AP1.5c: Rekursive Projects fuer Mega-Programme ohne Stream-Typ.

parent_project_id und container_kind ermoeglichen verschachtelte Projektstruktur; Arbeitspakete bleiben an Blatt-Projekten gebunden.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/migrations/014_project_hierarchy.sql

@@ -0,0 +1,12 @@
+-- AP1.5c: Rekursive Projects (parent_project_id, container_kind)
+
+ALTER TABLE projects
+    ADD COLUMN parent_project_id UUID NULL REFERENCES projects(id) ON DELETE SET NULL,
+    ADD COLUMN container_kind VARCHAR(32) NULL
+        CHECK (
+            container_kind IS NULL
+            OR container_kind IN ('project', 'stream', 'phase', 'release')
+        );
+
+CREATE INDEX idx_projects_parent ON projects(tenant_id, parent_project_id)
+    WHERE parent_project_id IS NOT NULL;

backend/routers/projects.py

@@ -19,6 +19,8 @@ class ProjectCreateRequest(BaseModel):
     title: str = Field(min_length=1, max_length=255)
     description: str = ""
     status: Literal["active", "paused", "completed", "archived"] = "active"
+    parent_project_id: Optional[str] = None
+    container_kind: Optional[Literal["project", "stream", "phase", "release"]] = None
     roadmap_item_id: Optional[str] = None
     sort_order: int = 0
     target_date: Optional[date] = None
@@ -28,6 +30,10 @@ class ProjectUpdateRequest(BaseModel):
     title: Optional[str] = Field(default=None, min_length=1, max_length=255)
     description: Optional[str] = None
     status: Optional[Literal["active", "paused", "completed", "archived"]] = None
+    parent_project_id: Optional[str] = None
+    clear_parent_project: bool = False
+    container_kind: Optional[Literal["project", "stream", "phase", "release"]] = None
+    clear_container_kind: bool = False
     roadmap_item_id: Optional[str] = None
     clear_roadmap_item: bool = False
     sort_order: Optional[int] = None
@@ -62,6 +68,8 @@ def create_initiative_project(
             title=body.title,
             description=body.description,
             status=body.status,
+            parent_project_id=body.parent_project_id,
+            container_kind=body.container_kind,
             roadmap_item_id=body.roadmap_item_id,
             sort_order=body.sort_order,
             target_date=body.target_date,
@@ -95,6 +103,10 @@ def update_project(
             title=body.title,
             description=body.description,
             status=body.status,
+            parent_project_id=body.parent_project_id,
+            clear_parent_project=body.clear_parent_project,
+            container_kind=body.container_kind,
+            clear_container_kind=body.clear_container_kind,
             roadmap_item_id=body.roadmap_item_id,
             clear_roadmap_item=body.clear_roadmap_item,
             sort_order=body.sort_order,
@@ -113,7 +125,11 @@ def delete_project(
     project_id: str,
     ctx: TenantContext = Depends(require_capability("kairo.project.manage")),
 ):
-    if not project_service.delete_project(
+    try:
-        tenant_id=ctx.tenant_id, project_id=project_id, user_id=ctx.user_id
+        deleted = project_service.delete_project(
-    ):
+            tenant_id=ctx.tenant_id, project_id=project_id, user_id=ctx.user_id
+        )
+    except ValueError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+    if not deleted:
         raise HTTPException(status_code=404, detail="Projekt nicht gefunden")

backend/services/actions.py

@@ -9,6 +9,7 @@ from psycopg2.extras import RealDictCursor
 from db import get_connection
 from services.audit import log_audit
 from services.initiatives import PRIORITIES, get_initiative
+from services.projects import project_is_leaf
 
 ActionStatus = Literal[
     "open", "ready", "in_progress", "blocked", "review_required", "done", "discarded"
@@ -116,6 +117,10 @@ def _validate_project_in_initiative(
             )
             if not cur.fetchone():
                 raise ValueError("Projekt gehört nicht zum Vorhaben")
+            if not project_is_leaf(tenant_id=tenant_id, project_id=project_id):
+                raise ValueError(
+                    "Arbeitspakete nur an Blatt-Projekten (ohne Unterprojekte)"
+                )
     finally:
         conn.close()
 

backend/services/projects.py

@@ -1,4 +1,4 @@
-"""Project service — operative Struktur unter Initiative (AP1.5)."""
+"""Project service — operative Struktur unter Initiative (AP1.5, AP1.5c)."""
 
 from __future__ import annotations
 
@@ -14,15 +14,21 @@ from services.initiatives import get_initiative
 ProjectStatus = Literal["active", "paused", "completed", "archived"]
 PROJECT_STATUSES = frozenset({"active", "paused", "completed", "archived"})
 
+ContainerKind = Literal["project", "stream", "phase", "release"]
+CONTAINER_KINDS = frozenset({"project", "stream", "phase", "release"})
+
+MAX_PROJECT_DEPTH = 5
+
 _PROJECT_COLUMNS = """
-    id, tenant_id, initiative_id, title, description, status,
+    id, tenant_id, initiative_id, parent_project_id, container_kind,
+    title, description, status,
     roadmap_item_id, sort_order, target_date, created_at, updated_at
 """
 
 
 def _serialize_row(row: dict[str, Any]) -> dict[str, Any]:
     result = dict(row)
-    for key in ("id", "tenant_id", "initiative_id", "roadmap_item_id"):
+    for key in ("id", "tenant_id", "initiative_id", "parent_project_id", "roadmap_item_id"):
         if result.get(key):
             result[key] = str(result[key])
     if result.get("target_date"):
@@ -42,6 +48,11 @@ def _validate_status(status: str) -> None:
         raise ValueError(f"Ungültiger Project-Status: {status}")
 
 
+def _validate_container_kind(container_kind: Optional[str]) -> None:
+    if container_kind is not None and container_kind not in CONTAINER_KINDS:
+        raise ValueError(f"Ungültiger container_kind: {container_kind}")
+
+
 def _validate_roadmap_item(
     cur, *, tenant_id: str, initiative_id: str, roadmap_item_id: Optional[str]
 ) -> None:
@@ -59,6 +70,151 @@ def _validate_roadmap_item(
         raise ValueError("Gate/Plan-Element gehört nicht zu diesem Vorhaben")
 
