diff --git a/src/mir/builder/control_flow/edgecfg/api/emit.rs b/src/mir/builder/control_flow/edgecfg/api/emit.rs
new file mode 100644
index 00000000..b4b0fed9
--- /dev/null
+++ b/src/mir/builder/control_flow/edgecfg/api/emit.rs
@@ -0,0 +1,298 @@
+/*!
+ * wires → MIR terminator 変換（Phase 266: SSOT）
+ *
+ * # 目的
+ * - EdgeStub の wires を MIR terminator に変換する唯一の入口
+ * - Phase 260 の terminator 語彙ルールを厳守
+ * - 1 block = 1 terminator 制約を強制
+ *
+ * # Phase 266 制約
+ * - Jump/Return のみ実装（Branch は Phase 267）
+ * - Return は target=None を許可（意味を持たない）
+ * - from ごとにグループ化して1本だけ許可
+ */
+
+use super::edge_stub::EdgeStub;
+use super::exit_kind::ExitKind;
+use crate::mir::basic_block::BasicBlockId;
+use crate::mir::instruction::MirInstruction;
+use std::collections::BTreeMap;
+
+/// wires → MIR terminator 変換（Phase 266 P1: SSOT）
+///
+/// # 責務
+/// - EdgeStub の target=Some(...) を MIR terminator に変換
+/// - BasicBlock::set_*_with_edge_args() を使って terminator + successor を同期
+/// - target=None の EdgeStub が混入したら Fail-Fast（Return を除く）
+///
+/// # 引数
+/// - `function`: MIR function（BasicBlock アクセス用）
+/// - `wires`: 配線済み EdgeStub のリスト（target=Some のみを期待、Return は target=None OK）
+///
+/// # 戻り値
+/// - `Ok(())`: 全 wire を MIR terminator に変換成功
+/// - `Err(String)`: target=None の EdgeStub を検出、または不正な kind、または複数 wire
+pub fn emit_wires(
+    function: &mut crate::mir::MirFunction,
+    wires: &[EdgeStub],
+) -> Result<(), String> {
+    // Step 1: from ごとにグループ化（1 block = 1 terminator 制約）
+    let mut by_block: BTreeMap<BasicBlockId, Vec<&EdgeStub>> = BTreeMap::new();
+    for stub in wires {
+        by_block.entry(stub.from).or_default().push(stub);
+    }
+
+    // Step 2: 各 block に対して1本だけ wire を許可
+    for (block_id, stubs) in by_block {
+        if stubs.len() > 1 {
+            return Err(format!(
+                "[emit_wires] Multiple wires from same block {:?} (count={}). \
+                 1 block = 1 terminator constraint violated.",
+                block_id,
+                stubs.len()
+            ));
+        }
+
+        let stub = stubs[0];
+
+        // Fail-Fast: target=None 検出（Return 以外）
+        let target = match stub.kind {
+            ExitKind::Return => None, // Return は target 不要
+            _ => {
+                // Normal/Break/Continue/Unwind は target 必須
+                Some(stub.target.ok_or_else(|| {
+                    format!(
+                        "[emit_wires] Unwired EdgeStub detected: from={:?}, kind={:?}. \
+                         Wires (except Return) must have target=Some(...). This is a contract violation.",
+                        stub.from, stub.kind
+                    )
+                })?)
+            }
+        };
+
+        // Block 取得
+        let block = function
+            .get_block_mut(stub.from)
+            .ok_or_else(|| format!("[emit_wires] Block {:?} not found", stub.from))?;
+
+        // ExitKind 別に terminator 生成
+        match stub.kind {
+            ExitKind::Normal | ExitKind::Break(_) | ExitKind::Continue(_) | ExitKind::Unwind => {
+                // Jump terminator（Phase 260 ルール: set_jump_with_edge_args を使用）
+                block.set_jump_with_edge_args(target.unwrap(), Some(stub.args.clone()));
+            }
+            ExitKind::Return => {
+                // Return terminator + metadata（Phase 260 例外ルール: set_terminator + set_return_env）
+                block.set_terminator(MirInstruction::Return {
+                    value: stub.args.values.first().copied(),
+                });
+                block.set_return_env(stub.args.clone());
+            }
+            _ => {
+                return Err(format!(
+                    "[emit_wires] Unsupported ExitKind: {:?}",
+                    stub.kind
+                ));
+            }
+        }
+    }
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::mir::basic_block::EdgeArgs;
+    use crate::mir::function::{FunctionSignature, MirFunction};
+    use crate::mir::join_ir::lowering::inline_boundary::JumpArgsLayout;
+    use crate::mir::types::MirType;
+    use crate::mir::{BasicBlock, EffectMask, ValueId};
+
+    /// テスト用の MirFunction を作成（最小構成）
+    fn create_test_function() -> MirFunction {
+        let signature = FunctionSignature {
+            name: "test_func".to_string(),
+            params: vec![],
+            return_type: MirType::Void,
