feat(cron): inherit agent timezone for default schedules

Make cron use the configured agent timezone when a cron expression omits tz or a one-shot ISO time has no offset. This keeps runtime context, heartbeat, and scheduling aligned around the same notion of time.

Made-with: Cursor

README.md

@@ -1361,7 +1361,7 @@ By default, nanobot uses `UTC` for runtime time context. If you want the agent t
 }
 ```
 
-This currently affects runtime time strings shown to the model, such as runtime context and heartbeat prompts.
+This affects runtime time strings shown to the model, such as runtime context and heartbeat prompts. It also becomes the default timezone for cron schedules when a cron expression omits `tz`, and for one-shot `at` times when the ISO datetime has no explicit offset.
 
 Common examples: `UTC`, `America/New_York`, `America/Los_Angeles`, `Europe/London`, `Europe/Berlin`, `Asia/Tokyo`, `Asia/Shanghai`, `Asia/Singapore`, `Australia/Sydney`.
 

nanobot/agent/loop.py

@@ -144,7 +144,7 @@ class AgentLoop:
         self.tools.register(MessageTool(send_callback=self.bus.publish_outbound))
         self.tools.register(SpawnTool(manager=self.subagents))
         if self.cron_service:
-            self.tools.register(CronTool(self.cron_service))
+            self.tools.register(CronTool(self.cron_service, default_timezone=timezone or "UTC"))
 
     async def _connect_mcp(self) -> None:
         """Connect to configured MCP servers (one-time, lazy)."""

nanobot/agent/tools/cron.py

@@ -12,8 +12,9 @@ from nanobot.cron.types import CronJobState, CronSchedule
 class CronTool(Tool):
     """Tool to schedule reminders and recurring tasks."""
 
-    def __init__(self, cron_service: CronService):
+    def __init__(self, cron_service: CronService, default_timezone: str = "UTC"):
         self._cron = cron_service
+        self._default_timezone = default_timezone
         self._channel = ""
         self._chat_id = ""
         self._in_cron_context: ContextVar[bool] = ContextVar("cron_in_context", default=False)
@@ -31,13 +32,26 @@ class CronTool(Tool):
         """Restore previous cron context."""
         self._in_cron_context.reset(token)
 
+    @staticmethod
+    def _validate_timezone(tz: str) -> str | None:
+        from zoneinfo import ZoneInfo
+
+        try:
+            ZoneInfo(tz)
+        except (KeyError, Exception):
+            return f"Error: unknown timezone '{tz}'"
+        return None
+
     @property
     def name(self) -> str:
         return "cron"
 
     @property
     def description(self) -> str:
-        return "Schedule reminders and recurring tasks. Actions: add, list, remove."
+        return (
+            "Schedule reminders and recurring tasks. Actions: add, list, remove. "
+            f"If tz is omitted, cron expressions and naive ISO times default to {self._default_timezone}."
+        )
 
     @property
     def parameters(self) -> dict[str, Any]:
@@ -60,11 +74,17 @@ class CronTool(Tool):
                 },
                 "tz": {
                     "type": "string",
-                    "description": "IANA timezone for cron expressions (e.g. 'America/Vancouver')",
+                    "description": (
+                        "Optional IANA timezone for cron expressions "
+                        f"(e.g. 'America/Vancouver'). Defaults to {self._default_timezone}."
+                    ),
                 },
                 "at": {
                     "type": "string",
-                    "description": "ISO datetime for one-time execution (e.g. '2026-02-12T10:30:00')",
+                    "description": (
+                        "ISO datetime for one-time execution "
+                        f"(e.g. '2026-02-12T10:30:00'). Naive values default to {self._default_timezone}."
+                    ),
                 },
                 "job_id": {"type": "string", "description": "Job ID (for remove)"},
             },
@@ -107,26 +127,29 @@ class CronTool(Tool):
         if tz and not cron_expr:
             return "Error: tz can only be used with cron_expr"
         if tz:
-            from zoneinfo import ZoneInfo
+            if err := self._validate_timezone(tz):
-
+                return err
-            try:
-                ZoneInfo(tz)
-            except (KeyError, Exception):
-                return f"Error: unknown timezone '{tz}'"
 
         # Build schedule
         delete_after = False
         if every_seconds:
             schedule = CronSchedule(kind="every", every_ms=every_seconds * 1000)
         elif cron_expr:
-            schedule = CronSchedule(kind="cron", expr=cron_expr, tz=tz)
+            effective_tz = tz or self._default_timezone
+            if err := self._validate_timezone(effective_tz):
+                return err
+            schedule = CronSchedule(kind="cron", expr=cron_expr, tz=effective_tz)
         elif at:
-            from datetime import datetime
+            from zoneinfo import ZoneInfo
 
             try:
                 dt = datetime.fromisoformat(at)
             except ValueError:
                 return f"Error: invalid ISO datetime format '{at}'. Expected format: YYYY-MM-DDTHH:MM:SS"
+            if dt.tzinfo is None:
+                if err := self._validate_timezone(self._default_timezone):
+                    return err
+                dt = dt.replace(tzinfo=ZoneInfo(self._default_timezone))
             at_ms = int(dt.timestamp() * 1000)
             schedule = CronSchedule(kind="at", at_ms=at_ms)
             delete_after = True

tests/cron/test_cron_tool_list.py

@@ -1,5 +1,7 @@
 """Tests for CronTool._list_jobs() output formatting."""
 
+from datetime import datetime, timezone
+
 from nanobot.agent.tools.cron import CronTool
 from nanobot.cron.service import CronService
 from nanobot.cron.types import CronJobState, CronSchedule
@@ -10,6 +12,11 @@ def _make_tool(tmp_path) -> CronTool:
     return CronTool(service)
 
 
+def _make_tool_with_tz(tmp_path, tz: str) -> CronTool:
+    service = CronService(tmp_path / "cron" / "jobs.json")
+    return CronTool(service, default_timezone=tz)
+
+
 # -- _format_timing tests --
 
 
@@ -236,6 +243,29 @@ def test_list_shows_next_run(tmp_path) -> None:
     assert "Next run:" in result
 
 
+def test_add_cron_job_defaults_to_tool_timezone(tmp_path) -> None:
+    tool = _make_tool_with_tz(tmp_path, "Asia/Shanghai")
+    tool.set_context("telegram", "chat-1")
+
+    result = tool._add_job("Morning standup", None, "0 8 * * *", None, None)
+
+    assert result.startswith("Created job")
+    job = tool._cron.list_jobs()[0]
+    assert job.schedule.tz == "Asia/Shanghai"
+
+
+def test_add_at_job_uses_default_timezone_for_naive_datetime(tmp_path) -> None:
+    tool = _make_tool_with_tz(tmp_path, "Asia/Shanghai")
+    tool.set_context("telegram", "chat-1")
+
+    result = tool._add_job("Morning reminder", None, None, None, "2026-03-25T08:00:00")
+
+    assert result.startswith("Created job")
+    job = tool._cron.list_jobs()[0]
+    expected = int(datetime(2026, 3, 25, 0, 0, 0, tzinfo=timezone.utc).timestamp() * 1000)
+    assert job.schedule.at_ms == expected
+
+
 def test_list_excludes_disabled_jobs(tmp_path) -> None:
     tool = _make_tool(tmp_path)
     job = tool._cron.add_job(