diff --git a/src/admin/resource-types.ts b/src/admin/resource-types.ts
new file mode 100644
index 0000000..60aa094
--- /dev/null
+++ b/src/admin/resource-types.ts
@@ -0,0 +1,295 @@
+/* ---------------------------------------------------------------------------
+ * Resource type definitions for the Backstage admin surface.
+ *
+ * Every admin-managed entity is declared as a single Resource<T> object.
+ * The shared components (AdminLayout, ResourceListView, ResourceEditPanel)
+ * consume these objects and never know about specific entities.
+ *
+ * Adding a new entity = write a Resource config + register it. That is the
+ * load-bearing invariant of the rebuild.
+ * ------------------------------------------------------------------------- */
+
+// ── Option (used for select / select-async / multi-select-async) ────────────
+export interface Option<V = string | number> {
+  value: V;
+  label: string;
+}
+
+// ── Pill variants (status/kind columns + pill display elsewhere) ────────────
+export interface PillVariant {
+  label: string;
+  /** CSS class defined in src/admin/admin.css — e.g. 'pill-published'. */
+  class: string;
+}
+export type PillVariants = Record<string, PillVariant>;
+
+// ── Field context — passed to visibleWhen / defaultValue resolvers ──────────
+export interface FieldContext {
+  /** Current form values keyed by field.key. */
+  formValues: Record<string, unknown>;
+  /** The item being edited, or null on create. */
+  item: Record<string, unknown> | null;
+  /** Acting admin's user id, available for current-user defaults. */
+  actingUserId: number;
+}
+
+// ── Fields ──────────────────────────────────────────────────────────────────
+interface FieldBase {
+  key: string;
+  label: string;
+  required?: boolean;
+  helperText?: string;
+  /** Default for create. Can be a literal or a resolver receiving FieldContext. */
+  defaultValue?: unknown | ((ctx: FieldContext) => unknown);
+  /** Hide the field entirely when this returns false. Re-evaluated on every render. */
+  visibleWhen?: (ctx: FieldContext) => boolean;
+  /** Display the field but disable editing. */
+  readOnly?: boolean;
+}
+
+export interface TextField extends FieldBase {
+  kind: 'text';
+  maxLength?: number;
+  pattern?: RegExp;
+  placeholder?: string;
+}
+export interface TextareaField extends FieldBase {
+  kind: 'textarea';
+  rows?: number;
+  maxLength?: number;
+  placeholder?: string;
+}
+export interface MarkdownField extends FieldBase {
+  kind: 'markdown';
+  rows?: number;
+  maxLength?: number;
+}
+export interface SelectField extends FieldBase {
+  kind: 'select';
+  options: Option[];
+}
+export interface SelectAsyncField extends FieldBase {
+  kind: 'select-async';
+  loadOptions: () => Promise<Option[]> | Option[];
+}
+export interface MultiSelectAsyncField extends FieldBase {
+  kind: 'multi-select-async';
+  loadOptions: () => Promise<Option[]> | Option[];
+}
+/** Series of free-text inputs — used for pulse options (2–4 entries). */
+export interface MultiTextField extends FieldBase {
+  kind: 'multi-text';
+  minItems?: number;
+  maxItems?: number;
+  placeholderEach?: string;
+}
+export interface DateField extends FieldBase {
+  kind: 'date';
+}
+export interface DatetimeField extends FieldBase {
+  kind: 'datetime';
+}
+export interface NumberField extends FieldBase {
+  kind: 'number';
+  min?: number;
+  max?: number;
+  step?: number;
+}
+/** Display-only — never edited; renders the value verbatim or via render(). */
+export interface ReadonlyField extends FieldBase {
+  kind: 'readonly';
+  render?: (value: unknown, item: Record<string, unknown> | null) => string;
+}
+
+export type Field =
+  | TextField
+  | TextareaField
+  | MarkdownField
+  | SelectField
+  | SelectAsyncField
+  | MultiSelectAsyncField
+  | MultiTextField
+  | DateField
+  | DatetimeField
+  | NumberField
+  | ReadonlyField;
+
+// ── Columns ─────────────────────────────────────────────────────────────────
+interface ColumnBase {
+  key: string;
+  label: string;
+  /** CSS grid-template-columns track (e.g. '1.7fr', '120px'). */
+  width?: string;
+  /** Primary column gets the larger title styling. At most one per columns array. */
+  primary?: boolean;
+  /** When set, the list can be sorted by this column. */
+  sortable?: boolean;
+}
+
+export interface TextColumn<T> extends ColumnBase {
+  kind?: 'text';
+  /** Override the default <td>{item[key]}</td> rendering. */
+  render?: (item: T) => { title: string; subtitle?: string };
+}
+export interface PillColumn<T> extends ColumnBase {
+  kind: 'pill';
+  pillVariants: PillVariants;
+  /** Override which value to look up in pillVariants (default = item[key]). */
+  valueOf?: (item: T) => string;
+}
+export interface RelativeDateColumn<T> extends ColumnBase {
+  kind: 'relative-date';
+  /** Shown when the value is null/undefined. */
+  emptyFallback?: string;
+  valueOf?: (item: T) => string | null | undefined;
+}
+export interface NumberColumn<T> extends ColumnBase {
+  kind: 'number';
+  valueOf?: (item: T) => number | null | undefined;
+}
