openclaw - 💡(How to fix) Fix String model config silently disables fallbacks (resolveAgentModelFallbackValues returns [] for strings) [1 pull requests]

Problem

When agents.defaults.model is set as a string (e.g. "anthropic/claude-opus-4-7"), the function resolveAgentModelFallbackValues() in src/config/model-input.ts returns an empty array — silently disabling all fallback behavior:

export function resolveAgentModelFallbackValues(model?: AgentModelConfig): string[] {
  if (!model || typeof model !== "object") {
    return [];  // string config = no fallbacks, no warning
  }
  return Array.isArray(model.fallbacks) ? model.fallbacks : [];
}

This is easy to trigger: if an agent or tool sets the model config to a string (e.g. via the model-switching tool), any previously configured fallbacks are silently lost.

Impact

• When the primary model returns overloaded_error, there is no fallback — the request fails entirely
• No warning is logged when fallbacks are lost
• The config appears valid (string model refs are accepted everywhere else)

Suggested fix

1. Log a warning when model config is a string and fallbacks would have been available in the previous config
2. The model-switching tool should preserve the existing config structure — update primary field without replacing the whole object
3. Consider auto-wrapping string configs: "model-name" → {primary: "model-name", fallbacks: []} with a deprecation warning

Environment

• OpenClaw v2026.5.6
• Discovered after an agent autonomously changed model config from object to string format