diff --git a/src/diff_risk_dashboard/report.py b/src/diff_risk_dashboard/report.py
index c536ff5..01069ef 100644
--- a/src/diff_risk_dashboard/report.py
+++ b/src/diff_risk_dashboard/report.py
@@ -1,26 +1,40 @@
 from __future__ import annotations
 
-from collections.abc import Mapping
 from typing import Any
 
 _SEVERITIES = ["CRITICAL", "HIGH", "MEDIUM", "LOW", "INFO"]
 
 
-def _get_counts(summary: Mapping[str, Any]) -> dict[str, int]:
-    counts: dict[str, int] = {}
-    by = summary.get("by_severity", {}) or {}
-    if isinstance(by, Mapping):
-        for sev in _SEVERITIES:
-            counts[sev] = int(by.get(sev, by.get(sev.lower(), 0)) or 0)
-    return counts
+def _norm_counts(summary: dict[str, Any]) -> dict[str, int]:
+    src = summary.get("by_severity") or {}
+    by = {str(k).upper(): int(v) for k, v in src.items()}
+    return {s: int(by.get(s, 0)) for s in _SEVERITIES}
 
 
-def to_markdown(summary: Mapping[str, Any]) -> str:
-    counts = _get_counts(summary)
-    total = int(summary.get("total", 0) or 0)
-    worst = str(summary.get("worst", "INFO") or "INFO").upper()
-    risk = str(summary.get("risk", summary.get("risk_level", "green")) or "green").lower()
+def to_markdown(summary: dict[str, Any]) -> str:
+    counts = _norm_counts(summary)
+    total = int(summary.get("total", sum(counts.values())))
+    worst = str(summary.get("worst") or summary.get("risk_level") or "INFO").upper()
+    risk = str(summary.get("risk_level", "green") or "green").lower()
     emoji = {"red": "🔴", "yellow": "🟡", "green": "🟢"}.get(risk, "🟢")
+
+    zero = total == 0 or sum(counts.values()) == 0
+    if zero:
+        # Zero-state: limpio y profesional
+        return "\n".join(
+            [
+                f"# Diff Risk Dashboard {emoji} — No findings",
+                "",
+                "> ✅ No findings. All severities are 0.",
+                "",
+                "| Severity | Count |",
+                "|---|---:|",
+                "| **TOTAL** | **0** |",
+                "",
+            ]
+        )
+
+    # Caso normal: tabla completa (compatibilidad con tests/README)
     lines = [
         f"# Diff Risk Dashboard {emoji} — Worst: **{worst}**",
         "",
@@ -29,5 +43,10 @@ def to_markdown(summary: Mapping[str, Any]) -> str:
     ]
     for sev in _SEVERITIES:
         lines.append(f"| {sev} | {counts.get(sev, 0)} |")
-    lines += [f"| **TOTAL** | **{total}** |", "", "> Generated by diff-risk-dashboard CLI"]
+    lines.append(f"| **TOTAL** | **{total}** |")
+    lines.append("")
     return "\n".join(lines)
+
+
+# Alias de compatibilidad
+render_markdown = to_markdown