docs: resolve AGENTS merge after board-detail updates

AGENTS.md

@@ -97,12 +97,17 @@ Kanbn4Droid is an unofficial app to connect to and manipulate data stored in sel
       - Pressing "Delete" in the modal dialog MUST show a second confirmation modal asking if the user is sure, with buttons for "Cancel" and "I'm sure".
       - Only on pressing "I'm sure" in the second confirmation modal dialog should a board delete request be sent to the API.
     - Long-pressing any of the buttons must show a tooltip with the button name.
-- The view has a floating + button that shows a modal dialog that allows creating a new card using the Kan.bn API.
-  - The new card is added to the top of the currently shown list.
+- The view has a floating + button that allows choosing between two options: "Add new list", "Add new card"
+  - The Add new list option shows a modal dialog that asks for a list title. The modal dialog has two buttons at the bottom for "Cancel" and "Create"
+    - The list is created using the Kan.bn API.
+    - The new list is added at the end of the lists in the current board after the current last list.
+  - The Add new card dialog shows a modal dialog that works as follows:
     - The modal dialog has a field for the card's name. This field is mandatory
     - Below the card name field there is a markdown-enabled text area for an optional card description.
     - Below the card description field there is an optional date field to set the card's due date.
     - Below the card's due date field there is an optional multi-value selector that allows choosing the card's tags from the tags available for the current board.
+    - The new card is created using the Kan.bn API.
+    - The new card is added to the top of the currently shown list.
 - The title bar of the view has two icon-only buttons for "Filter by tag" (icon is three bars of decreasing width, widest on top) and "Search" (icon is a leaning looking glass)
   - The filter by tag button opens a modal dialog that shows a multi-value selector that allows choosing from the tags available on the current board. The modal has a title that says "Filter by tag". The modal has buttons for "Cancel" and "Filter".
   - The search button a modal dialog that shows a text field that has the placeholder value "Search". The modal has a title that seas "Search by title". The modal has buttons for "Cancel" and "Search".
@@ -113,7 +118,18 @@ Kanbn4Droid is an unofficial app to connect to and manipulate data stored in sel
   - Tapping on the filter by tag or search buttonswhen either of them is applied disables the active filter.
 - When a card(s) is selected by a long press, the filter by tag and search buttons get hidden by the select all, move card and delete card buttons until all cards are deselected.
 - When a card(s) is selected by a long press, the back arrow in the title bar and the back system button remove all selections.
-- Current status: implemented in `BoardDetailActivity` with `ViewPager2` (one list per page), inline list-title edit, card rendering (title/tags/due date locale formatting and expiry color), cross-page card selection, page-scoped select-all, move dialog with list selector, two-step delete confirmation, mutation guards while in progress, and API-backed reload/reconciliation behavior through `BoardDetailViewModel` and `BoardDetailRepository`. Card move requests try these variants in order for compatibility across Kan.bn API versions: `PUT /api/v1/cards/{cardPublicId}` with `listPublicId`, then a GET+full-body `PUT /api/v1/cards/{cardPublicId}` payload (`title`, `description`, `index`, `listPublicId`, `dueDate`), then `PUT /api/v1/cards/{cardPublicId}` with `listId`, then `PATCH /api/v1/cards/{cardPublicId}` with `listId`. Board detail parsing now prefers public ids (`publicId`/`public_id`) over internal `id` values so follow-up card/list mutations target the correct API identifiers. Label chip border colors are hydrated from the Kan.bn `Get a label by public ID` endpoint (`colourCode`) and cached in-memory by `BoardDetailRepository` so each label color is fetched only once per app process. Selection action icons use local vector drawables (`ic_select_all_grid_24`, `ic_move_cards_horizontal_24`, `ic_delete_24`) with day/night resource variants so dark mode uses light icon fills automatically. Startup blocking dialogs are shown for missing board id and missing session.
+- Current status: implemented in `BoardDetailActivity` with `ViewPager2` (one list per page), inline list-title edit, and card rendering (title/tags/due date locale formatting and expiry color).
+  - FAB flows are implemented for both add-list and add-card dialogs.
+  - Filter/search behavior is local (no server roundtrip), and active filter/search icons are highlighted.
+  - Cross-page card selection is implemented. In selection mode, toolbar actions are replaced (filter/search hidden; select-all/move/delete shown).
+  - Select-all is page-scoped, move uses a list selector dialog, and delete uses two-step confirmation.
+  - Back handling clears selection from both the top-bar back arrow and the system back button before navigation.
+  - The screen includes mutation guards while in progress and API-backed reload/reconciliation behavior through `BoardDetailViewModel` and `BoardDetailRepository`.
+  - Card move requests try these variants for Kan.bn API compatibility: `PUT /api/v1/cards/{cardPublicId}` with `listPublicId`, then GET+full-body `PUT /api/v1/cards/{cardPublicId}` payload (`title`, `description`, `index`, `listPublicId`, `dueDate`), then `PUT /api/v1/cards/{cardPublicId}` with `listId`, then `PATCH /api/v1/cards/{cardPublicId}` with `listId`.
+  - Board detail parsing prefers public ids (`publicId`/`public_id`) over internal `id` values so follow-up card/list mutations target correct API identifiers.
+  - Label chip border colors are hydrated from Kan.bn `Get a label by public ID` (`colourCode`) and cached in-memory by `BoardDetailRepository` so each label color is fetched only once per app process.
+  - Selection action icons use local vector drawables (`ic_select_all_grid_24`, `ic_move_cards_horizontal_24`, `ic_delete_24`) with day/night variants so dark mode uses light icon fills automatically.
+  - Startup blocking dialogs are shown for missing board id and missing session.
 
 **Card detail view**
 - The view shows the card's title in bold letters. Tapping on the card's title allows editing it.

app/src/androidTest/java/space/hackenslacker/kanbn4droid/app/BoardDetailFlowTest.kt

@@ -9,10 +9,12 @@ import androidx.appcompat.content.res.AppCompatResources
 import androidx.test.core.app.ActivityScenario
 import androidx.test.core.app.ApplicationProvider
 import androidx.test.espresso.Espresso.onView
+import androidx.test.espresso.Espresso.pressBack
 import androidx.test.espresso.action.ViewActions.click
 import androidx.test.espresso.action.ViewActions.longClick
 import androidx.test.espresso.action.ViewActions.replaceText
 import androidx.test.espresso.assertion.ViewAssertions.matches
+import androidx.test.espresso.assertion.ViewAssertions.doesNotExist
 import androidx.test.espresso.intent.Intents
 import androidx.test.espresso.intent.matcher.IntentMatchers.hasComponent
 import androidx.test.espresso.intent.matcher.IntentMatchers.hasExtra
@@ -27,6 +29,8 @@ import androidx.viewpager2.widget.ViewPager2
 import com.google.android.material.color.MaterialColors
 import com.google.android.material.chip.Chip
 import java.text.DateFormat
+import java.time.LocalDate
+import java.time.ZoneId
 import java.util.ArrayDeque
 import java.util.Date
 import java.util.Locale
@@ -50,6 +54,7 @@ import space.hackenslacker.kanbn4droid.app.boarddetail.BoardDetailDataSource
 import space.hackenslacker.kanbn4droid.app.boarddetail.BoardListDetail
 import space.hackenslacker.kanbn4droid.app.boarddetail.BoardTagSummary
 import space.hackenslacker.kanbn4droid.app.boarddetail.CardBatchMutationResult
+import space.hackenslacker.kanbn4droid.app.boarddetail.CreatedEntityRef
 import space.hackenslacker.kanbn4droid.app.auth.ApiKeyStore
 import space.hackenslacker.kanbn4droid.app.auth.SessionStore
 import space.hackenslacker.kanbn4droid.app.boards.BoardsApiResult
@@ -63,6 +68,7 @@ class BoardDetailFlowTest {
 
     @Before
     fun setUp() {
+        observedStates.clear()
         MainActivity.dependencies.clear()
         MainActivity.dependencies.sessionStoreFactory = { InMemorySessionStore("https://kan.bn/") }
         MainActivity.dependencies.apiKeyStoreFactory = { InMemoryApiKeyStore("api") }
@@ -307,6 +313,251 @@ class BoardDetailFlowTest {
         }
     }
 
