diff --git a/errorlog.md b/errorlog.md
index ff886926..155dc4c3 100644
--- a/errorlog.md
+++ b/errorlog.md
@@ -17,6 +17,8 @@ Categories (the `[type]` tag): _(none)_ = skill/command execution failure ·
 
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+2026-06-21 | Howard-Home | git/submodule | [friction] Did feature work directly in the SHARED guru-rmm submodule working tree while a CONCURRENT Claude session was active in it. The other session switched branches (fix/audit-cleanup -> bugfix/bug-019 -> detached) and repointed my branch ref mid-work, and the working tree ended up with BOTH sessions' uncommitted changes mixed together. Wasted a recovery cycle. FIX: when doing submodule feature work and other sessions may be live (the /save note warns 3-4 sessions share one tree), create an isolated 'git worktree add <path> origin/main' FIRST, do all edits + commit + push-by-SHA there, then 'worktree remove' — never rely on the shared checkout's branch/HEAD surviving. Do NOT 'git checkout --' shared files to clean up (clobbers the other session's uncommitted work). [ctx: ref=git/submodule detached-HEAD + stale-audit friction]
+
 2026-06-21 | Howard-Home | bitdefender | GravityZone API error [policies.getPolicyDetails]: Invalid value for 'policyId' parameter. [ctx: cmd=policy]
 
 2026-06-21 | Howard-Home | bitdefender | GravityZone API error [network.getManagedEndpointDetails]: Invalid value for 'endpointId' parameter. Expected format: 24-char hex ID [ctx: cmd=endpoint]