MCP resume_path for Codex sessions #10122
Description
Discussed in #10121
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 #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
#10117 includes:
- Optional
resume_pathin 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 #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.