diff --git a/apps/tests/phase115_if_only_call_merge_min.hako b/apps/tests/phase115_if_only_call_merge_min.hako
new file mode 100644
index 00000000..062d2b84
--- /dev/null
+++ b/apps/tests/phase115_if_only_call_merge_min.hako
@@ -0,0 +1,25 @@
+// Phase 115: if-only call result merge parity
+// Test if-branch call result merge (LLVM fragile pattern)
+
+static box Main {
+  f(x) {
+    return x + 1
+  }
+
+  g(flag) {
+    local v
+    v = 0
+    if flag == 1 {
+      v = me.f(1)
+    } else {
+      v = me.f(2)
+    }
+    print(v)
+  }
+
+  main() {
+    me.g(1)
+    me.g(0)
+    return "OK"
+  }
+}
diff --git a/docs/development/current/main/01-JoinIR-Selfhost-INDEX.md b/docs/development/current/main/01-JoinIR-Selfhost-INDEX.md
index 4dccedce..f149c9da 100644
--- a/docs/development/current/main/01-JoinIR-Selfhost-INDEX.md
+++ b/docs/development/current/main/01-JoinIR-Selfhost-INDEX.md
@@ -66,17 +66,19 @@ JoinIR の箱構造と責務、ループ/if の lowering パターンを把握
     - `docs/development/current/main/phases/phase-113/README.md`
 16. Phase 114: if-only return+post parity（early return + post-if statements）
     - `docs/development/current/main/phases/phase-114/README.md`
-17. Phase 104: loop(true) break-only digits（VM + LLVM EXE）
+17. Phase 115: if-only call result merge parity（関数呼び出し結果 merge）
+    - `docs/development/current/main/phases/phase-115/README.md`
+18. Phase 104: loop(true) break-only digits（VM + LLVM EXE）
     - `docs/development/current/main/phases/phase-104/README.md`
-18. Phase 107: json_cur find_balanced_* depth scan（VM + LLVM EXE）
+19. Phase 107: json_cur find_balanced_* depth scan（VM + LLVM EXE）
     - `docs/development/current/main/phases/phase-107/README.md`
-19. Phase 108: Pattern2 policy router SSOT（入口の薄さを固定）
+20. Phase 108: Pattern2 policy router SSOT（入口の薄さを固定）
     - `docs/development/current/main/phases/phase-108/README.md`
-20. Phase 109: error_tags hints SSOT（Fail-Fast + hint の語彙固定）
+21. Phase 109: error_tags hints SSOT（Fail-Fast + hint の語彙固定）
     - `docs/development/current/main/phases/phase-109/README.md`
-21. MIR Builder（Context 分割の入口）
+22. MIR Builder（Context 分割の入口）
     - `src/mir/builder/README.md`
-22. Scope/BindingId（shadowing・束縛同一性の段階移行）
+23. Scope/BindingId（shadowing・束縛同一性の段階移行）
    - `docs/development/current/main/phase73-scope-manager-design.md`
    - `docs/development/current/main/PHASE_74_SUMMARY.md`
    - `docs/development/current/main/PHASE_75_SUMMARY.md`
diff --git a/docs/development/current/main/10-Now.md b/docs/development/current/main/10-Now.md
index 50607571..a041dc6a 100644
--- a/docs/development/current/main/10-Now.md
+++ b/docs/development/current/main/10-Now.md
@@ -1,5 +1,14 @@
 # Self Current Task — Now (main)
 
+## 2025-12-18：Phase 115 完了 ✅
+
+**Phase 115: if-only call result merge parity**
+- if-only で関数呼び出し結果を merge するパターンを VM/LLVM で固定
+- Fixture: phase115_if_only_call_merge_min.hako (expected: 2, 3)
+- Smoke: VM + LLVM EXE parity 検証済み
+- 回帰: Phase 103/113/114 維持確認
+- 入口: `docs/development/current/main/phases/phase-115/README.md`
+
