Consolidate JetBrains model pickers into a shared PickerPopup base

Goal

Remove duplication between the two list-picker popups in the JetBrains frontend by extracting a generic base, and make both consume it:

1. Prompt model picker — session/ui/model/ModelPicker.kt (showPopup) — single-select commit, search field, expand/collapse details panel, sections, per-row favorite (star) toggle.
2. Custom provider model picker — settings/providers/ProvidersSettingsUi.kt (showModelPopup inside CustomProviderDialog) — multi-select toggle, no search, no details, selection stored in the models text field.

The base must expose configurable options; the provider picker enables: multi-select, no expanded/details view, and extra header toolbar buttons ("Select All" / "Deselect All").

All work is under packages/kilo-jetbrains/frontend/. No backend/RPC/DTO changes. Files are Kilo-owned (no kilocode_change markers).

Resolved decisions

• Approach: Extract a generic PickerPopup<T> base; both pickers become thin configs.
• Selection state: Caller owns it. Base is selection-stateless: it calls checked(row) to render check state and onPrimary(row) on activation. Provider keeps the models text field as source of truth; prompt keeps its favorites callbacks.
• Select All / Deselect All: Two caller-supplied header toolbar buttons. Remove the in-list CustomModelRow.selectAll row entirely.
• Renderer: Extract a base renderer skeleton too; ModelPickerRenderer and the provider renderer extend it. Generalize the favorite hit-zone into a trailing click-zone helper.
• Location: New package ai/kilocode/client/ui/picker/ with PickerPopup<T> and PickerListRenderer<T>. PickerRow and ModelSearch stay where they are and are reused.

Base design

ui/picker/PickerPopup.kt — generic popup

Owns: JBList<T> + CollectionListModel<T>, createComponentPopupBuilder with the shared flags (requestFocus/focusable/cancelOnClickOutside/cancelKeyEnabled/cancelOnWindowDeactivation/ locateWithinScreenBounds, non-resizable, non-movable), popupBackground helper (move the duplicated NewUI -> Popup.BACKGROUND else getListBackground() here), header assembly, mouse hit-testing, keyboard bindings, auto-select-on-move + scrolling install, and size computation.

Config (constructor params / vars, defaults match current behavior):

• anchor: JComponent, placement: Placement (ABOVE / BELOW / UNDERNEATH). Prompt uses PopupShowOptions.aboveComponent / showUnderneathOf; provider uses showUnderneathOf(pick).
• rows: (query: String) -> List<T> — rebuilt when the search text changes. Provider passes a function that ignores query.
• renderer: PickerListRenderer<T>.
• checked: (T) -> Boolean — drives the row check icon (single: row.key == active; multi: isSelected(row)).
• sectionTitle: (rows: List<T>, index: Int) -> String? — optional; prompt supplies modelPickerSectionTitle, provider passes { _, _ -> null }.
• mode: Mode = Single | Multi.
  • Single: on primary click/ENTER call onPrimary(row) then popup.closeOk(null).
  • Multi: on primary click/SPACE/ENTER call onPrimary(row), repaint, stay open.
• onPrimary: (T) -> Unit. (Prompt decides activate-vs-clear inside based on row.item == null; provider toggles membership in the text field.)
• Optional trailing toggle: trailingHit: (list, bounds, point) -> Boolean and onTrailing: (T) -> Unit. Prompt supplies favorite hit-zone + favorite toggle; provider omits. Keyboard: in Single mode Shift+SPACE triggers trailing when present.
• search: Boolean — show SearchTextField in header CENTER. Prompt true; provider false.
• toolbar: List<JComponent> — extra header buttons placed in header WEST. Provider passes Select All / Deselect All; prompt passes empty.
• Optional details/expand: details: JComponent? + onPreview: (T?) -> Unit + expandStateKey: String?. When non-null, base shows the expand HoverIcon, EAST details panel, persists expanded state via PropertiesComponent, reserves details width when expanded, and Disposer.register(popup, details) if details is Disposable. Provider passes null (no expand toggle, no details).
• Sizing: minWidth, maxWidth, maxVisibleRows, emptyListHeight (defaults = current ModelPicker constants 420/760/10/120). Provider passes minWidth = 320 and a maxWidth that preserves today's look. Reuse the existing computeInitialPopupSize / computeListPreferredWidth / computeListPreferredHeight logic, moved into the base and parameterized by these constants + optional details width.

