feat: add configurable view-aware dashboards

README.md

@@ -10,6 +10,28 @@ The module owns the `/dashboard` route when installed. Core keeps only a minimal
 fallback home for installations where this module is absent.
 
 Modules contribute widgets through the `dashboard.widgets` WebUI capability.
-The first implementation stores personal widget visibility in browser storage;
-server-side layout persistence can be added later without changing the widget
-contract.
+Personal widget layouts are stored by the backend for each tenant, account, and
+active View. Configure mode supports adding, removing, ordering, sizing, and
+widget-specific settings. Existing browser-only layouts are used as a migration
+fallback until the first server save.
+
+Widget providers can declare supported sizes and a small configuration schema:
+
+```ts
+{
+  id: "example.summary",
+  surfaceId: "example.dashboard.summary",
+  title: "Example summary",
+  supportedSizes: ["small", "medium", "wide"],
+  defaultConfiguration: { limit: 10, showDetails: true },
+  configurationFields: [
+    { id: "limit", label: "Rows", kind: "number", min: 1, max: 50 },
+    { id: "showDetails", label: "Show details", kind: "boolean" }
+  ],
+  render: ({ configuration }) => <ExampleWidget configuration={configuration} />
+}
+```
+
+Every widget needs a matching View surface. The Dashboard catalogue filters
+contributions through the effective View before rendering them, while saved
+placements remain intact when a View or module temporarily hides a widget.

src/govoplan_dashboard/backend/db/__init__.py

@@ -0,0 +1,3 @@
+from govoplan_dashboard.backend.db.models import DashboardLayout
+
+__all__ = ["DashboardLayout"]

src/govoplan_dashboard/backend/db/models.py

@@ -0,0 +1,79 @@
+from __future__ import annotations
+
+import uuid
+from typing import Any
+
+from sqlalchemy import Index, Integer, JSON, String, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column
+
+from govoplan_core.db.base import Base, TimestampMixin
+
+
+def new_uuid() -> str:
+    return str(uuid.uuid4())
+
+
+class DashboardLayout(Base, TimestampMixin):
+    __tablename__ = "dashboard_layouts"
+    __table_args__ = (
+        UniqueConstraint(
+            "tenant_id",
+            "account_id",
+            "context_key",
+            name="uq_dashboard_layouts_actor_context",
+        ),
+        Index(
+            "ix_dashboard_layouts_actor",
+            "tenant_id",
+            "account_id",
+        ),
+    )
+
+    id: Mapped[str] = mapped_column(
+        String(36),
+        primary_key=True,
+        default=new_uuid,
+    )
+    tenant_id: Mapped[str] = mapped_column(
+        String(36),
+        nullable=False,
+        index=True,
+    )
+    account_id: Mapped[str] = mapped_column(
+        String(255),
+        nullable=False,
+        index=True,
+    )
+    context_key: Mapped[str] = mapped_column(
+        String(300),
+        nullable=False,
+        index=True,
+    )
+    view_id: Mapped[str | None] = mapped_column(
+        String(255),
+        nullable=True,
+        index=True,
+    )
+    layout_version: Mapped[int] = mapped_column(
+        Integer,
+        default=1,
+        nullable=False,
+    )
+    revision: Mapped[int] = mapped_column(
+        Integer,
+        default=1,
+        nullable=False,
+    )
+    placements: Mapped[list[dict[str, Any]]] = mapped_column(
+        JSON,
+        default=list,
+        nullable=False,
+    )
+    known_widget_ids: Mapped[list[str]] = mapped_column(
+        JSON,
+        default=list,
+        nullable=False,
+    )
+
+
+__all__ = ["DashboardLayout", "new_uuid"]

src/govoplan_dashboard/backend/manifest.py

@@ -1,8 +1,39 @@
 from __future__ import annotations
 
+from pathlib import Path
+
 from govoplan_core.core.access import CAPABILITY_AUTH_PERMISSION_EVALUATOR, CAPABILITY_AUTH_PRINCIPAL_RESOLVER
-from govoplan_core.core.modules import DocumentationTopic, FrontendModule, FrontendRoute, ModuleManifest, NavItem
+from govoplan_core.core.module_guards import (
+    drop_table_retirement_provider,
+    persistent_table_uninstall_guard,
+)
+from govoplan_core.core.modules import (
+    DocumentationTopic,
+    FrontendModule,
+    FrontendRoute,
+    MigrationSpec,
+    ModuleManifest,
+    NavItem,
+)
 from govoplan_core.core.views import ViewSurface
+from govoplan_core.db.base import Base
+from govoplan_dashboard.backend.db.models import DashboardLayout
+
+
+def _dashboard_router(_context):
+    from govoplan_dashboard.backend.router import router
+
+    return router
+
+
+def _tenant_summary(session, tenant_id: str) -> dict[str, int]:
+    return {
+        "dashboard_layouts": (
+            session.query(DashboardLayout)
+            .filter(DashboardLayout.tenant_id == tenant_id)
+            .count()
+        )
+    }
 
 
 manifest = ModuleManifest(
@@ -11,6 +42,28 @@ manifest = ModuleManifest(
     version="0.1.8",
     required_capabilities=(CAPABILITY_AUTH_PRINCIPAL_RESOLVER, CAPABILITY_AUTH_PERMISSION_EVALUATOR),
     optional_dependencies=("ops", "campaigns", "files", "mail", "tasks", "notifications", "reporting"),
+    route_factory=_dashboard_router,
+    tenant_summary_providers=(_tenant_summary,),
+    migration_spec=MigrationSpec(
+        module_id="dashboard",
+        metadata=Base.metadata,
+        script_location=str(Path(__file__).with_name("migrations") / "versions"),
+        retirement_supported=True,
+        retirement_provider=drop_table_retirement_provider(
+            DashboardLayout,
+            label="Dashboard",
+        ),
+        retirement_notes=(
+            "Destructive retirement removes personal Dashboard layouts after "
+            "the installer captures a database snapshot."
+        ),
+    ),
+    uninstall_guard_providers=(
+        persistent_table_uninstall_guard(
+            DashboardLayout,
+            label="Dashboard",
+        ),
+    ),
     nav_items=(NavItem(path="/dashboard", label="Dashboard", icon="dashboard", order=10),),
     frontend=FrontendModule(
         module_id="dashboard",
@@ -34,7 +87,8 @@ manifest = ModuleManifest(
             summary="The dashboard module owns the configurable home surface. Feature modules expose widgets through a narrow dashboard.widgets capability.",
             body=(
                 "Core only provides a minimal fallback home when the dashboard module is absent. "
-                "Dashboard widgets must be contributed through core contracts, not by importing sibling module components directly."
+                "Dashboard widgets must be contributed through core contracts, not by importing sibling module components directly. "
+                "Personal layouts are stored per tenant, account, and active View."
             ),
             layer="configured",
             documentation_types=("admin", "user"),

src/govoplan_dashboard/backend/migrations/__init__.py

@@ -0,0 +1 @@
+"""Dashboard database migrations."""

src/govoplan_dashboard/backend/migrations/versions/7b9d2f4a6c8e_v019_dashboard_layouts.py

@@ -0,0 +1,63 @@
+"""add personal and View-scoped dashboard layouts
+
+Revision ID: 7b9d2f4a6c8e
+Revises: None
+Create Date: 2026-07-29 10:00:00.000000
+"""
+
+from __future__ import annotations
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = "7b9d2f4a6c8e"
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "dashboard_layouts",
+        sa.Column("id", sa.String(length=36), nullable=False),
+        sa.Column("tenant_id", sa.String(length=36), nullable=False),
+        sa.Column("account_id", sa.String(length=255), nullable=False),
+        sa.Column("context_key", sa.String(length=300), nullable=False),
+        sa.Column("view_id", sa.String(length=255), nullable=True),
+        sa.Column("layout_version", sa.Integer(), nullable=False),
+        sa.Column("revision", sa.Integer(), nullable=False),
+        sa.Column("placements", sa.JSON(), nullable=False),
+        sa.Column("known_widget_ids", sa.JSON(), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False),
+        sa.PrimaryKeyConstraint("id", name=op.f("pk_dashboard_layouts")),
+        sa.UniqueConstraint(
+            "tenant_id",
+            "account_id",
+            "context_key",
+            name="uq_dashboard_layouts_actor_context",
+        ),
+    )
+    for column in (
+        "tenant_id",
+        "account_id",
+        "context_key",
+        "view_id",
+    ):
+        op.create_index(
+            op.f(f"ix_dashboard_layouts_{column}"),
+            "dashboard_layouts",
+            [column],
+            unique=False,
+        )
+    op.create_index(
+        "ix_dashboard_layouts_actor",
+        "dashboard_layouts",
+        ["tenant_id", "account_id"],
+        unique=False,
+    )
+
+
+def downgrade() -> None:
+    op.drop_table("dashboard_layouts")

src/govoplan_dashboard/backend/migrations/versions/__init__.py

@@ -0,0 +1 @@
+"""Dashboard migration revisions."""

src/govoplan_dashboard/backend/router.py

@@ -0,0 +1,123 @@
+from __future__ import annotations
+
+from fastapi import APIRouter, Depends, HTTPException, Query, status
+from sqlalchemy.exc import IntegrityError
+from sqlalchemy.orm import Session
+
+from govoplan_core.auth import ApiPrincipal, get_api_principal
+from govoplan_core.db.session import get_session
+from govoplan_dashboard.backend.db.models import DashboardLayout
+from govoplan_dashboard.backend.schemas import (
+    DashboardLayoutResponse,
+    DashboardLayoutUpdateRequest,
+)
+from govoplan_dashboard.backend.service import (
+    DashboardLayoutConflict,
+    DashboardLayoutLimitExceeded,
+    delete_dashboard_layout,
+    get_dashboard_layout,
+    normalize_view_id,
+    save_dashboard_layout,
+)
+
+
+router = APIRouter(prefix="/dashboard", tags=["dashboard"])
+
+
+def _response(
+    layout: DashboardLayout | None,
+    *,
+    view_id: str | None,
+) -> DashboardLayoutResponse:
+    if layout is None:
+        return DashboardLayoutResponse(
+            exists=False,
+            view_id=normalize_view_id(view_id),
+        )
+    return DashboardLayoutResponse(
+        exists=True,
+        view_id=layout.view_id,
+        layout_version=layout.layout_version,
+        revision=layout.revision,
+        placements=layout.placements,
+        known_widget_ids=layout.known_widget_ids,
+        updated_at=layout.updated_at,
+    )
+
+
+@router.get("/layout", response_model=DashboardLayoutResponse)
+def api_get_dashboard_layout(
+    view_id: str | None = Query(default=None, max_length=255),
+    session: Session = Depends(get_session),
+    principal: ApiPrincipal = Depends(get_api_principal),
+) -> DashboardLayoutResponse:
+    return _response(
+        get_dashboard_layout(
+            session,
+            tenant_id=principal.tenant_id,
+            account_id=principal.account_id,
+            view_id=view_id,
+        ),
+        view_id=view_id,
+    )
+
+
+@router.put("/layout", response_model=DashboardLayoutResponse)
+def api_save_dashboard_layout(
+    payload: DashboardLayoutUpdateRequest,
+    view_id: str | None = Query(default=None, max_length=255),
+    session: Session = Depends(get_session),
+    principal: ApiPrincipal = Depends(get_api_principal),
+) -> DashboardLayoutResponse:
+    try:
+        layout = save_dashboard_layout(
+            session,
+            tenant_id=principal.tenant_id,
+            account_id=principal.account_id,
+            view_id=view_id,
+            expected_revision=payload.expected_revision,
+            layout_version=payload.layout_version,
+            placements=payload.placements,
+            known_widget_ids=payload.known_widget_ids,
+        )
+        session.commit()
+    except DashboardLayoutConflict as exc:
+        session.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail=str(exc),
+        ) from exc
+    except DashboardLayoutLimitExceeded as exc:
+        session.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=str(exc),
+        ) from exc
+    except IntegrityError as exc:
+        session.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail=(
+                "The dashboard layout changed in another session. "
+                "Reload it before saving."
+            ),
+        ) from exc
+    return _response(layout, view_id=view_id)
+
+
+@router.delete("/layout", status_code=status.HTTP_204_NO_CONTENT)
+def api_delete_dashboard_layout(
+    view_id: str | None = Query(default=None, max_length=255),
+    session: Session = Depends(get_session),
+    principal: ApiPrincipal = Depends(get_api_principal),
+) -> None:
+    delete_dashboard_layout(
+        session,
+        tenant_id=principal.tenant_id,
+        account_id=principal.account_id,
+        view_id=view_id,
+    )
+    session.commit()
+
+
+__all__ = ["router"]

