(MOT-3882) feat(providers): provider-owned system prompts, operator-overridable

console/web/src/index.css

@@ -318,6 +318,16 @@
   margin: 0;
 }
 
+/* Textarea mode (`format: "textarea"`): wrap instead of scroll sideways,
+   cap the height so a 20k-char prompt doesn't swallow the form. */
+.workers-tab .env-lexical-editor--multiline {
+  white-space: pre-wrap;
+  word-break: break-word;
+  overflow-x: visible;
+  overflow-y: auto;
+  max-height: 24rem;
+}
+
 .workers-tab .env-lexical-placeholder {
   pointer-events: none;
   position: absolute;
@@ -329,6 +339,12 @@
   user-select: none;
   font-family: var(--font-sans);
   font-size: 15px;
+  overflow: hidden; /* never let a long placeholder spill past the box */
+}
+
+.workers-tab .env-lexical-placeholder--multiline {
+  align-items: flex-start;
+  padding-top: 7px;
 }
 
 /* iii-styled <details> rows: hide the native marker, rotate our own chevron */

console/web/src/pages/Configuration/tabs/WorkersTab/schema-form/NullableField.tsx

@@ -1,5 +1,7 @@
+import { useRef } from 'react'
 import { ModeToggle } from '@/components/ui/ModeToggle'
 import { cn } from '@/lib/utils'
+import type { JsonValue } from '../api'
 import { FieldDispatch, type FieldProps } from './FieldDispatch'
 import { FieldShell } from './FieldShell'
 import { pathToDomId } from './path'
@@ -15,12 +17,15 @@ const MODE_OPTIONS: { value: Mode; label: string }[] = [
 /**
  * Wrapper for schemas declared as `type: ["X", "null"]`. Renders a small
  * set/unset toggle on top of the inner field; when "unset" is selected,
- * the value is forced to `null` and the inner field disappears so the
- * operator isn't editing a control whose value is being ignored.
+ * the saved value is forced to `null` and the inner field disappears so
+ * the operator isn't editing a control whose value is being ignored.
  *
- * When the operator flips back to "set", we seed the inner field with
- * the schema-provided default (or a type-appropriate zero) so they don't
- * land on `null` and bounce back to the unset state on the next render.
+ * Flipping to "unset" does NOT discard what was typed: we stash the last
+ * set value in a ref and restore it when the operator flips back to "set",
+ * so toggling the mode is non-destructive. The first "set" (nothing
+ * stashed) seeds the schema default — for a provider `system_prompt`
+ * that's the provider-declared prompt, giving the operator an editable
+ * starting point instead of a blank box.
  */
 export function NullableField(props: FieldProps) {
   const { label, schema, value, onChange, required } = props
@@ -29,13 +34,19 @@ export function NullableField(props: FieldProps) {
   const innerSchema = withoutNull(schema)
   const mode: Mode = value === null || value === undefined ? 'unset' : 'set'
 
+  // Remember the last non-null value so unset→set round-trips the draft.
+  // Kept current on every render while set, so it captures live edits.
+  const lastSetRef = useRef<JsonValue | undefined>(undefined)
+  if (mode === 'set') lastSetRef.current = value
+
   function handleModeChange(next: Mode) {
     if (next === 'unset') {
       onChange(null)
     } else {
-      // Seed with the schema default (or type-appropriate zero) so the
-      // inner field has something to render once it appears.
-      onChange(schemaDefault(innerSchema))
+      // Restore the stashed draft; first time (nothing stashed) fall back
+      // to the schema default (the provider-declared prompt for a slice's
+      // system_prompt) or a type-appropriate zero.
+      onChange(lastSetRef.current ?? schemaDefault(innerSchema))
     }
   }
 

console/web/src/pages/Configuration/tabs/WorkersTab/schema-form/StringField.tsx

@@ -21,6 +21,11 @@ import { pathToDomId } from './path'
  *     structured strings whose grammar conflicts with `${…}` (typing a
  *     date and seeing a piece of it become a pill would be jarring).
  *
+ * `format: "textarea"` renders the same pill editor in multiline mode —
+ * for long-form prose values (system prompts, message templates) where a
+ * single-line input is unusable. Pills and `${VAR}` templating work
+ * exactly as in the single-line editor.
+ *
  * Single-value-enum strings hit `EnumField` via `FieldDispatch`, so we
  * don't need a code branch here.
  */
@@ -41,8 +46,13 @@ export function StringField(props: FieldProps) {
   const description =
     typeof schema.description === 'string' ? schema.description : undefined
   const format = typeof schema.format === 'string' ? schema.format : undefined
+  // In textarea mode the schema default is the editor's seed-on-set value
+  // (a full prompt), never a placeholder hint — showing it as a placeholder
+  // when the field is cleared would spill a multi-KB string out of the box.
   const placeholder =
-    typeof schema.default === 'string' ? schema.default : undefined
+    format !== 'textarea' && typeof schema.default === 'string'
+      ? schema.default
+      : undefined
   const useLexical = !format || !NON_TEMPLATED_FORMATS.has(format)
 
   return (
@@ -61,6 +71,7 @@ export function StringField(props: FieldProps) {
             value={current}
             onChange={onChange}
             placeholder={placeholder}
+            multiline={format === 'textarea'}
             aria-label={label}
           />
         ) : (

console/web/src/pages/Configuration/tabs/WorkersTab/schema-form/env-lexical/EnvLexicalInput.tsx