+            effects: EffectMask::PURE,
+        };
+        let entry_block = BasicBlockId(0);
+        MirFunction::new(signature, entry_block)
+    }
+
+    #[test]
+    fn test_emit_wires_jump_basic() {
+        // Setup: MirFunction with 2 blocks
+        let mut function = create_test_function();
+        let bb0 = BasicBlockId(0); // entry
+        let bb1 = BasicBlockId(1);
+        function.add_block(BasicBlock::new(bb1));
+
+        // Setup: wire (bb0 → bb1)
+        let stub = EdgeStub::with_target(
+            bb0,
+            ExitKind::Normal,
+            bb1,
+            EdgeArgs {
+                layout: JumpArgsLayout::CarriersOnly,
+                values: vec![ValueId(100)],
+            },
+        );
+
+        let wires = vec![stub];
+
+        // Execute
+        let result = emit_wires(&mut function, &wires);
+
+        // Verify: success
+        assert!(result.is_ok(), "emit_wires failed: {:?}", result.err());
+
+        // Verify: bb0 has Jump terminator
+        let block0 = function.get_block(bb0).unwrap();
+        assert!(
+            block0.is_terminated(),
+            "bb0 should have a terminator"
+        );
+
+        match &block0.terminator {
+            Some(MirInstruction::Jump { target, edge_args }) => {
+                assert_eq!(*target, bb1, "Jump target should be bb1");
+                assert!(edge_args.is_some(), "Jump should have edge_args");
+                let args = edge_args.as_ref().unwrap();
+                assert_eq!(
+                    args.values,
+                    vec![ValueId(100)],
+                    "Edge args values mismatch"
+                );
+            }
+            other => panic!("Expected Jump terminator, got {:?}", other),
+        }
+
+        // Verify: successors updated
+        assert!(
+            block0.successors.contains(&bb1),
+            "bb0 successors should contain bb1"
+        );
+    }
+
+    #[test]
+    fn test_emit_wires_return_basic() {
+        // Setup: MirFunction with 1 block
+        let mut function = create_test_function();
+        let bb0 = BasicBlockId(0); // entry
+
+        // Setup: Return wire（target=None OK、意味を持たない）
+        let stub = EdgeStub {
+            from: bb0,
+            kind: ExitKind::Return,
+            target: None, // Return は target 不要（emit_wires で無視される）
+            args: EdgeArgs {
+                layout: JumpArgsLayout::CarriersOnly,
+                values: vec![ValueId(200)],
+            },
+        };
+
+        let wires = vec![stub];
+
+        // Execute
+        let result = emit_wires(&mut function, &wires);
+
+        // Verify: success
+        assert!(result.is_ok(), "emit_wires failed: {:?}", result.err());
+
+        // Verify: bb0 has Return terminator
+        let block0 = function.get_block(bb0).unwrap();
+        match &block0.terminator {
+            Some(MirInstruction::Return { value }) => {
+                assert_eq!(
+                    *value,
+                    Some(ValueId(200)),
+                    "Return value mismatch"
+                );
+            }
+            other => panic!("Expected Return terminator, got {:?}", other),
+        }
+
+        // Verify: return_env set
+        let return_env = block0.return_env().expect("return_env should be set");
+        assert_eq!(
+            return_env.values,
+            vec![ValueId(200)],
+            "return_env values mismatch"
+        );
+    }
+
+    #[test]
+    fn test_emit_wires_unwired_stub_fails() {
+        // Setup: EdgeStub with target=None（Normal は target 必須）
+        let mut function = create_test_function();
+        let bb0 = BasicBlockId(0);
+
+        let stub = EdgeStub::without_args(bb0, ExitKind::Normal);
+        // stub.target = None（未配線）
+
+        let wires = vec![stub];
+
+        // Execute
+        let result = emit_wires(&mut function, &wires);
+
+        // Verify: failure
+        assert!(result.is_err(), "Expected error for unwired Normal stub");
+        let err_msg = result.unwrap_err();
+        assert!(
+            err_msg.contains("Unwired EdgeStub"),
+            "Error message should mention 'Unwired EdgeStub', got: {}",
+            err_msg
+        );
+    }
+
+    #[test]
+    fn test_emit_wires_multiple_from_same_block_fails() {
+        // Setup: 同じ from に2本の wire（1 block = 1 terminator 違反）
