Codex subagents inherit parent context by default, so code reviews start with the author's assumptions
Matt Pocock fixed a context inheritance issue in a Codex skill. By default, Codex makes subagents fork the parent agent's context, so code reviews and spec implementation inherit the author's reasoning and blind spots. The PR, community workarounds, and debate are all covered in this piece.
TypeScript community developer Matt Pocock posted an update on X (original tweet) fixing a skill issue for Codex users. Codex inherits the context window of most subagents from the parent agent—that is, it forks it. This default behavior causes problems for skills that rely on a clean context window; he specifically called out code review and implementing from a spec.
A context window can be understood as the conversation, code, and reasoning records the model can currently see. When a subagent forks the parent agent, it enters the new task carrying the parent agent's previous judgments. During code review, this inheritance turns into confirmation bias.
Commenter Kizuno18 put the mechanism plainly: if the parent agent spent 10 turns convincing itself that some edge case does not exist, the forked reviewer will inherit that rationalization. Adversarial code review or spec implementation should start from ground truth—that is, the git diff and the spec markdown—with zero conversational momentum.
Cozy also mentioned in a reply that forked context is costly for review-type skills. Reviewers inherit the author's assumptions and blind spots, whereas a fresh window will judge only the diff and the spec. Variable added: forking is useful when a subagent needs to know what you have tried; in review, it is harmful.
Matt's tweet includes a link to the fix: PR #1341. Someone in the replies asked whether this fix is a wording adjustment in the skill or whether Codex has a real switch. Daniel Ehrhardt said it feels like this should be a param, not something that relies only on a prompt.
Commenter vampmaxxing posted a calling pattern: spawn_agent agent_type=default fork_turns="none", and said that is enough. Whether this snippet covers all Codex versions was not elaborated in the tweet; the specific changes need to be checked in the PR. Aayushman Singh offered another approach: pass the diff and repo rules, and do not bring debugging history into it. Udoh Jeremiah asked whether agent frameworks should make context inheritance opt-in rather than enabled by default.
This fix is small, but its location is critical. How much context a subagent should inherit depends on the task. Review and spec implementation need a clean starting point; forking is useful for tasks that need to continue the history of attempts. Codex users should check whether their skills have been skewed by this default.
发布时间: 2026-10-30 06:38