 
+def _fetch_project_row(
+    cur, *, tenant_id: str, project_id: str, initiative_id: Optional[str] = None
+) -> Optional[dict[str, Any]]:
+    query = f"""
+        SELECT {_PROJECT_COLUMNS}
+        FROM projects
+        WHERE id = %s AND tenant_id = %s
+    """
+    params: list[Any] = [project_id, tenant_id]
+    if initiative_id is not None:
+        query += " AND initiative_id = %s"
+        params.append(initiative_id)
+    cur.execute(query, params)
+    row = cur.fetchone()
+    return dict(row) if row else None
+
+
+def _project_depth_from_map(
+    project_id: str, by_id: dict[str, dict[str, Any]], memo: dict[str, int]
+) -> int:
+    if project_id in memo:
+        return memo[project_id]
+    project = by_id.get(project_id)
+    if not project or not project.get("parent_project_id"):
+        memo[project_id] = 1
+        return 1
+    parent_id = str(project["parent_project_id"])
+    if parent_id == project_id:
+        raise ValueError("Zyklus in Project-Hierarchie")
+    depth = _project_depth_from_map(parent_id, by_id, memo) + 1
+    memo[project_id] = depth
+    return depth
+
+
+def _collect_descendant_ids(
+    project_id: str, by_parent: dict[str, list[str]]
+) -> set[str]:
+    result: set[str] = set()
+    stack = list(by_parent.get(project_id, []))
+    while stack:
+        child_id = stack.pop()
+        if child_id in result:
+            continue
+        result.add(child_id)
+        stack.extend(by_parent.get(child_id, []))
+    return result
+
+
+def _subtree_height(project_id: str, by_parent: dict[str, list[str]]) -> int:
+    children = by_parent.get(project_id, [])
+    if not children:
+        return 1
+    return 1 + max(_subtree_height(child_id, by_parent) for child_id in children)
+
+
+def _load_initiative_project_maps(
+    cur, *, tenant_id: str, initiative_id: str
+) -> tuple[dict[str, dict[str, Any]], dict[str, list[str]]]:
+    cur.execute(
+        f"""
+        SELECT {_PROJECT_COLUMNS}
+        FROM projects
+        WHERE tenant_id = %s AND initiative_id = %s
+        """,
+        (tenant_id, initiative_id),
+    )
+    rows = [dict(r) for r in cur.fetchall()]
+    by_id = {str(r["id"]): r for r in rows}
+    by_parent: dict[str, list[str]] = {}
+    for row in rows:
+        parent_id = row.get("parent_project_id")
+        if parent_id:
+            by_parent.setdefault(str(parent_id), []).append(str(row["id"]))
+    return by_id, by_parent
+
+
+def _validate_parent_project(
+    cur,
+    *,
+    tenant_id: str,
+    initiative_id: str,
+    project_id: Optional[str],
+    parent_project_id: Optional[str],
+) -> None:
+    if not parent_project_id:
+        return
+    if project_id and parent_project_id == project_id:
+        raise ValueError("Projekt kann nicht sein eigener Parent sein")
+
+    parent = _fetch_project_row(
+        cur, tenant_id=tenant_id, project_id=parent_project_id, initiative_id=initiative_id
+    )
+    if not parent:
+        raise ValueError("Parent-Projekt gehört nicht zu diesem Vorhaben")
+
+    by_id, by_parent = _load_initiative_project_maps(
+        cur, tenant_id=tenant_id, initiative_id=initiative_id
+    )
+    if project_id:
+        descendants = _collect_descendant_ids(project_id, by_parent)
+        if parent_project_id in descendants:
+            raise ValueError("Zyklus: Parent darf kein Nachfahr sein")
+
+    memo: dict[str, int] = {}
+    parent_depth = _project_depth_from_map(parent_project_id, by_id, memo)
+    subtree_height = (
+        _subtree_height(project_id, by_parent) if project_id else 1
+    )
+    if parent_depth + subtree_height > MAX_PROJECT_DEPTH:
+        raise ValueError(
+            f"Maximale Project-Tiefe ({MAX_PROJECT_DEPTH}) würde überschritten"
+        )
+
+
+def _attach_depths(projects: list[dict[str, Any]]) -> list[dict[str, Any]]:
+    if not projects:
+        return projects
+    by_id = {p["id"]: p for p in projects}
+    memo: dict[str, int] = {}
+    for project in projects:
+        project["depth"] = _project_depth_from_map(project["id"], by_id, memo)
+        project["has_children"] = any(
+            other.get("parent_project_id") == project["id"] for other in projects
+        )
+        project["is_leaf"] = not project["has_children"]
+    return projects
+
+
+def project_is_leaf(*, tenant_id: str, project_id: str) -> bool:
+    conn = get_connection()
+    try:
+        with conn.cursor() as cur:
+            cur.execute(
+                """
+                SELECT 1 FROM projects
+                WHERE parent_project_id = %s AND tenant_id = %s
+                LIMIT 1
+                """,
+                (project_id, tenant_id),
+            )
+            return cur.fetchone() is None
+    finally:
+        conn.close()
+
+
 def create_project(
     *,
     tenant_id: str,
@@ -66,6 +222,8 @@ def create_project(
     title: str,
     description: str = "",
     status: ProjectStatus = "active",
+    parent_project_id: Optional[str] = None,
+    container_kind: Optional[ContainerKind] = None,
     roadmap_item_id: Optional[str] = None,
     sort_order: int = 0,
     target_date: Optional[date] = None,
@@ -75,6 +233,7 @@ def create_project(
     if not title:
         raise ValueError("Titel ist erforderlich")
     _validate_status(status)
+    _validate_container_kind(container_kind)
     if not get_initiative(tenant_id=tenant_id, initiative_id=initiative_id):
         raise ValueError("Initiative nicht gefunden")
 
@@ -87,18 +246,28 @@ def create_project(
                 initiative_id=initiative_id,
                 roadmap_item_id=roadmap_item_id,
             )
+            _validate_parent_project(
+                cur,
+                tenant_id=tenant_id,
+                initiative_id=initiative_id,
+                project_id=None,
+                parent_project_id=parent_project_id,
+            )
             cur.execute(
                 f"""
                 INSERT INTO projects (
-                    tenant_id, initiative_id, title, description, status,
+                    tenant_id, initiative_id, parent_project_id, container_kind,
+                    title, description, status,
                     roadmap_item_id, sort_order, target_date
                 )
-                VALUES (%s, %s, %s, %s, %s, %s, %s, %s)
+                VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s)
                 RETURNING {_PROJECT_COLUMNS}
                 """,
                 (
                     tenant_id,
                     initiative_id,
+                    parent_project_id,
+                    container_kind,
                     title,
                     description,
                     status,
@@ -116,7 +285,12 @@ def create_project(
         "project.created",
         user_id=user_id,
         tenant_id=tenant_id,
-        details={"project_id": row["id"], "initiative_id": initiative_id, "title": title},
+        details={
+            "project_id": row["id"],
+            "initiative_id": initiative_id,
+            "title": title,
+            "parent_project_id": parent_project_id,
+        },
     )
     return row
 
@@ -139,7 +313,8 @@ def list_projects_for_initiative(
                 """,
                 (tenant_id, initiative_id),
             )
-            return [_serialize_row(dict(r)) for r in cur.fetchall()]
+            rows = [_serialize_row(dict(r)) for r in cur.fetchall()]
+            return _attach_depths(rows)
     finally:
         conn.close()
 
@@ -150,16 +325,25 @@ def get_project(*, tenant_id: str, project_id: str) -> Optional[dict[str, Any]]:
         with conn.cursor(cursor_factory=RealDictCursor) as cur:
             cur.execute(
                 f"""
-                SELECT {_PROJECT_COLUMNS}
+                SELECT initiative_id
                 FROM projects WHERE id = %s AND tenant_id = %s
                 """,
                 (project_id, tenant_id),
             )
             row = cur.fetchone()
-            return _serialize_row(dict(row)) if row else None
+            if not row:
+                return None
+            initiative_id = str(row["initiative_id"])
     finally:
         conn.close()
 
