Defaults an administrator can actually set

There were none. `workflow.DEFAULTS` was the only source, so 512x512, euler and
twenty steps were what every instance got whatever card it was running on -- and
512 square on an SDXL checkpoint is precisely what the tool's own description
warns produces duplicated limbs. The two ways round it were both bad: bake
literals into a template where the placeholders should be, or write prose in the
instructions box and hope.

Three rungs now, most specific winning, with DEFAULTS staying underneath as the
floor so an instance that sets nothing behaves exactly as it did and a floor
improved in code still reaches everybody. An empty box is "no opinion" rather
than zero, which matters: read as a number it would set every instance to zero
steps, and ComfyUI refuses that in a way that looks like a broken model.

The right control for each, because a text box is wrong for most of them. The
samplers and schedulers were already being discovered by the Test button, stored,
and read by nothing at all -- they are the pickers now. A stored value missing
from the list is kept as an option anyway, or opening this page and pressing Save
would silently clear a working setting. Checkpoints are chosen rather than typed,
and the instance default is a rung of its own instead of "whatever happens to be
first in a textarea somebody filled in some order".

And batch, at last: `batch_size` was a literal 1 in the base template, so an
administrator whose card can comfortably make four had no way of saying so.
Deliberately not something a model may set -- one asking for six because it is
unsure is the exact cost this must not invite.

The tool's schema restates the defaults it quotes. Every "Default 20." in there
was written when there was one set of defaults in the world; left alone, an
instance drawing at 1024 would go on telling the model 512, and the model reasons
from that sentence rather than ignoring it.

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

src/lembas/__init__.py

@@ -1,3 +1,3 @@
 """LLeMbas - a Middle-earth themed web UI for OpenAI-compatible LLM endpoints."""
 
-__version__ = "0.9.1"
+__version__ = "0.9.2"

src/lembas/api/admin_images.py

@@ -18,6 +18,7 @@ import json
 import logging
 import re
 from datetime import UTC, datetime
+from typing import Any
 
 from fastapi import APIRouter, Form, HTTPException, Request, Response, status
 from fastapi.responses import RedirectResponse
@@ -54,6 +55,27 @@ def _lines(text: str) -> list[str]:
     return seen
 
 
+def _number(raw: str, name: str, *, whole: bool = True) -> Any:
+    """A filled box as a clamped number, an empty one as "".
+
+    The empty string is load-bearing and is not a missing value: it is how an
+    administrator says "no opinion about this one", which `workflow.resolve`
+    reads as "fall through to the built-in floor". Turning it into a zero here
+    would silently set every instance to zero steps.
+    """
+    text = (raw or "").strip()
+    if not text:
+        return ""
+    try:
+        value = float(text)
+    except ValueError:
+        return ""
+    low, high = workflow_service.LIMITS.get(name, (None, None))
+    if low is not None:
+        value = min(max(value, low), high)
+    return int(value) if whole else value
+
+
 def _config(db: Db) -> comfy.Config:
     values = settings_store.images(db)
     return comfy.Config(
@@ -114,6 +136,21 @@ async def save_images(
     max_tries: int = Form(4),
     preserve_vram: bool = Form(False),
     instructions: str = Form(""),
+    # The generation defaults. Every one is a *string* even where it is a
+    # number, because "" is how an administrator says "no opinion" and an
+    # `int = Form(0)` cannot express that -- zero steps is a value, and one
+    # somebody could mean. `_number` below turns a filled box into a clamped
+    # number and an empty one back into "".
+    default_checkpoint: str = Form(""),
+    default_steps: str = Form(""),
+    default_cfg: str = Form(""),
+    default_width: str = Form(""),
+    default_height: str = Form(""),
+    default_sampler: str = Form(""),
+    default_scheduler: str = Form(""),
+    default_denoise: str = Form(""),
+    default_negative: str = Form(""),
+    default_batch: str = Form(""),
 ) -> Response:
     """Save the settings.
 
