diff --git a/argocd/base/statefulset.yaml b/argocd/base/statefulset.yaml
index 7bbb1bb4..6b0d3415 100644
--- a/argocd/base/statefulset.yaml
+++ b/argocd/base/statefulset.yaml
@@ -26,7 +26,7 @@ spec:
           # Note: use the *dev* version of the package here, so that
           # PRs can deploy `primer-service` container images that have
           # not yet been merged to `primer` `main`.
-          image: ghcr.io/hackworthltd/primer-service-dev:git-2bf2349473b60fc6a99e9a553dcd1b0fd9d54b5f
+          image: ghcr.io/hackworthltd/primer-service-dev:git-96236936906694bacf62c52cb718ba73e77c50ee
           ports:
             - containerPort: 8081
           env:
diff --git a/flake.lock b/flake.lock
index daa9db77..d601fd1b 100644
--- a/flake.lock
+++ b/flake.lock
@@ -150,11 +150,11 @@
     "flake-compat_5": {
       "flake": false,
       "locked": {
-        "lastModified": 1673956053,
-        "narHash": "sha256-4gtG9iQuiKITOjNQQeQIpoIB6b16fm+504Ch3sNKLd8=",
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
         "owner": "edolstra",
         "repo": "flake-compat",
-        "rev": "35bb57c0c8d8b62bbfd284272c928ceb64ddbde9",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
         "type": "github"
       },
       "original": {
@@ -166,11 +166,11 @@
     "flake-compat_6": {
       "flake": false,
       "locked": {
-        "lastModified": 1673956053,
-        "narHash": "sha256-4gtG9iQuiKITOjNQQeQIpoIB6b16fm+504Ch3sNKLd8=",
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
         "owner": "edolstra",
         "repo": "flake-compat",
-        "rev": "35bb57c0c8d8b62bbfd284272c928ceb64ddbde9",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
         "type": "github"
       },
       "original": {
@@ -269,11 +269,11 @@
         "nixpkgs-lib": "nixpkgs-lib_3"
       },
       "locked": {
-        "lastModified": 1693611461,
-        "narHash": "sha256-aPODl8vAgGQ0ZYFIRisxYG5MOGSkIczvu2Cd8Gb9+1Y=",
+        "lastModified": 1696343447,
+        "narHash": "sha256-B2xAZKLkkeRFG5XcHHSXXcP7To9Xzr59KXeZiRf4vdQ=",
         "owner": "hercules-ci",
         "repo": "flake-parts",
-        "rev": "7f53fdb7bdc5bb237da7fefef12d099e4fd611ca",
+        "rev": "c9afaba3dfa4085dbd2ccb38dfade5141e33d9d4",
         "type": "github"
       },
       "original": {
@@ -287,11 +287,11 @@
         "nixpkgs-lib": "nixpkgs-lib_4"
       },
       "locked": {
-        "lastModified": 1693611461,
-        "narHash": "sha256-aPODl8vAgGQ0ZYFIRisxYG5MOGSkIczvu2Cd8Gb9+1Y=",
+        "lastModified": 1696343447,
+        "narHash": "sha256-B2xAZKLkkeRFG5XcHHSXXcP7To9Xzr59KXeZiRf4vdQ=",
         "owner": "hercules-ci",
         "repo": "flake-parts",
-        "rev": "7f53fdb7bdc5bb237da7fefef12d099e4fd611ca",
+        "rev": "c9afaba3dfa4085dbd2ccb38dfade5141e33d9d4",
         "type": "github"
       },
       "original": {
@@ -411,14 +411,14 @@
     "ghc99": {
       "flake": false,
       "locked": {
-        "lastModified": 1693974777,
