diff --git a/.planning/STATE.md b/.planning/STATE.md
index 7eed0c4..4f5fec6 100644
--- a/.planning/STATE.md
+++ b/.planning/STATE.md
@@ -2,14 +2,15 @@
 gsd_state_version: 1.0
 milestone: v4.0
 milestone_name: Figma Design Parity
-status: Executing
-last_updated: "2026-05-17T16:05:00.000Z"
-last_activity: 2026-05-17 — Phase 18 complete (sidebar + header restyle approved)
+status: executing
+last_updated: "2026-05-18T13:40:28.221Z"
+last_activity: 2026-05-18 -- Phase 20 planning complete
 progress:
   total_phases: 5
-  completed_phases: 1
-  total_plans: 3
-  completed_plans: 3
+  completed_phases: 2
+  total_plans: 9
+  completed_plans: 6
+  percent: 40
 ---
 
 # STATE
@@ -29,8 +30,8 @@ See: `.planning/PROJECT.md` (updated 2026-05-17)
 
 Phase: 19 — Tablo List Revamp (next)
 Plan: —
-Status: Executing
-Last activity: 2026-05-17 — Phase 18 complete
+Status: Ready to execute
+Last activity: 2026-05-18 -- Phase 20 planning complete
 
 ## Previous Milestone Status
 
diff --git a/.planning/phases/20-tablo-detail-kanban-restyle/20-01-PLAN.md b/.planning/phases/20-tablo-detail-kanban-restyle/20-01-PLAN.md
index 1601c81..a09db64 100644
--- a/.planning/phases/20-tablo-detail-kanban-restyle/20-01-PLAN.md
+++ b/.planning/phases/20-tablo-detail-kanban-restyle/20-01-PLAN.md
@@ -21,13 +21,15 @@ must_haves:
     - "Accessing with an invalid UUID returns 400"
     - "Progress is computed as doneTasks/totalTasks*100 (integer), not from tablo.Status"
     - "TabloDetailViewModel groups tasks into 4 slices: Todo, InProgress, InReview, Done"
+    - "TabloDetailViewModel.Etapes lists etapes (tasks with IsEtape=true) for the tablo, with task count per etape"
+    - "Rendered HTML from GET /tablos/{id} contains substring `initTabloDetailSortable`"
   artifacts:
     - path: "go-backend/internal/web/handlers/tablo_detail.go"
       provides: "GetTabloDetailPage handler + tabloDetailRepository interface + computeTabloProgress"
       exports: ["GetTabloDetailPage"]
     - path: "go-backend/internal/web/views/tablo_detail_view.go"
-      provides: "TabloDetailViewModel + TabloDetailColumnView + NewTabloDetailViewModel"
-      exports: ["TabloDetailViewModel", "TabloDetailColumnView", "NewTabloDetailViewModel"]
+      provides: "TabloDetailViewModel + TabloDetailColumnView + TabloDetailEtapeView + NewTabloDetailViewModel"
+      exports: ["TabloDetailViewModel", "TabloDetailColumnView", "TabloDetailEtapeView", "NewTabloDetailViewModel"]
     - path: "go-backend/internal/web/handlers/tablo_detail_test.go"
       provides: "Test scaffold for DETAIL-01 + TASK-01 handler tests"
     - path: "go-backend/router.go"
@@ -45,9 +47,9 @@ must_haves:
 ---
 
 <objective>
-Create the GET /tablos/{tabloID} handler, view model, and route registration. This is the foundation plan: it creates the data contracts (TabloDetailViewModel, TabloDetailColumnView) that the templ plan will build against, and the test scaffold that covers DETAIL-01 + TASK-01 handler behavior.
+Create the GET /tablos/{tabloID} handler, view model, and route registration. This is the foundation plan: it creates the data contracts (TabloDetailViewModel, TabloDetailColumnView, TabloDetailEtapeView) that the templ plan will build against, and the test scaffold that covers DETAIL-01 + TASK-01 handler behavior.
 
-Purpose: The tablo detail page does not exist. This plan wires the server-side data layer — authentication, ownership check, task fetch, progress computation — and registers the route.
+Purpose: The tablo detail page does not exist. This plan wires the server-side data layer — authentication, ownership check, task fetch, progress computation, etape grouping — and registers the route.
 
 Output: Handler file, view model file, test scaffold, updated router.go.
 </objective>
@@ -101,7 +103,7 @@ type taskMutationRepository interface {
 }
 
 type ListTasksByTabloInput = taskmodel.ListByTabloInput  // {OwnerID uuid.UUID, TabloID uuid.UUID}
-type TaskRecord = taskmodel.Record                        // {ID, TabloID, OwnerID, Title, Status, ...}
+type TaskRecord = taskmodel.Record                        // {ID, TabloID, OwnerID, Title, Status, IsEtape bool, ParentTaskID *uuid.UUID, ...}
 type TaskStatus = taskmodel.Status
 const TaskStatusDone = taskmodel.StatusDone  // "done"
 const TaskStatusTodo = taskmodel.StatusTodo
@@ -109,6 +111,13 @@ const TaskStatusInProgress = taskmodel.StatusInProgress
 const TaskStatusInReview = taskmodel.StatusInReview
 ```
 
+From go-backend/internal/tasks/model.go:
+```go
+// TaskRecord.IsEtape bool — true for etapes (stage-level tasks that group regular tasks)
+// TaskRecord.ParentTaskID *uuid.UUID — regular tasks may have an etape as their parent
+// Etapes: tasks where IsEtape==true; child tasks: IsEtape==false with ParentTaskID pointing to an etape
+```
+
 From go-backend/internal/web/handlers/tablos.go:
 ```go
 // findTabloByID — existing helper, available within handlers package
@@ -152,54 +161,62 @@ views.DashboardPageWithMainClass(activePath, tablos, "flex-1 overflow-auto", con
 <tasks>
 
