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cmux/docs/agent-browser-port-spec.md
Lawrence Chen 50f0dd334d
Fix frozen terminals after split churn (#12) 
* Fix blank terminal after split operations and add visual tests

## Blank Terminal Fix
- Add `needsRefreshAfterWindowChange` flag in GhosttyTerminalView
- Force terminal refresh when view is added to window, even if size unchanged
- Add `ghostty_surface_refresh()` call in attachToView for same-view reattachment
- Add debug logging for surface attachment lifecycle (DEBUG builds only)

## Bonsplit Migration
- Add bonsplit as local Swift package (vendor/bonsplit submodule)
- Replace custom SplitTree with BonsplitController
- Add Panel protocol with TerminalPanel and BrowserPanel implementations
- Add SidebarTab as main tab container with BonsplitController
- Remove old Splits/ directory (SplitTree, SplitView, TerminalSplitTreeView)

## Visual Screenshot Tests
- Add test_visual_screenshots.py for automated visual regression testing
- Uses in-app screenshot API (CGWindowListCreateImage) - no screen recording needed
- Generates HTML report with before/after comparisons
- Tests: splits, browser panels, focus switching, close operations, rapid cycles
- Includes annotation fields for easy feedback

## Browser Shortcut (⌘⇧B)
- Add keyboard shortcut to open browser panel in current pane
- Add openBrowser() method to TabManager
- Add shortcut configuration in KeyboardShortcutSettings

## Screenshot Command
- Add 'screenshot' command to TerminalController for in-app window capture
- Returns OK with screenshot ID and path

## Other
- Add tests/visual_output/ and tests/visual_report.html to .gitignore

* Add browser title subscription and set tab height to 30px

- Subscribe to BrowserPanel.$pageTitle changes to update bonsplit tabs
- Update tab titles in real-time as page navigation occurs
- Clean up subscriptions when panels are removed
- Set bonsplit tab bar and tab height to 30px (in submodule)

* Fix socket API regressions in list_surfaces, list_bonsplit_tabs, focus_pane

- list_surfaces: Remove [terminal]/[browser] suffix to keep UUID-only format
  that clients and tests expect for parsing
- list_bonsplit_tabs --pane: Properly look up pane by UUID instead of
  creating a new PaneID (requires bonsplit PaneID.id to be public)
- focus_pane: Accept both UUID strings and integer indices as documented

* Fix browser panel stability and keyboard shortcuts

- Prevent WKWebView focus lifecycle crashes during split/view reshuffles
- Match bracket shortcuts via keyCode (Cmd+Shift+[ / ], Cmd+Ctrl+[ / ])
- Support Ghostty config goto_split:* keybinds when WebView is focused
- Add focus_webview/is_webview_focused socket commands and regression tests
- Rename SidebarTab to Workspace and update docs

* Make ctrl+enter keybind test skippable

Skip when the Ghostty keybind isn't configured or when osascript can't send keystrokes (no Accessibility permission), so VM runs stay green.

* Auto-focus browser omnibar when blank

When a browser surface is focused but no URL is loaded yet, focus the address bar instead of the WKWebView.

* Stabilize socket surface indexing

* Focus browser omnibar escape; add webview keybind UI tests

- Escape in omnibar now returns focus to WKWebView\n- Add UI tests for Cmd+Ctrl+H pane navigation with WebKit focused (including Ghostty config)\n- Avoid flaky element screenshots in UpdatePillUITests on the UTM VM

* Fix browser drag-to-split blanks and socket parsing

* Fix webview-focused shortcuts and stabilize browser splits

- Match ctrl/shift shortcuts by keyCode where needed (Ctrl+H, bracket keys)
- Load Ghostty goto_split triggers reliably and refresh on config load
- Add debug socket helpers: set_shortcut + simulate_shortcut for tests
- Convert browser goto_split/keybind tests to socket-based injection (no osascript)
- Bump bonsplit for drag-to-split fixes

* Fix split layout collapse and harden socket pane APIs

* Stabilize OSC 99 notification test timing

* Fix terminal focus routing after split reparent

* Support simulate_shortcut enter for focus routing test

* Stabilize terminal focus routing test

* Fix frozen new terminal tabs after many splits

* Fix frozen new terminal tabs after splits

* Fix terminal freeze on launch/new tabs

* Update ghostty submodule

* Fix terminal focus/render stalls after split churn

* Fix nested split collapsing existing pane

* Fix nested split collapse + stabilize new-surface focus

* Update bonsplit submodule

* Fix SIGINT test flake

* Remove bonsplit tab-switch crossfade

* Remove PROJECTS.md

* Remove bonsplit tab selection animation

* Ignore generated test reports

* Middle click closes tab

* Revert unintended .gitignore change

* Fix build after main merge

* Revert "Fix build after main merge"

This reverts commit 16bf9816d0856b5385d52f886aa5eb50f3c9d9a4.

