introduce separate SIMPLE_MODEL config for lightweight tasks

Add a distinct simple_model field alongside ai_model so operators can
route cheap, simple tasks (e.g. email-label translation) to a low-cost
model while keeping the strong model for parent conversations. The two
models can be from different providers (e.g. Gemini + Haiku). If
SIMPLE_MODEL is unset, falls back to AI_MODEL with a warning.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -6,14 +6,21 @@
 # ---------------------------------------------------------------
 
 # ---------------------------------------------------------------
-# AI Model (via litellm — supports any provider)
+# AI Models (via litellm — supports any provider)
 # ---------------------------------------------------------------
 # Use litellm model strings: "<provider>/<model-name>"
-# Examples:
+#
-#   anthropic/claude-opus-4-6   (default)
+# AI_MODEL   — primary model for conversation with parents (complex reasoning).
-#   openai/gpt-4o
+# SIMPLE_MODEL — lightweight model for simple tasks, e.g. email-label translation.
-#   gemini/gemini-2.0-flash
+#               Can be from a different provider than AI_MODEL.
+#               If unset, falls back to AI_MODEL with a warning in the logs.
+#
+# Examples — mixing providers:
+#   AI_MODEL=gemini/gemini-3-pro-preview   + SIMPLE_MODEL=gemini/gemini-3-flash
+#   AI_MODEL=anthropic/claude-opus-4-6     + SIMPLE_MODEL=anthropic/claude-haiku-4-5-20251001
+#   AI_MODEL=gemini/gemini-3-pro-preview   + SIMPLE_MODEL=anthropic/claude-haiku-4-5-20251001
 AI_MODEL=anthropic/claude-opus-4-6
+SIMPLE_MODEL=anthropic/claude-haiku-4-5-20251001
 
 # Extended thinking — Anthropic models only (leave unset to disable).
 # Enables a reasoning phase before the model's reply, which improves

chat_app.py

@@ -58,6 +58,7 @@ _notifier = AdminNotifier(
     indoor_email=_config.admin_email_indoor,
     outdoor_email=_config.admin_email_outdoor,
     cc_emails=[e.strip() for e in _config.admin_email_cc.split(",") if e.strip()],
+    model=_config.simple_model,
 )
 
 # ---------------------------------------------------------------------------

main.py

@@ -61,6 +61,7 @@ def build_components(config: Config):
         indoor_email=config.admin_email_indoor,
         outdoor_email=config.admin_email_outdoor,
         cc_emails=[e.strip() for e in config.admin_email_cc.split(",") if e.strip()],
+        model=config.simple_model,
     )
 
     agent = EmailAgent(

src/config.py

@@ -1,9 +1,12 @@
 """Configuration loaded from environment variables."""
 
+import logging
 import os
 from dataclasses import dataclass, field
 from pathlib import Path
 
+logger = logging.getLogger(__name__)
+
 try:
     from dotenv import load_dotenv
     load_dotenv()
@@ -13,10 +16,17 @@ except ImportError:
 
 @dataclass
 class Config:
-    # AI model — litellm format, e.g. "anthropic/claude-opus-4-6" or "openai/gpt-4o".
+    # Primary model for conversation with parents — litellm format.
     # The matching API key must be set as an env var (ANTHROPIC_API_KEY, OPENAI_API_KEY, …).
+    # Example: "anthropic/claude-opus-4-6", "google/gemini-2.0-flash", "openai/gpt-4o"
     ai_model: str = "anthropic/claude-opus-4-6"
 
+    # Lightweight model for simple tasks such as email-label translation.
+    # Can be from a different provider than ai_model.
+    # If not configured (SIMPLE_MODEL env var unset), falls back to ai_model with a warning.
+    # Example: "anthropic/claude-haiku-4-5-20251001", "openai/gpt-4o-mini"
+    simple_model: str = ""
+
     # Email — IMAP (receiving)
     imap_host: str = ""
     imap_port: int = 993
@@ -57,8 +67,18 @@ class Config:
 
     @classmethod
     def from_env(cls) -> "Config":
+        ai_model = os.getenv("AI_MODEL", "anthropic/claude-opus-4-6")
+        simple_model = os.getenv("SIMPLE_MODEL", "")
+        if not simple_model:
+            logger.warning(
+                "SIMPLE_MODEL not configured — falling back to AI_MODEL (%s) for simple tasks "
+                "(set SIMPLE_MODEL to a cheaper model, e.g. anthropic/claude-haiku-4-5-20251001)",
+                ai_model,
+            )
+            simple_model = ai_model
         return cls(
-            ai_model=os.getenv("AI_MODEL", "anthropic/claude-opus-4-6"),
+            ai_model=ai_model,
+            simple_model=simple_model,
             imap_host=os.getenv("IMAP_HOST", ""),
             imap_port=int(os.getenv("IMAP_PORT", "993")),
             imap_username=os.getenv("IMAP_USERNAME", ""),