diff --git a/Makefile b/Makefile
index 78c19c5..5aca9f1 100644
--- a/Makefile
+++ b/Makefile
@@ -7,8 +7,18 @@ clean:
 watch:
 	@dune build @all -w
 
-onix-lock:
+nix-lock:
+	nix run .#onix-lock
+
+.PHONY: onix-lock.json
+onix-lock.json:
 	onix lock ./imandra-document.opam --resolutions="ocaml-system=5.2.0" --lock-file ./onix-lock.json
-	onix lock ./imandra-document.opam --resolutions="ocaml-system=5.2.0,ocaml-lsp-server" --with-test=true --lock-file ./onix-lock-dev.json 
+
+.PHONY: onix-lock-dev.json
+onix-lock-dev.json:
+	onix lock ./imandra-document.opam --resolutions="ocaml-system=5.2.0,ocaml-lsp-server,utop" --with-test=true --lock-file ./onix-lock-dev.json
+
+.PHONY: lock
+lock: onix-lock.json onix-lock-dev.json
 	git add onix-lock.json onix-lock-dev.json
 
diff --git a/flake.lock b/flake.lock
index b750acc..73e8b0b 100644
--- a/flake.lock
+++ b/flake.lock
@@ -66,6 +66,7 @@
       "original": {
         "owner": "rizo",
         "repo": "onix",
+        "rev": "3740a2beb84bc21860385f8bbb0d5f557842de03",
         "type": "github"
       }
     },
diff --git a/flake.nix b/flake.nix
index db2e006..6a8e5fc 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,54 +3,100 @@
     nixpkgs.url = "nixpkgs/nixpkgs-unstable";
     flake-utils.url = "github:numtide/flake-utils";
 
-    onix.url = "github:rizo/onix";
-    onix.inputs.nixpkgs.follows = "nixpkgs";
+    onix = {
+      url = "github:rizo/onix/3740a2beb84bc21860385f8bbb0d5f557842de03";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
-  outputs = { self, nixpkgs, flake-utils, onix }@inputs:
-    flake-utils.lib.eachDefaultSystem (system:
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+      onix,
+    }@inputs:
+    flake-utils.lib.eachDefaultSystem (
+      system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
         onix' = onix.packages.${system}.latest;
-        opamFiles = [ 
+        compilerVersion = "5.2.0";
+        opamFiles = [
           ./imandra-document.opam
         ];
         onixEnv = onix'.env {
           path = ./.;
           roots = opamFiles;
           lock = ./onix-lock.json;
-          deps = { "ocaml-system" = "*"; };
+          deps = {
+            "ocaml-system" = compilerVersion;
+          };
         };
         onixEnvDev = onix'.env {
           path = ./.;
           roots = opamFiles;
           lock = ./onix-lock-dev.json;
           deps = {
-            "ocaml-system" = "*";
+            "ocaml-system" = compilerVersion;
             "ocaml-lsp-server" = "*";
+            "utop" = "*";
           };
         };
-
-      in rec {
+        onixLock =
+          let
+            shellHook = pkgs.writeText "onix-lock-shellHook" onixEnv.lock.shellHook;
+            lockPatched = pkgs.runCommand "onix-lock-shellHook-patched" { } ''
+              sed 's:--lock-file=/nix/store/.*/onix-lock.json::' "${shellHook}" > "$out"
+              chmod +x "$out"
+            '';
+          in
+          pkgs.writeShellApplication {
+            name = "onix-lock";
+            runtimeInputs = [ onix' ];
+            text = lockPatched;
+          };
+        onixLockDev =
+          let
+            shellHook = pkgs.writeText "onix-lock-dev-shellHook" onixEnvDev.lock.shellHook;
+            lockPatched = pkgs.runCommand "onix-lock-dev-shellHook-patched" { } ''
+              sed 's:--lock-file=/nix/store/.*/onix-lock-dev.json::' "${shellHook}" > "$out"
+              chmod +x "$out"
+            '';
+          in
+          pkgs.writeShellApplication {
+            name = "onix-lock-dev";
+            runtimeInputs = [ onix' ];
+            text = lockPatched;
+          };
+      in
+      rec {
         formatter = pkgs.nixfmt-rfc-style;
 
         packages.imandra-document = onixEnv.pkgs.imandra-document;
+        packages.default = onixEnv.pkgs.imandra-document;
 
