diff --git a/CLAUDE.md b/CLAUDE.md
index 0eb3c927b0e141a8a1d84b0afc832740c6ff7639..5e260faf4d9c4569ad8a7e144dc055669ffee13e 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -16,6 +16,22 @@ Submodules' `.git` directories are absorbed into `.git/modules/<name>/` of the superproject. Each clone's worktree contains a `.git` *file* (gitlink), not a directory — do not be confused by this.
 
 A pre-built inventory lives at `.claude/INDEX.md` — per-service GraphQL types, SQL tables, Python blueprints, Go packages, plus a cross-repo type map. Regenerated automatically by `sourcehut-refresh`; the `sourcehut-lookup` skill reads it first to skip a lot of grepping.
 
+## Skills backed up here
+
+`skills/` holds two globally-installed skills (`sourcehut-ci`, `sourcehut-custom-service`).
+`just install` rsyncs them into `~/.claude/skills/` and substitutes two root placeholders, so
+citations inside skill files use these prefixes and **never** absolute paths:
+
+- `mirror::<repo>/<path>::<symbol>` → `__SRHT_MIRROR__`, this repo — upstream's published source.
+- `family::<repo>/<path>::<symbol>` → `__SRHT_FAMILY__`, the parent directory holding the
+  instance's own repos (`sourcehut-*`, `sr-ht-ecore`, `sr-ht-core`, `sr-ht-api`).
+
+Cite symbols, never line numbers — they rot on the next refresh.
+
+Note that `sourcehut-custom-service` documents the **Go family that actually runs on this
+instance**, not upstream's Python+Go shape; read its `references/` before answering "how do I
+build a service", because upstream's answer differs on chrome, auth and federation.
+
 ## Production deviations (phoebe-lab)
 
 The user runs a patched SourceHut in production under `~/data/home/phoebe-lab/srht/`. Fixes not yet upstreamed are mirrored here in `patches/` for reference — they are **not applied** to the clones in this workspace. When answering questions about behavior that might diverge from upstream, check `patches/README.md` first. Currently tracked: