diff --git a/README.md b/README.md
index 7c2935c..ce988fb 100644
--- a/README.md
+++ b/README.md
@@ -109,6 +109,31 @@ tmux new -s zed-hours -d 'python3 tools/time_tracking/zed_tracker.py --project-r
 
 ---
 
+## Automatic sync (systemd user timer)
+
+`sync_all.py` syncs every configured project in one run. Configuration lives
+in `~/.config/zed-hours-sync/`:
+
+| File | Purpose |
+|---|---|
+| `env` | `ZED_HOURS_SERVER_URL`, `ZED_HOURS_SERVER_TOKEN`, `ZED_HOURS_DEVICE_ID` (keep mode 600) |
+| `projects.txt` | One project per line: `PATH [SLUG]`; slug defaults to the directory name |
+
+A systemd user pair drives it:
+
+- `zed-hours-sync.service` (oneshot; runs `sync_all.py` with the env file)
+- `zed-hours-sync.timer` (every 15 minutes, `Persistent=true` to catch up after sleep)
+
+Useful commands:
+
+```sh
+systemctl --user start zed-hours-sync.service            # run a sync now
+systemctl --user list-timers zed-hours-sync.timer        # next scheduled run
+journalctl --user -u zed-hours-sync.service -f           # live logs
+```
+
+---
+
 ## Generating a report
 
 ```bash
diff --git a/sync_all.py b/sync_all.py
new file mode 100755
index 0000000..6ee4afb
--- /dev/null
+++ b/sync_all.py
@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+"""Sync every configured Zed Hours project to the server in one run.
+
+Reads a project list from a simple config file (one project per line:
+`PATH [SLUG]`), validates the shared ZED_HOURS_* environment once, and
+invokes sync.py for each project that has a `.zed-hours/` directory.
+
+Designed for a systemd user timer: per-project failures are reported but do
+not stop the remaining projects; the run exits nonzero if any sync failed.
+"""
+
+import argparse
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+DEFAULT_CONFIG = Path.home() / ".config" / "zed-hours-sync" / "projects.txt"
+REQUIRED_SETTINGS = ("ZED_HOURS_SERVER_URL", "ZED_HOURS_SERVER_TOKEN", "ZED_HOURS_DEVICE_ID")
+
+
+def parse_config(config_path: Path) -> list[tuple[Path, str | None]]:
+    """Return (project_root, slug_or_None) pairs from the config file.
+
+    Paths with spaces are not supported; keep the `PATH [SLUG]` format simple.
+    """
+    projects: list[tuple[Path, str | None]] = []
+    for lineno, raw in enumerate(config_path.read_text(encoding="utf-8").splitlines(), 1):
+        line = raw.strip()
+        if not line or line.startswith("#"):
+            continue
+        parts = line.split()
+        if len(parts) == 1:
+            root, slug = parts[0], None
+        elif len(parts) == 2:
+            root, slug = parts
+        else:
+            raise ValueError(f"{config_path}:{lineno}: expected 'PATH [SLUG]', got: {line}")
+        root_path = Path(os.path.expanduser(root))
+        projects.append((root_path, slug))
+    return projects
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Sync all configured Zed Hours projects.")
+    parser.add_argument("--config", type=Path, default=DEFAULT_CONFIG, help="Project list file (default: %(default)s)")
+    args = parser.parse_args()
+
+    missing = [name for name in REQUIRED_SETTINGS if not os.environ.get(name, "").strip()]
+    if missing:
+        print(f"Missing environment variables: {', '.join(missing)}", file=sys.stderr)
+        return 2
+
+    if not args.config.exists():
+        print(f"Config file not found: {args.config}", file=sys.stderr)
+        return 2
+
+    try:
+        projects = parse_config(args.config)
+    except (OSError, ValueError) as exc:
+        print(f"Invalid config: {exc}", file=sys.stderr)
+        return 2
+
+    if not projects:
+        print(f"No projects configured in {args.config}.")
+        return 0
+
+    sync_script = Path(__file__).resolve().parent / "sync.py"
+    failed: list[str] = []
+
+    for root, slug in projects:
+        if not (root / ".zed-hours").is_dir():
+            print(f"Skipping {root}: no .zed-hours directory")
+            continue
+        command = [sys.executable, str(sync_script), "--project-root", str(root)]
+        if slug:
+            command += ["--project-slug", slug]
+        print(f"--- Syncing {root}" + (f" as '{slug}'" if slug else "") + " ---", flush=True)
+        result = subprocess.run(command, check=False)
+        if result.returncode != 0:
+            failed.append(str(root))
+
+    if failed:
+        print(f"Sync finished with failures: {', '.join(failed)}", file=sys.stderr)
+        return 1
+    print("Sync finished OK.")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
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