diff --git a/src/agentex/lib/adk/utils/_modules/client.py b/src/agentex/lib/adk/utils/_modules/client.py
index 725289631..5312b7b6a 100644
--- a/src/agentex/lib/adk/utils/_modules/client.py
+++ b/src/agentex/lib/adk/utils/_modules/client.py
@@ -1,3 +1,4 @@
+import os
 from typing import override
 
 import httpx
@@ -26,7 +27,50 @@ def auth_flow(self, request):
         yield request
 
 
+# HTTP timeouts for the AgentEx client, in seconds. Defaults match the SDK's
+# DEFAULT_TIMEOUT, so leaving these unset changes nothing.
+_TIMEOUT_ENV_DEFAULTS = {
+    "connect": ("AGENTEX_CLIENT_CONNECT_TIMEOUT_SECONDS", 5.0),
+    "read": ("AGENTEX_CLIENT_READ_TIMEOUT_SECONDS", 300.0),
+    "write": ("AGENTEX_CLIENT_WRITE_TIMEOUT_SECONDS", 300.0),
+    "pool": ("AGENTEX_CLIENT_POOL_TIMEOUT_SECONDS", 300.0),
+}
+
+
+def _timeout_from_env() -> httpx.Timeout:
+    """Build the client timeout from environment variables.
+
+    Read from ``os.environ`` rather than from ``EnvironmentVariables``. That model
+    is loaded by worker startup and by ``EnvAuth.auth_flow`` on every request, and
+    ``agentex.lib.adk.utils`` builds a client at import time, so a field added
+    there would make a malformed timeout break all three. Reading here keeps the
+    blast radius to the one value that is actually wrong.
+
+    The connect timeout is the one worth raising: an AgentEx backend accepts
+    connections serially, so connect latency grows with the number of callers and
+    the 5s default is reached when a few hundred are in flight.
+    """
+    values = {}
+    for field, (env_var, default) in _TIMEOUT_ENV_DEFAULTS.items():
+        raw = os.environ.get(env_var)
+        if raw is None or raw.strip() == "":
+            values[field] = default
+            continue
+        try:
+            values[field] = float(raw)
+        except ValueError as exc:
+            raise ValueError(f"{env_var} must be a number in seconds, got {raw!r}") from exc
+    return httpx.Timeout(**values)
+
+
 def create_async_agentex_client(**kwargs) -> AsyncAgentex:
+    """Create an AsyncAgentex client.
+
+    An explicit ``timeout=`` always wins; otherwise the timeout comes from the
+    AGENTEX_CLIENT_*_TIMEOUT_SECONDS environment variables.
+    """
+    if "timeout" not in kwargs:
+        kwargs["timeout"] = _timeout_from_env()
     client = AsyncAgentex(**kwargs)
     client._client.auth = EnvAuth()
     return client
diff --git a/tests/lib/test_client_timeout_env.py b/tests/lib/test_client_timeout_env.py
new file mode 100644
index 000000000..c0d2140a1
--- /dev/null
+++ b/tests/lib/test_client_timeout_env.py
@@ -0,0 +1,102 @@
+"""Timeouts for the AgentEx client are configurable by environment variable.
+
+The connect timeout is the one that matters in practice. An AgentEx backend
+accepts connections serially, so connect latency grows with the number of
+concurrent callers, and the 5s default is reached once a few hundred are in
+flight. Before this was configurable, the only way to change it was to pass
+``timeout=`` at every construction site, which application code cannot do for
+the client the ADK builds internally.
+"""
+
+from __future__ import annotations
+
+import httpx
+import pytest
+
+from agentex.lib.adk.utils._modules.client import (
+    _timeout_from_env,
+    create_async_agentex_client,
+)
+
+
+def test_defaults_match_the_sdk_default_timeout():
+    """An unconfigured process must behave exactly as it did before."""
