diff --git a/assets/styles.css b/assets/styles.css
index bfbe20b..2182215 100644
--- a/assets/styles.css
+++ b/assets/styles.css
@@ -416,7 +416,57 @@
   color: var(--color-background);
 }
 
-/* Mark as read button */
+/* Mark as read — split button group */
+.item-actions__mark-read-group {
+  display: inline-flex;
+  margin-left: auto;
+  position: relative;
+}
+
+.item-actions__mark-read-group .item-actions__mark-read {
+  border-bottom-right-radius: 0;
+  border-right: 0;
+  border-top-right-radius: 0;
+  margin-left: 0;
+}
+
+.item-actions__mark-read-caret {
+  border-bottom-left-radius: 0;
+  border-top-left-radius: 0;
+  font-size: 0.625rem;
+  padding: var(--space-xs) 6px;
+}
+
+.item-actions__mark-read-popover {
+  background: var(--color-background);
+  border: 1px solid var(--color-offset-active);
+  border-radius: var(--border-radius);
+  bottom: calc(100% + 4px);
+  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
+  padding: var(--space-xs);
+  position: absolute;
+  right: 0;
+  white-space: nowrap;
+  z-index: 10;
+}
+
+.item-actions__mark-source-read {
+  background: transparent;
+  border: 0;
+  border-radius: var(--border-radius);
+  color: var(--color-text);
+  cursor: pointer;
+  font-size: var(--font-size-small);
+  padding: var(--space-xs) var(--space-s);
+  text-align: left;
+  width: 100%;
+}
+
+.item-actions__mark-source-read:hover {
+  background: var(--color-offset);
+}
+
+/* Mark as read button (standalone, no split group) */
 .item-actions__mark-read {
   margin-left: auto;
 }
diff --git a/lib/controllers/timeline.js b/lib/controllers/timeline.js
index be13143..18f9815 100644
--- a/lib/controllers/timeline.js
+++ b/lib/controllers/timeline.js
@@ -9,6 +9,7 @@ import { proxyItemImages } from "../media/proxy.js";
 import { getChannel, getChannelById } from "../storage/channels.js";
 import {
   getTimelineItems,
+  markFeedItemsRead,
   markItemsRead,
   markItemsUnread,
   removeItems,
@@ -103,6 +104,22 @@ export async function action(request, response) {
       return response.json({ result: "ok", updated: count });
     }
 
+    case "mark_read_source": {
+      const feedId = request.body.feed;
+      if (!feedId) {
+        throw new IndiekitError("feed parameter required", {
+          status: 400,
+        });
+      }
+      const count = await markFeedItemsRead(
+        application,
+        channelDocument._id,
+        feedId,
+        userId,
+      );
+      return response.json({ result: "ok", updated: count });
+    }
+
     case "mark_unread": {
       validateEntries(entries);
       const count = await markItemsUnread(
diff --git a/lib/storage/items.js b/lib/storage/items.js
index 27cbb8a..4ff55e6 100644
--- a/lib/storage/items.js
+++ b/lib/storage/items.js
@@ -271,6 +271,7 @@ function transformToJf2(item, userId) {
     _id: item._id.toString(),
     _is_read: userId ? item.readBy?.includes(userId) : false,
     _channelId: item.channelId?.toString(),
+    _feedId: item.feedId?.toString(),
   };
 
   // Optional fields
@@ -695,6 +696,41 @@ export async function markItemsRead(application, channelId, entryIds, userId) {
   return result.modifiedCount;
 }
 
+/**
+ * Mark all items from a specific feed as read in a channel
+ * @param {object} application - Indiekit application
+ * @param {ObjectId|string} channelId - Channel ObjectId
+ * @param {ObjectId|string} feedId - Feed ObjectId
+ * @param {string} userId - User ID
+ * @returns {Promise<number>} Number of items updated
+ */
+export async function markFeedItemsRead(
+  application,
+  channelId,
+  feedId,
+  userId,
+) {
+  const collection = getCollection(application);
+  const channelObjectId =
+    typeof channelId === "string" ? new ObjectId(channelId) : channelId;
+  const feedObjectId =
+    typeof feedId === "string" ? new ObjectId(feedId) : feedId;
+
+  const result = await collection.updateMany(
+    { channelId: channelObjectId, feedId: feedObjectId },
+    { $addToSet: { readBy: userId } },
+  );
+
+  console.info(
+    `[Microsub] markFeedItemsRead: marked ${result.modifiedCount} items from feed ${feedId} as read`,
+  );
+
+  // Cleanup old read items
+  await cleanupOldReadItems(collection, channelObjectId, userId);
+
+  return result.modifiedCount;
+}
+
 /**
  * Mark items as unread
  * @param {object} application - Indiekit application
diff --git a/package.json b/package.json
index 3a610f5..4a11850 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@rmdes/indiekit-endpoint-microsub",
-  "version": "1.0.44",
+  "version": "1.0.45",
   "description": "Microsub endpoint for Indiekit. Enables subscribing to feeds and reading content using the Microsub protocol.",
   "keywords": [
     "indiekit",
diff --git a/views/channel.njk b/views/channel.njk
index 0aa3e27..ec87228 100644
--- a/views/channel.njk
+++ b/views/channel.njk
@@ -174,6 +174,84 @@
         }
       });
 
