diff --git a/flake.lock b/flake.lock
index 7344daf..0449b0a 100644
--- a/flake.lock
+++ b/flake.lock
@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1757464828,
-        "narHash": "sha256-1kkbbebts4G/pD7nvgjMN17/1ThDOcaQOOrm557YDvU=",
+        "lastModified": 1757594919,
+        "narHash": "sha256-5HtPkixhYyyJcMiH1vmeMO8YtvHKek/uG2sCXyRMnUQ=",
         "owner": "rstats-on-nix",
         "repo": "nixpkgs",
-        "rev": "31ddb30f2db45b8416e5dc89c68d602a59fd1b37",
+        "rev": "803291803ce9daaa9238ca0a7e815bfdd221abc8",
         "type": "github"
       },
       "original": {
@@ -19,11 +19,11 @@
     "nvimcom": {
       "flake": false,
       "locked": {
-        "lastModified": 1755532199,
-        "narHash": "sha256-mb8HCaMasPUP9JZUkH1sPrtdbhM2HMUkJEKDsRt6wTs=",
+        "lastModified": 1757588228,
+        "narHash": "sha256-5YLUqIh5lxy7qwKPxGtrQs8mruPLnC3b2pN6nIkD2Kk=",
         "owner": "R-nvim",
         "repo": "R.nvim",
-        "rev": "fd992e1c13ad3df794a30af2e937b994bf7bf4db",
+        "rev": "99e6bf5787cbcdecd8a8b11177d1928f3fc4860e",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index a5c8fef..dad0c52 100644
--- a/flake.nix
+++ b/flake.nix
@@ -29,36 +29,34 @@
 
     # The overlay that exposes custom R packages
     overlay = final: prev: let
+      readJSONFile = path: builtins.fromJSON (builtins.readFile path);
     in {
       extraRPackages = {
         ## H
-        httpgd = prev.rPackages.buildRPackage {
-          name = "httpgd";
-          src = prev.fetchgit {
-            url = "https://github.com/nx10/httpgd";
-            rev = "dd6ed3a687a2d7327bb28ca46725a0a203eb2a19";
-            sha256 = "sha256-vs6MTdVJXhTdzPXKqQR+qu1KbhF+vfyzZXIrFsuKMtU=";
+        httpgd = let
+          httpgdLatest = readJSONFile ./versions/httpgd.json;
+        in
+          prev.rPackages.buildRPackage {
+            name = "httpgd";
+            src = prev.fetchFromGitHub httpgdLatest;
+            propagatedBuildInputs = builtins.attrValues {
+              inherit
+                (prev.rPackages)
+                unigd
+                cpp11
+                AsioHeaders
+                ;
+            };
           };
-          propagatedBuildInputs = builtins.attrValues {
-            inherit
-              (prev.rPackages)
-              unigd
-              cpp11
-              AsioHeaders
-              ;
-          };
-        };
 
         ## M
-        musicMetadata = prev.rPackages.buildRPackage {
-          name = "musicMetadata";
-          src = prev.fetchgit {
-            url = "https://github.com/hannesdatta/musicMetadata";
-            branchName = "master";
-            rev = "1b7ca4c1fd208475e961b77edc90ad513b936879";
-            sha256 = "sha256-QK1Q6/ta2PqIrjdA6/oS1HxOMgZr/BO00OLjs3/O7EE=";
+        musicMetadata = let
+          musicMetadataLatest = readJSONFile ./versions/musicMetadata.json;
+        in
+          prev.rPackages.buildRPackage {
+            name = "musicMetadata";
+            src = prev.fetchFromGitHub musicMetadataLatest;
           };
-        };
 
         ## N
         nvimcom = prev.rPackages.buildRPackage {
@@ -73,16 +71,14 @@
         };
 
         ## S
-        synthdid = prev.rPackages.buildRPackage {
-          name = "synthdid";
-          src = prev.fetchFromGitHub {
-            owner = "synth-inference";
-            repo = "synthdid";
-            rev = "70c1ce3eac58e28c30b67435ca377bb48baa9b8a";
-            sha256 = "sha256-rxQqnpKWy4d9ZykRxfILu1lyT6Z3x++gFdC3sbm++pk=";
+        synthdid = let
+          synthdidLatest = readJSONFile ./versions/synthdid.json;
+        in
+          prev.rPackages.buildRPackage {
+            name = "synthdid";
+            src = prev.fetchFromGitHub synthdidLatest;
+            propagatedBuildInputs = [prev.rPackages.mvtnorm];
           };
-          propagatedBuildInputs = [prev.rPackages.mvtnorm];
-        };
       };
     };
   in {
@@ -97,6 +93,12 @@
         };
       in {
         default = pkgs.rWrapper.override {packages = builtins.attrValues pkgs.extraRPackages;};
+        franUpdate = pkgs.writeShellScriptBin "fran-update" ''
+          pg=${pkgs.nix-prefetch-github}/bin/nix-prefetch-github
+          $pg --json hannesdatta musicMetadata > versions/musicMetadata.json
+          $pg --json nx10 httpgd > versions/httpgd.json
+          $pg --json synth-inference synthdid > versions/synthdid.json
+        '';
       }
     );
     # Helpful for overlay users: expose a devShell with R including these pkgs
@@ -111,6 +113,12 @@
           self.packages."${system}".default
         ];
       };
+      update = pkgs.mkShell {
+        packages = [self.packages."${system}".franUpdate];
+        shellHook = ''
+          fran-update
+        '';
+      };
     });
   };
   nixConfig = {
diff --git a/synthdid.json b/synthdid.json
new file mode 100644
index 0000000..e69de29
diff --git a/versions/httpgd.json b/versions/httpgd.json
new file mode 100644
index 0000000..ad2940b
--- /dev/null
+++ b/versions/httpgd.json
@@ -0,0 +1,6 @@
+{
+    "owner": "nx10",
+    "repo": "httpgd",
+    "rev": "dd6ed3a687a2d7327bb28ca46725a0a203eb2a19",
+    "hash": "sha256-vs6MTdVJXhTdzPXKqQR+qu1KbhF+vfyzZXIrFsuKMtU="
+}
diff --git a/versions/musicMetadata.json b/versions/musicMetadata.json
new file mode 100644
index 0000000..d48b35c
--- /dev/null
+++ b/versions/musicMetadata.json
@@ -0,0 +1,6 @@
+{
+    "owner": "hannesdatta",
+    "repo": "musicMetadata",
+    "rev": "1b7ca4c1fd208475e961b77edc90ad513b936879",
+    "hash": "sha256-QK1Q6/ta2PqIrjdA6/oS1HxOMgZr/BO00OLjs3/O7EE="
+}
diff --git a/versions/synthdid.json b/versions/synthdid.json
new file mode 100644
index 0000000..6a5620a
--- /dev/null
+++ b/versions/synthdid.json
@@ -0,0 +1,6 @@
+{
+    "owner": "synth-inference",
+    "repo": "synthdid",
+    "rev": "70c1ce3eac58e28c30b67435ca377bb48baa9b8a",
+    "hash": "sha256-rxQqnpKWy4d9ZykRxfILu1lyT6Z3x++gFdC3sbm++pk="
+}