diff --git a/MICROCOSM_PLAN.md b/MICROCOSM_PLAN.md
index b7e56ba..7486f48 100644
--- a/MICROCOSM_PLAN.md
+++ b/MICROCOSM_PLAN.md
@@ -126,9 +126,14 @@ Source strings map directly to bsky interactions:
   verified the feed_thumbnail/feed_fullsize CDN URLs resolve (200 JPEG).
 - ✅ `hydrateProfileBasic(did)` → `ProfileViewBasic` (post author embedding).
 
+- ✅ viewer state (did *I* like/repost): reconstructed from Constellation
+  did-filtered backlinks -> like/repost record rkey -> at-uri. Wired into
+  `hydratePost` via `agent.did`. Verified live.
+- ✅ Image CDN swapped from Bluesky's `cdn.bsky.app` to the community-run
+  `cdn.blueat.net` (configurable via `IMG_CDN_URL`); same URL scheme, verified.
+
 Remaining for Phase 3 (follow-ups, non-blocking):
 - quote-record + video embeds (need a record fetch / video service)
-- viewer state (did *I* like/repost — Constellation `did` filter on my DID)
 - thread reply-tree assembly (replaces app.bsky.unspecced.getPostThreadV2)
 
 Original Phase 3 scope notes:
diff --git a/src/env/common.ts b/src/env/common.ts
index cc2ba3b..942d942 100644
--- a/src/env/common.ts
+++ b/src/env/common.ts
@@ -114,3 +114,13 @@ export const SPACEDUST_URL: string =
  * identify your project and a contact.
  */
 export const MICROCOSM_USER_AGENT = 'fih (microcosm client; scan@scanash.com)'
+
+/**
+ * Image CDN base used when reconstructing avatar/banner/feed image URLs from
+ * raw blob refs (during client-side hydration). Defaults to the community-run
+ * `cdn.blueat.net` mirror rather than Bluesky's first-party `cdn.bsky.app`, so
+ * the app doesn't depend on Bluesky CDN infrastructure. Same URL scheme:
+ * `<base>/img/<preset>/plain/<did>/<cid>@jpeg`.
+ */
+export const IMG_CDN_URL: string =
+  process.env.EXPO_PUBLIC_IMG_CDN_URL || 'https://cdn.blueat.net'
diff --git a/src/lib/microcosm/hydrate.ts b/src/lib/microcosm/hydrate.ts
index a9f6710..6e5c059 100644
--- a/src/lib/microcosm/hydrate.ts
+++ b/src/lib/microcosm/hydrate.ts
@@ -22,15 +22,18 @@ import {
 
 import {constellation} from '#/lib/microcosm'
 import {getRecordByUri, resolveMiniDoc} from '#/lib/microcosm/slingshot'
+import {IMG_CDN_URL} from '#/env'
 
 /**
- * Bluesky image CDN base. Avatars/banners are blob refs in the raw record; the
- * AppView rewrites them to CDN URLs. We reconstruct the same URLs.
+ * Image CDN base. Avatars/banners/feed images are blob refs in the raw record;
+ * the AppView rewrites them to CDN URLs and we reconstruct the same scheme
+ * (`<base>/img/<preset>/plain/<did>/<cid>@jpeg`). Defaults to the community-run
+ * `cdn.blueat.net` (see `IMG_CDN_URL`) instead of Bluesky's `cdn.bsky.app`.
  *
- * NOTE: this is still the bsky CDN. A fully host-independent build would instead
- * proxy blobs from the author's PDS (`<pds>/xrpc/com.atproto.sync.getBlob`).
+ * NOTE: a fully host-independent build would proxy blobs directly from the
+ * author's PDS (`<pds>/xrpc/com.atproto.sync.getBlob`).
  */
-const IMG_CDN = 'https://cdn.bsky.app/img'
+const IMG_CDN = `${IMG_CDN_URL}/img`
 
 type BlobRef = {ref?: {$link?: string}; $link?: string}
 
@@ -151,17 +154,66 @@ export async function hydrateProfile(
 }
 
 /**
- * Hydrate a `PostView` for a post at-uri from microcosm.
- * Embeds and viewer state are not reconstructed here (follow-up work).
+ * Reconstruct the viewer's interaction state for a post: whether the viewer has
+ * a like / repost record pointing at it, and the at-uri of that record (which
+ * the UI needs to undo the interaction). Found by filtering Constellation
+ * backlinks to the viewer's own DID.
+ */
+async function hydrateViewerState(
+  postUri: string,
+  viewerDid: string,
+  signal?: AbortSignal,
+): Promise<AppBskyFeedDefs.PostView['viewer']> {
+  const [likeRes, repostRes] = await Promise.all([
+    constellation
+      .getBacklinks(
+        {
+          subject: postUri,
+          source: constellation.Sources.likes,
+          did: [viewerDid],
+          limit: 1,
+        },
+        signal,
+      )
+      .catch(() => undefined),
+    constellation
+      .getBacklinks(
+        {
+          subject: postUri,
+          source: constellation.Sources.reposts,
+          did: [viewerDid],
+          limit: 1,
+        },
+        signal,
+      )
+      .catch(() => undefined),
+  ])
+
+  const likeRec = likeRes?.records?.[0]
+  const repostRec = repostRes?.records?.[0]
+  return {
+    like: likeRec
+      ? `at://${likeRec.did}/${likeRec.collection}/${likeRec.rkey}`
+      : undefined,
+    repost: repostRec
+      ? `at://${repostRec.did}/${repostRec.collection}/${repostRec.rkey}`
+      : undefined,
+  }
+}
+
+/**
+ * Hydrate a `PostView` for a post at-uri from microcosm. If `viewerDid` is
+ * provided, the viewer's like/repost state is reconstructed too.
  */
 export async function hydratePost(
   postUri: string,
+  viewerDid?: string,
   signal?: AbortSignal,
 ): Promise<AppBskyFeedDefs.PostView | undefined> {
   const parsed = parseAtUri(postUri)
   if (!parsed) return undefined
 
-  const [recordRes, author, likes, reposts, replies, quotes] =
+  const [recordRes, author, likes, reposts, replies, quotes, viewer] =
     await Promise.all([
       getRecordByUri(postUri, undefined, signal).catch(() => undefined),
       hydrateProfileBasic(parsed.did, signal).catch(() => undefined),
@@ -169,6 +221,9 @@ export async function hydratePost(
       constellation.repostCount(postUri, signal).catch(() => undefined),
       constellation.replyCount(postUri, signal).catch(() => undefined),
       constellation.quoteCount(postUri, signal).catch(() => undefined),
+      viewerDid
+        ? hydrateViewerState(postUri, viewerDid, signal).catch(() => undefined)
+        : Promise.resolve(undefined),
     ])
 
   if (!recordRes || !author) return undefined
@@ -187,6 +242,7 @@ export async function hydratePost(
     replyCount: replies?.total,
     quoteCount: quotes?.total,
     indexedAt: record?.createdAt ?? new Date().toISOString(),
+    viewer,
   }
 }
 
diff --git a/src/state/queries/post.ts b/src/state/queries/post.ts
index 52feca3..af5b75e 100644
--- a/src/state/queries/post.ts
+++ b/src/state/queries/post.ts
@@ -39,7 +39,7 @@ export function usePostQuery(uri: string | undefined) {
 
       if (MICROCOSM_ENABLED) {
         try {
-          const view = await hydratePost(urip.toString(), signal)
+          const view = await hydratePost(urip.toString(), agent.did, signal)
           if (view) return view
         } catch (e) {
           logger.debug('microcosm hydratePost failed, falling back', {