diff --git a/psf-memo-client/acceptance/lib/handlers.js b/psf-memo-client/acceptance/lib/handlers.js
index 73f7164..898336d 100644
--- a/psf-memo-client/acceptance/lib/handlers.js
+++ b/psf-memo-client/acceptance/lib/handlers.js
@@ -38,6 +38,9 @@ const ProfilePage = require('../../src/services/profile-page')
 const ThreadPage = require('../../src/services/thread-page')
 const TopicDiscoveryPage = require('../../src/services/topic-discovery-page')
 const TopicFeedPage = require('../../src/services/topic-feed-page')
+const MemoTopicFollow = require('../../src/services/memo-topic-follow')
+const MemoTopicPost = require('../../src/services/memo-topic-post')
+const TopicPostPage = require('../../src/services/topic-post-page')
 
 const MEMO_POST_PREFIX = MemoPost.MEMO_POST_PREFIX
 const MEMO_REPLY_PREFIX = MemoReply.MEMO_REPLY_PREFIX
@@ -47,6 +50,9 @@ const MEMO_SET_AVATAR_URL_PREFIX = MemoSetAvatarUrl.MEMO_SET_AVATAR_URL_PREFIX
 const MEMO_LIKE_PREFIX = MemoLike.MEMO_LIKE_PREFIX
 const MEMO_FOLLOW_PREFIX = MemoFollow.MEMO_FOLLOW_PREFIX
 const MEMO_UNFOLLOW_PREFIX = MemoFollow.MEMO_UNFOLLOW_PREFIX
+const MEMO_TOPIC_MESSAGE_PREFIX = MemoTopicPost.MEMO_TOPIC_MESSAGE_PREFIX
+const MEMO_TOPIC_FOLLOW_PREFIX = MemoTopicFollow.MEMO_TOPIC_FOLLOW_PREFIX
+const MEMO_TOPIC_UNFOLLOW_PREFIX = MemoTopicFollow.MEMO_TOPIC_UNFOLLOW_PREFIX
 
 // Default author address used by Gherkin steps that refer to "the author address".
 const AUTHOR_ADDRESS = 'bitcoincash:qz7v6ztvzu2f2xd2ww8pnx9vwk0g4ncvfvavktg0jc'
@@ -98,11 +104,13 @@ function makeProfiles () {
   const bios = {}
   const avatarUrls = {}
   const following = {}
+  const topicFollowing = {}
   return {
     names,
     bios,
     avatarUrls,
     following,
+    topicFollowing,
     setName: (addr, name) => { names[addr] = name },
     getName: (addr) => names[addr] || null,
     setBio: (addr, bio) => { bios[addr] = bio },
@@ -113,7 +121,12 @@ function makeProfiles () {
       if (!following[selfAddr]) following[selfAddr] = {}
       following[selfAddr][targetAddr] = isFollowing
     },
-    getFollowState: (selfAddr, targetAddr) => following[selfAddr]?.[targetAddr] || false
+    getFollowState: (selfAddr, targetAddr) => following[selfAddr]?.[targetAddr] || false,
+    setTopicFollowState: (selfAddr, room, isFollowing) => {
+      if (!topicFollowing[selfAddr]) topicFollowing[selfAddr] = {}
+      topicFollowing[selfAddr][room] = isFollowing
+    },
+    getTopicFollowState: (selfAddr, room) => topicFollowing[selfAddr]?.[room] || false
   }
 }
 
@@ -136,6 +149,7 @@ function makeMemoDb () {
   const topics = []
   const topicPosts = {}
   const topicCounts = new Map()
+  const topicFollow = new Map()
 
   return {
     posts,
@@ -171,6 +185,20 @@ function makeMemoDb () {
     setFollowState (followerAddr, followeeAddr, following) {
       followState[`${followerAddr}:${followeeAddr}`] = following
     },
+    setTopicFollowState (addr, room, following) {
+      if (!topicFollow.has(room)) topicFollow.set(room, new Map())
+      topicFollow.get(room).set(addr, following)
+    },
+    async getTopicFollowState (room, addr) {
+      return topicFollow.get(room)?.get(addr) || false
+    },
+    async getTopicFollowers (room) {
+      const addrs = []
+      for (const [addr, following] of (topicFollow.get(room) || new Map()).entries()) {
+        if (following) addrs.push(addr)
+      }
+      return addrs
+    },
     async getRecentPosts ({ limit = 100, offset = 0 } = {}) {
       const page = posts.slice(offset, offset + limit)
       return { posts: page, pagination: { total: posts.length, limit, offset, hasMore: offset + page.length < posts.length } }
@@ -212,6 +240,7 @@ function createWorld () {
   const memoReply = new MemoReply({ wallet, thread })
   const memoLike = new MemoLike({ wallet, feed })
   const memoFollow = new MemoFollow({ wallet, profiles })
+  const memoTopicFollow = new MemoTopicFollow({ wallet, profiles })
   const memoDb = makeMemoDb()
 
   const world = {
@@ -222,6 +251,7 @@ function createWorld () {
     memoReply,
     memoLike,
     memoFollow,
+    memoTopicFollow,
     memoDb,
     currentPath: null,
     menuOpen: false,
@@ -326,6 +356,13 @@ function findDisplayedPost (txid, world) {
   return null
 }
 
+// True when the currently displayed page is a topic feed (used to dispatch the
+// shared "Follow/Unfollow button" steps between the profile page and the topic
+// feed page).
+function isTopicFeedActive (world) {
+  return Boolean(world.currentPath && String(world.currentPath).startsWith('/topics/'))
+}
+
 // Handler registry. Each entry: { pattern, run }.
 // run receives (match, exampleStore, world, step).
 const handlers = [
@@ -1340,14 +1377,22 @@ const handlers = [
     name: 'click Follow button',
     pattern: /^I click the Follow button$/,
     async run (m, example, world) {
-      await world.profilePage.follow()
+      if (isTopicFeedActive(world)) {
+        await world.topicFeedPage.follow()
+      } else {
+        await world.profilePage.follow()
+      }
     }
   },
   {
     name: 'click Unfollow button',
     pattern: /^I click the Unfollow button$/,
     async run (m, example, world) {
-      await world.profilePage.unfollow()
+      if (isTopicFeedActive(world)) {
+        await world.topicFeedPage.unfollow()
+      } else {
+        await world.profilePage.unfollow()
+      }
     }
   },
   {
@@ -1471,12 +1516,23 @@ const handlers = [
   },
   {
     name: 'open topic feed',
-    pattern: /^I open the topic feed for "?(<topic>|[^"]+)"?$/,
+    pattern: /^I open the topic feed for (?:the topic )?"?(<topic>|[^"]+)"?$/,
     async run (m, example, world) {
       const room = resolveParam(m[1], example)
-      world.topicFeedPage = new TopicFeedPage({ memoDb: world.memoDb, room })
+      const myAddr = world.wallet.walletInfo.cashAddress
+      world.topicFeedPage = new TopicFeedPage({
+        memoDb: world.memoDb,
+        room,
+        myAddr,
+        memoTopicFollow: world.memoTopicFollow
+      })
       await world.topicFeedPage.load()
       world.currentPath = TopicFeedPage.topicFeedPath(room)
+
+      // Set up the topic post composer for this room so topic messages can be
+      // composed and broadcast, reflecting new posts onto the shared feed.
+      const memoTopicPost = new MemoTopicPost({ wallet: world.wallet, room, feed: world.feed })
+      world.topicPostPage = new TopicPostPage({ memoTopicPost })
     }
   },
   {
@@ -1503,6 +1559,147 @@ const handlers = [
         throw new Error(`Expected topic feed to be empty, but found ${Array.isArray(posts) ? posts.length : 'non-array'} posts.`)
       }
     }
+  },
+  {
+    name: 'API reports I do not follow topic',
+    pattern: /^the psf-memo-db API reports that I do not follow the topic (<topic>)$/,
+    run (m, example, world) {
+      const room = resolveParam(m[1], example)
+      const myAddr = world.wallet.walletInfo.cashAddress
+      world.memoDb.setTopicFollowState(myAddr, room, false)
+    }
+  },
+  {
+    name: 'API reports I follow topic',
+    pattern: /^the psf-memo-db API reports that I follow the topic (<topic>)$/,
+    run (m, example, world) {
+      const room = resolveParam(m[1], example)
+      const myAddr = world.wallet.walletInfo.cashAddress
+      world.memoDb.setTopicFollowState(myAddr, room, true)
+    }
+  },
+  {
+    name: 'topic feed page shows Follow button',
+    pattern: /^the topic feed page shows a Follow button$/,
+    run (m, example, world) {
+      if (!world.topicFeedPage) throw new Error('No topic feed page is loaded.')
+      if (!world.topicFeedPage.canFollow()) throw new Error('Topic feed cannot show a Follow button.')
+      if (world.topicFeedPage.isFollowing()) throw new Error('Topic feed shows Unfollow, but Follow was expected.')
+    }
+  },
+  {
+    name: 'topic feed page shows Unfollow button',
+    pattern: /^the topic feed page shows an Unfollow button$/,
+    run (m, example, world) {
+      if (!world.topicFeedPage) throw new Error('No topic feed page is loaded.')
+      if (!world.topicFeedPage.canFollow()) throw new Error('Topic feed cannot show an Unfollow button.')
+      if (!world.topicFeedPage.isFollowing()) throw new Error('Topic feed shows Follow, but Unfollow was expected.')
+    }
+  },
+  {
+    name: 'broadcasts topic-follow prefix',
+    pattern: /^the app broadcasts an OP_RETURN transaction with the Memo topic-follow prefix for the topic (<topic>)$/,
+    run (m, example, world) {
+      const room = resolveParam(m[1], example)
+      const broadcasts = world.wallet.broadcasts
+      if (!broadcasts.length) throw new Error('No OP_RETURN transaction was broadcast.')
+      const last = broadcasts[broadcasts.length - 1]
+      if (last.prefix !== MEMO_TOPIC_FOLLOW_PREFIX) {
+        throw new Error(`Expected Memo topic-follow prefix ${MEMO_TOPIC_FOLLOW_PREFIX}, got "${last.prefix}".`)
+      }
+      if (last.msg !== room) {
+        throw new Error(`Broadcast topic-follow payload did not match topic ${room}.`)
+      }
+    }
+  },
+  {
+    name: 'broadcasts topic-unfollow prefix',
+    pattern: /^the app broadcasts an OP_RETURN transaction with the Memo topic-unfollow prefix for the topic (<topic>)$/,
+    run (m, example, world) {
+      const room = resolveParam(m[1], example)
+      const broadcasts = world.wallet.broadcasts
+      if (!broadcasts.length) throw new Error('No OP_RETURN transaction was broadcast.')
+      const last = broadcasts[broadcasts.length - 1]
+      if (last.prefix !== MEMO_TOPIC_UNFOLLOW_PREFIX) {
+        throw new Error(`Expected Memo topic-unfollow prefix ${MEMO_TOPIC_UNFOLLOW_PREFIX}, got "${last.prefix}".`)
+      }
+      if (last.msg !== room) {
+        throw new Error(`Broadcast topic-unfollow payload did not match topic ${room}.`)
+      }
+    }
+  },
+  {
+    name: 'compose topic message',
+    pattern: /^I compose a topic message with the text "<([A-Za-z0-9_]+)>"$/,
+    run (m, example, world) {
+      const param = m[1]
+      if (!(param in example)) throw new Error(`Missing example value for "${param}"`)
+      world.topicPostPage.setInput(example[param])
+    }
+  },
+  {
+    name: 'submit topic message',
+    pattern: /^I submit the topic message$/,
+    async run (m, example, world) {
+      await world.topicPostPage.submit()
+    }
+  },
+  {
+    name: 'broadcasts topic-message prefix',
+    pattern: /^the app broadcasts an OP_RETURN transaction with the Memo topic-message prefix for the topic (<topic>)$/,
+    run (m, example, world) {
+      const room = resolveParam(m[1], example)
+      const broadcasts = world.wallet.broadcasts
+      if (!broadcasts.length) throw new Error('No OP_RETURN transaction was broadcast.')
+      const last = broadcasts[broadcasts.length - 1]
+      if (last.prefix !== MEMO_TOPIC_MESSAGE_PREFIX) {
+        throw new Error(`Expected Memo topic-message prefix ${MEMO_TOPIC_MESSAGE_PREFIX}, got "${last.prefix}".`)
+      }
+      const expectedPayload = room + world.topicPostPage.input
+      if (last.msg !== expectedPayload) {
+        throw new Error(`Broadcast topic-message payload did not match ${room} + input.`)
+      }
+    }
+  },
+  {
+    name: 'topic feed shows new post from my address',
+    pattern: /^the topic feed shows a new post from my address with the text "(.+)"$/,
+    run (m, example, world) {
+      const expectedText = resolveParam(m[1], example)
+      const myAddress = world.wallet.walletInfo.cashAddress
+      const found = world.feed.posts.find((p) => p.text === expectedText && p.address === myAddress)
+      if (!found) throw new Error(`Topic feed does not show the new post with text "${expectedText}".`)
+    }
+  },
+  {
+    name: 'topic post composer shows validation error',
+    pattern: /^the topic post composer shows a validation error$/,
+    run (m, example, world) {
+      if (world.topicPostPage.submitError !== 'topic_post_validation') {
+        throw new Error(`Expected topic_post_validation, got ${world.topicPostPage.submitError}.`)
+      }
+    }
+  },
+  {
+    name: 'topic post composer shows length error',
+    pattern: /^the topic post composer shows a length error$/,
+    run (m, example, world) {
+      if (world.topicPostPage.submitError !== 'topic_post_length') {
+        throw new Error(`Expected topic_post_length, got ${world.topicPostPage.submitError}.`)
+      }
+    }
+  },
+  {
+    name: 'topic post composer remaining byte count',
+    pattern: /^the topic post composer shows a remaining byte count of (<count>)$/,
+    run (m, example, world) {
+      const expected = parseInt(resolveParam(m[1], example), 10)
+      if (Number.isNaN(expected)) throw new Error(`Invalid expected count for "${m[1]}".`)
+      const actual = world.topicPostPage.remainingCount()
+      if (actual !== expected) {
+        throw new Error(`Expected ${expected} remaining bytes, got ${actual}.`)
+      }
+    }
   }
 ]
 
diff --git a/psf-memo-client/specs/topic-follow.feature b/psf-memo-client/specs/topic-follow.feature
index 1a3448a..4ad4b4a 100644
--- a/psf-memo-client/specs/topic-follow.feature
+++ b/psf-memo-client/specs/topic-follow.feature
@@ -1,3 +1,7 @@
+# acceptance-mutation-manifest-begin
+# {"version":1,"tested_at":"2026-08-28T20:08:33.247012122Z","feature_name":"Topic Follow","feature_path":"/home/trout/work/psf-memo/.worktrees/architect/psf-memo-client/specs/topic-follow.feature","background_hash":"e1d5f81f1ed083ac6934c429ca3cb4a0f8d4dac44c2eaa45c0960920bde2c017","implementation_hash":"unknown","scenarios":[]}
+# acceptance-mutation-manifest-end
+
 # Scenarios: Topic Follow - 1, Topic Follow - 2, Topic Follow - 3, Topic Follow - 4
 #
 # The topic feed page has a Follow/Unfollow button that broadcasts a Memo
diff --git a/psf-memo-client/specs/topic-post.feature b/psf-memo-client/specs/topic-post.feature
index da0719d..4db0dbf 100644
--- a/psf-memo-client/specs/topic-post.feature
+++ b/psf-memo-client/specs/topic-post.feature
@@ -1,3 +1,7 @@
+# acceptance-mutation-manifest-begin
+# {"version":1,"tested_at":"2026-08-28T20:08:37.622959822Z","feature_name":"Topic Post","feature_path":"/home/trout/work/psf-memo/.worktrees/architect/psf-memo-client/specs/topic-post.feature","background_hash":"e1d5f81f1ed083ac6934c429ca3cb4a0f8d4dac44c2eaa45c0960920bde2c017","implementation_hash":"unknown","scenarios":[]}
+# acceptance-mutation-manifest-end
+
 # Scenarios: Topic Post - 1, Topic Post - 2, Topic Post - 3, Topic Post - 4
 #
 # The topic feed page has a composer that broadcasts a Memo topic message
diff --git a/psf-memo-client/src/components/app-body/topic-feed/index.js b/psf-memo-client/src/components/app-body/topic-feed/index.js
index 33ae1ad..1086f9e 100644
--- a/psf-memo-client/src/components/app-body/topic-feed/index.js
+++ b/psf-memo-client/src/components/app-body/topic-feed/index.js
@@ -1,21 +1,26 @@
 /*
-  Display the posts for a single Memo topic.
+  Display the posts for a single Memo topic and provide topic post / follow
+  controls.
 */
 
