diff --git a/bun.lock b/bun.lock
index c7c16ff..22a8e7d 100644
--- a/bun.lock
+++ b/bun.lock
@@ -13,6 +13,7 @@
         "@sveltejs/adapter-node": "^5.5.4",
         "@sveltejs/kit": "^2.15.0",
         "@sveltejs/vite-plugin-svelte": "^5.0.0",
+        "@types/bun": "^1.3.13",
         "svelte": "^5.0.0",
         "svelte-check": "^4.0.0",
         "typescript": "^5.0.0",
@@ -169,6 +170,8 @@
 
     "@sveltejs/vite-plugin-svelte-inspector": ["@sveltejs/vite-plugin-svelte-inspector@4.0.1", "", { "dependencies": { "debug": "^4.3.7" }, "peerDependencies": { "@sveltejs/vite-plugin-svelte": "^5.0.0", "svelte": "^5.0.0", "vite": "^6.0.0" } }, "sha512-J/Nmb2Q2y7mck2hyCX4ckVHcR5tu2J+MtBEQqpDrrgELZ2uvraQcK/ioCV61AqkdXFgriksOKIceDcQmqnGhVw=="],
 
+    "@types/bun": ["@types/bun@1.3.13", "", { "dependencies": { "bun-types": "1.3.13" } }, "sha512-9fqXWk5YIHGGnUau9TEi+qdlTYDAnOj+xLCmSTwXfAIqXr2x4tytJb43E9uCvt09zJURKXwAtkoH4nLQfzeTXw=="],
+
     "@types/cookie": ["@types/cookie@0.6.0", "", {}, "sha512-4Kh9a6B2bQciAhf7FSuMRRkUWecJgJu9nPnx3yzpsfXX/c50REIqpHY4C82bXP90qrLtXtkDxTZosYO3UpOwlA=="],
 
     "@types/estree": ["@types/estree@1.0.8", "", {}, "sha512-dWHzHa2WqEXI/O1E9OjrocMTKJl2mSrEolh1Iomrv6U+JuNwaHXsXx9bLu5gG7BUWFIN0skIQJQ/L1rIex4X6w=="],
@@ -187,6 +190,8 @@
 
     "axobject-query": ["axobject-query@4.1.0", "", {}, "sha512-qIj0G9wZbMGNLjLmg1PT6v2mE9AH2zlnADJD/2tC6E00hgmhUOfEB6greHPAfLRSufHqROIUTkw6E+M3lH0PTQ=="],
 
+    "bun-types": ["bun-types@1.3.13", "", { "dependencies": { "@types/node": "*" } }, "sha512-QXKeHLlOLqQX9LgYaHJfzdBaV21T63HhFJnvuRCcjZiaUDpbs5ED1MgxbMra71CsryN/1dAoXuJJJwIv/2drVA=="],
+
     "chokidar": ["chokidar@4.0.3", "", { "dependencies": { "readdirp": "^4.0.1" } }, "sha512-Qgzu8kfBvo+cA4962jnP1KkS6Dop5NS6g7R5LFYJr4b8Ub94PPQXUksCw9PvXoeXPRRddRNC5C1JQUR2SMGtnA=="],
 
     "clsx": ["clsx@2.1.1", "", {}, "sha512-eYm0QWBtUrBWZWG0d386OGAw16Z995PiOVo2B7bjWSbHedGl5e0ZWaq65kOGgUSNesEIDkB9ISbTg/JK9dhCZA=="],
diff --git a/package.json b/package.json
index ac381b4..b517511 100644
--- a/package.json
+++ b/package.json
@@ -15,6 +15,7 @@
 		"@sveltejs/adapter-node": "^5.5.4",
 		"@sveltejs/kit": "^2.15.0",
 		"@sveltejs/vite-plugin-svelte": "^5.0.0",
+		"@types/bun": "^1.3.13",
 		"svelte": "^5.0.0",
 		"svelte-check": "^4.0.0",
 		"typescript": "^5.0.0",
diff --git a/src/lib/server/feedback.ts b/src/lib/server/feedback.ts
new file mode 100644
index 0000000..e82137e
--- /dev/null
+++ b/src/lib/server/feedback.ts
@@ -0,0 +1,64 @@
+/**
+ * Feedback feature — DB helpers + slug generator + rate-limit constants.
+ *
+ * Public participant routes and m's admin routes share the same primitives.
