Commit Graph

33 Commits

  • feat: split codex-common into smaller utils crates (#11422)
    We are removing feature-gated shared crates from the `codex-rs`
    workspace. `codex-common` grouped several unrelated utilities behind
    `[features]`, which made dependency boundaries harder to reason about
    and worked against the ongoing effort to eliminate feature flags from
    workspace crates.
    
    Splitting these utilities into dedicated crates under `utils/` aligns
    this area with existing workspace structure and keeps each dependency
    explicit at the crate boundary.
    
    ## What changed
    
    - Removed `codex-rs/common` (`codex-common`) from workspace members and
    workspace dependencies.
    - Added six new utility crates under `codex-rs/utils/`:
      - `codex-utils-cli`
      - `codex-utils-elapsed`
      - `codex-utils-sandbox-summary`
      - `codex-utils-approval-presets`
      - `codex-utils-oss`
      - `codex-utils-fuzzy-match`
    - Migrated the corresponding modules out of `codex-common` into these
    crates (with tests), and added matching `BUILD.bazel` targets.
    - Updated direct consumers to use the new crates instead of
    `codex-common`:
      - `codex-rs/cli`
      - `codex-rs/tui`
      - `codex-rs/exec`
      - `codex-rs/app-server`
      - `codex-rs/mcp-server`
      - `codex-rs/chatgpt`
      - `codex-rs/cloud-tasks`
    - Updated workspace lockfile entries to reflect the new dependency graph
    and removal of `codex-common`.
  • feat: replace custom mcp-types crate with equivalents from rmcp (#10349)
    We started working with MCP in Codex before
    https://crates.io/crates/rmcp was mature, so we had our own crate for
    MCP types that was generated from the MCP schema:
    
    
    https://github.com/openai/codex/blob/8b95d3e082376f4cb23e92641705a22afb28a9da/codex-rs/mcp-types/README.md
    
    Now that `rmcp` is more mature, it makes more sense to use their MCP
    types in Rust, as they handle details (like the `_meta` field) that our
    custom version ignored. Though one advantage that our custom types had
    is that our generated types implemented `JsonSchema` and `ts_rs::TS`,
    whereas the types in `rmcp` do not. As such, part of the work of this PR
    is leveraging the adapters between `rmcp` types and the serializable
    types that are API for us (app server and MCP) introduced in #10356.
    
    Note this PR results in a number of changes to
    `codex-rs/app-server-protocol/schema`, which merit special attention
    during review. We must ensure that these changes are still
    backwards-compatible, which is possible because we have:
    
    ```diff
    - export type CallToolResult = { content: Array<ContentBlock>, isError?: boolean, structuredContent?: JsonValue, };
    + export type CallToolResult = { content: Array<JsonValue>, structuredContent?: JsonValue, isError?: boolean, _meta?: JsonValue, };
    ```
    
    so `ContentBlock` has been replaced with the more general `JsonValue`.
    Note that `ContentBlock` was defined as:
    
    ```typescript
    export type ContentBlock = TextContent | ImageContent | AudioContent | ResourceLink | EmbeddedResource;
    ```
    
    so the deletion of those individual variants should not be a cause of
    great concern.
    
    Similarly, we have the following change in
    `codex-rs/app-server-protocol/schema/typescript/Tool.ts`:
    
    ```
    - export type Tool = { annotations?: ToolAnnotations, description?: string, inputSchema: ToolInputSchema, name: string, outputSchema?: ToolOutputSchema, title?: string, };
    + export type Tool = { name: string, title?: string, description?: string, inputSchema: JsonValue, outputSchema?: JsonValue, annotations?: JsonValue, icons?: Array<JsonValue>, _meta?: JsonValue, };
    ```
    
    so:
    
    - `annotations?: ToolAnnotations` ➡️ `JsonValue`
    - `inputSchema: ToolInputSchema` ➡️ `JsonValue`
    - `outputSchema?: ToolOutputSchema` ➡️ `JsonValue`
    
    and two new fields: `icons?: Array<JsonValue>, _meta?: JsonValue`
    
    ---
    [//]: # (BEGIN SAPLING FOOTER)
    Stack created with [Sapling](https://sapling-scm.com). Best reviewed
    with [ReviewStack](https://reviewstack.dev/openai/codex/pull/10349).
    * #10357
    * __->__ #10349
    * #10356
  • feat: introduce codex-utils-cargo-bin as an alternative to assert_cmd::Command (#8496)
    This PR introduces a `codex-utils-cargo-bin` utility crate that
    wraps/replaces our use of `assert_cmd::Command` and
    `escargot::CargoBuild`.
    
