From 980c830415d54029059f0266a7b3bf0c00ff64b4 Mon Sep 17 00:00:00 2001
From: Siddarth Kumar <siddarthkay@gmail.com>
Date: Tue, 26 May 2026 15:53:51 +0530
Subject: [PATCH] nix: set nim cache to proper tmp directory

Otherwise we end up with cache collisions like this in CI :

```
 > Error: cannot open '/tmp/nim/libsds_d/@z..@f..@f..@f..@f..@f..
 @ffgber@f6y2zz1uv2lzi4ln2717py8m0aix64u56-avz-hajenccrq-2.2.4@favz
 @fyvo@fflfgrz@frkprcgvbaf.nim.c'
```
---
 nix/shell.nix | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/nix/shell.nix b/nix/shell.nix
index 575d791..733508a 100644
--- a/nix/shell.nix
+++ b/nix/shell.nix
@@ -21,7 +21,9 @@ in pkgs.mkShell {
   ];
 
   # Avoid compiling Nim itself.
+  # Setting nim cache to proper tmp location avoids cache collision in CI
   shellHook = ''
     export USE_SYSTEM_NIM=1
+    export XDG_CACHE_HOME="$TMPDIR"
   '';
 }