+    @Test
+    fun toolbarNormalMode_showsFilterAndSearchActions() {
+        val scenario = launchBoardDetail()
+        onView(withText("Card 1")).check(matches(isDisplayed()))
+
+        awaitCondition {
+            var present = false
+            scenario.onActivity { activity ->
+                val menu = activity.findViewById<com.google.android.material.appbar.MaterialToolbar>(R.id.boardDetailToolbar).menu
+                present = menu.findItem(R.id.actionFilterByTag) != null && menu.findItem(R.id.actionSearch) != null
+            }
+            present
+        }
+
+        scenario.onActivity { activity ->
+            val menu = activity.findViewById<com.google.android.material.appbar.MaterialToolbar>(R.id.boardDetailToolbar).menu
+            assertNotNull(menu.findItem(R.id.actionFilterByTag))
+            assertNotNull(menu.findItem(R.id.actionSearch))
+        }
+    }
+
+    @Test
+    fun selectionMode_replacesFilterSearchWithSelectionActions() {
+        val scenario = launchBoardDetail()
+
+        onView(withText("Card 1")).perform(longClick())
+
+        scenario.onActivity { activity ->
+            val menu = activity.findViewById<com.google.android.material.appbar.MaterialToolbar>(R.id.boardDetailToolbar).menu
+            assertNotNull(menu.findItem(R.id.actionSelectAll))
+            assertNotNull(menu.findItem(R.id.actionMoveCards))
+            assertNotNull(menu.findItem(R.id.actionDeleteCards))
+            assertNull(menu.findItem(R.id.actionFilterByTag))
+            assertNull(menu.findItem(R.id.actionSearch))
+        }
+    }
+
+    @Test
+    fun fab_isVisible_andOpensAddChooser() {
+        launchBoardDetail()
+
+        onView(withId(R.id.boardDetailCreateFab)).check(matches(isDisplayed()))
+        onView(withId(R.id.boardDetailCreateFab)).perform(click())
+
+        onView(withText("Add new list")).inRoot(isDialog()).check(matches(isDisplayed()))
+        onView(withText("Add new card")).inRoot(isDialog()).check(matches(isDisplayed()))
+    }
+
+    @Test
+    fun fabChooser_addList_createAndValidationFlow() {
+        launchBoardDetail()
+
+        onView(withId(R.id.boardDetailCreateFab)).perform(click())
+        onView(withText(R.string.add_new_list)).inRoot(isDialog()).perform(click())
+        onView(withText(R.string.add_new_list)).inRoot(isDialog()).check(matches(isDisplayed()))
+
+        onView(withText(R.string.add_list)).inRoot(isDialog()).perform(click())
+        onView(withText(R.string.list_title_required)).inRoot(isDialog()).check(matches(isDisplayed()))
+
+        onView(withId(R.id.addListTitleInput)).inRoot(isDialog()).perform(replaceText("Created List"))
+        onView(withText(R.string.add_list)).inRoot(isDialog()).perform(click())
+
+        awaitCondition {
+            defaultDataSource.createListCalls == 1 && observedStates.lastOrNull()?.isMutating == false
+        }
+
+        assertEquals(1, defaultDataSource.createListCalls)
+        assertEquals("board-1", defaultDataSource.lastCreateListBoardId)
+        assertEquals("Created List", defaultDataSource.lastCreateListTitle)
+        assertTrue(
+            observedStates.lastOrNull()
+                ?.boardDetail
+                ?.lists
+                ?.any { it.title == "Created List" } == true,
+        )
+    }
+
+    @Test
+    fun fabChooser_addCard_createWithTagsAndClearDate() {
+        defaultDataSource.currentDetail = detailCreateCardDialogTagCatalog()
+        val scenario = launchBoardDetail()
+
+        onView(withId(R.id.boardDetailCreateFab)).perform(click())
+        onView(withText(R.string.add_new_card)).inRoot(isDialog()).perform(click())
+
+        onView(withId(R.id.addCardTitleInput)).inRoot(isDialog()).perform(replaceText("Created Card"))
+        onView(withId(R.id.addCardDescriptionInput)).inRoot(isDialog()).perform(replaceText("Body"))
+        onView(withText("Backend")).inRoot(isDialog()).perform(click())
+        onView(withId(R.id.addCardDueDateText)).inRoot(isDialog()).perform(click())
+        onView(withText(android.R.string.ok)).inRoot(isDialog()).perform(click())
+        awaitCondition {
+            observedStates.lastOrNull()?.addCardDueDate != null
+        }
+        scenario.onActivity { }
+        onView(withId(R.id.addCardClearDueDateAction)).inRoot(isDialog()).check(matches(isDisplayed()))
+        onView(withId(R.id.addCardClearDueDateAction)).inRoot(isDialog()).perform(click())
+        awaitCondition {
+            observedStates.lastOrNull()?.addCardDueDate == null
+        }
+        onView(withText(R.string.add_card)).inRoot(isDialog()).perform(click())
+
+        awaitCondition {
+            defaultDataSource.createCardCalls == 1 && observedStates.lastOrNull()?.isMutating == false
+        }
+
+        assertEquals(1, defaultDataSource.createCardCalls)
+        assertEquals("list-1", defaultDataSource.lastCreateCardListId)
+        assertEquals("Created Card", defaultDataSource.lastCreateCardTitle)
+        assertEquals("Body", defaultDataSource.lastCreateCardDescription)
+        assertEquals(setOf("tag-1"), defaultDataSource.lastCreateCardTagIds)
+        assertNull(defaultDataSource.lastCreateCardDueDate)
+    }
+
+    @Test
+    fun fabChooser_zeroLists_disablesAddCard_andShowsHelperMessage() {
+        defaultDataSource.currentDetail = BoardDetail(id = "board-1", title = "Board", lists = emptyList())
+        launchBoardDetail()
+
+        onView(withId(R.id.boardDetailCreateFab)).perform(click())
+        onView(withText(R.string.add_new_card)).inRoot(isDialog()).check(matches(not(isEnabled())))
+        onView(withText(R.string.create_a_list_first_to_add_cards)).inRoot(isDialog()).check(matches(isDisplayed()))
+    }
+
+    @Test
+    fun filters_applyTagAnyAndSearchAnd_keepAllListsVisible() {
+        defaultDataSource.currentDetail = detailFilterAndSearchThreeLists()
+        val scenario = launchBoardDetail()
+
+        onView(withContentDescription("Filter by tag")).perform(click())
+        onView(withText("Backend")).inRoot(isDialog()).perform(click())
+        onView(withText("Mobile")).inRoot(isDialog()).perform(click())
+        onView(withText(R.string.filter)).inRoot(isDialog()).perform(click())
+
+        onView(withContentDescription("Search")).perform(click())
+        onView(withId(R.id.searchTitleInput)).inRoot(isDialog()).perform(replaceText("Duke"))
+        onView(withText(R.string.search)).inRoot(isDialog()).perform(click())
+
+        onView(withText("Duke Backend")).check(matches(isDisplayed()))
+        scenario.onActivity { activity ->
+            activity.findViewById<ViewPager2>(R.id.boardDetailPager).setCurrentItem(1, false)
+        }
+        onView(withText("Duke Mobile")).check(matches(isDisplayed()))
+        scenario.onActivity { activity ->
+            activity.findViewById<ViewPager2>(R.id.boardDetailPager).setCurrentItem(2, false)
+        }
+        onView(withText("Done")).check(matches(isDisplayed()))
+        onView(withText(R.string.board_detail_empty_list)).check(matches(isDisplayed()))
+    }
+
+    @Test
+    fun filterAndSearchActions_showActiveTintWhenCriteriaApplied_andResetOnClear() {
+        defaultDataSource.currentDetail = detailFilterAndSearchThreeLists()
+        val scenario = launchBoardDetail()
+
+        onView(withContentDescription("Filter by tag")).perform(click())
+        onView(withText("Backend")).inRoot(isDialog()).perform(click())
+        onView(withText(R.string.filter)).inRoot(isDialog()).perform(click())
+
+        onView(withContentDescription("Search")).perform(click())
+        onView(withId(R.id.searchTitleInput)).inRoot(isDialog()).perform(replaceText("Duke"))
+        onView(withText(R.string.search)).inRoot(isDialog()).perform(click())
+
+        scenario.onActivity { activity ->
+            val menu = activity.findViewById<com.google.android.material.appbar.MaterialToolbar>(R.id.boardDetailToolbar).menu
+            val expectedActive = MaterialColors.getColor(
+                activity,
+                com.google.android.material.R.attr.colorPrimary,
+                Color.BLUE,
+            )
+            assertEquals(expectedActive, menu.findItem(R.id.actionFilterByTag).iconTintList?.defaultColor)
+            assertEquals(expectedActive, menu.findItem(R.id.actionSearch).iconTintList?.defaultColor)
+        }
+
+        onView(withContentDescription("Filter by tag")).perform(click())
+        onView(withContentDescription("Search")).perform(click())
+
+        scenario.onActivity { activity ->
+            val menu = activity.findViewById<com.google.android.material.appbar.MaterialToolbar>(R.id.boardDetailToolbar).menu
+            val expectedInactive = MaterialColors.getColor(
+                activity,
+                com.google.android.material.R.attr.colorOnSurfaceVariant,
+                Color.BLACK,
+            )
+            assertEquals(expectedInactive, menu.findItem(R.id.actionFilterByTag).iconTintList?.defaultColor)
+            assertEquals(expectedInactive, menu.findItem(R.id.actionSearch).iconTintList?.defaultColor)
+        }
+    }
+
+    @Test
+    fun activeFilterOrSearchIconTap_clearsCriterionImmediately() {
+        defaultDataSource.currentDetail = detailFilterAndSearchThreeLists()
+        val scenario = launchBoardDetail()
+
+        onView(withContentDescription("Filter by tag")).perform(click())
+        onView(withText("Backend")).inRoot(isDialog()).perform(click())
+        onView(withText(R.string.filter)).inRoot(isDialog()).perform(click())
+        onView(withText("Duke Mobile")).check(doesNotExist())
+
+        onView(withContentDescription("Filter by tag")).perform(click())
+        scenario.onActivity { activity ->
+            activity.findViewById<ViewPager2>(R.id.boardDetailPager).setCurrentItem(1, false)
+        }
+        onView(withText("Duke Mobile")).check(matches(isDisplayed()))
+
+        onView(withContentDescription("Search")).perform(click())
+        onView(withId(R.id.searchTitleInput)).inRoot(isDialog()).perform(replaceText("Backend"))
+        onView(withText(R.string.search)).inRoot(isDialog()).perform(click())
+        onView(withText(R.string.board_detail_empty_list)).check(matches(isDisplayed()))
+
+        onView(withContentDescription("Search")).perform(click())
+        scenario.onActivity { activity ->
+            activity.findViewById<ViewPager2>(R.id.boardDetailPager).setCurrentItem(1, false)
+        }
+        onView(withText("Duke Mobile")).check(matches(isDisplayed()))
+    }
+
+    @Test
+    fun selectionMode_hidesFilterAndSearchActions() {
+        val scenario = launchBoardDetail()
+
+        onView(withText("Card 1")).perform(longClick())
+
+        scenario.onActivity { activity ->
+            val menu = activity.findViewById<com.google.android.material.appbar.MaterialToolbar>(R.id.boardDetailToolbar).menu
+            assertNull(menu.findItem(R.id.actionFilterByTag))
+            assertNull(menu.findItem(R.id.actionSearch))
+            assertNotNull(menu.findItem(R.id.actionSelectAll))
+        }
+    }
+
+    @Test
+    fun backArrowAndSystemBack_clearSelectionBeforeNavigation() {
+        launchBoardDetail()
+        onView(withText("Card 1")).perform(longClick())
+        onView(withId(R.id.actionSelectAll)).check(matches(isDisplayed()))
+        onView(withContentDescription(androidx.appcompat.R.string.abc_action_bar_up_description)).perform(click())
+        onView(withId(R.id.actionFilterByTag)).check(matches(isDisplayed()))
+
+        launchBoardDetail()
+        onView(withText("Card 1")).perform(longClick())
+        onView(withId(R.id.actionSelectAll)).check(matches(isDisplayed()))
+        pressBack()
+        onView(withId(R.id.actionFilterByTag)).check(matches(isDisplayed()))
+    }
+
     @Test
     fun missingBoardIdShowsBlockingDialogAndFinishes() {
         val scenario = launchBoardDetail(boardId = null)
@@ -632,9 +883,88 @@ class BoardDetailFlowTest {
         var deleteGate: CompletableDeferred<Unit>? = null
         var moveCalls: Int = 0
         var deleteCalls: Int = 0
+        var createListCalls: Int = 0
+        var createCardCalls: Int = 0
         var lastMoveCardIds: Set<String> = emptySet()
         var lastDeleteCardIds: Set<String> = emptySet()
         var lastMoveTargetListId: String? = null
+        var lastCreateListBoardId: String? = null
+        var lastCreateListTitle: String? = null
+        var lastCreateCardListId: String? = null
+        var lastCreateCardTitle: String? = null
+        var lastCreateCardDescription: String? = null
+        var lastCreateCardDueDate: LocalDate? = null
+        var lastCreateCardTagIds: Set<String> = emptySet()
+        var createListResult: BoardsApiResult<CreatedEntityRef> = BoardsApiResult.Success(CreatedEntityRef("created-list"))
+        var createCardResult: BoardsApiResult<CreatedEntityRef> = BoardsApiResult.Success(CreatedEntityRef("created-card"))
+
+        override suspend fun createList(boardPublicId: String, title: String): BoardsApiResult<CreatedEntityRef> {
+            createListCalls += 1
+            lastCreateListBoardId = boardPublicId
+            lastCreateListTitle = title
+            val result = createListResult
+            if (result is BoardsApiResult.Success) {
+                val newId = result.value.publicId?.trim().orEmpty().ifBlank { "created-list-${createListCalls}" }
+                currentDetail = currentDetail.copy(
+                    lists = currentDetail.lists + BoardListDetail(
+                        id = newId,
+                        title = title,
+                        cards = emptyList(),
+                    ),
+                )
+            }
+            return result
+        }
+
+        override suspend fun createCard(
+            listPublicId: String,
+            title: String,
+            description: String?,
+            dueDate: LocalDate?,
+            tagPublicIds: Collection<String>,
+        ): BoardsApiResult<CreatedEntityRef> {
+            createCardCalls += 1
+            lastCreateCardListId = listPublicId
+            lastCreateCardTitle = title
+            lastCreateCardDescription = description
+            lastCreateCardDueDate = dueDate
+            lastCreateCardTagIds = tagPublicIds.toSet()
+
+            val result = createCardResult
+            if (result is BoardsApiResult.Success) {
+                val newId = result.value.publicId?.trim().orEmpty().ifBlank { "created-card-${createCardCalls}" }
+                val knownTagsById = currentDetail.lists
+                    .asSequence()
+                    .flatMap { list -> list.cards.asSequence() }
+                    .flatMap { card -> card.tags.asSequence() }
+                    .associateBy { tag -> tag.id }
+                val newTags = tagPublicIds.mapNotNull { knownTagsById[it] }
+                val dueAt = dueDate
+                    ?.atStartOfDay(ZoneId.systemDefault())
+                    ?.toInstant()
+                    ?.toEpochMilli()
+
+                currentDetail = currentDetail.copy(
+                    lists = currentDetail.lists.map { list ->
+                        if (list.id == listPublicId) {
+                            list.copy(
+                                cards = listOf(
+                                    BoardCardSummary(
+                                        id = newId,
+                                        title = title,
+                                        tags = newTags,
+                                        dueAtEpochMillis = dueAt,
+                                    ),
+                                ) + list.cards,
+                            )
+                        } else {
+                            list
+                        }
+                    },
+                )
+            }
+            return result
+        }
 
         override suspend fun getBoardDetail(boardId: String): BoardsApiResult<BoardDetail> {
             loadGate?.await()
@@ -962,5 +1292,74 @@ class BoardDetailFlowTest {
                 ),
             )
         }
+
+        fun detailCreateCardDialogTagCatalog(): BoardDetail {
+            return BoardDetail(
+                id = "board-1",
+                title = "Board",
+                lists = listOf(
+                    BoardListDetail(
+                        id = "list-1",
+                        title = "To Do",
+                        cards = listOf(
+                            BoardCardSummary(
+                                id = "card-1",
+                                title = "Existing",
+                                tags = listOf(
+                                    BoardTagSummary("tag-1", "Backend", "#008080"),
+                                    BoardTagSummary("tag-2", "Mobile", "#990000"),
+                                ),
+                                dueAtEpochMillis = null,
+                            ),
+                        ),
+                    ),
+                ),
+            )
+        }
+
+        fun detailFilterAndSearchThreeLists(): BoardDetail {
+            return BoardDetail(
+                id = "board-1",
+                title = "Board",
+                lists = listOf(
+                    BoardListDetail(
+                        id = "list-1",
+                        title = "To Do",
+                        cards = listOf(
+                            BoardCardSummary(
+                                id = "todo-duke-backend",
+                                title = "Duke Backend",
+                                tags = listOf(BoardTagSummary("tag-1", "Backend", "#008080")),
+                                dueAtEpochMillis = null,
+                            ),
+                        ),
+                    ),
+                    BoardListDetail(
+                        id = "list-2",
+                        title = "Doing",
+                        cards = listOf(
+                            BoardCardSummary(
+                                id = "doing-duke-mobile",
+                                title = "Duke Mobile",
+                                tags = listOf(BoardTagSummary("tag-2", "Mobile", "#009900")),
+                                dueAtEpochMillis = null,
+                            ),
+                        ),
+                    ),
+                    BoardListDetail(
+                        id = "list-3",
+                        title = "Done",
+                        cards = listOf(
+                            BoardCardSummary(
+                                id = "done-archived",
+                                title = "Archived",
+                                tags = listOf(BoardTagSummary("tag-3", "Ops", "#333333")),
+                                dueAtEpochMillis = null,
+                            ),
+                        ),
+                    ),
+                ),
+            )
+        }
     }
 }

app/src/main/java/space/hackenslacker/kanbn4droid/app/auth/KanbnApiClient.kt

@@ -4,6 +4,7 @@ import java.io.IOException
 import java.net.HttpURLConnection
 import java.net.URL
 import java.time.Instant
+import java.time.LocalDate
 import org.json.JSONArray
 import org.json.JSONObject
 import kotlinx.coroutines.Dispatchers
@@ -12,6 +13,7 @@ import space.hackenslacker.kanbn4droid.app.boarddetail.BoardCardSummary
 import space.hackenslacker.kanbn4droid.app.boarddetail.BoardDetail
 import space.hackenslacker.kanbn4droid.app.boarddetail.BoardListDetail
 import space.hackenslacker.kanbn4droid.app.boarddetail.BoardTagSummary
+import space.hackenslacker.kanbn4droid.app.boarddetail.CreatedEntityRef
 import space.hackenslacker.kanbn4droid.app.boards.BoardSummary
 import space.hackenslacker.kanbn4droid.app.boards.BoardTemplate
 import space.hackenslacker.kanbn4droid.app.boards.BoardsApiResult
@@ -62,6 +64,28 @@ interface KanbnApiClient {
         return BoardsApiResult.Failure("List rename is not implemented.")
     }
 
+    suspend fun createList(
+        baseUrl: String,
+        apiKey: String,
+        boardPublicId: String,
+        title: String,
+        appendIndex: Int,
+    ): BoardsApiResult<CreatedEntityRef> {
+        return BoardsApiResult.Failure("List creation is not implemented.")
+    }
+
+    suspend fun createCard(
+        baseUrl: String,
+        apiKey: String,
+        listPublicId: String,
+        title: String,
+        description: String?,
+        dueDate: LocalDate?,
+        tagPublicIds: List<String>,
+    ): BoardsApiResult<CreatedEntityRef> {
+        return BoardsApiResult.Failure("Card creation is not implemented.")
+    }
+
     suspend fun moveCard(baseUrl: String, apiKey: String, cardId: String, targetListId: String): BoardsApiResult<Unit> {
         return BoardsApiResult.Failure("Card move is not implemented.")
     }
@@ -269,6 +293,79 @@ class HttpKanbnApiClient : KanbnApiClient {
         }
     }
 
+    override suspend fun createList(
+        baseUrl: String,
+        apiKey: String,
+        boardPublicId: String,
+        title: String,
+        appendIndex: Int,
+    ): BoardsApiResult<CreatedEntityRef> {
+        return withContext(Dispatchers.IO) {
+            val payload =
+                "{" +
+                    "\"boardPublicId\":\"${jsonEscape(boardPublicId)}\"," +
+                    "\"name\":\"${jsonEscape(title)}\"," +
+                    "\"index\":$appendIndex" +
+                    "}"
+            request(
+                baseUrl = baseUrl,
+                path = "/api/v1/lists",
+                method = "POST",
+                apiKey = apiKey,
+                body = payload,
+            ) { code, body ->
+                if (code in 200..299) {
+                    parseCreatedEntityRef(body)
+                        ?.let { BoardsApiResult.Success(it) }
+                        ?: BoardsApiResult.Failure("Malformed create list response.")
+                } else {
+                    BoardsApiResult.Failure(serverMessage(body, code))
+                }
+            }
+        }
+    }
+
+    override suspend fun createCard(
+        baseUrl: String,
+        apiKey: String,
+        listPublicId: String,
+        title: String,
+        description: String?,
+        dueDate: LocalDate?,
+        tagPublicIds: List<String>,
+    ): BoardsApiResult<CreatedEntityRef> {
+        return withContext(Dispatchers.IO) {
+            val payloadFields = mutableListOf(
+                "\"listPublicId\":\"${jsonEscape(listPublicId)}\"",
+                "\"title\":\"${jsonEscape(title)}\"",
+                "\"index\":0",
+                "\"labelPublicIds\":${jsonStringArray(tagPublicIds)}",
+            )
+            if (description != null) {
+                payloadFields += "\"description\":\"${jsonEscape(description)}\""
+            }
+            if (dueDate != null) {
+                payloadFields += "\"dueDate\":\"${dueDate}T00:00:00Z\""
+            }
+            val payload = "{${payloadFields.joinToString(",")}}"
+            request(
+                baseUrl = baseUrl,
+                path = "/api/v1/cards",
+                method = "POST",
+                apiKey = apiKey,
+                body = payload,
+            ) { code, body ->
+                if (code in 200..299) {
+                    parseCreatedEntityRef(body)
+                        ?.let { BoardsApiResult.Success(it) }
+                        ?: BoardsApiResult.Failure("Malformed create card response.")
+                } else {
+                    BoardsApiResult.Failure(serverMessage(body, code))
+                }
+            }
+        }
+    }
+
     override suspend fun moveCard(
         baseUrl: String,
         apiKey: String,
@@ -667,6 +764,31 @@ class HttpKanbnApiClient : KanbnApiClient {
         return LabelDetail(id = id, colorHex = colorHex)
     }
 
