From 6a4c43333f7e8b3d13ccde310e2e70ace9dd588c Mon Sep 17 00:00:00 2001
From: agammann <161159040+agammann@users.noreply.github.com>
Date: Sun, 20 Sep 2026 15:07:16 -0700
Subject: [PATCH] fix: accept fractional seconds in ISO durations

---
 lib/types/string.js  |  2 +-
 test/types/string.js | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/lib/types/string.js b/lib/types/string.js
index 77578d59..ceacf738 100755
--- a/lib/types/string.js
+++ b/lib/types/string.js
@@ -29,7 +29,7 @@ const internals = {
         withoutPrefix: /^[0-9a-f]+$/i
     },
     ipRegex: ipRegex({ cidr: 'forbidden' }).regex,
-    isoDurationRegex: /^P(?!$)(\d+Y)?(\d+M)?(\d+W)?(\d+D)?(T(?=\d)(\d+H)?(\d+M)?(\d+S)?)?$/,
+    isoDurationRegex: /^P(?!$)(\d+Y)?(\d+M)?(\d+W)?(\d+D)?(T(?=\d)(\d+H)?(\d+M)?(\d+([.,]\d+)?S)?)?$/,
 
     guidBrackets: {
         '{': '}', '[': ']', '(': ')', '': ''
diff --git a/test/types/string.js b/test/types/string.js
index 3d28056e..70d34b33 100755
--- a/test/types/string.js
+++ b/test/types/string.js
@@ -5756,6 +5756,14 @@ describe('string', () => {
 
     describe('isoDuration()', () => {
 
+        it('rejects malformed fractional seconds', () => {
+
+            const schema = Joi.string().isoDuration();
+            for (const value of ['PT.5S', 'PT,5S', 'PT5.S', 'PT5,S', 'PT5.1.2S', 'PT5,1,2S', 'PT5.1S2M']) {
+                expect(schema.validate(value).error).to.be.an.error();
+            }
+        });
+
         it('validates isoDuration', () => {
 
             Helper.validate(Joi.string().isoDuration(), [
@@ -5768,6 +5776,10 @@ describe('string', () => {
                 ['P6M4DT12H30M5S', true],
                 ['PT10H20M5S', true],
                 ['PT40S', true],
+                ['PT4.4S', true],
+                ['PT4,4S', true],
+                ['PT0.001S', true],
+                ['P3Y6M4DT12H30M5.125S', true],
                 ['PT0S', true],
                 ['P0D', true],
                 ['P30S', false, {