diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7dbb067..19bdf4e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- **BREAKING: `user` is now required on every tenant-data endpoint** - The implicit `jpmschweitzer` default tenant (`DEFAULT_USER`) has been removed everywhere. All endpoints that read or write tenant data (`/query/*`, `/wiki/*`, `/vector/*`, `/graph/*`, `/ingest/*`, `/volatile/*`, `/documents/*`, `/stats`, `/rag/search`) now reject requests without an explicit, non-empty, non-whitespace `user` (HTTP 422), matching the existing `/maintenance/*` pattern. A shared validator (`require_user` dependency / `RequiredUser` model type) also rejects blank users. The Wiki.js change listener now skips changes whose notification email yields no user instead of attributing them to the production tenant. **Caller coordination required:** tatlock and the Scheduler ingest/prefetch/consolidation tasks must send an explicit `user` on every call — see the deploy checklist.
+
 ### Added
 
 - **Degradation signaling** - `HybridRAGResponse` now includes `source_status` (per-leg `'ok'`/`'failed'`/`'disabled'` for vector, graph, web, volatile, documents) and `degraded` (true when any enabled leg failed). Retrieval legs report errors instead of silently swallowing them; failed legs are logged at WARNING. Both fields are additive and optional, so clients that ignore them are unaffected.
diff --git a/PROJECT_CLAUDIFICATION_HANDOVER.md b/PROJECT_CLAUDIFICATION_HANDOVER.md
new file mode 100644
index 0000000..00ad36b
--- /dev/null
+++ b/PROJECT_CLAUDIFICATION_HANDOVER.md
@@ -0,0 +1,59 @@
+# Tatlock Claudification Handover - library-desk
+
+## Context
+
+Tatlock (the butler) is being upgraded to use Claude as its primary LLM backend instead of Ollama. This gives all agents 200k token context and improved reasoning. Library-desk is the backend for **The Librarian** agent.
+
+**Parent Issue:** See `/mnt/media/Projects/tatlock/PROJECT_CLAUDIFICATION.md`
+
+## Impact on library-desk
+
+Library-desk's API is consumed by The Librarian agent via `LibraryDeskClient`. With Claude's larger context and better reasoning:
+
+1. **Larger response payloads are now viable** - Claude can process more search results
+2. **Better synthesis** - Claude can better combine HybridRAG sources
+3. **Faster processing** - May need to review rate limiting
+
+## Required Changes
+
+### Priority: Low (No blocking changes)
+
+Library-desk likely works as-is. These are optimizations:
+
+- [ ] **Review `hybrid_search` response size limits**
+  - Current defaults may be conservative for 8k Ollama context
+  - Consider increasing `max_results` defaults for Claude's 200k context
+  - Add optional `context_budget` parameter?
+
+- [ ] **Review `smart_create` endpoint**
+  - Claude's reasoning may benefit from more research context
+  - Consider returning more source material for synthesis
+
+- [ ] **Evaluate response formats**
+  - Are responses optimized for LLM consumption?
+  - Could structured metadata help Claude's reasoning?
+
+### Priority: None (Infrastructure)
+
+- No API key changes needed (library-desk doesn't call LLMs directly)
+- No authentication changes
+- Existing endpoints remain compatible
+
+## Testing
+
+Once Tatlock is running with Claude backend:
+
+```bash
+# Test from Tatlock
+curl -X POST http://localhost:8777/v1/responses \
+  -H "Content-Type: application/json" \
+  -d '{"input": "Search for Docker networking best practices"}'
+
+# Verify Librarian delegation works with Claude
+```
+
+## Timeline
+
+- **Blocking:** No
+- **When to implement:** After Tatlock Phase 1 is tested and stable
+- **Effort:** ~2-4 hours for optimizations
diff --git a/src/core/dependencies.py b/src/core/dependencies.py
index 3df364f..75501bf 100644
--- a/src/core/dependencies.py
+++ b/src/core/dependencies.py
@@ -10,7 +10,7 @@ Provides FastAPI dependencies for service clients with:
 
 from functools import lru_cache
 from typing import Annotated
-from fastapi import Depends
+from fastapi import Depends, HTTPException, Query
 import logging
 
 import redis.asyncio as aioredis
@@ -38,6 +38,35 @@ logger = logging.getLogger(__name__)
 SettingsDep = Annotated[Settings, Depends(get_settings)]
 
 
+# Tenant user dependency
+def require_user(
+    user: str = Query(
+        ...,
+        description=(
+            "User identifier (tenant). Required — every operation is scoped to "
+            "this tenant's namespace (Qdrant collection, Neo4j labels, wiki path, "
+            "Redis keys). Requests without an explicit non-empty user are "
+            "rejected with 422. There is no default tenant."
+        ),
+    )
+) -> str:
+    """
+    FastAPI dependency: required tenant user query parameter.
+
+    Rejects missing (FastAPI returns 422 automatically), empty, and
+    whitespace-only user values. Use via the RequiredUserQuery alias.
+    """
+    from src.core.multi_tenancy import validate_required_user
+
+    try:
+        return validate_required_user(user)
+    except ValueError as e:
+        raise HTTPException(status_code=422, detail=str(e))
+
+
+RequiredUserQuery = Annotated[str, Depends(require_user)]
+
+
 # Client factory functions with @lru_cache for singletons
 @lru_cache
 def get_neo4j_client() -> Neo4jClient:
diff --git a/src/core/multi_tenancy.py b/src/core/multi_tenancy.py
index 8ca468c..330c806 100644
--- a/src/core/multi_tenancy.py
+++ b/src/core/multi_tenancy.py
@@ -8,9 +8,9 @@ Provides utilities for user namespace management across:
 """
 
 import re
+from typing import Annotated
 
-# Default user for all operations
-DEFAULT_USER = "jpmschweitzer"
+from pydantic import AfterValidator
 
 
 def sanitize_user_id(user_id: str) -> str:
@@ -186,6 +186,45 @@ def validate_user_id(user_id: str) -> bool:
     return True
 
 
+def validate_required_user(user: str) -> str:
+    """
+    Validate that a tenant user identifier is present and usable.
+
+    There is NO default tenant: every operation that touches tenant data
+    must receive an explicit user. Empty or whitespace-only values are
+    rejected, as are values that fail :func:`validate_user_id`.
+
+    Args:
+        user: Raw user identifier from a request
+
+    Returns:
+        The stripped user identifier
+
+    Raises:
+        ValueError: If the user is missing, blank, or invalid
+
+    Examples:
+        >>> validate_required_user("llm_tester")
+        'llm_tester'
+        >>> validate_required_user("  ")
+        Traceback (most recent call last):
+        ...
+        ValueError: user is required and must be a non-empty, non-whitespace string
+    """
+    if user is None or not str(user).strip():
+        raise ValueError(
+            "user is required and must be a non-empty, non-whitespace string"
+        )
+    stripped = str(user).strip()
+    if not validate_user_id(stripped):
+        raise ValueError(f"Invalid user identifier: {user!r}")
+    return stripped
+
+
+# Pydantic annotated type for request models: a required, validated tenant user.
+RequiredUser = Annotated[str, AfterValidator(validate_required_user)]
+
+
 def is_path_in_user_namespace(path: str, user_id: str) -> bool:
     """
     Check if a Wiki.js path belongs to user's namespace.
diff --git a/src/main.py b/src/main.py
index 0634a84..beeb653 100644
--- a/src/main.py
+++ b/src/main.py
@@ -18,9 +18,9 @@ from pathlib import Path
 
 from src.config import Settings, get_settings, __version__
 from src.core.dependencies import (
-    verify_api_key, QdrantDep, WikiJSDep, OllamaDep, Neo4jDep, PaperlessDep
+    verify_api_key, QdrantDep, WikiJSDep, OllamaDep, Neo4jDep, PaperlessDep,
+    RequiredUserQuery
 )
-from src.core.multi_tenancy import DEFAULT_USER
 
