diff --git a/next.config.mjs b/next.config.mjs
index a1a3fd5d7bb4..d668d6bc3baa 100644
--- a/next.config.mjs
+++ b/next.config.mjs
@@ -286,6 +286,9 @@ const nextConfig = {
       // (better-sqlite3 → node:sqlite → sql.js). Next traces sql-wasm.js but can
       // omit the runtime sql-wasm.wasm asset from the standalone bundle.
       "./node_modules/sql.js/dist/sql-wasm.wasm",
+      // tiktoken is server-externalized below so Node selects its CommonJS entry.
+      // That entry reads the tokenizer WASM beside itself at runtime.
+      "./node_modules/tiktoken/tiktoken_bg.wasm",
     ],
   },
   outputFileTracingExcludes: {
@@ -339,6 +342,10 @@ const nextConfig = {
     "tough-cookie",
     "@ngrok/ngrok",
     "@huggingface/transformers",
+    // The ESM entry imports tiktoken_bg.wasm as a module. Turbopack can compile
+    // that graph but omits the runtime asset, making provider routes fail during
+    // module evaluation. Keep Node's CommonJS loader and colocated WASM intact.
+    "tiktoken",
     // copilot-m365-web.ts imports 'ws' as a client-side WebSocket. When bundled,
     // ws cannot resolve its 'bufferutil' native addon (frame masking) and throws
     // TypeError: b.mask is not a function on the first outgoing frame, causing
diff --git a/src/lib/db/adapters/runtimeRequire.ts b/src/lib/db/adapters/runtimeRequire.ts
index e3e3b0e1c750..ad441eaac250 100644
--- a/src/lib/db/adapters/runtimeRequire.ts
+++ b/src/lib/db/adapters/runtimeRequire.ts
@@ -5,13 +5,17 @@
  * The standalone server is emitted as CommonJS chunks and externalizes the
  * native database packages. Keep those requests as static `require()` calls so
  * webpack preserves the external boundary. Development and tests run as ESM,
- * where `require` is unavailable; the `createRequire(import.meta.url)` fallback
- * handles those callers.
+ * where `require` is unavailable; the fallback anchors resolution to the real
+ * process entrypoint so Turbopack cannot replace it with an in-bundle resolver.
  */
 import * as nodeModule from "node:module";
 
+const esmRequire = nodeModule.createRequire(process.argv[1] || process.cwd());
+
 function esmRuntimeRequire(specifier: string): unknown {
-  return nodeModule.createRequire(import.meta.url)(specifier);
+  // Reflect keeps the optional request dynamic. A direct call is rewritten by
+  // Turbopack and fails at runtime as "Cannot find module as expression is too dynamic".
+  return Reflect.apply(esmRequire, undefined, [specifier]);
 }
 
 export function runtimeRequire(specifier: string): unknown {
diff --git a/tests/unit/turbopack-runtime-boundaries-12074.test.ts b/tests/unit/turbopack-runtime-boundaries-12074.test.ts
new file mode 100644
index 000000000000..449ea78c5d6e
--- /dev/null
+++ b/tests/unit/turbopack-runtime-boundaries-12074.test.ts
@@ -0,0 +1,34 @@
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import path from "node:path";
+import test from "node:test";
+import { pathToFileURL } from "node:url";
+
+const repoRoot = process.cwd();
+
+test("#12074: Turbopack keeps the WASM-backed tiktoken package external", async () => {
+  const configUrl = `${pathToFileURL(path.join(repoRoot, "next.config.mjs")).href}?phase5=${Date.now()}`;
+  const { default: nextConfig } = await import(configUrl);
+
+  assert.ok(
+    new Set(nextConfig.serverExternalPackages).has("tiktoken"),
+    "bundling tiktoken selects its ESM WASM entry and makes /api/providers fail with Missing tiktoken_bg.wasm"
+  );
+  assert.ok(
+    nextConfig.outputFileTracingIncludes?.["/*"]?.includes(
+      "./node_modules/tiktoken/tiktoken_bg.wasm"
+    ),
+    "the external tokenizer must retain its runtime WASM asset in standalone output"
+  );
+});
+
+test("#12074: the ESM SQLite loader stays outside Turbopack's module resolver", () => {
+  const source = fs.readFileSync(
+    path.join(repoRoot, "src/lib/db/adapters/runtimeRequire.ts"),
+    "utf8"
+  );
+
+  assert.doesNotMatch(source, /createRequire\(import\.meta\.url\)/);
+  assert.match(source, /createRequire\(process\.argv\[1\] \|\| process\.cwd\(\)\)/);
+  assert.match(source, /Reflect\.apply\(/);
+});