feat(install): re-add Antigravity as a wiring target

Antigravity discovers skills via a path-entries JSON
(~/.gemini/config/skills.json), not a symlink directory. One entry points
at $AGENTS_DIR — the same managed, surfaces-filtered, collision-resolved
directory Crush/OpenCode/Pi already read — so Antigravity sees exactly the
same skill set as every other harness, for free.

Requires jq; every other target in this script stays dependency-free on
purpose, so wire_antigravity skips with a warning (not a hard failure) if
jq is missing. Merges into skills.json rather than overwriting it: the
file is documented as user-editable (json_configs.md — e.g. a personal
skills dir), so a hand-added entry must survive a re-run.

Was previously removed as "unused" (mathias/skills#41 — Antigravity usage
picked back up). Mistral Vibe stays removed.

Closes #41

Bump-Type: minor

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -100,9 +100,11 @@ default to point into `~/dev`.
 | `AGENTS_SKILLS_DIR` | `$HOME/.agents/skills` |
 | `CRUSH_SKILLS_DIR` | `$HOME/.config/crush/skills` |
 | `OPENCODE_SKILLS_DIR` | `$HOME/.config/opencode/skills` |
+| `ANTIGRAVITY_SKILLS_JSON` | `$HOME/.gemini/config/skills.json` (registers `AGENTS_SKILLS_DIR` as a path entry; needs `jq`) |
 | `SKILLS_EXTRA_SOURCES` | unset (colon-separated extra source directories) |
 
-Antigravity and Mistral Vibe targets were removed — unused.
+The Mistral Vibe target was removed — unused. Antigravity's was removed for
+the same reason and re-added once it came back into use.
 
 ## Checking a host
 

install.sh

@@ -17,8 +17,8 @@
 #   /plugin install skills@mathias
 #
 # That path carries the hooks and MCP server definitions too, which symlinks
-# cannot. This script covers the harnesses with no plugin system: Crush, Pi
+# cannot. This script covers the harnesses with no plugin system: Crush, Pi,
-# and OpenCode.
+# OpenCode, and Antigravity.
 #
 # Wiring model — one managed directory, one link per harness:
 #
@@ -27,6 +27,13 @@
 #   ~/.config/crush/skills      -> ~/.agents/skills
 #   ~/.config/opencode/skills   -> ~/.agents/skills
 #
+# Antigravity has no symlink-directory discovery — it reads a path-entries
+# JSON instead (~/.gemini/config/skills.json:
+# {"entries":[{"path":"..."}]}). One entry points at ~/.agents/skills, so it
+# sees exactly the same surfaces-filtered, collision-resolved set every other
+# harness does. Requires jq; skipped with a warning if jq is unavailable —
+# every other target in this script stays dependency-free on purpose.
+#
 # ~/.agents/skills was itself a link to this checkout until #27. That encoded
 # an assumption nobody had stated — that this checkout is the ONLY source of
 # skills on the host — and on flamingo the only way to install this library
@@ -53,6 +60,7 @@ CHECKOUT_DIR="${SKILLS_CHECKOUT_DIR:-$HOME/.local/share/skills}"
 AGENTS_DIR="${AGENTS_SKILLS_DIR:-$HOME/.agents/skills}"
 CRUSH_DIR="${CRUSH_SKILLS_DIR:-$HOME/.config/crush/skills}"
 OPENCODE_DIR="${OPENCODE_SKILLS_DIR:-$HOME/.config/opencode/skills}"
+ANTIGRAVITY_SKILLS_JSON="${ANTIGRAVITY_SKILLS_JSON:-$HOME/.gemini/config/skills.json}"
 EXTRA_SOURCES="${SKILLS_EXTRA_SOURCES:-}"
 # Recorded beside the managed directory rather than inside it: a stray file in
 # there would look like a skill to every harness reading the dir.
@@ -213,6 +221,42 @@ link_dir() {
   log "linked $link → $target"
 }
 
+# wire_antigravity — register $AGENTS_DIR in Antigravity's skills.json.
+# Merges rather than overwrites: skills.json is a documented user-editable
+# config (json_configs.md), so a hand-added entry (e.g. a personal skills
+# dir) must survive a re-run untouched.
+wire_antigravity() {
+  if ! command -v jq >/dev/null 2>&1; then
+    log "Antigravity: jq not found — skipping (needed to merge $ANTIGRAVITY_SKILLS_JSON safely)"
+    return
+  fi
+
+  local existing already updated
+  mkdir -p "$(dirname "$ANTIGRAVITY_SKILLS_JSON")"
+
+  if [ -s "$ANTIGRAVITY_SKILLS_JSON" ]; then
+    existing="$(cat "$ANTIGRAVITY_SKILLS_JSON")"
+  else
+    existing='{}'
+  fi
+
+  already="$(printf '%s' "$existing" | jq --arg p "$AGENTS_DIR" \
+    '[.entries // [] | .[] | select(.path == $p)] | length' 2>/dev/null)" || {
+    log "Antigravity: $ANTIGRAVITY_SKILLS_JSON is not valid JSON — leaving it untouched"
+    return 1
+  }
+
+  if [ "$already" -gt 0 ]; then
+    log "Antigravity: $AGENTS_DIR already registered in $ANTIGRAVITY_SKILLS_JSON"
+    return
+  fi
+
+  updated="$(printf '%s' "$existing" | jq --arg p "$AGENTS_DIR" \
+    '.entries = ((.entries // []) + [{path: $p}])')"
+  printf '%s\n' "$updated" > "$ANTIGRAVITY_SKILLS_JSON"
+  log "Antigravity: registered $AGENTS_DIR in $ANTIGRAVITY_SKILLS_JSON"
+}
+
 main() {
   ensure_checkout
 
