Problem

When a cron job uses --channel quiubo without --to, OpenClaw core rejects with:

No delivery target resolved for channel "quiubo". Set delivery.to.

The Quiubo extension implements config.resolveDefaultTo() (added in bitlabs-com/quiubo#87), but core never calls it during cron delivery.

Root Cause

In src/cron/isolated-agent/delivery-target.ts, resolveDeliveryTarget() calls resolveSessionDeliveryTarget() which returns resolved.to. If resolved.to is falsy, core fails immediately at line ~3581:

if (!toCandidate) return {
    ok: false,
    error: new Error(`No delivery target resolved for channel "${channel}". Set delivery.to.`)
};

Core never checks plugin.config.resolveDefaultTo() as a fallback.

By contrast, the direct send path in resolveOutboundTarget() (reply-*.js ~line 31711) does call resolveDefaultTo:

const effectiveTo = params.to?.trim() || (params.cfg && plugin.config.resolveDefaultTo 
    ? plugin.config.resolveDefaultTo({ cfg: params.cfg, accountId }) 
    : void 0);

Expected Behavior

resolveDeliveryTarget should call plugin.config.resolveDefaultTo({ cfg, accountId }) as a fallback when toCandidate is empty, matching the behavior of resolveOutboundTarget.

Repro

openclaw cron add --name test --agent giskard --at +30s --channel quiubo --announce --message "hello"
# Result: runs, then fails with "No delivery target resolved"

Adding --to <groupId> works fine.

Impact

Any channel plugin that implements resolveDefaultTo (to auto-resolve targets from session state) is broken for cron delivery. This affects Quiubo and potentially other plugins with dynamic conversation targets.

Workaround

Always pass --to <targetId> when creating crons for channels without a static default target.