[ZacxDev]

What

The previews control on a mirrored window's session views is now shown only while that window has something to preview, and it lives in the header, not in a row above the chat.

• Protocol (no version bump, compatible both ways): muster-mirror -preview sends a new previews host to muster message on its existing mirror connection, a whole map of tmux window id to {offered, open} (counts only, no port or process). It is sent after the window list and again whenever it changes, and an empty map clears it. It follows the existing work/colors per-window-message convention: an older muster's read loop drops the unknown type, and an older host never sends one, so its windows show no button.
• Host source: previewhost.Host.Summary(). offered counts listener reports with no open preview on that port (the same set the gateway's session page lists as offers), and open counts open previews. It returns nil while no gateway tunnel serves the offer stream or while previews are off.
• Server state: in memory on the hub's per-host state (HostView.Previews, copied to SessionView.Previews). It is never kept for an offline host and never stored. A change nudges the owner's views (agent.changed), the same as work counts.
• UI:
  • A header Preview button with a count badge, beside the Rendered | Terminal switch. Below sm it is a 44x44 icon with the badge on its corner.
  • The button opens a side panel with the gateway session page in the sandboxed frame. From sm up the panel sits over the right of the page; on phones it takes the whole screen. Close or Escape unloads it.
  • The panel's header has a New tab hand-off, with the same tab-before-mint and noopener behaviour as before, plus a picker when there is more than one viewer plugin.
  • The sidebar row gets a small browser-window glyph. It is not a dot, because the waiting mark is already an accent dot.
• Gates: viewerPlugins() stays the first gate (no slot, no poll, no frame-src without a live viewer plugin). The counts only narrow it: the button is drawn only while offered + open > 0. frame-src follows the viewer plugins alone, so a button that appears after load can still frame its panel.
• Live updates: the button's slot polls GET /ui/mirror/preview-button every 10 s while the tab is visible. The session views hold no event stream, and this keeps it that way. A zero-count poll does not read the plugin store, and a revoked token removes the button at the next poll. The sidebar refreshes on its existing triggers.

Tests

• Go:
  • internal/mirror/previews_test.go: normalise, pinned wire bytes, hub arrival/nudge/clear/offline.
  • internal/mirrorhost/previews_test.go: send after the windows, re-send only on change, none without -preview, worst case fits one frame.
  • internal/previewhost/summary_test.go: offers minus open ports, nil without a tunnel or while off.
  • internal/api/plugin_chip_test.go: button only while counts > 0 on both views, the poll route's gates, the sidebar mark, the existing CSP/sandbox/gate tests adapted.
  • cmd/muster-mirror: the shipped build cannot take counts from the e2e file.
• Mutation sweep over the gates: 16 of 17 mutants killed, each by the named test. The one survivor, dropping the ok check in NormalizePreviews, is equivalent, because iteration is over listed windows and a zero entry is dropped anyway. A no-op control mutant survived, as it should.
• e2e:
  • previews.spec.ts drives the real chain through the button and panel, and adds a hidden-when-nothing case: a quiet @2 window on the real host's report gets no button and no sidebar mark, with @1 as the control.
  • plugin-chip.spec.ts plays the counts via MUSTER_MIRROR_E2E_PREVIEWS_FILE and covers the button appearing and disappearing live on an open page.
  • cls.spec.ts measures the views with the button.

e2e was not run locally; CI is the authority.

🤖 Generated with Claude Code

[ZacxDev]

Round 0 (requirements & deletion), recorded late from the round's report: verdict proceed to the checklist, no open premises, one deletion candidate.

D1 — the panel's multi-plugin <select> picker (internal/ui/plugin_chip.go:257-265): only reachable with ≥2 live viewer plugins; the deployed setup has one — keep only if multi-viewer owners are a real case

[ZacxDev]

Round 1 (nine-axis checklist) at 5a18cc1b: no 🔴, so the ladder ends here. One 🟡 and one 🟢 were fixed in bd8d22c5 and not re-audited. ef5877e6 only merges main, which brings in #591.

1. 🟡 the sidebar preview icon is drawn only when the owner has a live viewer plugin, the same gate as the view's Preview button
2. 🟢 Escape closes the preview panel only when it is not meant for another open dialog
3. 🟢 on phones, the full-screen panel keeps focus inside it: the content behind it is inert while it is open