Let a function node's own settings be edited

A python node's params reach process() as whatever its author put there,
but there was no way to put anything there: the settings form is built
from a type's declared schema, and a function node declares none.

Node types now say whether they take settings beyond their schema, and
the panel offers a key/value editor for the ones that do — named, typed
as text, number, on/off or JSON, and laid out like the port list beside
it. Rows are keyed by position rather than by name, so renaming a setting
does not remount the row and lose what was being typed into it.

Verified in the running app in both themes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011LF61rxW1FG5YCD2J9YqjY

NOTEPAD.md

@@ -74,6 +74,10 @@ Deferring because out of scope is fine, but don't mention deferring than.
   threshold. React Flow and Monaco are already lazy; a manualChunks split measured no better,
   so this needs route-level work on the shell rather than chunking config.
 
+- CHORE/INFRA: `bun run --filter frontend build` fails on this workspace with
+  `crypto.hash is not a function` — Vite 7 wants Node 20.12+ and the host has 18. The
+  Docker image builds fine, so it only bites local bundling; `bunx tsc` still type-checks.
+
 ## Blocked
 
 - FEAT/UI: a "Bug" icon on the node error bubble opening the logs panel at that node's

backend/app/flow/controller.py

@@ -101,6 +101,7 @@ class NodeType:
     # Constructor signatures differ per node type.
     cls: Any
     has_source: bool = False
+    free_params: bool = False
     params_schema: dict[str, Any] = field(default_factory=dict)
     #: Which installed package supplied this type, for the ones that are not
     #: built in.
@@ -118,6 +119,7 @@ NODE_TYPES: dict[str, NodeType] = {
         description="Your own Python code, run on every incoming message.",
         cls=Node,
         has_source=True,
+        free_params=True,
     ),
     "mqtt": NodeType(
         title="MQTT",
@@ -214,6 +216,7 @@ def node_type_info() -> list[NodeTypeInfo]:
             description=spec.description,
             params_schema=spec.params_schema,
             has_source=spec.has_source,
+            free_params=spec.free_params,
             plugin=spec.plugin,
         )
         for key, spec in NODE_TYPES.items()

backend/app/flow/schemas.py

@@ -155,5 +155,9 @@ class NodeTypeInfo(BaseModel):
     description: str
     params_schema: dict[str, Any] = Field(default_factory=dict)
     has_source: bool = False
+    #: Whether this type takes settings beyond the ones its schema declares.
+    #: A function node's params are its author's to name, and reach `process`
+    #: as whatever they put there.
+    free_params: bool = False
     #: The package a connector came from; empty for the built-in types.
     plugin: str | None = None

