Subagent spawn crashes with 'Cannot read properties of undefined (reading trim)'

Bug Description

When spawning subagents via sessions_spawn, the agent crashes with:

TypeError: Cannot read properties of undefined (reading 'trim')

The error occurs in buildAgentSystemPrompt() when processing context files where file.path is undefined.

Stack Trace

TypeError: Cannot read properties of undefined (reading 'trim')
    at file:///...dist/agents/system-prompt.js:437:46
    at Array.some (<anonymous>)
    at buildAgentSystemPrompt (file:///...dist/agents/system-prompt.js:436:42)
    at buildEmbeddedSystemPrompt (file:///...dist/agents/pi-embedded-runner/system-prompt.js:4:12)
    at runEmbeddedAttempt (file:///...dist/agents/pi-embedded-runner/run/attempt.js:280:30)

Root Cause

In src/agents/system-prompt.ts around line 538:

const hasSoulFile = contextFiles.some((file) => {
  const normalizedPath = file.path.trim().replace(/\\/g, "/");  // <-- crashes if file.path is undefined
  // ...
});

Fix

Change to:

const normalizedPath = (file.path ?? "").trim().replace(/\\/g, "/");

Environment

• OpenClaw version: 2026.2.1
• OS: macOS (Darwin 24.6.0 arm64)
• Node: v24.13.0

Impact

All sessions_spawn calls fail immediately (~20-30ms after start), making subagent functionality completely broken.

Additional Notes

During investigation, I also found other locations with similar patterns that may need guards:

• src/agents/subagent-registry.ts:420 - requesterSessionKey.trim()
• src/agents/subagent-announce.ts:152 - requesterSessionKey.trim()
• src/agents/pi-embedded-runner/lanes.ts:4 - key.trim()

These may not be the primary cause but are similar unsafe patterns.