Preserve agent-browser configuration during viewport setup and stream discovery

docs/specs/dor-browser.md

@@ -111,7 +111,7 @@ Source of truth: `lib/src/components/wall/AgentBrowserScreenModal.tsx`, `offered
 
 **Must preserve the current device-pixel ratio when DPR is omitted.** A ratio the provider cannot apply fails before changing dimensions; Playwright accepts only its context's current ratio. **Never turn an observed Playwright DPR into an explicit request for future contexts.** Presets describe viewport geometry, not devices.
 
-**Must apply initial dimensions before the destination page's first script runs**, for managed CLI, GUI and Tool launches. Deferred `pane-sync` launches start at a fixed size until placement. **Must engage sync when resolving that preset**, sending the actual pane dimensions on first attach. A failed initialization never navigates at a silently substituted size. **Must apply a renderer and viewport chosen together to the new renderer.**
+**Must apply initial dimensions before the destination page's first script runs**, for managed CLI, GUI and Tool launches. **Must preserve explicit launch configuration through preparation and stream discovery** (rationale). Deferred `pane-sync` starts fixed until placement. **Must engage sync when resolving that preset**, sending the actual pane dimensions on first attach. Failed initialization never navigates at a substituted size. **Must apply a renderer and viewport chosen together to the new renderer.**
 
 **Must query the active page's measured CSS dimensions and DPR**, never infer them from the pane or a screenshot. `dor`'s sizing commands share the Display modal's serialized writes (`docs/specs/dor-cli.md` → Browser viewport control).
 

docs/specs/dor-browser.rationale.md

@@ -16,6 +16,10 @@
 
 **Why a reuse is one intent.** Revealing the target and then asking for its mode and its URL separately sent `open <url>` in the same tick as a pop-out began its close/reopen, deterministically: the navigation raced the relaunch, which had already captured the old URL.
 
+## Viewport presets
+
+Viewport preparation with agent-browser 0.27.0 (Windows, 2026-10-21): dropping `--config` after the blank navigation replaced the temporary profile with the occupied default profile, failing the DPR query. The native daemon compares launch settings on each call; preparation and stream discovery therefore keep the browser configuration consistent while leaving output controls on the user command. The [0.39.1 launch hash](https://github.com/vercel-labs/agent-browser/blob/1165952d74ceed98fdc2dd97190ad41f44dd0e24/cli/src/native/actions.rs#L293-L330) also includes scrollbar and domain restrictions (checked 2026-10-21).
+
 ## Display Modal And Render Swaps
 
 **Why the iframe swap is eager.** A 1–3s daemon boot behind a modal that has already closed; and while the swap awaited `open`, a slow page held the iframe on screen for the whole load and a timed-out `open` dropped the swap silently — leaving an orphan `gui-<hex>` browser nobody could see or close.

dor/src/commands/browser-cli.ts

@@ -231,6 +231,30 @@ const AGENT_BROWSER_BOOLEAN_FLAGS = new Set([
   '--confirm-interactive', '--no-auto-dialog', '--verbose', '-v', '--quiet', '-q', '--debug', '--restore',
 ]);
 
+// Each native CLI call can reconfigure the daemon. Changing these options
+// between the blank page and the viewport writes can replace its browser.
+// Output flags stay on the user's command: quiet/boundaries would hide the DPR.
+const AGENT_BROWSER_LAUNCH_FLAGS = new Set([
+  '--config', '--profile', '--executable-path', '--extension', '--args', '--proxy', '--proxy-bypass',
+  '--user-agent', '--allow-file-access', '--headed', '--ignore-https-errors', '--color-scheme',
+  '--download-path', '--engine', '--enable', '--init-script', '--hide-scrollbars', '--allowed-domains',
+]);
+
+/** The same launch settings must accompany every internal native call. */
+function agentBrowserLaunchOptions(args: string[]): string[] {
+  const options: string[] = [];
+  for (let i = 0; i < args.length; i += 1) {
+    const arg = args[i]!;
+    if (arg === '--') break;
+    const name = arg.split('=', 1)[0]!;
+    const start = i;
+    if (AGENT_BROWSER_VALUE_FLAGS.has(name) && !arg.includes('=')) i += 1;
+    else if (AGENT_BROWSER_BOOLEAN_FLAGS.has(name) && ['true', 'false'].includes(args[i + 1] ?? '')) i += 1;
+    if (AGENT_BROWSER_LAUNCH_FLAGS.has(name)) options.push(...args.slice(start, i + 1));
+  }
+  return options;
+}
+
 /** Build a blank navigation with every launch option preserved. Unknown flags
  * are refused: guessing their arity could replace a flag value and let the
  * destination page run before its viewport is ready. */
@@ -429,6 +453,7 @@ export async function runBrowserCli(d: BrowserCliDescriptor, args: string[], opt
     ? exec(binaryPath ?? binary, argv, cwd, envOverride)
     : cwd === undefined ? exec(binaryPath ?? binary, argv) : exec(binaryPath ?? binary, argv, cwd);
 
