core/agent: unify provider finish_reason mapping

tests/test_agent/test_finish_reason.py

@@ -0,0 +1,32 @@
+"""Tests for the canonical finish_reason vocabulary shared by provider bridges."""
+
+from __future__ import annotations
+
+import pytest
+
+from plyngent.agent.finish_reason import chat_finish_reason
+
+
+@pytest.mark.parametrize(
+    ("raw", "has_tool_calls", "expected"),
+    [
+        (None, False, "stop"),
+        (None, True, "tool_calls"),
+        ("", False, "stop"),
+        ("end_turn", False, "stop"),
+        ("stop_sequence", False, "stop"),
+        ("completed", False, "stop"),
+        ("stop", False, "stop"),
+        ("max_tokens", False, "length"),
+        ("max_output_tokens", False, "length"),
+        ("length", False, "length"),
+        ("content_filter", False, "content_filter"),
+        ("refusal", False, "content_filter"),
+        ("tool_use", False, "tool_calls"),
+        ("tool_calls", False, "tool_calls"),
+        ("Tool_Use", False, "tool_calls"),
+        ("MAX_TOKENS", False, "length"),
+    ],
+)
+def test_chat_finish_reason(raw: str | None, has_tool_calls: bool, expected: str) -> None:
+    assert chat_finish_reason(raw, has_tool_calls=has_tool_calls) == expected