fix: K3 plan-variant slugs (k3-256k) now get K3's effort vocabulary

kimi_supported_efforts() used exact/prefix matching and missed Kimi
Coding plan variants like k3-256k, which fell back to the K2-era
low/medium/high set and mistranslated efforts on a K3 wire. Replaced
with the boundary-token regex from #76427 (credit @ruizanthony), which
matches k3/k3-256k/kimi-k3* without matching kimi-k2.6 or mk3000.

agent/reasoning_effort.py

@@ -36,8 +36,14 @@ Rules for call sites:
 
 from __future__ import annotations
 
+import re
 from typing import Optional, Sequence
 
+#: K3 slug detector — matches ``k3`` as a delimited token (``k3``,
+#: ``k3-256k``, ``kimi-k3``, ``kimi-k3-cot``) without matching K2-era names
+#: (``kimi-k2.6``). From #76427 by @ruizanthony.
+_KIMI_K3_SLUG_RE = re.compile(r"(?:^|[^a-z0-9])k3(?:[^a-z0-9]|$)")
+
 # Canonical low→high ordering used for nearest-level clamping. Superset of
 # hermes_constants.VALID_REASONING_EFFORTS ("none" included so an explicit
 # disable can be clamped too when a provider publishes it as a level).
@@ -124,11 +130,14 @@ SOLAR_EFFORTS: tuple[str, ...] = ("low", "medium", "high")
 def kimi_supported_efforts(model: Optional[str]) -> tuple[str, ...]:
     """Supported effort set for a Moonshot/Kimi model slug.
 
-    K3 is served as the bare slug ``k3`` and the ``kimi-k3*`` aliases; its
-    documented set is low/high/max. Everything earlier speaks low/medium/high.
+    K3 is served as the bare slug ``k3``, plan variants like ``k3-256k``,
+    and the ``kimi-k3*`` aliases; its documented set is low/high/max.
+    Everything earlier speaks low/medium/high. Boundary-matched so K2-era
+    names (``kimi-k2.6``) never match (detection regex from #76427 by
+    @ruizanthony).
     """
     m = (model or "").strip().lower().split("/")[-1]
-    if m == "k3" or m.startswith("kimi-k3"):
+    if _KIMI_K3_SLUG_RE.search(m):
         return KIMI_K3_EFFORTS
     return KIMI_K2_EFFORTS
 

tests/agent/test_reasoning_effort_module.py

@@ -112,13 +112,15 @@ class TestClampEffort:
 
 class TestKimiVocabulary:
     @pytest.mark.parametrize(
-        "model", ["k3", "kimi-k3", "kimi-k3-cot", "moonshotai/kimi-k3"]
+        "model",
+        ["k3", "kimi-k3", "kimi-k3-cot", "moonshotai/kimi-k3", "k3-256k"],
     )
     def test_k3_slugs(self, model):
         assert kimi_supported_efforts(model) is KIMI_K3_EFFORTS
 
     @pytest.mark.parametrize(
-        "model", ["kimi-k2.6", "moonshotai/kimi-k2-0905", "kimi-latest", None]
+        "model",
+        ["kimi-k2.6", "moonshotai/kimi-k2-0905", "kimi-latest", "mk3000", None],
     )
     def test_k2_era_slugs(self, model):
         assert kimi_supported_efforts(model) is KIMI_K2_EFFORTS