diff --git a/share/tools/web_config/webconfig.py b/share/tools/web_config/webconfig.py
index faf37729d..1fbec4f98 100755
--- a/share/tools/web_config/webconfig.py
+++ b/share/tools/web_config/webconfig.py
@@ -1544,7 +1544,10 @@ print("%sHit ENTER to stop.%s" % (ENTER_BOLD_MODE, EXIT_ATTRIBUTE_MODE))
 
 
 def runThing():
-    if isMacOS10_12_5_OrLater():
+    if os.environ.get("BROWSER") == "true":
+        # Don't start a browser in this case (see issue #11926)
+        pass
+    elif isMacOS10_12_5_OrLater():
         subprocess.check_call(["open", fileurl])
     elif is_wsl():
         cmd_path = find_executable("cmd.exe", COMMON_WSL_CMD_PATHS)
diff --git a/tests/checks/tmux-fish_config.fish b/tests/checks/tmux-fish_config.fish
new file mode 100644
index 000000000..cb7b46dc9
--- /dev/null
+++ b/tests/checks/tmux-fish_config.fish
@@ -0,0 +1,58 @@
+#RUN: %fish %s
+
+#REQUIRES: command -v tmux
+#REQUIRES: command -v wget
+#REQUIRES: command -v diff
+
+isolated-tmux-start
+
+# Widen the window because URLs can be fairly long and we do not want to deal
+# with wrapping.
+# We would prefer to redirect fish_config's output to a file instead and avoid
+# the issue altogether, but we need to extract the auth string and unfortunately,
+# because of buffering, the file will remain empty until the buffer is full or
+# fish_config exits.
+isolated-tmux resize-window -x 500
+
+isolated-tmux send-keys "BROWSER=true fish_config" Enter
+tmux-sleep
+isolated-tmux capture-pane -p
+# CHECK: prompt 0> BROWSER=true fish_config
+# CHECK: Web config started at file://{{.*}}.html
+# CHECK: If that doesn't work, try opening http://localhost:{{(\d{4})}}/{{\w+}}/
+# CHECK: Hit ENTER to stop.
+
+# Extract the URL from the output
+set -l base_url (isolated-tmux capture-pane -p | string match -r 'http://localhost:\d{4}/\w+/$')
+set -l host_port (dirname $base_url)
+
+# Check a bad URL (http://host:port/invalid_auth/)
+wget -q -O /dev/null $host_port/invalid_auth/ 2>/dev/null
+set -l last_status $status
+# Busybox's wget does not return the same code as GNU's. Currently this affects
+# the Alpine CI. If the Alpine image is update to GNU wget, we should be able to
+# safely assume everybody uses GNU's (until we told otherwise)
+switch "$(wget --version 2>&1)"
+    case '*GNU*'
+        test $last_status -eq 8
+    case '*busybox*'
+        test $last_status -eq 1
+    case '*'
+        # Only rely on the fish_config logs, which is the critical test.
+        # The status code is only a "nice to have"
+        true
+end
+or echo "Unexpected exit code ($last_status) from wget"
+
+isolated-tmux capture-pane -p -S 4
+# CHECK: {{.*}} code 403, message Forbidden, path /invalid_auth/
+
+# Check a good URL
+set -l workspace_root (path resolve -- (status dirname)/../../)
+diff -q "$workspace_root/share/tools/web_config/index.html" (wget -q -O - $base_url 2>/dev/null | psub -f)
+
+isolated-tmux send-keys Enter
+tmux-sleep
+isolated-tmux capture-pane -p -S 5
+# CHECK: Shutting down.
+# CHECK: prompt 1>