frontend/scripts/verify-params.mjs

@@ -0,0 +1,72 @@
+/** Feature check: the free-form settings editor on a function node. */
+import { mkdir } from "node:fs/promises"
+import { chromium } from "@playwright/test"
+
+const APP_URL = process.env.APP_URL || "http://app.localhost"
+const EMAIL = process.env.FIRST_SUPERUSER
+const PASSWORD = process.env.FIRST_SUPERUSER_PASSWORD
+const OUT = process.env.SCREENSHOT_DIR || "screenshots"
+
+const browser = await chromium.launch()
+for (const theme of ["light", "dark"]) {
+  const dir = `${OUT}/${theme}`
+  await mkdir(dir, { recursive: true })
+  const context = await browser.newContext({
+    viewport: { width: 1440, height: 900 },
+    colorScheme: theme,
+  })
+  await context.addInitScript((t) => {
+    localStorage.setItem("fluksio-ui-theme", t)
+  }, theme)
+  const page = await context.newPage()
+
+  await page.goto(`${APP_URL}/login`, { waitUntil: "networkidle" })
+  await page.getByTestId("email-input").fill(EMAIL)
+  await page.getByTestId("password-input").fill(PASSWORD)
+  await page.getByRole("button", { name: /log in/i }).click()
+  await page.waitForURL(`${APP_URL}/`, { timeout: 15000 })
+
+  await page.goto(`${APP_URL}/flows`, { waitUntil: "networkidle" })
+  const seed = page.getByTestId("create-first-flow")
+  if (await seed.count()) {
+    await seed.click()
+    await page.waitForURL(/\/flows\/.+/, { timeout: 15000 })
+  }
+  if (!(await page.locator(".react-flow__node").count())) {
+    await page.getByTestId("add-node").click()
+    await page
+      .getByRole("option", { name: /function/i })
+      .first()
+      .click()
+    await page.waitForSelector(".react-flow__node")
+  }
+  await page.locator(".react-flow__node").first().click()
+  await page.waitForSelector("[data-testid=node-panel]", { timeout: 15000 })
+
+  // Add two settings and give them values.
+  await page.getByTestId("add-param").click()
+  await page.waitForTimeout(300)
+  const names = page.getByLabel("Setting name")
+  const values = page.getByLabel("Setting value")
+  await names.first().fill("threshold")
+  await names.first().blur()
+  await page.waitForTimeout(200)
+  await page.getByLabel("Type").first().click()
+  await page.getByRole("option", { name: "number" }).click()
+  await page.waitForTimeout(200)
+  await values.first().fill("21.5")
+  await page.waitForTimeout(200)
+
+  await page.getByTestId("add-param").click()
+  await page.waitForTimeout(300)
+  await names.nth(1).fill("label")
+  await names.nth(1).blur()
+  await page.waitForTimeout(200)
+  await values.nth(1).fill("living room")
+  await page.waitForTimeout(1200)
+
+  await page.screenshot({ path: `${dir}/app-node-params.png` })
+  console.log(`  wrote ${dir}/app-node-params.png`)
+  await context.close()
+}
+await browser.close()

frontend/src/client/schemas.gen.ts

@@ -831,6 +831,11 @@ export const NodeTypeInfoSchema = {
             title: 'Has Source',
             default: false
         },
+        free_params: {
+            type: 'boolean',
+            title: 'Free Params',
+            default: false
+        },
         plugin: {
             anyOf: [
                 {

frontend/src/client/types.gen.ts

@@ -264,6 +264,7 @@ export type NodeTypeInfo = {
         [key: string]: unknown;
     };
     has_source?: boolean;
+    free_params?: boolean;
     plugin?: (string | null);
 };
 

frontend/src/components/Flow/NodePanel.tsx

@@ -48,6 +48,9 @@ const NO_SECRET = "__none__"
 
 const SECTION = PANEL_SECTION
 
+/** Settings the engine reads itself, so they are not the author's to name. */
+const RESERVED_PARAMS = new Set(["synchronous"])
+
 /**
  * A message name, typed freely or picked from the names already in play.
  *
@@ -253,6 +256,172 @@ function PortList({
   )
 }
 