@@ -224,6 +268,7 @@ main() {
 
   link_dir "$CRUSH_DIR" "$AGENTS_DIR"
   link_dir "$OPENCODE_DIR" "$AGENTS_DIR"
+  wire_antigravity
 
   log "done — $LINKED_COUNT skill(s) linked from $(sources | wc -l | tr -d ' ') source(s), ref=$REF"
   log "Claude Code: install the plugin instead — /plugin marketplace add $REPO_URL"

tests/install_test.sh

@@ -55,6 +55,7 @@ run_install() {
     AGENTS_SKILLS_DIR="$_f/home/.agents/skills" \
     CRUSH_SKILLS_DIR="$_f/home/.config/crush/skills" \
     OPENCODE_SKILLS_DIR="$_f/home/.config/opencode/skills" \
+    ANTIGRAVITY_SKILLS_JSON="$_f/home/.gemini/config/skills.json" \
     SKILLS_EXTRA_SOURCES="$_extra" \
     bash "$SUT" 2>&1)
   rc=$?
@@ -183,5 +184,53 @@ else
   no 'a source with no surfaces convention is linked as-is' "$out"
 fi
 
+# --- 9. Antigravity: the managed agents dir is registered, not the raw checkout
+# skills.json entries must point at $AGENTS_DIR — that's what already carries
+# surfaces-filtering, collision handling and multi-source merge. Pointing at
+# the checkout directly would bypass all of it and give Antigravity a
+# different skill set than every other harness.
+f=$(new_fixture antigravity)
+out=$(run_install "$f")
+AG="$f/home/.gemini/config/skills.json"
+if [ ! -f "$AG" ]; then
+  no 'Antigravity skills.json is created' "$out"
+elif ! command -v jq >/dev/null 2>&1; then
+  no 'jq available to verify Antigravity wiring' "(jq missing on test host)"
+else
+  registered=$(jq -r --arg p "$f/home/.agents/skills" '[.entries[]? | select(.path == $p)] | length' "$AG")
+  if [ "$registered" = "1" ]; then
+    ok 'Antigravity registers the managed agents dir, not the raw checkout'
+  else
+    no 'Antigravity registers the managed agents dir, not the raw checkout' "$(cat "$AG")"
+  fi
+fi
+
+# --- 10. Antigravity wiring is idempotent ------------------------------------
+f=$(new_fixture antigravity_idempotent)
+run_install "$f" >/dev/null
+out=$(run_install "$f")
+AG="$f/home/.gemini/config/skills.json"
+count=$(jq '.entries | length' "$AG" 2>/dev/null || echo "?")
+if [ "$count" = "1" ]; then
+  ok 'Antigravity wiring is idempotent (no duplicate entries)'
+else
+  no 'Antigravity wiring is idempotent (no duplicate entries)' "entries=$count"$'\n'"$out"
+fi
+
+# --- 11. Antigravity wiring preserves entries it doesn't own -----------------
+# A user may hand-edit skills.json to point at their own personal skills dir
+# (json_configs.md documents this). Our merge must not clobber it.
+f=$(new_fixture antigravity_preserve)
+mkdir -p "$f/home/.gemini/config"
+printf '{"entries":[{"path":"/Users/mathias/personal-skills"}]}' > "$f/home/.gemini/config/skills.json"
+out=$(run_install "$f")
+AG="$f/home/.gemini/config/skills.json"
+personal=$(jq -r '[.entries[]? | select(.path == "/Users/mathias/personal-skills")] | length' "$AG" 2>/dev/null || echo 0)
+if [ "$personal" = "1" ]; then
+  ok 'Antigravity wiring preserves pre-existing hand-authored entries'
+else
+  no 'Antigravity wiring preserves pre-existing hand-authored entries' "$(cat "$AG")"$'\n'"$out"
+fi
+
 printf '\ninstall: %d passed, %d failed\n' "$pass" "$fail"
 [ "$fail" -eq 0 ]