fix: harden sandbox writes and centralize atomic file writes

src/hooks/bundled/session-memory/handler.ts

@@ -11,6 +11,7 @@ import path from "node:path";
 import { resolveAgentWorkspaceDir } from "../../../agents/agent-scope.js";
 import type { OpenClawConfig } from "../../../config/config.js";
 import { resolveStateDir } from "../../../config/paths.js";
+import { writeFileWithinRoot } from "../../../infra/fs-safe.js";
 import { createSubsystemLogger } from "../../../logging/subsystem.js";
 import { resolveAgentIdFromSessionKey } from "../../../routing/session-key.js";
 import { hasInterSessionUserProvenance } from "../../../sessions/input-provenance.js";
@@ -305,8 +306,13 @@ const saveSessionToMemory: HookHandler = async (event) => {
 
     const entry = entryParts.join("\n");
 
-    // Write to new memory file
-    await fs.writeFile(memoryFilePath, entry, "utf-8");
+    // Write under memory root with alias-safe file validation.
+    await writeFileWithinRoot({
+      rootDir: memoryDir,
+      relativePath: filename,
+      data: entry,
+      encoding: "utf-8",
+    });
     log.debug("Memory file written successfully");
 
     // Log completion (but don't send user-visible confirmation - it's internal housekeeping)