diff --git a/README.md b/README.md
index 066e25f..500289d 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 RouteForge is a read-only routing preflight and explainability tool for BGP, RPKI, Registry/IRR and Routing Visibility checks.
 
-Current user-facing version: **v0.3.0-alpha**.
+Current user-facing version: **v0.4.0-alpha**.
 
 <!-- Screenshot gallery placeholder:
 - docs/screenshots/dashboard.png
@@ -32,7 +32,7 @@ Routing changes often require fast but traceable checks across multiple external
 
 ## Current Alpha Status
 
-RouteForge is a **functional alpha** release with production-like workflows for read-only validation and demo usage. Current release target: **v0.3.0-alpha**.
+RouteForge is a **functional alpha** release with production-like workflows for read-only validation and demo usage. Current release target: **v0.4.0-alpha**.
 
 ## Quickstart with Docker Compose
 
diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 11b37e7..d64b3ee 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -1,6 +1,6 @@
 # Release Notes
 
-## v0.3.0-alpha
+## v0.4.0-alpha
 
 **Product Demo & Release Readiness**
 
diff --git a/backend/app/api/routes_system.py b/backend/app/api/routes_system.py
index 005a55c..cd207d0 100644
--- a/backend/app/api/routes_system.py
+++ b/backend/app/api/routes_system.py
@@ -9,7 +9,7 @@
 def system_info():
     return {
         'name': 'RouteForge',
-        'version': 'v0.3.0-alpha',
+        'version': 'v0.4.0-alpha',
         'demo_mode': settings.demo_mode,
         'read_only': True,
         'data_sources': ['RIPEstat', 'RIPEstat Whois/Registry'],
diff --git a/backend/app/core/source_diagnostics.py b/backend/app/core/source_diagnostics.py
new file mode 100644
index 0000000..f497859
--- /dev/null
+++ b/backend/app/core/source_diagnostics.py
@@ -0,0 +1,55 @@
+from __future__ import annotations
+
+from typing import Any
+
+OK = "OK"
+CACHE_HIT = "CACHE_HIT"
+CACHE_MISS = "CACHE_MISS"
+EMPTY_RESPONSE = "EMPTY_RESPONSE"
+NO_DATA = "NO_DATA"
+TIMEOUT = "TIMEOUT"
+HTTP_ERROR = "HTTP_ERROR"
+PARSE_ERROR = "PARSE_ERROR"
+UNKNOWN_STRUCTURE = "UNKNOWN_STRUCTURE"
+RATE_LIMITED = "RATE_LIMITED"
+ERROR = "ERROR"
+
+KNOWN_SOURCE_STATUSES = {
+    OK,
+    CACHE_HIT,
+    CACHE_MISS,
+    EMPTY_RESPONSE,
+    NO_DATA,
+    TIMEOUT,
+    HTTP_ERROR,
+    PARSE_ERROR,
+    UNKNOWN_STRUCTURE,
+    RATE_LIMITED,
+    ERROR,
+}
+
+
+def make_source_diagnostic(
+    name: str,
+    endpoint: str,
+    status: str,
+    message: str,
+    duration_ms: int | None = None,
+    cached: bool | None = None,
+    cache_age_seconds: int | None = None,
+    http_status: int | None = None,
+    error_type: str | None = None,
+    details: dict[str, Any] | None = None,
+) -> dict[str, Any]:
+    return {
+        "name": name,
+        "endpoint": endpoint,
+        "status": status,
+        "message": message,
+        "duration_ms": duration_ms,
+        "cached": cached,
+        "cache_age_seconds": cache_age_seconds,
+        "http_status": http_status,
+        "error_type": error_type,
+        "details": details or {},
+    }
diff --git a/backend/app/main.py b/backend/app/main.py
index 308a924..efc9417 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -8,7 +8,7 @@
 from app.config import settings
 from app.database import Base, engine
 
-app = FastAPI(title="RouteForge", version="0.3.0")
+app = FastAPI(title="RouteForge", version="0.4.0")
 