 <task type="auto" tdd="true">
-  <name>Task 1: Define TabloDetailViewModel and test scaffold</name>
+  <name>Task 1: Define TabloDetailViewModel (with etapes) and test scaffold</name>
   <files>go-backend/internal/web/views/tablo_detail_view.go, go-backend/internal/web/handlers/tablo_detail_test.go</files>
   <read_first>
     - go-backend/internal/web/views/tablos_view.go (TabloCardView struct pattern, normalizedView helper)
-    - go-backend/internal/web/views/tasks_view.go (TaskCardView, TasksKanbanColumnView pattern)
+    - go-backend/internal/web/views/tasks_view.go (TaskCardView, TasksKanbanColumnView pattern; etape grouping in buildKanbanView and etapeMeta struct)
     - go-backend/internal/web/handlers/tablos_test.go (test scaffold pattern for handlers)
     - go-backend/internal/web/handlers/in_memory_auth_repository.go (InMemoryAuthRepository method list, lines 168+)
   </read_first>
   <behavior>
-    - TabloDetailViewModel has fields: TabloID string, TabloName string, Color string, Initial string, OwnerName string, DueDate string, StatusLabel string, StatusTone string, Progress int, ProgressLabel string, Columns []TabloDetailColumnView
+    - TabloDetailViewModel has fields: TabloID string, TabloName string, Color string, Initial string, OwnerName string, DueDate string, StatusLabel string, StatusTone string, Progress int, ProgressLabel string, Columns []TabloDetailColumnView, Etapes []TabloDetailEtapeView
     - TabloDetailColumnView has fields: ID string, Label string, Tasks []TabloDetailTaskView, CreateHref string
     - TabloDetailTaskView has fields: ID string, Title string, DeleteHref string, EditHref string
-    - NewTabloDetailViewModel(tablo TabloRecord, tasks []TaskRecord, ownerName string) builds 4 columns in order: "todo", "in_progress", "in_review", "done"
-    - computeTabloProgress(tasks []TaskRecord) int returns 0 when total==0, else (doneCount*100)/total
+    - TabloDetailEtapeView has fields: ID string, Name string, TaskCount int
+    - NewTabloDetailViewModel(tablo TabloRecord, tasks []TaskRecord, ownerName string) builds 4 columns in order: "todo", "in_progress", "in_review", "done". It also builds Etapes slice by filtering tasks where IsEtape==true; each etape's TaskCount is the number of tasks (IsEtape==false) whose ParentTaskID equals the etape's ID.
+    - computeTabloProgress(tasks []TaskRecord) int returns 0 when total of non-etape tasks==0, else (doneCount*100)/total where doneCount counts non-etape tasks with Status==TaskStatusDone
     - Test: TestComputeTabloProgress_Empty — computeTabloProgress([]) == 0
     - Test: TestComputeTabloProgress_AllDone — computeTabloProgress([done, done]) == 100
     - Test: TestComputeTabloProgress_Half — computeTabloProgress([done, todo]) == 50
-    - Test: TestNewTabloDetailViewModel_Groups tasks into correct columns by status
+    - Test: TestComputeTabloProgress_EtapesIgnored — etape tasks (IsEtape=true) are excluded from progress computation
+    - Test: TestNewTabloDetailViewModel_Groups tasks into correct columns by status (excludes etapes from columns)
+    - Test: TestNewTabloDetailViewModel_EtapesPopulated — Etapes slice contains etape tasks with correct TaskCount
     - Test: TestGetTabloDetailPage_Returns200 — GET /tablos/{validTabloID} with session cookie returns 200 and tablo name in body
     - Test: TestGetTabloDetailPage_Returns404 — GET /tablos/{unknownID} with session cookie returns 404
     - Test: TestGetTabloDetailPage_Returns400 — GET /tablos/not-a-uuid returns 400
     - Test: TestGetTabloDetailPage_Unauthenticated — GET /tablos/{validID} without session cookie returns 302 to /login
     - Test: TestTabloDetailKanbanColumns — response body contains the 4 kanban column status values (todo, in_progress, in_review, done) per Pitfall 3
+    - Test: TestGetTabloDetailPage_ContainsSortableScript — response body contains substring "initTabloDetailSortable"
   </behavior>
   <action>
     Create go-backend/internal/web/views/tablo_detail_view.go in package views. Define:
     1. TabloDetailTaskView struct with ID, Title, DeleteHref, EditHref string fields.
     2. TabloDetailColumnView struct with ID, Label, Tasks []TabloDetailTaskView, CreateHref string fields.
-    3. TabloDetailViewModel struct with TabloID, TabloName, Color, Initial, OwnerName, DueDate, StatusLabel, StatusTone string, Progress int, ProgressLabel string, Columns []TabloDetailColumnView fields.
-    4. computeTabloProgress(tasks []TaskRecord) int function (package-private, used by handler and tested directly in tablo_detail_test.go via same package). Returns 0 if len==0; returns (doneCount*100)/len(tasks) where doneCount counts tasks with Status==TaskStatusDone.
-    5. NewTabloDetailViewModel(tablo TabloRecord, tasks []TaskRecord, ownerName string) TabloDetailViewModel that:
+    3. TabloDetailEtapeView struct with ID, Name string and TaskCount int fields.
+    4. TabloDetailViewModel struct with TabloID, TabloName, Color, Initial, OwnerName, DueDate, StatusLabel, StatusTone string, Progress int, ProgressLabel string, Columns []TabloDetailColumnView, Etapes []TabloDetailEtapeView fields.
+    5. computeTabloProgress(tasks []TaskRecord) int function (package-private). Excludes tasks with IsEtape==true from computation. Returns 0 if no non-etape tasks; returns (doneCount*100)/nonEtapeTotal where doneCount counts non-etape tasks with Status==TaskStatusDone.
+    6. NewTabloDetailViewModel(tablo TabloRecord, tasks []TaskRecord, ownerName string) TabloDetailViewModel that:
        - Sets TabloID=tablo.ID.String(), TabloName=tablo.Name, Color=tablo.Color, Initial=projectInitial(tablo.Name)
        - Sets OwnerName=ownerName
        - Calls tabloStatusPresentation(tablo.Status) for StatusLabel, _, _, StatusTone (ignores the static progress int from tabloStatusPresentation — computes Progress via computeTabloProgress instead)
        - Sets Progress=computeTabloProgress(tasks), ProgressLabel=fmt.Sprintf("%d%%", progress)
        - Builds Columns slice of 4 TabloDetailColumnView in order: {ID:"todo", Label:"À faire"}, {ID:"in_progress", Label:"En cours"}, {ID:"in_review", Label:"En révision"}, {ID:"done", Label:"Terminé"}
-       - Populates each column's Tasks by filtering the tasks slice by Status; for each task: DeleteHref="/tasks/"+task.ID.String(), EditHref="/tasks/"+task.ID.String()+"/edit"
+       - Populates each column's Tasks by filtering non-etape tasks (IsEtape==false) by Status; for each task: DeleteHref="/tasks/"+task.ID.String(), EditHref="/tasks/"+task.ID.String()+"/edit"
        - Sets CreateHref="/tablos/"+tablo.ID.String()+"/tasks/create?status="+colID for each column
+       - Builds Etapes slice: for each task where IsEtape==true, create TabloDetailEtapeView{ID: task.ID.String(), Name: task.Title, TaskCount: count of tasks where IsEtape==false && ParentTaskID==&task.ID}
        - DueDate: tablo.UpdatedAt is not a due date — set DueDate="" (no due_date field on tablo model yet; template shows "—" fallback)
 
-    Create go-backend/internal/web/handlers/tablo_detail_test.go in package handlers. Import testing, net/http, net/http/httptest, strings, context, github.com/google/uuid, and xtablo-backend/internal/web/views. Use newTestRouter() from router_test.go test setup pattern: create a helper that builds an InMemoryAuthRepository, seeds a user, tablo, and tasks, and sets a session cookie. Test all 5 behaviors listed above with require/assert stdlib patterns (t.Fatal on unexpected).
+    Create go-backend/internal/web/views/tablo_detail_view_test.go in package views for view model unit tests. Test all behaviors marked Test: TestComputeTabloProgress_* and TestNewTabloDetailViewModel_*.
 
-    NOTE: computeTabloProgress and NewTabloDetailViewModel are in the views package; the test file for them should be go-backend/internal/web/views/tablo_detail_view_test.go (not in handlers). Create a second test file go-backend/internal/web/views/tablo_detail_view_test.go in package views for the view model unit tests (TestComputeTabloProgress_*, TestNewTabloDetailViewModel_Groups). The handler tests go in go-backend/internal/web/handlers/tablo_detail_test.go in package handlers.
+    Create go-backend/internal/web/handlers/tablo_detail_test.go in package handlers for handler integration tests. Use the router/test helper pattern from existing handlers tests. Test all behaviors marked Test: TestGetTabloDetailPage_* and TestTabloDetailKanbanColumns and TestGetTabloDetailPage_ContainsSortableScript.
+
+    NOTE: The TestGetTabloDetailPage_ContainsSortableScript test checks that the response body from GET /tablos/{id} contains the string "initTabloDetailSortable". This is the verifiable proxy for Sortable.js initialization — `go build` cannot verify runtime JS behavior, but it CAN verify the script tag is present in the rendered HTML.
   </action>
   <verify>
     <automated>cd /Users/arthur.belleville/Documents/perso/projects/xtablo-source/go-backend && go test ./internal/web/views/... -run "TestCompute|TestNewTabloDetail" -count=1 -v 2>&1 | tail -20</automated>
   </verify>
-  <done>go test ./internal/web/views/... -run "TestCompute|TestNewTabloDetail" passes; all 4 view-layer tests are green; tablo_detail_view.go compiles with TabloDetailViewModel exported.</done>
+  <done>go test ./internal/web/views/... -run "TestCompute|TestNewTabloDetail" passes; all view-layer tests are green; tablo_detail_view.go compiles with TabloDetailViewModel, TabloDetailEtapeView exported; etapes filtering logic verified by TestNewTabloDetailViewModel_EtapesPopulated.</done>
 </task>
 
 <task type="auto" tdd="true">
@@ -245,11 +262,11 @@ views.DashboardPageWithMainClass(activePath, tablos, "flex-1 overflow-auto", con
     IMPORTANT: views.TabloDetailPage does not exist yet. Add a temporary stub in go-backend/internal/web/views/tablo_detail_view.go:
       func TabloDetailPage(vm TabloDetailViewModel) templ.Component {
           return templ.ComponentFunc(func(ctx context.Context, w io.Writer) error {
-              _, err := fmt.Fprintf(w, "<div>%s</div>", vm.TabloName)
+              _, err := fmt.Fprintf(w, "<div>%s<script>function initTabloDetailSortable(){}</script></div>", vm.TabloName)
               return err
           })
       }
-    This stub will be replaced in Plan 02 with the real templ component. Import "context", "fmt", "io", "github.com/a-h/templ" for the stub.
+    The stub emits the tablo name AND the initTabloDetailSortable function name so that TestGetTabloDetailPage_ContainsSortableScript passes. This stub will be replaced in Plan 02 with the real templ component. Import "context", "fmt", "io", "github.com/a-h/templ" for the stub.
 
     Update go-backend/router.go: add mux.Get("/tablos/{tabloID}", authHandler.GetTabloDetailPage()) immediately before the existing mux.Get("/tablos/{tabloID}/edit", ...) line.
 
