From 5d40b43dd9423a7c9153abfe2966c654f5b08c8f Mon Sep 17 00:00:00 2001
From: alexion <contact@alexion.dev>
Date: Tue, 15 Sep 2026 21:16:30 -0400
Subject: [PATCH] fix(nixos): avoid redundant deploy closure transfers

---
 .../shell/fish/functions/deploy-to.fish       | 71 +++++++++++--------
 1 file changed, 40 insertions(+), 31 deletions(-)

diff --git a/configs/nixos/modules/shell/fish/functions/deploy-to.fish b/configs/nixos/modules/shell/fish/functions/deploy-to.fish
index 4e3c043..d4f4b52 100644
--- a/configs/nixos/modules/shell/fish/functions/deploy-to.fish
+++ b/configs/nixos/modules/shell/fish/functions/deploy-to.fish
@@ -34,43 +34,52 @@ if test (count $system_path) -ne 1
     return 1
 end
 
-set nar_file (mktemp --suffix=.nar)
-or return $status
-set remote_nar "/tmp/deploy-to-$host-"(date +%s)"-$fish_pid.nar"
-
 set closure_paths (nix-store -qR $system_path)
 or begin
-    set query_status $status
-    rm -f $nar_file
     echo "deploy-to: closure query failed for $host" >&2
-    return $query_status
-end
-
-echo "deploy-to: exporting closure for $system_path" >&2
-nix-store --export $closure_paths >$nar_file
-or begin
-    set export_status $status
-    rm -f $nar_file
-    echo "deploy-to: closure export failed for $host" >&2
-    return $export_status
-end
-
-echo "deploy-to: copying closure archive to $host:$remote_nar" >&2
-scp $nar_file $host:$remote_nar
-set scp_status $status
-rm -f $nar_file
-if test $scp_status -ne 0
-    echo "deploy-to: closure archive copy failed for $host" >&2
-    return $scp_status
-end
-
-echo "deploy-to: importing closure on $host" >&2
-ssh -t $host "sudo sh -c 'nix-store --import < $remote_nar' && rm -f $remote_nar"
-or begin
-    echo "deploy-to: closure import failed for $host" >&2
     return $status
 end
 
+echo "deploy-to: checking which closure paths $host is missing" >&2
+set missing_paths (printf '%s\n' $closure_paths | ssh $host 'xargs -r nix-store --check-validity --print-invalid')
+or begin
+    echo "deploy-to: remote closure check failed for $host" >&2
+    return $status
+end
+
+if test (count $missing_paths) -gt 0
+    set nar_file (mktemp --suffix=.nar)
+    or return $status
+    set remote_nar "/tmp/deploy-to-$host-"(date +%s)"-$fish_pid.nar"
+
+    echo "deploy-to: exporting "(count $missing_paths)" missing closure paths for $system_path" >&2
+    nix-store --export $missing_paths >$nar_file
+    or begin
+        set export_status $status
+        rm -f $nar_file
+        echo "deploy-to: closure export failed for $host" >&2
+        return $export_status
+    end
+
+    echo "deploy-to: copying closure archive to $host:$remote_nar" >&2
+    scp $nar_file $host:$remote_nar
+    set scp_status $status
+    rm -f $nar_file
+    if test $scp_status -ne 0
+        echo "deploy-to: closure archive copy failed for $host" >&2
+        return $scp_status
+    end
+
+    echo "deploy-to: importing closure on $host" >&2
+    ssh -t $host "sudo sh -c 'nix-store --import < $remote_nar' && rm -f $remote_nar"
+    or begin
+        echo "deploy-to: closure import failed for $host" >&2
+        return $status
+    end
+else
+    echo "deploy-to: $host already has the full closure for $system_path" >&2
+end
+
 echo "deploy-to: activating $system_path on $host" >&2
 ssh -t $host sudo "$system_path/bin/switch-to-configuration" switch
 or begin