[Bug]: In-app Browser opens a new tab for every navigation and never reuses or closes one — the tab strip fills with identical duplicate tabs #596

What happens

Using the in-app Browser (right-side FilePanel) in a Desktop session, every page visit appends a new tab. Nothing reuses or closes a tab, so after a few iterations the tab strip is full of identical entries with the same title and the same URL.

On my machine (3.1.10.145, Windows) the persisted tab registry currently holds:

session A: 9 tabs
  [0] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port>/index.html#/report
  [1] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port>/index.html#/report
  [2] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port>/index.html#/report
  [3] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port>/index.html#/report   <-- same URL x4
  [4] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port2>/index.html#/report
  [5] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port2>/index.html#/exec
  [6] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port3>/index.html#/project
  [7] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port3>/index.html#/scan
  [8] 合板预检 · Conform Pre-flight  http://127.0.0.1:<port3>/index.html#/colour

session B: 7 tabs, all http://localhost:<port>/home/analysis

The tab strip shows 7 tabs all titled "合板预检 · Conform Pre-flight" — visually indistinguishable from each other.

Steps to reproduce

1. Desktop app → open a session → use the in-app Browser on a page you iterate on (a local dev server is easiest: http://127.0.0.1:<port>/index.html#/report).
2. In the same session, have the agent look at that page several times (re-check after a change, re-read the report, ...), or open the same link again.
3. Look at the Browser tab strip: one new tab per visit, all with the same title and URL.

Expected and actual behavior

Expected: revisiting a URL the Browser already has open focuses/reuses that tab — or at minimum the agent can close the tabs it opened.

Actual: unbounded tab growth, all duplicates. No agent-side way to clean up, and the duplicates are persisted across restarts.

Root cause (from the shipped 3.1.10 main-process bundle)

1. navigate refuses to reuse a loaded tab. embedded-browser-manager.js → runAgentBrowserAction():

   if (tool === 'navigate' && hasLoadedBrowserPage(tab.url) && rawArgs.replaceCurrentTab !== true) {
     throw new Error('CURRENT_TAB_OCCUPIED: Current Browser tab already has a loaded page; retry with open_tab');
   }

   The tool schema (builtin-browser-defs.js) tells the model: "Set true only when the user explicitly asked to replace or reuse the currently loaded Browser tab. Omit it for blank tabs and use open_tab to preserve a loaded page." The provider guidance repeats it: "Use navigate only when the current FilePanel tab is absent or blank… use open_tab by default to preserve it." So for any already-loaded tab the model is steered to open_tab.

2. open_tab always creates a new tab. openAgentTab() calls this.openTab({ active: false, bounds: OFFSCREEN_BOUNDS, sessionId }), which allocates a fresh tabId + WebContentsView, then navigates it and returns openedInNewTab: true. There is no lookup for an existing tab with the same URL.

3. The agent cannot close tabs. BROWSER_BROKER_ACTIONS (dist/main/modules/local-runtime/utility/control.js) exposes open_tab but no close_tab. Nothing in the agent tool surface can destroy a tab.

4. The "new tab" IPC path only dedupes in-flight calls. createNewEmbeddedBrowserTab() keeps a pending map keyed by sessionId + initialUrl and returns the in-flight promise; sequential opens of the same URL are never deduped against existing tabs.

5. Persistence keeps the duplicates. persistent-browser-registry.js: MAX_PERSISTED_BROWSER_TABS_PER_SESSION = 10, .slice(-10), no URL dedup — up to 10 identical entries are persisted and restored, and older ones are silently dropped.

Net effect: N navigations = N tabs, with no reuse path and no close path.

Suggested fixes (any one helps a lot)

• open_tab: if a tab in the session already has the same normalized URL, focus + navigate it in place instead of creating a new one (or add an explicit reuse mode).
• Add a close_tab action, and/or auto-close agent-opened tabs when the turn that opened them ends.
• Let navigate replace the current tab by default when that tab was opened by the agent rather than by the user.
• Dedupe by URL in PersistentBrowserRegistry, and cap live tabs per session with LRU eviction.

Environment

• Desktop app 3.1.10.145, Windows 11 x64 (10.0.26200)
• In-app Browser provider: electron-file-panel
• Registry file: %APPDATA%/MiniMax/embedded-browser-tabs.json (electron-store, name embedded-browser-tabs)