Feature Request: Add TaskCompleted Hook Event

Description

Currently, Codex provides several hook events such as PreToolUse, PostToolUse, UserPromptSubmit, and Stop. However, there is no explicit hook that represents the completion of a full task (i.e., when the agent has finished executing a user request end-to-end).

I would like to propose introducing a new hook event: TaskCompleted.

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Motivation

While existing hooks cover turn-level and tool-level lifecycle events, they are still somewhat fragmented when building higher-level integrations.

A TaskCompleted hook would provide a clear and reliable signal that:

The agent has finished executing the entire task

No further actions or tool calls are expected

The final output is ready for downstream processing

This is especially useful for:

Logging and analytics pipelines

Triggering post-task automation (e.g., notifications, CI steps)

Persisting results or summaries

Integrating with external orchestration systems

Measuring task-level performance and success rates

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Proposed Behavior

The TaskCompleted hook should fire exactly once per task

It should run after the final response is generated

It should include structured metadata, such as:

Final response content

Task duration

Tools used (if applicable)

Status (success / failure / interrupted)

Example (conceptual):

{
"event": "TaskCompleted",
"data": {
"final_output": "...",
"duration_ms": 12345,
"tools_used": ["local_shell", "file_write"],
"status": "success"
}
}

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Why Existing Hooks Are Not Enough

Stop operates at turn scope, not full task scope

PostToolUse is too granular and tool-specific

There is no single event that reliably signals task-level completion

This makes it harder to build robust integrations without additional inference or custom patching.