Finding a thing that does not use your words

Three pieces, and the first one is that they are all optional.

Extraction stops being constants. Upload size, image edge, JPEG quality, PDF
pages, extracted characters, orphan age and the text-extension list are settings
now, read through a process-level snapshot rather than a session -- `prepare` and
everything under it are called from routes, tool runners and the startup sweep,
and several of those have no session in hand. Two things deliberately stayed
constants: the decompression-bomb guard, which is a guard and not a preference,
and ORPHAN_AGE, which would have been evaluated at import if it stayed in the
signature and pinned the shipped 24 hours whatever anybody set.

An embedding model is picked from the models an administrator flagged for it, and
one that has since lost its flag is *named* rather than dropped from the picker:
a setting that vanishes is one nobody can tell from a setting never made. Nothing
here is required. Choosing none means no chunk rows, no requests, and
retrieval.search returning exactly what fts.search_ids returns in exactly that
order -- asserted, because it is what makes this safe to land on an instance that
never asked for it.

The two rankings are fused by reciprocal rank fusion: ranks and not scores,
because bm25 is a corpus-dependent negative and cosine is 0..1, and normalising
them onto one scale means picking a constant nobody can tune without a labelled
set they do not have. RRF's one constant is famously insensitive and degrades to
whichever list is non-empty -- which is what turns "no embedding model" into a
branch that does not exist.

A record scores as its best chunk rather than its average, or a long document
about something else outranks a short one that says the thing. Width and model
are stored beside every vector and a mismatch is skipped, because vectors from
two spaces score against each other perfectly happily and mean nothing -- a
search that works and is wrong is the worst failure this can have, and a model
change now leaves stale rows ignored rather than trusted.

Indexing is fired and forgotten, and how a change is noticed is a session event
rather than a call in each of the ten library writers. That is a departure from
this codebase's taste for explicit seams, for the reason tool_label is a Jinja
global: a step every writer has to remember is one that gets forgotten, and here
forgetting is silent -- the record saves, keyword search still finds it, and only
its recall goes stale. Chunks are embedded before anything is deleted, so a
failure leaves the old index rather than half a new one.

Also: `embeddings` joins the model capabilities, and the three tool flags that
had shipped with no checkbox -- canvas, scheduling and helpers -- have one.

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

src/lembas/api/admin_models.py

@@ -23,7 +23,10 @@ router = APIRouter(tags=["admin-models"])
 
 # What the endpoint can do. Endpoints do not advertise any of this reliably, so
 # these are an administrator's assertion.
-PROTOCOL_CAPABILITIES = ("reasoning", "vision", "tools")
+# `embeddings` is the odd one out and is worth naming as such: the other three
+# say what a model can do in a *chat*, and this one says it is not for chatting
+# at all. It is what /admin/extraction picks from, and nothing else reads it.
+PROTOCOL_CAPABILITIES = ("reasoning", "vision", "tools", "embeddings")
 
 # Which tools this model is given. Distinct from the above: `tools` is whether a
 # tools array may be sent at all, these are what goes in it. Every one of them is
@@ -46,6 +49,9 @@ TOOL_CAPABILITIES = (
     ("tool_ask", "Ask the reader"),
     ("tool_report", "Reports"),
     ("tool_image", "Image generation"),
+    ("tool_scratch", "Canvas"),
+    ("tool_schedule", "Scheduling"),
+    ("tool_subagent", "Helpers"),
     ("tool_agent", "Agent execution"),
 )