    As you can infer from the introduction of `buck_project_root()` in this
    PR, I am attempting to make it possible to build Codex under
    [Buck2](https://buck2.build) as well as `cargo`. With Buck2, I hope to
    achieve faster incremental local builds (largely due to Buck2's
    [dice](https://buck2.build/docs/insights_and_knowledge/modern_dice/)
    build strategy, as well as benefits from its local build daemon) as well
    as faster CI builds if we invest in remote execution and caching.
    
    See
    https://buck2.build/docs/getting_started/what_is_buck2/#why-use-buck2-key-advantages
    for more details about the performance advantages of Buck2.
    
    Buck2 enforces stronger requirements in terms of build and test
    isolation. It discourages assumptions about absolute paths (which is key
    to enabling remote execution). Because the `CARGO_BIN_EXE_*` environment
    variables that Cargo provides are absolute paths (which
    `assert_cmd::Command` reads), this is a problem for Buck2, which is why
    we need this `codex-utils-cargo-bin` utility.
    
    My WIP-Buck2 setup sets the `CARGO_BIN_EXE_*` environment variables
    passed to a `rust_test()` build rule as relative paths.
    `codex-utils-cargo-bin` will resolve these values to absolute paths,
    when necessary.
    
    
    ---
    [//]: # (BEGIN SAPLING FOOTER)
    Stack created with [Sapling](https://sapling-scm.com). Best reviewed
    with [ReviewStack](https://reviewstack.dev/openai/codex/pull/8496).
    * #8498
    * __->__ #8496
  • chore: add cargo-deny configuration (#7119)
    - add GitHub workflow running cargo-deny on push/PR
    - document cargo-deny allowlist with workspace-dep notes and advisory
    ignores
    - align workspace crates to inherit version/edition/license for
    consistent checks
  • fix: separate codex mcp into codex mcp-server and codex app-server (#4471)
    This is a very large PR with some non-backwards-compatible changes.
    
    Historically, `codex mcp` (or `codex mcp serve`) started a JSON-RPC-ish
    server that had two overlapping responsibilities:
    
    - Running an MCP server, providing some basic tool calls.
    - Running the app server used to power experiences such as the VS Code
    extension.
    
    This PR aims to separate these into distinct concepts:
    
    - `codex mcp-server` for the MCP server
    - `codex app-server` for the "application server"
    
    Note `codex mcp` still exists because it already has its own subcommands
    for MCP management (`list`, `add`, etc.)
    
    The MCP logic continues to live in `codex-rs/mcp-server` whereas the
    refactored app server logic is in the new `codex-rs/app-server` folder.
    Note that most of the existing integration tests in
    `codex-rs/mcp-server/tests/suite` were actually for the app server, so
    all the tests have been moved with the exception of
    `codex-rs/mcp-server/tests/suite/mod.rs`.
    
    Because this is already a large diff, I tried not to change more than I
    had to, so `codex-rs/app-server/tests/common/mcp_process.rs` still uses
    the name `McpProcess` for now, but I will do some mechanical renamings
    to things like `AppServer` in subsequent PRs.
    
    While `mcp-server` and `app-server` share some overlapping functionality
    (like reading streams of JSONL and dispatching based on message types)
    and some differences (completely different message types), I ended up
    doing a bit of copypasta between the two crates, as both have somewhat
    similar `message_processor.rs` and `outgoing_message.rs` files for now,
    though I expect them to diverge more in the near future.
    
