LLeMbas/CLAUDE.md

# CLAUDE.md

Working notes for LLeMbas. Read this before changing anything.

## What it is

A self-hosted web UI for OpenAI-compatible LLM endpoints, written in Python and
themed after Middle-earth. Server-rendered FastAPI + Jinja + htmx; SQLite;
no JavaScript build step.

## Commands

```bash
. .venv/bin/activate
pip install -e ".[dev,search]"      # `search` adds ddgs for DuckDuckGo

lembas serve                        # http://127.0.0.1:8080
lembas info                         # paths + counts, useful when confused
lembas secret-key                   # generate LEMBAS_SECRET_KEY
lembas create-admin                 # create or promote an admin

pytest                              # 428 tests, ~26s
                                    # PLAN.md tracks what is and is not built
ruff check .                        # lint (line length 100)
python scripts/build_artwork.py     # regenerate artwork (SVG + PWA icons;
                                    # needs fonttools and cairosvg)
python scripts/fetch_vendor.py      # verify vendored JS against the lockfile
```

## Hard rules

These are the constraints the project is built around. Breaking one is a
redesign, not a tweak.

1. **No Node, no npm, no build step.** Browser libraries are downloaded once by
   `scripts/fetch_vendor.py`, hash-pinned in `scripts/vendor.lock.json`, and
   committed under `web/static/vendor/`.
2. **Nothing loads from a CDN at runtime.** A self-hosted tool must work
   offline and must not report page views to a third party.
3. **No hard-coded values outside `tokens.css`.** Every colour, space, radius
   and control height resolves through a CSS variable. `--control-h` is why
   buttons, inputs and selects line up: they all take their height from it, so
   a mixed row is flush by construction rather than by nudging.
4. **Additive-only schema changes.** SQLite only, no Alembic. `init_db()` runs
   `db/migrations.py:sync_schema()`, which creates missing tables *and* adds
   missing columns by diffing the models against the database. Renames, drops
   and retypes are still manual. See "Changing the schema" below.
5. **Secrets never reach the browser.** API keys are Fernet-encrypted at rest
   and only ever rendered masked.
6. **Model output is untrusted.** Everything from an endpoint goes through
   `services/markdown.py` (markdown-it → nh3) or `escape_text()`. Never
   `|safe` on anything that has not.

## The flavour rule

Middle-earth lives in the **artwork, theme names, empty states, loading lines
and error pages**. It does not live in the functional UI.

Chats are called *Chats*, not *Tales*. Folders are *Folders*, not *Chapters*.
Buttons say what they do. Someone who has never read the books must be able to
use this without a glossary. The two themes are named `moria` and `shire`, and
the 404 says "Not all those who wander are lost. This page, however, is." —
that is the right amount.

## Layout

```
src/lembas/
  main.py            app factory, lifespan, error handlers
  config.py          pydantic-settings, all LEMBAS_* variables
  cli.py             typer entry points
  api/
    deps.py          Db / CurrentUser / RequiredUser / AdminUser
    auth.py          register, login, logout
    pages.py         full-page routes (chat shell, settings)
    chats.py         messaging + the SSE stream
    folders.py       folder CRUD
    admin.py         connections + instance settings
    admin_models.py  model ordering, defaults, images, access
    admin_users.py   users, groups, permissions
    admin_audio.py   speech-to-text and text-to-speech endpoints
    admin_search.py  web search provider and credentials
    audio.py         transcribe, speak, voice discovery
    library.py       knowledge, notes, skills pages; memory CRUD
    files.py         upload, serve, remove attachments
    preferences.py   per-user theme, default model, password, audio
  db/
    base.py          Base, UUID/Timestamp mixins
    session.py       engine, SQLite pragmas, init_db, session_scope
    migrations.py    additive schema sync (tables + columns)
    models/          user, chat, connection, setting
  security/          passwords (argon2), sessions, permissions
  services/
    llm/openai_client.py   httpx streaming + model discovery
    search/          ddgs, SearXNG and Firecrawl behind one shape
    library/         documents, notes, memories, skills, FTS
    audio.py         OpenAI-shaped /v1/audio/* client
    fetch.py         URL retrieval, HTML to text, the SSRF guard
    sharing.py       one visibility rule for every library store
    harness.py       the operational prompt built from what a model has
    tools.py         tool registry, schemas, streamed-call reassembly
    chat.py          request building, endpoint resolution, titles
    markdown.py      markdown-it + pygments + nh3
    crypto.py        Fernet encrypt/decrypt/mask
    files.py         attachment validation, images, PDF/text extraction
    reasoning.py     splits thinking from the answer
    settings_store.py  runtime instance settings
    uploads.py       validated image storage
    sse.py           event framing
  web/
    templating.py    render() -- always use this, not TemplateResponse
    templates/       Jinja
    static/          css, js, vendor, img, sw.js
assets/              SVG masters and PWA icons (generated)
deploy/              systemd unit, nginx vhost, install/update scripts
```

