stack/docs/scratchpads/h1b-pane-idle-signal.md

H1b — tmux pane idle signal wiring

Objective

Feed classifyReadiness() a real idle signal on tmux 3.4 by deriving idleSeconds from the first available tmux timestamp source: pane activity, then window activity, then session activity.

Scope

• packages/mosaic/src/commands/fleet.ts
  • Extend buildTmuxListPanesCommand() format to include #{window_activity} and #{session_activity} after the existing fields.
  • Update parseTmuxListPanes() to choose the first non-empty finite positive timestamp and clamp future idle values to 0.
• packages/mosaic/src/commands/fleet.spec.ts
  • Cover pane/window/session activity parsing behavior, empty-field index alignment, null idle, future clamping, math correctness, and exact tmux format.

Out of Scope

• No changes to classifyReadiness(), thresholds, AgentPsRow, or fleet ps rendering.
• No merge by worker; orchestrator routes review/merge.
• Workers do not modify docs/TASKS.md.

PRD Alignment

Aligned with docs/fleet/PRD.md FR-1 and acceptance criteria for truthful mosaic fleet ps pane/pid/idle observability.

Plan

1. Sync branch from latest origin/main and install dependencies with required pnpm env.
2. Add/confirm reproducer tests for tmux 3.4 empty pane_activity and new fallback behavior.
3. Implement the focused parser/format change only.
4. Run required build, baseline gates, fleet vitest, and independent review.
5. Run pre-push queue guard, push branch, and open PR to main with Mosaic wrapper.

Progress

• 2026-06-24: Branch fix/fleet-pane-idle-activity created from origin/main @ ec8dd7c after fetching.
• 2026-06-24: Session-start generated local .mosaic/orchestrator/* changes on the previous release branch; stashed as coder1 session-start state before H1b to keep this branch clean.
• 2026-06-24: Added TDD coverage for the tmux 3.4 production case (pane_activity empty, window_activity populated), exact new list-panes format, null/future/multiple-source behavior.
• 2026-06-24: Implemented parser fallback without changing readiness classifier thresholds or render shape.

Verification Evidence

• pnpm install --store-dir "$HOME/.pnpm-store" — pass.
• Reproducer before implementation: pnpm --filter @mosaicstack/mosaic exec vitest run src/commands/fleet.spec.ts — failed as expected (old format, no fallback, negative future idle).
• npx turbo build --filter=@mosaicstack/mosaic^... — pass, 12/12 tasks successful.
• pnpm typecheck — pass, 41/41 tasks successful.
• pnpm lint — pass, 23/23 tasks successful.
• pnpm format:check — pass, all matched files use Prettier style.
• pnpm --filter @mosaicstack/mosaic exec vitest run src/commands/fleet.spec.ts — pass, 176 tests.
• ~/.config/mosaic/tools/codex/codex-code-review.sh --uncommitted — approve, 0 findings (reviewed supplied diff; sandbox file-inspection limitation noted by tool).

Risks / Blockers

• No current blocker.