 ## 2025-12-18：Phase 114 完了 ✅
 
 **Phase 114: if-only return+post parity**
diff --git a/docs/development/current/main/phases/phase-115/README.md b/docs/development/current/main/phases/phase-115/README.md
new file mode 100644
index 00000000..9035444c
--- /dev/null
+++ b/docs/development/current/main/phases/phase-115/README.md
@@ -0,0 +1,91 @@
+# Phase 115: If-Only Call Result Merge Parity
+
+**Status**: ✅ DONE
+**Date**: 2025-12-18
+
+## 背景
+
+LLVMバックエンドで壊れやすいパターン - if分岐内での関数呼び出し結果をマージするケース。
+
+### 問題パターン
+
+```hako
+fn f(x) { return x + 1 }
+fn g(flag) {
+    local v = 0
+    if flag == 1 { v = f(1) } else { v = f(2) }
+    print(v)
+}
+```
+
+このパターンでは：
+1. if/else両分岐で関数呼び出し `f()` が発生
+2. その結果を変数 `v` に代入
+3. if後にマージされた `v` を使用
+
+LLVM EXEモードでは、PHI node生成やSSA変換が正しく行われない可能性がある。
+
+## 実装内容
+
+### 1. テストフィクスチャ
+
+- **ファイル**: `/home/tomoaki/git/hakorune-selfhost/apps/tests/phase115_if_only_call_merge_min.hako`
+- **期待出力**: `2\n3`
+  - `g(1)` → `f(1)` → `1+1` → `2`
+  - `g(0)` → `f(2)` → `2+1` → `3`
+
+### 2. VM Smoke Test
+
+- **ファイル**: `/home/tomoaki/git/hakorune-selfhost/tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_vm.sh`
+- **環境変数**: `NYASH_DISABLE_PLUGINS=1 HAKO_JOINIR_STRICT=1`
+- **検証**: 数値行抽出して `2\n3` と比較
+
+### 3. LLVM EXE Smoke Test
+
+- **ファイル**: `/home/tomoaki/git/hakorune-selfhost/tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_llvm_exe.sh`
+- **利用**: `tools/smokes/v2/lib/llvm_exe_runner.sh`
+- **検証**: `EXPECTED='2\n3'`, `EXPECTED_LINES=2`
+
+## 検証コマンド
+
+```bash
+# VM smoke test
+bash tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_vm.sh
+
+# LLVM EXE smoke test
+bash tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_llvm_exe.sh
+
+# Phase 114回帰テスト（推奨）
+bash tools/smokes/v2/profiles/integration/apps/phase114_if_only_return_then_post_llvm_exe.sh
+```
+
+## 関連Phase
+
+- **Phase 103**: If-Only基本パリティ（制御フロー基礎）
+- **Phase 113**: If-Only部分代入パリティ（変数マージ）
+- **Phase 114**: If-Only return+post パリティ（early returnとpost-if文）
+- **Phase 115**: If-Only call result merge パリティ（関数呼び出し結果マージ） ← 今回
+
+## 技術的詳細
+
+### JoinIR → MIR変換
+
+If-Only Pattern 1では：
+1. Then/Else分岐それぞれで関数呼び出し
+2. 各分岐の終端で変数への代入
+3. Exit block入口でPHI node生成（then_value vs else_value）
+4. Post-if文でマージされた値を使用
+
+### LLVM SSA変換
+
+LLVM EXEモードでは：
+1. 関数呼び出し結果を一時レジスタに保持
+2. 各分岐終端でstore
+3. Exit block入口でload + phi
+4. Post-if文でphi結果を使用
+
+## Fail-Fast原則
+
+- プラグイン無効化（`NYASH_DISABLE_PLUGINS=1`）でコア機能のみテスト
+- JoinIR厳格モード（`HAKO_JOINIR_STRICT=1`）で不正な制御フローを即座に検出
+- 数値行のみ抽出して検証（余計なログを排除）
diff --git a/tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_llvm_exe.sh b/tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_llvm_exe.sh
new file mode 100644
index 00000000..a68b05c5
--- /dev/null
+++ b/tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_llvm_exe.sh
@@ -0,0 +1,38 @@
+#!/bin/bash
+# Phase 115: if-only call result merge parity (LLVM EXE)
+
+source "$(dirname "$0")/../../../lib/test_runner.sh"
+source "$(dirname "$0")/../../../lib/llvm_exe_runner.sh"
+export SMOKES_USE_PYVM=0
+require_env || exit 2
+
+llvm_exe_preflight_or_skip || exit 0
+
+# Phase 97/98/100 SSOT: plugin dlopen check → build only if needed → dlopen recheck.
