diff --git a/.claude/bun-ipv4-preload.js b/.claude/bun-ipv4-preload.js
new file mode 100644
index 00000000..3531b937
--- /dev/null
+++ b/.claude/bun-ipv4-preload.js
@@ -0,0 +1,159 @@
+// IPv4 強制パッチ for Claude Code + VPN (AnyConnect/Netskope)
+//
+// Bun の Happy Eyeball 実装が VPN 環境で IPv6 接続を試行してタイムアウトする問題の回避策。
+// BUN_OPTIONS="--preload=$HOME/.claude/bun-ipv4-preload.js" として使用する。
+//
+// 参考:
+// - https://github.com/oven-sh/bun/issues/25619
+// - https://github.com/oven-sh/bun/pull/26012
+
+import https from "node:https";
+import dns from "node:dns";
+import net from "node:net";
+import dnsPromises from "node:dns/promises";
+
+const originalHttpsRequest = https.request;
+const logEnabled = !!process.env.DEBUG_IPV4_PATCH;
+
+function log(...args) {
+  if (logEnabled) {
+    console.log("[IPv4 Patch]", ...args);
+  }
+}
+
+function normalizeLookupOptions(opts) {
+  if (typeof opts === "number") {
+    return { family: opts };
+  }
+  if (!opts || typeof opts !== "object") {
+    return {};
+  }
+  return opts;
+}
+
+// Use the OS resolver so VPN-provided DNS behavior is preserved.
+function lookupIPv4(hostname, opts, callback) {
+  const options = normalizeLookupOptions(opts);
+  dns.lookup(
+    hostname,
+    {
+      ...options,
+      family: 4,
+      all: Boolean(options.all),
+    },
+    (err, address, family) => {
+      if (err) {
+        return callback(err);
+      }
+      if (options.all) {
+        return callback(null, address);
+      }
+      return callback(null, address, family);
+    },
+  );
+}
+
+async function resolveIPv4(hostname) {
+  const result = await dnsPromises.lookup(hostname, { family: 4 });
+  return result.address;
+}
+
+// https.request を IPv4 強制に上書き
+// @ts-ignore
+https.request = function (...args) {
+  log("Custom https.request called with:", args);
+
+  let optionsIndex = -1;
+  if (typeof args[0] === "object" && !(args[0] instanceof URL)) {
+    optionsIndex = 0;
+    log("Detected options in args[0]");
+  } else if (typeof args[1] === "object") {
+    optionsIndex = 1;
+  }
+
+  if (optionsIndex !== -1) {
+    args[optionsIndex].lookup = lookupIPv4;
+    const host = args[optionsIndex].hostname || args[optionsIndex].host;
+    if (host) {
+      args[optionsIndex].headers = {
+        ...args[optionsIndex].headers,
+        Host: host,
+      };
+    }
+  } else if (typeof args[0] === "string" || args[0] instanceof URL) {
+    args.splice(1, 0, { family: 4, lookup: lookupIPv4 });
+  }
+
+  log("Modified args for IPv4:", args);
+  return originalHttpsRequest(...args);
+};
+
+// fetch を IPv4 強制に上書き
+const originalFetch = globalThis.fetch;
+globalThis.fetch = async (input, init) => {
+  log("Custom fetch called with:", input);
+
+  if (typeof input === "string" && !input.startsWith("http")) {
+    return originalFetch(input, init);
+  }
+
+  const requestUrl =
+    typeof input === "string"
+      ? new URL(input)
+      : input instanceof URL
+        ? input
+        : new URL(input.url);
+
+  try {
+    const ipv4 = await resolveIPv4(requestUrl.hostname);
+    const fetchUrl = new URL(requestUrl);
+    fetchUrl.hostname = ipv4;
+    const headers = new Headers(init?.headers);
+    headers.set("Host", requestUrl.host);
+    return originalFetch(fetchUrl, { ...init, headers });
+  } catch (e) {
