feat: add RHIZA_SYNC_SCHEDULE variable to override default sync cron

.rhiza/rhiza.mk

@@ -50,6 +50,11 @@ export PYTHON_VERSION
 RHIZA_VERSION ?= $(shell cat .rhiza/.rhiza-version 2>/dev/null || echo "0.10.2")
 export RHIZA_VERSION
 
+# Default sync schedule (cron expression for GitHub Actions sync workflow)
+# Override in your root Makefile to customise when sync runs.
+# Example: RHIZA_SYNC_SCHEDULE = 0 9 * * 1-5  (weekdays at 9 AM UTC)
+RHIZA_SYNC_SCHEDULE ?= 0 0 * * 1
+
 export UV_NO_MODIFY_PATH := 1
 export UV_VENV_CLEAR := 1
 
@@ -76,7 +81,7 @@ endef
 export RHIZA_LOGO
 
 # Declare phony targets for Rhiza Core
-.PHONY: print-logo sync sync-experimental materialize validate readme pre-sync post-sync pre-validate post-validate
+.PHONY: print-logo sync sync-experimental materialize validate readme pre-sync post-sync pre-validate post-validate _apply-sync-schedule
 
 # Hook targets (double-colon rules allow multiple definitions)
 # Note: pre-install/post-install are defined in bootstrap.mk
@@ -98,9 +103,16 @@ sync: pre-sync ## sync with template repository as defined in .rhiza/template.ym
 	else \
 		$(MAKE) install-uv; \
 		${UVX_BIN} "rhiza==$(RHIZA_VERSION)" sync .; \
+		$(MAKE) _apply-sync-schedule; \
 	fi
 	@$(MAKE) post-sync
 
+_apply-sync-schedule: ## (internal) apply RHIZA_SYNC_SCHEDULE override to GitHub Actions sync workflow
+	@if [ "$(RHIZA_SYNC_SCHEDULE)" != "0 0 * * 1" ] && [ -f .github/workflows/rhiza_sync.yml ]; then \
+		sed -i.bak "s|cron: '[^']*'|cron: '$(RHIZA_SYNC_SCHEDULE)'|" .github/workflows/rhiza_sync.yml && rm -f .github/workflows/rhiza_sync.yml.bak; \
+		printf "${BLUE}[INFO] Applied custom sync schedule: $(RHIZA_SYNC_SCHEDULE)${RESET}\n"; \
+	fi
+
 materialize: ## [DEPRECATED] use 'make sync' instead — materialize --force is now sync
 	@printf "${YELLOW}[WARN] 'make materialize' is deprecated and will be removed in a future release.${RESET}\n"
 	@printf "${YELLOW}[WARN] Please use 'make sync' instead (e.g. 'materialize --force' is now 'make sync').${RESET}\n"

