diff --git a/.envrc b/.envrc
new file mode 100644
index 000000000..3add3fcca
--- /dev/null
+++ b/.envrc
@@ -0,0 +1,3 @@
+use flake
+layout node
+eval "$shellHook" 
diff --git a/.gitignore b/.gitignore
index eabf4fd55..2336af8ef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -18,3 +18,4 @@ metals.sbt
 node_modules/
 package-lock.json
 target
+.direnv/
diff --git a/downstream-tests/scalafix.sbt b/downstream-tests/scalafix.sbt
index 094b38fc1..3515f51a1 100644
--- a/downstream-tests/scalafix.sbt
+++ b/downstream-tests/scalafix.sbt
@@ -10,7 +10,7 @@ ThisBuild / scalacOptions ++= {
 
 ThisBuild / semanticdbEnabled := true
 
-ThisBuild / semanticdbVersion := "4.5.9"
+ThisBuild / semanticdbVersion := "4.12.0"
 
 ThisBuild / scalafixScalaBinaryVersion := "2.13"
 
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 000000000..055567cf7
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,109 @@
+{
+  "nodes": {
+    "devshell": {
+      "inputs": {
+        "nixpkgs": [
+          "typelevel-nix",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1728330715,
+        "narHash": "sha256-xRJ2nPOXb//u1jaBnDP56M7v5ldavjbtR6lfGqSvcKg=",
+        "owner": "numtide",
+        "repo": "devshell",
+        "rev": "dd6b80932022cea34a019e2bb32f6fa9e494dfef",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "devshell",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "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": 1733376361,
+        "narHash": "sha256-aLJxoTDDSqB+/3orsulE6/qdlX6MzDLIITLZqdgMpqo=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "929116e316068c7318c54eb4d827f7d9756d5e9c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": [
+          "typelevel-nix",
+          "flake-utils"
+        ],
+        "nixpkgs": [
+          "typelevel-nix",
+          "nixpkgs"
+        ],
+        "typelevel-nix": "typelevel-nix"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "typelevel-nix": {
+      "inputs": {
+        "devshell": "devshell",
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      },
+      "locked": {
+        "lastModified": 1733783241,
+        "narHash": "sha256-nDM0W3EhiVJDFPCInPzJ9+QUyyjMTZhlTK8JGN7vfJQ=",
+        "owner": "typelevel",
+        "repo": "typelevel-nix",
+        "rev": "a4a46f0b1b94e150a1dda0a8f0f013696d9299fd",
+        "type": "github"
+      },
+      "original": {
+        "owner": "typelevel",
+        "repo": "typelevel-nix",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 000000000..e6885acf5
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,43 @@
+{
+  inputs = {
+    typelevel-nix.url = "github:typelevel/typelevel-nix";
+    nixpkgs.follows = "typelevel-nix/nixpkgs";
+    flake-utils.follows = "typelevel-nix/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, typelevel-nix }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs-x86_64 = import nixpkgs { system = "x86_64-darwin"; };
+        scala-cli-overlay = final: prev: { scala-cli = pkgs-x86_64.scala-cli; };
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ typelevel-nix.overlays.default scala-cli-overlay];
+        };
+      in
+      {
+        devShell = pkgs.devshell.mkShell {
+          imports = [ typelevel-nix.typelevelShell ];
+          packages = [
+            pkgs.nodePackages.typescript-language-server
+            pkgs.nodePackages.vscode-langservers-extracted
+            pkgs.nodePackages.prettier
+            pkgs.nodePackages.typescript
+            pkgs.nodePackages.graphqurl
+            pkgs.hasura-cli
+          ];
+          typelevelShell = {
+            nodejs.enable = true;
+            jdk.package = pkgs.jdk11;
+          };
+          env = [
+            {
+              name = "NODE_OPTIONS";
+              value = "--max-old-space-size=8192";
+            }
+          ];
+        };
+      }
+
+    );
+}
diff --git a/library/callback/src/main/scala-3/japgolly/scalajs/react/callback/CallbackOption.scala b/library/callback/src/main/scala-3/japgolly/scalajs/react/callback/CallbackOption.scala
index 0948c371c..5120167c3 100644
--- a/library/callback/src/main/scala-3/japgolly/scalajs/react/callback/CallbackOption.scala
+++ b/library/callback/src/main/scala-3/japgolly/scalajs/react/callback/CallbackOption.scala
@@ -183,7 +183,7 @@ final class CallbackOption[+A](val underlyingRepr: CallbackOption.UnderlyingRepr
   def asCallback: CallbackTo[Option[A]] =
     CallbackTo lift cbfn
 