@@ -258,7 +275,7 @@ views.DashboardPageWithMainClass(activePath, tablos, "flex-1 overflow-auto", con
   <verify>
     <automated>cd /Users/arthur.belleville/Documents/perso/projects/xtablo-source/go-backend && go test ./... -run "TestGetTabloDetailPage" -count=1 -v 2>&1 | tail -30</automated>
   </verify>
-  <done>All TestGetTabloDetailPage_* tests pass; go build ./... succeeds; GET /tablos/{validID} integration test returns 200 with tablo name in body.</done>
+  <done>All TestGetTabloDetailPage_* tests pass including TestGetTabloDetailPage_ContainsSortableScript; go build ./... succeeds; GET /tablos/{validID} integration test returns 200 with tablo name in body.</done>
 </task>
 
 </tasks>
@@ -284,11 +301,12 @@ views.DashboardPageWithMainClass(activePath, tablos, "flex-1 overflow-auto", con
 After Plan 01:
 - `cd go-backend && go build ./...` exits 0
 - `go test ./internal/web/views/... -run "TestCompute|TestNewTabloDetail" -count=1` all pass
-- `go test ./... -run "TestGetTabloDetailPage" -count=1` all pass
+- `go test ./... -run "TestGetTabloDetailPage" -count=1` all pass including TestGetTabloDetailPage_ContainsSortableScript
 - `go test ./... -count=1` full suite still green (no regressions)
 - router.go contains `mux.Get("/tablos/{tabloID}", authHandler.GetTabloDetailPage())`
 - tablo_detail.go defines tabloDetailRepository interface and GetTabloDetailPage method
-- tablo_detail_view.go exports TabloDetailViewModel, TabloDetailColumnView, NewTabloDetailViewModel
+- tablo_detail_view.go exports TabloDetailViewModel, TabloDetailColumnView, TabloDetailEtapeView, NewTabloDetailViewModel
+- TabloDetailViewModel.Etapes is populated from tasks where IsEtape==true
 </verification>
 
 <success_criteria>
@@ -296,7 +314,9 @@ After Plan 01:
 - GET /tablos/{validUUID} (authenticated, not owned) returns 404
 - GET /tablos/not-a-uuid returns 400
 - GET /tablos/{validUUID} (unauthenticated) returns 302 to /login
-- Progress computed from task statuses, not tablo.Status field
+- Progress computed from non-etape task statuses, not tablo.Status field
+- Etapes slice populated with etape tasks and their child task counts
+- Response body contains "initTabloDetailSortable" (verifiable via go test)
 - Full test suite (`go test ./... -count=1`) remains green
 </success_criteria>
 
diff --git a/.planning/phases/20-tablo-detail-kanban-restyle/20-02-PLAN.md b/.planning/phases/20-tablo-detail-kanban-restyle/20-02-PLAN.md
index 33871e4..8c45e72 100644
--- a/.planning/phases/20-tablo-detail-kanban-restyle/20-02-PLAN.md
+++ b/.planning/phases/20-tablo-detail-kanban-restyle/20-02-PLAN.md
@@ -8,6 +8,7 @@ depends_on:
 files_modified:
   - go-backend/internal/web/views/tablo_detail.templ
   - go-backend/internal/web/views/tablo_detail_view.go
+  - go-backend/internal/web/handlers/tablo_detail_tab.go
 autonomous: true
 requirements:
   - DETAIL-01
@@ -17,19 +18,25 @@ must_haves:
   truths:
     - "Tablo detail page renders a header with tablo name as h1 (font-size 1.75rem) and a metadata row"
     - "Tab bar renders Overview, Tasks, Files, Discussion, Events tabs; Tasks tab is active with class tab-nav-item--active"
+    - "Tab links use hx-get and hx-push-url=true targeting #tab-content — not plain href anchors"
     - "Kanban board renders exactly 4 columns in a .tablo-kanban-board flex container"
     - "Each column uses class tablo-kanban-column with data-status attribute set to the column ID"
+    - "Each column contains a hidden reorder form with id reorder-form-{status} for Sortable.js onEnd"
     - "Each task card uses class task-card and carries data-task-id"
     - "Drag handle element uses class task-drag-handle and is a child of .task-card"
     - "Empty column renders a .tablo-kanban-empty element with text 'Aucune tâche'"
-    - "Sortable.js init fires on DOMContentLoaded and htmx:afterSettle; task list containers use class sortable-column"
+    - "Rendered HTML from GET /tablos/{id} contains substring `initTabloDetailSortable`"
+    - "Etapes section renders below the kanban board listing each etape name and its task count"
   artifacts:
     - path: "go-backend/internal/web/views/tablo_detail.templ"
-      provides: "TabloDetailPage + all sub-components (header, tab bar, kanban board, task card)"
+      provides: "TabloDetailPage + all sub-components (header, tab bar, kanban board, task card, etapes section)"
       exports: ["TabloDetailPage"]
     - path: "go-backend/internal/web/views/tablo_detail_view.go"
       provides: "TabloDetailPage real templ component replaces stub from Plan 01"
       contains: "func TabloDetailPage"
+    - path: "go-backend/internal/web/handlers/tablo_detail_tab.go"
+      provides: "GET /tablos/{tabloID}/{tab} handler for tab content swaps"
+      exports: ["GetTabloDetailTab"]
   key_links:
     - from: "go-backend/internal/web/views/tablo_detail.templ"
       to: "go-backend/internal/web/views/tablo_detail_view.go"
@@ -37,16 +44,20 @@ must_haves:
       pattern: "TabloDetailViewModel"
     - from: ".tablo-kanban-board .sortable-column"
       to: "POST /tablos/{id}/tasks/reorder"
-      via: "Sortable.js onEnd -> #reorder-form submit"
-      pattern: "sortable-column"
+      via: "Sortable.js onEnd -> #reorder-form-{status} submit"
+      pattern: "reorder-form-"
+    - from: ".tablo-tab-bar a[hx-get]"
+      to: "GET /tablos/{tabloID}/{tab}"
+      via: "HTMX hx-get + hx-push-url=true"
+      pattern: "hx-get"
 ---
 
 <objective>
-Build the tablo_detail.templ components that render the tablo detail page: header section, tab bar, kanban board with 4 columns, task cards, empty state, and Sortable.js initialization script. Replace the stub TabloDetailPage function in tablo_detail_view.go with the real templ component.
+Build the tablo_detail.templ components that render the tablo detail page: header section, HTMX tab bar, kanban board with 4 columns (each with a hidden reorder form), task cards, empty state, etapes section, and Sortable.js initialization script. Replace the stub TabloDetailPage function in tablo_detail_view.go with the real templ component. Add a minimal tab handler for the tasks tab.
 
 Purpose: This plan produces the full HTML surface for DETAIL-01 and TASK-01. All CSS class names used here are defined in Plan 03's CSS work, so the visual output is unstyled at first but structurally correct.
 
-Output: tablo_detail.templ with all sub-components; tablo_detail_view.go stub removed and replaced by templ-generated component.
+Output: tablo_detail.templ with all sub-components; tablo_detail_view.go stub removed and replaced by templ-generated component; tablo_detail_tab.go with GetTabloDetailTab handler.
 </objective>
 
 <execution_context>
@@ -78,6 +89,12 @@ type TabloDetailColumnView struct {
     CreateHref string  // "/tablos/{id}/tasks/create?status={colID}"
 }
 
+type TabloDetailEtapeView struct {
+    ID        string
+    Name      string
+    TaskCount int
+}
+
 type TabloDetailViewModel struct {
     TabloID       string
     TabloName     string
@@ -90,6 +107,7 @@ type TabloDetailViewModel struct {
     Progress      int     // 0-100
     ProgressLabel string  // "{N}%"
     Columns       []TabloDetailColumnView  // always 4 columns
+    Etapes        []TabloDetailEtapeView   // may be empty
 }
 ```
 
@@ -117,10 +135,12 @@ From go-backend/internal/web/views/tasks.templ (for drag-and-drop reorder patter
 ```
 // Sortable.js init fires on DOMContentLoaded AND htmx:afterSettle
 // Uses: .sortable-column class on task list containers
-// Uses: data-status attribute on column containers  
+// Uses: data-status attribute on column containers
 // Uses: .task-drag-handle handle class
 // Uses: .task-card draggable class
-// Reorder form: #reorder-form (hidden form that submits task order to POST /tablos/{id}/tasks/reorder)
+// Reorder form: hidden form that submits task order to POST /tablos/{id}/tasks/reorder
+//   IMPORTANT: form id must be "reorder-form-{status}" — Sortable.js onEnd looks up
+//   getElementById('reorder-form-' + el.dataset.status)
 // Guard: if (el._sortable) return; prevents double-init after HTMX swap (Pitfall 4)
 ```
 
@@ -151,6 +171,8 @@ CSS class contract (defined in Plan 03, used here):
 .task-card-title            — task title text
 .task-card-delete           — delete icon button (opacity 0 at rest)
 .tablo-kanban-empty         — empty column message
+.tablo-etapes-section       — etapes section below kanban board
+.tablo-etape-row            — each etape row (name + task count)
 ```
 </interfaces>
 </context>
@@ -158,19 +180,20 @@ CSS class contract (defined in Plan 03, used here):
 <tasks>
 
 <task type="auto">
-  <name>Task 1: TabloDetailPage templ component — header, tab bar, kanban board</name>
-  <files>go-backend/internal/web/views/tablo_detail.templ</files>
+  <name>Task 1: TabloDetailPage templ component — header, HTMX tab bar, kanban board, etapes section</name>
+  <files>go-backend/internal/web/views/tablo_detail.templ, go-backend/internal/web/handlers/tablo_detail_tab.go</files>
   <read_first>
     - go-backend/internal/web/views/tablo_detail_view.go (TabloDetailViewModel fields — just created in Plan 01)
     - go-backend/internal/web/views/tablos.templ (TabloGridCard pattern, ActionIcon usage, badgeVariantForTone function name)
-    - go-backend/internal/web/views/tasks.templ (TasksKanbanLayout — for contrast; tablo-detail kanban is SEPARATE and must NOT reuse TasksKanbanLayout)
+    - go-backend/internal/web/views/tasks.templ (TasksKanbanLayout — for contrast; tablo-detail kanban is SEPARATE and must NOT reuse TasksKanbanLayout; also read the Sortable.js init script and reorder form pattern)
     - go-backend/internal/web/ui/badge.templ (BadgeProps fields)
     - go-backend/internal/web/ui/icon_button.templ (IconButtonProps fields)
     - go-backend/internal/web/ui/app.css lines 882-900 (existing .tab-nav, .tab-nav-item classes)
     - go-backend/internal/web/views/discussion_view.go (for badgeVariantForTone function — confirm it's in views package)
+    - go-backend/internal/web/handlers/tablos.go (renderTablosResponse pattern — for how DashboardContentSwapWithMainClass is called, to replicate in tab handler)
   </read_first>
   <action>
-    Create go-backend/internal/web/views/tablo_detail.templ in package views. Import "xtablo-backend/internal/web/ui".
+    Create go-backend/internal/web/views/tablo_detail.templ in package views. Import "xtablo-backend/internal/web/ui" and "strconv".
 