 # Configure logging
 logging.basicConfig(
@@ -151,7 +151,7 @@ async def health(settings: Settings = Depends(get_settings)) -> HealthResponse:
 
 @app.get("/stats", response_model=StatsResponse, tags=["System"])
 async def stats(
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     neo4j: Neo4jDep = None,
     qdrant: QdrantDep = None,
     wikijs: WikiJSDep = None,
@@ -290,8 +290,8 @@ async def get_repo_status(
 
 @app.post("/query/semantic", tags=["Query"])
 async def semantic_query(
+    user: RequiredUserQuery,
     query: str = Query(..., min_length=1, description="Search query text"),
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
     limit: int = Query(default=10, ge=1, le=100, description="Maximum results"),
     score_threshold: float = Query(default=0.5, ge=0.0, le=1.0, description="Minimum similarity score"),
     qdrant_client: QdrantDep = None,
@@ -331,8 +331,8 @@ async def semantic_query(
 
 @app.post("/query/graph", tags=["Query"])
 async def graph_query(
+    user: RequiredUserQuery,
     query: str = Query(..., description="Cypher query to execute"),
-    user: str = Query(default=DEFAULT_USER, description="User for scoping (auto-filters results)"),
     neo4j_client: Neo4jDep = None,
     wiki_client: WikiJSDep = None,
     api_key: str = Depends(verify_api_key)
diff --git a/src/models/graph.py b/src/models/graph.py
index 4da9a4e..6503a6d 100644
--- a/src/models/graph.py
+++ b/src/models/graph.py
@@ -8,6 +8,8 @@ from pydantic import BaseModel, Field
 from typing import List, Dict, Any, Optional
 from datetime import datetime
 
+from src.core.multi_tenancy import RequiredUser
+
 
 class GraphNode(BaseModel):
     """Graph node representation."""
@@ -45,9 +47,13 @@ class CypherQueryRequest(BaseModel):
         default_factory=dict,
         description="Query parameters"
     )
-    user: str = Field(
-        default="jpmschweitzer",
-        description="User for filtering (automatically scopes query)"
+    user: RequiredUser = Field(
+        ...,
+        description=(
+            "User identifier (tenant). Required. NOTE: raw Cypher queries are NOT "
+            "automatically scoped to this tenant — the endpoint is read-only and "
+            "intended for admin/debug use. Results may span all tenants."
+        )
     )
 
 
@@ -61,9 +67,9 @@ class CypherQueryResponse(BaseModel):
 class UpdateFromPageRequest(BaseModel):
     """Request to update graph from a wiki page."""
     page_id: int = Field(..., description="Wiki page ID to process")
-    user: str = Field(
-        default="jpmschweitzer",
-        description="User identifier for namespace scoping"
+    user: RequiredUser = Field(
+        ...,
+        description="User identifier (tenant). Required — graph writes are scoped to this tenant's labels."
     )
     force_refresh: bool = Field(
         default=False,
diff --git a/src/models/ingestion.py b/src/models/ingestion.py
index 4973d5f..c7b2b76 100644
--- a/src/models/ingestion.py
+++ b/src/models/ingestion.py
@@ -5,11 +5,13 @@ from pydantic import BaseModel, Field
 from typing import Optional, List, Dict, Any
 from datetime import datetime
 
+from src.core.multi_tenancy import RequiredUser
+
 
 class IngestionRequest(BaseModel):
     """Request to ingest a wiki page."""
     page_id: int = Field(..., description="Wiki page ID to ingest")
-    user: str = Field(default="jpmschweitzer", description="User identifier")
+    user: RequiredUser = Field(..., description="User identifier (tenant). Required — ingestion writes to this tenant's namespaces only.")
     force_refresh: bool = Field(
         default=False,
         description="Force re-ingestion even if page hasn't changed"
@@ -21,7 +23,7 @@ class IngestionRequest(BaseModel):
 class BatchIngestionRequest(BaseModel):
     """Request to ingest multiple wiki pages."""
     page_ids: List[int] = Field(..., description="List of wiki page IDs to ingest")
-    user: str = Field(default="jpmschweitzer", description="User identifier")
+    user: RequiredUser = Field(..., description="User identifier (tenant). Required — ingestion writes to this tenant's namespaces only.")
     force_refresh: bool = Field(default=False)
     skip_vectors: bool = Field(default=False)
     skip_graph: bool = Field(default=False)
diff --git a/src/models/rag_search.py b/src/models/rag_search.py
index 8cdfbf8..f29eb1b 100644
--- a/src/models/rag_search.py
+++ b/src/models/rag_search.py
@@ -8,7 +8,7 @@ from enum import Enum
 from typing import Optional, List
 from pydantic import BaseModel, Field
 
-from src.core.multi_tenancy import DEFAULT_USER
+from src.core.multi_tenancy import RequiredUser
 
 
 class SearchType(str, Enum):
@@ -37,9 +37,9 @@ class RAGSearchRequest(BaseModel):
         le=20,
         description="Maximum number of results (1-20)"
     )
-    user: str = Field(
-        default=DEFAULT_USER,
-        description="User identifier for rate limiting/personalization"
+    user: RequiredUser = Field(
+        ...,
+        description="User identifier (tenant). Required — used for rate limiting/personalization."
     )
 
 
diff --git a/src/models/vector.py b/src/models/vector.py
index 6f1a088..a3ea996 100644
--- a/src/models/vector.py
+++ b/src/models/vector.py
@@ -7,6 +7,8 @@ Provides models for semantic search, document chunks, and embeddings.
 from pydantic import BaseModel, Field
 from typing import List, Dict, Any, Optional
 
+from src.core.multi_tenancy import RequiredUser
+
 
 class DocumentChunk(BaseModel):
     """Document chunk with embedding."""
@@ -32,7 +34,7 @@ class SearchResult(BaseModel):
 class SearchRequest(BaseModel):
     """Semantic search request."""
     query: str = Field(..., min_length=1, description="Search query")
-    user: str = Field(default="jpmschweitzer", description="User identifier")
+    user: RequiredUser = Field(..., description="User identifier (tenant). Required — search is scoped to this tenant's collection.")
     limit: int = Field(default=10, ge=1, le=100, description="Maximum results")
     score_threshold: float = Field(default=0.5, ge=0.0, le=1.0, description="Minimum similarity score")
 
@@ -48,9 +50,9 @@ class SearchResponse(BaseModel):
 class VectorUpdateRequest(BaseModel):
     """Request to update vectors from a wiki page."""
     page_id: int = Field(..., description="Wiki page ID to process")
-    user: str = Field(
-        default="jpmschweitzer",
-        description="User identifier for namespace scoping"
+    user: RequiredUser = Field(
+        ...,
+        description="User identifier (tenant). Required — vectors are written to this tenant's collection."
     )
     force_refresh: bool = Field(
         default=False,
@@ -89,7 +91,7 @@ class CollectionListResponse(BaseModel):
 class DeletePageChunksRequest(BaseModel):
     """Request to delete all chunks for a page."""
     page_id: int = Field(..., description="Wiki page ID")
-    user: str = Field(default="jpmschweitzer", description="User identifier")
+    user: RequiredUser = Field(..., description="User identifier (tenant). Required — deletion is scoped to this tenant's collection.")
 
 
 class DeletePageChunksResponse(BaseModel):
diff --git a/src/models/wiki.py b/src/models/wiki.py
index 3b71bda..7ff0468 100644
--- a/src/models/wiki.py
+++ b/src/models/wiki.py
@@ -11,6 +11,8 @@ from pydantic import BaseModel, Field, field_validator
 from typing import Optional, List, Dict, Any
 from datetime import datetime
 
+from src.core.multi_tenancy import RequiredUser
+
 
 # Base models
 class WikiPageBase(BaseModel):
@@ -35,7 +37,7 @@ class WikiPageCreate(WikiPageBase):
     content: str = Field(..., description="Page content (markdown)")
     path: str = Field(..., min_length=1, max_length=500, description="Page path (e.g., '/projects/library-desk')")
     editor: str = Field(default="markdown", description="Editor type")
-    user: Optional[str] = Field(None, description="User identifier (defaults to configured user)")
+    user: RequiredUser = Field(..., description="User identifier (tenant). Required — the page is created inside this tenant's namespace.")
 
