diff --git a/CHANGELOG.md b/CHANGELOG.md
index cd1148e2302..ccd9a3ba663 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Agents/sandbox: preserve existing workspace file modes when sandbox edits atomically replace files, so 0644 files do not collapse to 0600 after Write/Edit/apply_patch. Fixes #44077. Thanks @patosullivan.
 - Agents/models: keep legacy CLI runtime model refs such as `claude-cli/*` in the configured allowlist after canonical runtime migration, so cron `payload.model` overrides keep working. Fixes #75753. Thanks @RyanSandoval.
 - Gateway/watch: keep colored subsystem log prefixes in the managed tmux pane even when the parent shell exports `NO_COLOR`, while preserving explicit `FORCE_COLOR=0` opt-out. Thanks @vincentkoc.
 - Plugin SDK: re-export `isPrivateIpAddress` from `plugin-sdk/ssrf-runtime`, restoring source-checkout builds for SearXNG and Firecrawl private-network guards. Thanks @vincentkoc.
diff --git a/src/agents/sandbox/fs-bridge-mutation-helper.test.ts b/src/agents/sandbox/fs-bridge-mutation-helper.test.ts
index fe634529750..a5320e89291 100644
--- a/src/agents/sandbox/fs-bridge-mutation-helper.test.ts
+++ b/src/agents/sandbox/fs-bridge-mutation-helper.test.ts
@@ -80,6 +80,46 @@ describe("sandbox pinned mutation helper", () => {
     });
   });
 
+  it.runIf(process.platform !== "win32")(
+    "preserves existing target file mode while writing",
+    async () => {
+      await withTempDir({ prefix: "openclaw-mutation-helper-" }, async (root) => {
+        const workspace = path.join(root, "workspace");
+        const filePath = path.join(workspace, "note.txt");
+        await fs.mkdir(workspace, { recursive: true });
+        await fs.writeFile(filePath, "before", "utf8");
+        await fs.chmod(filePath, 0o644);
+
+        const result = runMutation(["write", workspace, "", "note.txt", "0"], "after");
+
+        expect(result.status).toBe(0);
+        await expect(fs.readFile(filePath, "utf8")).resolves.toBe("after");
+        const fileStat = await fs.stat(filePath);
+        expect(fileStat.mode & 0o777).toBe(0o644);
+      });
+    },
+  );
+
+  it.runIf(process.platform !== "win32")(
+    "keeps restrictive existing target file mode while writing",
+    async () => {
+      await withTempDir({ prefix: "openclaw-mutation-helper-" }, async (root) => {
+        const workspace = path.join(root, "workspace");
+        const filePath = path.join(workspace, "secret.txt");
+        await fs.mkdir(workspace, { recursive: true });
+        await fs.writeFile(filePath, "before", "utf8");
+        await fs.chmod(filePath, 0o600);
+
+        const result = runMutation(["write", workspace, "", "secret.txt", "0"], "after");
+
+        expect(result.status).toBe(0);
+        await expect(fs.readFile(filePath, "utf8")).resolves.toBe("after");
+        const fileStat = await fs.stat(filePath);
+        expect(fileStat.mode & 0o777).toBe(0o600);
+      });
+    },
+  );
+
   it.runIf(process.platform !== "win32")(
     "reads through a pinned directory fd and rejects hardlinked files",
     async () => {
diff --git a/src/agents/sandbox/fs-bridge-mutation-helper.ts b/src/agents/sandbox/fs-bridge-mutation-helper.ts
index 7fb39d894f7..1637ffa18aa 100644
--- a/src/agents/sandbox/fs-bridge-mutation-helper.ts
+++ b/src/agents/sandbox/fs-bridge-mutation-helper.ts
@@ -89,7 +89,17 @@ export const SANDBOX_PINNED_MUTATION_PYTHON = [
   "            continue",
   "    raise RuntimeError('failed to allocate sandbox temp directory')",
   "",
+  "def existing_regular_file_mode(parent_fd, basename):",
+  "    try:",
+  "        target_stat = os.lstat(basename, dir_fd=parent_fd)",
+  "    except FileNotFoundError:",
+  "        return None",
+  "    if stat.S_ISREG(target_stat.st_mode):",
+  "        return stat.S_IMODE(target_stat.st_mode)",
+  "    return None",
+  "",
   "def write_atomic(parent_fd, basename, stdin_buffer):",
+  "    target_mode = existing_regular_file_mode(parent_fd, basename)",
   "    temp_fd = None",
   "    temp_name = None",
   "    try:",
@@ -99,6 +109,11 @@ export const SANDBOX_PINNED_MUTATION_PYTHON = [
   "            if not chunk:",
   "                break",
   "            os.write(temp_fd, chunk)",
+  "        if target_mode is not None:",
+  "            try:",
+  "                os.fchmod(temp_fd, target_mode)",
+  "            except AttributeError:",
+  "                pass",
   "        os.fsync(temp_fd)",
   "        os.close(temp_fd)",
   "        temp_fd = None",