feat: time-aware model routing for cron jobs (#889)

Error rate peaks at 18:00 (9.4%) during evening cron batches vs 4.0%
at 09:00 during interactive work. Route cron tasks to stronger models
during off-hours when user is not present to correct errors.

New agent/time_aware_routing.py:
- resolve_time_aware_model(): routes based on hour, error rate, task type
- Interactive sessions: always use base model (user corrects errors)
- Cron during business hours: use base model (low error rate)
- Cron during off-hours with high error rate (>6%): upgrade to strong model
- get_hour_error_rate(): error rates by hour from empirical audit
- is_off_hours(): 18:00-05:59 = off-hours
- RoutingDecision: model, provider, reason, hour, error_rate
- get_routing_report(): 24h forecast of routing decisions

Config via env vars:
- CRON_STRONG_MODEL (default: xiaomi/mimo-v2-pro)
- CRON_CHEAP_MODEL (default: qwen2.5:7b)
- CRON_ERROR_THRESHOLD (default: 6.0%)

Tests: tests/test_time_aware_routing.py (9 tests)

Closes #889

agent/time_aware_routing.py

@@ -0,0 +1,146 @@
+"""Time-aware model routing for cron jobs.
+
+Routes cron tasks to more capable models during off-hours when the user
+is not present to correct errors. Reduces error rates during high-error
+time windows (e.g., 18:00 evening batches).
+
+Usage:
+    from agent.time_aware_routing import resolve_time_aware_model
+    model = resolve_time_aware_model(base_model="mimo-v2-pro", is_cron=True)
+"""
+
+from __future__ import annotations
+
+import os
+import time
+from dataclasses import dataclass
+from typing import Dict, Optional
+
+
+# Error rate data from empirical audit (2026-04-12)
+# Higher error rates during these hours suggest routing to better models
+_HIGH_ERROR_HOURS = {
+    18: 9.4,  # 18:00 — 9.4% error rate (evening cron batches)
+    19: 8.1,
+    20: 7.5,
+    21: 6.8,
+    22: 6.2,
+    23: 5.9,
+    0:  5.5,
+    1:  5.2,
+}
+
+# Low error hours — default model is fine
+_LOW_ERROR_HOURS = set(range(6, 18))  # 06:00-17:59
+
+# Default fallback models by time zone
+_DEFAULT_STRONG_MODEL = os.getenv("CRON_STRONG_MODEL", "xiaomi/mimo-v2-pro")
+_DEFAULT_CHEAP_MODEL = os.getenv("CRON_CHEAP_MODEL", "qwen2.5:7b")
+_ERROR_THRESHOLD = float(os.getenv("CRON_ERROR_THRESHOLD", "6.0"))  # % error rate
+
+
+@dataclass
+class RoutingDecision:
+    """Result of time-aware routing."""
+    model: str
+    provider: str
+    reason: str
+    hour: int
+    error_rate: float
+    is_off_hours: bool
+
+
+def get_hour_error_rate(hour: int) -> float:
+    """Get expected error rate for a given hour (0-23)."""
+    return _HIGH_ERROR_HOURS.get(hour, 4.0)  # Default 4% for unlisted hours
+
+
+def is_off_hours(hour: int) -> bool:
+    """Check if hour is considered off-hours (higher error rates)."""
+    return hour not in _LOW_ERROR_HOURS
+
+
+def resolve_time_aware_model(
+    base_model: str = "",
+    base_provider: str = "",
+    is_cron: bool = False,
+    hour: Optional[int] = None,
+) -> RoutingDecision:
+    """Resolve model based on time of day and task type.
+
+    During off-hours (evening/night), routes to stronger models for cron
+    jobs to compensate for lack of human oversight.
+
+    Args:
+        base_model: The model that would normally be used.
+        base_provider: The provider for the base model.
+        is_cron: Whether this is a cron job (vs interactive session).
+        hour: Override hour (for testing). Defaults to current hour.
+
+    Returns:
+        RoutingDecision with model, provider, and reasoning.
+    """
+    if hour is None:
+        hour = time.localtime().tm_hour
+
+    error_rate = get_hour_error_rate(hour)
+    off_hours = is_off_hours(hour)
+
+    # Interactive sessions always use the base model (user can correct errors)
+    if not is_cron:
+        return RoutingDecision(
+            model=base_model or _DEFAULT_CHEAP_MODEL,
+            provider=base_provider,
+            reason="Interactive session — user can correct errors",
+            hour=hour,
+            error_rate=error_rate,
+            is_off_hours=off_hours,
+        )
+
+    # Cron jobs during low-error hours: use base model
+    if not off_hours and error_rate < _ERROR_THRESHOLD:
+        return RoutingDecision(
+            model=base_model or _DEFAULT_CHEAP_MODEL,
+            provider=base_provider,
+            reason=f"Low-error hours ({hour}:00, {error_rate}% expected)",
+            hour=hour,
+            error_rate=error_rate,
+            is_off_hours=False,
+        )
+
+    # Cron jobs during high-error hours: upgrade to stronger model
+    if error_rate >= _ERROR_THRESHOLD:
+        return RoutingDecision(
+            model=_DEFAULT_STRONG_MODEL,
+            provider="nous",
+            reason=f"High-error hours ({hour}:00, {error_rate}% expected) — using stronger model",
+            hour=hour,
+            error_rate=error_rate,
+            is_off_hours=True,
+        )
+
+    # Off-hours but low error: use base model
+    return RoutingDecision(
+        model=base_model or _DEFAULT_CHEAP_MODEL,
+        provider=base_provider,
+        reason=f"Off-hours but low error ({hour}:00, {error_rate}%)",
+        hour=hour,
+        error_rate=error_rate,
+        is_off_hours=off_hours,
+    )
+
+
+def get_routing_report() -> str:
+    """Get a report of time-based routing decisions for the next 24 hours."""
+    lines = ["Time-Aware Model Routing (24h forecast)", "=" * 40, ""]
+    lines.append(f"Error threshold: {_ERROR_THRESHOLD}%")
+    lines.append(f"Strong model: {_DEFAULT_STRONG_MODEL}")
+    lines.append(f"Cheap model: {_DEFAULT_CHEAP_MODEL}")
+    lines.append("")
+
+    for h in range(24):
+        decision = resolve_time_aware_model(is_cron=True, hour=h)
+        icon = "\U0001f7e2" if decision.model == _DEFAULT_CHEAP_MODEL else "\U0001f534"
+        lines.append(f"  {h:02d}:00 {icon} {decision.model:25s} ({decision.error_rate}% error)")
+
+    return "\n".join(lines)

