Bound GPU backbuffer layer retention

docs/engine-re.md

@@ -3876,11 +3876,15 @@ The port now gives op `0xd5` a dedicated non-presenting deadline wait which keep
 barrier held, while backbuffer `0x222` suspends that barrier and synchronously snapshots the exact callback
 state before returning. Incremental range publications preserve the preceding backbuffer: the software
 backend skips its black clear and the GPU backend appends the new draw layers over its retained stage.
-An explicit backbuffer `0x20e` disables preservation for the following publication, and ordinary `0x20c`
-continues to replace the retained stage as a full reconstruction. This removes the pre-animation
-full-popup frame and supplies the preserved pixels needed by the `[0,59999)` close endpoint without
-special-casing BUNKI handles. A one-frame black flicker is still visible at the end of close, however, so
-some later publication or retained-stage reset remains to be reconciled.
+An explicit backbuffer `0x20e` disables preservation for the following publication. Native
+`gfx_render_frame@0x4820b0`, used by ordinary `0x20c`, likewise has no implicit clear: it draws all visible
+objects over the selected target and leaves clearing to `0x20e`. The software backend can apply that rule
+literally to its pixel buffer. Godot GPU nodes require a separate retention policy: partial ranges append
+over the retained stage, nonempty full publications replace/reuse the existing Sprite2D pool, and empty
+full publications leave the preceding stage untouched. Treating every full publication as an append caused
+unbounded draw-node accumulation and rapid slowdown. This split removes the pre-animation full-popup frame
+and prevents BUNKI's post-close empty `0x20c`—issued after releasing both the capture and stable menu
+objects—from reconstructing an empty selected set over black, without stacking complete scenes.
 
 Surface text also remains modeled metadata rather than pixels. Selected-target publication now projects
 that metadata into the destination surface, and the final Godot labels inherit the retained object's
@@ -3892,8 +3896,10 @@ text trails even though preserving the underlying software pixels or GPU draw la
 
 Focused timed-callback boundary coverage passes with the complete 532-test engine suite. The Godot build
 is warning-free and the Himegari-targeted threaded frontend selftest passes. User testing confirmed the
-premature opening frame and accumulated text trails are gone. The close-only black frame remains the visual
-acceptance gap.
+premature opening frame and accumulated text trails are gone. The close-only black frame was traced to the
+port's incorrect implicit clear on an empty full `0x20c`. The first preservation correction over-retained
+GPU draw nodes; the bounded full/partial/empty publication policy passes the frontend selftest. User
+retesting accepted both the restored performance and close behavior on 2026-07-30.
 
 ### Formatted integers on text surfaces — opcode `0x205` (2026-07-21)
 

docs/opcode-reference.md

@@ -896,13 +896,13 @@ The worker clips the paired source and destination rectangles against both surfa
 - **evidence:** Ghidra /v2: op_0x20b_handler@0x422d50 converts x/y/width/height to an exclusive rectangle, clamps alpha to 255, repacks RGB to native ARGB, and calls the surface manager's rectangle-fill path at 0x4790e0. HISTORY.BIN clears each 600x30 name strip on temporary surface 0xc1 before draw-string.
 
 ### 0x20c `present-frame` (present-frame, argc 0)
-- **summary:** Present the composited frame; label_1235a uses this on the read/message-skip branch to expose the completed foreground endpoint immediately.
+- **summary:** Draw every visible retained object over the selected target without implicitly clearing it, then present the composited backbuffer; label_1235a uses this on the read/message-skip branch to expose the completed foreground endpoint immediately.
 - **grounding:** source=investigation, confidence=high
 - **depends on:** 0x223, 0x1c7, 0x1cc
 - **depended on by:** 0x21, 0x22, 0x23, 0x24, 0x25, 0x20d, 0x223
-- **evidence:** Ghidra: dispatch table FUN_00413860 param_1[0x26e9f]=gfx_op_0x20c_present_frame; 0x26e9f-0x26c93=0x20c. 2026-07-08.
+- **evidence:** Ghidra /v2: dispatch table FUN_00413860 param_1[0x26e9f]=gfx_op_0x20c_present_frame; 0x26e9f-0x26c93=0x20c. The handler calls gfx_render_frame@0x4820b0, which begins a D3D scene, consumes queued surface commands, draws all visible retained objects, ends the scene, and presents the backbuffer without calling d3d_clear_render_target_black; opcode 0x20e is the separate clear. Refined 2026-07-30.
 
-Native handler gfx_op_0x20c_present_frame -> gfx_render_frame @0x4820b0. This is an explicit retained-state publication boundary, not a continuously visible object-store mutation. The read/message-skip branch resets the animation service then presents; the port publishes and snaps pending 0x223 state here. Normal playback branches to 0x21c, which owns repeated render/wait/resume. Headless hosts remain non-blocking.
+Native handler gfx_op_0x20c_present_frame -> gfx_render_frame @0x4820b0. This is an explicit retained-state publication boundary, not a continuously visible object-store mutation. The renderer does not clear its selected target: opcode 0x20e owns explicit black clearing, so full-frame publication preserves preceding target pixels beneath its redraw. The read/message-skip branch resets the animation service then presents; the port publishes and snaps pending 0x223 state here. Normal playback branches to 0x21c, which owns repeated render/wait/resume. Headless hosts remain non-blocking.
 
 ### 0x20d `select-render-target` (select-render-target, argc 1)
 - **summary:** Select an offscreen surface slot as Direct3D render target 0, or restore the device backbuffer when the operand is at least 1000.