+    for project in list_projects_for_initiative(
+        tenant_id=tenant_id, initiative_id=initiative_id
+    ):
+        if project["id"] == project_id:
+            return project
+    return None
+
 
 def update_project(
     *,
@@ -169,6 +353,10 @@ def update_project(
     title: Optional[str] = None,
     description: Optional[str] = None,
     status: Optional[ProjectStatus] = None,
+    parent_project_id: Optional[str] = None,
+    clear_parent_project: bool = False,
+    container_kind: Optional[ContainerKind] = None,
+    clear_container_kind: bool = False,
     roadmap_item_id: Optional[str] = None,
     clear_roadmap_item: bool = False,
     sort_order: Optional[int] = None,
@@ -195,6 +383,29 @@ def update_project(
         _validate_status(status)
         updates.append("status = %s")
         params.append(status)
+    if clear_parent_project:
+        updates.append("parent_project_id = NULL")
+    elif parent_project_id is not None:
+        conn = get_connection()
+        try:
+            with conn.cursor() as cur:
+                _validate_parent_project(
+                    cur,
+                    tenant_id=tenant_id,
+                    initiative_id=existing["initiative_id"],
+                    project_id=project_id,
+                    parent_project_id=parent_project_id,
+                )
+        finally:
+            conn.close()
+        updates.append("parent_project_id = %s")
+        params.append(parent_project_id)
+    if clear_container_kind:
+        updates.append("container_kind = NULL")
+    elif container_kind is not None:
+        _validate_container_kind(container_kind)
+        updates.append("container_kind = %s")
+        params.append(container_kind)
     if clear_roadmap_item:
         updates.append("roadmap_item_id = NULL")
     elif roadmap_item_id is not None:
@@ -251,7 +462,7 @@ def update_project(
         tenant_id=tenant_id,
         details={"project_id": project_id},
     )
-    return result
+    return get_project(tenant_id=tenant_id, project_id=project_id)
 
 
 def delete_project(
@@ -260,6 +471,18 @@ def delete_project(
     conn = get_connection()
     try:
         with conn.cursor() as cur:
+            cur.execute(
+                """
+                SELECT 1 FROM projects
+                WHERE parent_project_id = %s AND tenant_id = %s
+                LIMIT 1
+                """,
+                (project_id, tenant_id),
+            )
+            if cur.fetchone():
+                raise ValueError(
+                    "Projekt hat Unterprojekte — zuerst löschen oder verschieben"
+                )
             cur.execute(
                 "UPDATE actions SET project_id = NULL WHERE project_id = %s AND tenant_id = %s",
                 (project_id, tenant_id),

backend/tests/test_ap15c_project_hierarchy.py

@@ -0,0 +1,111 @@
+"""AP1.5c — Rekursive Projects (parent_project_id)."""
+
+from __future__ import annotations
+
+from tests.factories import provision_user_in_tenant
+from tests.test_initiatives_actions import (
+    _auth,
+    _create_initiative,
+    _login,
+)
+
+
+def test_nested_projects_and_depth(client):
+    user = provision_user_in_tenant(tenant_role="member")
+    token = _login(client, user)
+    initiative_id = _create_initiative(client, token).json()["id"]
+
+    root = client.post(
+        f"/api/initiatives/{initiative_id}/projects",
+        json={"title": "Programm", "container_kind": "project"},
+        headers=_auth(token),
+    )
+    assert root.status_code == 201
+    root_id = root.json()["id"]
+
+    stream = client.post(
+        f"/api/initiatives/{initiative_id}/projects",
+        json={
+            "title": "Backend Stream",
+            "parent_project_id": root_id,
+            "container_kind": "stream",
+        },
+        headers=_auth(token),
+    )
+    assert stream.status_code == 201
+    stream_id = stream.json()["id"]
+
+    leaf = client.post(
+        f"/api/initiatives/{initiative_id}/projects",
+        json={"title": "API", "parent_project_id": stream_id},
+        headers=_auth(token),
+    )
+    assert leaf.status_code == 201
+    leaf_id = leaf.json()["id"]
+
+    listed = client.get(
+        f"/api/initiatives/{initiative_id}/projects",
+        headers=_auth(token),
+    )
+    assert listed.status_code == 200
+    items = {p["id"]: p for p in listed.json()}
+    assert items[stream_id]["parent_project_id"] == root_id
+    assert items[leaf_id]["depth"] == 3
+    assert items[leaf_id]["is_leaf"] is True
+    assert items[root_id]["has_children"] is True
+
+
+def test_action_only_on_leaf_project(client):
+    user = provision_user_in_tenant(tenant_role="member")
+    token = _login(client, user)
+    initiative_id = _create_initiative(client, token).json()["id"]
+
+    parent = client.post(
+        f"/api/initiatives/{initiative_id}/projects",
+        json={"title": "Container"},
+        headers=_auth(token),
+    ).json()
+    child = client.post(
+        f"/api/initiatives/{initiative_id}/projects",
+        json={"title": "Blatt", "parent_project_id": parent["id"]},
+        headers=_auth(token),
+    ).json()
+
+    blocked = client.post(
+        f"/api/initiatives/{initiative_id}/actions",
+        json={"title": "Am Container", "project_id": parent["id"]},
+        headers=_auth(token),
+    )
+    assert blocked.status_code == 400
+    assert "Blatt" in blocked.json()["detail"]
+
+    ok = client.post(
+        f"/api/initiatives/{initiative_id}/actions",
+        json={"title": "Am Blatt", "project_id": child["id"]},
+        headers=_auth(token),
+    )
+    assert ok.status_code == 201
+
+
+def test_cannot_delete_project_with_children(client):
+    user = provision_user_in_tenant(tenant_role="member")
+    token = _login(client, user)
+    initiative_id = _create_initiative(client, token).json()["id"]
+
+    parent = client.post(
+        f"/api/initiatives/{initiative_id}/projects",
+        json={"title": "Parent"},
+        headers=_auth(token),
+    ).json()
+    child = client.post(
+        f"/api/initiatives/{initiative_id}/projects",
+        json={"title": "Child", "parent_project_id": parent["id"]},
+        headers=_auth(token),
+    ).json()
+
+    resp = client.delete(f"/api/projects/{parent['id']}", headers=_auth(token))
+    assert resp.status_code == 400
+
+    client.delete(f"/api/projects/{child['id']}", headers=_auth(token))
+    ok = client.delete(f"/api/projects/{parent['id']}", headers=_auth(token))
+    assert ok.status_code == 204

backend/version.py

@@ -1,3 +1,3 @@
-APP_VERSION = "0.14.0-ap1.5"
+APP_VERSION = "0.14.1-ap1.5c"
-DB_SCHEMA_VERSION = "013"
+DB_SCHEMA_VERSION = "014"
 APP_NAME = "jinkendo-kairo"

docs/architecture/ADP_PO_Product_Layering_and_IA_Reset_v0.1.md

@@ -82,10 +82,12 @@ Minimaler Fix erlaubt: Tab-Beschreibung / Breadcrumb „Gates“ statt implizit
 
 ```text
 ✓ AP1.4b   Gate-Checkliste Backend + Minimal-Detail-Route
-→ AP1.5    Project, Task, Ausführung als Ist-Kern (NÄCHSTES CODE-PAKET)
+→ AP1.5    Project, Task, Ausführung als Ist-Kern ✓
+→ AP1.5c   Rekursive Projects (parent_project_id)
 → AP1.5b   IA/Begriffe: Gates vs. Ausführung, optionale Gate-Sicht
-→ AP1.6    Plan/Ist-Verknüpfung, Journey (Action/Backlog → Gate)
+→ AP1.6    Plan/Ist-Verknüpfung, Journey (Action/Backlog/Project → Gate)
-⏸ AP1.4c   Gate-UI (Modal, Checkliste-UX) — nach AP1.5
+→ AP1.5d   Rekursive Tasks (parent_task_id), Roll-up
+⏸ AP1.4c   Gate-UI (Modal, Checkliste-UX) — nach AP1.6
 → AP1.4d   Graph Engine (Gate-Kanten only)
 → AP1.4e   Methodenprofile (generic_operating ohne Gate-Zwang)
 ```
@@ -101,9 +103,9 @@ Initiative (Vorhaben / Programm)
 │         ▲
 │         │ zahlt ein (Evidence, Zuordnung)
 │         │
-├── [optional] Project                 ← AP1.5
+├── [optional] Project*                ← AP1.5c parent_project_id
 │         └── Action (Arbeitspaket)    ← Ist — „Plan zwischen Gates“
-│               └── Task               ← AP1.5 minimal
+│               └── Task*              ← AP1.5d parent_task_id
 │
 ├── Backlog → Commit → Action
 └── steering_context (Lifecycle, method_key)  ← getrennt von Gate-Graph
@@ -155,4 +157,4 @@ Initiative (Vorhaben / Programm)
 
