feat: Cost-aware Pro model selection — free Pro beats Flash, paid Pro loses to Flash

ai/models.py

@@ -30,6 +30,7 @@ model_image = None
 logic_model_name = "models/gemini-1.5-flash"
 writer_model_name = "models/gemini-1.5-flash"
 artist_model_name = "models/gemini-1.5-flash"
+pro_model_name = "models/gemini-2.0-pro-exp"   # Best available Pro for critical rewrites (prefer free/exp)
 image_model_name = None
 image_model_source = "None"
 

ai/setup.py

@@ -34,9 +34,10 @@ def get_optimal_model(base_type="pro"):
 
 def get_default_models():
     return {
-        "logic": {"model": "models/gemini-2.0-flash", "reason": "Fallback: Gemini 2.0 Flash for cost-effective logic and JSON adherence.", "estimated_cost": "$0.10/1M"},
+        "logic": {"model": "models/gemini-2.0-pro-exp", "reason": "Fallback: Gemini 2.0 Pro Exp (free) for cost-effective logic and JSON adherence.", "estimated_cost": "Free"},
         "writer": {"model": "models/gemini-2.0-flash", "reason": "Fallback: Gemini 2.0 Flash for fast, high-quality creative writing.", "estimated_cost": "$0.10/1M"},
         "artist": {"model": "models/gemini-2.0-flash", "reason": "Fallback: Gemini 2.0 Flash for visual prompt design.", "estimated_cost": "$0.10/1M"},
+        "pro_rewrite": {"model": "models/gemini-2.0-pro-exp", "reason": "Fallback: Gemini 2.0 Pro Exp (free) for critical chapter rewrites.", "estimated_cost": "Free"},
         "ranking": []
     }
 
@@ -78,25 +79,28 @@ def select_best_models(force_refresh=False):
         AVAILABLE_MODELS:
         {json.dumps(compatible)}
 
-        PRICING_CONTEXT (USD per 1M tokens, approximate):
-        - Gemini 2.5 Pro/Flash: Best quality/speed; check current pricing.
-        - Gemini 2.0 Flash: ~$0.10 Input / $0.40 Output. (Fast, cost-effective, excellent quality).
-        - Gemini 2.0 Pro Exp: Free experimental tier with strong reasoning.
-        - Gemini 1.5 Flash: ~$0.075 Input / $0.30 Output. (Legacy, still reliable).
-        - Gemini 1.5 Pro: ~$1.25 Input / $5.00 Output. (Legacy, expensive).
+        PRICING_CONTEXT (USD per 1M tokens, approximate — TIER determines preference):
+        - FREE TIER: Models with 'exp', 'beta', or 'preview' in name are typically free experimental tiers.
+          e.g. gemini-2.0-pro-exp = FREE. Use these whenever they exist.
+        - Gemini 2.5 Flash: ~$0.075 Input / $0.30 Output. Fast and very capable.
+        - Gemini 2.0 Flash: ~$0.10 Input / $0.40 Output. Cost-effective, excellent quality.
+        - Gemini 1.5 Flash: ~$0.075 Input / $0.30 Output. Legacy, still reliable.
+        - Gemini 2.5 Pro (stable/latest): ~$1.25+ Input / $5.00+ Output. EXPENSIVE — avoid unless free/exp.
+        - Gemini 1.5 Pro (stable): ~$1.25 Input / $5.00 Output. EXPENSIVE — avoid.
 