+/** Compact list of pills — for focus_tags, audience, etc. */
+export interface TagListColumn<T> extends ColumnBase {
+  kind: 'tag-list';
+  valueOf: (item: T) => string[];
+}
+
+export type Column<T> =
+  | TextColumn<T>
+  | PillColumn<T>
+  | RelativeDateColumn<T>
+  | NumberColumn<T>
+  | TagListColumn<T>;
+
+// ── Filters ─────────────────────────────────────────────────────────────────
+export interface Filter<T> {
+  key: string;
+  label: string;
+  predicate: (item: T) => boolean;
+  isDefault?: boolean;
+}
+
+// ── Search ──────────────────────────────────────────────────────────────────
+export interface SearchConfig<T> {
+  placeholder: string;
+  /** Object keys to search; coerced to string and matched case-insensitively. */
+  fields: (keyof T & string)[];
+}
+
+// ── Sort ────────────────────────────────────────────────────────────────────
+export interface SortConfig {
+  key: string;
+  direction: 'asc' | 'desc';
+}
+
+// ── List view config ────────────────────────────────────────────────────────
+export interface ListConfig<T> {
+  queryFn: () => T[] | Promise<T[]>;
+  /** Default column set. */
+  columns: Column<T>[];
+  /**
+   * Override columns when a specific filter is active. The key matches a
+   * Filter.key. Used by the Users resource (council vs pilots) to swap
+   * member_number/focus_tags for role/last_seen_at.
+   */
+  columnsByFilter?: Record<string, Column<T>[]>;
+  filters?: Filter<T>[];
+  search?: SearchConfig<T>;
+  defaultSort?: SortConfig;
+  pageSize?: number;
+}
+
+// ── Embedded sub-forms (the Pulse fieldset inside dispatch edit) ────────────
+export interface FormEmbed {
+  /** Unique key inside the parent form. */
+  key: string;
+  title: string;
+  /**
+   * Discriminator the panel uses to pick a renderer component.
+   * Keep this small — new embed kinds are explicit additions, not generic.
+   */
+  component: 'pulse-sub-form';
+  visibleWhen?: (ctx: FieldContext) => boolean;
+}
+
+// ── Form config ─────────────────────────────────────────────────────────────
+export interface FormConfig {
+  fields: Field[];
+  /** Optional embedded sub-form sections (e.g. pulse inside dispatch). */
+  embeds?: FormEmbed[];
+}
+
+// ── Op context — passed to CRUD ops and actions ─────────────────────────────
+export interface OpContext {
+  user: { id: number; role: string };
+}
+
+// ── CRUD operations ─────────────────────────────────────────────────────────
+export interface ResourceOps<T> {
+  /** Returns the new item's id. */
+  create?: (data: Record<string, unknown>, ctx: OpContext) => number | Promise<number>;
+  update?: (id: number, data: Record<string, unknown>, ctx: OpContext) => void | Promise<void>;
+  delete?: (id: number, ctx: OpContext) => void | Promise<void>;
+  getById?: (id: number) => T | null | Promise<T | null>;
+}
+
+// ── Action results — surfaced inside the edit panel ─────────────────────────
+/** No additional UI — just close the panel with a toast. */
+export interface ActionResultToast {
+  kind: 'toast';
+}
+/** Render the generated invite link in the panel with a Copy button. */
+export interface ActionResultInviteLink {
+  kind: 'invite-link';
+  url: string;
+}
+export type ActionResult = ActionResultToast | ActionResultInviteLink;
+
+// ── Actions (publish, archive, approve, etc.) ───────────────────────────────
+export interface ResourceAction<T> {
+  key: string;
+  label: string;
+  /** Hide the action when this returns false for the current item. */
+  visibleWhen?: (item: T) => boolean;
+  /** Confirm dialog text. If omitted, no confirmation is shown. */
+  confirmText?: string;
+  /** Destructive actions render in terracotta. */
+  destructive?: boolean;
+  handler: (id: number, ctx: OpContext) => ActionResult | void | Promise<ActionResult | void>;
+}
+
+// ── Notification count (sidebar badge in terracotta if > 0) ─────────────────
+export interface NotifyCount<T> {
+  /** Return the count of items needing attention (pending requests, stale drafts, etc.). */
+  count: (items: T[]) => number;
+}
+
+// ── Resource ────────────────────────────────────────────────────────────────
+export interface Resource<T = Record<string, unknown>> {
+  /** URL slug — /admin/<key>. */
+  key: string;
+  label: string;
+  pluralLabel: string;
+  singularLabel: string;
+  /** Matches a ResourceGroup.key in the registry. */
+  groupKey: string;
+  /** Optional one-line subtitle under the page title. */
+  description?: string;
+  /** Returns the member-facing URL for an item (for the "View on portal" link). */
+  publicRoutePattern?: (item: T) => string | null;
+  list: ListConfig<T>;
+  /** null marks the resource as read-only (no edit panel, no "+ New" button). */
+  form: FormConfig | null;
+  ops: ResourceOps<T>;
+  actions?: ResourceAction<T>[];
+  notifyCount?: NotifyCount<T>;
+}
+
+// ── Resource groups (sidebar sections) ──────────────────────────────────────
+export interface ResourceGroup {
+  key: string;
+  label: string;
+  // Each resource carries its own item type. Erase the generic at the
+  // registration boundary so different resources can coexist in one array.
