diff --git a/src/application/WebScriptExportService.ts b/src/application/WebScriptExportService.ts
index e8529ea181..d35341f437 100644
--- a/src/application/WebScriptExportService.ts
+++ b/src/application/WebScriptExportService.ts
@@ -8,6 +8,7 @@ import { ArtifactReaderFailure } from "../artifacts/ArtifactReader.js";
 import { publishWebScripts } from "../browser/assets/PublishWebScripts.js";
 import { selectScriptCapture } from "../browser/assets/ScriptCaptureAdapters.js";
 import {
+  AnalysisAccessDeniedError,
   AnalysisCancelledError,
   AnalysisInputError,
   AnalysisOutputError,
@@ -60,9 +61,9 @@ export const exportWebScriptsValidated = async (
     );
   try {
     options.signal?.throwIfAborted();
-    const bytes = await readFile(input.capture_path, {
-      signal: options.signal,
-    });
+    const read = await readCapture(input.capture_path, options.signal);
+    if (!read.ok) return read;
+    const bytes = read.value;
     const loaded = parseCapture(bytes);
     if (!loaded.ok) return loaded;
     options.signal?.throwIfAborted();
@@ -142,6 +143,40 @@ export const exportWebScriptsValidated = async (
   }
 };
 
+/**
+ * Read the caller-selected capture. A missing, non-file or unreadable
+ * selection is a caller or host-permission failure, not an export failure.
+ */
+const readCapture = async (
+  path: string,
+  signal: AbortSignal | undefined,
+): Promise<Result<Buffer, AnalysisError>> => {
+  try {
+    return ok(await readFile(path, { signal }));
+  } catch (cause: unknown) {
+    const code =
+      cause instanceof Error && "code" in cause ? String(cause.code) : "";
+    if (code === "EACCES" || code === "EPERM")
+      return err(
+        new AnalysisAccessDeniedError(OPERATION, path, code, { cause }),
+      );
+    if (code === "ENOENT" || code === "ENOTDIR" || code === "EISDIR")
+      return err(
+        new AnalysisInputError(OPERATION, { cause }, [
+          {
+            path: ["capture_path"],
+            reason: "invalid_value",
+            message:
+              code === "EISDIR"
+                ? `Selected capture is a directory, not a file: ${path}`
+                : `Selected capture could not be read (${code}): ${path}`,
+          },
+        ]),
+      );
+    throw cause;
+  }
+};
+
 const parseCapture = (
   bytes: Buffer,
 ): Result<ReturnType<typeof selectScriptCapture>, AnalysisError> => {
diff --git a/tests/boundary/filesystem/webScriptExport.test.ts b/tests/boundary/filesystem/webScriptExport.test.ts
index cae439fead..ebc13ca481 100644
--- a/tests/boundary/filesystem/webScriptExport.test.ts
+++ b/tests/boundary/filesystem/webScriptExport.test.ts
@@ -1,6 +1,8 @@
 import { createHash } from "node:crypto";
 import {
   access,
+  chmod,
+  mkdir,
   readFile,
   readdir,
   symlink,
@@ -8,13 +10,14 @@ import {
 } from "node:fs/promises";
 import { join } from "node:path";
 
-import { describe, expect, it } from "vitest";
+import { describe, expect, it, onTestFinished } from "vitest";
 
 import { analyzeJavaScriptApplication } from "../../../src/application/javascript/JavaScriptApplicationService.js";
 import { exportWebScripts } from "../../../src/application/WebScriptExportService.js";
 import { publishWebScripts } from "../../../src/browser/assets/PublishWebScripts.js";
 import { selectScriptCapture } from "../../../src/browser/assets/ScriptCaptureAdapters.js";
 import { javascriptApplicationAnalysisResultSchema } from "../../../src/domain/javascript/javascriptApplicationAnalysis.js";
+import { projectAnalysisError } from "../../../src/domain/analysisErrorProjection.js";
 import { webScriptExportResultSchema } from "../../../src/domain/webScriptExport.js";
 import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
 import {
@@ -247,9 +250,18 @@ describe("captured script publication failures and cleanup", () => {
       capture_path: `${input.capture_path}.missing`,
     });
     if (missing.ok) throw new Error("Expected unavailable input");
-    expect(missing.error.userMessage).toContain(
-      `${input.capture_path}.missing`,
-    );
+    expect(projectAnalysisError(missing.error)).toMatchObject({
+      code: "invalid_request",
+      details: {
+        issues: [
+          {
+            path: ["capture_path"],
+            reason: "invalid_value",
+            message: expect.stringContaining(`${input.capture_path}.missing`),
+          },
+        ],
+      },
+    });
     const relative = await exportWebScripts({
       ...input,
       capture_path: "capture.json",
@@ -258,3 +270,48 @@ describe("captured script publication failures and cleanup", () => {
     expect(relative.error._tag).toBe("AnalysisInputError");
   });
 });
+
+describe("captured script selection failures", () => {
+  it("reports a directory selected as the capture as invalid input", async () => {
+    const { root, input } = await setup();
+    const directory = join(root, "captures");
+    await mkdir(directory);
+
+    const result = await exportWebScripts({
+      ...input,
+      capture_path: directory,
+    });
+    if (result.ok) throw new Error("Expected invalid input");
+    expect(projectAnalysisError(result.error)).toMatchObject({
+      code: "invalid_request",
+      details: {
+        issues: [
+          {
+            path: ["capture_path"],
+            reason: "invalid_value",
+            message: expect.stringContaining(directory),
+          },
+        ],
+      },
+    });
+    await expect(access(input.output_directory)).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+  });
+
+  it.skipIf(process.platform === "win32" || process.getuid?.() === 0)(
+    "reports an unreadable capture as a host access denial",
+    async () => {
+      const { input } = await setup();
+      await chmod(input.capture_path, 0o000);
+      onTestFinished(() => chmod(input.capture_path, 0o600));
+
+      const result = await exportWebScripts(input);
+      if (result.ok) throw new Error("Expected access denial");
+      expect(projectAnalysisError(result.error)).toMatchObject({
+        code: "access_denied",
+        details: { path: input.capture_path, system_code: "EACCES" },
+      });
+    },
+  );
+});