ用 SSOT を用意する。
+
+更新日: 2025-12-20
+
+---
+
+## 1) ChatGPT Pro へ投げる文章（コピペ用）
+
+以下の条件で、段階移行できる設計を提案してください。
+
+### コンテキスト
+
+Nyash/Hakorune の JoinIR→MIR 経路で、`Jump/continuation/params/edge-args` が「暗黙 ABI（順序/長さ/役割/識別）」として散在し、パターン追加のたびに merge/optimizer/verify が連鎖で壊れました。最近は SSOT 化と Fail-Fast を進め、`JumpArgsLayout` を boundary に持たせて推測を排除しましたが、最終的には **block-parameterized CFG**（edge-args を第一級に持つ CFG）に収束させたいです。
+
+北極星（north star）: “Join-Explicit CFG Construction”
+
+### ゴール（最終形）
+
+- `Jump/continuation/params/edge-args` を第一級（explicit）として扱う
+- JoinIR↔MIR 間の暗黙 ABI を消し、変換を「意味解釈」ではなく「写像（mapping）」に縮退する
+- 長期的には JoinIR を builder DSL に降格できる状態にする（削除は急がない）
+
+### 制約 / 方針
+
+- フォールバックより Fail-Fast（prod/CI 既定で安全）
+- by-name ハードコード分岐は禁止（特定 Box 名での条件分岐など）
+- 新しい環境変数の増殖は禁止（既存 debug gate の範囲で）
+- 段階導入（Strangler）で、差分を小さく・可逆に
+
+### 質問（回答してほしいこと）
+
+1. **Normalized JoinIR の最小語彙**は何がよいか？
+   - `Jump(args)` / `Branch(then_args, else_args)` / `Return` / `Call` のセット
+   - `cond 付き Jump` を禁止し、`Branch` に寄せるべきか
+2. **ABI（役割・順序）SSOT をどこに置くべきか？**
+   - `JoinAbi`（sig/roles/special conts/alias）を新設するか、`JoinModule` に持たせるか
+   - boundary の `join_inputs/host_inputs` を Vec 順序のまま段階移行する案（最小差分）と、`ParamId→ValueId` 束縛にする案（最終形）
+3. **block-parameterized CFG 移行の最小ステップ**を、Phase で刻んで提示してほしい
+   - `jump_args` を BasicBlock メタから terminator operand に埋め込む手順（併存→移行→削除）
+   - verify / optimizer / printer / builder への影響の最小化
+4. **箱（Box）分割**は最小でどう切るべきか？
+   - “推測禁止” と “Fail-Fast” をどの箱に閉じ込めるか
+   - 例: `AbiBox`, `BoundaryContractCheckBox`, `ExitArgsPlumbingBox`, `CfgSuccessorSyncBox`
+5. **不変条件（invariants）**と検証地点の設計
+   - Normalizer直後 / merge直前 / `--verify` の各地点で、何を verify するのが最短で強いか
+
+### 期待する出力（形式）
+
+- 「いきなり最終形」ではなく、**段階移行（1フェーズ=小差分）**のマイルストーンを提示
+- 各フェーズの **受け入れ基準**（smoke/verify/contract）を明文化
+- 新規箱は最小（2〜3個から開始）で、増やす判断基準も書く
+
+---
+
+## 2) リポジトリ現状（SSOTメモ）
+
+### 最近の到達点（コミット）
+
+- `73ddc5f58` feat(joinir): Phase 257 P1.1/P1.2/P1.3（Pattern6 SSOT / PHI predecessor verify / LoopHeaderPhi 修正）
+- `23531bf64` feat(joinir): Phase 258 P0（index_of_string dynamic needle window scan）
+- `e4f57ea83` docs: Phase 257-259 SSOT 更新
+
+### 現在の “意味データが IR 外” の例
+
+- `jump_args` が `BasicBlock` のメタとして存在（DCE/verify が追う必要がある）
+- spans が `instructions` と並行 Vec（同期漏れで SPAN MISMATCH が起きる）
+
+---
+
+## 3) 最低限のソースコード断片（Pro に見せる用）
+
+### 3.1 `BasicBlock`（jump_args と span の現状）
+
+`src/mir/basic_block.rs:45`
+
+```rust
+pub struct BasicBlock {
+    pub id: BasicBlockId,
+    pub instructions: Vec<MirInstruction>,
+    pub instruction_spans: Vec<Span>,
+    pub terminator: Option<MirInstruction>,
+    pub terminator_span: Option<Span>,
+    pub predecessors: BTreeSet<BasicBlockId>,
+    pub successors: BTreeSet<BasicBlockId>,
+    // ...
+    pub jump_args: Option<Vec<ValueId>>, // Phase 246-EX: Jump args metadata
+}
+```
+
+### 3.2 `JumpArgsLayout`（推測排除の SSOT）
+
+`src/mir/join_ir/lowering/inline_boundary.rs:107`
+
+```rust
+pub enum JumpArgsLayout {
+    CarriersOnly,
+    ExprResultPlusCarriers,
+}
+```
+
+### 3.3 Exit args collection（layout に従うだけ）
+
+`src/mir/builder/control_flow/joinir/merge/exit_args_collector.rs:94`
+
+```rust
+pub fn collect(
+    &self,
+    exit_bindings: &[LoopExitBinding],
+    remapped_args: &[ValueId],
+    block_id: BasicBlockId,
+    strict_exit: bool,
+    layout: JumpArgsLayout,
+) -> Result<ExitArgsCollectionResult, String>
+```
+
+### 3.4 DCE が jump_args を use として数える（現状の暫定対応）
+
+`src/mir/passes/dce.rs:40`
+
+```rust
+if let Some(args) = &block.jump_args {
+    for &u in args {
+        used_values.insert(u);
+    }
+}
+```
+
+---
+
+## 4) 相談したい設計上の痛点（要約）
+
+- `jump_args` がメタなので、最適化/検証/表示/CFG更新が「忘れると壊れる」になりやすい
+- continuation の識別が ID/名前/legacy alias で揺れると merge が壊れる
+- “順序” が暗黙だと、expr_result と carrier が同一 ValueId のときにズレて誤配線になりやすい
+- spans が並行 Vec だと、パスが1箇所でも同期を忘れると壊れる
+- `this`/`me` の表面名と内部 `variable_map` キーがズレると、Pattern 側で receiver を取り違えやすい（SSOT不足）
+- `Branch` が入ると “edge-args の参照点” が曖昧になりやすい（then/else のどちらかだけ見て事故る）
+
+---
+
+## 5) 移行の北極星（既存 SSOT へのリンク）
+
+- North Star: `docs/development/current/main/design/join-explicit-cfg-construction.md`
+- Phase 256 で露出した契約論点: `docs/development/current/main/investigations/phase-256-joinir-contract-questions.md`
+
+## 6) 追加質問（receiver SSOT）
+
+`me` receiver の host ValueId を Pattern 側が直接 `"me"`/`"this"` で参照しないように、API/Box として封印したい。
+
+- どの層に置くべきか？（例: `joinir/api/receiver.rs`）
+- Fail-Fast の位置（builder で未登録なら即死？pattern detect の時点で弾く？）
+- `this`/`me` の将来拡張（Stage-3/4）に耐える最小設計は？
+
+---
+
+## 7) ChatGPT Pro 追記（設計レビュー観点）
+
+段階移行ロードマップの細部で、次の2点を優先して “迷子防止” を強化したい。
+
+1. **edge-args の参照 API は Branch 前提にする**
+   - `edge_args()` 単発は曖昧になりやすい
+   - 推奨: `out_edges()` / `edge_args_to(target)` のように「edge を列挙」できる形を SSOT にする
+2. **terminator operand の edge-args は “意味付き” にする**
+   - `Vec<ValueId>` だけだと layout（`CarriersOnly` / `ExprResultPlusCarriers`）の推測が残る
+   - 最小: `EdgeArgs { layout: JumpArgsLayout, values: Vec<ValueId> }` を同梱（将来は `ContSigId` に置換）
diff --git a/docs/development/current/main/phases/phase-260/README.md b/docs/development/current/main/phases/phase-260/README.md
new file mode 100644
index 00000000..f9684dae
--- /dev/null
+++ b/docs/development/current/main/phases/phase-260/README.md
@@ -0,0 +1,92 @@
+# Phase 260: Block-Parameterized CFG（edge-args）段階導入
+
+Status: Planned  
+Last updated: 2025-12-20
+
+## 目的（P0）
+
+JoinIR→MIR の暗黙 ABI（jump_args / carriers / expr_result slot / successors）を減らし、将来的な **block-parameterized CFG**（edge-args を第一級に持つCFG）へ収束するための「大工事パート」を開始する。
+
+このフェーズは “一括置換” ではなく、**併存導入（Strangler）**で可逆に進める。
+
+## 背景（Phase 256-259 で露出した型）
+
+- `jump_args` が IR 外メタとして存在すると、DCE/verify/CFG 更新が「忘れると壊れる」になる
+- spans が並行 Vec だと、最適化や変換で同期漏れが起きやすい
+- continuation / entry / exit の識別と args 順序が散在すると、推測・補正が増殖する
+
+North Star: `docs/development/current/main/design/join-explicit-cfg-construction.md`
+
+## 方針（2段正規化）
+
+- **Semantic Normalization（意味SSOT）**: terminator 語彙の固定（例: cond付きJumpを正規形から禁止しBranchへ）
+- **Plumbing Normalization（配線SSOT）**: edge-args / CFG successor / spans を IR 構造に閉じ込め、写像に縮退
+
+## スコープ（Phase 260）
+
+### In scope
+
+- MIR に「edge-args を持つ terminator 表現」を **併存導入**する（旧 `BasicBlock.jump_args` は残す）
+- “読む側” を単一APIに寄せる（`Branch` を含むので “複数 edge” 前提で一本化する）
+  - 例: `block.out_edges()` / `block.edge_args_to(target)`
+- 互換期間は **一致検証を Fail-Fast**（両方ある場合は矛盾で即死）
+
+### Out of scope（P0ではやらない）
+
+- `BasicBlock.jump_args` の削除（削除は Phase 261+）
+- spans の内部表現を `Vec<Spanned<_>>` に一気に切替（Phase 261+ で段階導入）
+- JoinIR を削除する（builder DSL 降格は長期）
+
+## 実装タスク（P0）
+
+1. `MirTerminator`（または既存 terminator に edge-args を持てる variant）を追加（併存導入）
+   - `Jump` だけでなく `Branch` を含むため、API は “複数 edge” を前提にする
+2. bridge が `Jump/Branch` の edge-args を terminator operand としてもセット（旧jump_argsも併記してよい）
+3. merge/ExitLine/DCE/verify/printer が参照する入口を一本化（読む側の Strangler）
+   - 推奨: `block.out_edges()` / `block.edge_args_to(target)` のような API（`edge_args()` 単発は Branch で曖昧）
+4. Fail-Fast 契約チェック（`--verify` 時に必須）
+   - “両方ある場合は一致” を verify で保証
+   - 追加: “terminator から計算した successors” と “block.successors キャッシュ” の一致も verify で保証（同期漏れを即死）
+
+## 受け入れ基準（P0）
+
+- `cargo build --release` が通る
+- `./tools/smokes/v2/run.sh --profile quick` が少なくとも悪化しない（same first FAIL 以上）
+- `--verify` の既存テストが壊れない（PHI/CFG検証が健全）
+- legacy 依存の “推測” が増えていない（新規の env var 追加なし）
+- `rg "jump_args"` を走らせて、移行コードと API 以外に参照が増えていない（読む側の寄せ漏れを検出）
+- DCE 回帰が 1 本以上あり、「edge-args だけで使われる値」が消されないことを固定できている
+
+## ロードマップ（P0→P3）
+
+### P0（併存導入の芯）
+
+- **単一参照API**を作る（Branch を含むので “複数 edge” 前提）
+  - 例: `BasicBlock::out_edges()` / `BasicBlock::edge_args_to(target)`
+- MIR terminator に edge-args を持てる表現を追加（旧 `jump_args` と **併存**）
+  - 推奨: `EdgeArgs { layout: JumpArgsLayout, values: Vec<ValueId> }` のように “意味（layout）” も同梱する
+- bridge が edge-args を terminator operand に必ず埋める（旧jump_argsも同内容でセットしてよい）
+- merge/ExitLine/DCE/verify/printer は参照点を `out_edges()`/`edge_args_to(...)` に寄せる
+- 両方ある場合の **一致検証を Fail-Fast**（`--verify` で必須）
+
+### P1（切替）
+
+- `jump_args` を読む経路を段階的に減らす（参照点は `out_edges()`/`edge_args_to(...)` のみ）
+- terminator 更新の **API一本化**（successors/preds の同期漏れを構造で潰す）
+  - 読む側だけでなく、書く側（terminator 設定/edge-args 設定）も API 経由に寄せる
+- DCE/verify が terminator operand から自然に use/pred を追えることを固定する
+
+### P2（削除）
+
+- `BasicBlock.jump_args` を削除（併存チェックも撤去）
+- `jump_args` 特例の DCE/verify コードを削除（terminator operand が SSOT）
+
+### P3（spans 収束）
+
+- `instructions` + `instruction_spans` の並行 Vec を段階導入で廃止
+  - 先に編集APIを一本化 → 最終的に `Vec<Spanned<MirInstruction>>` へ
+
+## メモ（設計SSOT）
+
+- 相談パケット: `docs/development/current/main/investigations/phase-259-block-parameterized-cfg-consult.md`
+- decisions: `docs/development/current/main/20-Decisions.md`
diff --git a/src/backend/mir_interpreter/exec.rs b/src/backend/mir_interpreter/exec.rs
index 8f9949a1..a91d9835 100644
--- a/src/backend/mir_interpreter/exec.rs
+++ b/src/backend/mir_interpreter/exec.rs
@@ -394,7 +394,7 @@ impl MirInterpreter {
                 };
                 Ok(BlockOutcome::Return(result))
             }
-            Some(MirInstruction::Jump { target }) => Ok(BlockOutcome::Next {
+            Some(MirInstruction::Jump { target, .. }) => Ok(BlockOutcome::Next {
                 target: *target,
                 predecessor: block.id,
             }),
@@ -402,6 +402,7 @@ impl MirInterpreter {
                 condition,
                 then_bb,
                 else_bb,
+                ..
             }) => {
                 // Dev counter: count branch terminators actually evaluated
                 self.branch_count = self.branch_count.saturating_add(1);
diff --git a/src/backend/wasm/codegen.rs b/src/backend/wasm/codegen.rs
index 4648ae94..deb08fce 100644
--- a/src/backend/wasm/codegen.rs
+++ b/src/backend/wasm/codegen.rs
@@ -388,7 +388,7 @@ impl WasmCodegen {
             }
 
