MAS-WP-0003-T04: Google Groups results (lower-cases members); T04 done

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 252470@bnt-lap001
Assistant-Session: ad628c8f-4be2-4979-94c9-76c7ed6f8241

docs/experiment-review.md

@@ -172,7 +172,30 @@ real failure in the run.
   nothing in the statute gives `ticket--…` resource meaning. See SCP-6
   (declared alternate separator) and SCP-7 (identifier case).
 
-**Still untested (T04):** a mailing list (VERP).
+**Mailing list (T04, Google Groups, 2026-10-18):**
+- **The member form accepted `=` and capitals:**
+  `ticket=GS-85QJ8WC09P+comments@` was accepted. The invitation was
+  delivered to it byte-identical (Auto-Submitted: auto-generated) and was
+  correlated to the ticket.
+- **After acceptance, Google stored the member in lower case.** The list
+  post arrived for `ticket=gs-85qj8wc09p+comments@`. The envelope sender
+  was the per-message bounce address
+  `coulomb-social+bncBDG…@googlegroups.com`, which tags the list's own
+  local-part and does not touch ours, so there is no collision with `=`
+  or `+`.
+- **With exact comparison the post did not match the ticket.** The service
+  quarantined it as an unknown resource and did not reply
+  (`Precedence: list`). That is correct under v0.1, but the post was lost
+  to the ticket.
+
+**T04 conclusion:**
+- SRS and list bounce addresses never collide with MAS syntax, because they
+  rewrite or tag the *sender*.
+- Facets survived every path.
+- The real risks are **provider forms**: IONOS refuses `=`, and **two of
+  two** forwarding/list providers (IONOS, Google Groups) lower-case the
+  recipient. Case-sensitive resource identifiers do not survive
+  forwarding or lists, which makes SCP-7 the most consequential proposal.
 
 ### Resource addressing: did it improve correlation?
 Yes. The service replies *from* `ticket=GS-…@great-service.example`, so an

docs/spec-change-proposals.md

@@ -100,7 +100,9 @@ to MAS addresses carrying an `@domain`. Pending: SRS and VERP (MAS-WP-0003
 T04).
 
 **Counter-evidence (T04):** the IONOS forwarding form refused `=` and
-forced lower case (SCP-6, SCP-7). Mail *clients* preserved MAS syntax;
+forced lower case. Google Groups accepted `=` but lower-cased the member
+address (SCP-6, SCP-7). SRS and list bounce addresses never collided with
+`=` or `+`. Mail *clients* preserved MAS syntax;
 provider *configuration forms* did not.
 
 **Proposal:** keep the normative text. Add an informative note recording
@@ -176,11 +178,17 @@ A candidate for v0.2 rather than errata.
 **Sections:** §6.2 Resource identifiers, §8 Address equivalence, §13.
 
 **Evidence:** the IONOS forwarding form forces destination addresses to
-lower case: `GS-85QJ8WC09P` became `gs-85qj8wc09p`. With the spec default
+lower case: `GS-85QJ8WC09P` became `gs-85qj8wc09p`. Google Groups did the
+same after a member accepted the invitation: the invitation was delivered
+mixed-case, but list mail went to the lower-cased address and was
+quarantined as an unknown resource. With the spec default
 (exact comparison) and a statute declaring `case: exact`, the identifier
 no longer matches. Many systems treat local-parts as case-insensitive in
 practice, despite RFC 5321.
 
+**Priority:** highest of this set. Two of two forwarding/list providers
+lower-cased the recipient.
+
 **Proposal:**
 - §6.2: "Generators SHOULD use resource identifiers whose meaning does not
   depend on letter case (for example lower-case only, or a case-insensitive

workplans/MAS-WP-0003-provider-live-test.md

@@ -167,7 +167,7 @@ address and what envelope recipient arrives.
 
 ```task
 id: MAS-WP-0003-T04
-status: progress
+status: done
 priority: medium
 state_hub_task_id: "97c88b4f-14c3-5f6c-8f31-6b9fc3afd236"
 ```
@@ -188,7 +188,17 @@ or are stripped.
   separator; the operator endorses the mapping) and SCP-7 (case-robust
   identifiers).
   Gmail forwarding: skipped (optional; would only add a second forwarder
-  that accepts `=`). Still open: one mailing list (VERP).
+  that accepts `=`).
+- 2026-10-18, Google Groups (`coulomb-social@googlegroups.com`): the member
+  form accepted `ticket=GS-85QJ8WC09P+comments@` unchanged. The invitation
+  (11:58:20Z) arrived byte-identical and was correlated; no auto-reply was
+  sent (Auto-Submitted). After acceptance, the list post (12:05:37Z)
+  arrived for the **lower-cased** `ticket=gs-85qj8wc09p+comments@`. Its
+  envelope sender was `coulomb-social+bnc…@googlegroups.com`, which does
+  not collide with our syntax, and the facet survived. Exact comparison
+  missed the ticket, so the post was quarantined with no reply
+  (Precedence: list). Correct per v0.1, but lost to the ticket. This is
+  the second provider to lower-case, so SCP-7 is now the highest priority.
 
 ## Cap total outbound mail