diff --git a/crates/sylpheed-formats/examples/leaf_keyframes.rs b/crates/sylpheed-formats/examples/leaf_keyframes.rs
new file mode 100644
index 00000000..99bce905
--- /dev/null
+++ b/crates/sylpheed-formats/examples/leaf_keyframes.rs
@@ -0,0 +1,32 @@
+//! Dump the keyframes of any nested `.rat` leaf by name.
+//!
+//!     cargo run -p sylpheed-formats --example leaf_keyframes -- GP_TITLE ptbtn00.rat 2 3 4
+use sylpheed_formats::{pak::PakArchive, ui_layout};
+use std::path::PathBuf;
+
+fn main() {
+    let root = PathBuf::from(std::env::var("SYLPHEED_DISC").expect("SYLPHEED_DISC"));
+    let argv: Vec<String> = std::env::args().skip(1).collect();
+    let pak = argv[0].clone();
+    let rec = argv[1].clone();
+    let builds: Vec<usize> = argv[2..].iter().filter_map(|a| a.parse().ok()).collect();
+    let ar = PakArchive::open(root.join(format!("dat/{pak}.pak"))).expect("pak");
+    for e in builds {
+        let Ok(by) = ar.read(&ar.entries()[e]) else { continue };
+        let Some(b) = ui_layout::parse_build(&by) else { continue };
+        let Some(&(lo, ls)) = b.records.get(rec.as_str()) else { continue };
+        let leaf = &by[lo..(lo + ls).min(by.len())];
+        println!("=== {pak} entry {e} — {rec} (leaf {ls} bytes) ===");
+        if let Some(u) = ui_layout::loop_length_units(leaf) { println!("    declared loop: {u} units"); }
+        if let Some(lb) = ui_layout::parse_build(leaf) {
+            for el in &lb.elements {
+                println!("  {} — {} keyframes", el.name, el.keyframes.len());
+                for (i, k) in el.keyframes.iter().enumerate() {
+                    println!("    kf{i:<2} t={:<5} x={:<6} y={:<6} fade={:08X} (alpha {:3})",
+                        k.time.map(|t| t.to_string()).unwrap_or_else(|| "-".into()),
+                        k.x, k.y, k.fade, k.fade >> 24);
+                }
+            }
+        }
+    }
+}
diff --git a/docs/re/label-check-and-the-alpha-80-refutation.md b/docs/re/label-check-and-the-alpha-80-refutation.md
new file mode 100644
index 00000000..469685ca
--- /dev/null
+++ b/docs/re/label-check-and-the-alpha-80-refutation.md
@@ -0,0 +1,77 @@
+# A check that reads the label, not the citation — and one refutation it turned up
+
+**Question:** do the element labels in my F5/F6 findings still agree with the
+declared data?
+
+**What the human looks at:** `python3 tools/re-capture/check_labels.py` — every
+line PASS. Then `--selftest`, which must FAIL.
+
+**What this does NOT cover:** labels with **no** declared counterpart. Named
+below; that gap is real and unclosed.
+
+## ✅ The check
+
+Three of my errors were the **label**, not the measurement — `0x3003` read as a
+different role from `0x3002`, and `ptcopyright` called "the plate" twice, the
+second time on a page written *after* I had corrected it. Every number was right.
+A correction living in one document did not reach the next one I wrote.
+
+`sylpheed-port` built `check-authored-vs-declared` for values with a declared
+counterpart, and named the gap it leaves: a value that exists only in a capture
+and names an element rests entirely on my label. **This is that case.** Each
+identification was originally *made* by matching a declared quantity, so each is
+re-derivable:
+
+```
+[PASS] 1.1841 vs 1.2000 ( 1.3%)  pteff03a is the 720-unit leaf, not a second 600
+[PASS] 1.3017 vs 1.3333 ( 2.4%)  pteff03a is the sy=800 strip
+[PASS] 0.0993 vs 0.1000 ( 0.7%)  the pulsing slot has the declared 120-unit period
+[PASS] 0.7500 vs 0.7333 ( 2.3%)  the -0.54 quad is ptcopyright (22-unit ramp)
+```
+
+Both captures, eight checks, all pass.
