diff --git a/.changeset/validation-asset-hardening.md b/.changeset/validation-asset-hardening.md
new file mode 100644
index 0000000..09a204b
--- /dev/null
+++ b/.changeset/validation-asset-hardening.md
@@ -0,0 +1,9 @@
+---
+"vitest-native": patch
+---
+
+Three hardening fixes:
+
+- **Prerelease peer versions no longer fail validation.** A prerelease sharing the minimum's major.minor (e.g. vitest `4.0.0-beta.3` against the `4.0.0` floor) parsed with `NaN` in the patch slot, failed the minimum check, and hard-errored at startup for installs running betas/RCs. Prerelease/build metadata is now stripped before comparison; a prerelease of the minimum itself is accepted.
+- **Mock-engine asset stubs match the native loader's semantics.** The extension match is now case-insensitive (`LOGO.PNG` stubs like `logo.png`), user-supplied `assetExts` entries are regex-escaped, and the stubbed basename is JSON-stringified so filenames containing quotes emit valid JS.
+- **The mock engine's Flow-strip transform skips unparseable files instead of throwing.** The `@flow` filter is a heuristic — the marker can appear inside a string or comment of a file `flow-remove-types` then fails to parse; that parse error previously took down the whole transform pipeline.
diff --git a/packages/vitest-native/src/plugin.ts b/packages/vitest-native/src/plugin.ts
index f82c8d8..ca224aa 100644
--- a/packages/vitest-native/src/plugin.ts
+++ b/packages/vitest-native/src/plugin.ts
@@ -608,8 +608,12 @@ export function reactNative(options?: VitestNativeOptions): Plugin {
         }
       }
 
-      // Build the asset regex from the resolved extensions list.
-      assetPattern = new RegExp(`\\.(${resolved.assetExts.join("|")})$`);
+      // Build the asset regex from the resolved extensions list. Extensions are
+      // escaped (user-supplied entries may contain regex metacharacters) and the
+      // match is case-insensitive ("LOGO.PNG" is an asset too — the native
+      // loader already lowercases; the engines must agree).
+      const escaped = resolved.assetExts.map((e) => e.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"));
+      assetPattern = new RegExp(`\\.(${escaped.join("|")})$`, "i");
     },
 
     resolveId(source, importer) {
@@ -724,10 +728,13 @@ export function reactNative(options?: VitestNativeOptions): Plugin {
       }
 
       // Asset imports have the same stable semantics under both engines.
+      // JSON.stringify the basename — filenames can contain quotes/backslashes,
+      // and raw interpolation would emit broken JS (same hazard class as the
+      // native loader, which already stringifies).
       const fsPath = stripFsPrefix(id);
       if (assetPattern.test(fsPath)) {
         const basename = fsPath.split("/").pop() ?? fsPath;
-        return `export default "${basename}";`;
+        return `export default ${JSON.stringify(basename)};`;
       }
 
       // Native engine serves RN from Node's CJS graph — nothing else to load here.
@@ -782,11 +789,25 @@ export function reactNative(options?: VitestNativeOptions): Plugin {
       if (!id.includes("react-native") || !id.endsWith(".js")) return undefined;
       if (!code.includes("@flow")) return undefined;
 
-      const stripped = flowRemoveTypes(code, { all: true });
-      return {
-        code: stripped.toString(),
-        map: stripped.generateMap(),
-      };
+      // The filters above are heuristics — "@flow" can appear inside a string
+      // or comment of a perfectly valid non-Flow file that flowRemoveTypes
+      // then fails to parse. Skipping is strictly better than throwing: a
+      // genuine Flow file that fails here would fail Vite's own parse next
+      // with a clearer error, while a false positive passes through untouched.
+      try {
+        const stripped = flowRemoveTypes(code, { all: true });
+        return {
+          code: stripped.toString(),
+          map: stripped.generateMap(),
+        };
+      } catch (e) {
+        if (diagnostics) {
+          console.warn(
+            `[vitest-native] Flow strip skipped for ${id} (parse failed: ${(e as Error)?.message}); serving the file untouched.`,
+          );
+        }
+        return undefined;
+      }
     },
   };
 }
diff --git a/packages/vitest-native/src/validate.ts b/packages/vitest-native/src/validate.ts
index d5e9934..5a135da 100644
--- a/packages/vitest-native/src/validate.ts
+++ b/packages/vitest-native/src/validate.ts
@@ -83,9 +83,18 @@ export function validateOptions(options: Record<string, unknown>): void {
 }
 
