From e375223500ca0fd919b0e504eab65c6ddb5e4233 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20Soko=C5=82owski?= <jakub@status.im>
Date: Fri, 13 Feb 2026 12:28:50 +0100
Subject: [PATCH] fix: nix /tmp permission errors on MacOS
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Because on MacOS Nix does not have proper filesystem namespacing like on
linux the /tmp filesystem is the real /tmp on the machine.

This can cause permission issues when different Nix build users creat it:

> cannot create directory: /tmp/nim/koch_d

Signed-off-by: Jakub Sokołowski <jakub@status.im>
---
 nix/default.nix | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/nix/default.nix b/nix/default.nix
index a030d5de..3ec55f7d 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -56,8 +56,6 @@ in stdenv.mkDerivation rec {
 
   # Disable CPU optimizations that make binary not portable.
   NIMFLAGS = "-d:disableMarchNative -d:git_revision_override=${revision}";
-  # Avoid Nim cache permission errors.
-  XDG_CACHE_HOME = "/tmp";
 
   makeFlags = targets ++ [
     "V=${toString verbosity}"
@@ -72,6 +70,8 @@ in stdenv.mkDerivation rec {
   '';
 
   configurePhase = ''
+    # Avoid Nim cache permission errors.
+    export XDG_CACHE_HOME=$TMPDIR
     patchShebangs . vendor/nimbus-build-system > /dev/null
     make nimbus-build-system-paths
   '';