refactor: unify boundary-safe reads for bootstrap and includes

src/agents/workspace.load-extra-bootstrap-files.test.ts

@@ -2,7 +2,7 @@ import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
 import { afterAll, beforeAll, describe, expect, it } from "vitest";
-import { loadExtraBootstrapFiles } from "./workspace.js";
+import { loadExtraBootstrapFiles, loadExtraBootstrapFilesWithDiagnostics } from "./workspace.js";
 
 describe("loadExtraBootstrapFiles", () => {
   let fixtureRoot = "";
@@ -69,4 +69,43 @@ describe("loadExtraBootstrapFiles", () => {
     expect(files[0]?.name).toBe("AGENTS.md");
     expect(files[0]?.content).toBe("linked agents");
   });
+
+  it("rejects hardlinked aliases to files outside workspace", async () => {
+    if (process.platform === "win32") {
+      return;
+    }
+
+    const rootDir = await createWorkspaceDir("hardlink");
+    const workspaceDir = path.join(rootDir, "workspace");
+    const outsideDir = path.join(rootDir, "outside");
+    await fs.mkdir(workspaceDir, { recursive: true });
+    await fs.mkdir(outsideDir, { recursive: true });
+    const outsideFile = path.join(outsideDir, "AGENTS.md");
+    const linkedFile = path.join(workspaceDir, "AGENTS.md");
+    await fs.writeFile(outsideFile, "outside", "utf-8");
+    try {
+      await fs.link(outsideFile, linkedFile);
+    } catch (err) {
+      if ((err as NodeJS.ErrnoException).code === "EXDEV") {
+        return;
+      }
+      throw err;
+    }
+
+    const files = await loadExtraBootstrapFiles(workspaceDir, ["AGENTS.md"]);
+    expect(files).toHaveLength(0);
+  });
+
+  it("skips oversized bootstrap files and reports diagnostics", async () => {
+    const workspaceDir = await createWorkspaceDir("oversized");
+    const payload = "x".repeat(2 * 1024 * 1024 + 1);
+    await fs.writeFile(path.join(workspaceDir, "AGENTS.md"), payload, "utf-8");
+
+    const { files, diagnostics } = await loadExtraBootstrapFilesWithDiagnostics(workspaceDir, [
+      "AGENTS.md",
+    ]);
+
+    expect(files).toHaveLength(0);
+    expect(diagnostics.some((d) => d.reason === "security")).toBe(true);
+  });
 });