Summary

The "Fallbacks (comma-separated)" input field in the /agents overview panel is empty when the agent has no per-agent model config (agents.list entry) — even though agents.defaults.model.fallbacks is correctly configured and the summary label above ("Primary Model") correctly displays the fallback count (e.g., openai/gpt-5-nano (+1 fallback)).

Steps to reproduce

1. Configure agents.defaults.model in openclaw.json with a primary and fallbacks array:

   "agents": {
     "defaults": {
       "model": {
         "primary": "openai/gpt-5-nano",
         "fallbacks": ["google/gemini-2.0-flash"]
       }
     }
   }

2. Do not create an agents.list entry (use only the implicit default agent).
3. Open Control UI at /agents → select the default agent → Overview tab.
4. Observe the "Fallbacks (comma-separated)" input field.

Expected behavior

The fallback input should display google/gemini-2.0-flash (inherited from agents.defaults.model.fallbacks), consistent with how the primary model field already inherits from defaults.

Actual behavior

The fallback input is empty (""), while the summary label correctly shows openai/gpt-5-nano (+1 fallback).

OpenClaw version

2026.2.19-2

Operating system

Ubuntu 24.04 (WSL2)

Install method

npm global

Logs, screenshots, and evidence

Root cause in ui/src/ui/views/agents.ts (renderAgentOverview):

// Line 393 — only checks entry, never falls back to defaults:
const modelFallbacks = resolveModelFallbacks(config.entry?.model);
const fallbackText = modelFallbacks ? modelFallbacks.join(", ") : "";

Compare with the primary model resolution a few lines above, which correctly chains entry ?? defaults:

const modelPrimary =
  resolveModelPrimary(config.entry?.model) || (...normalizeModelValue(model)...);
const defaultPrimary =
  resolveModelPrimary(config.defaults?.model) || ...;
const effectivePrimary = modelPrimary ?? defaultPrimary ?? null;

Fix: Apply the same ?? fallback pattern:

const modelFallbacks =
  resolveModelFallbacks(config.entry?.model) ?? resolveModelFallbacks(config.defaults?.model);

This is safe for all edge cases:

• No fallbacks configured anywhere → null → empty string ✅
• Fallbacks only in defaults → inherits correctly ✅
• Agent has own fallbacks → entry takes precedence ✅
• Agent explicitly sets fallbacks: [] → respected (empty array is truthy, ?? does not fall through) ✅

Impact and severity

• Affected: All users relying on agents.defaults.model.fallbacks without per-agent agents.list entries (common in single-agent setups)
• Severity: Low (display-only bug; backend fallback routing works correctly)
• Frequency: 100% reproducible
• Consequence: Confusing UX — users think their fallback is not configured when it actually is

Additional information

Related: #20924 (Save button stays disabled for default agent — same agents.defaults vs agents.list scenario).