-        devShells.onixLock = pkgs.mkShell { 
+        packages.onix-lock = onixLock;
+        packages.onix-lock-dev = onixLockDev;
+        devShells.onixLock = pkgs.mkShell {
           buildInputs = [
             onix'
-          ]; 
+          ];
         };
 
-        devShells.default = onixEnvDev.shell.overrideAttrs (final: prev: {
-          buildInputs = prev.buildInputs ++ [ 
-            pkgs.ocamlformat_0_22_4 
-            pkgs.dune_3
-            pkgs.ocaml
-            onix' 
-          ];
-        });
+        devShells.default = onixEnvDev.shell.overrideAttrs (
+          final: prev: {
+            buildInputs = prev.buildInputs ++ [
+              pkgs.ocamlformat_0_22_4
+              pkgs.dune_3
+              pkgs.ocaml
+              onix'
+            ];
+          }
+        );
 
-        packages.dev-shell = devShells.default.inputDerivation;
-      });
+        # Allows the default devshell to be cached
+        packages.devShell-default = devShells.default.inputDerivation;
+      }
+    );
 }
diff --git a/onix-lock-dev.json b/onix-lock-dev.json
index 0760257..e69bf51 100644
--- a/onix-lock-dev.json
+++ b/onix-lock-dev.json
@@ -3,7 +3,7 @@
    "repositories": [
      {
        "url": "https://github.com/ocaml/opam-repository.git",
-       "rev": "a6cd5e92975350b992cb58b4351df6fceefc8144"
+       "rev": "e57ab1a26e2a9ef176034f22915009039c5dc390"
      }
    ],
    "packages" : {
@@ -43,6 +43,16 @@
      "base-bigarray": {
        "version": "base"
      },
+     "base-bytes": {
+       "version": "base",
+       "depends": [
+         "ocaml",
+         "ocamlfind"
+       ],
+       "build-depends": [
+         "ocamlfind"
+       ]
+     },
      "base-domains": {
        "version": "base",
        "depends": [
@@ -126,6 +136,21 @@
          "dune-configurator"
        ]
      },
+     "cppo": {
+       "version": "1.7.0",
+       "src": {
+         "url": "https://github.com/ocaml-community/cppo/archive/refs/tags/v1.7.0.tar.gz",
+         "sha512": "cafa2f7add42912b413f39e1d9fb7a2a42a9be134128c179dfe353f35a6c32840720d2166a77d985941300cb945b9c424b38401d20027d814b25f3bac534506d"
+       },
+       "depends": [
+         "base-unix",
+         "dune",
+         "ocaml"
+       ],
+       "build-depends": [
+         "dune"
+       ]
+     },
      "csexp": {
        "version": "1.5.2",
        "src": {
@@ -278,6 +303,43 @@
          "dune"
        ]
      },
+     "lambda-term": {
+       "version": "3.3.2",
+       "src": {
+         "url": "https://github.com/ocaml-community/lambda-term/archive/refs/tags/3.3.2.tar.gz",
+         "sha512": "78648768644058337e22c79cf1fbb1a36472b24f11b1dc0461fc38419be6ec01b02d8d0ac45fed0bc99f91ba4c0f19d3bda113e834e064bee973b734527b9766"
+       },
+       "depends": [
+         "dune",
+         "logs",
+         "lwt",
+         "lwt_react",
+         "mew_vi",
+         "ocaml",
+         "react",
+         "zed"
+       ],
+       "build-depends": [
+         "dune"
+       ]
+     },
+     "logs": {
+       "version": "0.7.0",
+       "src": {
+         "url": "https://erratique.ch/software/logs/releases/logs-0.7.0.tbz",
+         "sha256": "86f4a02807eb1a297aae44977d9f61e419c31458a5d7b23c6f55575e8e69d5ca"
+       },
+       "depends": [
+         "base-threads",
+         "lwt",
+         "ocaml"
+       ],
+       "build-depends": [
+         "ocamlbuild",
+         "ocamlfind",
+         "topkg"
+       ]
+     },
      "lsp": {
        "version": "1.19.0",
        "src": {
@@ -296,6 +358,43 @@
          "dune"
        ]
      },
+     "lwt": {
+       "version": "5.9.0",
+       "src": {
+         "url": "https://github.com/ocsigen/lwt/archive/refs/tags/5.9.0.tar.gz",
