diff --git a/frontend/src/components/MessageInput.vue b/frontend/src/components/MessageInput.vue
index a838960..e0432af 100644
--- a/frontend/src/components/MessageInput.vue
+++ b/frontend/src/components/MessageInput.vue
@@ -13,6 +13,7 @@ import MediaThumbnailGroup from './MediaThumbnailGroup.vue'
 import AppTooltip from './AppTooltip.vue'
 import FilePickerPopup from './FilePickerPopup.vue'
 import SlashCommandPickerPopup from './SlashCommandPickerPopup.vue'
+import PromptHistoryPickerPopup from './PromptHistoryPickerPopup.vue'
 
 // Track visual viewport height for mobile keyboard handling
 useVisualViewport()
@@ -46,6 +47,10 @@ const isDraft = computed(() => session.value?.draft === true)
 const messageText = ref('')
 const textareaRef = ref(null)
 const fileInputRef = ref(null)
+
+// ── Prompt history picker ─────────────────────────────────────────────────
+const historyPickerRef = ref(null)
+const historyButtonId = useId()
 const attachButtonId = useId()
 const settingsButtonId = useId()
 const textareaAnchorId = useId()
@@ -194,7 +199,7 @@ const placeholderText = computed(() => {
     let text = 'Type your message... Use / for commands, @ for file paths'
     if (!settingsStore.isTouchDevice) {
         const keys = settingsStore.isMac ? '⌘↵ or Ctrl↵' : 'Ctrl↵ or Meta↵'
-        text += `, ${keys} to send`
+        text += `, Alt+PgUp for history, ${keys} to send`
     }
     return text
 })
@@ -437,6 +442,7 @@ watch(
 
 // Restore draft message when session changes
 watch(() => props.sessionId, async (newId) => {
+
     const draft = store.getDraftMessage(newId)
     messageText.value = draft?.message || ''
     // Adjust textarea height after the DOM updates with restored content
@@ -628,13 +634,78 @@ function onSlashCommandPickerClose() {
 
 /**
  * Handle keyboard shortcuts in textarea.
- * Cmd/Ctrl+Enter submits the message.
+ * Cmd/Ctrl+Enter submits, Alt+PageUp opens prompt history picker.
  */
 function onKeydown(event) {
     if ((event.metaKey || event.ctrlKey) && event.key === 'Enter') {
         event.preventDefault()
         handleSend()
+        return
+    }
+
+    // Alt+PageUp: open prompt history picker (or toggle to search if already open)
+    if (event.altKey && event.key === 'PageUp') {
+        event.preventDefault()
+        historyPickerRef.value?.open()  // open() handles already-open case (focuses search)
+        return
+    }
+
+    // Alt+PageDown: focus list in prompt history picker (if open)
+    if (event.altKey && event.key === 'PageDown') {
+        event.preventDefault()
+        historyPickerRef.value?.focusList()
+        return
+    }
+}
+
+/**
+ * Handle prompt history replace: overwrite textarea content with selected message.
+ */
+async function onHistoryReplace(text) {
+    messageText.value = text
+    if (textareaRef.value) {
+        textareaRef.value.value = text
+        const inner = textareaRef.value.shadowRoot?.querySelector('textarea')
+        if (inner) {
+            inner.value = text
+            const pos = text.length
+            inner.setSelectionRange(pos, pos)
+        }
     }
+    await nextTick()
+    textareaRef.value?.focus()
+    adjustTextareaHeight()
+}
+
+/**
+ * Handle prompt history insert: insert selected message at cursor position.
+ */
+async function onHistoryInsert(text) {
+    const inner = textareaRef.value?.shadowRoot?.querySelector('textarea')
+    const pos = inner?.selectionStart ?? messageText.value.length
+    const before = messageText.value.slice(0, pos)
+    const after = messageText.value.slice(pos)
+    const newText = before + text + after
+    const newPos = pos + text.length
+
+    messageText.value = newText
+    if (textareaRef.value) {
+        textareaRef.value.value = newText
+        if (inner) {
+            inner.value = newText
+            inner.setSelectionRange(newPos, newPos)
+        }
+    }
+    await nextTick()
+    textareaRef.value?.focus()
+    adjustTextareaHeight()
+}
+
+/**
+ * Handle prompt history picker close: return focus to textarea.
+ */
+function onHistoryPickerClose() {
+    textareaRef.value?.focus()
 }
 
 /**
@@ -820,6 +891,7 @@ async function handleSend() {
 
         // Clear draft message from store (and IndexedDB)
         store.clearDraftMessage(props.sessionId)
+    
 
         // Clear attachments from store and IndexedDB
         if (attachmentCount.value > 0) {
@@ -873,6 +945,7 @@ function handleCancel() {
  * restore dropdowns to their active (server-side) values.
  */
 async function handleReset() {
+
     // Clear text if any
     if (messageText.value) {
         messageText.value = ''
@@ -940,6 +1013,17 @@ async function handleReset() {
             @close="onSlashCommandPickerClose"
         />
 
