Per-model service tier default (codex: gpt-6.1-sol -> fast), tier:<x> / tier:none labels

executors.<x>.tier_defaults maps a model to the tier used when no label sets one;
a tier:<name> label sets it explicitly and tier:none drops the tier argument.

agentd/core.py

@@ -491,6 +491,8 @@ class Agentd:
                 r["model"] = label[6:]
             elif label.startswith("effort:"):
                 r["effort"] = label[7:]
+            elif label.startswith("tier:"):
+                r["tier"] = label[5:]
             elif label.startswith("cap:"):
                 caps.append(label[4:])
             elif parse_budget(label) is not None:
@@ -503,6 +505,10 @@ class Agentd:
         ecfg = self.cfg.executors[r["executor"]]
         r["model"] = r["model"] or (ecfg.get("models") or [None])[0]
         r["effort"] = r["effort"] or ecfg.get("default_effort")
+        if r["tier"] is None:  # per-model default unless a label set one; `tier:none` = no tier argument
+            r["tier"] = (ecfg.get("tier_defaults") or {}).get(r["model"])
+        if r["tier"] in ("none", ""):
+            r["tier"] = None
         return r
 
     def protocol(self, pcfg):