             // Control Flow Instructions (Critical for loops and conditions)
-            MirInstruction::Jump { target } => {
+            MirInstruction::Jump { target, .. } => {
                 // Unconditional jump to target basic block
                 // Use WASM br instruction to break to the target block
                 Ok(vec![format!("br $block_{}", target.as_u32())])
@@ -398,6 +398,7 @@ impl WasmCodegen {
                 condition,
                 then_bb,
                 else_bb,
+                ..
             } => {
                 // Conditional branch based on condition value
                 // Load condition value and branch accordingly
diff --git a/src/mir/basic_block.rs b/src/mir/basic_block.rs
index bcae9234..7f04ea09 100644
--- a/src/mir/basic_block.rs
+++ b/src/mir/basic_block.rs
@@ -6,6 +6,7 @@
 
 use super::{EffectMask, MirInstruction, SpannedInstRef, SpannedInstruction, ValueId};
 use crate::ast::Span;
+use crate::mir::join_ir::lowering::inline_boundary::JumpArgsLayout;
 use crate::runtime::get_global_ring0;
 use std::collections::BTreeSet; // Phase 69-3: HashSet → BTreeSet for determinism
 use std::fmt;
@@ -42,6 +43,20 @@ impl fmt::Display for BasicBlockId {
     }
 }
 
+/// Edge arguments for CFG edges (Phase 260 P0)
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct EdgeArgs {
+    pub layout: JumpArgsLayout,
+    pub values: Vec<ValueId>,
+}
+
+/// Outgoing edge from a basic block
+#[derive(Debug, Clone)]
+pub struct OutEdge {
+    pub target: BasicBlockId,
+    pub args: Option<EdgeArgs>,
+}
+
 /// A basic block in SSA form
 #[derive(Debug, Clone)]
 pub struct BasicBlock {
@@ -82,6 +97,8 @@ pub struct BasicBlock {
     /// all the Jump args (not just the first one) so that exit PHI can correctly
     /// merge carrier values from multiple exit paths.
     pub jump_args: Option<Vec<ValueId>>,
+    /// Phase 260 P0: Layout for legacy jump_args (for consistency checks)
+    pub jump_args_layout: Option<JumpArgsLayout>,
 }
 
 impl BasicBlock {
@@ -99,6 +116,7 @@ impl BasicBlock {
             reachable: false,
             sealed: false,
             jump_args: None, // Phase 246-EX: No jump args by default
+            jump_args_layout: None, // Phase 260 P0: Unknown by default
         }
     }
 
@@ -161,18 +179,23 @@ impl BasicBlock {
 
     /// Update successors based on the terminator instruction
     fn update_successors_from_terminator(&mut self) {
-        self.successors.clear();
+        self.successors = self.successors_from_terminator();
+    }
+
+    /// Compute successors from the terminator (SSOT for CFG verification)
+    pub fn successors_from_terminator(&self) -> BTreeSet<BasicBlockId> {
+        let mut successors = BTreeSet::new();
 
         if let Some(ref terminator) = self.terminator {
             match terminator {
                 MirInstruction::Branch {
                     then_bb, else_bb, ..
                 } => {
-                    self.successors.insert(*then_bb);
-                    self.successors.insert(*else_bb);
+                    successors.insert(*then_bb);
+                    successors.insert(*else_bb);
                 }
-                MirInstruction::Jump { target } => {
-                    self.successors.insert(*target);
+                MirInstruction::Jump { target, .. } => {
+                    successors.insert(*target);
                 }
                 MirInstruction::Return { .. } => {
                     // No successors for return
@@ -184,6 +207,140 @@ impl BasicBlock {
                 _ => unreachable!("Non-terminator instruction in terminator position"),
             }
         }
+
+        successors
+    }
+
+    /// Enumerate all outgoing CFG edges
+    pub fn out_edges(&self) -> Vec<OutEdge> {
+        match self.terminator {
+            Some(MirInstruction::Branch {
+                then_bb,
+                else_bb,
+                ref then_edge_args,
+                ref else_edge_args,
+                ..
+            }) => vec![
+                OutEdge {
+                    target: then_bb,
+                    args: then_edge_args.clone(),
+                },
+                OutEdge {
+                    target: else_bb,
+                    args: else_edge_args.clone(),
+                },
+            ],
+            Some(MirInstruction::Jump {
+                target,
+                ref edge_args,
+                ..
+            }) => vec![OutEdge {
+                target,
+                args: edge_args.clone().or_else(|| self.legacy_edge_args()),
+            }],
+            _ => Vec::new(),
+        }
+    }
+
+    /// Get edge args for a specific target (if present)
+    pub fn edge_args_to(&self, target: BasicBlockId) -> Option<EdgeArgs> {
+        self.out_edges()
+            .into_iter()
+            .find(|edge| edge.target == target)
+            .and_then(|edge| edge.args)
+    }
+
+    /// Set legacy jump args metadata (migration helper)
+    pub fn set_legacy_jump_args(&mut self, values: Vec<ValueId>, layout: Option<JumpArgsLayout>) {
+        self.jump_args = Some(values);
+        self.jump_args_layout = layout;
+    }
+
+    /// Clear legacy jump args metadata (migration helper)
+    pub fn clear_legacy_jump_args(&mut self) {
+        self.jump_args = None;
+        self.jump_args_layout = None;
+    }
+
+    /// Check if legacy jump args metadata exists
+    pub fn has_legacy_jump_args(&self) -> bool {
+        self.jump_args.is_some()
+    }
+
+    /// Access legacy jump args values (read-only, migration helper)
+    pub fn legacy_jump_args_values(&self) -> Option<&[ValueId]> {
+        self.jump_args.as_deref()
+    }
+
+    /// Access legacy jump args layout (read-only, migration helper)
+    pub fn legacy_jump_args_layout(&self) -> Option<JumpArgsLayout> {
+        self.jump_args_layout
+    }
+
+    /// Build edge args from legacy values with an explicit layout (migration helper)
+    pub fn legacy_edge_args_with_layout(&self, layout: JumpArgsLayout) -> Option<EdgeArgs> {
+        self.jump_args.as_ref().map(|values| EdgeArgs {
+            layout,
+            values: values.clone(),
+        })
+    }
+
+    /// Set jump terminator with edge args and legacy metadata (SSOT write helper)
+    pub fn set_jump_with_edge_args(&mut self, target: BasicBlockId, edge_args: Option<EdgeArgs>) {
+        let terminator = MirInstruction::Jump {
+            target,
+            edge_args: edge_args.clone(),
+        };
+        if !self.is_terminator(&terminator) {
+            panic!("Instruction is not a valid terminator: {:?}", terminator);
+        }
+
+        self.effects = self.effects | terminator.effects();
+        self.terminator = Some(terminator);
+        self.terminator_span = Some(Span::unknown());
+        if let Some(args) = edge_args {
+            self.jump_args = Some(args.values.clone());
+            self.jump_args_layout = Some(args.layout);
+        } else {
+            self.clear_legacy_jump_args();
+        }
+        self.update_successors_from_terminator();
+    }
+
+    /// Set branch terminator with per-edge args (clears legacy metadata)
+    pub fn set_branch_with_edge_args(
+        &mut self,
+        condition: ValueId,
+        then_bb: BasicBlockId,
+        then_edge_args: Option<EdgeArgs>,
+        else_bb: BasicBlockId,
+        else_edge_args: Option<EdgeArgs>,
+    ) {
+        let terminator = MirInstruction::Branch {
+            condition,
+            then_bb,
+            else_bb,
+            then_edge_args,
+            else_edge_args,
+        };
+        if !self.is_terminator(&terminator) {
+            panic!("Instruction is not a valid terminator: {:?}", terminator);
+        }
+
+        self.effects = self.effects | terminator.effects();
+        self.terminator = Some(terminator);
+        self.terminator_span = Some(Span::unknown());
+        self.clear_legacy_jump_args();
+        self.update_successors_from_terminator();
+    }
+
+    fn legacy_edge_args(&self) -> Option<EdgeArgs> {
+        let values = self.jump_args.as_ref()?;
+        let layout = self.jump_args_layout?;
+        Some(EdgeArgs {
+            layout,
+            values: values.clone(),
+        })
     }
 
     /// Add a predecessor
@@ -540,6 +697,8 @@ mod tests {
             condition: ValueId::new(0),
             then_bb,
             else_bb,
+            then_edge_args: None,
+            else_edge_args: None,
         };
 
         bb.add_instruction(branch_inst);
diff --git a/src/mir/builder.rs b/src/mir/builder.rs
index 7aa9041d..47130a0b 100644
--- a/src/mir/builder.rs
+++ b/src/mir/builder.rs
@@ -670,7 +670,7 @@ impl MirBuilder {
                 MirInstruction::Branch {
                     then_bb, else_bb, ..
                 } => (Some(*then_bb), Some(*else_bb), None),
-                MirInstruction::Jump { target } => (None, None, Some(*target)),
+                MirInstruction::Jump { target, .. } => (None, None, Some(*target)),
                 _ => (None, None, None),
             };
 