@@ -142,6 +179,20 @@ async def save_images(
             "max_tries": min(max(max_tries, 1), 10),
             "preserve_vram": preserve_vram,
             "instructions": instructions.strip()[:4000],
+            # Clamped here to the same bounds `workflow.LIMITS` uses on the way
+            # out. Twice, deliberately: a number stored by an earlier version,
+            # or written straight into the settings row, still has to be safe
+            # when a generation reads it.
+            "default_checkpoint": default_checkpoint.strip(),
+            "default_steps": _number(default_steps, "steps"),
+            "default_cfg": _number(default_cfg, "cfg", whole=False),
+            "default_width": _number(default_width, "width"),
+            "default_height": _number(default_height, "height"),
+            "default_sampler": default_sampler.strip(),
+            "default_scheduler": default_scheduler.strip(),
+            "default_denoise": _number(default_denoise, "denoise", whole=False),
+            "default_negative": default_negative.strip()[:500],
+            "default_batch": _number(default_batch, "batch"),
         },
         key=settings_store.IMAGES,
     )
@@ -212,7 +263,34 @@ def _workflow(db: Db, workflow_id: str) -> ImageWorkflow:
     return row
 
 
-def _detail(request: Request, row: ImageWorkflow, *, is_new: bool, error: str = "", **extra):
+def _placeholder_help(db: Db) -> list[tuple[str, str, str, str]]:
+    """Every placeholder, what it fills, and what it resolves to *today*.
+
+    The last column is the point. A legend listing names answers "what may I
+    write"; the question somebody actually has, standing in front of a workflow
+    that came out wrong, is "what happens if I leave this out" -- and the answer
+    moved the day instance defaults arrived. Resolved through the same call a
+    generation makes, so the two cannot disagree.
+    """
+    resolved = workflow_service.resolve({}, settings=settings_store.images(db))
+    out: list[tuple[str, str, str, str]] = []
+    for name in workflow_service.PLACEHOLDERS:
+        kind, what = workflow_service.DESCRIPTIONS.get(name, ("text", ""))
+        if name == "prompt":
+            shown = "whatever is asked for"
+        elif name == "seed":
+            shown = "a fresh random one"
+        elif name == "model":
+            shown = str(resolved.get("model") or "") or "the first checkpoint listed"
+        else:
+            shown = str(resolved.get(name, ""))
+        out.append((name, kind, what, shown))
+    return out
+
+
+def _detail(
+    request: Request, db: Db, row: ImageWorkflow, *, is_new: bool, error: str = "", **extra
+):
     return render(
         request,
         "admin/workflow_detail.html",
@@ -221,6 +299,7 @@ def _detail(request: Request, row: ImageWorkflow, *, is_new: bool, error: str =
             "is_new": is_new,
             "error": error,
             "placeholders": workflow_service.PLACEHOLDERS,
+            "placeholder_help": _placeholder_help(db),
             "workflow_text": extra.pop(
                 "workflow_text", json.dumps(row.workflow_json or {}, indent=2)
             ),
@@ -304,7 +383,7 @@ async def new_workflow(request: Request, db: Db, user: AdminUser) -> Response:
         workflow_json=json.loads(base.read_text(encoding="utf-8")),
         enabled=True,
     )
-    return _detail(request, draft, is_new=True)
+    return _detail(request, db, draft, is_new=True)
 
 
 @router.post("/workflows")
@@ -316,6 +395,7 @@ async def create_workflow(request: Request, db: Db, user: AdminUser) -> Response
     if problem:
         return _detail(
             request,
+            db,
             row,
             is_new=True,
             error=problem,
@@ -334,7 +414,7 @@ async def create_workflow(request: Request, db: Db, user: AdminUser) -> Response
 
 @router.get("/workflows/{workflow_id}/edit")
 async def edit_workflow(request: Request, db: Db, user: AdminUser, workflow_id: str) -> Response:
-    return _detail(request, _workflow(db, workflow_id), is_new=False)
+    return _detail(request, db, _workflow(db, workflow_id), is_new=False)
 
