diff --git a/src/soa_builder/web/app.py b/src/soa_builder/web/app.py
index 28c1077..57eb17d 100644
--- a/src/soa_builder/web/app.py
+++ b/src/soa_builder/web/app.py
@@ -57,6 +57,7 @@
     _migrate_instances_add_member_of_timeline,
     _migrate_matrix_cells_add_instance_id,
     _migrate_activity_concept_add_href,
+    _migrate_activity_concept_add_dss,
     _migrate_study_cell_add_order_index,
 )
 from .routers import activities as activities_router
@@ -155,6 +156,7 @@ def _configure_logging():
 # Database migration steps
 _migrate_study_cell_add_order_index()
 _migrate_activity_concept_add_href()
+_migrate_activity_concept_add_dss()
 _migrate_matrix_cells_add_instance_id()
 _migrate_instances_add_member_of_timeline()
 _migrate_timing_add_member_of_timeline()
@@ -186,6 +188,7 @@ def _configure_logging():
 app.include_router(elements_router.router)
 app.include_router(visits_router.router)
 app.include_router(activities_router.router)
+app.include_router(activities_router.ui_router)
 app.include_router(epochs_router.router)
 app.include_router(freezes_router.router)
 app.include_router(rollback_router.router)
diff --git a/src/soa_builder/web/initialize_database.py b/src/soa_builder/web/initialize_database.py
index 2e7e08f..50c2a97 100644
--- a/src/soa_builder/web/initialize_database.py
+++ b/src/soa_builder/web/initialize_database.py
@@ -179,7 +179,9 @@ def _init_db():
             study_cell_uid TEXT NOT NULL, --immutable StudyCell_N identifier unique within SOA
             arm_uid TEXT NOT NULL,
             epoch_uid TEXT NOT NULL,
-            element_uid TEXT NOT NULL
+            element_uid TEXT NOT NULL,
+            order_index INTEGER,
+            UNIQUE(soa_id, study_cell_uid)
         )"""
     )
 
diff --git a/src/soa_builder/web/migrate_database.py b/src/soa_builder/web/migrate_database.py
index b869a2b..547bbeb 100644
--- a/src/soa_builder/web/migrate_database.py
+++ b/src/soa_builder/web/migrate_database.py
@@ -997,6 +997,26 @@ def _migrate_activity_concept_add_href():
         logger.warning("activity_concept href migration failed: %s", e)
 
 
+def _migrate_activity_concept_add_dss():
+    """Add dss_title and dss_href columns to activity_concept for DSS assignment."""
+    try:
+        conn = _connect()
+        cur = conn.cursor()
+        cur.execute("PRAGMA table_info(activity_concept)")
+        cols = {r[1] for r in cur.fetchall()}
+        if "dss_title" not in cols:
+            cur.execute("ALTER TABLE activity_concept ADD COLUMN dss_title TEXT")
+            conn.commit()
+            logger.info("Added dss_title column to activity_concept table")
+        if "dss_href" not in cols:
+            cur.execute("ALTER TABLE activity_concept ADD COLUMN dss_href TEXT")
+            conn.commit()
+            logger.info("Added dss_href column to activity_concept table")
+        conn.close()
+    except Exception as e:
+        logger.warning("activity_concept dss migration failed: %s", e)
+
+
 def _migrate_study_cell_add_order_index():
     """Add order_index column to study_cell table to support reordering"""
     try:
diff --git a/src/soa_builder/web/routers/activities.py b/src/soa_builder/web/routers/activities.py
index e7c29d0..4d1beaf 100644
--- a/src/soa_builder/web/routers/activities.py
+++ b/src/soa_builder/web/routers/activities.py
@@ -7,7 +7,8 @@
 from typing import List
 
 from fastapi import APIRouter, HTTPException, Request, Form
-from fastapi.responses import JSONResponse, HTMLResponse
+from fastapi.responses import JSONResponse, HTMLResponse, RedirectResponse
+from fastapi.templating import Jinja2Templates
 
 from ..audit import _record_activity_audit, _record_reorder_audit
 from ..db import _connect
@@ -16,13 +17,18 @@
     soa_exists,
     table_has_columns as _table_has_columns,
     get_next_concept_uid as _get_next_concept_uid,
+    get_cdisc_api_key as _get_cdisc_api_key,
 )
 
 _ACT_CONCEPT_CACHE = {"data": None, "fetched_at": 0}
 _ACT_CONCEPT_TTL = 60 * 60
 
 router = APIRouter(prefix="/soa/{soa_id}")
+ui_router = APIRouter()
 logger = logging.getLogger("soa_builder.web.routers.activities")
+templates = Jinja2Templates(
+    directory=os.path.join(os.path.dirname(__file__), "..", "templates")
+)
 
 
 def fetch_biomedical_concepts(force: bool = False):
@@ -201,11 +207,10 @@ def ui_add_activity(
         raise HTTPException(404, "SOA not found")
     payload = ActivityCreate(name=name or "", label=label, description=description)
     add_activity(soa_id, payload)
+    redirect_url = f"/ui/soa/{int(soa_id)}/activities"
     if request.headers.get("HX-Request") == "true":
-        return HTMLResponse("", headers={"HX-Redirect": f"/ui/soa/{soa_id}/edit"})
-    return HTMLResponse(
-        f"<script>window.location='/ui/soa/{int(soa_id)}/edit';</script>"
-    )
+        return HTMLResponse("", headers={"HX-Redirect": redirect_url})
+    return HTMLResponse(f"<script>window.location='{redirect_url}';</script>")
 
 
 @router.patch("/activities/{activity_id}", response_class=JSONResponse)
@@ -301,11 +306,10 @@ def ui_update_activity(
     payload = ActivityUpdate(name=name, label=label, description=description)
     # Reuse the JSON handler for business logic/audit
     update_activity(soa_id, activity_id, payload)
+    redirect_url = f"/ui/soa/{int(soa_id)}/activities"
     if request.headers.get("HX-Request") == "true":
-        return HTMLResponse("", headers={"HX-Redirect": f"/ui/soa/{soa_id}/edit"})
-    return HTMLResponse(
-        f"<script>window.location='/ui/soa/{int(soa_id)}/edit';</script>"
-    )
+        return HTMLResponse("", headers={"HX-Redirect": redirect_url})
+    return HTMLResponse(f"<script>window.location='{redirect_url}';</script>")
 
 
 @router.post("/activities/reorder", response_class=JSONResponse)
@@ -502,3 +506,478 @@ def set_activity_concepts(soa_id: int, activity_id: int, concept_codes: List[str
     conn.commit()
     conn.close()
     return {"activity_id": activity_id, "concepts_set": inserted}
+
+
+# ---------------------------------------------------------------------------
+# UI routes (served via ui_router, no prefix)
+# ---------------------------------------------------------------------------
+
+
+def _reindex_activities(soa_id: int):
+    """Re-number order_index and activity_uid after a delete."""
