Michael Bolin
7d0b91d5d6
## Why MCP servers must forward sandbox policy unchanged to `codex sandbox --sandbox-state-json`, while interpreting launcher information to find the Codex CLI. Keep those contracts separate so consumers can preserve unknown policy fields. ## What changed - Accept the experimental `codex/sandbox-state` capability alongside the deprecated `codex/sandbox-state-meta` capability, and send identical policy values under both `_meta` keys. - Move `codexExecutable` out of the policy into `codex/sandbox-launcher`, supplied only when a verified CLI path is available for a local stdio server. - Replace stale sandbox metadata while retaining unrelated entries, and remove stale launcher metadata when no launcher is available. - Document the metadata contract and how servers should forward policy and retain authority for long-lived subprocesses. ## Testing Update unit and integration coverage for policy serialization, identical state aliases, launcher availability across execution environments, and stale metadata replacement. GitOrigin-RevId: e544c06e6e023953b1fc8069b7b1affa065262d1
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Codex MCP runtime
This crate manages Codex's MCP connections, tool calls, and their captured authority.
Sandbox request metadata
An MCP server advertises the experimental codex/sandbox-state capability to
receive sandbox metadata on tool calls. The deprecated capability name
codex/sandbox-state-meta opts into the same contract during migration.
Codex supplies these entries in the request's _meta object:
| Key | Value |
|---|---|
codex/sandbox-state |
Opaque policy to pass to codex sandbox --sandbox-state-json. |
codex/sandbox-state-meta |
An identical copy of that policy under the deprecated name. |
codex/sandbox-launcher |
When available, an object with an absolute codexExecutable path to a verified full Codex CLI on the MCP server's host. |
Use the launcher path to invoke sandbox --sandbox-state-json with the entire
state value serialized as one argument, followed by -- and the command to run.
The state contains neither launcher discovery data nor deprecation messages.
Preserve unknown policy fields by forwarding the original value rather than
deserializing and reconstructing it. The two state names are aliases, not separate
policies; new consumers should prefer codex/sandbox-state.
Launcher metadata is currently available only for local stdio servers. An HTTP endpoint, including loopback, or a remote executor does not establish a shared filesystem with the harness. Codex omits the launcher when its path is unknown, not representable as UTF-8, or fails the cached capability probe. Absence does not authorize a PATH search or unsandboxed fallback. Servers that require a launcher must fail closed or require an explicit operator opt-out.
The state and launcher describe the issuing call. Retain both when starting a
long-lived subprocess or caching policy-bound results; reject changed authority
before reusing them. Tool arguments supplied by the model are not authority.
See sandbox_metadata.rs for the wire types and
binding.rs for execution-environment selection.