+FILEBOX_SO="$NYASH_ROOT/plugins/nyash-filebox-plugin/libnyash_filebox_plugin.so"
+MAPBOX_SO="$NYASH_ROOT/plugins/nyash-map-plugin/libnyash_map_plugin.so"
+STRINGBOX_SO="$NYASH_ROOT/plugins/nyash-string-plugin/libnyash_string_plugin.so"
+CONSOLEBOX_SO="$NYASH_ROOT/plugins/nyash-console-plugin/libnyash_console_plugin.so"
+INTEGERBOX_SO="$NYASH_ROOT/plugins/nyash-integer-plugin/libnyash_integer_plugin.so"
+
+LLVM_REQUIRED_PLUGINS=(
+  "FileBox|$FILEBOX_SO|nyash-filebox-plugin"
+  "MapBox|$MAPBOX_SO|nyash-map-plugin"
+  "StringBox|$STRINGBOX_SO|nyash-string-plugin"
+  "ConsoleBox|$CONSOLEBOX_SO|nyash-console-plugin"
+  "IntegerBox|$INTEGERBOX_SO|nyash-integer-plugin"
+)
+LLVM_PLUGIN_BUILD_LOG="/tmp/phase115_if_only_call_merge_plugin_build.log"
+llvm_exe_ensure_plugins_or_fail || exit 1
+
+INPUT_HAKO="$NYASH_ROOT/apps/tests/phase115_if_only_call_merge_min.hako"
+OUTPUT_EXE="$NYASH_ROOT/tmp/phase115_if_only_call_merge_llvm_exe"
+
+EXPECTED=$'2\n3'
+EXPECTED_LINES=2
+LLVM_BUILD_LOG="/tmp/phase115_if_only_call_merge_build.log"
+if llvm_exe_build_and_run_numeric_smoke; then
+  test_pass "phase115_if_only_call_merge_llvm_exe: output matches expected (2\\n3)"
+else
+  exit 1
+fi
diff --git a/tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_vm.sh b/tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_vm.sh
new file mode 100644
index 00000000..1419fcbe
--- /dev/null
+++ b/tools/smokes/v2/profiles/integration/apps/phase115_if_only_call_merge_vm.sh
@@ -0,0 +1,55 @@
+#!/bin/bash
+# Phase 115: if-only call result merge parity (VM)
+#
+# Verifies that if-only with call result merge works correctly.
+
+source "$(dirname "$0")/../../../lib/test_runner.sh"
+source "$(dirname "$0")/../../../lib/output_validator.sh"
+export SMOKES_USE_PYVM=0
+require_env || exit 2
+
+PASS_COUNT=0
+FAIL_COUNT=0
+RUN_TIMEOUT_SECS=${RUN_TIMEOUT_SECS:-10}
+
+INPUT="$NYASH_ROOT/apps/tests/phase115_if_only_call_merge_min.hako"
+
+echo "[INFO] Phase 115: if-only call result merge parity (VM) - $INPUT"
+
+set +e
+OUTPUT=$(timeout "$RUN_TIMEOUT_SECS" env \
+  NYASH_DISABLE_PLUGINS=1 \
+  HAKO_JOINIR_STRICT=1 \
+  "$NYASH_BIN" --backend vm "$INPUT" 2>&1)
+EXIT_CODE=$?
+set -e
+
+if [ "$EXIT_CODE" -eq 124 ]; then
+  echo "[FAIL] hakorune timed out (>${RUN_TIMEOUT_SECS}s)"
+  FAIL_COUNT=$((FAIL_COUNT + 1))
+elif [ "$EXIT_CODE" -eq 0 ]; then
+  EXPECTED=$'2\n3'
+  if validate_numeric_output 2 "$EXPECTED" "$OUTPUT"; then
+    echo "[PASS] Output verified: 2\\n3"
+    PASS_COUNT=$((PASS_COUNT + 1))
+  else
+    echo "[INFO] output (tail):"
+    echo "$OUTPUT" | tail -n 50 || true
+    FAIL_COUNT=$((FAIL_COUNT + 1))
+  fi
+else
+  echo "[FAIL] hakorune failed with exit code $EXIT_CODE"
+  echo "[INFO] output (tail):"
+  echo "$OUTPUT" | tail -n 50 || true
+  FAIL_COUNT=$((FAIL_COUNT + 1))
+fi
+
+echo "[INFO] PASS: $PASS_COUNT, FAIL: $FAIL_COUNT"
+
+if [ "$FAIL_COUNT" -eq 0 ]; then
+  test_pass "phase115_if_only_call_merge_vm: All tests passed"
+  exit 0
+else
+  test_fail "phase115_if_only_call_merge_vm: $FAIL_COUNT test(s) failed"
+  exit 1
+fi