diff --git a/frontend/src/api.collections.test.js b/frontend/src/api.collections.test.js
new file mode 100644
index 0000000..f446a8c
--- /dev/null
+++ b/frontend/src/api.collections.test.js
@@ -0,0 +1,48 @@
+// §22 S2 — the API client builds collection-scoped URLs when a collection id is
+// supplied, and falls back to the project/default-collection paths otherwise.
+import { describe, it, expect, vi, afterEach } from 'vitest'
+import { listRFCs, getRFC, proposeRFC, listCollections } from './api.js'
+
+function mockFetch() {
+  const fn = vi.fn(async () => ({
+    ok: true,
+    status: 200,
+    json: async () => ({ items: [] }),
+  }))
+  global.fetch = fn
+  return fn
+}
+
+afterEach(() => { vi.restoreAllMocks() })
+
+describe('collection-scoped api URLs', () => {
+  it('listRFCs scopes to a collection when given one', async () => {
+    const f = mockFetch()
+    await listRFCs('ohm', 'features')
+    expect(f).toHaveBeenCalledWith('/api/projects/ohm/collections/features/rfcs')
+  })
+
+  it('listRFCs falls back to the project default path without a collection', async () => {
+    const f = mockFetch()
+    await listRFCs('ohm')
+    expect(f).toHaveBeenCalledWith('/api/projects/ohm/rfcs')
+  })
+
+  it('getRFC scopes to a collection when given one', async () => {
+    const f = mockFetch()
+    await getRFC('ohm', 'login', 'features')
+    expect(f).toHaveBeenCalledWith('/api/projects/ohm/collections/features/rfcs/login')
+  })
+
+  it('proposeRFC targets the collection-scoped propose route', async () => {
+    const f = mockFetch()
+    await proposeRFC('ohm', { title: 'T', slug: 's', pitch: 'p', tags: [], collectionId: 'features' })
+    expect(f.mock.calls[0][0]).toBe('/api/projects/ohm/collections/features/rfcs/propose')
+  })
+
+  it('listCollections hits the project collections route', async () => {
+    const f = mockFetch()
+    await listCollections('ohm')
+    expect(f).toHaveBeenCalledWith('/api/projects/ohm/collections')
+  })
+})
diff --git a/frontend/src/api.js b/frontend/src/api.js
index 35978ca..d64efd8 100644
--- a/frontend/src/api.js
+++ b/frontend/src/api.js
@@ -182,22 +182,50 @@ export async function getProject(projectId) {
   return jsonOrThrow(await fetch(`/api/projects/${projectId}`))
 }
 
-// §22.4 (Plan B): per-project serving. Given a projectId, read the
-// project-scoped routes so a non-default project's corpus renders; without
-// one, fall back to the default-project compat path.
-export async function listRFCs(projectId) {
+// §22.4 (Plan B) / §22 S2: per-collection serving. With a projectId + a
+// collectionId, read the collection-scoped routes; with only a projectId, the
+// project default-collection compat path; with neither, the unscoped path.
+export async function listRFCs(projectId, collectionId) {
+  if (projectId && collectionId) {
+    return jsonOrThrow(await fetch(`/api/projects/${projectId}/collections/${collectionId}/rfcs`))
+  }
   const url = projectId ? `/api/projects/${projectId}/rfcs` : '/api/rfcs'
   return jsonOrThrow(await fetch(url))
 }
 
-export async function getRFC(projectId, slug) {
+export async function getRFC(projectId, slug, collectionId) {
   // Back-compat: getRFC(slug) (one arg) still hits the unscoped default path.
   if (slug === undefined) {
     return jsonOrThrow(await fetch(`/api/rfcs/${projectId}`))
   }
+  if (collectionId) {
+    return jsonOrThrow(await fetch(`/api/projects/${projectId}/collections/${collectionId}/rfcs/${slug}`))
+  }
   return jsonOrThrow(await fetch(`/api/projects/${projectId}/rfcs/${slug}`))
 }
 
+// §22 S2: the collections of a project (for the /p/<project>/ directory).
+export async function listCollections(projectId) {
+  return jsonOrThrow(await fetch(`/api/projects/${projectId}/collections`))
+}
+
+// §22 S2: create-collection (deployment owner/admin). The backend commits a
+// .collection.yaml and re-mirrors the registry, returning the new collection.
+export async function createCollection(projectId, { collectionId, type, name, visibility, initialState }) {
+  const res = await fetch(`/api/projects/${projectId}/collections`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({
+      collection_id: collectionId,
+      type,
+      name: name || null,
+      visibility: visibility || null,
+      initial_state: initialState || null,
+    }),
+  })
+  return jsonOrThrow(res)
+}
+
 export async function listProposals(projectId) {
   const url = projectId ? `/api/projects/${projectId}/proposals` : '/api/proposals'
   return jsonOrThrow(await fetch(url))
@@ -209,8 +237,10 @@ export async function getProposal(prNumber) {
 
 // §22.4 (Plan B write): propose into a specific project when projectId is
 // given; else the default-project compat path.
-export async function proposeRFC(projectId, { title, slug, pitch, tags, proposedUseCase }) {
-  const url = projectId ? `/api/projects/${projectId}/rfcs/propose` : '/api/rfcs/propose'
+export async function proposeRFC(projectId, { title, slug, pitch, tags, proposedUseCase, collectionId }) {
+  const url = (projectId && collectionId)
+    ? `/api/projects/${projectId}/collections/${collectionId}/rfcs/propose`
+    : (projectId ? `/api/projects/${projectId}/rfcs/propose` : '/api/rfcs/propose')
   const res = await fetch(url, {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
diff --git a/frontend/src/lib/entryPaths.js b/frontend/src/lib/entryPaths.js
index 15c5f53..b780f5a 100644
--- a/frontend/src/lib/entryPaths.js
+++ b/frontend/src/lib/entryPaths.js
@@ -4,6 +4,7 @@
 // project-scoped, so the builders emit the default collection segment; the
 // collection-aware link layer (named collections) lands in S2. Components build
 // links via these helpers so that flip happens in one place.
+import { useParams } from 'react-router-dom'
 import { useProject } from '../components/ProjectLayout.jsx'
 import { useDeployment } from '../context/DeploymentProvider'
 
@@ -37,3 +38,10 @@ export function useProjectId() {
   const { defaultProjectId } = useDeployment()
   return (ctx && ctx.projectId) || defaultProjectId
 }
+
+// §22 S2 — the collection id a component should scope to: the `/c/:collectionId/`
+// route segment when present, else the project's default collection.
+export function useCollectionId() {
+  const { collectionId } = useParams()
+  return collectionId || DEFAULT_COLLECTION
+}