+  const nativeLaunchOptions = d.provider === 'agent-browser' ? agentBrowserLaunchOptions(rest) : [];
   let result: BrowserExecResult;
   let prebound = false;
   const explicitDevice = d.provider === 'agent-browser'
@@ -445,11 +470,11 @@ export async function runBrowserCli(d: BrowserCliDescriptor, args: string[], opt
       if (blank.exitCode !== 0) return fail(`Could not prepare the agent-browser viewport before navigation: ${blank.stderr.trim() || `agent-browser exited ${blank.exitCode}`}`);
       let dpr = launchViewport.dpr;
       if (dpr === undefined) {
-        const ratio = await run([...sessionArgs, 'eval', 'window.devicePixelRatio']);
+        const ratio = await run([...sessionArgs, ...nativeLaunchOptions, 'eval', 'window.devicePixelRatio']);
         dpr = ratio.exitCode === 0 ? parseNativeDpr(ratio.stdout) : undefined;
         if (dpr === undefined) return fail('Could not measure agent-browser DPR before navigation');
       }
-      const viewport = await run([...sessionArgs, 'set', 'viewport', String(launchViewport.width), String(launchViewport.height), String(dpr)]);
+      const viewport = await run([...sessionArgs, ...nativeLaunchOptions, 'set', 'viewport', String(launchViewport.width), String(launchViewport.height), String(dpr)]);
       if (viewport.exitCode !== 0) return fail(`Could not set the agent-browser viewport before navigation: ${viewport.stderr.trim() || `agent-browser exited ${viewport.exitCode}`}`);
     }
     const playwrightOpen = d.provider === 'playwright' && command === 'open' && launchViewport !== undefined && !explicitDevice;
@@ -499,7 +524,7 @@ export async function runBrowserCli(d: BrowserCliDescriptor, args: string[], opt
   if (result.exitCode === 0 && mayBind && binding.session !== undefined && !(client instanceof Error) && !prebound) {
     try {
       const statusArgs = d.streamStatus?.(binding.session);
-      const wsPort = statusArgs === undefined ? undefined : parseStreamPort((await run(statusArgs)).stdout);
+      const wsPort = statusArgs === undefined ? undefined : parseStreamPort((await run([...statusArgs, ...nativeLaunchOptions])).stdout);
       await client.browserSurface({
         provider: d.provider,
         key: flags.key,

dor/test/browser-viewport.test.mjs

@@ -103,6 +103,44 @@ test('agent-browser preparation preserves valued flags and only replaces the des
   assert.deepEqual(argsSeen[3].slice(2), ['--proxy', 'http://localhost:7890', 'open', 'http://localhost:5173', '--headers', '{"Authorization":"token"}']);
 });
 
+for (const flags of [
+  ['--config', '/tmp/browser.json', '--profile=/tmp/browser profile'],
+  ['--profile', '/tmp/browser', '--hide-scrollbars', 'true', '--allowed-domains=localhost'],
+  ['--headed', 'false', '--args', '--disable-gpu', '--proxy=http://localhost:7890', '--allow-file-access'],
+]) test('viewport preparation keeps browser launch options: ' + flags[0], async () => {
+  const calls = [];
+  const result = await runCli(['agent-browser', 'open', 'http://localhost:5173', ...flags, '--quiet'], {
+    env: { PWD: process.cwd() },
+    client: {
+      resolveBrowser: async () => ({ binding: { session: 'dormouse.1.default' }, fresh: true,
+        initialViewport: { mode: 'fixed', width: 1440, height: 900 }, launchViewport: { width: 1440, height: 900 } }),
+      browserSurface: async () => ({}),
+    },
+    execAgentBrowser: async (_binary, args) => {
+      calls.push(args);
+      return { exitCode: 0, stdout: args.includes('eval') ? '2\n' : '', stderr: '' };
+    },
+  });
+  assert.equal(result.exitCode, 0, result.stderr);
+  assert.deepEqual(calls[1], ['--session', 'dormouse.1.default', ...flags, 'eval', 'window.devicePixelRatio']);
+  assert.deepEqual(calls[2], ['--session', 'dormouse.1.default', ...flags, 'set', 'viewport', '1440', '900', '2']);
+  assert.deepEqual(calls[3], ['--session', 'dormouse.1.default', 'open', 'http://localhost:5173', ...flags, '--quiet']);
+  assert.deepEqual(calls[4], ['--session', 'dormouse.1.default', 'stream', 'status', '--json', ...flags]);
+});
+
+test('stream discovery preserves custom configuration after a non-navigation command', async () => {
+  const calls = [];
+  const result = await runCli(['agent-browser', '--config=/tmp/browser.json', 'eval', 'window.devicePixelRatio'], {
+    client: {
+      resolveBrowser: async () => ({ binding: { session: 'dormouse.1.default' }, fresh: false }),
+      browserSurface: async () => ({}),
+    },
+    execAgentBrowser: async (_binary, args) => { calls.push(args); return { exitCode: 0, stdout: '1', stderr: '' }; },
+  });
+  assert.equal(result.exitCode, 0, result.stderr);
+  assert.deepEqual(calls[1], ['--session', 'dormouse.1.default', 'stream', 'status', '--json', '--config=/tmp/browser.json']);
+});
+
 test('open-target sugar ignores a proxy flag value', async () => {
   const argsSeen = [];
   const options = {