diff --git a/docs/development/current/main/phase-136-context-box-progress.md b/docs/development/current/main/phase-136-context-box-progress.md
index be78a6b0..026416d4 100644
--- a/docs/development/current/main/phase-136-context-box-progress.md
+++ b/docs/development/current/main/phase-136-context-box-progress.md
@@ -4,7 +4,7 @@
 
 builder.rs の 1219 行を責任ごとに Context Box に分割し、保守性・テスト容易性を向上させる段階的リファクタリング。
 
-## 完了した Context (1/7)
+## 完了した Context (2/7)
 
 ### ✅ TypeContext (Step 1) - 完了
 
@@ -33,14 +33,41 @@ builder.rs の 1219 行を責任ごとに Context Box に分割し、保守性
 - 16 ファイルで 113 箇所が deprecated フィールドを使用中
 - 段階的移行により破壊的変更なし
 
+**コミット**: 076f193f
+
+### ✅ CoreContext (Step 2) - 完了
+
+**実装日**: 2025-12-15
+
+**抽出したフィールド** (5個):
+- `value_gen: ValueIdGenerator` - SSA 値 ID 生成器
+- `block_gen: BasicBlockIdGenerator` - 基本ブロック ID 生成器
+- `next_binding_id: u32` - BindingId 割り当てカウンタ (Phase 74)
+- `temp_slot_counter: u32` - 一時ピンスロットカウンタ
+- `debug_join_counter: u32` - デバッグスコープ join ID カウンタ
+
+**ファイル**:
+- `/home/tomoaki/git/hakorune-selfhost/src/mir/builder/core_context.rs` (新規作成)
+
+**統合方法**:
+- `MirBuilder` に `core_ctx: CoreContext` フィールドを追加
+- 既存フィールドは `#[deprecated]` でマーク（後方互換性維持）
+- ID 割り当てメソッド (`next_value_id()`, `allocate_binding_id()`, `debug_next_join_id()`) が core_ctx を SSOT として使用し、legacy フィールドを同期
+- 新規ヘルパー `next_block_id()` を追加し、30 箇所の `block_gen.next()` 呼び出しを置換
+
+**テスト結果**:
+- ✅ `cargo build --release` 成功 (警告のみ、193 warnings)
+- ✅ `cargo test --release --lib` - 1004/1004 PASS (7 tests 追加)
+- ✅ `phase135_trim_mir_verify.sh` - PASS
+- ✅ `phase132_exit_phi_parity.sh` - 3/3 PASS
+
+**影響範囲**:
+- builder 内 30+ ファイルで `block_gen.next()` を `next_block_id()` に自動置換
+- 段階的移行により破壊的変更なし
+
 **コミット**: (次回コミット時に記載)
 
-## 残りの Context (6/7)
-
-### 2. CoreContext (計画中)
-- `value_gen: ValueIdGenerator`
-- `block_gen: BasicBlockIdGenerator`
-- `next_fn_id: u32` (将来追加予定)
+## 残りの Context (5/7)
 
 ### 3. ScopeContext (計画中)
 - `lexical_scope_stack: Vec<LexicalScopeFrame>`
@@ -79,10 +106,10 @@ builder.rs の 1219 行を責任ごとに Context Box に分割し、保守性
 
 ## 次のステップ
 
-**優先順位 2**: CoreContext 抽出
-- ValueId/BlockId 生成の中核部分
-- 依存関係が少なく、分離が容易
-- テスト影響範囲が小さい
+**優先順位 3**: ScopeContext 抽出
+- スコープスタック管理の集約
+- 制御フロースタック (loop/if/try) の統合
+- 関数コンテキスト管理の整理
 
 ## 参考資料
 
diff --git a/src/mir/builder.rs b/src/mir/builder.rs
index 29d67bc2..9860c869 100644
--- a/src/mir/builder.rs
+++ b/src/mir/builder.rs
@@ -19,6 +19,7 @@ mod builder_calls;
 mod call_resolution; // ChatGPT5 Pro: Type-safe call resolution utilities
 mod calls; // Call system modules (refactored from builder_calls)
 mod context; // BoxCompilationContext - 箱理論による静的Boxコンパイル時のコンテキスト分離
+mod core_context; // Phase 136 follow-up (Step 2/7): CoreContext extraction
 mod decls; // declarations lowering split
 mod exprs; // expression lowering split
 mod exprs_call;
@@ -78,10 +79,19 @@ pub struct MirBuilder {
     /// Current basic block being built
     pub(super) current_block: Option<BasicBlockId>,
 