 
 @router.post("/workflows/{workflow_id}/delete")
@@ -363,6 +443,7 @@ async def update_workflow(request: Request, db: Db, user: AdminUser, workflow_id
         draft.id = row.id
         return _detail(
             request,
+            db,
             draft,
             is_new=False,
             error=problem,

src/lembas/services/images/base_workflow.json

@@ -24,7 +24,7 @@
     "inputs": {
       "width": "{{width}}",
       "height": "{{height}}",
-      "batch_size": 1
+      "batch_size": "{{batch}}"
     },
     "class_type": "EmptyLatentImage",
     "_meta": { "title": "Empty Latent Image" }

src/lembas/services/images/tool.py

@@ -27,6 +27,7 @@ from __future__ import annotations
 
 import json
 import logging
+import re
 from dataclasses import dataclass
 from typing import Any
 
@@ -196,6 +197,43 @@ def _choices(db, values: dict[str, Any]) -> tuple[list[Any], list[str]]:
     return rows, [str(name) for name in (values.get("checkpoints") or [])]
 
 
+_DEFAULT_SENTENCE = re.compile(r"Default ([^.,]+)([.,])")
+
+
+def _restate_defaults(schema: dict[str, Any], values: dict[str, Any]) -> None:
+    """Rewrite each "Default 20." to say what this instance actually uses.
+
+    Every one of those descriptions was written when there was one set of
+    defaults in the world. Now an administrator can move them, and a schema
+    still saying "Default 512" beside an instance that draws at 1024 is worse
+    than saying nothing: the model reasons from it, decides 512 is fine for the
+    SDXL checkpoint it was handed, and omits the parameter — arriving at the
+    right behaviour for the wrong reason, or the wrong one silently.
+
+    A rewrite rather than a `{default}` placeholder in the prose, because the
+    sentence around it differs per parameter and half of them go on to say what
+    to do *instead* of the default. The regex keeps the punctuation it found,
+    since `denoise` says "Default 1, which is…" and the rest use a full stop.
+    """
+    resolved = workflow.resolve({}, settings=values)
+    for name, spec in schema.get("properties", {}).items():
+        if name not in resolved or name in ("prompt", "seed", "model", "template"):
+            continue
+        shown = resolved[name]
+        # A float that is whole reads better as "8" than "8.0", and this is the
+        # text a model reasons about.
+        if isinstance(shown, float) and shown.is_integer():
+            shown = int(shown)
+        spec["description"] = _DEFAULT_SENTENCE.sub(
+            # Bound now rather than closed over: `shown` is a loop variable, and
+            # a lambda reading it later would restate every description with the
+            # last parameter's value.
+            lambda match, shown=shown: f"Default {shown}{match.group(2)}",
+            spec["description"],
+            count=1,
+        )
+
+
 def schema_for(db, values: dict[str, Any]) -> dict[str, Any]:
     """The parameter schema, with this instance's own choices in it.
 
@@ -207,6 +245,7 @@ def schema_for(db, values: dict[str, Any]) -> dict[str, Any]:
     """
     rows, checkpoints = _choices(db, values)
     schema = json.loads(json.dumps(SCHEMA))
+    _restate_defaults(schema, values)
     if rows:
         schema["properties"]["template"]["enum"] = [row.slug for row in rows]
         schema["properties"]["template"]["description"] = "Which workflow to use. " + "; ".join(
@@ -421,7 +460,12 @@ async def run(context: ToolContext, args: dict[str, Any]) -> ToolOutcome:
             {**event, "status": "error", "error": str(exc)},
         )
 
-    checkpoint = _checkpoint(str(args.get("model") or ""), context.image_checkpoint, checkpoints)
+    checkpoint = _checkpoint(
+        str(args.get("model") or ""),
+        context.image_checkpoint,
+        checkpoints,
+        instance_default=str(values.get("default_checkpoint") or ""),
+    )
     if checkpoint is None:
         return ToolOutcome(
             "No checkpoint is available. An administrator has to list them on the "
@@ -429,7 +473,7 @@ async def run(context: ToolContext, args: dict[str, Any]) -> ToolOutcome:
             {**event, "status": "error", "error": "No checkpoint."},
         )
 
-    given = {name: args.get(name) for name in workflow.PLACEHOLDERS if name in args}
+    given = {name: args.get(name) for name in workflow.MODEL_SETTABLE if name in args}
     given["model"] = checkpoint
     given["prompt"] = prompt
 
