diff --git a/lib/dev/deps/gh_integration.rb b/lib/dev/deps/gh_integration.rb
index 90be50f..a4274fe 100644
--- a/lib/dev/deps/gh_integration.rb
+++ b/lib/dev/deps/gh_integration.rb
@@ -178,8 +178,16 @@ def install_from_source(dep)
       sig { params(base_dir: Pathname, target_dir: Pathname).void }
       def publish_current(base_dir, target_dir)
         link = base_dir / "current"
+        desired = target_dir.basename.to_s
+        # A pointer that already resolves to the target is converged — skip
+        # the rewrite. The swap is not free idempotence but a write, and
+        # identities that can only read the shared tree (the ai-agent user
+        # on the human-owned engine tree, plans#26) crash on it (caught
+        # live at the plans#36 ceremony via dev install-deps).
+        return if File.symlink?(link.to_s) && File.readlink(link.to_s) == desired
+
         tmp = base_dir / ".current-#{Process.pid}-#{SecureRandom.hex(4)}"
-        File.symlink(target_dir.basename.to_s, tmp.to_s)
+        File.symlink(desired, tmp.to_s)
         File.rename(tmp.to_s, link.to_s)
       rescue StandardError
         FileUtils.rm_f(tmp.to_s) if tmp
diff --git a/test/dev/deps/gh_integration_test.rb b/test/dev/deps/gh_integration_test.rb
index 16c3439..c2bc74e 100644
--- a/test/dev/deps/gh_integration_test.rb
+++ b/test/dev/deps/gh_integration_test.rb
@@ -150,6 +150,33 @@ def build_integration(fixture_files, cache_dir)
     FileUtils.rm_rf(dir)
   end
 
+  test "install_all leaves an already-correct current pointer untouched — a read-only shared tree stays usable" do
+    Given "a published version whose current pointer already resolves to it, in a base dir the " \
+          "caller cannot write (the agent identity on the human-owned shared engine tree, plans#26)"
+    dir = Dir.mktmpdir("dev-gh-int-test-")
+    parts = build_split_archive(dir, "engine.tar.zst", part_size: 64)
+    install_dir = File.join(dir, "engines", "unreal-engine-css")
+    version_dir = File.join(install_dir, "5.6.1-css-83")
+    FileUtils.mkdir_p(version_dir)
+    File.write(File.join(version_dir, ".dev-gh-release"), "5.6.1-css-83")
+    File.symlink("5.6.1-css-83", File.join(install_dir, "current"))
+    FileUtils.chmod(0o555, install_dir)
+    dep = build_dependency(parts, install_dir)
+    integration = build_integration(parts, File.join(dir, "cache"))
+
+    When "installing again"
+    integration.install_all([dep])
+
+    Then "the converged pointer was recognized, not rewritten (caught live at the plans#36 " \
+         "ceremony: the unconditional rewrite crashed dev install-deps with EACCES)"
+    File.readlink(File.join(install_dir, "current")) == "5.6.1-css-83"
+    integration.download_count == 0
+
+    Cleanup
+    FileUtils.chmod(0o755, install_dir)
+    FileUtils.rm_rf(dir)
+  end
+
   test "install_all installs a new version alongside the existing one when the locked tag changes" do
     Given "an existing version dir for an older tag"
     dir = Dir.mktmpdir("dev-gh-int-test-")