diff --git a/crates/bsk-cli/skill/references/tabs-and-profiles.md b/crates/bsk-cli/skill/references/tabs-and-profiles.md
index c8130f25a..39b714bcd 100644
--- a/crates/bsk-cli/skill/references/tabs-and-profiles.md
+++ b/crates/bsk-cli/skill/references/tabs-and-profiles.md
@@ -59,7 +59,15 @@ A viewport screenshot does not issue a Canvas `capture_id`; use the existing
 Never invent tab IDs or keep a user tab across unrelated work. Do not repeat
 pending, denied or timed-out borrows. For `borrow_outcome_unknown`, inspect tab/
 session state first: the tab may already have moved. Do not bypass an outcome
-through another browser backend. `tab borrow --timeout 120s` changes only the
+through another browser backend. A borrow that returns `not_found` means the tab
+closed; ask the user to reopen it instead of substituting a new tab when the task
+depends on that tab's state.
+
+`confirmation_ui_unavailable` means no user window can show the prompt: the active
+tab of every normal window outside Agent Windows is a browser, blank or extension
+store page. Ask the user to bring an ordinary http(s) page to the front of a user
+window, then retry once. Opening a tab yourself does not help, because task tabs
+live in the Agent Window. `tab borrow --timeout 120s` changes only the
 confirmation wait (default 60s); custom waits require daemon and extension protocol 1.2+.
 
 The extension's saved Automation settings control borrow confirmation and human
diff --git a/packages/dsh-plugin-browserskill/skill/references/tabs-and-profiles.md b/packages/dsh-plugin-browserskill/skill/references/tabs-and-profiles.md
index 7d2387381..4fa293bab 100644
--- a/packages/dsh-plugin-browserskill/skill/references/tabs-and-profiles.md
+++ b/packages/dsh-plugin-browserskill/skill/references/tabs-and-profiles.md
@@ -43,5 +43,8 @@ Use `bsk_tabs` to list IDs before acting. Borrow for the immediate step and
 return promptly. Browser Automation settings
 govern confirmation and help; never change them to bypass a prompt or repeat
 pending/denied/expired borrows. Inspect unknown outcomes; follow version-error hints.
+`not_found` means the tab closed: ask the user to reopen it, not a substitute tab.
+`confirmation_ui_unavailable` means no user window shows an ordinary http(s) page in
+front; ask the user to bring one forward, then retry once. Task tabs cannot host it.
 Remote reads/actions require task-created or borrowed tabs; popups gain no control.
 An unowned tab inside the Agent Window needs a user move to a user window before borrowing.