diff --git a/.envrc b/.envrc
index 3550a30f2de38..f905841649e3c 100644
--- a/.envrc
+++ b/.envrc
@@ -1 +1,7 @@
 use flake
+
+# Per-worktree overrides (ports, DATABASE_URL, etc.) written by webmux/workmux
+# post-create hooks. Must come after `use flake` so they take precedence over
+# the flake's defaults.
+# shellcheck source=/dev/null
+[ -f .env.local ] && source .env.local
diff --git a/flake.nix b/flake.nix
index 135005b83d5d6..5f644d93dcf8d 100644
--- a/flake.nix
+++ b/flake.nix
@@ -229,13 +229,20 @@
         # ---------------------------------------------------------------
 
         devEnvVars = {
-          DATABASE_URL = "postgres://postgres:changeme@127.0.0.1:5432/windmill?sslmode=disable";
-          REMOTE = "http://127.0.0.1:8000";
-          REMOTE_LSP = "http://127.0.0.1:3001";
           NODE_ENV = "development";
           NODE_OPTIONS = "--max-old-space-size=16384";
         };
 
+        # Connection-specific defaults — set via shellHook so they respect
+        # pre-existing values (e.g. from webmux runtime.env / .env.local).
+        # Nix attrs are injected unconditionally and would override per-worktree
+        # values set by webmux before the interactive shell starts.
+        devShellHook = ''
+          export DATABASE_URL="''${DATABASE_URL:-postgres://postgres:changeme@127.0.0.1:5432/windmill?sslmode=disable}"
+          export REMOTE="''${REMOTE:-http://127.0.0.1:8000}"
+          export REMOTE_LSP="''${REMOTE_LSP:-http://127.0.0.1:3001}"
+        '';
+
         # ---------------------------------------------------------------
         # Helper scripts — base set (default + full)
         # ---------------------------------------------------------------
@@ -402,6 +409,7 @@
         # =============================================================
 
         devShells.default = pkgs.mkShell (buildEnvVars // commonRuntimeVars // devEnvVars // browserVars // {
+          shellHook = devShellHook;
           buildInputs = coreBuildInputs;
 
           packages = helperScriptsBase ++ [ playwrightWrapper ];
@@ -413,6 +421,7 @@
         # =============================================================
 
         devShells.full = pkgs.mkShell (buildEnvVars // commonRuntimeVars // extraRuntimeVars // devEnvVars // browserVars // {
+          shellHook = devShellHook;
           buildInputs = coreBuildInputs ++ extraRuntimes ++ (with pkgs; [
             # Python extras
             poetry