docs: confirm groupchat source evidence

docs/superpowers/plans/2026-07-09-stage-c-log-backed-receive-messages-loop.md

@@ -1049,15 +1049,15 @@ Implemented and verified in this loop:
 - If evidence exists, write a C10 implementation loop for group candidate extraction.
 - If evidence does not exist, mark `isphere_search_groups` blocked on additional roster/group evidence and choose the next read slice (`isphere_receive_files` or contact enrichment) instead.
 
-- [ ] **Step 1: Inspect current source evidence for group identifiers**
+- [x] **Step 1: Inspect current source evidence for group identifiers**
 
 Use existing ignored metadata/log summaries under `runs/` and committed schema notes. Do not commit raw logs.
 
-- [ ] **Step 2: Update matrix and next loop**
+- [x] **Step 2: Update matrix and next loop**
 
 Record whether group extraction can proceed from current evidence. Rewrite C10 accordingly.
 
-- [ ] **Step 3: Verify docs-only change and commit**
+- [x] **Step 3: Verify docs-only change and commit**
 
 Run:
 
@@ -1071,6 +1071,67 @@ Expected: all exit 0. Commit exact C9 paths only.
 
 ---
 
+## Loop C9 Result
+
+Evidence precheck result:
+
+- Committed schema notes mention group handling only as a possible mapping (`conversation_id` group JID and `conversation_type` `chat|groupchat|...`).
+- Existing ignored metadata summaries did not contain explicit group keywords.
+- A temporary ignored Go scanner decrypted selected N12-pre logs and output counts only, with no raw content committed:
+  - `PacketReader.ProcessPacket`: 245/245 decrypted, 86 `groupchat`, 86 conference, 24 MUC, 86 `type="groupchat"` hits.
+  - `Smark.SendReceive`: 1078/1078 decrypted, 24 `groupchat`, 658 conference, 631 MUC, 24 `type="groupchat"` hits.
+  - `SaveToDB`: 14/14 decrypted, no group hits.
+- Decision: `isphere_search_groups` can proceed from current log-backed evidence, but display names/member counts remain unavailable until roster/db/uia evidence is solved.
+
+---
+
+## Loop C10: Log-backed group candidate extraction
+
+**Goal:** Extract searchable group candidates from normalized log-backed groupchat messages using group/conference bare JIDs as stable group ids until richer display-name/member evidence is available.
+
+**Planned files:**
+- Create: `internal/isphere/groups.go`
+- Create: `internal/isphere/groups_test.go`
+- Modify: `docs/source-discovery/capability-source-matrix.md`
+- Modify: `docs/superpowers/plans/2026-07-09-stage-c-log-backed-receive-messages-loop.md`
+
+**Planned behavior:**
+- Consume `[]isphere.Message` records.
+- Extract groups from messages where `ConversationType == "groupchat"` or sender/receiver JID contains conference/MUC markers.
+- Group fields: `GroupID`, `DisplayName`, `Source`, `Confidence`, `RawRef`.
+- For now, `DisplayName` uses the bare group JID; `MemberCount` and `OwnerRef` remain nil/unknown at MCP layer.
+- Search query matches group JID/display name case-insensitively.
+- This loop does not register `isphere_search_groups`; registration comes after source behavior passes tests.
+
+- [ ] **Step 1: Write failing group extraction test**
+
+Create `internal/isphere/groups_test.go` and run:
+
+```powershell
+go test ./internal/isphere -run TestSearchGroupsFromMessagesMatchesGroupchatJIDs -v
+```
+
+Expected initial failure: group search types/functions do not exist.
+
+- [ ] **Step 2: Implement group extraction/search**
+
+Create `internal/isphere/groups.go` with minimal pure Go logic over normalized messages and synthetic groupchat fixtures.
+
+- [ ] **Step 3: Run full verification and rewrite Loop C11**
+
+Run:
+
+```powershell
+git diff --check
+go test ./...
+go build ./cmd/isphere-mcp
+powershell -NoProfile -ExecutionPolicy Bypass -File scripts/verify-go-mcp.ps1
+```
+
+Expected: all exit 0. Remove any generated root `isphere-mcp.exe` after build. Rewrite Loop C11 around registering `isphere_search_groups` from the C10 source behavior.
+
+---
+
 ## Self-Review
 
 - Spec coverage: the plan follows the user's cyclic requirement: plan first, implement one loop at a time, update the next loop after each result, and ask only on blockers.