Files
codex/codex-rs/tools
Channing Conger ef500f4d23 Move code mode behind an IPC host
Split the code-mode protocol and client from the V8-backed runtime so core and
app-server no longer link codex-code-mode in production. ThreadManager now
provisions durable code-mode sessions through a shared external host process,
while tests can still inject the in-process provider.

The IPC protocol uses a persistent stdin/stdout transport. Each frame is a
4-byte big-endian length followed by JSON, with a 16 MiB frame limit. Client
requests carry u64 request IDs so create, execute, wait, terminate, and shutdown
operations can be multiplexed over one process. Session IDs isolate durable
stored values. Execute returns an ExecutionStarted response immediately and an
asynchronous InitialResponse when the initial yield or completion is available.

Nested tool calls and notifications travel from the host back to the client as
delegate requests with their own IDs. Delegate responses, cancellation, and
cell-closed lifecycle messages use the same framed channel. Wire operations
encode errors as Result values. A dead connection fails pending operations,
cancels outstanding delegates, and lets the provider spawn a new host for later
sessions.

Build codex-code-mode-host with V8 pointer-compression sandbox support and add
it to canonical primary and app-server packages, legacy Linux and Windows
bundles, signing verification, installers, Python runtime packages, and release
CI for macOS, Linux, and Windows. The host is discovered next to the current
executable, through CODEX_CODE_MODE_HOST_PATH, or on PATH. OS-level seccomp or
seatbelt restrictions remain a follow-up to this cross-platform process split.

Benchmarks were run from release builds on Linux x86_64 with the V8 sandbox
profile and a text('ok') workload. Cold measurements used 30 samples, warm
session provisioning used 200, and warm command execution used 500. Values are
mean/p50/p95 in milliseconds:

- session startup: in-process 0.002/0.002/0.005, IPC 2.623/2.599/2.894
- fresh-session command: in-process 1.831/1.758/1.915, IPC 7.428/7.252/8.306
- warm session provisioning: in-process 0.002/0.002/0.003,
  IPC 0.471/0.463/0.581
- warm command: in-process 1.759/1.757/1.940, IPC 2.005/2.001/2.166

The steady-state median command overhead is approximately 0.244 ms. The median
fresh host plus first command cost is 7.252 ms.

Validation:

- 62/62 core code-mode integration tests passed against the external host
- focused protocol, client, runtime, host, tools, and trace tests passed
- Cargo and Bazel real-process host IPC tests passed
- 11/11 package builder tests passed
- Bazel lock verification, scoped Clippy fixes, and repository formatting passed
2026-06-10 14:38:41 -07:00
..
2026-06-10 14:38:41 -07:00
2026-06-10 14:38:41 -07:00

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, and ResponsesApiNamespaceTool
  • 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, and ToolOutput

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-core orchestration 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:

  1. Keep extension-owned executable-tool authoring in codex-extension-api.
  2. Move host-side planning/adaptation helpers here when they no longer need to stay coupled to codex-core.
  3. Leave compatibility-sensitive adapters in codex-core while downstream call sites are updated.
  4. 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.rs should remain exports-only.
  • Business logic should live in named module files such as foo.rs.
  • Unit tests for foo.rs should live in a sibling foo_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.