## Things that will bite you

**`render()`, not `TemplateResponse`.** `web/templating.py:render()` injects
`user`, `theme`, `version` and `allow_signup`. Templates assume they exist. If
you must call `templates.TemplateResponse` directly (the SSE path does, because
there is no `Request`), pass `user` explicitly — `chat/_message.html` renders
both roles and the user branch dereferences it.

**The message template is the state machine.** `chat/_message.html` renders an
incomplete assistant message as a streaming shell carrying `sse-connect`, and a
complete one as finished output. That is the *only* thing that starts a
generation. A consequence worth knowing: loading a page whose last reply is
unfinished restarts it, which is how a dropped connection recovers.

**SSE framing.** `services/sse.py:event()` splits payloads on newlines into
several `data:` lines. A raw newline in a single `data:` line truncates the
event — the failure shows up the first time a model emits a code block.

**Streaming opens its own database session.** `api/chats.py:_generate()` uses
`session_scope()`, not the request's session, because streaming outlives the
request handler.

**Escaping is chunk-safe on purpose.** `escape_text()` is `html.escape`, which
works character by character, so escaping stream chunks separately equals
escaping the whole string. `nh3.clean_text` would also be safe but escapes
spaces and slashes, tripling the size of every streamed token.

**The fence renderer is replaced, not configured.** markdown-it's `highlight`
option re-wraps output in `<pre><code>` unless the string starts with `<pre`,
which would nest a second `<pre>` inside our wrapper. `markdown.py` overrides
`renderer.rules["fence"]` instead. There is a regression test for this.

**SVG `<style>` is document-scoped.** Two text runs in one SVG sharing a class
name means the later rule recolours both. `build_artwork.py` takes class names
as parameters for exactly this reason.

**Gradient ids are document-global.** The `mark()` macro takes a `uid` because
two marks on one page with identical ids make the second silently reuse the
first one's gradients.

**Two kinds of settings.** `lembas.config` is deployment configuration read
from the environment at startup. `services/settings_store.py` is instance
settings an admin edits at runtime, stored in the `settings` table. Environment
variables seed the latter as an *initial* value only — once stored, the database
wins, or a toggle in the UI would silently revert on the next restart.

**Permissions are a union, and admins bypass them.** `security/permissions.py`
resolves a baseline (instance setting) widened by each group. A group grants;
it never denies — otherwise "why can this user not do X" needs a simulation of
every group to answer. Model *access* is separate: `models_visible_to()`.

**FastAPI cannot tell an empty form field from an absent one.** With
`x: str | None = Form(None)`, a submitted `x=` arrives as `None`, so "clear this
field" is indistinguishable from "leave it alone". `api/chats.py:update_chat`
reads `await request.form()` and checks key presence instead. Anything with a
clearable field must do the same.

**`Mapped[list]` without an element type is not a collection.** SQLAlchemy
treats a bare `Mapped[list]` as a scalar and hands back `None` instead of `[]`.
Always write `Mapped[list[Group]]`, with a `TYPE_CHECKING` import if the class
lives in another module.

**Reasoning arrives two ways.** A `reasoning_content` delta field (llama.cpp,
llama-swap, vLLM) or `<think>` tags inline in `content` (Ollama and friends).
`services/reasoning.py` handles the second with a streaming splitter, because
the tags arrive split across chunks. Reasoning is stored in `Message.reasoning`
and is deliberately **not** replayed as context on the next turn.

