diff --git a/B04_PreProcess/B04_PreProcess_Engine_Watershed_Analyze.py b/B04_PreProcess/B04_PreProcess_Engine_Watershed_Analyze.py
index 6534d92d..2fadf6dd 100644
--- a/B04_PreProcess/B04_PreProcess_Engine_Watershed_Analyze.py
+++ b/B04_PreProcess/B04_PreProcess_Engine_Watershed_Analyze.py
@@ -166,8 +166,12 @@ def preview_stages(
     """
     if len(vertices) < 2:
         return None
+    from B03_FileInput.B03_FileInput_Service_Chain import _log_steps
+
+    marks = [("시작", time.perf_counter())]
     route_line = LineString([(vertex.x, vertex.y) for vertex in vertices])
     region = resolve_primary_region(vertices, route_line, contour_features, stream_features)
+    marks.append(("1차 영역(resolve_primary_region)", time.perf_counter()))
     if region is None:
         return None
 
@@ -185,6 +189,7 @@ def preview_stages(
         logger.warning("배수유역: 등고선 하강 방향을 세우지 못해 흐름 판정을 건너뜁니다.")
         return StagePreview(region=region)
 
+    marks.append(("격자 확장·흐름 판정(expand_by_red_boundary)", time.perf_counter()))
     analysis = expansion.analysis
     spec = analysis.spec
     red = analysis.flow.reaches_road & analysis.flow.analyzed
@@ -194,6 +199,7 @@ def preview_stages(
     # 최종적으로 어느 도로 셀로 들어가는지를 봐야 하므로 도로만 흡수점으로 두고 다시 따라간다.
     routing = trace_flow(analysis.terrain, analysis.road) if analysis.road.count else None
     strength_curve = _preview_strength(analysis, routing, red, route_line.length)
+    marks.append(("흐름 강도(trace_flow)", time.perf_counter()))
 
     # ⑦ 2차 전체 배수유역 외곽선 = 적색 셀 전체의 외곽.
     boundary = outer_boundary(spec, red.reshape(spec.n_rows, spec.n_cols))
@@ -209,6 +215,8 @@ def preview_stages(
 
     # B05에 얹을 평균 흐름 화살표 — 셀 화살표는 도면 배율에서 안 보인다.
     flow_arrows = build_flow_arrows(analysis, analysis.flow)
+    marks.append(("외곽선·기본 관·화살표", time.perf_counter()))
+    _log_steps("배수유역 preview_stages", marks)
 
     logger.info(
         "배수유역: 단계 분석 %.1fs (확장 %d회, 최종 셀 %d개) — "
diff --git a/B04_PreProcess/B04_PreProcess_Router_Watershed.py b/B04_PreProcess/B04_PreProcess_Router_Watershed.py
index aec83a12..9beacc38 100644
--- a/B04_PreProcess/B04_PreProcess_Router_Watershed.py
+++ b/B04_PreProcess/B04_PreProcess_Router_Watershed.py
@@ -11,6 +11,7 @@ import asyncio
 import json
 import logging
 import math
+import time
 from pathlib import Path
 from typing import Any
 from uuid import UUID
@@ -389,9 +390,13 @@ async def get_primary_region(
             logger.info("배수유역: 저장된 분석 결과를 그대로 돌려줍니다 (%s).", stored_path)
             return {**saved, "from_cache": True}
 
+    from B03_FileInput.B03_FileInput_Service_Chain import _log_steps
+
+    marks = [("시작", time.perf_counter())]
     prepared = await _prepare(project_id)
     if isinstance(prepared, JSONResponse):
         return prepared
+    marks.append(("_prepare(도엽 읽기·좌표변환)", time.perf_counter()))
     preview = await asyncio.to_thread(
         preview_stages,
         prepared["vertices"],
@@ -403,6 +408,7 @@ async def get_primary_region(
             status_code=400,
             content={"status": "error", "message": "1차 배수유역을 정할 등고선이 없습니다."},
         )
+    marks.append(("preview_stages(유역 산정)", time.perf_counter()))
     region = preview.region
     to_lonlat = prepared["to_lonlat"]
     # 확장을 거치면 격자·해석 영역이 1차 영역보다 커진다. 최종본을 써야 화면과 어긋나지 않는다.
@@ -516,5 +522,7 @@ async def get_primary_region(
     _write_stage_arrays(prepared["stored_path"], preview, domain, spec)
     _write_road_routing(prepared["stored_path"], preview, spec, prepared["route_line"], to_lonlat)
     # 응답 자체를 캐시로 남긴다 — 다음 조회는 배열을 재조립하지 않고 이 파일을 그대로 준다.
+    marks.append(("응답 만들기·저장", time.perf_counter()))
+    _log_steps("배수유역 분석 내부", marks)
     _save_response(prepared["stored_path"], payload)
     return payload
diff --git a/B06_Section/B06_Section_Router_Confirm.py b/B06_Section/B06_Section_Router_Confirm.py
index c88978d8..8b5455f6 100644
--- a/B06_Section/B06_Section_Router_Confirm.py
+++ b/B06_Section/B06_Section_Router_Confirm.py
@@ -11,6 +11,7 @@
 import asyncio
 import json
 import logging
+import time
 from pathlib import Path
 from typing import Any
 from uuid import UUID
@@ -20,6 +21,7 @@ from fastapi import APIRouter, Body
 from fastapi.responses import JSONResponse
 
 from B03_FileInput.B03_FileInput_Repository import get_project_storage_relative_path
+from B03_FileInput.B03_FileInput_Service_Chain import _log_steps
 from B05_Profile.B05_Profile_Repository import confirm_route as confirm_route_status
 from B05_Profile.B05_Profile_Router_Confirm import _merge_uphill_overrides_into_longitudinal
 from B06_Section.B06_Section_Repository import (
@@ -212,6 +214,7 @@ async def save_sections(
     통째로 버려져 조작값이 사라진다. 그래서 여기서 정본 행을 만든다.
     """
     pool = get_db_pool()
+    marks = [("시작", time.perf_counter())]
     try:
         async with pool.acquire() as connection:
             existing = await get_longitudinal_section(connection, project_id, route_id)
@@ -240,6 +243,8 @@ async def save_sections(
                 request.standard_cross_section if request else None,
             )
 