 ---
 
-*Referenz: `Kairo_Corrected_MVP_Roadmap_v0.2.md` (PO-Korrektur 2026-07-06), `Sprint1_AP1_5_Hierarchy_Assignment_v0.1.md`*
+*Referenz: `Kairo_Corrected_MVP_Roadmap_v0.2.md` (PO-Korrektur 2026-07-06), `ADP_Recursive_Containers_and_Execution_Granularity_v0.1.md`, `Sprint1_AP1_5_Hierarchy_Assignment_v0.1.md`*

docs/architecture/ADP_Recursive_Containers_and_Execution_Granularity_v0.1.md

@@ -0,0 +1,198 @@
+# ADP — Rekursive Container & Ausführungs-Granularität v0.1
+
+**Status:** PO-Freigabe (2026-07-06)  
+**Stand:** 2026-07-06  
+**Auslöser:** PO-Review — Mega-Programme vs. normale Vorhaben; Granularität für Mensch vs. Agent  
+**Bezug:** `ADP_PO_Product_Layering_and_IA_Reset_v0.1.md`, Canonical OM v0.2, Target State §10–11
+
+---
+
+## Problem
+
+Zwei verwandte Fragen ohne feste Extra-Typen (`Stream`, `Subtask`, …):
+
+1. **Organisation:** Sehr große Programme brauchen optional **Project in Project**; normale Vorhaben nicht.
+2. **Ausführung:** Arbeitspakete und Aufgaben brauchen **methoden- und akteursabhängige Tiefe** — Menschen ~2–3 Untergliederungen, Agenten feiner.
+
+Fest codierte Ebenen (`Stream`, `WorkPackage`, `Subtask` als eigene Typen) wären für kleine Vorhaben überdimensioniert und duplizieren semantisch **Project** bzw. **Task**.
+
+---
+
+## Betroffene Regeln
+
+| Dokument | Regel |
+|----------|--------|
+| Canonical OM v0.2 §4 | Project optional; Action = Arbeitspaket; Task methodenabhängig |
+| Vision v0.2 §4 | Action ≠ atomare Aufgabe; Task-Hierarchie / WBS |
+| ADP Product Layering | Ist = Project → Action → Task; Gates orthogonal |
+| Target State §10–11 | Steuerbare Objekte inkl. `project`; `SteeringContext` mit `scope_type` |
+| Tenant Invariants | Kein paralleles Steering; Actor-first Assignments |
+
+---
+
+## Optionen (Struktur)
+
+| Option | Kurz | Pro | Contra |
+|--------|------|-----|--------|
+| A | Feste Typen `Stream`, `Subtask` | Klare UI-Labels | Schema-Ballast; Doppelung zu Project/Task |
+| B | **Rekursion gleicher Typen** (`parent_*_id`) | Ein Modell für klein + groß | Baum-UI; Roll-up-Regeln nötig |
+| C | Unbegrenzte Rekursion + Steuerung pro Ebene | Maximale Flexibilität | Steuerungs-Explosion; MVP-Verzögerung |
+
+---
+
+## Entscheidung (PO-Freigabe 2026-07-06)
+
+### 1. Organisations-Ebene: rekursives **Project**
+
+- **`parent_project_id`** nullable auf `projects` (Adjacency List).
+- Gleiche Initiative; **Zyklen verboten**; **max. Tiefe 5** (hard block).
+- Optional **`container_kind`** (Registry/Label): `project`, `stream`, `phase`, `release` — **nur Anzeige/Methoden-Hint**, keine Sonderlogik pro Kind.
+- **Kein** eigener Typ `Stream`.
+
+**Semantik nach Tiefe (UI, nicht Schema):**
+
+| Tiefe | Typisches Label | Beispiel |
+|-------|-----------------|----------|
+| 0 | Projekt | „Kairo MVP“ |
+| 1 | Stream / Phase | „Backend“, „Kumite“ |
+| 2+ | Teilprojekt | „API-Schicht“ |
+
+**Guardrails:**
+
+- Actions bevorzugt an **Blatt-Projects** oder direkt an Initiative (Warnung bei Container mit Kindern).
+- Gates (`roadmap_item_id`) an jeder Project-Tiefe oder Initiative — Plan/Ist in AP1.6.
+
+**Implementierung:** **AP1.5c** — Migration `014` o.ä.
+
+---
+
+### 2. Ausführungs-Ebene: rekursives **Task** (Haupthebel Granularität)
+
+- **`parent_task_id`** nullable auf `tasks` — gleiche Tabelle, Zeiger auf weitere Instanz.
+- **Max. Tiefe Schema:** 10 (Agent/API).
+- **Max. Tiefe UI (Menschen):** 3 Ebenen (Task → Subtask → Sub-Subtask) — **Policy**, kein Schema-Limit.
+- Roll-up: Action `done` wenn Task-Baum erfüllt (Regeln in AP1.5d); Task `done` wenn alle Kinder `done` oder explizit ohne Kinder.
+
+**Guardrails:**
+
+- **Steuerung bleibt auf Action** (Assignment, Blocker, Evidence, Next Action für Menschen).
+- Kein `steering_context` pro Task-Ebene.
+- Agenten: Blatt-Tasks als Ausführungsschritte; tiefe Bäume in UI **aggregiert** anzeigen.
+
+**Implementierung:** **AP1.5d** — **nach AP1.6** (Plan/Ist-Verknüpfung + Gate-Beitrag zuerst).
+
+---
+
+### 3. Action-Verschachtelung: **eingeschränkt**, nicht Default
+
+- **`parent_action_id`** nur für **`wbs_driven`** (später), max. Tiefe **2**.
+- Nur **Root-Action** aus Backlog-Commit; Kind-Actions = strukturelle Teilpakete desselben Commits.
+- Default-Vorhaben: **eine Action + Task-Baum** — kein Action-Baum.
+
+**Implementierung:** dokumentiert; Code **nicht** in AP1.5c/d — erst mit Methodenprofil / Structure Builder.
+
+---
+
+### 4. Steuerung: Vererbung, nicht Explosion
+
+**Stufe 1 (MVP bis AP1.6+):**
+
+```text
+Initiative     = einziger Steering-Root (steering_context, heute implementiert)
+Project*       = Struktur; erbt Initiative-Steuerung
+Action         = operative Steuerungs-Anker für Menschen (Assignment, Blocker, Evidence)
+Task*          = Ausführungsschritte; Roll-up, kein eigener Context
+```
+
+**Stufe 2 (später, Mega-Programme):**
+
+- Polymorpher `SteeringContext` (`scope_type`, `scope_id`) wie Target State.
+- Nur Projects mit `steering_root = true` oder explizitem Override — **nicht** jede Ebene.
+
+---
+
+## Schichtenmodell (Ziel)
+
+```text
+Initiative ── steering_context (Pflicht)
+│
+├── [optional] Project*                    parent_project_id
+│     └── Project* …
+│           └── Action                     Commit-Grenze (Root aus Backlog)
+│                 └── Task*                parent_task_id
+│                       └── Task* …
+│
+├── [optional] Gates (RoadmapItem)         orthogonal
+└── Backlog → Commit → Action (Root)
+```
+
+**Zwei orthogonale Dimensionen:**
+
+| Dimension | Rekursion | Mensch-Tiefe | Agent-Tiefe |
+|-----------|-----------|--------------|-------------|
+| Project (Organisation) | ja | 0–2 typisch | — |
+| Action (Arbeitspaket) | selten (WBS) | 1 | 1–2 |
+| Task (Ausführung) | ja | 2–3 | bis 10 |
+
+---
+
+## Repriorisierung (verbindlich)
+
+```text
+✓ AP1.5     Project, Task flach, Ausführung (0.14.0-ap1.5)
+→ AP1.5c    parent_project_id, Baum-UI, container_kind optional
+→ AP1.6     Plan/Ist-Verknüpfung, Journey
+→ AP1.5d    parent_task_id, Roll-up, UI-Tiefen-Policy
+⏸ AP1.4c   Gate-UI — weiter eingefroren
+→ AP1.4d    Gate-Graph
+→ AP1.7     Operational Actor Interface (unverändert)
+```
+
+AP1.5b (IA-Begriffe) kann parallel zu AP1.5c.
+
+---
+
+## Konsequenzen
+
+| Bereich | Konsequenz |
+|---------|------------|
+| Schema | Zwei Migrationen: Project-Baum, Task-Baum — getrennte APs |
+| UI | Baum/Outline statt nur flache Listen; Default collapsed ab Tiefe 2 |
+| API | Cycle-Detection; depth validation |
+| Tests | Klein (flach), Mega (Project-Tiefe 3), Agent (Task-Tiefe >3) |
+| Steering | Keine Änderung in AP1.5c/d außer Roll-up-Fortschritt |
+| Agent AP1.7 | Nutzt Task-Blätter; tiefe Zerlegung über AP1.5d |
+
+---
+
+## Risiko
+
+| Risiko | Mitigation |
+|--------|------------|
+| UI-Overload durch Tiefe | UI soft cap 3 Tasks; Mega-Projects collapsed |
+| Redundante Pfade (Project + Action + Task alle tief) | Guardrails + PO-Dokumentation |
+| Commit-Modell bei nested Actions | Nested Actions erst WBS-Profil; Default flach |
+| Steuerungs-Explosion | Stufe 1: nur Initiative-Context |
+
+---
+
+## Rückbaubarkeit
+
+- `parent_*_id` nullable — flache Nutzung bleibt Default.
+- `container_kind` optional — entfernbar ohne Schema-Bruch.
+- Polymorpher SteeringContext ist **Add-on**, kein Breaking Change für AP1.5c/d.
+
+---
+
+## Abnahme PO
+
+- [x] Rekursives Project statt Stream-Typ  
+- [x] Rekursives Task für Granularität (Mensch 2–3, Agent tiefer)  
+- [x] Steering-Root = Initiative (Stufe 1)  
+- [x] AP1.5c → AP1.6 → AP1.5d Reihenfolge  
+- [x] Implementierung AP1.5c  
+- [ ] Implementierung AP1.5d  
+
+---
+
+*Referenz: `Kairo_Corrected_MVP_Roadmap_v0.2.md` (Update 2026-07-06), `ADP_PO_Product_Layering_and_IA_Reset_v0.1.md`*