+        <!-- Prompt history picker popup triggered by Alt+PageUp -->
+        <PromptHistoryPickerPopup
+            ref="historyPickerRef"
+            :project-id="projectId"
+            :session-id="sessionId"
+            :anchor-id="textareaAnchorId"
+            @replace="onHistoryReplace"
+            @insert="onHistoryInsert"
+            @close="onHistoryPickerClose"
+        />
+
         <div class="message-input-toolbar">
             <!-- Attachments row: button on left, thumbnails on right -->
             <div class="message-input-attachments">
@@ -965,6 +1049,18 @@ async function handleReset() {
                 </wa-button>
                 <AppTooltip :for="attachButtonId">Attach files (images, PDF, text)</AppTooltip>
 
+                <!-- Prompt history button -->
+                <wa-button
+                    variant="neutral"
+                    appearance="plain"
+                    size="small"
+                    :id="historyButtonId"
+                    @click="historyPickerRef?.open()"
+                >
+                    <wa-icon name="clock-rotate-left"></wa-icon>
+                </wa-button>
+                <AppTooltip :for="historyButtonId">Prompt history (Alt+PgUp)</AppTooltip>
+
                 <!-- Attachment badge + popover -->
                 <template v-if="attachmentCount > 0">
                     <button
diff --git a/frontend/src/components/PromptHistoryPickerPopup.vue b/frontend/src/components/PromptHistoryPickerPopup.vue
new file mode 100644
index 0000000..1149c4a
--- /dev/null
+++ b/frontend/src/components/PromptHistoryPickerPopup.vue
@@ -0,0 +1,763 @@
+<script setup>
+/**
+ * PromptHistoryPickerPopup - A popup for browsing and selecting past user messages.
+ *
+ * Opens a wa-popup anchored to a given element, showing a filterable list
+ * of previous user messages from the current session in chronological order
+ * (oldest at top, newest at bottom).
+ *
+ * Messages are fetched from the backend API in pages (FETCH_SIZE at a time)
+ * and rendered via a virtual scroller with fixed item height.
+ *
+ * Each item has two action buttons:
+ * - Insert: inserts at the current cursor position (default action)
+ * - Replace: replaces the current textarea content
+ *
+ * Keyboard navigation:
+ * - ArrowUp/ArrowDown: navigate items
+ * - Enter: insert at cursor (default action, insert button is pre-highlighted)
+ * - Tab: focus replace button, Tab again returns to list
+ * - Escape: close popup
+ */
+
+import { ref, reactive, computed, watch, nextTick, onBeforeUnmount } from 'vue'
+import { apiFetch } from '../utils/api'
+
+const props = defineProps({
+    projectId: {
+        type: String,
+        required: true,
+    },
+    sessionId: {
+        type: String,
+        required: true,
+    },
+    anchorId: {
+        type: String,
+        required: true,
+    },
+})
+
+const emit = defineEmits(['replace', 'insert', 'close'])
+
+// ─── Constants ────────────────────────────────────────────────────────────
+
+const FETCH_SIZE = 100       // Messages per API request
+const ITEM_HEIGHT = 52       // Fixed pixel height per item
+const RENDER_BUFFER = 5      // Extra items to render above/below viewport
+const SEARCH_DEBOUNCE = 300  // ms
+
+// ─── Popup state ──────────────────────────────────────────────────────────
+
+const popupRef = ref(null)
+const isOpen = ref(false)
+const searchInputRef = ref(null)
+const listRef = ref(null)
+const loading = ref(false)
+
+// ─── Data ─────────────────────────────────────────────────────────────────
+
+const totalCount = ref(0)
+const totalUnfiltered = ref(0)
+const messages = reactive(new Map())  // index (in result set) → {index, originalIndex, text}
+const loadedPages = reactive(new Set())
+const fetchingPages = reactive(new Set())
+
+const searchQuery = ref('')
+const activeIndex = ref(0)
+// Which element has focus within the active item: 'list' | 'replace' | 'insert'
+const focusTarget = ref('list')
+// Which item was explicitly clicked/tapped — prevents first-tap-inserts on touch.
+// -1 means no item has been click-confirmed yet.
+const confirmedIndex = ref(-1)
+
+// Tracks the current search "version" — incremented on every search change
+// to discard stale API responses.
+let searchVersion = 0
+
+// ─── Virtual scroll state ─────────────────────────────────────────────────
+
+const scrollTopPx = ref(0)
+
+const totalHeight = computed(() => totalCount.value * ITEM_HEIGHT)
+
+const visibleStart = computed(() => Math.floor(scrollTopPx.value / ITEM_HEIGHT))
+const visibleEnd = computed(() => {
+    const containerH = listRef.value?.clientHeight || 300
