diff --git a/packages/quicktype-core/package.json b/packages/quicktype-core/package.json
index 3fd669c73..463b80236 100644
--- a/packages/quicktype-core/package.json
+++ b/packages/quicktype-core/package.json
@@ -48,6 +48,7 @@
     },
     "files": ["dist"],
     "browser": {
-        "fs": false
+        "fs": false,
+        "path": false
     }
 }
diff --git a/packages/quicktype-core/src/input/io/NodeIO.ts b/packages/quicktype-core/src/input/io/NodeIO.ts
index 2b3995c3b..0f5095dc4 100644
--- a/packages/quicktype-core/src/input/io/NodeIO.ts
+++ b/packages/quicktype-core/src/input/io/NodeIO.ts
@@ -1,5 +1,5 @@
-import * as fs from "node:fs";
-import * as path from "node:path";
+import * as fs from "fs";
+import * as path from "path";
 
 import { defined, exceptionToString } from "@glideapps/ts-necessities";
 import { isNode } from "browser-or-node";
diff --git a/test/check-no-node-imports.ts b/test/check-no-node-imports.ts
new file mode 100644
index 000000000..3e727b9ec
--- /dev/null
+++ b/test/check-no-node-imports.ts
@@ -0,0 +1,76 @@
+// This is the Node-only test harness, so "node:" imports are fine *here* —
+// the guard below only restricts packages/quicktype-core/src.
+import * as fs from "node:fs";
+import * as path from "node:path";
+
+// Guard: quicktype-core must stay bundleable for the browser.
+//
+// quicktype-core's package.json declares `"browser": { "fs": false }`, which
+// tells web bundlers (webpack, browserify, ...) to stub out the `fs` module.
+// That mapping only matches the *bare* specifier "fs" — an import of
+// "node:fs" (or any other "node:"-prefixed builtin) is NOT remapped, so it
+// breaks web bundles of quicktype-core even though the code behaves the same
+// under Node. This regression already happened once between 23.2.0 and
+// 23.2.5: see https://github.com/glideapps/quicktype/issues/2763.
+//
+// This check fails the test run if any "node:"-prefixed import sneaks back
+// into packages/quicktype-core/src. It is scoped to quicktype-core only: the
+// CLI in the root `src/` directory is Node-only and may use "node:" imports
+// freely.
+
+const coreSrcDir = path.join(
+    __dirname,
+    "..",
+    "packages",
+    "quicktype-core",
+    "src",
+);
+
+// Matches static imports/re-exports (`from "node:fs"`), dynamic imports
+// (`import("node:fs")`), and CommonJS requires (`require("node:fs")`).
+const nodeImportPattern = /(?:from\s+|import\s*\(\s*|require\s*\(\s*)["']node:/;
+
+function findNodeImports(dir: string): string[] {
+    const offenders: string[] = [];
+    for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
+        const fullPath = path.join(dir, entry.name);
+        if (entry.isDirectory()) {
+            offenders.push(...findNodeImports(fullPath));
+        } else if (entry.isFile() && entry.name.endsWith(".ts")) {
+            const lines = fs.readFileSync(fullPath, "utf8").split("\n");
+            for (let i = 0; i < lines.length; i++) {
+                if (nodeImportPattern.test(lines[i])) {
+                    offenders.push(
+                        `${path.relative(path.join(__dirname, ".."), fullPath)}:${i + 1}: ${lines[i].trim()}`,
+                    );
+                }
+            }
+        }
+    }
+
+    return offenders;
+}
+
+export function checkCoreHasNoNodePrefixedImports(): void {
+    const offenders = findNodeImports(coreSrcDir);
+    if (offenders.length > 0) {
+        const offenderList = offenders.map((o) => `    ${o}`).join("\n");
+        console.error(
+            `error: found "node:"-prefixed imports in packages/quicktype-core/src:
+
+${offenderList}
+
+quicktype-core must use bare builtin specifiers (e.g. "fs", not "node:fs"):
+its package.json's "browser" field only stubs bare specifiers, so "node:"
+imports break web bundlers. See https://github.com/glideapps/quicktype/issues/2763`,
+        );
+        process.exit(1);
+    }
+}
+
+// Allow running the check standalone:
+//   npx ts-node --project test/tsconfig.json test/check-no-node-imports.ts
+if (require.main === module) {
+    checkCoreHasNoNodePrefixedImports();
+    console.error('* quicktype-core has no "node:"-prefixed imports');
+}
diff --git a/test/test.ts b/test/test.ts
index f6015eafa..f9f4e316a 100755
--- a/test/test.ts
+++ b/test/test.ts
@@ -5,6 +5,7 @@ import { inParallel } from "./lib/multicore";
 import { execAsync, type Sample } from "./utils";
 import { type Fixture, allFixtures } from "./fixtures";
 import { affectedFixtures, divideParallelJobs } from "./buildkite";
+import { checkCoreHasNoNodePrefixedImports } from "./check-no-node-imports";
 
 const exit = require("exit");
 const CPUs = Number.parseInt(process.env.CPUs || "0", 10) || os.cpus().length;
@@ -16,6 +17,10 @@ const CPUs = Number.parseInt(process.env.CPUs || "0", 10) || os.cpus().length;
 export type WorkItem = { sample: Sample; fixtureName: string };
 
 async function main(sources: string[]) {
+    // Cheap sanity check, run before any fixture: quicktype-core must not
+    // use "node:"-prefixed imports or it breaks web bundlers (issue #2763).
+    checkCoreHasNoNodePrefixedImports();
+
     let fixtures = affectedFixtures();
     const fixturesFromCmdline = process.env.FIXTURE;
     if (fixturesFromCmdline) {