@@ -68,6 +68,12 @@ jobs:
 
       - name: Compute requisites after change
         run: ./tools/nix/list-requisites.sh > requisites-${{ matrix.system }}-after.list
+        env:
+          # Making sure we do not depend on eval-time fetches, which are not cached.
+          # The only exception is nixpkgs source tarballs.
+          NIX_CONFIG: |
+            restrict-eval = true
+            allowed-uris = https://github.com/NixOS/nixpkgs/archive/
 
       - name: Compute requisites before change
         run: |
 
@@ -46,13 +46,17 @@ args@{
           )
         }-pkg-config-only"
         {
+          __structuredAttrs = true;
+          strictDeps = true;
           nativeBuildInputs = [ pkgs.pkgconf ];
           buildInputs = [ dep ];
+          outputChecks.out.disallowedRequisites = [ pkgs.pkgconf ];
         }
         ''
           mkdir -p "$out/lib/pkgconfig"
-          for pc in $(pkgconf --list-package-names); do
-            ln -s "$(pkgconf --path "$pc")" "$out/lib/pkgconfig/"
+          for pc in $(pkgconf --env-only --list-package-names); do
+            PC_PATH="$(pkgconf --path "$pc")"
+            [ -z "$PC_PATH" ] || ln -s "$PC_PATH" "$out/lib/pkgconfig/"
           done
         ''
     ) old.buildInputs;
 
@@ -4,7 +4,7 @@ set -ex
 
 BASE_DIR=$(cd "$(dirname "$0")/../.." && pwd)
 
-OPTIONAL_FLAGS=$(nix-instantiate -I "nixpkgs=$BASE_DIR/tools/nix/pkgs.nix" --eval --strict --raw -E "
+OPTIONAL_FLAGS=$(nix-instantiate -I "$BASE_DIR" -I "nixpkgs=$BASE_DIR/tools/nix/pkgs.nix" --eval --strict --raw -E "
   (import <nixpkgs> {}).lib.concatMapStrings
     (n: ''--arg \${n} true '')
     (builtins.filter
@@ -16,7 +16,7 @@ OPTIONAL_FLAGS=$(nix-instantiate -I "nixpkgs=$BASE_DIR/tools/nix/pkgs.nix" --eva
 DRV=$(
   cd "$BASE_DIR"
   # shellcheck disable=SC2086
-  nix-instantiate -I "nixpkgs=./tools/nix/pkgs.nix" shell.nix \
+  nix-instantiate -I. -I "nixpkgs=./tools/nix/pkgs.nix" shell.nix \
     $OPTIONAL_FLAGS \
     --arg sharedLibDeps '{
       # Using an empty set as some build dependencies are required only in the absence of shared deps (e.g. Cargo).
 
@@ -1,10 +1,10 @@
 arg:
 let
   repo = "https://github.com/NixOS/nixpkgs";
-  rev = "c0ae35c6460f00dcac6a59063e080f826e620b28";
+  rev = "57f1c8965649ce5bcac5118a0d2e41f1fbdc56e5";
   nixpkgs = import (builtins.fetchTarball {
     url = "${repo}/archive/${rev}.tar.gz";
-    sha256 = "0hbdqzpiv8p44li7jng01mlg2zbb1ff18z3r250f4rjbqflbiwxs";
+    sha256 = "08gxbi52psc9wvflpfsli9fjvcv1jvzd70w6c8pxl4swjvfcsq3d";
   }) arg;
 in
 # Unstable channel no longer supports Intel architecture for macOS. We can use the 26.05 channel
 
@@ -1,10 +1,10 @@
 arg:
 let
   repo = "https://github.com/NixOS/nixpkgs";
-  rev = "0bb2eedc20e4739f29e8045034f2828ad7054f8f";
+  rev = "085af13c1607f4f73ab1e7a51071faf6577a7e87";
   nixpkgs = import (builtins.fetchTarball {
     url = "${repo}/archive/${rev}.tar.gz";
-    sha256 = "008j4dj5yrzww91qvp1lp2c9d1lkwc6i2dpainf5nkdkr3rwj8vy";
+    sha256 = "0wwdfxvwc19qymmjshf8qzw39dqyav1kgxna2ady9l7akqzanm1i";
   }) arg;
 in
 # Unstable channel no longer supports Intel architecture for macOS. We can use the 26.05 channel
@@ -38,23 +38,4 @@ else
           Cflags: -I${lib.getInclude boringssl}/include
         '';
       };
-
-    # TODO: remove pin once https://github.com/mozilla/sccache/issues/2869 is resolved
-    sccache = nixpkgs.callPackage (builtins.fetchurl {
-      url = "${repo}/raw/aff8a0b28396750446e5537a96461bc4facdb287/pkgs/by-name/sc/sccache/package.nix";
-      sha256 = "09dlc99sam9ld9jvzgcc00r4v4ls1cmbb0yim3mr895fpbs8b3qa";
-    }) { };
-
-    # TODO: remove this override once the pin we use has picked up https://github.com/NixOS/nixpkgs/pull/575002
-    uvwasi = nixpkgs.uvwasi.overrideAttrs (old: {
-      patches = old.patches ++ [
-        (nixpkgs.fetchpatch2 {
-          url = "https://github.com/nodejs/uvwasi/commit/fe602a6911207efd8dcfc070a752bcf76813c978.patch?full_index=1";
-          hash = "sha256-MyFvRuEhcqZR+Bz2pY9vani8U1iyQrDeni2kKKnJGEI=";
-        })
-      ];
-
-      buildInputs = [ ];
-      propagatedBuildInputs = old.buildInputs;
-    });
   }