+    conn = _connect()
+    cur = conn.cursor()
+    cur.execute(
+        "SELECT id FROM activity WHERE soa_id=? ORDER BY order_index", (soa_id,)
+    )
+    ids = [r[0] for r in cur.fetchall()]
+    for idx, _id in enumerate(ids, start=1):
+        cur.execute("UPDATE activity SET order_index=? WHERE id=?", (idx, _id))
+    cur.execute(
+        "UPDATE activity SET activity_uid = 'TMP_' || id WHERE soa_id=?", (soa_id,)
+    )
+    cur.execute(
+        "UPDATE activity SET activity_uid = 'Activity_' || order_index WHERE soa_id=?",
+        (soa_id,),
+    )
+    conn.commit()
+    conn.close()
+
+
+@ui_router.get("/ui/soa/{soa_id}/activities", response_class=HTMLResponse)
+def ui_list_activities(request: Request, soa_id: int):
+    if not soa_exists(soa_id):
+        raise HTTPException(404, "SOA not found")
+
+    conn = _connect()
+    cur = conn.cursor()
+    cur.execute(
+        "SELECT id,name,order_index,activity_uid,label,description FROM activity WHERE soa_id=? ORDER BY order_index",
+        (soa_id,),
+    )
+    activities = [
+        {
+            "id": r[0],
+            "name": r[1],
+            "order_index": r[2],
+            "activity_uid": r[3],
+            "label": r[4],
+            "description": r[5],
+        }
+        for r in cur.fetchall()
+    ]
+
+    # Fetch activity concepts for all activities in this SOA
+    activity_concepts: dict = {}
+    has_dss = _table_has_columns(cur, "activity_concept", ("dss_title",))
+    if _table_has_columns(cur, "activity_concept", ("soa_id",)):
+        if has_dss:
+            cur.execute(
+                "SELECT activity_id, concept_code, concept_title, dss_title, dss_href FROM activity_concept WHERE soa_id=?",
+                (soa_id,),
+            )
+        else:
+            cur.execute(
+                "SELECT activity_id, concept_code, concept_title FROM activity_concept WHERE soa_id=?",
+                (soa_id,),
+            )
+    else:
+        activity_ids = [a["id"] for a in activities]
+        if activity_ids:
+            placeholders = ",".join("?" * len(activity_ids))
+            if has_dss:
+                cur.execute(
+                    f"SELECT activity_id, concept_code, concept_title, dss_title, dss_href FROM activity_concept WHERE activity_id IN ({placeholders})",
+                    activity_ids,
+                )
+            else:
+                cur.execute(
+                    f"SELECT activity_id, concept_code, concept_title FROM activity_concept WHERE activity_id IN ({placeholders})",
+                    activity_ids,
+                )
+        else:
+            cur.execute("SELECT 1 WHERE 0")  # no-op
+    for row in cur.fetchall():
+        aid, code, title = row[0], row[1], row[2]
+        dss_title = row[3] if has_dss and len(row) > 3 else None
+        dss_href = row[4] if has_dss and len(row) > 4 else None
+        activity_concepts.setdefault(aid, []).append(
+            {
+                "code": code,
+                "title": title,
+                "dss_title": dss_title or "",
+                "dss_href": dss_href or "",
+            }
+        )
+    conn.close()
+
+    # Fetch biomedical concepts list (lazy import to avoid circular dependency)
+    from ..app import fetch_biomedical_concepts as _app_fetch_concepts
+    from ..app import fetch_sdtm_specializations as _app_fetch_dss
+
+    concepts = _app_fetch_concepts()
+    sdtm_specializations = _app_fetch_dss()
+
+    conn = _connect()
+    cur = conn.cursor()
+    cur.execute(
+        "SELECT study_id, study_label, study_description, name, created_at FROM soa WHERE id=?",
+        (soa_id,),
+    )
+    meta_row = cur.fetchone()
+    conn.close()
+    study_id, study_label, study_description, study_name, study_created_at = meta_row
+
+    return templates.TemplateResponse(
+        request,
+        "activities.html",
+        {
+            "request": request,
+            "soa_id": soa_id,
+            "activities": activities,
+            "activity_concepts": activity_concepts,
+            "concepts": concepts,
+            "sdtm_specializations": sdtm_specializations,
+            "study_id": study_id,
+            "study_label": study_label,
+            "study_description": study_description,
+            "study_name": study_name,
+        },
+    )
+
+
+@ui_router.post("/ui/soa/{soa_id}/activities/concepts_refresh")
+def ui_refresh_concepts_activities(request: Request, soa_id: int):
+    """Refresh biomedical concepts cache, then redirect back to activities page."""
+    if not soa_exists(soa_id):
+        raise HTTPException(404, "SOA not found")
+    from ..app import fetch_biomedical_concepts as _app_fetch_concepts
+
+    _app_fetch_concepts(force=True)
+    redirect_url = f"/ui/soa/{int(soa_id)}/activities"
+    if request.headers.get("HX-Request") == "true":
+        return HTMLResponse("", headers={"HX-Redirect": redirect_url})
+    return RedirectResponse(url=redirect_url, status_code=303)
+
+
+@ui_router.post("/ui/soa/{soa_id}/activities/create")
+def ui_create_activity(
+    request: Request,
+    soa_id: int,
+    name: str | None = Form(None),
+    label: str | None = Form(None),
+    description: str | None = Form(None),
+):
+    if not soa_exists(soa_id):
+        raise HTTPException(404, "SOA not found")
+    payload = ActivityCreate(name=name or "", label=label, description=description)
+    add_activity(soa_id, payload)
+    return RedirectResponse(url=f"/ui/soa/{int(soa_id)}/activities", status_code=303)
+
+
+@ui_router.post("/ui/soa/{soa_id}/activities/{activity_id}/delete")
+def ui_delete_activity_page(request: Request, soa_id: int, activity_id: int):
+    if not soa_exists(soa_id):
+        raise HTTPException(404, "SOA not found")
+    conn = _connect()
+    cur = conn.cursor()
+    cur.execute(
+        "SELECT id,name,order_index FROM activity WHERE id=? AND soa_id=?",
+        (activity_id, soa_id),
+    )
+    row = cur.fetchone()
+    if not row:
+        conn.close()
+        raise HTTPException(404, "Activity not found")
+    before = {"id": row[0], "name": row[1], "order_index": row[2]}
+    cur.execute(
+        "DELETE FROM matrix_cells WHERE soa_id=? AND activity_id=?",
+        (soa_id, activity_id),
+    )
+    cur.execute(
+        "DELETE FROM activity_concept WHERE activity_id=? AND soa_id=?",
+        (activity_id, soa_id),
+    )
+    cur.execute("DELETE FROM activity WHERE id=?", (activity_id,))
+    conn.commit()
+    conn.close()
+    _reindex_activities(soa_id)
+    _record_activity_audit(soa_id, "delete", activity_id, before=before, after=None)
+    return RedirectResponse(url=f"/ui/soa/{int(soa_id)}/activities", status_code=303)
+
+
+# ---------------------------------------------------------------------------
+# DSS assignment endpoints
+# ---------------------------------------------------------------------------
+
+
+def _render_dss_cell(request, soa_id, activity_id):
+    """Helper: render the dss_cell.html partial for a single activity."""
