Summary

When spawning sub-agents via sessions_spawn, the model parameter (whether from config agents.defaults.subagents.model or passed explicitly) is not being applied. The sub-agent runs on the main session model instead.

Steps to Reproduce

1. Set agents.defaults.subagents.model to a different model than the main session:

   {
     "agents": {
       "defaults": {
         "subagents": {
           "model": "anthropic/claude-sonnet-4"
         }
       }
     }
   }

2. Spawn a sub-agent:

   sessions_spawn({
     task: "What model are you running as?",
     label: "model-test"
   })

3. Or spawn with explicit model parameter:

   sessions_spawn({
     task: "What model are you running as?",
     model: "anthropic/claude-sonnet-4"
   })

Expected Behavior

• Sub-agent should run on anthropic/claude-sonnet-4
• modelApplied: true in spawn response should mean the model was actually applied

Actual Behavior

• Sub-agent runs on main session model (anthropic/claude-opus-4-5)
• modelApplied: true is returned (misleading)
• Session store entries show model and modelProvider fields but no modelOverride/providerOverride fields

Investigation Findings

Traced through the code:

1. sessions-spawn-tool.js correctly reads the config and calls sessions.patch:

   const resolvedModel = normalizeModelSelection(modelOverride) ??
       normalizeModelSelection(targetAgentConfig?.subagents?.model) ??
       normalizeModelSelection(cfg.agents?.defaults?.subagents?.model);
   
   await callGateway({
       method: "sessions.patch",
       params: { key: childSessionKey, model: resolvedModel },
   });

2. sessions-patch.js calls applyModelOverrideToSessionEntry which should set providerOverride and modelOverride on the session entry

3. Gateway agent method reads the entry and passes it through, including modelOverride: entry?.modelOverride

4. agentCommand calls resolveSession which loads the store again, and model selection code checks for sessionEntry.modelOverride

5. updateSessionStoreAfterAgentRun writes model and modelProvider (the actually-used model) back to the store, but the override should have been applied before the run

Possible Root Causes

• applyModelOverrideToSessionEntry may not be writing the override correctly for new sessions
• The override may be lost between sessions.patch completing and the agent method reading the entry (timing/caching?)
• agentCommand model selection may not be finding the override due to key mismatch or store path differences

Environment

• OpenClaw version: 2026.1.29
• Node: v24.13.0 / v25.4.0
• OS: macOS (Darwin arm64)

Workaround

None known - sub-agents always use the main session model regardless of config or explicit parameter.