 app.add_middleware(
     CORSMiddleware,
diff --git a/backend/app/services/asn_checker.py b/backend/app/services/asn_checker.py
index 1ab50c3..f07dfc2 100644
--- a/backend/app/services/asn_checker.py
+++ b/backend/app/services/asn_checker.py
@@ -39,8 +39,10 @@ def _extract_prefixes(self, announced_data: dict) -> list[str]:
     def check(self, asn_input: str) -> dict:
         asn = normalize_asn(asn_input)
         resource = format_asn(asn)
-        overview = self.client.get("as-overview", {"resource": resource})
-        prefixes = self.client.get("announced-prefixes", {"resource": resource})
+        overview, overview_diag = self.client.get_with_diagnostics("as-overview", {"resource": resource})
+        prefixes, prefixes_diag = self.client.get_with_diagnostics("announced-prefixes", {"resource": resource})
+        overview = overview or {}
+        prefixes = prefixes or {}
         announced_data = prefixes.get("data", {}) if isinstance(prefixes, dict) else {}
         extracted_prefixes = self._extract_prefixes(announced_data if isinstance(announced_data, dict) else {})
         rpki_batch = self._build_rpki_batch_metadata(prefixes, announced_data, extracted_prefixes)
@@ -77,6 +79,7 @@ def check(self, asn_input: str) -> dict:
                     "as_overview": overview.get("error") if isinstance(overview, dict) else None,
                     "announced_prefixes": prefixes.get("error") if isinstance(prefixes, dict) else None,
                 },
+                "source_diagnostics": [overview_diag, prefixes_diag],
                 "demo_mode": settings.demo_mode,
             },
             "sources": ["RIPEstat as-overview", "RIPEstat announced-prefixes"],
@@ -85,7 +88,8 @@ def check(self, asn_input: str) -> dict:
     def check_rpki_batch(self, asn_input: str, limit: int) -> dict:
         asn = normalize_asn(asn_input)
         resource = format_asn(asn)
-        prefixes_payload = self.client.get("announced-prefixes", {"resource": resource})
+        prefixes_payload, prefixes_diag = self.client.get_with_diagnostics("announced-prefixes", {"resource": resource})
+        prefixes_payload = prefixes_payload or {}
         announced_data = prefixes_payload.get("data", {}) if isinstance(prefixes_payload, dict) else {}
         extracted = self._extract_prefixes(announced_data if isinstance(announced_data, dict) else {})
         rpki_batch = self._build_rpki_batch_metadata(prefixes_payload, announced_data, extracted)
@@ -97,9 +101,18 @@ def check_rpki_batch(self, asn_input: str, limit: int) -> dict:
         has_critical = False
         has_warning = False
 
+        diag_agg = {"total_requests": 0, "ok": 0, "errors": 0, "timeouts": 0, "rate_limited": 0, "unknown_structure": 0}
         for prefix in selected:
             try:
                 rpki = rpki_checker.check(prefix, resource)
+                diag = rpki.get("source_diagnostic") or {}
+                diag_agg["total_requests"] += 1
+                st = diag.get("status")
+                if st == "OK": diag_agg["ok"] += 1
+                elif st == "TIMEOUT": diag_agg["timeouts"] += 1
+                elif st == "RATE_LIMITED": diag_agg["rate_limited"] += 1
+                elif st == "UNKNOWN_STRUCTURE": diag_agg["unknown_structure"] += 1
+                else: diag_agg["errors"] += 1 if st and st != "OK" else 0
                 raw_status = (rpki.get("raw_status") or "").strip().lower().replace("-", "_")
                 if raw_status in summary:
                     summary[raw_status] += 1
@@ -160,6 +173,7 @@ def check_rpki_batch(self, asn_input: str, limit: int) -> dict:
                 "results": results,
                 "rpki_batch": rpki_batch,
                 "announced_prefixes": announced_data if isinstance(announced_data, dict) else {},
+                "source_diagnostics": [prefixes_diag, {"name": "RIPEstat rpki-validation (batch)", "endpoint": "rpki-validation", "status": "OK" if diag_agg["errors"] == 0 and diag_agg["timeouts"] == 0 and diag_agg["rate_limited"] == 0 else "ERROR", "message": "Aggregated RPKI batch diagnostics", "details": diag_agg}],
                 "demo_mode": settings.demo_mode,
             },
         }
diff --git a/backend/app/services/prefix_checker.py b/backend/app/services/prefix_checker.py
index 47169c8..723341a 100644
--- a/backend/app/services/prefix_checker.py
+++ b/backend/app/services/prefix_checker.py
@@ -1,4 +1,5 @@
 from app.core.normalize import format_asn, normalize_asn, validate_prefix
+from app.core.source_diagnostics import NO_DATA, UNKNOWN_STRUCTURE
 from app.core.prefix_evaluation import evaluate_prefix_overall
 from app.core.status import CheckStatus
 from app.config import settings
@@ -22,12 +23,22 @@ def check(self, prefix: str, origin_as: str | None) -> dict:
         normalized_prefix = validate_prefix(prefix)
         normalized_origin = format_asn(normalize_asn(origin_as)) if origin_as else None
 
-        whois = self.ripe_db.whois(normalized_prefix)
-        routing_status = self.client.get("routing-status", {"resource": normalized_prefix})
+        whois, whois_diag = self.client.get_with_diagnostics("whois", {"resource": normalized_prefix})
+        whois = whois or {}
+        routing_status, routing_diag = self.client.get_with_diagnostics("routing-status", {"resource": normalized_prefix})
+        routing_status = routing_status or {}
         rpki_check = self.rpki.check(normalized_prefix, normalized_origin)
         registry_check = self.registry.check(normalized_prefix, normalized_origin, whois)
         routing_visibility_check = self.routing_visibility.check(normalized_prefix, normalized_origin, routing_status)
 