-  inline def map[B](f: A => B)(using inline ev: MapGuard[B]): CallbackOption[ev.Out] =
+  inline def map[B](f: A => B)(using ev: MapGuard[B]): CallbackOption[ev.Out] =
     unsafeMap(f)
 
   private[react] def unsafeMap[B](f: A => B): CallbackOption[B] =
@@ -192,7 +192,7 @@ final class CallbackOption[+A](val underlyingRepr: CallbackOption.UnderlyingRepr
   /**
    * Alias for `map`.
    */
-  inline def |>[B](f: A => B)(using inline ev: MapGuard[B]): CallbackOption[ev.Out] =
+  inline def |>[B](f: A => B)(using ev: MapGuard[B]): CallbackOption[ev.Out] =
     map(f)
 
   def flatMapOption[B](f: A => Option[B]): CallbackOption[B] =
diff --git a/library/callback/src/main/scala-3/japgolly/scalajs/react/callback/CallbackTo.scala b/library/callback/src/main/scala-3/japgolly/scalajs/react/callback/CallbackTo.scala
index 1a80ef18c..4863c657c 100644
--- a/library/callback/src/main/scala-3/japgolly/scalajs/react/callback/CallbackTo.scala
+++ b/library/callback/src/main/scala-3/japgolly/scalajs/react/callback/CallbackTo.scala
@@ -306,11 +306,11 @@ final class CallbackTo[+A] /*private[react]*/ (private[CallbackTo] val trampolin
   inline def runNow(): A =
     trampoline.run
 
-  inline def map[B](f: A => B)(using inline ev: MapGuard[B]): CallbackTo[ev.Out] =
+  inline def map[B](f: A => B)(using ev: MapGuard[B]): CallbackTo[ev.Out] =
     new CallbackTo(trampoline.map(f))
 
   /** Alias for `map`. */
-  inline def |>[B](inline f: A => B)(using inline ev: MapGuard[B]): CallbackTo[ev.Out] =
+  inline def |>[B](inline f: A => B)(using ev: MapGuard[B]): CallbackTo[ev.Out] =
     map(f)
 
   inline def flatMap[B](f: A => CallbackTo[B]): CallbackTo[B] =
@@ -589,7 +589,7 @@ final class CallbackTo[+A] /*private[react]*/ (private[CallbackTo] val trampolin
 
 
   /** Convenience-method to run additional code after this callback. */
-  inline def thenRun[B](inline runNext: B)(using inline ev: MapGuard[B]): CallbackTo[ev.Out] =
+  inline def thenRun[B](inline runNext: B)(using ev: MapGuard[B]): CallbackTo[ev.Out] =
     this >> CallbackTo(runNext)
 
   /** Convenience-method to run additional code before this callback. */
diff --git a/library/extra/src/main/scala/japgolly/scalajs/react/extra/router/Dsl.scala b/library/extra/src/main/scala/japgolly/scalajs/react/extra/router/Dsl.scala
index bc9aa8aed..fcf185d3d 100644
--- a/library/extra/src/main/scala/japgolly/scalajs/react/extra/router/Dsl.scala
+++ b/library/extra/src/main/scala/japgolly/scalajs/react/extra/router/Dsl.scala
@@ -87,7 +87,7 @@ object StaticDsl {
     val / = literal("/")
   }
 
-  abstract class RouteCommon[R[X] <: RouteCommon[R, X], A] {
+  trait RouteCommon[R[X] <: RouteCommon[R, X], A] {
 
     def parseThen(f: Option[A] => Option[A]): R[A]
 
@@ -159,7 +159,7 @@ object StaticDsl {
       // val g = p.matcher("").groupCount
       // if (g != matchGroups)
       //   sys.error(s"Error in regex: /${p.pattern}/. Expected $matchGroups match groups but detected $g.")
-      new Route(p, m => parse(i => m.group(i + 1)), a => Path(build(a)))
+      Route.forPattern(p, m => parse(i => m.group(i + 1)), a => Path(build(a)))
     }
   }
 
