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6d2168f06a
## Why
MCP runtime reuse was keyed by every ready selected-capability
environment, even when an environment contributed no MCP servers or
connectors.
For example:
1. a global stdio MCP is running;
2. a selected remote environment contains only a skill;
3. that environment becomes ready;
4. the MCP and connector projection stays exactly the same;
5. Codex nevertheless rebuilds the MCP manager and restarts the global
stdio process.
That restart can interrupt active calls and discard process-local state
even though nothing about MCP changed.
## What changes
When selected-environment availability changes, Codex now resolves the
candidate MCP and connector projection before deciding whether to
replace the runtime:
- if the winning MCP servers or their ownership change, rebuild as
before;
- if the selected connector snapshot changes, rebuild as before;
- if an enabled MCP is explicitly bound to an environment whose
availability changed, rebuild as before;
- otherwise, keep the exact live manager and processes, and update only
the availability input remembered by the snapshot.
```text
ready selected environments: [] -> [skills-env]
resolved MCP servers: {global_probe} -> {global_probe}
resolved connectors: {} -> {}
result: reuse manager; keep the same process
```
The comparison uses the resolved winning servers and their sources, so
plugin/config ownership remains part of the runtime identity.
## Existing stack coverage
The integration PR directly below this one already covers both rebuild
boundaries: a selected MCP becomes callable and a selected connector
tool becomes model-visible when their environment becomes available. It
also verifies that an unchanged selected MCP runtime keeps its process.
This PR does not add another remote-attachment integration scenario for
the no-change optimization. `environment/add` returns before readiness,
and app-server does not currently expose a deterministic readiness
signal for an environment that contributes only skills. Keeping a
fixed-delay test would add flake risk; adding a new readiness API would
be outside this fix.
## Scope and assumptions
- This does not change skill discovery, World State rendering, or plugin
metadata caching.
- This does not add file watching or hot reload behavior.
- This does not change disconnect/reconnect handling.
- Selected environment IDs and their capability contents retain the
stack's existing stability assumption.
- Delayed `required = true` executor MCP behavior remains out of scope.
codex-core
This crate implements the business logic for Codex. It is designed to be used by the various Codex UIs written in Rust.
Wine-exec integration tests
On x86-64 Linux, run the shared suite against the Windows exec server with
bazel test //codex-rs/core:core-all-wine-exec-test.
Local execution targets the host OS, Docker targets Linux, and Wine exec targets Windows. Choose the skip macro by what the test depends on:
skip_if_target_windows!: Windows target behavior.skip_if_host_windows!: Windows host constraints.skip_if_remote!: Local-only test behavior.skip_if_no_remote_env!: Remote-only test behavior.skip_if_wine_exec!: Wine-specific runner debt.
Dependencies
Note that codex-core makes some assumptions about certain helper utilities being available in the environment. Currently, this support matrix is:
macOS
Expects /usr/bin/sandbox-exec to be present.
When using the workspace-write sandbox policy, the Seatbelt profile allows
writes under the configured writable roots while keeping .git (directory or
pointer file), the resolved gitdir: target, and .codex read-only.
Network access and filesystem read/write roots are controlled by
SandboxPolicy. Seatbelt consumes the resolved policy and enforces it.
Seatbelt also keeps the legacy default preferences read access
(user-preference-read) needed for cfprefs-backed macOS behavior.
Linux
Expects the binary containing codex-core to run the equivalent of codex sandbox when arg0 is codex-linux-sandbox. See the codex-arg0 crate for details.
Legacy SandboxPolicy / sandbox_mode configs are still supported on Linux.
They can continue to use the legacy Landlock path when the split filesystem
policy is sandbox-equivalent to the legacy model after cwd resolution.
Split filesystem policies that need direct FileSystemSandboxPolicy
enforcement, such as read-only or denied carveouts under a broader writable
root, automatically route through bubblewrap. The legacy Landlock path is used
only when the split filesystem policy round-trips through the legacy
SandboxPolicy model without changing semantics. That includes overlapping
cases like /repo = write, /repo/a = none, /repo/a/b = write, where the
more specific writable child must reopen under a denied parent.
The Linux sandbox helper prefers the first bwrap found on PATH outside the
current working directory whenever it is available. If bwrap is present but
too old to support --argv0, the helper keeps using system bubblewrap and
switches to a no---argv0 compatibility path for the inner re-exec. If
bwrap is missing, it falls back to the bundled codex-resources/bwrap
binary shipped with Codex and Codex surfaces a startup warning through its
normal notification path instead of printing directly from the sandbox helper.
Codex also surfaces a startup warning when bubblewrap cannot create user
namespaces. WSL2 uses the normal Linux bubblewrap path. WSL1 is not supported
for bubblewrap sandboxing because it cannot create the required user
namespaces, so Codex rejects sandboxed shell commands that would enter the
bubblewrap path before invoking bwrap.
Windows
Legacy SandboxPolicy / sandbox_mode configs are still supported on
Windows. Legacy read-only and workspace-write policies imply full
filesystem read access; exact readable roots are represented by split
filesystem policies instead.
The elevated Windows sandbox also supports:
- legacy
ReadOnlyandWorkspaceWritebehavior - split filesystem policies that need exact readable roots, exact writable roots, or extra read-only carveouts under writable roots
- backend-managed system read roots required for basic execution, such as
C:\Windows,C:\Program Files,C:\Program Files (x86), andC:\ProgramData, when a split filesystem policy requests platform defaults
The unelevated restricted-token backend still supports the legacy full-read
Windows model for legacy ReadOnly and WorkspaceWrite behavior. It also
supports a narrow split-filesystem subset: full-read split policies whose
writable roots still match the legacy WorkspaceWrite root set, but add extra
read-only carveouts under those writable roots.
New [permissions] / split filesystem policies remain supported on Windows
only when they can be enforced directly by the selected Windows backend or
round-trip through the legacy SandboxPolicy model without changing semantics.
Policies that would require direct explicit unreadable carveouts (none) or
reopened writable descendants under read-only carveouts still fail closed
instead of running with weaker enforcement.
All Platforms
Expects the binary containing codex-core to simulate the virtual
apply_patch CLI when arg1 is --codex-run-as-apply-patch. See the
codex-arg0 crate for details.