diff --git a/agent/agent_runtime_helpers.py b/agent/agent_runtime_helpers.py
index 20699283e5..7b5b9b081a 100644
--- a/agent/agent_runtime_helpers.py
+++ b/agent/agent_runtime_helpers.py
@@ -2854,20 +2854,42 @@ def _apply_switched_provider_request_overrides(agent, new_provider):
     A ``custom_providers`` entry can carry an ``extra_body`` (e.g.
     ``chat_template_kwargs`` to toggle a local model's thinking). The gateway
     rebuild path carries this via ``request_overrides``; an *in-place* swap
-    (CLI / TUI ``/model``) must re-derive it for the new provider, otherwise the
-    previous provider's ``extra_body`` lingers. Non-provider overrides
-    (``service_tier`` / ``speed`` from ``/fast``) are preserved.
+    (CLI / TUI ``/model``) must re-derive it for the switched-to provider,
+    otherwise the previous provider's ``extra_body`` lingers.
+
+    The switched-to entry is matched by **provider key, base_url, and model** —
+    the same condition ``agent_init._merge_custom_provider_extra_body`` applies
+    at build time — via the shared ``_custom_provider_extra_body_for_agent``
+    matcher. Matching by name alone would let a *different* model selected at the
+    same named endpoint inherit an ``extra_body`` configured for another model.
+    A stale ``extra_body`` is always cleared when the switched-to provider/model
+    resolves none; non-provider overrides (``service_tier`` / ``speed`` from
+    ``/fast``) are preserved.
     """
-    from hermes_cli.runtime_provider import (
-        _get_named_custom_provider,
-        _custom_provider_request_overrides,
+    from agent.agent_init import _custom_provider_extra_body_for_agent
+
+    # Prefer the init-time cache (agent_init stores ``agent._custom_providers``
+    # right where it runs its own _merge_custom_provider_extra_body); fall back
+    # to a fresh load only if a caller built the agent without it.
+    custom_providers = getattr(agent, "_custom_providers", None)
+    if custom_providers is None:
+        try:
+            from hermes_cli.config import load_config, get_compatible_custom_providers
+            custom_providers = get_compatible_custom_providers(load_config())
+        except Exception:
+            custom_providers = []
+
+    new_extra_body = _custom_provider_extra_body_for_agent(
+        provider=new_provider,
+        model=getattr(agent, "model", "") or "",
+        base_url=getattr(agent, "base_url", "") or "",
+        custom_providers=custom_providers or [],
     )
-    cp = _get_named_custom_provider(new_provider)
-    new_ro = _custom_provider_request_overrides(cp) if cp else None
+
     overrides = dict(getattr(agent, "request_overrides", {}) or {})
-    overrides.pop("extra_body", None)
-    if new_ro and new_ro.get("extra_body"):
-        overrides["extra_body"] = new_ro["extra_body"]
+    overrides.pop("extra_body", None)  # always drop the previous provider's extra_body
+    if new_extra_body:
+        overrides["extra_body"] = dict(new_extra_body)
     agent.request_overrides = overrides
 
 
diff --git a/tests/agent/test_switch_model_request_overrides.py b/tests/agent/test_switch_model_request_overrides.py
index 30543e896d..512b71f9ed 100644
--- a/tests/agent/test_switch_model_request_overrides.py
+++ b/tests/agent/test_switch_model_request_overrides.py
@@ -5,6 +5,11 @@ Before the fix, agent_runtime_helpers.switch_model() swapped model/provider/
 base_url/api_key in place but never touched request_overrides, so a /model
 switch to a thinking-enabled custom provider in the TUI/CLI kept the old
 provider's extra_body.
+
+The switched-to entry is matched by provider key + base_url + model (the same
+condition agent_init._merge_custom_provider_extra_body uses at build time), so a
+*different* model selected at the same named endpoint does not inherit an
+extra_body configured for another model.
 """
 
 import agent.agent_runtime_helpers as arh
@@ -14,39 +19,99 @@ class _Agent:
     pass
 
