## Why `ToolRouter::tool_supports_parallel()` was still consulting configured specs when a handler lookup missed, even though parallel schedulability is really a property of the executable handler. Keeping that metadata on `ConfiguredToolSpec` duplicated state between the model-visible spec layer and the runtime handler layer. This change makes handlers the sole source of truth for parallel tool support and removes the extra spec wrapper that only existed to carry duplicated metadata. ## What changed - removed `ConfiguredToolSpec` and store plain `ToolSpec` values in the registry/router builder path - changed `ToolRouter::tool_supports_parallel()` to consult only the handler registry and fall back to `false` - simplified spec collection and test helpers to operate directly on `ToolSpec` - updated router/spec tests to cover handler-owned parallel behavior and the no-handler fallback ## Validation - `cargo test -p codex-tools` - `cargo test -p codex-core mcp_parallel_support_uses_handler_data` - `cargo test -p codex-core deferred_responses_api_tool_serializes_with_defer_loading` - `cargo test -p codex-core tools_without_handlers_do_not_support_parallel` - `cargo test -p codex-core request_plugin_install_can_be_registered_without_search_tool` ## Docs No documentation updates needed.
codex-tools
codex-tools is the host-side support crate for building, adapting, and
planning tool sets outside codex-core.
It is deliberately not the API that external tool owners should depend on.
Crates that contribute ordinary function tools through extensions should use
codex-tool-api, which owns only that small executable-tool seam.
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 config and discovery models used while assembling tool sets, including
ToolsConfig, discoverable-tool models, and request-plugin-install helpers - host adapters such as schema sanitization, MCP/dynamic conversion, code-mode augmentation, and image-detail normalization
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 become the extension-facing authoring API for executable tools
- 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 ordinary contributed function-tool authoring in
codex-tool-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.