**Attachments are typed by their bytes, not their name.** `services/files.py`
sniffs magic numbers; a `.png` full of text is stored as text. Images are
downscaled and re-encoded (a phone photo is megabytes of base64), PDFs have
their text extracted **once at upload** — re-extracting per request would let a
reply change because a parser was upgraded.

**Images only go to models marked `vision`.** Sending content parts to an
endpoint without multimodal support is not graceful degradation; most reject
the whole request. `build_request()` checks the capability and falls back to a
plain string. A plain text turn must *stay* a plain string for the same reason.

**Attachments are served, never linked.** Images reach the model as base64 data
URIs: a local endpoint has no route back to LLeMbas and a hosted one has no
credentials. Non-images are served `Content-Disposition: attachment` with
`nosniff`, so an uploaded `.html` cannot execute in this origin.

**Uploads are unbound until the message is sent.** `Attachment.message_id` is
null in the composer; `files.claim()` binds them, and only unclaimed rows owned
by that user, so a forged id cannot pull in someone else's file. Abandoned ones
are swept at startup.

**Generation is a background task; the SSE endpoint only follows it.**
`services/generation.py` owns the work and the registry; `api/chats.py:_follow`
watches a `Generation` and streams what it sees. Closing the connection does
NOT stop the reply -- that was the old behaviour and it cut answers off when
the reader navigated away. Any route that creates an assistant placeholder must
also call `generation.ensure()`.

**Stream frames carry whole blocks, not deltas.** Both `render` and `reasoning`
send the complete text each time. That is what makes reattaching mid-reply
work: a follower arriving late has no earlier fragments to append to. It also
means Markdown is re-rendered whole, which is required anyway -- a list or code
fence is only correct once its context exists.

**Stopping sets a flag the producer checks.** `generation.request_stop()`;
whatever arrived is kept and the message is marked `stopped`, which is distinct
from `error`. In-process, so single-worker only.

**Unread is polled, not pushed.** A browser on another chat has no connection
to the one that finished. `/api/chats/unread` returns out-of-band dot spans and
an `HX-Trigger` for the toast; `unread_notified` stops the same arrival being
announced every tick. Re-rendering the whole sidebar instead would reset the
folder open/closed state every 10 seconds.

**Editing rewinds, it does not branch.** `POST .../messages/{id}/edit` rewrites
a user turn and **deletes everything after it**. Branching would need a UI for
choosing between versions; "go back and try again from here" is what was asked
for and what other clients do. `Message.parent_id` still exists unused.

**Dialogs and toasts are ours, not the browser's.** `static/js/ui.js` provides
`lembas.notify/confirm/prompt`, and intercepts htmx's `htmx:confirm` so every
existing `hx-confirm` gets the themed dialog with no change at the call site.
Plain forms opt in with `data-confirm`, lone submit buttons with
`data-confirm-button`. Never add a `window.confirm` back.

**The model picker is hand-built.** A `<select>` renders only text in an
`<option>` -- no avatar, no description, no badges. `chat/_model_picker.html`
plus the picker block in `ui.js`; the value lives in a hidden input so it still
behaves as a form field.

**Chats are created lazily.** There is no endpoint that makes an empty chat.
"New chat" is a link to `/chat`, which renders a composer with no row behind
it; `POST /api/chats/start` writes the chat together with its first message.
That is why an opened-and-abandoned chat never appears in the sidebar. Tests
that just need a chat use the `make_chat` fixture rather than the HTTP flow.

**Admin lists are list-plus-detail, never a form per row.** `/admin/models`
renders compact rows with search, filter tabs and pagination; the full form
lives at `/admin/models/{id}/edit`. A connection can advertise a hundred models,
and a page that renders a form for each is unusable. Any future admin list
(tools, agents) should follow the same shape.

**Route order matters for static path segments.** FastAPI matches in
registration order, so `/admin/models/bulk` must be registered *before*
`/admin/models/{model_id}` or "bulk" is parsed as a model id and 404s. This has
already been a bug once.