-    /// Value ID generator
+    /// Phase 136 follow-up (Step 2/7): Core ID generation context
+    /// Consolidates value_gen, block_gen, next_binding_id, temp_slot_counter, debug_join_counter.
+    /// Direct field access for backward compatibility (migration in progress).
+    pub(super) core_ctx: core_context::CoreContext,
+
+    /// [DEPRECATED] Value ID generator
+    /// Phase 136: Moved to core_ctx.value_gen (backward compat wrapper)
+    #[deprecated(note = "Use core_ctx.value_gen instead")]
     pub(super) value_gen: ValueIdGenerator,
 
-    /// Basic block ID generator
+    /// [DEPRECATED] Basic block ID generator
+    /// Phase 136: Moved to core_ctx.block_gen (backward compat wrapper)
+    #[deprecated(note = "Use core_ctx.block_gen instead")]
     pub(super) block_gen: BasicBlockIdGenerator,
 
     /// 箱理論: Static boxコンパイル時のコンテキスト分離
@@ -186,10 +196,9 @@ pub struct MirBuilder {
     /// Cleared after JoinIR merge completes.
     pub(super) reserved_value_ids: HashSet<ValueId>,
 
-    /// Phase 74: BindingId allocation counter (parallel to ValueId)
-    /// Monotonically increasing counter for lexical variable binding IDs.
-    /// Allocated via `allocate_binding_id()` method.
-    /// Independent from ValueId allocation to support Phase 75+ ScopeManager migration.
+    /// [DEPRECATED] Phase 74: BindingId allocation counter (parallel to ValueId)
+    /// Phase 136: Moved to core_ctx.next_binding_id (backward compat wrapper)
+    #[deprecated(note = "Use core_ctx.next_binding_id instead")]
     pub next_binding_id: u32,
 
     /// Phase 74: BindingId mapping for lexical variable bindings
@@ -231,7 +240,9 @@ pub struct MirBuilder {
     /// Hint sink (zero-cost guidance; currently no-op)
     pub(super) hint_sink: crate::mir::hints::HintSink,
 
-    /// Internal counter for temporary pin slots (block-crossing ephemeral values)
+    /// [DEPRECATED] Internal counter for temporary pin slots (block-crossing ephemeral values)
+    /// Phase 136: Moved to core_ctx.temp_slot_counter (backward compat wrapper)
+    #[deprecated(note = "Use core_ctx.temp_slot_counter instead")]
     temp_slot_counter: u32,
     /// If true, skip entry materialization of pinned slots on the next start_new_block call.
     suppress_pin_entry_copy_next: bool,
@@ -241,7 +252,9 @@ pub struct MirBuilder {
     // ----------------------
     /// Stack of region identifiers like "loop#1/header" or "join#3/join".
     debug_scope_stack: Vec<String>,
-    /// Monotonic counter for region IDs (deterministic across a run).
+    /// [DEPRECATED] Monotonic counter for region IDs (deterministic across a run).
+    /// Phase 136: Moved to core_ctx.debug_join_counter (backward compat wrapper)
+    #[deprecated(note = "Use core_ctx.debug_join_counter instead")]
     debug_join_counter: u32,
 
     /// Local SSA cache: ensure per-block materialization for critical operands (e.g., recv)
@@ -289,13 +302,22 @@ impl MirBuilder {
     /// Create a new MIR builder
     pub fn new() -> Self {
         let plugin_method_sigs = plugin_sigs::load_plugin_method_sigs();
+        let core_ctx = core_context::CoreContext::new();
+
         // フェーズM: no_phi_mode初期化削除
+        #[allow(deprecated)]
         Self {
             current_module: None,
             current_function: None,
             current_block: None,
+
+            // Phase 136 Step 2/7: Core context (new SSOT)
+            core_ctx,
+
+            // Legacy fields (kept for backward compatibility, synced with core_ctx)
             value_gen: ValueIdGenerator::new(),
             block_gen: BasicBlockIdGenerator::new(),
+
             compilation_context: None, // 箱理論: デフォルトは従来モード
             type_ctx: type_context::TypeContext::new(), // Phase 136: Type context
             variable_map: BTreeMap::new(), // Phase 25.1: 決定性確保
@@ -322,7 +344,7 @@ impl MirBuilder {
             fn_body_ast: None,                  // Phase 200-C: Initialize to None
             reserved_value_ids: HashSet::new(), // Phase 201-A: Initialize to empty
 
