diff --git a/.cursor/rules/learnings-index.mdc b/.cursor/rules/learnings-index.mdc
index 23afd27..6ff67a0 100644
--- a/.cursor/rules/learnings-index.mdc
+++ b/.cursor/rules/learnings-index.mdc
@@ -57,11 +57,6 @@ propose a retirement, a consolidation, or a glob-scoped sub-index split.
 
 ## toolchain
 
-- [toolchain/rbenv-libruby-rpath-hijack] On Linux, an rbenv-built Ruby with
-  a Homebrew lib dir rpathed ahead of its own libdir silently runs a
-  same-minor brew libruby — bundler's Gemfile ruby-pin mismatch is the
-  symptom, not a project bug.
-  → .cursor/skills/learnings/rbenv-libruby-rpath-hijack/
 
 ## org tier
 
diff --git a/.cursor/skills/learnings/rbenv-libruby-rpath-hijack/SKILL.md b/.cursor/skills/learnings/rbenv-libruby-rpath-hijack/SKILL.md
deleted file mode 100644
index c7dce56..0000000
--- a/.cursor/skills/learnings/rbenv-libruby-rpath-hijack/SKILL.md
+++ /dev/null
@@ -1,40 +0,0 @@
----
-name: rbenv-libruby-rpath-hijack
-description: >-
-  MUST be used when diagnosing a Ruby version mismatch on Linux — bundler
-  failing a Gemfile ruby pin, or `ruby -v` disagreeing with the resolved
-  binstub — on a machine with both rbenv-built and Homebrew rubies.
----
-
-# rbenv libruby hijacked by Homebrew via rpath
-
-An rbenv-built Ruby whose binary carries a Homebrew lib dir in its rpath
-ahead of its own libdir loads a same-minor Homebrew Ruby's libruby at
-runtime (they share the soname `libruby.so.X.Y`), so the binary silently
-runs as the other version. Bundler then fails the Gemfile ruby pin with a
-mismatch that looks like a project bug — the real fault is the link, not
-the project. Linux-only: macOS dyld links libruby by absolute install
-name.
-
-Diagnosis cue: `command -v ruby` resolves to the correct rbenv binstub,
-but `ruby -v` reports a different version.
-
-Wrong:
-
-```sh
-# bundler says: your Ruby version is 3.4.5, your Gemfile requires 3.4.2
-# ...so edit the Gemfile pin, or rebuild the project's gems
-```
-
-Right:
-
-```sh
-command -v ruby        # right binstub?
-ruby -v                # different version => linker hijack, not a pin bug
-readelf -d "$(rbenv prefix)/bin/ruby" | grep -i rpath
-# fix the rpath ordering (own libdir first) or rebuild the rbenv Ruby
-# without the Homebrew lib dir in its rpath
-```
-
-learned-from: dev#75, root-causing cellbound-3d#151's CI ruby-pin failure.
-date: 2026-08-01