+        source_diagnostics = [rpki_check.get("source_diagnostic"), whois_diag, routing_diag]
+        if routing_visibility_check.get("raw", {}).get("structure_unknown"):
+            routing_diag["status"] = UNKNOWN_STRUCTURE
+            routing_diag["message"] = "Response received, but visible origins could not be extracted"
+        if not whois.get("data") and not whois.get("error"):
+            whois_diag["status"] = NO_DATA
+            whois_diag["message"] = "No registry data available in response"
+
         warnings: list[str] = []
         if whois.get("error") or routing_status.get("error"):
             warnings.append("Mindestens eine zusätzliche Datenquelle war nicht erreichbar.")
@@ -87,6 +98,7 @@ def check(self, prefix: str, origin_as: str | None) -> dict:
                     "routing_visibility": routing_visibility_check.get("raw", {}).get("routing_payload", {}).get("error") if isinstance(routing_visibility_check.get("raw"), dict) else None,
                 },
                 "warnings": warnings,
+                "source_diagnostics": [d for d in source_diagnostics if isinstance(d, dict)],
                 "demo_mode": settings.demo_mode,
             },
             "sources": ["RIPEstat rpki-validation", "RIPEstat routing-status", "RIPEstat whois", "RIPEstat routing visibility"],
diff --git a/backend/app/services/preflight_checker.py b/backend/app/services/preflight_checker.py
index eb3526b..c58b520 100644
--- a/backend/app/services/preflight_checker.py
+++ b/backend/app/services/preflight_checker.py
@@ -21,8 +21,10 @@ def check(self, prefix: str, planned_origin_as: str) -> dict:
         normalized_prefix = validate_prefix(prefix)
         normalized_origin = format_asn(normalize_asn(planned_origin_as))
 
-        whois = self.ripe_db.whois(normalized_prefix)
-        routing_status = self.client.get("routing-status", {"resource": normalized_prefix})
+        whois, whois_diag = self.client.get_with_diagnostics("whois", {"resource": normalized_prefix})
+        whois = whois or {}
+        routing_status, routing_diag = self.client.get_with_diagnostics("routing-status", {"resource": normalized_prefix})
+        routing_status = routing_status or {}
         rpki_check = self.rpki.check(normalized_prefix, normalized_origin)
         registry_check = self.registry.check(normalized_prefix, normalized_origin, whois)
         routing_visibility_check = self.routing_visibility.check(normalized_prefix, normalized_origin, routing_status)
@@ -64,6 +66,7 @@ def check(self, prefix: str, planned_origin_as: str) -> dict:
                     "registry": registry_check.get("raw", {}).get("error") if isinstance(registry_check.get("raw"), dict) else None,
                 },
                 "warnings": warnings,
+                "source_diagnostics": [d for d in [rpki_check.get("source_diagnostic"), whois_diag, routing_diag] if isinstance(d, dict)],
                 "demo_mode": settings.demo_mode,
             },
             "sources": ["RIPEstat rpki-validation", "RIPEstat whois", "RIPEstat routing-status"],
diff --git a/backend/app/services/ripe_stat_client.py b/backend/app/services/ripe_stat_client.py
index c887198..15059f1 100644
--- a/backend/app/services/ripe_stat_client.py
+++ b/backend/app/services/ripe_stat_client.py
@@ -1,7 +1,19 @@
+import time
+
 import httpx
 from sqlalchemy.orm import Session
 
 from app.config import settings
+from app.core.source_diagnostics import (
+    EMPTY_RESPONSE,
+    ERROR,
+    HTTP_ERROR,
+    OK,
+    PARSE_ERROR,
+    RATE_LIMITED,
+    TIMEOUT,
+    make_source_diagnostic,
+)
 from app.services.cache import get_cached, set_cached
 
