## Why
SQLite state was still being opened from consumer paths, including lazy
`OnceCell`-backed thread-store call sites. That let one process
construct multiple state DB connections for the same Codex home, which
makes SQLite lock contention and `database is locked` failures much
easier to hit.
State DB lifetime should be chosen by main-like entrypoints and tests,
then passed through explicitly. Consumers should use the supplied
`Option<StateDbHandle>` or `StateDbHandle` and keep their existing
filesystem fallback or error behavior when no handle is available.
The startup path also needs to keep the rollout crate in charge of
SQLite state initialization. Opening `codex_state::StateRuntime`
directly bypasses rollout metadata backfill, so entrypoints should
initialize through `codex_rollout::state_db` and receive a handle only
after required rollout backfills have completed.
## What Changed
- Initialize the state DB in main-like entrypoints for CLI, TUI,
app-server, exec, MCP server, and the thread-manager sample.
- Pass `Option<StateDbHandle>` through `ThreadManager`,
`LocalThreadStore`, app-server processors, TUI app wiring, rollout
listing/recording, personality migration, shell snapshot cleanup,
session-name lookup, and memory/device-key consumers.
- Remove the lazy local state DB wrapper from the thread store so
non-test consumers use only the supplied handle or their existing
fallback path.
- Make `codex_rollout::state_db::init` the local state startup path: it
opens/migrates SQLite, runs rollout metadata backfill when needed, waits
for concurrent backfill workers up to a bounded timeout, verifies
completion, and then returns the initialized handle.
- Keep optional/non-owning SQLite helpers, such as remote TUI local
reads, as open-only paths that do not run startup backfill.
- Switch app-server startup from direct
`codex_state::StateRuntime::init` to the rollout state initializer so
app-server cannot skip rollout backfill.
- Collapse split rollout lookup/list APIs so callers use the normal
methods with an optional state handle instead of `_with_state_db`
variants.
- Restore `getConversationSummary(ThreadId)` to delegate through
`ThreadStore::read_thread` instead of a LocalThreadStore-specific
rollout path special case.
- Keep DB-backed rollout path lookup keyed on the DB row and file
existence, without imposing the filesystem filename convention on
existing DB rows.
- Verify readable DB-backed rollout paths against `session_meta.id`
before returning them, so a stale SQLite row that points at another
thread's JSONL falls back to filesystem search and read-repairs the DB
row.
- Keep `debug prompt-input` filesystem-only so a one-off debug command
does not initialize or backfill SQLite state just to print prompt input.
- Keep goal-session test Codex homes alive only in the goal-specific
helper, rather than leaking tempdirs from the shared session test
helper.
- Update tests and call sites to pass explicit state handles where DB
behavior is expected and explicit `None` where filesystem-only behavior
is intended.
## Validation
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo check -p
codex-rollout -p codex-thread-store -p codex-app-server -p codex-core -p
codex-tui -p codex-exec -p codex-cli --tests`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-rollout state_db_`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-rollout find_thread_path`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-rollout find_thread_path -- --nocapture`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-rollout try_init_ -- --nocapture`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-rollout`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo clippy -p
codex-rollout --lib -- -D warnings`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-thread-store
read_thread_falls_back_when_sqlite_path_points_to_another_thread --
--nocapture`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-thread-store`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p codex-core
shell_snapshot`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p codex-core
--test all personality_migration`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p codex-core
--test all rollout_list_find`
- `RUST_MIN_STACK=8388608 CODEX_SKIP_VENDORED_BWRAP=1
CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p codex-core
--test all rollout_list_find::find_prefers_sqlite_path_by_id --
--nocapture`
- `RUST_MIN_STACK=8388608 CODEX_SKIP_VENDORED_BWRAP=1
CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p codex-core
--test all rollout_list_find -- --nocapture`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p codex-core
interrupt_accounts_active_goal_before_pausing`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-app-server get_auth_status -- --test-threads=1`
- `CODEX_SKIP_VENDORED_BWRAP=1
CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo test -p
codex-app-server --lib`
- `CODEX_SKIP_VENDORED_BWRAP=1
CARGO_TARGET_DIR=/tmp/codex-target-state-db cargo check -p codex-rollout
-p codex-app-server --tests`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db just fix -p codex-rollout
-p codex-thread-store -p codex-core -p codex-app-server -p codex-tui -p
codex-exec -p codex-cli`
- `CODEX_SKIP_VENDORED_BWRAP=1
CARGO_TARGET_DIR=/tmp/codex-target-state-db just fix -p codex-rollout -p
codex-app-server`
- `CARGO_TARGET_DIR=/tmp/codex-target-state-db just fix -p
codex-rollout`
- `CODEX_SKIP_VENDORED_BWRAP=1
CARGO_TARGET_DIR=/tmp/codex-target-state-db just fix -p codex-core`
- `just argument-comment-lint -p codex-core`
- `just argument-comment-lint -p codex-rollout`
Focused coverage added in `codex-rollout`:
- `recorder::tests::state_db_init_backfills_before_returning` verifies
the rollout metadata row exists before startup init returns.
