diff --git a/tests/tools/test_delegate.py b/tests/tools/test_delegate.py
index 356f72d88..9c93f05c7 100644
--- a/tests/tools/test_delegate.py
+++ b/tests/tools/test_delegate.py
@@ -69,7 +69,10 @@ class TestDelegateRequirements(unittest.TestCase):
         self.assertIn("tasks", props)
         self.assertIn("context", props)
         self.assertIn("toolsets", props)
-        self.assertIn("max_iterations", props)
+        # max_iterations is intentionally NOT exposed to the model — it's
+        # config-authoritative via delegation.max_iterations so users get
+        # predictable budgets.
+        self.assertNotIn("max_iterations", props)
         self.assertNotIn("maxItems", props["tasks"])  # removed — limit is now runtime-configurable
 
 
diff --git a/tools/delegate_tool.py b/tools/delegate_tool.py
index 7b0179c4c..2c35c7c7e 100644
--- a/tools/delegate_tool.py
+++ b/tools/delegate_tool.py
@@ -1558,7 +1558,18 @@ def delegate_task(
     # Load config
     cfg = _load_config()
     default_max_iter = cfg.get("max_iterations", DEFAULT_MAX_ITERATIONS)
-    effective_max_iter = max_iterations or default_max_iter
+    # Model-supplied max_iterations is ignored — the config value is authoritative
+    # so users get predictable budgets. The kwarg is retained for internal callers
+    # and tests; a model-emitted value here would only shrink the budget and
+    # surprise the user mid-run. Log and drop it if one slips through from a
+    # cached tool schema or a stale provider.
+    if max_iterations is not None and max_iterations != default_max_iter:
+        logger.debug(
+            "delegate_task: ignoring caller-supplied max_iterations=%s; "
+            "using delegation.max_iterations=%s from config",
+            max_iterations, default_max_iter,
+        )
+    effective_max_iter = default_max_iter
 
     # Resolve delegation credentials (provider:model pair).
     # When delegation.provider is configured, this resolves the full credential
@@ -2098,13 +2109,6 @@ DELEGATE_TASK_SCHEMA = {
                     "When provided, top-level goal/context/toolsets are ignored."
                 ),
             },
-            "max_iterations": {
-                "type": "integer",
-                "description": (
-                    "Max tool-calling turns per subagent (default: 50). "
-                    "Only set lower for simple tasks."
-                ),
-            },
             "role": {
                 "type": "string",
                 "enum": ["leaf", "orchestrator"],