docs/product/Kairo_Corrected_MVP_Roadmap_v0.2.md

@@ -7,6 +7,7 @@
 **Vision:** `Kairo_Vision_and_Product_Direction_v0.2.md`  
 **Ist-Stand:** `Kairo_Implementation_Truth_Table_v0.1.md`  
 **PO-ADP:** `ADP_PO_Product_Layering_and_IA_Reset_v0.1.md`  
+**Container-ADP:** `ADP_Recursive_Containers_and_Execution_Granularity_v0.1.md`
 
 ---
 
@@ -28,8 +29,8 @@
 | Entscheidung | |
 |--------------|--|
 | AP1.4b Backend | ✓ behalten (Kriterien, Verify, Reopen) |
-| Gate-UI-Politur (Modal, Graph-Workflow) | ⏸ **eingefroren** bis AP1.5 |
+| Gate-UI-Politur (Modal, Graph-Workflow) | ⏸ **eingefroren** bis AP1.6 |
-| Nächstes Code-Paket | **AP1.5** Hierarchie + Ausführung als Ist-Kern |
+| Nächstes Code-Paket | **AP1.5c** rekursive Projects |
 | Tab „Plan“ | fachlich **Gates / Zielzustände** — Umbenennung AP1.5b |
 | Graph Engine AP1.4d | Gate-Kanten only — **kein** Lifecycle-Workflow |
 
@@ -37,6 +38,24 @@ Siehe `ADP_PO_Product_Layering_and_IA_Reset_v0.1.md`.
 
 ---
 
+## 1.2 PO-Entscheidung 2026-07-06 — Rekursive Container & Task-Tiefe
+
+**Auslöser:** Mega-Programme vs. normale Vorhaben; Granularität Mensch vs. Agent.
+
+| Entscheidung | |
+|--------------|--|
+| Stream als eigener Typ | **Nein** — `Project` mit `parent_project_id` + optionalem `container_kind` |
+| Project in Project | **Ja** — AP1.5c |
+| Task → Subtask → … | **Ja** — `parent_task_id`; UI max. ~3 Ebenen; Schema tiefer für Agenten — AP1.5d |
+| Nested Actions | **Optional** später (`wbs_driven` only); nicht Default |
+| Steuerung pro Ebene | **Nein (Stufe 1)** — Initiative-Root; Action = Anker für Menschen |
+
+Siehe `ADP_Recursive_Containers_and_Execution_Granularity_v0.1.md`.
+
+**Reihenfolge:** AP1.5c → AP1.6 → AP1.5d
+
+---
+
 ## 2. Phasenübersicht
 
 ```text
@@ -47,11 +66,12 @@ Phase C  Dokumentation Welle 1–2                 ✓
 Phase D  IA-Skeleton AP1.2 + AP1.2c              ✓
 Phase E  Steering AP1.2, AP1.3                   ◐
 Phase F  Gate-Backend AP1.4 + AP1.4b             ✓ (Backend); UI minimal
-Phase G  **Ist-Hierarchie AP1.5**                ← **NÄCHSTES CODE**
+Phase G  Ist-Hierarchie AP1.5                    ✓
-Phase H  Plan/Ist-Verknüpfung AP1.6             geplant
+Phase G2 Rekursive Container AP1.5c–5d           ✓ 5c / → 5d nach AP1.6
-Phase I  Gate-Graph AP1.4d–4e                    nach AP1.5
+Phase H  Plan/Ist-Verknüpfung AP1.6             ← **NÄCHSTES CODE**
+Phase I  Gate-Graph AP1.4d–4e                    nach AP1.6
 Phase J  Portfolio & Kontext AP1.8               geplant
-Phase K  Agent Interface AP1.7                   geplant
+Phase K  Agent Interface AP1.7                   geplant (unverändert)
 Phase L  Validation AP0.10d (laufend PO)          parallel
 ```
 
