From 65d305ad061bda65f85b3545fcd18705326d174a Mon Sep 17 00:00:00 2001
From: Robby Russell <robby@planetargon.com>
Date: Mon, 7 Sep 2026 08:25:24 -0700
Subject: [PATCH] fix(init): bound the LocalHostName cache and don't cache
 lookup failures

Keying the cache on $HOST alone can't notice a LocalHostName rename
while HostName stays fixed, which would pin a stale identity forever.
Expire the entry after a day, like lib/grep.zsh does, so a rename is
picked up without giving up the fork on almost every start.

Only write the cache when scutil actually answered, so a transient
failure falls back to ${HOST/.*/} for that shell instead of pinning the
fallback name for the next day.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 oh-my-zsh.sh | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/oh-my-zsh.sh b/oh-my-zsh.sh
index a0d98c34d..4e45e9282 100644
--- a/oh-my-zsh.sh
+++ b/oh-my-zsh.sh
@@ -100,17 +100,23 @@ done
 # Figure out the SHORT hostname
 if [[ "$OSTYPE" = darwin* ]]; then
   # macOS's $HOST changes with dhcp, etc. Use LocalHostName if possible.
-  # scutil costs a fork on every start, so remember its answer against the
-  # $HOST it was looked up for and only ask again when $HOST changes.
+  # scutil costs a fork on every start, so remember its answer for a day
+  # (like lib/grep.zsh) and re-check sooner if $HOST changes.
   __omz_host_cache="$ZSH_CACHE_DIR/localhostname"
-  if [[ -r "$__omz_host_cache" ]]; then
+  __omz_host_cached=("$__omz_host_cache"(Nm-1))
+  if [[ -n "$__omz_host_cached" ]]; then
     { read -r __omz_host_key && read -r SHORT_HOST } < "$__omz_host_cache"
   fi
   if [[ "$__omz_host_key" != "$HOST" || -z "$SHORT_HOST" ]]; then
-    SHORT_HOST=$(scutil --get LocalHostName 2>/dev/null) || SHORT_HOST="${HOST/.*/}"
-    [[ ! -w "$ZSH_CACHE_DIR" ]] || print -rl -- "$HOST" "$SHORT_HOST" >| "$__omz_host_cache"
+    # only cache what scutil actually answered, so a transient failure
+    # doesn't pin the fallback name for a day
+    if SHORT_HOST=$(scutil --get LocalHostName 2>/dev/null) && [[ -n "$SHORT_HOST" ]]; then
+      [[ ! -w "$ZSH_CACHE_DIR" ]] || print -rl -- "$HOST" "$SHORT_HOST" >| "$__omz_host_cache"
+    else
+      SHORT_HOST="${HOST/.*/}"
+    fi
   fi
-  unset __omz_host_cache __omz_host_key
+  unset __omz_host_cache __omz_host_cached __omz_host_key
 else
   SHORT_HOST="${HOST/.*/}"
 fi