fix: OAuth flag stale after refresh/fallback, memory nudge never fires, dead code

- Update _is_anthropic_oauth in _try_refresh_anthropic_client_credentials()
  when token type changes during credential refresh
- Set _is_anthropic_oauth in _try_activate_fallback() Anthropic path
- Move _turns_since_memory and _iters_since_skill init to __init__ so
  nudge counters accumulate across run_conversation() calls in CLI mode
- Remove unreachable retry_count >= max_retries block after raise

Adds 7 regression tests. Salvaged from PR #1797 by @0xbyt4.

tests/test_run_agent.py

@@ -2717,3 +2717,135 @@ class TestNormalizeCodexDictArguments:
         msg, _ = agent._normalize_codex_response(response)
         tc = msg.tool_calls[0]
         assert tc.function.arguments == args_str
+
+
+# ---------------------------------------------------------------------------
+# OAuth flag and nudge counter fixes (salvaged from PR #1797)
+# ---------------------------------------------------------------------------
+
+
+class TestOAuthFlagAfterCredentialRefresh:
+    """_is_anthropic_oauth must update when token type changes during refresh."""
+
+    def test_oauth_flag_updates_api_key_to_oauth(self, agent):
+        """Refreshing from API key to OAuth token must set flag to True."""
+        agent.api_mode = "anthropic_messages"
+        agent._anthropic_api_key = "sk-ant-api-old"
+        agent._anthropic_client = MagicMock()
+        agent._is_anthropic_oauth = False
+
+        with (
+            patch("agent.anthropic_adapter.resolve_anthropic_token",
+                  return_value="sk-ant-setup-oauth-token"),
+            patch("agent.anthropic_adapter.build_anthropic_client",
+                  return_value=MagicMock()),
+        ):
+            result = agent._try_refresh_anthropic_client_credentials()
+
+        assert result is True
+        assert agent._is_anthropic_oauth is True
+
+    def test_oauth_flag_updates_oauth_to_api_key(self, agent):
+        """Refreshing from OAuth to API key must set flag to False."""
+        agent.api_mode = "anthropic_messages"
+        agent._anthropic_api_key = "sk-ant-setup-old"
+        agent._anthropic_client = MagicMock()
+        agent._is_anthropic_oauth = True
+
+        with (
+            patch("agent.anthropic_adapter.resolve_anthropic_token",
+                  return_value="sk-ant-api03-new-key"),
+            patch("agent.anthropic_adapter.build_anthropic_client",
+                  return_value=MagicMock()),
+        ):
+            result = agent._try_refresh_anthropic_client_credentials()
+
+        assert result is True
+        assert agent._is_anthropic_oauth is False
+
+
+class TestFallbackSetsOAuthFlag:
+    """_try_activate_fallback must set _is_anthropic_oauth for Anthropic fallbacks."""
+
+    def test_fallback_to_anthropic_oauth_sets_flag(self, agent):
+        agent._fallback_activated = False
+        agent._fallback_model = {"provider": "anthropic", "model": "claude-sonnet-4-6"}
+
+        mock_client = MagicMock()
+        mock_client.base_url = "https://api.anthropic.com/v1"
+        mock_client.api_key = "sk-ant-setup-oauth-token"
+
+        with (
+            patch("agent.auxiliary_client.resolve_provider_client",
+                  return_value=(mock_client, None)),
+            patch("agent.anthropic_adapter.build_anthropic_client",
+                  return_value=MagicMock()),
+            patch("agent.anthropic_adapter.resolve_anthropic_token",
+                  return_value=None),
+        ):
+            result = agent._try_activate_fallback()
+
+        assert result is True
+        assert agent._is_anthropic_oauth is True
+
+    def test_fallback_to_anthropic_api_key_clears_flag(self, agent):
+        agent._fallback_activated = False
+        agent._fallback_model = {"provider": "anthropic", "model": "claude-sonnet-4-6"}
+
+        mock_client = MagicMock()
+        mock_client.base_url = "https://api.anthropic.com/v1"
+        mock_client.api_key = "sk-ant-api03-regular-key"
+
+        with (
+            patch("agent.auxiliary_client.resolve_provider_client",
+                  return_value=(mock_client, None)),
+            patch("agent.anthropic_adapter.build_anthropic_client",
+                  return_value=MagicMock()),
+            patch("agent.anthropic_adapter.resolve_anthropic_token",
+                  return_value=None),
+        ):
+            result = agent._try_activate_fallback()
+
+        assert result is True
+        assert agent._is_anthropic_oauth is False
+
+
+class TestMemoryNudgeCounterPersistence:
+    """_turns_since_memory must persist across run_conversation calls."""
+
+    def test_counters_initialized_in_init(self):
+        """Counters must exist on the agent after __init__."""
+        with patch("run_agent.get_tool_definitions", return_value=[]):
+            a = AIAgent(
+                model="test", api_key="test-key", provider="openrouter",
+                skip_context_files=True, skip_memory=True,
+            )
+        assert hasattr(a, "_turns_since_memory")
+        assert hasattr(a, "_iters_since_skill")
+        assert a._turns_since_memory == 0
+        assert a._iters_since_skill == 0
+
+    def test_counters_not_reset_in_preamble(self):
+        """The run_conversation preamble must not zero the nudge counters."""
+        import inspect
+        src = inspect.getsource(AIAgent.run_conversation)
+        # The preamble resets many fields (retry counts, budget, etc.)
+        # before the main loop. Find that reset block and verify our
+        # counters aren't in it. The reset block ends at iteration_budget.
+        preamble_end = src.index("self.iteration_budget = IterationBudget")
+        preamble = src[:preamble_end]
+        assert "self._turns_since_memory = 0" not in preamble
+        assert "self._iters_since_skill = 0" not in preamble
+
+
+class TestDeadRetryCode:
+    """Unreachable retry_count >= max_retries after raise must not exist."""
+
+    def test_no_unreachable_max_retries_after_backoff(self):
+        import inspect
+        source = inspect.getsource(AIAgent.run_conversation)
+        occurrences = source.count("if retry_count >= max_retries:")
+        assert occurrences == 2, (
+            f"Expected 2 occurrences of 'if retry_count >= max_retries:' "
+            f"but found {occurrences}"
+        )