@@ -784,8 +784,9 @@ impl MirBuilder {
                                 condition,
                                 then_bb,
                                 else_bb,
+                                ..
                             } => format!("br {}, {}, {}", condition, then_bb, else_bb),
-                            MirInstruction::Jump { target } => format!("br {}", target),
+                            MirInstruction::Jump { target, .. } => format!("br {}", target),
                             _ => format!("{:?}", instruction),
                         }
                     );
diff --git a/src/mir/builder/control_flow/joinir/api/entry.rs b/src/mir/builder/control_flow/joinir/api/entry.rs
new file mode 100644
index 00000000..69a7f55b
--- /dev/null
+++ b/src/mir/builder/control_flow/joinir/api/entry.rs
@@ -0,0 +1,14 @@
+//! Entry function helpers (SSOT)
+
+use crate::mir::join_ir::{JoinFunction, JoinModule};
+
+/// Extract entry function from JoinModule (SSOT).
+///
+/// Priority: `join_module.entry` → fallback to `"main"`.
+pub(in crate::mir::builder) fn get_entry_function<'a>(
+    join_module: &'a JoinModule,
+    context: &str,
+) -> Result<&'a JoinFunction, String> {
+    // Re-exported from patterns/common as the SSOT entry point.
+    super::super::patterns::common::get_entry_function(join_module, context)
+}
diff --git a/src/mir/builder/control_flow/joinir/api/mod.rs b/src/mir/builder/control_flow/joinir/api/mod.rs
new file mode 100644
index 00000000..9f569273
--- /dev/null
+++ b/src/mir/builder/control_flow/joinir/api/mod.rs
@@ -0,0 +1,14 @@
+//! JoinIR integration API (SSOT entry points)
+//!
+//! Purpose: provide a small, stable surface for pattern lowerers and merge code.
+//! This reduces "where should I call this from?" drift and avoids re-implementing
+//! contract logic (SSOT, fail-fast checks) in each pattern.
+//!
+//! Policy:
+//! - Prefer SSOT helpers over ad-hoc logic in patterns.
+//! - Avoid guessing (order/layout/name) in callers; callers pass explicit intent.
+//! - Keep this module thin: mostly wrappers/re-exports with clear naming.
+
+pub(in crate::mir::builder) mod entry;
+pub(in crate::mir::builder) mod pipeline_contracts;
+pub(in crate::mir::builder) mod receiver;
diff --git a/src/mir/builder/control_flow/joinir/api/pipeline_contracts.rs b/src/mir/builder/control_flow/joinir/api/pipeline_contracts.rs
new file mode 100644
index 00000000..1b8e0d2d
--- /dev/null
+++ b/src/mir/builder/control_flow/joinir/api/pipeline_contracts.rs
@@ -0,0 +1,16 @@
+//! Pipeline contract helpers (SSOT)
+
+use crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary;
+use crate::mir::join_ir::JoinModule;
+
+/// Run all JoinIR pipeline contract checks (SSOT).
+///
+/// This is the preferred entry point for patterns that need to validate boundary
+/// assumptions before bridge/merge.
+pub(in crate::mir::builder) fn run_all_pipeline_checks(
+    join_module: &JoinModule,
+    boundary: &JoinInlineBoundary,
+) -> Result<(), String> {
+    super::super::merge::contract_checks::run_all_pipeline_checks(join_module, boundary)
+}
+
diff --git a/src/mir/builder/control_flow/joinir/api/receiver.rs b/src/mir/builder/control_flow/joinir/api/receiver.rs
new file mode 100644
index 00000000..a124885f
--- /dev/null
+++ b/src/mir/builder/control_flow/joinir/api/receiver.rs
@@ -0,0 +1,20 @@
+//! Receiver helpers (SSOT)
+//!
+//! Motivation: surface syntax uses `this` / `me`, but the MIR builder's `variable_map`
+//! registers the receiver under a specific key. Patterns must not guess that key.
+
+use crate::mir::builder::MirBuilder;
+use crate::mir::ValueId;
+
+/// Return the host ValueId for `me` receiver (SSOT).
+///
+/// Patterns should use this instead of hardcoding `"me"` / `"this"`.
+pub(in crate::mir::builder) fn get_me_host_id(builder: &MirBuilder, context: &str) -> Result<ValueId, String> {
+    builder
+        .variable_ctx
+        .variable_map
+        .get("me")
+        .copied()
+        .ok_or_else(|| format!("[{}] receiver 'me' not found in variable_map", context))
+}
+
diff --git a/src/mir/builder/control_flow/joinir/merge/contract_checks.rs b/src/mir/builder/control_flow/joinir/merge/contract_checks.rs
index 6c6936a3..200388ab 100644
--- a/src/mir/builder/control_flow/joinir/merge/contract_checks.rs
+++ b/src/mir/builder/control_flow/joinir/merge/contract_checks.rs
@@ -33,7 +33,7 @@ pub(super) fn verify_all_terminator_targets_exist(
         let Some(term) = &block.terminator else { continue };
 
         match term {
-            MirInstruction::Jump { target } => {
+            MirInstruction::Jump { target, .. } => {
                 if !func.blocks.contains_key(target)
                     && !contracts.allowed_missing_jump_targets.contains(target)
                 {
@@ -749,13 +749,21 @@ mod tests {
         let bb2 = BasicBlockId(2);
 
         let func = create_test_function(vec![
-            (bb0, Some(MirInstruction::Jump { target: bb1 })),
+            (
+                bb0,
+                Some(MirInstruction::Jump {
+                    target: bb1,
+                    edge_args: None,
+                }),
+            ),
             (
                 bb1,
                 Some(MirInstruction::Branch {
                     condition: ValueId(0),
                     then_bb: bb2,
                     else_bb: bb2,
+                    then_edge_args: None,
+                    else_edge_args: None,
                 }),
             ),
             (bb2, Some(MirInstruction::Return { value: None })),
@@ -775,7 +783,13 @@ mod tests {
         let bb0 = BasicBlockId(0);
         let bb99 = BasicBlockId(99); // Missing block
 
-        let func = create_test_function(vec![(bb0, Some(MirInstruction::Jump { target: bb99 }))]);
+        let func = create_test_function(vec![(
+            bb0,
+            Some(MirInstruction::Jump {
+                target: bb99,
+                edge_args: None,
+            }),
+        )]);
 
         let contracts = MergeContracts {
             allowed_missing_jump_targets: vec![],
@@ -795,7 +809,13 @@ mod tests {
         let bb0 = BasicBlockId(0);
         let bb_exit = BasicBlockId(100); // Missing but allowed
 
-        let func = create_test_function(vec![(bb0, Some(MirInstruction::Jump { target: bb_exit }))]);
+        let func = create_test_function(vec![(
+            bb0,
+            Some(MirInstruction::Jump {
+                target: bb_exit,
+                edge_args: None,
+            }),
+        )]);
 
         let contracts = MergeContracts {
             allowed_missing_jump_targets: vec![bb_exit],
diff --git a/src/mir/builder/control_flow/joinir/merge/instruction_rewriter.rs b/src/mir/builder/control_flow/joinir/merge/instruction_rewriter.rs
index 6a7ab16c..38d96620 100644
--- a/src/mir/builder/control_flow/joinir/merge/instruction_rewriter.rs
+++ b/src/mir/builder/control_flow/joinir/merge/instruction_rewriter.rs
@@ -391,7 +391,7 @@ pub(super) fn merge_and_rewrite(
             // We skip merging continuation functions, so any tail-call to k_exit must be
             // lowered as an exit jump to `exit_block_id` (and contribute exit values).
             let mut k_exit_lowering_decision: Option<LoweringDecision> = None;
-            let mut k_exit_jump_args: Option<Vec<ValueId>> = None;
+            let mut k_exit_edge_args: Option<crate::mir::EdgeArgs> = None;
 
             // Phase 177-3: Check if this block is the loop header with PHI nodes
             let is_loop_header_with_phi =
@@ -488,7 +488,10 @@ pub(super) fn merge_and_rewrite(
                         if let Some(decision) = tail_call_policy.classify_tail_call(callee_name, &remapped_args) {
                             // This is a k_exit tail call - policy says normalize to exit jump
                             k_exit_lowering_decision = Some(decision);
-                            k_exit_jump_args = old_block.jump_args.clone();
+                            if let Some(b) = boundary {
+                                k_exit_edge_args =
+                                    old_block.legacy_edge_args_with_layout(b.jump_args_layout);
+                            }
                             found_tail_call = true;
                             if debug {
                                 log!(
@@ -554,6 +557,8 @@ pub(super) fn merge_and_rewrite(
                         condition,
                         then_bb,
                         else_bb,
+                        then_edge_args,
+                        else_edge_args,
                     } => {
                         let remapped_then = skipped_entry_redirects
                             .get(&then_bb)
@@ -569,6 +574,8 @@ pub(super) fn merge_and_rewrite(
                             condition,
                             then_bb: remapped_then,
                             else_bb: remapped_else,
+                            then_edge_args,
+                            else_edge_args,
                         }
                     }
                     MirInstruction::Phi { dst, inputs, type_hint } => {
@@ -950,8 +957,9 @@ pub(super) fn merge_and_rewrite(
                     }
                 };
 
-                new_block.terminator = Some(MirInstruction::Jump {
+                new_block.set_terminator(MirInstruction::Jump {
                     target: actual_target,
+                    edge_args: None,
                 });
 
                 // DEBUG: Print final state after adding parameter bindings
@@ -979,7 +987,18 @@ pub(super) fn merge_and_rewrite(
             // Remap terminator (convert Return → Jump to exit) if not already set by tail call
             if !found_tail_call {
                 if let Some(ref term) = old_block.terminator {
-                    let remapped_term = match term {
+                    let remap_edge_args = |edge_args: &Option<crate::mir::EdgeArgs>| {
+                        edge_args.as_ref().map(|args| crate::mir::EdgeArgs {
+                            layout: args.layout,
+                            values: args
+                                .values
+                                .iter()
+                                .map(|&v| remapper.remap_value(v))
+                                .collect(),
+                        })
+                    };
+                    let mut remapped_term: Option<MirInstruction> = None;
+                    match term {
                         MirInstruction::Return { value } => {
                             // Convert Return to Jump to exit block
                             // All functions return to same exit block (Phase 189)
@@ -988,43 +1007,54 @@ pub(super) fn merge_and_rewrite(
                             //
                             // The JoinIR Jump instruction passes ALL carrier values in its args,
                             // but the JoinIR→MIR conversion in joinir_block_converter only preserved
-                            // the first arg in the Return value. We now use the jump_args metadata
+                            // the first arg in the Return value. We now use the legacy jump_args metadata
                             // to recover all the original Jump args.
-                            //
-                            if let Some(_ret_val) = value {
-                                // Phase 246-EX: Check if this block has jump_args metadata
-                                if let Some(ref jump_args) = old_block.jump_args {
-                                    log!(
-                                        verbose,
-                                        "[DEBUG-177] Phase 246-EX: Block {:?} has jump_args metadata: {:?}",
-                                        old_block.id, jump_args
-                                    );
+                            let mut exit_edge_args: Option<crate::mir::EdgeArgs> = None;
+                            if value.is_some() {
+                                if let Some(b) = boundary {
+                                    // Phase 246-EX: Check if this block has legacy jump_args metadata
+                                    if let Some(edge_args) =
+                                        old_block.legacy_edge_args_with_layout(b.jump_args_layout)
+                                    {
+                                        log!(
+                                            verbose,
+                                            "[DEBUG-177] Phase 246-EX: Block {:?} has legacy jump_args metadata: {:?}",
+                                            old_block.id, edge_args.values
+                                        );
 
-                                    // The jump_args are in JoinIR value space, remap them to HOST
-                                    let remapped_args: Vec<ValueId> = jump_args
-                                        .iter()
-                                        .map(|&arg| remapper.remap_value(arg))
-                                        .collect();
+                                        // The jump_args are in JoinIR value space, remap them to HOST
+                                        let remapped_args: Vec<ValueId> = edge_args
+                                            .values
+                                            .iter()
+                                            .map(|&arg| remapper.remap_value(arg))
+                                            .collect();
 
-                                    log!(
-                                        verbose,
-                                        "[DEBUG-177] Phase 246-EX: Remapped jump_args: {:?}",
-                                        remapped_args
-                                    );
+                                        log!(
+                                            verbose,
+                                            "[DEBUG-177] Phase 246-EX: Remapped jump_args: {:?}",
+                                            remapped_args
+                                        );
+
+                                        // Phase 118 P2: Use ExitArgsCollectorBox to collect exit values
+                                        let edge_args = crate::mir::EdgeArgs {
+                                            layout: edge_args.layout,
+                                            values: remapped_args,
+                                        };
+                                        exit_edge_args = Some(edge_args.clone());
 
-                                    // Phase 118 P2: Use ExitArgsCollectorBox to collect exit values
-                                    if let Some(b) = boundary {
                                         let collector = ExitArgsCollectorBox::new();
                                         let collection_result = collector.collect(
                                             &b.exit_bindings,
-                                            &remapped_args,
+                                            &edge_args.values,
                                             new_block_id,
                                             strict_exit,
-                                            b.jump_args_layout,
+                                            edge_args.layout,
                                         )?;
 
                                         // Add expr_result to exit_phi_inputs (if present)
-                                        if let Some(expr_result_val) = collection_result.expr_result_value {
+                                        if let Some(expr_result_val) =
+                                            collection_result.expr_result_value
+                                        {
                                             exit_phi_inputs.push((new_block_id, expr_result_val));
                                             log!(
                                                 verbose,
@@ -1034,7 +1064,9 @@ pub(super) fn merge_and_rewrite(
                                         }
 