src/govoplan_dashboard/backend/schemas.py

@@ -0,0 +1,92 @@
+from __future__ import annotations
+
+import math
+from datetime import datetime
+from typing import Annotated, Literal
+
+from pydantic import BaseModel, Field, field_validator, model_validator
+
+
+WidgetId = Annotated[str, Field(min_length=1, max_length=160)]
+ConfigurationValue = str | int | float | bool | None
+
+
+class DashboardWidgetPlacementPayload(BaseModel):
+    instance_id: str = Field(min_length=1, max_length=120)
+    widget_id: WidgetId
+    size: Literal["small", "medium", "wide", "full"] = "medium"
+    configuration: dict[str, ConfigurationValue] = Field(
+        default_factory=dict,
+        max_length=40,
+    )
+
+    @field_validator("configuration")
+    @classmethod
+    def validate_configuration(
+        cls,
+        value: dict[str, ConfigurationValue],
+    ) -> dict[str, ConfigurationValue]:
+        approximate_size = 0
+        for key, item in value.items():
+            if not key or len(key) > 120:
+                raise ValueError(
+                    "Widget configuration keys must contain 1 to 120 characters."
+                )
+            approximate_size += len(key)
+            if isinstance(item, str):
+                if len(item) > 4_000:
+                    raise ValueError(
+                        "Widget configuration text values may contain at most "
+                        "4,000 characters."
+                    )
+                approximate_size += len(item)
+            else:
+                approximate_size += len(str(item))
+            if isinstance(item, float) and not math.isfinite(item):
+                raise ValueError(
+                    "Widget configuration numbers must be finite."
+                )
+        if approximate_size > 32_000:
+            raise ValueError(
+                "A widget configuration may contain at most 32,000 characters."
+            )
+        return value
+
+
+class DashboardLayoutUpdateRequest(BaseModel):
+    expected_revision: int | None = Field(default=None, ge=0)
+    layout_version: Literal[1] = 1
+    placements: list[DashboardWidgetPlacementPayload] = Field(
+        default_factory=list,
+        max_length=100,
+    )
+    known_widget_ids: list[WidgetId] = Field(
+        default_factory=list,
+        max_length=500,
+    )
+
+    @model_validator(mode="after")
+    def validate_unique_ids(self) -> "DashboardLayoutUpdateRequest":
+        instance_ids = [item.instance_id for item in self.placements]
+        if len(instance_ids) != len(set(instance_ids)):
+            raise ValueError("Dashboard widget instance ids must be unique.")
+        return self
+
+
+class DashboardLayoutResponse(BaseModel):
+    exists: bool
+    view_id: str | None = None
+    layout_version: int = 1
+    revision: int = 0
+    placements: list[DashboardWidgetPlacementPayload] = Field(
+        default_factory=list
+    )
+    known_widget_ids: list[str] = Field(default_factory=list)
+    updated_at: datetime | None = None
+
+
+__all__ = [
+    "DashboardLayoutResponse",
+    "DashboardLayoutUpdateRequest",
+    "DashboardWidgetPlacementPayload",
+]

src/govoplan_dashboard/backend/service.py

@@ -0,0 +1,146 @@
+from __future__ import annotations
+
+from collections.abc import Sequence
+
+from sqlalchemy.orm import Session
+
+from govoplan_dashboard.backend.db.models import DashboardLayout
+from govoplan_dashboard.backend.schemas import DashboardWidgetPlacementPayload
+
+
+MAX_LAYOUT_CONTEXTS_PER_ACCOUNT = 100
+
+
+class DashboardLayoutConflict(ValueError):
+    pass
+
+
+class DashboardLayoutLimitExceeded(ValueError):
+    pass
+
+
+def normalize_view_id(view_id: str | None) -> str | None:
+    normalized = (view_id or "").strip()
+    if not normalized:
+        return None
+    if len(normalized) > 255:
+        raise ValueError("Dashboard View ids may contain at most 255 characters.")
+    return normalized
+
+
+def layout_context_key(view_id: str | None) -> str:
+    normalized = normalize_view_id(view_id)
+    return f"view:{normalized}" if normalized else "full"
+
+
+def get_dashboard_layout(
+    session: Session,
+    *,
+    tenant_id: str,
+    account_id: str,
+    view_id: str | None,
+) -> DashboardLayout | None:
+    return (
+        session.query(DashboardLayout)
+        .filter(
+            DashboardLayout.tenant_id == tenant_id,
+            DashboardLayout.account_id == account_id,
+            DashboardLayout.context_key == layout_context_key(view_id),
+        )
+        .one_or_none()
+    )
+
+
+def save_dashboard_layout(
+    session: Session,
+    *,
+    tenant_id: str,
+    account_id: str,
+    view_id: str | None,
+    expected_revision: int | None,
+    layout_version: int,
+    placements: Sequence[DashboardWidgetPlacementPayload],
+    known_widget_ids: Sequence[str],
+) -> DashboardLayout:
+    normalized_view_id = normalize_view_id(view_id)
+    layout = get_dashboard_layout(
+        session,
+        tenant_id=tenant_id,
+        account_id=account_id,
+        view_id=normalized_view_id,
+    )
+    current_revision = layout.revision if layout is not None else 0
+    if (
+        expected_revision is not None
+        and expected_revision != current_revision
+    ):
+        raise DashboardLayoutConflict(
+            "The dashboard layout changed in another session. Reload it before "
+            "saving."
+        )
+    if layout is None:
+        layout_count = (
+            session.query(DashboardLayout)
+            .filter(
+                DashboardLayout.tenant_id == tenant_id,
+                DashboardLayout.account_id == account_id,
+            )
+            .count()
+        )
+        if layout_count >= MAX_LAYOUT_CONTEXTS_PER_ACCOUNT:
+            raise DashboardLayoutLimitExceeded(
+                "At most 100 Dashboard layouts may be stored per account and tenant."
+            )
+        layout = DashboardLayout(
+            tenant_id=tenant_id,
+            account_id=account_id,
+            context_key=layout_context_key(normalized_view_id),
+            view_id=normalized_view_id,
+            layout_version=layout_version,
+            revision=1,
+            placements=[],
+            known_widget_ids=[],
+        )
+        session.add(layout)
+    else:
+        layout.layout_version = layout_version
+        layout.revision += 1
+    layout.placements = [
+        placement.model_dump(mode="json")
+        for placement in placements
+    ]
+    layout.known_widget_ids = list(dict.fromkeys(known_widget_ids))
+    session.flush()
+    return layout
+
+
+def delete_dashboard_layout(
+    session: Session,
+    *,
+    tenant_id: str,
+    account_id: str,
+    view_id: str | None,
+) -> bool:
+    layout = get_dashboard_layout(
+        session,
+        tenant_id=tenant_id,
+        account_id=account_id,
+        view_id=view_id,
+    )
+    if layout is None:
+        return False
+    session.delete(layout)
+    session.flush()
+    return True
+
+
+__all__ = [
+    "DashboardLayoutConflict",
+    "DashboardLayoutLimitExceeded",
+    "MAX_LAYOUT_CONTEXTS_PER_ACCOUNT",
+    "delete_dashboard_layout",
+    "get_dashboard_layout",
+    "layout_context_key",
+    "normalize_view_id",
+    "save_dashboard_layout",
+]

tests/test_dashboard_layouts.py

@@ -0,0 +1,208 @@
+from __future__ import annotations
+
+import unittest
+
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session, sessionmaker
+from sqlalchemy.pool import StaticPool
+
+from govoplan_core.auth import ApiPrincipal, get_api_principal
+from govoplan_core.core.access import PrincipalRef
+from govoplan_core.db.session import get_session
+from govoplan_dashboard.backend.db.models import DashboardLayout
+from govoplan_dashboard.backend.router import router
+
+
+def principal(
+    *,
+    tenant_id: str = "tenant-1",
+    account_id: str = "account-1",
+) -> ApiPrincipal:
+    return ApiPrincipal(
+        principal=PrincipalRef(
+            account_id=account_id,
+            membership_id=f"membership:{tenant_id}:{account_id}",
+            tenant_id=tenant_id,
+            scopes=frozenset(),
+            group_ids=frozenset(),
+        ),
+        account=object(),
+        user=object(),
+    )
+
+
+class DashboardLayoutApiTests(unittest.TestCase):
+    def setUp(self) -> None:
+        self.engine = create_engine(
+            "sqlite+pysqlite:///:memory:",
+            connect_args={"check_same_thread": False},
+            poolclass=StaticPool,
+        )
+        DashboardLayout.__table__.create(self.engine)
+        self.session_factory = sessionmaker(
+            bind=self.engine,
+            autoflush=False,
+            expire_on_commit=False,
+        )
+        self.active_principal = principal()
+        app = FastAPI()
+        app.include_router(router, prefix="/api/v1")
+
+        def session_dependency():
+            session = self.session_factory()
+            try:
+                yield session
+            finally:
+                session.close()
+
+        app.dependency_overrides[get_session] = session_dependency
+        app.dependency_overrides[get_api_principal] = (
+            lambda: self.active_principal
+        )
+        self.client = TestClient(app)
+
+    def tearDown(self) -> None:
+        self.client.close()
+        self.engine.dispose()
+
+    def test_layouts_are_isolated_by_account_and_view(self) -> None:
+        initial = self.client.get("/api/v1/dashboard/layout")
+        self.assertEqual(200, initial.status_code)
+        self.assertFalse(initial.json()["exists"])
+        self.assertEqual(0, initial.json()["revision"])
+
+        saved = self.client.put(
+            "/api/v1/dashboard/layout",
+            json={
+                "expected_revision": 0,
+                "layout_version": 1,
+                "placements": [
+                    {
+                        "instance_id": "instance-1",
+                        "widget_id": "dashboard.installed-modules",
+                        "size": "wide",
+                        "configuration": {
+                            "maxItems": 5,
+                            "showVersions": False,
+                        },
+                    }
+                ],
+                "known_widget_ids": ["dashboard.installed-modules"],
+            },
+        )
+        self.assertEqual(200, saved.status_code)
+        self.assertEqual(1, saved.json()["revision"])
+
+        view_layout = self.client.get(
+            "/api/v1/dashboard/layout",
+            params={"view_id": "view-files"},
+        )
+        self.assertEqual(200, view_layout.status_code)
+        self.assertFalse(view_layout.json()["exists"])
+
+        self.active_principal = principal(account_id="account-2")
+        other_account = self.client.get("/api/v1/dashboard/layout")
+        self.assertEqual(200, other_account.status_code)
+        self.assertFalse(other_account.json()["exists"])
+
+        self.active_principal = principal()
+        original = self.client.get("/api/v1/dashboard/layout")
+        self.assertTrue(original.json()["exists"])
+        self.assertEqual(
+            "dashboard.installed-modules",
+            original.json()["placements"][0]["widget_id"],
+        )
+        self.assertIs(
+            False,
+            original.json()["placements"][0]["configuration"]["showVersions"],
+        )
+
+    def test_stale_revision_is_rejected(self) -> None:
+        payload = {
+            "expected_revision": 0,
+            "layout_version": 1,
+            "placements": [],
+            "known_widget_ids": [],
+        }
+        first = self.client.put("/api/v1/dashboard/layout", json=payload)
+        self.assertEqual(200, first.status_code)
+
+        stale = self.client.put("/api/v1/dashboard/layout", json=payload)
+        self.assertEqual(409, stale.status_code)
+        self.assertIn("another session", stale.json()["detail"])
+
+    def test_duplicate_instance_ids_are_rejected(self) -> None:
+        placement = {
+            "instance_id": "duplicate",
+            "widget_id": "example.widget",
+            "size": "medium",
+            "configuration": {},
+        }
+        response = self.client.put(
+            "/api/v1/dashboard/layout",
+            json={
+                "expected_revision": 0,
+                "layout_version": 1,
+                "placements": [placement, placement],
+                "known_widget_ids": ["example.widget"],
+            },
+        )
+
+        self.assertEqual(422, response.status_code)
+        with Session(self.engine) as session:
+            self.assertEqual(0, session.query(DashboardLayout).count())
+
+    def test_oversized_widget_configuration_is_rejected(self) -> None:
+        response = self.client.put(
+            "/api/v1/dashboard/layout",
+            json={
+                "expected_revision": 0,
+                "layout_version": 1,
+                "placements": [
+                    {
+                        "instance_id": "instance-1",
+                        "widget_id": "example.widget",
+                        "size": "medium",
+                        "configuration": {"query": "x" * 4_001},
+                    }
+                ],
+                "known_widget_ids": ["example.widget"],
+            },
+        )
+
+        self.assertEqual(422, response.status_code)
+
+    def test_account_layout_context_limit_is_enforced(self) -> None:
+        with self.session_factory() as session:
+            session.add_all(
+                DashboardLayout(
+                    tenant_id="tenant-1",
+                    account_id="account-1",
+                    context_key=f"view:view-{index}",
+                    view_id=f"view-{index}",
+                    placements=[],
+                    known_widget_ids=[],
+                )
+                for index in range(100)
+            )
+            session.commit()
+
+        response = self.client.put(
+            "/api/v1/dashboard/layout",
+            params={"view_id": "one-too-many"},
+            json={
+                "expected_revision": 0,
+                "layout_version": 1,
+                "placements": [],
+                "known_widget_ids": [],
+            },
+        )
+
+        self.assertEqual(422, response.status_code)
+        self.assertIn("At most 100", response.json()["detail"])
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_migrations.py