**Pinning is not ordering.** The model picker is always in the administrator's
`position` order. Pinned models get shortcuts in the chat sidebar and nothing
else -- a picker whose order differs from the admin screen is just confusing.

**System prompts are precedence, not concatenation.** chat > model > instance,
most specific wins outright (`services/chat.py:effective_system_prompt`).
Stacking them reads well in a settings screen and badly in practice: two layers
that disagree give the model contradictory instructions and nobody can tell
which is losing.

**JSON columns need reassignment.** `user.settings_json["theme"] = x` on a
plain dict is not detected. The columns use `MutableDict` (`db/types.py`), but
the safe habit is `obj.field = {**obj.field, "k": v}`.

**`[hidden]` needs `!important`.** The browser's rule is `[hidden] { display:
none }`, which any class setting `display` outranks — and `.btn` is
`display: inline-flex`. That is not theoretical: it is why the old Stop button,
created and then `hidden = true`, sat permanently beside Send. `app.css` forces
the attribute to win. Anything toggled with `hidden` depends on that line.

**Send and Stop are one button.** `chat/_composer.html` renders both icons and
`ui.js` flips `data-composer-action` plus `type` (`submit` ↔ `button`) when a
message in the thread is still streaming. Do not add a second button back.

**The tool loop is inside one generation.** `services/generation.py:_run()` runs
up to `tools_service.MAX_ROUNDS` request rounds for a single reply: stream,
accumulate tool calls, run them, append the results, ask again. `Generation`
accumulates content across all of them, so text emitted before a tool call
survives. Tools are only offered when search is enabled, the user has
`tools.web_search`, **and** the model is flagged `tools` — sending a `tools`
array to an endpoint without support fails the whole request, exactly as images
do without `vision`.

**Tool-call arguments arrive in fragments.** `delta.tool_calls` carries an
`index`, a name that appears once, and an `arguments` string split across
chunks. `tools.ToolCallAccumulator` rejoins them keyed on `index` — not on
name, which breaks the moment a model calls one tool twice in a turn.

**Four stores, four different reasons.** `services/library/` — `documents`
(uploaded by a person, searched by the model), `notes` (written by the model,
searched), `memories` (short, and *injected whole* every turn), `skills` (index
injected, body fetched by tool). The shape of each follows from how it reaches
the model: a memory is capped short because it costs tokens on every request
forever, a note is not injected because a dozen would fill the window.

**Sharing goes through one helper, and admins do not bypass it.**
`services/sharing.py:visible_to()` is the only definition of who can see a
library item, and every listing and tool uses it. `permissions.resolve` gives an
admin everything, deliberately — but that is about configuration, which an admin
can grant themselves anyway. Reading someone's private notes is not the same
act, so `sharing` has no admin branch. Sharing grants **reading only**.

**FTS5 tables are outside the model-driven schema sync.** They are not
SQLAlchemy models, so `sync_schema()` cannot diff them; `db/migrations.py:
ensure_fts()` writes them out with `IF NOT EXISTS` and creates the triggers that
keep an external-content index correct. It runs at every startup and converges,
like the column sync beside it. `tests/conftest.py` calls `sync_schema` rather
than `create_all` so tests run against the same schema.

**A failed search rolls back.** One broken FTS statement otherwise leaves the
session unusable and every later query in the request fails too, which looks
nothing like a search problem.

**Knowledge attachments are copies.** Attaching a library document to a message
duplicates its text and its file (`files.copy_document`). Referencing it would
mean a conversation changing when a document is edited or deleted later — the
same reason PDF text is extracted once at upload.

**The link fetcher is an SSRF hole unless guarded.** `services/fetch.py` refuses
loopback, private and link-local addresses **after resolution** — a hostname
pointing at 127.0.0.1 walks past any check that only reads the URL — and follows
redirects by hand so every hop is checked. An admin can open it deliberately.
The URL can come from a model, which can be talked into things by a page it just
read.

**The harness is an exception to the prompt-precedence rule, on purpose.**
"System prompts are precedence, not concatenation" governs the three *authored*
layers, and it stands: exactly one still wins, and `effective_system_prompt`
still decides which. `services/harness.py` is a different axis — it describes
the machinery rather than the behaviour, nobody authored it, and there is
nothing for it to disagree with. It is prepended to whichever authored prompt
won, in one system message (several endpoints reject a second one), and
`build_request` is where the two meet.