 // Global npm libraries
 import React, { useState, useEffect } from 'react'
-import { Container, Row, Col, Spinner, Button } from 'react-bootstrap'
+import { Container, Row, Col, Spinner, Button, Form } from 'react-bootstrap'
 import { useParams } from 'react-router-dom'
 
 // Local libraries
 import MemoDb from '../../../services/memo-db'
 import TopicFeedPage from '../../../services/topic-feed-page'
+import MemoTopicPost from '../../../services/memo-topic-post'
+import TopicPostPage from '../../../services/topic-post-page'
+import MemoTopicFollow from '../../../services/memo-topic-follow'
 import PostFeedItem from '../../post-feed/post-feed-item'
 import PostThreadModal from '../../post-thread-modal'
 import {
   collectPostAddrs,
   loadThreadProfiles
 } from '../../post-thread-modal/thread-profiles'
+import { byteLength } from '../../../services/utf8'
 import '../../../App.css'
 import '../../post-feed/post-feed.css'
 
@@ -24,6 +29,8 @@ const PAGE_SIZE = 100
 function TopicFeed (props) {
   const { appData } = props
   const { room } = useParams()
+  const myAddr = appData?.wallet?.walletInfo?.cashAddress
+
   const [loading, setLoading] = useState(true)
   const [error, setError] = useState(null)
   const [posts, setPosts] = useState([])
@@ -33,6 +40,14 @@ function TopicFeed (props) {
   const [threadTxid, setThreadTxid] = useState(null)
   const [showThreadModal, setShowThreadModal] = useState(false)
 
+  const [composerInput, setComposerInput] = useState('')
+  const [composerErr, setComposerErr] = useState('')
+  const [postingTopic, setPostingTopic] = useState(false)
+
+  const [isFollowing, setIsFollowing] = useState(false)
+  const [followers, setFollowers] = useState([])
+  const [followSubmitting, setFollowSubmitting] = useState(false)
+
   const openThread = (txid) => {
     setThreadTxid(txid)
     setShowThreadModal(true)
@@ -44,14 +59,23 @@ function TopicFeed (props) {
   }
 
   useEffect(() => {
-    const loadPosts = async () => {
+    const loadFeed = async () => {
       setLoading(true)
       setError(null)
       setProfiles({})
 
       try {
         const memoDb = new MemoDb()
-        const page = new TopicFeedPage({ memoDb, room })
+        const memoTopicFollow = new MemoTopicFollow({
+          wallet: appData?.wallet,
+          profiles: appData?.profiles
+        })
+        const page = new TopicFeedPage({
+          memoDb,
+          room,
+          myAddr,
+          memoTopicFollow
+        })
         const data = await page.load({ limit: PAGE_SIZE, offset })
 
         const loadedPosts = data.posts || []
@@ -61,18 +85,22 @@ function TopicFeed (props) {
         setPosts(loadedPosts)
         setProfiles(profileMap)
         setPagination(data.pagination || null)
+        setIsFollowing(data.followState === true)
+        setFollowers(data.followers || [])
       } catch (err) {
         setError(err.message || `Failed to load posts for topic ${room}`)
         setPosts([])
         setProfiles({})
         setPagination(null)
+        setIsFollowing(false)
+        setFollowers([])
       }
 
       setLoading(false)
     }
 
-    loadPosts()
-  }, [room, offset])
+    loadFeed()
+  }, [room, offset, myAddr, appData?.wallet, appData?.profiles])
 
   const canGoBack = offset > 0
   const canGoNext = pagination?.hasMore ?? false
@@ -85,13 +113,140 @@ function TopicFeed (props) {
     setOffset((prev) => prev + PAGE_SIZE)
   }
 
+  const remainingBytes = () => {
+    return MemoTopicPost.MAX_TOPIC_MESSAGE_BYTES - byteLength(room) - byteLength(composerInput)
+  }
+
+  const handleComposerChange = (event) => {
+    setComposerInput(event.target.value)
+    setComposerErr('')
+  }
+
+  const handlePostTopic = async (event) => {
+    event.preventDefault()
+    setComposerErr('')
+    setPostingTopic(true)
+
+    try {
+      const memoTopicPost = new MemoTopicPost({
+        wallet: appData?.wallet,
+        room
+      })
+      const page = new TopicPostPage({ memoTopicPost })
+      page.setInput(composerInput)
+
+      const result = await page.submit()
+      if (!result.ok) {
+        if (result.error === 'topic_post_length') {
+          setComposerErr(`Topic message is too long. Maximum is ${MemoTopicPost.MAX_TOPIC_MESSAGE_BYTES} bytes.`)
+        } else if (result.error === 'topic_post_validation') {
+          setComposerErr('Topic message must not be empty.')
+        } else if (result.message) {
+          setComposerErr(`Failed to broadcast: ${result.message}`)
+        } else {
+          setComposerErr('Failed to post topic message.')
+        }
+      } else {
+        // Optimistically show the new post at the top of the feed.
+        const newPost = {
+          txid: result.txid,
+          addr: myAddr,
+          text: composerInput,
+          seen: Date.now(),
+          blockHeight: 0,
+          replyCount: 0,
+          likeCount: 0
+        }
+        setPosts((prev) => [newPost, ...prev])
+        setComposerInput('')
+      }
+    } catch (submitErr) {
+      setComposerErr(submitErr.message)
+    } finally {
+      setPostingTopic(false)
+    }
+  }
+
+  const handleFollowClick = async () => {
+    setFollowSubmitting(true)
+    setError(null)
+
+    try {
+      const memoTopicFollow = new MemoTopicFollow({
+        wallet: appData?.wallet,
+        profiles: appData?.profiles
+      })
+      const page = new TopicFeedPage({
+        memoDb: new MemoDb(),
+        room,
+        myAddr,
+        memoTopicFollow
+      })
+      await page.follow()
+      setIsFollowing(true)
+      if (myAddr && !followers.includes(myAddr)) {
+        setFollowers((prev) => [...prev, myAddr])
+      }
+    } catch (err) {
+      setError(`Failed to follow topic: ${err.message}`)
+    }
+
+    setFollowSubmitting(false)
+  }
+
+  const handleUnfollowClick = async () => {
+    setFollowSubmitting(true)
+    setError(null)
+
+    try {
+      const memoTopicFollow = new MemoTopicFollow({
+        wallet: appData?.wallet,
+        profiles: appData?.profiles
+      })
+      const page = new TopicFeedPage({
+        memoDb: new MemoDb(),
+        room,
+        myAddr,
+        memoTopicFollow
+      })
+      await page.unfollow()
+      setIsFollowing(false)
+      if (myAddr) {
+        setFollowers((prev) => prev.filter((addr) => addr !== myAddr))
+      }
+    } catch (err) {
+      setError(`Failed to unfollow topic: ${err.message}`)
+    }
+
+    setFollowSubmitting(false)
+  }
+
+  const showComposer = Boolean(myAddr)
+  const showFollowButton = Boolean(myAddr)
+
   return (
     <Container className='topic-feed-page'>
       <Row className='justify-content-center'>
         <Col lg={8} md={10} xs={12}>
           <header className='topic-feed-heading'>
-            <h1>#{room}</h1>
-            <p>Posts published in the {room} topic.</p>
+            <div className='topic-feed-heading-row'>
+              <div>
+                <h1>#{room}</h1>
+                <p>Posts published in the {room} topic.</p>
+              </div>
+
+              {showFollowButton && (
+                <Button
+                  variant={isFollowing ? 'outline-secondary' : 'primary'}
+                  onClick={isFollowing ? handleUnfollowClick : handleFollowClick}
+                  disabled={followSubmitting}
+                >
+                  {followSubmitting
+                    ? 'Working...'
+                    : (isFollowing ? 'Unfollow' : 'Follow')}
+                </Button>
+              )}
+            </div>
 
             {pagination && posts.length > 0 && (
               <span className='topic-feed-count'>
@@ -99,8 +254,42 @@ function TopicFeed (props) {
                 {pagination.offset + posts.length} of {pagination.total}
               </span>
             )}
+
+            {followers.length > 0 && (
+              <span className='topic-feed-follower-count'>
+                {followers.length} follower{followers.length === 1 ? '' : 's'}
+              </span>
+            )}
           </header>
 
+          {showComposer && (
+            <Form onSubmit={handlePostTopic} className='topic-post-composer mb-4'>
+              <Form.Group controlId='topic-post-message' className='mb-2'>
+                <Form.Control
+                  as='textarea'
+                  rows={3}
+                  value={composerInput}
+                  onChange={handleComposerChange}
+                  placeholder={`Post in #${room}...`}
+                />
+              </Form.Group>
+
+              <div className='topic-post-composer-footer'>
+                <p className='topic-post-counter mb-0'>
+                  {remainingBytes()} bytes remaining
+                </p>
+
+                <Button type='submit' variant='primary' disabled={postingTopic}>
+                  {postingTopic ? 'Posting...' : 'Post'}
+                </Button>
+              </div>
+
+              {composerErr && (
+                <p className='topic-post-error mt-2'>{composerErr}</p>
+              )}
+            </Form>
+          )}
+
           {error && (
             <p className='topic-feed-error'>
               {error}
diff --git a/psf-memo-client/src/services/memo-db.js b/psf-memo-client/src/services/memo-db.js
index f4c2aeb..a4c15bf 100644
--- a/psf-memo-client/src/services/memo-db.js
+++ b/psf-memo-client/src/services/memo-db.js
@@ -56,6 +56,33 @@ class MemoDb {
     return this.getPage(`/topics/${encodeURIComponent(room)}/posts`, 'getTopicPosts', opts)
   }
 
+  async getTopicFollowState (room, addr) {
+    try {
+      const result = await this.axios.get(
+        `${config.backend}/topics/${encodeURIComponent(room)}/follow/state`,
+        {
+          params: { addr }
+        }
+      )
+      return result.data.following === true
+    } catch (err) {
+      console.error('Error in getTopicFollowState()')
+      throw err
+    }
+  }
+
+  async getTopicFollowers (room) {
+    try {
+      const result = await this.axios.get(
+        `${config.backend}/topics/${encodeURIComponent(room)}/followers`
+      )
+      return result.data.followers || []
+    } catch (err) {
+      console.error('Error in getTopicFollowers()')
+      throw err
+    }
+  }
+
   // GET a paginated 'recent' listing endpoint.
   async getRecent (path, name, params) {
     try {
@@ -121,5 +148,5 @@ class MemoDb {
 export default MemoDb
 