                                         // Add carrier values to carrier_inputs
-                                        for (carrier_name, (block_id, value_id)) in collection_result.carrier_values {
+                                        for (carrier_name, (block_id, value_id)) in
+                                            collection_result.carrier_values
+                                        {
                                             carrier_inputs
                                                 .entry(carrier_name.clone())
                                                 .or_insert_with(Vec::new)
@@ -1045,16 +1077,14 @@ pub(super) fn merge_and_rewrite(
                                                 carrier_name, block_id, value_id
                                             );
                                         }
-                                    }
-                                } else {
-                                    // Fallback: Use header PHI dst (old behavior for blocks without jump_args)
-                                    log!(
-                                        verbose,
-                                        "[DEBUG-177] Phase 246-EX: Block {:?} has NO jump_args, using header PHI fallback",
-                                        old_block.id
-                                    );
+                                    } else {
+                                        // Fallback: Use header PHI dst (old behavior for blocks without jump_args)
+                                        log!(
+                                            verbose,
+                                            "[DEBUG-177] Phase 246-EX: Block {:?} has NO jump_args, using header PHI fallback",
+                                            old_block.id
+                                        );
 
-                                    if let Some(b) = boundary {
                                         if let Some(loop_var_name) = &b.loop_var_name {
                                             if let Some(phi_dst) =
                                                 loop_header_phi_info.get_carrier_phi(loop_var_name)
@@ -1102,11 +1132,16 @@ pub(super) fn merge_and_rewrite(
                                 }
                             }
 
-                            MirInstruction::Jump {
-                                target: exit_block_id,
+                            if let Some(edge_args) = exit_edge_args {
+                                new_block.set_jump_with_edge_args(exit_block_id, Some(edge_args));
+                            } else {
+                                new_block.set_terminator(MirInstruction::Jump {
+                                    target: exit_block_id,
+                                    edge_args: None,
+                                });
                             }
                         }
-                        MirInstruction::Jump { target } => {
+                        MirInstruction::Jump { target, edge_args } => {
                             // Phase 189 FIX: Remap block ID for Jump
                             // Phase 259 P0 FIX: Check skipped_entry_redirects first (for k_exit blocks)
                             let remapped_target = skipped_entry_redirects
@@ -1114,14 +1149,17 @@ pub(super) fn merge_and_rewrite(
                                 .or_else(|| local_block_map.get(target))
                                 .copied()
                                 .unwrap_or(*target);
-                            MirInstruction::Jump {
+                            remapped_term = Some(MirInstruction::Jump {
                                 target: remapped_target,
-                            }
+                                edge_args: remap_edge_args(edge_args),
+                            });
                         }
                         MirInstruction::Branch {
                             condition,
                             then_bb,
                             else_bb,
+                            then_edge_args,
+                            else_edge_args,
                         } => {
                             // Phase 189 FIX: Remap block IDs AND condition ValueId for Branch
                             // Phase 259 P0 FIX: Check skipped_entry_redirects first (for k_exit blocks)
@@ -1135,15 +1173,46 @@ pub(super) fn merge_and_rewrite(
                                 .or_else(|| local_block_map.get(else_bb))
                                 .copied()
                                 .unwrap_or(*else_bb);
-                            MirInstruction::Branch {
+                            remapped_term = Some(MirInstruction::Branch {
                                 condition: remapper.remap_value(*condition),
                                 then_bb: remapped_then,
                                 else_bb: remapped_else,
-                            }
+                                then_edge_args: remap_edge_args(then_edge_args),
+                                else_edge_args: remap_edge_args(else_edge_args),
+                            });
                         }
-                        _ => remapper.remap_instruction(term),
-                    };
-                    new_block.terminator = Some(remapped_term);
+                        _ => remapped_term = Some(remapper.remap_instruction(term)),
+                    }
+                    if let Some(term) = remapped_term {
+                        match term {
+                            MirInstruction::Jump { target, edge_args } => {
+                                if edge_args.is_some() {
+                                    new_block.set_jump_with_edge_args(target, edge_args);
+                                } else {
+                                    new_block.set_terminator(MirInstruction::Jump {
+                                        target,
+                                        edge_args: None,
+                                    });
+                                }
+                            }
+                            MirInstruction::Branch {
+                                condition,
+                                then_bb,
+                                then_edge_args,
+                                else_bb,
+                                else_edge_args,
+                            } => {
+                                new_block.set_branch_with_edge_args(
+                                    condition,
+                                    then_bb,
+                                    then_edge_args,
+                                    else_bb,
+                                    else_edge_args,
+                                );
+                            }
+                            _ => new_block.set_terminator(term),
+                        }
+                    }
                 }
             }
 
@@ -1153,23 +1222,31 @@ pub(super) fn merge_and_rewrite(
                 match decision {
                     LoweringDecision::NormalizeToExitJump { args } => {
                         // Collect exit values from k_exit arguments
+                        let mut exit_edge_args: Option<crate::mir::EdgeArgs> = None;
                         if let Some(b) = boundary {
                             let collector = ExitArgsCollectorBox::new();
-                            let exit_args: Vec<ValueId> = if let Some(ref jump_args) = k_exit_jump_args {
-                                jump_args
-                                    .iter()
-                                    .map(|&arg| remapper.remap_value(arg))
-                                    .collect()
-                            } else {
-                                args.clone()
+                            let exit_values: Vec<ValueId> =
+                                if let Some(ref edge_args) = k_exit_edge_args {
+                                    edge_args
+                                        .values
+                                        .iter()
+                                        .map(|&arg| remapper.remap_value(arg))
+                                        .collect()
+                                } else {
+                                    args.clone()
+                                };
+                            let edge_args = crate::mir::EdgeArgs {
+                                layout: b.jump_args_layout,
+                                values: exit_values,
                             };
+                            exit_edge_args = Some(edge_args.clone());
                             let collection_result =
                                 collector.collect(
                                     &b.exit_bindings,
-                                    &exit_args,
+                                    &edge_args.values,
                                     new_block_id,
                                     strict_exit,
-                                    b.jump_args_layout,
+                                    edge_args.layout,
                                 )?;
                             if let Some(expr_result_value) = collection_result.expr_result_value {
                                 exit_phi_inputs.push((collection_result.block_id, expr_result_value));
@@ -1189,8 +1266,17 @@ pub(super) fn merge_and_rewrite(
                         }
 
                         // Generate exit jump using policy box
-                        let exit_jump = tail_call_policy.rewrite_to_exit_jump(exit_block_id);
-                        new_block.terminator = Some(exit_jump.clone());
+                        let exit_jump = if let Some(edge_args) = exit_edge_args {
+                            new_block.set_jump_with_edge_args(exit_block_id, Some(edge_args));
+                            new_block.terminator.clone().unwrap_or(MirInstruction::Jump {
+                                target: exit_block_id,
+                                edge_args: None,
+                            })
+                        } else {
+                            let exit_jump = tail_call_policy.rewrite_to_exit_jump(exit_block_id);
+                            new_block.set_terminator(exit_jump.clone());
+                            exit_jump
+                        };
 
                         // Strict mode: verify the generated terminator matches contract
                         if strict_exit {
diff --git a/src/mir/builder/control_flow/joinir/merge/loop_header_phi_builder.rs b/src/mir/builder/control_flow/joinir/merge/loop_header_phi_builder.rs
index 51d27939..dd902cd7 100644
--- a/src/mir/builder/control_flow/joinir/merge/loop_header_phi_builder.rs
+++ b/src/mir/builder/control_flow/joinir/merge/loop_header_phi_builder.rs
@@ -361,7 +361,7 @@ impl LoopHeaderPhiBuilder {
                                 );
                             }
                         }
-                        crate::mir::MirInstruction::Jump { target } => {
+                        crate::mir::MirInstruction::Jump { target, .. } => {
                             block.successors.insert(*target);
                             if dev_debug {
                                 trace.stderr_if(
diff --git a/src/mir/builder/control_flow/joinir/merge/tail_call_lowering_policy.rs b/src/mir/builder/control_flow/joinir/merge/tail_call_lowering_policy.rs
index e642fe7c..1d83164d 100644
--- a/src/mir/builder/control_flow/joinir/merge/tail_call_lowering_policy.rs
+++ b/src/mir/builder/control_flow/joinir/merge/tail_call_lowering_policy.rs
@@ -96,6 +96,7 @@ impl TailCallLoweringPolicyBox {
     pub fn rewrite_to_exit_jump(&self, exit_block_id: BasicBlockId) -> MirInstruction {
         MirInstruction::Jump {
             target: exit_block_id,
+            edge_args: None,
         }
     }
 
@@ -121,8 +122,8 @@ impl TailCallLoweringPolicyBox {
         exit_block_id: BasicBlockId,
     ) -> Result<(), String> {
         match terminator {
-            MirInstruction::Jump { target } if *target == exit_block_id => Ok(()),
-            MirInstruction::Jump { target } => Err(crate::mir::join_ir::lowering::error_tags::freeze_with_hint(
+            MirInstruction::Jump { target, .. } if *target == exit_block_id => Ok(()),
+            MirInstruction::Jump { target, .. } => Err(crate::mir::join_ir::lowering::error_tags::freeze_with_hint(
                 "phase131/k_exit/wrong_jump_target",
                 &format!(
                     "skippable continuation tail call lowered to Jump {:?}, expected exit_block_id {:?}",
@@ -184,7 +185,7 @@ mod tests {
         let jump = policy.rewrite_to_exit_jump(exit_block);
         assert!(matches!(
             jump,
-            MirInstruction::Jump { target } if target == exit_block
+            MirInstruction::Jump { target, .. } if target == exit_block
         ));
     }
 
@@ -194,6 +195,7 @@ mod tests {
         let exit_block = BasicBlockId(42);
         let jump = MirInstruction::Jump {
             target: exit_block,
+            edge_args: None,
         };
 
         let result = policy.verify_exit_jump(&jump, exit_block);
@@ -206,6 +208,7 @@ mod tests {
         let exit_block = BasicBlockId(42);
         let wrong_jump = MirInstruction::Jump {
             target: BasicBlockId(99),
+            edge_args: None,
         };
 
         let result = policy.verify_exit_jump(&wrong_jump, exit_block);
diff --git a/src/mir/builder/control_flow/joinir/merge/tests/continuation_contract.rs b/src/mir/builder/control_flow/joinir/merge/tests/continuation_contract.rs
index d4120bbd..5ecc659b 100644
--- a/src/mir/builder/control_flow/joinir/merge/tests/continuation_contract.rs
+++ b/src/mir/builder/control_flow/joinir/merge/tests/continuation_contract.rs
@@ -33,7 +33,7 @@ fn case_a_pure_k_exit_return_is_skippable() {
     let mut func = make_function("join_func_2");
     let block = func.blocks.get_mut(&func.entry_block).unwrap();
     block.instructions.clear();
-    block.terminator = Some(MirInstruction::Return { value: None });
+    block.set_terminator(MirInstruction::Return { value: None });
     assert!(is_skippable_continuation(&func));
 }
 
@@ -52,8 +52,9 @@ fn case_b_k_exit_tailcall_post_k_is_not_skippable() {
         args: vec![],
         effects: EffectMask::CONTROL,
     });
-    block.terminator = Some(MirInstruction::Jump {
+    block.set_terminator(MirInstruction::Jump {
         target: BasicBlockId(1),
+        edge_args: None,
     });
     assert!(!is_skippable_continuation(&func));
 }
@@ -67,14 +68,15 @@ fn case_c_multi_block_continuation_is_not_skippable() {
     // Add a second block
     let second_block_id = BasicBlockId(1);
     let mut second_block = crate::mir::BasicBlock::new(second_block_id);
-    second_block.terminator = Some(MirInstruction::Return { value: None });
+    second_block.set_terminator(MirInstruction::Return { value: None });
     func.blocks.insert(second_block_id, second_block);
 
