[BUG] image_model config field is not wired into agent loop — images always route to primary model

[fernandostahelin]

Quick Summary

The image_model field in agents.defaults is accepted in config.json but has no effect. Image messages are always sent to the primary model_name, even when image_model points to a vision-capable model.

Environment & Tools

• PicoClaw Version: v0.2.3-nightly.20260314 (git: c68b4f3)
• Go Version: go 1.25.7
• AI Model & Provider: Cerebras (qwen-3-235b-a22b-instruct-2507) as primary, Gemini 2.5 Flash Lite as image_model
• Operating System: Linux arm64 (Docker on macOS)
• Channels: Telegram

📸 Steps to Reproduce

1. Configure config.json with a text-only primary model and a vision-capable image model:

   "agents": {
     "defaults": {
       "model_name": "cerebras-baristo",
       "image_model": "gemini-images",
       "fallbacks": ["claude-fallback"]
     }
   }

2. Add both models to model_list:

   "model_list": [
     {"model_name": "cerebras-baristo", "model": "cerebras/qwen-3-235b-a22b-instruct-2507", ...},
     {"model_name": "gemini-images", "model": "gemini/gemini-2.5-flash-lite", ...}
   ]

3. Send an image via Telegram

❌ Actual Behavior

Image messages are sent to the primary model (Cerebras/Qwen), which returns:

Status: 422
Body: {"message":"Content type 'image_url' is not supported by selected model. Only 'text' content type can be used."}

✅ Expected Behavior

Image messages should be routed to the image_model (Gemini) since it supports vision/multimodal input and the primary model does not.

💬 Additional Context

• ImageModel and ImageModelFallbacks are defined in pkg/config/config.go
• pkg/routing/features.go detects images via hasAttachments() and sets HasAttachments = true
• pkg/providers/fallback.go has an ExecuteImage() function for image-specific fallback chains
• However, selectCandidates() in pkg/agent/loop.go does not reference ImageModel — it only routes between primary and light model based on score
• The field appears partially implemented but not connected in the agent loop

Related: #1489 (lists image_model as undocumented)

[sipeed-bot]

@fernandostahelin Hi! This Issue has had no activity for over 2 weeks, so I'm closing it for now to keep things tidy. If it's still relevant, feel free to reopen it anytime and we'll pick it back up.