 // mutate4javascript-manifest-begin
-// {"version":1,"tested_at":"2026-08-28T15:36:17.287Z","module_hash":"77d15bc46bc63e2ffbd5fa7387b08a74db8e967482626f4f52211ceb60bd0633","functions":[{"id":"func/MemoDb.constructor","name":"MemoDb.constructor","line":9,"end_line":11,"hash":"188825ae5983840d4e1a4df182966ef012297c336ea3b763c87ea1c384654279"},{"id":"func/MemoDb.getRecentProfiles","name":"MemoDb.getRecentProfiles","line":13,"end_line":15,"hash":"cb819c72881b70f719f964c607f64be70b40377297c738897eee495bcf6dff4d"},{"id":"func/MemoDb.getRecentPosts","name":"MemoDb.getRecentPosts","line":17,"end_line":19,"hash":"7c0fd29c2fdc67a27a05a190e2e4294a698a1fe5223d8017ca82c4f890c2d094"},{"id":"func/MemoDb.getProfile","name":"MemoDb.getProfile","line":21,"end_line":23,"hash":"6a250c7205799b40dbe97b8f17ddaee6eace8cb435b0561d9ff8f5eac93d2b20"},{"id":"func/MemoDb.getProfilePic","name":"MemoDb.getProfilePic","line":25,"end_line":27,"hash":"d61dd5aebce32ef28b69ad56f2f7108d6b5f333a4d94cd83f05f01a09fa8f1d7"},{"id":"func/MemoDb.getName","name":"MemoDb.getName","line":29,"end_line":31,"hash":"3f841735b93180c6aeeb14a563bb6d4eb0ca5d395fb960267c8896b06c1e85f3"},{"id":"func/MemoDb.getFollowState","name":"MemoDb.getFollowState","line":33,"end_line":49,"hash":"d62eb85c742b40f2d319230c6ef59e21738063d31bccf1f37ebdc52c20bac994"},{"id":"func/MemoDb.getTopics","name":"MemoDb.getTopics","line":51,"end_line":53,"hash":"8d392b8a4b1bef405a9872c2564c51d9343df7b1c628d016258ee1c165f713ef"},{"id":"func/MemoDb.getTopicPosts","name":"MemoDb.getTopicPosts","line":55,"end_line":57,"hash":"4cc1e13334b5b4a2b72942cbc5f3cce8493254628f7d51da33d7be9c60ef9ff7"},{"id":"func/MemoDb.getRecent","name":"MemoDb.getRecent","line":60,"end_line":71,"hash":"1565fd17dced45fbf1b6d6fd6b8003521129bbd88046ff52a4eb61c17862530d"},{"id":"func/MemoDb.getPage","name":"MemoDb.getPage","line":74,"end_line":85,"hash":"986ec43d7699d642b25a9f4627aa5420cc685a247c3caa4671797778bc84e3b5"},{"id":"func/MemoDb.getLevelResource","name":"MemoDb.getLevelResource","line":88,"end_line":101,"hash":"c2fb7338918b1e69aa8a14f65ae687532c843f0641f04074947731691001e4ea"},{"id":"func/MemoDb.getPostsByAddr","name":"MemoDb.getPostsByAddr","line":103,"end_line":105,"hash":"45bbfef12cd8e35da1d71299153b2e54304664d5e3191c497f105ba17b134431"},{"id":"func/MemoDb.getPostThread","name":"MemoDb.getPostThread","line":107,"end_line":118,"hash":"ed5ef157b457f8d984ff6a9488a4dccf7a37b0ae65adb40005df90508426661f"}]}
+// {"version":1,"tested_at":"2026-08-28T18:23:08.799Z","module_hash":"c55696ecbf8f9c776dc025b308cefadf604950952002bc3a2f4a021f9c73085b","functions":[{"id":"func/MemoDb.constructor","name":"MemoDb.constructor","line":9,"end_line":11,"hash":"188825ae5983840d4e1a4df182966ef012297c336ea3b763c87ea1c384654279"},{"id":"func/MemoDb.getRecentProfiles","name":"MemoDb.getRecentProfiles","line":13,"end_line":15,"hash":"cb819c72881b70f719f964c607f64be70b40377297c738897eee495bcf6dff4d"},{"id":"func/MemoDb.getRecentPosts","name":"MemoDb.getRecentPosts","line":17,"end_line":19,"hash":"7c0fd29c2fdc67a27a05a190e2e4294a698a1fe5223d8017ca82c4f890c2d094"},{"id":"func/MemoDb.getProfile","name":"MemoDb.getProfile","line":21,"end_line":23,"hash":"6a250c7205799b40dbe97b8f17ddaee6eace8cb435b0561d9ff8f5eac93d2b20"},{"id":"func/MemoDb.getProfilePic","name":"MemoDb.getProfilePic","line":25,"end_line":27,"hash":"d61dd5aebce32ef28b69ad56f2f7108d6b5f333a4d94cd83f05f01a09fa8f1d7"},{"id":"func/MemoDb.getName","name":"MemoDb.getName","line":29,"end_line":31,"hash":"3f841735b93180c6aeeb14a563bb6d4eb0ca5d395fb960267c8896b06c1e85f3"},{"id":"func/MemoDb.getFollowState","name":"MemoDb.getFollowState","line":33,"end_line":49,"hash":"d62eb85c742b40f2d319230c6ef59e21738063d31bccf1f37ebdc52c20bac994"},{"id":"func/MemoDb.getTopics","name":"MemoDb.getTopics","line":51,"end_line":53,"hash":"8d392b8a4b1bef405a9872c2564c51d9343df7b1c628d016258ee1c165f713ef"},{"id":"func/MemoDb.getTopicPosts","name":"MemoDb.getTopicPosts","line":55,"end_line":57,"hash":"4cc1e13334b5b4a2b72942cbc5f3cce8493254628f7d51da33d7be9c60ef9ff7"},{"id":"func/MemoDb.getTopicFollowState","name":"MemoDb.getTopicFollowState","line":59,"end_line":72,"hash":"4f056870b5dee08dfffd7484f9d94cf1721297ffa4ea629dcc4208a8217b4d24"},{"id":"func/MemoDb.getTopicFollowers","name":"MemoDb.getTopicFollowers","line":74,"end_line":84,"hash":"65c9eff7e2afb949cc46b64f2091eed006d9b6800ca5aee6c7e8793ae13e3e94"},{"id":"func/MemoDb.getRecent","name":"MemoDb.getRecent","line":87,"end_line":98,"hash":"1565fd17dced45fbf1b6d6fd6b8003521129bbd88046ff52a4eb61c17862530d"},{"id":"func/MemoDb.getPage","name":"MemoDb.getPage","line":101,"end_line":112,"hash":"986ec43d7699d642b25a9f4627aa5420cc685a247c3caa4671797778bc84e3b5"},{"id":"func/MemoDb.getLevelResource","name":"MemoDb.getLevelResource","line":115,"end_line":128,"hash":"c2fb7338918b1e69aa8a14f65ae687532c843f0641f04074947731691001e4ea"},{"id":"func/MemoDb.getPostsByAddr","name":"MemoDb.getPostsByAddr","line":130,"end_line":132,"hash":"45bbfef12cd8e35da1d71299153b2e54304664d5e3191c497f105ba17b134431"},{"id":"func/MemoDb.getPostThread","name":"MemoDb.getPostThread","line":134,"end_line":145,"hash":"ed5ef157b457f8d984ff6a9488a4dccf7a37b0ae65adb40005df90508426661f"}]}
 // mutate4javascript-manifest-end
diff --git a/psf-memo-client/src/services/memo-topic-follow.js b/psf-memo-client/src/services/memo-topic-follow.js
new file mode 100644
index 0000000..b7c614d
--- /dev/null
+++ b/psf-memo-client/src/services/memo-topic-follow.js
@@ -0,0 +1,73 @@
+/*
+  Memo topic follow/unfollow behavior: compose, validate, and broadcast a
+  Memo topic follow (0x6d0d) or unfollow (0x6d0e) action.
+
+  A topic follow transaction carries the topic name as plain UTF-8 text. No
+  cashaddr conversion is needed.
+
+  The wallet and an injected profile store are used so this module stays
+  testable and free of UI/network concerns; environmentally unsuitable I/O
+  lives behind those small adapter boundaries.
+
+  Constants
+    MEMO_TOPIC_FOLLOW_PREFIX   : hex prefix for the Memo "topic follow" action (0x6d0d)
+    MEMO_TOPIC_UNFOLLOW_PREFIX : hex prefix for the Memo "topic unfollow" action (0x6d0e)
+*/
+
+const MEMO_TOPIC_FOLLOW_PREFIX = '6d0d'
+const MEMO_TOPIC_UNFOLLOW_PREFIX = '6d0e'
+
+class MemoTopicFollow {
+  constructor (deps = {}) {
+    this.wallet = deps.wallet
+    this.profiles = deps.profiles
+  }
+
+  validate (room) {
+    if (typeof room !== 'string' || room.trim().length === 0) {
+      const err = new Error('Topic name is required.')
+      err.code = 'topic_follow_validation'
+      throw err
+    }
+  }
+
+  async follow (room) {
+    return this._broadcastAction(room, MEMO_TOPIC_FOLLOW_PREFIX, true)
+  }
+
+  async unfollow (room) {
+    return this._broadcastAction(room, MEMO_TOPIC_UNFOLLOW_PREFIX, false)
+  }
+
+  async _broadcastAction (room, prefix, isFollowing) {
+    if (!this.wallet) {
+      throw new Error('Memo topic follow requires a wallet.')
+    }
+
+    this.validate(room)
+
+    await this.wallet.getUtxos()
+
+    const txid = await this.wallet.sendOpReturn(room, prefix)
+
+    this.reflect(txid, room, isFollowing)
+
+    return txid
+  }
+
+  reflect (txid, room, isFollowing) {
+    if (this.profiles && typeof this.profiles.setTopicFollowState === 'function') {
+      const myAddr = this.wallet?.walletInfo?.cashAddress
+      this.profiles.setTopicFollowState(myAddr, room, isFollowing)
+    }
+  }
+}
+
+MemoTopicFollow.MEMO_TOPIC_FOLLOW_PREFIX = MEMO_TOPIC_FOLLOW_PREFIX
+MemoTopicFollow.MEMO_TOPIC_UNFOLLOW_PREFIX = MEMO_TOPIC_UNFOLLOW_PREFIX
+
+module.exports = MemoTopicFollow
+
+// mutate4javascript-manifest-begin
+// {"version":1,"tested_at":"2026-08-28T18:19:01.010Z","module_hash":"f6fd04a72273df34505b97c8f790bba83a2d379d8325267f7904e3826749c686","functions":[{"id":"func/MemoTopicFollow.constructor","name":"MemoTopicFollow.constructor","line":21,"end_line":24,"hash":"dd4ee8221c4d849937d901f6383138aefe615763747cc6dab059db9291843b72"},{"id":"func/MemoTopicFollow.validate","name":"MemoTopicFollow.validate","line":26,"end_line":32,"hash":"e8392594d65c9a31e79a52afcdf92a0ddf111296cf24fa108b16d236405c61d4"},{"id":"func/MemoTopicFollow.follow","name":"MemoTopicFollow.follow","line":34,"end_line":36,"hash":"3a066e2f12efb2ec54f642e11d1eefd4e55d733589fe8266d9de8b3c6651265f"},{"id":"func/MemoTopicFollow.unfollow","name":"MemoTopicFollow.unfollow","line":38,"end_line":40,"hash":"cc714d188e5ba49eee63e0dda84a4ebc205af4ee783c346b647f5ac6645d90a2"},{"id":"func/MemoTopicFollow._broadcastAction","name":"MemoTopicFollow._broadcastAction","line":42,"end_line":56,"hash":"d191f210d5505f9bbb29c74fd02afe91f037a6e9c13a9514a4203a40cd28ff5f"},{"id":"func/MemoTopicFollow.reflect","name":"MemoTopicFollow.reflect","line":58,"end_line":63,"hash":"8f8ef1f3a088f66698f261e25e9b76243355bb02ec50334a37c799e3348b99ba"}]}
+// mutate4javascript-manifest-end
diff --git a/psf-memo-client/src/services/memo-topic-post.js b/psf-memo-client/src/services/memo-topic-post.js
new file mode 100644
index 0000000..7d08b70
--- /dev/null
+++ b/psf-memo-client/src/services/memo-topic-post.js
@@ -0,0 +1,89 @@
+/*
+  Memo topic message behavior: compose, validate, and broadcast a Memo
+  topic message (0x6d0c).
+
+  A topic message transaction carries the Memo topic-message protocol prefix
+  followed by the topic name and message bytes. The combined topic name plus
+  message must not exceed MAX_TOPIC_MESSAGE_BYTES.
+
+  The wallet and an injected feed store are used so this module stays
+  testable and free of UI/network concerns; environmentally unsuitable I/O
+  lives behind those small adapter boundaries.
+
+  Constants
+    MEMO_TOPIC_MESSAGE_PREFIX : hex prefix for the Memo topic message action (0x6d0c)
+    MAX_TOPIC_MESSAGE_BYTES   : maximum combined topic + message bytes (214)
+*/
+
+const MemoAction = require('./memo-action')
+const { byteLength } = require('./utf8')
+
+const MEMO_TOPIC_MESSAGE_PREFIX = '6d0c'
+const MAX_TOPIC_MESSAGE_BYTES = 214
+
+class MemoTopicPost extends MemoAction {
+  static config = {
+    prefix: MEMO_TOPIC_MESSAGE_PREFIX,
+    walletRequiredMsg: 'Memo topic post requires a wallet.',
+    lengthMessage: `Topic message is too long. Maximum is ${MAX_TOPIC_MESSAGE_BYTES} bytes.`,
+    emptyMessage: 'Topic message must not be empty.',
+    lengthCode: 'topic_post_length',
+    validationCode: 'topic_post_validation'
+  }
+
+  constructor (deps = {}) {
+    super(deps)
+    this.room = deps.room || ''
+    this.feed = deps.feed || null
+  }
+
+  // A topic message is over-length when the topic name plus the message
+  // exceed the combined byte budget.
+  isTooLong (message) {
+    return byteLength(this.room) + byteLength(message) > MAX_TOPIC_MESSAGE_BYTES
+  }
+
+  remainingBytes (message) {
+    return MAX_TOPIC_MESSAGE_BYTES - byteLength(this.room) - byteLength(message)
+  }
+
+  // Compose and broadcast a Memo topic message for the given message.
+  async post (message) {
+    const check = this.validate(message)
+    this._throwIfInvalid(check)
+
+    if (!this.wallet) {
+      throw new Error(this.walletRequiredMsg)
+    }
+
+    await this.wallet.getUtxos()
+
+    const payload = this.room + message
+    const txid = await this.wallet.sendOpReturn(payload, this.prefix)
+
+    this.reflect(txid, message)
+
+    return txid
+  }
+
+  // Record the new topic post on the injected feed when one is present.
+  reflect (txid, message) {
+    if (this.feed && typeof this.feed.addPost === 'function') {
+      this.feed.addPost({
+        txid,
+        address: this.wallet.walletInfo.cashAddress,
+        text: message,
+        room: this.room
+      })
+    }
+  }
+}
+
+MemoTopicPost.MEMO_TOPIC_MESSAGE_PREFIX = MEMO_TOPIC_MESSAGE_PREFIX
+MemoTopicPost.MAX_TOPIC_MESSAGE_BYTES = MAX_TOPIC_MESSAGE_BYTES
+
+module.exports = MemoTopicPost
+
+// mutate4javascript-manifest-begin
+// {"version":1,"tested_at":"2026-08-28T18:18:11.190Z","module_hash":"c73b1395983accf085921554a84c8ef9ad8014ba8d8ddfa794e051ae4a487f04","functions":[{"id":"func/MemoTopicPost.constructor","name":"MemoTopicPost.constructor","line":34,"end_line":38,"hash":"34483e7579cbde3babf17cc43f64bc6535537b6391169a75cb51025029283289"},{"id":"func/MemoTopicPost.isTooLong","name":"MemoTopicPost.isTooLong","line":42,"end_line":44,"hash":"a8d16816cf0aeda1be759f796aee75e9cc5d89ccbcc288b5d2551917121be27a"},{"id":"func/MemoTopicPost.remainingBytes","name":"MemoTopicPost.remainingBytes","line":46,"end_line":48,"hash":"11a07f6539fa6b74feabfdd258f83ede4556213951aa85266a959871ff616df1"},{"id":"func/MemoTopicPost.post","name":"MemoTopicPost.post","line":51,"end_line":67,"hash":"dec3508e4969efd3edfefbc0752ca4608bac9521fbda62cf2ce5d7bf0a5696c7"},{"id":"func/MemoTopicPost.reflect","name":"MemoTopicPost.reflect","line":70,"end_line":79,"hash":"8a136fe98fa6752b2247b9bc0064b9860cfa34e518abaa33e50e95833120d529"}]}
+// mutate4javascript-manifest-end
diff --git a/psf-memo-client/src/services/profiles.js b/psf-memo-client/src/services/profiles.js
index 72e0cd9..7ed2d6d 100644
--- a/psf-memo-client/src/services/profiles.js
+++ b/psf-memo-client/src/services/profiles.js
@@ -15,6 +15,7 @@ class Profiles {
     this.bios = new Map()
     this.avatarUrls = new Map()
     this.following = new Map()
+    this.topicFollowing = new Map()
   }
 
   setName (addr, name) {
@@ -49,21 +50,40 @@ class Profiles {
 
   // Track whether the current wallet follows a given address.
   setFollowState (selfAddr, targetAddr, isFollowing) {
-    if (!selfAddr || !targetAddr) return
-    if (!this.following.has(selfAddr)) {
-      this.following.set(selfAddr, new Map())
-    }
-    this.following.get(selfAddr).set(targetAddr, isFollowing)
+    this._setMapState(this.following, selfAddr, targetAddr, isFollowing)
   }
 
   getFollowState (selfAddr, targetAddr) {
-    if (!selfAddr || !targetAddr) return false
-    return this.following.get(selfAddr)?.get(targetAddr) || false
+    return this._getMapState(this.following, selfAddr, targetAddr)
+  }
+
+  // Track whether the current wallet follows a given topic.
+  setTopicFollowState (selfAddr, room, isFollowing) {
+    this._setMapState(this.topicFollowing, selfAddr, room, isFollowing)
+  }
+
+  getTopicFollowState (selfAddr, room) {
+    return this._getMapState(this.topicFollowing, selfAddr, room)
+  }
+
+  // Set a boolean value on a per-self-address nested map.
+  _setMapState (map, selfAddr, key, value) {
+    if (!selfAddr || !key) return
+    if (!map.has(selfAddr)) {
+      map.set(selfAddr, new Map())
+    }
+    map.get(selfAddr).set(key, value)
+  }
+
+  // Read a boolean value from a per-self-address nested map.
+  _getMapState (map, selfAddr, key) {
+    if (!selfAddr || !key) return false
+    return map.get(selfAddr)?.get(key) || false
   }
 }
 