-        "narHash": "sha256-r+uFw44X9XVPdDtxylfBuFL+l+5q5cX+vDVT7SCTHB8=",
-        "ref": "hkm/bump-Cabal",
-        "rev": "b2bddd0b8214ac1db6239cc25f7c0aabeb2ebb70",
-        "revCount": 61879,
+        "lastModified": 1695427505,
+        "narHash": "sha256-j0hXl6uEI+Uwf37z3WLuQZN4S0XqGtiepELv2Gl2aHU=",
+        "ref": "refs/heads/master",
+        "rev": "b8e4fe2318798185228fb5f8214ba2384ac95b4f",
+        "revCount": 61951,
         "submodules": true,
         "type": "git",
-        "url": "https://gitlab.haskell.org/hamishmack/ghc"
+        "url": "https://gitlab.haskell.org/ghc/ghc"
       },
       "original": {
         "submodules": true,
@@ -569,11 +569,11 @@
     "hackage": {
       "flake": false,
       "locked": {
-        "lastModified": 1694823894,
-        "narHash": "sha256-B6gVQFZpUe+TntqifuhBOmmEAzjiRWGraVQIR1T9YGI=",
+        "lastModified": 1696638186,
+        "narHash": "sha256-h5wT7jZ3bM07ZvdTSm2j2CdX5EP0LXsk3+9x3QHEE8I=",
         "owner": "input-output-hk",
         "repo": "hackage.nix",
-        "rev": "643f1c0424e5604b7676b5b48000ca1bc0c2d7b8",
+        "rev": "aa653b3c276f617aa0f61095ecbc16860c98480a",
         "type": "github"
       },
       "original": {
@@ -620,11 +620,11 @@
         "pre-commit-hooks-nix": "pre-commit-hooks-nix_3"
       },
       "locked": {
-        "lastModified": 1694821803,
-        "narHash": "sha256-jl3TcxkYEst8sXz1Rfp/SvRjEbcMkSAOIjPU2/AuJEw=",
+        "lastModified": 1696633938,
+        "narHash": "sha256-1eQH0S3G/eI3PTqxCw3hmLh6eOS0wQfBcsYp410Bvjc=",
         "owner": "hackworthltd",
         "repo": "hacknix",
-        "rev": "5c6afdb546b4f362d4e749d6d85b8dfc7389265a",
+        "rev": "d4ac93da22f1d83e2a264b63c6f5d615e21e46b7",
         "type": "github"
       },
       "original": {
@@ -648,6 +648,7 @@
         "hls-1.10": "hls-1.10",
         "hls-2.0": "hls-2.0",
         "hls-2.2": "hls-2.2",
+        "hls-2.3": "hls-2.3",
         "hpc-coveralls": "hpc-coveralls",
         "hydra": "hydra",
         "iserv-proxy": "iserv-proxy",
@@ -667,11 +668,11 @@
         "stackage": "stackage"
       },
       "locked": {
-        "lastModified": 1694825384,
-        "narHash": "sha256-sswi86nY4y7atyZATPIMG/pqC2kod8zfgGbUzpYA/rU=",
+        "lastModified": 1696639789,
+        "narHash": "sha256-BAmIp51KVXDwvjugNp1QbBEGqHX/Ad6n0oS/9qWvWHY=",
         "owner": "input-output-hk",
         "repo": "haskell.nix",
-        "rev": "a2d08de6034a838e1a276707669237933255c3bd",
+        "rev": "140825afb68fddce0df5873ffcc214a3f40e2524",
         "type": "github"
       },
       "original": {
@@ -731,6 +732,23 @@
         "type": "github"
       }
     },
+    "hls-2.3": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1695910642,
+        "narHash": "sha256-tR58doOs3DncFehHwCLczJgntyG/zlsSd7DgDgMPOkI=",
+        "owner": "haskell",
+        "repo": "haskell-language-server",
+        "rev": "458ccdb55c9ea22cd5d13ec3051aaefb295321be",
+        "type": "github"
