openclaw - 💡(How to fix) Fix sessions_spawn(model=...) override silently dropped — written to runtime fields instead of override fields [1 comments, 2 participants]

Summary

Subagent runs spawned via sessions_spawn(model=...) (or the gateway subagent.spawn method's model param) silently ignore the requested model and run on the agent's resolved primary instead. The spawn response returns modelApplied: true, which is misleading.

Root Cause

In dist/subagent-spawn--QfZonyO.js, persistInitialChildSessionRuntimeModel writes the resolved override into the runtime/last-used fields:

store[target.canonicalKey] = mergeSessionEntry(store[target.canonicalKey], {
    model,
    ...provider ? { modelProvider: provider } : {}
});

But the agent runtime (dist/agent-command-BxeGYLZy.js, around line 510) reads explicit overrides from a different pair of fields:

const hasStoredOverride = Boolean(sessionEntry?.modelOverride || sessionEntry?.providerOverride);
// ...
const storedProviderOverride = sessionEntry?.providerOverride?.trim();
let storedModelOverride = sessionEntry?.modelOverride?.trim();

Mismatched field names → override silently dropped → run falls back to agent default.

buildDirectChildSessionPatch has the same problem (writes entry.model / entry.modelProvider from patch.model).

The gateway agent method DOES accept a provider/model request field, but subagent-spawn never passes them through; it relies entirely on the persisted entry to carry the override — and the persist writes to the wrong fields.

Reproduction

1. Spawn any agent with a model override that differs from its primary, e.g. sessions_spawn(agentId="research", model="github-copilot/claude-sonnet-4.6", task="Reply OK").
2. Inspect the trajectory (~/.openclaw/agents/<agent>/sessions/<sessionId>.trajectory.jsonl) — provider/modelId show the agent default, not the override.
3. Inspect ~/.openclaw/agents/<agent>/sessions/sessions.json — modelOverride/providerOverride are missing on the new entry; only model/modelProvider are set.

Fix

Change persistInitialChildSessionRuntimeModel (and analogous code in buildDirectChildSessionPatch) to write to the override fields:

store[target.canonicalKey] = mergeSessionEntry(store[target.canonicalKey], {
    modelOverride: model,
    modelOverrideSource: "user",
    ...provider ? { providerOverride: provider } : {}
});

Verified locally on 2026.4.26: spawning with sonnet-4.6 override now produces provider: github-copilot, modelId: claude-sonnet-4.6 in the trajectory, and the corresponding model_change entry is emitted.

Severity

• Silent failure — no error surfaced to caller.
• modelApplied: true in the spawn response is incorrect when the override is dropped.
• Affects any caller relying on per-spawn model selection (e.g. model bake-offs, A/B comparisons, escalation patterns).

Affected Version

openclaw 2026.4.26 (latest as of this report). Likely present in earlier versions — the divergent runtime vs override field convention pre-dates the dist file's current shape.