[Bug]: Button Sign In From graph template is not rendered correctly

[raffifu]

Bug Description

OS: NixOS

I have encountered an issue when trying to use devtools in graph template. It didn't render correctly and cause i can't sign in. Here's my project setup

# pyproject.yaml
[project]
name = "your_app_name"
version = "0.1.0"
description = "A Microsoft Teams bot with Azure Graph integration"
readme = "README.md"
requires-python = ">=3.12"
dependencies = [
    "microsoft-teams-apps",
    "microsoft-teams-graph",
    "microsoft-teams-devtools",
    "dotenv"
]

[dependency-groups]
dev = [
    "pyright>=1.1.406",
]

[project.scripts]
start = "src.main:main"
typecheck = "pyright.cli:entrypoint"

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

[tool.hatch.build.targets.wheel]
packages = ["src"]

# received activity
{
    "id": "8f92fca7-9a7e-4af4-c743-4a330a3ec9ea",
    "type": "activity.sent",
    "body": {
        "id": "9ad6a909-7fa1-46aa-b0a1-78ab63bb0580",
        "activityParams": {
            "from": {
                "id": "",
                "role": "user",
                "name": ""
            },
            "conversation": {
                "id": "devtools",
                "conversationType": "personal",
                "name": "default",
                "isGroup": false
            },
            "type": "message",
            "recipient": {
                "id": "devtools",
                "role": "bot",
                "name": "devtools"
            },
            "inputHint": "acceptingInput",
            "attachments": [
                {
                    "contentType": "application/vnd.microsoft.card.oauth",
                    "content": {
                        "text": "Please Sign In...",
                        "connectionName": "something",
                        "tokenExchangeResource": null,
                        "tokenPostResource": {
                            "sasUrl": "https://token.botframework.com/api/sas/postToken?expiry="
                        },
                        "buttons": [
                            {
                                "type": "signin",
                                "title": "Sign In",
                                "image": null,
                                "text": null,
                                "displayText": null,
                                "value": "https://token.botframework.com/api/oauth/signin?signin=",
                                "channelData": null,
                                "imageAltText": null
                            }
                        ]
                    }
                }
            ]
        },
        "from": {
            "id": "",
            "aadObjectId": null,
            "role": "user",
            "properties": null,
            "name": ""
        },
        "conversation": {
            "id": "devtools",
            "tenantId": null,
            "conversationType": "personal",
            "name": "default",
            "isGroup": false
        },
        "type": "message",
        "recipient": {
            "id": "devtools",
            "aadObjectId": null,
            "role": "bot",
            "properties": null,
            "name": "devtools"
        },
        "inputHint": "acceptingInput",
        "attachments": [
            {
                "id": null,
                "contentType": "application/vnd.microsoft.card.oauth",
                "contentUrl": null,
                "content": {
                    "text": "Please Sign In...",
                    "connectionName": "something",
                    "tokenExchangeResource": null,
                    "tokenPostResource": {
                        "sasUrl": "https://token.botframework.com/api/sas/postToken?expiry="
                    },
                    "buttons": [
                        {
                            "type": "signin",
                            "title": "Sign In",
                            "image": null,
                            "text": null,
                            "displayText": null,
                            "value": "https://token.botframework.com/api/oauth/signin?signin=",
                            "channelData": null,
                            "imageAltText": null
                        }
                    ]
                },
                "name": null,
                "thumbnailUrl": null
            }
        ]
    },
    "sentAt": "2026-03-10T08:22:56.557678",
    "chat": {
        "id": "devtools",
        "conversationType": "personal",
        "name": "default",
        "isGroup": false
    }
}

Steps to Reproduce

1. Initialize the project

npx @microsoft/teams.cli@latest new python your_app_name --template graph

2. Add microsoft-teams-devtools as dependencies in pyproject.yaml
3. Run uv venv && uv sync && uv run src/main.py
4. open devtools in browser http://localhost:3979/devtools
5. Type start and enter

Expected Behavior

It should rendered correctly, like this

Note: I'm taking this screenshot from teams

Actual Behavior

Sign in button not generated correctly

SDK Version

2.0.0a17

Python Version

3.12.12

Additional Context

No response

[raffifu]

Update
This also happen in teams.ts