     @field_validator("path")
     @classmethod
@@ -106,7 +108,7 @@ class DossierCreate(BaseModel):
     title: str = Field(..., min_length=1, max_length=200, description="Human-readable title")
     description: str = Field(..., min_length=1, description="Dossier description")
     create_index_page: bool = Field(default=True, description="Create an index page for the dossier")
-    user: Optional[str] = Field(None, description="User identifier")
+    user: RequiredUser = Field(..., description="User identifier (tenant). Required.")
 
     @field_validator("name")
     @classmethod
@@ -198,7 +200,7 @@ class WikiSmartCreateRequest(BaseModel):
     topic: str = Field(..., min_length=1, max_length=500, description="Topic to research and create page about")
     path: Optional[str] = Field(None, description="Page path (auto-generated from topic if not provided)")
     tags: List[str] = Field(default_factory=list, description="Tags for the page")
-    user: Optional[str] = Field(None, description="User identifier")
+    user: RequiredUser = Field(..., description="User identifier (tenant). Required — research results and the created page are scoped to this tenant.")
     include_web_research: bool = Field(default=True, description="Include web search results")
     include_wiki_search: bool = Field(default=True, description="Include existing wiki knowledge")
 
diff --git a/src/routers/documents.py b/src/routers/documents.py
index 55ddf85..f733be4 100644
--- a/src/routers/documents.py
+++ b/src/routers/documents.py
@@ -29,7 +29,7 @@ from src.core.dependencies import (
     Neo4jDep,
     WikiJSDep,
 )
-from src.core.multi_tenancy import DEFAULT_USER
+from src.core.dependencies import RequiredUserQuery
 from src.config import get_settings
 
 logger = logging.getLogger(__name__)
@@ -50,7 +50,7 @@ async def receive_webhook(
     ollama: OllamaDep,
     neo4j: Neo4jDep,
     wiki: WikiJSDep,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
 ):
     """
     Receive webhook events from Paperless-ngx.
@@ -161,9 +161,9 @@ async def capture_webhook(request: Request):
 
 @router.post("/webhook-simple", response_model=WebhookResponse)
 async def receive_webhook_simple(
+    user: RequiredUserQuery,
     doc_url: str = Query(..., description="Paperless document URL containing ID"),
     title: str = Query(default="", description="Document title"),
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
     paperless: PaperlessDep = None,
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
@@ -347,7 +347,7 @@ async def search_documents(
     request: DocumentSearchRequest,
     qdrant: QdrantDep,
     ollama: OllamaDep,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     api_key: str = Depends(verify_api_key),
 ):
     """
diff --git a/src/routers/graph.py b/src/routers/graph.py
index a6d3db0..5629108 100644
--- a/src/routers/graph.py
+++ b/src/routers/graph.py
@@ -15,8 +15,9 @@ from src.models.graph import (
     MindMapResponse
 )
 from src.services.graph_service import GraphService
-from src.core.dependencies import Neo4jDep, WikiJSDep, verify_api_key
-from src.core.multi_tenancy import DEFAULT_USER
+from src.core.dependencies import (
+    Neo4jDep, WikiJSDep, verify_api_key, RequiredUserQuery
+)
 
 logger = logging.getLogger(__name__)
 
@@ -49,7 +50,7 @@ async def execute_cypher_query(
     {
         "query": "MATCH (d:Document) RETURN d LIMIT 10",
         "parameters": {},
-        "user": "jpmschweitzer"
+        "user": "<tenant>"
     }
     ```
 
@@ -70,7 +71,7 @@ async def execute_cypher_query(
 
 @router.get("/nodes", response_model=NodeListResponse)
 async def list_nodes(
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     node_type: Optional[str] = Query(default=None, description="Node type filter"),
     limit: int = Query(default=100, ge=1, le=500, description="Maximum nodes"),
     graph_service: GraphService = Depends(get_graph_service),
@@ -81,7 +82,7 @@ async def list_nodes(
 
     Optionally filter by node type (Document, Person, Project, Concept, etc.).
 
-    **Example:** `/graph/nodes?user=jpmschweitzer&node_type=Document&limit=50`
+    **Example:** `/graph/nodes?user=<tenant>&node_type=Document&limit=50`
     """
     try:
         return await graph_service.list_nodes(
@@ -97,7 +98,7 @@ async def list_nodes(
 @router.get("/nodes/{node_id}", response_model=GraphNodeDetail)
 async def get_node(
     node_id: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     graph_service: GraphService = Depends(get_graph_service),
     api_key: str = Depends(verify_api_key)
 ):
@@ -106,7 +107,7 @@ async def get_node(
 
     Returns the node, its relationships, and connected nodes.
 
-    **Example:** `/graph/nodes/4:abc123def:0?user=jpmschweitzer`
+    **Example:** `/graph/nodes/4:abc123def:0?user=<tenant>`
     """
     try:
         node = await graph_service.get_node(node_id, user)
@@ -123,7 +124,7 @@ async def get_node(
 @router.post("/update-from-page/{page_id}", response_model=GraphUpdateSummary)
 async def update_graph_from_page(
     page_id: int,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     force_refresh: bool = Query(default=False, description="Force re-extraction"),
     graph_service: GraphService = Depends(get_graph_service),
     api_key: str = Depends(verify_api_key)
@@ -143,7 +144,7 @@ async def update_graph_from_page(
     - Called manually by user/Librarian to refresh graph
     - Called by Scheduler for batch processing
 
-    **Example:** `POST /graph/update-from-page/4?user=jpmschweitzer`
+    **Example:** `POST /graph/update-from-page/4?user=<tenant>`
 
     **Returns:** Summary with nodes/relationships created and entities extracted
     """
@@ -171,8 +172,8 @@ async def update_graph_from_page(
 
 @router.post("/mindmap", response_model=MindMapResponse)
 async def generate_mindmap(
+    user: RequiredUserQuery,
     center_node_id: str = Query(..., description="Central node ID"),
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
     depth: int = Query(default=2, ge=1, le=5, description="Traversal depth"),
     graph_service: GraphService = Depends(get_graph_service),
     api_key: str = Depends(verify_api_key)
@@ -205,7 +206,7 @@ async def generate_mindmap(
 
 @router.post("/generate-entity-pages")
 async def generate_entity_pages(
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     min_mentions: int = Query(default=5, ge=1, le=100, description="Minimum mentions threshold"),
     entity_types: Optional[List[str]] = Query(default=None, description="Entity types to process"),
     graph_service: GraphService = Depends(get_graph_service),
diff --git a/src/routers/hybrid_rag.py b/src/routers/hybrid_rag.py
index 89f44d5..4467c7f 100644
--- a/src/routers/hybrid_rag.py
+++ b/src/routers/hybrid_rag.py
@@ -5,14 +5,15 @@ Provides endpoint for combining vector, graph, volatile cache, and web search
 with RRF fusion and LLM re-ranking.
 """
 
-from fastapi import APIRouter, HTTPException, Depends, Query
+from fastapi import APIRouter, HTTPException, Depends
 import logging
 
 from src.models.hybrid_rag import HybridRAGRequest, HybridRAGResponse
 from src.services.hybrid_rag_service import HybridRAGService
 from src.core.dependencies import (
     Neo4jDep, WikiJSDep, QdrantDep, OllamaDep,
-    SearXNGDep, ContentExtractorDep, verify_api_key, get_settings
+    SearXNGDep, ContentExtractorDep, verify_api_key, get_settings,
+    RequiredUserQuery
 )
 from src.config import Settings
 