* Revert "Merge remote-tracking branch 'origin/main' into fix/blank-terminal-and-visual-tests"

This reverts commit 7c20fb53fd71fea7a19a3673f2dd73e5f0c783c4, reversing
changes made to 0aff107d787bc9d8bbc28220090b4ca7af72e040.

* Remove tab close fade animation

* Use terminal.fill icon

* Make terminal tab icon smaller

* Match browser globe tab icon size

* Bonsplit: tab min width 48 and tighter close button

* Bonsplit: smaller tab title font

* Show unread notification badge in bonsplit tabs and improve UI polish

Sync unread notification state to bonsplit tab badges (blue dot).
Improve EmptyPanelView with Terminal/Browser buttons and shortcut hints.
Add tooltips to close tab button and search overlay buttons.

* Fix reload.sh single-instance safety check on macOS

Replace GNU-only `ps -o etimes=` with portable `ps -o etime=` and
parse the dd-hh:mm:ss format manually for macOS compatibility.

* Centralize keyboard shortcut definitions into Action enum

Replace per-shortcut boilerplate with a single Action enum that holds
the label, defaults key, and default binding for each shortcut. All
call sites now use shortcut(for:). Settings UI is data-driven via
ForEach(Action.allCases). Titlebar tooltips update dynamically when
shortcuts are changed. Remove duplicate .keyboardShortcut() modifiers
from menu items that are already handled by the event monitor.

* Fix WKWebView consuming app menu shortcuts and close panel confirmation

Add CmuxWebView subclass that routes key equivalents through the main
menu before WebKit, so Cmd+N/Cmd+W/tab switching work when a browser
pane is focused. Fix Cmd+W close-panel path: bypass Bonsplit delegate
gating after the user confirms the running-process dialog by tracking
forceCloseTabIds. Add unit tests (CmuxWebViewKeyEquivalentTests) and
UI test scaffolding (MenuKeyEquivalentRoutingUITests) with a new
cmux-unit Xcode scheme.

* Update CLAUDE.md and PROJECTS.md with recent changes

CLAUDE.md: enforce --tag for reload commands, add cleanup safety rules.
PROJECTS.md: log notification badge, reload.sh fix, Cmd+W fix, WebView
key equiv fix, and centralized shortcuts work.

* Keep selection index stable on close

* Add concepts page documenting terminology hierarchy

New docs page explaining Window > Workspace > Pane > Surface > Panel
hierarchy with aligned ASCII diagram. Updated tabs.mdx and splits.mdx
to use consistent terminology (workspace instead of tab, surface
instead of panel) and corrected outdated CLI command references.

* Update bonsplit submodule

* WIP: improve split close stability and UI regressions

* Close terminal panel on child exit; hide terminal dirty dot

* Fix split close/focus regressions and stabilize UI tests

* Add unread Dock/Cmd+Tab badge with settings toggle

* Fix browser-surface shortcuts and Cmd+L browser opening

* Snapshot current workspace state before regression fixes

* Update bonsplit submodule snapshot

* Stabilize split-close regression capture and sidebar resize assertions

* Change default Show Notifications shortcut from Cmd+Shift+I to Cmd+I

* Fix update check readiness race, enable release update logging, and improve checking spinner

* Restore terminal file drop, fix browser omnibar click focus, and add panel workspace ID mutation for surface moves

* Add Cmd+digit workspace hints, titlebar shortcut pills, sidebar drag-reorder, and workspace placement settings

* Add v2 browser automation API, surface move/reorder commands, and short-handle ref system to TerminalController

* Add CLI browser command surface, --id-format flag, and move/reorder commands

* Extend test clients with move/reorder APIs, ref-handle support, and increased timeouts

* Harden test runner scripts with deterministic builds, retry logic, and robust socket readiness

* Stabilize existing test suites with focus-wait helpers, increased timeouts, and API shape updates

