## Why
We want to remove implicit use of `$CODEX_HOME` from `codex-core` and
make embedders responsible for supplying user-level instructions. This
also ensures user instructions load when no primary environment is
selected.
## What changed
Stacked on #27415, which makes `codex exec` surface thread-scoped
runtime warnings.
- Added `UserInstructionsProvider` to `codex-extension-api`, with
absolute source attribution and recoverable loading warnings.
- Added `codex-home` with the filesystem-backed provider for
`AGENTS.override.md` and `AGENTS.md`, preserving precedence, fallback,
trimming, lossy UTF-8 handling, and the existing uncapped global
instruction size.
- Removed global instruction loading from `Config` and require
`ThreadManager` callers to inject a provider.
- Load provider instructions once for each fresh root runtime, including
runtimes without a primary environment. Running sessions retain their
snapshot, while child agents inherit the parent snapshot without
invoking the provider.
- Keep provider instructions separate while loading project `AGENTS.md`,
then assemble the model-visible instructions with the existing ordering,
source attribution, warning, and turn-context behavior.
- Wired the Codex home provider through the CLI, app server, MCP server,
core facade, and thread-manager sample.
## Validation
- `just test -p codex-home -p codex-extension-api`
- `just test -p codex-core agents_md`
- `just test -p codex-core guardian`
- `just test -p codex-app-server
thread_start_without_selected_environment_includes_only_global_instruction_source`
- `just test -p codex-exec warning`
- `just bazel-lock-check`
## Why
[#21736](https://github.com/openai/codex/pull/21736) introduces the
typed extension API, but the runtime does not yet carry a registry
through thread/session startup or give contributors host-owned stores to
read from. This PR wires that host-side path so later feature migrations
can move product-specific behavior behind typed contributions without
adding another bespoke seam directly to `codex-core`.
## What changed
- Thread `ExtensionRegistry<Config>` through `ThreadManager`,
`CodexSpawnArgs`, `Session`, and sub-agent spawn paths.
- Wire `ThreadStartContributor` and `ContextContributor`
- Expose the small supporting surface needed by non-core callers that
construct threads directly, including `empty_extension_registry()`
through `codex-core-api`.
This PR lands the host plumbing only: the app-server registry is still
empty, and concrete feature migrations are intended to follow
separately.
## Summary
`cargo test` has entails both running standard Rust tests and doctests.
It turns out that the doctest discovery is fairly slow, and it's a cost
you pay even for crates that don't include any doctests.
This PR disables doctests with `doctest = false` for crates that lack
any doctests.
For the collection of crates below, this speeds up test execution by
>4x.
E.g., before this PR:
```
Benchmark 1: cargo test -p codex-utils-absolute-path -p codex-utils-cache -p codex-utils-cli -p codex-utils-home-dir -p codex-utils-output-truncation -p codex-utils-path -p codex-utils-string -p codex-utils-template -p codex-utils-elapsed -p codex-utils-json-to-toml
Time (mean ± σ): 1.849 s ± 4.455 s [User: 0.752 s, System: 1.367 s]
Range (min … max): 0.418 s … 14.529 s 10 runs
```
And after:
```
Benchmark 1: cargo test -p codex-utils-absolute-path -p codex-utils-cache -p codex-utils-cli -p codex-utils-home-dir -p codex-utils-output-truncation -p codex-utils-path -p codex-utils-string -p codex-utils-template -p codex-utils-elapsed -p codex-utils-json-to-toml
Time (mean ± σ): 428.6 ms ± 6.9 ms [User: 187.7 ms, System: 219.7 ms]
Range (min … max): 418.0 ms … 436.8 ms 10 runs
```
For a single crate, with >2x speedup, before:
```
Benchmark 1: cargo test -p codex-utils-string
Time (mean ± σ): 491.1 ms ± 9.0 ms [User: 229.8 ms, System: 234.9 ms]
Range (min … max): 480.9 ms … 512.0 ms 10 runs
```
And after:
```
Benchmark 1: cargo test -p codex-utils-string
Time (mean ± σ): 213.9 ms ± 4.3 ms [User: 112.8 ms, System: 84.0 ms]
Range (min … max): 206.8 ms … 221.0 ms 13 runs
```
Co-authored-by: Codex <noreply@openai.com>
## Why
Follow-up to #20291.
The v2 item-event-to-notification translation had been embedded in
`app-server/src/bespoke_event_handling.rs`, which made it hard to reuse
anywhere else. This PR moves that stateless mapping into shared protocol
code so other entry points can produce the same `ServerNotification`
payloads without copying app-server logic.
That also lets `thread-manager-sample` demonstrate the same notification
surface that the app server exposes, instead of only printing the final
assistant message.
## What changed
- move `item_event_to_server_notification` into
`codex-app-server-protocol::protocol::event_mapping`
- keep the mapper tests next to the shared implementation in
`codex-app-server-protocol`
- re-export the mapper from `codex-core-api` so lightweight consumers
can use it without reaching into `app-server-protocol` directly
- simplify `app-server/src/bespoke_event_handling.rs` so it delegates
the stateless event-to-notification projection to the shared helper
- update `thread-manager-sample` to:
- print mapped notifications as newline-delimited JSON
- use the shared mapper through `codex-core-api`
- enable the default feature set so the sample exposes the normal tool
surface
- use a `read_only` permission profile so shell commands can run in the
sample without widening permissions
## Testing
- `cargo test -p codex-app-server-protocol`
- `cargo test -p codex-core-api`
- `cargo test -p codex-app-server bespoke_event_handling::tests`
- `cargo test -p codex-thread-manager-sample`
- `cargo run -p codex-thread-manager-sample -- "briefly explore the repo
with pwd and ls, then summarize it"`
Summary:
- Add a checked-in codex-core public API listing generated by
cargo-public-api.
- Add scripts/regen-public-api.sh with an embedded crate list,
auto-install for cargo-public-api 0.51.0, pinned nightly, and --check
mode.
- Add Rust CI jobs on the codex Linux x64 runner pool to verify the
listing stays up to date.
Testing:
- bash -n scripts/regen-public-api.sh
- just regen-public-api --check
- yq '.' .github/workflows/rust-ci.yml
.github/workflows/rust-ci-full.yml
- git diff --check
Adam Perry @ OpenAI ·
jif-oai ·
Charlie Marsh ·
pakrym-oai ·