+      // Handle caret toggle for mark-source-read popover
+      timeline.addEventListener('click', (e) => {
+        const caret = e.target.closest('.item-actions__mark-read-caret');
+        if (!caret) return;
+
+        e.preventDefault();
+        e.stopPropagation();
+
+        // Close other open popovers
+        for (const p of timeline.querySelectorAll('.item-actions__mark-read-popover:not([hidden])')) {
+          if (p !== caret.nextElementSibling) p.hidden = true;
+        }
+
+        const popover = caret.nextElementSibling;
+        if (popover) popover.hidden = !popover.hidden;
+      });
+
+      // Handle mark-source-read button
+      timeline.addEventListener('click', async (e) => {
+        const button = e.target.closest('.item-actions__mark-source-read');
+        if (!button) return;
+
+        e.preventDefault();
+        e.stopPropagation();
+
+        const feedId = button.dataset.feedId;
+        if (!feedId) return;
+
+        button.disabled = true;
+
+        try {
+          const formData = new URLSearchParams();
+          formData.append('action', 'timeline');
+          formData.append('method', 'mark_read_source');
+          formData.append('channel', channelUid);
+          formData.append('feed', feedId);
+
+          const response = await fetch(microsubApiUrl, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+            body: formData.toString(),
+            credentials: 'same-origin'
+          });
+
+          if (response.ok) {
+            // Animate out all cards from this feed
+            const cards = timeline.querySelectorAll(`.item-card[data-feed-id="${feedId}"]`);
+            for (const card of cards) {
+              card.style.transition = 'opacity 0.3s ease, transform 0.3s ease';
+              card.style.opacity = '0';
+              card.style.transform = 'translateX(-20px)';
+            }
+            setTimeout(() => {
+              for (const card of [...cards]) {
+                card.remove();
+              }
+              if (timeline.querySelectorAll('.item-card').length === 0) {
+                location.reload();
+              }
+            }, 300);
+          } else {
+            button.disabled = false;
+          }
+        } catch (error) {
+          console.error('Error marking source as read:', error);
+          button.disabled = false;
+        }
+      });
+
+      // Close popovers on outside click
+      document.addEventListener('click', (e) => {
+        if (!e.target.closest('.item-actions__mark-read-group')) {
+          for (const p of timeline.querySelectorAll('.item-actions__mark-read-popover:not([hidden])')) {
+            p.hidden = true;
+          }
+        }
+      });
+
       // Handle save-for-later buttons
       timeline.addEventListener('click', async (e) => {
         const button = e.target.closest('.item-actions__save-later');
diff --git a/views/partials/item-card.njk b/views/partials/item-card.njk
index f5ae360..15ec77b 100644
--- a/views/partials/item-card.njk
+++ b/views/partials/item-card.njk
@@ -4,6 +4,7 @@
 #}
 <article class="item-card{% if item._is_read %} item-card--read{% endif %}"
          data-item-id="{{ item._id }}"
+         data-feed-id="{{ item._feedId or '' }}"
          data-is-read="{{ item._is_read | default(false) }}">
 
