A thread you can test
Extensions
4 notes move from the word to a real choice at work — understand it first, then decide whether to use it.
Each note stands alone, or becomes the next step in this thread.
THE QUESTION THIS PAGE ANSWERS
ANSWER FIRSTWhat is Extensions, and which AI decisions does it change?
Codex turns sub-agents into graph nodes: edges are Open or Closed, messages enqueue before they wake, and closing an edge leaves history intact This page keeps the related concepts, common mistakes, and practical notes in one reading thread.
First decide whether you are blocked by a definition, a choice, or verification; then choose the closest of the 4 notes below.
Start with “A Multi-agent Graph Must Be Persisted,” then restate the conclusion using your own task.
Do not treat every method in a topic as interchangeable. The answer changes with the input, risk, and acceptance bar.
THIS QUESTION THREAD
Put the word back inside the choice it changes.
A Multi-agent Graph Must Be Persisted
Codex turns sub-agents into graph nodes: edges are Open or Closed, messages enqueue before they wake, and closing an edge leaves history intact
What a hook can change is set by the event contract
Codex’s hook protocol names eleven events and four handler types, but the runtime table only loads commands and MCP. In one turn: what each hook gets, what it can change, and when it’s already too late
MCP comes in: the model sees translated names
When Codex takes an external MCP, tools pass a translation layer before the model sees them: prefix, sanitize, hash on collision. The skill catalog stays up; the body arrives only when named
Migration only keeps fields that map
Codex migrates from Claude Code and Cursor: detect lists the assets, import only keeps fields that map, plugins install from the user level only