 
@@ -10,21 +22,69 @@ def __init__(self, db: Session):
         self.db = db
 
     def get(self, endpoint: str, params: dict) -> dict:
+        payload, _diagnostic = self.get_with_diagnostics(endpoint, params)
+        return payload or {"error": "empty response", "endpoint": endpoint, "params": params}
+
+    def get_with_diagnostics(self, endpoint: str, params: dict) -> tuple[dict | None, dict]:
+        started = time.perf_counter()
         if settings.demo_mode:
-            return self._get_demo_data(endpoint, params)
-        cached = get_cached(self.db, endpoint, params)
-        if cached:
-            return cached
+            payload = self._get_demo_data(endpoint, params)
+            return payload, make_source_diagnostic(
+                name=f"RIPEstat {endpoint}",
+                endpoint=endpoint,
+                status=OK,
+                message="Demo data returned",
+                duration_ms=int((time.perf_counter() - started) * 1000),
+                cached=False,
+                details={"demo_mode": True},
+            )
+
+        cached_payload = get_cached(self.db, endpoint, params)
+        if cached_payload:
+            return cached_payload, make_source_diagnostic(
+                name=f"RIPEstat {endpoint}",
+                endpoint=endpoint,
+                status=OK,
+                message="RIPEstat response returned from cache",
+                duration_ms=int((time.perf_counter() - started) * 1000),
+                cached=True,
+            )
+
         url = f"{settings.ripestat_base_url.rstrip('/')}/{endpoint}/data.json"
         try:
             with httpx.Client(timeout=settings.http_timeout_seconds) as client:
                 resp = client.get(url, params=params)
+                if resp.status_code == 429:
+                    return {"error": "rate limited", "endpoint": endpoint, "params": params}, make_source_diagnostic(
+                        name=f"RIPEstat {endpoint}", endpoint=endpoint, status=RATE_LIMITED, message="RIPEstat rate limit reached", duration_ms=int((time.perf_counter() - started) * 1000), cached=False, http_status=resp.status_code, error_type="http_429"
+                    )
                 resp.raise_for_status()
                 data = resp.json()
+        except httpx.TimeoutException as exc:
+            return {"error": str(exc), "endpoint": endpoint, "params": params}, make_source_diagnostic(
+                name=f"RIPEstat {endpoint}", endpoint=endpoint, status=TIMEOUT, message="RIPEstat did not respond before timeout", duration_ms=int((time.perf_counter() - started) * 1000), cached=False, error_type=type(exc).__name__
+            )
+        except httpx.HTTPStatusError as exc:
+            return {"error": str(exc), "endpoint": endpoint, "params": params}, make_source_diagnostic(
+                name=f"RIPEstat {endpoint}", endpoint=endpoint, status=HTTP_ERROR, message="RIPEstat responded with HTTP error", duration_ms=int((time.perf_counter() - started) * 1000), cached=False, http_status=exc.response.status_code, error_type=type(exc).__name__
+            )
+        except ValueError as exc:
+            return {"error": str(exc), "endpoint": endpoint, "params": params}, make_source_diagnostic(
+                name=f"RIPEstat {endpoint}", endpoint=endpoint, status=PARSE_ERROR, message="RIPEstat response could not be parsed as JSON", duration_ms=int((time.perf_counter() - started) * 1000), cached=False, error_type=type(exc).__name__
+            )
         except Exception as exc:
-            return {"error": str(exc), "endpoint": endpoint, "params": params}
+            return {"error": str(exc), "endpoint": endpoint, "params": params}, make_source_diagnostic(
+                name=f"RIPEstat {endpoint}", endpoint=endpoint, status=ERROR, message="RIPEstat request failed", duration_ms=int((time.perf_counter() - started) * 1000), cached=False, error_type=type(exc).__name__
+            )
+
+        if not data:
+            return data, make_source_diagnostic(
+                name=f"RIPEstat {endpoint}", endpoint=endpoint, status=EMPTY_RESPONSE, message="RIPEstat returned an empty response", duration_ms=int((time.perf_counter() - started) * 1000), cached=False
+            )
         set_cached(self.db, endpoint, params, data)
-        return data
+        return data, make_source_diagnostic(
+            name=f"RIPEstat {endpoint}", endpoint=endpoint, status=OK, message="RIPEstat response received", duration_ms=int((time.perf_counter() - started) * 1000), cached=False
+        )
 
     def _get_demo_data(self, endpoint: str, params: dict) -> dict:
         resource = str(params.get("resource", "")).upper()
diff --git a/backend/app/services/routing_visibility_checker.py b/backend/app/services/routing_visibility_checker.py
index 6c6cf51..0c6761a 100644
--- a/backend/app/services/routing_visibility_checker.py
+++ b/backend/app/services/routing_visibility_checker.py
@@ -23,15 +23,15 @@ def check(self, prefix: str, origin_as: str | None, routing_payload: dict | None
 
         if not visible_origins:
             return {
-                "status": CheckStatus.WARNING.value,
-                "summary": "Prefix visibility unclear",
-                "explanation": "Es wurden Routingdaten gefunden, aber kein klares sichtbares Origin-AS extrahiert.",
-                "risk": "Das Prefix könnte nicht sichtbar sein oder die Datenstruktur wurde nicht eindeutig erkannt.",
+                "status": CheckStatus.UNKNOWN.value,
+                "summary": "Routing visibility could not be determined",
+                "explanation": "RIPEstat routing-status returned data, but RouteForge could not extract visible Origin-AS information from the response.",
+                "risk": "Die Datenstruktur war nicht eindeutig auswertbar.",
                 "recommendations": [
                     "Prüfe das Prefix zusätzlich über ein Looking Glass.",
                     "Prüfe, ob das Prefix aktuell announced werden soll.",
                 ],
-                "raw": raw,
+                "raw": {**raw, "structure_unknown": True},
             }
 
         if not expected_origin:
@@ -41,7 +41,7 @@ def check(self, prefix: str, origin_as: str | None, routing_payload: dict | None
                 "explanation": "Für das Prefix wurden sichtbare Origin-ASNs gefunden. Ohne erwartetes Origin-AS erfolgt kein Konsistenzabgleich.",
                 "risk": "Die Sichtbarkeit ist grundsätzlich erkennbar, aber die erwartete Origin-Zuordnung wurde nicht geprüft.",
                 "recommendations": ["Gib ein erwartetes Origin-AS an, um die Sichtbarkeit vollständig zu bewerten."],
-                "raw": raw,
+                "raw": {**raw, "structure_unknown": True},
             }
 
         if expected_origin in visible_origins:
@@ -51,7 +51,7 @@ def check(self, prefix: str, origin_as: str | None, routing_payload: dict | None
                 "explanation": "Das Prefix wird mit dem erwarteten Origin-AS im Routing sichtbar.",
                 "risk": "Keine offensichtliche Routing-Visibility-Inkonsistenz erkannt.",
                 "recommendations": ["Routing-Sichtbarkeit weiter überwachen."],
-                "raw": raw,
+                "raw": {**raw, "structure_unknown": True},
             }
 