- `state_db::tests::try_init_waits_for_concurrent_startup_backfill`
verifies startup waits for another worker to finish backfill instead of
disabling the handle for the process.
-
`state_db::tests::try_init_times_out_waiting_for_stuck_startup_backfill`
verifies startup does not hang indefinitely on a stuck backfill lease.
-
`tests::find_thread_path_accepts_existing_state_db_path_without_canonical_filename`
verifies DB-backed lookup accepts valid existing rollout paths even when
the filename does not include the thread UUID.
-
`tests::find_thread_path_falls_back_when_db_path_points_to_another_thread`
verifies DB-backed lookup ignores a stale row whose existing path
belongs to another thread and read-repairs the row after filesystem
fallback.
Focused coverage updated in `codex-core`:
- `rollout_list_find::find_prefers_sqlite_path_by_id` now uses a
DB-preferred rollout file with matching `session_meta.id`, so it still
verifies that valid SQLite paths win without depending on stale/empty
rollout contents.
`cargo test -p codex-app-server thread_list_respects_search_term_filter
-- --test-threads=1 --nocapture` was attempted locally but timed out
waiting for the app-server test harness `initialize` response before
reaching the changed thread-list code path.
`bazel test //codex-rs/thread-store:thread-store-unit-tests
--test_output=errors` was attempted locally after the thread-store fix,
but this container failed before target analysis while fetching `v8+`
through BuildBuddy/direct GitHub. The equivalent local crate coverage,
including `cargo test -p codex-thread-store`, passes.
A plain local `cargo check -p codex-rollout -p codex-app-server --tests`
also requires system `libcap.pc` for `codex-linux-sandbox`; the
follow-up app-server check above used `CODEX_SKIP_VENDORED_BWRAP=1` in
this container.
- Build one app-server process ThreadStore from startup config and share
it with ThreadManager and CodexMessageProcessor.
- Remove per-thread/fork store reconstruction so effective thread config
cannot switch the persistence backend.
- Add params to ThreadStore create/resume for specifying thread
metadata, since otherwise the metadata from store creation would be used
(incorrectly).
Summary:
- Add codex-thread-manager-sample, a one-shot binary that starts a
ThreadManager thread, submits a prompt, and prints the final assistant
output.
- Pass ThreadStore into ThreadManager::new and expose
thread_store_from_config for existing callsites.
- Build the sample Config directly with only --model and prompt inputs.
Verification:
- just fmt
- cargo check -p codex-thread-manager-sample -p codex-app-server -p
codex-mcp-server
- git diff --check
Tests: Not run per request.
## Why
MultiAgentV2 sessions need startup guidance that matches the role of the
thread that is actually being created. Root agents and subagents have
different responsibilities, and forked subagents can inherit parent
rollout history. If the parent hint is carried into the child context,
the child can see stale or conflicting developer guidance before its own
session-specific context is added.
## What changed
- Added `features.multi_agent_v2.root_agent_usage_hint_text` and
`features.multi_agent_v2.subagent_usage_hint_text` config fields,
including schema/config parsing support.
- Injected the matching root or subagent hint into the initial context
as its own developer message when `multi_agent_v2` is enabled.
