diff --git a/persistent-memory.d/2026-09-22-instrument-errors.md b/persistent-memory.d/2026-09-22-instrument-errors.md
index 5b3461c..2927358 100644
--- a/persistent-memory.d/2026-09-22-instrument-errors.md
+++ b/persistent-memory.d/2026-09-22-instrument-errors.md
@@ -69,3 +69,41 @@ session will read it, not left as a lesson someone remembers.
 
 Related: [[2026-09-21-booth-two-dead-controls]] — same family, found by the
 operator rather than by me, because I read templates instead of rendering them.
+
+## Addendum — the sixth, and the one that cost an operator approval
+
+`[2026-09-22, later]` Found by svos-dev verifying a mechanism I had merely
+inferred, and it corrects my own framing.
+
+I told the operator that D-0010's `/clear` "cost nothing by luck of the delivery
+mechanism". **It was not luck.** `svos/server/bifrost.py:1322` composes
+`typed_text=f"[MIRANDA {card_id}] {text}"` — every relayed string is prefixed
+with the card id, so a slash command never begins the line and the receiving
+harness reads it as prose. **`pane_send` structurally cannot execute a harness
+command in a target pane.** A property of the tool, on every send.
+
+Which makes the card worse than a misroute. It promised: *"Approve to type
+/clear into terminal_2 and clear booth-dev's context."* **That effect was never
+achievable** — not with the right pane, not with identity resolved perfectly.
+And the executed event recorded `{"sent": true}`: true about the bytes, false
+about the effect.
+
+Three defects in one approved action — wrong pane, an impossible promise, and a
+receipt reporting success for an outcome that never occurred. Only the first was
+visible to anyone.
+
+**Why this one is the sharpest of the set.** Every other instrument error here
+cost an agent some triage time. This one *consumed an operator approval*: Vuong
+approved an action believing it would take effect, and the system reported that
+it had. A receipt that describes the bytes rather than the outcome is the same
+class as `restic ls`'s header line or systemd's `●` — an instrument reporting
+cleanly about something it never checked — but pointed at the human whose
+judgement the whole approval gate exists to capture.
+
+The general form, worth carrying beyond SVOS: **`{"sent": true}` is a claim
+about transmission, never about effect.** Any receipt that cannot distinguish
+the two will eventually report success for something that did not happen.
+
+Fix is svos-dev's (identity asserted where telemetry can claim the pane,
+disclosed as title-only where it cannot; and `pane_send` refusing or the card
+declaring text whose leading token is a harness command it cannot deliver).