@@ -71,13 +91,15 @@ Phase L  Validation AP0.10d (laufend PO)          parallel
 | AP1.2c | 0.12.0-ap1.2c | IA-Skeleton |
 | AP1.4 | 0.13.0-ap1.4 | RoadmapItem / Gates Minimal |
 | AP1.4b | 0.13.1-ap1.4b | Gate-Checkliste Backend + Detail-Route |
+| AP1.5 | 0.14.0-ap1.5 | Project, Task flach, Ausführung-Tab |
 | DOC PO | 2026-07-06 | ADP Product Layering & IA-Reset |
+| DOC Container | 2026-07-06 | ADP Recursive Containers & Execution Granularity |
 
 ---
 
 ## 4. Nächste Pakete (verbindliche Reihenfolge — PO 2026-07-06)
 
-### AP1.5 — Hierarchie & Ist-Ebene (**NÄCHSTES CODE-PAKET**)
+### AP1.5 — Hierarchie & Ist-Ebene ✓
 
 **Ziel:** Operativer Plan zwischen Gates — Project, Task, Ausführung-Tab; Gates optional nutzbar.
 
@@ -94,6 +116,22 @@ Phase L  Validation AP0.10d (laufend PO)          parallel
 
 ---
 
+### AP1.5c — Rekursive Projects ✓
+
+**Ziel:** Project-Baum für Mega-Programme; normale Vorhaben unverändert flach.
+
+| Scope | |
+|-------|--|
+| `parent_project_id`, Zyklen-Check, max. Tiefe 5 |
+| Optional `container_kind` (Label) |
+| Baum-UI in Ausführung; Actions nur an Blatt-Projects |
+| **Kein** eigener Steering-Context pro Project |
+
+**ADP:** `ADP_Recursive_Containers_and_Execution_Granularity_v0.1.md`  
+**Version:** `0.14.1-ap1.5c`
+
+---
+
 ### AP1.5b — IA-Begriffe Gates vs. Ausführung
 
 | Scope | |
@@ -106,17 +144,35 @@ Phase L  Validation AP0.10d (laufend PO)          parallel
 
 ---
 
-### AP1.6 — Plan/Ist-Verknüpfung & Journey
+### AP1.6 — Plan/Ist-Verknüpfung & Journey (**NÄCHSTES CODE-PAKET**)
 
-Backlog/Action → RoadmapItem; Decision-Spur; Journey-Timeline.
+Backlog/Action/Project/Task → RoadmapItem; Decision-Spur; Journey-Timeline.
 
-**Nach AP1.5** — Gates bekommen Bedeutung durch Ist-Bezug.
+**Nach AP1.5c** — Gates bekommen Bedeutung durch Ist-Bezug (auch auf Project-Ebenen).
 
 **Version:** `0.15.0-ap1.6`
 
 ---
 
-### AP1.4c — Gate-UI-Politur ⏸ (eingefroren bis AP1.5)
+### AP1.5d — Rekursive Tasks & Roll-up
+
+**Ziel:** Task-Baum (`parent_task_id`); Mensch UI max. ~3 Ebenen; Agent tiefer.
+
+| Scope | |
+|-------|--|
+| Migration `parent_task_id`, Cycle/Depth-Validation |
+| Roll-up Status Action ↔ Task-Baum |
+| Gate-Beitrag auf Blatt-Tasks (Fortsetzung AP1.6) |
+| UI: Outline, collapsed default ab Tiefe 2 |
+| **Kein** nested Action (Default) |
+
+**ADP:** `ADP_Recursive_Containers_and_Execution_Granularity_v0.1.md`  
+**Nach AP1.6**  
+**Version:** `0.15.1-ap1.5d`
+
+---
+
+### AP1.4c — Gate-UI-Politur ⏸ (eingefroren bis AP1.6)
 
 Modal Gate anlegen/bearbeiten; Checkliste-UX; Fortschritt in Liste.
 
@@ -134,7 +190,7 @@ Modal Gate anlegen/bearbeiten; Checkliste-UX; Fortschritt in Liste.
 | Deprecate `sequencing_mode` am Item |
 | Read Models: blocked, ready, fulfillment_ratio |
 
-**Version:** `0.14.1-ap1.4d` (nach AP1.5)
+**Version:** `0.15.2-ap1.4d` (nach AP1.6)
 
 ---
 
@@ -204,7 +260,7 @@ Criteria, Waive/Defer, Reopen, Detail-Route. Version `0.13.1-ap1.4b`
 
