feat(pipeline): A/B mode for strength sweep (old-vs-new depth maps)

--alt-work renders each test frame from a second depth dir alongside the
new full-range maps, so the GPU run proves the rev-3 normalization fix
(018909b) beats the washed-out rev-2 maps rather than just looking
better. Persisted the rev-2 maps under tools/out/compare/rev2_depths so
the A/B is reproducible. Doc updated with the one-shot command.

Workstation note: host 192.168.1.26 is up but ComfyUI (:8188) wasn't
running this iteration — needs a manual start before the sweep.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.dev/2026-06-15-diffusion-pipeline-reliability.md

@@ -42,15 +42,20 @@ With a weak signal you crank strength to force adherence; a strong signal wants
 *less*. `bake_atlas.py` defaults `--strength 0.85`.
 
 1. Re-probe the workstation: `python3 tools/comfy-spike/comfy.py probe http://192.168.1.26:8188`
-2. **Strength sweep** (tool already written, validated):
+   (2026-06-15 iter 2: host pings but **port 8188 closed — ComfyUI not running**; needs a
+   manual start on the workstation before any of the below.)
+2. **A/B + strength sweep in one run** (tool written & validated; old rev-2 maps persisted
+   to `tools/out/compare/rev2_depths/` so the fix is provable, not just "looks better"):
    ```
    python3 tools/comfy-spike/sweep_strength.py http://192.168.1.26:8188 \
-       --seed-dir tools/out/atlas/7 --open r8_N --closed r0_N \
-       --strengths 0.55,0.7,0.85,1.0
+       --seed-dir tools/out/atlas/7 --alt-work tools/out/compare/rev2_depths \
+       --open r8_N --closed r0_N --strengths 0.55,0.7,0.85,1.0
    ```
-   → `tools/out/compare/sweep_<run>.png`. Read adherence: does the rendered passage
-   land on the black recess? does the closed wall stay a wall (no phantom door)?
-   Pick the lowest strength that still honors geometry, update `bake_atlas.py` default.
+   → `tools/out/compare/sweep_<run>.png`: each frame gets a NEW row (full-range maps) and
+   an OLD row (washed-out rev-2) across every strength. Read adherence: does the rendered
+   passage land on the black recess? does the closed wall stay a wall (no phantom door)?
+   Expect NEW ≫ OLD; pick the lowest strength that still honors geometry, update
+   `bake_atlas.py --strength 0.85` default. (Drop `--alt-work` once the win is confirmed.)
 3. Then re-bake a full atlas at the chosen strength and spot-check a montage vs the
    old `acc8137`/`a12bcbb` bakes.
 

tools/comfy-spike/sweep_strength.py

@@ -73,6 +73,8 @@ def main():
     ap = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
     ap.add_argument("url")
     ap.add_argument("--seed-dir", default=os.path.join(REPO, "tools", "out", "atlas", "7"))
+    ap.add_argument("--alt-work", default="", help="optional 2nd depth dir to A/B (e.g. tools/out/compare/rev2_depths "
+                    "= the old washed-out maps); adds an OLD row per frame so old-vs-new adherence is conclusive")
     ap.add_argument("--open", default="r8_N", help="frame id for the open-passage test")
     ap.add_argument("--closed", default="r0_N", help="frame id for the closed-wall test")
     ap.add_argument("--strengths", default="0.55,0.7,0.85,1.0")
@@ -84,21 +86,24 @@ def main():
     strengths = [float(s) for s in a.strengths.split(",") if s.strip()]
     run = os.getpid()
     cases = [(a.open, OPEN_BODY), (a.closed, WALL_BODY)]
+    # (source-tag, depth-dir): NEW always; OLD too when --alt-work is given.
+    sources = [("NEW", work)] + ([("OLD", a.alt_work)] if a.alt_work else [])
 
     rows = []
     for frame, body in cases:
-        depth = os.path.join(work, f"{frame}_depth.png")
-        if not os.path.exists(depth):
-            sys.exit(f"!! missing depth map {depth} — bake the atlas first")
         prompt = STYLE + body
-        imgs = {}
-        for s in strengths:
-            prefix = f"sweep_{frame}_{int(s*100)}_{run}"
-            print(f"[{frame} @ strength {s}] rendering ...", flush=True)
-            out = render(a.url, depth, prompt, s, a.seed, prefix, a.wait)
-            if out:
-                imgs[s] = out
-        rows.append((frame, depth, imgs))
+        for tag, srcdir in sources:
+            depth = os.path.join(srcdir, f"{frame}_depth.png")
+            if not os.path.exists(depth):
+                sys.exit(f"!! missing depth map {depth} — bake the atlas first")
+            imgs = {}
+            for s in strengths:
+                prefix = f"sweep_{frame}_{tag}_{int(s*100)}_{run}"
+                print(f"[{frame}·{tag} @ strength {s}] rendering ...", flush=True)
+                out = render(a.url, depth, prompt, s, a.seed, prefix, a.wait)
+                if out:
+                    imgs[s] = out
+            rows.append((f"{frame}·{tag}", depth, imgs))
 
     out_dir = os.path.join(REPO, "tools", "out", "compare")
     os.makedirs(out_dir, exist_ok=True)