@@ -0,0 +1,49 @@
+from __future__ import annotations
+
+import tempfile
+import unittest
+from pathlib import Path
+
+from alembic.runtime.migration import MigrationContext
+from sqlalchemy import create_engine, inspect
+
+from govoplan_core.db.migrations import migrate_database
+from govoplan_dashboard.backend.manifest import get_manifest
+
+
+class DashboardMigrationTests(unittest.TestCase):
+    def test_migration_creates_dashboard_layouts_and_head(self) -> None:
+        with tempfile.TemporaryDirectory(
+            prefix="govoplan-dashboard-migration-"
+        ) as directory:
+            url = f"sqlite:///{Path(directory) / 'dashboard.db'}"
+            migrate_database(
+                database_url=url,
+                enabled_modules=("dashboard",),
+                manifest_factories=(get_manifest,),
+            )
+            engine = create_engine(url)
+            try:
+                with engine.connect() as connection:
+                    self.assertIn(
+                        "7b9d2f4a6c8e",
+                        set(
+                            MigrationContext.configure(
+                                connection
+                            ).get_current_heads()
+                        ),
+                    )
+                    self.assertEqual(
+                        {"dashboard_layouts"},
+                        {
+                            name
+                            for name in inspect(connection).get_table_names()
+                            if name.startswith("dashboard_")
+                        },
+                    )
+            finally:
+                engine.dispose()
+
+
+if __name__ == "__main__":
+    unittest.main()

webui/package.json

@@ -13,12 +13,15 @@
     },
     "./styles/dashboard.css": "./src/styles/dashboard.css"
   },
+  "scripts": {
+    "test:dashboard-layout": "node --experimental-strip-types tests/dashboard-layout.test.ts"
+  },
   "peerDependencies": {
     "@govoplan/core-webui": "^0.1.8",
     "lucide-react": "^1.23.0",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
-    "react-router-dom": "^7.1.1"
+    "react-router-dom": ">=7.18.2 <8"
   },
   "peerDependenciesMeta": {
     "@govoplan/core-webui": {

webui/src/api/dashboard.ts

@@ -0,0 +1,53 @@
+import {
+  apiFetch,
+  apiPath,
+  type ApiSettings,
+  type DashboardWidgetConfiguration,
+  type DashboardWidgetSize
+} from "@govoplan/core-webui";
+
+export type DashboardWidgetPlacementResponse = {
+  instance_id: string;
+  widget_id: string;
+  size: DashboardWidgetSize;
+  configuration: DashboardWidgetConfiguration;
+};
+
+export type DashboardLayoutResponse = {
+  exists: boolean;
+  view_id: string | null;
+  layout_version: number;
+  revision: number;
+  placements: DashboardWidgetPlacementResponse[];
+  known_widget_ids: string[];
+  updated_at: string | null;
+};
+
+export type DashboardLayoutUpdate = {
+  expected_revision: number | null;
+  layout_version: 1;
+  placements: DashboardWidgetPlacementResponse[];
+  known_widget_ids: string[];
+};
+
+function layoutPath(viewId: string | null): string {
+  return apiPath("/api/v1/dashboard/layout", { view_id: viewId });
+}
+
+export function fetchDashboardLayout(
+  settings: ApiSettings,
+  viewId: string | null
+): Promise<DashboardLayoutResponse> {
+  return apiFetch<DashboardLayoutResponse>(settings, layoutPath(viewId));
+}
+
+export function saveDashboardLayout(
+  settings: ApiSettings,
+  viewId: string | null,
+  payload: DashboardLayoutUpdate
+): Promise<DashboardLayoutResponse> {
+  return apiFetch<DashboardLayoutResponse>(settings, layoutPath(viewId), {
+    method: "PUT",
+    body: JSON.stringify(payload)
+  });
+}

webui/src/features/dashboard/DashboardGrid.tsx

@@ -0,0 +1,368 @@
+import {
+  useEffect,
+  useLayoutEffect,
+  useRef,
+  useState,
+  type HTMLAttributes,
+  type DragEvent as ReactDragEvent,
+  type ReactNode
+} from "react";
+import {
+  GripVertical,
+  Settings2,
+  Trash2
+} from "lucide-react";
+import {
+  Card,
+  IconButton,
+  type ApiSettings,
+  type AuthInfo,
+  type DashboardWidgetContribution,
+  type EffectiveViewProjection,
+  type PlatformWebModule
+} from "@govoplan/core-webui";
+import {
+  dashboardMasonryRowSpan,
+  defaultWidgetSize,
+  widgetIsConfigurable,
+  type DashboardWidgetPlacement
+} from "./dashboardLayout";
+import {
+  dashboardGridPreview,
+  type DashboardDragItem,
+  type DashboardDropTarget
+} from "./dashboardEditorTypes";
+
+type DashboardGridProps = {
+  placements: DashboardWidgetPlacement[];
+  widgetById: Map<string, DashboardWidgetContribution>;
+  settings: ApiSettings;
+  auth: AuthInfo;
+  modules: PlatformWebModule[];
+  effectiveView: EffectiveViewProjection | null;
+  refreshKey: number;
+  configuring: boolean;
+  dragItem: DashboardDragItem | null;
+  dropTarget: DashboardDropTarget | null;
+  onDragStart: (event: ReactDragEvent, item: DashboardDragItem) => void;
+  onDragEnd: () => void;
+  onDragOver: (event: ReactDragEvent<HTMLElement>, instanceId: string) => void;
+  onDragOverEnd: (event: ReactDragEvent<HTMLElement>) => void;
+  onDrop: (
+    event: ReactDragEvent<HTMLElement>,
+    placement: DashboardWidgetPlacement
+  ) => void;
+  onDropPreview: (event: ReactDragEvent<HTMLElement>) => void;
+  onDropAtEnd: (event: ReactDragEvent<HTMLElement>) => void;
+  onRemove: (instanceId: string) => void;
+  onConfigure: (instanceId: string) => void;
+};
+
+export default function DashboardGrid({
+  placements,
+  widgetById,
+  settings,
+  auth,
+  modules,
+  effectiveView,
+  refreshKey,
+  configuring,
+  dragItem,
+  dropTarget,
+  onDragStart,
+  onDragEnd,
+  onDragOver,
+  onDragOverEnd,
+  onDrop,
+  onDropPreview,
+  onDropAtEnd,
+  onRemove,
+  onConfigure
+}: DashboardGridProps) {
+  const showingEmptyPreview =
+    configuring
+    && dragItem?.kind === "catalogue"
+    && dropTarget !== null;
+  if (!placements.length && !showingEmptyPreview) {
+    return (
+      <div
+        className={`dashboard-empty-state${configuring ? " is-drop-target" : ""}`}
+        onDragOver={(event) => {
+          if (!configuring) return;
+          onDragOverEnd(event);
+        }}
+        onDrop={configuring ? onDropAtEnd : undefined}
+      >
+        <h2>No widgets on this Dashboard</h2>
+        <p className="muted">
+          {configuring
+            ? "Drag a widget here from the library."
+            : "Open Configure to add widgets provided by active modules."}
+        </p>
+      </div>
+    );
+  }
+
+  const catalogueWidget =
+    dragItem?.kind === "catalogue"
+      ? widgetById.get(dragItem.widgetId)
+      : null;
+  const previewItems = dashboardGridPreview(
+    placements,
+    configuring ? dragItem : null,
+    configuring ? dropTarget : null,
+    catalogueWidget ? defaultWidgetSize(catalogueWidget) : "medium"
+  );
+
+  return (
+    <div
+      className={`dashboard-widget-grid${configuring ? " is-configuring" : ""}`}
+      onDragOver={(event) => {
+        if (!configuring || event.target !== event.currentTarget) return;
+        onDragOverEnd(event);
+      }}
+      onDrop={configuring ? onDropAtEnd : undefined}
+    >
+      {previewItems.map((item) => {
+        if (item.kind === "catalogue") {
+          const widget = widgetById.get(item.widgetId);
+          return (
+            <DashboardDropPlaceholder
+              key={`catalogue-placeholder:${item.widgetId}`}
+              title={widget?.title ?? "New widget"}
+              size={item.size}
+              onDragOver={(event) => event.preventDefault()}
+              onDrop={onDropPreview}
+            />
+          );
+        }
+        const placement = item.placement;
+        const widget = widgetById.get(placement.widgetId);
+        if (!widget) return null;
+        if (item.placeholder) {
+          return (
+            <DashboardDropPlaceholder
+              key={placement.instanceId}
+              title={widget.title}
+              size={placement.size}
+              preserveHeight
+              onDragOver={(event) => event.preventDefault()}
+              onDrop={onDropPreview}
+            >
+              <Card title={widget.title}>
+                <DashboardWidgetContent
+                  widget={widget}
+                  placement={placement}
+                  settings={settings}
+                  auth={auth}
+                  modules={modules}
+                  effectiveView={effectiveView}
+                  refreshKey={refreshKey}
+                />
+              </Card>
+            </DashboardDropPlaceholder>
+          );
+        }
+        return (
+          <DashboardMasonryItem
+            key={placement.instanceId}
+            className={`dashboard-widget dashboard-widget-${placement.size}`}
+            onDragOver={
+              configuring
+                ? (event) => onDragOver(event, placement.instanceId)
+                : undefined
+            }
+            onDrop={
+              configuring
+                ? (event) => onDrop(event, placement)
+                : undefined
+            }
+          >
+            <Card
+              title={widget.title}
+              collapsible={!configuring}
+              collapseKey={`dashboard-widget:${placement.instanceId}`}
+              actions={
+                configuring ? (
+                  <div className="dashboard-widget-actions">
+                    <IconButton
+                      label={`Drag ${widget.title}`}
+                      icon={<GripVertical size={16} />}
+                      variant="ghost"
+                      className="dashboard-widget-drag-handle"
+                      draggable
+                      onDragStart={(event) =>
+                        onDragStart(event, {
+                          kind: "placement",
+                          instanceId: placement.instanceId
+                        })
+                      }
+                      onDragEnd={onDragEnd}
+                    />
+                    {widgetIsConfigurable(widget) && (
+                      <IconButton
+                        label={`Configure ${widget.title}`}
+                        icon={<Settings2 size={16} />}
+                        variant="ghost"
+                        onClick={() => onConfigure(placement.instanceId)}
+                      />
+                    )}
+                    <IconButton
+                      label={`Remove ${widget.title}`}
+                      icon={<Trash2 size={16} />}
+                      variant="ghost"
+                      onClick={() => onRemove(placement.instanceId)}
+                    />
+                  </div>
+                ) : undefined
+              }
+            >
+              <DashboardWidgetContent
+                widget={widget}
+                placement={placement}
+                settings={settings}
+                auth={auth}
+                modules={modules}
+                effectiveView={effectiveView}
+                refreshKey={refreshKey}
+              />
+            </Card>
+          </DashboardMasonryItem>
+        );
+      })}
+      {configuring && (
+        <div
+          className="dashboard-grid-end-drop-target"
+          onDragOver={onDragOverEnd}
+          onDrop={onDropAtEnd}
+        >
+          Drop here to place the widget last
+        </div>
+      )}
+    </div>
+  );
+}
+
+function DashboardDropPlaceholder({
+  title,
+  size,
+  preserveHeight = false,
+  onDragOver,
+  onDrop,
+  children
+}: {
+  title: string;
+  size: DashboardWidgetPlacement["size"];
+  preserveHeight?: boolean;
+  onDragOver: (event: ReactDragEvent<HTMLElement>) => void;
+  onDrop: (event: ReactDragEvent<HTMLElement>) => void;
+  children?: ReactNode;
+}) {
+  return (
+    <DashboardMasonryItem
+      className={[
+        "dashboard-widget",
+        `dashboard-widget-${size}`,
+        "dashboard-widget-drop-placeholder",
+        preserveHeight ? "preserves-widget-height" : ""
+      ]
+        .filter(Boolean)
+        .join(" ")}
+      onDragOver={onDragOver}
+      onDrop={onDrop}
+      aria-label={`Place ${title} here`}
+    >
+      {children && (
+        <div className="dashboard-widget-placeholder-content">
+          {children}
+        </div>
+      )}
+      <div className="dashboard-widget-placeholder-surface">
+        <GripVertical size={18} aria-hidden="true" />
+        <strong>{title}</strong>
+      </div>
+    </DashboardMasonryItem>
+  );
+}
+
+function DashboardMasonryItem({
+  children,
+  ...props
+}: HTMLAttributes<HTMLElement>) {
+  const itemRef = useRef<HTMLElement>(null);
+
+  useLayoutEffect(() => {
+    const item = itemRef.current;
+    const grid = item?.parentElement;
+    if (!item || !grid) return undefined;
+
+    const updateSpan = () => {
+      const gridStyles = window.getComputedStyle(grid);
+      const itemStyles = window.getComputedStyle(item);
+      const rowHeight = Number.parseFloat(gridStyles.gridAutoRows);
+      const bottomGap = Number.parseFloat(itemStyles.marginBottom);
+      const nextSpan = dashboardMasonryRowSpan(
+        item.getBoundingClientRect().height,
+        rowHeight,
+        bottomGap
+      );
+      const gridRowEnd = `span ${nextSpan}`;
+      if (item.style.gridRowEnd !== gridRowEnd) {
+        item.style.gridRowEnd = gridRowEnd;
+      }
+    };
+
+    updateSpan();
+    if (typeof ResizeObserver === "undefined") return undefined;
+    const observer = new ResizeObserver(updateSpan);
+    observer.observe(item);
+    return () => observer.disconnect();
+  }, []);
+
+  return (
+    <section ref={itemRef} {...props}>
+      {children}
+    </section>
+  );
+}
+
+function DashboardWidgetContent({
+  widget,
+  placement,
+  settings,
+  auth,
+  modules,
+  effectiveView,
+  refreshKey
+}: {
+  widget: DashboardWidgetContribution;
+  placement: DashboardWidgetPlacement;
+  settings: ApiSettings;
+  auth: AuthInfo;
+  modules: PlatformWebModule[];
+  effectiveView: EffectiveViewProjection | null;
+  refreshKey: number;
+}) {
+  const [scheduledRefreshKey, setScheduledRefreshKey] = useState(0);
+
+  useEffect(() => {
+    if (!widget.refreshIntervalMs) return undefined;
+    const interval = window.setInterval(
+      () => setScheduledRefreshKey((value) => value + 1),
+      Math.max(widget.refreshIntervalMs, 5_000)
+    );
+    return () => window.clearInterval(interval);
+  }, [widget.refreshIntervalMs]);
+
+  return widget.render({
+    settings,
+    auth,
+    modules,
+    effectiveView,
+    instanceId: placement.instanceId,
+    widgetId: widget.id,
+    refreshKey: refreshKey + scheduledRefreshKey,
+    size: placement.size,
+    configuration: placement.configuration
+  });
+}