@@ -7,6 +7,7 @@ import { HistoryPlugin } from '@lexical/react/LexicalHistoryPlugin'
 import { OnChangePlugin } from '@lexical/react/LexicalOnChangePlugin'
 import { PlainTextPlugin } from '@lexical/react/LexicalPlainTextPlugin'
 import {
+  $createLineBreakNode,
   $createParagraphNode,
   $createTextNode,
   $getRoot,
@@ -31,6 +32,13 @@ interface EnvLexicalInputProps {
   onChange: (next: string) => void
   placeholder?: string
   disabled?: boolean
+  /**
+   * Textarea mode for long-form values (`format: "textarea"`): Enter
+   * inserts a line break instead of being swallowed, text wraps, and the
+   * surface grows to several rows. Newlines round-trip as `\n` — the
+   * single paragraph gains `LineBreakNode`s, whose text content is `\n`.
+   */
+  multiline?: boolean
   /** Forwarded to the underlying content-editable surface. */
   'aria-label'?: string
 }
@@ -64,6 +72,7 @@ export function EnvLexicalInput({
   onChange,
   placeholder,
   disabled,
+  multiline,
   'aria-label': ariaLabel,
 }: EnvLexicalInputProps) {
   // Track the value we last emitted so we can detect external changes
@@ -95,9 +104,9 @@ export function EnvLexicalInput({
     <LexicalComposer initialConfig={initialConfig}>
       <div
         className={cn(
-          'relative w-full border border-rule bg-bg px-3 min-h-9 text-ink',
+          'relative w-full border border-rule bg-bg px-3 text-ink',
           'focus-within:border-ink transition-colors',
-          'flex items-center',
+          multiline ? 'min-h-36 flex items-start' : 'min-h-9 flex items-center',
           disabled && 'opacity-40 pointer-events-none',
         )}
       >
@@ -108,19 +117,27 @@ export function EnvLexicalInput({
               aria-label={ariaLabel}
               aria-placeholder={placeholder ?? ''}
               placeholder={
-                <div className="env-lexical-placeholder">
+                <div
+                  className={cn(
+                    'env-lexical-placeholder',
+                    multiline && 'env-lexical-placeholder--multiline',
+                  )}
+                >
                   {placeholder ?? ''}
                 </div>
               }
-              className="env-lexical-editor flex-1 py-[7px] outline-none"
+              className={cn(
+                'env-lexical-editor flex-1 py-[7px] outline-none',
+                multiline && 'env-lexical-editor--multiline',
+              )}
             />
           }
           ErrorBoundary={LexicalErrorBoundary}
         />
         <HistoryPlugin />
         <ClearEditorPlugin />
         <EnvPlaceholderTransformPlugin />
-        <SingleLinePlugin />
+        {!multiline && <SingleLinePlugin />}
         <EditablePlugin disabled={disabled} />
         <ChangePlugin
           onChange={(text) => {
@@ -216,16 +233,20 @@ function ExternalValueSyncPlugin({
  * One-shot initializer: clear the editor and rebuild a single paragraph
  * with text + env-placeholder pills based on the template string. Used
  * both at mount (via `initialConfig.editorState`) and on external resync.
+ * Newlines inside text segments become `LineBreakNode`s so multiline
+ * values render as lines and still round-trip to `\n` via getTextContent.
  */
 function seedEditorFromTemplate(editor: LexicalEditor, template: string) {
   const root = $getRoot()
   root.clear()
   const paragraph = $createParagraphNode()
   for (const segment of parseTemplate(template)) {
     if (segment.kind === 'text') {
-      if (segment.text.length > 0) {
-        paragraph.append($createTextNode(segment.text))
-      }
+      const lines = segment.text.split('\n')
+      lines.forEach((line, i) => {
+        if (i > 0) paragraph.append($createLineBreakNode())
+        if (line.length > 0) paragraph.append($createTextNode(line))
+      })
     } else {
       paragraph.append(
         $createEnvPlaceholderNode(segment.variable, segment.defaultValue),

harness/README.md

@@ -150,15 +150,21 @@ retries) and their defaults live in [`src/config.rs`](src/config.rs).
 
 ## System prompt
 
-When `options.system_prompt` is omitted (or empty), the harness assembles the
-engine-grounded identity prompt at send time: four provider-specific variants
-(`anthropic`, `openai` → gpt, `kimi`, and a step-by-step default for local
-runtimes) selected from `provider`, plus an optional `mode` (`plan` | `ask` |
-`agent`) that prepends a short operating-mode paragraph. A non-empty
-`system_prompt` is combined with the default prompt per
-`options.system_prompt_strategy`: `override` (default) uses it verbatim, while
-`enrich` appends it to the default prompt. Prompt bodies live in
-[`prompts/`](prompts/) and are tested in [`src/prompt/tests.rs`](src/prompt/tests.rs).
+The identity prompt is assembled once at send/spawn time. The harness asks the
+llm-router for the effective per-provider prompt (`router::system_prompt::get`
+with the request's `provider`): provider workers declare their own identity
+prompt at registration, and operators can override it per provider by setting
+`system_prompt` in the `llm-router` configuration entry (unset = provider
+default). When the router serves nothing — router absent, unknown provider,
+or no declared prompt — the harness falls back to its embedded step-by-step
+default prompt ([`prompts/default.txt`](prompts/default.txt)).
+
+An optional `mode` (`plan` | `ask` | `agent`) prepends a short operating-mode
+paragraph. A non-empty `options.system_prompt` is combined with the built-in
+prompt per `options.system_prompt_strategy`: `enrich` (default) appends it to
+the built-in prompt, while `override` uses it verbatim. Assembly is tested in
+[`src/prompt/tests.rs`](src/prompt/tests.rs); provider-specific prompt bodies
+live in each provider worker (`provider-*/prompts/identity.txt`).
 
 ## Custom trigger types