+      },
+      "original": {
+        "owner": "haskell",
+        "ref": "2.3.0.0",
+        "repo": "haskell-language-server",
+        "type": "github"
+      }
+    },
     "hpc-coveralls": {
       "flake": false,
       "locked": {
@@ -848,11 +866,11 @@
         "nixpkgs": "nixpkgs_3"
       },
       "locked": {
-        "lastModified": 1694810318,
-        "narHash": "sha256-LuvrVj2oj9TzdnnwtQUClqcXjpgwCP01FFVBM7azGV8=",
+        "lastModified": 1696360011,
+        "narHash": "sha256-HpPv27qMuPou4acXcZ8Klm7Zt0Elv9dgDvSJaomWb9Y=",
         "owner": "LnL7",
         "repo": "nix-darwin",
-        "rev": "80bb201f4925cdda5a7a3c7b1900fb26bb2af2e8",
+        "rev": "8b6ea26d5d2e8359d06278364f41fbc4b903b28a",
         "type": "github"
       },
       "original": {
@@ -923,11 +941,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1693791338,
-        "narHash": "sha256-wHmtB5H8AJTUaeGHw+0hsQ6nU4VyvVrP2P4NeCocRzY=",
+        "lastModified": 1696058303,
+        "narHash": "sha256-eNqKWpF5zG0SrgbbtljFOrRgFgRzCc4++TMFADBMLnc=",
         "owner": "nix-community",
         "repo": "nixos-generators",
-        "rev": "8ee78470029e641cddbd8721496da1316b47d3b4",
+        "rev": "150f38bd1e09e20987feacb1b0d5991357532fb5",
         "type": "github"
       },
       "original": {
@@ -1031,11 +1049,11 @@
     },
     "nixpkgs-2305": {
       "locked": {
-        "lastModified": 1690680713,
-        "narHash": "sha256-NXCWA8N+GfSQyoN7ZNiOgq/nDJKOp5/BHEpiZP8sUZw=",
+        "lastModified": 1695416179,
+        "narHash": "sha256-610o1+pwbSu+QuF3GE0NU5xQdTHM3t9wyYhB9l94Cd8=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "b81af66deb21f73a70c67e5ea189568af53b1e8c",
+        "rev": "715d72e967ec1dd5ecc71290ee072bcaf5181ed6",
         "type": "github"
       },
       "original": {
@@ -1084,11 +1102,11 @@
     "nixpkgs-lib_3": {
       "locked": {
         "dir": "lib",
-        "lastModified": 1693471703,
-        "narHash": "sha256-0l03ZBL8P1P6z8MaSDS/MvuU8E75rVxe5eE1N6gxeTo=",
+        "lastModified": 1696019113,
+        "narHash": "sha256-X3+DKYWJm93DRSdC5M6K5hLqzSya9BjibtBsuARoPco=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "3e52e76b70d5508f3cec70b882a29199f4d1ee85",
+        "rev": "f5892ddac112a1e9b3612c39af1b72987ee5783a",
         "type": "github"
       },
       "original": {
@@ -1102,11 +1120,11 @@
     "nixpkgs-lib_4": {
       "locked": {
         "dir": "lib",
-        "lastModified": 1693471703,
-        "narHash": "sha256-0l03ZBL8P1P6z8MaSDS/MvuU8E75rVxe5eE1N6gxeTo=",
+        "lastModified": 1696019113,
+        "narHash": "sha256-X3+DKYWJm93DRSdC5M6K5hLqzSya9BjibtBsuARoPco=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "3e52e76b70d5508f3cec70b882a29199f4d1ee85",
+        "rev": "f5892ddac112a1e9b3612c39af1b72987ee5783a",
         "type": "github"
       },
       "original": {
@@ -1199,11 +1217,11 @@
     },
     "nixpkgs-unstable": {
       "locked": {
-        "lastModified": 1690720142,
