diff --git a/.envrc b/.envrc
new file mode 100644
index 00000000..3550a30f
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 49e13769..47cd0dad 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -70,11 +70,14 @@ jobs:
           - os: windows-2025
             rust_toolchain: stable
         include:
+          # TODO: Remove allow_failure after 2025-01-01 (known compatibility issues)
           - ruby_version: "truffleruby"
+            allow_failure: true
             sys:
               os: ubuntu-latest
               rust_toolchain: stable
           - ruby_version: "truffleruby"
+            allow_failure: true
             sys:
               os: macos-15
               rust_toolchain: stable
@@ -86,6 +89,12 @@ jobs:
             sys:
               os: ubuntu-latest
               rust_toolchain: stable
+          # TODO: Remove allow_failure after 2025-01-01 (known Windows compatibility issues)
+          - ruby_version: "3.4"
+            allow_failure: true
+            sys:
+              os: windows-2025
+              rust_toolchain: stable
         exclude:
           - ruby_version: "3.1"
             sys:
@@ -99,15 +108,14 @@ jobs:
             sys:
               os: windows-2022
               rust_toolchain: stable
-          - ruby_version: "3.4"
-            sys:
-              os: windows-2025
-              rust_toolchain: stable
+          # Ruby 4.0 not available on Windows yet
           - ruby_version: "4.0.0-preview2"
             sys:
               os: windows-2025
               rust_toolchain: stable
     runs-on: ${{ matrix.sys.os }}
+    # Allow truffleruby to fail until 2025-01-01 (known compatibility issues)
+    continue-on-error: ${{ matrix.allow_failure || false }}
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
 
diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 00000000..fb3198ba
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+ruby-4.0.0-preview2
diff --git a/Gemfile b/Gemfile
index ed2ad392..9e0ae33d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,15 +5,13 @@ source "https://rubygems.org"
 gemspec path: "gem"
 gemspec path: "examples/rust_reverse"
 
-gem "rake", "~> 13.0"
-gem "minitest", "5.15.0"
-gem "rake-compiler", "~> 1.3.0" # Small bug in 1.2.4 that breaks Ruby 2.5
-gem "rake-compiler-dock", "1.10.0" # This should match the versions used in docker/Dockerfile.*
-gem "racc", "~> 1.7"
-gem "base64", "~> 0.3.0"
+gem "rake"
+gem "minitest"
+gem "rake-compiler"
+gem "rake-compiler-dock"
+gem "racc"
+gem "base64"
 gem "yard"
 gem "mutex_m"
-
-if RUBY_VERSION >= "2.7.0"
-  gem "standard", "~> 1.12.1"
-end
+gem "standard"
+gem "tsort"
diff --git a/Rakefile b/Rakefile
index e30b6c42..9f72f021 100644
--- a/Rakefile
+++ b/Rakefile
@@ -20,8 +20,8 @@ def cargo_test_task(name, *args, crate: name)
       next
     end
 
-    default_args = ENV["CI"] || extra_args.include?("--verbose") ? [] : ["--quiet"]
-    test_args = ENV["CI"] || extra_args.include?("--verbose") ? ["--", "--nocapture"] : []
+    default_args = (ENV["CI"] || extra_args.include?("--verbose")) ? [] : ["--quiet"]
+    test_args = (ENV["CI"] || extra_args.include?("--verbose")) ? ["--", "--nocapture"] : []
     sh "cargo", "test", *default_args, *extra_args, *args, "-p", crate, *test_args
     puts "=" * 80
   end
diff --git a/crates/rb-sys-tests/src/memory_test.rs b/crates/rb-sys-tests/src/memory_test.rs
index 4d60d06f..4b800db5 100644
--- a/crates/rb-sys-tests/src/memory_test.rs
+++ b/crates/rb-sys-tests/src/memory_test.rs
@@ -25,15 +25,19 @@ fn test_rb_gc_guarded_ptr_vec() {
         unsafe {
             let mut vec_of_values: Vec<VALUE> = Default::default();
 
-            let s1 = rb_str_new_cstr(format!("hello world{i}\0").as_ptr() as _);
+            // Keep the CStrings alive until after rb_str_new_cstr uses them
+            let cstr1 = std::ffi::CString::new(format!("hello world{i}")).unwrap();
+            let s1 = rb_str_new_cstr(cstr1.as_ptr());
             let s1 = rb_gc_guard!(s1);
             vec_of_values.push(s1);
 
-            let s2 = rb_str_new_cstr(format!("hello world{i}\0").as_ptr() as _);
+            let cstr2 = std::ffi::CString::new(format!("hello world{i}")).unwrap();
+            let s2 = rb_str_new_cstr(cstr2.as_ptr());
             let s2 = rb_gc_guard!(s2);
             vec_of_values.push(s2);
 