 | Thema | Bis wann |
 |-------|----------|
-| Gate-UI-Politur (Modal, Graph-Workflow) | **Nach AP1.5** (PO 2026-07-06) |
+| Gate-UI-Politur (Modal, Graph-Workflow) | **Nach AP1.6** (PO 2026-07-06) |
 | Prompt/KI/MCP produktiv | Ist-Hierarchie + Plan/Ist |
 | Method Designer UI | AP1.3+ |
 | Gantt / Kalender | nach Plan/Ist |
@@ -230,12 +286,14 @@ MVP-nah wenn:
 0.12.0-ap1.2c  ✓ IA-Skeleton
 0.13.0-ap1.4   ✓ RoadmapItem / Gates Backend
 0.13.1-ap1.4b  ✓ Gate-Checkliste Backend
-0.14.0-ap1.5   → Hierarchie (Project, Task) — NÄCHSTES
+0.14.0-ap1.5   ✓ Hierarchie (Project, Task flach)
-0.15.0-ap1.6   → Journey / Plan-Ist
+0.14.1-ap1.5c  ✓ Rekursive Projects
-0.14.1-ap1.4d  → Gate-Graph (nach AP1.5)
+0.15.0-ap1.6   → Journey / Plan-Ist — NÄCHSTES
+0.15.1-ap1.5d  → Rekursive Tasks / Roll-up
+0.15.2-ap1.4d  → Gate-Graph
 0.16.0-ap1.7   → Agent Interface
 0.17.0-ap1.8   → Portfolio + Kontext
 ```
 ---
 
-*Siehe auch: `ADP_PO_Product_Layering_and_IA_Reset_v0.1.md`, `Sprint1_AP1_5_Hierarchy_Assignment_v0.1.md`, `Kairo_MVP_Usability_Recovery_Plan_v0.2.md`*
+*Siehe auch: `ADP_Recursive_Containers_and_Execution_Granularity_v0.1.md`, `ADP_PO_Product_Layering_and_IA_Reset_v0.1.md`, `Sprint1_AP1_5_Hierarchy_Assignment_v0.1.md`, `Kairo_MVP_Usability_Recovery_Plan_v0.2.md`*

docs/product/Kairo_Implementation_Truth_Table_v0.1.md

@@ -1,7 +1,7 @@
 # Kairo — Implementation Truth Table v0.1
 
 **Status:** living document — bei jedem AP aktualisieren  
-**Stand:** 2026-07-06 (nach AP1.5)  
+**Stand:** 2026-07-06 (nach AP1.5c)  
 **Zweck:** Ehrliche Trennung von **implementiert**, **teilweise**, **nur API/Schema**, **nur Dokumentiert**
 
 Verhindert, dass Zielbild-Dokumente als Ist-Stand gelesen werden.
@@ -30,7 +30,7 @@ Verhindert, dass Zielbild-Dokumente als Ist-Stand gelesen werden.
 | Capabilities | ✓ | Keine Objekt-Sichtbarkeit |
 | Auth / Session | ✓ | |
 | Audit (Auth/Admin) | ◐ | Nicht für alle OM-Events |
-| Migrationen nummeriert | ✓ | Schema 013 |
+| Migrationen nummeriert | ✓ | Schema 014 |
 
 ---
 
@@ -39,7 +39,7 @@ Verhindert, dass Zielbild-Dokumente als Ist-Stand gelesen werden.
 | Element | Stand | Anmerkung |
 |---------|-------|-----------|
 | Initiative | ✓ | |
-| Project | ◐ | AP1.5 GUI + API |
+| Project | ◐ | AP1.5 + AP1.5c: Baum (`parent_project_id`), Blatt-Regel für Actions |
 | Action | ✓ | UI: Arbeitspaket (interim Maßnahme) |
 | ActionAssignment | ✓ | |
 | BacklogItem | ✓ | |

frontend/src/components/ActionForm.jsx

@@ -1,6 +1,7 @@
 import { ACTION_STATUSES, PRIORITIES } from '../constants/status.js'
 import { ACTION_STATUS_LABELS, PRIORITY_LABELS } from '../constants/status.js'
 import { ActorSelect } from './ActorSelect.jsx'
+import { flattenLeafProjectOptions, getLeafProjects } from '../utils/projectTree.js'
 
 function isoToLocalInput(iso) {
   if (!iso) return ''
@@ -38,6 +39,8 @@ export function ActionForm({
   }
 
   const defaultActors = initial.assigned_actor_ids || []
+  const leafProjects = getLeafProjects(projects)
+  const projectOptions = flattenLeafProjectOptions(projects)
 
   return (
     <form className="form workspace-form" onSubmit={handleSubmit}>
@@ -77,14 +80,14 @@ export function ActionForm({
           defaultValue={isoToLocalInput(initial.due_at)}
         />
       </label>
-      {projects.length > 0 && (
+      {leafProjects.length > 0 && (
         <label>
-          Projekt (optional)
+          Projekt (optional, Blatt-Ebene)
           <select name="project_id" defaultValue={initial.project_id || ''}>
             <option value="">— keins —</option>
-            {projects.map((p) => (
+            {projectOptions.map(({ project, label }) => (
-              <option key={p.id} value={p.id}>
+              <option key={project.id} value={project.id}>
-                {p.title}
+                {label}
               </option>
             ))}
           </select>

frontend/src/components/ProjectsSection.jsx

@@ -1,6 +1,80 @@
-import { useState } from 'react'
+import { useMemo, useState } from 'react'
 import { EmptyState } from './EmptyState.jsx'
 import { StatusBadge } from './StatusBadge.jsx'
+import {
+  buildProjectsByParent,
+  containerKindLabel,
+  flattenProjectOptions,
+} from '../utils/projectTree.js'
+
+function ProjectTreeNodes({
+  projects,
+  parentId,
+  depth,
+  selectedProjectId,
+  onSelectProject,
+  canManage,
+  onDelete,
+  busy,
+}) {
+  const byParent = useMemo(() => buildProjectsByParent(projects), [projects])
+  const nodes = byParent.get(parentId || '') || []
+
+  if (nodes.length === 0) return null
+
+  return (
+    <ul className="project-tree-children">
+      {nodes.map((project) => (
+        <li key={project.id} className="project-tree-branch">
+          <div className="list-item card-list-item project-tree-item">
+            <div className="list-item-main">
+              <button
+                type="button"
+                className="link-button"
+                onClick={() =>
+                  onSelectProject(selectedProjectId === project.id ? '' : project.id)
+                }
+              >
+                <strong>{project.title}</strong>
+              </button>
+              {project.container_kind && (
+                <span className="project-kind-badge muted">
+                  {containerKindLabel(project.container_kind)}
+                </span>
+              )}
+              {project.description && (
+                <p className="list-item-desc muted">{project.description}</p>
+              )}
+            </div>
+            <div className="list-item-meta action-controls">
+              <StatusBadge kind="initiative" status={project.status} />
+              {canManage && (
+                <button
+                  type="button"
+                  className="btn btn-secondary"
+                  disabled={busy}
+                  onClick={() => onDelete(project.id)}
+                >
+                  Löschen
+                </button>
+              )}
+            </div>
+          </div>
+          <ProjectTreeNodes
+            projects={projects}
+            parentId={project.id}
+            depth={depth + 1}
+            selectedProjectId={selectedProjectId}
+            onSelectProject={onSelectProject}
+            canManage={canManage}
+            onDelete={onDelete}
+            busy={busy}
+          />
+        </li>
+      ))}
+    </ul>
+  )
+}
 
 export function ProjectsSection({
   projects,
@@ -13,37 +87,65 @@ export function ProjectsSection({
 }) {
   const [title, setTitle] = useState('')
   const [description, setDescription] = useState('')
+  const [parentProjectId, setParentProjectId] = useState('')
+  const [containerKind, setContainerKind] = useState('')
   const [showForm, setShowForm] = useState(false)
 
+  const parentOptions = useMemo(
+    () => flattenProjectOptions(projects),
+    [projects]
+  )
+
   async function handleSubmit(e) {
     e.preventDefault()
     if (!title.trim()) return
     await onCreate({
       title: title.trim(),
       description: description.trim(),
+      parent_project_id: parentProjectId || undefined,
+      container_kind: containerKind || undefined,
     })
     setTitle('')
     setDescription('')
+    setParentProjectId('')
+    setContainerKind('')
     setShowForm(false)
   }
 
+  function openFormUnderSelected() {
+    setParentProjectId(selectedProjectId || '')
+    setShowForm(true)
+  }
+
   return (
     <section className="card projects-section">
       <div className="section-header">
         <div>
           <h2>Projekte</h2>
           <p className="section-lead muted">
-            Operative Struktur — Arbeitspakete gruppieren. Zielzustände (Gates) sind optional.
+            Operative Struktur — verschachtelbar für große Vorhaben. Arbeitspakete nur an
+            Blatt-Projekten. Gates optional.
           </p>
         </div>
         {canManage && (
-          <button
+          <div className="section-header-actions">
-            type="button"
+            {selectedProjectId && (
-            className="btn btn-primary btn-block-mobile"
+              <button
-            onClick={() => setShowForm((v) => !v)}
+                type="button"
-          >
+                className="btn btn-secondary btn-block-mobile"
-            {showForm ? 'Abbrechen' : 'Projekt'}
+                onClick={openFormUnderSelected}
-          </button>
+              >
+                Unterprojekt
+              </button>
+            )}
+            <button
+              type="button"