@@ -441,14 +485,16 @@ async def run(context: ToolContext, args: dict[str, Any]) -> ToolOutcome:
     kept: tuple[bytes, dict[str, Any]] | None = None
     # What the last attempt actually asked for, so a failure can name concrete
     # numbers back at the model rather than saying "try something smaller".
-    params_used: dict[str, Any] = workflow.resolve(given)
+    params_used: dict[str, Any] = workflow.resolve(given, settings=values)
 
     try:
         for number in range(1, tries + 1):
             if preserve:
                 await _unload_llm(context)
 
-            params = workflow.resolve({**given, "seed": args.get("seed") if number == 1 else None})
+            params = workflow.resolve(
+                {**given, "seed": args.get("seed") if number == 1 else None}, settings=values
+            )
             params_used = params
             refs = await comfy.await_images(
                 config, await comfy.submit(config, workflow.fill(template, params))
@@ -571,17 +617,26 @@ def _pick(rows: list[Any], wanted: str, chat_default: str, values: dict[str, Any
     return rows[0] if rows else None
 
 
-def _checkpoint(wanted: str, chat_default: str, available: list[str]) -> str | None:
+def _checkpoint(
+    wanted: str, chat_default: str, available: list[str], *, instance_default: str = ""
+) -> str | None:
     """The checkpoint to draw with, on the same ladder.
 
-    A name the instance does not have is ignored rather than passed through: it
-    would reach ComfyUI, be refused, and cost a round to discover -- and the
-    model was shown the list it may choose from.
+    Most specific first: what the model named, then this chat's own, then the
+    instance default, then whatever is first in the list. The instance rung is
+    the new one -- without it, "the default" was position zero in a textarea an
+    administrator had typed in some order, which is a default by accident.
+
+    A name the instance does not have is ignored at every rung rather than
+    passed through: it would reach ComfyUI, be refused, and cost a round to
+    discover -- and the model was shown the list it may choose from.
     """
     if wanted and wanted in available:
         return wanted
     if chat_default and chat_default in available:
         return chat_default
+    if instance_default and instance_default in available:
+        return instance_default
     return available[0] if available else None
 
 

src/lembas/services/images/workflow.py

@@ -40,12 +40,25 @@ PLACEHOLDERS = (
     "sampler",
     "scheduler",
     "denoise",
+    # How many pictures one run produces. Late to the list, and the reason is
+    # worth stating: `batch_size` was a literal `1` in the base template, so an
+    # administrator whose card can comfortably make four at a time had no way of
+    # saying so short of editing the JSON. Not a tool parameter -- a model asking
+    # for six images because it is unsure is exactly the cost this should not
+    # invite -- so it fills from the instance default and nowhere else.
+    "batch",
 )
 
-# The defaults, taken from the base template. `seed` is deliberately absent: it
-# has no fixed default, because one would make every generation that did not
-# name a seed identical -- and would make the retry loop produce the same
-# rejected image four times over.
+# What a model may name. Everything else in `PLACEHOLDERS` fills from a default.
+MODEL_SETTABLE = tuple(name for name in PLACEHOLDERS if name != "batch")
+
+# The floor, taken from the base template. An instance's own defaults sit above
+# this (see `resolve`), and this stays as the last resort so a fresh install
+# behaves exactly as it always did.
+#
+# `seed` is deliberately absent: it has no fixed default, because one would make
+# every generation that did not name a seed identical -- and would make the
+# retry loop produce the same rejected image four times over.
 DEFAULTS: dict[str, Any] = {
     "negative": "text, watermark",
     "steps": 20,
@@ -55,6 +68,26 @@ DEFAULTS: dict[str, Any] = {
     "sampler": "euler",
     "scheduler": "normal",
     "denoise": 1.0,
+    "batch": 1,
+}
+
+# What each hole is for, and what it lands as. Read by the workflow editor, so
+# somebody writing a template is told what `{{sampler}}` fills without reading
+# this file -- and in particular is told the two names that do not match
+# ComfyUI's own, which is the mistake that costs an afternoon.
+DESCRIPTIONS: dict[str, tuple[str, str]] = {
+    "model": ("text", "The checkpoint. Fills ComfyUI's `ckpt_name`, not `model`."),
+    "prompt": ("text", "What to draw. The only value a model must supply."),
+    "negative": ("text", "What to keep out of the picture."),
+    "seed": ("number", "The noise seed. Absent or negative means a fresh random one."),
+    "steps": ("number", "How many denoising steps. More is slower, not always better."),
+    "cfg": ("number", "How closely to follow the prompt. A decimal."),
+    "width": ("number", "Pixels across. A multiple of 64."),
+    "height": ("number", "Pixels down. A multiple of 64."),
+    "sampler": ("text", "The sampling method. Fills ComfyUI's `sampler_name`, not `sampler`."),
+    "scheduler": ("text", "The noise schedule."),
+    "denoise": ("number", "How much of the latent to redraw. 1.0 for text-to-image."),
+    "batch": ("number", "How many images one run makes. Fills `batch_size`."),
 }
 
