Summary

When agents.defaults.model.fallbacks is configured globally (e.g. ["deepseek/deepseek-v4-flash", "moonshot/kimi-k2.6"]), this fallback list is not inherited by isolated cron sessions when the agent's model config is a plain string.

Expected: Cron sessions should fall back to agents.defaults.model.fallbacks when the agent has no explicit fallbacks configured.

Actual: Cron sessions get an empty fallback chain ([]), causing single-point-of-failure on the primary model.

Root Cause

In resolveSelectedModelFallbacksOverride (agent-scope.ts):

// When agent model config is a string like "deepseek/deepseek-v4-pro":
if (typeof raw === "string") return resolvePrimaryStringValue(raw) ? [] : undefined;
//                                                   ↑ returns [] (empty)
//                 "explicitly no fallbacks" — should be undefined to allow fallthrough

A string model config returns [] (semantically "no fallbacks explicitly set"), which prevents resolveFallbackCandidatesUncached from falling through to global defaults:

// In resolveFallbackCandidatesUncached (model-fallback.ts):
const modelFallbacks = params.fallbacksOverride !== void 0
    ? params.fallbacksOverride           // ← receives [], used as-is
    : resolveAgentModelFallbackValues(params.cfg?.agents?.defaults?.model);  // never reached

Since [] !== undefined is true, the global agents.defaults.model.fallbacks is never consulted.

Full Call Chain

resolveCronFallbacksOverride()                    // run-session-state.ts
  → useSubagentFallbacks = false                  // main agent, not subagent
  → No payload.fallbacks                          // skip priority 1
  → Skip priority 2 (useSubagentFallbacks=false)
  → resolveEffectiveModelFallbacks(hasSessionModelOverride=false)
    → resolveAgentModelFallbacksOverride("main")
      → resolveSelectedModelFallbacksOverride("deepseek/deepseek-v4-pro")
        → returns []  ← BUG: treats string model as "explicitly no fallbacks"

Impact

• Isolated cron sessions without per-job payload.fallbacks have no model fallback chain
• The global agents.defaults.model.fallbacks config is silently ignored
• If the primary model times out or fails, there's no alternative to try

Temporary Workaround

Explicitly set payload.fallbacks on each cron job:

{
  "payload": {
    "kind": "agentTurn",
    "fallbacks": ["deepseek/deepseek-v4-flash", "moonshot/kimi-k2.6"]
  }
}

Proposed Fix

In resolveSelectedModelFallbacksOverride, when the agent model is a plain string (primary ref only, no explicit fallbacks field), return undefined instead of []:

// Before:
if (typeof raw === "string") return resolvePrimaryStringValue(raw) ? [] : undefined;

// After:
if (typeof raw === "string") return undefined;  // let caller fall through to defaults

Or alternatively, in resolveEffectiveModelFallbacks, when hasSessionModelOverride is false, fall through to global defaults:

if (!params.hasSessionModelOverride) {
    return agentFallbacksOverride ?? resolveAgentModelFallbackValues(params.cfg.agents?.defaults?.model);
}

Environment

• OpenClaw 2026.6.1 (latest at time of report)
• Agent config:

  {
    "agents": {
      "defaults": {
        "model": {
          "primary": "deepseek/deepseek-v4-pro",
          "fallbacks": ["deepseek/deepseek-v4-flash", "moonshot/kimi-k2.6"]
        }
      },
      "list": [
        { "id": "main", "model": "deepseek/deepseek-v4-pro" }
      ]
    }
  }

• Isolated cron jobs without explicit payload.fallbacks reproduce the issue; adding payload.fallbacks works around it.

Verification

Confirmed by code inspection of the following source modules in dist/:

• agent-scope-BcYNOCQG.js — resolveSelectedModelFallbacksOverride returns [] for string models
• run-session-state-D-DIroy6.js — resolveCronFallbacksOverride priority chain
• model-fallback-hP2QoTn4.js — resolveFallbackCandidatesUncached checks fallbacksOverride !== undefined
• isolated-agent-Cw8sZTVo.js — resolveCronModelSelection determines useSubagentFallbacks