feat(phai): add refresh_session ACP method for Codex#1722
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tatoalo
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Apr 20, 2026
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Problem
The Codex adapter doesn't implement
_posthog/refresh_session, so the sandbox agent-server's pre-prompt MCP refresh (added for Claude in #1717) silently falls through to "method not found" when the session is Codex-backed.Changes
Mirrors the Claude refresh shape (#1717), adapted to Codex's subprocess model:
extMethodonCodexAcpAgenthandling_posthog/refresh_sessionwith the same payload validation (mcpServersrequired, array-typed) and in-flight guard (promptRunning) as the Claude side.refreshSession(mcpServers)by respawning thecodex-acpsubprocess: abort the current controller, cancel the stale connection, kill the process, spawn a fresh one with the samecodexProcessOptions, replay the snapshottedinitializerequest, then callloadSessionwith the new MCP set to rehydrate conversation history from disk.promptRunningaroundprompt()to enforce the between-turns contract.codexProcessOptions,processCallbacks, andlastInitRequeston the agent so refresh doesn't need re-plumbing.Why respawn instead of hot-swapping MCPs on the running subprocess? codex-acp disables the user's local MCPs via spawn-time CLI args (
-c mcp_servers.<name>.enabled=false), and session-level MCP binding happens atnewSession/loadSessiontime. Respawning gives the caller-supplied server set the same overwrite guarantee the Claude path relies on.How did you test this?
codex-agent.refresh.test.ts(6 tests): methodNotFound, missing-payload rejection, non-array rejection, in-flight guard, happy-path subprocess/connection swap with state preservation, and cancel-throws resilience.pnpm --filter agent test— 263/263 pass.pnpm --filter agent typecheck— clean.pnpm --filter agent exec biome checkon the changed files — clean.