webui/src/features/dashboard/DashboardPage.tsx

@@ -1,29 +1,72 @@
-import { useEffect, useMemo, useState } from "react";
-import { RefreshCw, RotateCcw, SlidersHorizontal } from "lucide-react";
 import {
-  AdminSelectionList,
+  useEffect,
+  useMemo,
+  useState,
+  type DragEvent as ReactDragEvent
+} from "react";
+import {
+  RefreshCw,
+  Save,
+  SlidersHorizontal,
+  X
+} from "lucide-react";
+import {
   Button,
-  Card,
+  DismissibleAlert,
+  LoadingFrame,
   MetricCard,
   PageScrollViewport,
   PageTitle,
   dashboardWidgetsForModules,
   hasAnyScope,
   hasScope,
+  isApiError,
   useEffectiveView,
   usePlatformModules,
+  useUnsavedDraftGuard,
   type ApiSettings,
   type AuthInfo,
-  type DashboardWidgetContribution,
-  type DashboardWidgetSize
+  type DashboardWidgetContribution
 } from "@govoplan/core-webui";
+import {
+  fetchDashboardLayout,
+  saveDashboardLayout
+} from "../../api/dashboard";
+import DashboardGrid from "./DashboardGrid";
+import WidgetConfigurationDialog from "./WidgetConfigurationDialog";
+import WidgetLibrary from "./WidgetLibrary";
+import {
+  appendPlacement,
+  defaultDashboardLayout,
+  insertPlacement,
+  layoutFromResponse,
+  layoutUpdatePayload,
+  layoutsEqual,
+  localLayoutKey,
+  MAX_DASHBOARD_WIDGETS,
+  readLocalLayout,
+  reconcileDashboardLayout,
+  removePlacement,
+  reorderPlacement,
+  updatePlacement,
+  writeLocalLayout,
+  type DashboardLayoutState,
+  type DashboardWidgetPlacement
+} from "./dashboardLayout";
+import type {
+  DashboardDragItem,
+  DashboardDropTarget
+} from "./dashboardEditorTypes";
 
-type DashboardLayout = {
-  visible: string[];
-  known: string[];
-};
+type LayoutSource = "server" | "browser" | "default";
 
-export default function DashboardPage({ settings, auth }: { settings: ApiSettings; auth: AuthInfo }) {
+export default function DashboardPage({
+  settings,
+  auth
+}: {
+  settings: ApiSettings;
+  auth: AuthInfo;
+}) {
   const modules = usePlatformModules();
   const effectiveView = useEffectiveView();
   const widgets = useMemo(
@@ -33,44 +76,295 @@ export default function DashboardPage({ settings, auth }: { settings: ApiSetting
       ),
     [auth, effectiveView, modules]
   );
-  const widgetSignature = widgets.map((widget) => widget.id).join("|");
-  const storageKey = `govoplan.dashboard.layout:${auth.active_tenant?.id ?? auth.tenant.id}:${auth.user.id}`;
-  const [layout, setLayout] = useState<DashboardLayout>(() => defaultLayout(widgets));
+  const widgetSignature = JSON.stringify(
+    widgets.map((widget) => ({
+      id: widget.id,
+      allowMultiple: widget.allowMultiple ?? false,
+      defaultVisible: widget.defaultVisible ?? true,
+      defaultSize: widget.defaultSize ?? "medium",
+      supportedSizes: widget.supportedSizes ?? [],
+      defaultConfiguration: widget.defaultConfiguration ?? {}
+    }))
+  );
+  const tenantId = auth.active_tenant?.id ?? auth.tenant.id;
+  const accountId = auth.user.account_id || auth.user.id;
+  const viewId = effectiveView?.activeViewId ?? null;
+  const storageKey = localLayoutKey(tenantId, accountId, viewId);
+  const legacyStorageKey = viewId === null
+    ? `govoplan.dashboard.layout:${tenantId}:${auth.user.id}`
+    : null;
+  const initialLayout = useMemo(
+    () => defaultDashboardLayout(widgets),
+    [widgets]
+  );
+  const [savedLayout, setSavedLayout] = useState<DashboardLayoutState>(initialLayout);
+  const [draftLayout, setDraftLayout] = useState<DashboardLayoutState>(initialLayout);
+  const [layoutSource, setLayoutSource] = useState<LayoutSource>("default");
+  const [loading, setLoading] = useState(true);
+  const [saving, setSaving] = useState(false);
   const [configuring, setConfiguring] = useState(false);
   const [refreshKey, setRefreshKey] = useState(0);
+  const [error, setError] = useState("");
+  const [notice, setNotice] = useState("");
+  const [libraryQuery, setLibraryQuery] = useState("");
+  const [dragItem, setDragItem] = useState<DashboardDragItem | null>(null);
+  const [dropTarget, setDropTarget] = useState<DashboardDropTarget | null>(null);
+  const [editingInstanceId, setEditingInstanceId] = useState<string | null>(null);
 
   useEffect(() => {
-    setLayout(readLayout(storageKey) ?? defaultLayout(widgets));
-  }, [storageKey, widgetSignature]);
+    let active = true;
+    setLoading(true);
+    setError("");
+    setNotice("");
+    setConfiguring(false);
+    setEditingInstanceId(null);
 
-  const visibleWidgetIds = useMemo(() => {
-    const known = new Set(layout.known);
-    const visible = new Set(layout.visible);
-    for (const widget of widgets) {
-      if (!known.has(widget.id) && widget.defaultVisible !== false) visible.add(widget.id);
-    }
-    const availableIds = new Set(widgets.map((widget) => widget.id));
-    return widgets.map((widget) => widget.id).filter((id) => availableIds.has(id) && visible.has(id));
-  }, [layout, widgets]);
-  const visibleWidgets = widgets.filter((widget) => visibleWidgetIds.includes(widget.id));
-  const hiddenCount = Math.max(widgets.length - visibleWidgets.length, 0);
-
-  function saveLayout(next: DashboardLayout) {
-    setLayout(next);
-    writeLayout(storageKey, next);
-  }
-
-  function setVisibleWidgets(selected: string[]) {
-    const allIds = widgets.map((widget) => widget.id);
-    const nextVisible = new Set(selected);
-    saveLayout({
-      known: allIds,
-      visible: allIds.filter((id) => nextVisible.has(id))
+    void fetchDashboardLayout(settings, viewId)
+      .then((response) => {
+        if (!active) return;
+        const local = readLocalLayout(storageKey, legacyStorageKey, widgets);
+        const source: LayoutSource = response.exists
+          ? "server"
+          : local
+            ? "browser"
+            : "default";
+        const base = response.exists
+          ? layoutFromResponse(response)
+          : local
+            ? { ...local, revision: 0 }
+            : defaultDashboardLayout(widgets);
+        const next = reconcileDashboardLayout(base, widgets);
+        setSavedLayout(next);
+        setDraftLayout(next);
+        setLayoutSource(source);
+      })
+      .catch((reason) => {
+        if (!active) return;
+        const local = readLocalLayout(storageKey, legacyStorageKey, widgets);
+        const next = reconcileDashboardLayout(
+          local ?? defaultDashboardLayout(widgets),
+          widgets
+        );
+        setSavedLayout(next);
+        setDraftLayout(next);
+        setLayoutSource(local ? "browser" : "default");
+        setError(
+          `The saved Dashboard layout could not be loaded. ${
+            local
+              ? "The browser fallback is shown."
+              : "The module defaults are shown."
+          } ${errorMessage(reason)}`
+        );
+      })
+      .finally(() => {
+        if (active) setLoading(false);
       });
+
+    return () => {
+      active = false;
+    };
+  }, [
+    legacyStorageKey,
+    settings.accessToken,
+    settings.apiBaseUrl,
+    settings.apiKey,
+    storageKey,
+    viewId,
+    widgetSignature
+  ]);
+
+  const dirty = configuring && !layoutsEqual(savedLayout, draftLayout);
+  useUnsavedDraftGuard({
+    dirty,
+    onSave: persistLayout,
+    onDiscard: discardChanges,
+    title: "Unsaved Dashboard layout",
+    message: "Save or discard the Dashboard arrangement before leaving this page."
+  });
+
+  const activeLayout = configuring ? draftLayout : savedLayout;
+  const widgetById = useMemo(
+    () => new Map(widgets.map((widget) => [widget.id, widget])),
+    [widgets]
+  );
+  const renderedPlacements = activeLayout.placements.filter((placement) =>
+    widgetById.has(placement.widgetId)
+  );
+  const placedWidgetIds = new Set(
+    draftLayout.placements.map((placement) => placement.widgetId)
+  );
+  const libraryWidgets = widgets.filter((widget) => {
+    if (!widget.allowMultiple && placedWidgetIds.has(widget.id)) return false;
+    if (!libraryQuery.trim()) return true;
+    const query = libraryQuery.trim().toLocaleLowerCase();
+    return [widget.title, widget.description, widget.category, widget.moduleId, widget.id]
+      .filter(Boolean)
+      .some((value) => String(value).toLocaleLowerCase().includes(query));
+  });
+  const hiddenCount = widgets.filter(
+    (widget) => !placedWidgetIds.has(widget.id)
+  ).length;
+  const editingPlacement = editingInstanceId
+    ? draftLayout.placements.find(
+        (placement) => placement.instanceId === editingInstanceId
+      ) ?? null
+    : null;
+  const editingWidget = editingPlacement
+    ? widgetById.get(editingPlacement.widgetId) ?? null
+    : null;
+  const viewLabel = effectiveView?.activeViewName ?? "Full interface";
+
+  async function persistLayout(): Promise<boolean> {
+    setSaving(true);
+    setError("");
+    setNotice("");
+    try {
+      const response = await saveDashboardLayout(
+        settings,
+        viewId,
+        layoutUpdatePayload(draftLayout)
+      );
+      const next = reconcileDashboardLayout(layoutFromResponse(response), widgets);
+      setSavedLayout(next);
+      setDraftLayout(next);
+      setLayoutSource("server");
+      setConfiguring(false);
+      writeLocalLayout(storageKey, next);
+      setNotice(`Dashboard layout saved for ${viewLabel}.`);
+      return true;
+    } catch (reason) {
+      setError(errorMessage(reason));
+      return false;
+    } finally {
+      setSaving(false);
+    }
   }
 
-  function resetLayout() {
-    saveLayout(defaultLayout(widgets));
+  function discardChanges() {
+    setDraftLayout(savedLayout);
+    setConfiguring(false);
+    setEditingInstanceId(null);
+    setDragItem(null);
+    setDropTarget(null);
+  }
+
+  function beginConfiguration() {
+    setDraftLayout(savedLayout);
+    setConfiguring(true);
+    setError("");
+    setNotice("");
+  }
+
+  function updateDraft(updater: (layout: DashboardLayoutState) => DashboardLayoutState) {
+    setDraftLayout((current) => updater(current));
+  }
+
+  function addWidget(widget: DashboardWidgetContribution) {
+    updateDraft((layout) => appendPlacement(layout, widget));
+  }
+
+  function startDrag(event: ReactDragEvent, item: DashboardDragItem) {
+    event.dataTransfer.effectAllowed = item.kind === "catalogue" ? "copy" : "move";
+    event.dataTransfer.setData("application/x-govoplan-dashboard", JSON.stringify(item));
+    setDragItem(item);
+    setDropTarget(null);
+  }
+
+  function finishDrag() {
+    setDragItem(null);
+    setDropTarget(null);
+  }
+
+  function markDropTarget(
+    event: ReactDragEvent<HTMLElement>,
+    instanceId: string
+  ) {
+    if (!dragItem) return;
+    event.preventDefault();
+    event.dataTransfer.dropEffect = dragItem.kind === "catalogue" ? "copy" : "move";
+    const bounds = event.currentTarget.getBoundingClientRect();
+    const verticalPosition = (event.clientY - bounds.top) / bounds.height;
+    const edge =
+      verticalPosition < 0.3
+      || (
+        verticalPosition <= 0.7
+        && event.clientX < bounds.left + bounds.width / 2
+      )
+        ? "before"
+        : "after";
+    setDropTarget((current) =>
+      current?.kind === "placement"
+      && current.instanceId === instanceId
+      && current.edge === edge
+        ? current
+        : { kind: "placement", instanceId, edge }
+    );
+  }
+
+  function markEndDropTarget(event: ReactDragEvent<HTMLElement>) {
+    if (!dragItem) return;
+    event.preventDefault();
+    event.dataTransfer.dropEffect = dragItem.kind === "catalogue" ? "copy" : "move";
+    setDropTarget((current) =>
+      current?.kind === "end" ? current : { kind: "end" }
+    );
+  }
+
+  function dropOnPlacement(
+    event: ReactDragEvent<HTMLElement>,
+    target: DashboardWidgetPlacement
+  ) {
+    event.preventDefault();
+    event.stopPropagation();
+    if (!dragItem) return;
+    const edge = dropTarget?.kind === "placement"
+      && dropTarget.instanceId === target.instanceId
+      ? dropTarget.edge
+      : "after";
+    if (dragItem.kind === "placement") {
+      updateDraft((layout) =>
+        reorderPlacement(layout, dragItem.instanceId, target.instanceId, edge)
+      );
+    } else {
+      const widget = widgetById.get(dragItem.widgetId);
+      if (widget) {
+        updateDraft((layout) =>
+          insertPlacement(layout, widget, target.instanceId, edge)
+        );
+      }
+    }
+    finishDrag();
+  }
+
+  function dropOnPreview(event: ReactDragEvent<HTMLElement>) {
+    if (dropTarget?.kind === "placement") {
+      const target = renderedPlacements.find(
+        (placement) => placement.instanceId === dropTarget.instanceId
+      );
+      if (target) {
+        dropOnPlacement(event, target);
+        return;
+      }
+    }
+    dropAtEnd(event);
+  }
+
+  function dropAtEnd(event: ReactDragEvent<HTMLElement>) {
+    event.preventDefault();
+    event.stopPropagation();
+    if (!dragItem) return;
+    if (dragItem.kind === "placement") {
+      const last = draftLayout.placements.at(-1);
+      if (last) {
+        updateDraft((layout) =>
+          reorderPlacement(layout, dragItem.instanceId, last.instanceId, "after")
+        );
+      }
+    } else {
+      const widget = widgetById.get(dragItem.widgetId);
+      if (widget) addWidget(widget);
+    }
+    finishDrag();
   }
 