- Filtered configured MultiAgentV2 usage-hint developer messages out of
forked parent history so a child thread receives fresh guidance for its
own session source/config.
- Added targeted coverage for config parsing, initial-context rendering,
feature-config deserialization, and forked-history filtering.
## Context examples
With this config:
```toml
[features.multi_agent_v2]
enabled = true
root_agent_usage_hint_text = "Root guidance."
subagent_usage_hint_text = "Subagent guidance."
```
A root thread initial context renders the root hint as a standalone
developer message:
```text
[developer]
<existing developer context, when present>
[developer]
Root guidance.
```
A subagent thread initial context renders the subagent hint instead:
```text
[developer]
<existing developer context, when present>
[developer]
Subagent guidance.
```
When a subagent forks parent history, any parent developer message whose
text exactly matches the configured MultiAgentV2 root or subagent hint
is omitted from the forked history before the child receives its fresh
subagent hint.
## Why
Guardian analytics includes time-to-first-token, but the Guardian
reviewer runs as a normal Codex session and `TurnCompleteEvent` did not
expose TTFT. The timing needs to flow through the standard
turn-completion protocol so Guardian review analytics can consume the
same value as the rest of the session machinery.
## What changed
Adds optional `time_to_first_token_ms` to `TurnCompleteEvent` and
populates it from `TurnTiming`. The value is carried through app-server
thread history, rollout reconstruction, TUI/app-server adapters, and
Guardian review session handling.
Guardian review analytics now captures TTFT from the reviewer
turn-complete event when available. Existing tests and fixtures are
updated to set the new optional field to `None` where TTFT is not
relevant.
## Verification
- `cargo clippy -p codex-tui --tests -- -D warnings`
- `cargo clippy -p codex-core --lib --tests -- -D warnings`
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/17696).
* __->__ #17696
* #17695
* #17693
* #18278
* #18953
## Summary
- add experimental turn/start.environments params for per-turn
environment id + cwd selections
- pass selections through core protocol ops and resolve them with
EnvironmentManager before TurnContext creation
- treat omitted selections as default behavior, empty selections as no
environment, and non-empty selections as first environment/cwd as the
turn primary
## Testing
- ran `just fmt`
- ran `just write-app-server-schema`
- not run: unit tests for this stacked PR
---------
Co-authored-by: Codex <noreply@openai.com>
# Summary
- implement local ThreadStore archive/unarchive operations
- implement local ThreadStore read_thread operation
- break up the various ThreadStore local method implementations into
separate files
- migrate app-server archive/unarchive and core archive fixture to use
ThreadStore (but not all read operations yet!)
- use the ThreadStore's read operation as a proxy check for thread
persistence/existence in the app server code
- move all other filesystem operations related to archive (path
validation etc) into the local thread store.
# Tests
- add dedicated local store archive/unarchive tests
The rollout writer now keeps an owned/monitored task handle, returns
real Result acks for flush/persist/shutdown, retries failed flushes by
reopening the rollout file, and keeps buffered items until they are
successfully written. Session flushes are now real durability barriers
for fork/rollback/read-after-write paths, while turn completion surfaces
a warning if the rollout still cannot be saved after recovery.
## Summary
App-server v2 already receives turn-scoped `clientMetadata`, but the
Rust app-server was dropping it before the outbound Responses request.
This change keeps the fix lightweight by threading that metadata through
the existing turn-metadata path rather than inventing a new transport.
## What we're trying to do and why
We want turn-scoped metadata from the app-server protocol layer,
especially fields like Hermes/GAAS run IDs, to survive all the way to
the actual Responses API request so it is visible in downstream
websocket request logging and analytics.
The specific bug was:
- app-server protocol uses camelCase `clientMetadata`
- Responses transport already has an existing turn metadata carrier:
`x-codex-turn-metadata`
- websocket transport already rewrites that header into
`request.request_body.client_metadata["x-codex-turn-metadata"]`
- but the Rust app-server never parsed or stored `clientMetadata`, so
nothing from the app-server request was making it into that existing
path
This PR fixes that without adding a new header or a second metadata
channel.
## How we did it
### Protocol surface
- Add optional `clientMetadata` to v2 `TurnStartParams` and
`TurnSteerParams`
- Regenerate the JSON schema / TypeScript fixtures
- Update app-server docs to describe the field and its behavior
### Runtime plumbing
- Add a dedicated core op for app-server user input carrying turn-scoped
metadata: `Op::UserInputWithClientMetadata`
- Wire `turn/start` and `turn/steer` through that op / signature path
instead of dropping the metadata at the message-processor boundary
- Store the metadata in `TurnMetadataState`
### Transport behavior
- Reuse the existing serialized `x-codex-turn-metadata` payload
- Merge the new app-server `clientMetadata` into that JSON additively
- Do **not** replace built-in reserved fields already present in the
turn metadata payload
- Keep websocket behavior unchanged at the outer shape level: it still
sends only `client_metadata["x-codex-turn-metadata"]`, but that JSON
string now contains the merged fields
- Keep HTTP fallback behavior unchanged except that the existing
`x-codex-turn-metadata` header now includes the merged fields too
### Request shape before / after
Before, a websocket `response.create` looked like:
```json
{
"type": "response.create",
"client_metadata": {
"x-codex-turn-metadata": "{\"session_id\":\"...\",\"turn_id\":\"...\"}"
}
}
```
Even if the app-server caller supplied `clientMetadata`, it was not
represented there.
After, the same request shape is preserved, but the serialized payload
now includes the new turn-scoped fields:
```json
{
"type": "response.create",
"client_metadata": {
"x-codex-turn-metadata": "{\"session_id\":\"...\",\"turn_id\":\"...\",\"fiber_run_id\":\"fiber-start-123\",\"origin\":\"gaas\"}"
}
}
```
## Validation
### Targeted tests added / updated
- protocol round-trip coverage for `clientMetadata` on `turn/start` and
`turn/steer`
- protocol round-trip coverage for `Op::UserInputWithClientMetadata`
- `TurnMetadataState` merge test proving client metadata is added
without overwriting reserved built-in fields
- websocket request-shape test proving outbound `response.create`
contains merged metadata inside
`client_metadata["x-codex-turn-metadata"]`
- app-server integration tests proving:
- `turn/start` forwards `clientMetadata` into the outbound Responses
request path
- websocket warmup + real turn request both behave correctly
- `turn/steer` updates the follow-up request metadata
### Commands run
- `just write-app-server-schema`
- `cargo test -p codex-app-server-protocol`
- `cargo test -p codex-protocol`
- `cargo test -p codex-core
turn_metadata_state_merges_client_metadata_without_replacing_reserved_fields
--lib`
- `cargo test -p codex-core --test all
responses_websocket_preserves_custom_turn_metadata_fields`
- `cargo test -p codex-app-server --test all client_metadata`
- `cargo test -p codex-app-server --test all
turn_start_forwards_client_metadata_to_responses_websocket_request_body_v2
-- --nocapture`
- `just fmt`
- `just fix -p codex-core -p codex-protocol -p codex-app-server-protocol
-p codex-app-server`
- `just fix -p codex-exec -p codex-tui-app-server`
- `just argument-comment-lint`
### Full suite note
`cargo test` in `codex-rs` still fails in:
-
`suite::v2::turn_interrupt::turn_interrupt_resolves_pending_command_approval_request`
I verified that same failure on a clean detached `HEAD` worktree with an
isolated `CARGO_TARGET_DIR`, so it is not caused by this patch.
## Description
Add requirements.toml support for `allowed_approvals_reviewers =
["user", "guardian_subagent"]`, so admins can now restrict the use of
guardian mode.
Note: If a user sets a reviewer that isn’t allowed by requirements.toml,
config loading falls back to the first allowed reviewer and emits a
startup warning.
The table below describes the possible admin controls.
| Admin intent | `requirements.toml` | User `config.toml` | End result |
|---|---|---|---|
| Leave Guardian optional | omit `allowed_approvals_reviewers` or set
`["user", "guardian_subagent"]` | user chooses `approvals_reviewer =
"user"` or `"guardian_subagent"` | Guardian off for `user`, on for
`guardian_subagent` + `approval_policy = "on-request"` |
| Force Guardian off | `allowed_approvals_reviewers = ["user"]` | any
user value | Effective reviewer is `user`; Guardian off |
| Force Guardian on | `allowed_approvals_reviewers =
["guardian_subagent"]` and usually `allowed_approval_policies =
["on-request"]` | any user reviewer value; user should also have
`approval_policy = "on-request"` unless policy is forced | Effective
reviewer is `guardian_subagent`; Guardian on when effective approval
policy is `on-request` |
| Allow both, but default to manual if user does nothing |
`allowed_approvals_reviewers = ["user", "guardian_subagent"]` | omit
`approvals_reviewer` | Effective reviewer is `user`; Guardian off |
| Allow both, and user explicitly opts into Guardian |
`allowed_approvals_reviewers = ["user", "guardian_subagent"]` |
`approvals_reviewer = "guardian_subagent"` and `approval_policy =
"on-request"` | Guardian on |
| Invalid admin config | `allowed_approvals_reviewers = []` | anything |
Config load error |
- Keep only parent system/developer/user messages plus assistant
final-answer messages in forked child history.
- Strip parent tool/reasoning items and remove the unmatched synthetic
spawn output.
## Why
`codex-core` was re-exporting APIs owned by sibling `codex-*` crates,
which made downstream crates depend on `codex-core` as a proxy module
instead of the actual owner crate.
Removing those forwards makes crate boundaries explicit and lets leaf
crates drop unnecessary `codex-core` dependencies. In this PR, this
reduces the dependency on `codex-core` to `codex-login` in the following
files:
```
codex-rs/backend-client/Cargo.toml
codex-rs/mcp-server/tests/common/Cargo.toml
```
## What
- Remove `codex-rs/core/src/lib.rs` re-exports for symbols owned by
`codex-login`, `codex-mcp`, `codex-rollout`, `codex-analytics`,
`codex-protocol`, `codex-shell-command`, `codex-sandboxing`,
`codex-tools`, and `codex-utils-path`.
- Delete the `default_client` forwarding shim in `codex-rs/core`.
- Update in-crate and downstream callsites to import directly from the
owning `codex-*` crate.
- Add direct Cargo dependencies where callsites now target the owner
crate, and remove `codex-core` from `codex-rs/backend-client`.
Adds this:
```
properties.insert(
"fork_turns".to_string(),
JsonSchema::String {
description: Some(
"Optional MultiAgentV2 fork mode. Use `none`, `all`, or a positive integer string such as `3` to fork only the most recent turns."
.to_string(),
),
},
);
```
---------
Co-authored-by: Codex <noreply@openai.com>
## Why
`argument-comment-lint` was green in CI even though the repo still had
many uncommented literal arguments. The main gap was target coverage:
the repo wrapper did not force Cargo to inspect test-only call sites, so
examples like the `latest_session_lookup_params(true, ...)` tests in
`codex-rs/tui_app_server/src/lib.rs` never entered the blocking CI path.
This change cleans up the existing backlog, makes the default repo lint
path cover all Cargo targets, and starts rolling that stricter CI
enforcement out on the platform where it is currently validated.
## What changed
- mechanically fixed existing `argument-comment-lint` violations across
the `codex-rs` workspace, including tests, examples, and benches
- updated `tools/argument-comment-lint/run-prebuilt-linter.sh` and
`tools/argument-comment-lint/run.sh` so non-`--fix` runs default to
`--all-targets` unless the caller explicitly narrows the target set
- fixed both wrappers so forwarded cargo arguments after `--` are
preserved with a single separator
- documented the new default behavior in
`tools/argument-comment-lint/README.md`
- updated `rust-ci` so the macOS lint lane keeps the plain wrapper
invocation and therefore enforces `--all-targets`, while Linux and
Windows temporarily pass `-- --lib --bins`
That temporary CI split keeps the stricter all-targets check where it is
already cleaned up, while leaving room to finish the remaining Linux-
and Windows-specific target-gated cleanup before enabling
`--all-targets` on those runners. The Linux and Windows failures on the
intermediate revision were caused by the wrapper forwarding bug, not by
additional lint findings in those lanes.
## Validation
- `bash -n tools/argument-comment-lint/run.sh`
- `bash -n tools/argument-comment-lint/run-prebuilt-linter.sh`
- shell-level wrapper forwarding check for `-- --lib --bins`
- shell-level wrapper forwarding check for `-- --tests`
- `just argument-comment-lint`
- `cargo test` in `tools/argument-comment-lint`
- `cargo test -p codex-terminal-detection`
## Follow-up
- Clean up remaining Linux-only target-gated callsites, then switch the
Linux lint lane back to the plain wrapper invocation.
- Clean up remaining Windows-only target-gated callsites, then switch
the Windows lint lane back to the plain wrapper invocation.
Add environment manager that is a singleton and is created early in
app-server (before skill manager, before config loading).
Use an environment variable to point to a running exec server.
Make the inter-agent communication start a turn
As part of this, we disable the v2 notifier to prevent some odd
behaviour where the agent restart working while you're talking to it for
example
Show all plugin marketplaces in the /plugins popup by removing the
`openai-curated` marketplace filter, and update plugin popup
copy/tests/snapshots to match the new behavior in both TUI codepaths.
## Summary
- update the self-serve business usage-based limit message to direct
users to their admin for additional credits
- add a focused unit test for the self_serve_business_usage_based plan
branch
Added also:
If you are at a rate limit but you still have credits, codex cli would
tell you to switch the model. We shouldnt do this if you have credits so
fixed this.
## Test
- launched the source-built CLI and verified the updated message is
shown for the self-serve business usage-based plan
Send input now sends messages as assistant message and with this format:
```
author: /root/worker_a
recipient: /root/worker_a/tester
other_recipients: []
Content: bla bla bla. Actual content. Only text for now
```
This PR add an URI-based system to reference agents within a tree. This
comes from a sync between research and engineering.
The main agent (the one manually spawned by a user) is always called
`/root`. Any sub-agent spawned by it will be `/root/agent_1` for example
where `agent_1` is chosen by the model.
Any agent can contact any agents using the path.
Paths can be used either in absolute or relative to the calling agents
Resume is not supported for now on this new path
- Split the feature system into a new `codex-features` crate.
- Cut `codex-core` and workspace consumers over to the new config and
warning APIs.
Co-authored-by: Ahmed Ibrahim <219906144+aibrahim-oai@users.noreply.github.com>
Co-authored-by: Codex <noreply@openai.com>
Add a representation of the agent graph. This is now used for:
* Cascade close agents (when I close a parent, it close the kids)
* Cascade resume (oposite)
Later, this will also be used for post-compaction stuffing of the
context
Direct fix for: https://github.com/openai/codex/issues/14458
Make `interrupted` an agent state and make it not final. As a result, a
`wait` won't return on an interrupted agent and no notification will be
send to the parent agent.
The rationals are:
* If a user interrupt a sub-agent for any reason, you don't want the
parent agent to instantaneously ask the sub-agent to restart
* If a parent agent interrupt a sub-agent, no need to add a noisy
notification in the parent agen
## Why
PR #13783 moved the `codex.rs` unit tests into `codex_tests.rs`. This
applies the same extraction pattern across the rest of `codex-rs/core`
so the production modules stay focused on runtime code instead of large
inline test blocks.
Keeping the tests in sibling files also makes follow-up edits easier to
review because product changes no longer have to share a file with
hundreds or thousands of lines of test scaffolding.
## What changed
- replaced each inline `mod tests { ... }` in `codex-rs/core/src/**`
with a path-based module declaration
- moved each extracted unit test module into a sibling `*_tests.rs`
file, using `mod_tests.rs` for `mod.rs` modules
- preserved the existing `cfg(...)` guards and module-local structure so
the refactor remains structural rather than behavioral
## Testing
- `cargo test -p codex-core --lib` (`1653 passed; 0 failed; 5 ignored`)
- `just fix -p codex-core`
- `cargo fmt --check`
- `cargo shear`
Ruslan Nigmatullin