+
+**The control is the point.** `--selftest` points the plate label at
+`ptcopyright` — the exact error I made — and it must fail:
+
+```
+[FAIL] 0.0180 vs 0.1000 (82.0%)  the pulsing slot has the declared 120-unit period
+OK: mislabel detected (2 failures)
+```
+
+82–83 % against a 5 % tolerance, and the other three still pass, so the failure
+is localised rather than a global break.
+
+## 🔴 Refutation — the port's "all five figures are also declared on the disc"
+
+Attempted against their audit, and it **lands for one of the five**.
+
+`ptbtn00f`'s **peak alpha of 80** is a figure I measured and sent them. The disc
+does not declare it:
+
+* `ptbtn00.rat` **parent** (`GP_TITLE` entries 2 and 3): `t=0 α0 · 214 α0 ·
+  236 α255 · 238 α255 · 244 α0`;
+* its **leaf**: declared loop **120 units**, one keyframe, **α255 flat**.
+
+**Nothing declares 80, and nothing in the declaration pulses at all.** The
+*period* is declared and checks out; the *amplitude* is capture-only. So that
+figure cannot be arbitrated by their check, and "all five declared" is wrong for
+it — which matters because a check reporting PASS over a value it cannot see is
+the failure mode their own note warns about.
+
+## 🟡 And it opens a fourth label question — not mine originally
+
+The corpus says *"the plate pulses via **`ptbtn00f`** on a declared 120-unit
+loop"*. The 120-unit loop belongs to **`ptbtn00.rat`**, whose leaf contains
+**`ptbtn00.t32`** — there is no `ptbtn00f` in it. `ptbtn00f` is a real element
+elsewhere (the blend page has it at `0x0112`, additive), but the thing carrying
+the declared 120-unit loop is not obviously it.
+
+Recorded as 🟡, not corrected: my check verifies the **period**, which is what the
+identification rests on, and the period is right whichever name is attached.
+
+## Reach
+
+The check covers labels made by matching a declared quantity. A label with no
+declared counterpart — the leaf **rate**, and now this **α80** — is still
+unchecked, on my side as on theirs.
diff --git a/tools/re-capture/check_labels.py b/tools/re-capture/check_labels.py
new file mode 100755
index 00000000..9cd1e090
--- /dev/null
+++ b/tools/re-capture/check_labels.py
@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+"""Re-derive every element LABEL in the F5/F6 findings from captures + disc.
+
+⚠️ WHY THIS EXISTS. Three of my errors were the label, not the measurement:
+`0x3003` read as a different role from `0x3002`; `ptcopyright` called "the plate"
+in the clock-conflict page; and `ptcopyright` called "the plate" AGAIN in the F6
+page, written after that correction. Every number was right. What it was pointed
+at was not, and a correction in one document did not reach the next.
+
+sylpheed-port has `check-authored-vs-declared` for values with a declared
+counterpart. It cannot cover a value that exists only in a capture and names an
+element -- that one rests entirely on my label. This is that case.
+
+Each identification below was originally MADE by matching a declared quantity, so
+each is re-derivable. If a label drifts, the agreement it was built on breaks.
