diff --git a/nushell/modules/pj_completions.nu b/nushell/modules/pj_completions.nu
index 4177422..05d4bcd 100644
--- a/nushell/modules/pj_completions.nu
+++ b/nushell/modules/pj_completions.nu
@@ -4,6 +4,9 @@ const pj_completion_base_dir = ($pj_cache_dir | path join 'nu_scripts' 'custom-c
 const pj_completion_commands = [git ssh cargo uv rustup make pytest rg tar vscode winget zig]
 const pj_completion_noop_module = ($pj_cache_dir | path join 'noop.nu')
 const pj_completion_registry_module = ($pj_cache_dir | path join 'pj_completions_registry.nu')
+const pj_completion_marker_root = ($pj_cache_dir | path join '.pj-completion-ok')
+const pj_completion_version = (version).version
+const pj_completion_marker_dir = ($pj_completion_marker_root | path join $pj_completion_version)
 const pj_completion_bootstrap_module = if ($pj_completion_registry_module | path exists) {
     $pj_completion_registry_module
 } else {
@@ -14,6 +17,54 @@ def _pj_completion_script_path [name: string] {
     ($pj_completion_base_dir | path join $name $"($name)-completions.nu")
 }
 
+def _pj_completion_marker_path [name: string] {
+    ($pj_completion_marker_dir | path join $name)
+}
+
+# Check whether a completion script can still be parsed by the running Nushell.
+# Third-party completion scripts occasionally use syntax that a newer Nushell
+# rejects; such files must never be pulled into the config or the whole shell
+# fails to start.
+def _pj_completion_file_valid [file: string] {
+    if not ($file | path exists) {
+        return false
+    }
+    let probe = (do -i { ^$nu.current-exe --no-config-file -c $"use \"($file)\"" } | complete)
+    ($probe.exit_code == 0)
+}
+
+# Ensure per-version validity markers exist. A marker is only written for a
+# completion file that parses under the current Nushell version, so the generated
+# registry can safely gate each `use` on its marker.
+def _pj_completion_ensure_markers [] {
+    if ($pj_completion_marker_dir | path exists) {
+        return {created: false, invalid: []}
+    }
+
+    mkdir $pj_completion_marker_dir
+    let results = ($pj_completion_commands | each {|name|
+        let file = (_pj_completion_script_path $name)
+        let valid = (_pj_completion_file_valid $file)
+        if $valid {
+            touch (_pj_completion_marker_path $name)
+        }
+        {command: $name, valid: $valid}
+    })
+
+    let invalid = ($results | where {|it| not $it.valid } | get command)
+    {created: true, invalid: $invalid}
+}
+
+def _pj_completion_report [result: record] {
+    if ($result.invalid | is-empty) {
+        print "[pj completion] all completion files are compatible with the current Nushell."
+    } else {
+        print "[pj completion] warning: incompatible completion files were disabled:"
+        $result.invalid | each {|name| print $"  - ($name)" }
+        print "[pj completion] run `pj completion -u` to refresh the cached nu_scripts."
+    }
+}
+
 def _pj_required_completion_files [] {
     $pj_completion_commands | each {|name|
         {
@@ -27,16 +78,20 @@ def _pj_completion_registry_lines [] {
     let header = [
         "# Auto-generated by `pj completion sync`."
         "# Edit pj_completion_commands in pj_completions.nu, then re-run sync."
+        "# Each module is only loaded when it was validated for the running Nushell version."
         "const pj_registry_dir = (path self | path dirname)"
         "const pj_completion_base_dir = ($pj_registry_dir | path join 'nu_scripts' 'custom-completions')"
         "const pj_completion_noop_module = ($pj_registry_dir | path join 'noop.nu')"
+        "const pj_completion_marker_dir = ($pj_registry_dir | path join '.pj-completion-ok' (version).version)"
         ""
     ]
 
     let lines = ($pj_completion_commands | each {|name|
         [
             (
-                "export use (if ((($pj_completion_base_dir | path join '"
+                "export use (if ((($pj_completion_marker_dir | path join '"
+                + $name
+                + "') | path exists) and (($pj_completion_base_dir | path join '"
                 + $name
                 + "' '"
                 + $name
@@ -55,15 +110,17 @@ def _pj_completion_registry_lines [] {
 
 def _pj_completion_help [] {
     print "pj completion commands:"
-    print "  pj completion             Check required completion files from existing cache."
+    print "  pj completion             Validate cached completion files for the current Nushell."
     print "  pj completion -u          Update cache, or clone nu_scripts when cache is missing."
     print "  pj completion -f          Force re-clone cached nu_scripts repository."
-    print "  pj completion sync        Regenerate cache registry and restart Nushell."
+    print "  pj completion sync        Regenerate cache registry, revalidate, and restart Nushell."
     print "  pj completion -s          Same as `pj completion sync`."
+    print "  pj completion doctor      Show which completion files are enabled or disabled."
     print "  pj completion -h          Show this help message."
 }
 