 module.exports = Profiles
 
 // mutate4javascript-manifest-begin
-// {"version":1,"tested_at":"2026-08-27T17:52:37.432Z","module_hash":"f729d4125eea29c45c4a0d7bd691a5f590512922f2ba78c85756643638fb0859","functions":[{"id":"func/Profiles.constructor","name":"Profiles.constructor","line":13,"end_line":18,"hash":"574f0b3772f783646c283c6ddc4d5ff200ca1f9918ab1fa668205003f885d4d3"},{"id":"func/Profiles.setName","name":"Profiles.setName","line":20,"end_line":23,"hash":"5a36c6e237798608de0bedd8744b75000c0eec5c0a6a64c870a25bcdf20aed21"},{"id":"func/Profiles.getName","name":"Profiles.getName","line":25,"end_line":28,"hash":"2fcb9d84687ea0f3b24f3e34c0a72eda55a4e869b87e08a7f4551321a4166198"},{"id":"func/Profiles.setBio","name":"Profiles.setBio","line":30,"end_line":33,"hash":"3825665ead1ba9bb217694c45a17bb2e11c78ffa053e5e90111a4b9208183b56"},{"id":"func/Profiles.getBio","name":"Profiles.getBio","line":35,"end_line":38,"hash":"2e9708249db4a0e4fa642cbe52e6216144ec91283281c61dee2ff3cc3d8f1572"},{"id":"func/Profiles.setAvatarUrl","name":"Profiles.setAvatarUrl","line":40,"end_line":43,"hash":"e4ccb0164fee4ab6cc3a1290fb4bf85e4a79f2227ca72872b1f10bc616926fd9"},{"id":"func/Profiles.getAvatarUrl","name":"Profiles.getAvatarUrl","line":45,"end_line":48,"hash":"0aa58dc15fd519e553136d04d1954e18084f79a6cd9349dc89b1136cf0a22a2b"},{"id":"func/Profiles.setFollowState","name":"Profiles.setFollowState","line":51,"end_line":57,"hash":"aa527936b6ca92a502e93e8241803318700c528e05f68ff7fb6fac1d410c197c"},{"id":"func/Profiles.getFollowState","name":"Profiles.getFollowState","line":59,"end_line":62,"hash":"299a44adb289026bf3b89a21947fc23bf05f5a40f07abb7f1bbd311c0479f562"}]}
+// {"version":1,"tested_at":"2026-08-28T18:21:58.102Z","module_hash":"1cec5125fb228d43d47e4ec171eb43c492f2bd773ca315748df78a16071e2802","functions":[{"id":"func/Profiles.constructor","name":"Profiles.constructor","line":13,"end_line":19,"hash":"247804207ec0220b6e6507f6beb6f86023a7c08b50737a52a0dbb99d262993d3"},{"id":"func/Profiles.setName","name":"Profiles.setName","line":21,"end_line":24,"hash":"5a36c6e237798608de0bedd8744b75000c0eec5c0a6a64c870a25bcdf20aed21"},{"id":"func/Profiles.getName","name":"Profiles.getName","line":26,"end_line":29,"hash":"2fcb9d84687ea0f3b24f3e34c0a72eda55a4e869b87e08a7f4551321a4166198"},{"id":"func/Profiles.setBio","name":"Profiles.setBio","line":31,"end_line":34,"hash":"3825665ead1ba9bb217694c45a17bb2e11c78ffa053e5e90111a4b9208183b56"},{"id":"func/Profiles.getBio","name":"Profiles.getBio","line":36,"end_line":39,"hash":"2e9708249db4a0e4fa642cbe52e6216144ec91283281c61dee2ff3cc3d8f1572"},{"id":"func/Profiles.setAvatarUrl","name":"Profiles.setAvatarUrl","line":41,"end_line":44,"hash":"e4ccb0164fee4ab6cc3a1290fb4bf85e4a79f2227ca72872b1f10bc616926fd9"},{"id":"func/Profiles.getAvatarUrl","name":"Profiles.getAvatarUrl","line":46,"end_line":49,"hash":"0aa58dc15fd519e553136d04d1954e18084f79a6cd9349dc89b1136cf0a22a2b"},{"id":"func/Profiles.setFollowState","name":"Profiles.setFollowState","line":52,"end_line":54,"hash":"805cafb46052f91bfa0a123842c25ff8ee0f7f4a7e661f51d289b0487738dbd4"},{"id":"func/Profiles.getFollowState","name":"Profiles.getFollowState","line":56,"end_line":58,"hash":"48fdf5a632825946c391146628cd6f51b4eb0169c7a6d6b89c795ff554e62b07"},{"id":"func/Profiles.setTopicFollowState","name":"Profiles.setTopicFollowState","line":61,"end_line":63,"hash":"54ab980e42018d64fbacee7d80347d530791b7ba21d8fac46f5ed85f33903f98"},{"id":"func/Profiles.getTopicFollowState","name":"Profiles.getTopicFollowState","line":65,"end_line":67,"hash":"90ce88799dda5477e20ce4de17404dace55abf1d2f2c1c87671e94fc2f270205"},{"id":"func/Profiles._setMapState","name":"Profiles._setMapState","line":70,"end_line":76,"hash":"13d2cad84be961b89482970f55f107d93fa1bdc10636dc64844c6a9263e88583"},{"id":"func/Profiles._getMapState","name":"Profiles._getMapState","line":79,"end_line":82,"hash":"c1c8966a797533614d35c7a13deb8f757572127ebcbde1d234c7d966346d89a8"}]}
 // mutate4javascript-manifest-end
diff --git a/psf-memo-client/src/services/topic-feed-page.js b/psf-memo-client/src/services/topic-feed-page.js
index fd222a1..4b16ca4 100644
--- a/psf-memo-client/src/services/topic-feed-page.js
+++ b/psf-memo-client/src/services/topic-feed-page.js
@@ -10,8 +10,12 @@ class TopicFeedPage {
   constructor (deps = {}) {
     this.memoDb = deps.memoDb || null
     this.room = deps.room || null
+    this.myAddr = deps.myAddr || null
+    this.memoTopicFollow = deps.memoTopicFollow || null
     this.posts = []
     this.pagination = null
+    this.followState = false
+    this.followers = []
   }
 
   async load ({ limit = 100, offset = 0 } = {}) {
@@ -25,8 +29,53 @@ class TopicFeedPage {
     const data = await this.memoDb.getTopicPosts(this.room, { limit, offset })
     this.posts = data.posts || []
     this.pagination = data.pagination || null
+    this.followState = await this._loadFollowState()
+    this.followers = await this._loadFollowers()
 
-    return { posts: this.posts, pagination: this.pagination }
+    return { posts: this.posts, pagination: this.pagination, followState: this.followState, followers: this.followers }
+  }
+
+  async _loadFollowState () {
+    if (this.myAddr) {
+      return this.memoDb.getTopicFollowState(this.room, this.myAddr)
+    }
+    return false
+  }
+
+  async _loadFollowers () {
+    return this.memoDb.getTopicFollowers(this.room)
+  }
+
+  canFollow () {
+    return Boolean(this.myAddr)
+  }
+
+  isFollowing () {
+    return this.followState === true
+  }
+
+  async follow () {
+    return this._setFollowState('follow', true)
+  }
+
+  async unfollow () {
+    return this._setFollowState('unfollow', false)
+  }
+
+  async _setFollowState (method, nextState) {
+    if (!this.memoTopicFollow) {
+      throw new Error('Topic feed page requires a memo topic follow handler.')
+    }
+    await this.memoTopicFollow[method](this.room)
+    this.followState = nextState
+    if (nextState) {
+      if (!this.followers.includes(this.myAddr)) {
+        this.followers = [...this.followers, this.myAddr]
+      }
+    } else {
+      this.followers = this.followers.filter((addr) => addr !== this.myAddr)
+    }
+    return { ok: true }
   }
 
   getPost (txid) {
@@ -41,5 +90,5 @@ TopicFeedPage.topicFeedPath = function (room) {
 module.exports = TopicFeedPage
 
 // mutate4javascript-manifest-begin
-// {"version":1,"tested_at":"2026-08-28T15:35:01.465Z","module_hash":"d6433e58dfe8e7d0095074424340477c0abcfdcac7f611e2267ed04232936a1d","functions":[{"id":"func/TopicFeedPage.constructor","name":"TopicFeedPage.constructor","line":10,"end_line":15,"hash":"5d839555bdd88de97e47d68ef4dd2bad3a657ec4f9ce93991d332902bb4c371e"},{"id":"func/TopicFeedPage.load","name":"TopicFeedPage.load","line":17,"end_line":30,"hash":"ddf4ed21448879fa579225491125e343ebc129ef08445da811d98e79c6c29042"},{"id":"func/TopicFeedPage.getPost","name":"TopicFeedPage.getPost","line":32,"end_line":34,"hash":"1a6ae1a02b0f79b5b62a2b2324a5f1edbd743bec004fe73cfef7970bead56885"}]}
+// {"version":1,"tested_at":"2026-08-28T18:24:48.504Z","module_hash":"236ec55785bb69ac64c4a610ef4a5f8a8b03fae7b717d79c14c7fd2e755775e6","functions":[{"id":"func/TopicFeedPage.constructor","name":"TopicFeedPage.constructor","line":10,"end_line":19,"hash":"e6ee69c9caa13fcc05c7739fc185767f906c907a3031cf2c02abaab9220daca5"},{"id":"func/TopicFeedPage.load","name":"TopicFeedPage.load","line":21,"end_line":36,"hash":"ef85636d06f2b1eb6afd19b276bd8b9728ee35122d4424b3faf468de4a0e23a4"},{"id":"func/TopicFeedPage._loadFollowState","name":"TopicFeedPage._loadFollowState","line":38,"end_line":43,"hash":"d1984bb94b4f2e7c98c39524fc2fd0080dc5cff10e775a17c68856c2e3a2c249"},{"id":"func/TopicFeedPage._loadFollowers","name":"TopicFeedPage._loadFollowers","line":45,"end_line":47,"hash":"8b19d3623b4a872f4abe879ceda7e4018edf60efff03d037fe795b6558222b37"},{"id":"func/TopicFeedPage.canFollow","name":"TopicFeedPage.canFollow","line":49,"end_line":51,"hash":"2f82c2096bf6f542b60cf20d82cd70f366652fcce3a38ff14e82164d5ee86cad"},{"id":"func/TopicFeedPage.isFollowing","name":"TopicFeedPage.isFollowing","line":53,"end_line":55,"hash":"9fc0470db7ffea2da96d2dbbdceff55562e1f7e84377fbb0e8b60d53cc723b40"},{"id":"func/TopicFeedPage.follow","name":"TopicFeedPage.follow","line":57,"end_line":59,"hash":"7674b789a9d3c48e0f7a6e553613bac99b2f38449fcdd17faa3c6d7cd2773bdd"},{"id":"func/TopicFeedPage.unfollow","name":"TopicFeedPage.unfollow","line":61,"end_line":63,"hash":"69d278b09da1f284be6adacb7264f9c06ac71c42f8e8f1baf9e34d5b24a891fb"},{"id":"func/TopicFeedPage._setFollowState","name":"TopicFeedPage._setFollowState","line":65,"end_line":79,"hash":"698f22cdfc2c088446c732cf01864d8859b299e066c199eb542bc965413f48b4"},{"id":"func/TopicFeedPage.getPost","name":"TopicFeedPage.getPost","line":81,"end_line":83,"hash":"1a6ae1a02b0f79b5b62a2b2324a5f1edbd743bec004fe73cfef7970bead56885"}]}
 // mutate4javascript-manifest-end
diff --git a/psf-memo-client/src/services/topic-post-page.js b/psf-memo-client/src/services/topic-post-page.js
new file mode 100644
index 0000000..d305db9
--- /dev/null
+++ b/psf-memo-client/src/services/topic-post-page.js
@@ -0,0 +1,56 @@
+/*
+  Topic Post Page behavior: compose and broadcast a Memo topic message, with
+  a byte counter that counts down from the combined topic limit.
+
+  This is the testable controller behind the topic message composer on the
+  React "Topic Feed" page. It wraps the Memo topic-post behavior
+  (src/services/memo-topic-post.js) and adds page-level concerns: holding the
+  current input, computing the remaining byte count, surfacing
+  validation/length errors, and refreshing the topic feed after a successful
+  post.
+
+  The memoTopicPost and navigate concerns are injected so this module stays
+  free of UI/network concerns; environmentally unsuitable I/O lives behind
+  those small adapter boundaries.
+*/
+
+const PageController = require('./page-controller')
+const MemoTopicPost = require('./memo-topic-post')
+
+class TopicPostPage extends PageController {
+  constructor (deps = {}) {
+    super(deps)
+    this.memoTopicPost = deps.memoTopicPost || null
+    this.postingTopic = false
+    this.validationCodes = ['topic_post_validation', 'topic_post_length']
+  }
+
+  // Bytes remaining for the message given the topic name.
+  remainingCount () {
+    if (!this.memoTopicPost) {
+      throw new Error('Topic post page requires a memo topic post handler.')
+    }
+    return this.memoTopicPost.remainingBytes(this.input)
+  }
+
+  // Set the in-flight flag.
+  _setBusy (value) {
+    this.postingTopic = value
+  }
+
+  // Run the memo topic post action for the current input.
+  async _perform (input) {
+    if (!this.memoTopicPost) {
+      throw new Error('Topic post page requires a memo topic post handler.')
+    }
+    return this.memoTopicPost.post(input)
+  }
+}
+
+TopicPostPage.MAX_TOPIC_MESSAGE_BYTES = MemoTopicPost.MAX_TOPIC_MESSAGE_BYTES
+
+module.exports = TopicPostPage
+
+// mutate4javascript-manifest-begin
+// {"version":1,"tested_at":"2026-08-28T18:20:31.541Z","module_hash":"34b7d1b6936611010fd664764742b2d395db9b9c23699dc7ae0e938230d74847","functions":[{"id":"func/TopicPostPage.constructor","name":"TopicPostPage.constructor","line":21,"end_line":26,"hash":"a93d04b51599074b2e2aa3c85dda465e77fec20b43c73c76c3e153e98bdc1366"},{"id":"func/TopicPostPage.remainingCount","name":"TopicPostPage.remainingCount","line":29,"end_line":34,"hash":"e289a1a02748206cfb0967677fcff1ab92f2ceede8c6727d9b203538298e92e2"},{"id":"func/TopicPostPage._setBusy","name":"TopicPostPage._setBusy","line":37,"end_line":39,"hash":"4cc342945de59ccc4284e845c45fbd4c78508638c30fda621892d5554da2c985"},{"id":"func/TopicPostPage._perform","name":"TopicPostPage._perform","line":42,"end_line":47,"hash":"5900159e55ddb681034e06db3ec42e2e00d80cf99148f2bc99e15c766794fd7a"}]}
+// mutate4javascript-manifest-end
diff --git a/psf-memo-client/test/property/topic-post.property.test.js b/psf-memo-client/test/property/topic-post.property.test.js
new file mode 100644
index 0000000..6138b24
--- /dev/null
+++ b/psf-memo-client/test/property/topic-post.property.test.js
@@ -0,0 +1,79 @@
+/*
+  Property tests for the Memo topic-post byte accounting.
+
+  The unit tests probe isTooLong and remainingBytes at a few fixed fixtures.
+  These properties pin down invariants that hold over broad random UTF-8
+  inputs (mixed byte widths):
+
+    - byte accounting: remainingBytes(msg) always equals the combined byte
+      budget minus the room and message byte lengths.
+    - consistency: isTooLong(msg) is true exactly when remainingBytes(msg)
+      is negative.
+    - monotonicity: appending bytes never flips a too-long message back to
+      being accepted.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const { seededRandom, forAll } = require('./harness')
+const MemoTopicPost = require('../../src/services/memo-topic-post')
+const { byteLength } = require('../../src/services/utf8')
+
+const rng = seededRandom(20260901)
+const MAX = MemoTopicPost.MAX_TOPIC_MESSAGE_BYTES
+
+// Characters with distinct UTF-8 byte widths: 1, 1, 1, 2, 3, and 4 bytes.
+const CHARS = ['a', 'b', ' ', '\u00e9', '\u20ac', '\ud83d\ude00']
+
+function textGen () {
+  const len = Math.floor(rng() * 140)
+  let out = ''
+  for (let i = 0; i < len; i++) {
+    out += CHARS[Math.floor(rng() * CHARS.length)]
+  }
+  return out
+}
+
+function postInputGen () {
+  return () => ({ room: textGen(), msg: textGen() })
+}
+
+test('remainingBytes equals the byte budget minus room and message bytes', async () => {
+  await forAll(
+    postInputGen(),
+    ({ room, msg }) => {
+      const post = new MemoTopicPost({ room })
+      return post.remainingBytes(msg) === MAX - byteLength(room) - byteLength(msg)
+    },
+    { label: 'remainingBytes byte accounting' }
+  )
+})
+
+test('isTooLong is true exactly when remainingBytes is negative', async () => {
+  await forAll(
+    postInputGen(),
+    ({ room, msg }) => {
+      const post = new MemoTopicPost({ room })
+      return post.isTooLong(msg) === (post.remainingBytes(msg) < 0)
+    },
+    { label: 'isTooLong / remainingBytes consistency' }
+  )
+})
+
+test('isTooLong is monotonic as message bytes are appended', async () => {
+  await forAll(
+    () => {
+      const { room, msg } = postInputGen()()
+      const extra = textGen()
+      return { room, msg, extra }
+    },
+    ({ room, msg, extra }) => {
+      const post = new MemoTopicPost({ room })
+      // Appending bytes can only make a message longer, so a too-long
+      // message must remain too-long once more bytes are added.
+      return !(post.isTooLong(msg) && !post.isTooLong(msg + extra))
+    },
+    { label: 'isTooLong monotonicity' }
+  )
+})
diff --git a/psf-memo-client/test/property/topic-services.property.test.js b/psf-memo-client/test/property/topic-services.property.test.js
index fa5b1c0..2d7dc6d 100644
--- a/psf-memo-client/test/property/topic-services.property.test.js
+++ b/psf-memo-client/test/property/topic-services.property.test.js
@@ -64,7 +64,10 @@ test('TopicFeedPage.getPost finds any loaded post', async () => {
       return posts
     },
     async (posts) => {
-      const memoDb = { async getTopicPosts () { return { posts, pagination: { total: posts.length } } } }
+      const memoDb = {
+        async getTopicPosts () { return { posts, pagination: { total: posts.length } } },
+        async getTopicFollowers () { return [] }
+      }
       const page = new TopicFeedPage({ memoDb, room: 'bitcoin' })
       await page.load()
 
