## Summary
- reduce public module visibility across Rust crates, preferring private
or crate-private modules with explicit crate-root public exports
- update external call sites and tests to use the intended public crate
APIs instead of reaching through module trees
- add the module visibility guideline to AGENTS.md
## Validation
- `cargo check --workspace --all-targets --message-format=short` passed
before the final fix/format pass
- `just fix` completed successfully
- `just fmt` completed successfully
- `git diff --check` passed
## 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`.
## Why
`codex-mcp` already owns the shared MCP API surface, including `auth`,
`McpConfig`, `CODEX_APPS_MCP_SERVER_NAME`, and tool-name helpers in
[`codex-rs/codex-mcp/src/mcp/mod.rs`](https://github.com/openai/codex/blob/f61e85dbfb5373cde6827d232ac8ea447c237e81/codex-rs/codex-mcp/src/mcp/mod.rs#L1-L35).
Re-exporting that surface from `codex_core::mcp` gives downstream crates
two import paths for the same API and hides the real crate dependency.
This PR keeps `codex_core::mcp` focused on the local `McpManager`
wrapper in
[`codex-rs/core/src/mcp.rs`](https://github.com/openai/codex/blob/f61e85dbfb5373cde6827d232ac8ea447c237e81/codex-rs/core/src/mcp.rs#L13-L40)
and makes consumers import shared MCP APIs from `codex_mcp` directly.
## What
- Remove the `codex_mcp::mcp` re-export surface from `core/src/mcp.rs`.
- Update `codex-core` internals plus `codex-app-server`, `codex-cli`,
and `codex-tui` test code to import MCP APIs from `codex_mcp::mcp`
directly.
- Add explicit `codex-mcp` dependencies where those crates now use that
API surface, and refresh `Cargo.lock`.
## Verification
- `just bazel-lock-check`
- `cargo test -p codex-core -p codex-cli -p codex-tui`
- `codex-cli` passed.
- `codex-core` still fails five unrelated config tests in
`core/src/config/config_tests.rs` (`approvals_reviewer_*` and
`smart_approvals_alias_*`).
- A broader `cargo test -p codex-core -p codex-app-server -p codex-cli
-p codex-tui` run previously hung in `codex-app-server` test
`in_process_start_uses_requested_session_source_for_thread_start`.
- Split MCP runtime/server code out of `codex-core` into the new
`codex-mcp` crate. New/moved public structs/types include `McpConfig`,
`McpConnectionManager`, `ToolInfo`, `ToolPluginProvenance`,
`CodexAppsToolsCacheKey`, and the `McpManager` API
(`codex_mcp::mcp::McpManager` plus the `codex_core::mcp::McpManager`
wrapper/shim). New/moved functions include `with_codex_apps_mcp`,
`configured_mcp_servers`, `effective_mcp_servers`,
`collect_mcp_snapshot`, `collect_mcp_snapshot_from_manager`,
`qualified_mcp_tool_name_prefix`, and the MCP auth/skill-dependency
helpers. Why: this creates a focused MCP crate boundary and shrinks
`codex-core` without forcing every consumer to migrate in the same PR.
- Move MCP server config schema and persistence into `codex-config`.
New/moved structs/enums include `AppToolApproval`,
`McpServerToolConfig`, `McpServerConfig`, `RawMcpServerConfig`,
`McpServerTransportConfig`, `McpServerDisabledReason`, and
`codex_config::ConfigEditsBuilder`. New/moved functions include
`load_global_mcp_servers` and
`ConfigEditsBuilder::replace_mcp_servers`/`apply`. Why: MCP TOML
parsing/editing is config ownership, and this keeps config
validation/round-tripping (including per-tool approval overrides and
inline bearer-token rejection) in the config crate instead of
`codex-core`.
- Rewire `codex-core`, app-server, and plugin call sites onto the new
crates. Updated `Config::to_mcp_config(&self, plugins_manager)`,
`codex-rs/core/src/mcp.rs`, `codex-rs/core/src/connectors.rs`,
`codex-rs/core/src/codex.rs`,
`CodexMessageProcessor::list_mcp_server_status_task`, and
`utils/plugins/src/mcp_connector.rs` to build/pass the new MCP
config/runtime types. Why: plugin-provided MCP servers still merge with
user-configured servers, and runtime auth (`CodexAuth`) is threaded into
`with_codex_apps_mcp` / `collect_mcp_snapshot` explicitly so `McpConfig`
stays config-only.
pakrym-oai