-        CRITERIA:
-        - LOGIC: Needs JSON adherence, plot consistency, and instruction following. COST IS THE PRIORITY — use Flash unless no Flash 2.x exists.
-          -> Prefer: Gemini 2.5 Flash > 2.0 Flash > 1.5 Flash > 2.5 Pro > 2.0 Pro > 1.5 Pro
-        - WRITER: Needs creativity, prose quality, long-form text generation, and speed.
-          -> Prefer: Gemini 2.5 Flash > 2.0 Flash > 1.5 Flash (balance quality/cost; avoid Pro)
-        - ARTIST: Needs rich visual description, prompt understanding for cover art design.
-          -> Prefer: Gemini 2.0 Flash > 1.5 Flash (speed and visual understanding)
+        CRITERIA (cost is the primary constraint):
+        - LOGIC: Needs JSON adherence, plot consistency, instruction following.
+          -> Prefer by EFFECTIVE COST: Free/Exp Pro (e.g. 2.0-pro-exp) > Flash 2.5 > Flash 2.0 > Flash 1.5 > paid Pro (AVOID)
+          -> Rule: A free Pro beats Flash. A paid Pro loses to any Flash.
+        - WRITER: Needs creativity, prose quality, long-form text generation. Flash is sufficient for prose.
+          -> Prefer: Flash 2.5 > Flash 2.0 > Flash 1.5. Do NOT use Pro — Flash quality is adequate for fiction writing.
+        - ARTIST: Needs visual description and prompt quality for cover art design.
+          -> Prefer: Flash 2.0 > Flash 1.5 (speed and visual understanding)
 
         CONSTRAINTS:
-        - Strongly prefer Flash over Pro for all roles — Pro models are expensive and only used selectively at runtime for critical rewrites.
+        - A free/experimental Pro model is ALWAYS preferred over Flash for the Logic role.
+        - Flash is ALWAYS preferred over a paid Pro model for ALL roles.
         - Strongly prefer Gemini 2.x over 1.5 where available.
-        - Avoid 'experimental' or 'preview' only if a stable 2.x version exists; otherwise experimental 2.x is fine.
         - 'thinking' models are too slow/expensive for any role.
         - Provide a ranking of ALL available models from best to worst overall.
 
@@ -105,8 +109,12 @@ def select_best_models(force_refresh=False):
             "logic": {{ "model": "string", "reason": "string", "estimated_cost": "$X.XX/1M" }},
             "writer": {{ "model": "string", "reason": "string", "estimated_cost": "$X.XX/1M" }},
             "artist": {{ "model": "string", "reason": "string", "estimated_cost": "$X.XX/1M" }},
+            "pro_rewrite": {{ "model": "string", "reason": "string", "estimated_cost": "$X.XX/1M" }},
             "ranking": [ {{ "model": "string", "reason": "string", "estimated_cost": "string" }} ]
         }}
+
+        NOTE: "pro_rewrite" is the best available Pro model for rare, critical chapter rewrites.
+        Prefer free/experimental Pro (e.g. gemini-2.0-pro-exp) over paid Pro. If no Pro exists, use best Flash.
         """
 
         try:
@@ -187,6 +195,7 @@ def init_models(force=False):
     logic_name, logic_cost = get_model_details(selected_models['logic'])
     writer_name, writer_cost = get_model_details(selected_models['writer'])
     artist_name, artist_cost = get_model_details(selected_models['artist'])
+    pro_name, pro_cost = get_model_details(selected_models.get('pro_rewrite', {'model': 'models/gemini-2.0-pro-exp', 'estimated_cost': 'Free'}))
 
     logic_name = logic_name if config.MODEL_LOGIC_HINT == "AUTO" else config.MODEL_LOGIC_HINT
     writer_name = writer_name if config.MODEL_WRITER_HINT == "AUTO" else config.MODEL_WRITER_HINT
@@ -195,8 +204,9 @@ def init_models(force=False):
     models.logic_model_name = logic_name
     models.writer_model_name = writer_name
     models.artist_model_name = artist_name
+    models.pro_model_name = pro_name
 
-    utils.log("SYSTEM", f"Models: Logic={logic_name} ({logic_cost}) | Writer={writer_name} ({writer_cost}) | Artist={artist_name}")
+    utils.log("SYSTEM", f"Models: Logic={logic_name} ({logic_cost}) | Writer={writer_name} ({writer_cost}) | Artist={artist_name} | Pro-Rewrite={pro_name} ({pro_cost})")
 
     utils.update_pricing(logic_name, logic_cost)
     utils.update_pricing(writer_name, writer_cost)