+    private fun parseCreatedEntityRef(body: String): CreatedEntityRef? {
+        if (body.isBlank()) {
+            return null
+        }
+
+        val root = parseJsonObject(body) ?: return null
+        val data = root["data"]
+        val entity = when (data) {
+            is Map<*, *> -> {
+                (data["card"] as? Map<*, *>)
+                    ?: (data["list"] as? Map<*, *>)
+                    ?: data
+            }
+
+            else -> {
+                (root["card"] as? Map<*, *>)
+                    ?: (root["list"] as? Map<*, *>)
+                    ?: root
+            }
+        }
+
+        val publicId = extractString(entity, "publicId", "public_id", "id")
+        return CreatedEntityRef(publicId = publicId.ifBlank { null })
+    }
+
     private fun parseLists(board: Map<*, *>): List<BoardListDetail> {
         return extractObjectArray(board, "lists", "items", "data").mapNotNull { rawList ->
             val id = extractId(rawList)
@@ -781,6 +903,10 @@ class HttpKanbnApiClient : KanbnApiClient {
         return builder.toString()
     }
 
+    private fun jsonStringArray(values: List<String>): String {
+        return values.joinToString(prefix = "[", postfix = "]", separator = ",") { "\"${jsonEscape(it)}\"" }
+    }
+
     private class MiniJsonParser(private val input: String) {
         private var index = 0
 

app/src/main/java/space/hackenslacker/kanbn4droid/app/boarddetail/BoardDetailActivity.kt

@@ -1,22 +1,38 @@
 package space.hackenslacker.kanbn4droid.app.boarddetail
 
+import android.app.DatePickerDialog
 import android.content.Intent
 import android.os.Bundle
+import android.view.LayoutInflater
 import android.view.Menu
 import android.view.MenuItem
 import android.view.View
+import android.widget.CheckBox
+import android.widget.LinearLayout
 import android.widget.Button
 import android.widget.ProgressBar
 import android.widget.TextView
+import androidx.appcompat.content.res.AppCompatResources
 import androidx.activity.viewModels
 import androidx.appcompat.app.AlertDialog
 import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
+import androidx.core.graphics.drawable.DrawableCompat
+import androidx.core.widget.doAfterTextChanged
 import androidx.lifecycle.lifecycleScope
 import androidx.recyclerview.widget.RecyclerView
 import androidx.viewpager2.widget.ViewPager2
 import com.google.android.material.appbar.MaterialToolbar
+import com.google.android.material.button.MaterialButton
+import com.google.android.material.color.MaterialColors
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
+import com.google.android.material.floatingactionbutton.FloatingActionButton
+import com.google.android.material.textfield.TextInputEditText
+import com.google.android.material.textfield.TextInputLayout
 import com.google.android.material.snackbar.Snackbar
+import java.text.DateFormat
+import java.time.ZoneId
+import java.util.Date
 import kotlinx.coroutines.launch
 import space.hackenslacker.kanbn4droid.app.MainActivity
 import space.hackenslacker.kanbn4droid.app.CardDetailPlaceholderActivity
@@ -42,8 +58,14 @@ class BoardDetailActivity : AppCompatActivity() {
     private lateinit var fullScreenErrorContainer: View
     private lateinit var fullScreenErrorText: TextView
     private lateinit var retryButton: Button
+    private lateinit var createFab: FloatingActionButton
 
     private var inlineTitleErrorMessage: String? = null
+    private var fabChooserDialog: AlertDialog? = null
+    private var addListDialog: AlertDialog? = null
+    private var addCardDialog: AlertDialog? = null
+    private var filterDialog: AlertDialog? = null
+    private var searchDialog: AlertDialog? = null
     private var moveDialog: AlertDialog? = null
     private var deleteSecondConfirmationDialog: AlertDialog? = null
     private var dismissMoveDialogWhenMutationEnds: Boolean = false
@@ -105,6 +127,42 @@ class BoardDetailActivity : AppCompatActivity() {
         }
     }
 
+    override fun onCreateOptionsMenu(menu: Menu): Boolean {
+        renderToolbarMenu(menu, viewModel.uiState.value)
+        return true
+    }
+
+    override fun onPrepareOptionsMenu(menu: Menu): Boolean {
+        renderToolbarMenu(menu, viewModel.uiState.value)
+        return super.onPrepareOptionsMenu(menu)
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return when (item.itemId) {
+            R.id.actionFilterByTag -> {
+                viewModel.onTagFilterIconTapped()
+                true
+            }
+
+            R.id.actionSearch -> {
+                viewModel.onSearchIconTapped()
+                true
+            }
+
+            R.id.actionSelectAll,
+            R.id.actionMoveCards,
+            R.id.actionDeleteCards,
+            -> handleSelectionAction(item)
+
+            else -> super.onOptionsItemSelected(item)
+        }
+    }
+
+    override fun onPostResume() {
+        super.onPostResume()
+        renderSelectionActions(viewModel.uiState.value)
+    }
+
     private fun bindViews() {
         toolbar = findViewById(R.id.boardDetailToolbar)
         pager = findViewById(R.id.boardDetailPager)
@@ -113,6 +171,7 @@ class BoardDetailActivity : AppCompatActivity() {
         fullScreenErrorContainer = findViewById(R.id.boardDetailFullScreenErrorContainer)
         fullScreenErrorText = findViewById(R.id.boardDetailFullScreenErrorText)
         retryButton = findViewById(R.id.boardDetailRetryButton)
+        createFab = findViewById(R.id.boardDetailCreateFab)
     }
 
     private fun setupToolbar() {
@@ -120,11 +179,14 @@ class BoardDetailActivity : AppCompatActivity() {
         supportActionBar?.setDisplayHomeAsUpEnabled(true)
         supportActionBar?.title = intent.getStringExtra(EXTRA_BOARD_TITLE).orEmpty()
         toolbar.setNavigationOnClickListener {
-            onBackPressedDispatcher.onBackPressed()
+            onBackPressed()
         }
         retryButton.setOnClickListener {
             viewModel.retryLoad()
         }
+        createFab.setOnClickListener {
+            viewModel.openFabChooser()
+        }
     }
 
     private fun setupPager() {
@@ -228,7 +290,7 @@ class BoardDetailActivity : AppCompatActivity() {
         }
         initialProgress.visibility = if (state.isInitialLoading && state.boardDetail == null) View.VISIBLE else View.GONE
 
-        val boardLists = state.boardDetail?.lists.orEmpty()
+        val boardLists = state.filteredBoardDetail?.lists.orEmpty()
         val applyPagerState = {
             pagerAdapter.submit(
                 lists = boardLists,
@@ -260,7 +322,10 @@ class BoardDetailActivity : AppCompatActivity() {
         }
 
         renderSelectionActions(state)
+        invalidateOptionsMenu()
         renderOpenDialogs(state)
+        createFab.isEnabled = !state.isMutating
+        createFab.visibility = if (state.selectedCardIds.isEmpty()) View.VISIBLE else View.GONE
     }
 
     private fun showBlockingStartupErrorAndFinish(message: String) {
@@ -275,6 +340,75 @@ class BoardDetailActivity : AppCompatActivity() {
     }
 
     private fun renderOpenDialogs(state: BoardDetailUiState) {
+        if (state.isFabChooserOpen && fabChooserDialog == null) {
+            showFabChooserDialog(state)
+        } else if (!state.isFabChooserOpen) {
+            fabChooserDialog?.dismiss()
+            fabChooserDialog = null
+        }
+
+        if (state.isAddListDialogOpen && addListDialog == null) {
+            showAddListDialog(state)
+        }
+        addListDialog?.let { dialog ->
+            val titleLayout = dialog.findViewById<TextInputLayout>(R.id.addListTitleLayout)
+            val titleInput = dialog.findViewById<TextInputEditText>(R.id.addListTitleInput)
+            titleLayout?.error = state.addListTitleError
+            titleInput?.isEnabled = !state.isMutating
+            dialog.getButton(AlertDialog.BUTTON_POSITIVE)?.isEnabled = !state.isMutating
+            dialog.getButton(AlertDialog.BUTTON_NEGATIVE)?.isEnabled = !state.isMutating
+            if (!state.isAddListDialogOpen) {
+                dialog.dismiss()
+                addListDialog = null
+            }
+        }
+
+        if (state.isAddCardDialogOpen && addCardDialog == null) {
+            showAddCardDialog(state)
+        }
+        addCardDialog?.let { dialog ->
+            val titleLayout = dialog.findViewById<TextInputLayout>(R.id.addCardTitleLayout)
+            val titleInput = dialog.findViewById<TextInputEditText>(R.id.addCardTitleInput)
+            val descriptionInput = dialog.findViewById<TextInputEditText>(R.id.addCardDescriptionInput)
+            val dueDateText = dialog.findViewById<TextView>(R.id.addCardDueDateText)
+            val clearDueDateAction = dialog.findViewById<TextView>(R.id.addCardClearDueDateAction)
+            titleLayout?.error = state.addCardTitleError
+            titleInput?.isEnabled = !state.isMutating
+            descriptionInput?.isEnabled = !state.isMutating
+            dueDateText?.text = formatDueDateForDialog(state.addCardDueDate)
+            dueDateText?.isEnabled = !state.isMutating
+            clearDueDateAction?.visibility = if (state.addCardDueDate != null) View.VISIBLE else View.GONE
+            clearDueDateAction?.isEnabled = !state.isMutating
+            dialog.getButton(AlertDialog.BUTTON_POSITIVE)?.isEnabled = !state.isMutating
+            dialog.getButton(AlertDialog.BUTTON_NEGATIVE)?.isEnabled = !state.isMutating
+            if (!state.isAddCardDialogOpen) {
+                dialog.dismiss()
+                addCardDialog = null
+            }
+        }
+
+        if (state.isFilterDialogOpen && filterDialog == null) {
+            showFilterDialog(state)
+        }
+        if (!state.isFilterDialogOpen) {
+            filterDialog?.dismiss()
+            filterDialog = null
+        }
+
+        if (state.isSearchDialogOpen && searchDialog == null) {
+            showSearchDialog(state)
+        }
+        searchDialog?.let { dialog ->
+            val input = dialog.findViewById<TextInputEditText>(R.id.searchTitleInput)
+            input?.isEnabled = !state.isMutating
+            dialog.getButton(AlertDialog.BUTTON_POSITIVE)?.isEnabled = !state.isMutating
+            dialog.getButton(AlertDialog.BUTTON_NEGATIVE)?.isEnabled = !state.isMutating
+            if (!state.isSearchDialogOpen) {
+                dialog.dismiss()
+                searchDialog = null
+            }
+        }
+
         val activeMoveDialog = moveDialog
         if (activeMoveDialog != null) {
             val lists = state.boardDetail?.lists.orEmpty()
@@ -322,18 +456,38 @@ class BoardDetailActivity : AppCompatActivity() {
     }
 
     private fun renderSelectionActions(state: BoardDetailUiState) {
-        val inSelection = state.selectedCardIds.isNotEmpty()
-        toolbar.menu.clear()
-        if (!inSelection) {
+        // Kept for compatibility with existing call sites; menu rendering is delegated to
+        // framework options menu callbacks.
+    }
+
+    private fun renderToolbarMenu(menu: Menu, state: BoardDetailUiState) {
+        menu.clear()
+        if (state.selectedCardIds.isNotEmpty()) {
+            menu.add(Menu.NONE, R.id.actionSelectAll, Menu.NONE, getString(R.string.select_all)).apply {
+                setIcon(R.drawable.ic_select_all_grid_24)
+                setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS)
+                tooltipText = getString(R.string.select_all)
+            }
+            menu.add(Menu.NONE, R.id.actionMoveCards, Menu.NONE, getString(R.string.move_cards)).apply {
+                setIcon(R.drawable.ic_move_cards_horizontal_24)
+                setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS)
+                tooltipText = getString(R.string.move_cards)
+            }
+            menu.add(Menu.NONE, R.id.actionDeleteCards, Menu.NONE, getString(R.string.delete_cards)).apply {
+                setIcon(R.drawable.ic_delete_24)
+                setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS)
+                tooltipText = getString(R.string.delete_cards)
+            }
             return
         }
-        toolbar.inflateMenu(R.menu.menu_board_detail_selection)
-        toolbar.menu.findItem(R.id.actionSelectAll)?.tooltipText = getString(R.string.select_all)
-        toolbar.menu.findItem(R.id.actionMoveCards)?.tooltipText = getString(R.string.move_cards)
-        toolbar.menu.findItem(R.id.actionDeleteCards)?.tooltipText = getString(R.string.delete_cards)
-        toolbar.setOnMenuItemClickListener { item ->
-            handleSelectionAction(item)
-        }
+
+        menuInflater.inflate(R.menu.menu_board_detail_main, menu)
+        val filterItem = menu.findItem(R.id.actionFilterByTag)
+        val searchItem = menu.findItem(R.id.actionSearch)
+        filterItem?.tooltipText = getString(R.string.filter_by_tag)
+        searchItem?.tooltipText = getString(R.string.search)
+        tintMainMenuIcon(filterItem, state.activeTagFilterIds.isNotEmpty())
+        tintMainMenuIcon(searchItem, state.activeTitleQuery.isNotBlank())
     }
 
     private fun handleSelectionAction(item: MenuItem): Boolean {
@@ -357,6 +511,241 @@ class BoardDetailActivity : AppCompatActivity() {
         }
     }
 