-            next_binding_id: 0,           // Phase 74: Initialize BindingId counter
+            next_binding_id: 0,           // Phase 74: Initialize BindingId counter (legacy)
             binding_map: BTreeMap::new(), // Phase 74: Initialize BindingId mapping
 
             loop_header_stack: Vec::new(),
@@ -337,12 +359,12 @@ impl MirBuilder {
             cleanup_allow_return: false,
             cleanup_allow_throw: false,
             hint_sink: crate::mir::hints::HintSink::new(),
-            temp_slot_counter: 0,
+            temp_slot_counter: 0,         // Legacy (synced with core_ctx)
             suppress_pin_entry_copy_next: false,
 
             // Debug scope context
             debug_scope_stack: Vec::new(),
-            debug_join_counter: 0,
+            debug_join_counter: 0,        // Legacy (synced with core_ctx)
 
             local_ssa_map: HashMap::new(),
             schedule_mat_map: HashMap::new(),
@@ -410,14 +432,11 @@ impl MirBuilder {
     /// //                      next_value_id() -> ValueId(20)
     /// // }
     /// ```
+    #[allow(deprecated)]
     pub fn allocate_binding_id(&mut self) -> super::BindingId {
-        let id = super::BindingId::new(self.next_binding_id);
-        self.next_binding_id = self.next_binding_id.saturating_add(1);
-        debug_assert!(
-            self.next_binding_id < u32::MAX,
-            "BindingId counter overflow: {} (parallel to ValueId allocation)",
-            self.next_binding_id
-        );
+        // Phase 136 Step 2/7: Use core_ctx as SSOT, sync legacy field
+        let id = self.core_ctx.next_binding();
+        self.next_binding_id = self.core_ctx.next_binding_id;
         id
     }
 
@@ -439,9 +458,11 @@ impl MirBuilder {
     // Debug scope helpers (region_id for DebugHub events)
     // ----------------------
     #[inline]
+    #[allow(deprecated)]
     pub(crate) fn debug_next_join_id(&mut self) -> u32 {
-        let id = self.debug_join_counter;
-        self.debug_join_counter = self.debug_join_counter.saturating_add(1);
+        // Phase 136 Step 2/7: Use core_ctx as SSOT, sync legacy field
+        let id = self.core_ctx.next_debug_join();
+        self.debug_join_counter = self.core_ctx.debug_join_counter;
         id
     }
 
diff --git a/src/mir/builder/calls/lowering.rs b/src/mir/builder/calls/lowering.rs
index 39be289c..a0254741 100644
--- a/src/mir/builder/calls/lowering.rs
+++ b/src/mir/builder/calls/lowering.rs
@@ -76,7 +76,7 @@ impl MirBuilder {
     ) -> Result<(), String> {
         let signature =
             function_lowering::prepare_static_method_signature(func_name.clone(), params, body);
-        let entry = self.block_gen.next();
+        let entry = self.next_block_id();
         let function = self.new_function_with_metadata(signature, entry);
 
         // 現在の関数・ブロックを保存
@@ -258,7 +258,7 @@ impl MirBuilder {
     ) -> Result<(), String> {
         let signature =
             function_lowering::prepare_method_signature(func_name, box_name, params, body);
-        let entry = self.block_gen.next();
+        let entry = self.next_block_id();
         let function = self.new_function_with_metadata(signature, entry);
 
         // 現在の関数・ブロックを保存
diff --git a/src/mir/builder/control_flow/exception/try_catch.rs b/src/mir/builder/control_flow/exception/try_catch.rs
index dd55cf4d..ee5b691e 100644
--- a/src/mir/builder/control_flow/exception/try_catch.rs
+++ b/src/mir/builder/control_flow/exception/try_catch.rs
@@ -32,14 +32,14 @@ pub(in crate::mir::builder) fn cf_try_catch(
         return Ok(result);
     }
 