-        "narHash": "sha256-GywuiZjBKfFkntQwpNQfL+Ksa2iGjPprBGL0/psgRZM=",
+        "lastModified": 1695318763,
+        "narHash": "sha256-FHVPDRP2AfvsxAdc+AsgFJevMz5VBmnZglFUMlxBkcY=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "3acb5c4264c490e7714d503c7166a3fde0c51324",
+        "rev": "e12483116b3b51a185a33a272bf351e357ba9a99",
         "type": "github"
       },
       "original": {
@@ -1337,11 +1355,11 @@
         "nixpkgs-stable": "nixpkgs-stable_3"
       },
       "locked": {
-        "lastModified": 1694364351,
-        "narHash": "sha256-oadhSCqopYXxURwIA6/Anpe5IAG11q2LhvTJNP5zE6o=",
+        "lastModified": 1696516544,
+        "narHash": "sha256-8rKE8Je6twTNFRTGF63P9mE3lZIq917RAicdc4XJO80=",
         "owner": "cachix",
         "repo": "pre-commit-hooks.nix",
-        "rev": "4f883a76282bc28eb952570afc3d8a1bf6f481d7",
+        "rev": "66c352d33e0907239e4a69416334f64af2c685cc",
         "type": "github"
       },
       "original": {
@@ -1362,11 +1380,11 @@
         "nixpkgs-stable": "nixpkgs-stable_4"
       },
       "locked": {
-        "lastModified": 1694364351,
-        "narHash": "sha256-oadhSCqopYXxURwIA6/Anpe5IAG11q2LhvTJNP5zE6o=",
+        "lastModified": 1696516544,
+        "narHash": "sha256-8rKE8Je6twTNFRTGF63P9mE3lZIq917RAicdc4XJO80=",
         "owner": "cachix",
         "repo": "pre-commit-hooks.nix",
-        "rev": "4f883a76282bc28eb952570afc3d8a1bf6f481d7",
+        "rev": "66c352d33e0907239e4a69416334f64af2c685cc",
         "type": "github"
       },
       "original": {
@@ -1389,17 +1407,17 @@
         "pre-commit-hooks-nix": "pre-commit-hooks-nix_4"
       },
       "locked": {
-        "lastModified": 1695132280,
-        "narHash": "sha256-GdBceddjUaxsv/Bvu5uSK0X2aTjSoPBOnSW1KTgxTeo=",
+        "lastModified": 1700488236,
+        "narHash": "sha256-Y7bFygT7pKVCY/7r4KA75/XZil3F4a19AxN5UwqARfI=",
         "owner": "hackworthltd",
         "repo": "primer",
-        "rev": "2bf2349473b60fc6a99e9a553dcd1b0fd9d54b5f",
+        "rev": "96236936906694bacf62c52cb718ba73e77c50ee",
         "type": "github"
       },
       "original": {
         "owner": "hackworthltd",
         "repo": "primer",
-        "rev": "2bf2349473b60fc6a99e9a553dcd1b0fd9d54b5f",
+        "rev": "96236936906694bacf62c52cb718ba73e77c50ee",
         "type": "github"
       }
     },
@@ -1421,11 +1439,11 @@
     "stackage": {
       "flake": false,
       "locked": {
-        "lastModified": 1694822954,
-        "narHash": "sha256-9RLqpS5AoyNYMLrViEuZpuxPEpWAC2J2JWZ6yANEx3w=",
+        "lastModified": 1696464547,
+        "narHash": "sha256-NABJBlKDwsQox6yrKZ8saWdhjLwQEGIwpmJlClaeO1A=",
         "owner": "input-output-hk",
         "repo": "stackage.nix",
-        "rev": "2d5f46010ec834c3c652ef0a1b1c17b1c9e56da4",
+        "rev": "844c3b4c520cb4ead6113f6ba25dc2ad33e21273",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index b0a6db98..57c33cf7 100644
--- a/flake.nix
+++ b/flake.nix
@@ -19,7 +19,7 @@
 
