diff --git a/home/shell.nix b/home/shell.nix
index c539dc2..ecba544 100644
--- a/home/shell.nix
+++ b/home/shell.nix
@@ -96,6 +96,15 @@ in
       # runs before oh-my-zsh/compinit so the exec replaces the shell before
       # that setup is wasted. Guards, each preventing a real breakage:
       #   interactive only -> don't hijack scp / `ssh host cmd` / scripted shells
+      #   stdout is a tty  -> VS Code (macOS) resolves the shell environment on
+      #                       startup by running an interactive login shell with
+      #                       stdout piped, no controlling terminal. Without this
+      #                       guard `exec tmux` runs there, fails ("open terminal
+      #                       failed: not a terminal"), exits non-zero, and VS
+      #                       Code reports "Unable to resolve your shell
+      #                       environment". A real terminal always has a tty here.
+      #   not VS Code env  -> also skip VS Code's env-resolution probe explicitly,
+      #                       in case a future version allocates a pty for it.
       #   $TMUX empty      -> a pane's zsh won't re-exec tmux (infinite loop)
       #   not SSH          -> don't force inbound SSH logins into a server tmux
       #   not VS Code      -> its integrated terminal manages itself
@@ -103,6 +112,8 @@ in
       #   $NO_TMUX unset   -> escape hatch: `NO_TMUX=1 <term>` opens a bare shell
       (lib.mkOrder 200 ''
         if [[ $- == *i* ]] \
+          && [[ -t 1 ]] \
+          && [[ -z "$VSCODE_RESOLVING_ENVIRONMENT" ]] \
           && [[ -z "$TMUX" ]] \
           && [[ -z "$NO_TMUX" ]] \
           && [[ -z "$SSH_CONNECTION" && -z "$SSH_TTY" ]] \