@@ -192,30 +192,28 @@ object StaticDsl {
   }
 
   /**
-   * A complete route.
+   * A `Route` translates a `Path` into an instance of model `A` and vice versa.
    */
-  final class Route[A](pattern: Pattern,
-                       parseFn: Matcher => Option[A],
-                       buildFn: A => Path) extends RouteCommon[Route, A] with RouterMacros.ForRoute[A] {
-    override def toString =
-      s"Route($pattern)"
-
+  case class Route[A](parse: Path => Option[A], pathFor: A => Path) extends RouteCommon[Route, A] {
     override def parseThen(f: Option[A] => Option[A]): Route[A] =
-      new Route(pattern, f compose parseFn, buildFn)
+      Route(f compose parse, pathFor)
 
     override def pmap[B](b: A => Option[B])(a: B => A): Route[B] =
-      new Route(pattern, parseFn(_) flatMap b, buildFn compose a)
-
-    def parse(path: Path): Option[A] = {
-      val m = pattern.matcher(path.value)
-      if (m.matches)
-        parseFn(m)
-      else
-        None
-    }
+      Route(parse(_) flatMap b, pathFor compose a)
+  }
 
-    def pathFor(a: A): Path =
-      buildFn(a)
+  object Route {
+    def forPattern[A](pattern: Pattern, parseFn: Matcher => Option[A], buildFn: A => Path): Route[A] =
+      new Route(
+        p => {
+          val m = pattern.matcher(p.value)
+          if (m.matches)
+            parseFn(m)
+          else
+            None
+        },
+        buildFn
+      )
   }
 
   // ===================================================================================================================
diff --git a/library/project/Dependencies.scala b/library/project/Dependencies.scala
index d48d315d0..821296cfc 100644
--- a/library/project/Dependencies.scala
+++ b/library/project/Dependencies.scala
@@ -9,23 +9,23 @@ object Dependencies {
   object Ver {
 
     // Externally observable
-    val cats                  = "2.7.0"
-    val catsEffect            = "3.3.11"
-    val microlibs             = "4.2.1"
+    val cats                  = "2.12.0"
+    val catsEffect            = "3.5.4"
+    val microlibs             = "4.1.0"
     val monocle2              = "2.1.0"
-    val monocle3              = "3.1.0"
-    val scala2                = "2.13.8"
-    val scala3                = "3.1.2"
-    val scalaJsDom            = "2.0.0"
-    val sourcecode            = "0.2.8"
+    val monocle3              = "3.2.0"
+    val scala2                = "2.13.15"
+    val scala3                = "3.3.0"
+    val scalaJsDom            = "2.8.0"
+    val sourcecode            = "0.4.2"
 
     // Internal
     val betterMonadicFor      = "0.3.1"
     val catsTestkitScalaTest  = "2.1.5"
     val disciplineScalaTest   = "2.1.5"
     val fastTextEncoding      = "1.0.6"
-    val kindProjector         = "0.13.2"
-    val macrotaskExecutor     = "1.0.0"
+    val kindProjector         = "0.13.3"
+    val macrotaskExecutor     = "1.1.1"
     val nyaya                 = "1.0.0"
     val reactJs               = "18.2.0"
     val scalaJsJavaTime       = "1.0.0"
diff --git a/library/project/plugins.sbt b/library/project/plugins.sbt
index 0d5f5d427..29f96510d 100644
--- a/library/project/plugins.sbt
+++ b/library/project/plugins.sbt
@@ -2,7 +2,7 @@ libraryDependencies ++= Seq(
   "org.scala-js" %% "scalajs-env-jsdom-nodejs" % "1.1.0",
   "org.scala-js" %% "scalajs-env-selenium"     % "1.1.1")
 
-addSbtPlugin("ch.epfl.scala"  % "sbt-scalafix"       % "0.10.1")
-addSbtPlugin("com.github.sbt" % "sbt-ci-release"     % "1.5.10")
+addSbtPlugin("ch.epfl.scala"  % "sbt-scalafix"       % "0.12.1")
+addSbtPlugin("com.github.sbt" % "sbt-ci-release"     % "1.5.12")
 addSbtPlugin("org.scala-js"   % "sbt-jsdependencies" % "1.0.2")
 addSbtPlugin("org.scala-js"   % "sbt-scalajs"        % "1.16.0")
diff --git a/library/scalafix.sbt b/library/scalafix.sbt
index fbe1c58c3..14bc20874 100644
--- a/library/scalafix.sbt
+++ b/library/scalafix.sbt
@@ -8,4 +8,4 @@ ThisBuild / scalacOptions ++= {
 ThisBuild / semanticdbEnabled := true
 
 // NOTE: Upgrade downstream-tests/scalafix.sbt too!
-ThisBuild / semanticdbVersion := "4.5.9"
+ThisBuild / semanticdbVersion := "4.12.0"