diff --git a/binstub_patch.rb b/binstub_patch.rb
index 00599425f..02a1aabdb 100644
--- a/binstub_patch.rb
+++ b/binstub_patch.rb
@@ -1,4 +1,18 @@
 unless ENV["APPBUNDLER_ALLOW_RVM"]
   ENV["APPBUNDLER_ALLOW_RVM"] = "true"
-  ENV["GEM_PATH"] = [File.expand_path(File.join(__dir__, "..", "vendor")), ENV["GEM_PATH"]].compact.join(File::PATH_SEPARATOR)
 end
+
+# Prepend the package vendor dir, the current user's gem dir, and the Chef gem dir to
+# GEM_PATH so that:
+#   1. Ohai's vendored dependencies are always found.
+#   2. Plugins installed via `gem install <plugin>` are discoverable on both
+#      Linux (~/.gem/ruby/VERSION) and Windows (%USERPROFILE%\.gem\ruby\VERSION).
+#   3. Gems installed via `chef gem install` (~/.chef/ruby/VERSION/gems) are immediately available.
+#
+# This block runs before appbundler's env_sanitizer (which calls Gem.clear_paths and
+# re-reads GEM_PATH from ENV), so these additions are always picked up correctly.
+ohai_vendor = File.expand_path(File.join(__dir__, "..", "vendor"))
+# chef-cli gem install places gems under ~/.chef/ruby/RUBY_API_VERSION/gems
+chef_gem_dir = File.join(Dir.home, ".chef", "ruby", RbConfig::CONFIG["ruby_version"], "gems")
+existing_paths = ENV["GEM_PATH"]&.split(File::PATH_SEPARATOR) || []
+ENV["GEM_PATH"] = ([ohai_vendor, Gem.user_dir, chef_gem_dir] + existing_paths).uniq.join(File::PATH_SEPARATOR)
diff --git a/habitat/aarch64-darwin/plan.sh b/habitat/aarch64-darwin/plan.sh
index 70341303b..695bf7760 100644
--- a/habitat/aarch64-darwin/plan.sh
+++ b/habitat/aarch64-darwin/plan.sh
@@ -1,6 +1,15 @@
 export HAB_BLDR_CHANNEL="base-2025"
 export HAB_REFRESH_CHANNEL="base-2025"
 ruby_pkg="core/ruby3_4"
+# Derive the Ruby API version (e.g. 3.4.0) from the packaged Ruby's on-disk gem layout
+# rather than executing `ruby -e`. Invoking the hab-provided ruby during the build can
+# silently fail (its runtime library paths aren't set up here), which would leave
+# ruby_gem_version empty and corrupt every GEM_PATH entry that uses it.
+ruby_gem_version="$(basename "$(pkg_path_for "${ruby_pkg}")/lib/ruby/gems/"*)"
+if [[ -z "$ruby_gem_version" ]]; then
+  build_line "WARNING: unable to determine Ruby API version from ${ruby_pkg}; falling back to 3.4.0"
+  ruby_gem_version="3.4.0"
+fi
 pkg_name="ohai"
 pkg_origin="chef"
 pkg_maintainer="The Chef Maintainers <humans@chef.io>"
@@ -117,7 +126,12 @@ set -e
 export PATH="$(pkg_path_for ${ruby_pkg})/bin:/sbin:/usr/sbin:/usr/local/sbin:/usr/local/bin:/usr/bin:/bin:$pkg_prefix/vendor/bin:\$PATH"
 export DYLD_LIBRARY_PATH="$(pkg_path_for core/libarchive)/lib:\$DYLD_LIBRARY_PATH"
 export GEM_HOME="$pkg_prefix/vendor"
-export GEM_PATH="$pkg_prefix/vendor"
+# GEM_PATH includes the flat vendor tree, the bundler-nested vendor tree
+# (vendor/ruby/VERSION, where train-core and other runtime deps are installed), the
+# standard user gem dir (~/.gem/ruby/VERSION), and the Chef gem dir
+# (~/.chef/ruby/VERSION/gems) so that both ohai's own runtime deps and plugins installed
+# via 'gem install' or 'chef gem install' are found at runtime.
+export GEM_PATH="$pkg_prefix/vendor:$pkg_prefix/vendor/ruby/${ruby_gem_version}:\${HOME}/.gem/ruby/${ruby_gem_version}:\${HOME}/.chef/ruby/${ruby_gem_version}/gems"
 