+        let mut function = create_test_function();
+        let bb0 = BasicBlockId(0);
+        let bb1 = BasicBlockId(1);
+        let bb2 = BasicBlockId(2);
+        function.add_block(BasicBlock::new(bb1));
+        function.add_block(BasicBlock::new(bb2));
+
+        let stub1 = EdgeStub {
+            from: bb0,
+            kind: ExitKind::Normal,
+            target: Some(bb1),
+            args: EdgeArgs {
+                layout: JumpArgsLayout::CarriersOnly,
+                values: vec![],
+            },
+        };
+
+        let stub2 = EdgeStub {
+            from: bb0, // 同じ from
+            kind: ExitKind::Normal,
+            target: Some(bb2),
+            args: EdgeArgs {
+                layout: JumpArgsLayout::CarriersOnly,
+                values: vec![],
+            },
+        };
+
+        let wires = vec![stub1, stub2];
+
+        // Execute
+        let result = emit_wires(&mut function, &wires);
+
+        // Verify: failure
+        assert!(
+            result.is_err(),
+            "Expected error for multiple wires from same block"
+        );
+        let err_msg = result.unwrap_err();
+        assert!(
+            err_msg.contains("Multiple wires from same block"),
+            "Error message should mention 'Multiple wires from same block', got: {}",
+            err_msg
+        );
+    }
+}
+
diff --git a/src/mir/builder/control_flow/edgecfg/api/mod.rs b/src/mir/builder/control_flow/edgecfg/api/mod.rs
index 7dd45496..0ee73e79 100644
--- a/src/mir/builder/control_flow/edgecfg/api/mod.rs
+++ b/src/mir/builder/control_flow/edgecfg/api/mod.rs
@@ -20,6 +20,7 @@ pub mod edge_stub;
 pub mod frag;
 pub mod compose;
 pub mod verify;
+pub mod emit; // Phase 266: 追加
 
 // 公開型（安定）
 pub use exit_kind::ExitKind;
@@ -31,3 +32,7 @@ pub(crate) use compose::{seq, if_, loop_, cleanup};
 
 // 検証関数
 pub use verify::verify_frag_invariants;
+pub use verify::verify_frag_invariants_strict; // Phase 266: strict 版追加
+
+// Phase 266: wires → MIR terminator 変換
+pub use emit::emit_wires;
diff --git a/src/mir/builder/control_flow/edgecfg/api/verify.rs b/src/mir/builder/control_flow/edgecfg/api/verify.rs
index 1c28ad1c..ca58b11a 100644
--- a/src/mir/builder/control_flow/edgecfg/api/verify.rs
+++ b/src/mir/builder/control_flow/edgecfg/api/verify.rs
@@ -89,6 +89,64 @@ pub fn verify_frag_invariants(frag: &Frag) -> Result<(), String> {
     Ok(())
 }
 
+/// Frag の不変条件を厳格検証（Phase 266: strict 版、警告→Err 化）
+///
+/// # 検証項目
+/// - wires/exits 分離契約（厳格）
+///   - exits に target=Some があったら Err
+///   - wires に target=None があったら Err（Return を除く）
+///
+/// # 戻り値
+/// - Ok(()): 検証成功
+/// - Err(String): 検証失敗（エラーメッセージ）
+///
+/// # 使用箇所
+/// - Phase 266 の emit_wires() と PoC テストのみ
+/// - Phase 267+ で段階的に既存コードへ適用
+///
+/// # Phase 266 の設計判断
+/// - 既存の `verify_frag_invariants()` は警告のまま維持（段階導入を壊さない）
+/// - 新規に `verify_frag_invariants_strict()` を追加し、P266 の PoC/emit 側だけ strict を使う
+pub fn verify_frag_invariants_strict(frag: &Frag) -> Result<(), String> {
+    use super::exit_kind::ExitKind;
+
+    // 1. exits と wires の両方が空の場合は警告（非致命的）
+    if frag.exits.is_empty() && frag.wires.is_empty() {
+        #[cfg(debug_assertions)]
+        eprintln!(
+            "[verify_frag_strict] Warning: Frag entry={:?} has no exits and no wires (dead end?)",
+            frag.entry
+        );
+    }
+
+    // 2. exits 内に target=Some がいたら Err（厳格）
+    for (kind, stubs) in &frag.exits {
+        for stub in stubs {
+            if stub.target.is_some() {
+                return Err(format!(
+                    "[verify_frag_strict] Exits[{:?}] contains wired EdgeStub (target={:?}). \
+                     Wired stubs must be in wires instead.",
+                    kind, stub.target
+                ));
+            }
+        }
+    }
+
+    // 3. wires 内に target=None がいたら Err（Return を除く、厳格）
+    for stub in &frag.wires {
+        // Return は target 不要なので許可
+        if stub.target.is_none() && !matches!(stub.kind, ExitKind::Return) {
+            return Err(format!(
+                "[verify_frag_strict] Wires contains unwired EdgeStub (from={:?}, kind={:?}). \
+                 Wires (except Return) must have target=Some(...). This should be in exits instead.",
+                stub.from, stub.kind
+            ));
+        }
+    }
+
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;