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  resources: Resource<any>[];
+}
diff --git a/src/admin/validate.ts b/src/admin/validate.ts
new file mode 100644
index 0000000..e1caee4
--- /dev/null
+++ b/src/admin/validate.ts
@@ -0,0 +1,116 @@
+/* ---------------------------------------------------------------------------
+ * Form validation derived from a Resource's field definitions.
+ *
+ * Returns a map of field.key → error message. Empty object = valid.
+ * Server-side authoritative; the client may show hints, but every POST
+ * must call this before writing to the DB.
+ * ------------------------------------------------------------------------- */
+
+import type { Field, FieldContext, Resource } from './resource-types';
+
+export type ValidationErrors = Record<string, string>;
+
+export interface ValidateArgs {
+  resource: Resource;
+  data: Record<string, unknown>;
+  /** Existing item being edited, or null on create. */
+  item: Record<string, unknown> | null;
+  actingUserId: number;
+}
+
+export function validateForResource(args: ValidateArgs): ValidationErrors {
+  const { resource, data, item, actingUserId } = args;
+  const errors: ValidationErrors = {};
+
+  if (!resource.form) return errors;
+
+  const ctx: FieldContext = { formValues: data, item, actingUserId };
+
+  for (const field of resource.form.fields) {
+    if (field.readOnly) continue;
+    if (field.visibleWhen && !field.visibleWhen(ctx)) continue;
+
+    const value = data[field.key];
+    const error = validateField(field, value);
+    if (error) errors[field.key] = error;
+  }
+
+  return errors;
+}
+
+function validateField(field: Field, value: unknown): string | null {
+  const isEmpty =
+    value === undefined ||
+    value === null ||
+    value === '' ||
+    (Array.isArray(value) && value.length === 0);
+
+  if (field.required && isEmpty) {
+    return `${field.label} is required`;
+  }
+  if (isEmpty) return null;
+
+  switch (field.kind) {
+    case 'text':
+    case 'textarea':
+    case 'markdown': {
+      if (typeof value !== 'string') return `${field.label} must be text`;
+      if ('maxLength' in field && field.maxLength && value.length > field.maxLength) {
+        return `${field.label} must be ${field.maxLength} characters or fewer`;
+      }
+      if (field.kind === 'text' && field.pattern && !field.pattern.test(value)) {
+        return `${field.label} is not in the expected format`;
+      }
+      return null;
+    }
+
+    case 'select':
+    case 'select-async': {
+      // Empty already handled. Anything else is accepted at the validate layer;
+      // option membership is enforced by the route handler against a fresh option list.
