## Summary
Add the extension-backed standalone `web.run` tool so Codex can call the
standalone search endpoint through the `codex-api` search client and
return its encrypted output to Responses.
- gate the new tool behind `standalone_web_search`
- install the extension in the app-server thread registry and hide
hosted `web_search` when standalone search is enabled for OpenAI
providers so the two paths stay mutually exclusive
- build search context from persisted history using a small tail
heuristic: previous user message, assistant text between the last two
user turns capped at about 1k tokens, and current user message
## Test Plan
- `cargo test -p codex-web-search-extension`
- `cargo test -p codex-api`
- `cargo test -p codex-core
hosted_tools_follow_provider_auth_model_and_config_gates`
## Why
The goal extension already emits `ThreadGoalUpdated` events, but
production app-server thread extensions were built with the default
no-op extension event sink. That meant extension-driven goal updates
could be produced without ever reaching app-server clients.
## What changed
- Build app-server thread extensions with a host-provided
`ExtensionEventSink`.
- Add an app-server sink that converts extension `ThreadGoalUpdated`
events into `ServerNotification::ThreadGoalUpdated` broadcasts.
- Use the existing bounded outgoing message channel via `try_send` so
event forwarding cannot create an unbounded queue.
- Pass `NoopExtensionEventSink` in app-server tests that construct a
`ThreadManager` without an app-server host.
- Refresh `Cargo.lock` for the existing `codex-memories-extension`
`codex-otel` dependency.
## Verification
- `just test -p codex-app-server
extensions::tests::app_server_event_sink_forwards_thread_goal_updates`
## Summary
- let the memories extension capture the process-global OTEL metrics
client at install time
- keep app-server/TUI/exec extension construction APIs unchanged
- store the metrics client for future memory metrics without emitting
any metrics yet
## Test plan
- `just fmt`
- `just bazel-lock-update`
- `just bazel-lock-check`
- Not run: tests/clippy per request; CI will cover them
## Why
Memory prompt injection should be owned by the extension path that
app-server composes at runtime, not by an inlined special case inside
`codex-core`. This keeps `codex-core` focused on session orchestration
while allowing the memories extension to own its app-server prompt
behavior.
## What Changed
- Registers `codex-memories-extension` in the app-server extension
registry.
- Moves the memory developer-instruction injection out of
`core/src/session/mod.rs` and into the memories extension prompt
contributor.
- Adds config-change handling so the extension keeps its per-thread
memory settings in sync after startup.
- Leaves memories read/retrieval tools unregistered for now so this PR
only changes prompt injection.
- Removes the stale `cargo-shear` ignore now that app-server depends on
the extension crate.
## Validation
Not run locally; validation is left to CI.
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
## Why
[#21736](https://github.com/openai/codex/pull/21736) introduces the
typed extension API, but the runtime does not yet carry a registry
through thread/session startup or give contributors host-owned stores to
read from. This PR wires that host-side path so later feature migrations
can move product-specific behavior behind typed contributions without
adding another bespoke seam directly to `codex-core`.
## What changed
- Thread `ExtensionRegistry<Config>` through `ThreadManager`,
`CodexSpawnArgs`, `Session`, and sub-agent spawn paths.
- Wire `ThreadStartContributor` and `ContextContributor`
- Expose the small supporting surface needed by non-core callers that
construct threads directly, including `empty_extension_registry()`
through `codex-core-api`.
This PR lands the host plumbing only: the app-server registry is still
empty, and concrete feature migrations are intended to follow
separately.
sayan-oai