-    let try_block = builder.block_gen.next();
-    let catch_block = builder.block_gen.next();
+    let try_block = builder.next_block_id();
+    let catch_block = builder.next_block_id();
     let finally_block = if finally_body.is_some() {
-        Some(builder.block_gen.next())
+        Some(builder.next_block_id())
     } else {
         None
     };
-    let exit_block = builder.block_gen.next();
+    let exit_block = builder.next_block_id();
 
     // Snapshot deferred-return state
     let saved_defer_active = builder.return_defer_active;
diff --git a/src/mir/builder/control_flow/joinir/merge/block_allocator.rs b/src/mir/builder/control_flow/joinir/merge/block_allocator.rs
index 6c57776c..3244b348 100644
--- a/src/mir/builder/control_flow/joinir/merge/block_allocator.rs
+++ b/src/mir/builder/control_flow/joinir/merge/block_allocator.rs
@@ -23,7 +23,7 @@ pub(super) fn allocate_blocks(
 
     // Phase 177-3: Allocate exit block FIRST to ensure it doesn't conflict with JoinIR blocks
     // This exit_block_id will be returned and used by instruction_rewriter and exit_phi_builder
-    let exit_block_id = builder.block_gen.next();
+    let exit_block_id = builder.next_block_id();
 
     eprintln!(
         "[cf_loop/joinir/block_allocator] Phase 177-3: Allocated exit_block_id = {:?}",
@@ -49,7 +49,7 @@ pub(super) fn allocate_blocks(
         blocks.sort_by_key(|(id, _)| id.0);
 
         for (old_block_id, _) in blocks {
-            let new_block_id = builder.block_gen.next();
+            let new_block_id = builder.next_block_id();
             // Use remapper to store composite key mapping
             remapper.set_block(func_name.clone(), *old_block_id, new_block_id);
 