* Add terminal file drop e2e regression test

* Add v2 browser API, CLI ref resolution, and surface move/reorder test suites

* Add unit tests for shortcut hints, workspace reorder, drop planner, and update UI test stabilization

* Add cmux-debug-windows skill with snapshot script and agent config

* Update project docs: mark browser parity and move/reorder phases complete, add parallel agent workflow guidelines

* Update bonsplit submodule: re-entrant setPosition guard, tab shortcut hints, and moveTab/reorderTab API

* Add browser agent UX improvements: snapshot refs, placement reuse, diagnostics, and skill docs

- Upgrade browser.snapshot to emit accessibility tree text with element refs (eN)
- Add right-sibling pane reuse policy for browser.open_split placement
- Add rich not_found diagnostics with retry logic for selector actions
- Support --snapshot-after for post-action verification on mutating commands
- Allow browser fill with empty text for clearing inputs
- Default CLI --id-format to refs-first (UUIDs opt-in via --id-format uuids|both)
- Format legacy new-pane/new-surface output with short surface refs
- Add skills/cmuxterm-browser/ and skills/cmuxterm/ end-user skill docs
- Add regression tests for placement policy, snapshot refs, diagnostics, and ID defaults

* Update bonsplit submodule: keep raster favicons in color when inactive
2026-02-13 16:45:31 -08:00

16 KiB
Raw Blame History

Agent-Browser Port Spec

Last updated: February 13, 2026
Source inventory snapshot: vercel-labs/agent-browser @ 03a8cb9

This document tracks implemented behavior and remaining parity gaps for the cmux browser port.

Goals

  1. Provide an LLM-friendly browser automation API in cmux with stable handles.
  2. Keep v1 CLI/socket behavior working while v2 reaches full parity.
  3. Port agent-browser command surface (where meaningful for WKWebView).
  4. Ensure move/reorder operations preserve surface_id identity.
  5. Rebuild/port tests so both v1 and v2 suites pass before deprecating v1.

Validation Status

As of February 12, 2026:

  1. ./scripts/run-tests-v1.sh passes on cmux-vm.
  2. ./scripts/run-tests-v2.sh passes on cmux-vm.
  3. Browser parity suites passing in v2: test_browser_api_comprehensive.py, test_browser_api_p0.py, test_browser_api_extended_families.py, test_browser_api_unsupported_matrix.py, and test_browser_cli_agent_port.py.
  4. Visual suite note: tests/test_visual_screenshots.py and tests_v2/test_visual_screenshots.py both report D12 (Nested: Close Top of T-shape) as a known non-blocking VM failure when it reproduces (VIEW_DETACHED).

Concepts (Canonical Terms)

  1. window: native macOS window.
  2. workspace: sidebar entry within a window (often called "tab" in UI).
  3. pane: split region inside a workspace.
  4. surface: tab within a pane (terminal or browser). This is the primary automation target.
  5. panel: internal implementation term; CLI/API should prefer surface.

Terminology decision:

  • Public v2 API and new CLI docs should standardize on surface and pane.
  • Keep --panel as compatibility alias in CLI until v1 is retired.

Self-Identify Requirement

system.identify is the canonical "where am I?" call for agents and should remain first-class.

Required response fields for agent workflows:

  1. focused.window_id
  2. focused.workspace_id
  3. focused.pane_id
  4. focused.surface_id
  5. caller validation result when caller context is supplied

Recommended extension for browser workflows:

  1. focused.surface_type
  2. focused.browser.url
  3. focused.browser.title
  4. focused.browser.loading

Agent-Browser Command Inventory

Top-Level CLI Verbs (from cli/src/commands.rs)

  1. open|goto|navigate
  2. back
  3. forward
  4. reload
  5. click
  6. dblclick
  7. fill
  8. type
  9. hover
  10. focus
  11. check
  12. uncheck
  13. select
  14. drag
  15. upload
  16. download
  17. press|key
  18. keydown
  19. keyup
  20. scroll
  21. scrollintoview|scrollinto
  22. wait
  23. screenshot
  24. pdf
  25. snapshot
  26. eval
  27. close|quit|exit
  28. connect
  29. get
  30. is
  31. find
  32. mouse
  33. set
  34. network
  35. storage
  36. cookies
  37. tab
  38. window
  39. frame
  40. dialog
  41. trace
  42. record
  43. console
  44. errors
  45. highlight
  46. state
  47. tap
  48. swipe
  49. device