     Define the following templ components in this order:
 
@@ -178,7 +201,9 @@ CSS class contract (defined in Plan 03, used here):
        - Outer div class="tablo-detail-page"
        - @TabloDetailHeader(vm)
        - @TabloDetailTabBar(vm.TabloID)
-       - div class="tablo-kanban-board" containing: @TabloDetailKanbanBoard(vm.Columns, vm.TabloID)
+       - div id="tab-content":
+         * @TabloDetailKanbanBoard(vm.Columns, vm.TabloID)
+         * if len(vm.Etapes) > 0: @TabloDetailEtapesSection(vm.Etapes)
        - @TabloDetailSortableScript(vm.TabloID)
 
     2. TabloDetailHeader(vm TabloDetailViewModel) — header section:
@@ -194,15 +219,21 @@ CSS class contract (defined in Plan 03, used here):
            - div class="project-progress-track" style="min-width:120px" with inner div class="tablo-progress-bar" style={ "width:" + vm.ProgressLabel }
            - strong { vm.ProgressLabel }
 
-    3. TabloDetailTabBar(tabloID string) — tab navigation:
+    3. TabloDetailTabBar(tabloID string) — HTMX tab navigation:
        - nav element class="tablo-tab-bar"
        - 5 anchor elements for: "Vue d'ensemble", "Tâches", "Fichiers", "Discussion", "Événements"
-       - Tab IDs/slugs: "overview", "tasks", "files", "discussion", "events"
-       - Each anchor: class="tab-nav-item" with href={ "/tablos/" + tabloID + "#" + slug }
+       - Tab slugs: "overview", "tasks", "files", "discussion", "events"
+       - Each anchor MUST use HTMX attributes (per UI-SPEC locked interaction contract):
+           hx-get="/tablos/{tabloID}/{slug}"
+           hx-target="#tab-content"
+           hx-push-url="true"
+           class="tab-nav-item"
        - "Tâches" tab (tasks slug): class="tab-nav-item tab-nav-item--active" (Phase 20 always shows tasks tab active)
-       - No hx-get on tabs in Phase 20 — tab switching is Phase 21 scope; use plain href anchors
+       - Do NOT use plain href="#slug" anchors — the UI-SPEC requires HTMX push-url navigation for all tabs.
+       - Use templ.SafeURL for the hx-get value to satisfy templ's URL safety requirements.
 
-    4. TabloDetailKanbanBoard(columns []TabloDetailColumnView, tabloID string) — kanban board:
+    4. TabloDetailKanbanBoard(columns []TabloDetailColumnView, tabloID string) — renders the kanban board:
+       - Outer div class="tablo-kanban-board"
        - For each column: @TabloDetailKanbanColumn(col, tabloID)
 
     5. TabloDetailKanbanColumn(col TabloDetailColumnView, tabloID string) — single column:
@@ -210,10 +241,18 @@ CSS class contract (defined in Plan 03, used here):
        - div class="tablo-kanban-column-header":
          * span class="tablo-kanban-column-title" containing { col.Label }
          * span class="tablo-kanban-task-count" containing { strconv.Itoa(len(col.Tasks)) }
-         * a class="tablo-kanban-add-link" href={ col.CreateHref } containing "+ Ajouter"
+         * a class="tablo-kanban-add-link" href={ templ.SafeURL(col.CreateHref) } containing "+ Ajouter"
        - div id={ "task-list-" + col.ID } class="task-list sortable-column" data-status={ col.ID }:
          * if len(col.Tasks) == 0: div class="tablo-kanban-empty" { "Aucune tâche" }
          * else: for _, task := range col.Tasks { @TabloDetailTaskCard(task, tabloID) }
+       - Hidden reorder form (REQUIRED for Sortable.js onEnd):
+           <form id={ "reorder-form-" + col.ID }
+                 style="display:none"
+                 hx-post={ "/tablos/" + tabloID + "/tasks/reorder?status=" + col.ID }
+                 hx-target={ "#task-list-" + col.ID }
+                 hx-swap="innerHTML">
+             <!-- Sortable.js onEnd will populate this form's inputs before calling requestSubmit() -->
+           </form>
        - div id={ "create-zone-" + col.ID } (empty create zone for HTMX task create swap)
 
     6. TabloDetailTaskCard(task TabloDetailTaskView, tabloID string) — task card:
@@ -234,15 +273,33 @@ CSS class contract (defined in Plan 03, used here):
              },
            })
 
-    7. TabloDetailSortableScript(tabloID string) — JavaScript block:
-       Use a templ @raw block (or templ.Raw) to emit the Sortable.js init script that:
+    7. TabloDetailEtapesSection(etapes []TabloDetailEtapeView) — etapes list below kanban:
+       - section element class="tablo-etapes-section"
+       - h2 or h3 heading: "Étapes" (French)
+       - ul element: for each etape, render a li class="tablo-etape-row" containing:
+           span class="tablo-etape-name" { etape.Name }
+           span class="tablo-etape-count" { strconv.Itoa(etape.TaskCount) + " tâche(s)" }
+
+    8. TabloDetailSortableScript(tabloID string) — JavaScript block:
+       Use templ.Raw to emit the Sortable.js init script that:
        - Defines function initTabloDetailSortable()
-       - Calls document.querySelectorAll('.sortable-column').forEach(function(el) { if (el._sortable) return; el._sortable = Sortable.create(el, { group: 'tablo-tasks', animation: 150, handle: '.task-drag-handle', draggable: '.task-card', onEnd: function(evt) { /* submit hidden reorder form */ var form = document.getElementById('reorder-form-' + el.dataset.status); if (form) form.requestSubmit(); } }); })
+       - Calls document.querySelectorAll('.sortable-column').forEach(function(el) { if (el._sortable) return; el._sortable = Sortable.create(el, { group: 'tablo-tasks', animation: 150, handle: '.task-drag-handle', draggable: '.task-card', onEnd: function(evt) { var form = document.getElementById('reorder-form-' + el.dataset.status); if (form) form.requestSubmit(); } }); })
        - Calls document.addEventListener('DOMContentLoaded', initTabloDetailSortable)
        - Calls document.addEventListener('htmx:afterSettle', initTabloDetailSortable)
        Wrap in <script> tag.
 
+    Create go-backend/internal/web/handlers/tablo_detail_tab.go in package handlers. This handles GET /tablos/{tabloID}/{tab} for HTMX tab swaps:
+    - Define GetTabloDetailTab() http.HandlerFunc on *AuthHandler
+    - Auth check; redirect /login on failure
+    - Parse tabloID from path; 400 on invalid UUID
+    - Parse tab slug from path (chi: r.PathValue("tab"))
+    - For tab == "tasks": fetch tablo + tasks, build TabloDetailViewModel, return views.TabloDetailKanbanBoard(vm.Columns, tabloID.String()) rendered as HTMX partial (no dashboard layout wrapper — just the fragment)
+    - For other tabs ("overview", "files", "discussion", "events"): return a simple HTML fragment: `<div class="tab-coming-soon">Cette section arrive bientôt.</div>`
+    - Register route in router.go: mux.Get("/tablos/{tabloID}/{tab}", authHandler.GetTabloDetailTab()) — add immediately after the mux.Get("/tablos/{tabloID}", ...) line
+
     CRITICAL rules:
+    - Tab links MUST use hx-get + hx-target="#tab-content" + hx-push-url="true" — plain href="#slug" anchors are FORBIDDEN per the UI-SPEC interaction contract
+    - Each kanban column MUST contain a hidden form with id="reorder-form-{col.ID}" — Sortable.js onEnd calls getElementById('reorder-form-' + el.dataset.status)
     - Do NOT import or call TasksKanbanLayout — tablo-detail kanban is a separate surface (RESEARCH Anti-Patterns)
     - Do NOT add a task view switcher (Board/List/Gantt) — UI-SPEC says this is Phase 21
     - All strings in French per UI-SPEC Copywriting Contract
@@ -253,17 +310,18 @@ CSS class contract (defined in Plan 03, used here):
   <verify>
     <automated>cd /Users/arthur.belleville/Documents/perso/projects/xtablo-source/go-backend && just generate 2>&1 | tail -5 && go build ./... 2>&1</automated>
   </verify>
-  <done>just generate succeeds (tablo_detail_templ.go generated); go build ./... exits 0; tablo_detail.templ defines TabloDetailPage, TabloDetailHeader, TabloDetailTabBar, TabloDetailKanbanBoard, TabloDetailKanbanColumn, TabloDetailTaskCard, TabloDetailSortableScript.</done>
+  <done>just generate succeeds (tablo_detail_templ.go generated); go build ./... exits 0; tablo_detail.templ defines TabloDetailPage, TabloDetailHeader, TabloDetailTabBar, TabloDetailKanbanBoard, TabloDetailKanbanColumn, TabloDetailTaskCard, TabloDetailEtapesSection, TabloDetailSortableScript; each column contains a hidden reorder form; tab links use hx-get.</done>
 </task>
 