+    private fun tintMainMenuIcon(item: MenuItem?, isActive: Boolean) {
+        val drawableRes = when (item?.itemId) {
+            R.id.actionFilterByTag -> R.drawable.ic_filter_list_24
+            R.id.actionSearch -> R.drawable.ic_search_24
+            else -> null
+        } ?: return
+        val icon = AppCompatResources.getDrawable(this, drawableRes)?.mutate() ?: return
+        val wrapped = DrawableCompat.wrap(icon)
+        val tintColor = if (isActive) {
+            MaterialColors.getColor(this, com.google.android.material.R.attr.colorPrimary, ContextCompat.getColor(this, android.R.color.holo_blue_light))
+        } else {
+            MaterialColors.getColor(this, com.google.android.material.R.attr.colorOnSurfaceVariant, ContextCompat.getColor(this, android.R.color.black))
+        }
+        DrawableCompat.setTint(wrapped, tintColor)
+        item?.icon = wrapped
+        item?.iconTintList = android.content.res.ColorStateList.valueOf(tintColor)
+    }
+
+    private fun showFabChooserDialog(state: BoardDetailUiState) {
+        val root = LinearLayout(this).apply {
+            orientation = LinearLayout.VERTICAL
+            setPadding(48, 24, 48, 24)
+        }
+        val addListButton = MaterialButton(this).apply {
+            text = getString(R.string.add_new_list)
+            setOnClickListener {
+                viewModel.openAddListDialog()
+            }
+        }
+        val addCardButton = MaterialButton(this).apply {
+            text = getString(R.string.add_new_card)
+            isEnabled = state.canAddCard
+            setOnClickListener {
+                viewModel.openAddCardDialog()
+            }
+        }
+        val helperText = TextView(this).apply {
+            text = getString(R.string.create_a_list_first_to_add_cards)
+            visibility = if (state.canAddCard) View.GONE else View.VISIBLE
+            setPadding(8, 4, 8, 0)
+        }
+        root.addView(addListButton)
+        root.addView(addCardButton)
+        root.addView(helperText)
+
+        val dialog = MaterialAlertDialogBuilder(this)
+            .setView(root)
+            .setOnDismissListener {
+                if (fabChooserDialog != null) {
+                    viewModel.closeFabChooser()
+                }
+                fabChooserDialog = null
+            }
+            .create()
+        fabChooserDialog = dialog
+        dialog.show()
+    }
+
+    private fun showAddListDialog(state: BoardDetailUiState) {
+        val dialogView = LayoutInflater.from(this).inflate(R.layout.dialog_add_list, null)
+        val titleLayout: TextInputLayout = dialogView.findViewById(R.id.addListTitleLayout)
+        val titleInput: TextInputEditText = dialogView.findViewById(R.id.addListTitleInput)
+        titleInput.setText(state.addListTitleDraft)
+        titleInput.doAfterTextChanged { viewModel.updateAddListTitle(it?.toString().orEmpty()) }
+
+        val dialog = MaterialAlertDialogBuilder(this)
+            .setTitle(R.string.add_new_list)
+            .setView(dialogView)
+            .setNegativeButton(R.string.cancel, null)
+            .setPositiveButton(R.string.add_list, null)
+            .create()
+        dialog.setOnShowListener {
+            dialog.getButton(AlertDialog.BUTTON_POSITIVE)?.setOnClickListener {
+                titleLayout.error = null
+                viewModel.createList()
+            }
+        }
+        dialog.setOnDismissListener {
+            if (addListDialog != null && viewModel.uiState.value.isAddListDialogOpen) {
+                viewModel.cancelAddListDialog()
+            }
+            addListDialog = null
+        }
+        addListDialog = dialog
+        dialog.show()
+    }
+
+    private fun showAddCardDialog(state: BoardDetailUiState) {
+        val dialogView = LayoutInflater.from(this).inflate(R.layout.dialog_add_card, null)
+        val titleInput: TextInputEditText = dialogView.findViewById(R.id.addCardTitleInput)
+        val descriptionInput: TextInputEditText = dialogView.findViewById(R.id.addCardDescriptionInput)
+        val dueDateText: TextView = dialogView.findViewById(R.id.addCardDueDateText)
+        val clearDueDateAction: TextView = dialogView.findViewById(R.id.addCardClearDueDateAction)
+        val tagsPlaceholderText: TextView = dialogView.findViewById(R.id.addCardTagsPlaceholderText)
+        val tagsContainer: LinearLayout = dialogView.findViewById(R.id.addCardTagsContainer)
+        val tags = state.boardDetail
+            ?.lists
+            .orEmpty()
+            .flatMap { it.cards }
+            .flatMap { it.tags }
+            .distinctBy { it.id }
+            .sortedBy { it.name.lowercase() }
+
+        titleInput.setText(state.addCardTitleDraft)
+        descriptionInput.setText(state.addCardDescriptionDraft)
+        titleInput.doAfterTextChanged { viewModel.updateAddCardTitle(it?.toString().orEmpty()) }
+        descriptionInput.doAfterTextChanged { viewModel.updateAddCardDescription(it?.toString().orEmpty()) }
+        dueDateText.text = formatDueDateForDialog(state.addCardDueDate)
+        clearDueDateAction.visibility = if (state.addCardDueDate != null) View.VISIBLE else View.GONE
+        dueDateText.setOnClickListener { openAddCardDatePicker(state.addCardDueDate) }
+        clearDueDateAction.setOnClickListener { viewModel.clearDueDate() }
+        tagsPlaceholderText.visibility = if (tags.isEmpty()) View.VISIBLE else View.GONE
+        tags.forEach { tag ->
+            val checkBox = CheckBox(this).apply {
+                text = tag.name
+                isChecked = state.addCardSelectedTagIds.contains(tag.id)
+                setOnCheckedChangeListener { _, _ ->
+                    viewModel.toggleAddCardTag(tag.id)
+                }
+            }
+            tagsContainer.addView(checkBox)
+        }
+
+        val dialog = MaterialAlertDialogBuilder(this)
+            .setTitle(R.string.add_new_card)
+            .setView(dialogView)
+            .setNegativeButton(R.string.cancel, null)
+            .setPositiveButton(R.string.add_card, null)
+            .create()
+        dialog.setOnShowListener {
+            dialog.getButton(AlertDialog.BUTTON_POSITIVE)?.setOnClickListener {
+                viewModel.createCard()
+            }
+        }
+        dialog.setOnDismissListener {
+            if (addCardDialog != null && viewModel.uiState.value.isAddCardDialogOpen) {
+                viewModel.cancelAddCardDialog()
+            }
+            addCardDialog = null
+        }
+        addCardDialog = dialog
+        dialog.show()
+    }
+
+    private fun openAddCardDatePicker(currentDate: java.time.LocalDate?) {
+        val seed = currentDate ?: java.time.LocalDate.now()
+        DatePickerDialog(
+            this,
+            { _, year, month, dayOfMonth ->
+                viewModel.setDueDate(java.time.LocalDate.of(year, month + 1, dayOfMonth))
+            },
+            seed.year,
+            seed.monthValue - 1,
+            seed.dayOfMonth,
+        ).show()
+    }
+
+    private fun formatDueDateForDialog(dueDate: java.time.LocalDate?): String {
+        if (dueDate == null) {
+            return getString(R.string.due_date)
+        }
+        val epochMillis = dueDate
+            .atStartOfDay(ZoneId.systemDefault())
+            .toInstant()
+            .toEpochMilli()
+        return DateFormat.getDateInstance(DateFormat.MEDIUM).format(Date(epochMillis))
+    }
+
+    private fun showFilterDialog(state: BoardDetailUiState) {
+        val dialogView = LayoutInflater.from(this).inflate(R.layout.dialog_filter_tags, null)
+        val container: LinearLayout = dialogView.findViewById(R.id.filterTagsContainer)
+        val tags = state.boardDetail
+            ?.lists
+            .orEmpty()
+            .flatMap { it.cards }
+            .flatMap { it.tags }
+            .distinctBy { it.id }
+            .sortedBy { it.name.lowercase() }
+
+        tags.forEach { tag ->
+            val checkBox = CheckBox(this).apply {
+                text = tag.name
+                isChecked = state.pendingTagFilterIds.contains(tag.id)
+                setOnCheckedChangeListener { _, _ ->
+                    val selected = mutableSetOf<String>()
+                    for (i in 0 until container.childCount) {
+                        val child = container.getChildAt(i)
+                        if (child is CheckBox && child.isChecked) {
+                            selected.add(tags[i].id)
+                        }
+                    }
+                    viewModel.updatePendingTagFilterIds(selected)
+                }
+            }
+            container.addView(checkBox)
+        }
+
+        val dialog = MaterialAlertDialogBuilder(this)
+            .setTitle(R.string.filter_by_tag)
+            .setView(dialogView)
+            .setNegativeButton(R.string.cancel) { _, _ -> viewModel.cancelFilterDialog() }
+            .setPositiveButton(R.string.filter) { _, _ -> viewModel.applyFilterDialog() }
+            .create()
+        dialog.setOnDismissListener {
+            if (filterDialog != null && viewModel.uiState.value.isFilterDialogOpen) {
+                viewModel.cancelFilterDialog()
+            }
+            filterDialog = null
+        }
+        filterDialog = dialog
+        dialog.show()
+    }
+
+    private fun showSearchDialog(state: BoardDetailUiState) {
+        val dialogView = LayoutInflater.from(this).inflate(R.layout.dialog_search_title, null)
+        val input: TextInputEditText = dialogView.findViewById(R.id.searchTitleInput)
+        input.setText(state.pendingTitleQuery)
+        input.doAfterTextChanged { viewModel.updatePendingTitleQuery(it?.toString().orEmpty()) }
+
+        val dialog = MaterialAlertDialogBuilder(this)
+            .setTitle(R.string.search_by_title)
+            .setView(dialogView)
+            .setNegativeButton(R.string.cancel) { _, _ -> viewModel.cancelSearchDialog() }
+            .setPositiveButton(R.string.search) { _, _ -> viewModel.applySearchDialog() }
+            .create()
+        dialog.setOnDismissListener {
+            if (searchDialog != null && viewModel.uiState.value.isSearchDialogOpen) {
+                viewModel.cancelSearchDialog()
+            }
+            searchDialog = null
+        }
+        searchDialog = dialog
+        dialog.show()
+    }
+
     private fun showMoveCardsDialog() {
         val lists = viewModel.uiState.value.boardDetail?.lists.orEmpty()
         if (lists.isEmpty()) {

app/src/main/java/space/hackenslacker/kanbn4droid/app/boarddetail/BoardDetailModels.kt

@@ -25,6 +25,10 @@ data class BoardTagSummary(
     val colorHex: String,
 )
 
+data class CreatedEntityRef(
+    val publicId: String?,
+)
+
 sealed interface CardBatchMutationResult {
     data object Success : CardBatchMutationResult
     data class PartialSuccess(

app/src/main/java/space/hackenslacker/kanbn4droid/app/boarddetail/BoardDetailRepository.kt

@@ -3,6 +3,7 @@ package space.hackenslacker.kanbn4droid.app.boarddetail
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
+import java.time.LocalDate
 import space.hackenslacker.kanbn4droid.app.auth.ApiKeyStore
 import space.hackenslacker.kanbn4droid.app.auth.KanbnApiClient
 import space.hackenslacker.kanbn4droid.app.auth.LabelDetail
@@ -69,6 +70,81 @@ class BoardDetailRepository(
         )
     }
 
+    suspend fun createList(boardPublicId: String, title: String): BoardsApiResult<CreatedEntityRef> {
+        val normalizedBoardPublicId = boardPublicId.trim()
+        if (normalizedBoardPublicId.isBlank()) {
+            return BoardsApiResult.Failure("Board id is required")
+        }
+
+        val normalizedTitle = title.trim()
+        if (normalizedTitle.isBlank()) {
+            return BoardsApiResult.Failure("List title is required")
+        }
+
+        val session = when (val sessionResult = session()) {
+            is BoardsApiResult.Success -> sessionResult.value
+            is BoardsApiResult.Failure -> return sessionResult
+        }
+
+        val appendIndex = when (
+            val boardDetailResult = apiClient.getBoardDetail(
+                baseUrl = session.baseUrl,
+                apiKey = session.apiKey,
+                boardId = normalizedBoardPublicId,
+            )
+        ) {
+            is BoardsApiResult.Success -> boardDetailResult.value.lists.size
+            is BoardsApiResult.Failure -> return BoardsApiResult.Failure(boardDetailResult.message)
+        }
+
+        return apiClient.createList(
+            baseUrl = session.baseUrl,
+            apiKey = session.apiKey,
+            boardPublicId = normalizedBoardPublicId,
+            title = normalizedTitle,
+            appendIndex = appendIndex,
+        )
+    }
+
+    suspend fun createCard(
+        listPublicId: String,
+        title: String,
+        description: String?,
+        dueDate: LocalDate?,
+        tagPublicIds: Collection<String>,
+    ): BoardsApiResult<CreatedEntityRef> {
+        val normalizedListPublicId = listPublicId.trim()
+        if (normalizedListPublicId.isBlank()) {
+            return BoardsApiResult.Failure("List id is required")
+        }
+
+        val normalizedTitle = title.trim()
+        if (normalizedTitle.isBlank()) {
+            return BoardsApiResult.Failure("Card title is required")
+        }
+
+        val normalizedDescription = description?.trim()?.takeIf { it.isNotBlank() }
+        val normalizedTagPublicIds = tagPublicIds
+            .map { it.trim() }
+            .filter { it.isNotBlank() }
+            .distinct()
+
+        val session = when (val sessionResult = session()) {
+            is BoardsApiResult.Success -> sessionResult.value
+            is BoardsApiResult.Failure -> return sessionResult
+        }
+
+        return apiClient.createCard(
+            baseUrl = session.baseUrl,
+            apiKey = session.apiKey,
+            listPublicId = normalizedListPublicId,
+            title = normalizedTitle,
+            description = normalizedDescription,
+            dueDate = dueDate,
+            tagPublicIds = normalizedTagPublicIds,
+        )
+    }
+
     suspend fun moveCards(cardIds: Collection<String>, targetListId: String): CardBatchMutationResult {
         val normalizedTargetListId = targetListId.trim()
         if (normalizedTargetListId.isBlank()) {

app/src/main/java/space/hackenslacker/kanbn4droid/app/boarddetail/BoardDetailViewModel.kt

@@ -3,6 +3,7 @@ package space.hackenslacker.kanbn4droid.app.boarddetail
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.viewModelScope
+import java.time.LocalDate
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharedFlow
@@ -13,6 +14,8 @@ import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
 import space.hackenslacker.kanbn4droid.app.boards.BoardsApiResult
 
+private const val ADD_CARD_DISABLED_MESSAGE = "Create a list first to add cards."
+
 data class BoardDetailUiState(
     val isInitialLoading: Boolean = false,
     val isRefreshing: Boolean = false,
@@ -23,7 +26,35 @@ data class BoardDetailUiState(
     val selectedCardIds: Set<String> = emptySet(),
     val editingListId: String? = null,
     val editingListTitle: String = "",
+    val pendingTagFilterIds: Set<String> = emptySet(),
+    val pendingTitleQuery: String = "",
+    val activeTagFilterIds: Set<String> = emptySet(),
+    val activeTitleQuery: String = "",
+    val isFabChooserOpen: Boolean = false,
+    val isAddListDialogOpen: Boolean = false,
+    val isAddCardDialogOpen: Boolean = false,
+    val isFilterDialogOpen: Boolean = false,
+    val isSearchDialogOpen: Boolean = false,
+    val addListTitleDraft: String = "",
+    val addListTitleError: String? = null,
+    val addCardTitleDraft: String = "",
+    val addCardTitleError: String? = null,
+    val addCardDescriptionDraft: String = "",
+    val addCardDueDate: LocalDate? = null,
+    val addCardSelectedTagIds: Set<String> = emptySet(),
+) {
+    val canAddCard: Boolean
+        get() = boardDetail?.lists?.isNotEmpty() == true
+
+    val addCardDisabledMessage: String?
+        get() = if (canAddCard) null else ADD_CARD_DISABLED_MESSAGE
+
+    val filteredBoardDetail: BoardDetail?
+        get() = boardDetail?.withFilteredCards(
+            tagFilterIds = activeTagFilterIds,
+            titleQuery = activeTitleQuery,
         )
+}
 
 sealed interface BoardDetailUiEvent {
     data class NavigateToCardPlaceholder(val cardId: String) : BoardDetailUiEvent
@@ -33,6 +64,15 @@ sealed interface BoardDetailUiEvent {
 
 interface BoardDetailDataSource {
     suspend fun getBoardDetail(boardId: String): BoardsApiResult<BoardDetail>
+    suspend fun createList(boardPublicId: String, title: String): BoardsApiResult<CreatedEntityRef>
+    suspend fun createCard(
+        listPublicId: String,
+        title: String,
+        description: String?,
+        dueDate: LocalDate?,
+        tagPublicIds: Collection<String>,
+    ): BoardsApiResult<CreatedEntityRef>
+
     suspend fun moveCards(cardIds: Collection<String>, targetListId: String): CardBatchMutationResult
     suspend fun deleteCards(cardIds: Collection<String>): CardBatchMutationResult
     suspend fun renameList(listId: String, newTitle: String): BoardsApiResult<Unit>
@@ -45,6 +85,26 @@ internal class BoardDetailRepositoryDataSource(
         return repository.getBoardDetail(boardId)
     }
 
+    override suspend fun createList(boardPublicId: String, title: String): BoardsApiResult<CreatedEntityRef> {
+        return repository.createList(boardPublicId, title)
+    }
+
+    override suspend fun createCard(
+        listPublicId: String,
+        title: String,
+        description: String?,
+        dueDate: LocalDate?,
+        tagPublicIds: Collection<String>,
+    ): BoardsApiResult<CreatedEntityRef> {
+        return repository.createCard(
+            listPublicId = listPublicId,
+            title = title,
+            description = description,
+            dueDate = dueDate,
+            tagPublicIds = tagPublicIds,
+        )
+    }
+
     override suspend fun moveCards(cardIds: Collection<String>, targetListId: String): CardBatchMutationResult {
         return repository.moveCards(cardIds, targetListId)
     }
@@ -88,7 +148,7 @@ class BoardDetailViewModel(
 
     fun selectAllOnCurrentPage() {
         val current = _uiState.value
-        val pageCards = current.boardDetail
+        val pageCards = current.filteredBoardDetail
             ?.lists
             ?.getOrNull(current.currentPageIndex)
             ?.cards
@@ -129,6 +189,298 @@ class BoardDetailViewModel(
         return true
     }
 
