diff --git a/server/services/report.test.ts b/server/services/report.test.ts
new file mode 100644
index 0000000..9b3b9c5
--- /dev/null
+++ b/server/services/report.test.ts
@@ -0,0 +1,22 @@
+// server/services/report.test.ts
+import { describe, it, expect } from "vitest";
+import { buildReportMarkdown } from "./report.js";
+import type { ExecutionResult } from "@shared/types.js";
+
+const exec: ExecutionResult = {
+  executionId: "exec_1", machineId: "m1", startedAt: "2026-06-04T12:00:00Z",
+  finishedAt: "2026-06-04T12:05:00Z", mode: "manual", action: "apt_full_upgrade",
+  status: "ok", rebootRequiredAfterRun: true,
+  importantLogLines: ["Inst libc6 [2.31-13] (2.31-13+deb11u5 Debian [amd64])"],
+  rawLogRef: "reports/m1/exec_1.log", reportRef: "reports/m1/exec_1.md",
+};
+
+describe("buildReportMarkdown", () => {
+  it("contient l'en-tête, le statut et les lignes importantes", () => {
+    const md = buildReportMarkdown(exec, "deb-01");
+    expect(md).toContain("# Rapport d'exécution — deb-01");
+    expect(md).toContain("apt_full_upgrade");
+    expect(md).toContain("Redémarrage requis : oui");
+    expect(md).toContain("Inst libc6");
+  });
+});
diff --git a/server/services/report.ts b/server/services/report.ts
new file mode 100644
index 0000000..4f397fe
--- /dev/null
+++ b/server/services/report.ts
@@ -0,0 +1,25 @@
+// server/services/report.ts
+import type { ExecutionResult } from "@shared/types.js";
+
+export function buildReportMarkdown(exec: ExecutionResult, machineName: string): string {
+  const lines = exec.importantLogLines.map((l) => `    ${l}`).join("\n");
+  return `# Rapport d'exécution — ${machineName}
+
+- Exécution : ${exec.executionId}
+- Action : ${exec.action}
+- Statut : ${exec.status}
+- Début : ${exec.startedAt}
+- Fin : ${exec.finishedAt}
+- Redémarrage requis : ${exec.rebootRequiredAfterRun ? "oui" : "non"}
+
+## Lignes importantes
+
+\`\`\`
+${lines || "    (aucune)"}
+\`\`\`
+
+## Log brut
+
+Référence : \`${exec.rawLogRef}\`
+`;
+}