diff --git a/.github/actions/nix-cachix-setup/action.yml b/.github/actions/nix-cachix-setup/action.yml
index 860cb26..f46180c 100644
--- a/.github/actions/nix-cachix-setup/action.yml
+++ b/.github/actions/nix-cachix-setup/action.yml
@@ -21,6 +21,11 @@ inputs:
       Run the bundled `cache-nix-action` Nix store restore/save (default). Set to 'false' if the caller pins a different cache-nix-action version and runs it itself.
     required: false
     default: 'true'
+  gc-max-store-size-linux:
+    description: >-
+      `gc-max-store-size-linux` for the bundled cache-nix-action: the store is garbage-collected down to this size before a new cache is saved. Defaults to `8G`; a caller running a smaller or larger build passes its own budget (e.g. `1G` for a docs/subgraph build, `10G` for a webapp build).
+    required: false
+    default: 8G
   gc-max-store-size-macos:
     description: >-
       Optional `gc-max-store-size-macos` for the bundled cache-nix-action. Left empty (the action's own default) unless a caller needs to cap the macOS store before saving.
@@ -68,5 +73,5 @@ runs:
       with:
         primary-key: nix-${{ runner.os }}-${{ hashFiles('**/*.nix', '**/flake.lock') }}
         restore-prefixes-first-match: nix-${{ runner.os }}-
-        gc-max-store-size-linux: 8G
+        gc-max-store-size-linux: ${{ inputs.gc-max-store-size-linux }}
         gc-max-store-size-macos: ${{ inputs.gc-max-store-size-macos }}