 # ComfyUI's own ranges, read off `/object_info`. Clamped rather than refused: a
@@ -66,6 +99,10 @@ LIMITS: dict[str, tuple[float, float]] = {
     "width": (64, 2048),
     "height": (64, 2048),
     "denoise": (0.0, 1.0),
+    # Not ComfyUI's ceiling, which is 4096, but a sane one: this multiplies
+    # every generation's time and VRAM, and an administrator who wants more than
+    # eight at once wants a different workflow rather than a bigger number here.
+    "batch": (1, 8),
 }
 
 # ComfyUI's seed is a uint64. Generated here rather than left to the far side
@@ -80,12 +117,43 @@ def random_seed() -> int:
     return secrets.randbelow(MAX_SEED)
 
 
-def resolve(given: dict[str, Any]) -> dict[str, Any]:
-    """The full parameter set: what was asked for, over the defaults.
+def instance_defaults(values: dict[str, Any] | None) -> dict[str, Any]:
+    """The `default_*` keys out of the image settings, as placeholder names.
 
-    Absent and null are both "no opinion". A model that emits `"seed": null`
-    rather than omitting the key is common enough that treating it as a request
-    for seed zero would be a bug nobody could see.
+    Only the ones actually set: an absent or empty key means "no opinion", and
+    must fall through to `DEFAULTS` rather than land as an empty string in a
+    workflow. That is the same reading `resolve` gives a model's own arguments,
+    and it is why an administrator can set two of these and leave the rest.
+    """
+    out: dict[str, Any] = {}
+    for name in PLACEHOLDERS:
+        if name in ("prompt", "seed", "model"):
+            # A default prompt is not a thing; a default seed would make every
+            # picture identical; the checkpoint has its own setting and its own
+            # per-chat override, resolved before this is reached.
+            continue
+        value = (values or {}).get(f"default_{name}")
+        if value is None or value == "":
+            continue
+        out[name] = value
+    return out
+
+
+def resolve(given: dict[str, Any], *, settings: dict[str, Any] | None = None) -> dict[str, Any]:
+    """The full parameter set: what was asked for, over what this instance
+    prefers, over the built-in floor.
+
+    Three rungs, most specific winning, and the middle one is the new part. For
+    the whole life of this feature there were only two -- so 512x512, euler and
+    twenty steps were the values every instance got, whatever card it was
+    running on, and the only ways to move them were to bake literals into a
+    template instead of placeholders or to write prose in the instructions box
+    and hope. `DEFAULTS` stays underneath so an instance that sets nothing
+    behaves exactly as it did.
+
+    Absent and null are both "no opinion", at both levels. A model that emits
+    `"seed": null` rather than omitting the key is common enough that treating
+    it as a request for seed zero would be a bug nobody could see.
 
     **A negative seed means random**, which is what `-1` means in ComfyUI's own
     interface, in A1111, and in every other thing that has ever asked somebody
@@ -94,14 +162,17 @@ def resolve(given: dict[str, Any]) -> dict[str, Any]:
     a perfectly valid *fixed* seed, so "give me something new" produced the same
     picture every time. Exactly the wrong answer, arrived at silently.
     """
-    values: dict[str, Any] = {**DEFAULTS}
+    values: dict[str, Any] = {**DEFAULTS, **instance_defaults(settings)}
     for name, value in (given or {}).items():
-        if name in PLACEHOLDERS and value is not None and value != "":
+        # `batch` is absent from `MODEL_SETTABLE`, so a model naming it is
+        # ignored here rather than refused -- the tool schema never offered it,
+        # and one that invents the key has guessed rather than misbehaved.
+        if name in MODEL_SETTABLE and value is not None and value != "":
             values[name] = value
 