 <task type="auto">
   <name>Task 2: Replace TabloDetailPage stub + wire templ component + run handler tests</name>
-  <files>go-backend/internal/web/views/tablo_detail_view.go</files>
+  <files>go-backend/internal/web/views/tablo_detail_view.go, go-backend/router.go</files>
   <read_first>
     - go-backend/internal/web/views/tablo_detail_view.go (current stub — remove the ComponentFunc stub)
     - go-backend/internal/web/views/tablo_detail.templ (just created — TabloDetailPage is now a real templ component)
     - go-backend/internal/web/views/tablo_detail_templ.go (generated by just generate — confirm TabloDetailPage signature)
-    - go-backend/internal/web/handlers/tablo_detail_test.go (handler tests that verify 200 + tablo name in body)
+    - go-backend/internal/web/handlers/tablo_detail_test.go (handler tests that verify 200 + tablo name in body + "initTabloDetailSortable" in body)
+    - go-backend/router.go (add GET /tablos/{tabloID}/{tab} route for GetTabloDetailTab)
   </read_first>
   <action>
     Edit go-backend/internal/web/views/tablo_detail_view.go:
@@ -273,14 +331,18 @@ CSS class contract (defined in Plan 03, used here):
 
     After removing the stub, the real TabloDetailPage comes from tablo_detail_templ.go (generated by just generate). Verify with go build.
 
+    Edit go-backend/router.go:
+    - Add mux.Get("/tablos/{tabloID}/{tab}", authHandler.GetTabloDetailTab()) immediately after the mux.Get("/tablos/{tabloID}", ...) line added in Plan 01
+
     Then run the full handler tests to confirm the integration is correct:
     - TestGetTabloDetailPage_Returns200 should now render real HTML with the tablo name inside the TabloDetailHeader h1
-    - Update the test assertion if needed: the response body should contain the tablo name string
+    - TestGetTabloDetailPage_ContainsSortableScript should find "initTabloDetailSortable" in the rendered HTML (now from the real templ component's script block)
+    - Update any test assertions if needed: the response body should contain the tablo name string
   </action>
   <verify>
     <automated>cd /Users/arthur.belleville/Documents/perso/projects/xtablo-source/go-backend && go test ./... -run "TestGetTabloDetailPage|TestComputeTabloProgress|TestNewTabloDetail|TestTabloDetail" -count=1 -v 2>&1 | tail -30</automated>
   </verify>
-  <done>All TestGetTabloDetailPage_* and view model tests pass; go build ./... exits 0; no stub function remains in tablo_detail_view.go; generated tablo_detail_templ.go exports TabloDetailPage(TabloDetailViewModel) templ.Component.</done>
+  <done>All TestGetTabloDetailPage_* and view model tests pass; go build ./... exits 0; no stub function remains in tablo_detail_view.go; generated tablo_detail_templ.go exports TabloDetailPage(TabloDetailViewModel) templ.Component; router.go contains both /tablos/{tabloID} and /tablos/{tabloID}/{tab} routes.</done>
 </task>
 
 </tasks>
@@ -291,6 +353,7 @@ CSS class contract (defined in Plan 03, used here):
 | Boundary | Description |
 |----------|-------------|
 | Template rendering | TabloDetailViewModel data flows from handler into templ — ensure no raw HTML injection |
+| Tab slug routing | {tab} path value used to select partial response — must not allow arbitrary content injection |
 
 ## STRIDE Threat Register
 
@@ -298,6 +361,7 @@ CSS class contract (defined in Plan 03, used here):
 |-----------|----------|-----------|-------------|-----------------|
 | T-20-04 | Tampering | TabloDetailTaskCard — task.Title rendered in HTML | mitigate | templ auto-escapes all { expr } interpolations — no raw HTML emission for user data |
 | T-20-05 | Tampering | Sortable.js onEnd — data-status attribute used in form ID | mitigate | data-status comes from hardcoded column IDs ("todo", "in_progress", "in_review", "done") — not user input |
+| T-20-07 | Tampering | GetTabloDetailTab — {tab} slug used in switch, not reflected into HTML | mitigate | Tab slug used only as switch key; "coming soon" text is hardcoded; tab slug never interpolated into HTML |
 | T-20-SC | Tampering | npm/pip/cargo installs | accept | No package installs — pure templ + CSS |
 </threat_model>
 
@@ -307,17 +371,22 @@ After Plan 02:
 - `go build ./...` exits 0
 - `go test ./... -run "TestGetTabloDetailPage|TestComputeTabloProgress|TestNewTabloDetail|TestTabloDetail" -count=1` all pass
 - `go test ./... -count=1` full suite green
-- tablo_detail.templ defines 7 templ components including TabloDetailPage and TabloDetailTaskCard
+- tablo_detail.templ defines 8 templ components including TabloDetailPage, TabloDetailTaskCard, TabloDetailEtapesSection
 - Task cards use class="task-card" and data-task-id attribute
 - Task list containers use class="task-list sortable-column"
 - Drag handle uses class="task-drag-handle"
 - Empty column uses class="tablo-kanban-empty" with text "Aucune tâche"
+- Each column has a hidden form with id="reorder-form-{status}"
+- Tab links use hx-get + hx-target="#tab-content" + hx-push-url="true"
+- Etapes section renders below kanban board when vm.Etapes is non-empty
 </verification>
 
 <success_criteria>
-- GET /tablos/{validID} (authenticated) returns 200 with h1 containing tablo name, .tablo-kanban-board div, and 4 .tablo-kanban-column elements in the response body
+- GET /tablos/{validID} (authenticated) returns 200 with h1 containing tablo name, .tablo-kanban-board div, 4 .tablo-kanban-column elements, hidden reorder forms, and etapes section in the response body
 - Full test suite green
 - Sortable.js init script present in rendered HTML with DOMContentLoaded and htmx:afterSettle listeners
+- Tab links use hx-get targeting #tab-content (not plain href anchors)
+- Hidden reorder forms present per column: id="reorder-form-todo", id="reorder-form-in_progress", etc.
 - No TasksKanbanLayout referenced in tablo_detail.templ
 </success_criteria>
 
diff --git a/.planning/phases/20-tablo-detail-kanban-restyle/20-03-PLAN.md b/.planning/phases/20-tablo-detail-kanban-restyle/20-03-PLAN.md
index 121d8c2..8d956b4 100644
--- a/.planning/phases/20-tablo-detail-kanban-restyle/20-03-PLAN.md
+++ b/.planning/phases/20-tablo-detail-kanban-restyle/20-03-PLAN.md
@@ -25,9 +25,10 @@ must_haves:
     - "app.css contains a .tablo-progress-bar rule with background var(--color-brand-primary) — NOT var(--project-color)"
     - "app.css contains a .tablo-files-table-wrapper rule with border-radius 12px"
     - "app.css .task-list rule is updated to include gap 8px and padding 8px"
+    - "app.css contains a .tablo-etapes-section rule and a .tablo-etape-row rule"
   artifacts:
     - path: "go-backend/internal/web/ui/app.css"
-      provides: "All tablo detail + kanban restyle CSS rules"
+      provides: "All tablo detail + kanban restyle + etapes section CSS rules"
       contains: ".tablo-detail-header"
   key_links:
     - from: "go-backend/internal/web/views/tablo_detail.templ"
@@ -37,7 +38,7 @@ must_haves:
 ---
 
 <objective>
-Apply all CSS changes from the UI-SPEC to app.css: new tablo detail header styles, kanban board layout, task card restyle (column-flex, hover shadow, opacity-based drag handle), progress bar fill fix, files table wrapper, and updated task-list gap. This plan runs in parallel with Plan 02 since CSS class names are already locked in the UI-SPEC.
+Apply all CSS changes from the UI-SPEC to app.css: new tablo detail header styles, kanban board layout, task card restyle (column-flex, hover shadow, opacity-based drag handle), progress bar fill fix, files table wrapper, etapes section, and updated task-list gap. This plan runs in parallel with Plan 02 since CSS class names are already locked in the UI-SPEC.
 
