fix(sessions): stop leaking file path as prompt content on read failure (#108546)

* fix(sessions): stop leaking file path as prompt content on read failure

When readFileSync fails for a valid file path, resolvePromptInput returns
the raw path string as prompt content instead of undefined. This injects
filesystem paths into the LLM context. The existing console.error warning
still fires; the caller already handles undefined returns correctly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test: cover unreadable prompt paths

* test: use tracked resource loader temp dirs

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Peter Steinberger <peter@steipete.me>
Co-authored-by: Peter Steinberger <steipete@gmail.com>
(cherry picked from commit c924819292)

src/agents/sessions/resource-loader.test.ts

@@ -1,16 +1,15 @@
 // Resource loader tests cover compatibility wiring for SDK prompt transform
 // aliases.
-import { mkdtempSync, rmSync } from "node:fs";
-import { tmpdir } from "node:os";
-import { join } from "node:path";
-import { describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { useAutoCleanupTempDirTracker } from "../../../test/helpers/temp-dir.js";
 import { DefaultResourceLoader } from "./resource-loader.js";
 
+const tempDirs = useAutoCleanupTempDirTracker(afterEach);
+
 describe("DefaultResourceLoader", () => {
-  it("keeps deprecated SDK prompt override aliases wired to prompt transforms", async () => {
-    // These aliases are deprecated but shipped SDK surface, so they still map
-    // through the same transform path as the current options.
-    const root = mkdtempSync(join(tmpdir(), "openclaw-resource-loader-"));
+  it("does not use unreadable prompt file paths as prompt content", async () => {
+    const root = tempDirs.make("openclaw-resource-loader-");
+    const consoleError = vi.spyOn(console, "error").mockImplementation(() => {});
     try {
       const loader = new DefaultResourceLoader({
         cwd: root,
@@ -20,18 +19,41 @@ describe("DefaultResourceLoader", () => {
         noPromptTemplates: true,
         noThemes: true,
         noContextFiles: true,
-        systemPrompt: "base",
-        appendSystemPrompt: ["tail"],
-        systemPromptOverride: (base) => `${base ?? ""} legacy`,
-        appendSystemPromptOverride: (base) => [...base, "legacy"],
+        systemPrompt: root,
+        appendSystemPrompt: [root],
       });
 
       await loader.reload();
 
-      expect(loader.getSystemPrompt()).toBe("base legacy");
-      expect(loader.getAppendSystemPrompt()).toEqual(["tail", "legacy"]);
+      expect(loader.getSystemPrompt()).toBeUndefined();
+      expect(loader.getAppendSystemPrompt()).toEqual([]);
+      expect(consoleError).toHaveBeenCalledTimes(2);
     } finally {
-      rmSync(root, { force: true, recursive: true });
+      consoleError.mockRestore();
     }
   });
+
+  it("keeps deprecated SDK prompt override aliases wired to prompt transforms", async () => {
+    // These aliases are deprecated but shipped SDK surface, so they still map
+    // through the same transform path as the current options.
+    const root = tempDirs.make("openclaw-resource-loader-");
+    const loader = new DefaultResourceLoader({
+      cwd: root,
+      agentDir: root,
+      noExtensions: true,
+      noSkills: true,
+      noPromptTemplates: true,
+      noThemes: true,
+      noContextFiles: true,
+      systemPrompt: "base",
+      appendSystemPrompt: ["tail"],
+      systemPromptOverride: (base) => `${base ?? ""} legacy`,
+      appendSystemPromptOverride: (base) => [...base, "legacy"],
+    });
+
+    await loader.reload();
+
+    expect(loader.getSystemPrompt()).toBe("base legacy");
+    expect(loader.getAppendSystemPrompt()).toEqual(["tail", "legacy"]);
+  });
 });

src/agents/sessions/resource-loader.ts

@@ -64,7 +64,7 @@ function resolvePromptInput(input: string | undefined, description: string): str
       console.error(
         chalk.yellow(`Warning: Could not read ${description} file ${input}: ${String(error)}`),
       );
-      return input;
+      return undefined;
     }
   }