         return {
@@ -71,7 +71,7 @@ def _result_unknown(self, payload: dict | None) -> dict:
         return {
             "status": CheckStatus.UNKNOWN.value,
             "summary": "Routing visibility could not be determined",
-            "explanation": "Die Sichtbarkeit des Prefixes im globalen Routing konnte aus den verfügbaren Daten nicht zuverlässig bestimmt werden.",
+            "explanation": "RIPEstat routing-status did not respond before the configured timeout or returned no usable payload.",
             "risk": "Die Bewertung ist unvollständig.",
             "recommendations": [
                 "Prüfe die Rohdaten.",
diff --git a/backend/app/templates/report.html.j2 b/backend/app/templates/report.html.j2
index 6bfc45f..641f81c 100644
--- a/backend/app/templates/report.html.j2
+++ b/backend/app/templates/report.html.j2
@@ -49,6 +49,9 @@
   <li><strong>Risiko:</strong> {{ report.checks.routing_visibility.risk if report.checks and report.checks.routing_visibility else '-' }}</li>
 </ul>
 
+<h2>Data Source Diagnostics</h2>
+{% if report.details and report.details.source_diagnostics %}<table border="1" cellpadding="6" cellspacing="0"><tr><th>Quelle</th><th>Endpoint</th><th>Status</th><th>Dauer</th><th>Cache</th><th>Message</th></tr>{% for d in report.details.source_diagnostics %}<tr><td>{{ d.name or '-' }}</td><td>{{ d.endpoint or '-' }}</td><td>{{ d.status or '-' }}</td><td>{{ d.duration_ms if d.duration_ms is not none else '-' }}</td><td>{{ 'HIT' if d.cached is sameas true else ('MISS' if d.cached is sameas false else '-') }}</td><td>{{ d.message or '-' }}{% if d.details %}<details><summary>Details</summary><pre>{{ d.details | tojson(indent=2) }}</pre></details>{% endif %}</td></tr>{% endfor %}</table>{% else %}<p>No source diagnostics available.</p>{% endif %}
+
 <h2>Rohdaten</h2>
 <h3>RPKI Rohdaten</h3>
 <pre>{{ (report.checks.rpki.raw if report.checks and report.checks.rpki else {}) | tojson(indent=2) }}</pre>
diff --git a/backend/app/templates/report.md.j2 b/backend/app/templates/report.md.j2
index b9a5baf..62035b5 100644
--- a/backend/app/templates/report.md.j2
+++ b/backend/app/templates/report.md.j2
@@ -41,6 +41,15 @@
 - Erklärung: {{ report.checks.routing_visibility.explanation if report.checks and report.checks.routing_visibility else '-' }}
 - Risiko: {{ report.checks.routing_visibility.risk if report.checks and report.checks.routing_visibility else '-' }}
 