   return (
@@ -82,101 +376,185 @@ export default function DashboardPage({ settings, auth }: { settings: ApiSetting
             <p>Personal workspace assembled from installed module widgets.</p>
           </div>
           <div className="button-row compact-actions">
-          <Button onClick={() => setRefreshKey((value) => value + 1)}><RefreshCw size={16} /> Refresh</Button>
-          <Button onClick={() => setConfiguring((value) => !value)}><SlidersHorizontal size={16} /> Configure</Button>
-        </div>
-      </div>
-
-      <div className="metric-grid dashboard-summary-grid">
-        <MetricCard label="Installed modules" value={modules.length} tone="info" detail={moduleLabels(modules)} />
-        <MetricCard label="Available widgets" value={widgets.length} tone="neutral" detail="Provided by active modules" />
-        <MetricCard label="Visible widgets" value={visibleWidgets.length} tone="good" detail={hiddenCount ? `${hiddenCount} hidden` : "All shown"} />
-        <MetricCard label="Layout" value="personal" tone="neutral" detail="Saved in this browser" />
-      </div>
-
-      {configuring &&
-      <Card
-        title="Dashboard widgets"
-        actions={<Button onClick={resetLayout}><RotateCcw size={16} /> Reset</Button>}>
-          {widgets.length === 0 ? <p className="muted">No installed module exposes dashboard widgets yet.</p> :
-        <AdminSelectionList
-          options={widgets.map((widget) => ({ id: widget.id, label: widget.title, description: widget.description ?? widget.id }))}
-          selected={visibleWidgetIds}
-          onChange={setVisibleWidgets}
-        />
-        }
-        </Card>
-      }
-
-      {visibleWidgets.length === 0 ?
-      <Card title="No widgets selected">
-        <p className="muted">Open Configure and select at least one widget. Modules can add more widgets by exposing the dashboard.widgets capability.</p>
-      </Card> :
-      <div className="dashboard-widget-grid">
-          {visibleWidgets.map((widget) =>
-        <section key={widget.id} className={`dashboard-widget dashboard-widget-${widgetSize(widget)}`}>
-              <Card title={widget.title} collapsible collapseKey={`dashboard-widget:${widget.id}`}>
-                {widget.render({
-              settings,
-              auth,
-              modules,
-              widgetId: widget.id,
-              refreshKey,
-              size: widgetSize(widget)
-            })}
-              </Card>
-            </section>
+            {!configuring && (
+              <>
+                <Button onClick={() => setRefreshKey((value) => value + 1)}>
+                  <RefreshCw size={16} /> Refresh
+                </Button>
+                <Button onClick={beginConfiguration}>
+                  <SlidersHorizontal size={16} /> Configure
+                </Button>
+              </>
+            )}
+            {configuring && (
+              <>
+                <Button onClick={discardChanges} disabled={saving}>
+                  <X size={16} /> Cancel
+                </Button>
+                <Button
+                  variant="primary"
+                  onClick={() => void persistLayout()}
+                  disabled={saving || !dirty}
+                >
+                  <Save size={16} /> {saving ? "Saving..." : "Save layout"}
+                </Button>
+              </>
             )}
           </div>
-      }
         </div>
-    </PageScrollViewport>);
+
+        {error && (
+          <DismissibleAlert tone="danger" resetKey={error} floating>
+            {error}
+          </DismissibleAlert>
+        )}
+        {notice && !error && (
+          <DismissibleAlert tone="success" resetKey={notice} floating>
+            {notice}
+          </DismissibleAlert>
+        )}
+
+        <div className="metric-grid dashboard-summary-grid">
+          <MetricCard
+            label="Installed modules"
+            value={modules.length}
+            tone="info"
+            detail={moduleLabels(modules)}
+          />
+          <MetricCard
+            label="Available widgets"
+            value={widgets.length}
+            tone="neutral"
+            detail="Provided by active modules"
+          />
+          <MetricCard
+            label="On dashboard"
+            value={renderedPlacements.length}
+            tone="good"
+            detail={hiddenCount ? `${hiddenCount} available to add` : "All shown"}
+          />
+          <MetricCard
+            label="Layout"
+            value={viewLabel}
+            tone="neutral"
+            detail={layoutSourceLabel(layoutSource)}
+          />
+        </div>
+
+        <LoadingFrame loading={loading} label="Loading Dashboard layout">
+          {configuring ? (
+            <div className="dashboard-config-workspace">
+              <WidgetLibrary
+                widgets={libraryWidgets}
+                atCapacity={draftLayout.placements.length >= MAX_DASHBOARD_WIDGETS}
+                query={libraryQuery}
+                onQueryChange={setLibraryQuery}
+                onReset={() =>
+                  setDraftLayout({
+                    ...defaultDashboardLayout(widgets),
+                    revision: savedLayout.revision
+                  })
+                }
+                onAdd={addWidget}
+                onDragStart={startDrag}
+                onDragEnd={finishDrag}
+              />
+
+              <DashboardGrid
+                placements={renderedPlacements}
+                widgetById={widgetById}
+                settings={settings}
+                auth={auth}
+                modules={modules}
+                effectiveView={effectiveView}
+                refreshKey={refreshKey}
+                configuring
+                dragItem={dragItem}
+                dropTarget={dropTarget}
+                onDragStart={startDrag}
+                onDragEnd={finishDrag}
+                onDragOver={markDropTarget}
+                onDragOverEnd={markEndDropTarget}
+                onDrop={dropOnPlacement}
+                onDropPreview={dropOnPreview}
+                onDropAtEnd={dropAtEnd}
+                onRemove={(instanceId) =>
+                  updateDraft((layout) => removePlacement(layout, instanceId))
+                }
+                onConfigure={setEditingInstanceId}
+              />
+            </div>
+          ) : (
+            <DashboardGrid
+              placements={renderedPlacements}
+              widgetById={widgetById}
+              settings={settings}
+              auth={auth}
+              modules={modules}
+              effectiveView={effectiveView}
+              refreshKey={refreshKey}
+              configuring={false}
+              dragItem={null}
+              dropTarget={null}
+              onDragStart={startDrag}
+              onDragEnd={finishDrag}
+              onDragOver={markDropTarget}
+              onDragOverEnd={markEndDropTarget}
+              onDrop={dropOnPlacement}
+              onDropPreview={dropOnPreview}
+              onDropAtEnd={dropAtEnd}
+              onRemove={() => undefined}
+              onConfigure={() => undefined}
+            />
+          )}
+        </LoadingFrame>
+      </div>
+
+      <WidgetConfigurationDialog
+        open={Boolean(editingPlacement && editingWidget)}
+        widget={editingWidget}
+        placement={editingPlacement}
+        onClose={() => setEditingInstanceId(null)}
+        onSave={(placement) => {
+          updateDraft((layout) => updatePlacement(layout, placement));
+          setEditingInstanceId(null);
+        }}
+      />
+    </PageScrollViewport>
+  );
 }
 
-function canUseWidget(auth: AuthInfo, widget: DashboardWidgetContribution): boolean {
-  if (widget.allOf?.length && !widget.allOf.every((scope) => hasScope(auth, scope))) return false;
+function canUseWidget(
+  auth: AuthInfo,
+  widget: DashboardWidgetContribution
+): boolean {
+  if (
+    widget.allOf?.length
+    && !widget.allOf.every((scope) => hasScope(auth, scope))
+  ) {
+    return false;
+  }
   if (widget.anyOf?.length && !hasAnyScope(auth, widget.anyOf)) return false;
   return true;
 }
 
-function widgetSize(widget: DashboardWidgetContribution): DashboardWidgetSize {
-  return widget.defaultSize ?? "medium";
-}
-
-function defaultLayout(widgets: DashboardWidgetContribution[]): DashboardLayout {
-  const ids = widgets.map((widget) => widget.id);
-  return {
-    known: ids,
-    visible: widgets.filter((widget) => widget.defaultVisible !== false).map((widget) => widget.id)
-  };
-}
-
-function readLayout(storageKey: string): DashboardLayout | null {
-  if (typeof window === "undefined") return null;
-  try {
-    const raw = window.localStorage.getItem(storageKey);
-    if (!raw) return null;
-    const parsed = JSON.parse(raw) as Partial<DashboardLayout>;
-    if (!Array.isArray(parsed.visible) || !Array.isArray(parsed.known)) return null;
-    return {
-      visible: parsed.visible.filter((id): id is string => typeof id === "string"),
-      known: parsed.known.filter((id): id is string => typeof id === "string")
-    };
-  } catch {
-    return null;
-  }
-}
-
-function writeLayout(storageKey: string, layout: DashboardLayout): void {
-  if (typeof window === "undefined") return;
-  try {
-    window.localStorage.setItem(storageKey, JSON.stringify(layout));
-  } catch {
-    // localStorage may be unavailable in restricted browsing contexts.
-  }
-}
-
 function moduleLabels(modules: Array<{ id: string }>): string {
   if (!modules.length) return "Core shell only";
   return modules.slice(0, 4).map((module) => module.id).join(", ");
 }
+
+function layoutSourceLabel(source: LayoutSource): string {
+  if (source === "server") return "Saved for your account";
+  if (source === "browser") return "Browser layout; save to synchronize";
+  return "Module defaults";
+}
+
+function errorMessage(error: unknown): string {
+  if (isApiError(error)) {
+    if (error.status === 409) {
+      return "This layout changed in another session. Reload the page before saving again.";
+    }
+    return error.message;
+  }
+  return error instanceof Error ? error.message : "The Dashboard request failed.";
+}