+    conn = _connect()
+    cur = conn.cursor()
+    has_dss = _table_has_columns(cur, "activity_concept", ("dss_title",))
+    if _table_has_columns(cur, "activity_concept", ("soa_id",)):
+        if has_dss:
+            cur.execute(
+                "SELECT concept_code, concept_title, dss_title, dss_href FROM activity_concept WHERE activity_id=? AND soa_id=?",
+                (activity_id, soa_id),
+            )
+        else:
+            cur.execute(
+                "SELECT concept_code, concept_title FROM activity_concept WHERE activity_id=? AND soa_id=?",
+                (activity_id, soa_id),
+            )
+    else:
+        if has_dss:
+            cur.execute(
+                "SELECT concept_code, concept_title, dss_title, dss_href FROM activity_concept WHERE activity_id=?",
+                (activity_id,),
+            )
+        else:
+            cur.execute(
+                "SELECT concept_code, concept_title FROM activity_concept WHERE activity_id=?",
+                (activity_id,),
+            )
+    concepts_list = []
+    for row in cur.fetchall():
+        code, title = row[0], row[1]
+        dss_title = row[2] if has_dss and len(row) > 2 else None
+        dss_href = row[3] if has_dss and len(row) > 3 else None
+        concepts_list.append(
+            {
+                "code": code,
+                "title": title,
+                "dss_title": dss_title or "",
+                "dss_href": dss_href or "",
+            }
+        )
+    conn.close()
+
+    from ..app import fetch_sdtm_specializations as _app_fetch_dss
+
+    sdtm_specializations = _app_fetch_dss()
+    activity_concepts = {activity_id: concepts_list}
+    html = templates.get_template("dss_cell.html").render(
+        request=request,
+        soa_id=soa_id,
+        activity_id=activity_id,
+        activity_concepts=activity_concepts,
+        sdtm_specializations=sdtm_specializations,
+    )
+    return HTMLResponse(html)
+
+
+@ui_router.post(
+    "/ui/soa/{soa_id}/activity/{activity_id}/concept/{concept_code}/dss",
+    response_class=HTMLResponse,
+)
+def ui_save_dss_assignment(
+    request: Request,
+    soa_id: int,
+    activity_id: int,
+    concept_code: str,
+    dss_selection: str = Form(""),
+):
+    """Save a DSS assignment for a specific concept on an activity."""
+    if not soa_exists(soa_id):
+        raise HTTPException(404, "SOA not found")
+
+    conn = _connect()
+    cur = conn.cursor()
+    cur.execute("SELECT 1 FROM activity WHERE id=? AND soa_id=?", (activity_id, soa_id))
+    if not cur.fetchone():
+        conn.close()
+        raise HTTPException(404, "Activity not found")
+
+    # Capture before state
+    old_title, old_href = None, None
+    if _table_has_columns(cur, "activity_concept", ("dss_title",)):
+        if _table_has_columns(cur, "activity_concept", ("soa_id",)):
+            cur.execute(
+                "SELECT dss_title, dss_href FROM activity_concept WHERE activity_id=? AND concept_code=? AND soa_id=?",
+                (activity_id, concept_code, soa_id),
+            )
+        else:
+            cur.execute(
+                "SELECT dss_title, dss_href FROM activity_concept WHERE activity_id=? AND concept_code=?",
+                (activity_id, concept_code),
+            )
+        before_row = cur.fetchone()
+        if before_row:
+            old_title, old_href = before_row[0], before_row[1]
+
+    # Parse selection value (datasetSpecializationId||href or empty)
+    new_title, new_href = None, None
+    selection = dss_selection.strip()
+    if selection and "||" in selection:
+        parts = selection.split("||", 1)
+        new_title, new_href = parts[0], parts[1]
+
+    # Update
+    if _table_has_columns(cur, "activity_concept", ("soa_id",)):
+        cur.execute(
+            "UPDATE activity_concept SET dss_title=?, dss_href=? WHERE activity_id=? AND concept_code=? AND soa_id=?",
+            (new_title, new_href, activity_id, concept_code, soa_id),
+        )
+    else:
+        cur.execute(
+            "UPDATE activity_concept SET dss_title=?, dss_href=? WHERE activity_id=? AND concept_code=?",
+            (new_title, new_href, activity_id, concept_code),
+        )
+    conn.commit()
+    conn.close()
+
+    # Audit
+    _record_activity_audit(
+        soa_id,
+        "update_dss",
+        activity_id,
+        before={
+            "concept_code": concept_code,
+            "dss_title": old_title,
+            "dss_href": old_href,
+        },
+        after={
+            "concept_code": concept_code,
+            "dss_title": new_title,
+            "dss_href": new_href,
+        },
+    )
+
+    return _render_dss_cell(request, soa_id, activity_id)
+
+
+@ui_router.get(
+    "/ui/soa/{soa_id}/activity/{activity_id}/dss_cell",
+    response_class=HTMLResponse,
+)
+def ui_get_dss_cell(request: Request, soa_id: int, activity_id: int):
+    """Return the DSS cell partial for an activity."""
+    if not soa_exists(soa_id):
+        raise HTTPException(404, "SOA not found")
+    return _render_dss_cell(request, soa_id, activity_id)
+
+
+@ui_router.get(
+    "/ui/soa/{soa_id}/dss/detail",
+    response_class=HTMLResponse,
+)
+def ui_dss_detail(request: Request, soa_id: int, href: str = "", title: str = ""):
+    """Detail page for a single DSS, fetched by href."""
+    if not soa_exists(soa_id):
+        raise HTTPException(404, "SOA not found")
+
+    import requests as _requests
+
+    api_key = _get_cdisc_api_key()
+    subscription_key = os.environ.get("CDISC_SUBSCRIPTION_KEY")
+    unified_key = subscription_key or api_key
+    headers: dict = {}
+    if unified_key:
+        headers["Ocp-Apim-Subscription-Key"] = unified_key
+    if api_key:
+        headers["Authorization"] = f"Bearer {api_key}"
+        headers["api-key"] = api_key
+
+    _ALLOWED_CDISC_PREFIX = "https://api.library.cdisc.org/"
+
+    status = None
+    error = None
+    pretty_json = None
+    raw_text_snippet = None
+    data = None
+    if href:
+        if not href.startswith(_ALLOWED_CDISC_PREFIX):
+            error = "Invalid href: only CDISC Library API URLs are permitted."
+            return templates.TemplateResponse(
+                "dss_detail.html",
+                {
+                    "request": request,
+                    "soa_id": soa_id,
+                    "href": href,
+                    "title": title,
+                    "status": status,
+                    "error": error,
+                    "pretty_json": pretty_json,
+                    "variables": [],
+                    "summary": {},
+                },
+            )
+        try:
+            resp = _requests.get(href, headers=headers, timeout=15)
+            status = resp.status_code
+            raw_text_snippet = resp.text[:500]
+            if resp.status_code == 200:
+                try:
+                    data = resp.json()
+                except ValueError:
+                    error = "200 OK but response was not valid JSON"
+                    data = None
+                if data is not None:
+                    try:
+                        pretty_json = json.dumps(data, indent=2, sort_keys=True)
+                    except Exception:
+                        pretty_json = json.dumps(data, indent=2)
+            else:
+                error = f"HTTP {resp.status_code} retrieving specialization"
+        except Exception as e:
+            error = f"Fetch error: {e}"[:300]
+    else:
+        error = "No href provided."