+## Data Source Diagnostics
+{% if report.details and report.details.source_diagnostics %}
+| Quelle | Endpoint | Status | Dauer | Cache | Message |
+|---|---|---|---:|---|---|
+{% for d in report.details.source_diagnostics %}| {{ d.name or '-' }} | {{ d.endpoint or '-' }} | {{ d.status or '-' }} | {{ d.duration_ms if d.duration_ms is not none else '-' }} | {{ 'HIT' if d.cached is sameas true else ('MISS' if d.cached is sameas false else '-') }} | {{ d.message or '-' }} |
+{% endfor %}
+{% else %}No source diagnostics available.
+{% endif %}
+
 ## Rohdaten
 ### RPKI Rohdaten
 ```json
diff --git a/backend/pyproject.toml b/backend/pyproject.toml
index 04818ed..9065ed7 100644
--- a/backend/pyproject.toml
+++ b/backend/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "routeforge-backend"
-version = "0.3.0"
+version = "0.4.0"
 description = "RouteForge backend"
 requires-python = ">=3.12"
 dependencies = [
diff --git a/backend/tests/test_api_smoke.py b/backend/tests/test_api_smoke.py
index d805622..8b3618b 100644
--- a/backend/tests/test_api_smoke.py
+++ b/backend/tests/test_api_smoke.py
@@ -111,6 +111,7 @@ def test_preflight_check() -> None:
     assert 'registry' in checks
     assert 'routing_visibility' in checks
     assert payload.get('details', {}).get('preflight_mode') is True
+    assert isinstance(payload.get('details', {}).get('source_diagnostics'), list)
     assert payload.get('details', {}).get('resource_holder')
     assert payload.get('details', {}).get('preflight_decision') in {'GO', 'CAUTION', 'NO-GO', 'UNKNOWN'}
 
diff --git a/backend/tests/test_routing_visibility_checker.py b/backend/tests/test_routing_visibility_checker.py
index 7c5f51f..592af63 100644
--- a/backend/tests/test_routing_visibility_checker.py
+++ b/backend/tests/test_routing_visibility_checker.py
@@ -32,7 +32,7 @@ def test_payload_without_extractable_origins_is_warning():
     c = RoutingVisibilityChecker()
     payload = {"data": {"routes": [{"prefix": "193.0.6.0/24"}]}}
     result = c.check("193.0.6.0/24", "AS3333", payload)
-    assert result["status"] == "WARNING"
+    assert result["status"] == "UNKNOWN"
 
 
 def test_numeric_asn_is_normalized_to_as_prefix():
diff --git a/backend/tests/test_source_diagnostics.py b/backend/tests/test_source_diagnostics.py
new file mode 100644
index 0000000..76c2087
--- /dev/null
+++ b/backend/tests/test_source_diagnostics.py
@@ -0,0 +1,23 @@
+from app.core.source_diagnostics import KNOWN_SOURCE_STATUSES, OK, TIMEOUT, make_source_diagnostic
+
+
+def test_make_source_diagnostic_shape() -> None:
+    d = make_source_diagnostic("RIPEstat routing-status", "routing-status", OK, "ok", duration_ms=12, cached=False)
+    assert d["name"] == "RIPEstat routing-status"
+    assert d["endpoint"] == "routing-status"
+    assert d["status"] == OK
+    assert d["duration_ms"] == 12
+    assert d["cached"] is False
+    assert isinstance(d["details"], dict)
+
+
+def test_make_source_diagnostic_optional_defaults() -> None:
+    d = make_source_diagnostic("x", "y", TIMEOUT, "timeout")
+    assert d["duration_ms"] is None
+    assert d["http_status"] is None
+    assert d["error_type"] is None
+
+
+def test_known_status_values_present() -> None:
+    for value in [OK, TIMEOUT, "HTTP_ERROR", "PARSE_ERROR", "UNKNOWN_STRUCTURE", "RATE_LIMITED", "CACHE_HIT", "CACHE_MISS", "EMPTY_RESPONSE", "NO_DATA", "ERROR"]:
+        assert value in KNOWN_SOURCE_STATUSES
diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index a2074bd..58544d8 100644
--- a/frontend/package-lock.json
+++ b/frontend/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "routeforge-frontend",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "routeforge-frontend",
-      "version": "0.3.0",
+      "version": "0.4.0",
       "dependencies": {
         "react": "^18.3.1",
         "react-dom": "^18.3.1"
diff --git a/frontend/package.json b/frontend/package.json
index 799b54e..70a56f6 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -1,6 +1,6 @@
 {
   "name": "routeforge-frontend",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "private": true,
   "type": "module",
   "scripts": {
diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index 1e1f1dd..e68c238 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -15,7 +15,7 @@ export default function App() {
   const [copyMessage, setCopyMessage] = useState('')
   const [system, setSystem] = useState<SystemInfo | null>(null)
   useEffect(() => { getReports().then(setReports).catch(() => setReports([])); getSystemInfo().then(setSystem).catch(() => null) }, [])
-  const systemLine = useMemo(() => system ? `${system.name} ${system.version} · mode=${system.demo_mode ? 'DEMO' : 'LIVE'} · read_only=${String(system.read_only)}` : 'RouteForge v0.3.0-alpha · read-only preflight checks', [system])
+  const systemLine = useMemo(() => system ? `${system.name} ${system.version} · mode=${system.demo_mode ? 'DEMO' : 'LIVE'} · read_only=${String(system.read_only)}` : 'RouteForge v0.4.0-alpha · read-only preflight checks', [system])
   const title = { dashboard: 'Dashboard', asn: 'ASN Check', prefix: 'Prefix Check', preflight: 'Preflight Check', reports: 'Reports', about: 'About RouteForge' }[active]
   const notify = (message: string) => {
     setCopyMessage(message)
@@ -37,7 +37,7 @@ export default function App() {
 
