diff --git a/PROJECT_STATE.md b/PROJECT_STATE.md
index 3def7b0..d58e9a0 100644
--- a/PROJECT_STATE.md
+++ b/PROJECT_STATE.md
@@ -2314,3 +2314,18 @@ evidence yet."
   focused Unraid contracts **19 passed** and the full suite **208 passed, 1 warning**.
 - Exact next action: harden MCP per-client authorization and evidence completeness, then
   replace inferred n8n status with explicit heartbeat/execution telemetry.
+
+## MCP trust boundary and trace completeness (2026-08-10)
+
+- The MCP API now validates the ITWorx Hub delegated client-id shape in addition to the
+  shared service secret, supports an explicit tenant assertion and rejects cross-tenant
+  calls. Readiness and project-bound client identities remain compatible with the Hub's
+  documented connector contract; arbitrary/spoofed labels no longer enter the audit log.
+- Every successful tool response returns `X-Correlation-Id`, `X-Tenant-Id` and
+  `Cache-Control: no-store`. Knowledge calls additionally expose available versus
+  returned source counts and persist tenant, locale and source coverage in their audit
+  metadata. `contracts/mcp-tools.json` is versioned to 1.2.0 with this trust contract.
+- Evidence: ruff and mypy passed; focused MCP tests **14 passed** and full Unraid suite
+  **210 passed, 1 warning**.
+- Exact next action: add authenticated n8n workflow heartbeats and execution results,
+  surface stale/healthy workflow state, then update generated contracts and E2E coverage.
diff --git a/backend/app/api/deps.py b/backend/app/api/deps.py
index 5f76470..2fbf7a9 100644
--- a/backend/app/api/deps.py
+++ b/backend/app/api/deps.py
@@ -1,6 +1,9 @@
 from __future__ import annotations
 
+import hmac
+import re
 from collections.abc import Generator
+from dataclasses import dataclass
 
 from fastapi import Depends, Header, HTTPException, Request, status
 from sqlalchemy.orm import Session
@@ -60,12 +63,30 @@ def require_operations_manager(
     return user
 
 
+@dataclass(frozen=True)
+class McpClientContext:
+    client_id: str
+    tenant: str
+
+
+_MCP_CLIENT_ID = re.compile(
+    r"^itworx-mcp-hub:(?:readiness|mobilityops:[A-Za-z0-9][A-Za-z0-9._:-]{0,127})$"
+)
+
+
 def require_mcp_service_token(
     x_service_token: str = Header(..., alias="X-Service-Token"),
-    x_client_id: str = Header(default="unknown-mcp-client", alias="X-Client-Id"),
-) -> str:
-    if x_service_token != settings.mcp_hub_service_token:
+    x_client_id: str = Header(..., alias="X-Client-Id", min_length=1, max_length=180),
+    x_tenant_id: str | None = Header(default=None, alias="X-Tenant-Id", max_length=120),
+) -> McpClientContext:
+    if not hmac.compare_digest(x_service_token, settings.mcp_hub_service_token):
         raise HTTPException(
             status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid service token"
         )
-    return x_client_id
+    if not _MCP_CLIENT_ID.fullmatch(x_client_id):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN, detail="Untrusted MCP client identity"
+        )
+    if x_tenant_id is not None and x_tenant_id != settings.ragcore_tenant:
+        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Tenant mismatch")
+    return McpClientContext(client_id=x_client_id, tenant=settings.ragcore_tenant)
diff --git a/backend/app/api/routers/mcp_integrations.py b/backend/app/api/routers/mcp_integrations.py
index c4128e5..8713c1a 100644
--- a/backend/app/api/routers/mcp_integrations.py
+++ b/backend/app/api/routers/mcp_integrations.py
@@ -3,11 +3,11 @@ from __future__ import annotations
 import uuid
 from datetime import date
 
-from fastapi import APIRouter, Depends, Header, Query
+from fastapi import APIRouter, Depends, Header, Query, Response
 from sqlalchemy import select
 from sqlalchemy.orm import Session
 
-from app.api.deps import get_db, require_mcp_service_token
+from app.api.deps import McpClientContext, get_db, require_mcp_service_token
 from app.core.config import get_settings
 from app.core.errors import AppError
 from app.models.booking import Booking
@@ -42,7 +42,8 @@ def get_correlation_id(
 
 
 def _audit_service_request(
-    db: Session, *, client_id: str, tool: str, status_label: str, correlation_id: str
+    db: Session, *, client_id: str, tool: str, status_label: str, correlation_id: str,
+    metadata: dict[str, object] | None = None,
 ) -> None:
     record_audit_event(
         db,
@@ -51,43 +52,53 @@ def _audit_service_request(
         action="mcp_tool_request",
         entity_type="mcp_tool",
         correlation_id=uuid.UUID(correlation_id),
-        metadata={"tool": tool, "status": status_label},
+        metadata={"tool": tool, "status": status_label, **(metadata or {})},
     )
     db.commit()
 
