build(amm): load amm_client_ffi via absolute store-path id + DYLD fallback on macOS

flake.nix

@@ -71,8 +71,14 @@
                 cp programs/amm/client-ffi/amm_client_ffi.h $out/include/
               ''
               + pkgs.lib.optionalString pkgs.stdenv.isDarwin ''
+                # Set the dylib's install-name to its ABSOLUTE store path (NOT
+                # @rpath): the logos module builder links this lib into the plugin
+                # but never stages it into the plugin's runtime rpath, so an
+                # @rpath id fails to dlopen at launch. An absolute /nix/store id
+                # is recorded in the plugin's LC_LOAD_DYLIB, kept in the closure
+                # by Nix, and resolved directly at runtime — no rpath needed.
                 if [ -f $out/lib/libamm_client_ffi.dylib ]; then
-                  install_name_tool -id @rpath/libamm_client_ffi.dylib $out/lib/libamm_client_ffi.dylib
+                  install_name_tool -id "$out/lib/libamm_client_ffi.dylib" $out/lib/libamm_client_ffi.dylib
                 fi
               '';
           }
@@ -108,9 +114,27 @@
       appApps = appOutputs.apps or { };
       appPkgs = appOutputs.packages or { };
 
+      # Wrap the app launcher to export DYLD_FALLBACK_LIBRARY_PATH pointing at the
+      # amm_client_ffi lib. The logos module builder links the plugin against
+      # @rpath/libamm_client_ffi.dylib but does NOT stage that dylib into the
+      # plugin-dir it loads at runtime, so dlopen fails with "Failed to load UI
+      # plugin". Adding the crate's store lib dir to DYLD's fallback search path
+      # lets the loader find it (the store path stays in the closure).
+      wrapWithDyld = system: app:
+        let
+          pkgs = import nixpkgs { inherit system; overlays = [ rust-overlay.overlays.default ]; };
+          ammFfi = crateOutputs.packages.${system}.amm_client_ffi;
+        in
+        app // {
+          program = "${pkgs.writeShellScript "run-amm-ui" ''
+            export DYLD_FALLBACK_LIBRARY_PATH="${ammFfi}/lib''${DYLD_FALLBACK_LIBRARY_PATH:+:$DYLD_FALLBACK_LIBRARY_PATH}"
+            exec ${app.program} "$@"
+          ''}";
+        };
+
       renamedApps = builtins.mapAttrs (
         system: attrs:
-        (builtins.removeAttrs attrs [ "default" ]) // (if attrs ? default then { amm-ui = attrs.default; } else { })
+        (builtins.removeAttrs attrs [ "default" ]) // (if attrs ? default then { amm-ui = wrapWithDyld system attrs.default; } else { })
       ) appApps;
 
       mergedPackages = builtins.mapAttrs (

programs/amm/client-ffi/Cargo.toml

@@ -1,10 +1,17 @@
 [package]
 name = "amm_client_ffi"
 version = "0.1.0"
+# 2021 (not the repo's 2024): matches amm_core and keeps plain #[no_mangle]
+# (edition 2024 requires #[unsafe(no_mangle)]).
 edition = "2021"
 
 [lib]
 name = "amm_client_ffi"
+# The logos module builder's macOS find_library only locates SHARED libs
+# (lib<name>.dylib), never a static .a — so we must ship the cdylib. The flake
+# gives the dylib an ABSOLUTE store-path install-name (not @rpath), so the plugin
+# links it by its /nix/store path (kept in the closure) and dlopen resolves it at
+# runtime without any rpath staging. staticlib/rlib kept for other consumers/tests.
 crate-type = ["staticlib", "cdylib", "rlib"]
 
 [lints]

programs/amm/client-ffi/build.rs

@@ -5,4 +5,6 @@ fn main() {
         .expect("cbindgen")
         .write_to_file(format!("{crate_dir}/amm_client_ffi.h"));
     println!("cargo:rerun-if-changed=src/lib.rs");
+    println!("cargo:rerun-if-changed=src");
+    println!("cargo:rerun-if-changed=cbindgen.toml");
 }