     # Note: don't override any of primer's Nix flake inputs, or else
     # we won't hit its binary cache.
-    primer.url = github:hackworthltd/primer/2bf2349473b60fc6a99e9a553dcd1b0fd9d54b5f;
+    primer.url = github:hackworthltd/primer/96236936906694bacf62c52cb718ba73e77c50ee;
 
     flake-parts.url = "github:hercules-ci/flake-parts";
   };
diff --git a/src/components/SelectionInfo/index.tsx b/src/components/SelectionInfo/index.tsx
index c63fd953..af21f1c9 100644
--- a/src/components/SelectionInfo/index.tsx
+++ b/src/components/SelectionInfo/index.tsx
@@ -23,10 +23,11 @@ const TypeOrKindTree = (p: {
     fitView({ padding });
   };
 
+  const tk = p.typeOrKind.contents;
   return (
     <TreeReactFlowOne
       {...defaultTreeReactFlowProps}
-      tree={p.typeOrKind.contents}
+      tree={tk.tag === "Ok" ? tk.contents : tk.expected}
       level={p.level}
       zoomBarProps={{ padding }}
       onNodesChange={onNodesChange}
diff --git a/src/primer-api/model/index.ts b/src/primer-api/model/index.ts
index 03728cda..bcaf4f35 100644
--- a/src/primer-api/model/index.ts
+++ b/src/primer-api/model/index.ts
@@ -53,6 +53,11 @@ export * from './nodeFlavorPrimBody';
 export * from './nodeFlavorTextBody';
 export * from './nodeSelection';
 export * from './nodeType';
+export * from './okOrMismatch';
+export * from './okOrMismatchOneOf';
+export * from './okOrMismatchOneOfTag';
+export * from './okOrMismatchOneOfThree';
+export * from './okOrMismatchOneOfThreeTag';
 export * from './option';
 export * from './options';
 export * from './paginatedMeta';
diff --git a/src/primer-api/model/okOrMismatch.ts b/src/primer-api/model/okOrMismatch.ts
new file mode 100644
index 00000000..91dcab2f
--- /dev/null
+++ b/src/primer-api/model/okOrMismatch.ts
@@ -0,0 +1,11 @@
+/**
+ * Generated by orval v6.19.1 🍺
+ * Do not edit manually.
+ * Primer backend API
+ * A backend service implementing a pedagogic functional programming language.
+ * OpenAPI spec version: 0.7
+ */
+import type { OkOrMismatchOneOf } from './okOrMismatchOneOf';
+import type { OkOrMismatchOneOfThree } from './okOrMismatchOneOfThree';
+
+export type OkOrMismatch = OkOrMismatchOneOf | OkOrMismatchOneOfThree;
diff --git a/src/primer-api/model/okOrMismatchOneOf.ts b/src/primer-api/model/okOrMismatchOneOf.ts
new file mode 100644
index 00000000..7e7be1c8
--- /dev/null
+++ b/src/primer-api/model/okOrMismatchOneOf.ts
@@ -0,0 +1,14 @@
+/**
+ * Generated by orval v6.19.1 🍺
+ * Do not edit manually.
+ * Primer backend API
+ * A backend service implementing a pedagogic functional programming language.
+ * OpenAPI spec version: 0.7
+ */
+import type { Tree } from './tree';
+import type { OkOrMismatchOneOfTag } from './okOrMismatchOneOfTag';
+
+export type OkOrMismatchOneOf = {
+  contents: Tree;
+  tag: OkOrMismatchOneOfTag;
+};
diff --git a/src/primer-api/model/okOrMismatchOneOfTag.ts b/src/primer-api/model/okOrMismatchOneOfTag.ts
new file mode 100644
index 00000000..ac4cd272
--- /dev/null
+++ b/src/primer-api/model/okOrMismatchOneOfTag.ts
@@ -0,0 +1,15 @@
+/**
+ * Generated by orval v6.19.1 🍺
+ * Do not edit manually.
+ * Primer backend API
+ * A backend service implementing a pedagogic functional programming language.