+    fun openFabChooser() {
+        _uiState.update { it.copy(isFabChooserOpen = true) }
+    }
+
+    fun closeFabChooser() {
+        _uiState.update { it.copy(isFabChooserOpen = false) }
+    }
+
+    fun openAddListDialog() {
+        _uiState.update {
+            it.copy(
+                isFabChooserOpen = false,
+                isAddListDialogOpen = true,
+                addListTitleError = null,
+            )
+        }
+    }
+
+    fun updateAddListTitle(title: String) {
+        _uiState.update {
+            it.copy(
+                addListTitleDraft = title,
+                addListTitleError = null,
+            )
+        }
+    }
+
+    fun cancelAddListDialog() {
+        _uiState.update {
+            it.copy(
+                isAddListDialogOpen = false,
+                addListTitleDraft = "",
+                addListTitleError = null,
+            )
+        }
+    }
+
+    fun createList() {
+        val snapshot = _uiState.value
+        if (snapshot.isMutating) {
+            return
+        }
+        val detail = snapshot.boardDetail ?: return
+        val title = snapshot.addListTitleDraft.trim()
+        if (title.isBlank()) {
+            setAddListLocalValidationError("List title is required")
+            return
+        }
+        val expectedIndex = detail.lists.size
+
+        viewModelScope.launch {
+            beginCreateListMutation()
+            when (val result = repository.createList(detail.id, title)) {
+                is BoardsApiResult.Success -> {
+                    closeAddListDialogAndResetDrafts()
+                    when (val reload = reloadDetailAndReconcile()) {
+                        is BoardsApiResult.Success -> {
+                            endMutation()
+                            val warning = verifyCreatedList(result.value.publicId, expectedIndex, reload.value)
+                            if (warning != null) {
+                                _events.emit(BoardDetailUiEvent.ShowWarning(warning))
+                            }
+                        }
+
+                        is BoardsApiResult.Failure -> {
+                            endMutation()
+                            emitRefreshFailureWarning()
+                        }
+                    }
+                }
+
+                is BoardsApiResult.Failure -> {
+                    endMutation()
+                    _events.emit(BoardDetailUiEvent.ShowServerError(result.message))
+                }
+            }
+        }
+    }
+
+    fun openAddCardDialog() {
+        val snapshot = _uiState.value
+        if (!snapshot.canAddCard) {
+            _uiState.update { it.copy(isFabChooserOpen = false, isAddCardDialogOpen = false) }
+            return
+        }
+
+        _uiState.update {
+            it.copy(
+                isFabChooserOpen = false,
+                isAddCardDialogOpen = true,
+                addCardTitleError = null,
+            )
+        }
+    }
+
+    fun updateAddCardTitle(title: String) {
+        _uiState.update {
+            it.copy(
+                addCardTitleDraft = title,
+                addCardTitleError = null,
+            )
+        }
+    }
+
+    fun updateAddCardDescription(description: String) {
+        _uiState.update { it.copy(addCardDescriptionDraft = description) }
+    }
+
+    fun setDueDate(dueDate: LocalDate) {
+        _uiState.update { it.copy(addCardDueDate = dueDate) }
+    }
+
+    fun clearDueDate() {
+        _uiState.update { it.copy(addCardDueDate = null) }
+    }
+
+    fun toggleAddCardTag(tagId: String) {
+        val normalizedTagId = tagId.trim()
+        if (normalizedTagId.isBlank()) {
+            return
+        }
+
+        _uiState.update {
+            val next = it.addCardSelectedTagIds.toMutableSet()
+            if (!next.add(normalizedTagId)) {
+                next.remove(normalizedTagId)
+            }
+            it.copy(addCardSelectedTagIds = next)
+        }
+    }
+
+    fun cancelAddCardDialog() {
+        _uiState.update { it.resetAddCardDrafts().copy(isAddCardDialogOpen = false) }
+    }
+
+    fun createCard() {
+        val snapshot = _uiState.value
+        if (snapshot.isMutating) {
+            return
+        }
+        val detail = snapshot.boardDetail ?: return
+        val currentList = detail.lists.getOrNull(snapshot.currentPageIndex) ?: return
+        val title = snapshot.addCardTitleDraft.trim()
+        if (title.isBlank()) {
+            setAddCardLocalValidationError("Card title is required")
+            return
+        }
+
+        viewModelScope.launch {
+            beginCreateCardMutation()
+            when (
+                val result = repository.createCard(
+                    listPublicId = currentList.id,
+                    title = title,
+                    description = snapshot.addCardDescriptionDraft,
+                    dueDate = snapshot.addCardDueDate,
+                    tagPublicIds = snapshot.addCardSelectedTagIds,
+                )
+            ) {
+                is BoardsApiResult.Success -> {
+                    closeAddCardDialogAndResetDrafts()
+                    when (val reload = reloadDetailAndReconcile()) {
+                        is BoardsApiResult.Success -> {
+                            endMutation()
+                            val warning = verifyCreatedCard(
+                                createdCardId = result.value.publicId,
+                                targetListId = currentList.id,
+                                detail = reload.value,
+                            )
+                            if (warning != null) {
+                                _events.emit(BoardDetailUiEvent.ShowWarning(warning))
+                            }
+                        }
+
+                        is BoardsApiResult.Failure -> {
+                            endMutation()
+                            emitRefreshFailureWarning()
+                        }
+                    }
+                }
+
+                is BoardsApiResult.Failure -> {
+                    endMutation()
+                    _events.emit(BoardDetailUiEvent.ShowServerError(result.message))
+                }
+            }
+        }
+    }
+
+    fun openFilterDialog() {
+        _uiState.update {
+            it.copy(
+                isFilterDialogOpen = true,
+                pendingTagFilterIds = it.activeTagFilterIds,
+            )
+        }
+    }
+
+    fun updatePendingTagFilterIds(tagIds: Set<String>) {
+        _uiState.update {
+            it.copy(
+                pendingTagFilterIds = tagIds
+                    .map { id -> id.trim() }
+                    .filter { id -> id.isNotBlank() }
+                    .toSet(),
+            )
+        }
+    }
+
+    fun applyFilterDialog() {
+        _uiState.update {
+            it.copy(
+                activeTagFilterIds = it.pendingTagFilterIds,
+                isFilterDialogOpen = false,
+            )
+        }
+    }
+
+    fun cancelFilterDialog() {
+        _uiState.update {
+            it.copy(
+                pendingTagFilterIds = it.activeTagFilterIds,
+                isFilterDialogOpen = false,
+            )
+        }
+    }
+
+    fun onTagFilterIconTapped() {
+        val snapshot = _uiState.value
+        if (snapshot.activeTagFilterIds.isNotEmpty()) {
+            _uiState.update {
+                it.copy(
+                    activeTagFilterIds = emptySet(),
+                    pendingTagFilterIds = emptySet(),
+                    isFilterDialogOpen = false,
+                )
+            }
+            return
+        }
+
+        openFilterDialog()
+    }
+
+    fun openSearchDialog() {
+        _uiState.update {
+            it.copy(
+                isSearchDialogOpen = true,
+                pendingTitleQuery = it.activeTitleQuery,
+            )
+        }
+    }
+
+    fun updatePendingTitleQuery(query: String) {
+        _uiState.update { it.copy(pendingTitleQuery = query) }
+    }
+
+    fun applySearchDialog() {
+        _uiState.update {
+            val trimmed = it.pendingTitleQuery.trim()
+            it.copy(
+                activeTitleQuery = trimmed,
+                pendingTitleQuery = trimmed,
+                isSearchDialogOpen = false,
+            )
+        }
+    }
+
+    fun cancelSearchDialog() {
+        _uiState.update {
+            it.copy(
+                pendingTitleQuery = it.activeTitleQuery,
+                isSearchDialogOpen = false,
+            )
+        }
+    }
+
+    fun onSearchIconTapped() {
+        val snapshot = _uiState.value
+        if (snapshot.activeTitleQuery.isNotBlank()) {
+            _uiState.update {
+                it.copy(
+                    activeTitleQuery = "",
+                    pendingTitleQuery = "",
+                    isSearchDialogOpen = false,
+                )
+            }
+            return
+        }
+
+        openSearchDialog()
+    }
+
     fun moveSelectedCards(targetListId: String) {
         val snapshot = _uiState.value
         if (snapshot.isMutating) {
@@ -191,9 +543,9 @@ class BoardDetailViewModel(
             when (val result = repository.renameList(editingListId, trimmedTitle)) {
                 is BoardsApiResult.Success -> {
                     _uiState.update { it.copy(editingListId = null, editingListTitle = "") }
-                    val reloadFailureMessage = tryReloadDetailAndReconcile()
+                    val reloadResult = reloadDetailAndReconcile()
                     _uiState.update { it.copy(isMutating = false) }
-                    if (reloadFailureMessage != null) {
+                    if (reloadResult is BoardsApiResult.Failure) {
                         _events.emit(
                             BoardDetailUiEvent.ShowWarning(
                                 "Changes applied, but refresh failed. Pull to refresh.",
@@ -276,9 +628,9 @@ class BoardDetailViewModel(
             when (val result = mutation(selectedIds)) {
                 is CardBatchMutationResult.Success -> {
                     _uiState.update { it.copy(selectedCardIds = emptySet()) }
-                    val reloadFailureMessage = tryReloadDetailAndReconcile()
+                    val reloadResult = reloadDetailAndReconcile()
                     _uiState.update { it.copy(isMutating = false) }
-                    if (reloadFailureMessage != null) {
+                    if (reloadResult is BoardsApiResult.Failure) {
                         _events.emit(
                             BoardDetailUiEvent.ShowWarning(
                                 "Changes applied, but refresh failed. Pull to refresh.",
@@ -288,8 +640,8 @@ class BoardDetailViewModel(
                 }
 
                 is CardBatchMutationResult.PartialSuccess -> {
-                    val reloadFailureMessage = tryReloadDetailAndReconcile()
-                    if (reloadFailureMessage == null) {
+                    val reloadResult = reloadDetailAndReconcile()
+                    if (reloadResult is BoardsApiResult.Success) {
                         val visibleIds = allVisibleCardIds(_uiState.value.boardDetail)
                         _uiState.update {
                             it.copy(selectedCardIds = result.failedCardIds.intersect(visibleIds))
@@ -325,14 +677,14 @@ class BoardDetailViewModel(
         }
     }
 
-    private suspend fun tryReloadDetailAndReconcile(): String? {
+    private suspend fun reloadDetailAndReconcile(): BoardsApiResult<BoardDetail> {
         return when (val result = repository.getBoardDetail(boardId)) {
             is BoardsApiResult.Success -> {
                 _uiState.update { reconcileWithNewDetail(it, result.value) }
-                null
+                result
             }
 
-            is BoardsApiResult.Failure -> result.message
+            is BoardsApiResult.Failure -> result
         }
     }
 
@@ -358,6 +710,8 @@ class BoardDetailViewModel(
             selectedCardIds = prunedSelection,
             editingListId = if (hasEditedList) current.editingListId else null,
             editingListTitle = if (hasEditedList) current.editingListTitle else "",
+            pendingTagFilterIds = current.pendingTagFilterIds.intersect(availableTagIds(detail)),
+            activeTagFilterIds = current.activeTagFilterIds.intersect(availableTagIds(detail)),
         )
     }
 
@@ -377,6 +731,96 @@ class BoardDetailViewModel(
             .toSet()
     }
 
+    private fun availableTagIds(detail: BoardDetail): Set<String> {
+        return detail.lists
+            .asSequence()
+            .flatMap { list -> list.cards.asSequence() }
+            .flatMap { card -> card.tags.asSequence() }
+            .map { tag -> tag.id }
+            .toSet()
+    }
+
+    private fun verifyCreatedList(createdListId: String?, expectedIndex: Int, detail: BoardDetail): String? {
+        val normalizedId = createdListId?.trim().orEmpty()
+        if (normalizedId.isBlank()) {
+            return CREATE_NON_DETERMINISTIC_WARNING
+        }
+        val actualIndex = detail.lists.indexOfFirst { list -> list.id == normalizedId }
+        if (actualIndex < 0) {
+            return CREATE_NON_DETERMINISTIC_WARNING
+        }
+        return if (actualIndex != expectedIndex) CREATE_LIST_PLACEMENT_WARNING else null
+    }
+
+    private fun verifyCreatedCard(createdCardId: String?, targetListId: String, detail: BoardDetail): String? {
+        val normalizedId = createdCardId?.trim().orEmpty()
+        if (normalizedId.isBlank()) {
+            return CREATE_NON_DETERMINISTIC_WARNING
+        }
+        val list = detail.lists.firstOrNull { it.id == targetListId }
+            ?: return CREATE_NON_DETERMINISTIC_WARNING
+        val actualIndex = list.cards.indexOfFirst { card -> card.id == normalizedId }
+        if (actualIndex < 0) {
+            return CREATE_NON_DETERMINISTIC_WARNING
+        }
+        return if (actualIndex != 0) CREATE_CARD_PLACEMENT_WARNING else null
+    }
+
+    private fun setAddListLocalValidationError(message: String) {
+        _uiState.update { it.copy(addListTitleError = message) }
+    }
+
+    private fun setAddCardLocalValidationError(message: String) {
+        _uiState.update { it.copy(addCardTitleError = message) }
+    }
+
+    private fun beginCreateListMutation() {
+        _uiState.update {
+            it.copy(
+                isMutating = true,
+                addListTitleError = null,
+            )
+        }
+    }
+
+    private fun beginCreateCardMutation() {
+        _uiState.update {
+            it.copy(
+                isMutating = true,
+                addCardTitleError = null,
+            )
+        }
+    }
+
+    private fun closeAddListDialogAndResetDrafts() {
+        _uiState.update { it.resetAddListDrafts().copy(isAddListDialogOpen = false) }
+    }
+
+    private fun closeAddCardDialogAndResetDrafts() {
+        _uiState.update { it.resetAddCardDrafts().copy(isAddCardDialogOpen = false) }
+    }
+
+    private fun endMutation() {
+        _uiState.update { it.copy(isMutating = false) }
+    }
+
+    private suspend fun emitRefreshFailureWarning() {
+        _events.emit(
+            BoardDetailUiEvent.ShowWarning(
+                "Changes applied, but refresh failed. Pull to refresh.",
+            ),
+        )
+    }
+
+    private companion object {
+        const val CREATE_LIST_PLACEMENT_WARNING =
+            "List created, but server ordering differed. Pull to refresh if needed."
+        const val CREATE_CARD_PLACEMENT_WARNING =
+            "Card created, but server ordering differed. Pull to refresh if needed."
+        const val CREATE_NON_DETERMINISTIC_WARNING =
+            "Created item could not be deterministically verified. Pull to refresh if needed."
+    }
+
     class Factory(
         private val boardId: String,
         private val repository: BoardDetailRepository,
@@ -393,3 +837,47 @@ class BoardDetailViewModel(
         }
     }
 }
+
+private fun BoardDetailUiState.resetAddCardDrafts(): BoardDetailUiState {
+    return copy(
+        addCardTitleDraft = "",
+        addCardTitleError = null,
+        addCardDescriptionDraft = "",
+        addCardDueDate = null,
+        addCardSelectedTagIds = emptySet(),
+    )
+}
+
+private fun BoardDetailUiState.resetAddListDrafts(): BoardDetailUiState {
+    return copy(
+        addListTitleDraft = "",
+        addListTitleError = null,
+    )
+}
+
+private fun BoardDetail.withFilteredCards(tagFilterIds: Set<String>, titleQuery: String): BoardDetail {
+    val normalizedTitleQuery = titleQuery.trim()
+    if (tagFilterIds.isEmpty() && normalizedTitleQuery.isEmpty()) {
+        return this
+    }
+
+    return copy(
+        lists = lists.map { list ->
+            list.copy(
+                cards = list.cards.filter { card ->
+                    val matchesTags = if (tagFilterIds.isEmpty()) {
+                        true
+                    } else {
+                        card.tags.any { tag -> tag.id in tagFilterIds }
+                    }
+                    val matchesTitle = if (normalizedTitleQuery.isEmpty()) {
+                        true
+                    } else {
+                        card.title.contains(normalizedTitleQuery, ignoreCase = true)
+                    }
+                    matchesTags && matchesTitle
+                },
+            )
+        },
+    )
+}

