## Why
Client-created response items enter history without IDs, so their
identity is lost across rollout persistence and resume. IDs should be
assigned once at the history-recording boundary, while IDs returned by
the server must remain unchanged.
The Responses API validates item IDs using type-specific prefixes.
Locally generated IDs therefore use the matching prefix plus a
hyphenated UUIDv7, keeping them valid while distinguishable from
server-generated IDs. Because this changes persisted history and
provider request shapes, the behavior is opt-in behind the
under-development `item_ids` feature. Compaction triggers remain request
controls whose API shape does not accept an ID.
## What changed
- Register the disabled-by-default `item_ids` feature and expose it in
`config.schema.json`.
- Make supported optional `ResponseItem` IDs serializable and expose
them in the generated app-server schemas.
- When `item_ids` is enabled, assign an ID during conversation-history
preparation if an item has no ID.
- Generate type-prefixed, hyphenated UUIDv7 IDs using the Responses API
item conventions.
- Preserve existing server IDs without rewriting them.
- Persist assigned IDs in rollouts and include them in subsequent
Responses requests.
- Remove the unsupported ID field from `CompactionTrigger` and document
why it has no ID.
- Add integration coverage for enabled ID persistence, preservation of
server IDs, and omission of generated IDs while the feature is disabled.
`prepare_conversation_items_for_history` is the single response-item ID
allocation boundary.
## Test plan
- `just test -p codex-features`
- `just test -p codex-core
response_item_ids_persist_across_resume_and_preserve_server_ids`
- `just test -p codex-core
non_openai_responses_requests_omit_item_turn_metadata`
- `just test -p codex-core
resize_all_images_prepares_failures_before_history_insertion`
- `just test -p codex-protocol`
- `just test -p codex-app-server-protocol`
- `just test -p codex-api azure_default_store_attaches_ids_and_headers`
## Why
`ResponseItem` variants do not have a consistent internal ID shape: some
variants carry required IDs, some carry optional IDs, and some cannot
represent an ID at all. The existing fields also use inconsistent serde,
TypeScript, and JSON-schema annotations. A single enum-level access path
is needed before history recording can assign and retain IDs.
This PR establishes that internal model only. It intentionally does not
generate or serialize IDs; allocation and wire persistence are isolated
in the stacked follow-up.
## What changed
- Give every concrete `ResponseItem` variant an `Option<String>` ID
field.
- Apply the same internal-only annotations to every ID field:
`#[serde(default, skip_serializing)]`, `#[ts(skip)]`, and
`#[schemars(skip)]`.
- Add `ResponseItem::id()` and `ResponseItem::set_id()` as the shared
accessors.
- Preserve IDs when history items are rewritten for truncation.
- Adapt consumers that previously assumed reasoning and image-generation
IDs were required.
- Regenerate app-server schemas so the hidden fields are represented
consistently.
The serde catch-all `ResponseItem::Other` remains ID-less because it
must remain a unit variant.
## Test plan
- `cargo check --tests -p codex-core -p codex-api -p codex-rollout-trace
-p codex-image-generation-extension`
- `just test -p codex-protocol`
- `just test -p codex-app-server-protocol`
- `just test -p codex-api -p codex-rollout-trace -p
codex-image-generation-extension`
- `just test -p codex-core event_mapping`
## Why
to support a new bring your own search tool in Responses
API(https://developers.openai.com/api/docs/guides/tools-tool-search#client-executed-tool-search)
we migrating our bm25 search tool to use official way to execute search
on client and communicate additional tools to the model.
## What
- replace the legacy `search_tool_bm25` flow with client-executed
`tool_search`
- add protocol, SSE, history, and normalization support for
`tool_search_call` and `tool_search_output`
- return namespaced Codex Apps search results and wire namespaced
follow-up tool calls back into MCP dispatch
### What
add wiring for `phase` field on `ResponseItem::Message` to lay
groundwork for differentiating model preambles and final messages.
currently optional.
follows pattern in #9698.
updated schemas with `just write-app-server-schema` so we can see type
changes.
### Tests
Updated existing tests for SSE parsing and hydrating from history
Adds a new feature
`enable_request_compression` that will compress using zstd requests to
the codex-backend. Currently only enabled for codex-backend so only enabled for openai providers when using chatgpt::auth even when the feature is enabled
Added a new info log line too for evaluating the compression ratio and
overhead off compressing before requesting. You can enable with
`RUST_LOG=$RUST_LOG,codex_client::transport=info`
```
2026-01-06T00:09:48.272113Z INFO codex_client::transport: Compressed request body with zstd pre_compression_bytes=28914 post_compression_bytes=11485 compression_duration_ms=0
```
pakrym-oai