     // Entry block jumps to second block
     let entry_block = func.blocks.get_mut(&func.entry_block).unwrap();
     entry_block.instructions.clear();
-    entry_block.terminator = Some(MirInstruction::Jump {
+    entry_block.set_terminator(MirInstruction::Jump {
         target: second_block_id,
+        edge_args: None,
     });
 
     assert!(!is_skippable_continuation(&func));
@@ -91,6 +93,6 @@ fn case_d_continuation_with_instructions_is_not_skippable() {
         dst: ValueId(0),
         value: crate::mir::types::ConstValue::Integer(42),
     });
-    block.terminator = Some(MirInstruction::Return { value: None });
+    block.set_terminator(MirInstruction::Return { value: None });
     assert!(!is_skippable_continuation(&func));
 }
diff --git a/src/mir/builder/control_flow/joinir/mod.rs b/src/mir/builder/control_flow/joinir/mod.rs
index 9da34838..accbb0e4 100644
--- a/src/mir/builder/control_flow/joinir/mod.rs
+++ b/src/mir/builder/control_flow/joinir/mod.rs
@@ -10,6 +10,7 @@
 //! - Control tree capability guard (control_tree_capability_guard.rs) ✅ Phase 112
 
 pub(in crate::mir::builder) mod control_tree_capability_guard;
+pub(in crate::mir::builder) mod api;
 pub(in crate::mir::builder) mod legacy; // Phase 132-R0 Task 4: Legacy routing isolation
 pub(in crate::mir::builder) mod loop_context;
 pub(in crate::mir::builder) mod merge;
diff --git a/src/mir/builder/emission/branch.rs b/src/mir/builder/emission/branch.rs
index 7351b015..a3610a27 100644
--- a/src/mir/builder/emission/branch.rs
+++ b/src/mir/builder/emission/branch.rs
@@ -18,6 +18,8 @@ pub fn emit_conditional(
             condition: cond,
             then_bb,
             else_bb,
+            then_edge_args: None,
+            else_edge_args: None,
         })
     }
 }
@@ -28,6 +30,9 @@ pub fn emit_jump(b: &mut MirBuilder, target: BasicBlockId) -> Result<(), String>
         crate::mir::ssot::cf_common::set_jump(func, cur_bb, target);
         Ok(())
     } else {
-        b.emit_instruction(MirInstruction::Jump { target })
+        b.emit_instruction(MirInstruction::Jump {
+            target,
+            edge_args: None,
+        })
     }
 }
diff --git a/src/mir/builder/joinir_id_remapper.rs b/src/mir/builder/joinir_id_remapper.rs
index 1d66cbb3..8387deb9 100644
--- a/src/mir/builder/joinir_id_remapper.rs
+++ b/src/mir/builder/joinir_id_remapper.rs
@@ -102,7 +102,25 @@ impl JoinIrIdRemapper {
                 vals.extend(args.iter().copied());
                 vals
             }
-            Branch { condition, .. } => vec![*condition],
+            Branch {
+                condition,
+                then_edge_args,
+                else_edge_args,
+                ..
+            } => {
+                let mut vals = vec![*condition];
+                if let Some(args) = then_edge_args {
+                    vals.extend(args.values.iter().copied());
+                }
+                if let Some(args) = else_edge_args {
+                    vals.extend(args.values.iter().copied());
+                }
+                vals
+            }
+            Jump { edge_args, .. } => edge_args
+                .as_ref()
+                .map(|args| args.values.clone())
+                .unwrap_or_default(),
             Return { value } => value.iter().copied().collect(),
             Phi { dst, inputs, .. } => {
                 let mut vals = vec![*dst];
@@ -177,8 +195,15 @@ impl JoinIrIdRemapper {
     /// 命令を新しい ID空間にリマップ
     pub fn remap_instruction(&self, inst: &MirInstruction) -> MirInstruction {
         use crate::mir::MirInstruction::*;
+        use crate::mir::EdgeArgs;
 
         let remap = |v: ValueId| self.value_map.get(&v).copied().unwrap_or(v);
+        let remap_edge_args = |edge_args: &Option<EdgeArgs>| {
+            edge_args.as_ref().map(|args| EdgeArgs {
+                layout: args.layout,
+                values: args.values.iter().map(|&v| remap(v)).collect(),
+            })
+        };
 
         match inst {
             Const { dst, value } => Const {
@@ -431,8 +456,28 @@ impl JoinIrIdRemapper {
                 then_val: remap(*then_val),
                 else_val: remap(*else_val),
             },
-            // Pass through unchanged (Branch/Jump/Return handled separately)
-            Branch { .. } | Jump { .. } | Return { .. } | Nop | Safepoint => inst.clone(),
+            Branch {
+                condition,
+                then_bb,
+                else_bb,
+                then_edge_args,
+                else_edge_args,
+            } => Branch {
+                condition: remap(*condition),
+                then_bb: *then_bb,
+                else_bb: *else_bb,
+                then_edge_args: remap_edge_args(then_edge_args),
+                else_edge_args: remap_edge_args(else_edge_args),
+            },
+            Jump { target, edge_args } => Jump {
+                target: *target,
+                edge_args: remap_edge_args(edge_args),
+            },
+            Return { value } => Return {
+                value: value.map(remap),
+            },
+            // Pass through unchanged
+            Nop | Safepoint => inst.clone(),
         }
     }
 
diff --git a/src/mir/control_tree/normalized_shadow/loop_true_break_once.rs b/src/mir/control_tree/normalized_shadow/loop_true_break_once.rs
index 80a23437..406cefe9 100644
--- a/src/mir/control_tree/normalized_shadow/loop_true_break_once.rs
+++ b/src/mir/control_tree/normalized_shadow/loop_true_break_once.rs
@@ -728,7 +728,7 @@ mod tests {
             "k_exit must return Some(value)"
         );
 
-        // Bridge sanity: tail-call blocks must carry jump_args metadata for merge collection.
+        // Bridge sanity: tail-call blocks must carry legacy jump_args metadata for merge collection.
         // This is required for DirectValue mode (no PHI) to reconnect carriers safely.
         let mir_module = crate::mir::join_ir_vm_bridge::bridge_joinir_to_mir(&module)
             .expect("bridge_joinir_to_mir failed");
@@ -744,8 +744,8 @@ mod tests {
             .get(&entry)
             .expect("missing loop_body entry block");
         assert!(
-            entry_block.jump_args.is_some(),
-            "loop_body entry block must have jump_args metadata in bridged MIR"
+            entry_block.has_legacy_jump_args(),
+            "loop_body entry block must have legacy jump_args metadata in bridged MIR"
         );
 
         // Loop-only (the routing path in real lowering): still must encode loop_step as a tail-call.
diff --git a/src/mir/function.rs b/src/mir/function.rs
index d37bd904..9e90c4d7 100644
--- a/src/mir/function.rs
+++ b/src/mir/function.rs
@@ -335,7 +335,10 @@ impl MirFunction {
     ) -> Result<(), String> {
         if let Some(bb) = self.get_block_mut(bb_id) {
             if !bb.is_terminated() {
-                bb.set_terminator(MirInstruction::Jump { target });
+                bb.set_terminator(MirInstruction::Jump {
+                    target,
+                    edge_args: None,
+                });
             }
             Ok(())
         } else {
@@ -357,6 +360,8 @@ impl MirFunction {
                 condition,
                 then_bb,
                 else_bb,
+                then_edge_args: None,
+                else_edge_args: None,
             });
             Ok(())
         } else {
diff --git a/src/mir/function_emission.rs b/src/mir/function_emission.rs
index 3d8a988f..da27a7da 100644
--- a/src/mir/function_emission.rs
+++ b/src/mir/function_emission.rs
@@ -63,6 +63,9 @@ pub fn emit_return_value(f: &mut MirFunction, bb: BasicBlockId, value: ValueId)
 #[inline]
 pub fn emit_jump(f: &mut MirFunction, bb: BasicBlockId, target: BasicBlockId) {
     if let Some(block) = f.get_block_mut(bb) {
-        block.add_instruction(MirInstruction::Jump { target });
+        block.add_instruction(MirInstruction::Jump {
+            target,
+            edge_args: None,
+        });
     }
 }
diff --git a/src/mir/instruction.rs b/src/mir/instruction.rs
index 14abdf4e..9a397244 100644
--- a/src/mir/instruction.rs
+++ b/src/mir/instruction.rs
@@ -4,7 +4,7 @@
  * SSA-form instructions with effect tracking for optimization
  */
 
-use super::{EffectMask, ValueId};
+use super::{EdgeArgs, EffectMask, ValueId};
 use crate::mir::definitions::Callee; // Import Callee from unified definitions
 use crate::mir::types::{
     BarrierOp, BinaryOp, CompareOp, ConstValue, MirType, TypeOpKind, UnaryOp, WeakRefOp,
@@ -116,11 +116,19 @@ pub enum MirInstruction {
         condition: ValueId,
         then_bb: super::BasicBlockId,
         else_bb: super::BasicBlockId,
+        /// Optional edge args for then branch (Phase 260 P0)
+        then_edge_args: Option<EdgeArgs>,
+        /// Optional edge args for else branch (Phase 260 P0)
+        else_edge_args: Option<EdgeArgs>,
     },
 
     /// Unconditional jump
     /// `jmp %target_bb`
-    Jump { target: super::BasicBlockId },
+    Jump {
+        target: super::BasicBlockId,
+        /// Optional edge args for jump (Phase 260 P0)
+        edge_args: Option<EdgeArgs>,
+    },
 
     /// Return from function
     /// `ret %value` or `ret void`
diff --git a/src/mir/instruction/methods.rs b/src/mir/instruction/methods.rs
index bec6ecc5..098a594d 100644
--- a/src/mir/instruction/methods.rs
+++ b/src/mir/instruction/methods.rs
@@ -176,6 +176,31 @@ impl MirInstruction {
             return used;
         }
 
+        match self {
+            MirInstruction::Branch {
+                condition,
+                then_edge_args,
+                else_edge_args,
+                ..
+            } => {
+                let mut used = vec![*condition];
+                if let Some(args) = then_edge_args {
+                    used.extend(args.values.iter().copied());
+                }
+                if let Some(args) = else_edge_args {
+                    used.extend(args.values.iter().copied());
+                }
+                return used;
+            }
+            MirInstruction::Jump { edge_args, .. } => {
+                return edge_args
+                    .as_ref()
+                    .map(|args| args.values.clone())
+                    .unwrap_or_default();
+            }
+            _ => {}
+        }
+
         if let Some(used) = inst_meta::used_via_meta(self) {
             return used;
         }
diff --git a/src/mir/join_ir/lowering/if_merge.rs b/src/mir/join_ir/lowering/if_merge.rs
index a95eb525..ddcad92b 100644
--- a/src/mir/join_ir/lowering/if_merge.rs
+++ b/src/mir/join_ir/lowering/if_merge.rs
@@ -132,6 +132,7 @@ impl IfMergeLowerer {
                 condition,
                 then_bb,
                 else_bb,
+                ..
             } => IfBranch {
                 cond: *condition,
                 then_block: *then_bb,
diff --git a/src/mir/join_ir/lowering/if_select.rs b/src/mir/join_ir/lowering/if_select.rs
index 63ef086c..24824b2c 100644
--- a/src/mir/join_ir/lowering/if_select.rs
+++ b/src/mir/join_ir/lowering/if_select.rs
@@ -142,6 +142,7 @@ impl IfSelectLowerer {
                 condition,
                 then_bb,
                 else_bb,
+                ..
             } => IfBranch {
                 cond: *condition,
                 then_block: *then_bb,
@@ -263,13 +264,13 @@ impl IfSelectLowerer {
     ) -> Option<BasicBlockId> {
         // then が Jump で終わるか確認
         let then_target = match then_block.terminator.as_ref()? {
-            MirInstruction::Jump { target } => *target,
+            MirInstruction::Jump { target, .. } => *target,
             _ => return None,
         };
 
         // else が Jump で終わるか確認
         let else_target = match else_block.terminator.as_ref()? {
-            MirInstruction::Jump { target } => *target,
+            MirInstruction::Jump { target, .. } => *target,
             _ => return None,
         };
 
@@ -312,7 +313,7 @@ impl IfSelectLowerer {
 
         // then ブロックが Jump で終わるか確認
         let merge_block_id = match then_block.terminator.as_ref()? {
-            MirInstruction::Jump { target } => *target,
+            MirInstruction::Jump { target, .. } => *target,
             _ => return None,
         };
 
@@ -339,7 +340,7 @@ impl IfSelectLowerer {
 
         // else ブロックも同じ merge ブロックに Jump するか確認
         let else_merge = match else_block.terminator.as_ref()? {
-            MirInstruction::Jump { target } => *target,
+            MirInstruction::Jump { target, .. } => *target,
             _ => return None,
         };
 
diff --git a/src/mir/join_ir_vm_bridge/joinir_block_converter.rs b/src/mir/join_ir_vm_bridge/joinir_block_converter.rs
index dd35de4b..7e1712e7 100644
--- a/src/mir/join_ir_vm_bridge/joinir_block_converter.rs
+++ b/src/mir/join_ir_vm_bridge/joinir_block_converter.rs
@@ -268,6 +268,8 @@ impl JoinIrBlockConverter {
             condition: *cond,
             then_bb: then_block,
             else_bb: else_block,
+            then_edge_args: None,
+            else_edge_args: None,
         };
         Self::finalize_block(
             mir_func,
@@ -290,8 +292,9 @@ impl JoinIrBlockConverter {
             effects: EffectMask::WRITE,
         });
         then_block_obj.instruction_spans.push(Span::unknown());
-        then_block_obj.terminator = Some(MirInstruction::Jump {
+        then_block_obj.set_terminator(MirInstruction::Jump {
             target: merge_block,
+            edge_args: None,
         });
         mir_func.blocks.insert(then_block, then_block_obj);
 