 function satisfiesMinimum(version: string, minimum: string): boolean {
+  // Strip prerelease/build metadata before splitting — "4.0.0-beta.3" split
+  // on "." as ["4","0","0-beta","3"] put NaN in the PATCH slot, so a
+  // prerelease sharing the minimum's major.minor (e.g. vitest 4.0.0-beta.x
+  // against the 4.0.0 floor) failed the check and hard-errored at startup —
+  // exactly the early-adopter installs that run betas. A prerelease of the
+  // minimum itself is accepted (deliberate: rejecting it would re-break that
+  // cohort; vite/vitest don't publish patch-level prereleases, so the
+  // security-floor bypass this theoretically allows doesn't occur on npm).
   const parse = (v: string) =>
     v
       .replace(/^[^0-9]*/, "")
+      .split(/[-+]/)[0]
       .split(".")
       .map(Number);
   const [aMaj, aMin = 0, aPat = 0] = parse(version);
diff --git a/packages/vitest-native/tests/plugin-hardening.test.ts b/packages/vitest-native/tests/plugin-hardening.test.ts
new file mode 100644
index 0000000..bd2271b
--- /dev/null
+++ b/packages/vitest-native/tests/plugin-hardening.test.ts
@@ -0,0 +1,76 @@
+/**
+ * Hardening regressions for the plugin's asset stubbing and Flow-strip
+ * transform (mock engine).
+ */
+import { describe, it, expect } from "vitest";
+import path from "node:path";
+import fs from "node:fs";
+import { fileURLToPath } from "node:url";
+import { reactNative } from "../src/index.js";
+import { gestureHandler } from "../src/presets/index.js";
+
+const HERE = path.dirname(fileURLToPath(import.meta.url));
+function findUp(rel: string, start: string): string {
+  let dir = start;
+  for (;;) {
+    const candidate = path.join(dir, rel);
+    if (fs.existsSync(candidate)) return candidate;
+    const parent = path.dirname(dir);
+    if (parent === dir) throw new Error(`${rel} not found from ${start}`);
+    dir = parent;
+  }
+}
+const projectRoot = path.dirname(findUp("package.json", HERE));
+const SERVE_ENV = { command: "serve", mode: "test" } as const;
+
+async function makePlugin() {
+  const plugin = reactNative({ engine: "mock", presets: [gestureHandler()] }) as any;
+  await plugin.config({ root: projectRoot }, SERVE_ENV);
+  await plugin.configResolved({ root: projectRoot });
+  return plugin;
+}
+
+describe("asset stubbing (mock engine)", () => {
+  it("matches asset extensions case-insensitively, like the native loader", async () => {
+    const plugin = await makePlugin();
+    expect(plugin.load("/proj/assets/LOGO.PNG")).toBe(`export default "LOGO.PNG";`);
+    expect(plugin.load("/proj/assets/Icon.TTF")).toBe(`export default "Icon.TTF";`);
+  });
+
+  it("emits valid JS for basenames containing quotes", async () => {
+    const plugin = await makePlugin();
+    const code = plugin.load(`/proj/assets/we"ird.png`);
+    // Assert the PROPERTY (the emitted literal round-trips to the basename),
+    // not the mechanism — raw interpolation would emit a syntax error here.
+    const literal = code.replace(/^export default /, "").replace(/;$/, "");
+    expect(JSON.parse(literal)).toBe(`we"ird.png`);
+  });
+});
+
+describe("Flow-strip transform guard (mock engine)", () => {
+  it("still strips genuine Flow sources in react-native ecosystem packages", async () => {
+    const plugin = await makePlugin();
+    const result = plugin.transform(
+      `// @flow\ntype Props = { x: number };\nmodule.exports = function f(p: Props) { return p.x; };`,
+      "/proj/node_modules/react-native-thing/lib/f.js",
+    );
+    expect(result).toBeTruthy();
+    expect(result.code).not.toContain("Props");
+    expect(result.code).toContain("return p.x");
+  });
+
+  it("skips files the stripper cannot parse instead of throwing", async () => {
+    const plugin = await makePlugin();
+    // "@flow" appears in a string of a file that is not valid input for the
+    // stripper — previously this threw and took down the whole transform
+    // pipeline; now it passes through untouched.
+    let result: unknown = "not called";
+    expect(() => {
+      result = plugin.transform(
+        `const marker = "@flow"; const = broken;`,
+        "/proj/node_modules/react-native-thing/lib/broken.js",
+      );
+    }).not.toThrow();
+    expect(result).toBeUndefined();
+  });
+});
diff --git a/packages/vitest-native/tests/validation.test.ts b/packages/vitest-native/tests/validation.test.ts
index bd73a5e..d6b54e8 100644
--- a/packages/vitest-native/tests/validation.test.ts
+++ b/packages/vitest-native/tests/validation.test.ts
@@ -1,4 +1,7 @@
 import { describe, it, expect, vi } from "vitest";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
 import { validatePeerDependency } from "../src/validate.js";
 import { reactNative } from "../src/index.js";
 