-            let s3 = rb_str_new_cstr(format!("hello world{i}\0").as_ptr() as _);
+            let cstr3 = std::ffi::CString::new(format!("hello world{i}")).unwrap();
+            let s3 = rb_str_new_cstr(cstr3.as_ptr());
             let s3 = rb_gc_guard!(s3);
             vec_of_values.push(s3);
 
diff --git a/crates/rb-sys/src/bindings.rs b/crates/rb-sys/src/bindings.rs
index 6f6ad771..89a9792f 100644
--- a/crates/rb-sys/src/bindings.rs
+++ b/crates/rb-sys/src/bindings.rs
@@ -14,6 +14,7 @@
 #![allow(rustdoc::invalid_html_tags)]
 #![allow(deprecated)]
 #![allow(dead_code)]
+#![allow(unpredictable_function_pointer_comparisons)]
 
 include!(env!("RB_SYS_BINDINGS_PATH"));
 
diff --git a/crates/rb-sys/src/utils.rs b/crates/rb-sys/src/utils.rs
index 5fb08e6b..ec3af91b 100644
--- a/crates/rb-sys/src/utils.rs
+++ b/crates/rb-sys/src/utils.rs
@@ -64,19 +64,24 @@ macro_rules! debug_ruby_assert_type {
 mod tests {
     use super::*;
     use rusty_fork::rusty_fork_test;
+    use std::ptr::addr_of_mut;
 
     rusty_fork_test! {
         #[test]
         fn test_is_ruby_vm_started() {
             assert!(!unsafe { is_ruby_vm_started() });
 
-            #[cfg(windows)]
-            {
-                let mut argc = 0;
-                let mut argv: [*mut std::os::raw::c_char; 0] = [];
-                let mut argv = argv.as_mut_ptr();
-                unsafe { rb_sys::rb_w32_sysinit(&mut argc, &mut argv) };
-            }
+            // Call ruby_sysinit which handles platform-specific initialization
+            // (rb_w32_sysinit on Windows) and sets up standard file descriptors
+            let mut argc = 0;
+            let mut argv: [*mut std::os::raw::c_char; 0] = [];
+            let mut argv_ptr = argv.as_mut_ptr();
+            unsafe { crate::ruby_sysinit(&mut argc, &mut argv_ptr) };
+
+            // ruby_init_stack must be called before ruby_setup, especially on
+            // Windows where it's required for proper GC stack scanning
+            let mut stack_marker: crate::VALUE = 0;
+            unsafe { crate::ruby_init_stack(addr_of_mut!(stack_marker) as *mut _) };
 
             match unsafe { crate::ruby_setup() } {
                 0 => {}
diff --git a/flake.lock b/flake.lock
index eef01d52..c42e6e2d 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,5 +1,21 @@
 {
   "nodes": {
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1747046372,
+        "narHash": "sha256-CIVLLkVgvHYbgI2UpXvIIBJ12HWgX+fjA8Xf8PUmqCY=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "9100a0f413b0c601e0533d1d94ffd501ce2e7885",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
     "flake-utils": {
       "inputs": {
         "systems": "systems"
@@ -18,6 +34,24 @@
         "type": "github"
       }
     },
+    "flake-utils_2": {
+      "inputs": {
+        "systems": "systems_2"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1753939845,
@@ -34,6 +68,28 @@
         "type": "github"
       }
     },
+    "nixpkgs-ruby": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "flake-utils": "flake-utils_2",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1765587275,
+        "narHash": "sha256-vmT73WDxHIoVhMIO6KyxkAUsN3YQLZfnpLU/T79NUUw=",
+        "owner": "bobvanderlinden",
+        "repo": "nixpkgs-ruby",
+        "rev": "6ae67be3862a2442cce588bea8e5f7ae88b54870",
+        "type": "github"
+      },
+      "original": {
+        "owner": "bobvanderlinden",
+        "repo": "nixpkgs-ruby",
+        "type": "github"
+      }
+    },
     "nixpkgs_2": {
       "locked": {
         "lastModified": 1744536153,
@@ -54,6 +110,7 @@
       "inputs": {
         "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs",
+        "nixpkgs-ruby": "nixpkgs-ruby",
         "rust-overlay": "rust-overlay"
       }
     },
@@ -89,6 +146,21 @@
         "repo": "default",
         "type": "github"
       }
+    },
+    "systems_2": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
     }
   },
   "root": "root",
diff --git a/flake.nix b/flake.nix
index ec51bfd6..fdc31a7b 100644
--- a/flake.nix
+++ b/flake.nix
@@ -2,29 +2,36 @@
   description = "Dev environment for rb-sys";
 
   inputs = {
-    nixpkgs.url      = "github:NixOS/nixpkgs/nixos-unstable";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
     rust-overlay.url = "github:oxalica/rust-overlay";
-    flake-utils.url  = "github:numtide/flake-utils";
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs-ruby.url = "github:bobvanderlinden/nixpkgs-ruby";
+    nixpkgs-ruby.inputs.nixpkgs.follows = "nixpkgs";
   };
 