+ * OpenAPI spec version: 0.7
+ */
+
+export type OkOrMismatchOneOfTag = typeof OkOrMismatchOneOfTag[keyof typeof OkOrMismatchOneOfTag];
+
+
+// eslint-disable-next-line @typescript-eslint/no-redeclare
+export const OkOrMismatchOneOfTag = {
+  Ok: 'Ok',
+} as const;
diff --git a/src/primer-api/model/okOrMismatchOneOfThree.ts b/src/primer-api/model/okOrMismatchOneOfThree.ts
new file mode 100644
index 00000000..e9f9b1eb
--- /dev/null
+++ b/src/primer-api/model/okOrMismatchOneOfThree.ts
@@ -0,0 +1,15 @@
+/**
+ * Generated by orval v6.19.1 🍺
+ * Do not edit manually.
+ * Primer backend API
+ * A backend service implementing a pedagogic functional programming language.
+ * OpenAPI spec version: 0.7
+ */
+import type { Tree } from './tree';
+import type { OkOrMismatchOneOfThreeTag } from './okOrMismatchOneOfThreeTag';
+
+export type OkOrMismatchOneOfThree = {
+  expected: Tree;
+  got: Tree;
+  tag: OkOrMismatchOneOfThreeTag;
+};
diff --git a/src/primer-api/model/okOrMismatchOneOfThreeTag.ts b/src/primer-api/model/okOrMismatchOneOfThreeTag.ts
new file mode 100644
index 00000000..0bf78732
--- /dev/null
+++ b/src/primer-api/model/okOrMismatchOneOfThreeTag.ts
@@ -0,0 +1,15 @@
+/**
+ * Generated by orval v6.19.1 🍺
+ * Do not edit manually.
+ * Primer backend API
+ * A backend service implementing a pedagogic functional programming language.
+ * OpenAPI spec version: 0.7
+ */
+
+export type OkOrMismatchOneOfThreeTag = typeof OkOrMismatchOneOfThreeTag[keyof typeof OkOrMismatchOneOfThreeTag];
+
+
+// eslint-disable-next-line @typescript-eslint/no-redeclare
+export const OkOrMismatchOneOfThreeTag = {
+  Mismatch: 'Mismatch',
+} as const;
diff --git a/src/primer-api/model/typeOrKindOneOf.ts b/src/primer-api/model/typeOrKindOneOf.ts
index af380393..48561138 100644
--- a/src/primer-api/model/typeOrKindOneOf.ts
+++ b/src/primer-api/model/typeOrKindOneOf.ts
@@ -5,10 +5,10 @@
  * A backend service implementing a pedagogic functional programming language.
  * OpenAPI spec version: 0.7
  */
-import type { Tree } from './tree';
+import type { OkOrMismatch } from './okOrMismatch';
 import type { TypeOrKindOneOfTag } from './typeOrKindOneOfTag';
 
 export type TypeOrKindOneOf = {
-  contents: Tree;
+  contents: OkOrMismatch;
   tag: TypeOrKindOneOfTag;
 };
diff --git a/src/primer-api/model/typeOrKindOneOfThree.ts b/src/primer-api/model/typeOrKindOneOfThree.ts
index 7ec05080..d2e7d08f 100644
--- a/src/primer-api/model/typeOrKindOneOfThree.ts
+++ b/src/primer-api/model/typeOrKindOneOfThree.ts
@@ -5,10 +5,10 @@
  * A backend service implementing a pedagogic functional programming language.
  * OpenAPI spec version: 0.7
  */
-import type { Tree } from './tree';
+import type { OkOrMismatch } from './okOrMismatch';
 import type { TypeOrKindOneOfThreeTag } from './typeOrKindOneOfThreeTag';
 
 export type TypeOrKindOneOfThree = {
-  contents: Tree;
+  contents: OkOrMismatch;
   tag: TypeOrKindOneOfThreeTag;
 };