.rhiza/tests/sync/test_sync_schedule.py

@@ -0,0 +1,128 @@
+"""Tests for the RHIZA_SYNC_SCHEDULE override mechanism.
+
+These tests validate that users can override the default sync schedule
+(cron expression) used in the GitHub Actions sync workflow, and that
+the override is applied correctly during `make sync`.
+
+Security Notes:
+- S101 (assert usage): Asserts are used in pytest tests to validate conditions
+- S603/S607 (subprocess usage): Any subprocess calls are for testing sync targets
+  in isolated environments with controlled inputs
+- Test code operates in a controlled environment with trusted inputs
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from sync.conftest import run_make, strip_ansi
+
+
+class TestSyncScheduleVariable:
+    """Tests for the RHIZA_SYNC_SCHEDULE Makefile variable."""
+
+    def test_default_sync_schedule_value(self, logger):
+        """RHIZA_SYNC_SCHEDULE should default to '0 0 * * 1' (weekly Monday)."""
+        proc = run_make(logger, ["print-RHIZA_SYNC_SCHEDULE"], dry_run=False)
+        out = strip_ansi(proc.stdout)
+        assert "Value of RHIZA_SYNC_SCHEDULE:" in out
+        assert "0 0 * * 1" in out
+
+    def test_sync_schedule_overridable_via_env(self, logger, tmp_path: Path):
+        """RHIZA_SYNC_SCHEDULE should be overridable via environment variable."""
+        import os
+
+        env = os.environ.copy()
+        env["RHIZA_SYNC_SCHEDULE"] = "0 9 * * 1-5"
+
+        proc = run_make(logger, ["print-RHIZA_SYNC_SCHEDULE"], dry_run=False, env=env)
+        out = strip_ansi(proc.stdout)
+        assert "0 9 * * 1-5" in out
+
+    def test_sync_schedule_overridable_via_makefile(self, logger, tmp_path: Path):
+        """RHIZA_SYNC_SCHEDULE should be overridable in root Makefile."""
+        makefile = tmp_path / "Makefile"
+        original = makefile.read_text()
+        new_content = "RHIZA_SYNC_SCHEDULE = 0 6 * * *\n\n" + original
+        makefile.write_text(new_content)
+
+        proc = run_make(logger, ["print-RHIZA_SYNC_SCHEDULE"], dry_run=False)
+        out = strip_ansi(proc.stdout)
+        assert "0 6 * * *" in out
+
+
+class TestApplySyncSchedule:
+    """Tests for the _apply-sync-schedule target."""
+
+    def test_apply_sync_schedule_skips_when_default(self, logger, tmp_path: Path):
+        """_apply-sync-schedule should not modify files when using default schedule."""
+        # Create a mock workflow file matching the actual rhiza_sync.yml format
+        workflow_dir = tmp_path / ".github" / "workflows"
+        workflow_dir.mkdir(parents=True)
+        workflow_file = workflow_dir / "rhiza_sync.yml"
+        original_content = "on:\n  schedule:\n    - cron: '0 0 * * 1'  # Weekly on Monday\n"
+        workflow_file.write_text(original_content)
+
+        proc = run_make(logger, ["_apply-sync-schedule"], dry_run=False)
+        assert proc.returncode == 0
+
+        # File should remain unchanged
+        assert workflow_file.read_text() == original_content
+
+    def test_apply_sync_schedule_patches_workflow(self, logger, tmp_path: Path):
+        """_apply-sync-schedule should patch workflow when schedule is overridden."""
+        # Create a mock workflow file matching the actual rhiza_sync.yml format
+        workflow_dir = tmp_path / ".github" / "workflows"
+        workflow_dir.mkdir(parents=True)
+        workflow_file = workflow_dir / "rhiza_sync.yml"
+        workflow_file.write_text("on:\n  schedule:\n    - cron: '0 0 * * 1'  # Weekly on Monday\n")
+
+        # Override the schedule via Makefile
+        makefile = tmp_path / "Makefile"
+        original = makefile.read_text()
+        new_content = "RHIZA_SYNC_SCHEDULE = 0 9 * * 1-5\n\n" + original
+        makefile.write_text(new_content)
+
+        proc = run_make(logger, ["_apply-sync-schedule"], dry_run=False)
+        assert proc.returncode == 0
+
+        # File should be patched
+        patched = workflow_file.read_text()
+        assert "0 9 * * 1-5" in patched
+        assert "0 0 * * 1" not in patched
+
+    def test_apply_sync_schedule_handles_missing_workflow(self, logger, tmp_path: Path):
+        """_apply-sync-schedule should succeed even if workflow file is missing."""
+        # Override the schedule but don't create workflow file
+        makefile = tmp_path / "Makefile"
+        original = makefile.read_text()
+        new_content = "RHIZA_SYNC_SCHEDULE = 0 6 * * *\n\n" + original
+        makefile.write_text(new_content)
+
+        proc = run_make(logger, ["_apply-sync-schedule"], dry_run=False)
+        assert proc.returncode == 0
+
+    def test_apply_sync_schedule_prints_info(self, logger, tmp_path: Path):
+        """_apply-sync-schedule should print info message when patching."""
+        # Create a mock workflow file matching the actual rhiza_sync.yml format
+        workflow_dir = tmp_path / ".github" / "workflows"
+        workflow_dir.mkdir(parents=True)
+        workflow_file = workflow_dir / "rhiza_sync.yml"
+        workflow_file.write_text("on:\n  schedule:\n    - cron: '0 0 * * 1'\n")
+
+        # Override the schedule
+        makefile = tmp_path / "Makefile"
+        original = makefile.read_text()
+        new_content = "RHIZA_SYNC_SCHEDULE = 0 12 * * 0\n\n" + original
+        makefile.write_text(new_content)
+
+        proc = run_make(logger, ["_apply-sync-schedule"], dry_run=False)
+        out = strip_ansi(proc.stdout)
+        assert "Applied custom sync schedule" in out
+        assert "0 12 * * 0" in out
+
+    def test_sync_target_calls_apply_schedule(self, logger):
+        """The sync target should include _apply-sync-schedule in dry-run output."""
+        proc = run_make(logger, ["sync"])
+        out = proc.stdout
+        assert "_apply-sync-schedule" in out

docs/CUSTOMIZATION.md

@@ -123,10 +123,44 @@ PYTHON_VERSION = 3.12
 # Override test coverage threshold (default: 90)
 COVERAGE_FAIL_UNDER = 80
 
+# Override the sync schedule (default: weekly on Monday at midnight UTC)
+# Uses cron syntax: minute hour day-of-month month day-of-week
+RHIZA_SYNC_SCHEDULE = 0 9 * * 1-5  # Weekdays at 9 AM UTC
+
 # Include the Rhiza API (template-managed)
 include .rhiza/rhiza.mk
 ```
 
+### Sync Schedule Override
+
+The `RHIZA_SYNC_SCHEDULE` variable controls the cron schedule for the GitHub Actions sync workflow (`.github/workflows/rhiza_sync.yml`). Since this file is template-managed and overwritten during sync, the schedule is automatically patched after each `make sync` to preserve your custom value.
+
+**Default:** `0 0 * * 1` (weekly on Monday at midnight UTC)
+
+**Examples:**
+
+```makefile
+# Daily at 6 AM UTC
+RHIZA_SYNC_SCHEDULE = 0 6 * * *
+
+# Weekdays at 9 AM UTC
+RHIZA_SYNC_SCHEDULE = 0 9 * * 1-5
+
+# First day of each month at midnight UTC
+RHIZA_SYNC_SCHEDULE = 0 0 1 * *
+
+# Every 6 hours
+RHIZA_SYNC_SCHEDULE = 0 */6 * * *
+```
+
+Set this in your root `Makefile` (before the `include` line) and it will be applied automatically every time `make sync` runs. The override is also visible in the sync output:
+
+```
+[INFO] Applied custom sync schedule: 0 9 * * 1-5
+```
+
+> **Note:** For GitLab CI, the sync schedule is configured via the GitLab UI (Settings → CI/CD → Pipeline schedules), so this variable only affects GitHub Actions.
+
 ### On-Demand Configuration
 
 You can also pass variables directly to `make` for one-off commands: