feat: make built-in MCPs first-class runtime servers

[jif-oai]

DISCLAIMER

This is experimental and no production service must rely on this

Why

Built-in MCPs are product-owned runtime capabilities, but they were previously flattened into the same config-backed stdio path as user-configured servers. That made them depend on a hidden codex builtin-mcp re-exec path, exposed them through config-oriented CLI flows, and erased distinctions the runtime needs to preserve—most notably whether an MCP call should count as external context for memory-mode pollution.

What changed

• Model product-owned built-ins separately from config-backed MCP servers via BuiltinMcpServer and EffectiveMcpServer.
• Launch built-ins in process through a reusable async transport instead of the hidden builtin-mcp stdio subcommand.
• Keep config-oriented CLI operations such as codex mcp list/get/login/logout scoped to configured servers, while merging built-ins only into the effective runtime server set.
• Retain server metadata after launch so parallel-tool support and context classification come from the live server set; built-in memories is now classified as local Codex state rather than external context.

Test plan

• cargo test -p codex-mcp
• cargo test -p codex-core --test suite builtin_memories_mcp_call_does_not_mark_thread_memory_mode_polluted_when_configured

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: e71090ea16

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[jif-oai]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

codex/codex-rs/builtin-mcps/Cargo.toml

Line 18 in c53fd0a

tokio = { workspace = true, features = ["io-util"] }

Regenerate the Bazel lock for new Rust deps

This commit changes Rust dependencies/features, including adding tokio to codex-builtin-mcps, but does not include the corresponding MODULE.bazel.lock update. Bazel derives crate deps from the lock data, so just bazel-lock-check/Bazel builds can fail or miss this new dependency until just bazel-lock-update is run.

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[jif-oai]

Codex is wrong...