+    log("IPv4 resolve failed, falling back:", e);
+  }
+
+  return originalFetch(input, init);
+};
+
+// net.connect / net.createConnection を IPv4 強制に上書き
+const originalConnect = net.connect;
+const originalCreateConnection = net.createConnection;
+
+function injectFamily4(args) {
+  if (args.length === 0) return args;
+  const arg0 = args[0];
+
+  if (arg0 !== null && typeof arg0 === "object") {
+    arg0.family = 4;
+    return args;
+  }
+
+  const port = Number(arg0);
+  if (!Number.isNaN(port)) {
+    const options = { port: port, family: 4 };
+    let callback;
+    if (typeof args[1] === "string") {
+      options.host = args[1];
+      callback = args[2];
+    } else if (typeof args[1] === "function") {
+      callback = args[1];
+    }
+    const newArgs = [options];
+    if (callback) newArgs.push(callback);
+    return newArgs;
+  }
+
+  return args;
+}
+
+net.connect = function (...args) {
+  return originalConnect.apply(this, injectFamily4(args));
+};
+
+net.createConnection = function (...args) {
+  log("Custom net.createConnection called with:", args);
+  return originalCreateConnection.apply(this, injectFamily4(args));
+};
diff --git a/.zshrc b/.zshrc
index ece99e1f..f5b85cb5 100644
--- a/.zshrc
+++ b/.zshrc
@@ -537,12 +537,15 @@ if which plenv > /dev/null; then eval "$(plenv init - zsh)"; fi
 export RENOVATE_SAFETY_LANGUAGE=ja
 
 # claude code
-# 削除済みの Bun preload を過去シェルから引き継いだ場合に無効化する
-case "${BUN_OPTIONS:-}" in
-  *"$HOME/.claude/bun-ipv4-preload.js"*) unset BUN_OPTIONS ;;
-esac
 export MAX_THINKING_TOKENS=31999
 export DISABLE_AUTOUPDATER=1
+# VPN (AnyConnect) 環境での IPv6 Happy Eyeball タイムアウト回避
+# https://github.com/oven-sh/bun/issues/25619
+if [[ -f "$HOME/.claude/bun-ipv4-preload.js" ]]; then
+  export BUN_OPTIONS="--preload=$HOME/.claude/bun-ipv4-preload.js"
+elif [[ "${BUN_OPTIONS:-}" == "--preload=$HOME/.claude/bun-ipv4-preload.js" ]]; then
+  unset BUN_OPTIONS
+fi
 
 export PATH="/opt/homebrew/opt/openjdk@21/bin:$PATH"
 export PATH="/opt/homebrew/opt/postgresql@17/bin:$PATH"
diff --git a/symlink.sh b/symlink.sh
index 91633f5b..56414b19 100755
--- a/symlink.sh
+++ b/symlink.sh
@@ -92,7 +92,7 @@ ln -snfv "$DOT_DIRECTORY/ghostty/config" "$GHOSTTY_DIR/config"
 # Claude
 mkdir -p "$HOME/.claude"
 # 既存のシンボリンクの循環参照をチェック
-for link in "$HOME/.claude/settings.json" "$HOME/.claude/CLAUDE.md" "$HOME/.claude/commands" "$HOME/.claude/skills" "$HOME/.claude/statusline.sh"; do
+for link in "$HOME/.claude/settings.json" "$HOME/.claude/CLAUDE.md" "$HOME/.claude/commands" "$HOME/.claude/skills" "$HOME/.claude/statusline.sh" "$HOME/.claude/bun-ipv4-preload.js"; do
     if ! check_circular_link "$link"; then
         echo "  -> 削除: $link"
         rm -f "$link"
@@ -102,6 +102,7 @@ ln -snfv "$DOT_DIRECTORY/.claude/settings.json"       "$HOME/.claude/settings.js
 ln -snfv "$DOT_DIRECTORY/.claude/commands"            "$HOME/.claude/commands"
 ln -snfv "$DOT_DIRECTORY/.claude/CLAUDE.md"           "$HOME/.claude/CLAUDE.md"
 ln -snfv "$DOT_DIRECTORY/.claude/statusline.sh"      "$HOME/.claude/statusline.sh"
+ln -snfv "$DOT_DIRECTORY/.claude/bun-ipv4-preload.js" "$HOME/.claude/bun-ipv4-preload.js"
 if [ -d "$DOT_DIRECTORY/.claude/skills" ]; then
     ln -snfv "$DOT_DIRECTORY/.claude/skills"           "$HOME/.claude/skills"
 fi