diff --git a/doc/source/admin/galaxy_options.rst b/doc/source/admin/galaxy_options.rst
index b64062ec8cd..5dd5ccf20ec 100644
--- a/doc/source/admin/galaxy_options.rst
+++ b/doc/source/admin/galaxy_options.rst
@@ -5688,8 +5688,10 @@
     ``retries`` sets the pydantic-ai retry budget (tool calls and
     output validation); it defaults to 3. Raise it if a model
     intermittently fails to produce conforming output ("Exceeded
-    maximum output retries"); custom_tool's producer defaults to 0
-    since it runs its own reflection loop.
+    maximum output retries"). custom_tool's producer keeps a budget of
+    0 because it runs its own reflection loop; a shared ``default``
+    block does not change that -- set ``custom_tool.retries``
+    explicitly to override it.
 :Default: ``None``
 :Type: any
 
diff --git a/lib/galaxy/agents/base.py b/lib/galaxy/agents/base.py
index fa38b184fcb..d69d02b6996 100644
--- a/lib/galaxy/agents/base.py
+++ b/lib/galaxy/agents/base.py
@@ -29,6 +29,7 @@ from typing import (
 
 import yaml
 
+from galaxy.exceptions import ConfigurationError
 from galaxy.managers.context import ProvidesUserContext
 from galaxy.model import User
 from galaxy.schema.agents import (
@@ -817,6 +818,19 @@ class BaseGalaxyAgent(ABC):
                 return self.deps.config.ai_api_base_url
         return default
 
+    def _get_agent_specific_config(self, key: str, default: Any = None) -> Any:
+        """Read a value only from this agent's own ``inference_services`` block.
+
+        Unlike :meth:`_get_agent_config`, this skips the shared ``default`` block so a
+        caller-pinned builtin is overridden only by an explicit per-agent entry.
+        """
+        inference_config = getattr(self.deps.config, "inference_services", {})
+        if isinstance(inference_config, dict):
+            agent_specific = inference_config.get(self.agent_type, {})
+            if isinstance(agent_specific, dict) and key in agent_specific:
+                return agent_specific[key]
+        return default
+
     def _get_model_name(self) -> str:
         return self._get_agent_config("model", "gpt-4o-mini")
 
@@ -864,10 +878,26 @@ class BaseGalaxyAgent(ABC):
     def _get_retries(self, default: Optional[int] = None) -> int:
         """Retry budget for the agent's pydantic-ai ``Agent(retries=...)``.
 
-        ``default`` lets a caller override the builtin (e.g. custom_tool's producer
-        keeps 0 so its own reflection loop owns the retry).
+        With no ``default``, the budget resolves per-agent > ``default`` block >
+        builtin (:attr:`DEFAULT_AGENT_RETRIES`). A caller-pinned ``default`` (e.g.
+        custom_tool's producer keeps 0 so its own reflection loop owns the retry) is
+        a correctness requirement, not a tunable: only an explicit per-agent
+        ``retries`` overrides it -- a shared ``default`` block must not silently
+        re-enable pydantic-ai retries there.
         """
-        return int(self._get_agent_config("retries", self.DEFAULT_AGENT_RETRIES if default is None else default))
+        if default is None:
+            raw = self._get_agent_config("retries", self.DEFAULT_AGENT_RETRIES)
+        else:
+            raw = self._get_agent_specific_config("retries", default)
+        try:
+            retries = int(raw)
+        except (TypeError, ValueError):
+            retries = None
+        if retries is None or retries < 0:
+            raise ConfigurationError(
+                f"inference_services 'retries' for agent '{self.agent_type}' must be a non-negative integer, got {raw!r}"
+            )
+        return retries
 
     async def _call_agent_from_tool(
         self,
diff --git a/lib/galaxy/config/sample/galaxy.yml.sample b/lib/galaxy/config/sample/galaxy.yml.sample
index 5e470624224..ab22fbd2ec4 100644
--- a/lib/galaxy/config/sample/galaxy.yml.sample
+++ b/lib/galaxy/config/sample/galaxy.yml.sample
@@ -3084,8 +3084,10 @@ galaxy:
   # ``retries`` sets the pydantic-ai retry budget (tool calls and output
   # validation); it defaults to 3. Raise it if a model intermittently
   # fails to produce conforming output ("Exceeded maximum output
-  # retries"); custom_tool's producer defaults to 0 since it runs its
-  # own reflection loop.
+  # retries"). custom_tool's producer keeps a budget of 0 because it
+  # runs its own reflection loop; a shared ``default`` block does not
+  # change that -- set ``custom_tool.retries`` explicitly to override
+  # it.
   #inference_services: null
 
