diff --git a/.last-branch b/.last-branch
index f412f8f..05058de 100644
--- a/.last-branch
+++ b/.last-branch
@@ -1 +1 @@
-v20260103-20-reports-export-html-open-new-tab
+v20260104-01-reports-output-format-save-fix
diff --git a/containers/backupchecks/src/backend/app/main/routes_reporting_api.py b/containers/backupchecks/src/backend/app/main/routes_reporting_api.py
index 1711e03..25f2792 100644
--- a/containers/backupchecks/src/backend/app/main/routes_reporting_api.py
+++ b/containers/backupchecks/src/backend/app/main/routes_reporting_api.py
@@ -139,9 +139,12 @@ def api_reports_create():
     name = (payload.get("name") or "").strip() or "Report"
     description = (payload.get("description") or "").strip() or None
     report_type = (payload.get("report_type") or "one-time").strip() or "one-time"
-    output_format = (payload.get("output_format") or "csv").strip() or "csv"
+    output_format = (payload.get("output_format") or "csv").strip().lower() or "csv"
     schedule = (payload.get("schedule") or "").strip() or None
 
+    if output_format not in ("csv", "html", "pdf"):
+        return {"error": "Invalid output_format. Use csv, html, or pdf."}, 400
+
     report_config = payload.get("report_config")
     if report_config is not None and not isinstance(report_config, (dict, list, str)):
         report_config = None
@@ -406,6 +409,7 @@ def api_reports_update(report_id: int):
     - name
     - description
     - report_config
+    - output_format
     """
     err = _require_reporting_role()
     if err is not None:
@@ -420,6 +424,13 @@ def api_reports_update(report_id: int):
         desc = (payload.get("description") or "").strip()
         report.description = desc or None
 
+    if "output_format" in payload:
+        fmt = (payload.get("output_format") or "").strip().lower()
+        if fmt:
+            if fmt not in ("csv", "html", "pdf"):
+                return {"error": "Invalid output_format. Use csv, html, or pdf."}, 400
+            report.output_format = fmt
+
     if "report_config" in payload:
         rc = payload.get("report_config")
         if rc is None:
diff --git a/containers/backupchecks/src/backend/app/models.py b/containers/backupchecks/src/backend/app/models.py
index 04a4627..a66644c 100644
--- a/containers/backupchecks/src/backend/app/models.py
+++ b/containers/backupchecks/src/backend/app/models.py
@@ -536,7 +536,7 @@ class ReportDefinition(db.Model):
     # one-time | scheduled
     report_type = db.Column(db.String(32), nullable=False, default="one-time")
 
-    # csv | pdf (pdf is future)
+    # csv | html | pdf
     output_format = db.Column(db.String(16), nullable=False, default="csv")
 
     # customer scope for report generation
diff --git a/docs/changelog.md b/docs/changelog.md
index f98f049..602bda9 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -181,6 +181,15 @@
 - Changed HTML report handling to open in a new browser tab instead of triggering a file download.
 - Enabled proper inline rendering of HTML reports to support graphical preview and layout validation.
 
+---
+
+## v20260104-01-reports-output-format-save-fix
+
+- Fixed an issue where the selected report output format (HTML/PDF) was not persisted when saving or editing a report.
+- The report update endpoint now correctly stores the chosen output_format instead of always reverting to CSV.
+- Added validation and normalization for output_format values during report creation and update.
+- Ensured that selecting HTML as output no longer results in CSV being generated or downloaded.
+
 ================================================================================================================================================
 
 ## v0.1.15