@@ -56,7 +57,7 @@ def get_hybrid_rag_service(
 @router.post("/hybrid", response_model=HybridRAGResponse)
 async def hybrid_search(
     request: HybridRAGRequest,
-    user: str = Query(default="jpmschweitzer", description="User identifier for multi-tenancy"),
+    user: RequiredUserQuery,
     hybrid_rag_service: HybridRAGService = Depends(get_hybrid_rag_service),
     api_key: str = Depends(verify_api_key)
 ):
@@ -72,11 +73,13 @@ async def hybrid_search(
     6. **Context Formatting**: Format for LLM consumption
     7. **Persistence**: Store for Librarian knowledge consolidation
 
-    **Example Request:**
+    **Multi-tenancy:** the `user` query parameter is REQUIRED — all retrieval
+    legs and persistence are scoped to that tenant's namespaces.
+
+    **Example Request** (`POST /query/hybrid?user=<tenant>`):
     ```json
     {
         "query": "What's the weather in Rotterdam?",
-        "user": "jpmschweitzer",
         "config": {
             "vector_limit": 10,
             "graph_limit": 10,
diff --git a/src/routers/ingestion.py b/src/routers/ingestion.py
index 9fcdafd..09f2920 100644
--- a/src/routers/ingestion.py
+++ b/src/routers/ingestion.py
@@ -13,7 +13,7 @@ from src.models.ingestion import (
     BatchIngestionRequest,
     BatchIngestionResult
 )
-from src.core.dependencies import get_ingestion_service, verify_api_key
+from src.core.dependencies import get_ingestion_service, verify_api_key, RequiredUserQuery
 
 router = APIRouter(prefix="/ingest", tags=["Document Ingestion"])
 
@@ -52,7 +52,7 @@ async def ingest_page(
       -H "Content-Type: application/json" \
       -d '{
         "page_id": 19,
-        "user": "jpmschweitzer",
+        "user": "<tenant>",
         "force_refresh": false
       }'
     ```
@@ -104,7 +104,7 @@ async def ingest_batch(
       -H "Content-Type: application/json" \
       -d '{
         "page_ids": [19, 20, 21, 22],
-        "user": "jpmschweitzer",
+        "user": "<tenant>",
         "max_concurrent": 3
       }'
     ```
@@ -123,8 +123,8 @@ async def ingest_batch(
 
 @router.post("/all", response_model=BatchIngestionResult)
 async def ingest_all_pages(
-    user: str = Query(default="jpmschweitzer", description="User identifier"),
-    path_prefix: Optional[str] = Query(None, description="Path prefix filter (e.g., 'users/jpmschweitzer/tech')"),
+    user: RequiredUserQuery,
+    path_prefix: Optional[str] = Query(None, description="Path prefix filter within the user's namespace (e.g., 'users/<tenant>/tech')"),
     force_refresh: bool = Query(False, description="Force re-ingestion of all pages"),
     max_concurrent: int = Query(3, ge=1, le=10, description="Maximum concurrent ingestion tasks"),
     ingestion: IngestionService = Depends(get_ingestion_service),
@@ -151,11 +151,11 @@ async def ingest_all_pages(
 
     ```bash
     # Ingest all pages for user
-    curl -X POST "http://192.168.86.149:8089/ingest/all?user=jpmschweitzer" \
+    curl -X POST "http://192.168.86.149:8089/ingest/all?user=<tenant>" \
       -H "Authorization: Bearer $API_KEY"
 
     # Ingest only tech docs
-    curl -X POST "http://192.168.86.149:8089/ingest/all?user=jpmschweitzer&path_prefix=users/jpmschweitzer/tech" \
+    curl -X POST "http://192.168.86.149:8089/ingest/all?user=<tenant>&path_prefix=users/<tenant>/tech" \
       -H "Authorization: Bearer $API_KEY"
     ```
     """
diff --git a/src/routers/maintenance.py b/src/routers/maintenance.py
index ba1a9e1..33b26d2 100644
--- a/src/routers/maintenance.py
+++ b/src/routers/maintenance.py
@@ -22,7 +22,6 @@ from src.core.dependencies import (
     QdrantDep, OllamaDep, PaperlessDep, verify_api_key
 )
 from src.config import get_settings
-from src.core.multi_tenancy import DEFAULT_USER
 from datetime import datetime, timezone
 
 logger = logging.getLogger(__name__)
@@ -262,6 +261,14 @@ def _matches_test_user_path(path: str) -> bool:
     return any(path_lower.startswith(prefix) for prefix in TEST_USER_PATH_PREFIXES)
 
 
+def _tenant_from_path(path: str) -> str:
+    """Extract the tenant user from a 'users/{tenant}/...' wiki path."""
+    parts = path.lstrip("/").split("/")
+    if len(parts) >= 2 and parts[0] == "users":
+        return parts[1]
+    raise ValueError(f"Cannot derive tenant from path: {path}")
+
+
 # ========== Endpoints ==========
 
 @router.post("/cleanup/vectors", response_model=VectorCleanupResponse)
@@ -652,12 +659,14 @@ async def cleanup_test_data(
                 page_path = page["path"]
 
                 try:
-                    # Delete vector chunks for this page (using DEFAULT_USER collection)
-                    chunks_removed = await vector_service.delete_page_chunks(page_id, DEFAULT_USER)
+                    # Delete vector chunks/graph node scoped to the tenant that
+                    # owns the page (derived from its users/{tenant}/ path)
+                    tenant = _tenant_from_path(page_path)
+                    chunks_removed = await vector_service.delete_page_chunks(page_id, tenant)
                     vector_deleted += chunks_removed
 
                     # Delete graph node for this page (returns count, may be 0 if no node)
-                    graph_removed = await graph_service.delete_page(page_id, DEFAULT_USER)
+                    graph_removed = await graph_service.delete_page(page_id, tenant)
                     graph_deleted += graph_removed
 
                     # Delete wiki page (raises exception on failure, returns None on success)
diff --git a/src/routers/tools.py b/src/routers/tools.py
index bc7cd8a..a956282 100644
--- a/src/routers/tools.py
+++ b/src/routers/tools.py
@@ -25,10 +25,9 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 ToolParameter(
                     name="user",
                     type=ParameterType.STRING,
-                    description="User identifier",
-                    required=False,
-                    default="jpmschweitzer",
-                    example="jpmschweitzer"
+                    description="User identifier (tenant). Required - all operations are scoped to this tenant's namespace",
+                    required=True,
+                    example="llm_tester"
                 ),
                 ToolParameter(
                     name="tag",
@@ -66,9 +65,8 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 ToolParameter(
                     name="user",
                     type=ParameterType.STRING,
-                    description="User identifier for access control",
-                    required=False,
-                    default="jpmschweitzer"
+                    description="User identifier (tenant) for access control. Required",
+                    required=True
                 ),
             ],
             returns="Complete page object with content",
@@ -119,9 +117,8 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 ToolParameter(
                     name="user",
                     type=ParameterType.STRING,
-                    description="User identifier",
-                    required=False,
-                    default="jpmschweitzer"
+                    description="User identifier (tenant). Required - all operations are scoped to this tenant's namespace",
+                    required=True
                 ),
             ],
             returns="Created page object",
@@ -130,7 +127,7 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 "path": "/projects/my-project",
                 "content": "# My Project\n\nProject description here.",
                 "tags": ["projects"],
-                "user": "jpmschweitzer"
+                "user": "<tenant>"
             },
             fast=True
         ),
@@ -175,9 +172,8 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 ToolParameter(
                     name="user",
                     type=ParameterType.STRING,
-                    description="User identifier",
-                    required=False,
-                    default="jpmschweitzer"
+                    description="User identifier (tenant). Required - all operations are scoped to this tenant's namespace",
+                    required=True
                 ),
             ],
             returns="Updated page object",
@@ -200,9 +196,8 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 ToolParameter(
                     name="user",
                     type=ParameterType.STRING,
-                    description="User identifier",
-                    required=False,
-                    default="jpmschweitzer"
+                    description="User identifier (tenant). Required - all operations are scoped to this tenant's namespace",
+                    required=True
                 ),
             ],
             returns="Success confirmation",
@@ -225,9 +220,8 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 ToolParameter(
                     name="user",
                     type=ParameterType.STRING,
-                    description="User identifier",
-                    required=False,
-                    default="jpmschweitzer"
+                    description="User identifier (tenant). Required - all operations are scoped to this tenant's namespace",
+                    required=True
                 ),
                 ToolParameter(
                     name="limit",
@@ -250,9 +244,8 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 ToolParameter(
                     name="user",
                     type=ParameterType.STRING,
-                    description="User identifier",
-                    required=False,
-                    default="jpmschweitzer"
+                    description="User identifier (tenant). Required - all operations are scoped to this tenant's namespace",
+                    required=True
                 ),
             ],
             returns="List of dossiers with page counts",
@@ -275,9 +268,8 @@ def get_wiki_tools() -> list[ToolDefinition]:
                 ToolParameter(
                     name="user",
                     type=ParameterType.STRING,
-                    description="User identifier",
-                    required=False,
-                    default="jpmschweitzer"
+                    description="User identifier (tenant). Required - all operations are scoped to this tenant's namespace",
+                    required=True
                 ),
                 ToolParameter(
                     name="limit",
diff --git a/src/routers/vector.py b/src/routers/vector.py
index ebb121f..2083538 100644
--- a/src/routers/vector.py
+++ b/src/routers/vector.py
@@ -18,8 +18,9 @@ from src.services.vector_service import VectorService
 from src.clients.qdrant_client import QdrantClientWrapper
 from src.clients.wikijs_client import WikiJSClient
 from src.clients.ollama_client import OllamaClient
-from src.core.dependencies import QdrantDep, WikiJSDep, OllamaDep, verify_api_key
-from src.core.multi_tenancy import DEFAULT_USER
+from src.core.dependencies import (
+    QdrantDep, WikiJSDep, OllamaDep, verify_api_key, RequiredUserQuery
+)
 