   return <Layout active={active} onNav={setActive} systemLine={systemLine} title={title} demoMode={Boolean(system?.demo_mode)}>
     {active === 'dashboard' && <section className='space-y-4'>
-      <article className='rf-card p-6'><h1 className='text-2xl font-bold'>RouteForge v0.3.0-alpha</h1><p className='mt-2 text-slate-600'>Modernes read-only Operator-Tool für Preflight Checks von ASN, Prefix, RPKI und Registry/IRR.</p><p className='mt-3 rf-alert border-slate-200 bg-slate-50 text-slate-700'>Security-Modell: ausschließlich read-only, keine writes/deployments.</p></article>
+      <article className='rf-card p-6'><h1 className='text-2xl font-bold'>RouteForge v0.4.0-alpha</h1><p className='mt-2 text-slate-600'>Modernes read-only Operator-Tool für Preflight Checks von ASN, Prefix, RPKI und Registry/IRR.</p><p className='mt-3 rf-alert border-slate-200 bg-slate-50 text-slate-700'>Security-Modell: ausschließlich read-only, keine writes/deployments.</p></article>
       <div className='grid gap-3 md:grid-cols-3'>{[['ASN Check', 'asn'], ['Prefix Check', 'prefix'], ['Preflight Check', 'preflight'], ['Reports', 'reports']].map(([x, key]) => <button key={x} onClick={() => setActive(key as NavKey)} className='rf-card p-4 text-left hover:border-blue-300'><h3 className='font-semibold'>{x}</h3></button>)}</div>
       <article className='rf-card p-4'><h2 className='mb-2 font-semibold'>Letzte Reports</h2>{reports.length === 0 ? <div className='rounded-xl border border-dashed border-slate-300 p-6 text-sm text-slate-500'>Noch keine Reports vorhanden.</div> : <div className='overflow-x-auto'><table className='w-full text-sm'><thead><tr className='border-b text-left'><th className='py-2'>Zeit</th><th>Typ</th><th>Resource</th><th>Holder</th><th>Status</th></tr></thead><tbody>{reports.slice(0, 8).map(r => <tr key={r.report_id} className='border-b border-slate-100'><td className='py-2'>{new Date(r.created_at).toLocaleString()}</td><td>{r.check_type === 'preflight' ? 'Preflight' : r.check_type}</td><td>{r.input_resource}</td><td>{r.holder || 'Unknown'}</td><td><StatusBadge status={r.status} /></td></tr>)}</tbody></table></div>}</article>
     </section>}
@@ -45,6 +45,6 @@ export default function App() {
     {active === 'prefix' && <PrefixCheckForm />}
     {active === 'preflight' && <PreflightCheckForm />}
     {active === 'reports' && <section className='rf-card p-4'><h2 className='mb-3 text-xl font-semibold'>Reports</h2>{reports.length===0 ? <div className='rounded-xl border border-dashed border-slate-300 p-6 text-sm text-slate-500'>Noch keine Reports vorhanden.</div> : <div className='overflow-x-auto'><table className='w-full text-sm'><thead><tr className='border-b text-left'><th>Zeitpunkt</th><th>Typ</th><th>Resource</th><th>Origin-AS</th><th>Holder</th><th>Status</th><th>Kurzfassung</th><th>Actions</th></tr></thead><tbody>{reports.map(r=><tr key={r.report_id} className='border-b border-slate-100'><td className='py-2'>{new Date(r.created_at).toLocaleString()}</td><td>{r.check_type === 'preflight' ? 'Preflight' : r.check_type}</td><td>{r.input_resource}</td><td>{r.origin_as || '-'}</td><td>{r.holder || 'Unknown'}</td><td><StatusBadge status={r.status} /></td><td>{r.summary}</td><td><div className='flex flex-wrap gap-1'><button className='rf-btn-secondary' onClick={() => window.open(`/api/reports/${r.report_id}`, '_blank')}>Open</button><button className='rf-btn-secondary' onClick={async ()=>copyText(await getReportSummary(r.report_id), 'Summary copied')}>Copy Summary</button><button className='rf-btn-secondary' onClick={async ()=>downloadText(`routeforge-report-${r.report_id}.md`, await getReportMarkdown(r.report_id), 'text/markdown;charset=utf-8')}>Download Markdown</button><button className='rf-btn-secondary' onClick={async ()=>downloadText(`routeforge-report-${r.report_id}.html`, await getReportHtml(r.report_id), 'text/html;charset=utf-8')}>Download HTML</button></div></td></tr>)}</tbody></table></div>}{copyMessage && <p className='mt-2 text-sm text-slate-600'>{copyMessage}</p>}</section>}
-    {active === 'about' && <section className='rf-card p-5 space-y-2 text-sm text-slate-700'><p>RouteForge liefert nachvollziehbare Routing-Preflightchecks für technische Operator-Workflows.</p><p><b>Datenquellen:</b> RPKI Validator APIs und Registry/IRR Quellen.</p><p><b>Modell:</b> read-only Betrieb.</p><p><b>Limitations:</b> Externe Datenquellen können unvollständig oder verzögert sein.</p><p><b>Version:</b> v0.3.0-alpha</p></section>}
+    {active === 'about' && <section className='rf-card p-5 space-y-2 text-sm text-slate-700'><p>RouteForge liefert nachvollziehbare Routing-Preflightchecks für technische Operator-Workflows.</p><p><b>Datenquellen:</b> RPKI Validator APIs und Registry/IRR Quellen.</p><p><b>Modell:</b> read-only Betrieb.</p><p><b>Limitations:</b> Externe Datenquellen können unvollständig oder verzögert sein.</p><p><b>Version:</b> v0.4.0-alpha</p></section>}
   </Layout>
 }
diff --git a/frontend/src/components/Layout.tsx b/frontend/src/components/Layout.tsx
index 9a9b3f0..f4288dc 100644
--- a/frontend/src/components/Layout.tsx
+++ b/frontend/src/components/Layout.tsx
@@ -27,7 +27,7 @@ export function Layout({ children, active, onNav, systemLine, title, demoMode }:
           <div className='flex flex-wrap gap-2 text-xs font-semibold'>
