Status overlay prefers stale GJC history over active Codex pane

[Cheol-H-Jeong]

Problem

In the k-pol nmux-linux window, the main pane was switched from GJC to Codex, but nmux-linux still rendered the status overlay as if GJC owned the project.

Observed live state:

• tmux list-panes for nmux-linux:7 showed the main pane command as node with title ⠸ k-pol.
• The process tree under the main pane was:
  • /bin/bash
  • node /home/cheol/.local/bin/codex
  • OpenAI Codex vendor binary
• The right status pane still showed:
  • 작업 소스 gjc · k-pol
  • 메인 pane node
  • stale GJC user-command history

Expected

When the active main pane process tree contains Codex, nmux-linux should:

• identify the main pane as agent:codex in the status overlay;
• prefer Codex rollout/plan data for that project;
• avoid showing stale GJC command history just because old .gjc transcripts exist for the same cwd.

Root cause

pickActiveTaskSource() unconditionally prioritizes readGjcSource() before all other task sources. This was correct when GJC was the primary agent, but it breaks mixed-agent panes: a project with historical GJC transcripts will mask a currently running Codex TUI forever.

taskOverlayStatusContext() also hides process-tree agent detection by default behind NMUX_TASK_OVERLAY_DETECT_AGENT=1, so a Codex node wrapper appears as generic node in the overlay.

Fix direction

• Detect the active main-pane agent from the process tree by default.
• Pass that active agent into task-source selection.
• If the active agent is non-GJC, prefer its source and do not fall back to stale GJC history.
• Keep the existing GJC-first behavior only when GJC is the active agent or no active agent is known.

Verification target

Add tests proving that an active Codex pane selects Codex source over stale GJC source, and that node /path/to/codex is identified as Codex.

[Cheol-H-Jeong]

Fixed and verified locally.

What changed:

• status overlay now detects the active main-pane agent from the process tree by default;
• source selection receives the active agent and no longer lets stale GJC transcripts mask an active Codex TUI;
• Codex sessions without update_plan now fall back to recent user prompts, so read-only/review/QA Codex sessions still appear in the overlay;
• Codex session_meta cwd detection no longer requires parsing the entire long first JSONL line, which was truncated by the old 8KB read.

Live verification on k-pol after reinstalling and refreshing overlays:

상태판  · k-pol
상태  실행 중(running)
작업 소스  codex · 2026-07-19T19:22:55
메인 pane  agent:codex
[ ] TASK: Perform independent visual Q...

Regression checks:

npm test
# tests 57, pass 57, fail 0

npm run check
# node syntax checks + shell syntax checks passed

The running nmux-linux install under ~/.local/bin was updated and the active session overlays/watchers were refreshed without killing the k-pol Codex main pane.

[Cheol-H-Jeong]

[github-issue-solver] 구현 에이전트가 PR #32을 생성했습니다: #32

[Cheol-H-Jeong]

[github-issue-solver] 검증 실패: PR #32은 머지하지 않았습니다. 이 이슈는 자동 재시도하지 않고 verification_failed 상태로 남깁니다.