   {# Context bar for interactions (Aperture pattern) #}
@@ -198,6 +199,33 @@
       <span class="visually-hidden">Bookmark</span>
     </a>
     {% if not item._is_read %}
+    {% if item._feedId %}
+    <span class="item-actions__mark-read-group">
+      <button type="button"
+              class="item-actions__button item-actions__mark-read"
+              data-action="mark-read"
+              data-item-id="{{ item._id }}"
+              {% if item._channelUid %}data-channel-uid="{{ item._channelUid }}"{% endif %}
+              {% if item._channelId %}data-channel-id="{{ item._channelId }}"{% endif %}
+              title="Mark as read">
+        {{ icon("checkboxChecked") }}
+        <span class="visually-hidden">Mark read</span>
+      </button>
+      <button type="button"
+              class="item-actions__button item-actions__mark-read-caret"
+              aria-label="More mark-read options"
+              title="More options">&#9662;</button>
+      <div class="item-actions__mark-read-popover" hidden>
+        <button type="button"
+                class="item-actions__mark-source-read"
+                data-feed-id="{{ item._feedId }}"
+                {% if item._channelUid %}data-channel-uid="{{ item._channelUid }}"{% endif %}
+                {% if item._channelId %}data-channel-id="{{ item._channelId }}"{% endif %}>
+          Mark {{ item._source.name or item.author.name or "source" }} as read
+        </button>
+      </div>
+    </span>
+    {% else %}
     <button type="button"
             class="item-actions__button item-actions__mark-read"
             data-action="mark-read"
@@ -209,6 +237,7 @@
       <span class="visually-hidden">Mark read</span>
     </button>
     {% endif %}
+    {% endif %}
     {% if application.readlaterEndpoint %}
     <button type="button"
             class="item-actions__button item-actions__save-later"
diff --git a/views/timeline.njk b/views/timeline.njk
index 2fc4cf7..5f1a6ba 100644
--- a/views/timeline.njk
+++ b/views/timeline.njk
@@ -152,6 +152,88 @@
         }
       });
 
+      // Handle caret toggle for mark-source-read popover
+      timeline.addEventListener('click', (e) => {
+        const caret = e.target.closest('.item-actions__mark-read-caret');
+        if (!caret) return;
+
+        e.preventDefault();
+        e.stopPropagation();
+
+        // Close other open popovers
+        for (const p of timeline.querySelectorAll('.item-actions__mark-read-popover:not([hidden])')) {
+          if (p !== caret.nextElementSibling) p.hidden = true;
+        }
+
+        const popover = caret.nextElementSibling;
+        if (popover) popover.hidden = !popover.hidden;
+      });
+
+      // Handle mark-source-read button
+      timeline.addEventListener('click', async (e) => {
+        const button = e.target.closest('.item-actions__mark-source-read');
+        if (!button) return;
+
+        e.preventDefault();
+        e.stopPropagation();
+
+        const feedId = button.dataset.feedId;
+        const channelUid = button.dataset.channelUid;
+        const channelId = button.dataset.channelId;
+        if (!feedId || (!channelUid && !channelId)) return;
+
+        button.disabled = true;
+
+        try {
+          const formData = new URLSearchParams();
+          formData.append('action', 'timeline');
+          formData.append('method', 'mark_read_source');
+          formData.append('channel', channelUid || channelId);
+          formData.append('feed', feedId);
+
+          const response = await fetch(microsubApiUrl, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+            body: formData.toString(),
+            credentials: 'same-origin'
+          });
+
+          if (response.ok) {
+            // Animate out all cards from this feed
+            const cards = timeline.querySelectorAll(`.item-card[data-feed-id="${feedId}"]`);
+            for (const card of cards) {
+              card.style.transition = 'opacity 0.3s ease, transform 0.3s ease';
+              card.style.opacity = '0';
+              card.style.transform = 'translateX(-20px)';
+            }
+            setTimeout(() => {
+              for (const card of [...cards]) {
+                const wrapper = card.closest('.timeline-view__item');
+                if (wrapper) wrapper.remove();
+                else card.remove();
+              }
+              if (timeline.querySelectorAll('.item-card').length === 0) {
+                location.reload();
+              }
+            }, 300);
+          } else {
+            button.disabled = false;
+          }
+        } catch (error) {
+          console.error('Error marking source as read:', error);
+          button.disabled = false;
+        }
+      });
+
+      // Close popovers on outside click
+      document.addEventListener('click', (e) => {
+        if (!e.target.closest('.item-actions__mark-read-group')) {
+          for (const p of timeline.querySelectorAll('.item-actions__mark-read-popover:not([hidden])')) {
+            p.hidden = true;
+          }
+        }
+      });
+
       // Handle save-for-later buttons
       timeline.addEventListener('click', async (e) => {
         const button = e.target.closest('.item-actions__save-later');