**A model's tool flags default to on when `tools` is on.** Rows configured
before the per-tool split have no `tool_*` keys. Reading absent as off would
silently take web search away from every model already set up for it, so
`tools.enabled_tools` treats absent as inherited.

**Tool results are not replayed.** Like reasoning, `Message.tool_calls_json` is
stored and rendered but never fed back as context. The answer already contains
what the model made of the results; replaying stale results and the schema into
every later request wastes the window and reliably sends a small model into a
search loop. The sources stay visible in the transcript.

**Search results are untrusted.** Hard rule 6 covers them as much as model
output. `chat/_tool_activity.html` escapes everything and only renders `http`
and `https` URLs as links — a result carrying a `javascript:` URL must never
become an anchor.

**A message bubble is rendered from four places.** `pages.py`,
`chats.post_message`, `chats.regenerate` and `chats._follow`. Each needs
`audio_service.template_flags(db, user)` or the speaker button's conditions are
undefined; the template uses `| default(false)` so a missed one degrades to no
button rather than an exception. `_follow` also passes `just_finished`, which is
what read-aloud-automatically keys off — without it, reopening a chat would
start reading its last reply out loud.

**Dictation audio never touches disk.** `api/audio.py` reads it into memory,
capped, and streams it upstream. It is not an attachment: it has no owner, no
row, and nothing would ever sweep it.

**The service worker must skip `/api/`.** A reply is an endless event stream and
passing one through a worker turns it into one delivery at the end, or nothing.
`static/js/sw.js` bails out on `/api/`, `/auth/`, `/admin/` and any request
accepting `text/event-stream`. It is served from `GET /sw.js` rather than the
static mount because a worker's scope is the path it came from.

## Changing the schema

There is no Alembic, but there *is* `db/migrations.py`. It compares the declared
models against the live database and issues `ALTER TABLE ... ADD COLUMN` for
anything missing, so adding a column to a model is free: restart and it appears,
with existing rows backfilled from a type-derived default.

It cannot rename, drop or retype a column, or add a UNIQUE/PRIMARY KEY to an
existing table — SQLite mostly cannot do those with ALTER TABLE either. Those
need the create-copy-swap dance by hand; record them in `MANUAL_STEPS` so a
failure has somewhere to point.

Because the runner exists, forward-looking columns are cheap now. `Message.parent_id`
and `content_parts_json` (branching, multimodal) predate it and are still unread.

## Artwork

Do not hand-edit files in `assets/` — they are generated. Change
`scripts/build_artwork.py` and re-run it. It also copies the few files the app
serves into `web/static/img/`.

The leaf geometry is defined once (`LEAF_BLADE`, `LEAF_MIDRIB`, …) and reused by
the icon, favicon, lockup and banner. The 64×64 mark must stay legible at 16px:
the favicon variant drops the score lines, rim and veins because they turn to
mud at that size. The icon sprite is a **template partial**
(`templates/partials/icons.html`), not an asset, because same-document
`<use href="#id">` is universally supported and the cross-document form is not.

The `mark()` macro in `_macros.html` duplicates the mark geometry so it can be
inlined and themed. If the mark changes, update both.

## Deployment

`deploy/` holds a systemd unit template, an nginx vhost template, and
install/update scripts. Both templates are parameterised (`__PREFIX__`,
`__SITE_HOST__`, …) and substituted at install time, so nothing host-specific is
committed here. See `deploy/README.md`.

This repository is **public**. Keep deployment-specific hostnames, ports and
internal infrastructure detail out of it — those belong in whatever private
notes describe the machine.

## Not built yet

Custom tools and MCP, agentic execution (local subprocess and SSH connection
profiles), image generation. Nav entries mark where each one goes. The tool
loop in `services/generation.py` is what they plug into — a new tool is a
`ToolDef` in `services/tools.py:REGISTRY` plus a permission and a capability
flag, not a new code path.

No OCR: a scanned PDF is stored with an explanatory `extraction_error` rather
than silently contributing nothing.