@@ -302,8 +305,9 @@ impl JoinIrBlockConverter {
             src: *receiver,
         });
         else_block_obj.instruction_spans.push(Span::unknown());
-        else_block_obj.terminator = Some(MirInstruction::Jump {
+        else_block_obj.set_terminator(MirInstruction::Jump {
             target: merge_block,
+            edge_args: None,
         });
         mir_func.blocks.insert(else_block, else_block_obj);
 
@@ -428,8 +432,8 @@ impl JoinIrBlockConverter {
                 // Without this, tail-call blocks look like "no args", forcing fallbacks that can
                 // produce undefined ValueIds in DirectValue mode.
                 if let Some(block) = mir_func.blocks.get_mut(&self.current_block_id) {
-                    if block.jump_args.is_none() {
-                        block.jump_args = Some(args.to_vec());
+                    if !block.has_legacy_jump_args() {
+                        block.set_legacy_jump_args(args.to_vec(), None);
                     }
                 }
 
@@ -484,6 +488,8 @@ impl JoinIrBlockConverter {
                     condition: *cond_var,
                     then_bb: exit_block_id,
                     else_bb: continue_block_id,
+                    then_edge_args: None,
+                    else_edge_args: None,
                 };
 
                 Self::finalize_block(
@@ -497,7 +503,7 @@ impl JoinIrBlockConverter {
                 let mut exit_block = crate::mir::BasicBlock::new(exit_block_id);
 
                 // Phase 246-EX: Store Jump args in metadata for exit PHI construction
-                exit_block.jump_args = Some(args.to_vec());
+                exit_block.set_legacy_jump_args(args.to_vec(), None);
 
                 // Phase 256 P1.9: Generate tail call to continuation
                 exit_block.instructions.push(MirInstruction::Const {
@@ -513,7 +519,7 @@ impl JoinIrBlockConverter {
                     effects: EffectMask::PURE,
                 });
                 exit_block.instruction_spans.push(Span::unknown());
-                exit_block.terminator = Some(MirInstruction::Return { value: Some(call_result_id) });
+                exit_block.set_terminator(MirInstruction::Return { value: Some(call_result_id) });
                 mir_func.blocks.insert(exit_block_id, exit_block);
 
                 // Continue block
@@ -539,8 +545,8 @@ impl JoinIrBlockConverter {
 
                 // Preserve jump args as metadata (SSOT for ExitLine/jump_args wiring).
                 if let Some(block) = mir_func.blocks.get_mut(&self.current_block_id) {
-                    if block.jump_args.is_none() {
-                        block.jump_args = Some(args.to_vec());
+                    if !block.has_legacy_jump_args() {
+                        block.set_legacy_jump_args(args.to_vec(), None);
                     }
                 }
 
@@ -631,6 +637,8 @@ impl JoinIrBlockConverter {
             condition: *cond,
             then_bb: then_block,
             else_bb: else_block,
+            then_edge_args: None,
+            else_edge_args: None,
         };
         Self::finalize_block(
             mir_func,
@@ -648,8 +656,9 @@ impl JoinIrBlockConverter {
             });
             then_block_obj.instruction_spans.push(Span::unknown());
         }
-        then_block_obj.terminator = Some(MirInstruction::Jump {
+        then_block_obj.set_terminator(MirInstruction::Jump {
             target: merge_block,
+            edge_args: None,
         });
         mir_func.blocks.insert(then_block, then_block_obj);
 
@@ -662,8 +671,9 @@ impl JoinIrBlockConverter {
             });
             else_block_obj.instruction_spans.push(Span::unknown());
         }
-        else_block_obj.terminator = Some(MirInstruction::Jump {
+        else_block_obj.set_terminator(MirInstruction::Jump {
             target: merge_block,
+            edge_args: None,
         });
         mir_func.blocks.insert(else_block, else_block_obj);
 
@@ -752,6 +762,8 @@ impl JoinIrBlockConverter {
                 condition: *cond_var,
                 then_bb: next_true_block,
                 else_bb: final_else_block,
+                then_edge_args: None,
+                else_edge_args: None,
             };
 
             if level == 0 {
@@ -775,8 +787,9 @@ impl JoinIrBlockConverter {
             });
             then_block_obj.instruction_spans.push(Span::unknown());
         }
-        then_block_obj.terminator = Some(MirInstruction::Jump {
+        then_block_obj.set_terminator(MirInstruction::Jump {
             target: merge_block,
+            edge_args: None,
         });
         mir_func.blocks.insert(then_block, then_block_obj);
 
@@ -789,8 +802,9 @@ impl JoinIrBlockConverter {
             });
             else_block_obj.instruction_spans.push(Span::unknown());
         }
-        else_block_obj.terminator = Some(MirInstruction::Jump {
+        else_block_obj.set_terminator(MirInstruction::Jump {
             target: merge_block,
+            edge_args: None,
         });
         mir_func.blocks.insert(final_else_block, else_block_obj);
 
@@ -842,7 +856,7 @@ impl JoinIrBlockConverter {
                 block.instructions = instructions;
                 block.instruction_spans = vec![Span::unknown(); inst_count];
             }
-            block.terminator = Some(terminator);
+            block.set_terminator(terminator);
         }
     }
 
diff --git a/src/mir/join_ir_vm_bridge/normalized_bridge/direct.rs b/src/mir/join_ir_vm_bridge/normalized_bridge/direct.rs
index 8cb87e3f..6a70234c 100644
--- a/src/mir/join_ir_vm_bridge/normalized_bridge/direct.rs
+++ b/src/mir/join_ir_vm_bridge/normalized_bridge/direct.rs
@@ -140,32 +140,40 @@ fn lower_normalized_function_direct(
                     let merge_bb = BasicBlockId(next_block_id);
                     next_block_id += 1;
 
-                    finalize_block(
-                        &mut mir_func,
-                        current_block_id,
-                        mem::take(&mut current_insts),
-                        MirInstruction::Branch {
-                            condition: cond,
-                            then_bb,
-                            else_bb,
-                        },
-                        None,
-                    );
+                        finalize_block(
+                            &mut mir_func,
+                            current_block_id,
+                            mem::take(&mut current_insts),
+                            MirInstruction::Branch {
+                                condition: cond,
+                                then_bb,
+                                else_bb,
+                                then_edge_args: None,
+                                else_edge_args: None,
+                            },
+                            None,
+                        );
 
-                    finalize_block(
-                        &mut mir_func,
-                        then_bb,
-                        Vec::new(),
-                        MirInstruction::Jump { target: merge_bb },
-                        None,
-                    );
-                    finalize_block(
-                        &mut mir_func,
-                        else_bb,
-                        Vec::new(),
-                        MirInstruction::Jump { target: merge_bb },
-                        None,
-                    );
+                        finalize_block(
+                            &mut mir_func,
+                            then_bb,
+                            Vec::new(),
+                            MirInstruction::Jump {
+                                target: merge_bb,
+                                edge_args: None,
+                            },
+                            None,
+                        );
+                        finalize_block(
+                            &mut mir_func,
+                            else_bb,
+                            Vec::new(),
+                            MirInstruction::Jump {
+                                target: merge_bb,
+                                edge_args: None,
+                            },
+                            None,
+                        );
 
                     current_block_id = merge_bb;
                     current_insts = vec![MirInstruction::Phi {
@@ -240,6 +248,8 @@ fn lower_normalized_function_direct(
                         condition: cond_remapped,
                         then_bb,
                         else_bb,
+                        then_edge_args: None,
+                        else_edge_args: None,
                     },
                     None,
                 );
@@ -298,7 +308,7 @@ fn lower_normalized_function_direct(
             block.instruction_spans = vec![Span::unknown(); block.instructions.len()];
         }
         if block.terminator.is_none() {
-            block.terminator = Some(MirInstruction::Return { value: None });
+            block.set_terminator(MirInstruction::Return { value: None });
         }
     }
 
@@ -398,7 +408,7 @@ fn build_exit_or_tail_branch(
             .or_insert_with(|| BasicBlock::new(block_id));
         block.instructions = insts;
         block.instruction_spans = vec![Span::unknown(); block.instructions.len()];
-        block.terminator = Some(term);
+        block.set_terminator(term);
         return Ok(());
     }
 
@@ -410,8 +420,8 @@ fn build_exit_or_tail_branch(
         .or_insert_with(|| BasicBlock::new(block_id));
     block.instructions.clear();
     block.instruction_spans.clear();
-    block.terminator = Some(MirInstruction::Return { value: ret_val });
-    block.jump_args = Some(env.to_vec());
+    block.set_terminator(MirInstruction::Return { value: ret_val });
+    block.set_legacy_jump_args(env.to_vec(), None);
     Ok(())
 }
 
@@ -455,6 +465,10 @@ fn finalize_block(
         .or_insert_with(|| BasicBlock::new(block_id));
     block.instructions = instructions;
     block.instruction_spans = vec![Span::unknown(); block.instructions.len()];
-    block.terminator = Some(terminator);
-    block.jump_args = jump_args;
+    block.set_terminator(terminator);
+    if let Some(args) = jump_args {
+        block.set_legacy_jump_args(args, None);
+    } else {
+        block.clear_legacy_jump_args();
+    }
 }
diff --git a/src/mir/loop_api.rs b/src/mir/loop_api.rs
index b63e7cbb..d6def64e 100644
--- a/src/mir/loop_api.rs
+++ b/src/mir/loop_api.rs
@@ -55,7 +55,10 @@ pub fn build_simple_loop<L: LoopBuilderApi>(
     let after = lb.new_block();
 
     // Jump to header
-    lb.emit(MirInstruction::Jump { target: header })?;
+    lb.emit(MirInstruction::Jump {
+        target: header,
+        edge_args: None,
+    })?;
 
     // Header: branch on provided condition
     lb.start_new_block(header)?;
@@ -63,12 +66,17 @@ pub fn build_simple_loop<L: LoopBuilderApi>(
         condition,
         then_bb: body,
         else_bb: after,
+        then_edge_args: None,
+        else_edge_args: None,
     })?;
 
     // Body
     lb.start_new_block(body)?;
     build_body(lb)?;
-    lb.emit(MirInstruction::Jump { target: header })?;
+    lb.emit(MirInstruction::Jump {
+        target: header,
+        edge_args: None,
+    })?;
 
     // After: return void value
     lb.start_new_block(after)?;
diff --git a/src/mir/mod.rs b/src/mir/mod.rs
index 0bcc8b21..5a5eb473 100644
--- a/src/mir/mod.rs
+++ b/src/mir/mod.rs
@@ -53,7 +53,7 @@ pub mod verification;
 pub mod verification_types; // extracted error types // Optimization subpasses (e.g., type_hints) // Phase 25.1f: Loop/If 共通ビュー（ControlForm）
 
 // Re-export main types for easy access
-pub use basic_block::{BasicBlock, BasicBlockId, BasicBlockIdGenerator};
+pub use basic_block::{BasicBlock, BasicBlockId, BasicBlockIdGenerator, EdgeArgs, OutEdge};
 pub use binding_id::BindingId; // Phase 74: BindingId infrastructure
 pub use builder::MirBuilder;
 
diff --git a/src/mir/optimizer.rs b/src/mir/optimizer.rs
index 92ae72a6..22c5b331 100644
--- a/src/mir/optimizer.rs
+++ b/src/mir/optimizer.rs
@@ -524,7 +524,7 @@ mod tests {
     }
 
