## Why Codex still models model-visible tools and executable behavior largely inside `codex-core`, which makes it harder to evolve the tool system toward a single reusable abstraction for built-ins, MCP-backed tools, dynamic tools, and later tools injected from outside core. This PR takes the next incremental step in that direction by moving the common execution-facing pieces out of core and separating them from core-only orchestration. The intent is to let shared tool abstractions improve in one place, while `codex-core` keeps the parts that are still inherently host-specific today, such as `ToolInvocation`, dispatch wiring, and hook integration. This PR is mostly moving things around. The only interesting piece is this abstraction: https://github.com/openai/codex/pull/22359/changes#diff-81af519002548ba51ed102bdaaf77e081d40a1e73a6e5f9b104bbbc96a6f1b3dR13 ## What changed - Added `codex_tools::ToolExecutor<Invocation>` as the shared execution trait for model-visible tools. - Moved the reusable execution support types from `codex-core` into `codex-tools`: - `FunctionCallError` - `ToolPayload` - `ToolOutput` - Refactored core tool implementations so that execution behavior lives on `ToolExecutor<ToolInvocation>`, while `ToolHandler` remains the core-local extension point for hook payloads, telemetry tags, diff consumers, and other orchestration concerns. - Kept the registry and dispatch flow behaviorally unchanged while making the shared/extracted boundary explicit across built-in, MCP, dynamic, extension-backed, shell, and multi-agent tool handlers. ## Verification - `cargo test -p codex-tools` - `just fix -p codex-tools` - `just fix -p codex-core` - `cargo test -p codex-core` progressed through the updated tool surfaces and then hit the existing unrelated multi-agent stack overflow in `tools::handlers::multi_agents::tests::tool_handlers_cascade_close_and_resume_and_keep_explicitly_closed_subtrees_closed`.
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.