    One material change is that of the initialize handshake for `codex
    app-server`, as we no longer use the MCP types for that handshake.
    Instead, we update `codex-rs/protocol/src/mcp_protocol.rs` to add an
    `Initialize` variant to `ClientRequest`, which takes the `ClientInfo`
    object we need to update the `USER_AGENT_SUFFIX` in
    `codex-rs/app-server/src/message_processor.rs`.
    
    One other material change is in
    `codex-rs/app-server/src/codex_message_processor.rs` where I eliminated
    a use of the `send_event_as_notification()` method I am generally trying
    to deprecate (because it blindly maps an `EventMsg` into a
    `JSONNotification`) in favor of `send_server_notification()`, which
    takes a `ServerNotification`, as that is intended to be a custom enum of
    all notification types supported by the app server. So to make this
    update, I had to introduce a new variant of `ServerNotification`,
    `SessionConfigured`, which is a non-backwards compatible change with the
    old `codex mcp`, and clients will have to be updated after the next
    release that contains this PR. Note that
    `codex-rs/app-server/tests/suite/list_resume.rs` also had to be update
    to reflect this change.
    
    I introduced `codex-rs/utils/json-to-toml/src/lib.rs` as a small utility
    crate to avoid some of the copying between `mcp-server` and
    `app-server`.
  • [mcp-server] Expose fuzzy file search in MCP (#2677)
    ## Summary
    Expose a simple fuzzy file search implementation for mcp clients to work
    with
    
    ## Testing
    - [x] Tested locally
  • chore: unify cargo versions (#4044)
    Unify cargo versions at root
  • Switch to uuid_v7 and tighten ConversationId usage (#3819)
    Make sure conversations have a timestamp.
  • feat: add UserInfo request to JSON-RPC server (#3428)
    This adds a simple endpoint that provides the email address encoded in
    `$CODEX_HOME/auth.json`.
    
    As noted, for now, we do not hit the server to verify this is the user's
    true email address.
  • Set a user agent suffix when used as a mcp server (#3395)
    This automatically adds a user agent suffix whenever the CLI is used as
    a MCP server
  • feat: Run cargo shear during CI (#3338)
    Run cargo shear as part of the CI to ensure no unused dependencies
  • Added new auth-related methods and events to mcp server (#2496)
    This PR adds the following:
    * A getAuthStatus method on the mcp server. This returns the auth method
    currently in use (chatgpt or apikey) or none if the user is not
    authenticated. It also returns the "preferred auth method" which
    reflects the `preferred_auth_method` value in the config.
    * A logout method on the mcp server. If called, it logs out the user and
    deletes the `auth.json` file — the same behavior in the cli's `/logout`
    command.
    * An `authStatusChange` event notification that is sent when the auth
    status changes due to successful login or logout operations.
    * Logic to pass command-line config overrides to the mcp server at
    startup time. This allows use cases like `codex mcp -c
    preferred_auth_method=apikey`.
  • chore: move mcp-server/src/wire_format.rs to protocol/src/mcp_protocol.rs (#2423)
    The existing `wire_format.rs` should share more types with the
    `codex-protocol` crate (like `AskForApproval` instead of maintaining a
    parallel `CodexToolCallApprovalPolicy` enum), so this PR moves
    `wire_format.rs` into `codex-protocol`, renaming it as
    `mcp-protocol.rs`. We also de-dupe types, where appropriate.
    
    ---
    [//]: # (BEGIN SAPLING FOOTER)
    Stack created with [Sapling](https://sapling-scm.com). Best reviewed
    with [ReviewStack](https://reviewstack.dev/openai/codex/pull/2423).
    * #2424
    * __->__ #2423
  • Added MCP server command to enable authentication using ChatGPT (#2373)
    This PR adds two new APIs for the MCP server: 1) loginChatGpt, and 2)
    cancelLoginChatGpt. The first starts a login server and returns a local
    URL that allows for browser-based authentication, and the second
    provides a way to cancel the login attempt. If the login attempt
    succeeds, a notification (in the form of an event) is sent to a
    subscriber.
    