+              className="btn btn-primary btn-block-mobile"
+              onClick={() => setShowForm((v) => !v)}
+            >
+              {showForm ? 'Abbrechen' : 'Projekt'}
+            </button>
+          </div>
         )}
       </div>
 
@@ -67,6 +169,32 @@ export function ProjectsSection({
               rows={2}
             />
           </label>
+          {parentOptions.length > 0 && (
+            <label>
+              Unter (optional)
+              <select
+                value={parentProjectId}
+                onChange={(e) => setParentProjectId(e.target.value)}
+              >
+                <option value="">— oberste Ebene —</option>
+                {parentOptions.map(({ project, label }) => (
+                  <option key={project.id} value={project.id}>
+                    {label}
+                  </option>
+                ))}
+              </select>
+            </label>
+          )}
+          <label>
+            Art (optional)
+            <select value={containerKind} onChange={(e) => setContainerKind(e.target.value)}>
+              <option value="">— Standard —</option>
+              <option value="project">Projekt</option>
+              <option value="stream">Stream</option>
+              <option value="phase">Phase</option>
+              <option value="release">Release</option>
+            </select>
+          </label>
           <button type="submit" className="btn btn-primary" disabled={busy}>
             Anlegen
           </button>
@@ -77,7 +205,7 @@ export function ProjectsSection({
         <EmptyState message="Noch keine Projekte — optional. Du kannst auch direkt Arbeitspakete anlegen." />
       )}
 
-      <ul className="item-list project-filter-list">
+      <ul className="item-list project-filter-list project-tree-list">
         <li className="list-item card-list-item">
           <button
             type="button"
@@ -87,38 +215,17 @@ export function ProjectsSection({
             Alle Arbeitspakete
           </button>
         </li>
-        {projects.map((project) => (
-          <li key={project.id} className="list-item card-list-item">
-            <div className="list-item-main">
-              <button
-                type="button"
-                className="link-button"
-                onClick={() =>
-                  onSelectProject(selectedProjectId === project.id ? '' : project.id)
-                }
-              >
-                <strong>{project.title}</strong>
-              </button>
-              {project.description && (
-                <p className="list-item-desc muted">{project.description}</p>
-              )}
-            </div>
-            <div className="list-item-meta action-controls">
-              <StatusBadge kind="initiative" status={project.status} />
-              {canManage && (
-                <button
-                  type="button"
-                  className="btn btn-secondary"
-                  disabled={busy}
-                  onClick={() => onDelete(project.id)}
-                >
-                  Löschen
-                </button>
-              )}
-            </div>
-          </li>
-        ))}
       </ul>
+      <ProjectTreeNodes
+        projects={projects}
+        parentId=""
+        depth={1}
+        selectedProjectId={selectedProjectId}
+        onSelectProject={onSelectProject}
+        canManage={canManage}
+        onDelete={onDelete}
+        busy={busy}
+      />
     </section>
   )
 }

frontend/src/context/InitiativeOperationsContext.jsx

@@ -67,6 +67,7 @@ import { listSteeringMethods, updateInitiativeSteeringMethod } from '../api/stee
 import { useCapabilities } from '../hooks/useCapabilities.js'
 import { useActors } from '../hooks/useActors.js'
 import { useSession } from './SessionContext.jsx'
+import { collectProjectSubtreeIds } from '../utils/projectTree.js'
 
 const InitiativeOperationsContext = createContext(null)
 
@@ -154,17 +155,25 @@ export function InitiativeOperationsProvider({ children }) {
     load()
   }, [load])
 
+  const selectedLeafProjectId = useMemo(() => {
+    if (!selectedProjectId) return ''
+    const match = projects.find((p) => p.id === selectedProjectId)
+    if (match?.is_leaf) return selectedProjectId
+    return ''
+  }, [selectedProjectId, projects])
+
   const visibleActions = useMemo(
     () => {
       let list = hideDone
         ? actions.filter((a) => a.status !== 'done' && a.status !== 'discarded')
         : actions
       if (selectedProjectId) {
-        list = list.filter((a) => a.project_id === selectedProjectId)
+        const subtreeIds = collectProjectSubtreeIds(projects, selectedProjectId)
+        list = list.filter((a) => a.project_id && subtreeIds.has(a.project_id))
       }
       return list
     },
-    [actions, hideDone, selectedProjectId]
+    [actions, hideDone, selectedProjectId, projects]
   )
 
   const actionContextById = useMemo(
@@ -200,7 +209,7 @@ export function InitiativeOperationsProvider({ children }) {
             : []
       await createInitiativeAction(id, {
         ...payload,
-        project_id: payload.project_id || selectedProjectId || undefined,
+        project_id: payload.project_id || selectedLeafProjectId || undefined,
         assigned_actor_ids: assigned,
       })
       setShowActionForm(false)

frontend/src/styles/components.css

@@ -426,6 +426,38 @@
   margin-bottom: 1rem;
 }
 
+.section-header-actions {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.5rem;
+  align-items: center;
+}
+
+.project-tree-list {
+  margin-bottom: 0;
+}
+
+.project-tree-children {
+  list-style: none;
+  margin: 0;
+  padding: 0 0 0 0.75rem;
+  border-left: 2px solid var(--jk-border, #e2e8f0);
+}
+
+.project-tree-branch {
+  list-style: none;
+  margin: 0.35rem 0 0;
+}
+
+.project-tree-item {
+  margin-left: 0;
+}
+
+.project-kind-badge {
+  font-size: 0.75rem;
+  margin-left: 0.35rem;
+}
+
 .section-header h2 {
   margin: 0;
   font-size: 1rem;

frontend/src/utils/projectTree.js

@@ -0,0 +1,80 @@
+/** AP1.5c — Project-Baum Hilfsfunktionen */
+
+const CONTAINER_KIND_LABELS = {
+  project: 'Projekt',
+  stream: 'Stream',
+  phase: 'Phase',
+  release: 'Release',
+}
+
+export function containerKindLabel(kind) {
+  if (!kind) return null
+  return CONTAINER_KIND_LABELS[kind] || kind
+}
+
+export function buildProjectsByParent(projects) {
+  const byParent = new Map()
+  for (const project of projects) {
+    const key = project.parent_project_id || ''
+    if (!byParent.has(key)) byParent.set(key, [])
+    byParent.get(key).push(project)
+  }
+  for (const list of byParent.values()) {
+    list.sort((a, b) => (a.sort_order ?? 0) - (b.sort_order ?? 0) || a.title.localeCompare(b.title))
+  }
+  return byParent
+}
+
+export function collectProjectSubtreeIds(projects, rootId) {
+  const byParent = buildProjectsByParent(projects)
+  const ids = new Set([rootId])
+  const stack = [rootId]
+  while (stack.length) {
+    const current = stack.pop()
+    for (const child of byParent.get(current) || []) {
+      if (!ids.has(child.id)) {
+        ids.add(child.id)
+        stack.push(child.id)
+      }
+    }
+  }
+  return ids
+}
+
+export function getLeafProjects(projects) {
+  const parentIds = new Set(
+    projects.map((p) => p.parent_project_id).filter(Boolean)
+  )
+  return projects.filter((p) => !parentIds.has(p.id))
+}
+
+export function projectOptionLabel(project, depth = 1) {
+  const prefix = depth > 1 ? `${'— '.repeat(depth - 1)}` : ''
+  const kind = containerKindLabel(project.container_kind)
+  const kindSuffix = kind ? ` (${kind})` : ''
+  return `${prefix}${project.title}${kindSuffix}`
+}
+
+export function flattenLeafProjectOptions(projects, parentId = '', depth = 1) {
+  const byParent = buildProjectsByParent(projects)
+  const result = []
+  for (const project of byParent.get(parentId) || []) {
+    const children = byParent.get(project.id) || []
+    if (children.length === 0) {
+      result.push({ project, depth, label: projectOptionLabel(project, depth) })
+    } else {
+      result.push(...flattenLeafProjectOptions(projects, project.id, depth + 1))
+    }
+  }
+  return result
+}
+
+export function flattenProjectOptions(projects, parentId = '', depth = 1) {
+  const byParent = buildProjectsByParent(projects)
+  const result = []
+  for (const project of byParent.get(parentId) || []) {
+    result.push({ project, depth, label: projectOptionLabel(project, depth) })
+    result.push(...flattenProjectOptions(projects, project.id, depth + 1))
+  }
+  return result
+}