     #[test]
-    fn test_dce_keeps_jump_args_values() {
+    fn test_dce_keeps_edge_args_values() {
         let signature = FunctionSignature {
             name: "main".to_string(),
             params: vec![],
@@ -533,6 +533,7 @@ mod tests {
         };
         let mut func = MirFunction::new(signature, BasicBlockId::new(0));
         let bb0 = BasicBlockId::new(0);
+        let bb1 = BasicBlockId::new(1);
         let mut b0 = BasicBlock::new(bb0);
         let v0 = ValueId::new(0);
         let v1 = ValueId::new(1);
@@ -541,9 +542,17 @@ mod tests {
             value: ConstValue::Integer(1),
         });
         b0.add_instruction(MirInstruction::Copy { dst: v1, src: v0 });
-        b0.add_instruction(MirInstruction::Return { value: None });
-        b0.jump_args = Some(vec![v1]);
+        b0.set_jump_with_edge_args(
+            bb1,
+            Some(crate::mir::EdgeArgs {
+                layout: crate::mir::join_ir::lowering::inline_boundary::JumpArgsLayout::CarriersOnly,
+                values: vec![v1],
+            }),
+        );
         func.add_block(b0);
+        let mut exit_block = BasicBlock::new(bb1);
+        exit_block.set_terminator(MirInstruction::Return { value: None });
+        func.add_block(exit_block);
         let mut module = MirModule::new("test".to_string());
         module.add_function(func);
 
@@ -555,7 +564,7 @@ mod tests {
             .instructions
             .iter()
             .any(|inst| matches!(inst, MirInstruction::Copy { .. }));
-        assert!(has_copy, "Copy used only by jump_args should not be eliminated");
+        assert!(has_copy, "Copy used only by edge args should not be eliminated");
     }
 
     #[test]
diff --git a/src/mir/passes/dce.rs b/src/mir/passes/dce.rs
index 96c3dd87..045f9a14 100644
--- a/src/mir/passes/dce.rs
+++ b/src/mir/passes/dce.rs
@@ -37,9 +37,11 @@ fn eliminate_dead_code_in_function(function: &mut MirFunction) -> usize {
                 used_values.insert(u);
             }
         }
-        if let Some(args) = &block.jump_args {
-            for &u in args {
-                used_values.insert(u);
+        for edge in block.out_edges() {
+            if let Some(args) = edge.args {
+                for u in args.values {
+                    used_values.insert(u);
+                }
             }
         }
     }
@@ -108,7 +110,7 @@ mod tests {
     use crate::mir::{BasicBlockId, ConstValue, EffectMask, FunctionSignature, MirInstruction, MirType};
 
     #[test]
-    fn test_dce_keeps_jump_args_values() {
+    fn test_dce_keeps_edge_args_values() {
         let mut module = MirModule::new("dce_test".to_string());
 
         let sig = FunctionSignature {
@@ -122,6 +124,7 @@ mod tests {
         let v1 = ValueId(1);
         let v2 = ValueId(2);
         let v_dead = ValueId(3);
+        let bb1 = BasicBlockId(1);
 
         {
             let bb0 = func.blocks.get_mut(&BasicBlockId(0)).unwrap();
@@ -141,10 +144,20 @@ mod tests {
             });
             bb0.instruction_spans.push(Span::unknown());
 
-            // SSOT: jump_args is a semantic use-site (ExitLine, continuation args).
-            bb0.jump_args = Some(vec![v2]);
+            // SSOT: edge args are semantic use-sites (ExitLine, continuation args).
+            bb0.set_jump_with_edge_args(
+                bb1,
+                Some(crate::mir::EdgeArgs {
+                    layout: crate::mir::join_ir::lowering::inline_boundary::JumpArgsLayout::CarriersOnly,
+                    values: vec![v2],
+                }),
+            );
         }
 
+        let mut exit_block = crate::mir::BasicBlock::new(bb1);
+        exit_block.set_terminator(MirInstruction::Return { value: None });
+        func.add_block(exit_block);
+
         module.add_function(func);
 
         let eliminated = eliminate_dead_code(&mut module);
@@ -156,7 +169,7 @@ mod tests {
         // Contract: spans must stay aligned with instructions.
         assert_eq!(bb0.instructions.len(), bb0.instruction_spans.len());
 
-        // Contract: values that appear only in jump_args must be kept (and their deps).
+        // Contract: values that appear only in edge args must be kept (and their deps).
         assert!(bb0
             .instructions
             .iter()
diff --git a/src/mir/printer_helpers.rs b/src/mir/printer_helpers.rs
index 896e7f5e..b53baf39 100644
--- a/src/mir/printer_helpers.rs
+++ b/src/mir/printer_helpers.rs
@@ -232,11 +232,12 @@ pub fn format_instruction(
             condition,
             then_bb,
             else_bb,
+            ..
         } => {
             format!("br {}, label {}, label {}", condition, then_bb, else_bb)
         }
 
-        MirInstruction::Jump { target } => {
+        MirInstruction::Jump { target, .. } => {
             format!("br label {}", target)
         }
 
diff --git a/src/mir/ssot/cf_common.rs b/src/mir/ssot/cf_common.rs
index 9f4bc950..f19815fb 100644
--- a/src/mir/ssot/cf_common.rs
+++ b/src/mir/ssot/cf_common.rs
@@ -30,6 +30,8 @@ pub fn set_branch(
             condition,
             then_bb,
             else_bb,
+            then_edge_args: None,
+            else_edge_args: None,
         });
     }
     if let Some(tb) = f.get_block_mut(then_bb) {
@@ -43,7 +45,10 @@ pub fn set_branch(
 /// Set an unconditional jump terminator and register predecessor on target block.
 pub fn set_jump(f: &mut MirFunction, cur_bb: BasicBlockId, target: BasicBlockId) {
     if let Some(bb) = f.get_block_mut(cur_bb) {
-        bb.set_terminator(MirInstruction::Jump { target });
+        bb.set_terminator(MirInstruction::Jump {
+            target,
+            edge_args: None,
+        });
     }
     if let Some(tb) = f.get_block_mut(target) {
         tb.add_predecessor(cur_bb);
diff --git a/src/mir/utils/control_flow.rs b/src/mir/utils/control_flow.rs
index 6b68aa42..1e23df6a 100644
--- a/src/mir/utils/control_flow.rs
+++ b/src/mir/utils/control_flow.rs
@@ -63,6 +63,7 @@ pub fn capture_actual_predecessor_and_jump(
         // 既存control_flowモジュールと同じパターンを使用
         builder.emit_instruction(super::super::MirInstruction::Jump {
             target: target_block,
+            edge_args: None,
         })?;
         Ok(Some(cur_id))
     } else {
diff --git a/src/mir/verification/cfg.rs b/src/mir/verification/cfg.rs
index 2c70bdbd..c4d5bb2a 100644
--- a/src/mir/verification/cfg.rs
+++ b/src/mir/verification/cfg.rs
@@ -1,13 +1,23 @@
 use crate::mir::function::MirFunction;
 use crate::mir::verification::utils;
 use crate::mir::verification_types::VerificationError;
-use crate::mir::{BasicBlockId, ValueId};
+use crate::mir::{BasicBlockId, MirInstruction, ValueId};
 use std::collections::{HashMap, HashSet};
 
 /// Verify CFG references and reachability
 pub fn check_control_flow(function: &MirFunction) -> Result<(), Vec<VerificationError>> {
     let mut errors = Vec::new();
     for (block_id, block) in &function.blocks {
+        let expected_successors = block.successors_from_terminator();
+        if expected_successors != block.successors {
+            errors.push(VerificationError::ControlFlowError {
+                block: *block_id,
+                reason: format!(
+                    "Successors cache mismatch: cached={:?}, expected={:?}",
+                    block.successors, expected_successors
+                ),
+            });
+        }
         for successor in &block.successors {
             if !function.blocks.contains_key(successor) {
                 errors.push(VerificationError::ControlFlowError {
@@ -16,6 +26,62 @@ pub fn check_control_flow(function: &MirFunction) -> Result<(), Vec<Verification
                 });
             }
         }
+
+        // Phase 260 P0: Fail-fast if terminator edge-args and legacy jump_args diverge.
+        if let Some(term) = &block.terminator {
+            match term {
+                MirInstruction::Jump {
+                    edge_args: Some(edge_args),
+                    ..
+                } => {
+                    if block.has_legacy_jump_args() {
+                        let Some(legacy_layout) = block.legacy_jump_args_layout() else {
+                            errors.push(VerificationError::ControlFlowError {
+                                block: *block_id,
+                                reason: "Legacy jump_args layout missing with edge-args present"
+                                    .to_string(),
+                            });
+                            continue;
+                        };
+                        let legacy_values = block.legacy_jump_args_values().unwrap_or_default();
+                        if edge_args.values.as_slice() != legacy_values {
+                            errors.push(VerificationError::ControlFlowError {
+                                block: *block_id,
+                                reason: format!(
+                                    "Edge-args values mismatch: edge_args={:?}, legacy={:?}",
+                                    edge_args.values, legacy_values
+                                ),
+                            });
+                        }
+                        if edge_args.layout != legacy_layout {
+                            errors.push(VerificationError::ControlFlowError {
+                                block: *block_id,
+                                reason: format!(
+                                    "Edge-args layout mismatch: edge_args={:?}, legacy={:?}",
+                                    edge_args.layout, legacy_layout
+                                ),
+                            });
+                        }
+                    }
+                }
+                MirInstruction::Branch {
+                    then_edge_args,
+                    else_edge_args,
+                    ..
+                } => {
+                    if block.has_legacy_jump_args()
+                        && (then_edge_args.is_some() || else_edge_args.is_some())
+                    {
+                        errors.push(VerificationError::ControlFlowError {
+                            block: *block_id,
+                            reason: "Legacy jump_args present on multi-edge terminator with edge-args"
+                                .to_string(),
+                        });
+                    }
+                }
+                _ => {}
+            }
+        }
     }
     // Unreachable blocks are allowed in MIR.
     // They are created intentionally by break/continue/return statements via
diff --git a/src/runner/json_v1_bridge.rs b/src/runner/json_v1_bridge.rs
index 385ab271..017f95b5 100644
--- a/src/runner/json_v1_bridge.rs
+++ b/src/runner/json_v1_bridge.rs
@@ -233,12 +233,15 @@ pub fn try_parse_v1_to_module(json: &str) -> Result<Option<MirModule>, String> {
                             condition: ValueId::new(cond),
                             then_bb: BasicBlockId::new(then_bb),
                             else_bb: BasicBlockId::new(else_bb),
+                            then_edge_args: None,
+                            else_edge_args: None,
                         });
                     }
                     "jump" => {
                         let target = require_u64(inst, "target", "jump target")? as u32;
                         block_ref.add_instruction(MirInstruction::Jump {
                             target: BasicBlockId::new(target),
+                            edge_args: None,
                         });
                     }
                     "phi" => {
diff --git a/src/runner/mir_json_emit.rs b/src/runner/mir_json_emit.rs
index 21854ff1..8c886796 100644
--- a/src/runner/mir_json_emit.rs
+++ b/src/runner/mir_json_emit.rs
@@ -512,10 +512,11 @@ pub fn emit_mir_json_for_harness(
                             condition,
                             then_bb,
                             else_bb,
+                            ..
                         } => {
                             insts.push(json!({"op":"branch","cond": condition.as_u32(), "then": then_bb.as_u32(), "else": else_bb.as_u32()}));
                         }
-                        I::Jump { target } => {
+                        I::Jump { target, .. } => {
                             insts.push(json!({"op":"jump","target": target.as_u32()}));
                         }
                         I::Return { value } => {
@@ -528,8 +529,8 @@ pub fn emit_mir_json_for_harness(
                 if let Some(term) = &bb.terminator {
                     match term {
                         I::Return { value } => insts.push(json!({"op":"ret","value": value.map(|v| v.as_u32())})),
-                        I::Jump { target } => insts.push(json!({"op":"jump","target": target.as_u32()})),
-                        I::Branch { condition, then_bb, else_bb } => insts.push(json!({"op":"branch","cond": condition.as_u32(), "then": then_bb.as_u32(), "else": else_bb.as_u32()})),
+                        I::Jump { target, .. } => insts.push(json!({"op":"jump","target": target.as_u32()})),
+                        I::Branch { condition, then_bb, else_bb, .. } => insts.push(json!({"op":"branch","cond": condition.as_u32(), "then": then_bb.as_u32(), "else": else_bb.as_u32()})),
                         _ => {}
                     }
                 }
@@ -874,10 +875,11 @@ pub fn emit_mir_json_for_harness_bin(
                             condition,
                             then_bb,
                             else_bb,
+                            ..
                         } => {
                             insts.push(json!({"op":"branch","cond": condition.as_u32(), "then": then_bb.as_u32(), "else": else_bb.as_u32()}));
                         }
-                        I::Jump { target } => {
+                        I::Jump { target, .. } => {
                             insts.push(json!({"op":"jump","target": target.as_u32()}));
                         }
                         I::Return { value } => {
@@ -890,8 +892,8 @@ pub fn emit_mir_json_for_harness_bin(
                 if let Some(term) = &bb.terminator {
                     match term {
                     I::Return { value } => insts.push(json!({"op":"ret","value": value.map(|v| v.as_u32())})),
-                    I::Jump { target } => insts.push(json!({"op":"jump","target": target.as_u32()})),
-                    I::Branch { condition, then_bb, else_bb } => insts.push(json!({"op":"branch","cond": condition.as_u32(), "then": then_bb.as_u32(), "else": else_bb.as_u32()})),
+                    I::Jump { target, .. } => insts.push(json!({"op":"jump","target": target.as_u32()})),
+                    I::Branch { condition, then_bb, else_bb, .. } => insts.push(json!({"op":"branch","cond": condition.as_u32(), "then": then_bb.as_u32(), "else": else_bb.as_u32()})),
                     _ => {} }
                 }
                 blocks.push(json!({"id": bid.as_u32(), "instructions": insts}));
diff --git a/src/runner/mir_json_v0.rs b/src/runner/mir_json_v0.rs
index 8bd4e264..111a6be7 100644
--- a/src/runner/mir_json_v0.rs
+++ b/src/runner/mir_json_v0.rs
@@ -144,12 +144,15 @@ pub fn parse_mir_v0_to_module(json: &str) -> Result<MirModule, String> {
                             condition: ValueId::new(cond),
                             then_bb: BasicBlockId::new(then_bb),
                             else_bb: BasicBlockId::new(else_bb),
+                            then_edge_args: None,
+                            else_edge_args: None,
                         });
                     }
                     "jump" => {
                         let target = require_u64(inst, "target", "jump target")? as u32;
                         block_ref.add_instruction(MirInstruction::Jump {
                             target: BasicBlockId::new(target),
+                            edge_args: None,
                         });
                     }
                     "phi" => {
diff --git a/src/tests/mir_joinir_if_select.rs b/src/tests/mir_joinir_if_select.rs
index 382a3683..d9b14ce6 100644
--- a/src/tests/mir_joinir_if_select.rs
+++ b/src/tests/mir_joinir_if_select.rs
@@ -30,17 +30,19 @@ mod tests {
 