    I also added a timeout mechanism for the existing login server. The
    loginChatGpt code path uses a 10-minute timeout by default, so if the
    user fails to complete the login flow in that timeframe, the login
    server automatically shuts down. I tested the timeout code by manually
    setting the timeout to a much lower number and confirming that it works
    as expected when used e2e.
  • Auto format toml (#1745)
    Add recommended extension and configure it to auto format prompt.
  • Mcp protocol (#1715)
    - Add typed MCP protocol surface in
    `codex-rs/mcp-server/src/mcp_protocol.rs` for `requests`, `responses`,
    and `notifications`
    - Requests: `NewConversation`, `Connect`, `SendUserMessage`,
    `GetConversations`
    - Message content parts: `Text`, `Image` (`ImageUrl`/`FileId`, optional
    `ImageDetail`), File (`Url`/`Id`/`inline Data`)
    - Responses: `ToolCallResponseEnvelope` with optional `isError` and
    `structuredContent` variants (`NewConversation`, `Connect`,
    `SendUserMessageAccepted`, `GetConversations`)
    - Notifications: `InitialState`, `ConnectionRevoked`, `CodexEvent`,
    `Cancelled`
    - Uniform `_meta` on `notifications` via `NotificationMeta`
    (`conversationId`, `requestId`)
    - Unit tests validate JSON wire shapes for key
    `requests`/`responses`/`notifications`
  • fix: create separate test_support crates to eliminate #[allow(dead_code)] (#1667)
    Because of a quirk of how implementation tests work in Rust, we had a
    number of `#[allow(dead_code)]` annotations that were misleading because
    the functions _were_ being used, just not by all integration tests in a
    `tests/` folder, so when compiling the test that did not use the
    function, clippy would complain that it was unused.
    
    This fixes things by create a "test_support" crate under the `tests/`
    folder that is imported as a dev dependency for the respective crate.
  • [mcp-server] Add reply tool call (#1643)
    ## Summary
    Adds a new mcp tool call, `codex-reply`, so we can continue existing
    sessions. This is a first draft and does not yet support sessions from
    previous processes.
    
    ## Testing
    - [x] tested with mcp client
  • test: add integration test for MCP server (#1633)
    This PR introduces a single integration test for `cargo mcp`, though it
    also introduces a number of reusable components so that it should be
    easier to introduce more integration tests going forward.
    
    The new test is introduced in `codex-rs/mcp-server/tests/elicitation.rs`
    and the reusable pieces are in `codex-rs/mcp-server/tests/common`.
    
    The test itself verifies new functionality around elicitations
    introduced in https://github.com/openai/codex/pull/1623 (and the fix
    introduced in https://github.com/openai/codex/pull/1629) by doing the
    following:
    
    - starts a mock model provider with canned responses for
    `/v1/chat/completions`
    - starts the MCP server with a `config.toml` to use that model provider
    (and `approval_policy = "untrusted"`)
    - sends the `codex` tool call which causes the mock model provider to
    request a shell call for `git init`
    - the MCP server sends an elicitation to the client to approve the
    request
    - the client replies to the elicitation with `"approved"`
    - the MCP server runs the command and re-samples the model, getting a
    `"finish_reason": "stop"`
    - in turn, the MCP server sends the final response to the original
    `codex` tool call
    - verifies that `git init` ran as expected
    
    To test:
    
    ```
    cargo test shell_command_approval_triggers_elicitation
    ```
    
    In writing this test, I discovered that `ExecApprovalResponse` does not
    conform to `ElicitResult`, so I added a TODO to fix that, since I think
    that should be updated in a separate PR. As it stands, this PR does not
    update any business logic, though it does make a number of members of
    the `mcp-server` crate `pub` so they can be used in the test.
    
    One additional learning from this PR is that
    `std::process::Command::cargo_bin()` from the `assert_cmd` trait is only
    available for `std::process::Command`, but we really want to use
    `tokio::process::Command` so that everything is async and we can
    leverage utilities like `tokio::time::timeout()`. The trick I came up
    with was to use `cargo_bin()` to locate the program, and then to use
    `std::process::Command::get_program()` when constructing the
    `tokio::process::Command`.
  • feat: leverage elicitations in the MCP server (#1623)
    This updates the MCP server so that if it receives an
    `ExecApprovalRequest` from the `Codex` session, it in turn sends an [MCP
    elicitation](https://modelcontextprotocol.io/specification/draft/client/elicitation)
    to the client to ask for the approval decision. Upon getting a response,
    it forwards the client's decision via `Op::ExecApproval`.
    
    Admittedly, we should be doing the same thing for
    `ApplyPatchApprovalRequest`, but this is our first time experimenting
    with elicitations, so I'm inclined to defer wiring that code path up
    until we feel good about how this one works.
    
    ---
    [//]: # (BEGIN SAPLING FOOTER)
    Stack created with [Sapling](https://sapling-scm.com). Best reviewed
    with [ReviewStack](https://reviewstack.dev/openai/codex/pull/1623).
    * __->__ #1623
    * #1622
    * #1621
    * #1620
  • chore(rs): update dependencies (#1494)
    ### Chores
    - Update cargo dependencies
    - Remove unused cargo dependencies
    - Fix clippy warnings
    - Update Dockerfile (package.json requires node 22)
    - Let Dependabot update bun, cargo, devcontainers, docker,
    github-actions, npm (nix still not supported)
    
    ### TODO
    - Upgrade dependencies with breaking changes
    
    ```shell
    $ cargo update --verbose
       Unchanged crossterm v0.28.1 (available: v0.29.0)
       Unchanged schemars v0.8.22 (available: v1.0.4)
    ```
  • feat: add support for -c/--config to override individual config items (#1137)
    This PR introduces support for `-c`/`--config` so users can override
    individual config values on the command line using `--config
    name=value`. Example:
    
    ```
    codex --config model=o4-mini
    ```
    
    Making it possible to set arbitrary config values on the command line
    results in a more flexible configuration scheme and makes it easier to
    provide single-line examples that can be copy-pasted from documentation.
    
    Effectively, it means there are four levels of configuration for some
    values:
    
    - Default value (e.g., `model` currently defaults to `o4-mini`)
    - Value in `config.toml` (e.g., user could override the default to be
    `model = "o3"` in their `config.toml`)
    - Specifying `-c` or `--config` to override `model` (e.g., user can
    include `-c model=o3` in their list of args to Codex)
    - If available, a config-specific flag can be used, which takes
    precedence over `-c` (e.g., user can specify `--model o3` in their list
    of args to Codex)
    
    Now that it is possible to specify anything that could be configured in
    `config.toml` on the command line using `-c`, we do not need to have a
    custom flag for every possible config option (which can clutter the
    output of `--help`). To that end, as part of this PR, we drop support
    for the `--disable-response-storage` flag, as users can now specify `-c
    disable_response_storage=true` to get the equivalent functionality.
    
    Under the hood, this works by loading the `config.toml` into a
    `toml::Value`. Then for each `key=value`, we create a small synthetic
    TOML file with `value` so that we can run the TOML parser to get the
    equivalent `toml::Value`. We then parse `key` to determine the point in
    the original `toml::Value` to do the insert/replace. Once all of the
    overrides from `-c` args have been applied, the `toml::Value` is
    deserialized into a `ConfigToml` and then the `ConfigOverrides` are
    applied, as before.
  • fix: overhaul how we spawn commands under seccomp/landlock on Linux (#1086)
    Historically, we spawned the Seatbelt and Landlock sandboxes in
    substantially different ways:
    
    For **Seatbelt**, we would run `/usr/bin/sandbox-exec` with our policy
    specified as an arg followed by the original command:
    
    
    https://github.com/openai/codex/blob/d1de7bb383552e8fadd94be79d65d188e00fd562/codex-rs/core/src/exec.rs#L147-L219
    
    For **Landlock/Seccomp**, we would do
    `tokio::runtime::Builder::new_current_thread()`, _invoke
    Landlock/Seccomp APIs to modify the permissions of that new thread_, and
    then spawn the command:
    
    
    https://github.com/openai/codex/blob/d1de7bb383552e8fadd94be79d65d188e00fd562/codex-rs/core/src/exec_linux.rs#L28-L49
    
    While it is neat that Landlock/Seccomp supports applying a policy to
    only one thread without having to apply it to the entire process, it
    requires us to maintain two different codepaths and is a bit harder to
    reason about. The tipping point was
    https://github.com/openai/codex/pull/1061, in which we had to start
    building up the `env` in an unexpected way for the existing
    Landlock/Seccomp approach to continue to work.
    