   # YAML file with capability hints for agent inference models. Maps
diff --git a/lib/galaxy/config/schemas/config_schema.yml b/lib/galaxy/config/schemas/config_schema.yml
index 9f05a1b0b32..9758ae5afda 100644
--- a/lib/galaxy/config/schemas/config_schema.yml
+++ b/lib/galaxy/config/schemas/config_schema.yml
@@ -4211,8 +4211,9 @@ mapping:
           Per-agent or default-block ``retries`` sets the pydantic-ai retry budget
           (tool calls and output validation); it defaults to 3. Raise it if a model
           intermittently fails to produce conforming output ("Exceeded maximum output
-          retries"); custom_tool's producer defaults to 0 since it runs its own
-          reflection loop.
+          retries"). custom_tool's producer keeps a budget of 0 because it runs its
+          own reflection loop; a shared ``default`` block does not change that -- set
+          ``custom_tool.retries`` explicitly to override it.
 
       agent_model_capabilities_file:
         type: str
diff --git a/test/unit/app/test_agents.py b/test/unit/app/test_agents.py
index 427fb6d8a51..8d918632e89 100644
--- a/test/unit/app/test_agents.py
+++ b/test/unit/app/test_agents.py
@@ -84,6 +84,7 @@ from galaxy.agents.page_assistant import (
     FullReplacementEdit,
     SectionPatchEdit,
 )
+from galaxy.exceptions import ConfigurationError
 from galaxy.schema.agents import ConfidenceLevel
 from galaxy.tool_util_models import UserToolSource
 from galaxy.util.unittest_utils import pytestmark_live_llm
@@ -191,6 +192,37 @@ class TestAgentUnitMocked:
         producer = CustomToolAgent(self.deps)
         assert producer.agent._max_output_retries == 0
 
+    def test_producer_retries_default_ignores_default_block(self):
+        # custom_tool's producer pins retries=0 so its own reflection loop owns
+        # the retry. A shared `default` block must NOT silently re-enable
+        # pydantic-ai retries there -- only an explicit per-agent entry may.
+        producer = CustomToolAgent(self.deps)
+
+        self.mock_config.inference_services = {"default": {"retries": 5}}
+        assert producer._get_retries(default=0) == 0
+        # The normal (critic) lookup still honors the default block.
+        assert producer._get_retries() == 5
+
+        # An explicit custom_tool entry still overrides the pinned builtin.
+        self.mock_config.inference_services = {"custom_tool": {"retries": 7}}
+        assert producer._get_retries(default=0) == 7
+
+    def test_invalid_retries_config_raises_configuration_error(self):
+        # Non-numeric, blank, or negative `retries` is operator misconfiguration;
+        # it must surface as a clear ConfigurationError rather than a bare
+        # TypeError/ValueError (which the manager mistakes for an unknown-agent
+        # fallback) or a silently-broken negative budget that fails every request.
+        router = QueryRouterAgent(self.deps)
+
+        for bad in ("three", None, -1):
+            self.mock_config.inference_services = {"default": {"retries": bad}}
+            with pytest.raises(ConfigurationError, match="retries"):
+                router._get_retries()
+
+        # 0 is valid (custom_tool's producer relies on it) and must not raise.
+        self.mock_config.inference_services = {"default": {"retries": 0}}
+        assert router._get_retries() == 0
+
     @pytest.mark.asyncio
     async def test_router_falls_back_on_output_retry_exhaustion(self):
         # When the model never produces a valid structured output, pydantic-ai