 logger = logging.getLogger(__name__)
 
@@ -52,7 +53,7 @@ async def semantic_search(
     ```json
     {
         "query": "how to configure docker",
-        "user": "jpmschweitzer",
+        "user": "<tenant>",
         "limit": 10,
         "score_threshold": 0.5
     }
@@ -77,7 +78,7 @@ async def semantic_search(
 @router.post("/update-from-page/{page_id}", response_model=VectorUpdateSummary)
 async def update_vectors_from_page(
     page_id: int,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     force_refresh: bool = Query(default=False, description="Force re-embedding"),
     vector_service: VectorService = Depends(get_vector_service),
     api_key: str = Depends(verify_api_key)
@@ -96,7 +97,7 @@ async def update_vectors_from_page(
     - Called manually by user/Librarian to refresh vectors
     - Called by Scheduler for batch processing
 
-    **Example:** `POST /vector/update-from-page/5?user=jpmschweitzer`
+    **Example:** `POST /vector/update-from-page/5?user=<tenant> (user is REQUIRED)`
 
     **Returns:** Summary with chunks created and processing time
     """
@@ -125,7 +126,7 @@ async def update_vectors_from_page(
 @router.delete("/pages/{page_id}", response_model=DeletePageChunksResponse)
 async def delete_page_chunks(
     page_id: int,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     vector_service: VectorService = Depends(get_vector_service),
     api_key: str = Depends(verify_api_key)
 ):
@@ -134,7 +135,7 @@ async def delete_page_chunks(
 
     This is automatically called when a page is deleted from the wiki.
 
-    **Example:** `DELETE /vector/pages/5?user=jpmschweitzer`
+    **Example:** `DELETE /vector/pages/5?user=<tenant> (user is REQUIRED)`
     """
     try:
         deleted_count = await vector_service.delete_page_chunks(
diff --git a/src/routers/volatile.py b/src/routers/volatile.py
index 9fc16ac..be0e93f 100644
--- a/src/routers/volatile.py
+++ b/src/routers/volatile.py
@@ -28,7 +28,7 @@ from src.core.dependencies import (
     get_news_provider,
     get_alphavantage_provider,
 )
-from src.core.multi_tenancy import DEFAULT_USER
+from src.core.dependencies import RequiredUserQuery
 from src.config import get_settings
 
 logger = logging.getLogger(__name__)
@@ -48,7 +48,7 @@ def get_volatile_service(qdrant: QdrantDep, ollama: OllamaDep) -> VolatileCacheS
 
 @router.get("/stats", response_model=VolatileStatsResponse)
 async def get_stats(
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
     api_key: str = Depends(verify_api_key)
@@ -72,7 +72,7 @@ async def get_stats(
 
 @router.get("/scheduled", response_model=VolatileScheduledResponse)
 async def get_scheduled(
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
     api_key: str = Depends(verify_api_key)
@@ -134,8 +134,8 @@ def _get_namespace_description(ns: VolatileNamespace) -> str:
 
 @router.get("/search")
 async def search_volatile(
+    user: RequiredUserQuery,
     q: str = Query(..., min_length=1, description="Search query"),
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
     limit: int = Query(default=5, ge=1, le=20, description="Maximum results"),
     threshold: float = Query(default=0.75, ge=0.5, le=1.0, description="Minimum similarity score"),
     qdrant: QdrantDep = None,
@@ -166,10 +166,10 @@ async def search_volatile(
 
 @router.post("/store", response_model=VolatileRecordResponse)
 async def store_volatile(
+    user: RequiredUserQuery,
     namespace: str = Query(..., description="Data namespace (weather, news, etc.)"),
     key: str = Query(..., description="Record key (e.g., 'rotterdam', 'nos-headlines')"),
     request: VolatileRecordCreate = None,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
     api_key: str = Depends(verify_api_key)
@@ -232,7 +232,7 @@ async def store_volatile(
 @router.post("/fetch/weather/{city}")
 async def fetch_weather(
     city: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     ttl: int = Query(default=7200, ge=60, le=86400, description="TTL in seconds (default 2 hours)"),
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
@@ -246,7 +246,7 @@ async def fetch_weather(
 
     **Example:**
     ```
-    POST /volatile/fetch/weather/amsterdam?user=jpmschweitzer
+    POST /volatile/fetch/weather/amsterdam?user=<tenant>
     ```
     """
     volatile_service = get_volatile_service(qdrant, ollama)
@@ -273,7 +273,7 @@ async def fetch_weather(
 @router.post("/fetch/forecast/{city}")
 async def fetch_forecast(
     city: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     days: int = Query(default=7, ge=1, le=16, description="Forecast days (1-16)"),
     ttl: int = Query(default=86400, ge=60, le=604800, description="TTL in seconds (default 24 hours)"),
     qdrant: QdrantDep = None,
@@ -288,7 +288,7 @@ async def fetch_forecast(
 
     **Example:**
     ```
-    POST /volatile/fetch/forecast/amsterdam?user=jpmschweitzer&days=7
+    POST /volatile/fetch/forecast/amsterdam?user=<tenant>&days=7
     ```
     """
     volatile_service = get_volatile_service(qdrant, ollama)
@@ -314,8 +314,8 @@ async def fetch_forecast(
 
 @router.post("/fetch/news/{category}")
 async def fetch_news(
+    user: RequiredUserQuery,
     category: str = "general",
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
     limit: int = Query(default=10, ge=1, le=50, description="Max headlines"),
     ttl: int = Query(default=7200, ge=60, le=86400, description="TTL in seconds"),
     qdrant: QdrantDep = None,
@@ -330,7 +330,7 @@ async def fetch_news(
 
