PreToolUse hook input missing agent_id for tmux/pane-based teammates

Summary

For PreToolUse hooks fired by teammate (Agent-tool) tool calls, the hook input includes agent_id when the teammate runs in in-process mode, but omits agent_id when the teammate runs in tmux/pane-based mode. Same teammate, same Agent invocation, same hook script — different payload depending on teammateMode.

This breaks hook scripts that branch on agent_id to distinguish main-agent vs subagent calls.

Repro

Hook script (force_background_bash.py, registered for PreToolUse on Bash):

import json, sys
data = json.load(sys.stdin)
is_main = not data.get("agent_id")  # documented contract: agent_id set only for subagent calls
# ... applies different rules based on is_main

Spawn the same teammate via Agent (with team_name/name) and have them run a Bash call.

| Mode | agent_id in hook input | Hook treats teammate as |
|---|---|---|
| In-process (no tmux) | present | subagent |
| Pane-based (tmux) | absent | main agent |

Concrete observed effect with the hook above:

• In-process teammate: Bash with timeout: 35000 runs synchronously (subagent rules — no auto-promote); explicit run_in_background: true is blocked.
• Pane-based teammate (tmux): same Bash call gets auto-promoted to background (main-agent rules); explicit run_in_background: true is allowed.

Expected

agent_id semantics in PreToolUse hook input should be consistent across teammate spawn modes — a teammate is a teammate regardless of whether the harness chose in-process or pane-based execution.

Related

• #29068 (closed) — added agent_id to common hook input
• #24175 (closed/stale) — lifecycle hook firing inconsistency between in-process and pane-based teammates. This issue is narrower: PreToolUse does fire in both modes here, but with different payloads.

Environment

• Claude Code 2.1.119
• Linux
• Reproduces with a vanilla Agent call using team_name/name and a PreToolUse hook reading agent_id from stdin.

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