fix(contrib): reject explicitly empty permission options

docs/contrib.md

@@ -24,6 +24,7 @@ The helpers under `acp.contrib` package recurring patterns we saw in integration
 
 - `ToolCallTracker.start()/progress()/append_stream_text()` emits canonical `ToolCallStart` / `ToolCallProgress` updates and keeps an in-memory view via `view()` or `tool_call_model()`.
 - `PermissionBroker.request_for()` wraps `requestPermission` RPCs. It reuses tracker state (or a provided `ToolCall`), lets you append extra content, and defaults to Approve / Approve for session / Reject options.
+- Omit `options` or pass `None` to use broker defaults. An explicit empty option list raises `MissingPermissionOptionsError` before the permission request is sent; the same applies to empty `default_options` when no per-request options are supplied.
 - `default_permission_options()` exposes that canonical option triple if you need to customise it.
 
 > Tip: Keep one tracker near the agent event loop. Emit notifications through it and share the tracker with `PermissionBroker` so permission prompts always match the latest tool call state.

src/acp/contrib/permissions.py

@@ -56,7 +56,8 @@ def __init__(
         self._requester = requester
         self._tracker = tracker
         self._default_options = tuple(
-            option.model_copy(deep=True) for option in (default_options or default_permission_options())
+            option.model_copy(deep=True)
+            for option in (default_permission_options() if default_options is None else default_options)
         )
 
     async def request_for(
@@ -84,7 +85,9 @@ async def request_for(
             existing.append(ContentToolCallContent(content=TextContentBlock(text=description)))
             tool_call.content = existing
 
-        option_set = tuple(option.model_copy(deep=True) for option in (options or self._default_options))
+        option_set = tuple(
+            option.model_copy(deep=True) for option in (self._default_options if options is None else options)
+        )
         if not option_set:
             raise MissingPermissionOptionsError()
 

tests/contrib/test_contrib_permissions.py

@@ -2,7 +2,7 @@
 
 import pytest
 
-from acp.contrib.permissions import PermissionBroker, default_permission_options
+from acp.contrib.permissions import MissingPermissionOptionsError, PermissionBroker, default_permission_options
 from acp.contrib.tool_calls import ToolCallTracker
 from acp.schema import (
     AllowedOutcome,
@@ -58,6 +58,60 @@ async def requester(request: RequestPermissionRequest):
     assert recorded == ["allow"]
 
 
+@pytest.mark.asyncio
+async def test_permission_broker_none_uses_standard_options():
+    tracker = ToolCallTracker(id_factory=lambda: "standard")
+    tracker.start("external", title="Standard options")
+    recorded: list[list[str]] = []
+
+    async def requester(request: RequestPermissionRequest):
+        recorded.append([option.option_id for option in request.options])
+        return RequestPermissionResponse(outcome=AllowedOutcome(option_id="approve", outcome="selected"))
+
+    broker = PermissionBroker("session", requester, tracker=tracker, default_options=None)
+    await broker.request_for("external", options=None)
+    assert recorded == [["approve", "approve_for_session", "reject"]]
+
+
+@pytest.mark.asyncio
+async def test_permission_broker_custom_default_and_override():
+    tracker = ToolCallTracker(id_factory=lambda: "reject-only")
+    tracker.start("external", title="Reject only")
+    reject = PermissionOption(option_id="reject", name="Reject", kind="reject_once")
+    allow = PermissionOption(option_id="allow", name="Allow", kind="allow_once")
+    recorded: list[list[str]] = []
+
+    async def requester(request: RequestPermissionRequest):
+        recorded.append([option.option_id for option in request.options])
+        return RequestPermissionResponse(
+            outcome=AllowedOutcome(option_id=request.options[0].option_id, outcome="selected")
+        )
+
+    broker = PermissionBroker("session", requester, tracker=tracker, default_options=[reject])
+    await broker.request_for("external")
+    await broker.request_for("external", options=[allow])
+    assert recorded == [["reject"], ["allow"]]
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(("default_options", "options"), [(None, []), ([], None)])
+async def test_permission_broker_rejects_empty_option_sources(default_options, options):
+    tracker = ToolCallTracker(id_factory=lambda: "empty")
+    tracker.start("external", title="No options")
+    recorded: list[RequestPermissionRequest] = []
+
+    async def requester(request: RequestPermissionRequest):
+        recorded.append(request)
+        return RequestPermissionResponse(
+            outcome=AllowedOutcome(option_id=request.options[0].option_id, outcome="selected")
+        )
+
+    broker = PermissionBroker("session", requester, tracker=tracker, default_options=default_options)
+    with pytest.raises(MissingPermissionOptionsError, match="requires at least one permission option"):
+        await broker.request_for("external", options=options)
+    assert recorded == []
+
+
 def test_default_permission_options_shape():
     options = default_permission_options()
     assert len(options) == 3