     **Example:**
     ```
-    POST /volatile/fetch/news/tech?user=jpmschweitzer&limit=15
+    POST /volatile/fetch/news/tech?user=<tenant>&limit=15
     ```
     """
     volatile_service = get_volatile_service(qdrant, ollama)
@@ -359,7 +359,7 @@ async def fetch_news(
 @router.post("/fetch/stock/{symbol}")
 async def fetch_stock(
     symbol: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     ttl: int = Query(default=600, ge=60, le=3600, description="TTL in seconds (default 10 min)"),
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
@@ -372,7 +372,7 @@ async def fetch_stock(
 
     **Example:**
     ```
-    POST /volatile/fetch/stock/AAPL?user=jpmschweitzer
+    POST /volatile/fetch/stock/AAPL?user=<tenant>
     ```
     """
     volatile_service = get_volatile_service(qdrant, ollama)
@@ -407,8 +407,8 @@ async def fetch_stock(
 @router.post("/fetch/crypto/{symbol}")
 async def fetch_crypto(
     symbol: str,
+    user: RequiredUserQuery,
     market: str = Query(default="USD", description="Market currency"),
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
     ttl: int = Query(default=600, ge=60, le=3600, description="TTL in seconds (default 10 min)"),
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
@@ -421,7 +421,7 @@ async def fetch_crypto(
 
     **Example:**
     ```
-    POST /volatile/fetch/crypto/BTC?market=EUR&user=jpmschweitzer
+    POST /volatile/fetch/crypto/BTC?market=EUR&user=<tenant>
     ```
     """
     volatile_service = get_volatile_service(qdrant, ollama)
@@ -456,7 +456,7 @@ async def fetch_crypto(
 @router.post("/fetch/sun/{city}")
 async def fetch_sun_times(
     city: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     ttl: int = Query(default=172800, ge=60, le=604800, description="TTL in seconds (default 48 hours)"),
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
@@ -469,7 +469,7 @@ async def fetch_sun_times(
 
     **Example:**
     ```
-    POST /volatile/fetch/sun/rotterdam?user=jpmschweitzer
+    POST /volatile/fetch/sun/rotterdam?user=<tenant>
     ```
 
     **Response data includes:**
@@ -502,7 +502,7 @@ async def fetch_sun_times(
 @router.post("/fetch/air_quality/{city}")
 async def fetch_air_quality(
     city: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     ttl: int = Query(default=7200, ge=60, le=86400, description="TTL in seconds (default 2 hours)"),
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
@@ -515,7 +515,7 @@ async def fetch_air_quality(
 
     **Example:**
     ```
-    POST /volatile/fetch/air_quality/rotterdam?user=jpmschweitzer
+    POST /volatile/fetch/air_quality/rotterdam?user=<tenant>
     ```
 
     **Response data includes:**
@@ -548,7 +548,7 @@ async def fetch_air_quality(
 @router.post("/fetch/environment/{city}")
 async def fetch_environment(
     city: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     weather_ttl: int = Query(default=7200, ge=60, le=86400, description="Weather TTL in seconds (default 2 hours)"),
     air_quality_ttl: int = Query(default=7200, ge=60, le=86400, description="Air quality TTL in seconds (default 2 hours)"),
     qdrant: QdrantDep = None,
@@ -564,7 +564,7 @@ async def fetch_environment(
 
     **Example:**
     ```
-    POST /volatile/fetch/environment/rotterdam?user=jpmschweitzer
+    POST /volatile/fetch/environment/rotterdam?user=<tenant>
     ```
 
     **Response includes:**
@@ -607,7 +607,7 @@ async def fetch_environment(
 async def get_record(
     namespace: str,
     key: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
     api_key: str = Depends(verify_api_key)
@@ -617,7 +617,7 @@ async def get_record(
 
     **Example:**
     ```
-    GET /volatile/weather/rotterdam?user=jpmschweitzer
+    GET /volatile/weather/rotterdam?user=<tenant>
     ```
     """
     service = get_volatile_service(qdrant, ollama)
@@ -636,7 +636,7 @@ async def get_record(
 async def delete_record(
     namespace: str,
     key: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     qdrant: QdrantDep = None,
     ollama: OllamaDep = None,
     api_key: str = Depends(verify_api_key)
diff --git a/src/routers/wiki.py b/src/routers/wiki.py
index efefd63..237db7a 100644
--- a/src/routers/wiki.py
+++ b/src/routers/wiki.py
@@ -24,9 +24,9 @@ from src.clients.qdrant_client import QdrantClientWrapper
 from src.clients.ollama_client import OllamaClient
 from src.core.dependencies import (
     WikiJSDep, Neo4jDep, QdrantDep, OllamaDep, SearXNGDep, ContentExtractorDep,
-    verify_api_key, get_settings, get_hybrid_rag_service, get_ingestion_service
+    verify_api_key, get_settings, get_hybrid_rag_service, get_ingestion_service,
+    RequiredUserQuery
 )
-from src.core.multi_tenancy import DEFAULT_USER
 from src.services.hybrid_rag_service import HybridRAGService
 from src.services.wiki_page_writer import WikiPageWriter
 from src.services.entity_linking_utils import apply_bidirectional_entity_linking
@@ -62,7 +62,7 @@ def get_vector_service(
 # Page operations
 @router.get("/pages", response_model=WikiPageList)
 async def list_pages(
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     tag: Optional[str] = Query(default=None, description="Filter by tag (dossier)"),
     limit: int = Query(default=50, ge=1, le=200, description="Maximum pages to return"),
     wiki_service: WikiService = Depends(get_wiki_service),
@@ -87,7 +87,7 @@ async def list_pages(
 @router.get("/pages/{page_id}", response_model=WikiPage)
 async def get_page(
     page_id: int,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     wiki_service: WikiService = Depends(get_wiki_service),
     api_key: str = Depends(verify_api_key)
 ):
@@ -139,14 +139,16 @@ async def create_page(
         "content": "# Architecture\\n\\nThis describes...",
         "description": "Architecture documentation",
         "tags": ["projects", "architecture"],
-        "user": "jpmschweitzer"
+        "user": "<tenant>"
     }
     ```
+
+    The `user` field is REQUIRED (no default tenant).
     """
     try:
         page = await wiki_service.create_page(page_data)
 
-        user = page_data.user or DEFAULT_USER
+        user = page_data.user
 
         # Schedule BOTH graph and vector updates in background (non-blocking)
         background_tasks.add_task(
@@ -214,7 +216,7 @@ async def smart_create_page(
     - Entity linking statistics (forward/backward links)
     """
     try:
-        user = request.user or DEFAULT_USER
+        user = request.user
 