             <span className={`rounded-full border px-3 py-1 ${demoMode ? 'border-amber-300 bg-amber-50 text-amber-700' : 'border-emerald-300 bg-emerald-50 text-emerald-700'}`}>{demoMode ? 'DEMO' : 'LIVE'}</span>
             <span className='rounded-full border border-blue-200 bg-blue-50 px-3 py-1 text-blue-700'>READ-ONLY</span>
-            <span className='rounded-full border border-slate-200 bg-slate-50 px-3 py-1 text-slate-700'>v0.3.0-alpha</span>
+            <span className='rounded-full border border-slate-200 bg-slate-50 px-3 py-1 text-slate-700'>v0.4.0-alpha</span>
           </div>
         </header>
         <main className='space-y-4'>{children}</main>
diff --git a/frontend/src/components/ReportView.tsx b/frontend/src/components/ReportView.tsx
index 939072d..4bb2bfe 100644
--- a/frontend/src/components/ReportView.tsx
+++ b/frontend/src/components/ReportView.tsx
@@ -1,6 +1,6 @@
 import { useState } from 'react'
 import { getReportHtml, getReportMarkdown, getReportSummary } from '../api'
-import type { CheckResponse, RpkiBatchResult } from '../types'
+import type { CheckResponse, RpkiBatchResult, SourceDiagnostic } from '../types'
 import { RawDataPanel } from './RawDataPanel'
 import { StatusBadge } from './StatusBadge'
 
@@ -21,6 +21,7 @@ export function ReportView({ report }: { report: CheckResponse }) {
   const reportId = Number((report as { report_id?: number; id?: number; details?: { report_id?: number } }).report_id ?? (report as { id?: number }).id ?? (report.details as { report_id?: number } | undefined)?.report_id)
   const hasReportId = Number.isFinite(reportId) && reportId > 0
   const rpkiBatch = details.rpki_batch as { message?: string } | undefined
+  const sourceDiagnostics = (Array.isArray(details.source_diagnostics) ? details.source_diagnostics : []) as SourceDiagnostic[]
 
   const notify = (message: string) => {
     setCopyMessage(message)
@@ -74,6 +75,9 @@ export function ReportView({ report }: { report: CheckResponse }) {
       {[['RPKI', rpki], ['Registry/IRR', registry], ['Routing Visibility', routingVisibility] as const].map(([title, item]) => item && <article key={title} className='rf-card p-4'><div className='mb-2 flex items-center gap-2'><h4 className='font-semibold'>{title}</h4><StatusBadge status={item.status || 'UNKNOWN'} /></div><p className='text-sm'>{item.summary || '-'}</p></article>)}
     </section>
 
+
+    {sourceDiagnostics.length > 0 && <section className='rf-card p-4 space-y-2'><h4 className='font-semibold'>Data Source Diagnostics</h4><div className='overflow-x-auto'><table className='w-full text-sm'><thead><tr className='border-b text-left'><th className='py-2'>Source</th><th>Endpoint</th><th>Status</th><th>Duration</th><th>Cache</th><th>Message</th></tr></thead><tbody>{sourceDiagnostics.map((d, idx) => <tr key={`${d.name}-${idx}`} className='border-b border-slate-100'><td>{d.name || '-'}</td><td className='font-mono'>{d.endpoint || '-'}</td><td><StatusBadge status={d.status || 'UNKNOWN'} /></td><td>{typeof d.duration_ms === 'number' ? `${d.duration_ms} ms` : '-'}</td><td>{d.cached === true ? 'HIT' : d.cached === false ? 'MISS' : '-'}</td><td>{d.message || '-'}</td></tr>)}</tbody></table></div></section>}
+
     <details className='rf-card p-4'><summary className='cursor-pointer text-sm font-semibold'>Technische Details</summary><pre className='mt-3 overflow-auto rounded-xl bg-slate-50 p-3 text-xs'>{JSON.stringify({ input: report.input, holder: details.resource_holder, warnings: details.warnings, source_errors: details.source_errors }, null, 2)}</pre></details>
     {sortedResults.length > 0 && <section className='rf-card p-4'><h4 className='mb-2 font-semibold'>Batch Results</h4><div className='overflow-x-auto'><table className='w-full text-sm'><thead><tr className='border-b text-left'><th className='py-2'>Status</th><th>Prefix</th><th>Summary</th></tr></thead><tbody>{sortedResults.map((item, idx) => <tr key={`${item.prefix}-${idx}`} className='border-b border-slate-100'><td className='py-2'><StatusBadge status={item.status || 'UNKNOWN'} /></td><td className='font-mono'>{item.prefix}</td><td>{item.summary || '-'}</td></tr>)}</tbody></table></div></section>}
     {sortedResults.length === 0 && ((details.checked_prefixes as number | undefined) === 0 || rpkiBatch?.message) && <section className='rf-card p-4'><h4 className='mb-2 font-semibold'>Keine Prefixe geprüft</h4><p className='text-sm text-slate-700'>{rpkiBatch?.message || report.explanation || 'Keine Daten verfügbar.'}</p></section>}
diff --git a/frontend/src/types.ts b/frontend/src/types.ts
index 35e0a14..936cc9a 100644
--- a/frontend/src/types.ts
+++ b/frontend/src/types.ts
@@ -18,6 +18,20 @@ export type RpkiBatchResult = {
   raw?: Record<string, unknown>
 }
 
+
+export type SourceDiagnostic = {
+  name?: string
+  endpoint?: string
+  status?: string
+  message?: string
+  duration_ms?: number | null
+  cached?: boolean | null
+  cache_age_seconds?: number | null
+  http_status?: number | null
+  error_type?: string | null
+  details?: Record<string, unknown>
+}
+
 export type CheckResponse = {
   report_id: number
   status: string
@@ -45,6 +59,7 @@ export type CheckResponse = {
     demo_mode?: boolean
     source_errors?: unknown
     warnings?: unknown
+    source_diagnostics?: SourceDiagnostic[]
     [key: string]: unknown
   }
   markdown: string