     seed = _whole(values.get("seed"), default=-1)
     values["seed"] = random_seed() if seed < 0 else seed % (MAX_SEED + 1)
-    for name in ("steps", "width", "height"):
+    for name in ("steps", "width", "height", "batch"):
         values[name] = _clamp(_whole(values.get(name), DEFAULTS[name]), name)
     for name in ("cfg", "denoise"):
         values[name] = _clamp(_decimal(values.get(name), DEFAULTS[name]), name)

src/lembas/services/settings_store.py

@@ -260,6 +260,31 @@ def _images_defaults() -> dict[str, Any]:
         "samplers": [],
         "schedulers": [],
         "default_workflow_id": "",
+        # What a generation uses when nothing names otherwise. Empty means "no
+        # opinion" for every one of them, falling through to
+        # `workflow.DEFAULTS` -- which is why they are empty here rather than
+        # holding a copy of that dict. A copy would freeze an instance on
+        # whatever this file said the day it was installed, and would make
+        # improving a floor in code reach nobody.
+        #
+        # These exist because for the whole life of this feature there were
+        # none: 512x512, euler and twenty steps were what every instance got
+        # whatever card it was running on, and the only ways to move them were
+        # to bake literals into a template instead of placeholders, or to write
+        # prose in the instructions box and hope.
+        "default_checkpoint": "",
+        "default_steps": "",
+        "default_cfg": "",
+        "default_width": "",
+        "default_height": "",
+        "default_sampler": "",
+        "default_scheduler": "",
+        "default_denoise": "",
+        "default_negative": "",
+        # How many pictures one run makes. Not offered to the model at all --
+        # see workflow.MODEL_SETTABLE -- because a model asking for six because
+        # it is unsure is exactly the cost this must not invite.
+        "default_batch": "",
         # 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

src/lembas/web/static/css/admin.css

@@ -203,6 +203,24 @@ a.tabs__tab { text-decoration: none; }
   flex-wrap: wrap;
 }
 
+/*
+  Two or three short fields on one line.
+
+  Numbers with their own units — width and height, steps and cfg and denoise —
+  read as a set and take a fraction of the width each, so stacking them makes a
+  card that is mostly whitespace and a form that is mostly scrolling. Auto-fit
+  rather than a fixed count: the same markup gives three columns on a wide
+  screen and one on a narrow one with no breakpoint, which matters because
+  `chat.css` has a test refusing media queries and this file should not drift
+  from that habit without a reason.
+*/
+.field-row {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(9rem, 1fr));
+  gap: var(--sp-3);
+}
+.field-row > .field { margin-bottom: var(--sp-4); }
+
 /* Legacy aliases so existing admin templates keep their spacing. */
 .form-grid { display: block; }
 .connection__head { display: flex; align-items: center; justify-content: space-between;

src/lembas/web/static/js/ui.js

@@ -759,6 +759,32 @@
   document.addEventListener("htmx:afterSettle", scan);
 })();
 
+/*
+  Two number fields set together.
+
+  Image sizes come in pairs and nobody types 1024 and then 1536; they pick
+  "portrait". A button rather than a select of pairs, because a select would
+  have to enumerate every combination somebody might want and these are only
+  the common ones — the two boxes are still there and still authoritative.
+
+  Delegated and keyed on the attributes rather than on the image page's ids, so
+  the next screen with a paired number wants no new code.
+*/
+document.addEventListener("click", function (event) {
+  var preset = event.target.closest("[data-width][data-height]");
+  if (!preset) return;
+  var row = preset.closest("[data-size-presets]");
+  if (!row) return;
+  event.preventDefault();
+
+  var form = preset.closest("form");
+  if (!form) return;
+  var width = form.querySelector('[name="default_width"]');
+  var height = form.querySelector('[name="default_height"]');
+  if (width) width.value = preset.dataset.width;
+  if (height) height.value = preset.dataset.height;
+});
+
 /*
   A toast asked for by the server.
 