         # Build services
         wiki_service = WikiService(wiki_client)
@@ -294,7 +296,7 @@ async def update_page(
     page_id: int,
     page_data: WikiPageUpdate,
     background_tasks: BackgroundTasks,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     wiki_service: WikiService = Depends(get_wiki_service),
     graph_service: GraphService = Depends(get_graph_service),
     vector_service: VectorService = Depends(get_vector_service),
@@ -353,7 +355,7 @@ async def update_page(
 async def delete_page(
     page_id: int,
     background_tasks: BackgroundTasks,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     wiki_service: WikiService = Depends(get_wiki_service),
     vector_service: VectorService = Depends(get_vector_service),
     graph_service: GraphService = Depends(get_graph_service),
@@ -402,7 +404,7 @@ async def delete_page(
 async def move_page(
     page_id: int,
     move_data: WikiPageMove,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     wiki_service: WikiService = Depends(get_wiki_service),
     api_key: str = Depends(verify_api_key)
 ):
@@ -445,8 +447,8 @@ async def move_page(
 # Search operations
 @router.get("/search", response_model=WikiSearchResponse)
 async def search_pages(
+    user: RequiredUserQuery,
     q: str = Query(..., min_length=1, description="Search query"),
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
     limit: int = Query(default=20, ge=1, le=100, description="Maximum results"),
     wiki_service: WikiService = Depends(get_wiki_service),
     api_key: str = Depends(verify_api_key)
@@ -487,7 +489,7 @@ async def search_pages(
 # Dossier operations
 @router.get("/dossiers", response_model=DossierList)
 async def list_dossiers(
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     wiki_service: WikiService = Depends(get_wiki_service),
     api_key: str = Depends(verify_api_key)
 ):
@@ -510,7 +512,7 @@ async def list_dossiers(
 @router.get("/dossiers/{dossier_name}/pages", response_model=WikiPageList)
 async def get_dossier_pages(
     dossier_name: str,
-    user: str = Query(default=DEFAULT_USER, description="User identifier"),
+    user: RequiredUserQuery,
     limit: int = Query(default=100, ge=1, le=500, description="Maximum pages"),
     wiki_service: WikiService = Depends(get_wiki_service),
     api_key: str = Depends(verify_api_key)
diff --git a/src/services/consolidation_service.py b/src/services/consolidation_service.py
index c01235d..e79a27a 100644
--- a/src/services/consolidation_service.py
+++ b/src/services/consolidation_service.py
@@ -398,7 +398,7 @@ class ConsolidationService:
         query: str,
         web_results: List[Dict[str, Any]],
         keywords: List[str],
-        user: str = "jpmschweitzer"
+        user: str
     ) -> Optional[Dict[str, Any]]:
         """
         Analyze web results with Ollama for novel information.
@@ -977,7 +977,7 @@ JSON:"""
         query: str,
         web_results: List[Dict[str, Any]],
         keywords: List[str],
-        user: str = "jpmschweitzer"
+        user: str
     ) -> MemoryRoutingResult:
         """
         Unified classification of web results for memory routing.
diff --git a/src/services/wiki_change_listener.py b/src/services/wiki_change_listener.py
index dee699c..85a34ba 100644
--- a/src/services/wiki_change_listener.py
+++ b/src/services/wiki_change_listener.py
@@ -103,8 +103,17 @@ class WikiChangeListener:
             }
             event = event_map.get(operation, 'page.update')
 
-            # Extract user from email
-            user = user_email.split('@')[0] if '@' in user_email else 'jpmschweitzer'
+            # Extract user from email. There is NO default tenant: if no user
+            # can be derived from the notification, skip processing instead of
+            # attributing the change to an arbitrary tenant.
+            if '@' in user_email and user_email.split('@')[0].strip():
+                user = user_email.split('@')[0].strip()
+            else:
+                logger.warning(
+                    f"Skipping page {page_id} change: cannot derive tenant user "
+                    f"from notification email {user_email!r}"
+                )
+                return
 
             # Process the change
             await self._process_page_change(
diff --git a/src/services/wiki_service.py b/src/services/wiki_service.py
index 43f454a..98b3bb1 100644
--- a/src/services/wiki_service.py
+++ b/src/services/wiki_service.py
@@ -12,7 +12,7 @@ from typing import List, Optional, Dict, Any
 import logging
 
 from src.clients.wikijs_client import WikiJSClient
-from src.core.multi_tenancy import get_wikijs_namespace, validate_user_id, DEFAULT_USER
+from src.core.multi_tenancy import get_wikijs_namespace, validate_user_id
 from src.models.wiki import (
     WikiPage, WikiPageSummary, WikiPageList,
     WikiPageCreate, WikiPageUpdate,
@@ -184,7 +184,7 @@ class WikiService:
         Raises:
             ValueError: If creation fails
         """
-        user = page_data.user or DEFAULT_USER
+        user = page_data.user
 
         # Ensure path is in user's namespace
         full_path = self._ensure_user_path(page_data.path, user)
diff --git a/tests/test_multi_tenancy.py b/tests/test_multi_tenancy.py
index d4e277b..7c69e88 100644
--- a/tests/test_multi_tenancy.py
+++ b/tests/test_multi_tenancy.py
@@ -7,8 +7,8 @@ from src.core.multi_tenancy import (
     get_wikijs_namespace,
     get_neo4j_user_label,
     validate_user_id,
+    validate_required_user,
     is_path_in_user_namespace,
-    DEFAULT_USER
 )
 
 
@@ -46,8 +46,8 @@ class TestQdrantCollectionName:
     def test_email_user(self):
         assert get_qdrant_collection_name("john@example.com") == "library_desk_john_at_example_com"
 
-    def test_default_user(self):
-        assert get_qdrant_collection_name(DEFAULT_USER) == f"library_desk_{DEFAULT_USER}"
+    def test_test_tenant(self):
+        assert get_qdrant_collection_name("llm_tester") == "library_desk_llm_tester"
 
 
 class TestWikijsNamespace:
@@ -99,6 +99,41 @@ class TestValidateUserId:
         assert validate_user_id("___") is False
 
 
+class TestValidateRequiredUser:
+    """Test the required-user validator (no default tenant)."""
+
+    def test_no_default_user_constant(self):
+        """The DEFAULT_USER escape hatch must not exist anymore."""
+        import src.core.multi_tenancy as mt
+        assert not hasattr(mt, "DEFAULT_USER")
+
+    def test_valid_user_returned(self):
+        assert validate_required_user("llm_tester") == "llm_tester"
+
+    def test_valid_user_stripped(self):
+        assert validate_required_user("  llm_tester  ") == "llm_tester"
+
+    def test_empty_rejected(self):
+        with pytest.raises(ValueError):
+            validate_required_user("")
+
+    def test_whitespace_rejected(self):
+        with pytest.raises(ValueError):
+            validate_required_user("   ")
+
+    def test_none_rejected(self):
+        with pytest.raises(ValueError):
+            validate_required_user(None)
+
+    def test_no_alphanumeric_rejected(self):
+        with pytest.raises(ValueError):
+            validate_required_user("___")
+
+    def test_too_long_rejected(self):
+        with pytest.raises(ValueError):
+            validate_required_user("a" * 101)
+
+
 class TestPathInNamespace:
     """Test path namespace checking."""
 
diff --git a/tests/test_rag_search.py b/tests/test_rag_search.py
index 386aaec..b70cce6 100644
--- a/tests/test_rag_search.py
+++ b/tests/test_rag_search.py
@@ -37,12 +37,19 @@ class TestRAGSearchModels:
     """Tests for RAG search Pydantic models."""
 
     def test_search_request_defaults(self):
-        """Test RAGSearchRequest with default values."""
-        request = RAGSearchRequest(query="test query")
+        """Test RAGSearchRequest defaults (user is required, no default tenant)."""
+        request = RAGSearchRequest(query="test query", user="llm_tester")
 
         assert request.query == "test query"
         assert request.search_type == SearchType.WEB
         assert request.limit == 10
+        assert request.user == "llm_tester"
+
+    def test_search_request_requires_user(self):
+        """A request without an explicit user must be rejected."""
+        import pytest
+        with pytest.raises(ValueError):
+            RAGSearchRequest(query="test query")
 
