diff --git a/gittensor/cli/miner_commands/post.py b/gittensor/cli/miner_commands/post.py
index 233ce286..933f06aa 100644
--- a/gittensor/cli/miner_commands/post.py
+++ b/gittensor/cli/miner_commands/post.py
@@ -39,6 +39,9 @@
     'rejected': '[red]✗[/red]',
     'no_response': '[yellow]—[/yellow]',
 }
+_PAT_GRAPHQL_ACCESS_ERROR = (
+    '[red]PAT lacks GraphQL API access. Fine-grained PATs need "Public Repositories (read-only)" permission.[/red]'
+)
 
 
 @click.command()
@@ -214,9 +217,27 @@ def _validate_pat_locally(pat: str) -> str | None:
             timeout=GITHUB_HTTP_TIMEOUT_SECONDS,
         )
         if gql_resp.status_code != 200:
-            err_console.print(
-                '[red]PAT lacks GraphQL API access. Fine-grained PATs need "Public Repositories (read-only)" permission.[/red]'
-            )
+            err_console.print(_PAT_GRAPHQL_ACCESS_ERROR)
+            return None
+
+        try:
+            gql_data = gql_resp.json()
+        except ValueError:
+            return None
+
+        if not isinstance(gql_data, dict):
+            err_console.print(_PAT_GRAPHQL_ACCESS_ERROR)
+            return None
+
+        errors = gql_data.get('errors')
+        if errors:
+            err_console.print(_PAT_GRAPHQL_ACCESS_ERROR)
+            return None
+
+        response_data = gql_data.get('data')
+        viewer = response_data.get('viewer') if isinstance(response_data, dict) else None
+        if viewer is None:
+            err_console.print(_PAT_GRAPHQL_ACCESS_ERROR)
             return None
 
         return login
diff --git a/tests/cli/test_miner_commands.py b/tests/cli/test_miner_commands.py
index c7ec1140..39baddc8 100644
--- a/tests/cli/test_miner_commands.py
+++ b/tests/cli/test_miner_commands.py
@@ -4,7 +4,7 @@
 
 import json
 from types import SimpleNamespace
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 import pytest
 from click.testing import CliRunner
@@ -18,6 +18,7 @@
     _pat_post_row_category,
     _require_validator_axons,
 )
+from gittensor.cli.miner_commands.post import _validate_pat_locally
 
 
 def _fake_metagraph(rows: list[tuple[float, bool, float]]):
@@ -31,11 +32,55 @@ def _fake_metagraph(rows: list[tuple[float, bool, float]]):
     )
 
 
+def _mock_http_response(status_code: int = 200, payload=None, json_error=None):
+    response = MagicMock()
+    response.status_code = status_code
+    if json_error is not None:
+        response.json.side_effect = json_error
+    else:
+        response.json.return_value = payload if payload is not None else {}
+    return response
+
+
 @pytest.fixture
 def runner():
     return CliRunner()
 
 
+class TestValidatePatLocally:
+    @patch('gittensor.cli.miner_commands.post.requests.post')
+    @patch('gittensor.cli.miner_commands.post.requests.get')
+    def test_valid_viewer_returns_login(self, mock_get, mock_post):
+        mock_get.return_value = _mock_http_response(200, {'login': 'octocat'})
+        mock_post.return_value = _mock_http_response(200, {'data': {'viewer': {'login': 'octocat'}}})
+
+        assert _validate_pat_locally('ghp_valid') == 'octocat'
+
+    @pytest.mark.parametrize(
+        'payload',
+        [
+            {'data': {'viewer': None}},
+            {'data': None},
+            {'errors': [{'message': 'Bad credentials'}]},
+        ],
+    )
+    @patch('gittensor.cli.miner_commands.post.requests.post')
+    @patch('gittensor.cli.miner_commands.post.requests.get')
+    def test_graphql_body_rejections_return_none(self, mock_get, mock_post, payload):
+        mock_get.return_value = _mock_http_response(200, {'login': 'octocat'})
+        mock_post.return_value = _mock_http_response(200, payload)
+
+        assert _validate_pat_locally('ghp_scopeless') is None
+
+    @patch('gittensor.cli.miner_commands.post.requests.post')
+    @patch('gittensor.cli.miner_commands.post.requests.get')
+    def test_graphql_json_decode_error_returns_none(self, mock_get, mock_post):
+        mock_get.return_value = _mock_http_response(200, {'login': 'octocat'})
+        mock_post.return_value = _mock_http_response(200, json_error=ValueError('not json'))
+
+        assert _validate_pat_locally('ghp_bad_json') is None
+
+
 class TestMinerPost:
     @patch('gittensor.cli.miner_commands.post.click.prompt', return_value='ghp_fake')
     @patch('gittensor.cli.miner_commands.post._validate_pat_locally', return_value=None)