+    timeout = _timeout_from_env()
+    assert timeout.connect == 5.0
+    assert timeout.read == 300.0
+    assert timeout.write == 300.0
+    assert timeout.pool == 300.0
+
+
+def test_connect_timeout_is_configurable(monkeypatch):
+    monkeypatch.setenv("AGENTEX_CLIENT_CONNECT_TIMEOUT_SECONDS", "30")
+    timeout = _timeout_from_env()
+    assert timeout.connect == 30.0
+    # the others are untouched
+    assert timeout.read == 300.0
+
+
+def test_all_four_are_configurable(monkeypatch):
+    monkeypatch.setenv("AGENTEX_CLIENT_CONNECT_TIMEOUT_SECONDS", "30")
+    monkeypatch.setenv("AGENTEX_CLIENT_READ_TIMEOUT_SECONDS", "120")
+    monkeypatch.setenv("AGENTEX_CLIENT_WRITE_TIMEOUT_SECONDS", "90")
+    monkeypatch.setenv("AGENTEX_CLIENT_POOL_TIMEOUT_SECONDS", "60")
+    timeout = _timeout_from_env()
+    assert (timeout.connect, timeout.read, timeout.write, timeout.pool) == (
+        30.0,
+        120.0,
+        90.0,
+        60.0,
+    )
+
+
+def test_an_empty_value_falls_back_to_the_default():
+    """An unset variable and one set to the empty string mean the same thing."""
+    with pytest.MonkeyPatch.context() as mp:
+        mp.setenv("AGENTEX_CLIENT_CONNECT_TIMEOUT_SECONDS", "")
+        assert _timeout_from_env().connect == 5.0
+
+
+def test_client_picks_up_the_env_timeout(monkeypatch):
+    monkeypatch.setenv("AGENTEX_CLIENT_CONNECT_TIMEOUT_SECONDS", "30")
+    client = create_async_agentex_client(api_key="test", base_url="http://localhost:5003")
+    # client.timeout is float | Timeout | None; narrow before reading a component.
+    assert isinstance(client.timeout, httpx.Timeout)
+    assert client.timeout.connect == 30.0
+
+
+def test_explicit_timeout_wins_over_the_environment(monkeypatch):
+    monkeypatch.setenv("AGENTEX_CLIENT_CONNECT_TIMEOUT_SECONDS", "30")
+    client = create_async_agentex_client(
+        api_key="test",
+        base_url="http://localhost:5003",
+        timeout=httpx.Timeout(connect=7.0, read=8.0, write=9.0, pool=10.0),
+    )
+    assert isinstance(client.timeout, httpx.Timeout)
+    assert client.timeout.connect == 7.0
+
+
+def test_env_auth_is_still_attached():
+    """The factory's original job must survive the change."""
+    client = create_async_agentex_client(api_key="test", base_url="http://localhost:5003")
+    assert client._client.auth is not None
+
+
+def test_a_bad_value_names_the_variable(monkeypatch):
+    """A malformed value is a configuration error, so it must not be swallowed."""
+    monkeypatch.setenv("AGENTEX_CLIENT_CONNECT_TIMEOUT_SECONDS", "not-a-number")
+    with pytest.raises(ValueError, match="AGENTEX_CLIENT_CONNECT_TIMEOUT_SECONDS"):
+        _timeout_from_env()
+
+
+def test_the_timeout_does_not_depend_on_the_shared_environment_model(monkeypatch):
+    """Regression: these must not become EnvironmentVariables fields.
+
+    That model has required fields, is loaded by worker startup and by
+    EnvAuth.auth_flow on every request, and agentex.lib.adk.utils builds a
+    client at import time. Routing timeouts through it makes all three depend
+    on a fully configured environment.
+    """
+    monkeypatch.delenv("AGENT_NAME", raising=False)
+    monkeypatch.delenv("ACP_URL", raising=False)
+    assert _timeout_from_env().connect == 5.0