+        marks.append(("기본설계 계산(미지정 측점)", time.perf_counter()))
+
         async with pool.acquire() as connection:
             await connection.begin()
             try:
@@ -294,6 +299,7 @@ async def confirm_sections(
             missing = await get_cross_sections_missing_design_chainages(connection, route_id)
             known = await get_cross_section_chainages(connection, route_id)
 
+        marks.append(("조회(종단·경로·미지정 측점)", time.perf_counter()))
         project_root = Path(resolve_stored_project_path(stored_path))
         # 행 자체가 없는 측점(구조물 등 비정규)도 확정 대상에 넣는다 — 정본이 없으면
         # 조회 때마다 프리뷰가 다시 계산돼 3D·수량이 확정 결과가 아니게 된다(2026-08-24).
@@ -336,8 +342,11 @@ async def confirm_sections(
                 await connection.rollback()
                 raise
 
+        marks.append(("확정 저장(트랜잭션)", time.perf_counter()))
+
         # 편집이 들어간 **뒤** 서버가 정본을 다시 낸다(임시저장과 같은 자리).
         await _recompute_stored_designs(project_id, route_id)
+        marks.append(("서버 재계산", time.perf_counter()))
 
         # 측구 방향(design.ditch_side) 변경을 B05 종단 정본 stations.uphill_side에 역반영한다(E-7).
         # 파일 기반·비치명적: 실패해도 확정은 유지한다.
@@ -363,6 +372,8 @@ async def confirm_sections(
                 project_id,
                 route_id,
             )
+        marks.append(("측구 방향 B05 역반영", time.perf_counter()))
+        _log_steps("B06 확정", marks)
         return SectionConfirmResponse(project_id=str(project_id), route_id=route_id)
     except Exception:
         logger.exception("B06 종횡단 확정 실패: project_id=%s", project_id)
diff --git a/B06_Section/B06_Section_Server_Calc_Prebuild.py b/B06_Section/B06_Section_Server_Calc_Prebuild.py
index 78645c13..fb9d7fb4 100644
--- a/B06_Section/B06_Section_Server_Calc_Prebuild.py
+++ b/B06_Section/B06_Section_Server_Calc_Prebuild.py
@@ -25,11 +25,13 @@ from __future__ import annotations
 import asyncio
 import json
 import logging
+import time
 from pathlib import Path
 from typing import Any
 from uuid import UUID
 
 from B03_FileInput.B03_FileInput_Repository import get_project_storage_relative_path
+from B03_FileInput.B03_FileInput_Service_Chain import _log_steps
 from B06_Section.B06_Section_Repository import (
     get_longitudinal_section,
     merge_longitudinal_section_data,
@@ -99,6 +101,7 @@ async def _recompute(project_id: UUID | str, route_id: int) -> int:
     from B06_Section.B06_Section_Router import get_section_detail
 
     project_uuid = UUID(str(project_id))
+    marks = [("시작", time.perf_counter())]
     # 상세 만들기(파일 읽기 위주)와 DB 두 건은 서로 기다릴 이유가 없다 — 같이 보낸다.
     # 원격 DB 라 순차로 내면 왕복이 그대로 더해진다(질의 하나 약 12ms, 2026-09-06 실측).
     pool = get_db_pool()
@@ -107,6 +110,7 @@ async def _recompute(project_id: UUID | str, route_id: int) -> int:
         run_with_connection(get_project_storage_relative_path, project_uuid),
         run_with_connection(get_longitudinal_section, project_uuid, route_id),
     )
+    marks.append(("종횡단 상세+DB 조회(병렬)", time.perf_counter()))
     payload = getattr(response, "model_dump", None)
     if payload is None:  # JSONResponse = 실패
         logger.warning("서버 재계산: 종횡단 상세를 못 받음 (route_id=%s)", route_id)
@@ -128,12 +132,15 @@ async def _recompute(project_id: UUID | str, route_id: int) -> int:
         if json.dumps(item.get("design"), sort_keys=True, default=str) != before[index]
     ]
 
+    marks.append(("포장·세월교 보정", time.perf_counter()))
+
     output = await asyncio.to_thread(
         run_bundle_json,
         BUNDLE,
         _NPM_SCRIPT,
         {"detail": detail, "context": _mass_haul_context()},
     )
+    marks.append(("Node 번들(면적·유토곡선)", time.perf_counter()))
     if not isinstance(output, dict):
         output = {}
     rows = output.get("areas")
@@ -182,6 +189,8 @@ async def _recompute(project_id: UUID | str, route_id: int) -> int:
         except Exception:
             await connection.rollback()
             raise
+    marks.append(("정본 저장", time.perf_counter()))
+    _log_steps("서버 재계산 내부", marks)
     logger.info(
         "서버 재계산: route_id=%s 설계 보정 %s곳, 구조물 면적 %s곳, 유토곡선 %s",
         route_id,