From 007eb8002919182e3c2149c7a089ef8f44ffcab4 Mon Sep 17 00:00:00 2001
From: Jake Hillion <jake@hillion.co.uk>
Date: Mon, 12 Jan 2026 16:04:11 +0000
Subject: [PATCH] nix: enable cachix

Enable cachix and push to it in the pipeline.yml workflow. This won't
cache a huge amount yet but will automatically extend our caching as we
build more of the repo with Nix in CI. It can also be used by local
users by accepting our cache to improve the speed of local builds.

Test plan:
- CI
---
 .github/workflows/pipeline.yml | 12 ++++++++++++
 flake.nix                      | 11 +++++------
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/pipeline.yml b/.github/workflows/pipeline.yml
index e78c3198..af4a67e3 100644
--- a/.github/workflows/pipeline.yml
+++ b/.github/workflows/pipeline.yml
@@ -20,6 +20,12 @@ jobs:
         with:
           nix_path: nixpkgs=channel:nixos-unstable
 
+      - uses: cachix/cachix-action@v14
+        name: Configure Cachix
+        with:
+          name: exo
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+
       - name: Configure git user
         run: |
           git config --local user.email "github-actions@users.noreply.github.com"
@@ -101,6 +107,12 @@ jobs:
         with:
           nix_path: nixpkgs=channel:nixos-unstable
 
+      - uses: cachix/cachix-action@v14
+        name: Configure Cachix
+        with:
+          name: exo
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+
       - name: Run nix flake check
         run: |
           nix flake check
diff --git a/flake.nix b/flake.nix
index f405aea7..86fdb2e1 100644
--- a/flake.nix
+++ b/flake.nix
@@ -16,12 +16,11 @@
     };
   };
 
-  # TODO: figure out caching story
-  # nixConfig = {
-  #   # nix community cachix
-  #   extra-trusted-public-keys = "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=";
-  #   extra-substituters = "https://nix-community.cachix.org";
-  # };
+  nixConfig = {
+    # nix community cachix
+    extra-trusted-public-keys = "exo.cachix.org-1:okq7hl624TBeAR3kV+g39dUFSiaZgLRkLsFBCuJ2NZI=";
+    extra-substituters = "https://exo.cachix.org";
+  };
 
   outputs =
     inputs: