## Why
Next slice needed to make progress on the `remote_env_windows` test is
to support passing a Windows cwd for the remote environment and using
that environment's native shell. This lets the test run a real Windows
process instead of only recording an early path or shell mismatch.
## What
- change `TurnEnvironmentSelection.cwd` from `AbsolutePathBuf` to
`PathUri`
- convert local cwd values to URIs when constructing selections
- preserve a remote primary cwd instead of replacing it with the local
legacy fallback
- prefer the selected environment's discovered shell for unified exec,
falling back to the session shell when unavailable
- convert back to a host-native absolute path at current native-only
consumer boundaries
- reject or deny unsupported foreign cwd values at the existing
request-permissions boundary, with TODOs for its future migration
- extend the hermetic Wine test to execute Windows PowerShell in
`C:\windows` and verify successful process completion
- record the current app-server rejection against the same Wine-backed
remote Windows fixture when its cwd is supplied as a native Windows path
## Why
`PathUri::from_abs_path` can fail for absolute paths that do not have a
normal `file:` URI representation, forcing filesystem call sites to
handle a conversion error even though the original path can be preserved
losslessly.
## What
Make `from_abs_path` infallible and migrate its callers. Unrepresentable
paths use `file:///%00/bad/path/<base64>`, encoding Unix bytes or
Windows UTF-16LE; `to_abs_path` validates and decodes that fallback. The
leading encoded null reserves a namespace that cannot collide with a
real Unix or Windows path, and fallback URIs remain opaque to lexical
path operations.
## Validation
Added path-URI coverage for Unix null and non-UTF-8 paths, Windows
device/verbatim and non-Unicode paths, serialization, malformed
fallbacks, opaque lexical operations, invalid native payloads, and
literal `/bad/path` collision resistance.
## Why
Sandbox cwd values can cross app-server and exec-server host boundaries.
They should retain URI semantics until the receiving host validates them
instead of being interpreted early as native paths.
## What
- Carry `PathUri` through filesystem sandbox contexts, sandbox commands,
and transform inputs.
- Convert command and policy cwd once in `SandboxManager::transform`,
then keep launch requests native.
- Preserve sandbox cwd over remote filesystem transport and reject
non-native URIs without fallback.
- Cache paired native/URI turn-environment cwd values during migration,
with immutable access to keep them synchronized.
- Extend existing protocol, forwarding, transform, and core runtime
tests.
## Why
We already have the machinery to support multiple environments on a
single thread, but we only show the model the contents of `AGENTS.md`
files in the primary environment.
We should show the model all of the relevant project instructions when
we know there's more than one environment.
## Known Gaps
As discussed in the RFC, this implementation:
1. doesn't handle environments being added/removed to/from the thread
after its creation
2. it doesn't enforce an aggregate context budget across environments,
and instead applies the configured project maximum independently to each
environment
## Implementation
- Discover project instructions in environment order with an independent
byte budget per environment and preserve source provenance/order.
- Keep the legacy fragment byte-for-byte when exactly one environment
contributes project instructions; use environment-labeled sections when
two or more environments contribute.
- Freeze the complete rendered fragment in `LoadedAgentsMd`, insert it
directly into requests, and recognize both layouts in contextual and
memory filtering.
- Add exact rendering, independent-budget, source-order,
creation-snapshot, and consumer coverage without changing app-server
schemas.
## Why
Turn construction passed resolved environments through several layers
while leaving the environment shell unresolved. As a result,
model-visible environment context could fall back to the session shell
instead of reporting the selected remote environment's shell.
Resolve environment metadata at the turn-context boundary so each turn
carries the shell that belongs to its selected environment. Keep request
validation in app-server, where invalid selections can be returned as
straightforward JSON-RPC errors without coupling core turn construction
to that policy.
## What changed
- resolve environment selections eagerly in
`new_turn_context_from_configuration`
- store the full resolved `Shell` on each `TurnEnvironment`
- simplify the now-redundant resolved-environment constructor plumbing
- keep duplicate and unknown-environment validation as a small
app-server preflight
- add a remote-environment integration test that runs a full
`test_codex` turn and verifies the model-visible environment message
reports `bash`
## Testing
- `cargo check -p codex-core --test all -p codex-app-server`
- `remote_test_env_exposes_bash_shell_to_model` on the Linux
remote-executor harness
Skip turn git metadata enrichment when a turn has remote or multiple
executors, so we do not report the orchestrator checkout as executor
workspace metadata.
Test: `just test -p codex-core` (blocked by existing
`Session::conversation_id` compile error in `close_agent.rs`).
## Summary
- make EnvironmentProvider::snapshot path-free and keep providers
focused on provider-owned remote environments
- let provider snapshots request local inclusion via include_local, with
environments.toml including local and CODEX_EXEC_SERVER_URL excluding
local
- move reserved local environment construction into EnvironmentManager
using ExecServerRuntimePaths
Follow-up to https://github.com/openai/codex/pull/20667
## Testing
- just fmt
- git diff --check
- devbox: bazel build --bes_backend= --bes_results_url=
//codex-rs/exec-server:exec-server
- devbox: bazel test --bes_backend= --bes_results_url=
//codex-rs/exec-server:exec-server-unit-tests
Co-authored-by: Codex <noreply@openai.com>
## Why
The earlier PRs add stdio transport support and the config-backed
environment provider, but the feature remains inert until normal Codex
entrypoints construct `EnvironmentManager` with enough context to
discover `CODEX_HOME/environments.toml`. This final stack PR activates
the provider while preserving the legacy `CODEX_EXEC_SERVER_URL`
fallback when no environments file exists.
**Stack position:** this is PR 5 of 5. It is the product wiring PR that
activates the configured environment provider added in PR 4.
## What Changed
- Thread `codex_home` into `EnvironmentManagerArgs`.
- Change `EnvironmentManager::new(...)` to load the provider from
`CODEX_HOME`.
- Preserve legacy behavior by falling back to
`DefaultEnvironmentProvider::from_env()` when `environments.toml` is
absent.
- Make `environments.toml`-backed managers start new threads with all
configured environments, default first, while keeping the legacy env-var
path single-default.
- Update the app-server, TUI, exec, MCP server, connector, prompt-debug,
and thread-manager-sample callsites to pass `codex_home` and handle
provider-loading errors.
## Self-Review Notes
- The multi-environment startup path is intentionally tied to the
`environments.toml` provider. Using `>1` configured environment as the
only signal would also expand the legacy `CODEX_EXEC_SERVER_URL`
provider because it keeps `local` addressable alongside `remote`.
- The startup environment list is still derived inside
`EnvironmentManager`; the provider only says whether its snapshot should
start new threads with all configured environments.
- The thread-manager sample was updated to pass the current
`ThreadManager::new(...)` installation id argument so the stack compiles
under Bazel.
## Stack
- 1. https://github.com/openai/codex/pull/20663 - Add stdio exec-server
listener
- 2. https://github.com/openai/codex/pull/20664 - Add stdio exec-server
client transport
- 3. https://github.com/openai/codex/pull/20665 - Make environment
providers own default selection
- 4. https://github.com/openai/codex/pull/20666 - Add CODEX_HOME
environments TOML provider
- **5. This PR:** https://github.com/openai/codex/pull/20667 - Load
configured environments from CODEX_HOME
Split from original draft: https://github.com/openai/codex/pull/20508
## Validation
- `just fmt`
- `git diff --check`
- `bazel build --config=remote --strategy=remote
--remote_download_toplevel
//codex-rs/thread-manager-sample:codex-thread-manager-sample`
- `bazel test --config=remote --strategy=remote
--remote_download_toplevel
//codex-rs/exec-server:exec-server-unit-tests`
- `bazel test --config=remote --strategy=remote
--remote_download_toplevel --test_sharding_strategy=disabled
--test_arg=default_thread_environment_selections_use_manager_default_id
//codex-rs/core:core-unit-tests`
- `bazel test --config=remote --strategy=remote
--remote_download_toplevel --test_sharding_strategy=disabled
--test_arg=start_thread_uses_all_default_environments_from_codex_home
//codex-rs/core:core-unit-tests`
## Documentation
This activates `CODEX_HOME/environments.toml`; user-facing documentation
should be added before this stack is treated as a documented public
workflow.
---------
Co-authored-by: Codex <noreply@openai.com>
## Summary
- make resolved turn environment shell metadata optional instead of
hard-coding bash
- render environment context shells from explicit environment metadata
when present, falling back to the existing session shell
- update environment context tests for inherited PowerShell-style
fallback and explicit per-environment shell override
## Testing
- Not run (not requested; formatted with `just fmt`).
Co-authored-by: Codex <noreply@openai.com>
## Why
This is a prep PR in the multi-environment process-tool stack. It
separates ownership/config cleanup from the behavior change that teaches
process tools to route by selected environment, so the follow-up PR can
focus on model-facing `environment_id` behavior.
## Stack
1. https://github.com/openai/codex/pull/20646 - `EnvironmentContext`
rendering for selected environments
2. https://github.com/openai/codex/pull/20669 - selected-environment
ownership and tool config prep (this PR)
3. https://github.com/openai/codex/pull/20647 - process-tool
`environment_id` routing
## What Changed
- keep the resolved turn environment list wrapped in
`ResolvedTurnEnvironments` through `TurnContext` instead of unwrapping
it back to a raw `Vec`
- add `TurnContext::resolve_path_against` so cwd-relative path
resolution has one shared helper
- replace the old tool config boolean with `ToolEnvironmentMode::{None,
Single, Multiple}`
## Testing
- Tests not run locally; this prep refactor is covered by GitHub CI for
the stack.
Co-authored-by: Codex <noreply@openai.com>
## Why
The model needs a way to see which environments are available during a
multi-environment turn without changing the legacy single-environment
prompt surface or pulling replay/persistence changes into the same
review.
## Stack
1. https://github.com/openai/codex/pull/20646 - `EnvironmentContext`
rendering for selected environments (this PR)
2. https://github.com/openai/codex/pull/20669 - selected-environment
ownership and tool config prep
3. https://github.com/openai/codex/pull/20647 - process-tool
`environment_id` routing
## What Changed
- extend `environment_context` so multi-environment turns render an
`<environments>` block with the selected environment ids and cwd values
- keep zero- and single-environment turns on the existing cwd-only
render path
- keep replay and persistence paths on the legacy surface for now so
this PR stays scoped to live prompt rendering
- add focused coverage in
`codex-rs/core/src/context/environment_context_tests.rs`
## Testing
- CI
---------
Co-authored-by: Codex <noreply@openai.com>
## Summary
- make selected turn environments the source of truth for session
runtime cwd and MCP runtime environment selection
- keep local/no-selection fallback behavior intact
- add coverage for duplicate selected environments, cwd resolution, and
MCP runtime environment selection
## Validation
- git diff --check
- rustfmt was run on touched Rust files during the implementation
workflow
CI should provide the full Bazel/test signal.
---------
Co-authored-by: Codex <noreply@openai.com>
## Summary
- Change `EnvironmentProvider` to return concrete `Environment`
instances instead of `EnvironmentConfigurations`.
- Make `DefaultEnvironmentProvider` provide the provider-visible `local`
environment plus optional `remote` environment from
`CODEX_EXEC_SERVER_URL`.
- Keep `EnvironmentManager` as the concrete cache while exposing its own
explicit local environment for `local_environment()` fallback paths.
## Validation
- `just fmt`
- `git diff --check`
---------
Co-authored-by: Codex <noreply@openai.com>
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