Draw a picture, on a ComfyUI you are running

The last unbuilt capability, and built the way CLAUDE.md said it had to be: a
ToolDef reaching resolve_tools plus a permission and a capability flag, not a new
code path. The only genuinely new UI is one branch in the transcript.

services/images/ is three modules. comfy.py speaks HTTP -- submit, poll /history,
fetch the PNG, /free, and an /object_info discovery for the admin page only.
Polled and not socketed, because holding a connection open for the length of a
generation is the live-connection state the whole ssh.py design forbids, and the
thing being waited for takes tens of seconds anyway. The base URL is exempt from
the SSRF guard by construction, exactly as Connection.base_url and the audio
endpoints are -- said out loud in the docstring, because a default of
127.0.0.1:8188 is precisely the shape that guard exists to refuse and therefore
reads as a hole rather than a decision.

workflow.py fills a template, and the one thing that matters is that it walks the
parsed JSON rather than the text of it. A value that is exactly "{{steps}}"
becomes the number 20; ComfyUI validates types and refuses the string. A
placeholder inside a longer string is still text, which is what makes
"{{prompt}}, masterpiece" work -- and text substitution would additionally mean a
prompt containing a quotation mark produced a document that no longer parses, on
the one input guaranteed to hold arbitrary text. Which node holds the prompt is
the administrator's statement rather than a guess from node types: sniffing for
the first CLIPTextEncode works on the shipped workflow and on nothing else, and
swaps positive for negative the first time somebody reorders them. seed has no
fixed default, because one would make every unspecified generation identical and
make the retry loop redraw the same rejected picture four times.

tool.py is one call, one finished image. Returning every attempt to the
conversation would cost a round each, make the ceiling advisory rather than
enforced, and walk the reader past every reject -- so the reviewer lives inside
the tool and is asked about *bytes*: an attempt about to be discarded should not
leave an Attachment behind, so it sees a downscaled preview built in memory and
only the kept image is written. Anything that goes wrong in review is a keep;
losing a picture because a judging request timed out would be the check
destroying the thing it was checking. The last attempt is kept whatever the
verdict, so a request always produces something. Rejects are recorded, not
stored.

Preserve VRAM unloads the chat's own connection and nothing else, because the
memory being freed belongs to one machine: local llama-swap answers GET /unload,
and a box on the network has no reason to be unloaded when ComfyUI wants memory
here. The swap goes round the review rather than round the tool, which costs two
model loads per retry -- so the two settings are independent and the page warns
when both are on. Nothing loads the LLM back: the reply's next request does, and
that step exists in the description and not in the code, so the code says so.

Two rules elsewhere had to be drawn for the first time. message_payload sends
images only on user turns -- no assistant message had ever carried one, and the
moment one does the multimodal list form on an assistant turn is rejected by
OpenAI and most local runners, breaking every later turn in the chat. And
files.store gained keep_original, because _process_image turns anything without
alpha into JPEG q85 at 1400px: right for a phone photo, a visible loss on the one
output this feature exists to produce.

/image sends the ordinary message with force_tool, which becomes tool_choice for
the first round only -- left in place the reply would draw a picture, be asked
again, and draw another. FORCEABLE_TOOLS is an allow list because the name is
read off a form.

ToolContext gained chat_id, and that fixed a tool nobody had ever successfully
run: _run_scratch_write read context.chat_id on a dataclass with no such field,
so every call raised AttributeError, swallowed by run_tool's blanket except into
"the scratch_write tool failed" -- indistinguishable from a model calling it
wrongly. The test that existed asserted the family and the risk, which are
properties of the declaration rather than of the code.

Verified against the real ComfyUI 0.27.0 on this machine rather than against
documentation: every endpoint shape here was read off it, a generation ran end to
end through the client, the reviewer was shown a matching and a mismatched prompt
and answered KEEP and RETRY correctly, and the unload hook fired for the local
llama-swap and not for the remote box.