diff --git a/psf-memo-client/test/unit/memo-topic-follow.test.js b/psf-memo-client/test/unit/memo-topic-follow.test.js
new file mode 100644
index 0000000..ad1895b
--- /dev/null
+++ b/psf-memo-client/test/unit/memo-topic-follow.test.js
@@ -0,0 +1,113 @@
+/*
+  Unit tests for the Memo topic follow/unfollow behavior.
+
+  A topic follow or unfollow transaction carries the topic name as plain UTF-8
+  text with the Memo topic-follow (0x6d0d) or topic-unfollow (0x6d0e) prefix.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert/strict')
+const MemoTopicFollow = require('../../src/services/memo-topic-follow')
+
+const MY_ADDRESS = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+
+function makeWallet (address = MY_ADDRESS) {
+  return {
+    walletInfo: { cashAddress: address },
+    broadcasts: [],
+    async getUtxos () {
+      return []
+    },
+    async sendOpReturn (msg, prefix) {
+      this.broadcasts.push({ msg, prefix })
+      return 'aa'.repeat(32)
+    }
+  }
+}
+
+function makeProfiles () {
+  const state = {}
+  return {
+    state,
+    setTopicFollowState: (selfAddr, room, isFollowing) => {
+      if (!state[selfAddr]) state[selfAddr] = {}
+      state[selfAddr][room] = isFollowing
+    },
+    getTopicFollowState: (selfAddr, room) => state[selfAddr]?.[room] || false
+  }
+}
+
+test('follow broadcasts with the Memo topic-follow prefix and topic name', async () => {
+  const wallet = makeWallet()
+  const memoTopicFollow = new MemoTopicFollow({ wallet })
+
+  await memoTopicFollow.follow('bitcoin')
+
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, MemoTopicFollow.MEMO_TOPIC_FOLLOW_PREFIX)
+  assert.equal(wallet.broadcasts[0].msg, 'bitcoin')
+})
+
+test('unfollow broadcasts with the Memo topic-unfollow prefix and topic name', async () => {
+  const wallet = makeWallet()
+  const memoTopicFollow = new MemoTopicFollow({ wallet })
+
+  await memoTopicFollow.unfollow('bitcoin')
+
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, MemoTopicFollow.MEMO_TOPIC_UNFOLLOW_PREFIX)
+  assert.equal(wallet.broadcasts[0].msg, 'bitcoin')
+})
+
+test('follow reflects the new state on the profile store', async () => {
+  const wallet = makeWallet()
+  const profiles = makeProfiles()
+  const memoTopicFollow = new MemoTopicFollow({ wallet, profiles })
+
+  await memoTopicFollow.follow('bitcoin')
+
+  assert.equal(profiles.getTopicFollowState(MY_ADDRESS, 'bitcoin'), true)
+})
+
+test('unfollow reflects the new state on the profile store', async () => {
+  const wallet = makeWallet()
+  const profiles = makeProfiles()
+  const memoTopicFollow = new MemoTopicFollow({ wallet, profiles })
+
+  await memoTopicFollow.unfollow('bitcoin')
+
+  assert.equal(profiles.getTopicFollowState(MY_ADDRESS, 'bitcoin'), false)
+})
+
+test('follow rejects an empty topic name', async () => {
+  const wallet = makeWallet()
+  const memoTopicFollow = new MemoTopicFollow({ wallet })
+
+  await assert.rejects(
+    () => memoTopicFollow.follow(''),
+    { code: 'topic_follow_validation', message: /Topic name is required/ }
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('follow requires a wallet', async () => {
+  const memoTopicFollow = new MemoTopicFollow({})
+
+  await assert.rejects(
+    () => memoTopicFollow.follow('bitcoin'),
+    /requires a wallet/
+  )
+})
+
+test('follow surfaces a broadcast failure', async () => {
+  const wallet = makeWallet()
+  wallet.sendOpReturn = async () => { throw new Error('broadcast failed') }
+  const memoTopicFollow = new MemoTopicFollow({ wallet })
+
+  await assert.rejects(
+    () => memoTopicFollow.follow('bitcoin'),
+    /broadcast failed/
+  )
+})
diff --git a/psf-memo-client/test/unit/memo-topic-post.test.js b/psf-memo-client/test/unit/memo-topic-post.test.js
new file mode 100644
index 0000000..a6f21f4
--- /dev/null
+++ b/psf-memo-client/test/unit/memo-topic-post.test.js
@@ -0,0 +1,124 @@
+/*
+  Unit tests for the Memo topic message behavior.
+
+  A topic message combines the topic name and message text, then broadcasts
+  it with the Memo topic-message prefix (0x6d0c). The combined topic + message
+  must not exceed 214 bytes.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert/strict')
+const MemoTopicPost = require('../../src/services/memo-topic-post')
+
+function makeWallet (address = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d') {
+  return {
+    walletInfo: { cashAddress: address },
+    broadcasts: [],
+    async getUtxos () {
+      return []
+    },
+    async sendOpReturn (msg, prefix) {
+      this.broadcasts.push({ msg, prefix })
+      return 'aa'.repeat(32)
+    }
+  }
+}
+
+test('post broadcasts topic name and message with the topic-message prefix', async () => {
+  const wallet = makeWallet()
+  const memoTopicPost = new MemoTopicPost({ wallet, room: 'bitcoin' })
+
+  await memoTopicPost.post('hello bitcoin')
+
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, MemoTopicPost.MEMO_TOPIC_MESSAGE_PREFIX)
+  assert.equal(wallet.broadcasts[0].msg, 'bitcoinhello bitcoin')
+})
+
+test('post reflects the new topic post on the injected feed', async () => {
+  const wallet = makeWallet()
+  const added = []
+  const feed = {
+    addPost (post) {
+      added.push(post)
+    }
+  }
+  const memoTopicPost = new MemoTopicPost({ wallet, room: 'cash', feed })
+
+  await memoTopicPost.post('hello cash')
+
+  assert.equal(added.length, 1)
+  assert.equal(added[0].text, 'hello cash')
+  assert.equal(added[0].room, 'cash')
+  assert.equal(added[0].address, wallet.walletInfo.cashAddress)
+})
+
+test('post rejects an empty message', async () => {
+  const wallet = makeWallet()
+  const memoTopicPost = new MemoTopicPost({ wallet, room: 'bitcoin' })
+
+  await assert.rejects(
+    () => memoTopicPost.post(''),
+    { code: 'topic_post_validation', message: /must not be empty/ }
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('post rejects a message that exceeds the combined byte limit', async () => {
+  const wallet = makeWallet()
+  const memoTopicPost = new MemoTopicPost({ wallet, room: 'bitcoin' })
+  // "bitcoin" is 7 bytes; 214 - 7 = 207. Use 208 ASCII 'a' characters.
+  const message = 'a'.repeat(208)
+
+  await assert.rejects(
+    () => memoTopicPost.post(message),
+    { code: 'topic_post_length', message: /too long/ }
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('post accepts a message at the combined byte limit', async () => {
+  const wallet = makeWallet()
+  const memoTopicPost = new MemoTopicPost({ wallet, room: 'bitcoin' })
+  const message = 'a'.repeat(207)
+
+  await memoTopicPost.post(message)
+
+  assert.equal(wallet.broadcasts.length, 1)
+})
+
+test('remainingBytes accounts for the topic name', () => {
+  const memoTopicPost = new MemoTopicPost({ room: 'bitcoin' })
+
+  assert.equal(memoTopicPost.remainingBytes(''), 207)
+  assert.equal(memoTopicPost.remainingBytes('hello'), 202)
+})
+
+test('remainingBytes counts UTF-8 bytes', () => {
+  const memoTopicPost = new MemoTopicPost({ room: 'bitcoin' })
+
+  // 'é' is 2 UTF-8 bytes.
+  assert.equal(memoTopicPost.remainingBytes('é'), 205)
+})
+
+test('post requires a wallet', async () => {
+  const memoTopicPost = new MemoTopicPost({ room: 'bitcoin' })
+
+  await assert.rejects(
+    () => memoTopicPost.post('hello'),
+    /requires a wallet/
+  )
+})
+
+test('post surfaces a broadcast failure', async () => {
+  const wallet = makeWallet()
+  wallet.sendOpReturn = async () => { throw new Error('broadcast failed') }
+  const memoTopicPost = new MemoTopicPost({ wallet, room: 'bitcoin' })
+
+  await assert.rejects(
+    () => memoTopicPost.post('hello'),
+    /broadcast failed/
+  )
+})
diff --git a/psf-memo-client/test/unit/profiles.test.js b/psf-memo-client/test/unit/profiles.test.js
index 531a0bb..98d5f1f 100644
--- a/psf-memo-client/test/unit/profiles.test.js
+++ b/psf-memo-client/test/unit/profiles.test.js
@@ -134,6 +134,85 @@ test('follow state storage is independent per self address', () => {
   assert.equal(profiles.getFollowState(otherSelfAddr, targetAddr), false)
 })
 
+test('setTopicFollowState stores and getTopicFollowState retrieves topic follow state', () => {
+  const profiles = new Profiles()
+  const selfAddr = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+  const room = 'bitcoin'
+
+  profiles.setTopicFollowState(selfAddr, room, true)
+
+  assert.equal(profiles.getTopicFollowState(selfAddr, room), true)
+})
+
+test('getTopicFollowState returns false for an unknown topic relationship', () => {
+  const profiles = new Profiles()
+  const selfAddr = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+
+  assert.equal(profiles.getTopicFollowState(selfAddr, 'bitcoin'), false)
+})
+
+test('setTopicFollowState with no self address does nothing', () => {
+  const profiles = new Profiles()
+
+  profiles.setTopicFollowState('', 'bitcoin', true)
+
+  assert.equal(profiles.getTopicFollowState('', 'bitcoin'), false)
+})
+
+test('setTopicFollowState with no room does nothing', () => {
+  const profiles = new Profiles()
+  const selfAddr = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+
+  profiles.setTopicFollowState(selfAddr, '', true)
+
+  assert.equal(profiles.getTopicFollowState(selfAddr, ''), false)
+})
+
+test('_setMapState stores nothing when either input is missing', () => {
+  const profiles = new Profiles()
+
+  // Missing self address, present room.
+  profiles.setTopicFollowState('', 'bitcoin', true)
+  // Present self address, missing room.
+  profiles.setTopicFollowState('bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d', '', true)
+
+  assert.equal(profiles.topicFollowing.size, 0)
+})
+
+test('_getMapState ignores stored state when either input is missing', () => {
+  const profiles = new Profiles()
+
+  // Manually store under a missing room to prove the read guard alone reports
+  // not-following instead of leaking the stored value.
+  profiles.topicFollowing.set('bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d', new Map([['', true]]))
+
+  assert.equal(profiles.getTopicFollowState('bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d', ''), false)
+})
+
+test('topic follow state storage is independent per self address', () => {
+  const profiles = new Profiles()
+  const selfAddr = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+  const otherSelfAddr = 'bitcoincash:qpm2qsznhks23z7629mms6s4cwef74vcwvy22gdx6a'
+
+  profiles.setTopicFollowState(selfAddr, 'bitcoin', true)
+  profiles.setTopicFollowState(otherSelfAddr, 'bitcoin', false)
+
+  assert.equal(profiles.getTopicFollowState(selfAddr, 'bitcoin'), true)
+  assert.equal(profiles.getTopicFollowState(otherSelfAddr, 'bitcoin'), false)
+})
+
+test('topic follow state storage is independent of address follow state', () => {
+  const profiles = new Profiles()
+  const selfAddr = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+  const targetAddr = 'bitcoincash:qr95sy3j9xwd2ap32xkykttr4cvcu7as4y0qverfuy'
+
+  profiles.setFollowState(selfAddr, targetAddr, true)
+  profiles.setTopicFollowState(selfAddr, 'bitcoin', true)
+
+  assert.equal(profiles.getFollowState(selfAddr, targetAddr), true)
+  assert.equal(profiles.getTopicFollowState(selfAddr, 'bitcoin'), true)
+})
+
 test('avatar URL storage is independent of name and bio storage', () => {
   const profiles = new Profiles()
   const addr = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
diff --git a/psf-memo-client/test/unit/topic-feed-page.test.js b/psf-memo-client/test/unit/topic-feed-page.test.js
index 89e2e17..92a6c18 100644
--- a/psf-memo-client/test/unit/topic-feed-page.test.js
+++ b/psf-memo-client/test/unit/topic-feed-page.test.js
@@ -8,10 +8,32 @@ const test = require('node:test')
 const assert = require('node:assert/strict')
 const TopicFeedPage = require('../../src/services/topic-feed-page')
 
-function makeMemoDb (posts, pagination) {
+const MY_ADDRESS = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+
+function makeMemoDb (posts, pagination, { following = false, followers = [] } = {}) {
   return {
     async getTopicPosts (room, { limit, offset }) {
       return { posts, pagination }
+    },
+    async getTopicFollowState (room, addr) {
+      return following
+    },
+    async getTopicFollowers (room) {
+      return followers
+    }
+  }
+}
+
+function makeMemoTopicFollow () {
+  return {
+    broadcasts: [],
+    async follow (room) {
+      this.broadcasts.push({ action: 'follow', room })
+      return 'aa'.repeat(32)
+    },
+    async unfollow (room) {
+      this.broadcasts.push({ action: 'unfollow', room })
+      return 'bb'.repeat(32)
     }
   }
 }
@@ -34,6 +56,12 @@ test('load forwards limit and offset to the memo db client', async () => {
     async getTopicPosts (room, params) {
       calls.push({ room, params })
       return { posts: [], pagination: {} }
+    },
+    async getTopicFollowState () {
+      return false
+    },
+    async getTopicFollowers () {
+      return []
     }
   }
   const page = new TopicFeedPage({ memoDb, room: 'bitcoin' })
@@ -49,6 +77,12 @@ test('load defaults limit and offset', async () => {
     async getTopicPosts (room, params) {
       calls.push(params)
       return { posts: [], pagination: {} }
+    },
+    async getTopicFollowState () {
+      return false
+    },
+    async getTopicFollowers () {
+      return []
     }
   }
   const page = new TopicFeedPage({ memoDb, room: 'bitcoin' })
@@ -85,6 +119,13 @@ test('load throws when no room is provided', async () => {
   )
 })
 
+test('starts not following and with no followers', () => {
+  const page = new TopicFeedPage({ room: 'bitcoin' })
+
+  assert.equal(page.followState, false)
+  assert.deepEqual(page.followers, [])
+})
+
 test('getPost returns a loaded post by txid', async () => {
   const posts = [{ txid: 'a'.repeat(64), text: 'hello bitcoin' }]
   const page = new TopicFeedPage({ memoDb: makeMemoDb(posts, {}), room: 'bitcoin' })
@@ -102,6 +143,86 @@ test('getPost returns null for an unknown txid', async () => {
   assert.equal(page.getPost('c'.repeat(64)), null)
 })
 