+         "sha512": "35574743df40170a8d1676254952c060090421a40d5f8ad37a6691f4f8bb0e28fca61f5efff1050edc4f8a3ffa2f06a1e23d0c084c89bfc105c1235e249bbc75"
+       },
+       "depends": [
+         "base-threads",
+         "base-unix",
+         "dune",
+         "dune-configurator",
+         "ocaml",
+         "ocplib-endian"
+       ],
+       "build-depends": [
+         "cppo",
+         "dune",
+         "dune-configurator"
+       ]
+     },
+     "lwt_react": {
+       "version": "1.2.0",
+       "src": {
+         "url": "https://github.com/ocsigen/lwt/archive/5.6.0.tar.gz",
+         "sha512": "d616389bc9e0da11f25843ab7541ac2d40c9543700a89455f14115b339bbe58cef2b8acf0ae97fd54e15a4cb93149cfe1ebfda301aa93933045f76b7d9344160"
+       },
+       "depends": [
+         "dune",
+         "lwt",
+         "ocaml",
+         "react"
+       ],
+       "build-depends": [
+         "cppo",
+         "dune"
+       ]
+     },
      "merlin-lib": {
        "version": "5.2.1-502",
        "src": {
@@ -311,6 +410,38 @@
          "dune"
        ]
      },
+     "mew": {
+       "version": "0.1.0",
+       "src": {
+         "url": "https://github.com/kandu/mew/archive/0.1.0.tar.gz",
+         "sha256": "64d38ceb52ef574cb314bdd693f7e4a9c9e483e80a58595db22f2df76a8a59e6"
+       },
+       "depends": [
+         "dune",
+         "ocaml",
+         "result",
+         "trie"
+       ],
+       "build-depends": [
+         "dune"
+       ]
+     },
+     "mew_vi": {
+       "version": "0.5.0",
+       "src": {
+         "url": "https://github.com/kandu/mew_vi/archive/0.5.0.tar.gz",
+         "sha256": "a692fa7cdcc9e80fd9387c4f61677776b9fc15f9f7175b4220fcd1a73d1bafda"
+       },
+       "depends": [
+         "dune",
+         "mew",
+         "ocaml",
+         "react"
+       ],
+       "build-depends": [
+         "dune"
+       ]
+     },
      "ocaml": {
        "version": "5.2.0",
        "depends": [
@@ -476,6 +607,22 @@
          "dune"
        ]
      },
+     "ocplib-endian": {
+       "version": "1.2",
+       "src": {
+         "url": "https://github.com/OCamlPro/ocplib-endian/archive/refs/tags/1.2.tar.gz",
+         "sha512": "2e70be5f3d6e377485c60664a0e235c3b9b24a8d6b6a03895d092c6e40d53810bfe1f292ee69e5181ce6daa8a582bfe3d59f3af889f417134f658812be5b8b85"
+       },
+       "depends": [
+         "base-bytes",
+         "dune",
+         "ocaml"
+       ],
+       "build-depends": [
+         "cppo",
+         "dune"
+       ]
+     },
      "ordering": {
        "version": "3.16.1",
        "src": {
@@ -534,6 +681,35 @@
          "dune"
        ]
      },
+     "react": {
+       "version": "1.2.2",
+       "src": {
+         "url": "https://erratique.ch/software/react/releases/react-1.2.2.tbz",
+         "sha512": "18cdd544d484222ba02db6bd9351571516532e7a1c107b59bbe39193837298f5c745eab6754f8bc6ff125b387be7018c6d6e6ac99f91925a5e4f53af688522b1"
+       },
+       "depends": [
+         "ocaml"
+       ],
+       "build-depends": [
+         "ocamlbuild",
+         "ocamlfind",
+         "topkg"
+       ]
+     },
+     "result": {
+       "version": "1.5",
+       "src": {
+         "url": "https://github.com/janestreet/result/releases/download/1.5/result-1.5.tbz",
+         "sha256": "7c3a5e238558f4c1a4f5acca816bc705a0e12f68dc0005c61ddbf2e6cab8ee32"
+       },
+       "depends": [
+         "dune",
+         "ocaml"
+       ],
+       "build-depends": [
+         "dune"
+       ]
+     },
      "seq": {
        "version": "base",
        "src-extra": {
@@ -565,10 +741,10 @@
        ]
      },
      "spawn": {
-       "version": "v0.15.1",
+       "version": "v0.17.0",
        "src": {
-         "url": "https://github.com/janestreet/spawn/archive/v0.15.1.tar.gz",
-         "sha256": "9afdee314fab6c3fcd689ab6eb5608d6b78078e6dede3953a47debde06c19d50"