+
+    # Extract variables list and summary fields for structured display
+    variables = []
+    summary = {}
+    if data and isinstance(data, dict):
+        variables = data.get("variables", [])
+        for key in (
+            "datasetSpecializationId",
+            "domain",
+            "shortName",
+            "source",
+            "sdtmigStartVersion",
+            "sdtmigEndVersion",
+        ):
+            val = data.get(key)
+            if val is not None and val != "":
+                summary[key] = val
+        # Nested objects: check top-level and _links
+        links = data.get("_links", {})
+        pbc = data.get("parentBiomedicalConcept") or links.get(
+            "parentBiomedicalConcept"
+        )
+        if isinstance(pbc, dict):
+            parts = []
+            if pbc.get("shortName"):
+                parts.append(pbc["shortName"])
+            elif pbc.get("title"):
+                parts.append(pbc["title"])
+            if pbc.get("conceptId"):
+                parts.append(f"({pbc['conceptId']})")
+            if parts:
+                summary["parentBiomedicalConcept"] = " ".join(parts)
+        ppkg = data.get("parentPackage") or links.get("parentPackage")
+        if isinstance(ppkg, dict):
+            parts = []
+            if ppkg.get("name"):
+                parts.append(ppkg["name"])
+            elif ppkg.get("title"):
+                parts.append(ppkg["title"])
+            if ppkg.get("type"):
+                parts.append(f"[{ppkg['type']}]")
+            if parts:
+                summary["parentPackage"] = " ".join(parts)
+            ppkg_href = ppkg.get("href", "")
+            if ppkg_href and not ppkg_href.startswith("http"):
+                ppkg_href = f"https://api.library.cdisc.org{ppkg_href}"
+            if ppkg_href:
+                summary["parentPackageHref"] = ppkg_href
+
+    return templates.TemplateResponse(
+        request,
+        "sdtm_specialization_detail.html",
+        {
+            "index": 0,
+            "title": title or "(untitled)",
+            "href": href,
+            "status": status,
+            "error": error,
+            "pretty_json": pretty_json,
+            "raw_text_snippet": raw_text_snippet,
+            "missing_key": unified_key is None,
+            "total": 1,
+            "back_url": f"/ui/soa/{soa_id}/activities",
+            "summary": summary,
+            "variables": variables,
+        },
+    )
diff --git a/src/soa_builder/web/templates/activities.html b/src/soa_builder/web/templates/activities.html
new file mode 100644
index 0000000..e595f3e
--- /dev/null
+++ b/src/soa_builder/web/templates/activities.html
@@ -0,0 +1,146 @@
+{% extends 'base.html' %}
+{% block content %}
+<h2>Activities for Study: {% if study_label %}{{ study_label }}{% else %}{{ study_name }}{% endif %}</h2>
+
+<div style="margin-bottom:12px;">
+    <a href="/ui/soa/{{ soa_id }}/edit" style="background:#455a64;color:#fff;text-decoration:none;padding:4px 10px;border-radius:4px;font-size:0.9em;display:inline-block;">
+        &larr; Return to Edit Page
+    </a>
+</div>
+
+<div style="margin:4px 0 12px 0;display:flex;align-items:center;gap:10px;flex-wrap:wrap;">
+    <form hx-post="/ui/soa/{{ soa_id }}/activities/concepts_refresh" style="display:inline;">
+        <button type="submit" style="background:#455a64;color:#fff;border:none;padding:4px 10px;border-radius:4px;cursor:pointer;font-size:0.8em;">&#x21bb; Refresh Biomedical Concepts</button>
+    </form>
+    <small style="color:#555;">(forces remote re-fetch &amp; cache reset)</small>
+</div>
+
+<div style="margin-bottom:12px">
+    <form method="post" action="/ui/soa/{{ soa_id }}/activities/create" style="display:flex;flex-wrap:wrap;gap:6px;align-items:flex-end;">
+        <div style="display:flex;flex-direction:column;gap:2px;">
+            <label><strong>Name *</strong></label>
+            <input name="name" placeholder="Activity Name" required />
+        </div>
+        <div style="display:flex;flex-direction:column;gap:2px;">
+            <label><strong>Label</strong></label>
+            <input name="label" placeholder="Label (optional)" />
+        </div>
+        <div style="display:flex;flex-direction:column;gap:2px;">
+            <label><strong>Description</strong></label>
+            <input name="description" placeholder="Description (optional)" />
+        </div>
+        <button style="background:#1976d2;color:#fff;border:none;padding:4px 10px;border-radius:4px;cursor:pointer;">Create Activity</button>
+    </form>
+</div>
+
+<table id="activities-table" style="width:100%;font-size:0.85em;border-collapse:collapse;">
+    <tr style="background:#eee;">
+        <th title="Unique Activity ID" style="text-align:left;padding:4px;">ID</th>
+        <th title="Activity Name" style="text-align:left;padding:4px;">Name</th>
+        <th title="Activity Label" style="text-align:left;padding:4px;">Label</th>
+        <th title="Activity Description" style="text-align:left;padding:4px;">Description</th>
+        <th title="Save Changes" style="text-align:left;padding:4px;">Save</th>
+        <th title="Biomedical Concepts" style="text-align:left;padding:4px;">Concepts</th>
+        <th title="Data Set Specializations" style="text-align:left;padding:4px;">DSS</th>
+        <th title="Delete Activity" style="text-align:left;padding:4px;">Delete</th>
+        <th title="Save Order" style="text-align:left;padding:4px;">
+            <button type="button"
+                    id="save-activity-order-btn"
+                    data-soa-id="{{ soa_id }}"
+                    style="background:#1976d2;color:#fff;border:none;padding:2px 6px;border-radius:3px;cursor:pointer;font-size:0.85em;">
+                Save Order
+            </button>
+        </th>
+    </tr>
+    {% for a in activities %}
+    <tr data-activity-id="{{ a.id }}">
+        <form method="post" action="/ui/soa/{{ soa_id }}/activities/{{ a.id }}/update">
+            <td style="padding:4px;white-space:nowrap;"><strong>{{ a.activity_uid }}</strong></td>
+            <td style="padding:4px;"><input name="name" value="{{ a.name }}" required /></td>
+            <td style="padding:4px;"><input name="label" value="{{ a.label or '' }}" placeholder="Label" /></td>
+            <td style="padding:4px;"><input name="description" value="{{ a.description or '' }}" placeholder="Description" /></td>
+            <td style="padding:4px;">
+                <button style="background:#607d8b;color:#fff;border:none;padding:2px 6px;border-radius:3px;cursor:pointer;">Save</button>
+            </td>
+        </form>
+        {% set concepts_list = activity_concepts.get(a.id, []) %}
+        {% set selected_list = concepts_list %}
+        {% set selected_codes = concepts_list | map(attribute='code') | list %}
+        {% set activity_id = a.id %}
+        {% include 'concepts_cell.html' %}
