[HARDENING] PENDING-104 ADDENDUM 2: the concurrency frequency, measured

The item declared its own frequency unobservable and left the option space
undrafted for that reason. Jurist-directed measurement, no new id: 5 truly
overlapping session pairs across 44 real sessions on 3 distinct days in a
32-day window, disaggregated because two of the five are sub-four-minute
boundary artifacts and three are substantive.

Recorded with the item's limits rather than as a clean figure: the measure
is an upper bound (a resumed session's interval includes idle time), and a
first attempt returned 29 pairs on 14 days by bucketing timestamps into
clock hours, which counts a session ending at 17:10 and another starting
at 17:16 as concurrent. That error was caught by internal inconsistency —
29 cannot be a subset of 5 — and not by a control. It is recorded in the
item because the near-miss was a fivefold overstatement of the frequency
the steward is being asked to rule on.

Controls pass in both directions: must-detect on the documented 2026-08-31
collision, must-not-flag on a sequential handoff.

The judgement is left open. The frequency is observed; whether it warrants
a mechanism is not settled by observing it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017vKkg2EJF1rGwdFdBogwqx

PENDING.md

@@ -6553,7 +6553,23 @@ The block is filed with a trigger date **already in the past**, deliberately, so
 **Not filed as a new item, deliberately** — this is ADDENDUM 1's mechanism with the writer count changed, and a separate number would split one class across two dockets. **Also a datum for PENDING-89**: the digest and the sibling are differently positioned readers, and the sibling caught what the digest asserted. Constraint 6 working, on a day it was not being tested.
 
 **Files affected:** none.
-**Awaiting:** Steward authorization — the option space is not drafted here, because whether concurrent sessions are worth a mechanism is a steward judgement about how often two are run at once, which the executor cannot observe.
+**⚠ MEASURED 2026-09-01 — the frequency this item declared unobservable.** Jurist-directed, no new id, number only.
+
+| | |
+|---|---|
+| real sessions in window (mumble transcripts excluded) | **44** |
+| window | 2026-07-31 → 2026-09-01 (32 days) |
+| **truly overlapping session pairs** | **5** |
+| **distinct days carrying concurrency** | **3** |
+
+`2026-08-25 · 4 s` · `2026-08-27 · 3 h 36 m` · `2026-08-31 · 3 m 24 s` · `2026-08-31 · 28 m` · `2026-08-31 · 50 m`.
+**Disaggregated, because the total is not the decision-relevant number:** two of the five are under four minutes and are plausibly start/stop boundary artifacts; **three are substantive** (28 m, 50 m, 3 h 36 m), and all three fall on the two days this register already treats as incidents. Both controls pass — must-detect on the documented 2026-08-31 collision, must-not-flag on a sequential handoff.
+
+⚠ **The measure is an upper bound**: a resumed session's interval includes idle time, so two sessions can be counted as overlapping while only one was being worked.
+
+⚠ **A first attempt at this number returned 29 pairs on 14 days and was wrong** — it bucketed timestamps by clock hour, which counts a session ending at 17:10 and another starting at 17:16 as concurrent. It was caught because 29 pairs could not be a subset of 5, not by a control. **The frequency was nearly overstated fivefold in this item**, and the recorded figure is 5.
+
+**Awaiting:** Steward authorization. The option space is still not drafted here — the frequency is now observed, but *whether it is worth a mechanism* remains the steward's judgement, and the observation does not settle it in either direction.
 
 ---