diff --git a/.opencode/skills/cctest-recipe-upstream/SKILL.md b/.opencode/skills/cctest-recipe-upstream/SKILL.md
index 52bac6f..1db8420 100644
--- a/.opencode/skills/cctest-recipe-upstream/SKILL.md
+++ b/.opencode/skills/cctest-recipe-upstream/SKILL.md
@@ -80,4 +80,11 @@ one upgrade commit. Guard: while preparing, run
 `git merge-base <head_ref> <base_ref>`; if the result is older than a few commits below upstream
 `origin/main`, cherry-pick the upgrade commit(s) onto fresh upstream `origin/main` (branch
 `<head_ref>-rebased`), push THAT to the autonomic mirror, and emit the fetch/push/compare commands
-using the rebased branch instead of the raw one.
+using the rebased branch instead of the raw one. Also fix the stale `origin/main` wording above:
+the upstream base branch may be `master`, not `main` — derive it from the remotes.
+
+**Branch-name mismatch mirror vs upstream.** The mirror and upstream can use different base-branch
+names (gitea: mirror `main`, upstream `master`). When emitting step 3 (the post-merge release),
+NEVER hardcode `main` — derive the upstream default branch from the existing remotes (`git
+remote show origin` or `git ls-remote --symref origin HEAD`) and emit `git checkout <that>;
+git fetch origin; git merge --ff-only origin/<that>;` before `abra recipe release`.
diff --git a/scripts/gen-cctest-skills.py b/scripts/gen-cctest-skills.py
index 8ea4d21..7d1d9e0 100644
--- a/scripts/gen-cctest-skills.py
+++ b/scripts/gen-cctest-skills.py
@@ -108,7 +108,14 @@ one upgrade commit. Guard: while preparing, run
 `git merge-base <head_ref> <base_ref>`; if the result is older than a few commits below upstream
 `origin/main`, cherry-pick the upgrade commit(s) onto fresh upstream `origin/main` (branch
 `<head_ref>-rebased`), push THAT to the autonomic mirror, and emit the fetch/push/compare commands
-using the rebased branch instead of the raw one.
+using the rebased branch instead of the raw one. Also fix the stale `origin/main` wording above:
+the upstream base branch may be `master`, not `main` — derive it from the remotes.
+
+**Branch-name mismatch mirror vs upstream.** The mirror and upstream can use different base-branch
+names (gitea: mirror `main`, upstream `master`). When emitting step 3 (the post-merge release),
+NEVER hardcode `main` — derive the upstream default branch from the existing remotes (`git
+remote show origin` or `git ls-remote --symref origin HEAD`) and emit `git checkout <that>;
+git fetch origin; git merge --ff-only origin/<that>;` before `abra recipe release`.
 """,
 }