app/src/main/res/drawable/ic_filter_list_24.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M4,7h16v2H4zM7,11h10v2H7zM10,15h4v2h-4z" />
+
+</vector>

app/src/main/res/drawable/ic_search_24.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M15.5,14h-0.79l-0.28,-0.27a6,6 0,1 0,-1.41,1.41l0.27,0.28v0.79L20,21.5L21.5,20zM10,14a4,4 0,1 1,0 -8a4,4 0,0 1,0 8z" />
+
+</vector>

app/src/main/res/layout/activity_board_detail.xml

@@ -68,4 +68,13 @@
                 android:text="@string/retry" />
         </LinearLayout>
     </FrameLayout>
+
+    <com.google.android.material.floatingactionbutton.FloatingActionButton
+        android:id="@+id/boardDetailCreateFab"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom|end"
+        android:layout_margin="16dp"
+        android:contentDescription="@string/board_detail_add"
+        app:srcCompat="@android:drawable/ic_input_add" />
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

app/src/main/res/layout/dialog_add_card.xml

@@ -0,0 +1,102 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:paddingStart="24dp"
+        android:paddingTop="8dp"
+        android:paddingEnd="24dp"
+        android:paddingBottom="8dp">
+
+        <com.google.android.material.textfield.TextInputLayout
+            android:id="@+id/addCardTitleLayout"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:hint="@string/card_title">
+
+            <com.google.android.material.textfield.TextInputEditText
+                android:id="@+id/addCardTitleInput"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:inputType="textCapSentences|text"
+                android:maxLines="1" />
+        </com.google.android.material.textfield.TextInputLayout>
+
+        <com.google.android.material.textfield.TextInputLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:hint="@string/description">
+
+            <com.google.android.material.textfield.TextInputEditText
+                android:id="@+id/addCardDescriptionInput"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:gravity="top|start"
+                android:inputType="textMultiLine|textCapSentences"
+                android:minLines="3" />
+        </com.google.android.material.textfield.TextInputLayout>
+
+        <LinearLayout
+            android:id="@+id/addCardDueDateRow"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:gravity="center_vertical"
+            android:orientation="horizontal">
+
+            <TextView
+                android:id="@+id/addCardDueDateText"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:text="@string/due_date"
+                android:textAppearance="@style/TextAppearance.Material3.BodyLarge" />
+
+            <TextView
+                android:id="@+id/addCardClearDueDateAction"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:paddingStart="8dp"
+                android:paddingTop="4dp"
+                android:paddingEnd="8dp"
+                android:paddingBottom="4dp"
+                android:text="@string/clear_due_date"
+                android:textAppearance="@style/TextAppearance.Material3.LabelLarge" />
+        </LinearLayout>
+
+        <LinearLayout
+            android:id="@+id/addCardTagSection"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:orientation="vertical">
+
+            <TextView
+                android:id="@+id/addCardTagsLabel"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:text="@string/add_card_tags"
+                android:textAppearance="@style/TextAppearance.Material3.TitleSmall" />
+
+            <TextView
+                android:id="@+id/addCardTagsPlaceholderText"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="4dp"
+                android:text="@string/add_card_tags_placeholder"
+                android:textAppearance="@style/TextAppearance.Material3.BodyMedium" />
+
+            <LinearLayout
+                android:id="@+id/addCardTagsContainer"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp"
+                android:orientation="vertical" />
+        </LinearLayout>
+    </LinearLayout>
+</ScrollView>

app/src/main/res/layout/dialog_add_list.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:paddingStart="24dp"
+    android:paddingTop="8dp"
+    android:paddingEnd="24dp"
+    android:paddingBottom="8dp">
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:id="@+id/addListTitleLayout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:hint="@string/list_title_hint">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:id="@+id/addListTitleInput"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:inputType="textCapSentences|text"
+            android:maxLines="1" />
+    </com.google.android.material.textfield.TextInputLayout>
+
+</LinearLayout>

app/src/main/res/layout/dialog_filter_tags.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:paddingStart="24dp"
+        android:paddingTop="8dp"
+        android:paddingEnd="24dp"
+        android:paddingBottom="8dp">
+
+        <TextView
+            android:id="@+id/filterTagsPlaceholderText"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/filter_tags_placeholder"
+            android:textAppearance="@style/TextAppearance.Material3.BodyMedium" />
+
+        <LinearLayout
+            android:id="@+id/filterTagsContainer"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:orientation="vertical" />
+    </LinearLayout>
+</ScrollView>

app/src/main/res/layout/dialog_search_title.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:paddingStart="24dp"
+    android:paddingTop="8dp"
+    android:paddingEnd="24dp"
+    android:paddingBottom="8dp">
+
+    <com.google.android.material.textfield.TextInputLayout
+        android:id="@+id/searchTitleLayout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:hint="@string/search">
+
+        <com.google.android.material.textfield.TextInputEditText
+            android:id="@+id/searchTitleInput"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:inputType="text"
+            android:maxLines="1" />
+    </com.google.android.material.textfield.TextInputLayout>
+
+</LinearLayout>

app/src/main/res/menu/menu_board_detail_main.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/actionFilterByTag"
+        android:icon="@drawable/ic_filter_list_24"
+        android:title="@string/filter_by_tag"
+        app:showAsAction="always" />
+
+    <item
+        android:id="@+id/actionSearch"
+        android:icon="@drawable/ic_search_24"
+        android:title="@string/search"
+        app:showAsAction="always" />
+</menu>

app/src/main/res/values/strings.xml

@@ -50,4 +50,22 @@
     <string name="card_detail_placeholder_subtitle">Card detail view is coming soon.</string>
     <string name="board_detail_unable_to_open_board">Unable to open board.</string>
     <string name="board_detail_session_expired">Session expired. Please sign in again.</string>
+    <string name="board_detail_add">Add</string>
+    <string name="filter_by_tag">Filter by tag</string>
+    <string name="search">Search</string>
+    <string name="search_by_title">Search by title</string>
+    <string name="filter">Filter</string>
+    <string name="add_new_list">Add new list</string>
+    <string name="add_new_card">Add new card</string>
+    <string name="add_list">Add list</string>
+    <string name="add_card">Add card</string>
+    <string name="create_a_list_first_to_add_cards">Create a list first to add cards.</string>
+    <string name="card_title">Card title</string>
+    <string name="card_title_required">Card title is required</string>
+    <string name="description">Description</string>
+    <string name="due_date">Due date</string>
+    <string name="clear_due_date">Clear date</string>
+    <string name="add_card_tags">Tags</string>
+    <string name="add_card_tags_placeholder">Select one or more tags.</string>
+    <string name="filter_tags_placeholder">Select tags to include.</string>
 </resources>

app/src/test/java/space/hackenslacker/kanbn4droid/app/auth/HttpKanbnApiClientBoardDetailParsingTest.kt

@@ -6,6 +6,7 @@ import java.net.InetSocketAddress
 import java.net.ServerSocket
 import java.net.Socket
 import java.time.Instant
+import java.time.LocalDate
 import java.util.concurrent.CopyOnWriteArrayList
 import java.util.concurrent.Executors
 import java.util.concurrent.TimeUnit
@@ -17,10 +18,160 @@ import org.junit.Assert.assertNull
 import org.junit.Assert.assertTrue
 import org.junit.Test
 import space.hackenslacker.kanbn4droid.app.boarddetail.BoardDetail
+import space.hackenslacker.kanbn4droid.app.boarddetail.CreatedEntityRef
 import space.hackenslacker.kanbn4droid.app.boards.BoardsApiResult
 
 class HttpKanbnApiClientBoardDetailParsingTest {
 
+    @Test
+    fun createList_sendsAppendIndexPayload_andParsesPublicIdFallbacks() = runTest {
+        TestServer().use { server ->
+            server.register(
+                path = "/api/v1/lists",
+                method = "POST",
+                status = 200,
+                responseBody = """{"list":{"public_id":"list-new"}}""",
+            )
+
+            val result = HttpKanbnApiClient().createList(
+                baseUrl = server.baseUrl,
+                apiKey = "api",
+                boardPublicId = "board-1",
+                title = "Sprint",
+                appendIndex = 7,
+            )
+
+            assertTrue(result is BoardsApiResult.Success<*>)
+            val createdRef = (result as BoardsApiResult.Success<*>).value as CreatedEntityRef
+            assertEquals("list-new", createdRef.publicId)
+
+            val request = server.findRequest("POST", "/api/v1/lists")
+            assertNotNull(request)
+            assertEquals("{\"boardPublicId\":\"board-1\",\"name\":\"Sprint\",\"index\":7}", request?.body)
+        }
+    }
+
+    @Test
+    fun createList_parsesCreatedRefPublicId_fromPublicIdPublic_idAndIdKeys() = runTest {
+        TestServer().use { server ->
+            server.registerSequence(
+                path = "/api/v1/lists",
+                method = "POST",
+                responses = listOf(
+                    200 to """{"list":{"publicId":"list-from-publicId"}}""",
+                    200 to """{"list":{"public_id":"list-from-public_id"}}""",
+                    200 to """{"list":{"id":"list-from-id"}}""",
+                ),
+            )
+
+            val client = HttpKanbnApiClient()
+            val first = client.createList(server.baseUrl, "api", "board-1", "List A", 0)
+            val second = client.createList(server.baseUrl, "api", "board-1", "List B", 1)
+            val third = client.createList(server.baseUrl, "api", "board-1", "List C", 2)
+
+            assertEquals("list-from-publicId", (first as BoardsApiResult.Success<CreatedEntityRef>).value.publicId)
+            assertEquals("list-from-public_id", (second as BoardsApiResult.Success<CreatedEntityRef>).value.publicId)
+            assertEquals("list-from-id", (third as BoardsApiResult.Success<CreatedEntityRef>).value.publicId)
+        }
+    }
+
+    @Test
+    fun createCard_serializesLocalDateAsUtcMidnight() = runTest {
+        TestServer().use { server ->
+            server.register(path = "/api/v1/cards", method = "POST", status = 200, responseBody = """{"publicId":"card-new"}""")
+
+            val result = HttpKanbnApiClient().createCard(
+                baseUrl = server.baseUrl,
+                apiKey = "api",
+                listPublicId = "list-1",
+                title = "Card",
+                description = "Description",
+                dueDate = LocalDate.of(2026, 3, 16),
+                tagPublicIds = listOf("tag-1"),
+            )
+
+            assertTrue(result is BoardsApiResult.Success<*>)
+            val request = server.findRequest("POST", "/api/v1/cards")
+            assertNotNull(request)
+            assertTrue(request?.body?.contains("\"dueDate\":\"2026-03-16T00:00:00Z\"") == true)
+            assertTrue(request?.body?.contains("\"description\":\"Description\"") == true)
+        }
+    }
+
+    @Test
+    fun createCard_sendsTopIndex_andOmittedDueDateWhenNull() = runTest {
+        TestServer().use { server ->
+            server.register(path = "/api/v1/cards", method = "POST", status = 200, responseBody = """{"publicId":"card-new"}""")
+
+            val result = HttpKanbnApiClient().createCard(
+                baseUrl = server.baseUrl,
+                apiKey = "api",
+                listPublicId = "list-1",
+                title = "Card",
+                description = null,
+                dueDate = null,
+                tagPublicIds = emptyList(),
+            )
+
+            assertTrue(result is BoardsApiResult.Success<*>)
+            val request = server.findRequest("POST", "/api/v1/cards")
+            assertNotNull(request)
+            assertTrue(request?.body?.contains("\"index\":0") == true)
+            assertTrue(request?.body?.contains("\"dueDate\"") == false)
+            assertTrue(request?.body?.contains("\"description\"") == false)
+        }
+    }
+
+    @Test
+    fun createCard_returnsCreatedRefWithNullPublicIdWhenResponseHasNoId() = runTest {
+        TestServer().use { server ->
+            server.register(
+                path = "/api/v1/cards",
+                method = "POST",
+                status = 200,
+                responseBody = """{"card":{"title":"Card without id"}}""",
+            )
+
+            val result = HttpKanbnApiClient().createCard(
+                baseUrl = server.baseUrl,
+                apiKey = "api",
+                listPublicId = "list-1",
+                title = "Card",
+                description = null,
+                dueDate = null,
+                tagPublicIds = emptyList(),
+            )
+
+            assertTrue(result is BoardsApiResult.Success<*>)
+            val createdRef = (result as BoardsApiResult.Success<*>).value as CreatedEntityRef
+            assertNull(createdRef.publicId)
+        }
+    }
+
+    @Test
+    fun createCard_parsesCreatedRefPublicId_fromPublicIdPublic_idAndIdKeys() = runTest {
+        TestServer().use { server ->
+            server.registerSequence(
+                path = "/api/v1/cards",
+                method = "POST",
+                responses = listOf(
+                    200 to """{"card":{"publicId":"card-from-publicId"}}""",
+                    200 to """{"card":{"public_id":"card-from-public_id"}}""",
+                    200 to """{"card":{"id":"card-from-id"}}""",
+                ),
+            )
+
+            val client = HttpKanbnApiClient()
+            val first = client.createCard(server.baseUrl, "api", "list-1", "Card A", null, null, emptyList())
+            val second = client.createCard(server.baseUrl, "api", "list-1", "Card B", null, null, emptyList())
+            val third = client.createCard(server.baseUrl, "api", "list-1", "Card C", null, null, emptyList())
+
+            assertEquals("card-from-publicId", (first as BoardsApiResult.Success<CreatedEntityRef>).value.publicId)
+            assertEquals("card-from-public_id", (second as BoardsApiResult.Success<CreatedEntityRef>).value.publicId)
+            assertEquals("card-from-id", (third as BoardsApiResult.Success<CreatedEntityRef>).value.publicId)
+        }
+    }
+
     @Test
     fun getBoardDetailParsesWrappedPayloadWithDueDateVariants() = runTest {
         TestServer().use { server ->

app/src/test/java/space/hackenslacker/kanbn4droid/app/boarddetail/BoardDetailModelsTest.kt

@@ -6,6 +6,15 @@ import org.junit.Test
 
 class BoardDetailModelsTest {
 
+    @Test
+    fun createdEntityRef_allowsMissingPublicIdForFallbackVerificationPath() {
+        val withPublicId = CreatedEntityRef(publicId = "card-123")
+        val withoutPublicId = CreatedEntityRef(publicId = null)
+
+        assertEquals("card-123", withPublicId.publicId)
+        assertNull(withoutPublicId.publicId)
+    }
+
     @Test
     fun boardDetailModelsExposeRequiredFields() {
         val tag = BoardTagSummary(

app/src/test/java/space/hackenslacker/kanbn4droid/app/boarddetail/BoardDetailRepositoryTest.kt

@@ -1,6 +1,7 @@
 package space.hackenslacker.kanbn4droid.app.boarddetail
 
 import kotlinx.coroutines.test.runTest
+import java.time.LocalDate
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertTrue
 import org.junit.Test
@@ -207,6 +208,156 @@ class BoardDetailRepositoryTest {
         assertEquals("New title", apiClient.lastListTitle)
     }
 