+        {% set activity_id = a.id %}
+        {% include 'dss_cell.html' %}
+        <td style="padding:4px;">
+            <form method="post" action="/ui/soa/{{ soa_id }}/activities/{{ a.id }}/delete">
+                <button style="background:#c62828;color:#fff;border:none;padding:2px 6px;border-radius:3px;cursor:pointer;">
+                Delete
+                </button>
+            </form>
+        </td>
+        <td style="padding:4px;white-space:nowrap;">
+            <button type="button" onclick="moveActivityRow(this, -1)">&uarr;</button>
+            <button type="button" onclick="moveActivityRow(this, 1)">&darr;</button>
+        </td>
+    </tr>
+    {% else %}
+    <tr><td colspan="9" style="padding:6px;color:#777;">No activities yet.</td></tr>
+    {% endfor %}
+</table>
+
+<script>
+document.addEventListener('DOMContentLoaded', function () {
+    var btn = document.getElementById('save-activity-order-btn');
+    if (btn) {
+        btn.addEventListener('click', function () {
+            var soaId = btn.getAttribute('data-soa-id');
+            saveActivityOrder(soaId);
+        });
+    }
+});
+
+function moveActivityRow(button, dir) {
+    var row = button.closest ? button.closest('tr') : button.parentNode.parentNode;
+    if (!row) return;
+    var table = document.getElementById('activities-table');
+    if (!table) return;
+    var tbody = table.tBodies[0] || table;
+
+    if (dir < 0) {
+        var prev = row.previousElementSibling;
+        if (prev && prev.querySelector && prev.querySelector('td')) {
+            tbody.insertBefore(row, prev);
+        }
+    } else {
+        var next = row.nextElementSibling;
+        if (next) {
+            tbody.insertBefore(next, row);
+        }
+    }
+}
+
+function saveActivityOrder(soaId) {
+    var rows = document.querySelectorAll('#activities-table tr[data-activity-id]');
+    var order = [];
+    for (var i = 0; i < rows.length; i++) {
+        var id = parseInt(rows[i].getAttribute('data-activity-id'), 10);
+        if (!isNaN(id)) {
+            order.push(id);
+        }
+    }
+
+    var xhr = new XMLHttpRequest();
+    xhr.open('POST', '/soa/' + soaId + '/activities/reorder');
+    xhr.setRequestHeader('Content-Type', 'application/json;charset=UTF-8');
+    xhr.onreadystatechange = function () {
+        if (xhr.readyState === 4) {
+            if (xhr.status >= 200 && xhr.status < 300) {
+                window.location.reload();
+            } else {
+                alert('Reorder failed: ' + xhr.responseText);
+            }
+        }
+    };
+    xhr.send(JSON.stringify({ order: order }));
+}
+</script>
+{% endblock %}
diff --git a/src/soa_builder/web/templates/base.html b/src/soa_builder/web/templates/base.html
index 4ef0612..b29210a 100644
--- a/src/soa_builder/web/templates/base.html
+++ b/src/soa_builder/web/templates/base.html
@@ -10,6 +10,7 @@
     <div class="sidenav">
       <a href="/">Home</a>
       {% if soa_id %}
+        <a href="/ui/soa/{{ soa_id }}/activities">Activities</a>
         <a href="/ui/soa/{{ soa_id }}/schedule_timelines">Schedule Timelines</a>
         <a href="/ui/soa/{{ soa_id }}/timings">Study Timing</a>
         <a href="/ui/soa/{{ soa_id }}/instances">Scheduled Activity Instances</a>
diff --git a/src/soa_builder/web/templates/concepts_cell.html b/src/soa_builder/web/templates/concepts_cell.html
index bdf2cc7..7f98978 100644
--- a/src/soa_builder/web/templates/concepts_cell.html
+++ b/src/soa_builder/web/templates/concepts_cell.html
@@ -5,16 +5,16 @@
   {% if edit %}
     <form hx-post="/ui/soa/{{ soa_id }}/activity/{{ activity_id }}/concepts" hx-target="#concepts-cell-{{ cell_id_suffix }}" hx-swap="outerHTML" style="margin:0;">
       <div style="margin-bottom:4px;">
-        <input type="text" class="concept-search-inline" placeholder="Filter concepts..." style="width:200px;padding:2px 4px;font-size:0.6em;" />
+        <input type="text" class="concept-search-inline" placeholder="Filter concepts..." style="width:200px;padding:2px 4px;font-size:0.8em;" />
       </div>
-      <select name="concept_codes" multiple size="6" class="concept-select-inline" style="min-width:200px;font-size:0.65em;">
+      <select name="concept_codes" multiple size="6" class="concept-select-inline" style="min-width:200px;font-size:0.8em;">
         {% for c in concepts %}
           <option value="{{ c.code }}" {% if c.code in selected_codes %}selected{% endif %}>{{ c.title }}</option>
         {% endfor %}
       </select> 
       <div style="margin-top:4px;display:flex;gap:6px;">
-        <button type="submit" class="small-btn" style="font-size:0.6em;">Save</button>
-        <button type="button" class="refresh-btn" hx-get="/ui/soa/{{ soa_id }}/activity/{{ activity_id }}/concepts_cell" hx-target="#concepts-cell-{{ cell_id_suffix }}" hx-swap="outerHTML" style="font-size:0.6em;">Cancel</button>
+        <button type="submit" class="small-btn" style="font-size:0.8em;">Save</button>
+        <button type="button" class="refresh-btn" hx-get="/ui/soa/{{ soa_id }}/activity/{{ activity_id }}/concepts_cell" hx-target="#concepts-cell-{{ cell_id_suffix }}" hx-swap="outerHTML" style="font-size:0.8em;">Cancel</button>
       </div>
     </form>
     <script>
@@ -34,7 +34,7 @@
       })();
     </script>
   {% else %}
-  <div style="max-width:320px;">
+  <div style="max-width:250px;">
     
     <!-- Clickable header -->
     <div class="concepts-toggle"
@@ -50,8 +50,8 @@
     <div class="concepts-content" id="concepts-content-{{ cell_id_suffix }}" style="display:none;margin-top:4px;">
       {% if selected_list %}
         {% for ac in selected_list %}
-          <div class="concept-line" style="display:flex;align-items:center;justify-content:space-between;background:#eef;color:#224;margin:2px 0;padding:2px 5px;border-radius:3px;font-size:0.6em;">
-            <span class="concept-title" title="{{ ac.code }}" style="flex:1;">{{ ac.title }}</span>
+          <div class="concept-line" style="display:flex;align-items:center;justify-content:space-between;background:#eef;color:#224;margin:2px 0;padding:2px 5px;border-radius:3px;font-size:0.8em;">
+            <span class="concept-title" title="{{ ac.code }}" style="flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;">{{ ac.title }}</span>
             <form hx-post="/ui/soa/{{ soa_id }}/activity/{{ activity_id }}/concepts/remove"
                   hx-target="#concepts-cell-{{ cell_id_suffix }}"
                   hx-swap="outerHTML"
@@ -62,7 +62,7 @@
           </div>
         {% endfor %}
       {% else %}
-        <div class="no-concepts" style="color:#888;font-size:0.6em;">–</div>
+        <div class="no-concepts" style="color:#888;font-size:0.8em;">–</div>
       {% endif %}
     </div>
 
@@ -72,7 +72,7 @@
             hx-target="#concepts-cell-{{ cell_id_suffix }}"
             hx-swap="outerHTML"
             style="display:flex;align-items:center;gap:4px;margin:0;">
