release v2.6.0

The cutover's first real lesson ships: tool_choice "required" was a
workaround for a backend that ignored it, and became an unbreakable
tool loop on a backend that obeys it every request (~80 s arithmetic
turns, observed). The health check now learns which server answers
behind OLLAMA_HOST (/props is llama-server's own surface) and only
Ollama gets the advisory nudge. Probed unforced on llama-server: 3/3
tool calls via the --jinja template.

Also carries BACKEND_SLOT_PINNING (default off) for the P3 pilot.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/anthropic/test_model_selector.py

@@ -120,3 +120,20 @@ class TestWithSlotPinning:
         monkeypatch.setattr(config, "PREFER_CLOUD_BACKEND", True)
         base = model_selector.get_tool_choice_settings()
         assert model_selector.with_slot_pinning(base, slot=1) is base
+
+
+class TestLocalFlavorToolChoice:
+    def test_llama_server_flavor_sends_no_tool_choice(self, local_first, monkeypatch):
+        monkeypatch.setattr(model_selector, "_local_flavor", "llama-server")
+        settings = model_selector.get_tool_choice_settings()
+        assert not settings.get("extra_body")
+
+    def test_ollama_flavor_keeps_advisory_required(self, local_first, monkeypatch):
+        monkeypatch.setattr(model_selector, "_local_flavor", "ollama")
+        settings = model_selector.get_tool_choice_settings()
+        assert settings["extra_body"] == {"tool_choice": "required"}
+
+    def test_unknown_flavor_defaults_to_ollama_semantics(self, local_first, monkeypatch):
+        monkeypatch.setattr(model_selector, "_local_flavor", None)
+        settings = model_selector.get_tool_choice_settings()
+        assert settings["extra_body"] == {"tool_choice": "required"}

tests/contracts/test_service_contracts.py

@@ -114,16 +114,18 @@ class TestLocalBackendContract:
         )
 
     async def test_openai_compat_tool_calling(self):
-        # Mirrors the request PydanticAI's OpenAIChatModel sends for the
-        # orchestration phase, including the extra_body tool_choice.
+        # Mirrors the orchestration-phase request on llama-server: tools
+        # attached, NO tool_choice. The backend must call the tool unforced
+        # — "required" is deliberately absent because llama-server enforces
+        # it on every request in a run, which turns the tool loop
+        # unbreakable (observed at cutover: ~80 s turns).
         response = await _post_or_skip(
             f"{OLLAMA}/v1/chat/completions",
-            "ollama",
+            "local-backend",
             {
                 "model": config.OLLAMA_DEFAULT_MODEL,
                 "messages": [{"role": "user", "content": "What is 6 * 7? Use the calculator."}],
                 "tools": [CALCULATOR_TOOL],
-                "tool_choice": "required",
                 "stream": False,
             },
             timeout=config.OLLAMA_TIMEOUT,