+test('load fetches follow state when myAddr is provided', async () => {
+  const page = new TopicFeedPage({
+    memoDb: makeMemoDb([], {}, { following: true }),
+    room: 'bitcoin',
+    myAddr: MY_ADDRESS
+  })
+
+  const result = await page.load()
+
+  assert.equal(result.followState, true)
+  assert.equal(page.isFollowing(), true)
+})
+
+test('load returns following=false when no myAddr is provided', async () => {
+  const page = new TopicFeedPage({ memoDb: makeMemoDb([], {}), room: 'bitcoin' })
+
+  const result = await page.load()
+
+  assert.equal(result.followState, false)
+})
+
+test('load fetches followers list', async () => {
+  const followers = ['bitcoincash:a', 'bitcoincash:b']
+  const page = new TopicFeedPage({
+    memoDb: makeMemoDb([], {}, { followers }),
+    room: 'bitcoin'
+  })
+
+  const result = await page.load()
+
+  assert.deepEqual(result.followers, followers)
+})
+
+test('follow broadcasts and updates local state', async () => {
+  const memoTopicFollow = makeMemoTopicFollow()
+  const page = new TopicFeedPage({
+    memoDb: makeMemoDb([], {}),
+    room: 'bitcoin',
+    myAddr: MY_ADDRESS,
+    memoTopicFollow
+  })
+
+  const result = await page.follow()
+
+  assert.equal(result.ok, true)
+  assert.equal(page.isFollowing(), true)
+  assert.deepEqual(memoTopicFollow.broadcasts, [{ action: 'follow', room: 'bitcoin' }])
+  assert.ok(page.followers.includes(MY_ADDRESS))
+})
+
+test('unfollow broadcasts and updates local state', async () => {
+  const memoTopicFollow = makeMemoTopicFollow()
+  const page = new TopicFeedPage({
+    memoDb: makeMemoDb([], {}),
+    room: 'bitcoin',
+    myAddr: MY_ADDRESS,
+    memoTopicFollow
+  })
+
+  const result = await page.unfollow()
+
+  assert.equal(result.ok, true)
+  assert.equal(page.isFollowing(), false)
+  assert.deepEqual(memoTopicFollow.broadcasts, [{ action: 'unfollow', room: 'bitcoin' }])
+  assert.ok(!page.followers.includes(MY_ADDRESS))
+})
+
+test('follow requires a memo topic follow handler', async () => {
+  const page = new TopicFeedPage({
+    memoDb: makeMemoDb([], {}),
+    room: 'bitcoin',
+    myAddr: MY_ADDRESS
+  })
+
+  await assert.rejects(
+    () => page.follow(),
+    /requires a memo topic follow handler/
+  )
+})
+
 test('exposes the topic feed path for a room', () => {
   assert.equal(TopicFeedPage.topicFeedPath('bitcoin'), '/topics/bitcoin')
 })
diff --git a/psf-memo-client/test/unit/topic-post-page.test.js b/psf-memo-client/test/unit/topic-post-page.test.js
new file mode 100644
index 0000000..cdda058
--- /dev/null
+++ b/psf-memo-client/test/unit/topic-post-page.test.js
@@ -0,0 +1,103 @@
+/*
+  Unit tests for the Topic Post Page controller.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert/strict')
+const TopicPostPage = require('../../src/services/topic-post-page')
+
+function makeMemoTopicPost (room = 'bitcoin') {
+  const maxBytes = 214
+  return {
+    room,
+    posts: [],
+    async post (message) {
+      if (typeof message !== 'string' || message.trim().length === 0) {
+        const err = new Error('Topic message must not be empty.')
+        err.code = 'topic_post_validation'
+        throw err
+      }
+      if (room.length + message.length > maxBytes) {
+        const err = new Error(`Topic message is too long. Maximum is ${maxBytes} bytes.`)
+        err.code = 'topic_post_length'
+        throw err
+      }
+      this.posts.push(message)
+      return 'aa'.repeat(32)
+    },
+    remainingBytes (message) {
+      return maxBytes - room.length - (message ? message.length : 0)
+    }
+  }
+}
+
+test('submit posts the current input', async () => {
+  const memoTopicPost = makeMemoTopicPost()
+  const page = new TopicPostPage({ memoTopicPost })
+  page.setInput('hello bitcoin')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, true)
+  assert.deepEqual(memoTopicPost.posts, ['hello bitcoin'])
+})
+
+test('remainingCount delegates to the memo topic post handler', () => {
+  const memoTopicPost = makeMemoTopicPost()
+  const page = new TopicPostPage({ memoTopicPost })
+  page.setInput('hello')
+
+  assert.equal(page.remainingCount(), 202)
+})
+
+test('submit returns a validation error for empty input', async () => {
+  const memoTopicPost = makeMemoTopicPost()
+  const page = new TopicPostPage({ memoTopicPost })
+  page.setInput('')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'topic_post_validation')
+})
+
+test('submit returns a length error for over-long input', async () => {
+  const memoTopicPost = makeMemoTopicPost()
+  const page = new TopicPostPage({ memoTopicPost })
+  page.setInput('a'.repeat(300))
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'topic_post_length')
+})
+
+test('submit requires a memo topic post handler', async () => {
+  const page = new TopicPostPage({})
+  page.setInput('hello')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'broadcast')
+})
+
+test('remainingCount requires a memo topic post handler', () => {
+  const page = new TopicPostPage({})
+
+  assert.throws(
+    () => page.remainingCount(),
+    /requires a memo topic post handler/
+  )
+})
+
+test('exposes the combined byte limit', () => {
+  assert.equal(TopicPostPage.MAX_TOPIC_MESSAGE_BYTES, 214)
+})
+
+test('starts not busy', () => {
+  const page = new TopicPostPage({})
+  assert.equal(page.postingTopic, false)
+})
diff --git a/psf-memo-db/acceptance/lib/handlers.js b/psf-memo-db/acceptance/lib/handlers.js
index 78c20ea..124442e 100644
--- a/psf-memo-db/acceptance/lib/handlers.js
+++ b/psf-memo-db/acceptance/lib/handlers.js
@@ -20,6 +20,8 @@ import ListFollowing from '../../src/use-cases/list-following.js'
 import ListFollowers from '../../src/use-cases/list-followers.js'
 import ListTopics from '../../src/use-cases/list-topics.js'
 import ListTopicPosts from '../../src/use-cases/list-topic-posts.js'
+import TopicFollowState from '../../src/use-cases/topic-follow-state.js'
+import ListTopicFollowers from '../../src/use-cases/list-topic-followers.js'
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url))
 const tmpDir = path.resolve(__dirname, '..', '..', 'tmp', 'acceptance')
@@ -96,6 +98,8 @@ async function createWorld () {
   const listFollowers = new ListFollowers({ adapters })
   const listTopics = new ListTopics({ adapters })
   const listTopicPosts = new ListTopicPosts({ adapters })
+  const topicFollowState = new TopicFollowState({ adapters })
+  const listTopicFollowers = new ListTopicFollowers({ adapters })
 
   let lastResponse = null
 
@@ -109,6 +113,8 @@ async function createWorld () {
     listFollowers,
     listTopics,
     listTopicPosts,
+    topicFollowState,
+    listTopicFollowers,
     postHeightsIteratorCounter,
     addrPostHeightsIteratorCounter,
     postChildrenIteratorCounter,
@@ -153,6 +159,11 @@ async function loadFixture (world, name) {
     return
   }
 
+  if (name === 'topic-follows') {
+    await loadTopicFollows(world)
+    return
+  }
+
   if (name !== 'three-top-level-posts-and-one-reply') {
     throw new Error(`Unknown fixture: ${name}`)
   }
@@ -364,6 +375,19 @@ async function loadTopicsWithPosts (world) {
   }
 }
 
+async function loadTopicFollows (world) {
+  const entries = [
+    { key: 'bitcoin:addr-a', room: 'bitcoin', addr: 'addr-a', type: 'follow', unfollow: false },
+    { key: 'bitcoin:addr-b', room: 'bitcoin', addr: 'addr-b', type: 'follow', unfollow: false },
+    { key: 'bitcoin:addr-c', room: 'bitcoin', addr: 'addr-c', type: 'follow', unfollow: true },
+    { key: 'cash:addr-a', room: 'cash', addr: 'addr-a', type: 'follow', unfollow: false }
+  ]
+
+  for (const entry of entries) {
+    await world.adapters.level.roomsDb.put(entry.key, entry)
+  }
+}
+
 const handlers = [
   {
     name: 'db instance with posts and postHeights stores',
@@ -780,6 +804,64 @@ const handlers = [
         throw new Error(`Expected no posts, got ${Array.isArray(posts) ? posts.length : 'non-array'}`)
       }
     }
+  },
+  {
+    name: 'db instance with rooms store',
+    pattern: /^a psf-memo-db instance with a rooms store$/,
+    async run () {
+      // World is already created with the rooms store.
+    }
+  },
+  {
+    name: 'load fixture into rooms store',
+    pattern: /^the fixture "(.+)" is loaded into the rooms store$/,
+    async run (m, example, world) {
+      await loadFixture(world, m[1])
+    }
+  },
+  {
+    name: 'request topic follow state',
+    pattern: /^the client requests the topic follow state for room (<[A-Za-z0-9_]+>) and address (<[A-Za-z0-9_]+>)$/,
+    async run (m, example, world) {
+      const room = resolveParam(m[1], example)
+      const addr = resolveParam(m[2], example)
+      const resp = await world.topicFollowState.execute({ room, addr })
+      world.setLastResponse(resp)
+    }
+  },
+  {
+    name: 'topic follow state reports following',
+    pattern: /^the topic follow state reports following (<following>)$/,
+    run (m, example, world) {
+      const expected = resolveParam(m[1], example) === 'true'
+      const actual = world.getLastResponse().following
+      if (actual !== expected) {
+        throw new Error(`Expected following ${expected}, got ${actual}`)
+      }
+    }
+  },
+  {
+    name: 'request topic followers list',
+    pattern: /^the client requests the topic followers list for room (<[A-Za-z0-9_]+>)$/,
+    async run (m, example, world) {
+      const room = resolveParam(m[1], example)
+      const resp = await world.listTopicFollowers.execute({ room })
+      world.setLastResponse(resp)
+    }
+  },
+  {
+    name: 'topic followers list contains addresses',
+    pattern: /^the topic followers list contains the addresses (<expected>)$/,
+    run (m, example, world) {
+      const raw = resolveParam(m[1], example).trim()
+      const expected = raw.length === 0 ? [] : raw.split(',').map((s) => s.trim())
+      const actual = world.getLastResponse().followers
+      const expectedSet = new Set(expected)
+      const actualSet = new Set(actual)
+      if (expectedSet.size !== actualSet.size || !expectedSet.isSubsetOf(actualSet)) {
+        throw new Error(`Expected topic followers ${expected.join(',')}, got ${actual.join(',')}`)
+      }
+    }
   }
 ]
 
diff --git a/psf-memo-db/specs/topic-follow-read.feature b/psf-memo-db/specs/topic-follow-read.feature
index a86a6c7..d9a8271 100644
--- a/psf-memo-db/specs/topic-follow-read.feature
+++ b/psf-memo-db/specs/topic-follow-read.feature
@@ -1,3 +1,7 @@
+# acceptance-mutation-manifest-begin
+# {"version":1,"tested_at":"2026-08-28T20:09:23.829689449Z","feature_name":"Topic Follow Read","feature_path":"/home/trout/work/psf-memo/.worktrees/architect/psf-memo-db/specs/topic-follow-read.feature","background_hash":"bf41600ace5aaae19b01881936ae5ec595b53abbb9829b5f7927f43a830ded38","implementation_hash":"unknown","scenarios":[]}
+# acceptance-mutation-manifest-end
+
 # Scenarios: Topic Follow Read - 1, Topic Follow Read - 2
 #
 # The indexer stores topic follows in the rooms store keyed `${room}:${addr}`
diff --git a/psf-memo-db/src/adapters/topic-query.js b/psf-memo-db/src/adapters/topic-query.js
index 2b340f0..07f6d8d 100644
--- a/psf-memo-db/src/adapters/topic-query.js
+++ b/psf-memo-db/src/adapters/topic-query.js
@@ -24,8 +24,11 @@ class TopicQuery {
 
     this.listTopics = this.listTopics.bind(this)
     this.getTopicPostTxids = this.getTopicPostTxids.bind(this)
+    this.isFollowingRoom = this.isFollowingRoom.bind(this)
+    this.listRoomFollowers = this.listRoomFollowers.bind(this)
     this.roomFromKey = this.roomFromKey.bind(this)
     this.txidFromKey = this.txidFromKey.bind(this)
+    this.followAddrFromValue = this.followAddrFromValue.bind(this)
   }
 
   roomFromKey (key, value) {
@@ -75,10 +78,42 @@ class TopicQuery {
 
     return { txids, total }
   }
+
+  // Return true when addr has an active follow record for room.
+  async isFollowingRoom (addr, room) {
+    const key = `${room}:${addr}`
+    try {
+      const record = await this.roomsDb.get(key)
+      return record?.type === 'follow' && record?.unfollow !== true
+    } catch (err) {
+      if (err.notFound) return false
+      throw err
+    }
+  }
+
+  // Return the cash addresses that currently follow the room.
+  async listRoomFollowers (room) {
+    const start = `${room}:`
+    const end = `${room}:\uffff`
+    const followers = []
+    for await (const [key, value] of this.roomsDb.iterator({ gte: start, lte: end })) {
+      if (value?.type !== 'follow') continue
+      if (value?.unfollow === true) continue
+      const addr = this.followAddrFromValue(value, key)
+      if (addr) followers.push(addr)
+    }
+    return followers
+  }
+
+  followAddrFromValue (value, key) {
+    if (value && typeof value.addr === 'string') return value.addr
+    const parts = String(key).split(':')
+    return parts.length > 1 ? parts[parts.length - 1] : null
+  }
 }
 
 export default TopicQuery
 
 // mutate4javascript-manifest-begin
-// {"version":1,"tested_at":"2026-08-28T14:46:39.922Z","module_hash":"515aa0e8cfdc7d596b270d5c4b82e2f33efa7f074ea406b6850007402d69f2e2","functions":[{"id":"func/TopicQuery.constructor","name":"TopicQuery.constructor","line":14,"end_line":29,"hash":"1c1e10e3ee613b0cd141a941849ce28a99eac688142629c7781ded6e5e15c938"},{"id":"func/TopicQuery.roomFromKey","name":"TopicQuery.roomFromKey","line":31,"end_line":34,"hash":"4175916ac2bb8f9f102c70750f336ed980db2a30a1f8f35645534303408aaece"},{"id":"func/TopicQuery.txidFromKey","name":"TopicQuery.txidFromKey","line":36,"end_line":39,"hash":"4f5f5c456f1e74a60acff54d1d5e2d982be53886c2a77c6eff3293133efa9c87"},{"id":"func/TopicQuery.listTopics","name":"TopicQuery.listTopics","line":41,"end_line":57,"hash":"9c524ef62e22d7a434768dc431c360f9c81b0c2a321b162a614f7f7e1e011e08"},{"id":"func/TopicQuery.getTopicPostTxids","name":"TopicQuery.getTopicPostTxids","line":59,"end_line":77,"hash":"4e0fccf874560249152d04d13879c24fbae0271bf7835716789dfafcff7dbd04"}]}
+// {"version":1,"tested_at":"2026-08-28T19:16:59.454Z","module_hash":"7b5597f76aed02abe591e652087cb1c560dd17a1154a62299f50f60303aa6e87","functions":[{"id":"func/TopicQuery.constructor","name":"TopicQuery.constructor","line":14,"end_line":32,"hash":"08f209a40b4ffc2962e5f399e78936005f3286ec37123a043850b12e0c20833b"},{"id":"func/TopicQuery.roomFromKey","name":"TopicQuery.roomFromKey","line":34,"end_line":37,"hash":"4175916ac2bb8f9f102c70750f336ed980db2a30a1f8f35645534303408aaece"},{"id":"func/TopicQuery.txidFromKey","name":"TopicQuery.txidFromKey","line":39,"end_line":42,"hash":"4f5f5c456f1e74a60acff54d1d5e2d982be53886c2a77c6eff3293133efa9c87"},{"id":"func/TopicQuery.listTopics","name":"TopicQuery.listTopics","line":44,"end_line":60,"hash":"9c524ef62e22d7a434768dc431c360f9c81b0c2a321b162a614f7f7e1e011e08"},{"id":"func/TopicQuery.getTopicPostTxids","name":"TopicQuery.getTopicPostTxids","line":62,"end_line":80,"hash":"4e0fccf874560249152d04d13879c24fbae0271bf7835716789dfafcff7dbd04"},{"id":"func/TopicQuery.isFollowingRoom","name":"TopicQuery.isFollowingRoom","line":83,"end_line":92,"hash":"a0cf48cc6f4842adf65830b41d536cd6a078c7adf6b837e57259491157e2e97d"},{"id":"func/TopicQuery.listRoomFollowers","name":"TopicQuery.listRoomFollowers","line":95,"end_line":106,"hash":"351d71881e8b0953366056f223a6f06326e8ecd946277abc372ae5771c0b0f08"},{"id":"func/TopicQuery.followAddrFromValue","name":"TopicQuery.followAddrFromValue","line":108,"end_line":112,"hash":"2ce68c35f539e1fd7694774059b4b2afd096014c99a87c7538f3cbb70e26c3c7"}]}
 // mutate4javascript-manifest-end
diff --git a/psf-memo-db/src/controllers/rest-api/topics/controller.js b/psf-memo-db/src/controllers/rest-api/topics/controller.js
index 67e8417..2ebda83 100644
--- a/psf-memo-db/src/controllers/rest-api/topics/controller.js
+++ b/psf-memo-db/src/controllers/rest-api/topics/controller.js
@@ -17,6 +17,8 @@ class TopicsRESTControllerLib {
 
     this.getTopics = this.getTopics.bind(this)
     this.getTopicPosts = this.getTopicPosts.bind(this)
+    this.getTopicFollowState = this.getTopicFollowState.bind(this)
+    this.getTopicFollowers = this.getTopicFollowers.bind(this)
     this.handleError = this.handleError.bind(this)
   }
 