 
-def test_switch_applies_new_provider_extra_body(monkeypatch):
+# Two entries share the same named endpoint / base_url but pin different models —
+# the exact case a name-only match got wrong.
+CUSTOM_PROVIDERS = [
+    {
+        "name": "main-think",
+        "base_url": "http://10.0.0.1:8000/v1",
+        "model": "think-model",
+        "extra_body": {"chat_template_kwargs": {"enable_thinking": True}},
+    },
+    {
+        "name": "main-plain",
+        "base_url": "http://10.0.0.1:8000/v1",
+        "model": "plain-model",
+        "extra_body": {"chat_template_kwargs": {"enable_thinking": False}},
+    },
+]
+
+
+def _agent(*, model, base_url, request_overrides, custom_providers=CUSTOM_PROVIDERS):
     a = _Agent()
-    a.request_overrides = {"service_tier": "priority"}  # pre-existing /fast override
-    monkeypatch.setattr(
-        "hermes_cli.runtime_provider._get_named_custom_provider",
-        lambda name: {"name": "main-think",
-                      "extra_body": {"chat_template_kwargs": {"enable_thinking": True}}},
+    # switch_model() sets these on the live agent before calling the helper.
+    a.model = model
+    a.base_url = base_url
+    a.provider = "custom"
+    a.request_overrides = request_overrides
+    a._custom_providers = custom_providers  # init-time cache the helper reads
+    return a
+
+
+def test_switch_applies_matched_provider_extra_body():
+    """Switching to the matching provider+model applies its extra_body and
+    preserves non-provider overrides (service_tier/speed from /fast)."""
+    a = _agent(
+        model="think-model",
+        base_url="http://10.0.0.1:8000/v1",
+        request_overrides={"service_tier": "priority"},
     )
     arh._apply_switched_provider_request_overrides(a, "custom:main-think")
     assert a.request_overrides["extra_body"] == {"chat_template_kwargs": {"enable_thinking": True}}
     assert a.request_overrides["service_tier"] == "priority"  # preserved
 
 
-def test_switch_to_noncustom_clears_stale_extra_body(monkeypatch):
-    a = _Agent()
-    a.request_overrides = {
-        "extra_body": {"chat_template_kwargs": {"enable_thinking": True}},
-        "service_tier": "priority",
-    }
-    monkeypatch.setattr(
-        "hermes_cli.runtime_provider._get_named_custom_provider", lambda name: None
+def test_switch_to_noncustom_clears_stale_extra_body():
+    """Switching to a built-in provider clears the previous provider's extra_body."""
+    a = _agent(
+        model="claude-x",
+        base_url="https://api.anthropic.com",
+        request_overrides={
+            "extra_body": {"chat_template_kwargs": {"enable_thinking": True}},
+            "service_tier": "priority",
+        },
     )
     arh._apply_switched_provider_request_overrides(a, "anthropic")
     assert "extra_body" not in a.request_overrides  # stale extra_body cleared
     assert a.request_overrides["service_tier"] == "priority"  # preserved
 
 
-def test_switch_from_none_overrides(monkeypatch):
-    a = _Agent()
-    a.request_overrides = None
-    monkeypatch.setattr(
-        "hermes_cli.runtime_provider._get_named_custom_provider",
-        lambda name: {"name": "main", "extra_body": {"chat_template_kwargs": {"enable_thinking": False}}},
+def test_switch_from_none_overrides():
+    """A None request_overrides is handled and gets the matched extra_body."""
+    a = _agent(
+        model="plain-model",
+        base_url="http://10.0.0.1:8000/v1",
+        request_overrides=None,
     )
-    arh._apply_switched_provider_request_overrides(a, "custom:main")
+    arh._apply_switched_provider_request_overrides(a, "custom:main-plain")
     assert a.request_overrides == {"extra_body": {"chat_template_kwargs": {"enable_thinking": False}}}
+
+
+def test_switch_to_different_model_same_endpoint_does_not_inherit():
+    """Review regression: selecting a *different* model while naming a custom
+    provider must NOT inherit that provider's extra_body when the models differ.
+
+    'main-think' pins 'think-model'. Selecting 'plain-model' under
+    custom:main-think must not carry enable_thinking=True — the model-aware
+    matcher rejects the mismatch and the stale extra_body is cleared. (A
+    name-only match would have wrongly carried it over.)
+    """
+    a = _agent(
+        model="plain-model",  # differs from main-think's pinned 'think-model'
+        base_url="http://10.0.0.1:8000/v1",
+        request_overrides={"extra_body": {"chat_template_kwargs": {"enable_thinking": True}}},
+    )
+    arh._apply_switched_provider_request_overrides(a, "custom:main-think")
+    assert "extra_body" not in a.request_overrides  # not inherited; stale cleared
+
+
+def test_switch_endpoint_mismatch_does_not_inherit():
+    """A matching provider *name* but a different base_url must not match either
+    (endpoint identity is part of the condition)."""
+    a = _agent(
+        model="think-model",
+        base_url="http://10.9.9.9:8000/v1",  # different endpoint than the entry
+        request_overrides={"extra_body": {"chat_template_kwargs": {"enable_thinking": True}}},
+    )
+    arh._apply_switched_provider_request_overrides(a, "custom:main-think")
+    assert "extra_body" not in a.request_overrides  # base_url mismatch -> cleared