+ */
+import { randomBytes } from 'node:crypto';
+import { fdb } from './fdb';
+
+const BASE62_ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+const SLUG_LENGTH = 32;
+
+export const RATE_LIMIT = {
+	post: { max: 30, windowMs: 5 * 60_000 },
+	submit: { max: 10, windowMs: 5 * 60_000 },
+};
+
+/** 32-char base62 slug — ~190 bits of entropy. */
+export function generateSlug(): string {
+	const buf = randomBytes(SLUG_LENGTH * 2);
+	let out = '';
+	for (let i = 0; i < SLUG_LENGTH; i++) {
+		out += BASE62_ALPHABET[buf[i] % BASE62_ALPHABET.length];
+	}
+	return out;
+}
+
+export interface FeedbackInstance {
+	id: string;
+	slug: string;
+	title: string;
+	description: string | null;
+	owner_user_id: string;
+	form_definition: unknown | null;
+	chat_enabled: boolean;
+	status: 'open' | 'closed';
+	closed_at: string | null;
+	created_at: string;
+	updated_at: string;
+}
+
+export async function getInstanceBySlug(slug: string): Promise<FeedbackInstance | null> {
+	const { data, error } = await fdb()
+		.from('feedback_instances')
+		.select('*')
+		.eq('slug', slug)
+		.maybeSingle();
+	if (error) throw error;
+	return data as FeedbackInstance | null;
+}
+
+export async function getInstanceById(id: string): Promise<FeedbackInstance | null> {
+	const { data, error } = await fdb()
+		.from('feedback_instances')
+		.select('*')
+		.eq('id', id)
+		.maybeSingle();
+	if (error) throw error;
+	return data as FeedbackInstance | null;
+}
+
+export function clampUserAgent(ua: string | null): string | null {
+	if (!ua) return null;
+	return ua.slice(0, 500);
+}
diff --git a/src/lib/server/public-scope.test.ts b/src/lib/server/public-scope.test.ts
new file mode 100644
index 0000000..51a376f
--- /dev/null
+++ b/src/lib/server/public-scope.test.ts
@@ -0,0 +1,110 @@
+import { describe, test, expect } from 'bun:test';
+import {
+	evaluatePolicy,
+	isAllowlisted,
+	isApiPath,
+	PUBLIC_API_ALLOWLIST,
+} from './public-scope';
+import type { RequestState } from './request-context';
+
+function makeState(over: Partial<RequestState> = {}): RequestState {
+	return {
+		pathname: '/api/test',
+		method: 'GET',
+		userId: null,
+		authChecked: false,
+		dbAccessed: false,
+		visibilityFiltered: false,
+		...over,
+	};
+}
+
+describe('isApiPath', () => {
+	test('matches /api/* prefixes', () => {
+		expect(isApiPath('/api/foo')).toBe(true);
+		expect(isApiPath('/api/')).toBe(true);
+		expect(isApiPath('/foo')).toBe(false);
+	});
+});
+
+describe('isAllowlisted', () => {
+	test.each([
+		['/api/auth/sign-in', true],
+		['/api/auth', true],
+		['/api/public/feedback/abc', true],
+		['/api/public/feedback/abc/posts', true],
+		['/api/public', true],
+		['/api/admin/feedback', false],
+		['/api/admin/feedback/123', false],
+		['/api/authority', false], // must NOT match prefix-only
+		['/api/publication', false],
+	] as [string, boolean][])('%s → %s', (path: string, expected: boolean) => {
+		expect(isAllowlisted(path)).toBe(expected);
+	});
+
+	test('allowlist non-empty', () => {
+		expect(PUBLIC_API_ALLOWLIST.length).toBeGreaterThan(0);
+	});
+});
+
+describe('evaluatePolicy', () => {
+	test('non-api → allow', () => {
+		const d = evaluatePolicy({
+			pathname: '/about',
+			userId: null,
+			responseStatus: 200,
+			state: makeState(),
+		});
+		expect(d.allow).toBe(true);
+	});
+
+	test('authenticated /api/* → allow', () => {
+		const d = evaluatePolicy({
+			pathname: '/api/admin/feedback',
+			userId: 'u1',
+			responseStatus: 200,
+			state: makeState({ userId: 'u1', dbAccessed: true }),
+		});
+		expect(d.allow).toBe(true);
+	});
+
+	test('allowlisted /api/public/* → allow', () => {
+		const d = evaluatePolicy({
+			pathname: '/api/public/feedback/abc',
+			userId: null,
+			responseStatus: 200,
+			state: makeState({ pathname: '/api/public/feedback/abc', dbAccessed: true }),
+		});
+		expect(d.allow).toBe(true);
+	});
+
+	test('anonymous DB access without filter → block', () => {
+		const d = evaluatePolicy({