@@ -86,10 +88,63 @@ class TopicsRESTControllerLib {
       this.handleError(ctx, err)
     }
   }
+
+  /**
+   * @api {get} /topics/:room/follow/state Check topic follow state
+   * @apiPermission public
+   * @apiName GetTopicFollowState
+   * @apiGroup REST Topics
+   *
+   * @apiDescription Returns whether an address follows a topic.
+   *
+   * @apiParam {String} room Topic name
+   * @apiQuery {String} addr Cash address to check
+   *
+   * @apiExample Example usage:
+   * curl -X GET "localhost:5021/topics/bitcoin/follow/state?addr=bitcoincash:q..."
+   *
+   * @apiSuccess {String} room Topic name
+   * @apiSuccess {String} addr Checked cash address
+   * @apiSuccess {Boolean} following True when an active topic follow exists
+   */
+  async getTopicFollowState (ctx) {
+    try {
+      const { room } = ctx.params
+      const { addr } = ctx.query
+      ctx.body = await this.useCases.topicFollowState.execute({ room, addr })
+    } catch (err) {
+      this.handleError(ctx, err)
+    }
+  }
+
+  /**
+   * @api {get} /topics/:room/followers List topic followers
+   * @apiPermission public
+   * @apiName GetTopicFollowers
+   * @apiGroup REST Topics
+   *
+   * @apiDescription Returns the addresses that currently follow a topic.
+   *
+   * @apiParam {String} room Topic name
+   *
+   * @apiExample Example usage:
+   * curl -X GET "localhost:5021/topics/bitcoin/followers"
+   *
+   * @apiSuccess {String} room Topic name
+   * @apiSuccess {String[]} followers Array of follower cash addresses
+   */
+  async getTopicFollowers (ctx) {
+    try {
+      const { room } = ctx.params
+      ctx.body = await this.useCases.listTopicFollowers.execute({ room })
+    } catch (err) {
+      this.handleError(ctx, err)
+    }
+  }
 }
 
 export default TopicsRESTControllerLib
 
 // mutate4javascript-manifest-begin
-// {"version":1,"tested_at":"2026-08-28T15:26:54.488Z","module_hash":"64ac0a8aa7c2e0b575a89161ceb19c59e6618448eaf767ef5bbccc3ce174afaa","functions":[{"id":"func/TopicsRESTControllerLib.constructor","name":"TopicsRESTControllerLib.constructor","line":8,"end_line":21,"hash":"63d2092a2bd7946dd11bdf0c4ff102e31c47a0ed6ad56a0652f26e1760d525f9"},{"id":"func/TopicsRESTControllerLib.handleError","name":"TopicsRESTControllerLib.handleError","line":23,"end_line":30,"hash":"b9ba0c7b9752ac2fda3cf058a983a8b6708715e2e4dc882903ab5ef369956e03"},{"id":"func/TopicsRESTControllerLib.getTopics","name":"TopicsRESTControllerLib.getTopics","line":47,"end_line":53,"hash":"b89a696bcd1d601ef86754974dbf181baf2ece7d592674ba4fd87887725d6fa8"},{"id":"func/TopicsRESTControllerLib.getTopicPosts","name":"TopicsRESTControllerLib.getTopicPosts","line":80,"end_line":88,"hash":"8ad5f9b1749968c3fbfea95683bb388a5d99eda0b8fe7a4dce3447d6d47e6dba"}]}
+// {"version":1,"tested_at":"2026-08-28T19:53:31.127Z","module_hash":"4c3f3e9152899ed272cb583e558c4522c0f54c37a0ae728f3ec6bc40248a3fdc","functions":[{"id":"func/TopicsRESTControllerLib.constructor","name":"TopicsRESTControllerLib.constructor","line":8,"end_line":23,"hash":"bacd230f3777dda39ec134a69a9a7c1801cb3cd09c0cc86659df324540053028"},{"id":"func/TopicsRESTControllerLib.handleError","name":"TopicsRESTControllerLib.handleError","line":25,"end_line":32,"hash":"b9ba0c7b9752ac2fda3cf058a983a8b6708715e2e4dc882903ab5ef369956e03"},{"id":"func/TopicsRESTControllerLib.getTopics","name":"TopicsRESTControllerLib.getTopics","line":49,"end_line":55,"hash":"b89a696bcd1d601ef86754974dbf181baf2ece7d592674ba4fd87887725d6fa8"},{"id":"func/TopicsRESTControllerLib.getTopicPosts","name":"TopicsRESTControllerLib.getTopicPosts","line":82,"end_line":90,"hash":"8ad5f9b1749968c3fbfea95683bb388a5d99eda0b8fe7a4dce3447d6d47e6dba"},{"id":"func/TopicsRESTControllerLib.getTopicFollowState","name":"TopicsRESTControllerLib.getTopicFollowState","line":110,"end_line":118,"hash":"6d72fecc2bf46276cd00d39cc1c19ed6647beed1f2f3ba187a2c085ed4308611"},{"id":"func/TopicsRESTControllerLib.getTopicFollowers","name":"TopicsRESTControllerLib.getTopicFollowers","line":136,"end_line":143,"hash":"2bcd22520d962c008a3255f5cf6cf536fdeb738d036d3c6b6d61d5d5cf040615"}]}
 // mutate4javascript-manifest-end
diff --git a/psf-memo-db/src/controllers/rest-api/topics/index.js b/psf-memo-db/src/controllers/rest-api/topics/index.js
index d092516..7b83997 100644
--- a/psf-memo-db/src/controllers/rest-api/topics/index.js
+++ b/psf-memo-db/src/controllers/rest-api/topics/index.js
@@ -26,6 +26,8 @@ class TopicsRouter {
   attach (app) {
     this.router.get('/', this.topicsRESTController.getTopics)
     this.router.get('/:room/posts', this.topicsRESTController.getTopicPosts)
+    this.router.get('/:room/follow/state', this.topicsRESTController.getTopicFollowState)
+    this.router.get('/:room/followers', this.topicsRESTController.getTopicFollowers)
     app.use(this.router.routes())
     app.use(this.router.allowedMethods())
   }
diff --git a/psf-memo-db/src/use-cases/index.js b/psf-memo-db/src/use-cases/index.js
index 3f9b371..eecc365 100644
--- a/psf-memo-db/src/use-cases/index.js
+++ b/psf-memo-db/src/use-cases/index.js
@@ -11,6 +11,8 @@ import ListFollowing from './list-following.js'
 import ListFollowers from './list-followers.js'
 import ListTopics from './list-topics.js'
 import ListTopicPosts from './list-topic-posts.js'
+import TopicFollowState from './topic-follow-state.js'
+import ListTopicFollowers from './list-topic-followers.js'
 
 class UseCases {
   constructor (localConfig = {}) {
@@ -31,6 +33,8 @@ class UseCases {
     this.listFollowers = null
     this.listTopics = null
     this.listTopicPosts = null
+    this.topicFollowState = null
+    this.listTopicFollowers = null
   }
 
   async start () {
@@ -70,6 +74,14 @@ class UseCases {
       adapters: this.adapters
     })
 
+    this.topicFollowState = new TopicFollowState({
+      adapters: this.adapters
+    })
+
+    this.listTopicFollowers = new ListTopicFollowers({
+      adapters: this.adapters
+    })
+
     console.log('Use cases initialized.')
 
     return true
@@ -77,3 +89,7 @@ class UseCases {
 }
 
 export default UseCases
+
+// mutate4javascript-manifest-begin
+// {"version":1,"tested_at":"2026-08-28T20:07:25.668Z","module_hash":"4056d0f29e6828f95ab07f34186b3cef9d93f244c3d6914aa52463abdc224f32","functions":[{"id":"func/UseCases.constructor","name":"UseCases.constructor","line":18,"end_line":38,"hash":"bf14b8bc15f8a9ad966bb4d2a2de92072be3ec695af1aef5604495f5cf681e34"},{"id":"func/UseCases.start","name":"UseCases.start","line":40,"end_line":88,"hash":"f6fbf584c0e6786294a352fdae4e7a01fef1d24d31ca5202a33f5ed5e1772020"}]}
+// mutate4javascript-manifest-end
diff --git a/psf-memo-db/src/use-cases/list-topic-followers.js b/psf-memo-db/src/use-cases/list-topic-followers.js
new file mode 100644
index 0000000..204e270
--- /dev/null
+++ b/psf-memo-db/src/use-cases/list-topic-followers.js
@@ -0,0 +1,30 @@
+/*
+  Use case: list the addresses that currently follow a Memo topic.
+
+  Returns { room, followers: string[] }.
+*/
+
+import { ListUseCase } from './lib/use-case.js'
+
+class ListTopicFollowers extends ListUseCase {
+  constructor (localConfig = {}) {
+    super(localConfig, { useCaseName: 'ListTopicFollowers', adapterName: 'topicQuery' })
+  }
+
+  async execute (inObj = {}) {
+    const { room } = inObj
+    if (!room || typeof room !== 'string') {
+      throw new Error('room is required')
+    }
+
+    const followers = await this.adapters.topicQuery.listRoomFollowers(room)
+
+    return { room, followers }
+  }
+}
+
+export default ListTopicFollowers
+
+// mutate4javascript-manifest-begin
+// {"version":1,"tested_at":"2026-08-28T20:05:30.757Z","module_hash":"c2df7f5656fb718fe66f800585bef77d926c25b780925c4bafcb05a4888c7bb3","functions":[{"id":"func/ListTopicFollowers.constructor","name":"ListTopicFollowers.constructor","line":10,"end_line":12,"hash":"032be6dff5472c86a00dbfece93708dcfb41f0d5fa3d5aa9a08c3e97ca5a922e"},{"id":"func/ListTopicFollowers.execute","name":"ListTopicFollowers.execute","line":14,"end_line":23,"hash":"744248c669d8dbf5ced565d5a3328c9273ebac5f5db44bb5e947e7d26d4177a6"}]}
+// mutate4javascript-manifest-end
diff --git a/psf-memo-db/src/use-cases/topic-follow-state.js b/psf-memo-db/src/use-cases/topic-follow-state.js
new file mode 100644
index 0000000..6fe9031
--- /dev/null
+++ b/psf-memo-db/src/use-cases/topic-follow-state.js
@@ -0,0 +1,33 @@
+/*
+  Use case: report whether an address follows a Memo topic.
+
+  Returns { room, addr, following: boolean }.
+*/
+
+import { ListUseCase } from './lib/use-case.js'
+
+class TopicFollowState extends ListUseCase {
+  constructor (localConfig = {}) {
+    super(localConfig, { useCaseName: 'TopicFollowState', adapterName: 'topicQuery' })
+  }
+
+  async execute (inObj = {}) {
+    const { room, addr } = inObj
+    if (!room || typeof room !== 'string') {
+      throw new Error('room is required')
+    }
+    if (!addr || typeof addr !== 'string') {
+      throw new Error('addr is required')
+    }
+
+    const following = await this.adapters.topicQuery.isFollowingRoom(addr, room)
+
+    return { room, addr, following }
+  }
+}
+
+export default TopicFollowState
+
+// mutate4javascript-manifest-begin
+// {"version":1,"tested_at":"2026-08-28T19:53:30.917Z","module_hash":"48b427de8b141c64275851761259c085142d7137817712cebaa6d42eea27a366","functions":[{"id":"func/TopicFollowState.constructor","name":"TopicFollowState.constructor","line":10,"end_line":12,"hash":"028e260fea5ad97395eaa65be5eaea9aa3134ae1a37c530b96b66df6e864fb0b"},{"id":"func/TopicFollowState.execute","name":"TopicFollowState.execute","line":14,"end_line":26,"hash":"7474d322e757cdb2ab2a03c65f17456c33196811171b478dd813fbc020d8e4bf"}]}
+// mutate4javascript-manifest-end
diff --git a/psf-memo-db/test/property/topic-follow-query.property.test.js b/psf-memo-db/test/property/topic-follow-query.property.test.js
new file mode 100644
index 0000000..3e0b3eb
--- /dev/null
+++ b/psf-memo-db/test/property/topic-follow-query.property.test.js
@@ -0,0 +1,156 @@
+/*
+  Property tests for the TopicQuery topic-follow read side.
+
+  The unit tests probe isFollowingRoom and listRoomFollowers at a few fixed
+  fixtures. These properties pin down invariants that hold over broad random
+  follow-record sets:
+
+    - listRoomFollowers conservation: for every room the returned set equals
+      exactly the active (non-unfollowed) follow addresses for that room,
+      regardless of surrounding post/follow records.
+    - isFollowingRoom round trip: an address is reported following a room
+      exactly when an active follow record for that room:addr exists.
+    - followAddrFromValue recovery: the follower address is recovered from a
+      `${room}:${addr}` key.
+*/
+
+import test from 'node:test'
+
+import { seededRandom, forAll, intGen } from './harness.js'
+import TopicQuery from '../../src/adapters/topic-query.js'
+
+const rng = seededRandom(20260831)
+
+// In-memory rooms store mirroring the LevelDB contract TopicQuery relies on:
+// both an iterator over key/value entries (listRoomFollowers, listTopics) and
+// a point get that throws notFound (isFollowingRoom).
+function makeRoomsDb (entries) {
+  const store = new Map(entries.map((e) => [e.key, e.value]))
+  return {
+    async get (key) {
+      if (!store.has(key)) {
+        const err = new Error('not found')
+        err.notFound = true
+        throw err
+      }
+      return store.get(key)
+    },
+    async * iterator (opts = {}) {
+      const { gte, lte } = opts
+      let keys = Array.from(store.keys()).sort()
+      if (gte !== undefined) keys = keys.filter((k) => k >= gte)
+      if (lte !== undefined) keys = keys.filter((k) => k <= lte)
+      for (const key of keys) {
+        yield [key, store.get(key)]
+      }
+    }
+  }
+}
+
+function makeQuery (entries) {
+  return new TopicQuery({
+    roomsDb: makeRoomsDb(entries),
+    postsDb: {}
+  })
+}
+
+// Random set of rooms and topic follow records. Each room has some candidate
+// addresses; not every address follows, and a follow may later be unfollowed.
+function followSetGen () {
+  return () => {
+    const roomCount = intGen(rng, 1, 4)()
+    const rooms = []
+    const entries = []
+    for (let i = 0; i < roomCount; i++) {
+      const room = `room-${i}`
+      rooms.push(room)
+
+      const addrCount = intGen(rng, 1, 6)()
+      for (let j = 0; j < addrCount; j++) {
+        const addr = `bitcoincash:q${i}-${j}`
+        if (rng() < 0.35) continue
+        entries.push({
+          key: `${room}:${addr}`,
+          value: {
+            type: 'follow',
+            room,
+            addr,
+            unfollow: rng() < 0.4
+          }
+        })
+      }
+
+      // A stray post entry in the same room must not count as a follower.
+      if (rng() < 0.5) {
+        entries.push({
+          key: `${room}:post-${i}`,
+          value: { type: 'post', room }
+        })
+      }
+    }
+    return { rooms, entries }
+  }
+}
+
+test('listRoomFollowers returns exactly the active follow addresses for a room', async () => {
+  await forAll(
+    followSetGen(),
+    async ({ rooms, entries }) => {
+      const query = makeQuery(entries)
+
+      for (const room of rooms) {
+        const got = await query.listRoomFollowers(room)
+        const expected = Array.from(
+          new Set(
+            entries
+              .filter((e) => e.value.type === 'follow' && e.value.room === room && e.value.unfollow !== true && e.value.addr)
+              .map((e) => e.value.addr)
+          )
+        )
+        const want = expected.sort((a, b) => a.localeCompare(b))
+        const received = got.slice().sort((a, b) => a.localeCompare(b))
+        if (JSON.stringify(received) !== JSON.stringify(want)) return false
+      }
+      return true
+    },
+    { label: 'listRoomFollowers conservation' }
+  )
+})
+
+test('isFollowingRoom is true exactly for active follow records', async () => {
+  await forAll(
+    followSetGen(),
+    async ({ entries }) => {
+      const query = makeQuery(entries)
+
+      for (const e of entries) {
+        if (e.value.type !== 'follow') continue
+        const { room, addr } = e.value
+        const following = await query.isFollowingRoom(addr, room)
+        if (following !== (e.value.unfollow !== true)) return false
+      }
+
+      // A room:addr never recorded is never following.
+      const unseen = await query.isFollowingRoom('bitcoincash:qunseen', 'room-99')
+      if (unseen !== false) return false
+      return true
+    },
+    { label: 'isFollowingRoom round trip' }
+  )
+})
+
+test('followAddrFromValue recovers the address from a room:addr record', async () => {
+  await forAll(
+    followSetGen(),
+    ({ entries }) => {
+      const query = makeQuery([])
+      for (const e of entries) {
+        if (e.value.type !== 'follow') continue
+        const addr = query.followAddrFromValue(e.value, e.key)
+        if (addr !== e.value.addr) return false
+      }
+      return true
+    },
+    { label: 'followAddrFromValue recovery' }
+  )
+})
diff --git a/psf-memo-db/test/unit/adapters/topic-query.unit.js b/psf-memo-db/test/unit/adapters/topic-query.unit.js
index 37a71e6..f10e444 100644
--- a/psf-memo-db/test/unit/adapters/topic-query.unit.js
+++ b/psf-memo-db/test/unit/adapters/topic-query.unit.js
@@ -2,6 +2,41 @@ import { assert } from 'chai'
 import sinon from 'sinon'
 import TopicQuery from '../../../src/adapters/topic-query.js'
 