Header layout: BorderLayout with toolbar row WEST, search CENTER (empty when search=false), expand HoverIcon EAST (only when details present). Preserve AbstractPopup.customizeSearchFieldLook and background wiring.

Keyboard (registered on both the list and, when present, the search editor):

• UP/DOWN → move selection (search field only; list uses ScrollingUtil).
• ENTER → primary on selected row.
• ESC → popup.cancel().
• Single + trailing present → Shift+SPACE → trailing on selected row.
• Multi → SPACE → primary (toggle) on selected row.

Mouse (mouseReleased, UIUtil.isActionClick): resolve row via locationToIndex + getCellBounds/contains; if trailing present and trailingHit → onTrailing + consume; else onPrimary (Single closes, Multi consumes + repaints).

ui/picker/PickerListRenderer.kt — renderer skeleton

Abstract ListCellRenderer<T> base: PickerRow wrap + optional top GroupHeaderSeparator (driven by sectionTitle) + [check icon | content | trailing] layout with the shared transparent row + UiStyle.Gap.md/lg/md/pad insets. Provides:

• check icon column (AllIcons.Actions.Checked / EmptyIcon), set from checked(row).
• protected content: JComponent slot and optional trailing: JComponent slot.
• section separator top panel wiring (top/sep from ModelPickerRenderer).
• a companion trailingClickZone(list, bounds, point, width) generalizing ModelPickerRenderer.isFavoriteClick (keep FAVORITE_CLICK_AREA_WIDTH behavior).

Ordered implementation tasks

1. Create ui/picker/PickerListRenderer.kt: base renderer skeleton with check column, PickerRow wrap, top section separator, content/trailing slots, transparent row + insets, and the trailingClickZone helper (moved/generalized from ModelPickerRenderer.isFavoriteClick / favoriteInset).
2. Create ui/picker/PickerPopup.kt: generic popup per the design above, including the moved popupBackground helper and the sizing helpers (parameterized).
3. Refactor ModelPickerRenderer to extend PickerListRenderer: content = title (SimpleColoredComponent) + warn + free/BYOK badges + provider label; trailing = favorite star; check via checked. Keep existing internal test accessors (starIcon, badgeVisible, badgeText, byokVisible, warningVisible, warningTooltip) and the DATA_COLLECTED/checked/empty companion members so ModelPickerTest compiles unchanged.
4. Refactor ModelPicker.showPopup to build a PickerPopup<ModelPickerRow> configured as: Single mode; rows = { q -> modelPickerRows(items, favorites(), q, allowEmpty, emptyText, includeSmall) }; checked = { it.key == selected?.key }; sectionTitle = ::modelPickerSectionTitle; onPrimary = { row -> row.item?.let(::activate) ?: clear() }; trailing = favorite hit-zone + onFavoriteToggle; search = true; details = ModelDetailsPanel with expandStateKey = MODEL_PICKER_EXPANDED_KEY; placement from placement; sizing constants = current values. Keep ModelPicker's public API (setItems, select, clearSelection, open, callbacks, Placement, Item) and test hooks (selectedForTest, selectionKeyForTest, expandedForTest) unchanged so PromptPanel, settings/models, and settings/agents consumers are unaffected.
5. Add provider picker renderer (small subclass of PickerListRenderer<String> in settings/providers/, or a shared simple text renderer): content = a JBLabel showing the model id; no trailing; check via checked.
6. Rewrite CustomProviderDialog.showModelPopup(ids) to build a PickerPopup<String>: Multi mode; rows = { _ -> ids } (raw model ids, no select-all row); checked = { it in modelIds().toSet() }; onPrimary = { toggleModel(it) }; sectionTitle = { _, _ -> null }; search = false; toolbar = listOf(selectAllButton, deselectAllButton); details = null; minWidth = 320; anchor = pick, placement UNDERNEATH.
7. Extract provider selection mutations into testable helpers on/near CustomProviderDialog operating on the models text field: toggleModel(id), selectAllModels(ids), clearModels() (reuse existing modelIds() / setModelIds()). Wire the two toolbar buttons to selectAllModels(ids) and clearModels().
8. Remove dead code: CustomModelRow, customModelRows, CustomModelRowRenderer, CUSTOM_MODEL_POPUP_MIN_WIDTH/CUSTOM_MODEL_POPUP_MAX_ROWS (fold into base config), and the now-duplicated inline popupBackground in ProvidersSettingsUi.kt.
9. Strings: add a "Deselect All" key to KiloBundle.properties (e.g. settings.providers.customModelsDeselectAll=Deselect All); reuse existing settings.providers.customModelsSelectAll for "Select All".