     def test_search_request_custom_values(self):
         """Test RAGSearchRequest with custom values."""
diff --git a/tests/test_required_user.py b/tests/test_required_user.py
new file mode 100644
index 0000000..4e19f0e
--- /dev/null
+++ b/tests/test_required_user.py
@@ -0,0 +1,117 @@
+"""
+Offline unit tests: every tenant-data endpoint must REQUIRE an explicit user.
+
+A request without a user (query param or body field) must be rejected with
+422 before any service is touched. Empty/whitespace users are also rejected.
+
+No external services are contacted: validation failures short-circuit the
+request before the endpoint body executes.
+"""
+
+import pytest
+from fastapi.testclient import TestClient
+
+from src.main import app
+from src.core.dependencies import verify_api_key
+
+
+@pytest.fixture(scope="module")
+def client():
+    """TestClient with API-key auth stubbed out (no lifespan startup)."""
+    app.dependency_overrides[verify_api_key] = lambda: "test-key"
+    try:
+        # No context manager: startup/lifespan events are NOT triggered,
+        # so no connections to external services are attempted.
+        yield TestClient(app)
+    finally:
+        app.dependency_overrides.pop(verify_api_key, None)
+
+
+QUERY_PARAM_ENDPOINTS = [
+    ("GET", "/stats"),
+    ("POST", "/query/semantic?query=test"),
+    ("POST", "/query/graph?query=MATCH%20(n)%20RETURN%20n"),
+    ("GET", "/wiki/pages"),
+    ("GET", "/wiki/pages/1"),
+    ("PUT", "/wiki/pages/1"),
+    ("DELETE", "/wiki/pages/1"),
+    ("GET", "/wiki/search?q=test"),
+    ("GET", "/wiki/dossiers"),
+    ("POST", "/vector/update-from-page/1"),
+    ("DELETE", "/vector/pages/1"),
+    ("GET", "/graph/nodes"),
+    ("POST", "/graph/update-from-page/1"),
+    ("POST", "/graph/generate-entity-pages"),
+    ("POST", "/ingest/all"),
+    ("GET", "/volatile/stats"),
+    ("GET", "/volatile/search?q=test"),
+    ("POST", "/volatile/store?namespace=weather&key=test"),
+    ("GET", "/volatile/weather/rotterdam"),
+    ("DELETE", "/volatile/weather/rotterdam"),
+    ("POST", "/documents/webhook-simple?doc_url=http://x/documents/1/"),
+]
+
+
+@pytest.mark.unit
+class TestUserQueryParamRequired:
+    """Endpoints with a user query parameter must 422 without it."""
+
+    @pytest.mark.parametrize("method,path", QUERY_PARAM_ENDPOINTS)
+    def test_missing_user_is_422(self, client, method, path):
+        response = client.request(method, path, json={})
+        assert response.status_code == 422, (
+            f"{method} {path} returned {response.status_code}, expected 422"
+        )
+
+    @pytest.mark.parametrize("blank", ["", " ", "%20%20"])
+    def test_blank_user_is_422(self, client, blank):
+        response = client.get(f"/wiki/pages?user={blank}")
+        assert response.status_code == 422
+
+    def test_hybrid_query_missing_user_is_422(self, client):
+        response = client.post("/query/hybrid", json={"query": "test"})
+        assert response.status_code == 422
+
+    def test_hybrid_query_whitespace_user_is_422(self, client):
+        response = client.post("/query/hybrid?user=%20", json={"query": "test"})
+        assert response.status_code == 422
+
+
+@pytest.mark.unit
+class TestUserBodyFieldRequired:
+    """Request models with a user field must reject missing/blank values."""
+
+    def test_ingest_page_missing_user_is_422(self, client):
+        response = client.post("/ingest/page", json={"page_id": 1})
+        assert response.status_code == 422
+
+    def test_ingest_page_blank_user_is_422(self, client):
+        response = client.post("/ingest/page", json={"page_id": 1, "user": "  "})
+        assert response.status_code == 422
+
+    def test_ingest_batch_missing_user_is_422(self, client):
+        response = client.post("/ingest/batch", json={"page_ids": [1]})
+        assert response.status_code == 422
+
+    def test_wiki_create_page_missing_user_is_422(self, client):
+        response = client.post(
+            "/wiki/pages",
+            json={"title": "T", "path": "/t", "content": "c"},
+        )
+        assert response.status_code == 422
+
+    def test_wiki_smart_create_missing_user_is_422(self, client):
+        response = client.post("/wiki/pages/smart-create", json={"topic": "T"})
+        assert response.status_code == 422
+
+    def test_vector_search_missing_user_is_422(self, client):
+        response = client.post("/vector/search", json={"query": "test"})
+        assert response.status_code == 422
+
+    def test_graph_query_missing_user_is_422(self, client):
+        response = client.post("/graph/query", json={"query": "MATCH (n) RETURN n"})
+        assert response.status_code == 422
+
+    def test_rag_search_missing_user_is_422(self, client):
+        response = client.post("/rag/search", json={"query": "test"})
+        assert response.status_code == 422
diff --git a/tests/test_smart_create.py b/tests/test_smart_create.py
index 7310a52..03cc1c9 100644
--- a/tests/test_smart_create.py
+++ b/tests/test_smart_create.py
@@ -26,15 +26,20 @@ class TestWikiSmartCreateRequest:
     """Tests for WikiSmartCreateRequest model validation."""
 
     def test_minimal_request(self):
-        """Test request with only required field."""
-        request = WikiSmartCreateRequest(topic="Docker containers")
+        """Test request with only required fields (topic AND user)."""
+        request = WikiSmartCreateRequest(topic="Docker containers", user="llm_tester")
         assert request.topic == "Docker containers"
         assert request.path is None
         assert request.tags == []
-        assert request.user is None
+        assert request.user == "llm_tester"
         assert request.include_web_research is True
         assert request.include_wiki_search is True
 
+    def test_user_is_required(self):
+        """A request without an explicit user must be rejected."""
+        with pytest.raises(ValueError):
+            WikiSmartCreateRequest(topic="Docker containers")
+
     def test_full_request(self):
         """Test request with all fields."""
         request = WikiSmartCreateRequest(
@@ -68,7 +73,8 @@ class TestWikiSmartCreateRequest:
         """Test that path without leading slash gets one added."""
         request = WikiSmartCreateRequest(
             topic="Test",
-            path="technology/test"
+            path="technology/test",
+            user="llm_tester"
         )
         assert request.path == "/technology/test"
 
@@ -76,7 +82,8 @@ class TestWikiSmartCreateRequest:
         """Test that trailing slash is removed."""
         request = WikiSmartCreateRequest(
             topic="Test",
-            path="/technology/test/"
+            path="/technology/test/",
+            user="llm_tester"
         )
         assert request.path == "/technology/test"
 
@@ -84,7 +91,8 @@ class TestWikiSmartCreateRequest:
         """Test that duplicate tags are removed."""
         request = WikiSmartCreateRequest(
             topic="Test",
-            tags=["devops", "devops", "containers", "devops"]
+            tags=["devops", "devops", "containers", "devops"],
+            user="llm_tester"
         )
         assert len(request.tags) == 2
         assert "devops" in request.tags
@@ -94,7 +102,8 @@ class TestWikiSmartCreateRequest:
         """Test that tag whitespace is cleaned."""
         request = WikiSmartCreateRequest(
             topic="Test",
-            tags=["  devops  ", "containers", "  ", ""]
+            tags=["  devops  ", "containers", "  ", ""],
+            user="llm_tester"
         )
         assert "devops" in request.tags
         assert "containers" in request.tags
@@ -536,7 +545,8 @@ class TestSmartCreateEndpoint:
         # For now, we test the model validation
         request = WikiSmartCreateRequest(
             topic="Test Topic",
-            tags=["test"]
+            tags=["test"],
+            user="llm_tester"
         )
         assert request.topic == "Test Topic"
 
@@ -546,8 +556,8 @@ class TestSmartCreateEndpoint:
             WikiSmartCreateRequest(topic="")
 
     def test_request_accepts_minimal_input(self):
-        """Test that only topic is required."""
-        request = WikiSmartCreateRequest(topic="Minimal test")
+        """Test that topic and user are the only required fields."""
+        request = WikiSmartCreateRequest(topic="Minimal test", user="llm_tester")
         assert request.topic == "Minimal test"
         assert request.include_web_research is True  # default
         assert request.include_wiki_search is True  # default
diff --git a/tests/test_wiki_change_listener.py b/tests/test_wiki_change_listener.py
index 2270dd9..c8c62b0 100644
--- a/tests/test_wiki_change_listener.py
+++ b/tests/test_wiki_change_listener.py
@@ -231,9 +231,8 @@ class TestWikiChangeListener:
                 'UPDATE:123:invaliduser'
             )
 
-            # Should use default user
-            call_args = mock_process.call_args[1]
-            assert call_args['user'] == 'jpmschweitzer'
+            # No default tenant: change must be skipped entirely
+            mock_process.assert_not_awaited()
 
     @pytest.mark.asyncio
     async def test_process_page_delete_calls_cleanup(self, listener):