+    @Test
+    fun createCard_callsApiWithPublicIdsAndTopIndex() = runTest {
+        val apiClient = FakeBoardDetailApiClient()
+        val repository = createRepository(apiClient = apiClient)
+
+        val result = repository.createCard(
+            listPublicId = " list-1 ",
+            title = " Card title ",
+            description = "  Description  ",
+            dueDate = LocalDate.of(2026, 3, 16),
+            tagPublicIds = listOf(" tag-1 ", "", "tag-2", "tag-1", "   ", " tag-2"),
+        )
+
+        assertTrue(result is BoardsApiResult.Success<*>)
+        assertEquals("list-1", apiClient.lastCreateCardListPublicId)
+        assertEquals("Card title", apiClient.lastCreateCardTitle)
+        assertEquals("Description", apiClient.lastCreateCardDescription)
+        assertEquals(LocalDate.of(2026, 3, 16), apiClient.lastCreateCardDueDate)
+        assertEquals(listOf("tag-1", "tag-2"), apiClient.lastCreateCardTagPublicIds)
+    }
+
+    @Test
+    fun createCard_sendsNullDescriptionWhenBlankAfterTrim() = runTest {
+        val apiClient = FakeBoardDetailApiClient()
+        val repository = createRepository(apiClient = apiClient)
+
+        val result = repository.createCard(
+            listPublicId = "list-1",
+            title = "Card",
+            description = "   ",
+            dueDate = null,
+            tagPublicIds = emptyList(),
+        )
+
+        assertTrue(result is BoardsApiResult.Success<*>)
+        assertEquals(null, apiClient.lastCreateCardDescription)
+    }
+
+    @Test
+    fun createCard_delegatesWhenDueDateIsNull() = runTest {
+        val apiClient = FakeBoardDetailApiClient()
+        val repository = createRepository(apiClient = apiClient)
+
+        val result = repository.createCard(
+            listPublicId = "list-1",
+            title = "Card",
+            description = "Description",
+            dueDate = null,
+            tagPublicIds = listOf("tag-1"),
+        )
+
+        assertTrue(result is BoardsApiResult.Success<*>)
+        assertEquals("list-1", apiClient.lastCreateCardListPublicId)
+        assertEquals("Card", apiClient.lastCreateCardTitle)
+        assertEquals(null, apiClient.lastCreateCardDueDate)
+    }
+
+    @Test
+    fun createListRejectsBlankTitle() = runTest {
+        val repository = createRepository()
+
+        val result = repository.createList(boardPublicId = "board-1", title = "   ")
+
+        assertTrue(result is BoardsApiResult.Failure)
+        assertEquals("List title is required", (result as BoardsApiResult.Failure).message)
+    }
+
+    @Test
+    fun createListRejectsBlankBoardPublicId() = runTest {
+        val repository = createRepository()
+
+        val result = repository.createList(boardPublicId = "   ", title = "New List")
+
+        assertTrue(result is BoardsApiResult.Failure)
+        assertEquals("Board id is required", (result as BoardsApiResult.Failure).message)
+    }
+
+    @Test
+    fun createListDelegatesToApiWithTrimmedIds() = runTest {
+        val apiClient = FakeBoardDetailApiClient().apply {
+            boardDetailResult = BoardsApiResult.Success(
+                BoardDetail(
+                    id = "board-1",
+                    title = "Board",
+                    lists = listOf(
+                        BoardListDetail(id = "list-1", title = "One", cards = emptyList()),
+                        BoardListDetail(id = "list-2", title = "Two", cards = emptyList()),
+                        BoardListDetail(id = "list-3", title = "Three", cards = emptyList()),
+                    ),
+                ),
+            )
+        }
+        val repository = createRepository(apiClient = apiClient)
+
+        val result = repository.createList(boardPublicId = " board-1 ", title = " New List ")
+
+        assertTrue(result is BoardsApiResult.Success<*>)
+        assertEquals("board-1", apiClient.lastBoardId)
+        assertEquals("board-1", apiClient.lastCreateListBoardPublicId)
+        assertEquals("New List", apiClient.lastCreateListTitle)
+        assertEquals(3, apiClient.lastCreateListAppendIndex)
+    }
+
+    @Test
+    fun createListPropagatesFailureWhenBoardDetailPrefetchFails() = runTest {
+        val apiClient = FakeBoardDetailApiClient().apply {
+            boardDetailResult = BoardsApiResult.Failure("Cannot load board")
+        }
+        val repository = createRepository(apiClient = apiClient)
+
+        val result = repository.createList(boardPublicId = "board-1", title = "New List")
+
+        assertTrue(result is BoardsApiResult.Failure)
+        assertEquals("Cannot load board", (result as BoardsApiResult.Failure).message)
+        assertEquals("board-1", apiClient.lastBoardId)
+        assertEquals(null, apiClient.lastCreateListBoardPublicId)
+    }
+
+    @Test
+    fun createCardRejectsBlankListPublicId() = runTest {
+        val repository = createRepository()
+
+        val result = repository.createCard(
+            listPublicId = "  ",
+            title = "Card",
+            description = null,
+            dueDate = null,
+            tagPublicIds = emptyList(),
+        )
+
+        assertTrue(result is BoardsApiResult.Failure)
+        assertEquals("List id is required", (result as BoardsApiResult.Failure).message)
+    }
+
+    @Test
+    fun createCardRejectsBlankTitle() = runTest {
+        val repository = createRepository()
+
+        val result = repository.createCard(
+            listPublicId = "list-1",
+            title = "   ",
+            description = null,
+            dueDate = null,
+            tagPublicIds = emptyList(),
+        )
+
+        assertTrue(result is BoardsApiResult.Failure)
+        assertEquals("Card title is required", (result as BoardsApiResult.Failure).message)
+    }
+
     @Test
     fun getBoardDetailValidatesBoardId() = runTest {
         val repository = createRepository()
@@ -454,6 +605,8 @@ class BoardDetailRepositoryTest {
             BoardsApiResult.Success(listOf(WorkspaceSummary("ws-1", "Main")))
         var boardDetailResult: BoardsApiResult<BoardDetail> = BoardsApiResult.Success(sampleBoardDetail())
         var renameListResult: BoardsApiResult<Unit> = BoardsApiResult.Success(Unit)
+        var createListResult: BoardsApiResult<CreatedEntityRef> = BoardsApiResult.Success(CreatedEntityRef("list-new"))
+        var createCardResult: BoardsApiResult<CreatedEntityRef> = BoardsApiResult.Success(CreatedEntityRef("card-new"))
         var moveOutcomes: Map<String, BoardsApiResult<Unit>> = emptyMap()
         var deleteOutcomes: Map<String, BoardsApiResult<Unit>> = emptyMap()
         var labelByIdResults: Map<String, BoardsApiResult<LabelDetail>> = emptyMap()
@@ -466,6 +619,14 @@ class BoardDetailRepositoryTest {
         var deletedCardIds: MutableList<String> = mutableListOf()
         var lastMoveTargetListId: String? = null
         var getLabelByPublicIdCalls: MutableList<String> = mutableListOf()
+        var lastCreateListBoardPublicId: String? = null
+        var lastCreateListTitle: String? = null
+        var lastCreateListAppendIndex: Int? = null
+        var lastCreateCardListPublicId: String? = null
+        var lastCreateCardTitle: String? = null
+        var lastCreateCardDescription: String? = null
+        var lastCreateCardDueDate: LocalDate? = null
+        var lastCreateCardTagPublicIds: List<String> = emptyList()
 
         override suspend fun healthCheck(baseUrl: String, apiKey: String): AuthResult = AuthResult.Success
 
@@ -497,6 +658,36 @@ class BoardDetailRepositoryTest {
             return renameListResult
         }
 
+        override suspend fun createList(
+            baseUrl: String,
+            apiKey: String,
+            boardPublicId: String,
+            title: String,
+            appendIndex: Int,
+        ): BoardsApiResult<CreatedEntityRef> {
+            lastCreateListBoardPublicId = boardPublicId
+            lastCreateListTitle = title
+            lastCreateListAppendIndex = appendIndex
+            return createListResult
+        }
+
+        override suspend fun createCard(
+            baseUrl: String,
+            apiKey: String,
+            listPublicId: String,
+            title: String,
+            description: String?,
+            dueDate: LocalDate?,
+            tagPublicIds: List<String>,
+        ): BoardsApiResult<CreatedEntityRef> {
+            lastCreateCardListPublicId = listPublicId
+            lastCreateCardTitle = title
+            lastCreateCardDescription = description
+            lastCreateCardDueDate = dueDate
+            lastCreateCardTagPublicIds = tagPublicIds
+            return createCardResult
+        }
+
         override suspend fun moveCard(
             baseUrl: String,
             apiKey: String,

app/src/test/java/space/hackenslacker/kanbn4droid/app/boarddetail/BoardDetailViewModelTest.kt

@@ -10,8 +10,11 @@ import kotlinx.coroutines.test.advanceUntilIdle
 import kotlinx.coroutines.test.resetMain
 import kotlinx.coroutines.test.runTest
 import kotlinx.coroutines.test.setMain
+import kotlinx.coroutines.withTimeoutOrNull
+import java.time.LocalDate
 import org.junit.After
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
 import org.junit.Assert.assertNull
 import org.junit.Assert.assertTrue
 import org.junit.Before
@@ -49,7 +52,19 @@ class BoardDetailViewModelTest {
     }
 
     @Test
-    fun backPressClearsSelectionWhenSelectionActive() = runTest {
+    fun selectAllWithActiveFilter_selectsOnlyVisibleCardsOnCurrentPage() = runTest {
+        val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithFilterFixture())
+
+        viewModel.openFilterDialog()
+        viewModel.updatePendingTagFilterIds(setOf("tag-b"))
+        viewModel.applyFilterDialog()
+        viewModel.selectAllOnCurrentPage()
+
+        assertEquals(setOf("card-2"), viewModel.uiState.value.selectedCardIds)
+    }
+
+    @Test
+    fun backPressWithSelection_clearsSelectionAndReturnsTrue() = runTest {
         val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithTwoLists())
 
         viewModel.onCardLongPressed("card-1")
@@ -58,6 +73,344 @@ class BoardDetailViewModelTest {
         assertTrue(viewModel.uiState.value.selectedCardIds.isEmpty())
     }
 