CLI Subcommands

  1. get: text|html|value|attr|url|title|count|box|styles
  2. is: visible|enabled|checked
  3. find: role|text|label|placeholder|alt|title|testid|first|last|nth
  4. mouse: move|down|up|wheel
  5. set: viewport|device|geo|geolocation|offline|headers|credentials|auth|media
  6. network: route|unroute|requests
  7. storage: local|session + get|set|clear
  8. cookies: default get, plus set|clear
  9. tab: default list, plus new|list|close|<index>
  10. window: new
  11. frame: <selector>|main
  12. dialog: accept|dismiss
  13. trace: start|stop
  14. record: start|stop|restart
  15. state: save|load
  16. device: list

Global Flags

  1. --json
  2. --full|-f
  3. --headed
  4. --debug
  5. --session
  6. --headers
  7. --executable-path
  8. --extension (repeatable)
  9. --cdp
  10. --profile
  11. --state
  12. --proxy
  13. --proxy-bypass
  14. --args
  15. --user-agent
  16. -p|--provider
  17. --ignore-https-errors
  18. --allow-file-access
  19. --device

Protocol Actions in src/protocol.ts

Counts:

  1. total actions: 125
  2. directly emitted by CLI parser: 93
  3. protocol-only (not directly emitted by CLI parser): 32

Protocol-only action names:

  1. addinitscript
  2. addscript
  3. addstyle
  4. bringtofront
  5. clear
  6. clipboard
  7. content
  8. dispatch
  9. evalhandle
  10. expose
  11. har_start
  12. har_stop
  13. innertext
  14. input_keyboard
  15. input_mouse
  16. input_touch
  17. inserttext
  18. keyboard
  19. locale
  20. multiselect
  21. pause
  22. permissions
  23. responsebody
  24. screencast_start
  25. screencast_stop
  26. selectall
  27. setcontent
  28. setvalue
  29. timezone
  30. useragent
  31. video_start
  32. video_stop

cmux Target API (v2)

Already Present in cmux

  1. system.ping
  2. system.capabilities
  3. system.identify
  4. window.list|current|focus|create|close
  5. workspace.list|create|select|current|close|move_to_window
  6. pane.list|focus|surfaces|create
  7. surface.list|focus|split|create|close|drag_to_split|refresh|health|send_text|send_key|trigger_flash
  8. browser.open_split|navigate|back|forward|reload|url.get|focus_webview|is_webview_focused
  9. notification methods and debug/test methods

New Browser Parity Method Families (Proposed)

P0 (core parity for daily automation):

  1. browser.snapshot
  2. browser.eval
  3. browser.wait
  4. browser.click
  5. browser.dblclick
  6. browser.type
  7. browser.fill
  8. browser.press|keydown|keyup
  9. browser.hover|focus
  10. browser.check|uncheck
  11. browser.select
  12. browser.scroll|scroll_into_view
  13. browser.get.* (url|title|text|html|value|attr|count|box|styles)
  14. browser.is.* (visible|enabled|checked)
  15. browser.screenshot
  16. browser.focus_webview and browser.is_webview_focused (already present, keep)

P1 (important but not blocking initial parity):

  1. browser.find.* locators (role|text|label|placeholder|alt|title|testid|nth|first|last)
  2. browser.frame.select
  3. browser.frame.main
  4. browser.dialog.respond
  5. browser.download.wait
  6. browser.tab.* compatibility aliases mapped to cmux surfaces
  7. browser.console.list
  8. browser.errors.list
  9. browser.highlight
  10. browser.state.save|load (browser state in cmux context)

P2 (advanced parity / optional):

  1. network interception/mocking equivalents (route|unroute|requests|responsebody)
  2. emulation/settings (viewport|media|offline|geolocation|permissions|headers|credentials|useragent|locale|timezone|device)
  3. trace/video/screencast/har equivalents
  4. script injection utilities (addinitscript|addscript|addstyle|dispatch|expose|evalhandle)
  5. raw input device injection (input_mouse|input_keyboard|input_touch)

Object/Handle Semantics

  1. stable handles: window_id, workspace_id, pane_id, surface_id
  2. browser refs (@e1) are session-local and ephemeral
  3. move/reorder must preserve surface_id
  4. responses may include index for debugging/order, but requests should accept IDs

CLI Spec (Proposed)

Primary form:

cmux browser --surface <surface-id> <agent-browser-style-command...>

Shorthand:

cmux browser <surface-id> <agent-browser-style-command...>

Agent discovery:

cmux identify
cmux capabilities
cmux browser identify --surface <surface-id>   # wrapper over system.identify + browser fields

Flash:

cmux trigger-flash [--workspace <id>] [--surface <id>]

Compatibility:

  1. Keep v1 commands.
  2. Add v1->v2 shim for migrated browser/surface commands.
  3. Keep --panel as alias for --surface during migration.

