MCP resume_path for Codex sessions

Discussed in https://github.com/openai/codex/discussions/10121

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^{Originally posted by rabsef-bicrym January 28, 2026}
I would like to propose adding resume_path support to the Codex MCP tool so MCP clients can resume prior sessions across desktop and mobile. A tested implementation is available in openai/codex#10117.

Motivation

• Cross-device continuity: start a session on desktop and resume on mobile (or the other way around)
• Better MCP UX: treats Codex as stateful when used through MCP, instead of stateless
• Parity with other CLI workflows: keeps Codex competitive in Happy-style multi-surface use

This matters for MCP clients like Happy CLI that provide a mobile surface on top of a local Codex process.

Implementation

openai/codex#10117 includes:

• Optional resume_path in the MCP tool schema
• MCP runner logic that resumes from the rollout path when provided
• Backward compatibility for existing callers
• Tests covering schema updates and legacy payload compatibility

This simply exposes existing Codex resume behavior through MCP.

Contribution policy

I’ve read the invitation-only contribution update and understand the shift toward high‑signal discussion and prioritization. Sharing this here in case it aligns with the roadmap or a known need (in addition to the use case of Happy CLI resume).

Companion work

Happy CLI side: slopus/happy-cli#151 uses the MCP resume-path to provide a clean resume picker and consistent mobile/desktop experience.

Request

If this is aligned, I’d appreciate feedback on the approach in openai/codex#10117. If there’s a preferred shape for MCP resume or a different path the team wants, I’m happy to adjust or drop the change.
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