@@ -26,6 +29,52 @@ describe("validatePeerDependency", () => {
     });
     expect(result).toBeNull();
   });
+
+  // Prerelease versions previously parsed to NaN ("4.0.0-beta.3" → [4, NaN, …])
+  // and failed the minimum check — a hard startup error for exactly the
+  // early-adopter installs that run betas/RCs.
+  describe("prerelease versions", () => {
+    function withFixture(version: string, fn: (root: string) => void): void {
+      const tmp = fs.mkdtempSync(path.join(os.tmpdir(), "vn-prerelease-"));
+      try {
+        const pkgDir = path.join(tmp, "node_modules", "fixture-pkg");
+        fs.mkdirSync(pkgDir, { recursive: true });
+        fs.writeFileSync(path.join(tmp, "package.json"), JSON.stringify({ name: "consumer" }));
+        fs.writeFileSync(
+          path.join(pkgDir, "package.json"),
+          JSON.stringify({ name: "fixture-pkg", version, main: "index.js" }),
+        );
+        fs.writeFileSync(path.join(pkgDir, "index.js"), "module.exports = {};");
+        fn(tmp);
+      } finally {
+        fs.rmSync(tmp, { recursive: true, force: true });
+      }
+    }
+
+    it("accepts a prerelease of a version above the minimum", () => {
+      withFixture("4.1.0-beta.3", (root) => {
+        expect(validatePeerDependency("fixture-pkg", "4.0.0", root)).toBeNull();
+      });
+    });
+
+    it("accepts a prerelease of the minimum itself", () => {
+      withFixture("4.0.0-beta.3", (root) => {
+        expect(validatePeerDependency("fixture-pkg", "4.0.0", root)).toBeNull();
+      });
+    });
+
+    it("still rejects a prerelease below the minimum", () => {
+      withFixture("3.9.0-rc.1", (root) => {
+        expect(validatePeerDependency("fixture-pkg", "4.0.0", root)).toContain("requires");
+      });
+    });
+
+    it("still rejects a prerelease of the excluded next major", () => {
+      withFixture("5.0.0-alpha.1", (root) => {
+        expect(validatePeerDependency("fixture-pkg", "4.0.0", root, 5)).toContain("supports");
+      });
+    });
+  });
 });
 
 describe("engine option", () => {