As explained in the issue JRA-35413, the json response given by Stash does not match the configured Base URL when hitting stashinstance/stash/rest/capabilities/navigation.

While trying to create a branche from JIRA, it results to a call to the wrong address within the user's browser. As rsmart says as designed for JIRA:

The URL that create branch uses is given to it by stash (its baseURL in the json response at: stashinstance/rest/capabilities/navigation)

Here is my configuration:

• In the Stash 2.10 instance:
  • Stash Base URL: https://full.stash.address.com/stash
• In the JIRA 6.1 instance, configured Stash Application Link:
  • Application URL: http://localhost:7990/stash
  • Display URL: https://full.stash.address.com/stash

When trying to create a branch from JIRA, the instance hit http://localhost:7990/stash/rest/capabilities/navigation, the JSON answer is:

{
    "create-branch":[{
            "href": "http://localhost:7990/stash/plugins/servlet/create-branch",
            "label": "Stash",
            "icon": "http://localhost:7990/stash/plugins/servlet/create-branch/icon.png",
            "tooltip": "",
            "lang": "en-GB",
            "weight":300
        }]
}

After rsmart comment here, it seems the JSON answer from the Stash instance should always be as configured in the Stash instance Base URL:

"href": "https://full.stash.address.com/stash/plugins/servlet/create-branch"