diff --git a/client/internal/debug/upload.go b/client/internal/debug/upload.go
index 30aa73b91..4166ef1e6 100644
--- a/client/internal/debug/upload.go
+++ b/client/internal/debug/upload.go
@@ -183,7 +183,11 @@ func getURLHash(url string) string {
 // backticks, angle brackets, parens and braces — so the match does not run past
 // the URL and swallow the prose after it. TrimRight below then drops trailing
 // sentence punctuation, which a bare URL at the end of a clause picks up.
-var urlInText = regexp.MustCompile("https?://[^\\s\"'`<>\\[\\]{}()]+")
+//
+// Square brackets are both a wrapper and part of the syntax: they delimit an
+// IPv6 host. The leading group takes a bracketed host when there is one, so an
+// IPv6 URL is still matched and redacted rather than left whole.
+var urlInText = regexp.MustCompile("https?://(?:\\[[^\\]\\s]+\\])?[^\\s\"'`<>\\[\\]{}()]*")
 
 // redactedError keeps the original error reachable for errors.Is/As while
 // presenting a message with every URL cut down to scheme://host.
diff --git a/client/internal/debug/upload_redact_test.go b/client/internal/debug/upload_redact_test.go
index bea5227e9..b873f6784 100644
--- a/client/internal/debug/upload_redact_test.go
+++ b/client/internal/debug/upload_redact_test.go
@@ -68,6 +68,19 @@ func TestRedactURLsInError(t *testing.T) {
 			err:  errors.New("use `https://b.example.com/p` instead"),
 			want: "use `https://b.example.com` instead",
 		},
+		{
+			// Square brackets delimit an IPv6 host, so excluding them from the
+			// match entirely leaves an IPv6 URL — signed query and all —
+			// untouched in the message.
+			name: "bracketed IPv6 host is still redacted",
+			err:  errors.New(`upload failed: Put "https://[2001:db8::1]/k?X-Amz-Signature=abc123": timeout`),
+			want: `upload failed: Put "https://[2001:db8::1]": timeout`,
+		},
+		{
+			name: "IPv6 host with a port is still redacted",
+			err:  errors.New(`Get "https://[2001:db8::1]:8443/upload-url?id=deadbeef": no such host`),
+			want: `Get "https://[2001:db8::1]:8443": no such host`,
+		},
 	}
 
 	for _, tc := range tests {