Summary

Currently, heartbeat.model only accepts a string (single model). It would be valuable to support the same fallback chain format used by agents — either an array of models or an object with primary/fallbacks.

Use Case

When running heartbeats on free-tier or rate-limited models (e.g., NVIDIA NIM, OpenRouter free models), the heartbeat can fail silently if the primary model is unavailable. There is no way to specify a fallback model for heartbeats like you can for agent sessions.

Proposed Behavior

Allow heartbeat.model to accept either:

• A string (current behavior): "nvidia/kimi-k2.5"
• An array (fallback chain): ["nvidia/kimi-k2.5", "nvidia/minimaxai/minimax-m2.1"]
• An object (matching agent format): { "primary": "...", "fallbacks": ["..."] }

This should apply to both agents.defaults.heartbeat.model and per-agent heartbeat.model.

Context

Heartbeats are critical for proactive agent behavior. When the heartbeat model is rate-limited or down, the agent goes silent. Fallback support would make heartbeats resilient.

Filed via OpenClaw agent session