webui/src/features/dashboard/WidgetConfigurationDialog.tsx

@@ -0,0 +1,201 @@
+import { useEffect, useMemo, useState } from "react";
+import {
+  Button,
+  Dialog,
+  FormField,
+  SegmentedControl,
+  ToggleSwitch,
+  type DashboardWidgetConfiguration,
+  type DashboardWidgetConfigurationField,
+  type DashboardWidgetConfigurationValue,
+  type DashboardWidgetContribution,
+  type DashboardWidgetSize
+} from "@govoplan/core-webui";
+import {
+  defaultWidgetSize,
+  supportedWidgetSizes,
+  type DashboardWidgetPlacement
+} from "./dashboardLayout";
+
+type WidgetConfigurationDialogProps = {
+  open: boolean;
+  widget: DashboardWidgetContribution | null;
+  placement: DashboardWidgetPlacement | null;
+  onClose: () => void;
+  onSave: (placement: DashboardWidgetPlacement) => void;
+};
+
+export default function WidgetConfigurationDialog({
+  open,
+  widget,
+  placement,
+  onClose,
+  onSave
+}: WidgetConfigurationDialogProps) {
+  const [size, setSize] = useState<DashboardWidgetSize>("medium");
+  const [configuration, setConfiguration] = useState<DashboardWidgetConfiguration>({});
+
+  useEffect(() => {
+    if (!open || !widget || !placement) return;
+    setSize(placement.size);
+    setConfiguration({
+      ...(widget.defaultConfiguration ?? {}),
+      ...placement.configuration
+    });
+  }, [open, placement, widget]);
+
+  const invalidConfiguration = useMemo(
+    () => (widget?.configurationFields ?? []).some((field) => {
+      const value = configuration[field.id];
+      if (field.required && valueIsEmpty(value)) return true;
+      if (field.kind !== "number" || value === null || value === undefined) {
+        return false;
+      }
+      if (typeof value !== "number" || !Number.isFinite(value)) return true;
+      if (field.min !== undefined && value < field.min) return true;
+      return field.max !== undefined && value > field.max;
+    }),
+    [configuration, widget]
+  );
+
+  if (!widget || !placement) return null;
+  const supportedSizes = supportedWidgetSizes(widget);
+
+  function setValue(id: string, value: DashboardWidgetConfigurationValue) {
+    setConfiguration((current) => ({ ...current, [id]: value }));
+  }
+
+  function reset() {
+    setSize(defaultWidgetSize(widget));
+    setConfiguration({ ...(widget.defaultConfiguration ?? {}) });
+  }
+
+  return (
+    <Dialog
+      open={open}
+      title={`Configure ${widget.title}`}
+      onClose={onClose}
+      className="dashboard-widget-config-dialog"
+      footer={
+        <>
+          <Button type="button" variant="ghost" onClick={reset}>Reset</Button>
+          <span className="dialog-footer-spacer" />
+          <Button type="button" onClick={onClose}>Cancel</Button>
+          <Button
+            type="button"
+            variant="primary"
+            disabled={invalidConfiguration}
+            onClick={() => onSave({ ...placement, size, configuration })}
+          >
+            Apply
+          </Button>
+        </>
+      }
+    >
+      {supportedSizes.length > 1 && (
+        <FormField label="Widget size">
+          <SegmentedControl
+            options={supportedSizes.map((candidate) => ({
+              id: candidate,
+              label: sizeLabel(candidate)
+            }))}
+            value={size}
+            onChange={setSize}
+            ariaLabel="Widget size"
+            role="group"
+            size="equal"
+            width="fill"
+          />
+        </FormField>
+      )}
+      {(widget.configurationFields ?? []).map((field) => (
+        <ConfigurationField
+          key={field.id}
+          field={field}
+          value={configuration[field.id] ?? widget.defaultConfiguration?.[field.id] ?? null}
+          onChange={(value) => setValue(field.id, value)}
+        />
+      ))}
+    </Dialog>
+  );
+}
+
+function ConfigurationField({
+  field,
+  value,
+  onChange
+}: {
+  field: DashboardWidgetConfigurationField;
+  value: DashboardWidgetConfigurationValue;
+  onChange: (value: DashboardWidgetConfigurationValue) => void;
+}) {
+  if (field.kind === "boolean") {
+    return (
+      <ToggleSwitch
+        label={field.label}
+        help={field.description}
+        checked={value === true}
+        onChange={onChange}
+      />
+    );
+  }
+
+  if (field.kind === "select") {
+    return (
+      <FormField label={field.label} help={field.description}>
+        <select
+          value={typeof value === "string" ? value : ""}
+          required={field.required}
+          onChange={(event) => onChange(event.target.value)}
+        >
+          <option value="" disabled={field.required}>
+            {field.required ? "Select an option" : "None"}
+          </option>
+          {(field.options ?? []).map((option) => (
+            <option key={option.value} value={option.value}>{option.label}</option>
+          ))}
+        </select>
+      </FormField>
+    );
+  }
+
+  if (field.kind === "number") {
+    return (
+      <FormField label={field.label} help={field.description}>
+        <input
+          type="number"
+          value={typeof value === "number" ? value : ""}
+          required={field.required}
+          min={field.min}
+          max={field.max}
+          step={field.step}
+          placeholder={field.placeholder}
+          onChange={(event) => {
+            const next = event.target.value;
+            onChange(next === "" ? null : Number(next));
+          }}
+        />
+      </FormField>
+    );
+  }
+
+  return (
+    <FormField label={field.label} help={field.description}>
+      <input
+        type="text"
+        value={typeof value === "string" ? value : ""}
+        required={field.required}
+        placeholder={field.placeholder}
+        onChange={(event) => onChange(event.target.value)}
+      />
+    </FormField>
+  );
+}
+
+function valueIsEmpty(value: DashboardWidgetConfigurationValue | undefined): boolean {
+  return value === null || value === undefined || value === "";
+}
+
+function sizeLabel(size: DashboardWidgetSize): string {
+  return size.charAt(0).toUpperCase() + size.slice(1);
+}

webui/src/features/dashboard/WidgetLibrary.tsx

@@ -0,0 +1,99 @@
+import type { DragEvent as ReactDragEvent } from "react";
+import { GripVertical, Plus, RotateCcw, Search } from "lucide-react";
+import {
+  IconButton,
+  type DashboardWidgetContribution
+} from "@govoplan/core-webui";
+import type { DashboardDragItem } from "./dashboardEditorTypes";
+
+type WidgetLibraryProps = {
+  widgets: DashboardWidgetContribution[];
+  atCapacity: boolean;
+  query: string;
+  onQueryChange: (query: string) => void;
+  onReset: () => void;
+  onAdd: (widget: DashboardWidgetContribution) => void;
+  onDragStart: (
+    event: ReactDragEvent,
+    item: DashboardDragItem
+  ) => void;
+  onDragEnd: () => void;
+};
+
+export default function WidgetLibrary({
+  widgets,
+  atCapacity,
+  query,
+  onQueryChange,
+  onReset,
+  onAdd,
+  onDragStart,
+  onDragEnd
+}: WidgetLibraryProps) {
+  return (
+    <aside className="dashboard-widget-library" aria-label="Widget library">
+      <div className="dashboard-widget-library-controls">
+        <div className="dashboard-widget-library-header">
+          <h2>Widget library</h2>
+        </div>
+        <label className="dashboard-widget-search">
+          <Search size={16} aria-hidden="true" />
+          <input
+            type="search"
+            value={query}
+            placeholder="Search widgets"
+            onChange={(event) => onQueryChange(event.target.value)}
+          />
+        </label>
+      </div>
+      <div className="dashboard-widget-library-list">
+        {widgets.map((widget) => (
+          <div
+            key={widget.id}
+            className={`dashboard-widget-library-item${atCapacity ? " is-disabled" : ""}`}
+            draggable={!atCapacity}
+            onDragStart={(event) =>
+              onDragStart(event, { kind: "catalogue", widgetId: widget.id })
+            }
+            onDragEnd={onDragEnd}
+          >
+            <GripVertical size={16} aria-hidden="true" />
+            <div>
+              <strong>{widget.title}</strong>
+              <span>{widget.description ?? widget.category ?? widget.moduleId}</span>
+            </div>
+            <IconButton
+              label={`Add ${widget.title}`}
+              icon={<Plus size={16} />}
+              variant="ghost"
+              disabledReason={
+                atCapacity
+                  ? "A Dashboard can contain at most 100 widgets."
+                  : undefined
+              }
+              onClick={() => onAdd(widget)}
+            />
+          </div>
+        ))}
+        {widgets.length === 0 && !atCapacity && (
+          <p className="muted dashboard-widget-library-empty">
+            {query.trim()
+              ? "No available widgets match the search."
+              : "All available widgets are already on this Dashboard."}
+          </p>
+        )}
+        {atCapacity && (
+          <p className="muted dashboard-widget-library-empty">
+            This Dashboard has reached the 100-widget limit.
+          </p>
+        )}
+      </div>
+      <IconButton
+        label="Reset to module defaults"
+        icon={<RotateCcw size={16} />}
+        variant="ghost"
+        onClick={onReset}
+      />
+    </aside>
+  );
+}

webui/src/features/dashboard/dashboardEditorTypes.ts

@@ -0,0 +1,96 @@
+import type { DashboardWidgetSize } from "@govoplan/core-webui";
+import type { DashboardWidgetPlacement } from "./dashboardLayout";
+
+export type DashboardDragItem =
+  | { kind: "placement"; instanceId: string }
+  | { kind: "catalogue"; widgetId: string };
+
+export type DashboardDropTarget =
+  | {
+      kind: "placement";
+      instanceId: string;
+      edge: "before" | "after";
+    }
+  | { kind: "end" };
+
+export type DashboardGridPreviewItem =
+  | {
+      kind: "placement";
+      placement: DashboardWidgetPlacement;
+      placeholder: boolean;
+    }
+  | {
+      kind: "catalogue";
+      widgetId: string;
+      size: DashboardWidgetSize;
+    };
+
+export function dashboardGridPreview(
+  placements: DashboardWidgetPlacement[],
+  dragItem: DashboardDragItem | null,
+  dropTarget: DashboardDropTarget | null,
+  catalogueSize: DashboardWidgetSize = "medium"
+): DashboardGridPreviewItem[] {
+  const items: DashboardGridPreviewItem[] = placements.map((placement) => ({
+    kind: "placement",
+    placement,
+    placeholder: false
+  }));
+  if (!dragItem || !dropTarget) return items;
+
+  if (dragItem.kind === "catalogue") {
+    const insertionIndex = previewInsertionIndex(
+      placements,
+      dropTarget,
+      null
+    );
+    items.splice(insertionIndex, 0, {
+      kind: "catalogue",
+      widgetId: dragItem.widgetId,
+      size: catalogueSize
+    });
+    return items;
+  }
+
+  const sourceIndex = placements.findIndex(
+    (placement) => placement.instanceId === dragItem.instanceId
+  );
+  if (sourceIndex < 0) return items;
+  const source = placements[sourceIndex];
+  const remaining = placements.filter(
+    (placement) => placement.instanceId !== dragItem.instanceId
+  );
+  const insertionIndex = previewInsertionIndex(
+    remaining,
+    dropTarget,
+    sourceIndex
+  );
+  const preview: DashboardGridPreviewItem[] = remaining.map((placement) => ({
+    kind: "placement",
+    placement,
+    placeholder: false
+  }));
+  preview.splice(insertionIndex, 0, {
+    kind: "placement",
+    placement: source,
+    placeholder: true
+  });
+  return preview;
+}
+
+function previewInsertionIndex(
+  placements: DashboardWidgetPlacement[],
+  target: DashboardDropTarget,
+  fallbackIndex: number | null
+): number {
+  if (target.kind === "end") return placements.length;
+  const targetIndex = placements.findIndex(
+    (placement) => placement.instanceId === target.instanceId
+  );
+  if (targetIndex < 0) {
+    return fallbackIndex === null
+      ? placements.length
+      : Math.min(fallbackIndex, placements.length);
+  }
+  return targetIndex + (target.edge === "after" ? 1 : 0);
+}