+			pathname: '/api/admin/feedback',
+			userId: null,
+			responseStatus: 200,
+			state: makeState({ dbAccessed: true }),
+		});
+		expect(d.allow).toBe(false);
+	});
+
+	test('anonymous, no DB access → allow', () => {
+		const d = evaluatePolicy({
+			pathname: '/api/admin/feedback',
+			userId: null,
+			responseStatus: 200,
+			state: makeState({ dbAccessed: false }),
+		});
+		expect(d.allow).toBe(true);
+	});
+
+	test('error response (>=400) → allow (let handler stand)', () => {
+		const d = evaluatePolicy({
+			pathname: '/api/admin/feedback',
+			userId: null,
+			responseStatus: 401,
+			state: makeState({ dbAccessed: true }),
+		});
+		expect(d.allow).toBe(true);
+	});
+});
diff --git a/src/lib/server/rate-limit.test.ts b/src/lib/server/rate-limit.test.ts
new file mode 100644
index 0000000..48139f9
--- /dev/null
+++ b/src/lib/server/rate-limit.test.ts
@@ -0,0 +1,35 @@
+import { describe, test, expect, beforeEach } from 'bun:test';
+import { checkRate, _resetRateLimitForTests } from './rate-limit';
+
+// generateSlug lives in feedback.ts which transitively imports $env/dynamic/private
+// (via flex → supabase). bun:test can't resolve SvelteKit's virtual modules, so the
+// slug generator is exercised at runtime via the create-instance integration path
+// rather than here. The rate limiter is pure and lives in its own module.
+
+describe('checkRate', () => {
+	beforeEach(() => _resetRateLimitForTests());
+
+	test('allows up to max calls, then blocks', () => {
+		const opts = { max: 3, windowMs: 60_000 };
+		expect(checkRate('k', opts)).toBe(true);
+		expect(checkRate('k', opts)).toBe(true);
+		expect(checkRate('k', opts)).toBe(true);
+		expect(checkRate('k', opts)).toBe(false);
+	});
+
+	test('different keys are independent', () => {
+		const opts = { max: 1, windowMs: 60_000 };
+		expect(checkRate('a', opts)).toBe(true);
+		expect(checkRate('b', opts)).toBe(true);
+		expect(checkRate('a', opts)).toBe(false);
+		expect(checkRate('b', opts)).toBe(false);
+	});
+
+	test('window reset re-allows calls', async () => {
+		const opts = { max: 1, windowMs: 10 };
+		expect(checkRate('w', opts)).toBe(true);
+		expect(checkRate('w', opts)).toBe(false);
+		await new Promise((r) => setTimeout(r, 20));
+		expect(checkRate('w', opts)).toBe(true);
+	});
+});
diff --git a/src/lib/server/rate-limit.ts b/src/lib/server/rate-limit.ts
new file mode 100644
index 0000000..5635c39
--- /dev/null
+++ b/src/lib/server/rate-limit.ts
@@ -0,0 +1,53 @@
+/**
+ * In-memory per-key rate limiter with sliding window.
+ *
+ * Lives in the SvelteKit Node process — sufficient for single-instance deploys.
+ * If the app ever scales horizontally, replace with Redis or a DB-backed store
+ * keyed the same way.
+ *
+ * Usage:
+ *   const allowed = checkRate(`fb:post:${ip}:${slug}`, { max: 30, windowMs: 5*60_000 });
+ *   if (!allowed) return tooMany();
+ */
+
+interface Bucket {
+	count: number;
+	resetAt: number;
+}
+
+const buckets = new Map<string, Bucket>();
+
+const MAX_BUCKETS = 10_000;
+
+function sweep(now: number): void {
+	if (buckets.size < MAX_BUCKETS) return;
+	for (const [key, b] of buckets) {
+		if (b.resetAt <= now) buckets.delete(key);
+	}
+}
+
+export interface RateOpts {
+	max: number;
+	windowMs: number;
+}
+
+export function checkRate(key: string, opts: RateOpts): boolean {
+	const now = Date.now();
+	const existing = buckets.get(key);
+
+	if (!existing || existing.resetAt <= now) {
+		sweep(now);
+		buckets.set(key, { count: 1, resetAt: now + opts.windowMs });
+		return true;
+	}
+
+	if (existing.count >= opts.max) return false;
+
+	existing.count += 1;
+	return true;
+}
+
+/** Test-only: reset all buckets. */
+export function _resetRateLimitForTests(): void {
+	buckets.clear();
+}
diff --git a/src/lib/server/schemas.ts b/src/lib/server/schemas.ts
new file mode 100644
index 0000000..a2599f9
--- /dev/null
+++ b/src/lib/server/schemas.ts
@@ -0,0 +1,109 @@
+/**
+ * Zod schemas for fdbck request body validation.
