diff --git a/docs/pfi/ops-lessons-playbook.md b/docs/pfi/ops-lessons-playbook.md
index 84ec6da..4fec345 100644
--- a/docs/pfi/ops-lessons-playbook.md
+++ b/docs/pfi/ops-lessons-playbook.md
@@ -359,6 +359,28 @@ themselves: they waste attention and misdirect, but they cannot silently destroy
 a good artifact. A post-mortem that lumps all three together loses the half that
 decides what to do about it.
 
+### Filter on the ARTIFACT, not on the name pointing at it
+
+Measured 2026-09-09 while quantifying how much traffic had reached a tune that
+failed a safety gate. The gateway alias `trial` had pointed at three different
+artifacts across the day, so the obvious query — *"how many calls to `trial`?"* —
+answers a question about a **name**, not about the **thing**:
+
+| filtered on | rows |
+|---|---|
+| `model_group = 'trial'` (the alias) | **363** |
+| `model = 'hosted_vllm/erp-tune-v7-nvfp4a16'` (the artifact) | **77** |
+
+**Wrong by 4.7x, in the direction that looks careful.** Reporting 363 would have
+overstated the operator's own exposure nearly fivefold, and nothing about the
+query would have looked sloppy — an alias is what a caller types, so counting it
+feels like counting usage.
+
+**The rule:** when the question is *"what did this artifact do"*, filter on the
+artifact's identity, never on a mutable pointer to it. A name that has been
+repointed carries the history of everything it ever pointed at. Same family as §3
+(identity, not resemblance): an alias resembles the thing and is not it.
+
 ### A fourth variant: the instrument read a surface MID-TRANSITION
 
 Added 2026-09-09 from a near-miss brokkr-smithy-dev caught and did not send.