A time in no particular zone, and a preview missing what it previews

The first audit pass: everything from 0.8.1 to 0.9.8 read as a whole rather
than one feature at a time, starting with what a model is actually told.

Four of these had shipped as correct. The date line carried a timezone
variable that resolves to nothing until somebody chooses one -- so every
default account was told times were "in  unless they say otherwise", while
two comments asserted the line disappeared instead. The prompt preview
built its variables without a chat, which is what eleven fragments are
gated on, so the whole agent surface was absent from it whatever was
ticked. Plan mode was instructed to keep its plan current with a tool that
mode withdraws. And knowledge_get returned a document whole where every
sibling reader caps and says so, its description promising exactly that.

The subagent guidance was wrong in both directions at once: it denied a
documented parameter and named seven of twenty-three allowed commands.
Both halves are pinned by tests against the real list and the real schema
now, because prose and a constant drift the moment one is edited alone.

docs/notes/audit-0.9.md carries the findings that are not fixed here, with
why -- the ones whose fix would change what a feature does are the user's
call, not this pass's.

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

src/lembas/services/prompts.py

@@ -219,8 +219,14 @@ VARIABLES: tuple[Variable, ...] = (
         "The current plan",
         "The plan this agent chat is working to, with its ids, finished phases "
         "collapsed and the active one shown in full. Empty when there is none, "
-        "which is what keeps both the plan section and plan_update's guidance "
-        "out of every chat that is not carrying one.",
+        "which is what keeps the plan section out of every chat not carrying one.",
+    ),
+    Variable(
+        "plan_editable",
+        "The plan, when it can be changed",
+        "The same text as {{plan}}, but blank in Plan mode -- where plan_update "
+        "is withdrawn and the turn ends with plan_submit instead. Gates that "
+        "tool's guidance, so a mode without the tool is not told to use it.",
     ),
     Variable(
         "agent_instructions",
@@ -614,9 +620,10 @@ BUILTIN: tuple[Fragment, ...] = (
         order=20,
         variables=("today", "timezone"),
         hint="A model has no clock. Without this it cannot tell whether what it "
-        "recalls is current, and will not think to check. The timezone line "
-        "carries its own variable, so it disappears on an instance where nobody "
-        "has chosen one rather than announcing the server's as a decision.",
+        "recalls is current, and will not think to check. {{timezone}} is the "
+        "reader's own zone, or the server's where they have not chosen one -- "
+        "the same zone the date above is already stated in, so it names a value "
+        "rather than making a decision.",
         default=(
             "Today is {{today}}. Your training data stops well before this, so treat "
             "anything time-sensitive as something to check rather than something you "
@@ -1314,20 +1321,28 @@ BUILTIN: tuple[Fragment, ...] = (
         families=("subagent",),
         requires=("agent_target",),
         hint="The agent-chat half, gated on `agent_target` so it appears only "
-        "where there is a machine. What it has to say is what a helper cannot "
-        "do there, because the failure otherwise is a model planning a whole "
-        "phase around a helper that will refuse every step of it — a helper "
-        "reads and may run a short list of read-only commands, and nothing "
-        "else, whatever mode this chat is in.",
+        "where there is a machine. What it has to say is where the edge is, "
+        "because the failure otherwise is a model planning a whole phase around "
+        "a helper that will refuse every step of it. Two edges, and they are "
+        "different: **commands** are pinned to a read-only list in every mode, "
+        "since an unattended chat cannot approve anything; **files** may be "
+        "written, but only by a helper asked for with write and only from Edit "
+        "or Auto. An earlier version denied the second outright — which is a "
+        "documented parameter of the tool beside it — and named seven of the "
+        "twenty-three allowed commands, so a model avoided commands it had.",
         default=(
             "- A helper on this machine reads and reports. It can list and read files "
-            "and run the ordinary read-only commands — ls, cat, grep, find, git status, "
-            "git log, git diff — and nothing else, in every mode, because there is "
-            "nobody there to approve anything. Send one to find out where something "
-            "lives, to read a subsystem and describe it, or to check whether a pattern "
-            "holds across a tree; make the changes yourself once it reports.\n"
-            "- Do not send one to build, test, install or run anything: it will be "
-            "refused a step in and come back having done nothing.\n"
+            "and run the read-only commands — ls, pwd, cat, head, tail, wc, file, stat, "
+            "du, df, tree, find, grep, rg, and git status, log, show, diff, branch and "
+            "remote. Send one to find out where something lives, to read a subsystem "
+            "and describe it, or to check whether a pattern holds across a tree.\n"
+            "- Do not send one to build, test, install or run anything. That list is "
+            "the whole of what it may run, in every mode, because there is nobody "
+            "there to approve anything else — a helper asked to run the tests is "
+            "refused a step in and comes back having done nothing.\n"
+            "- A helper asked for with write can also write and edit files, and only "
+            "from Edit or Auto mode. Use it for a mechanical change across many files "
+            "that you have already decided on; keep the deciding for yourself.\n"
             "- Ask for what you want back, not for a summary. “The three files that "
             "define X and what each does” is usable; “look into X” comes back as prose "
             "you have to read the codebase to check."
@@ -1539,12 +1554,14 @@ BUILTIN: tuple[Fragment, ...] = (
         group=GROUP_TOOLS,
         order=255,
         families=("agent",),
-        requires=("plan",),
-        hint="Appears once a plan exists, which is also when plan_update is "
-        "offered. It is about doing the bookkeeping as the work goes rather "
-        "than at the end -- a plan updated only at the end is a report, and "
-        "the point of it is being able to see where things are while they are "
-        "still moving.",
+        requires=("plan_editable",),
+        hint="Appears when plan_update is actually offered: a plan exists and "
+        "this is not Plan mode, which withdraws it in favour of plan_submit. "
+        "Gated on {{plan}} it appeared in Plan mode too, telling a model to "
+        "use a tool it did not have. It is about doing the bookkeeping as the "
+        "work goes rather than at the end -- a plan updated only at the end is "
+        "a report, and the point of it is being able to see where things are "
+        "while they are still moving.",
         default=(
             "- There is a plan for this work, set out below. Keep it current with "
             "plan_update as you go rather than at the end: mark a task “doing” when "
@@ -1567,16 +1584,18 @@ BUILTIN: tuple[Fragment, ...] = (
         requires=("plan",),
         variables=("plan",),
         hint="The plan as it stands, including what has already been ticked "
-        "off. A plan the model cannot see is a plan it cannot update, which "
-        "is what the whole of plan_update depends on. The ids are shown "
-        "because they are what plan_update takes.",
+        "off. A plan the model cannot see is a plan it cannot work to. Shown in "
+        "every mode including Plan, where the tool for changing it is withdrawn "
+        "-- so this says what the plan *is* and leaves how to change it to "
+        "`tool.plan_update`, which is gated on that tool actually being there. "
+        "The ids are shown because they are what plan_update takes.",
         default=(
             "### The current plan\n"
             "\n"
             "{{plan}}\n"
             "\n"
-            "This is the plan as it stands now. Change it with plan_update rather "
-            "than restating it in your answer, and quote the ids above."
+            "This is the plan as it stands now. Work to it, and quote the ids above "
+            "rather than restating the plan in your answer."
         ),
     ),
     Fragment(