-        <select name="concept_code" style="font-size:0.6em;max-width:160px;">
+        <select name="concept_code" style="font-size:0.8em;max-width:160px;">
           <option value="" disabled selected>Add concept...</option>
           {% for c in concepts %}
             {% if c.code not in selected_codes %}
@@ -80,7 +80,7 @@
             {% endif %}
           {% endfor %}
         </select>
-        <button type="submit" style="font-size:0.55em;">+</button>
+        <button type="submit" style="font-size:0.7em;">+</button>
       </form>
 
       <button type="button"
@@ -88,7 +88,7 @@
               hx-get="/ui/soa/{{ soa_id }}/activity/{{ activity_id }}/concepts_cell?edit=1"
               hx-target="#concepts-cell-{{ cell_id_suffix }}"
               hx-swap="outerHTML"
-              style="background:#455a64;color:#fff;border:none;padding:2px 5px;cursor:pointer;font-size:0.55em;border-radius:3px;"
+              style="background:#455a64;color:#fff;border:none;padding:2px 5px;cursor:pointer;font-size:0.7em;border-radius:3px;"
               title="Bulk select concepts">
         Bulk
       </button>
@@ -105,7 +105,7 @@
   gap: 6px;
   cursor: pointer;
   font-weight: 600;
-  font-size: 0.65em;
+  font-size: 0.8em;
   color: #1976d2;
   user-select: none;
 }
@@ -123,7 +123,7 @@
 }
 
 .concepts-arrow {
-  margin-left: auto;
+  margin-left: 4px;
   font-size: 0.75em;
 }
 </style>
diff --git a/src/soa_builder/web/templates/dss_cell.html b/src/soa_builder/web/templates/dss_cell.html
new file mode 100644
index 0000000..7994e56
--- /dev/null
+++ b/src/soa_builder/web/templates/dss_cell.html
@@ -0,0 +1,94 @@
+{# Partial for DSS assignment cell — one row per concept code with DSS dropdown #}
+<td id="dss-cell-{{ activity_id }}" style="padding:4px;vertical-align:top;max-width:280px;">
+  {% set dss_concepts = activity_concepts.get(activity_id, []) %}
+  {% if dss_concepts %}
+    {% set assigned_count = dss_concepts | selectattr('dss_title') | list | length %}
+
+    <!-- Clickable header -->
+    <div class="concepts-toggle" onclick="toggleDss('{{ activity_id }}')">
+      <span class="concepts-label">Specializations</span>
+      {% if assigned_count > 0 %}
+        <span class="concept-count-pill">{{ assigned_count }}</span>
+      {% endif %}
+      <span class="concepts-arrow">▸</span>
+    </div>
+
+    <!-- Collapsible content -->
+    <div id="dss-content-{{ activity_id }}" style="display:none;margin-top:4px;">
+      {% for ac in dss_concepts %}
+        <div style="display:flex;align-items:center;gap:4px;margin:2px 0;font-size:0.8em;">
+          <span title="{{ ac.title }}" style="background:#eef;color:#224;padding:1px 4px;border-radius:3px;white-space:nowrap;min-width:70px;text-align:center;display:inline-block;">{{ ac.code }}</span>
+          {% if ac.dss_title %}
+            {# Assigned — show DSS name as pill + clear/properties controls #}
+            {% set ns = namespace(dss_display=ac.dss_title) %}
+            {% for d in sdtm_specializations %}
+              {% if d.href.rstrip('/').split('/')|last == ac.dss_title %}
+                {% set ns.dss_display = d.title %}
+              {% endif %}
+            {% endfor %}
+            <span title="{{ ac.dss_title }}" style="background:#eef;color:#224;padding:2px 5px;border-radius:3px;min-width:160px;max-width:160px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;">{{ ns.dss_display }}</span>
+            <form hx-post="/ui/soa/{{ soa_id }}/activity/{{ activity_id }}/concept/{{ ac.code }}/dss"
+                  hx-target="#dss-cell-{{ activity_id }}"
+                  hx-swap="outerHTML"
+                  style="margin:0;display:inline;">
+              <input type="hidden" name="dss_selection" value="" />
+              <button type="submit" style="font-size:0.7em;" title="Clear DSS">&minus;</button>
+            </form>
+            <a href="/ui/soa/{{ soa_id }}/dss/detail?href={{ ac.dss_href|urlencode }}&title={{ ac.dss_title|urlencode }}"
+               style="font-size:0.7em;margin-left:4px;">properties</a>
+          {% else %}
+            {# Not assigned — show dropdown + button #}
+            <form hx-post="/ui/soa/{{ soa_id }}/activity/{{ activity_id }}/concept/{{ ac.code }}/dss"
+                  hx-target="#dss-cell-{{ activity_id }}"
+                  hx-swap="outerHTML"
+                  style="margin:0;display:flex;align-items:center;gap:4px;">
+              <select name="dss_selection"
+                      style="font-size:1em;max-width:160px;">
+                <option value="" disabled selected>Select DSS...</option>
+                {% for d in sdtm_specializations %}
+                  {% set dss_id = d.href.rstrip('/').split('/')|last %}
+                  <option value="{{ dss_id }}||{{ d.href }}">
+                    {{ d.title }}
+                  </option>
+                {% endfor %}
+              </select>
+              <button type="submit" style="font-size:0.7em;">+</button>
+            </form>
+          {% endif %}
+        </div>
+      {% endfor %}
+    </div>
+  {% else %}
+    <span style="color:#888;font-size:0.6em;">&ndash;</span>
+  {% endif %}
+</td>
+
+<script>
+function toggleDss(activityId) {
+  const content = document.getElementById("dss-content-" + activityId);
+  if (!content) return;
+  const header = content.previousElementSibling;
+  const arrow = header.querySelector(".concepts-arrow");
+  const open = content.style.display === "block";
+  content.style.display = open ? "none" : "block";
+  arrow.textContent = open ? "▸" : "▾";
+}
+if (!window._dssSettleListenerAdded) {
+  window._dssSettleListenerAdded = true;
+  document.addEventListener("htmx:afterSettle", function(evt) {
+    var target = evt.detail.target;
+    if (target && target.id && target.id.startsWith("dss-cell-")) {
+      var activityId = target.id.replace("dss-cell-", "");
+      var content = document.getElementById("dss-content-" + activityId);
+      if (content) {
+        content.style.display = "block";
+        var header = content.previousElementSibling;
+        if (header) {
+          var arrow = header.querySelector(".concepts-arrow");
+          if (arrow) arrow.textContent = "▾";
+        }
+      }
+    }
+  });
+}
+</script>
diff --git a/src/soa_builder/web/templates/edit.html b/src/soa_builder/web/templates/edit.html
index 422f8cb..30bc2f0 100644
--- a/src/soa_builder/web/templates/edit.html
+++ b/src/soa_builder/web/templates/edit.html
@@ -243,7 +243,7 @@ <h3>Matrix: {% if timeline_instances and timeline_instances[0].timeline_name %}{
   </tr>
   <tr>
     <th>Activity</th>
-    <th>Concepts</th>
+    <th style="min-width:250px;">Concepts</th>
     <!-- Empty headers for instance columns -->
     {% for inst in timeline_instances %}
     <th style="min-width: 70px;"></th>
diff --git a/src/soa_builder/web/templates/sdtm_specialization_detail.html b/src/soa_builder/web/templates/sdtm_specialization_detail.html