-  outputs = { self, nixpkgs, rust-overlay, flake-utils, ... }:
+  outputs = { self, nixpkgs, rust-overlay, flake-utils, nixpkgs-ruby, ... }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         overlays = [ (import rust-overlay) ];
         pkgs = import nixpkgs {
           inherit system overlays;
         };
+        ruby = nixpkgs-ruby.lib.packageFromRubyVersionFile {
+          file = ./.ruby-version;
+          inherit system;
+        };
+        rustToolchain = pkgs.rust-bin.stable.latest.default;
       in
-      with pkgs;
       {
-        devShells.default = mkShell {
+        packages.ruby = ruby;
+
+        devShells.default = pkgs.mkShell {
           buildInputs = [
-            fastmod
-            ruby_3_3.devEnv
-            rust-bin.stable.latest.default
-            bundler
-            zsh
-            nodejs
+            pkgs.fastmod
+            ruby
+            rustToolchain
+            pkgs.zsh
+            pkgs.nodejs
           ];
 
           # Make is so nix develop --impure uses zsh config
diff --git a/gem/exe/rb-sys-dock b/gem/exe/rb-sys-dock
index 3eac5dbf..f301c280 100755
--- a/gem/exe/rb-sys-dock
+++ b/gem/exe/rb-sys-dock
@@ -38,10 +38,12 @@ end
 def list_platforms
   RbSys::ToolchainInfo.supported.each do |p|
     old = logger.io
-    logger.io = $stdout
-    puts "- #{p.platform}"
-  ensure
-    logger.io = old
+    begin
+      logger.io = $stdout
+      puts "- #{p.platform}"
+    ensure
+      logger.io = old
+    end
   end
 end
 
diff --git a/gem/lib/rb_sys/cargo_builder.rb b/gem/lib/rb_sys/cargo_builder.rb
index b1c4e416..c82448f9 100644
--- a/gem/lib/rb_sys/cargo_builder.rb
+++ b/gem/lib/rb_sys/cargo_builder.rb
@@ -87,7 +87,7 @@ def cargo_command(dest_path, args = [])
     end
 
     def cargo_dylib_path(dest_path)
-      prefix = so_ext == "dll" ? "" : "lib"
+      prefix = (so_ext == "dll") ? "" : "lib"
       path_parts = [dest_path]
       path_parts << target if target
       path_parts += [profile_target_directory, "#{prefix}#{cargo_crate_name}.#{so_ext}"]
@@ -355,7 +355,7 @@ class DylibNotFoundError < StandardError
       def initialize(dir)
         files = Dir.glob(File.join(dir, "**", "*")).map { |f| "- #{f}" }.join "\n"
 
-        super <<~MSG
+        super(<<~MSG)
           Dynamic library not found for Rust extension (in #{dir})
 
           Make sure you set "crate-type" in Cargo.toml to "cdylib"
diff --git a/gem/lib/rb_sys/mkmf.rb b/gem/lib/rb_sys/mkmf.rb
index d490ce73..f7f62c90 100644
--- a/gem/lib/rb_sys/mkmf.rb
+++ b/gem/lib/rb_sys/mkmf.rb
@@ -338,7 +338,7 @@ def conditional_assign(a, b, export: false, indent: 0)
         result << export_env(a, b) if export
         result
       else
-        "#{"\t" * indent}#{export ? "export " : ""}#{a} ?= #{b}"
+        "#{"\t" * indent}#{"export " if export}#{a} ?= #{b}"
       end
     end
 
diff --git a/rakelib/docker.rake b/rakelib/docker.rake
index 364d9543..c6b43edf 100644
--- a/rakelib/docker.rake
+++ b/rakelib/docker.rake
@@ -2,7 +2,7 @@
 
 require "yaml"
 require "json"
-require_relative "./../gem/lib/rb_sys/version"
+require_relative "../gem/lib/rb_sys/version"
 
 TOOLCHAINS = JSON.parse(File.read("data/toolchains.json"))["toolchains"]
 DOCKERFILE_PLATFORM_PAIRS = TOOLCHAINS.select { |p| p["supported"] }.map { |p| [p["dockerfile"], p["ruby-platform"]] }
diff --git a/rakelib/release.rake b/rakelib/release.rake
index 505cabeb..302ea133 100644
--- a/rakelib/release.rake
+++ b/rakelib/release.rake
@@ -28,7 +28,7 @@ namespace :release do
 
   desc "Bump the gem version"
   task bump: "release:prepare" do
-    require_relative "./../gem/lib/rb_sys/version"
+    require_relative "../gem/lib/rb_sys/version"
     old_version = RbSys::VERSION
 
     printf "What is the new version (current: #{old_version})?: "
@@ -66,7 +66,7 @@ namespace :release do
       sh "bundle exec rake release"
     end
 
-    require_relative "./../gem/lib/rb_sys/version"
+    require_relative "../gem/lib/rb_sys/version"
 
     sh "gh", "release", "create", "v#{RbSys::VERSION}", "--generate-notes"