src/lembas/web/templates/admin/images.html

@@ -100,6 +100,143 @@
     <div id="images-test-result"></div>
   </section>
 
+  <section class="card">
+    <h2 class="card__title">What a generation uses by default</h2>
+    <p class="card__lede">
+      What every picture is drawn with unless the model names otherwise. Leave a
+      box empty to use the built-in value shown beside it — the built-ins are
+      SD1.5-era, and 512×512 on an SDXL checkpoint is what produces the
+      duplicated limbs.
+    </p>
+
+    <div class="field">
+      <label class="field__label" for="default_checkpoint">Checkpoint</label>
+      {# A select rather than a box, from the list above. Typing a name that is
+         not there produced a picture drawn with whatever happened to be first,
+         with nothing anywhere saying so. #}
+      <select class="select" id="default_checkpoint" name="default_checkpoint">
+        <option value="">The first in the list above</option>
+        {% for name in values.checkpoints or [] %}
+        <option value="{{ name }}" {{ 'selected' if values.default_checkpoint == name }}>
+          {{ name }}
+        </option>
+        {% endfor %}
+      </select>
+    </div>
+
+    <div class="field-row">
+      <div class="field">
+        <label class="field__label" for="default_width">Width</label>
+        <input class="input" type="number" id="default_width" name="default_width"
+               min="64" max="2048" step="64" placeholder="512"
+               value="{{ values.default_width }}">
+      </div>
+      <div class="field">
+        <label class="field__label" for="default_height">Height</label>
+        <input class="input" type="number" id="default_height" name="default_height"
+               min="64" max="2048" step="64" placeholder="512"
+               value="{{ values.default_height }}">
+      </div>
+    </div>
+    {# The five sizes anybody actually picks. Buttons rather than a select
+       because they set two fields at once, and a select of pairs would have to
+       name every combination somebody might want. #}
+    <div class="btn-row" data-size-presets>
+      {% for label, w, h in [
+        ("512²", 512, 512), ("768²", 768, 768), ("1024²", 1024, 1024),
+        ("1024×1536", 1024, 1536), ("1536×1024", 1536, 1024)
+      ] %}
+      <button class="btn btn--sm" type="button"
+              data-width="{{ w }}" data-height="{{ h }}">{{ label }}</button>
+      {% endfor %}
+    </div>
+
+    <div class="field-row">
+      <div class="field">
+        <label class="field__label" for="default_steps">Steps</label>
+        <input class="input" type="number" id="default_steps" name="default_steps"
+               min="1" max="150" step="1" placeholder="20"
+               value="{{ values.default_steps }}">
+      </div>
+      <div class="field">
+        <label class="field__label" for="default_cfg">Guidance (cfg)</label>
+        <input class="input" type="number" id="default_cfg" name="default_cfg"
+               min="0" max="30" step="0.5" placeholder="8"
+               value="{{ values.default_cfg }}">
+      </div>
+      <div class="field">
+        <label class="field__label" for="default_denoise">Denoise</label>
+        <input class="input" type="number" id="default_denoise" name="default_denoise"
+               min="0" max="1" step="0.05" placeholder="1"
+               value="{{ values.default_denoise }}">
+      </div>
+    </div>
+
+    <div class="field-row">
+      <div class="field">
+        <label class="field__label" for="default_sampler">Sampler</label>
+        {# From what the Test button read off ComfyUI. There are forty-odd and
+           spelling one wrong is a refused workflow, so it is picked rather than
+           typed — and the current value is kept as an option even when the list
+           has not been read, or saving this page would quietly clear it. #}
+        <select class="select" id="default_sampler" name="default_sampler">
+          <option value="">euler (built-in)</option>
+          {% for name in values.samplers or [] %}
+          <option value="{{ name }}" {{ 'selected' if values.default_sampler == name }}>
+            {{ name }}
+          </option>
+          {% endfor %}
+          {% if values.default_sampler and values.default_sampler not in (values.samplers or []) %}
+          <option value="{{ values.default_sampler }}" selected>
+            {{ values.default_sampler }} (not in this ComfyUI's list)
+          </option>
+          {% endif %}
+        </select>
+      </div>
+      <div class="field">
+        <label class="field__label" for="default_scheduler">Scheduler</label>
+        <select class="select" id="default_scheduler" name="default_scheduler">
+          <option value="">normal (built-in)</option>
+          {% for name in values.schedulers or [] %}
+          <option value="{{ name }}" {{ 'selected' if values.default_scheduler == name }}>
+            {{ name }}
+          </option>
+          {% endfor %}
+          {% if values.default_scheduler
+                and values.default_scheduler not in (values.schedulers or []) %}
+          <option value="{{ values.default_scheduler }}" selected>
+            {{ values.default_scheduler }} (not in this ComfyUI's list)
+          </option>
+          {% endif %}
+        </select>
+      </div>
+      <div class="field">
+        <label class="field__label" for="default_batch">Images per run</label>
+        <input class="input" type="number" id="default_batch" name="default_batch"
+               min="1" max="8" step="1" placeholder="1"
+               value="{{ values.default_batch }}">
+      </div>
+    </div>
+    {% if not values.samplers %}
+    <p class="field__hint">
+      Press <strong>Test &amp; read what it has</strong> above to fill the sampler
+      and scheduler lists from your ComfyUI.
+    </p>
+    {% endif %}
+
+    <div class="field">
+      <label class="field__label" for="default_negative">Negative prompt</label>
+      <input class="input" type="text" id="default_negative" name="default_negative"
+             placeholder="text, watermark" value="{{ values.default_negative }}">
+      <p class="field__hint">
+        Used when the model does not write one of its own. It writes one often,
+        so this is a floor rather than something always applied — “always add
+        these words” belongs in the instructions below, where the model is told
+        to include them.
+      </p>
+    </div>
+  </section>
+
   <section class="card">
     <h2 class="card__title">Checking the result</h2>
     <div class="field">

