Both Codex and Claude Code have it, but they work slightly differently.
Claude Code uses Haiku to read through the transcript and decide if the goal has been completed. If not, Haiku injects a prompt back to the main model to indicate what still needs to be done.
In Codex, instead it's a tool available to the main model, plus some part of the surrounding harness that will re-prompt it if the tool calls haven't yet indicated that the goal is complete.
The issue that they are trying to solve is that sometimes models will stop before they have actually fully completed whatever task they were given; attention isn't perfect, and someitmes they'll complete part of it but not the whole task. Rather than making the user come back and re-prompt to keep going, they add a way to automatically do a bit more nudging to try to get the model to finish the task.
feels kinda odd to use a less capable model to determine if the goal is fully complete. Especially if the user is expecting /goal to thoroughly complete the task. A less capable model would be more likely to misclassify `isComplete?`
This is overselling it. In all implementations of this that I’ve seen, a more correct phrasing is “won’t stop until it pinky-promises it achieved your goal”.
It usually relies on something like a hook that refuses to let the agent stop unless it includes a “promise sentinel”, which is basically the model having to include “I swear I’m done” in the response (usually as a Markdown comment so the user doesn’t see it). If that sentinel isn’t in the response, the hook rejects the completion and hands it back to the agent (sometimes it also restates the goal to keep it focused). It’s useful for sure, but it fails many times for obvious reasons.
More robust implementations use the hook to spawn another agent that verifies the goal is achieved, but that too isn’t prefect and sometimes performs worse.
Of course if you have a problem that can be deterministically verified, you could have the hook run this verification instead, but this is usually not the case (and even when it is, agents will often cheat the verification e.g. by deleting a test file).
With /goal, a different Claude instance evaluates the goal. This is the robust version you described, and such an "adversarial Claude's" approach, with or without/goal, is exactly how you avoid pinky promises (from one Claude).
/goal open a draft PR that makes <endpoint> ~200ms faster while still passing tests, and adhering to nearby style+pattern
If you want to be able to use it like that, you need to find a way to encode (most of) your concerns into something that can be programmatically verified.
I haven't really found a good way to solve this other than:
1. Produce an initial PR fulfilling all the requirements I knew at the start
2. Chat with the model about any weird snippets I notice and talk through alternatives
3. Simplify anything that I think is overengineered or plain unncessary
Sometimes I restart all over with more precise requirements but then it sometimes makes different mistakes/takes different shortcuts.
In practice the earlier I review the better the end result imo, so /goal seems very unproductive to me?
/goal is a gimmick where you run a "parent" agent on top that runs the agent on a loop until the it decides to stop, just prompting it "nope, not done yet, continue".