tests/test_time_aware_routing.py

@@ -0,0 +1,58 @@
+"""Tests for time-aware model routing."""
+
+import pytest
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+from agent.time_aware_routing import (
+    resolve_time_aware_model,
+    get_hour_error_rate,
+    is_off_hours,
+    get_routing_report,
+)
+
+
+class TestErrorRates:
+    def test_evening_high_error(self):
+        assert get_hour_error_rate(18) == 9.4
+        assert get_hour_error_rate(19) == 8.1
+
+    def test_morning_low_error(self):
+        assert get_hour_error_rate(9) == 4.0
+        assert get_hour_error_rate(12) == 4.0
+
+    def test_default_for_unknown(self):
+        assert get_hour_error_rate(15) == 4.0
+
+
+class TestOffHours:
+    def test_evening_is_off_hours(self):
+        assert is_off_hours(20) is True
+        assert is_off_hours(2) is True
+
+    def test_business_hours_not_off(self):
+        assert is_off_hours(9) is False
+        assert is_off_hours(14) is False
+
+
+class TestRouting:
+    def test_interactive_uses_base_model(self):
+        d = resolve_time_aware_model("my-model", "my-provider", is_cron=False, hour=18)
+        assert d.model == "my-model"
+        assert "Interactive" in d.reason
+
+    def test_cron_low_error_uses_base(self):
+        d = resolve_time_aware_model("cheap-model", is_cron=True, hour=10)
+        assert d.model == "cheap-model"
+
+    def test_cron_high_error_upgrades(self):
+        d = resolve_time_aware_model("cheap-model", is_cron=True, hour=18)
+        assert d.model != "cheap-model"
+        assert d.is_off_hours is True
+
+    def test_routing_report(self):
+        report = get_routing_report()
+        assert "Time-Aware Model Routing" in report
+        assert "18:00" in report