 Purpose: Without these CSS rules, the templ components from Plan 02 render unstyled. This plan is the visual half of the restyle.
 
@@ -151,7 +152,7 @@ Output: Updated app.css with all new and modified CSS blocks from UI-SPEC.
 </task>
 
 <task type="auto">
-  <name>Task 2: Kanban board, task card, files table, and task-list gap CSS</name>
+  <name>Task 2: Kanban board, task card, etapes section, files table, and task-list gap CSS</name>
   <files>go-backend/internal/web/ui/app.css</files>
   <read_first>
     - go-backend/internal/web/ui/app.css (read lines 1283-1350 — existing .task-list, .task-row, .task-body, .task-check rules; understand what to modify vs what to add)
@@ -277,39 +278,79 @@ Output: Updated app.css with all new and modified CSS blocks from UI-SPEC.
       }
     This change affects both the global tasks page and the tablo detail page equally — gap between cards is desired everywhere.
 
+    Add etapes section CSS:
+
+    BLOCK 27: .tablo-etapes-section — etapes list below kanban board
+      border-top: 1px solid var(--color-border-muted);
+      margin-top: 24px;
+      padding-top: 24px;
+
+    BLOCK 28: .tablo-etapes-section h2, .tablo-etapes-section h3 — section heading
+      color: var(--color-text-primary);
+      font-size: 1rem;
+      font-weight: 600;
+      margin: 0 0 12px 0;
+
+    BLOCK 29: .tablo-etapes-section ul — list reset
+      list-style: none;
+      margin: 0;
+      padding: 0;
+      display: flex;
+      flex-direction: column;
+      gap: 8px;
+
+    BLOCK 30: .tablo-etape-row — each etape row
+      align-items: center;
+      background: var(--color-surface-default);
+      border: 1px solid var(--color-border-default);
+      border-radius: 8px;
+      display: flex;
+      gap: 12px;
+      justify-content: space-between;
+      padding: 10px 16px;
+
+    BLOCK 31: .tablo-etape-name — etape stage name
+      color: var(--color-text-primary);
+      font-size: 0.875rem;
+      font-weight: 500;
+
+    BLOCK 32: .tablo-etape-count — task count label
+      color: var(--color-text-secondary);
+      font-size: 0.75rem;
+
     Add files table wrapper CSS:
 
-    BLOCK 27: .tablo-files-table-wrapper — wrapper for the files table
+    BLOCK 33: .tablo-files-table-wrapper — wrapper for the files table
       border: 1px solid var(--color-border-default);
       border-radius: 12px;
       overflow: hidden;
 
-    BLOCK 28: .tablo-files-table-wrapper thead tr
+    BLOCK 34: .tablo-files-table-wrapper thead tr
       background: var(--color-surface-muted);
 
-    BLOCK 29: .tablo-files-table-wrapper thead th
+    BLOCK 35: .tablo-files-table-wrapper thead th
       color: var(--color-text-muted);
       font-size: 0.75rem;
       font-weight: 600;
       letter-spacing: 0.04em;
       text-transform: uppercase;
 
-    BLOCK 30: .tablo-files-table-wrapper tbody tr
+    BLOCK 36: .tablo-files-table-wrapper tbody tr
       border-bottom: 1px solid var(--color-border-default);
 
-    BLOCK 31: .tablo-files-table-wrapper tbody tr:hover
+    BLOCK 37: .tablo-files-table-wrapper tbody tr:hover
       background: var(--color-surface-subtle);
 
     CRITICAL checks before saving:
-    - .tablo-progress-bar uses "background: var(--color-brand-primary)" — grep to verify
+    - .tablo-progress-bar uses "background: var(--color-brand-primary)" — verify with grep after writing
     - .task-card and .task-row are SEPARATE rules — .task-row must NOT be removed (it is used by the global tasks page)
     - .tasks-section border-radius (1rem) must NOT be changed — only .tablo-kanban-column gets 0.75rem
     - All opacity transitions use "0.12s ease" consistent with design system
   </action>
   <verify>
-    <automated>grep -v "^[[:space:]]*//" /Users/arthur.belleville/Documents/perso/projects/xtablo-source/go-backend/internal/web/ui/app.css | grep -c "tablo-kanban-board\|tablo-kanban-column\|task-card\b\|task-drag-handle\|tablo-files-table-wrapper\|tablo-kanban-empty"</automated>
+    <automated>grep "background: var(--color-brand-primary)" /Users/arthur.belleville/Documents/perso/projects/xtablo-source/go-backend/internal/web/ui/app.css</automated>
   </verify>
-  <done>grep count returns 6 or more; .task-card block exists with flex-direction: column; .task-drag-handle exists with opacity: 0; .task-card:hover .task-drag-handle exists with opacity: 1; .tablo-kanban-board exists with overflow-x: auto; .task-list updated to include gap: 8px; .task-row unchanged.</done>
+  <done>grep returns at least one line containing "background: var(--color-brand-primary)" (the .tablo-progress-bar rule); .task-card block exists with flex-direction: column; .task-drag-handle exists with opacity: 0; .task-card:hover .task-drag-handle exists with opacity: 1; .tablo-kanban-board exists with overflow-x: auto; .task-list updated to include gap: 8px; .task-row unchanged; .tablo-etapes-section and .tablo-etape-row rules present.</done>
 </task>
 
 </tasks>
@@ -332,14 +373,16 @@ Output: Updated app.css with all new and modified CSS blocks from UI-SPEC.
 <verification>
 After Plan 03:
 - grep for "tablo-kanban-board" in app.css returns at least one match with "overflow-x: auto"
-- grep for "tablo-progress-bar" in app.css returns a match with "background: var(--color-brand-primary)"
+- grep for ".tablo-progress-bar" in app.css returns a match with "background: var(--color-brand-primary)"
 - grep for "tablo-progress-bar" does NOT return "var(--project-color)"
-- grep for ".task-card\b" in app.css returns the column-flex card rule
+- grep for ".task-card" in app.css returns the column-flex card rule (flex-direction: column)
 - grep for ".task-drag-handle" returns opacity: 0 rule
 - grep for ".task-card:hover .task-drag-handle" returns opacity: 1 rule
 - grep for ".task-row" still returns the original horizontal rule (not removed)
 - grep for ".tasks-section" still has border-radius: 1rem (not changed to 0.75rem)
 - grep for ".task-list" returns updated rule with gap: 8px
+- grep for ".tablo-etapes-section" returns a CSS rule
+- grep for ".tablo-etape-row" returns a CSS rule
 - go build ./... still exits 0 (CSS is static — no compilation risk, but verify Go still compiles cleanly)
 </verification>
 
@@ -350,6 +393,7 @@ After Plan 03:
 - Visual: drag handle appears on card hover (opacity transition, not display toggle)
 - Visual: delete icon appears on card hover
 - Visual: empty columns show "Aucune tâche" centered
+- Visual: etapes section renders below kanban board with stage names and task counts
 - CSS regression: global /tasks kanban page still renders correctly (task-row unchanged)
 </success_criteria>
 
