A reply can stop and ask you something

Three features turn out to be one mechanism: a command waiting to be
approved, a question the model wants answered, and "this reply is waiting
for you" are all — stop the generation, put an interactive block in the
bubble, wait for a POST, carry on. So there is one primitive, and the only
thing using it so far is `ask_user`: a model can offer you a few answers
and a box to write your own.

The shell executor is not here yet. This lands first on purpose, because
it is the riskiest machinery in the feature and it is worth having working
before any subprocess exists to complicate it.

Two things about where the pause sits. It pauses a round, not a call: a
round's calls run together under a semaphore, and parking four coroutines
on four separate answers inside that gather would queue them behind each
other invisibly. And Stop had to be taught about it — `cancel` is read
between streamed chunks and there are no chunks while paused, so the
button did nothing at all until `request_stop` learned to resolve the
pause itself.

Also here: a risk class on every tool (read, write, execute), which is
what the four permission modes will be a table over, and the systemd unit
loses ProtectKernelTunables. That last one is not tidying — it
bind-mounts /proc/sys read-only, which stops bubblewrap mounting /proc at
all, and the obvious workaround would expose this process's environment
and with it the encryption key.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/lembas/services/custom_tools.py

@@ -51,7 +51,7 @@ from lembas.services import fetch as fetch_service
 from lembas.services import tool_access
 from lembas.services.crypto import decrypt
 from lembas.services.prompts import VARIABLE_PATTERN
-from lembas.services.tools import ToolContext, ToolDef, ToolOutcome
+from lembas.services.tools import RISK_READ, RISK_WRITE, ToolContext, ToolDef, ToolOutcome
 
 log = logging.getLogger(__name__)
 
@@ -141,11 +141,23 @@ def tool_defs(
             description=row.description or f"Call the {row.name} tool.",
             parameters=_schema_of(row),
             run=_runner(spec_from(row)),
+            risk=_risk_of(row),
         )
         for row in tool_access.visible_custom_tools(db, user, everything=everything)
     ]
 
 
+def _risk_of(row: CustomTool) -> str:
+    """What calling this tool does to the world, as far as the method says.
+
+    The method is all there is to go on, and it is a reasonable proxy: GET and
+    HEAD are defined to be safe, and everything else is a request to change
+    something. Guessing wrong in the cautious direction only means an agent
+    chat asks about a call it need not have.
+    """
+    return RISK_READ if (row.method or "GET").upper() in ("GET", "HEAD") else RISK_WRITE
+
+
 def _schema_of(row: CustomTool) -> dict[str, Any]:
     schema = dict(row.parameters_json or {})
     if schema.get("type") != "object":