Problem

When a sub-agent (spawned via sessions_spawn) runs an exec tool call that fails (non-zero exit code or stderr output), the error notification is delivered to the parent session's Telegram channel as a visible warning message.

This happens despite both suppression flags being set:

• messages.suppressToolErrors: true
• tools.exec.notifyOnExit: false

Expected Behavior

Sub-agent exec failures should be contained within the sub-agent session. The parent session's channel should not receive inline exec error notifications from child sessions.

Current Behavior

Every failed exec in a sub-agent produces a visible Telegram message in the parent chat like:

Warning: Exec: pty ... failed: [PTY escape codes...]

This includes raw PTY escape codes, making it doubly noisy.

Analysis

• suppressToolErrors only covers non-mutating tool-failure warnings (per feat: add messages.suppressToolErrors config option #16620)
• notifyOnExit only covers background exec completion system events (per [Bug]: Background exec completion notifications can interrupt active agent turn #8997)
• Neither covers the inline exec error display path that formats Exec warning messages when a command fails during an active agent turn
• The issue is specifically that this display path routes to the parent session's channel rather than staying within the sub-agent session

Reproduction

1. Set messages.suppressToolErrors: true and tools.exec.notifyOnExit: false
2. Spawn a sub-agent via sessions_spawn
3. Sub-agent runs an exec command that fails (e.g., Python syntax error, missing module)
4. Parent session's Telegram chat receives the exec failure notification

Environment

• OpenClaw: 2026.2.15
• Channel: Telegram
• Provider: Anthropic (Claude Opus 4.6)
• OS: Windows 10 (x64)