## What changed
- Add a shared, read-only `ConversationHistorySnapshot` capability to the extension API.
- Include the snapshot in `ToolStartInput`, preserving conversation order while excluding contextual user messages.
- Avoid acquiring a history snapshot when no tool lifecycle contributors are registered.
## Testing
- Verify snapshots share existing response items, remain stable as history changes, and filter contextual user messages.
- Verify tool-start callbacks receive the history available for successive tool calls.
GitOrigin-RevId: 822cae33781dd876ea628f104be08d8a449a4900
## What changed
- Add an optional `ExtensionMetrics` capability to thread, turn-input, and world-state contributors, backed by session telemetry in the host.
- Record skill counts, omissions, and truncated description characters for extension-rendered catalogs, tagged by the catalog surface.
- Preserve host session attribution on extension metrics, including the effective model for each turn, and prevent extension tags from overriding host metadata.
- Avoid duplicate host-catalog samples by recording world-state metrics only when the section is published or changes.
## Testing
- Cover metric values and surface tags, session metadata preservation, turn-level model changes, and host world-state publication behavior.
GitOrigin-RevId: 9059e521943a8f81df25a38b03692eddbc1d990d
## Why
Extension warnings need a stable thread target even when they are emitted outside an active turn.
## What changed
- Add `ExtensionWarning` and a dedicated `ExtensionEventSink::emit_warning` path with an explicit thread ID and optional turn ID.
- Deliver extension warnings as thread-scoped app-server `warning` notifications, preserving listener ordering and waiting briefly for a subscriber when no listener is active.
- Move skills warnings to the new path, limiting provider catalog warnings to four messages of 256 bytes each.
## Testing
- Cover warning routing, ordering, UTF-8-safe truncation, subscriber fallback, and invalid thread IDs.
- Verify skills warning bounds and app-server delivery of executor catalog budget warnings.
GitOrigin-RevId: 4dcb1ba7f17c0edb1a9d548f9568e0c734bffc15
## What
- Add a small extension capability for injecting model-visible response
items into the active turn
- Have the goal extension inject hidden goal-context steering when
tool-finish accounting reaches `BudgetLimited`
- Cover the extension backend path with an assertion on the injected
steering item
## Why
PR #23696 persists and emits the budget-limited goal update from
tool-finish accounting, but it leaves the model unaware of that
transition. The existing core runtime steers the model to wrap up in
this case; the extension path should do the same through an explicit
host capability.
## Testing
- `just fmt`
- `cargo test -p codex-goal-extension`
- `cargo test -p codex-extension-api`
## Why
Extensions can already expose typed contributions and receive host
capabilities such as `AgentSpawner`, but they do not have a typed way to
send protocol events back through the host. Extensions that need to
surface progress or status should not have to own persistence, ordering,
transport fanout, or logging decisions themselves.
## What
- Add `ExtensionEventSink`, a host-provided fire-and-forget sink for
`codex_protocol::protocol::Event`.
- Add `NoopExtensionEventSink` so hosts that do not expose extension
event emission keep the existing empty-registry behavior.
- Store the sink on `ExtensionRegistryBuilder` / `ExtensionRegistry`,
with `with_event_sink(...)` and `event_sink()` accessors, and re-export
the new capability from `codex-extension-api`.
## Testing
- Not run locally; PR metadata/body update only.
Part 1 of guardian as extension. This bind all the logic to spawn
another agent from an extension and it adds `ThreadId` in the start
thread collaborator
felixxia-oai