+/** The value types a free-form setting can hold, and how to read one back. */
+const FREE_TYPES = ["text", "number", "on/off", "json"] as const
+type FreeType = (typeof FREE_TYPES)[number]
+
+function freeTypeOf(value: unknown): FreeType {
+  if (typeof value === "boolean") return "on/off"
+  if (typeof value === "number") return "number"
+  if (value !== null && typeof value === "object") return "json"
+  return "text"
+}
+
+function castTo(type: FreeType, raw: string): unknown {
+  if (type === "number") return Number(raw) || 0
+  if (type === "on/off") return raw === "true"
+  if (type === "json") {
+    try {
+      return JSON.parse(raw)
+    } catch {
+      // Half-typed JSON is normal while editing; keep the text until it parses.
+      return raw
+    }
+  }
+  return raw
+}
+
+function asText(value: unknown): string {
+  if (value === null || value === undefined) return ""
+  if (typeof value === "object") return JSON.stringify(value)
+  return String(value)
+}
+
+/**
+ * Settings a node type does not declare.
+ *
+ * A function node's parameters are its author's to name — they arrive in
+ * `process` as whatever was put here — so there is no schema to render and the
+ * keys are typed in alongside the values.
+ */
+function FreeParamsForm({
+  params,
+  reserved,
+  onChange,
+}: {
+  params: Record<string, unknown>
+  reserved: Set<string>
+  onChange: (next: Record<string, unknown>) => void
+}) {
+  const [freshKey, setFreshKey] = useState<string | null>(null)
+  const entries = Object.entries(params).filter(([key]) => !reserved.has(key))
+
+  const rename = (from: string, to: string) => {
+    if (to === from) return
+    // Rebuilt rather than patched, so the settings keep the order they were
+    // typed in instead of jumping around as one is renamed.
+    const next: Record<string, unknown> = {}
+    for (const [key, value] of Object.entries(params)) {
+      next[key === from ? to : key] = value
+    }
+    onChange(next)
+  }
+
+  return (
+    <div className="grid gap-2">
+      <div className="flex items-center justify-between">
+        <span className={SECTION}>Settings</span>
+        <Button
+          variant="ghost"
+          size="sm"
+          className="h-7 text-xs text-muted-foreground"
+          data-testid="add-param"
+          onClick={() => {
+            let name = "setting"
+            for (let i = 2; name in params; i++) name = `setting${i}`
+            setFreshKey(name)
+            onChange({ ...params, [name]: "" })
+          }}
+        >
+          Add
+        </Button>
+      </div>
+
+      {entries.length === 0 ? (
+        <p className="text-sm text-muted-foreground">
+          Values your code reads from <code>params</code>.
+        </p>
+      ) : null}
+
+      {entries.map(([key, value], index) => {
+        const type = freeTypeOf(value)
+        return (
+          // Keyed by position, not by name: renaming a setting must not
+          // remount its row and take the half-typed value with it.
+          <div key={`param-${index}`} className="flex items-center gap-1.5">
+            <Input
+              defaultValue={key}
+              placeholder="name"
+              aria-label="Setting name"
+              autoFocus={key === freshKey}
+              className="h-8 flex-1 text-sm"
+              onBlur={(event) => rename(key, event.target.value.trim() || key)}
+            />
+            <Select
+              value={type}
+              onValueChange={(next) =>
+                onChange({
+                  ...params,
+                  [key]: castTo(next as FreeType, asText(value)),
+                })
+              }
+            >
+              <SelectTrigger
+                className="!h-8 w-[86px] text-sm"
+                aria-label="Type"
+              >
+                <SelectValue />
+              </SelectTrigger>
+              <SelectContent>
+                {FREE_TYPES.map((option) => (
+                  <SelectItem key={option} value={option}>
+                    {option}
+                  </SelectItem>
+                ))}
+              </SelectContent>
+            </Select>
+            {type === "on/off" ? (
+              <Switch
+                checked={value === true}
+                aria-label="Value"
+                onCheckedChange={(checked) =>
+                  onChange({ ...params, [key]: checked })
+                }
+              />
+            ) : (
+              <Input
+                value={asText(value)}
+                placeholder="value"
+                aria-label="Setting value"
+                className="h-8 flex-1 text-sm"
+                onChange={(event) =>
+                  onChange({
+                    ...params,
+                    [key]: castTo(type, event.target.value),
+                  })
+                }
+              />
+            )}
+            <Button
+              variant="ghost"
+              size="icon-sm"
+              className="text-muted-foreground"
+              aria-label="Remove setting"
+              onClick={() => {
+                const next = { ...params }
+                delete next[key]
+                onChange(next)
+              }}
+            >
+              <X />
+            </Button>
+          </div>
+        )
+      })}
+    </div>
+  )
+}
+
 /** A small form built from the node type's declared parameters. */
 function ParamsForm({
   schema,
@@ -557,6 +726,13 @@ function PanelBody({
           params={node.params ?? {}}
           onChange={(params) => onChange({ ...node, params })}
         />
+        {nodeType?.free_params ? (
+          <FreeParamsForm
+            params={node.params ?? {}}
+            reserved={RESERVED_PARAMS}
+            onChange={(params) => onChange({ ...node, params })}
+          />
+        ) : null}
         {hasSource ? (
           <SharingSection flow={flow} node={node} onShared={onShared} />
         ) : null}