webui/src/features/dashboard/dashboardLayout.ts

@@ -0,0 +1,445 @@
+import type {
+  DashboardWidgetConfiguration,
+  DashboardWidgetContribution,
+  DashboardWidgetSize
+} from "@govoplan/core-webui";
+import type {
+  DashboardLayoutResponse,
+  DashboardLayoutUpdate,
+  DashboardWidgetPlacementResponse
+} from "../../api/dashboard";
+
+export type DashboardWidgetPlacement = {
+  instanceId: string;
+  widgetId: string;
+  size: DashboardWidgetSize;
+  configuration: DashboardWidgetConfiguration;
+};
+
+export type DashboardLayoutState = {
+  layoutVersion: 1;
+  revision: number;
+  knownWidgetIds: string[];
+  placements: DashboardWidgetPlacement[];
+};
+
+type LegacyDashboardLayout = {
+  visible: string[];
+  known: string[];
+};
+
+const SIZES: DashboardWidgetSize[] = ["small", "medium", "wide", "full"];
+export const MAX_DASHBOARD_WIDGETS = 100;
+
+export function createWidgetPlacement(
+  widget: DashboardWidgetContribution
+): DashboardWidgetPlacement {
+  return {
+    instanceId: newInstanceId(),
+    widgetId: widget.id,
+    size: defaultWidgetSize(widget),
+    configuration: { ...(widget.defaultConfiguration ?? {}) }
+  };
+}
+
+export function defaultDashboardLayout(
+  widgets: DashboardWidgetContribution[]
+): DashboardLayoutState {
+  return {
+    layoutVersion: 1,
+    revision: 0,
+    knownWidgetIds: widgets.map((widget) => widget.id),
+    placements: widgets
+      .filter((widget) => widget.defaultVisible !== false)
+      .slice(0, MAX_DASHBOARD_WIDGETS)
+      .map(createWidgetPlacement)
+  };
+}
+
+export function reconcileDashboardLayout(
+  layout: DashboardLayoutState,
+  widgets: DashboardWidgetContribution[]
+): DashboardLayoutState {
+  const widgetById = new Map(widgets.map((widget) => [widget.id, widget]));
+  const seenInstances = new Set<string>();
+  const seenWidgets = new Set<string>();
+  const placements = layout.placements.flatMap((placement) => {
+    if (!placement.instanceId || seenInstances.has(placement.instanceId)) return [];
+    const widget = widgetById.get(placement.widgetId);
+    if (widget && !widget.allowMultiple && seenWidgets.has(widget.id)) return [];
+    seenInstances.add(placement.instanceId);
+    seenWidgets.add(placement.widgetId);
+    return [normalizePlacement(placement, widget)];
+  });
+  const known = new Set(layout.knownWidgetIds);
+
+  for (const widget of widgets) {
+    if (
+      placements.length < MAX_DASHBOARD_WIDGETS
+      && !known.has(widget.id)
+      && widget.defaultVisible !== false
+    ) {
+      placements.push(createWidgetPlacement(widget));
+    }
+    known.add(widget.id);
+  }
+
+  return {
+    layoutVersion: 1,
+    revision: layout.revision,
+    knownWidgetIds: [...known],
+    placements: placements.slice(0, MAX_DASHBOARD_WIDGETS)
+  };
+}
+
+export function layoutFromResponse(
+  response: DashboardLayoutResponse
+): DashboardLayoutState {
+  return {
+    layoutVersion: 1,
+    revision: response.revision,
+    knownWidgetIds: uniqueStrings(response.known_widget_ids),
+    placements: response.placements.map(placementFromResponse)
+  };
+}
+
+export function layoutUpdatePayload(
+  layout: DashboardLayoutState
+): DashboardLayoutUpdate {
+  return {
+    expected_revision: layout.revision,
+    layout_version: 1,
+    placements: layout.placements.map(placementToResponse),
+    known_widget_ids: uniqueStrings(layout.knownWidgetIds)
+  };
+}
+
+export function appendPlacement(
+  layout: DashboardLayoutState,
+  widget: DashboardWidgetContribution
+): DashboardLayoutState {
+  if (
+    layout.placements.length >= MAX_DASHBOARD_WIDGETS
+    || (
+      !widget.allowMultiple
+      && layout.placements.some((placement) => placement.widgetId === widget.id)
+    )
+  ) {
+    return layout;
+  }
+  return {
+    ...layout,
+    knownWidgetIds: uniqueStrings([...layout.knownWidgetIds, widget.id]),
+    placements: [...layout.placements, createWidgetPlacement(widget)]
+  };
+}
+
+export function insertPlacement(
+  layout: DashboardLayoutState,
+  widget: DashboardWidgetContribution,
+  targetInstanceId: string,
+  edge: "before" | "after"
+): DashboardLayoutState {
+  if (
+    layout.placements.length >= MAX_DASHBOARD_WIDGETS
+    || (
+      !widget.allowMultiple
+      && layout.placements.some((placement) => placement.widgetId === widget.id)
+    )
+  ) {
+    return layout;
+  }
+  const targetIndex = layout.placements.findIndex(
+    (placement) => placement.instanceId === targetInstanceId
+  );
+  if (targetIndex < 0) return appendPlacement(layout, widget);
+  const insertionIndex = targetIndex + (edge === "after" ? 1 : 0);
+  return {
+    ...layout,
+    knownWidgetIds: uniqueStrings([...layout.knownWidgetIds, widget.id]),
+    placements: [
+      ...layout.placements.slice(0, insertionIndex),
+      createWidgetPlacement(widget),
+      ...layout.placements.slice(insertionIndex)
+    ]
+  };
+}
+
+export function removePlacement(
+  layout: DashboardLayoutState,
+  instanceId: string
+): DashboardLayoutState {
+  return {
+    ...layout,
+    placements: layout.placements.filter(
+      (placement) => placement.instanceId !== instanceId
+    )
+  };
+}
+
+export function updatePlacement(
+  layout: DashboardLayoutState,
+  nextPlacement: DashboardWidgetPlacement
+): DashboardLayoutState {
+  return {
+    ...layout,
+    placements: layout.placements.map((placement) =>
+      placement.instanceId === nextPlacement.instanceId
+        ? nextPlacement
+        : placement
+    )
+  };
+}
+
+export function reorderPlacement(
+  layout: DashboardLayoutState,
+  sourceInstanceId: string,
+  targetInstanceId: string,
+  edge: "before" | "after"
+): DashboardLayoutState {
+  if (sourceInstanceId === targetInstanceId) return layout;
+  const source = layout.placements.find(
+    (placement) => placement.instanceId === sourceInstanceId
+  );
+  if (!source) return layout;
+  const remaining = layout.placements.filter(
+    (placement) => placement.instanceId !== sourceInstanceId
+  );
+  const targetIndex = remaining.findIndex(
+    (placement) => placement.instanceId === targetInstanceId
+  );
+  if (targetIndex < 0) return layout;
+  const insertionIndex = targetIndex + (edge === "after" ? 1 : 0);
+  return {
+    ...layout,
+    placements: [
+      ...remaining.slice(0, insertionIndex),
+      source,
+      ...remaining.slice(insertionIndex)
+    ]
+  };
+}
+
+export function dashboardMasonryRowSpan(
+  height: number,
+  rowHeight: number,
+  bottomGap: number
+): number {
+  const safeHeight = Number.isFinite(height) ? Math.max(0, height) : 0;
+  const safeRowHeight =
+    Number.isFinite(rowHeight) && rowHeight > 0 ? rowHeight : 4;
+  const safeBottomGap =
+    Number.isFinite(bottomGap) ? Math.max(0, bottomGap) : 0;
+  return Math.max(1, Math.ceil((safeHeight + safeBottomGap) / safeRowHeight));
+}
+
+export function layoutsEqual(
+  left: DashboardLayoutState,
+  right: DashboardLayoutState
+): boolean {
+  return JSON.stringify(comparableLayout(left)) === JSON.stringify(comparableLayout(right));
+}
+
+export function localLayoutKey(
+  tenantId: string,
+  accountId: string,
+  viewId: string | null
+): string {
+  return [
+    "govoplan.dashboard.layout.v2",
+    encodeURIComponent(tenantId),
+    encodeURIComponent(accountId),
+    encodeURIComponent(viewId ?? "full")
+  ].join(":");
+}
+
+export function readLocalLayout(
+  storageKey: string,
+  legacyStorageKey: string | null,
+  widgets: DashboardWidgetContribution[]
+): DashboardLayoutState | null {
+  if (typeof window === "undefined") return null;
+  try {
+    const current = window.localStorage.getItem(storageKey);
+    if (current) return parseStoredLayout(JSON.parse(current));
+    if (!legacyStorageKey) return null;
+    const legacy = window.localStorage.getItem(legacyStorageKey);
+    if (!legacy) return null;
+    return migrateLegacyLayout(JSON.parse(legacy), widgets);
+  } catch {
+    return null;
+  }
+}
+
+export function writeLocalLayout(
+  storageKey: string,
+  layout: DashboardLayoutState
+): void {
+  if (typeof window === "undefined") return;
+  try {
+    window.localStorage.setItem(storageKey, JSON.stringify(layout));
+  } catch {
+    // Browser storage is only a resilience and migration fallback.
+  }
+}
+
+export function defaultWidgetSize(
+  widget: DashboardWidgetContribution
+): DashboardWidgetSize {
+  const supported = supportedWidgetSizes(widget);
+  return supported.includes(widget.defaultSize ?? "medium")
+    ? widget.defaultSize ?? "medium"
+    : supported[0];
+}
+
+export function supportedWidgetSizes(
+  widget: DashboardWidgetContribution
+): DashboardWidgetSize[] {
+  const supported = (widget.supportedSizes ?? [widget.defaultSize ?? "medium"])
+    .filter((size): size is DashboardWidgetSize => SIZES.includes(size));
+  return supported.length ? [...new Set(supported)] : ["medium"];
+}
+
+export function widgetIsConfigurable(
+  widget: DashboardWidgetContribution
+): boolean {
+  return Boolean(
+    widget.configurationFields?.length
+    || supportedWidgetSizes(widget).length > 1
+  );
+}
+
+function normalizePlacement(
+  placement: DashboardWidgetPlacement,
+  widget: DashboardWidgetContribution | undefined
+): DashboardWidgetPlacement {
+  if (!widget) return placement;
+  const supported = supportedWidgetSizes(widget);
+  return {
+    ...placement,
+    size: supported.includes(placement.size)
+      ? placement.size
+      : defaultWidgetSize(widget),
+    configuration: {
+      ...(widget.defaultConfiguration ?? {}),
+      ...placement.configuration
+    }
+  };
+}
+
+function placementFromResponse(
+  placement: DashboardWidgetPlacementResponse
+): DashboardWidgetPlacement {
+  return {
+    instanceId: placement.instance_id,
+    widgetId: placement.widget_id,
+    size: placement.size,
+    configuration: { ...placement.configuration }
+  };
+}
+
+function placementToResponse(
+  placement: DashboardWidgetPlacement
+): DashboardWidgetPlacementResponse {
+  return {
+    instance_id: placement.instanceId,
+    widget_id: placement.widgetId,
+    size: placement.size,
+    configuration: { ...placement.configuration }
+  };
+}
+
+function parseStoredLayout(value: unknown): DashboardLayoutState | null {
+  if (!value || typeof value !== "object") return null;
+  const candidate = value as Partial<DashboardLayoutState>;
+  if (!Array.isArray(candidate.placements) || !Array.isArray(candidate.knownWidgetIds)) {
+    return null;
+  }
+  const placements = candidate.placements.flatMap((item) => {
+    if (!item || typeof item !== "object") return [];
+    const placement = item as Partial<DashboardWidgetPlacement>;
+    if (
+      typeof placement.instanceId !== "string"
+      || typeof placement.widgetId !== "string"
+      || !SIZES.includes(placement.size as DashboardWidgetSize)
+      || !placement.configuration
+      || typeof placement.configuration !== "object"
+      || Array.isArray(placement.configuration)
+    ) {
+      return [];
+    }
+    return [{
+      instanceId: placement.instanceId,
+      widgetId: placement.widgetId,
+      size: placement.size as DashboardWidgetSize,
+      configuration: sanitizeConfiguration(placement.configuration)
+    }];
+  });
+  return {
+    layoutVersion: 1,
+    revision: typeof candidate.revision === "number" ? candidate.revision : 0,
+    knownWidgetIds: uniqueStrings(candidate.knownWidgetIds),
+    placements
+  };
+}
+
+function migrateLegacyLayout(
+  value: unknown,
+  widgets: DashboardWidgetContribution[]
+): DashboardLayoutState | null {
+  if (!value || typeof value !== "object") return null;
+  const candidate = value as Partial<LegacyDashboardLayout>;
+  if (!Array.isArray(candidate.visible) || !Array.isArray(candidate.known)) {
+    return null;
+  }
+  const visible = new Set(uniqueStrings(candidate.visible));
+  const widgetById = new Map(widgets.map((widget) => [widget.id, widget]));
+  return {
+    layoutVersion: 1,
+    revision: 0,
+    knownWidgetIds: uniqueStrings(candidate.known),
+    placements: [...visible].flatMap((widgetId) => {
+      const widget = widgetById.get(widgetId);
+      return widget ? [createWidgetPlacement(widget)] : [];
+    })
+  };
+}
+
+function uniqueStrings(values: unknown[]): string[] {
+  return [...new Set(values.filter((value): value is string => typeof value === "string"))];
+}
+
+function sanitizeConfiguration(
+  value: Record<string, unknown>
+): DashboardWidgetConfiguration {
+  return Object.fromEntries(
+    Object.entries(value).filter(([key, item]) =>
+      key.length > 0
+      && key.length <= 120
+      && (
+        item === null
+        || typeof item === "string"
+        || typeof item === "boolean"
+        || (typeof item === "number" && Number.isFinite(item))
+      )
+    )
+  ) as DashboardWidgetConfiguration;
+}
+
+function comparableLayout(layout: DashboardLayoutState) {
+  return {
+    layoutVersion: layout.layoutVersion,
+    knownWidgetIds: layout.knownWidgetIds,
+    placements: layout.placements
+  };
+}
+
+function newInstanceId(): string {
+  if (
+    typeof globalThis.crypto !== "undefined"
+    && typeof globalThis.crypto.randomUUID === "function"
+  ) {
+    return globalThis.crypto.randomUUID();
+  }
+  return `widget-${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 12)}`;
+}

webui/src/features/dashboard/widgets/InstalledModulesWidget.tsx

@@ -1,16 +1,52 @@
-import { StatusBadge, type PlatformWebModule } from "@govoplan/core-webui";
+import {
+  StatusBadge,
+  type DashboardWidgetConfiguration,
+  type PlatformWebModule
+} from "@govoplan/core-webui";
 
-export default function InstalledModulesWidget({ modules }: { modules: PlatformWebModule[] }) {
+export default function InstalledModulesWidget({
+  modules,
+  configuration
+}: {
+  modules: PlatformWebModule[];
+  configuration: DashboardWidgetConfiguration;
+}) {
   if (!modules.length) return <p className="muted">No WebUI modules are active.</p>;
+  const maxItems = clampNumber(configuration.maxItems, 1, 50, 8);
+  const showVersions = configuration.showVersions !== false;
+  const sortBy = configuration.sortBy === "label" ? "label" : "module";
+  const visibleModules = [...modules]
+    .sort((left, right) => {
+      const leftValue = sortBy === "label" ? left.label : left.id;
+      const rightValue = sortBy === "label" ? right.label : right.id;
+      return String(leftValue).localeCompare(String(rightValue));
+    })
+    .slice(0, maxItems);
+  const remaining = Math.max(modules.length - visibleModules.length, 0);
 
   return (
+    <>
       <dl className="detail-list dashboard-compact-list">
-      {modules.map((module) =>
+        {visibleModules.map((module) =>
         <div key={module.id}>
             <dt><StatusBadge status="success" label={module.id} /></dt>
-          <dd><strong>{module.label}</strong><span className="muted"> v{module.version}</span></dd>
+            <dd>
+              <strong>{module.label}</strong>
+              {showVersions && <span className="muted"> v{module.version}</span>}
+            </dd>
           </div>
         )}
-    </dl>);
+      </dl>
+      {remaining > 0 && <p className="muted dashboard-widget-overflow">+{remaining} more active modules</p>}
+    </>);
 }
 
+function clampNumber(
+  value: DashboardWidgetConfiguration[string],
+  minimum: number,
+  maximum: number,
+  fallback: number
+): number {
+  if (typeof value !== "number" || !Number.isFinite(value)) return fallback;
+  return Math.min(maximum, Math.max(minimum, Math.round(value)));
+}

webui/src/module.ts

@@ -17,7 +17,41 @@ const dashboardWidgets: DashboardWidgetsUiCapability = {
       category: "Platform",
       order: 10,
       defaultSize: "medium",
-      render: ({ modules }) => createElement(InstalledModulesWidget, { modules })
+      supportedSizes: ["small", "medium", "wide"],
+      defaultConfiguration: {
+        maxItems: 8,
+        showVersions: true,
+        sortBy: "module"
+      },
+      configurationFields: [
+        {
+          id: "maxItems",
+          label: "Maximum modules",
+          description: "Limit how many active modules are listed.",
+          kind: "number",
+          min: 1,
+          max: 50,
+          step: 1,
+          required: true
+        },
+        {
+          id: "sortBy",
+          label: "Sort modules by",
+          kind: "select",
+          required: true,
+          options: [
+            { value: "module", label: "Module id" },
+            { value: "label", label: "Display name" }
+          ]
+        },
+        {
+          id: "showVersions",
+          label: "Show module versions",
+          kind: "boolean"
+        }
+      ],
+      render: ({ modules, configuration }) =>
+        createElement(InstalledModulesWidget, { modules, configuration })
     }
   ]
 };

webui/src/styles/dashboard.css

@@ -11,12 +11,23 @@
 .dashboard-widget-grid {
   display: grid;
   grid-template-columns: repeat(4, minmax(220px, 1fr));
-  gap: 18px;
+  grid-auto-flow: row dense;
+  grid-auto-rows: 4px;
+  column-gap: 18px;
+  row-gap: 0;
   align-items: start;
 }
 