         // Entry block (bb0): branch on cond
         let mut entry = BasicBlock::new(BasicBlockId::new(0));
-        entry.terminator = Some(MirInstruction::Branch {
+        entry.set_terminator(MirInstruction::Branch {
             condition: ValueId(0), // cond parameter
             then_bb: BasicBlockId::new(1),
             else_bb: BasicBlockId::new(2),
+            then_edge_args: None,
+            else_edge_args: None,
         });
         blocks.insert(BasicBlockId::new(0), entry);
 
         // Then block (bb1): return 10
         // NOTE: Pattern matcher expects empty blocks (Return only)
         let mut then_block = BasicBlock::new(BasicBlockId::new(1));
-        then_block.terminator = Some(MirInstruction::Return {
+        then_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(1)), // Assumes ValueId(1) is const 10
         });
         blocks.insert(BasicBlockId::new(1), then_block);
@@ -48,7 +50,7 @@ mod tests {
         // Else block (bb2): return 20
         // NOTE: Pattern matcher expects empty blocks (Return only)
         let mut else_block = BasicBlock::new(BasicBlockId::new(2));
-        else_block.terminator = Some(MirInstruction::Return {
+        else_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(2)), // Assumes ValueId(2) is const 20
         });
         blocks.insert(BasicBlockId::new(2), else_block);
@@ -78,10 +80,12 @@ mod tests {
 
         // Entry block (bb0): branch on cond
         let mut entry = BasicBlock::new(BasicBlockId::new(0));
-        entry.terminator = Some(MirInstruction::Branch {
+        entry.set_terminator(MirInstruction::Branch {
             condition: ValueId(0), // cond
             then_bb: BasicBlockId::new(1),
             else_bb: BasicBlockId::new(2),
+            then_edge_args: None,
+            else_edge_args: None,
         });
         blocks.insert(BasicBlockId::new(0), entry);
 
@@ -92,8 +96,9 @@ mod tests {
             dst: ValueId(3),  // x
             src: ValueId(10), // Assumes ValueId(10) is const 100
         });
-        then_block.terminator = Some(MirInstruction::Jump {
+        then_block.set_terminator(MirInstruction::Jump {
             target: BasicBlockId::new(3),
+            edge_args: None,
         });
         blocks.insert(BasicBlockId::new(1), then_block);
 
@@ -104,14 +109,15 @@ mod tests {
             dst: ValueId(3),  // x
             src: ValueId(20), // Assumes ValueId(20) is const 200
         });
-        else_block.terminator = Some(MirInstruction::Jump {
+        else_block.set_terminator(MirInstruction::Jump {
             target: BasicBlockId::new(3),
+            edge_args: None,
         });
         blocks.insert(BasicBlockId::new(2), else_block);
 
         // Merge block (bb3): return x
         let mut merge_block = BasicBlock::new(BasicBlockId::new(3));
-        merge_block.terminator = Some(MirInstruction::Return {
+        merge_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(3)),
         });
         blocks.insert(BasicBlockId::new(3), merge_block);
@@ -408,10 +414,12 @@ mod tests {
 
         // Entry block (bb0): branch on cond
         let mut entry = BasicBlock::new(BasicBlockId::new(0));
-        entry.terminator = Some(MirInstruction::Branch {
+        entry.set_terminator(MirInstruction::Branch {
             condition: ValueId(0), // cond
             then_bb: BasicBlockId::new(1),
             else_bb: BasicBlockId::new(2),
+            then_edge_args: None,
+            else_edge_args: None,
         });
         blocks.insert(BasicBlockId::new(0), entry);
 
@@ -425,7 +433,7 @@ mod tests {
             dst: ValueId(4), // y = 2
             value: crate::mir::ConstValue::Integer(2),
         });
-        then_block.terminator = Some(MirInstruction::Return {
+        then_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(10)), // result (x + y computed elsewhere)
         });
         blocks.insert(BasicBlockId::new(1), then_block);
@@ -440,7 +448,7 @@ mod tests {
             dst: ValueId(4), // y = 4 (same dst as then!)
             value: crate::mir::ConstValue::Integer(4),
         });
-        else_block.terminator = Some(MirInstruction::Return {
+        else_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(20)), // result (x + y computed elsewhere)
         });
         blocks.insert(BasicBlockId::new(2), else_block);
@@ -470,10 +478,12 @@ mod tests {
 
         // Entry block (bb0): branch on cond
         let mut entry = BasicBlock::new(BasicBlockId::new(0));
-        entry.terminator = Some(MirInstruction::Branch {
+        entry.set_terminator(MirInstruction::Branch {
             condition: ValueId(0), // cond
             then_bb: BasicBlockId::new(1),
             else_bb: BasicBlockId::new(2),
+            then_edge_args: None,
+            else_edge_args: None,
         });
         blocks.insert(BasicBlockId::new(0), entry);
 
@@ -491,7 +501,7 @@ mod tests {
             dst: ValueId(5), // z = 30
             value: crate::mir::ConstValue::Integer(30),
         });
-        then_block.terminator = Some(MirInstruction::Return {
+        then_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(10)), // result (x + y + z computed elsewhere)
         });
         blocks.insert(BasicBlockId::new(1), then_block);
@@ -510,7 +520,7 @@ mod tests {
             dst: ValueId(5), // z = 60 (same dst as then!)
             value: crate::mir::ConstValue::Integer(60),
         });
-        else_block.terminator = Some(MirInstruction::Return {
+        else_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(20)), // result (x + y + z computed elsewhere)
         });
         blocks.insert(BasicBlockId::new(2), else_block);
@@ -632,23 +642,25 @@ mod tests {
             dst: ValueId(2),
             value: crate::mir::ConstValue::Integer(20),
         });
-        entry.terminator = Some(MirInstruction::Branch {
+        entry.set_terminator(MirInstruction::Branch {
             condition: ValueId(0), // cond parameter
             then_bb: BasicBlockId::new(1),
             else_bb: BasicBlockId::new(2),
+            then_edge_args: None,
+            else_edge_args: None,
         });
         blocks.insert(BasicBlockId::new(0), entry);
 
         // Then block (bb1): return 10
         let mut then_block = BasicBlock::new(BasicBlockId::new(1));
-        then_block.terminator = Some(MirInstruction::Return {
+        then_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(1)), // const 10
         });
         blocks.insert(BasicBlockId::new(1), then_block);
 
         // Else block (bb2): return 20
         let mut else_block = BasicBlock::new(BasicBlockId::new(2));
-        else_block.terminator = Some(MirInstruction::Return {
+        else_block.set_terminator(MirInstruction::Return {
             value: Some(ValueId(2)), // const 20
         });
         blocks.insert(BasicBlockId::new(2), else_block);
diff --git a/src/tests/phase67_generic_type_resolver.rs b/src/tests/phase67_generic_type_resolver.rs
index 0579e4a5..e492dea8 100644
--- a/src/tests/phase67_generic_type_resolver.rs
+++ b/src/tests/phase67_generic_type_resolver.rs
@@ -95,10 +95,12 @@ fn phase67_ab_test_resolve_from_phi_equivalence() {
             dst: cond,
             value: ConstValue::Bool(true),
         });
-    f.get_block_mut(entry).unwrap().terminator = Some(MirInstruction::Branch {
+    f.get_block_mut(entry).unwrap().set_terminator(MirInstruction::Branch {
         condition: cond,
         then_bb,
         else_bb,
+        then_edge_args: None,
+        else_edge_args: None,
     });
 
     // Then: v2 = 42
@@ -109,7 +111,10 @@ fn phase67_ab_test_resolve_from_phi_equivalence() {
             dst: v2,
             value: ConstValue::Integer(42),
         });
-    f.get_block_mut(then_bb).unwrap().terminator = Some(MirInstruction::Jump { target: merge_bb });
+    f.get_block_mut(then_bb).unwrap().set_terminator(MirInstruction::Jump {
+        target: merge_bb,
+        edge_args: None,
+    });
 
     // Else: v3 = 0
     let v3 = f.next_value_id();
@@ -119,7 +124,10 @@ fn phase67_ab_test_resolve_from_phi_equivalence() {
             dst: v3,
             value: ConstValue::Integer(0),
         });
-    f.get_block_mut(else_bb).unwrap().terminator = Some(MirInstruction::Jump { target: merge_bb });
+    f.get_block_mut(else_bb).unwrap().set_terminator(MirInstruction::Jump {
+        target: merge_bb,
+        edge_args: None,
+    });
 
     // Merge: v4 = phi(v2 from then, v3 from else)
     let v4 = f.next_value_id();
diff --git a/tests/mir_verification_unit.rs b/tests/mir_verification_unit.rs
index dccf83a9..27fdb57d 100644
--- a/tests/mir_verification_unit.rs
+++ b/tests/mir_verification_unit.rs
@@ -130,6 +130,8 @@ fn test_merge_use_before_phi_detected() {
             condition: cond,
             then_bb,
             else_bb,
+            then_edge_args: None,
+            else_edge_args: None,
         });
     }
 
@@ -139,7 +141,10 @@ fn test_merge_use_before_phi_detected() {
         dst: v1,
         value: ConstValue::String("A".to_string()),
     });
-    b1.add_instruction(MirInstruction::Jump { target: merge_bb });
+    b1.add_instruction(MirInstruction::Jump {
+        target: merge_bb,
+        edge_args: None,
+    });
     f.add_block(b1);
 
     let v2 = f.next_value_id(); // %2
@@ -148,7 +153,10 @@ fn test_merge_use_before_phi_detected() {
         dst: v2,
         value: ConstValue::String("B".to_string()),
     });
-    b2.add_instruction(MirInstruction::Jump { target: merge_bb });
+    b2.add_instruction(MirInstruction::Jump {
+        target: merge_bb,
+        edge_args: None,
+    });
     f.add_block(b2);
 
     let mut b3 = BasicBlock::new(merge_bb);
diff --git a/tests/wasm_string_constants.rs b/tests/wasm_string_constants.rs
index 55964cfe..3239b651 100644
--- a/tests/wasm_string_constants.rs
+++ b/tests/wasm_string_constants.rs
@@ -146,7 +146,7 @@ fn build_string_const_mir_module() -> MirModule {
     });
 
     // return %str
-    block.terminator = Some(MirInstruction::Return {
+    block.set_terminator(MirInstruction::Return {
         value: Some(str_value),
     });
 
@@ -193,7 +193,7 @@ fn build_multiple_string_const_mir_module() -> MirModule {
     });
 
     // return %str1
-    block.terminator = Some(MirInstruction::Return {
+    block.set_terminator(MirInstruction::Return {
         value: Some(str1_value),
     });