+         "url": "https://github.com/janestreet/spawn/releases/download/v0.17.0/spawn-v0.17.0.tbz",
+         "sha256": "33fbb5cd4c3387a6829095cfa73d5fc2eff572be61647e6052010bfbd0c2df49"
        },
        "depends": [
          "dune",
@@ -612,6 +788,92 @@
          "ocamlfind"
        ]
      },
+     "trie": {
+       "version": "1.0.0",
+       "src": {
+         "url": "https://github.com/kandu/trie/archive/1.0.0.tar.gz",
+         "sha256": "c2f8054ea44216e6a3a961b28f7630e0e3dbfbd1b504ae741be230cbe32498ea"
+       },
+       "depends": [
+         "dune",
+         "ocaml"
+       ],
+       "build-depends": [
+         "dune"
+       ]
+     },
+     "uchar": {
+       "version": "0.0.2",
+       "src": {
+         "url": "https://github.com/ocaml/uchar/releases/download/v0.0.2/uchar-0.0.2.tbz",
+         "sha256": "47397f316cbe76234af53c74a1f9452154ba3bdb54fced5caac959f50f575af0"
+       },
+       "depends": [
+         "ocaml"
+       ],
+       "build-depends": [
+         "ocamlbuild"
+       ]
+     },
+     "utop": {
+       "version": "2.14.0",
+       "src": {
+         "url": "https://github.com/ocaml-community/utop/releases/download/2.14.0/utop-2.14.0.tbz",
+         "sha256": "0fd5a9bc5b458524a71463a1fe0cd16f9b7be13673ae303118b7216e0d273ba9"
+       },
+       "depends": [
+         "base-threads",
+         "base-unix",
+         "cppo",
+         "dune",
+         "lambda-term",
+         "logs",
+         "lwt",
+         "lwt_react",
+         "ocaml",
+         "ocamlfind",
+         "react",
+         "xdg",
+         "zed"
+       ],
+       "build-depends": [
+         "cppo",
+         "dune",
+         "ocamlfind"
+       ]
+     },
+     "uucp": {
+       "version": "16.0.0",
+       "src": {
+         "url": "https://erratique.ch/software/uucp/releases/uucp-16.0.0.tbz",
+         "sha512": "5c06d8cadb2b011b1e4ac52e14732044f6ab8e9c11e1184950ff8629b26bd173f1264247623a635b8aa4033e287bfe42d709994f19a3d79f7cbfd20158aa4992"
+       },
+       "depends": [
+         "ocaml"
+       ],
+       "build-depends": [
+         "ocamlbuild",
+         "ocamlfind",
+         "topkg"
+       ]
+     },
+     "uuseg": {
+       "version": "16.0.0",
+       "src": {
+         "url": "https://erratique.ch/software/uuseg/releases/uuseg-16.0.0.tbz",
+         "sha512": "355139aee2a72baddf3d811e522948456147546ee946b6eca20f57711865770d4b8d32ea01a7338b8e6cdedb4423ee65cee387704bb9c0c057bcbd65012679b8"
+       },
+       "depends": [
+         "ocaml",
+         "uucp",
+         "uutf"
+       ],
+       "build-depends": [
+         "ocamlbuild",
+         "ocamlfind",
+         "topkg"
+       ]
+     },
      "uutf": {
        "version": "1.0.3",
        "src": {
@@ -671,6 +933,26 @@
        "build-depends": [
          "ocamlfind"
        ]
+     },
+     "zed": {
+       "version": "3.2.3",
+       "src": {
+         "url": "https://github.com/ocaml-community/zed/archive/refs/tags/3.2.3.tar.gz",
+         "sha512": "637f75129550f6459417549d44bed16bdc62721d2e9e0c6bb5bfab30c5bc6478de15faece8c091b56f238375cb79a7bc176375400e543120bb31d7ea626b7c5b"
+       },
+       "depends": [
+         "dune",
+         "ocaml",
+         "react",
+         "result",
+         "uchar",
+         "uucp",
+         "uuseg",
+         "uutf"
+       ],
+       "build-depends": [
+         "dune"
+       ]
      }
    }
 }
diff --git a/onix-lock.json b/onix-lock.json
index c28519a..13401eb 100644
--- a/onix-lock.json
+++ b/onix-lock.json
@@ -3,7 +3,7 @@
    "repositories": [
      {
        "url": "https://github.com/ocaml/opam-repository.git",
-       "rev": "a6cd5e92975350b992cb58b4351df6fceefc8144"
+       "rev": "e57ab1a26e2a9ef176034f22915009039c5dc390"
      }
    ],
    "packages" : {