A ceiling for a chat, and a nudge for an agent that stops early

MAX_ROUNDS = 1 was wrong, and wrong in a way worth writing down. The loop
already ends the moment a round comes back with no tool calls -- that is the
model saying it has what it needs, and it is the termination condition every
agentic harness uses. A round limit was never a schedule; it exists to catch the
case where the model never says so. One is low enough to stop being a ceiling
and start being a schedule: it overrode the model's judgement on every single
turn.

And it broke something concrete. Several built-ins are two-step pairs --
knowledge_get and notes_get read a document "by the id a search returned" -- so
one round left the library searchable and not readable. That is not an edge
case, it is the library working at half depth, and I understated it as "cannot
search the web and then read a result" when the change went in.

It is a setting now, under General, default 5, with 0 meaning no ceiling. The
loop and the harness both read settings_store.chat_rounds, so the model is never
told a budget that is not its own; tools.MAX_ROUNDS is the fallback for callers
with no session and a test pins the two equal. core.rounds goes back to naming
the number, and vanishes entirely when there is no ceiling rather than promising
zero rounds.

The other half of "let it decide how long to go": an agent reply that ends while
its plan still has open tasks is asked once to carry on. Only against a plan,
because that is the one thing there is to be objectively wrong about -- a model
with no plan that says it has finished is believed, and arguing with it would be
guessing. At most twice in a row, with the count reset the moment it calls a
tool again, so the bound is on consecutive stops rather than on stops in total.
Never in Plan mode and never past plan_submit, which ends the turn on purpose.
Giving up is recorded as an event rather than left silent.

The model's own words go back with the nudge, which turned up a real bug on the
way: ReasoningSplitter holds back a few characters against a <think> tag split
across chunks, so round_text at the end of a round was missing its tail. That
text is echoed as an assistant turn for tool rounds too, so a model has been
occasionally asked to continue from a transcript where it trailed off
mid-sentence. Flushed per round now.

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

src/lembas/services/prompts.py

@@ -628,17 +628,21 @@ BUILTIN: tuple[Fragment, ...] = (
         order=110,
         when_tools=True,
         requires=("round_budget",),
-        hint="An ordinary chat only. It gets ONE round of tool calls, and the "
-        "thing worth saying about one round is 'ask for everything at once' — "
-        "which is different in kind from what is true of an agent chat's two "
-        "hundred, not a different number in the same sentence. So this is "
-        "gated on `round_budget`, which `_agent_values` blanks, and the agent "
-        "case is its own fragment below.",
+        variables=("max_rounds",),
+        hint="An ordinary chat only, and only when it has a ceiling at all. "
+        "What is worth telling a model with a budget is different in kind "
+        "from what is worth telling one that should keep going until the work "
+        "is done — not the same sentence with a different number in it — so "
+        "this is gated on `round_budget`, which `_agent_values` blanks and "
+        "which is also blank when an administrator has set no ceiling. The "
+        "agent case is its own fragment below.",
         default=(
-            "You get one round of tool calls, and then you have to answer with what "
-            "came back. Ask for everything you need at once — several tools can be "
-            "called in the same round. If what comes back is not enough, say what you "
-            "would look up next rather than answering as though it were."
+            "You get at most {{max_rounds}} rounds of tool calls before you have to "
+            "answer with what you have. Several tools can be called in one round, so "
+            "ask for everything you need at once rather than one thing at a time. "
+            "Plan within that: two careful searches beat six that run out halfway. If "
+            "what comes back is not enough, say what you would look up next rather "
+            "than answering as though it were."
         ),
     ),
     Fragment(