 export def "pj completion sync" [
+    --no-restart(-n) # Regenerate the registry without restarting Nushell.
     --help(-h)
 ] {
     if $help {
@@ -75,14 +132,46 @@ export def "pj completion sync" [
     let content = ((_pj_completion_registry_lines) | str join "\n")
     $content | save -f $pj_completion_registry_module
     print $"[pj completion] synced: ($pj_completion_registry_module)"
-    print "[pj completion] restarting Nushell..."
-    exec nu
+
+    # Invalidate validation markers so files are re-checked against the current Nushell.
+    if ($pj_completion_marker_root | path exists) {
+        rm -rf $pj_completion_marker_root
+    }
+    let ensure = (_pj_completion_ensure_markers)
+    _pj_completion_report $ensure
+
+    if not $no_restart {
+        print "[pj completion] restarting Nushell..."
+        exec nu
+    }
+}
+
+# Show which completion files are enabled or disabled for the current Nushell version.
+export def "pj completion doctor" [] {
+    let enabled = ($pj_completion_commands | where {|name| (_pj_completion_marker_path $name) | path exists })
+    let disabled = ($pj_completion_commands | where {|name| not ((_pj_completion_marker_path $name) | path exists) })
+    print $"Nushell version: ($pj_completion_version)"
+    print $"Marker dir:      ($pj_completion_marker_dir)"
+    print "Enabled:"
+    if ($enabled | is-empty) {
+        print "  (none)"
+    } else {
+        $enabled | each {|name| print $"  - ($name)" }
+    }
+    print "Disabled:"
+    if ($disabled | is-empty) {
+        print "  (none)"
+    } else {
+        $disabled | each {|name| print $"  - ($name)" }
+    }
+    null
 }
 
 export def "pj completion" [
     --update(-u) # Update cached repo, or clone when cache is missing.
     --force(-f) # Force re-clone cached nu_scripts repository.
     --sync(-s) # Regenerate static registry and restart Nushell.
+    --no-restart(-n) # Used with --sync: regenerate without restarting Nushell.
     --help(-h) # Show help.
 ] {
     if $help {
@@ -91,7 +180,7 @@ export def "pj completion" [
     }
 
     if $sync {
-        pj completion sync
+        pj completion sync --no-restart=($no_restart)
         return
     }
 
@@ -154,6 +243,13 @@ export def "pj completion" [
         $missing | each {|it| print $"  - ($it.command): ($it.file)" }
     }
 
+    # The cache changed, so previously validated markers are no longer trustworthy.
+    if ($pj_completion_marker_root | path exists) {
+        rm -rf $pj_completion_marker_root
+    }
+    let ensure = (_pj_completion_ensure_markers)
+    _pj_completion_report $ensure
+
     print "[pj completion] ok"
     {
         cache_dir: $cache_dir
@@ -161,6 +257,7 @@ export def "pj completion" [
         completion_dir: $completion_dir
         commands: $pj_completion_commands
         missing_files: $missing
+        disabled: $ensure.invalid
     }
 }
 
@@ -178,14 +275,22 @@ export-env {
         }
     })
 
-    if not ($pj_completion_registry_module | path exists) {
+    let registry_missing = (not ($pj_completion_registry_module | path exists))
+    if $registry_missing {
         mkdir $pj_cache_dir
         let content = ((_pj_completion_registry_lines) | str join "\n")
         $content | save -f $pj_completion_registry_module
+    }
 
+    # A marker is only written when a file parses under the current Nushell, so a
+    # broken (outdated) third-party completion can never stop the shell from loading.
+    let ensure = (_pj_completion_ensure_markers)
+
+    if ($registry_missing or $ensure.created) {
         if (($env.PJ_COMPLETION_BOOTSTRAPPED? | default "0") != "1") {
             load-env { PJ_COMPLETION_BOOTSTRAPPED: "1" }
-            print "[pj completion] generated cache registry, restarting Nushell..."
+            _pj_completion_report $ensure
+            print "[pj completion] restarting Nushell..."
             exec nu
         }
     }
diff --git a/nushell/modules/pj_prompt.nu b/nushell/modules/pj_prompt.nu
index 59c9181..54bd1c6 100644
--- a/nushell/modules/pj_prompt.nu
+++ b/nushell/modules/pj_prompt.nu
@@ -1,6 +1,6 @@
 def _pj_detect_os_key [] {
     let os_name = ($nu.os-info.name? | default "" | into string | str lowercase)
-    if ($os_name | str contains "darwin") {
+    if (($os_name | str contains "macos") or ($os_name | str contains "darwin") or ($os_name | str contains "mac")) {
         return "Macos"
     }
     if ($os_name | str contains "windows") {