Fire mode: Escape hatch

[0nko]

Task/Issue URL: https://app.asana.com/1/137249556945/project/72649045549333/task/1215736845374133?focus=true

Description

This PR adds the Fire mode support to escape hatch.

Steps to test this PR

Prerequisites

• Internal build with androidBrowserConfig.showNTPAfterIdleReturn enabled (feature-flag inventory).
• Settings → General → After inactivity → Choose an inactivity interval → Always (immediate), and set what you see to New Tab Page.
• fireMode.fireTabs enabled for scenarios 1–5; disabled for scenario 6.
• Cold-start note: a quick swipe-and-reopen often keeps the process alive (a warm start). For a true cold start, force-stop the app (App info → Force stop, or adb shell am force-stop com.duckduckgo.mobile.android.debug) before relaunching.

1. Cold start — last tab was a Regular tab

• Open a Regular tab on a real site (e.g. example.com); background it.
• Cold start the app.
• Expect: opens in Regular mode on the NTP with a "Return to… <site>" hatch; tapping it returns to that tab.

2. Cold start — last tab was a Fire tab

• Enter Fire mode, open a Fire tab on a site / Duck.ai chat.
• Cold start the app.
• Expect: opens in Regular mode; the hatch shows "Last used Fire Tab" with the fire placeholder icon, and never the Fire tab's real title/URL/favicon (privacy).
• Tap the hatch → switches into Fire mode and opens that exact Fire tab — not a new/blank Fire tab.

2b. Cold start — Fire tab, returned from the search / input screen

• Repeat scenario 2's setup (cold start with the last-used tab being a Fire tab).
• On the Regular-mode NTP, tap the address bar / search to open the input screen — the same "Last used Fire Tab" hatch appears there.
• Tap it → switches into Fire mode and opens that exact Fire tab (not a new/blank Fire tab).

3. Hot start in Fire mode

• In Fire mode, background the app, then reopen (warm — don't kill the process).
• Expect: a new Fire tab opens, with no escape hatch.

4. Hot start in Regular mode

• In Regular mode, background the app, then reopen.
• Expect: existing behavior — the hatch returns to the last Regular tab.

5. Fire-target hatch controls

• On the Fire-target hatch (scenario 2), overflow ⋮ → Close Tab removes the Fire tab; Undo restores it. (Known: the 🔥 burn button is a no-op for Fire tabs for now, pending cross-mode single-tab clearing.)

6. fireTabs OFF reverts cleanly

• Disable the flag in the internal feature-flag inventory (dev settings → Feature flags → fireMode → turn off fireTabs), then fully restart the app (Fire-mode availability is cached per process).
• Repeat scenario 2's setup.
• Expect: the hatch behaves like the previous Regular-only escape hatch — no "Last used Fire Tab"; only Regular tabs are offered.

---

Note

Medium Risk
Changes browser mode switching, first-screen/launch behavior after activity recreate, and cross-repo tab lifecycle; privacy behavior for Fire targets is intentional but must stay correct under edge cases (flag off, Fire mode active, stale idle state).

Overview
Extends the after-idle “Return to…” escape hatch so it can offer the user’s most recently used tab across Regular and Fire (when fireTabs is available), not just the last Regular tab.

A new EscapeHatchTargetResolver picks the winner by last-access time and returns tab id + owning BrowserMode. The hatch UI shows “Last used Fire Tab” with a fire placeholder for Fire targets and does not surface Fire tab title, URL, or favicon in Regular-mode UI. Close/undo/commit for the hatch routes tab mutations to the correct mode’s TabRepository.

Tapping the hatch (NTP or input screen) now goes through openExistingTabInMode, which stashes PendingAction.OpenExistingTab across activity recreate via the existing switchModeThen / PendingModeSwitch bundle path. The input screen result adds TAB_MODE_PARAM alongside tab id.

ModeSwitchRecreateSignal marks programmatic mode-switch recreates so FirstScreenHandler skips launch/inactivity handling that would otherwise inject an extra NTP and override the deferred open-tab action. ShowOnAppLaunchOptionHandler is updated to respect current mode (e.g. no Regular-only “specific page” / LUT analytics in Fire; NTP-after-idle hatch classification only in Regular).

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[0nko]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Fire mode: Escape hatch #8917 👈 (View in Graphite)
• Fire Mode: Prepare fire dialog #8902
• Fire Mode: Disable chat sync  #8792
• Fire Mode: Separate Duck chat data #8791
• Fire Mode: Empty state pages #8748
• Fire Mode: Launch NTP in different modes #8742
• Fire Mode: Duck.ai and input widget theme overlay #8725
• Fire Mode: Themes and styles #8714
• develop

This stack of pull requests is managed by Graphite. Learn more about stacking.

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