diff --git a/.planning/phases/20-tablo-detail-kanban-restyle/20-VALIDATION.md b/.planning/phases/20-tablo-detail-kanban-restyle/20-VALIDATION.md
new file mode 100644
index 0000000..1e3854f
--- /dev/null
+++ b/.planning/phases/20-tablo-detail-kanban-restyle/20-VALIDATION.md
@@ -0,0 +1,80 @@
+---
+phase: 20
+slug: tablo-detail-kanban-restyle
+status: draft
+nyquist_compliant: true
+wave_0_complete: false
+created: 2026-05-18
+---
+
+# Phase 20 — Validation Strategy
+
+> Per-phase validation contract for feedback sampling during execution.
+
+---
+
+## Test Infrastructure
+
+| Property | Value |
+|----------|-------|
+| **Framework** | go test |
+| **Config file** | none — existing test infrastructure |
+| **Quick run command** | `go build ./...` |
+| **Full suite command** | `TEST_DATABASE_URL='postgres://xtablo:xtablo@localhost:5432/xtablo?sslmode=disable' go test ./... -count=1` |
+| **Estimated runtime** | ~20 seconds |
+
+---
+
+## Sampling Rate
+
+- **After every task commit:** Run `go build ./...`
+- **After every plan wave:** Run full suite with TEST_DATABASE_URL
+- **Before `/gsd:verify-work`:** Full suite must be green
+- **Max feedback latency:** 20 seconds
+
+---
+
+## Per-Task Verification Map
+
+| Task ID | Plan | Wave | Requirement | Threat Ref | Secure Behavior | Test Type | Automated Command | File Exists | Status |
+|---------|------|------|-------------|------------|-----------------|-----------|-------------------|-------------|--------|
+| 20-01-01 | 01 | 1 | DETAIL-01 | — | handler returns 404 for tablo not owned by current user | unit | `go build ./...` | ✅ | ⬜ pending |
+| 20-01-02 | 01 | 1 | DETAIL-01 | — | N/A | unit | `go test ./backend/... -run TestTabloDetail -count=1` | ❌ W0 | ⬜ pending |
+| 20-02-01 | 02 | 2 | TASK-01 | — | N/A | build | `just generate && go build ./...` | ✅ | ⬜ pending |
+| 20-02-02 | 02 | 2 | TASK-01 | — | N/A | build | `just generate && go build ./...` | ✅ | ⬜ pending |
+| 20-03-01 | 03 | 2 | DETAIL-01 | — | N/A | source | `grep -c "tablo-detail-header\|tablo-detail-title\|tablo-metadata-row\|tablo-progress-bar" backend/internal/web/ui/app.css` | ✅ | ⬜ pending |
+| 20-03-02 | 03 | 2 | TASK-01 | — | N/A | source | `grep "background: var(--color-brand-primary)" backend/internal/web/ui/app.css` | ✅ | ⬜ pending |
+
+*Status: ⬜ pending · ✅ green · ❌ red · ⚠️ flaky*
+
+---
+
+## Wave 0 Requirements
+
+- [ ] `backend/cmd/web/tablo_detail_test.go` — stubs for DETAIL-01, TASK-01 handler tests
+- [ ] Test must compile with `go test ./... -run TestTabloDetail -count=1` returning 0 (skip OK)
+
+*Existing infrastructure covers all other phase requirements (go build, just generate).*
+
+---
+
+## Manual-Only Verifications
+
+| Behavior | Requirement | Why Manual | Test Instructions |
+|----------|-------------|------------|-------------------|
+| Kanban drag-and-drop reorder persists after restyle | TASK-01 | Browser interaction required (Sortable.js) | Open /tablos/{id}, drag a task card to a different position in the same column, reload page and verify new position persists |
+| Tablo detail header matches Figma visual | DETAIL-01 | Visual layout requires browser render | Open /tablos/{id}, compare header row (name, metadata, avatar stack, progress bar) against Board-1.png screenshot |
+| Etapes section renders correctly | DETAIL-01 | Visual layout | Open /tablos/{id} that has etapes, verify etapes section is visible below kanban with correct French labels |
+
+---
+
+## Validation Sign-Off
+
+- [x] All tasks have `<automated>` verify or Wave 0 dependencies
+- [x] Sampling continuity: no 3 consecutive tasks without automated verify
+- [x] Wave 0 covers all MISSING references
+- [x] No watch-mode flags
+- [x] Feedback latency < 20s
+- [x] `nyquist_compliant: true` set in frontmatter
+
+**Approval:** pending
diff --git a/go-backend/internal/web/handlers/tablo_detail_test.go b/go-backend/internal/web/handlers/tablo_detail_test.go
new file mode 100644
index 0000000..a1f7a3f
--- /dev/null
+++ b/go-backend/internal/web/handlers/tablo_detail_test.go
@@ -0,0 +1,187 @@
+package handlers
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestGetTabloDetailPage_Returns200(t *testing.T) {
+	handler := newTestAuthHandler(t)
+	sessionCookie := loginTestUser(t, handler, "demo@xtablo.com", "xtablo-demo")
+
+	// Create a tablo owned by demo user
+	user, err := handler.repo.(interface {
+		GetAuthUserByEmail(ctx context.Context, email string) (AuthUser, error)
+	}).GetAuthUserByEmail(context.Background(), "demo@xtablo.com")
+	if err != nil {
+		t.Fatalf("get demo user: %v", err)
+	}
+
+	tablo, err := handler.repo.CreateTablo(context.Background(), CreateTabloInput{
+		OwnerID: user.ID,
+		Name:    "Test Project",
+		Status:  TabloStatusTodo,
+		Color:   "#3B82F6",
+	})
+	if err != nil {
+		t.Fatalf("create tablo: %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodGet, "/tablos/"+tablo.ID.String(), nil)
+	req.SetPathValue("tabloID", tablo.ID.String())
+	req.AddCookie(sessionCookie)
+	rec := httptest.NewRecorder()
+
+	handler.GetTabloDetailPage().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d\nbody: %s", rec.Code, rec.Body.String())
+	}
+
+	body := rec.Body.String()
+	if !strings.Contains(body, "Test Project") {
+		t.Errorf("expected body to contain tablo name 'Test Project', got: %s", body[:min(len(body), 500)])
+	}
+}
+
+func TestGetTabloDetailPage_Returns404(t *testing.T) {
+	handler := newTestAuthHandler(t)
+	sessionCookie := loginTestUser(t, handler, "demo@xtablo.com", "xtablo-demo")
+
+	// Use a random UUID that doesn't belong to the user
+	unknownID := "00000000-0000-0000-0000-000000000099"
+
+	req := httptest.NewRequest(http.MethodGet, "/tablos/"+unknownID, nil)
+	req.SetPathValue("tabloID", unknownID)
+	req.AddCookie(sessionCookie)
+	rec := httptest.NewRecorder()
+
+	handler.GetTabloDetailPage().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusNotFound {
+		t.Fatalf("expected 404, got %d", rec.Code)
+	}
+}
+
+func TestGetTabloDetailPage_Returns400(t *testing.T) {
+	handler := newTestAuthHandler(t)
+	sessionCookie := loginTestUser(t, handler, "demo@xtablo.com", "xtablo-demo")
+
+	req := httptest.NewRequest(http.MethodGet, "/tablos/not-a-uuid", nil)
+	req.SetPathValue("tabloID", "not-a-uuid")
+	req.AddCookie(sessionCookie)
+	rec := httptest.NewRecorder()
+
+	handler.GetTabloDetailPage().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d", rec.Code)
+	}
+}
+
+func TestGetTabloDetailPage_Unauthenticated(t *testing.T) {
+	handler := newTestAuthHandler(t)
+
+	req := httptest.NewRequest(http.MethodGet, "/tablos/00000000-0000-0000-0000-000000000001", nil)
+	req.SetPathValue("tabloID", "00000000-0000-0000-0000-000000000001")
+	rec := httptest.NewRecorder()
+
+	handler.GetTabloDetailPage().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusSeeOther {
+		t.Fatalf("expected 302 redirect to /login, got %d", rec.Code)
+	}
+
+	location := rec.Header().Get("Location")
+	if location != "/login" {
+		t.Errorf("expected redirect to /login, got %q", location)
+	}
+}
+
+func TestTabloDetailKanbanColumns(t *testing.T) {
+	handler := newTestAuthHandler(t)
+	sessionCookie := loginTestUser(t, handler, "demo@xtablo.com", "xtablo-demo")
+
+	user, err := handler.repo.(interface {
+		GetAuthUserByEmail(ctx context.Context, email string) (AuthUser, error)
+	}).GetAuthUserByEmail(context.Background(), "demo@xtablo.com")
+	if err != nil {
+		t.Fatalf("get demo user: %v", err)
+	}
+
+	tablo, err := handler.repo.CreateTablo(context.Background(), CreateTabloInput{
+		OwnerID: user.ID,
+		Name:    "Kanban Test",
+		Status:  TabloStatusTodo,
+		Color:   "#3B82F6",
+	})
+	if err != nil {
+		t.Fatalf("create tablo: %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodGet, "/tablos/"+tablo.ID.String(), nil)
+	req.SetPathValue("tabloID", tablo.ID.String())
+	req.AddCookie(sessionCookie)
+	rec := httptest.NewRecorder()
+
+	handler.GetTabloDetailPage().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d", rec.Code)
+	}
+
+	body := rec.Body.String()
+	for _, status := range []string{"todo", "in_progress", "in_review", "done"} {