    This PR overhauls things so that we do similar things for Mac and Linux.
    It turned out that we were already building our own "helper binary"
    comparable to Mac's `sandbox-exec` as part of the `cli` crate:
    
    
    https://github.com/openai/codex/blob/d1de7bb383552e8fadd94be79d65d188e00fd562/codex-rs/cli/Cargo.toml#L10-L12
    
    We originally created this to build a small binary to include with the
    Node.js version of the Codex CLI to provide support for Linux
    sandboxing.
    
    Though the sticky bit is that, at this point, we still want to deploy
    the Rust version of Codex as a single, standalone binary rather than a
    CLI and a supporting sandboxing binary. To satisfy this goal, we use
    "the arg0 trick," in which we:
    
    * use `std::env::current_exe()` to get the path to the CLI that is
    currently running
    * use the CLI as the `program` for the `Command`
    * set `"codex-linux-sandbox"` as arg0 for the `Command`
    
    A CLI that supports sandboxing should check arg0 at the start of the
    program. If it is `"codex-linux-sandbox"`, it must invoke
    `codex_linux_sandbox::run_main()`, which runs the CLI as if it were
    `codex-linux-sandbox`. When acting as `codex-linux-sandbox`, we make the
    appropriate Landlock/Seccomp API calls and then use `execvp(3)` to spawn
    the original command, so do _replace_ the process rather than spawn a
    subprocess. Incidentally, we do this before starting the Tokio runtime,
    so the process should only have one thread when `execvp(3)` is called.
    
    Because the `core` crate that needs to spawn the Linux sandboxing is not
    a CLI in its own right, this means that every CLI that includes `core`
    and relies on this behavior has to (1) implement it and (2) provide the
    path to the sandboxing executable. While the path is almost always
    `std::env::current_exe()`, we needed to make this configurable for
    integration tests, so `Config` now has a `codex_linux_sandbox_exe:
    Option<PathBuf>` property to facilitate threading this through,
    introduced in https://github.com/openai/codex/pull/1089.
    
    This common pattern is now captured in
    `codex_linux_sandbox::run_with_sandbox()` and all of the `main.rs`
    functions that should use it have been updated as part of this PR.
    
    The `codex-linux-sandbox` crate added to the Cargo workspace as part of
    this PR now has the bulk of the Landlock/Seccomp logic, which makes
    `core` a bit simpler. Indeed, `core/src/exec_linux.rs` and
    `core/src/landlock.rs` were removed/ported as part of this PR. I also
    moved the unit tests for this code into an integration test,
    `linux-sandbox/tests/landlock.rs`, in which I use
    `env!("CARGO_BIN_EXE_codex-linux-sandbox")` as the value for
    `codex_linux_sandbox_exe` since `std::env::current_exe()` is not
    appropriate in that case.
  • feat: add mcp subcommand to CLI to run Codex as an MCP server (#934)
    Previously, running Codex as an MCP server required a standalone binary
    in our Cargo workspace, but this PR makes it available as a subcommand
    (`mcp`) of the main CLI.
    