 
+def _set_trace_headers(response: Response, correlation_id: str, tenant: str) -> None:
+    response.headers["X-Correlation-Id"] = correlation_id
+    response.headers["X-Tenant-Id"] = tenant
+    response.headers["Cache-Control"] = "no-store"
+
+
 @router.get("/operations-summary", response_model=OperationsSummaryOut)
 def operations_summary(
+    response: Response,
     db: Session = Depends(get_db),
-    client_id: str = Depends(require_mcp_service_token),
+    client: McpClientContext = Depends(require_mcp_service_token),
     correlation_id: str = Depends(get_correlation_id),
 ) -> OperationsSummaryOut:
     metrics = compute_metrics(db)
+    _set_trace_headers(response, correlation_id, client.tenant)
     _audit_service_request(
         db,
-        client_id=client_id,
+        client_id=client.client_id,
         tool="fleet_ops_get_operations_summary",
         status_label="ok",
         correlation_id=correlation_id,
     )
-    return OperationsSummaryOut(tenant=settings.ragcore_tenant, metrics=metrics)
+    return OperationsSummaryOut(tenant=client.tenant, metrics=metrics)
 
 
 @router.get("/attention-vehicles", response_model=list[AttentionVehicleOut])
 def attention_vehicles(
+    response: Response,
     minimum_severity: str = Query(default="medium", pattern="^(low|medium|high)$"),
     date_filter: date | None = Query(default=None, alias="date"),
     limit: int = Query(default=20, ge=1, le=50),
     db: Session = Depends(get_db),
-    client_id: str = Depends(require_mcp_service_token),
+    client: McpClientContext = Depends(require_mcp_service_token),
     correlation_id: str = Depends(get_correlation_id),
 ) -> list[AttentionVehicleOut]:
     results = list_attention_vehicles(
         db, minimum_severity=minimum_severity, on_or_before=date_filter, limit=limit
     )
+    _set_trace_headers(response, correlation_id, client.tenant)
     _audit_service_request(
         db,
-        client_id=client_id,
+        client_id=client.client_id,
         tool="fleet_ops_list_attention_vehicles",
         status_label="ok",
         correlation_id=correlation_id,
@@ -98,15 +109,17 @@ def attention_vehicles(
 @router.get("/vehicles/{vehicle_ref}", response_model=McpVehicleDetailOut)
 def vehicle_details(
     vehicle_ref: str,
+    response: Response,
     db: Session = Depends(get_db),
-    client_id: str = Depends(require_mcp_service_token),
+    client: McpClientContext = Depends(require_mcp_service_token),
     correlation_id: str = Depends(get_correlation_id),
 ) -> McpVehicleDetailOut:
+    _set_trace_headers(response, correlation_id, client.tenant)
     vehicle = db.scalar(select(Vehicle).where(Vehicle.public_ref == vehicle_ref))
     if vehicle is None:
         _audit_service_request(
             db,
-            client_id=client_id,
+            client_id=client.client_id,
             tool="fleet_ops_get_vehicle_details",
             status_label="not_found",
             correlation_id=correlation_id,
@@ -128,7 +141,7 @@ def vehicle_details(
 
     _audit_service_request(
         db,
-        client_id=client_id,
+        client_id=client.client_id,
         tool="fleet_ops_get_vehicle_details",
         status_label="ok",
         correlation_id=correlation_id,
@@ -150,18 +163,29 @@ def vehicle_details(
 @router.post("/search-knowledge", response_model=GroundedAnswer)
 def search_knowledge(
     body: McpKnowledgeSearchRequest,
+    response: Response,
     db: Session = Depends(get_db),
-    client_id: str = Depends(require_mcp_service_token),
+    client: McpClientContext = Depends(require_mcp_service_token),
     correlation_id: str = Depends(get_correlation_id),
 ) -> GroundedAnswer:
     provider = get_knowledge_provider()
     answer = provider.ask(body.question, correlation_id, language=body.locale)
+    source_count_available = len(answer.sources)
     answer.sources = answer.sources[: body.max_sources]
+    _set_trace_headers(response, correlation_id, client.tenant)
+    response.headers["X-Sources-Available"] = str(source_count_available)
+    response.headers["X-Sources-Returned"] = str(len(answer.sources))
     _audit_service_request(
         db,
-        client_id=client_id,
+        client_id=client.client_id,
         tool="fleet_ops_search_knowledge",
         status_label=answer.evidence_state,
         correlation_id=correlation_id,
+        metadata={
+            "tenant": client.tenant,
+            "locale": body.locale,
+            "sources_available": source_count_available,
+            "sources_returned": len(answer.sources),
+        },
     )
     return answer
diff --git a/backend/tests/test_auth.py b/backend/tests/test_auth.py
index bb5fe02..954b428 100644
--- a/backend/tests/test_auth.py
+++ b/backend/tests/test_auth.py
@@ -75,7 +75,7 @@ def test_demo_reset_preserves_integration_telemetry(ops_client, client):
         "/api/v1/integrations/mcp/operations-summary",
         headers={
             "X-Service-Token": settings.mcp_hub_service_token,
-            "X-Client-Id": "reset-probe",
+            "X-Client-Id": "itworx-mcp-hub:mobilityops:reset-probe",
         },
     )
     assert probe.status_code == 200
@@ -83,4 +83,4 @@ def test_demo_reset_preserves_integration_telemetry(ops_client, client):
 