Tests

• Keep passing unchanged: ModelPickerTest.kt (row builder + renderer + ModelSearch + favorite hit-zone). Because ModelPickerRenderer keeps its accessors and companion members and modelPickerRows/ModelPickerRow are untouched, these should compile and pass as-is. Verify the favorite hit-zone tests still reference a working symbol (either keep ModelPickerRenderer.isFavoriteClick delegating to PickerListRenderer.trailingClickZone, or update the 3 call sites in ModelPickerTest.kt to the new helper).
• Update ProvidersSettingsUiTest.kt:
  • Replace test custom model rows start with select all (there is no select-all row anymore) with tests for the extracted helpers: toggleModel adds/removes an id in the text field; selectAllModels(ids) sets all; clearModels() empties it.
  • Keep existing add/edit/delete and dialog-close tests working.
• New: a small PickerListRenderer/PickerPopup unit test where feasible without a live popup — e.g. trailingClickZone geometry (mirroring the current isFavoriteClick tests) and the provider text renderer check-state. Avoid asserting live-popup internals; follow the existing pattern of testing renderers/row-builders/pure helpers directly (per package AGENTS "test the real implementation, no mocks").

Validation

From packages/kilo-jetbrains/:

• ./gradlew typecheck
• ./gradlew test (iterate with --tests ai.kilocode.client.session.ui.model.ModelPickerTest and --tests ai.kilocode.client.settings.providers.ProvidersSettingsUiTest).
• Manual smoke via ./gradlew runIde:
  • Prompt model picker: search, arrow/enter select, favorite star toggle, expand/collapse details, placement — all unchanged.
  • Add custom provider → fetch models → popup shows model list with "Select All"/"Deselect All" toolbar buttons, per-row multi-select toggles, no details/expand, selection reflected in the Model IDs field; Save persists selected models.

Risks / notes

• ModelPicker's public API and test hooks must stay stable — several settings screens depend on it. Only the popup internals move.
• The details/expand panel is Disposable; the base must register it with the popup exactly as today to avoid leaks.
• Sizing differs (prompt 420/760 dynamic + details; provider fixed 320). Parameterize rather than hard-code; keep provider width visually equivalent to current.
• Popups are hard to unit test; keep coverage on pure helpers/renderers, not live-popup behavior.
• Keyboard/mouse semantics differ by mode (single-commit-close vs multi-toggle-stay-open) and by presence of a trailing toggle — encode these in the base mode, don't special-case callers.

Out of scope

• The other picker popups (ModePicker, ReasoningPicker, SessionAccountOverlay) — not part of this consolidation.
• Adding search to the provider picker (kept off to match current behavior; base supports it).
• Any backend/RPC/DTO or CLI changes.