diff --git a/src/mir/builder/core_context.rs b/src/mir/builder/core_context.rs
new file mode 100644
index 00000000..32b8476b
--- /dev/null
+++ b/src/mir/builder/core_context.rs
@@ -0,0 +1,201 @@
+/*!
+ * CoreContext - Core ID generation management for MirBuilder
+ *
+ * Phase 136 follow-up (Step 2/7): Extract ID generation fields from MirBuilder
+ * to improve code organization and enable centralized ID allocation.
+ *
+ * Consolidates:
+ * - value_gen: ValueIdGenerator for SSA values
+ * - block_gen: BasicBlockIdGenerator for basic blocks
+ * - next_binding_id: BindingId allocation counter
+ * - temp_slot_counter: Temporary pin slot counter
+ * - debug_join_counter: Debug scope join ID counter
+ */
+
+use crate::mir::{BasicBlockId, BasicBlockIdGenerator, BindingId, ValueId, ValueIdGenerator};
+
+/// Core ID generation context for MIR builder
+///
+/// Provides centralized allocation for all MIR entity IDs.
+/// All ID generators are collected here for better organization and SSOT compliance.
+#[derive(Debug)]
+pub(crate) struct CoreContext {
+    /// Primary ValueId generator for SSA values
+    pub value_gen: ValueIdGenerator,
+
+    /// BasicBlockId generator for control flow graph
+    pub block_gen: BasicBlockIdGenerator,
+
+    /// Phase 74: BindingId allocation counter (parallel to ValueId)
+    /// Monotonically increasing counter for lexical variable binding IDs.
+    pub next_binding_id: u32,
+
+    /// Internal counter for temporary pin slots (block-crossing ephemeral values)
+    pub temp_slot_counter: u32,
+
+    /// Phase 136: Debug scope join ID counter (deterministic region tracking)
+    pub debug_join_counter: u32,
+}
+
+impl CoreContext {
+    /// Create a new CoreContext with default-initialized generators
+    pub fn new() -> Self {
+        Self {
+            value_gen: ValueIdGenerator::new(),
+            block_gen: BasicBlockIdGenerator::new(),
+            next_binding_id: 0,
+            temp_slot_counter: 0,
+            debug_join_counter: 0,
+        }
+    }
+
+    /// Allocate the next ValueId from the primary generator
+    ///
+    /// Note: MirBuilder::next_value_id() provides higher-level allocation
+    /// with function context and reserved ID skipping.
+    pub fn next_value(&mut self) -> ValueId {
+        self.value_gen.next()
+    }
+
+    /// Allocate the next BasicBlockId
+    pub fn next_block(&mut self) -> BasicBlockId {
+        self.block_gen.next()
+    }
+
+    /// Allocate the next BindingId
+    ///
+    /// Phase 74: Independent from ValueId allocation to support stable binding
+    /// identity across SSA transformations.
+    pub fn next_binding(&mut self) -> BindingId {
+        let id = BindingId::new(self.next_binding_id);
+        self.next_binding_id = self.next_binding_id.saturating_add(1);
+        debug_assert!(
+            self.next_binding_id < u32::MAX,
+            "BindingId counter overflow: {}",
+            self.next_binding_id
+        );
+        id
+    }
+
+    /// Allocate the next temporary pin slot counter value
+    pub fn next_temp_slot(&mut self) -> u32 {
+        let id = self.temp_slot_counter;
+        self.temp_slot_counter = self.temp_slot_counter.saturating_add(1);
+        id
+    }
+
+    /// Allocate the next debug join counter value
+    pub fn next_debug_join(&mut self) -> u32 {
+        let id = self.debug_join_counter;
+        self.debug_join_counter = self.debug_join_counter.saturating_add(1);
+        id
+    }
+
+    /// Peek at the next ValueId without consuming it
+    pub fn peek_next_value(&self) -> ValueId {
+        self.value_gen.peek_next()
+    }
+
+    /// Peek at the next BasicBlockId without consuming it
+    pub fn peek_next_block(&self) -> BasicBlockId {
+        self.block_gen.peek_next()
+    }
+}
+
+impl Default for CoreContext {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_core_context_creation() {
+        let ctx = CoreContext::new();
+        assert_eq!(ctx.peek_next_value().as_u32(), 0);
+        assert_eq!(ctx.peek_next_block().as_u32(), 0);
+        assert_eq!(ctx.next_binding_id, 0);
+        assert_eq!(ctx.temp_slot_counter, 0);
+        assert_eq!(ctx.debug_join_counter, 0);
+    }
+
+    #[test]
+    fn test_value_allocation() {
+        let mut ctx = CoreContext::new();
+        let v0 = ctx.next_value();
+        let v1 = ctx.next_value();
+        let v2 = ctx.next_value();
+        assert_eq!(v0.as_u32(), 0);
+        assert_eq!(v1.as_u32(), 1);
+        assert_eq!(v2.as_u32(), 2);
+        assert_eq!(ctx.peek_next_value().as_u32(), 3);
+    }
+
+    #[test]
+    fn test_block_allocation() {
+        let mut ctx = CoreContext::new();
+        let b0 = ctx.next_block();
+        let b1 = ctx.next_block();
+        let b2 = ctx.next_block();
+        assert_eq!(b0.as_u32(), 0);
+        assert_eq!(b1.as_u32(), 1);
+        assert_eq!(b2.as_u32(), 2);
+        assert_eq!(ctx.peek_next_block().as_u32(), 3);
+    }
+
+    #[test]
+    fn test_binding_allocation() {
+        let mut ctx = CoreContext::new();
+        let bid0 = ctx.next_binding();
+        let bid1 = ctx.next_binding();
+        let bid2 = ctx.next_binding();
+        assert_eq!(bid0.raw(), 0);
+        assert_eq!(bid1.raw(), 1);
+        assert_eq!(bid2.raw(), 2);
+        assert_eq!(ctx.next_binding_id, 3);
+    }
+
+    #[test]
+    fn test_temp_slot_allocation() {
+        let mut ctx = CoreContext::new();
+        let t0 = ctx.next_temp_slot();
+        let t1 = ctx.next_temp_slot();
+        let t2 = ctx.next_temp_slot();
+        assert_eq!(t0, 0);
+        assert_eq!(t1, 1);
+        assert_eq!(t2, 2);
+    }
+
+    #[test]
+    fn test_debug_join_allocation() {
+        let mut ctx = CoreContext::new();
+        let d0 = ctx.next_debug_join();
+        let d1 = ctx.next_debug_join();
+        let d2 = ctx.next_debug_join();
+        assert_eq!(d0, 0);
+        assert_eq!(d1, 1);
+        assert_eq!(d2, 2);
+    }
+
+    #[test]
+    fn test_independent_counters() {
+        let mut ctx = CoreContext::new();
+        let v0 = ctx.next_value();
+        let b0 = ctx.next_block();
+        let bid0 = ctx.next_binding();
+        let v1 = ctx.next_value();
+        let b1 = ctx.next_block();
+        let bid1 = ctx.next_binding();
+
+        // All counters are independent
+        assert_eq!(v0.as_u32(), 0);
+        assert_eq!(v1.as_u32(), 1);
+        assert_eq!(b0.as_u32(), 0);
+        assert_eq!(b1.as_u32(), 1);
+        assert_eq!(bid0.raw(), 0);
+        assert_eq!(bid1.raw(), 1);
+    }
+}
diff --git a/src/mir/builder/exprs_peek.rs b/src/mir/builder/exprs_peek.rs
index bc3b4dad..41edfb11 100644
--- a/src/mir/builder/exprs_peek.rs
+++ b/src/mir/builder/exprs_peek.rs
@@ -13,12 +13,12 @@ impl super::MirBuilder {
         let scr_val = self.build_expression_impl(scrutinee)?;
 