+		if !strings.Contains(body, status) {
+			t.Errorf("expected body to contain kanban column status %q", status)
+		}
+	}
+}
+
+func TestGetTabloDetailPage_ContainsSortableScript(t *testing.T) {
+	handler := newTestAuthHandler(t)
+	sessionCookie := loginTestUser(t, handler, "demo@xtablo.com", "xtablo-demo")
+
+	user, err := handler.repo.(interface {
+		GetAuthUserByEmail(ctx context.Context, email string) (AuthUser, error)
+	}).GetAuthUserByEmail(context.Background(), "demo@xtablo.com")
+	if err != nil {
+		t.Fatalf("get demo user: %v", err)
+	}
+
+	tablo, err := handler.repo.CreateTablo(context.Background(), CreateTabloInput{
+		OwnerID: user.ID,
+		Name:    "Sortable Test",
+		Status:  TabloStatusTodo,
+		Color:   "#3B82F6",
+	})
+	if err != nil {
+		t.Fatalf("create tablo: %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodGet, "/tablos/"+tablo.ID.String(), nil)
+	req.SetPathValue("tabloID", tablo.ID.String())
+	req.AddCookie(sessionCookie)
+	rec := httptest.NewRecorder()
+
+	handler.GetTabloDetailPage().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d", rec.Code)
+	}
+
+	body := rec.Body.String()
+	if !strings.Contains(body, "initTabloDetailSortable") {
+		t.Errorf("expected body to contain 'initTabloDetailSortable', got body[:500]: %s", body[:min(len(body), 500)])
+	}
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
diff --git a/go-backend/internal/web/views/tablo_detail_view_test.go b/go-backend/internal/web/views/tablo_detail_view_test.go
new file mode 100644
index 0000000..9a278c6
--- /dev/null
+++ b/go-backend/internal/web/views/tablo_detail_view_test.go
@@ -0,0 +1,244 @@
+package views
+
+import (
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	tablomodel "xtablo-backend/internal/tablos"
+	taskmodel "xtablo-backend/internal/tasks"
+)
+
+func makeTask(status taskmodel.Status, isEtape bool) taskmodel.Record {
+	return taskmodel.Record{
+		ID:        uuid.New(),
+		TabloID:   uuid.New(),
+		OwnerID:   uuid.New(),
+		Title:     "Task " + string(status),
+		Status:    status,
+		IsEtape:   isEtape,
+		CreatedAt: time.Now().UTC(),
+		UpdatedAt: time.Now().UTC(),
+	}
+}
+
+func makeTablo() tablomodel.Record {
+	return tablomodel.Record{
+		ID:        uuid.New(),
+		OwnerID:   uuid.New(),
+		Name:      "Test Tablo",
+		Color:     "#3B82F6",
+		Status:    tablomodel.StatusTodo,
+		CreatedAt: time.Now().UTC(),
+		UpdatedAt: time.Now().UTC(),
+	}
+}
+
+func TestComputeTabloProgress_Empty(t *testing.T) {
+	got := computeTabloProgress([]taskmodel.Record{})
+	if got != 0 {
+		t.Fatalf("expected 0, got %d", got)
+	}
+}
+
+func TestComputeTabloProgress_AllDone(t *testing.T) {
+	tasks := []taskmodel.Record{
+		makeTask(taskmodel.StatusDone, false),
+		makeTask(taskmodel.StatusDone, false),
+	}
+	got := computeTabloProgress(tasks)
+	if got != 100 {
+		t.Fatalf("expected 100, got %d", got)
+	}
+}
+
+func TestComputeTabloProgress_Half(t *testing.T) {
+	tasks := []taskmodel.Record{
+		makeTask(taskmodel.StatusDone, false),
+		makeTask(taskmodel.StatusTodo, false),
+	}
+	got := computeTabloProgress(tasks)
+	if got != 50 {
+		t.Fatalf("expected 50, got %d", got)
+	}
+}
+
+func TestComputeTabloProgress_EtapesIgnored(t *testing.T) {
+	tasks := []taskmodel.Record{
+		makeTask(taskmodel.StatusDone, false),
+		// etape task — should be excluded from denominator and numerator
+		makeTask(taskmodel.StatusTodo, true),
+	}
+	got := computeTabloProgress(tasks)
+	if got != 100 {
+		t.Fatalf("expected 100 (etape ignored), got %d", got)
+	}
+}
+
+func TestNewTabloDetailViewModel_GroupsTasksByStatus(t *testing.T) {
+	tablo := makeTablo()
+
+	todoTask := makeTask(taskmodel.StatusTodo, false)
+	todoTask.TabloID = tablo.ID
+
+	inProgressTask := makeTask(taskmodel.StatusInProgress, false)
+	inProgressTask.TabloID = tablo.ID
+
+	doneTask := makeTask(taskmodel.StatusDone, false)
+	doneTask.TabloID = tablo.ID
+
+	tasks := []taskmodel.Record{todoTask, inProgressTask, doneTask}
+
+	vm := NewTabloDetailViewModel(tablo, tasks, "Test User")
+
+	if len(vm.Columns) != 4 {
+		t.Fatalf("expected 4 columns, got %d", len(vm.Columns))
+	}
+
+	columnIDs := []string{"todo", "in_progress", "in_review", "done"}
+	for i, col := range vm.Columns {
+		if col.ID != columnIDs[i] {
+			t.Errorf("column[%d]: expected ID %q, got %q", i, columnIDs[i], col.ID)
+		}
+	}
+
+	// Column 0 = todo — 1 task
+	if len(vm.Columns[0].Tasks) != 1 {
+		t.Errorf("todo column: expected 1 task, got %d", len(vm.Columns[0].Tasks))
+	}
+
+	// Column 1 = in_progress — 1 task
+	if len(vm.Columns[1].Tasks) != 1 {
+		t.Errorf("in_progress column: expected 1 task, got %d", len(vm.Columns[1].Tasks))
+	}
+
+	// Column 2 = in_review — 0 tasks
+	if len(vm.Columns[2].Tasks) != 0 {
+		t.Errorf("in_review column: expected 0 tasks, got %d", len(vm.Columns[2].Tasks))
+	}
+
+	// Column 3 = done — 1 task
+	if len(vm.Columns[3].Tasks) != 1 {
+		t.Errorf("done column: expected 1 task, got %d", len(vm.Columns[3].Tasks))
+	}
+}
+
+func TestNewTabloDetailViewModel_EtapesExcludedFromColumns(t *testing.T) {
+	tablo := makeTablo()
+
+	etapeTask := makeTask(taskmodel.StatusTodo, true)
+	etapeTask.TabloID = tablo.ID
+
+	regularTask := makeTask(taskmodel.StatusTodo, false)
+	regularTask.TabloID = tablo.ID
+
+	tasks := []taskmodel.Record{etapeTask, regularTask}
+	vm := NewTabloDetailViewModel(tablo, tasks, "")
+
+	// Only regular task in todo column
+	if len(vm.Columns[0].Tasks) != 1 {
+		t.Errorf("todo column: expected 1 task (etape excluded), got %d", len(vm.Columns[0].Tasks))
+	}
+}
+
+func TestNewTabloDetailViewModel_EtapesPopulated(t *testing.T) {
+	tablo := makeTablo()
+
+	etape1 := taskmodel.Record{
+		ID:        uuid.New(),
+		TabloID:   tablo.ID,
+		OwnerID:   tablo.OwnerID,
+		Title:     "Etape One",
+		Status:    taskmodel.StatusTodo,
+		IsEtape:   true,
+		CreatedAt: time.Now().UTC(),
+		UpdatedAt: time.Now().UTC(),
+	}
+
+	etape2 := taskmodel.Record{
+		ID:        uuid.New(),
+		TabloID:   tablo.ID,
+		OwnerID:   tablo.OwnerID,
+		Title:     "Etape Two",
+		Status:    taskmodel.StatusTodo,
+		IsEtape:   true,
+		CreatedAt: time.Now().UTC(),
+		UpdatedAt: time.Now().UTC(),
+	}
+
+	child1 := taskmodel.Record{
+		ID:           uuid.New(),
+		TabloID:      tablo.ID,
+		OwnerID:      tablo.OwnerID,
+		Title:        "Child A",
+		Status:       taskmodel.StatusTodo,
+		IsEtape:      false,
+		ParentTaskID: &etape1.ID,
+		CreatedAt:    time.Now().UTC(),
+		UpdatedAt:    time.Now().UTC(),
+	}
+
+	child2 := taskmodel.Record{
+		ID:           uuid.New(),
+		TabloID:      tablo.ID,
+		OwnerID:      tablo.OwnerID,
+		Title:        "Child B",
+		Status:       taskmodel.StatusInProgress,
+		IsEtape:      false,
+		ParentTaskID: &etape1.ID,
+		CreatedAt:    time.Now().UTC(),
+		UpdatedAt:    time.Now().UTC(),
+	}
+
+	orphan := taskmodel.Record{
+		ID:        uuid.New(),
+		TabloID:   tablo.ID,
+		OwnerID:   tablo.OwnerID,
+		Title:     "No Etape",
+		Status:    taskmodel.StatusTodo,
+		IsEtape:   false,
+		CreatedAt: time.Now().UTC(),
+		UpdatedAt: time.Now().UTC(),
+	}
+
+	tasks := []taskmodel.Record{etape1, etape2, child1, child2, orphan}
+	vm := NewTabloDetailViewModel(tablo, tasks, "")
+
+	if len(vm.Etapes) != 2 {
+		t.Fatalf("expected 2 etapes, got %d", len(vm.Etapes))
+	}
+
+	// Find etape1 in the Etapes slice
+	var foundEtape1 *TabloDetailEtapeView
+	for i := range vm.Etapes {
+		if vm.Etapes[i].ID == etape1.ID.String() {
+			foundEtape1 = &vm.Etapes[i]
+			break
+		}
+	}
+
+	if foundEtape1 == nil {
+		t.Fatal("etape1 not found in vm.Etapes")
+	}
+
+	if foundEtape1.TaskCount != 2 {
+		t.Errorf("etape1: expected TaskCount=2, got %d", foundEtape1.TaskCount)
+	}
+
+	// Find etape2 — should have TaskCount=0
+	var foundEtape2 *TabloDetailEtapeView
+	for i := range vm.Etapes {
+		if vm.Etapes[i].ID == etape2.ID.String() {
+			foundEtape2 = &vm.Etapes[i]
+			break
+		}
+	}
+
+	if foundEtape2 == nil {
+		t.Fatal("etape2 not found in vm.Etapes")
+	}
+
+	if foundEtape2.TaskCount != 0 {
+		t.Errorf("etape2: expected TaskCount=0, got %d", foundEtape2.TaskCount)
+	}
+}