diff --git a/docs/modernization/debt.md b/docs/modernization/debt.md
index e4d7d01..224b428 100644
--- a/docs/modernization/debt.md
+++ b/docs/modernization/debt.md
@@ -282,6 +282,10 @@ agent or engineer to remove them without reconstructing context from chat.
   callback body now routes through `stroke_draw_pad_face_callback_body(...)`;
   the retained path still owns the concrete pad shader setup, face selection,
   and copy wiring.
+- 2026-06-13: DEBT-0036 was narrowed again. `Canvas::draw_merge()` temporary
+  paint branch now routes through `draw_merge_temporary_paint_branch(...)`;
+  the retained path still owns the concrete temporary-paint setup, texture
+  binding, and draw ordering.
 - 2026-06-13: DEBT-0036 was narrowed again. `Canvas::stroke_draw()` main-pass
   live face orchestration now routes through
   `execute_legacy_canvas_stroke_live_pass_with_face_framebuffers(...)`; the
diff --git a/docs/modernization/tasks.md b/docs/modernization/tasks.md
index bdc4e8c..2157158 100644
--- a/docs/modernization/tasks.md
+++ b/docs/modernization/tasks.md
@@ -1821,6 +1821,40 @@ ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_composito
 | --- | --- | ---: | --- | --- |
 | 2026-06-13 | STR-018 | +1 renderer boundary and OpenGL parity | `ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_compositor|pp_paint_renderer_stroke_execution" --output-on-failure` | `037be1a7` |
 
+### STR-031 - Extract Draw Merge Temporary Paint Branch
+
+Status: Done
+Score: +1 renderer boundary and OpenGL parity
+Debt: `DEBT-0036`
+Scope: `src/canvas.cpp`, `src/legacy_canvas_draw_merge_services.h`, `tests/paint_renderer/compositor_tests.cpp`
+
+Goal:
+
+Move the inline temporary paint branch in `Canvas::draw_merge()` into a
+retained helper so the callsite keeps only branch selection and concrete GL
+object wiring.
+
+Done Checks:
+
+- `Canvas::draw_merge()` no longer builds the temporary paint branch inline.
+- Regression coverage proves the extracted helper preserves paint-branch order.
+- `docs/modernization/debt.md` records the reduced draw-merge temporary-paint
+  surface.
+
+Closeout: `91d4da09`
+
+Validation:
+
+```powershell
+ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_compositor|pp_paint_renderer_stroke_execution" --output-onfailure
+```
+
+### Completed Task Log
+
+| Date | Task | Score | Validation | Commit |
+| --- | --- | ---: | --- | --- |
+| 2026-06-13 | STR-031 | +1 renderer boundary and OpenGL parity | `ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_compositor|pp_paint_renderer_stroke_execution" --output-onfailure` | `91d4da09` |
+
 ### STR-012 - Extract Preview Final Composite Orchestration
 
 Status: Done