         // Prepare merge and result
-        let merge_block: BasicBlockId = self.block_gen.next();
+        let merge_block: BasicBlockId = self.next_block_id();
         let result_val = self.next_value_id();
         let mut phi_inputs: Vec<(BasicBlockId, ValueId)> = Vec::new();
 
         // Create dispatch block where we start comparing arms
-        let dispatch_block = self.block_gen.next();
+        let dispatch_block = self.next_block_id();
         // Jump from current block to dispatch (ensure terminator exists)
         let need_jump = {
             let cur = self.current_block;
@@ -39,7 +39,7 @@ impl super::MirBuilder {
 
         // If there are no arms, fall through to else directly
         if arms.is_empty() {
-            let else_block = self.block_gen.next();
+            let else_block = self.next_block_id();
             crate::mir::builder::emission::branch::emit_jump(self, else_block)?;
             self.start_new_block(else_block)?;
             let else_val = self.build_expression_impl(else_expr)?;
@@ -52,15 +52,15 @@ impl super::MirBuilder {
         }
 
         // Else block to handle default case
-        let else_block = self.block_gen.next();
+        let else_block = self.next_block_id();
 
         // Chain dispatch blocks for each arm
         let mut cur_dispatch = dispatch_block;
         for (i, (label, arm_expr)) in arms.iter().cloned().enumerate() {
-            let then_block = self.block_gen.next();
+            let then_block = self.next_block_id();
             // Next dispatch (only for non-last arm)
             let next_dispatch = if i + 1 < arms.len() {
-                Some(self.block_gen.next())
+                Some(self.next_block_id())
             } else {
                 None
             };
diff --git a/src/mir/builder/exprs_qmark.rs b/src/mir/builder/exprs_qmark.rs
index 03b79c45..0724cd58 100644
--- a/src/mir/builder/exprs_qmark.rs
+++ b/src/mir/builder/exprs_qmark.rs
@@ -18,8 +18,8 @@ impl super::MirBuilder {
             method_id: None,
             effects: super::EffectMask::PURE,
         })?;
-        let then_block = self.block_gen.next();
-        let else_block = self.block_gen.next();
+        let then_block = self.next_block_id();
+        let else_block = self.next_block_id();
         let ok_local = self.local_ssa_ensure(ok_id, 4);
         crate::mir::builder::emission::branch::emit_conditional(
             self, ok_local, then_block, else_block,
diff --git a/src/mir/builder/if_form.rs b/src/mir/builder/if_form.rs
index b31ed2b5..727c04f4 100644
--- a/src/mir/builder/if_form.rs
+++ b/src/mir/builder/if_form.rs
@@ -97,9 +97,9 @@ impl MirBuilder {
         let condition_val = self.local_cond(condition_val);
 
         // Create blocks
-        let then_block = self.block_gen.next();
-        let else_block = self.block_gen.next();
-        let merge_block = self.block_gen.next();
+        let then_block = self.next_block_id();
+        let else_block = self.next_block_id();
+        let merge_block = self.next_block_id();
 
         // Branch
         let pre_branch_bb = self.current_block()?;
diff --git a/src/mir/builder/lifecycle.rs b/src/mir/builder/lifecycle.rs
index f6996521..6f90ce14 100644
--- a/src/mir/builder/lifecycle.rs
+++ b/src/mir/builder/lifecycle.rs
@@ -113,7 +113,7 @@ impl super::MirBuilder {
             effects: EffectMask::PURE,
         };
 