    Ran this with:
    
    ```
    RUST_LOG=debug npx @modelcontextprotocol/inspector cargo run --bin codex -- mcp
    ```
    
    and verified it worked as expected in the inspector at
    `http://127.0.0.1:6274/`.
  • Workspace lints and disallow unwrap (#855)
    Sets submodules to use workspace lints. Added denying unwrap as a
    workspace level lint, which found a couple of cases where we could have
    propagated errors. Also manually labeled ones that were fine by my eye.
  • Update submodules version to come from the workspace (#850)
    Tie the version of submodules to the workspace version.
  • Update cargo to 2024 edition (#842)
    Some effects of this change:
    - New formatting changes across many files. No functionality changes
    should occur from that.
    - Calls to `set_env` are considered unsafe, since this only happens in
    tests we wrap them in `unsafe` blocks
  • chore: introduce codex-common crate (#843)
    I started this PR because I wanted to share the `format_duration()`
    utility function in `codex-rs/exec/src/event_processor.rs` with the TUI.
    The question was: where to put it?
    
    `core` should have as few dependencies as possible, so moving it there
    would introduce a dependency on `chrono`, which seemed undesirable.
    `core` already had this `cli` feature to deal with a similar situation
    around sharing common utility functions, so I decided to:
    
    * make `core` feature-free
    * introduce `common`
    * `common` can have as many "special interest" features as it needs,
    each of which can declare their own deps
    * the first two features of common are `cli` and `elapsed`
    
    In practice, this meant updating a number of `Cargo.toml` files,
    replacing this line:
    
    ```toml
    codex-core = { path = "../core", features = ["cli"] }
    ```
    
    with these:
    
    ```toml
    codex-core = { path = "../core" }
    codex-common = { path = "../common", features = ["cli"] }
    ```
    
    Moving `format_duration()` into its own file gave it some "breathing
    room" to add a unit test, so I had Codex generate some tests and new
    support for durations over 1 minute.
  • feat: make Codex available as a tool when running it as an MCP server (#811)
    This PR replaces the placeholder `"echo"` tool call in the MCP server
    with a `"codex"` tool that calls Codex. Events such as
    `ExecApprovalRequest` and `ApplyPatchApprovalRequest` are not handled
    properly yet, but I have `approval_policy = "never"` set in my
    `~/.codex/config.toml` such that those codepaths are not exercised.
    
    The schema for this MPC tool is defined by a new `CodexToolCallParam`
    struct introduced in this PR. It is fairly similar to `ConfigOverrides`,
    as the param is used to help create the `Config` used to start the Codex
    session, though it also includes the `prompt` used to kick off the
    session.
    
    This PR also introduces the use of the third-party `schemars` crate to
    generate the JSON schema, which is verified in the
    `verify_codex_tool_json_schema()` unit test.
    
    Events that are dispatched during the Codex session are sent back to the
    MCP client as MCP notifications. This gives the client a way to monitor
    progress as the tool call itself may take minutes to complete depending
    on the complexity of the task requested by the user.
    
    In the video below, I launched the server via:
    
    ```shell
    mcp-server$ RUST_LOG=debug npx @modelcontextprotocol/inspector cargo run --
    ```
    
    In the video, you can see the flow of:
    
    * requesting the list of tools
    * choosing the **codex** tool
    * entering a value for **prompt** and then making the tool call
    
    Note that I left the other fields blank because when unspecified, the
    values in my `~/.codex/config.toml` were used:
    
    
    https://github.com/user-attachments/assets/1975058c-b004-43ef-8c8d-800a953b8192
    
    Note that while using the inspector, I did run into
    https://github.com/modelcontextprotocol/inspector/issues/293, though the
    tip about ensuring I had only one instance of the **MCP Inspector** tab
    open in my browser seemed to fix things.
  • feat: introduce mcp-server crate (#792)
    This introduces the `mcp-server` crate, which contains a barebones MCP
    server that provides an `echo` tool that echoes the user's request back
    to them.
    
    To test it out, I launched
    [modelcontextprotocol/inspector](https://github.com/modelcontextprotocol/inspector)
    like so:
    
    ```
    mcp-server$ npx @modelcontextprotocol/inspector cargo run --
    ```
    
    and opened up `http://127.0.0.1:6274` in my browser:
    
    
    ![image](https://github.com/user-attachments/assets/83fc55d4-25c2-4497-80cd-e9702283ff93)
    
    I also had to make a small fix to `mcp-types`, adding
    `#[serde(untagged)]` to a number of `enum`s.