src/lembas/web/templates/admin/workflow_detail.html

@@ -75,15 +75,46 @@
         <code>"{{ '{{prompt}}' }}, masterpiece"</code> works. Anything you leave out
         takes its default.
       </p>
-      <p class="field__hint">
-        Available:
-        {% for name in placeholders %}<code>{{ '{{' ~ name ~ '}}' }}</code>{{ ", " if not loop.last }}{% endfor %}.
-        <code>{{ '{{prompt}}' }}</code> is required — without it every image would
-        be the same.
-      </p>
     </div>
   </section>
 
+  <section class="card">
+    <h2 class="card__title">The placeholders</h2>
+    <p class="card__lede">
+      Every hole a template may carry, what it fills, and what it resolves to
+      right now. <code>{{ '{{prompt}}' }}</code> is required — without it every
+      image would be the same one, whatever anybody typed.
+    </p>
+    {# The current value beside each name, the way /admin/prompts shows a
+       variable's. A legend that lists names and not values answers "what may I
+       write" and not "what will happen", and the second is the question
+       somebody has while looking at a workflow that came out wrong. #}
+    <div class="ref-list">
+      {% for name, kind, what, current in placeholder_help %}
+      <div class="ref-row">
+        <code>{{ '{{' ~ name ~ '}}' }}</code>
+        <span>
+          {{ what }}
+          {% if name == "prompt" %}<strong>Required.</strong>{% endif %}
+        </span>
+        <code class="faint">{{ current }}</code>
+      </div>
+      {% endfor %}
+    </div>
+    <p class="field__hint">
+      Two of these are not spelled the way ComfyUI spells them, which is the
+      mistake that costs an afternoon: <code>{{ '{{model}}' }}</code> fills
+      <code>ckpt_name</code> and <code>{{ '{{sampler}}' }}</code> fills
+      <code>sampler_name</code>.
+    </p>
+    <p class="field__hint">
+      The right-hand column is what an omitted placeholder resolves to today —
+      the instance defaults from the image settings page, falling back to the
+      built-in floor. A model may override any of them except
+      <code>{{ '{{batch}}' }}</code>, which is yours alone.
+    </p>
+  </section>
+
   <div class="btn-row">
     <button class="btn btn--primary" type="submit">
       {{ "Add workflow" if is_new else "Save changes" }}