codex exec --json omits spawn_agent function calls from the event stream

Codex version

codex-cli 0.147.0

Problem

codex exec --json omits the spawn_agent function call and its result from stdout even though both records are persisted in the session rollout JSONL. The stream may later emit a collab_tool_call for wait, but consumers never receive the matching spawn event, target, prompt, or result.

The same gap affects unified custom tool calls: with features.unified_exec=true, calls such as the unified exec tool are persisted in the rollout but omitted from --json. Setting features.unified_exec=false makes standard command_execution events visible, but does not make spawn_agent visible.

Reproduction

codex exec --json \
  --skip-git-repo-check \
  --sandbox danger-full-access \
  -c 'features.multi_agent=true' \
  -c 'features.unified_exec=false' \
  'Call spawn_agent exactly once with fork_turns none, wait for it, then reply only DONE.'

Observed stdout contains thread.started, turn.started, sometimes collab_tool_call for wait, the final agent_message, and turn.completed, but no spawn call/result. The matching rollout JSONL contains a namespaced function_call with name: "spawn_agent" and its function_call_output.

Expected behavior

--json should expose all tool calls needed by API/SDK consumers to reconstruct the turn, including namespaced collaboration calls and their results. At minimum, a successful spawn should emit a correlated event containing its call ID, target agent type/name, prompt/task metadata, and spawned agent/thread ID.

_{🤖 Created by Jarvis via Realmroot}

Start with the codex exec --json event stream and compare its output with the persisted session rollout JSONL. Reproduce the issue using the command shown, including spawn_agent and unified tool calls, then trace how those records are converted into stdout events. Done means consumers receive correlated spawn and custom-tool call and result events with the required metadata.