+ */
+import { z } from 'zod';
+
+const FeedbackQuestionBaseSchema = z.object({
+	id: z.string().min(1).max(64),
+	label: z.string().min(1).max(200),
+	required: z.boolean().optional(),
+	help: z.string().max(500).optional(),
+});
+
+export const FeedbackQuestionSchema = z.discriminatedUnion('type', [
+	FeedbackQuestionBaseSchema.extend({
+		type: z.literal('short_text'),
+		placeholder: z.string().max(100).optional(),
+	}),
+	FeedbackQuestionBaseSchema.extend({
+		type: z.literal('long_text'),
+		placeholder: z.string().max(100).optional(),
+	}),
+	FeedbackQuestionBaseSchema.extend({
+		type: z.literal('single_choice'),
+		options: z.array(z.string().min(1).max(200)).min(2).max(20),
+	}),
+	FeedbackQuestionBaseSchema.extend({
+		type: z.literal('multi_choice'),
+		options: z.array(z.string().min(1).max(200)).min(2).max(20),
+	}),
+	FeedbackQuestionBaseSchema.extend({
+		type: z.literal('scale'),
+		min: z.number().int().min(0).max(100),
+		max: z.number().int().min(1).max(100),
+		min_label: z.string().max(50).optional(),
+		max_label: z.string().max(50).optional(),
+	}),
+	FeedbackQuestionBaseSchema.extend({
+		type: z.literal('boolean'),
+	}),
+]);
+
+export const FeedbackFormDefinitionSchema = z.object({
+	intro: z.string().max(2000).optional(),
+	outro: z.string().max(2000).optional(),
+	questions: z.array(FeedbackQuestionSchema).min(1).max(50),
+}).refine(
+	(def) => {
+		const ids = def.questions.map((q) => q.id);
+		return new Set(ids).size === ids.length;
+	},
+	{ message: 'Question ids must be unique' },
+);
+
+export const FeedbackInstanceCreateSchema = z.object({
+	title: z.string().min(1).max(200),
+	description: z.string().max(2000).optional(),
+	form_definition: FeedbackFormDefinitionSchema.nullable().optional(),
+	chat_enabled: z.boolean().optional(),
+}).refine(
+	(v) => v.form_definition != null || v.chat_enabled === true,
+	{ message: 'Either form_definition or chat_enabled must be set' },
+);
+
+export const FeedbackInstanceUpdateSchema = z.object({
+	title: z.string().min(1).max(200).optional(),
+	description: z.string().max(2000).nullable().optional(),
+	form_definition: FeedbackFormDefinitionSchema.nullable().optional(),
+	chat_enabled: z.boolean().optional(),
+	status: z.enum(['open', 'closed']).optional(),
+});
+
+const ANSWER_MAX = 5000;
+
+export const FeedbackSubmissionSchema = z.object({
+	display_name: z.string().max(80).nullable().optional()
+		.transform((v) => (v && v.trim() ? v.trim().replace(/[\r\n]+/g, ' ') : null)),
+	client_session_id: z.string().min(1).max(100),
+	answers: z.record(
+		z.string().min(1).max(64),
+		z.union([
+			z.string().max(ANSWER_MAX),
+			z.number(),
+			z.boolean(),
+			z.array(z.string().max(200)).max(20),
+			z.null(),
+		]),
+	),
+	company: z.string().max(200).optional(), // honeypot
+});
+
+export const FeedbackPostSchema = z.object({
+	display_name: z.string().max(80).nullable().optional()
+		.transform((v) => (v && v.trim() ? v.trim().replace(/[\r\n]+/g, ' ') : null)),
+	client_session_id: z.string().min(1).max(100),
+	body: z.string().min(1).max(2000),
+	company: z.string().max(200).optional(), // honeypot
+});
+
+export const FeedbackPostHideSchema = z.object({
+	hidden: z.boolean(),
+});
+
+export const SignInSchema = z.object({
+	email: z.string().email(),
+	password: z.string().min(6).max(200),
+});
+
+export type FeedbackQuestion = z.infer<typeof FeedbackQuestionSchema>;
+export type FeedbackFormDefinition = z.infer<typeof FeedbackFormDefinitionSchema>;
diff --git a/tsconfig.json b/tsconfig.json
index a8f10c8..782ad14 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -9,6 +9,7 @@
 		"skipLibCheck": true,
 		"sourceMap": true,
 		"strict": true,
-		"moduleResolution": "bundler"
+		"moduleResolution": "bundler",
+		"types": ["bun"]
 	}
 }