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

src/lembas/services/settings_store.py

@@ -29,6 +29,7 @@ DEFAULT_CHAT_ROUNDS = 0
 SEARCH = "search"
 PROMPTS = "prompts"
 AGENTS = "agents"
+IMAGES = "images"
 
 
 def _general_defaults() -> dict[str, Any]:
@@ -232,12 +233,52 @@ def _prompts_defaults() -> dict[str, Any]:
     }
 
 
+def _images_defaults() -> dict[str, Any]:
+    """Generating pictures on a ComfyUI somebody else is running."""
+    return {
+        "enabled": False,
+        "base_url": "",
+        "api_key_encrypted": "",
+        # A generation is tens of seconds and a queue in front of it can be
+        # minutes. Far longer than any other timeout here, because the thing
+        # being waited for genuinely takes that long.
+        "timeout": 600.0,
+        # What this ComfyUI advertises, discovered by the Test button and stored
+        # so the request path never has to ask. The checkpoints are also the
+        # enum a model chooses from, which is why an empty list means the tool
+        # is not offered: a model naming a checkpoint that does not exist gets a
+        # refusal from ComfyUI and spends a round finding out.
+        "checkpoints": [],
+        "samplers": [],
+        "schedulers": [],
+        "default_workflow_id": "",
+        # Whether a vision model looks at what came back and says whether to
+        # keep it. Deliberately independent of `preserve_vram` below: on a
+        # machine that can hold both models this costs nothing, and on one that
+        # cannot it costs two model loads per retry, which is a judgement only
+        # the person running it can make.
+        "review_enabled": False,
+        # Which model judges. Empty means the chat's own, when it has vision.
+        "review_model_id": "",
+        "max_tries": 4,
+        # Unload the chat's own LLM while ComfyUI works, and free ComfyUI
+        # afterwards. For a machine that cannot hold both at once. Off by
+        # default: it makes every generation slower, and most people have the
+        # memory.
+        "preserve_vram": False,
+        # Instance-wide guidance, injected into the harness beside the tool's
+        # own. Where "always add these words to the negative prompt" lives.
+        "instructions": "",
+    }
+
+
 _DEFAULTS: dict[str, Any] = {
     GENERAL: _general_defaults,
     AUDIO: _audio_defaults,
     SEARCH: _search_defaults,
     PROMPTS: _prompts_defaults,
     AGENTS: _agents_defaults,
+    IMAGES: _images_defaults,
 }
 
 
@@ -350,3 +391,34 @@ def agents(db: DBSession) -> dict[str, Any]:
     )
     values["background_max_jobs"] = min(max(int(values.get("background_max_jobs") or 0), 1), 100)
     return values
+
+
+def images(db: DBSession) -> dict[str, Any]:
+    """Image generation settings, with the numbers clamped.
+
+    Clamped on read rather than on save, for the reason `agents` gives: a value
+    stored by an earlier version cannot bite either. `max_tries` has a floor of
+    one because zero would mean the tool generates nothing at all and reports
+    success -- there is no reading of "no tries" that anybody wants, unlike the
+    zeroes above, which each mean something.
+    """
+    values = get_group(db, IMAGES)
+    values["timeout"] = min(max(float(values.get("timeout") or 0), 10.0), 3600.0)
+    values["max_tries"] = min(max(int(values.get("max_tries") or 1), 1), 10)
+    for name in ("checkpoints", "samplers", "schedulers"):
+        stored = values.get(name)
+        values[name] = [str(item) for item in stored] if isinstance(stored, list) else []
+    return values
+
+
+def images_ready(db: DBSession) -> bool:
+    """Whether image generation can actually happen.
+
+    Three things, and the checkpoint list is the one worth stating: without it a
+    model has nothing to name, and ComfyUI refuses a workflow whose checkpoint
+    does not exist -- so offering the tool would be offering a round that ends
+    in a refusal. Read by the tool gate, which is why it lives here beside the
+    values rather than in `tools.py` with the other gates.
+    """
+    values = images(db)
+    return bool(values["enabled"] and values["base_url"] and values["checkpoints"])