diff --git a/evals/async-state/12-rn-jotai-atomwithstorage-async-rehydrate-guard/app/App.tsx b/evals/async-state/12-rn-jotai-atomwithstorage-async-rehydrate-guard/app/App.tsx
index c0f9ec1e..7e7d8670 100644
--- a/evals/async-state/12-rn-jotai-atomwithstorage-async-rehydrate-guard/app/App.tsx
+++ b/evals/async-state/12-rn-jotai-atomwithstorage-async-rehydrate-guard/app/App.tsx
@@ -25,17 +25,25 @@ export default function App() {
   const [preferences, setPreferences] = useAtom(preferencesAtom)
 
   const toggleTheme = () => {
-    return setPreferences((previous) => ({
-      ...previous,
-      theme: previous.theme === 'light' ? 'dark' : 'light',
-    }))
+    return setPreferences(async (previous) => {
+      const previousValue = await previous
+
+      return {
+        ...previousValue,
+        theme: previousValue.theme === 'light' ? 'dark' : 'light',
+      }
+    })
   }
 
   const toggleCompact = () => {
-    return setPreferences((previous) => ({
-      ...previous,
-      compact: !previous.compact,
-    }))
+    return setPreferences(async (previous) => {
+      const previousValue = await previous
+
+      return {
+        ...previousValue,
+        compact: !previousValue.compact,
+      }
+    })
   }
 