Move/Reorder Spec (Required)

Required capabilities:

  1. reorder surfaces within a pane
  2. move surfaces between panes in same workspace
  3. move surfaces across workspaces
  4. move surfaces across windows
  5. reorder workspaces within window

Proposed methods:

  1. surface.move with surface_id + destination (pane_id or workspace_id/window_id) + placement (before_surface_id|after_surface_id|start|end)
  2. surface.reorder with surface_id + sibling anchor (before_surface_id|after_surface_id)
  3. workspace.reorder with workspace_id + anchor (before_workspace_id|after_workspace_id)

Hard invariant:

  1. surface_id must remain unchanged after all move/reorder operations.

Comprehensive TODO

Phase 0: Contract + Routing

  • Lock method names/payload schemas for all new browser.* methods.
  • Add schema validation for each new method with strict error codes (invalid_params, not_found, invalid_state).
  • Add browser command group in CLI/cmux.swift that accepts agent-browser-style command grammar.
  • Add --surface mandatory targeting (with fallback from system.identify when explicitly desired).
  • Add consistent JSON output mode for all browser commands.
  • Implement short-ref allocator and resolver for window/pane/workspace/surface (window:N, workspace:N, pane:N, surface:N).
  • Add --id-format refs|uuids|both across relevant CLI commands (--json default refs, plain-text default refs).
  • Ensure browser placement APIs always return decision-rich metadata (resolved target pane, created splits, resulting handles).

Phase 1: Core Browser Parity (P0)

  • Implement browser.snapshot (with refs).
  • Implement browser.eval.
  • Implement browser.wait variants: selector, timeout, URL pattern, load state, function, text.
  • Implement click family: click, dblclick, hover, focus.
  • Implement input family: type, fill, press, keydown, keyup.
  • Implement checkbox/select family: check, uncheck, select.
  • Implement scrolling family: scroll, scroll_into_view.
  • Implement getters: text/html/value/attr/url/title/count/box/styles.
  • Implement state checks: visible/enabled/checked.
  • Implement screenshots (surface/full-page where feasible).

Phase 2: Locator + Session Parity (P1)

  • Implement browser.find.role.
  • Implement browser.find.text.
  • Implement browser.find.label.
  • Implement browser.find.placeholder.
  • Implement browser.find.alt.
  • Implement browser.find.title.
  • Implement browser.find.testid.
  • Implement browser.find.nth|first|last.
  • Implement frame context switching (frame.select, frame.main).
  • Implement dialog handling (accept, dismiss, optional prompt text).
  • Implement download waiting.
  • Implement console/error buffers and retrieval.
  • Implement highlight helper.
  • Implement browser state save/load format.

Phase 3: Move/Reorder + Window/Workspace Integration

  • Implement surface.move with handle-based destination rules.
  • Implement surface.reorder within pane.
  • Implement cross-workspace surface moves.
  • Implement cross-window surface moves.
  • Implement workspace.reorder.
  • Add CLI commands for tab/surface reordering and moving (move-surface, reorder-surface, reorder-workspace).
  • Add response payloads that confirm final window_id/workspace_id/pane_id/surface_id.
  • Add explicit invariants tests for surface_id stability.

Phase 4: Advanced/Optional Parity (P2)

  • Evaluate feasibility of request interception/mocking in WKWebView; implement supported subset.
  • Add emulation settings that are feasible in WKWebView.
  • Add trace/recording equivalents where practical.
  • Add script/style injection helpers.
  • Document unsupported commands with explicit error not_supported.

Phase 5: Compatibility + Migration

  • Add v1-to-v2 shim for migrated command families.
  • Keep existing v1 behavior unchanged while shim is active.
  • Document v1/v2 mapping table for all browser/topology commands.
  • Add deprecation warnings only after parity + test completion.