+function makeRoomsDb (records = {}) {
+  const store = new Map(Object.entries(records))
+  return {
+    async get (key) {
+      if (!store.has(key)) {
+        const err = new Error('not found')
+        err.notFound = true
+        throw err
+      }
+      return store.get(key)
+    },
+    iterator (opts = {}) {
+      const entries = Array.from(store.entries()).sort((a, b) => a[0].localeCompare(b[0]))
+      const { gte, lte } = opts
+      const filtered = entries.filter(([key]) => {
+        if (gte && key < gte) return false
+        if (lte && key > lte) return false
+        return true
+      })
+      let i = 0
+      return {
+        [Symbol.asyncIterator] () {
+          return this
+        },
+        async next () {
+          if (i >= filtered.length) return { value: undefined, done: true }
+          const entry = filtered[i++]
+          return { value: entry, done: false }
+        },
+        async close () {}
+      }
+    }
+  }
+}
+
 describe('#TopicQuery', () => {
   let uut
   let sandbox
@@ -11,7 +46,8 @@ describe('#TopicQuery', () => {
   beforeEach(() => {
     sandbox = sinon.createSandbox()
     roomsDb = {
-      iterator: sandbox.stub()
+      iterator: sandbox.stub(),
+      get: sandbox.stub()
     }
     postsDb = {
       get: sandbox.stub()
@@ -194,4 +230,103 @@ describe('#TopicQuery', () => {
       assert.equal(result.total, 2)
     })
   })
+
+  describe('#isFollowingRoom', () => {
+    it('should return false when no follow record exists', async () => {
+      const err = new Error('not found')
+      err.notFound = true
+      roomsDb.get.withArgs('bitcoin:addr-x').rejects(err)
+
+      const result = await uut.isFollowingRoom('addr-x', 'bitcoin')
+      assert.equal(result, false)
+    })
+
+    it('should return true for an active follow record', async () => {
+      roomsDb.get.withArgs('bitcoin:addr-a').resolves({ room: 'bitcoin', addr: 'addr-a', type: 'follow', unfollow: false })
+
+      const result = await uut.isFollowingRoom('addr-a', 'bitcoin')
+      assert.equal(result, true)
+    })
+
+    it('should return false for an unfollow record', async () => {
+      roomsDb.get.withArgs('bitcoin:addr-c').resolves({ room: 'bitcoin', addr: 'addr-c', type: 'follow', unfollow: true })
+
+      const result = await uut.isFollowingRoom('addr-c', 'bitcoin')
+      assert.equal(result, false)
+    })
+
+    it('should return false for a non-follow record', async () => {
+      roomsDb.get.withArgs('bitcoin:addr-a').resolves({ room: 'bitcoin', txid: 'post-1', type: 'post' })
+
+      const result = await uut.isFollowingRoom('addr-a', 'bitcoin')
+      assert.equal(result, false)
+    })
+
+    it('should rethrow non-not-found errors', async () => {
+      roomsDb.get.withArgs('bitcoin:addr-a').rejects(new Error('db down'))
+
+      try {
+        await uut.isFollowingRoom('addr-a', 'bitcoin')
+        assert.fail('Expected error')
+      } catch (err) {
+        assert.include(err.message, 'db down')
+      }
+    })
+  })
+
+  describe('#listRoomFollowers', () => {
+    it('should return active followers for a room', async () => {
+      const query = new TopicQuery({
+        roomsDb: makeRoomsDb({
+          'bitcoin:addr-a': { room: 'bitcoin', addr: 'addr-a', type: 'follow', unfollow: false },
+          'bitcoin:addr-b': { room: 'bitcoin', addr: 'addr-b', type: 'follow', unfollow: false },
+          'bitcoin:addr-c': { room: 'bitcoin', addr: 'addr-c', type: 'follow', unfollow: true },
+          'cash:addr-a': { room: 'cash', addr: 'addr-a', type: 'follow', unfollow: false }
+        }),
+        postsDb
+      })
+
+      const result = await query.listRoomFollowers('bitcoin')
+      assert.deepEqual(result, ['addr-a', 'addr-b'])
+    })
+
+    it('should fall back to the key address when the value has no addr', async () => {
+      const query = new TopicQuery({
+        roomsDb: makeRoomsDb({
+          'bitcoin:addr-a': { room: 'bitcoin', type: 'follow', unfollow: false }
+        }),
+        postsDb
+      })
+
+      const result = await query.listRoomFollowers('bitcoin')
+      assert.deepEqual(result, ['addr-a'])
+    })
+
+    it('should return an empty array for a room with no followers', async () => {
+      const query = new TopicQuery({
+        roomsDb: makeRoomsDb({}),
+        postsDb
+      })
+
+      const result = await query.listRoomFollowers('lone')
+      assert.deepEqual(result, [])
+    })
+  })
+
+  describe('#followAddrFromValue', () => {
+    it('should return the addr from the value when present', () => {
+      const result = uut.followAddrFromValue({ addr: 'addr-a' }, 'bitcoin:addr-a')
+      assert.equal(result, 'addr-a')
+    })
+
+    it('should fall back to the last key segment when the value has no addr', () => {
+      const result = uut.followAddrFromValue({ room: 'bitcoin', type: 'follow' }, 'bitcoin:addr-a')
+      assert.equal(result, 'addr-a')
+    })
+
+    it('should return null when the key has no address segment', () => {
+      const result = uut.followAddrFromValue({ room: 'lone', type: 'follow' }, 'lone')
+      assert.equal(result, null)
+    })
+  })
 })
diff --git a/psf-memo-db/test/unit/controllers/topics.controller.unit.js b/psf-memo-db/test/unit/controllers/topics.controller.unit.js
index afd7851..3cb34dd 100644
--- a/psf-memo-db/test/unit/controllers/topics.controller.unit.js
+++ b/psf-memo-db/test/unit/controllers/topics.controller.unit.js
@@ -24,6 +24,19 @@ describe('#TopicsRESTController', () => {
             posts: [{ txid: 'post-300', blockHeight: 300 }],
             pagination: { limit: 100, offset: 0, total: 1, hasMore: false }
           })
+        },
+        topicFollowState: {
+          execute: sandbox.stub().resolves({
+            room: 'bitcoin',
+            addr: 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d',
+            following: true
+          })
+        },
+        listTopicFollowers: {
+          execute: sandbox.stub().resolves({
+            room: 'bitcoin',
+            followers: ['bitcoincash:a', 'bitcoincash:b']
+          })
         }
       }
     })
@@ -59,6 +72,38 @@ describe('#TopicsRESTController', () => {
     assert.equal(ctx.body.posts[0].txid, 'post-300')
   })
 
+  it('should return topic follow state from use case', async () => {
+    const ctx = {
+      params: { room: 'bitcoin' },
+      query: { addr: 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d' },
+      body: null,
+      throw: sandbox.stub()
+    }
+    await uut.getTopicFollowState(ctx)
+
+    assert.equal(uut.useCases.topicFollowState.execute.callCount, 1)
+    assert.deepEqual(uut.useCases.topicFollowState.execute.firstCall.args[0], {
+      room: 'bitcoin',
+      addr: 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+    })
+    assert.equal(ctx.body.following, true)
+  })
+
+  it('should return topic followers from use case', async () => {
+    const ctx = {
+      params: { room: 'bitcoin' },
+      body: null,
+      throw: sandbox.stub()
+    }
+    await uut.getTopicFollowers(ctx)
+
+    assert.equal(uut.useCases.listTopicFollowers.execute.callCount, 1)
+    assert.deepEqual(uut.useCases.listTopicFollowers.execute.firstCall.args[0], {
+      room: 'bitcoin'
+    })
+    assert.deepEqual(ctx.body.followers, ['bitcoincash:a', 'bitcoincash:b'])
+  })
+
   it('should throw a 500 when the use case fails without a status', async () => {
     uut.useCases.listTopics.execute = sandbox.stub().rejects(new Error('boom'))
     const ctx = { body: null, throw: sandbox.stub() }
diff --git a/psf-memo-db/test/unit/use-cases/list-topic-followers.unit.js b/psf-memo-db/test/unit/use-cases/list-topic-followers.unit.js
new file mode 100644
index 0000000..34f502c
--- /dev/null
+++ b/psf-memo-db/test/unit/use-cases/list-topic-followers.unit.js
@@ -0,0 +1,70 @@
+import { assert } from 'chai'
+import ListTopicFollowers from '../../../src/use-cases/list-topic-followers.js'
+
+function makeAdapters (followers) {
+  return {
+    topicQuery: {
+      async listRoomFollowers (room) {
+        return followers
+      }
+    }
+  }
+}
+
+describe('#ListTopicFollowers', () => {
+  it('should throw when adapters is missing', () => {
+    assert.throws(() => new ListTopicFollowers({}), /Adapters required/)
+  })
+
+  it('should throw when topicQuery adapter is missing', () => {
+    assert.throws(() => new ListTopicFollowers({ adapters: {} }), /topicQuery adapter required/)
+  })
+
+  it('should return the followers list', async () => {
+    const useCase = new ListTopicFollowers({ adapters: makeAdapters(['bitcoincash:a', 'bitcoincash:b']) })
+    const result = await useCase.execute({ room: 'bitcoin' })
+    assert.deepEqual(result, {
+      room: 'bitcoin',
+      followers: ['bitcoincash:a', 'bitcoincash:b']
+    })
+  })
+
+  it('should return an empty list', async () => {
+    const useCase = new ListTopicFollowers({ adapters: makeAdapters([]) })
+    const result = await useCase.execute({ room: 'lone' })
+    assert.deepEqual(result, {
+      room: 'lone',
+      followers: []
+    })
+  })
+
+  it('should reject a missing room', async () => {
+    const useCase = new ListTopicFollowers({ adapters: makeAdapters([]) })
+    try {
+      await useCase.execute({})
+      assert.fail('expected error')
+    } catch (err) {
+      assert.match(err.message, /room is required/)
+    }
+  })
+
+  it('should reject an empty-string room', async () => {
+    const useCase = new ListTopicFollowers({ adapters: makeAdapters([]) })
+    try {
+      await useCase.execute({ room: '' })
+      assert.fail('expected error')
+    } catch (err) {
+      assert.match(err.message, /room is required/)
+    }
+  })
+
+  it('should reject a non-string room', async () => {
+    const useCase = new ListTopicFollowers({ adapters: makeAdapters([]) })
+    try {
+      await useCase.execute({ room: 42 })
+      assert.fail('expected error')
+    } catch (err) {
+      assert.match(err.message, /room is required/)
+    }
+  })
+})
diff --git a/psf-memo-db/test/unit/use-cases/topic-follow-state.unit.js b/psf-memo-db/test/unit/use-cases/topic-follow-state.unit.js
new file mode 100644
index 0000000..4c3747c
--- /dev/null
+++ b/psf-memo-db/test/unit/use-cases/topic-follow-state.unit.js
@@ -0,0 +1,92 @@
+import { assert } from 'chai'
+import TopicFollowState from '../../../src/use-cases/topic-follow-state.js'
+
+function makeAdapters (followingResult) {
+  return {
+    topicQuery: {
+      async isFollowingRoom (addr, room) {
+        return followingResult
+      }
+    }
+  }
+}
+
+describe('#TopicFollowState', () => {
+  it('should throw when adapters is missing', () => {
+    assert.throws(() => new TopicFollowState({}), /Adapters required/)
+  })
+
+  it('should throw when topicQuery adapter is missing', () => {
+    assert.throws(() => new TopicFollowState({ adapters: {} }), /topicQuery adapter required/)
+  })
+
+  it('should return following=true', async () => {
+    const useCase = new TopicFollowState({ adapters: makeAdapters(true) })
+    const result = await useCase.execute({ room: 'bitcoin', addr: 'bitcoincash:addr-a' })
+    assert.deepEqual(result, {
+      room: 'bitcoin',
+      addr: 'bitcoincash:addr-a',
+      following: true
+    })
+  })
+
+  it('should return following=false', async () => {
+    const useCase = new TopicFollowState({ adapters: makeAdapters(false) })
+    const result = await useCase.execute({ room: 'bitcoin', addr: 'bitcoincash:addr-a' })
+    assert.deepEqual(result, {
+      room: 'bitcoin',
+      addr: 'bitcoincash:addr-a',
+      following: false
+    })
+  })
+
+  it('should reject a missing room', async () => {
+    const useCase = new TopicFollowState({ adapters: makeAdapters(false) })
+    try {
+      await useCase.execute({ addr: 'bitcoincash:addr-a' })
+      assert.fail('expected error')
+    } catch (err) {
+      assert.match(err.message, /room is required/)
+    }
+  })
+
+  it('should reject a missing addr', async () => {
+    const useCase = new TopicFollowState({ adapters: makeAdapters(false) })
+    try {
+      await useCase.execute({ room: 'bitcoin' })
+      assert.fail('expected error')
+    } catch (err) {
+      assert.match(err.message, /addr is required/)
+    }
+  })
+
+  it('should reject an empty-string room', async () => {
+    const useCase = new TopicFollowState({ adapters: makeAdapters(false) })
+    try {
+      await useCase.execute({ room: '', addr: 'bitcoincash:addr-a' })
+      assert.fail('expected error')
+    } catch (err) {
+      assert.match(err.message, /room is required/)
+    }
+  })
+
+  it('should reject an empty-string addr', async () => {
+    const useCase = new TopicFollowState({ adapters: makeAdapters(false) })
+    try {
+      await useCase.execute({ room: 'bitcoin', addr: '' })
+      assert.fail('expected error')
+    } catch (err) {
+      assert.match(err.message, /addr is required/)
+    }
+  })
+
+  it('should reject a non-string room', async () => {
+    const useCase = new TopicFollowState({ adapters: makeAdapters(false) })
+    try {
+      await useCase.execute({ room: 42, addr: 'bitcoincash:addr-a' })
+      assert.fail('expected error')
+    } catch (err) {
+      assert.match(err.message, /room is required/)
+    }
+  })
+})