   return (
diff --git a/evals/tsconfig.expo.json b/evals/tsconfig.expo.json
deleted file mode 100644
index 2dd6fa5e..00000000
--- a/evals/tsconfig.expo.json
+++ /dev/null
@@ -1,20 +0,0 @@
-{
-  "extends": "./tsconfig.json",
-  "include": [
-    "expo-router/**/*.ts",
-    "expo-router/**/*.tsx",
-    "expo-sdk/**/*.ts",
-    "expo-sdk/**/*.tsx",
-    "expo-ui/**/*.ts",
-    "expo-ui/**/*.tsx"
-  ],
-  "exclude": [
-    // Pre-migration baseline for eval 01: it intentionally imports theming from
-    // '@react-navigation/native' (that is the eval's whole premise). That package's
-    // global ReactNavigation.Theme augmentation merges into this shared program and
-    // conflicts with expo-router's vendored theming types, breaking the idiomatic
-    // SDK 56 reference in the same program. The reference stays idiomatic; we exclude
-    // only the deliberately-legacy baseline file from the typecheck gate.
-    "expo-router/01-rn-expo-router-sdk56-react-navigation-imports/app/_layout.tsx"
-  ]
-}
diff --git a/evals/tsconfig.json b/evals/tsconfig.json
index 1b75f851..43dd6d1f 100644
--- a/evals/tsconfig.json
+++ b/evals/tsconfig.json
@@ -12,5 +12,14 @@
     "**/example/**/*.tsx",
     "**/reference/**/*.ts",
     "**/reference/**/*.tsx"
+  ],
+  "exclude": [
+    // Pre-migration baseline for eval 01: it intentionally imports theming from
+    // '@react-navigation/native' (that is the eval's whole premise). That package's
+    // global ReactNavigation.Theme augmentation merges into this shared program and
+    // conflicts with expo-router's vendored theming types, breaking the idiomatic
+    // SDK 56 reference in the same program. The reference stays idiomatic; we exclude
+    // only the deliberately-legacy baseline file from the typecheck gate.
+    "expo-router/01-rn-expo-router-sdk56-react-navigation-imports/app/_layout.tsx"
   ]
 }
diff --git a/package.json b/package.json
index a43c1dc1..3adfd67b 100644
--- a/package.json
+++ b/package.json
@@ -9,7 +9,7 @@
     "bench:run": "bun runner/run.ts",
     "bench:judge": "bun runner/judge.ts",
     "typecheck": "tsc --noEmit",
-    "typecheck:expo-evals": "tsc -p evals/tsconfig.expo.json --noEmit"
+    "typecheck:evals": "bun scripts/typecheck-evals.ts"
   },
   "devDependencies": {
     "@types/node": "^25.2.2",
diff --git a/scripts/typecheck-evals.ts b/scripts/typecheck-evals.ts
new file mode 100644
index 00000000..016540d9
--- /dev/null
+++ b/scripts/typecheck-evals.ts
@@ -0,0 +1,133 @@
+import path from 'node:path'
+import ts from 'typescript'
+
+import { discoverEvals } from '../runner/utils/discovery'
+
+/*
+  Each eval declares its own global type augmentations (e.g. react-navigation's
+  `declare global { namespace ReactNavigation { interface RootParamList ... } } }`).
+  Compiling every eval into one shared tsc program merges those global interfaces
+  across unrelated evals and produces false conflicts. So instead of one program
+  for all of evals/, this creates one isolated program per eval directory,
+  sharing a single compiler host so common files (react-native types, lib.d.ts,
+  ...) are only parsed once.
+ */
+
+const CONFIG_PATH = path.join(process.cwd(), 'evals/tsconfig.json')
+
+const formatHost: ts.FormatDiagnosticsHost = {
+  getCurrentDirectory: () => process.cwd(),
+  getCanonicalFileName: (fileName) => fileName,
+  getNewLine: () => ts.sys.newLine,
+}
+
+function loadProgramInputs() {
+  const configFile = ts.readConfigFile(CONFIG_PATH, ts.sys.readFile)
+
+  if (configFile.error) {
+    console.error(ts.formatDiagnostic(configFile.error, formatHost))
+    process.exit(1)
+  }
+
+  const parsed = ts.parseJsonConfigFileContent(
+    configFile.config,
+    ts.sys,
+    path.dirname(CONFIG_PATH)
+  )
+
+  if (parsed.errors.length > 0) {
+    console.error(ts.formatDiagnostics(parsed.errors, formatHost))
+    process.exit(1)
+  }
+
+  return {
+    fileNames: parsed.fileNames.map((f) => path.resolve(f)),
+    options: parsed.options,
+  }
+}
+
+function createSharedHost(options: ts.CompilerOptions) {
+  const host = ts.createCompilerHost(options)
+  const sourceFileCache = new Map<string, ts.SourceFile | undefined>()
+  const originalGetSourceFile = host.getSourceFile.bind(host)
+
+  host.getSourceFile = (
+    fileName,
+    languageVersionOrOptions,
+    onError,
+    shouldCreateNewSourceFile
+  ) => {
+    if (!shouldCreateNewSourceFile && sourceFileCache.has(fileName)) {
+      return sourceFileCache.get(fileName)
+    }
+
+    const sourceFile = originalGetSourceFile(
+      fileName,
+      languageVersionOrOptions,
+      onError,
+      shouldCreateNewSourceFile
+    )
+    sourceFileCache.set(fileName, sourceFile)
+    return sourceFile
+  }
+
+  return host
+}
+
+async function main() {
+  const { fileNames, options } = loadProgramInputs()
+  const evals = await discoverEvals()
+  const host = createSharedHost(options)
+
+  const filesByEval = new Map<string, string[]>()
+
+  for (const fileName of fileNames) {
+    const owner = evals.find((evalEntry) =>
+      fileName.startsWith(evalEntry.evalPath + path.sep)
+    )
+
+    if (!owner) {
+      continue
+    }
+
+    const files = filesByEval.get(owner.evalId) ?? []
+    files.push(fileName)
+    filesByEval.set(owner.evalId, files)
+  }
+
+  let checkedCount = 0
+  let failedCount = 0
+
+  for (const evalEntry of evals) {
+    const files = filesByEval.get(evalEntry.evalId)
+
+    if (!files || files.length === 0) {
+      continue
+    }
+
+    checkedCount += 1
+
+    const program = ts.createProgram({ rootNames: files, options, host })
+    const diagnostics = ts
+      .getPreEmitDiagnostics(program)
+      .filter((diagnostic) => diagnostic.file !== undefined)
+
+    if (diagnostics.length > 0) {
+      failedCount += 1
+      console.error(`\n${evalEntry.evalId}`)
+      console.error(
+        ts.formatDiagnosticsWithColorAndContext(diagnostics, formatHost)
+      )
+    }
+  }
+
+  console.log(
+    `\ntypecheck:evals — ${checkedCount - failedCount}/${checkedCount} evals passed`
+  )
+
+  if (failedCount > 0) {
+    process.exit(1)
+  }
+}
+
+main()
diff --git a/tsconfig.json b/tsconfig.json
index 792a6c13..5abf159c 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -30,6 +30,11 @@
     "noUnusedParameters": false,
     "noPropertyAccessFromIndexSignature": false
   },
-  "include": ["runner/**/*.ts", "evals/**/*.ts", "evals/**/*.tsx"],
+  "include": [
+    "runner/**/*.ts",
+    "scripts/**/*.ts",
+    "evals/**/*.ts",
+    "evals/**/*.tsx"
+  ],
   "exclude": ["**/node_modules", "**/Pods", "evals/"]
 }