 .dashboard-widget {
   min-width: 0;
+  position: relative;
+  align-self: start;
+  margin-bottom: 18px;
+}
+
+.dashboard-widget > .card {
+  height: auto;
+  margin-bottom: 0;
 }
 
 .dashboard-widget-small {
@@ -41,10 +52,275 @@
   margin-bottom: 0;
 }
 
+.dashboard-config-workspace {
+  display: flex;
+  min-width: 0;
+  flex-direction: column;
+  gap: 18px;
+}
+
+.dashboard-widget-library {
+  display: grid;
+  grid-template-columns: minmax(200px, 260px) minmax(0, 1fr) 36px;
+  align-items: center;
+  min-width: 0;
+  min-height: 84px;
+  overflow: hidden;
+  border: var(--border-line);
+  border-radius: var(--radius);
+  background: var(--surface);
+  box-shadow: var(--shadow-xs);
+}
+
+.dashboard-widget-library-controls {
+  align-self: stretch;
+  display: grid;
+  align-content: center;
+  gap: 7px;
+  min-width: 0;
+  padding: 9px 12px;
+  border-right: var(--border-line);
+  background: var(--panel-header);
+}
+
+.dashboard-widget-library-header {
+  display: flex;
+  align-items: center;
+}
+
+.dashboard-widget-library-header h2 {
+  margin: 0;
+  font-size: 16px;
+}
+
+.dashboard-widget-search {
+  display: grid;
+  grid-template-columns: auto minmax(0, 1fr);
+  align-items: center;
+  gap: 8px;
+  min-height: 0;
+  margin: 0;
+  padding: 4px 8px;
+  border: var(--border-line);
+  border-radius: 5px;
+  background: var(--surface);
+}
+
+.dashboard-widget-search:focus-within {
+  box-shadow: var(--accent-ring-soft);
+}
+
+.dashboard-widget-search input[type="search"] {
+  height: auto;
+  min-height: 0;
+  min-width: 0;
+  padding: 1px 0;
+  border: 0;
+  box-shadow: none;
+  font: inherit;
+  font-size: 13px;
+  line-height: 1.35;
+}
+
+.dashboard-widget-library-list {
+  display: flex;
+  min-width: 0;
+  align-self: stretch;
+  overflow-x: auto;
+  overflow-y: hidden;
+  border-right: var(--border-line);
+}
+
+.dashboard-widget-library-item {
+  flex: 0 0 min(250px, 32vw);
+  display: grid;
+  grid-template-columns: 18px minmax(0, 1fr) 36px;
+  align-items: center;
+  gap: 10px;
+  min-height: 70px;
+  padding: 9px 10px 9px 12px;
+  border-right: var(--border-line);
+  cursor: grab;
+}
+
+.dashboard-widget-library-item:hover {
+  background: var(--hover-tint-soft);
+}
+
+.dashboard-widget-library-item:active {
+  cursor: grabbing;
+}
+
+.dashboard-widget-library-item.is-disabled {
+  cursor: default;
+  opacity: .7;
+}
+
+.dashboard-widget-library-item > div {
+  display: grid;
+  min-width: 0;
+  gap: 3px;
+}
+
+.dashboard-widget-library-item strong,
+.dashboard-widget-library-item span {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.dashboard-widget-library-item span {
+  color: var(--muted);
+  font-size: 12px;
+}
+
+.dashboard-widget-library-empty {
+  flex: 1 0 auto;
+  margin: 0;
+  padding: 18px 16px;
+}
+
+.dashboard-widget-grid.is-configuring .dashboard-widget {
+  cursor: default;
+}
+
+.dashboard-widget-grid.is-configuring .card-header {
+  align-items: center;
+  flex-wrap: nowrap;
+  gap: 6px;
+  padding: 12px 16px;
+}
+
+.dashboard-widget-grid.is-configuring .card-header > h2 {
+  order: 2;
+  flex: 1 1 auto;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.dashboard-widget-grid.is-configuring .card-actions {
+  display: contents;
+}
+
+.dashboard-widget-actions {
+  display: contents;
+}
+
+.dashboard-widget-actions > * {
+  order: 3;
+}
+
+.dashboard-widget-drag-handle {
+  order: 1;
+  flex: 0 0 auto;
+  cursor: grab;
+}
+
+.dashboard-widget-drag-handle:active {
+  cursor: grabbing;
+}
+
+.dashboard-widget-drop-placeholder {
+  min-height: 142px;
+  border: 2px dashed var(--accent);
+  border-radius: var(--radius);
+  background: var(--accent-hover-bg);
+  color: var(--text);
+}
+
+.dashboard-widget-drop-placeholder.preserves-widget-height {
+  border: 0;
+  background: transparent;
+}
+
+.dashboard-widget-placeholder-content {
+  visibility: hidden;
+}
+
+.dashboard-widget-placeholder-surface {
+  position: absolute;
+  inset: 0;
+  z-index: 2;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 8px;
+  min-height: 142px;
+  padding: 16px;
+  border: 2px dashed var(--accent);
+  border-radius: var(--radius);
+  background: var(--accent-hover-bg);
+  color: var(--text);
+  text-align: center;
+  pointer-events: none;
+}
+
+.dashboard-grid-end-drop-target,
+.dashboard-empty-state.is-drop-target {
+  display: grid;
+  min-height: 74px;
+  place-items: center;
+  border: 2px dashed var(--line-dark);
+  border-radius: var(--radius);
+  color: var(--muted);
+  font-size: 13px;
+  font-weight: 700;
+}
+
+.dashboard-grid-end-drop-target {
+  grid-column: 1 / -1;
+  grid-row-end: span 19;
+}
+
+.dashboard-grid-end-drop-target:hover,
+.dashboard-empty-state.is-drop-target:hover {
+  border-color: var(--accent);
+  background: var(--accent-hover-bg);
+  color: var(--text);
+}
+
+.dashboard-empty-state {
+  min-height: 220px;
+  padding: 32px;
+  text-align: center;
+}
+
+.dashboard-empty-state h2 {
+  margin: 0 0 8px;
+  font-size: 18px;
+}
+
+.dashboard-empty-state p {
+  margin: 0;
+}
+
+.dashboard-widget-config-dialog {
+  width: min(620px, 100%);
+}
+
+.dashboard-widget-config-dialog .dialog-body {
+  display: grid;
+  gap: 18px;
+}
+
+.dashboard-widget-config-dialog .dialog-footer-spacer {
+  flex: 1 1 auto;
+}
+
+.dashboard-widget-overflow {
+  margin: 12px 0 0;
+}
+
 @media (max-width: 1120px) {
   .dashboard-widget-grid {
     grid-template-columns: repeat(2, minmax(220px, 1fr));
   }
+
+  .dashboard-widget-library {
+    grid-template-columns: minmax(200px, 240px) minmax(0, 1fr) 36px;
+  }
 }
 
 @media (max-width: 900px) {
@@ -53,6 +329,29 @@
     grid-template-columns: 1fr;
   }
 
+  .dashboard-widget-library {
+    grid-template-columns: minmax(0, 1fr) 36px;
+  }
+
+  .dashboard-widget-library-controls {
+    grid-column: 1;
+    grid-row: 1;
+    border-right: 0;
+  }
+
+  .dashboard-widget-library-list {
+    grid-column: 1 / -1;
+    grid-row: 2;
+    min-height: 70px;
+    border-top: var(--border-line);
+    border-right: 0;
+    border-left: 0;
+  }
+
+  .dashboard-widget-library-item {
+    flex-basis: min(250px, 72vw);
+  }
+
   .dashboard-widget-small,
   .dashboard-widget-medium,
   .dashboard-widget-wide,

webui/tests/dashboard-layout.test.ts

@@ -0,0 +1,170 @@
+import assert from "node:assert/strict";
+import {
+  appendPlacement,
+  dashboardMasonryRowSpan,
+  defaultDashboardLayout,
+  layoutUpdatePayload,
+  reconcileDashboardLayout,
+  removePlacement,
+  reorderPlacement
+} from "../src/features/dashboard/dashboardLayout.ts";
+import { dashboardGridPreview } from "../src/features/dashboard/dashboardEditorTypes.ts";
+
+const widgets = [
+  {
+    id: "one",
+    surfaceId: "one.widget",
+    title: "One",
+    moduleId: "one",
+    defaultSize: "small" as const,
+    supportedSizes: ["small", "medium"] as const,
+    defaultConfiguration: { count: 3 },
+    render: () => null
+  },
+  {
+    id: "two",
+    surfaceId: "two.widget",
+    title: "Two",
+    moduleId: "two",
+    defaultVisible: false,
+    defaultSize: "medium" as const,
+    render: () => null
+  }
+];
+
+const defaults = defaultDashboardLayout(widgets);
+assert.deepEqual(defaults.knownWidgetIds, ["one", "two"]);
+assert.equal(defaults.placements.length, 1);
+assert.equal(defaults.placements[0].widgetId, "one");
+assert.deepEqual(defaults.placements[0].configuration, { count: 3 });
+
+const withTwo = appendPlacement(defaults, widgets[1]);
+assert.deepEqual(
+  withTwo.placements.map((placement) => placement.widgetId),
+  ["one", "two"]
+);
+assert.equal(
+  appendPlacement(withTwo, widgets[1]).placements.length,
+  2,
+  "single-instance widgets must not be duplicated"
+);
+
+const reordered = reorderPlacement(
+  withTwo,
+  withTwo.placements[1].instanceId,
+  withTwo.placements[0].instanceId,
+  "before"
+);
+assert.deepEqual(
+  reordered.placements.map((placement) => placement.widgetId),
+  ["two", "one"]
+);
+
+const removed = removePlacement(reordered, reordered.placements[0].instanceId);
+assert.deepEqual(
+  removed.placements.map((placement) => placement.widgetId),
+  ["one"]
+);
+
+const placementPreview = dashboardGridPreview(
+  withTwo.placements,
+  {
+    kind: "placement",
+    instanceId: withTwo.placements[0].instanceId
+  },
+  {
+    kind: "placement",
+    instanceId: withTwo.placements[1].instanceId,
+    edge: "after"
+  }
+);
+assert.deepEqual(
+  placementPreview.map((item) =>
+    item.kind === "placement"
+      ? `${item.placement.widgetId}:${item.placeholder}`
+      : item.widgetId
+  ),
+  ["two:false", "one:true"],
+  "placement previews must show the prospective order"
+);
+
+const cataloguePreview = dashboardGridPreview(
+  withTwo.placements,
+  { kind: "catalogue", widgetId: "three" },
+  {
+    kind: "placement",
+    instanceId: withTwo.placements[0].instanceId,
+    edge: "after"
+  },
+  "wide"
+);
+assert.deepEqual(
+  cataloguePreview.map((item) =>
+    item.kind === "placement"
+      ? item.placement.widgetId
+      : `${item.widgetId}:${item.size}`
+  ),
+  ["one", "three:wide", "two"],
+  "catalogue previews must reserve the prospective widget size"
+);
+
+const unavailablePlacement = {
+  instanceId: "unavailable-instance",
+  widgetId: "temporarily-disabled",
+  size: "wide" as const,
+  configuration: { mode: "summary" }
+};
+const reconciled = reconcileDashboardLayout(
+  {
+    layoutVersion: 1,
+    revision: 4,
+    knownWidgetIds: ["temporarily-disabled"],
+    placements: [unavailablePlacement]
+  },
+  widgets
+);
+assert.equal(
+  reconciled.placements[0],
+  unavailablePlacement,
+  "temporarily unavailable contributions must retain their placement"
+);
+assert.equal(
+  reconciled.placements[1].widgetId,
+  "one",
+  "new default-visible widgets are announced into existing layouts"
+);
+assert.equal(reconciled.revision, 4);
+
+const payload = layoutUpdatePayload(reconciled);
+assert.equal(payload.expected_revision, 4);
+assert.equal(payload.placements[0].instance_id, "unavailable-instance");
+assert.equal(payload.placements[0].configuration.mode, "summary");
+
+const repeatingWidget = {
+  ...widgets[0],
+  id: "repeating",
+  allowMultiple: true,
+  defaultVisible: false
+};
+let bounded = defaultDashboardLayout([repeatingWidget]);
+for (let index = 0; index < 105; index += 1) {
+  bounded = appendPlacement(bounded, repeatingWidget);
+}
+assert.equal(
+  bounded.placements.length,
+  100,
+  "client layout helpers must enforce the server placement limit"
+);
+
+assert.equal(
+  dashboardMasonryRowSpan(142, 4, 18),
+  40,
+  "masonry spans must reserve the widget height and inter-widget gap"
+);
+assert.equal(
+  dashboardMasonryRowSpan(0, Number.NaN, Number.NaN),
+  1,
+  "masonry spans must remain valid while a widget is mounting"
+);
+
+console.log("Dashboard layout tests passed.");