 exec $(pkg_path_for ${ruby_pkg})/bin/ruby $pkg_prefix/libexec/ohai "\$@"
 EOF
diff --git a/habitat/plan.ps1 b/habitat/plan.ps1
index 47299d532..445a60dcf 100644
--- a/habitat/plan.ps1
+++ b/habitat/plan.ps1
@@ -85,6 +85,19 @@ function Invoke-Install {
 	 Write-BuildLine "** generating binstubs for ohai with precise version pins $project_root $pkg_prefix/bin " 
             Invoke-Expression -Command "appbundler.bat $project_root $pkg_prefix/bin ohai"
             If ($lastexitcode -ne 0) { Exit $lastexitcode }
+
+        Write-BuildLine "** patching binstubs for direct execution and dynamic plugin loading"
+        $binstubPatch = Get-Content -Path "$project_root\binstub_patch.rb"
+        Get-ChildItem "$pkg_prefix\bin" | Where-Object { $_.Extension -notin @(".bat", ".ps1") } | ForEach-Object {
+            $lines = Get-Content -Path $_.FullName
+            $matchLine = $lines | Select-String -Pattern 'require "rubygems"' | Select-Object -First 1
+            if ($matchLine) {
+                $lineNum = $matchLine.LineNumber  # 1-based; insert patch after this line
+                $newLines = $lines[0..($lineNum - 1)] + $binstubPatch + $lines[$lineNum..($lines.Count - 1)]
+                Set-Content -Path $_.FullName -Value $newLines
+            }
+        }
+
 	Write-BuildLine " ** Running the ohai project's 'rake install' to install the path-based gems so they look like any other installed gem."
 
         If ($lastexitcode -ne 0) { Exit $lastexitcode }
diff --git a/habitat/plan.sh b/habitat/plan.sh
index 36c0e8804..417e84808 100644
--- a/habitat/plan.sh
+++ b/habitat/plan.sh
@@ -1,6 +1,15 @@
 export HAB_BLDR_CHANNEL="base-2025"
 export HAB_REFRESH_CHANNEL="base-2025"
 ruby_pkg="core/ruby3_4"
+# Derive the Ruby API version (e.g. 3.4.0) from the packaged Ruby's on-disk gem layout
+# rather than executing `ruby -e`. Invoking the hab-provided ruby during the build can
+# silently fail (its runtime library paths aren't set up here), which would leave
+# ruby_gem_version empty and corrupt every GEM_PATH entry that uses it.
+ruby_gem_version="$(basename "$(pkg_path_for "${ruby_pkg}")/lib/ruby/gems/"*)"
+if [[ -z "$ruby_gem_version" ]]; then
+  build_line "WARNING: unable to determine Ruby API version from ${ruby_pkg}; falling back to 3.4.0"
+  ruby_gem_version="3.4.0"
+fi
 pkg_name="ohai"
 pkg_origin="chef"
 pkg_maintainer="The Chef Maintainers <humans@chef.io>"
@@ -99,7 +108,12 @@ set -e
 export PATH="$(pkg_path_for ${ruby_pkg})/bin:/sbin:/usr/sbin:/usr/local/sbin:/usr/local/bin:/usr/bin:/bin:\$PATH"
 export LD_LIBRARY_PATH="$(pkg_path_for core/libarchive)/lib:\$LD_LIBRARY_PATH"
 export GEM_HOME="$pkg_prefix/vendor"
-export GEM_PATH="$pkg_prefix/vendor"
+# GEM_PATH includes the flat vendor tree, the bundler-nested vendor tree
+# (vendor/ruby/VERSION, where train-core and other runtime deps are installed), the
+# standard user gem dir (~/.gem/ruby/VERSION), and the Chef gem dir
+# (~/.chef/ruby/VERSION/gems) so that both ohai's own runtime deps and plugins installed
+# via 'gem install' or 'chef gem install' are found at runtime.
+export GEM_PATH="$pkg_prefix/vendor:$pkg_prefix/vendor/ruby/${ruby_gem_version}:\${HOME}/.gem/ruby/${ruby_gem_version}:\${HOME}/.chef/ruby/${ruby_gem_version}/gems"
 
 exec $(pkg_path_for ${ruby_pkg})/bin/ruby $pkg_prefix/libexec/ohai "\$@"
 EOF