## Description This PR adds an optional `metadata` field to `ResponseItem` for Responses API calls. Only mechanical plumbing, no actual values populated and sent yet. Turns out just adding a new field to `ResponseItem` has quite a large blast radius already. This change is backwards compatible because `metadata` is optional and omitted when absent, so existing response items and rollout history without it still deserialize and requests that do not set it keep the same wire shape. For provider compatibility, we strip out `metadata` before non-OpenAI Responses requests so Azure and AWS Bedrock never see this field. My followup PR here will actually make use of it to start storing and passing along `turn_id`: https://github.com/openai/codex/pull/28360 ## What changed - Added `ResponseItemMetadata` with optional `turn_id`, plus optional `metadata` on Responses API item variants and inter-agent communication. - Preserved item metadata through response-item rewrites such as truncation, missing tool-output synthesis, compaction history rebuilding, visible-history conversion, rollout/resume, and generated app-server schemas/types. - Strip item metadata from non-OpenAI Responses requests while preserving it for OpenAI-shaped requests. - Updated the mechanical fixture/test construction churn required by the new optional field.
codex-tools
codex-tools is the shared support crate for building, adapting, and executing
model-visible tools outside codex-core.
Today this crate owns the host-facing tool models and helpers that no longer
need to live in core/src/tools/spec.rs or core/src/client_common.rs:
- aggregate host models such as
ToolSpec,ConfiguredToolSpec,LoadableToolSpec,ResponsesApiNamespace, andResponsesApiNamespaceTool - host discovery models used while assembling tool sets, including discoverable-tool models and request-plugin-install helpers
- host adapters such as schema sanitization, MCP/dynamic conversion, code-mode augmentation, and image-detail normalization
- shared executable-tool contracts such as
ToolExecutor,ToolCall, andToolOutput
That extraction is the first step in a longer migration. The goal is not to
move all of core/src/tools into this crate in one shot. Instead, the plan is
to peel off reusable pieces in reviewable increments while keeping
compatibility-sensitive orchestration in codex-core until the surrounding
boundaries are ready.
Vision
Over time, this crate should hold host-side tool machinery that is shared by multiple consumers, for example:
- host-visible aggregate tool models
- tool-set planning and discovery helpers
- MCP and dynamic-tool adaptation into Responses API shapes
- code-mode compatibility shims that do not depend on
codex-core - other narrowly scoped host utilities that multiple crates need
The corresponding non-goals are just as important:
- do not move
codex-coreorchestration here prematurely - do not pull
Session/TurnContext/ approval flow / runtime execution logic into this crate unless those dependencies have first been split into stable shared interfaces - do not turn this crate into a grab-bag for unrelated helper code
Migration approach
The expected migration shape is:
- Keep extension-owned executable-tool authoring in
codex-extension-api. - Move host-side planning/adaptation helpers here when they no longer need to
stay coupled to
codex-core. - Leave compatibility-sensitive adapters in
codex-corewhile downstream call sites are updated. - Only extract higher-level host infrastructure after the crate boundaries are clear and independently testable.
Crate conventions
This crate should start with stricter structure than core/src/tools so it
stays easy to grow:
src/lib.rsshould remain exports-only.- Business logic should live in named module files such as
foo.rs. - Unit tests for
foo.rsshould live in a siblingfoo_tests.rs. - The implementation file should wire tests with:
#[cfg(test)]
#[path = "foo_tests.rs"]
mod tests;
If this crate starts accumulating code that needs runtime state from
codex-core, that is a sign to revisit the extraction boundary before adding
more here.