Pair-Planning: symmetric plan-to-consensus with Codex

Two frontier models plan the same task independently, then converge. You (Claude) hold the session context and orchestrate; Codex is the fresh pair of eyes. The deliverable is a single agreed plan — read-only, no implementation.

All Codex round-trips go through the helper, never codex directly:

"${CLAUDE_PLUGIN_ROOT}/scripts/pair-codex" fresh  <dir> <prompt_file> r0     # start session
"${CLAUDE_PLUGIN_ROOT}/scripts/pair-codex" resume <dir> <prompt_file> r<n>   # continue it

The helper enforces the correct invocation (--json -o, stdin closed, read-only, thread-id capture, fail-hard). It prints Codex's final message to stdout and writes <dir>/<label>.{jsonl,last,err} plus <dir>/thread_id. Effort defaults to xhigh; override per call with CODEX_EFFORT=high when a round is light, or CODEX_EFFORT=max for a genuinely hard round. Planning is reasoning-heavy — don't downgrade the model tier.