## Why
Users have indicated that they want an agent to be able to create a new
goal for itself after completing the previous goal. Currently, that's
not possible because agents cannot overwrite an existing goal even if
it's complete. This PR removes this limitation and allows `create_goal`
to overwrite an existing goal if it is in the `complete` state.
## What changed
`create_goal` now replaces the existing goal only when its status is
`complete`. The replacement is performed atomically in the goal store,
creates a fresh active goal with reset usage, and continues to reject
creation while any unfinished goal exists. App server clients see a
single `thread/goal/updated` event when the previous goal is replaced
with the new one.
The tool description and error message now reflect these semantics.
## What didn't change
Agents are not allowed to create a new goal (overwrite their existing
goal) if an existing goal is still active, blocked, paused, or in any
other state other than "completed".
## Stack
1. [#26547](https://github.com/openai/codex/pull/26547) - [1 of 2] Align
goal extension with core behavior
2. [#26548](https://github.com/openai/codex/pull/26548) - [2 of 2] Move
goal runtime to extension
## Why
The goal runtime is moving out of `codex-core` and into
`codex-goal-extension`. This first PR brings the extension back in line
with the current core behavior before the follow-up PR switches
app-server sessions over to the extension, so that review can focus on
ownership and wiring rather than hidden behavior drift.
## What Changed
- Updates the extension `create_goal` and `update_goal` tool
schemas/descriptions to match the current core wording for explicit
token budgets, blocked-goal audits, resumed blocked goals, and
system-owned budget/usage-limit transitions.
- Marks `codex-goal-extension` as the live `/goal` extension crate
rather than an unwired sketch.
- Looks up the live thread before reading goal state for idle
continuation, so continuation setup exits early when no live thread can
accept the automatic turn.
## Why
The goal extension can create and surface goals, but the live
turn-accounting path still stopped short of persisting active-goal
progress. That leaves token and wall-clock usage, plus
`ThreadGoalUpdated` events, out of sync with the extension boundary once
work actually advances or a goal transitions out of active state.
## What changed
- Teach `GoalAccountingState` to track the current turn, active goal,
token deltas, and wall-clock progress snapshots against the persisted
goal id.
- Flush active-goal accounting from tool-finish, turn-stop, and
turn-abort lifecycle hooks, and emit `ThreadGoalUpdated` events when
persisted progress changes.
- Route `create_goal` and `update_goal` through the same accounting
state so new goals start from the right baseline, final progress is
flushed before status changes, and `update_goal` can mark a goal
`blocked` as well as `complete`.
- Keep budget-limited goals accruing through the end of the turn while
clearing local active-goal state once a turn or explicit update is
finished.
- Expand backend and lifecycle coverage around store ids, baseline
reset, tool-finish accounting, budget-limited carry-through, and
blocked-goal updates.
## Testing
- Added focused backend coverage in
`codex-rs/ext/goal/tests/goal_extension_backend.rs` for baseline reset,
tool-finish accounting, budget-limited turns, and blocked-goal updates.
- Extended `codex-rs/core/src/session/tests.rs` to assert that lifecycle
inputs expose the expected session, thread, and turn store ids.
Eric Traut