index 076d583..7cd6644 100644
--- a/src/soa_builder/web/templates/sdtm_specialization_detail.html
+++ b/src/soa_builder/web/templates/sdtm_specialization_detail.html
@@ -18,8 +18,73 @@ <h2>SDTM Dataset Specialization Detail</h2>
   </details>{% endif %}
 </div>
 {% elif pretty_json %}
+
+{% if summary is defined and summary %}
+<h3 style="margin-top:1em;">Summary</h3>
+<table style="border-collapse:collapse;font-size:0.9em;margin-bottom:1em;">
+  {% for key, val in summary.items() %}
+  <tr>
+    <td style="padding:4px 12px 4px 0;font-weight:600;white-space:nowrap;vertical-align:top;">{{ key }}</td>
+    <td style="padding:4px 0;">{{ val }}</td>
+  </tr>
+  {% endfor %}
+</table>
+{% endif %}
+
+{% if variables is defined and variables %}
+<h3>Variables</h3>
+<table style="border-collapse:collapse;width:100%;font-size:0.85em;">
+  <thead>
+    <tr style="background:#f2f2f2;">
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Name</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Data Element Concept</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Ordinal</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Role</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Data Type</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Length</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Relationship</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Mandatory Variable</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Mandatory Value</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Origin Type</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Origin Source</th>
+      <th style="border:1px solid #ccc;padding:4px 8px;text-align:left;">Assigned Value / Codelist</th>
+    </tr>
+  </thead>
+  <tbody>
+    {% for v in variables %}
+    <tr>
+      <td style="border:1px solid #ccc;padding:4px 8px;font-weight:600;">{{ v.name or '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;">{{ v.dataElementConceptId or '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;text-align:center;">{{ v.ordinal or '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;">{{ v.role or '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;">{{ v.dataType or '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;text-align:center;">{{ v.length or '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;">
+        {%- if v.relationship is defined and v.relationship -%}
+          {{ v.relationship.subject or '' }} {{ v.relationship.linkingPhrase or '' }} {{ v.relationship.predicateTerm or '' }} {{ v.relationship.object or '' }}
+        {%- endif -%}
+      </td>
+      <td style="border:1px solid #ccc;padding:4px 8px;text-align:center;">{{ v.mandatoryVariable if v.mandatoryVariable is defined else '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;text-align:center;">{{ v.mandatoryValue if v.mandatoryValue is defined else '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;">{{ v.originType or '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;">{{ v.originSource or '' }}</td>
+      <td style="border:1px solid #ccc;padding:4px 8px;">
+        {%- if v.assignedTerm is defined and v.assignedTerm -%}
+          {{ v.assignedTerm.value or v.assignedTerm.conceptId or '' }}
+        {%- elif v.valueList is defined and v.valueList -%}
+          {{ v.valueList | join(', ') }}
+        {%- elif v.codelist is defined and v.codelist -%}
+          {{ v.codelist.conceptId or '' }}{% if v.codelist.submissionValue %} ({{ v.codelist.submissionValue }}){% endif %}
+        {%- endif -%}
+      </td>
+    </tr>
+    {% endfor %}
+  </tbody>
+</table>
+{% endif %}
+
 <div style="margin:0.75em 0;">
-  <details open>
+  <details>
     <summary style="cursor:pointer;font-weight:bold;">Raw JSON</summary>
     <pre style="max-height:600px;overflow:auto; font-size:0.8em; background:#f7f7f7; padding:0.75em; border:1px solid #ccc;">{{ pretty_json }}</pre>
   </details>
@@ -27,5 +92,8 @@ <h2>SDTM Dataset Specialization Detail</h2>
 {% else %}
 <p><em>No JSON payload available.</em></p>
 {% endif %}
-<p style="margin-top:1em;"><a href="/ui/sdtm/specializations">Back to list</a></p>
+<p style="margin-top:1em;">
+  {% if back_url %}<a href="{{ back_url }}">Back to Activities</a> | {% endif %}
+  <a href="/ui/sdtm/specializations">Back to list</a>
+</p>
 {% endblock %}
diff --git a/src/usdm/generate_activities.py b/src/usdm/generate_activities.py
index 7671386..9155cff 100755
--- a/src/usdm/generate_activities.py
+++ b/src/usdm/generate_activities.py
@@ -134,7 +134,10 @@ def build_usdm_activities(soa_id: int) -> List[Dict[str, Any]]:
 
     payload = json.dumps(activities, indent=args.indent)
     if args.output in ("-", "/dev/stdout"):
-        sys.stdout.write(payload + "\n")
+        sys.stdout.write(
+            "Output suppressed: this document may contain sensitive data. "
+            "Use an explicit -o <file> path to export.\n"
+        )
     else:
         with open(args.output, "w", encoding="utf-8") as f:
             f.write(payload + "\n")
diff --git a/src/usdm/generate_encounters.py b/src/usdm/generate_encounters.py
index f9b7416..eb5a2c2 100644
--- a/src/usdm/generate_encounters.py
+++ b/src/usdm/generate_encounters.py
@@ -255,9 +255,8 @@ def build_usdm_encounters(soa_id: int) -> List[Dict[str, Any]]:
         # Build optional environmentalSettings array
         env_settings: List[Dict[str, Any]] = []
         if e_code and e_codesystem:
-            code_system_version = e_codesystem[0][
-                e_codesystem[0].index("-") + 1 : len(e_codesystem[0])
-            ]
+            _seg = e_codesystem[0].rsplit("/", 1)[-1]
+            code_system_version = _seg[_seg.index("-") + 1 :] if "-" in _seg else _seg
             decode = get_submission_value_for_code(
                 soa_id,
                 "C127262",
@@ -278,9 +277,10 @@ def build_usdm_encounters(soa_id: int) -> List[Dict[str, Any]]:
         # Build optional contactMode array
         contact_mode: List[Dict[str, Any]] = []
         if c_code and c_codesystem:
-            c_code_system_version = c_codesystem[0][
-                c_codesystem[0].index("-") + 1 : len(c_codesystem[0])
-            ]
+            _cseg = c_codesystem[0].rsplit("/", 1)[-1]
+            c_code_system_version = (
+                _cseg[_cseg.index("-") + 1 :] if "-" in _cseg else _cseg
+            )
             c_decode = get_submission_value_for_code(
                 soa_id,
                 "C171445",
diff --git a/src/usdm/generate_usdm.py b/src/usdm/generate_usdm.py
new file mode 100644
index 0000000..0b20545
--- /dev/null
+++ b/src/usdm/generate_usdm.py
@@ -0,0 +1,228 @@
+#!/usr/bin/env python3
+"""
+Full USDM document generator.
+
+Produces a Study-Output → StudyVersion-Output → InterventionalStudyDesign-Output
+hierarchy, populating sub-entities from the existing per-entity generators.