Phase 6: Docs + Examples

  • Update docs/v2-api-migration.md with browser parity status.
  • Add dedicated browser automation doc in docs-site.
  • Add examples for LLM workflow: identify -> choose surface -> snapshot -> act -> verify.
  • Add explicit "surface vs pane vs workspace vs window" section to CLI docs.

Test Port Plan (Comprehensive)

Port Targets from agent-browser

  1. src/browser.test.ts -> ported/adapted into:
    • tests_v2/test_browser_api_p0.py
    • tests_v2/test_browser_api_comprehensive.py
    • tests_v2/test_browser_api_unsupported_matrix.py
  2. src/actions.test.ts -> adapted negative coverage in tests_v2/test_browser_api_comprehensive.py (invalid_params, not_found, timeout).
  3. src/protocol.test.ts -> adapted browser command/shape validation in tests_v2/test_browser_api_unsupported_matrix.py and existing CLI/cmux.swift command grammar checks.
  4. test/file-access.test.ts and test/launch-options.test.ts -> partially applicable to WKWebView; currently tracked as follow-up parity work (not blocking current browser method coverage).
  5. src/daemon.test.ts, src/stream-server.test.ts, test/serverless.test.ts, src/ios-manager.test.ts -> out-of-scope for cmux browser parity (different transport/runtime).

Implemented cmux Browser Suites

  1. tests_v2/test_browser_api_p0.py
  2. tests_v2/test_browser_api_comprehensive.py
  3. tests_v2/test_browser_api_unsupported_matrix.py
  4. tests_v2/test_browser_goto_split.py
  5. tests_v2/test_browser_panel_stability.py
  6. tests_v2/test_browser_custom_keybinds.py

Test Design Rules

  1. Prefer deterministic local fixtures (embedded HTML or local HTTP server), not public websites.
  2. Every command gets at least one positive and one negative test.
  3. Every handle-accepting API gets tests for UUID target and index-compat shim target.
  4. Every move/reorder test asserts surface_id stability pre/post operation.
  5. Browser tests must verify behavior from both focused and unfocused webview states.
  6. Self-identify tests must validate focused and caller fields.

Migration Gate Criteria

  1. New browser parity tests in tests_v2/ pass.
  2. Existing v2 regression suites still pass.
  3. v1 suites still pass with shim active.
  4. No regressions in existing window/workspace/surface workflows.

Planned verification commands at implementation completion:

  1. ssh cmux-vm 'cd /Users/cmux/GhosttyTabs && ./scripts/run-tests-v2.sh'
  2. ssh cmux-vm 'cd /Users/cmux/GhosttyTabs && ./scripts/run-tests-v1.sh'

Decision Log (Locked - February 12, 2026)

  1. cmux browser tab ... maps to browser surface tabs only (no separate workspace-level tab meaning inside browser namespace).
  2. Default browser placement without explicit target is caller-relative: reuse the nearest right sibling pane; if none exists, split right from the caller pane.
  3. Deeply nested layouts use local split ancestry: choose the nearest right sibling leaf in the caller's subtree path and avoid reshuffling unrelated panes.
  4. Network parity target is full parity (not block-only phase).
  5. Output shape is cmux-native overall, but browser.snapshot and selector not_found diagnostics intentionally mirror agent-browser semantics for agent usability.
  6. ID model accepts UUIDs and short refs.
  7. Short ref format uses full words and colon: surface:N, pane:N, workspace:N, window:N.
  8. Short refs are global per daemon, monotonic, and never reused until daemon restart.
  9. Plain-text CLI output defaults to short refs.
  10. JSON output defaults to short refs (UUIDs available via --id-format uuids|both).
  11. CLI supports --id-format refs|uuids|both for output shaping.
  12. Browser create/move commands should expose enough placement/result metadata for agents to make deterministic follow-up decisions.
  13. Reuse behavior is implicit by default (caller-relative right-pane reuse); explicit handles can still force deterministic targeting.
  14. browser fill accepts empty text and treats it as a clear operation.
  15. Mutating browser actions can opt into post-action verification snapshots via snapshot_after (--snapshot-after in CLI), returning post_action_snapshot (+ refs/title/url).
  16. Legacy new-pane/new-surface plain output prefers short surface:N refs under default CLI ID formatting.

Remaining Open Decisions

  1. Unsupported command policy: strict not_supported errors vs best-effort fallback for commands that cannot be implemented on WKWebView with correct semantics.
  2. Whether to expose protocol-only agent-browser actions in first public release of cmux browser or gate them behind a second rollout phase.