     assert client.post("/api/v1/demo/login", json={"role": "operations_manager"}).status_code == 200
     events = client.get("/api/v1/audit", params={"action": "mcp_tool_request"}).json()
-    assert any(event["actor_label"] == "reset-probe" for event in events)
+    assert any(event["actor_label"].endswith(":reset-probe") for event in events)
diff --git a/backend/tests/test_mcp_integrations.py b/backend/tests/test_mcp_integrations.py
index 70d1876..4b19a8a 100644
--- a/backend/tests/test_mcp_integrations.py
+++ b/backend/tests/test_mcp_integrations.py
@@ -5,7 +5,7 @@ def _headers(token: str | None = None, client_id: str = "test-mcp-client"):
     settings = get_settings()
     return {
         "X-Service-Token": token if token is not None else settings.mcp_hub_service_token,
-        "X-Client-Id": client_id,
+        "X-Client-Id": f"itworx-mcp-hub:mobilityops:{client_id}",
     }
 
 
@@ -16,12 +16,31 @@ def test_operations_summary_requires_service_token(client):
     assert response.status_code == 401
 
 
+def test_operations_summary_rejects_spoofed_client_identity(client):
+    settings = get_settings()
+    response = client.get(
+        "/api/v1/integrations/mcp/operations-summary",
+        headers={"X-Service-Token": settings.mcp_hub_service_token, "X-Client-Id": "spoofed"},
+    )
+    assert response.status_code == 403
+
+
+def test_operations_summary_rejects_cross_tenant_request(client):
+    response = client.get(
+        "/api/v1/integrations/mcp/operations-summary",
+        headers={**_headers(), "X-Tenant-Id": "another-tenant"},
+    )
+    assert response.status_code == 403
+
+
 def test_operations_summary_returns_metrics(client):
     response = client.get("/api/v1/integrations/mcp/operations-summary", headers=_headers())
     assert response.status_code == 200
     body = response.json()
     assert "metrics" in body
     assert body["metrics"]["available"] >= 0
+    assert response.headers["x-correlation-id"]
+    assert response.headers["x-tenant-id"] == get_settings().ragcore_tenant
 
 
 def test_attention_vehicles_filters_by_severity(client):
@@ -72,6 +91,8 @@ def test_search_knowledge_grounded_and_respects_max_sources(client):
     body = response.json()
     assert body["evidence_state"] == "grounded"
     assert len(body["sources"]) == 1
+    assert int(response.headers["x-sources-available"]) >= 1
+    assert response.headers["x-sources-returned"] == "1"
 
 
 def test_mcp_tool_requests_are_audited(client, ops_client):
@@ -118,7 +139,7 @@ def test_operations_summary_mints_correlation_id_when_none_supplied(client, ops_
     )
     assert response.status_code == 200
     events = ops_client.get("/api/v1/audit", params={"action": "mcp_tool_request"}).json()
-    matching = [e for e in events if e["actor_label"] == "no-correlation-probe"]
+    matching = [e for e in events if e["actor_label"].endswith(":no-correlation-probe")]
     assert len(matching) >= 1
     assert matching[0]["correlation_id"]  # a fresh UUID was minted, not left empty
 
diff --git a/contracts/mcp-tools.json b/contracts/mcp-tools.json
index 14de04a..b952e1b 100644
--- a/contracts/mcp-tools.json
+++ b/contracts/mcp-tools.json
@@ -1,8 +1,19 @@
 {
   "_note": "Fleet Ops's own published tool contract. The live ITWorx MCP Hub connector (ITWorx_MCP_Hub repo, connectors/mobilityops/) wraps these under its own dotted namespace (mobilityops.operations.summary, .attention.list, .vehicle.get, .knowledge.search) -- that naming is Hub-owned. deprecated_aliases below are Fleet Ops's own prior internal audit-label names, kept only so existing clients/dashboards referencing them don't break.",
   "provider_id": "mobilityops",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "required_scope": "mobilityops.read",
+  "authentication": {
+    "service_header": "X-Service-Token",
+    "client_header": "X-Client-Id",
+    "client_pattern": "^itworx-mcp-hub:(readiness|mobilityops:[A-Za-z0-9][A-Za-z0-9._:-]{0,127})$",
+    "optional_tenant_header": "X-Tenant-Id",
+    "tenant_must_match": "northstar-mobility-demo"
+  },
+  "observability": {
+    "response_headers": ["X-Correlation-Id", "X-Tenant-Id", "Cache-Control"],
+    "knowledge_response_headers": ["X-Sources-Available", "X-Sources-Returned"]
+  },
   "tools": [
     {
       "name": "fleet_ops_get_operations_summary",