+
+    python3 check_labels.py            # check
+    python3 check_labels.py --selftest # prove it can fail
+"""
+import sys, collections
+sys.path.insert(0, __file__.rsplit('/', 1)[0])
+from read_draws import read
+
+CAPS = {'f6': '/sylph-home/re/f6/xenia_re_ui_draws_01.log',
+        'f6b': '/sylph-home/re/f6b/xenia_re_ui_draws_01.log'}
+SWEEP_PAGE = '8154'
+PTCOPY_X = (-0.54, 0.54, 0.54, -0.54)
+
+def features(path, swap_plate=False):
+    fr = read(path); fs = sorted(fr)
+    f = {}
+    pairs = []
+    for fm in fs:
+        adds = [q for q in fr[fm] if q.blend == '0x01010101' and q.page.startswith(SWEEP_PAGE)]
+        if len(adds) >= 2: pairs.append((fm, adds[0], adds[1]))
+    def cycles(idx, sign):
+        out = []
+        for i in range(1, len(pairs)):
+            d = pairs[i][idx].cx - pairs[i-1][idx].cx
+            if (sign > 0 and d < -1.0) or (sign < 0 and d > 1.0): out.append(pairs[i][0])
+        return out
+    ca, cb = cycles(1, +1), cycles(2, -1)
+    f['pteff03_period']  = ca[1] - ca[0]
+    f['pteff03a_period'] = cb[1] - cb[0]
+    import math
+    def length(q):
+        pts = [(x*640, y*360) for x, y in q.verts]
+        return max(math.dist(pts[i], pts[j]) for i in range(4) for j in range(i+1, 4))
+    f['pteff03_len']  = sum(length(p[1]) for p in pairs) / len(pairs)
+    f['pteff03a_len'] = sum(length(p[2]) for p in pairs) / len(pairs)
+    # parent ramp: sweep quad A's alpha climbing to full from its cycle start
+    start = ca[0]
+    seq = [(fm, a.alpha) for fm, a, _ in pairs if fm >= start]
+    f['parent_ramp'] = next(fm for fm, al in seq if al >= 239) - start
+    # ptcopyright: fade-in length of the -0.54..0.54 quad
+    cop = [(fm, q.alpha) for fm in fs for q in fr[fm]
+           if tuple(round(v[0], 2) for v in q.verts) == PTCOPY_X]
+    f['ptcopyright_ramp'] = next(fm for fm, a in cop if a >= 255) - cop[0][0]
+    # ptbtn00f: the slot that comes and goes
+    slots = collections.defaultdict(list)
+    for fm in fs:
+        for q in fr[fm]: slots[(q.page[:4], round(q.cx, 2))].append(fm)
+    cands = []
+    for k, v in slots.items():
+        if len(v) < 200: continue
+        gaps = sum(1 for i in range(1, len(v)) if v[i]-v[i-1] > 1)
+        if gaps >= 8: cands.append((gaps, k, v))
+    cands.sort(reverse=True)
+    if swap_plate and len(cands) > 0:      # selftest: point the label at ptcopyright instead
+        f['pulse_period'] = f['ptcopyright_ramp']
+    else:
+        v = cands[0][2]
+        ons = [v[0]] + [v[i] for i in range(1, len(v)) if v[i]-v[i-1] > 1]
+        per = sorted(ons[i]-ons[i-1] for i in range(1, len(ons)))
+        f['pulse_period'] = per[len(per)//2]
+    return f
+
+# label -> (derived ratio, declared value, tolerance, what the label asserts)
+def checks(f):
+    return [
+      ("pteff03a is the 720-unit leaf (not a second copy of the 600)",
+       f['pteff03a_period']/f['pteff03_period'], 720/600, 0.05),
+      ("pteff03a is the sy=800 strip, pteff03 the sy=600",
+       f['pteff03a_len']/f['pteff03_len'], 800/600, 0.06),
+      ("the pulsing slot is ptbtn00f (120-unit loop vs the sweep's 600 leaf units)",
+       f['pulse_period']/f['pteff03_period'], 0.1, 0.05),
+      ("the -0.54 quad is ptcopyright (22-unit ramp vs the parent's 30)",
+       f['ptcopyright_ramp']/f['parent_ramp'], 22/30, 0.08),
+    ]
+
+def run(swap=False):
+    bad = 0
+    for name, path in CAPS.items():
+        f = features(path, swap_plate=swap)
+        print(f"  {name}:")
+        for label, got, want, tol in checks(f):
+            err = abs(got-want)/want
+            ok = err <= tol
+            bad += not ok
+            print(f"    [{'PASS' if ok else 'FAIL'}] {got:.4f} vs {want:.4f} ({err*100:4.1f}%, tol {tol*100:.0f}%)  {label}")
+    return bad
+
+if __name__ == '__main__':
+    if '--selftest' in sys.argv:
+        print("SELFTEST — the plate label deliberately pointed at ptcopyright.")
+        print("A check that cannot fail here would not have caught the real error.\n")
+        bad = run(swap=True)
+        print(f"\n{'OK: mislabel detected' if bad else 'BROKEN: mislabel NOT detected'} ({bad} failures)")
+        sys.exit(0 if bad else 1)
+    print("Element labels in the F5/F6 findings, re-derived from captures + disc:\n")
+    bad = run()
+    print(f"\n{'all labels agree' if not bad else str(bad)+' LABEL(S) DRIFTED'}")
+    sys.exit(1 if bad else 0)