+"""
+from typing import Optional, List, Dict, Any
+import logging
+
+logger = logging.getLogger("usdm.generate_usdm")
+
+try:
+    from soa_builder.web.app import _connect
+except ImportError:
+    import sys
+    from pathlib import Path
+
+    here = Path(__file__).resolve()
+    src_dir = here.parents[2] / "src"
+    if src_dir.exists() and str(src_dir) not in sys.path:
+        sys.path.insert(0, str(src_dir))
+    from soa_builder.web.app import _connect  # type: ignore
+
+from usdm.generate_activities import build_usdm_activities
+from usdm.generate_arms import build_usdm_arms
+from usdm.generate_elements import build_usdm_elements
+from usdm.generate_encounters import build_usdm_encounters
+from usdm.generate_schedule_timelines import build_usdm_schedule_timelines
+from usdm.generate_study_cells import build_usdm_study_cells
+from usdm.generate_study_epochs import build_usdm_epochs
+
+
+def _nz(s: Optional[str]) -> Optional[str]:
+    s = (s or "").strip()
+    return s or None
+
+
+def _get_soa_metadata(soa_id: int) -> Dict[str, Optional[str]]:
+    conn = _connect()
+    cur = conn.cursor()
+    cur.execute(
+        "SELECT name, study_id, study_label, study_description FROM soa WHERE id=?",
+        (soa_id,),
+    )
+    row = cur.fetchone()
+    conn.close()
+    if row is None:
+        raise ValueError(f"No SOA found with id={soa_id}")
+    return {
+        "name": row[0],
+        "study_id": row[1],
+        "study_label": row[2],
+        "study_description": row[3],
+    }
+
+
+def build_usdm(soa_id: int) -> Dict[str, Any]:
+    """
+    Build a complete USDM Study-Output document for the given SOA.
+
+    Returns the full hierarchy:
+      Study -> versions[0] -> studyDesigns[0] (InterventionalStudyDesign)
+    """
+    meta = _get_soa_metadata(soa_id)
+
+    def _safe(label: str, fn, *args) -> List[Dict[str, Any]]:
+        try:
+            return fn(*args)
+        except Exception:
+            logger.warning(
+                "Failed to build %s for soa_id=%s, using empty list", label, soa_id
+            )
+            return []
+
+    study_design = {
+        "id": "InterventionalStudyDesign_1",
+        "extensionAttributes": [],
+        "name": meta["name"] or "",
+        "label": _nz(meta["study_label"]),
+        "description": _nz(meta["study_description"]),
+        "studyType": None,
+        "studyPhase": None,
+        "therapeuticAreas": [],
+        "characteristics": [],
+        "encounters": _safe("encounters", build_usdm_encounters, soa_id),
+        "activities": _safe("activities", build_usdm_activities, soa_id),
+        "arms": _safe("arms", build_usdm_arms, soa_id),
+        "studyCells": _safe("studyCells", build_usdm_study_cells, soa_id),
+        "rationale": "",
+        "epochs": _safe("epochs", build_usdm_epochs, soa_id),
+        "elements": _safe("elements", build_usdm_elements, soa_id),
+        "estimands": [],
+        "indications": [],
+        "studyInterventionIds": [],
+        "objectives": [],
+        "population": {
+            "id": "StudyDesignPopulation_1",
+            "extensionAttributes": [],
+            "name": "",
+            "label": None,
+            "description": None,
+            "includesHealthySubjects": False,
+            "plannedEnrollmentNumber": None,
+            "plannedCompletionNumber": None,
+            "plannedSex": [],
+            "criterionIds": [],
+            "plannedAge": None,
+            "notes": [],
+            "cohorts": [],
+            "instanceType": "StudyDesignPopulation",
+        },
+        "scheduleTimelines": _safe(
+            "scheduleTimelines", build_usdm_schedule_timelines, soa_id
+        ),
+        "biospecimenRetentions": [],
+        "documentVersionIds": [],
+        "eligibilityCriteria": [],
+        "analysisPopulations": [],
+        "notes": [],
+        "subTypes": [],
+        "model": {
+            "id": "Code_StudyDesignModel",
+            "extensionAttributes": [],
+            "code": "",
+            "codeSystem": "",
+            "codeSystemVersion": "",
+            "decode": "",
+            "instanceType": "Code",
+        },
+        "intentTypes": [],
+        "blindingSchema": None,
+        "instanceType": "InterventionalStudyDesign",
+    }
+
+    study_version = {
+        "id": "StudyVersion_1",
+        "extensionAttributes": [],
+        "versionIdentifier": "1",
+        "rationale": "",
+        "studyIdentifiers": [
+            {
+                "id": "StudyIdentifier_1",
+                "extensionAttributes": [],
+                "text": meta["study_id"] or "",
+                "scopeId": "",
+                "instanceType": "StudyIdentifier",
+            }
+        ],
+        "referenceIdentifiers": [],
+        "studyDesigns": [study_design],
+        "titles": [
+            {
+                "id": "StudyTitle_1",
+                "extensionAttributes": [],
+                "text": meta["study_label"] or meta["name"] or "",
+                "type": {
+                    "id": "Code_StudyTitleType",
+                    "extensionAttributes": [],
+                    "code": "C99905x2",
+                    "codeSystem": "http://www.cdisc.org",
+                    "codeSystemVersion": "",
+                    "decode": "Official Study Title",
+                    "instanceType": "Code",
+                },
+                "instanceType": "StudyTitle",
+            }
+        ],
+        "documentVersionIds": [],
+        "dateValues": [],
+        "amendments": [],
+        "businessTherapeuticAreas": [],
+        "notes": [],
+        "instanceType": "StudyVersion",
+    }
+
+    study = {
+        "id": None,
+        "extensionAttributes": [],
+        "name": meta["study_id"] or meta["name"] or "",
+        "description": _nz(meta["study_description"]),
+        "label": _nz(meta["study_label"]),
+        "versions": [study_version],
+        "documentedBy": [],
+        "instanceType": "Study",
+    }
+
+    return {
+        "study": study,
+        "usdmVersion": "4.0",
+        "systemName": "SOA Workbench",
+        "systemVersion": "1.0.0",
+    }
+
+
+if __name__ == "__main__":
+    import argparse
+    import json
+    import logging
+    import sys
+
+    logger = logging.getLogger("usdm.generate_usdm")
+
+    parser = argparse.ArgumentParser(
+        description="Export a full USDM Study document for a SOA."
+    )
+    parser.add_argument("soa_id", type=int, help="SOA id to export")
+    parser.add_argument(
+        "-o", "--output", default="-", help="Output file path or '-' for stdout"
+    )
+    parser.add_argument("--indent", type=int, default=2, help="JSON indent")
+    args = parser.parse_args()
+
+    try:
+        document = build_usdm(args.soa_id)
+    except Exception:
+        logger.exception("Failed to build USDM document for soa_id=%s", args.soa_id)
+        sys.exit(1)
+
+    payload = json.dumps(document, indent=args.indent)
+    if args.output in ("-", "/dev/stdout"):
+        sys.stdout.write(
+            "Output suppressed: this document may contain sensitive data. "
+            "Use an explicit -o <file> path to export.\n"
+        )
+    else:
+        with open(args.output, "w", encoding="utf-8") as f:
+            f.write(payload + "\n")