I discovered that `cargo build` worked for the entire workspace, but not
for the `mcp-client` or `core` crates.
* `mcp-client` failed to build because it underspecified the set of
features it needed from `tokio`.
* `core` failed to build because it was using a "feature" of its own
crate in the default, no-feature version.
This PR fixes the builds and adds a check in CI to defend against this
sort of thing going forward.
Cleans up the signature for `new_stdio_client()` to more closely mirror
how MCP servers are declared in config files (`command`, `args`, `env`).
Also takes a cue from Claude Code where the MCP server is launched with
a restricted `env` so that it only includes "safe" things like `USER`
and `PATH` (see the `create_env_for_mcp_server()` function introduced in
this PR for details) by default, as it is common for developers to have
sensitive API keys present in their environment that should only be
forwarded to the MCP server when the user has explicitly configured it
to do so.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/831).
* #829
* __->__ #831
This PR introduces an initial `McpClient` that we will use to give Codex
itself programmatic access to foreign MCPs. This does not wire it up in
Codex itself yet, but the new `mcp-client` crate includes a `main.rs`
for basic testing for now.
Manually tested by sending a `tools/list` request to Codex's own MCP
server:
```
codex-rs$ cargo build
codex-rs$ cargo run --bin codex-mcp-client ./target/debug/codex-mcp-server
{
"tools": [
{
"description": "Run a Codex session. Accepts configuration parameters matching the Codex Config struct.",
"inputSchema": {
"properties": {
"approval-policy": {
"description": "Execution approval policy expressed as the kebab-case variant name (`unless-allow-listed`, `auto-edit`, `on-failure`, `never`).",
"enum": [
"auto-edit",
"unless-allow-listed",
"on-failure",
"never"
],
"type": "string"
},
"cwd": {
"description": "Working directory for the session. If relative, it is resolved against the server process's current working directory.",
"type": "string"
},
"disable-response-storage": {
"description": "Disable server-side response storage.",
"type": "boolean"
},
"model": {
"description": "Optional override for the model name (e.g. \"o3\", \"o4-mini\")",
"type": "string"
},
"prompt": {
"description": "The *initial user prompt* to start the Codex conversation.",
"type": "string"
},
"sandbox-permissions": {
"description": "Sandbox permissions using the same string values accepted by the CLI (e.g. \"disk-write-cwd\", \"network-full-access\").",
"items": {
"enum": [
"disk-full-read-access",
"disk-write-cwd",
"disk-write-platform-user-temp-folder",
"disk-write-platform-global-temp-folder",
"disk-full-write-access",
"network-full-access"
],
"type": "string"
},
"type": "array"
}
},
"required": [
"prompt"
],
"type": "object"
},
"name": "codex"
}
]
}
```
This Pull Request addresses an issue where the output of commands
executed in the raw-exec utility was being truncated due to restrictive
limits on the number of lines and bytes collected. The truncation caused
the message [Output truncated: too many lines or bytes] to appear when
processing large outputs, which could hinder the functionality of the
CLI.
Changes Made
Increased the maximum output limits in the
[createTruncatingCollector](https://github.com/openai/codex/pull/575)
utility:
Bytes: Increased from 10 KB to 100 KB.
Lines: Increased from 256 lines to 1024 lines.
Installed the @types/node package to resolve missing type definitions
for [NodeJS](https://github.com/openai/codex/pull/575) and
[Buffer](https://github.com/openai/codex/pull/575).
Verified and fixed any related errors in the
[createTruncatingCollector](https://github.com/openai/codex/pull/575)
implementation.
Issue Solved:
This PR ensures that larger outputs can be processed without truncation,
improving the usability of the CLI for commands that generate extensive
output. https://github.com/openai/codex/issues/509
---------
Co-authored-by: Michael Bolin <bolinfest@gmail.com>
