port: the contract I read is 3185 lines shorter than the contract

docs/port/HANDOFF.md on main is 926 lines, last touched 9ca1eb5 on 2026-08-29.
The live one is 4111 lines at 27938aa, +3930/-745 across 96 commits I have never
read, several of them addressed to the port by name. The Decoder writes HANDOFF
on origin/auto/no-disc-and-menu-captures; main is a hundred-odd commits behind
it; I open main's copy every iteration as instructed.

So the rule meant to prevent this cannot detect it. tools/port/blocked-provenance
recovers each row's derivation from history rather than memory -- git log -S on
the row's key phrase -- and all 27 open rows derive from 9ca1eb5, because
HANDOFF-on-main has not moved. A constant cannot separate a fresh row from a
rotten one. Withdrawn in BLOCKED.md: 'HANDOFF has not moved in four milestones'
was missing the qualifier that carried its meaning.

The tool's first version silently missed its own known positive: P6 looping vs
712cac8, whose 9.44 s answer this port already ships. 'looping' did not stem to
'loop', 'menu' was stoplisted, and a >=2-shared-words threshold dropped the rest.
The threshold was the defect -- two common words outscored one rare one -- so
ranking is now by log(N/df) with no cutoff at all, and the control passes at rank
1 of 7 without touching the stoplist. Every discard is counted: struck rows,
sub-rank pairs, stoplisted words. Same rule applied to check-claims, which now
reports the 40 occurrences it suppresses; the Decoder reached it the same day
from the opposite failure, a silent suppression path making a clean run
unfalsifiable.

The reading list found two open rows already answered: the plate's pulse period
(120, not 105) and the main menu having no idle self-return, which refutes the B
row's own reasoning.

Refutation attempted on '+0x08 is the loop length', the claim the port was about
to build on. It survives: their falsifier re-run on my own read of the disc gives
0 violations in 1781 records, and on the eight records this port animates their
table reproduces cell for cell. Adopted -- screen.rs exports loop_length_units
and ScreenView._loop_period prefers it, announcing any disagreement rather than
silently resolving it. The value does not change: authored/timing.json already
had 120 from a wall-clock measurement, so a disc field and an emulator stopwatch
agree while sharing no instrument.

Two asks filed: the field is exposed in no public API on any ref, so the port
reads four bytes it should not own; and eleven focus records declare the same
120-unit cycle while only the plate is authored to animate, which is behavioural
and not mine to infer.

Every asserting check passes; oracle RMSEs unchanged, as 120 == 120 predicts.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF

crates/sylpheed-export/src/screen.rs

@@ -108,10 +108,44 @@ pub struct FocusElement {
     pub keyframes: Vec<Keyframe>,
 }
 
+/// A nested record's declared cycle length, or `None` if the span is not one.
+///
+/// Guarded rather than trusted: the magic is checked and the header must fit,
+/// because an offset that has drifted returns a plausible number otherwise.
+fn record_loop_units(bundle: &[u8], off: usize, size: usize) -> Option<u32> {
+    let span = bundle.get(off..off.checked_add(size)?)?;
+    if span.len() < 12 || &span[..4] != b"RATC" {
+        return None;
+    }
+    Some(u32::from_be_bytes(span[8..12].try_into().ok()?))
+}
+
 #[derive(Serialize)]
 pub struct Focus {
     /// The `.rat` leaf this came from, e.g. `ptbtn01f.rat`.
     pub record: String,
+    /// The record header's `+0x08`: **where the cycle restarts**, in keyframe
+    /// units — which is not the same thing as the last keyframe's time.
+    ///
+    /// `ptbtn00f`, the `PRESS Ⓐ` plate's glow, ramps 0→80→0 over **105** units
+    /// inside a **120**-unit cycle and rests dark for the remaining 15. Deriving
+    /// the period from the largest keyframe time — what the port did until now —
+    /// runs it 14 % fast and deletes the dark rest entirely.
+    ///
+    /// Decoded by the Decoder (`07e93ce`, `docs/re/structures/ui-record-loop-length.md`,
+    /// delivered in HANDOFF `27938aa`) and **re-run here before adoption**, with
+    /// their falsifier and their non-triviality control:
+    /// `cargo run -p sylpheed-export --example record_loop_control`. Disc-wide
+    /// 1 781 timed records, 92.3 % exact, 7.7 % hold, **0 declaring less than
+    /// their own last pose**; on the eight records this port animates, seven
+    /// exact and `ptbtn00f` the one hold.
+    ///
+    /// ⚠️ Read here rather than through `sylpheed_formats` because the field is
+    /// exposed in **no public API on any ref** — it lives in an example and a
+    /// test. `parse_build` publishes each record's `(offset, size)`, so this is
+    /// four big-endian bytes at a documented offset inside a span whose magic is
+    /// checked, not a second decoder. **Delete it the day the crate exposes it.**
+    pub loop_length_units: Option<u32>,
     /// Back-to-front, in the leaf's own declaration order.
     pub elements: Vec<FocusElement>,
 }
@@ -453,7 +487,11 @@ pub fn export_build(
             Ok(if fes.is_empty() {
                 None
             } else {
-                Some(Focus { record: rec.to_string(), elements: fes })
+                Some(Focus {
+                    record: rec.to_string(),
+                    loop_length_units: record_loop_units(bundle, off, size),
+                    elements: fes,
+                })
             })
         };
 
@@ -510,7 +548,11 @@ pub fn export_build(
                         });
                     }
                     if !fes.is_empty() {
-                        focus = Some(Focus { record: rec, elements: fes });
+                        focus = Some(Focus {
+                            record: rec,
+                            loop_length_units: record_loop_units(bundle, off, size),
+                            elements: fes,
+                        });
                     }
                 }
             }