diff --git a/src/libponyc/codegen/genexe.cc b/src/libponyc/codegen/genexe.cc
index 826d69f0bcba..897afba953bb 100644
--- a/src/libponyc/codegen/genexe.cc
+++ b/src/libponyc/codegen/genexe.cc
@@ -22,6 +22,7 @@ LLD_HAS_DRIVER(wasm)
 #include "../type/lookup.h"
 #include "../../libponyrt/mem/pool.h"
 #include "ponyassert.h"
+#include "nix.h"
 #include <string.h>
 
 #include <llvm/Support/raw_ostream.h>
@@ -38,6 +39,8 @@ LLD_HAS_DRIVER(wasm)
 #  include <llvm/TargetParser/Triple.h>
 #endif
 
+static bool dir_has_arch_libc_crt(const char* dir, uint16_t target_machine);
+
 #if defined(PONY_SANITIZER)
 // Generated at configure time (top-level CMakeLists.txt, PONY_SANITIZERS_ENABLED
 // block): the sanitizer runtime link fragment captured from the compiler driver.
@@ -965,6 +968,9 @@ static bool link_exe_lld_elf(compile_t* c, ast_t* program,
 
   program_lib_build_args_embedded(program, c->opt);
 
+  std::vector<const char*> env_libdirs;
+  nix_collect_link_libdirs(c->opt->strtab, env_libdirs);
+
   const char* sys_triple = system_triple(c->opt);
   bool is_freebsd = target_is_freebsd(c->opt->triple);
   bool is_dragonfly = target_is_dragonfly(c->opt->triple);
@@ -996,7 +1002,11 @@ static bool link_exe_lld_elf(compile_t* c, ast_t* program,
     return false;
   }
 
-  const char* dynlinker = dynamic_linker_path(c);
+  // Prefer a Nix-provided ELF interpreter (baked default or environment);
+  // fall back to the built-in FHS search when none is configured.
+  const char* dynlinker = nix_dynamic_linker(c->opt->strtab);
+  if(dynlinker[0] == '\0')
+    dynlinker = dynamic_linker_path(c);
   if(!c->opt->staticbin && dynlinker == NULL)
   {
     errorf(errors, NULL,
@@ -1009,10 +1019,23 @@ static bool link_exe_lld_elf(compile_t* c, ast_t* program,
   const char* libc_crt_dir = find_libc_crt_dir(sysroot, sys_triple,
     target_machine, c->opt->strtab);
   if(libc_crt_dir == NULL)
+  {
+    for(size_t i = 0; i < env_libdirs.size(); i++)
+    {
+      if(dir_has_arch_libc_crt(env_libdirs[i], target_machine))
+      {
+        libc_crt_dir = env_libdirs[i];
+        break;
+      }
+    }
+  }
+  if(libc_crt_dir == NULL)
   {
     errorf(errors, NULL,
       "could not find a libc crt startup object (crt1.o or crt0.o) "
-      "matching target architecture '%s' in sysroot '%s'",
+      "matching target architecture '%s' in sysroot '%s'\n"
+      "  On NixOS systems, set PONY_LINK_LIBDIRS to the directory holding "
+      "the arch-matching libc startup object (crt1.o or crt0.o).",
       c->opt->triple, sysroot);
     return false;
   }
@@ -1305,6 +1328,21 @@ static bool link_exe_lld_elf(compile_t* c, ast_t* program,
     }
   }
 
+/*
+  Add /nix/store lib directories to the embedded linker args
+*/
+  for(size_t i = 0; i < env_libdirs.size(); i++)
+  {
+    snprintf(buf, sizeof(buf), "-L%s", env_libdirs[i]);
+    args.push_back(stringtab(c->opt->strtab, buf));
+
+    if(!c->opt->staticbin)
+    {
+      args.push_back("-rpath");
+      args.push_back(env_libdirs[i]);
+    }
+  }
+
   // Standard system library fallback paths. The paths above cover
   // distro-specific locations (libc_crt_dir, gcc_lib_dir, etc.) but miss
   // common install locations like /usr/local/lib (where libraries built
@@ -1732,9 +1770,10 @@ static const char* find_macos_sdk_path(strtable_t* strtab)
     pclose(f);
   }
 
-  // Hardcoded fallback.
+  // Fall back to the Nix apple-sdk when xcrun is unavailable. The unversioned
+  // MacOSX.sdk symlink keeps this independent of the SDK version.
   const char* fallback =
-    "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib";
+    "@apple-sdk@/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib";
 
   struct stat st;
   if(stat(fallback, &st) == 0 && S_ISDIR(st.st_mode))
@@ -1947,6 +1986,31 @@ static bool link_exe_lld_macho(compile_t* c, ast_t* program,
     }
   }
 
+/*
+  Add /nix/store lib directories to the embedded Mach-O linker args, mirroring
+  the ELF path. On NixOS the C++ standard library, buildInputs and user FFI
+  libraries live under /nix/store, not in the SDK's usr/lib or the Homebrew and
+  /usr/local fallbacks above. nix_collect_link_libdirs() (see nix.h) gathers
+  them from the baked PONY_NIX_LINK_LIBDIRS default, the PONY_LINK_LIBDIRS /
+  NIX_LDFLAGS env vars, and the cc-wrapper's $NIX_CC/nix-support/cc-ldflags
+  (which carries the -L<libc++> path on Darwin). Without this,
+  `use "lib:c++" if osx` (as used by pony-compiler) fails to link with
+  "library not found for -lc++".
+*/
+  std::vector<const char*> env_libdirs;
+  nix_collect_link_libdirs(c->opt->strtab, env_libdirs);
+  for(size_t i = 0; i < env_libdirs.size(); i++)
+  {
+    snprintf(buf, sizeof(buf), "-L%s", env_libdirs[i]);
+    args.push_back(stringtab(c->opt->strtab, buf));
+
+    if(!c->opt->staticbin)
+    {
+      args.push_back("-rpath");
+      args.push_back(env_libdirs[i]);
+    }
+  }
+
   // Object file.
   args.push_back(file_o);
 
@@ -2417,3 +2481,21 @@ bool genexe(compile_t* c, ast_t* program)
 
   return true;
 }
+
+// Does `dir` hold a libc startup object (crt1.o / crt0.o) whose ELF machine
+// matches the target? Used to pick the crt directory out of the Nix libdirs
+// gathered by nix_collect_link_libdirs().
+static bool dir_has_arch_libc_crt(const char* dir, uint16_t target_machine)
+{
+  static const char* sentinels[] = { "crt1.o", "crt0.o" };
+  char buf[PATH_MAX];
+
+  for(size_t j = 0; j < sizeof(sentinels) / sizeof(sentinels[0]); j++)
+  {
+    snprintf(buf, sizeof(buf), "%s/%s", dir, sentinels[j]);
+    if(file_exists(buf) && elf_matches_target(buf, target_machine))
+      return true;
+  }
+
+  return false;
+}