+    @Test
+    fun openAddCardWhenNoLists_setsCanAddCardFalse_andMessage() = runTest {
+        val viewModel = newLoadedViewModel(
+            this,
+            FakeBoardDetailDataSource(),
+            detailWithoutLists(),
+        )
+
+        viewModel.openAddCardDialog()
+
+        assertFalse(viewModel.uiState.value.canAddCard)
+        assertEquals("Create a list first to add cards.", viewModel.uiState.value.addCardDisabledMessage)
+        assertFalse(viewModel.uiState.value.isAddCardDialogOpen)
+    }
+
+    @Test
+    fun applyFilters_tagAnyAndQueryAnd_keepsAllLists_filtersCardsOnly() = runTest {
+        val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithFilterFixture())
+
+        viewModel.openFilterDialog()
+        viewModel.updatePendingTagFilterIds(setOf("tag-b"))
+        viewModel.applyFilterDialog()
+        viewModel.openSearchDialog()
+        viewModel.updatePendingTitleQuery("duke")
+        viewModel.applySearchDialog()
+
+        val filtered = viewModel.uiState.value.filteredBoardDetail
+        assertEquals(2, filtered?.lists?.size)
+        assertEquals(listOf("card-2"), filtered?.lists?.get(0)?.cards?.map { it.id })
+        assertTrue(filtered?.lists?.get(1)?.cards?.isEmpty() == true)
+    }
+
+    @Test
+    fun tapActiveTagFilterIcon_clearsTagFilter_withoutOpeningDialog() = runTest {
+        val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithFilterFixture())
+
+        viewModel.openFilterDialog()
+        viewModel.updatePendingTagFilterIds(setOf("tag-a"))
+        viewModel.applyFilterDialog()
+        viewModel.onTagFilterIconTapped()
+
+        assertTrue(viewModel.uiState.value.activeTagFilterIds.isEmpty())
+        assertTrue(viewModel.uiState.value.pendingTagFilterIds.isEmpty())
+        assertFalse(viewModel.uiState.value.isFilterDialogOpen)
+    }
+
+    @Test
+    fun cancelFilterDialog_restoresPendingFromActive() = runTest {
+        val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithFilterFixture())
+
+        viewModel.openFilterDialog()
+        viewModel.updatePendingTagFilterIds(setOf("tag-a"))
+        viewModel.applyFilterDialog()
+        viewModel.openFilterDialog()
+        viewModel.updatePendingTagFilterIds(setOf("tag-b"))
+        viewModel.cancelFilterDialog()
+
+        assertEquals(setOf("tag-a"), viewModel.uiState.value.activeTagFilterIds)
+        assertEquals(setOf("tag-a"), viewModel.uiState.value.pendingTagFilterIds)
+        assertFalse(viewModel.uiState.value.isFilterDialogOpen)
+    }
+
+    @Test
+    fun cancelAndSuccess_resetAddDrafts() = runTest {
+        val repository = FakeBoardDetailDataSource(
+            boardDetailResults = ArrayDeque(
+                listOf(
+                    BoardsApiResult.Success(detailWithSingleList()),
+                    BoardsApiResult.Success(detailWithSingleListAndAppendedList()),
+                    BoardsApiResult.Success(detailWithSingleListAndNewTopCard()),
+                ),
+            ),
+            createListResult = BoardsApiResult.Success(CreatedEntityRef("list-new")),
+            createCardResult = BoardsApiResult.Success(CreatedEntityRef("card-new")),
+        )
+        val viewModel = newLoadedViewModel(this, repository)
+
+        viewModel.openAddListDialog()
+        viewModel.updateAddListTitle("Temp list")
+        viewModel.cancelAddListDialog()
+        assertEquals("", viewModel.uiState.value.addListTitleDraft)
+        assertFalse(viewModel.uiState.value.isAddListDialogOpen)
+
+        viewModel.openAddCardDialog()
+        viewModel.updateAddCardTitle("Temp card")
+        viewModel.updateAddCardDescription("temp")
+        viewModel.toggleAddCardTag("tag-a")
+        viewModel.setDueDate(LocalDate.of(2026, 1, 2))
+        viewModel.cancelAddCardDialog()
+        assertEquals("", viewModel.uiState.value.addCardTitleDraft)
+        assertEquals("", viewModel.uiState.value.addCardDescriptionDraft)
+        assertTrue(viewModel.uiState.value.addCardSelectedTagIds.isEmpty())
+        assertNull(viewModel.uiState.value.addCardDueDate)
+        assertFalse(viewModel.uiState.value.isAddCardDialogOpen)
+
+        viewModel.openAddListDialog()
+        viewModel.updateAddListTitle("New list")
+        viewModel.createList()
+        advanceUntilIdle()
+        assertEquals("", viewModel.uiState.value.addListTitleDraft)
+        assertFalse(viewModel.uiState.value.isAddListDialogOpen)
+
+        viewModel.openAddCardDialog()
+        viewModel.updateAddCardTitle("New card")
+        viewModel.updateAddCardDescription("desc")
+        viewModel.toggleAddCardTag("tag-a")
+        viewModel.setDueDate(LocalDate.of(2026, 2, 3))
+        viewModel.createCard()
+        advanceUntilIdle()
+        assertEquals("", viewModel.uiState.value.addCardTitleDraft)
+        assertEquals("", viewModel.uiState.value.addCardDescriptionDraft)
+        assertTrue(viewModel.uiState.value.addCardSelectedTagIds.isEmpty())
+        assertNull(viewModel.uiState.value.addCardDueDate)
+        assertFalse(viewModel.uiState.value.isAddCardDialogOpen)
+    }
+
+    @Test
+    fun createFailure_keepsAddDialogsOpenWithDrafts() = runTest {
+        val repository = FakeBoardDetailDataSource(
+            boardDetailResults = ArrayDeque(listOf(BoardsApiResult.Success(detailWithSingleList()))),
+            createListResult = BoardsApiResult.Failure("List create failed"),
+            createCardResult = BoardsApiResult.Failure("Card create failed"),
+        )
+        val viewModel = newLoadedViewModel(this, repository)
+
+        viewModel.openAddListDialog()
+        viewModel.updateAddListTitle("My list")
+        viewModel.createList()
+        advanceUntilIdle()
+        assertTrue(viewModel.uiState.value.isAddListDialogOpen)
+        assertEquals("My list", viewModel.uiState.value.addListTitleDraft)
+
+        viewModel.openAddCardDialog()
+        viewModel.updateAddCardTitle("My card")
+        viewModel.updateAddCardDescription("desc")
+        viewModel.toggleAddCardTag("tag-a")
+        viewModel.setDueDate(LocalDate.of(2026, 3, 4))
+        viewModel.createCard()
+        advanceUntilIdle()
+        assertTrue(viewModel.uiState.value.isAddCardDialogOpen)
+        assertEquals("My card", viewModel.uiState.value.addCardTitleDraft)
+        assertEquals("desc", viewModel.uiState.value.addCardDescriptionDraft)
+        assertEquals(setOf("tag-a"), viewModel.uiState.value.addCardSelectedTagIds)
+        assertEquals(LocalDate.of(2026, 3, 4), viewModel.uiState.value.addCardDueDate)
+    }
+
+    @Test
+    fun createList_blankTitle_setsLocalError_andRejectsBeforeRepositoryCall() = runTest {
+        val repository = FakeBoardDetailDataSource(
+            boardDetailResults = ArrayDeque(listOf(BoardsApiResult.Success(detailWithSingleList()))),
+        )
+        val viewModel = newLoadedViewModel(this, repository)
+
+        viewModel.openAddListDialog()
+        viewModel.updateAddListTitle("   ")
+        viewModel.createList()
+        advanceUntilIdle()
+
+        assertEquals(0, repository.createListCalls)
+        assertEquals("List title is required", viewModel.uiState.value.addListTitleError)
+        assertTrue(viewModel.uiState.value.isAddListDialogOpen)
+        val event = withTimeoutOrNull(50) { viewModel.events.first() }
+        assertNull(event)
+
+        viewModel.updateAddListTitle("Valid")
+        assertNull(viewModel.uiState.value.addListTitleError)
+    }
+
+    @Test
+    fun createCard_blankTitle_setsLocalError_andRejectsBeforeRepositoryCall() = runTest {
+        val repository = FakeBoardDetailDataSource(
+            boardDetailResults = ArrayDeque(listOf(BoardsApiResult.Success(detailWithSingleList()))),
+        )
+        val viewModel = newLoadedViewModel(this, repository)
+
+        viewModel.openAddCardDialog()
+        viewModel.updateAddCardTitle("   ")
+        viewModel.createCard()
+        advanceUntilIdle()
+
+        assertEquals(0, repository.createCardCalls)
+        assertEquals("Card title is required", viewModel.uiState.value.addCardTitleError)
+        assertTrue(viewModel.uiState.value.isAddCardDialogOpen)
+        val event = withTimeoutOrNull(50) { viewModel.events.first() }
+        assertNull(event)
+
+        viewModel.updateAddCardTitle("Valid")
+        assertNull(viewModel.uiState.value.addCardTitleError)
+    }
+
+    @Test
+    fun setDueDate_updatesCardDraftDueDate() = runTest {
+        val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithSingleList())
+
+        viewModel.openAddCardDialog()
+        viewModel.setDueDate(LocalDate.of(2026, 4, 5))
+
+        assertEquals(LocalDate.of(2026, 4, 5), viewModel.uiState.value.addCardDueDate)
+    }
+
+    @Test
+    fun clearDueDate_resetsCardDraftDueDate() = runTest {
+        val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithSingleList())
+
+        viewModel.openAddCardDialog()
+        viewModel.setDueDate(LocalDate.of(2026, 4, 5))
+        viewModel.clearDueDate()
+
+        assertNull(viewModel.uiState.value.addCardDueDate)
+    }
+
+    @Test
+    fun createListPlacementMismatch_emitsExactWarning() = runTest {
+        val repository = FakeBoardDetailDataSource(
+            boardDetailResults = ArrayDeque(
+                listOf(
+                    BoardsApiResult.Success(detailWithSingleList()),
+                    BoardsApiResult.Success(detailWithListPlacementMismatch()),
+                ),
+            ),
+            createListResult = BoardsApiResult.Success(CreatedEntityRef("list-new")),
+        )
+        val viewModel = newLoadedViewModel(this, repository)
+        val eventDeferred = async { viewModel.events.first() }
+
+        viewModel.openAddListDialog()
+        viewModel.updateAddListTitle("New list")
+        viewModel.createList()
+        advanceUntilIdle()
+
+        val event = eventDeferred.await()
+        assertTrue(event is BoardDetailUiEvent.ShowWarning)
+        assertEquals(
+            "List created, but server ordering differed. Pull to refresh if needed.",
+            (event as BoardDetailUiEvent.ShowWarning).message,
+        )
+    }
+
+    @Test
+    fun createCardPlacementMismatch_emitsExactWarning() = runTest {
+        val repository = FakeBoardDetailDataSource(
+            boardDetailResults = ArrayDeque(
+                listOf(
+                    BoardsApiResult.Success(detailWithSingleList()),
+                    BoardsApiResult.Success(detailWithCardPlacementMismatch()),
+                ),
+            ),
+            createCardResult = BoardsApiResult.Success(CreatedEntityRef("card-new")),
+        )
+        val viewModel = newLoadedViewModel(this, repository)
+        val eventDeferred = async { viewModel.events.first() }
+
+        viewModel.openAddCardDialog()
+        viewModel.updateAddCardTitle("New card")
+        viewModel.createCard()
+        advanceUntilIdle()
+
+        val event = eventDeferred.await()
+        assertTrue(event is BoardDetailUiEvent.ShowWarning)
+        assertEquals(
+            "Card created, but server ordering differed. Pull to refresh if needed.",
+            (event as BoardDetailUiEvent.ShowWarning).message,
+        )
+    }
+
+    @Test
+    fun createFallbackNonDeterministic_emitsExactWarning() = runTest {
+        val repository = FakeBoardDetailDataSource(
+            boardDetailResults = ArrayDeque(
+                listOf(
+                    BoardsApiResult.Success(detailWithSingleList()),
+                    BoardsApiResult.Success(detailWithSingleListAndAppendedList()),
+                ),
+            ),
+            createListResult = BoardsApiResult.Success(CreatedEntityRef(null)),
+        )
+        val viewModel = newLoadedViewModel(this, repository)
+        val eventDeferred = async { viewModel.events.first() }
+
+        viewModel.openAddListDialog()
+        viewModel.updateAddListTitle("New list")
+        viewModel.createList()
+        advanceUntilIdle()
+
+        val event = eventDeferred.await()
+        assertTrue(event is BoardDetailUiEvent.ShowWarning)
+        assertEquals(
+            "Created item could not be deterministically verified. Pull to refresh if needed.",
+            (event as BoardDetailUiEvent.ShowWarning).message,
+        )
+    }
+
+    @Test
+    fun createSuccess_refreshFailure_emitsExactWarning() = runTest {
+        val repository = FakeBoardDetailDataSource(
+            boardDetailResults = ArrayDeque(
+                listOf(
+                    BoardsApiResult.Success(detailWithSingleList()),
+                    BoardsApiResult.Failure("refresh failed"),
+                ),
+            ),
+            createListResult = BoardsApiResult.Success(CreatedEntityRef("list-new")),
+        )
+        val viewModel = newLoadedViewModel(this, repository)
+        val eventDeferred = async { viewModel.events.first() }
+
+        viewModel.openAddListDialog()
+        viewModel.updateAddListTitle("New list")
+        viewModel.createList()
+        advanceUntilIdle()
+
+        val event = eventDeferred.await()
+        assertTrue(event is BoardDetailUiEvent.ShowWarning)
+        assertEquals(
+            "Changes applied, but refresh failed. Pull to refresh.",
+            (event as BoardDetailUiEvent.ShowWarning).message,
+        )
+    }
+
+    @Test
+    fun applySearch_withWhitespaceOnlyQuery_trimsToEmptyAndClearsActiveState() = runTest {
+        val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithFilterFixture())
+
+        viewModel.openSearchDialog()
+        viewModel.updatePendingTitleQuery("Duke")
+        viewModel.applySearchDialog()
+        viewModel.openSearchDialog()
+        viewModel.updatePendingTitleQuery("   ")
+        viewModel.applySearchDialog()
+
+        assertEquals("", viewModel.uiState.value.activeTitleQuery)
+        assertEquals("", viewModel.uiState.value.pendingTitleQuery)
+        val filtered = viewModel.uiState.value.filteredBoardDetail
+        assertEquals(2, filtered?.lists?.size)
+        assertEquals(2, filtered?.lists?.get(0)?.cards?.size)
+        assertEquals(1, filtered?.lists?.get(1)?.cards?.size)
+    }
+
     @Test
     fun cardTapWithoutSelectionEmitsNavigateEvent() = runTest {
         val viewModel = newLoadedViewModel(this, FakeBoardDetailDataSource(), detailWithTwoLists())
@@ -506,15 +859,26 @@ class BoardDetailViewModelTest {
 
     private class FakeBoardDetailDataSource(
         val boardDetailResults: ArrayDeque<BoardsApiResult<BoardDetail>> = ArrayDeque(),
+        var createListResult: BoardsApiResult<CreatedEntityRef> = BoardsApiResult.Success(CreatedEntityRef("list-created")),
+        var createCardResult: BoardsApiResult<CreatedEntityRef> = BoardsApiResult.Success(CreatedEntityRef("card-created")),
         var moveCardsResult: CardBatchMutationResult = CardBatchMutationResult.Success,
         var deleteCardsResult: CardBatchMutationResult = CardBatchMutationResult.Success,
         var renameListResult: BoardsApiResult<Unit> = BoardsApiResult.Success(Unit),
         var moveGate: CompletableDeferred<Unit>? = null,
         var renameGate: CompletableDeferred<Unit>? = null,
     ) : BoardDetailDataSource {
+        var createListCalls: Int = 0
+        var createCardCalls: Int = 0
         var moveCalls: Int = 0
         var deleteCalls: Int = 0
         var renameCalls: Int = 0
+        var lastCreateListBoardId: String? = null
+        var lastCreateListTitle: String? = null
+        var lastCreateCardListId: String? = null
+        var lastCreateCardTitle: String? = null
+        var lastCreateCardDescription: String? = null
+        var lastCreateCardDueDate: LocalDate? = null
+        var lastCreateCardTagIds: List<String> = emptyList()
         var lastRenameListId: String? = null
         var lastRenameTitle: String? = null
 
@@ -526,6 +890,29 @@ class BoardDetailViewModelTest {
             }
         }
 
+        override suspend fun createList(boardPublicId: String, title: String): BoardsApiResult<CreatedEntityRef> {
+            createListCalls += 1
+            lastCreateListBoardId = boardPublicId
+            lastCreateListTitle = title
+            return createListResult
+        }
+
+        override suspend fun createCard(
+            listPublicId: String,
+            title: String,
+            description: String?,
+            dueDate: LocalDate?,
+            tagPublicIds: Collection<String>,
+        ): BoardsApiResult<CreatedEntityRef> {
+            createCardCalls += 1
+            lastCreateCardListId = listPublicId
+            lastCreateCardTitle = title
+            lastCreateCardDescription = description
+            lastCreateCardDueDate = dueDate
+            lastCreateCardTagIds = tagPublicIds.toList()
+            return createCardResult
+        }
+
         override suspend fun moveCards(cardIds: Collection<String>, targetListId: String): CardBatchMutationResult {
             moveCalls += 1
             moveGate?.await()
@@ -561,6 +948,14 @@ class BoardDetailViewModelTest {
             )
         }
 
+        fun detailWithoutLists(): BoardDetail {
+            return BoardDetail(
+                id = "board-1",
+                title = "Board",
+                lists = emptyList(),
+            )
+        }
+
         fun detailWithTwoLists(): BoardDetail {
             return BoardDetail(
                 id = "board-1",
@@ -583,6 +978,117 @@ class BoardDetailViewModelTest {
             )
         }
 
+        fun detailWithFilterFixture(): BoardDetail {
+            return BoardDetail(
+                id = "board-1",
+                title = "Board",
+                lists = listOf(
+                    BoardListDetail(
+                        id = "list-1",
+                        title = "To Do",
+                        cards = listOf(
+                            BoardCardSummary(
+                                id = "card-1",
+                                title = "Alpha",
+                                tags = listOf(BoardTagSummary("tag-a", "A", "#111111")),
+                                dueAtEpochMillis = null,
+                            ),
+                            BoardCardSummary(
+                                id = "card-2",
+                                title = "Duke Nukem",
+                                tags = listOf(BoardTagSummary("tag-b", "B", "#222222")),
+                                dueAtEpochMillis = null,
+                            ),
+                        ),
+                    ),
+                    BoardListDetail(
+                        id = "list-2",
+                        title = "Doing",
+                        cards = listOf(
+                            BoardCardSummary(
+                                id = "card-3",
+                                title = "Bravo",
+                                tags = listOf(BoardTagSummary("tag-b", "B", "#222222")),
+                                dueAtEpochMillis = null,
+                            ),
+                        ),
+                    ),
+                ),
+            )
+        }
+
+        fun detailWithSingleListAndAppendedList(): BoardDetail {
+            return BoardDetail(
+                id = "board-1",
+                title = "Board",
+                lists = listOf(
+                    BoardListDetail(
+                        id = "list-1",
+                        title = "To Do",
+                        cards = listOf(BoardCardSummary("card-1", "Card 1", emptyList(), null)),
+                    ),
+                    BoardListDetail(
+                        id = "list-new",
+                        title = "New list",
+                        cards = emptyList(),
+                    ),
+                ),
+            )
+        }
+
+        fun detailWithSingleListAndNewTopCard(): BoardDetail {
+            return BoardDetail(
+                id = "board-1",
+                title = "Board",
+                lists = listOf(
+                    BoardListDetail(
+                        id = "list-1",
+                        title = "To Do",
+                        cards = listOf(
+                            BoardCardSummary("card-new", "New card", emptyList(), null),
+                            BoardCardSummary("card-1", "Card 1", emptyList(), null),
+                        ),
+                    ),
+                ),
+            )
+        }
+
+        fun detailWithListPlacementMismatch(): BoardDetail {
+            return BoardDetail(
+                id = "board-1",
+                title = "Board",
+                lists = listOf(
+                    BoardListDetail(
+                        id = "list-new",
+                        title = "New list",
+                        cards = emptyList(),
+                    ),
+                    BoardListDetail(
+                        id = "list-1",
+                        title = "To Do",
+                        cards = listOf(BoardCardSummary("card-1", "Card 1", emptyList(), null)),
+                    ),
+                ),
+            )
+        }
+
+        fun detailWithCardPlacementMismatch(): BoardDetail {
+            return BoardDetail(
+                id = "board-1",
+                title = "Board",
+                lists = listOf(
+                    BoardListDetail(
+                        id = "list-1",
+                        title = "To Do",
+                        cards = listOf(
+                            BoardCardSummary("card-1", "Card 1", emptyList(), null),
+                            BoardCardSummary("card-new", "New card", emptyList(), null),
+                        ),
+                    ),
+                ),
+            )
+        }
+
         fun detailWithThreeLists(): BoardDetail {
             return BoardDetail(
                 id = "board-1",

docs/superpowers/plans/2026-03-16-board-detail-add-create-filter-implementation.md

@@ -0,0 +1,9 @@
+# 2026-03-16 Board Detail Add/Create/Filter Implementation
+
+## Execution Verification
+
+Recorded at: 2026-03-16T15:56:23-04:00
+
+- `./gradlew test` - PASS
+- `./gradlew connectedDebugAndroidTest` - PASS
+- `./gradlew assembleDebug` - PASS