+      return null;
+    }
+
+    case 'multi-select-async': {
+      if (!Array.isArray(value)) return `${field.label} must be a list`;
+      return null;
+    }
+
+    case 'multi-text': {
+      if (!Array.isArray(value)) return `${field.label} must be a list`;
+      const filled = value.filter(
+        (v) => typeof v === 'string' && v.trim() !== '',
+      );
+      if (field.minItems !== undefined && filled.length < field.minItems) {
+        return `${field.label} requires at least ${field.minItems} entries`;
+      }
+      if (field.maxItems !== undefined && filled.length > field.maxItems) {
+        return `${field.label} allows at most ${field.maxItems} entries`;
+      }
+      return null;
+    }
+
+    case 'number': {
+      const n = typeof value === 'number' ? value : Number(value);
+      if (!Number.isFinite(n)) return `${field.label} must be a number`;
+      if (field.min !== undefined && n < field.min) {
+        return `${field.label} must be at least ${field.min}`;
+      }
+      if (field.max !== undefined && n > field.max) {
+        return `${field.label} must be no more than ${field.max}`;
+      }
+      return null;
+    }
+
+    case 'date':
+    case 'datetime': {
+      if (typeof value !== 'string') return `${field.label} must be a date`;
+      const t = Date.parse(value);
+      if (Number.isNaN(t)) return `${field.label} is not a valid date`;
+      return null;
+    }
+
+    case 'readonly':
+      return null;
+  }
+}
diff --git a/tests/admin-validate.test.ts b/tests/admin-validate.test.ts
new file mode 100644
index 0000000..fc2140e
--- /dev/null
+++ b/tests/admin-validate.test.ts
@@ -0,0 +1,113 @@
+import { describe, it, expect } from 'vitest';
+import { validateForResource } from '../src/admin/validate';
+import type { Resource } from '../src/admin/resource-types';
+
+// Minimal resource fixture covering the field kinds the validator handles.
+const resource: Resource = {
+  key: 'fixtures',
+  label: 'Fixture',
+  pluralLabel: 'Fixtures',
+  singularLabel: 'Fixture',
+  groupKey: 'system',
+  list: { queryFn: () => [], columns: [] },
+  ops: {},
+  form: {
+    fields: [
+      { key: 'title', label: 'Title', kind: 'text', required: true, maxLength: 5 },
+      { key: 'kind', label: 'Kind', kind: 'select', options: [{ value: 'a', label: 'A' }] },
+      {
+        key: 'options',
+        label: 'Options',
+        kind: 'multi-text',
+        minItems: 2,
+        maxItems: 4,
+      },
+      { key: 'count', label: 'Count', kind: 'number', min: 0, max: 10 },
+      {
+        key: 'extras',
+        label: 'Extras',
+        kind: 'text',
+        // Only visible when kind === 'a'
+        visibleWhen: (ctx) => ctx.formValues.kind === 'a',
+        required: true,
+      },
+    ],
+  },
+};
+
+const baseArgs = { resource, item: null, actingUserId: 1 };
+
+describe('validateForResource', () => {
+  it('reports required fields that are empty', () => {
+    const errors = validateForResource({ ...baseArgs, data: {} });
+    expect(errors.title).toBe('Title is required');
+  });
+
+  it('reports maxLength violations on text fields', () => {
+    const errors = validateForResource({ ...baseArgs, data: { title: 'too long' } });
+    expect(errors.title).toMatch(/5 characters or fewer/);
+  });
+
+  it('skips fields hidden by visibleWhen', () => {
+    // kind = 'b' hides the 'extras' required field — no error expected
+    const errors = validateForResource({
+      ...baseArgs,
+      data: { title: 'ok', kind: 'b' },
+    });
+    expect(errors.extras).toBeUndefined();
+  });
+
+  it('enforces visibleWhen-revealed required fields', () => {
+    const errors = validateForResource({
+      ...baseArgs,
+      data: { title: 'ok', kind: 'a' },
+    });
+    expect(errors.extras).toBe('Extras is required');
+  });
+
+  it('enforces multi-text min/max items', () => {
+    const tooFew = validateForResource({
+      ...baseArgs,
+      data: { title: 'ok', options: ['only-one'] },
+    });
+    expect(tooFew.options).toMatch(/at least 2/);
+
+    const tooMany = validateForResource({
+      ...baseArgs,
+      data: { title: 'ok', options: ['1', '2', '3', '4', '5'] },
+    });
+    expect(tooMany.options).toMatch(/at most 4/);
+  });
+
+  it('enforces number min/max', () => {
+    const tooHigh = validateForResource({
+      ...baseArgs,
+      data: { title: 'ok', count: 99 },
+    });
+    expect(tooHigh.count).toMatch(/no more than 10/);
+  });
+
+  it('returns no errors when every field is valid', () => {
+    const errors = validateForResource({
+      ...baseArgs,
+      data: {
+        title: 'ok',
+        kind: 'a',
+        options: ['x', 'y'],
+        count: 5,
+        extras: 'fine',
+      },
+    });
+    expect(errors).toEqual({});
+  });
+
+  it('treats form: null as always valid', () => {
+    const readOnly: Resource = { ...resource, form: null };
+    const errors = validateForResource({
+      ...baseArgs,
+      resource: readOnly,
+      data: {},
+    });
+    expect(errors).toEqual({});
+  });
+});