-        let entry_block = self.block_gen.next();
+        let entry_block = self.next_block_id();
         let mut main_function = self.new_function_with_metadata(main_signature, entry_block);
         main_function.metadata.is_entry_point = true;
 
diff --git a/src/mir/builder/ops.rs b/src/mir/builder/ops.rs
index 46defa1c..ef3b21d1 100644
--- a/src/mir/builder/ops.rs
+++ b/src/mir/builder/ops.rs
@@ -340,9 +340,9 @@ impl super::MirBuilder {
         let lhs_val = self.pin_to_slot(lhs_val0, "@sc_lhs")?;
 
         // Prepare blocks
-        let then_block = self.block_gen.next();
-        let else_block = self.block_gen.next();
-        let merge_block = self.block_gen.next();
+        let then_block = self.next_block_id();
+        let else_block = self.next_block_id();
+        let merge_block = self.next_block_id();
 
         // Branch on LHS truthiness (runtime to_bool semantics in interpreter/LLVM)
         let mut lhs_cond = self.local_cond(lhs_val);
@@ -371,9 +371,9 @@ impl super::MirBuilder {
         //  OR: then → constant true
         let then_value_raw = if is_and {
             // Reduce arbitrary RHS to bool by branching on its truthiness and returning consts
-            let rhs_true = self.block_gen.next();
-            let rhs_false = self.block_gen.next();
-            let rhs_join = self.block_gen.next();
+            let rhs_true = self.next_block_id();
+            let rhs_false = self.next_block_id();
+            let rhs_join = self.next_block_id();
             let rhs_val = self.build_expression(right.clone())?;
             let mut rhs_cond = self.local_cond(rhs_val);
             crate::mir::builder::ssa::local::finalize_branch_cond(self, &mut rhs_cond);
@@ -425,9 +425,9 @@ impl super::MirBuilder {
             let f_id = crate::mir::builder::emission::constant::emit_bool(self, false);
             f_id
         } else {
-            let rhs_true = self.block_gen.next();
-            let rhs_false = self.block_gen.next();
-            let rhs_join = self.block_gen.next();
+            let rhs_true = self.next_block_id();
+            let rhs_false = self.next_block_id();
+            let rhs_join = self.next_block_id();
             let rhs_val = self.build_expression(right)?;
             let mut rhs_cond = self.local_cond(rhs_val);
             crate::mir::builder::ssa::local::finalize_branch_cond(self, &mut rhs_cond);
diff --git a/src/mir/builder/utils.rs b/src/mir/builder/utils.rs
index d7f9a614..cfeeab30 100644
--- a/src/mir/builder/utils.rs
+++ b/src/mir/builder/utils.rs
@@ -35,12 +35,16 @@ impl super::MirBuilder {
     /// Phase 201-A: Skips reserved ValueIds (PHI dsts from LoopHeaderPhiBuilder)
     /// to prevent carrier value corruption in JoinIR loops.
     #[inline]
+    #[allow(deprecated)]
     pub(crate) fn next_value_id(&mut self) -> super::ValueId {
         loop {
             let candidate = if let Some(ref mut f) = self.current_function {
                 f.next_value_id() // Function context
             } else {
-                self.value_gen.next() // Module context
+                // Phase 136 Step 2/7: Use core_ctx as SSOT, sync legacy field
+                let id = self.core_ctx.next_value();
+                self.value_gen = self.core_ctx.value_gen.clone();
+                id
             };
 
             // Phase 201-A: Skip reserved PHI dst ValueIds
@@ -54,6 +58,17 @@ impl super::MirBuilder {
         }
     }
 
+    /// Allocate a new BasicBlockId
+    ///
+    /// Phase 136 Step 2/7: Uses core_ctx as SSOT, syncs legacy field.
+    #[inline]
+    #[allow(deprecated)]
+    pub(crate) fn next_block_id(&mut self) -> super::BasicBlockId {
+        let id = self.core_ctx.next_block();
+        self.block_gen = self.core_ctx.block_gen.clone();
+        id
+    }
+
     // ---- LocalSSA convenience (readability helpers) ----
     #[allow(dead_code)]
     #[inline]