+    return Math.ceil((scrollTopPx.value + containerH) / ITEM_HEIGHT)
+})
+
+const renderStart = computed(() => Math.max(0, visibleStart.value - RENDER_BUFFER))
+const renderEnd = computed(() => Math.min(totalCount.value, visibleEnd.value + RENDER_BUFFER))
+
+const renderedItems = computed(() => {
+    const items = []
+    for (let i = renderStart.value; i < renderEnd.value; i++) {
+        const msg = messages.get(i)
+        items.push(msg || { index: i, original_index: i, text: null })
+    }
+    return items
+})
+
+// ─── Page fetching ────────────────────────────────────────────────────────
+
+function pageFor(index) {
+    return Math.floor(index / FETCH_SIZE)
+}
+
+function resetData() {
+    messages.clear()
+    loadedPages.clear()
+    fetchingPages.clear()
+    totalCount.value = 0
+    totalUnfiltered.value = 0
+    confirmedIndex.value = -1
+    searchVersion++
+}
+
+async function fetchPage(pageNum) {
+    if (loadedPages.has(pageNum) || fetchingPages.has(pageNum)) return
+    fetchingPages.add(pageNum)
+
+    const version = searchVersion
+    const offset = pageNum * FETCH_SIZE
+    const query = searchQuery.value.trim()
+    const params = new URLSearchParams({
+        offset: String(offset),
+        limit: String(FETCH_SIZE),
+    })
+    if (query) params.set('q', query)
+
+    try {
+        const url = `/api/projects/${props.projectId}/sessions/${props.sessionId}/user-messages/?${params}`
+        const response = await apiFetch(url)
+        if (!response.ok || version !== searchVersion) return
+
+        const data = await response.json()
+        if (version !== searchVersion) return  // Stale
+
+        totalCount.value = data.total
+        totalUnfiltered.value = data.total_unfiltered
+        for (const msg of data.messages) {
+            messages.set(msg.index, msg)
+        }
+        loadedPages.add(pageNum)
+    } finally {
+        fetchingPages.delete(pageNum)
+    }
+}
+
+function ensureVisible(startIdx, endIdx) {
+    const startPage = pageFor(startIdx)
+    const endPage = pageFor(Math.max(0, endIdx - 1))
+    for (let p = startPage; p <= endPage; p++) {
+        fetchPage(p)
+    }
+}
+
+// ─── Open / close ─────────────────────────────────────────────────────────
+
+async function open() {
+    if (isOpen.value) {
+        // Already open: toggle focus to search input
+        focusSearchInput()
+        return
+    }
+
+    searchQuery.value = ''
+    isOpen.value = true
+    focusTarget.value = 'list'
+    loading.value = true
+    resetData()
+
+    // Fetch first page to get total count
+    await fetchPage(0)
+
+    if (totalCount.value === 0) {
+        loading.value = false
+        await nextTick()
+        listRef.value?.focus()
+        return
+    }
+
+    // Also fetch the last page so we can display the most recent messages
+    const lastPage = pageFor(totalCount.value - 1)
+    if (lastPage > 0) {
+        await fetchPage(lastPage)
+    }
+
+    activeIndex.value = totalCount.value - 1
+    loading.value = false
+
+    await nextTick()
+    await nextTick()
+
+    listRef.value?.focus()
+    scrollToIndex(activeIndex.value)
+}
+
+/**
+ * Focus the list container (called from outside via Alt+PageDown).
+ */
+function focusList() {
+    if (!isOpen.value) return
+    focusTarget.value = 'list'
+    listRef.value?.focus()
+}
+
+function close() {
+    isOpen.value = false
+    resetData()
+    searchQuery.value = ''
+    emit('close')
+}
+
+// ─── Scroll management ───────────────────────────────────────────────────
+
+function onScroll() {
+    scrollTopPx.value = listRef.value?.scrollTop || 0
+    ensureVisible(renderStart.value, renderEnd.value)
+}
+
+function scrollToIndex(index) {
+    const container = listRef.value
+    if (!container) return
+    const top = index * ITEM_HEIGHT
+    const bottom = top + ITEM_HEIGHT
+    if (top < container.scrollTop) {
+        container.scrollTop = top
+    } else if (bottom > container.scrollTop + container.clientHeight) {
+        container.scrollTop = bottom - container.clientHeight
+    }
+}
+
+// ─── Focus management ─────────────────────────────────────────────────────
+
+function focusSearchInput() {
+    focusTarget.value = 'list'
+    try {
+        searchInputRef.value?.focus()
+    } catch {
+        // wa-input.focus() can throw if the shadow DOM isn't ready yet.
+    }
+}
+
+function focusActionButton(action) {
+    focusTarget.value = action
+    const container = listRef.value
+    if (!container) return
+    const itemEl = container.querySelector(`[data-index="${activeIndex.value}"]`)
+    const btn = itemEl?.querySelector(`.action-${action}`)
+    if (btn) {
+        btn.tabIndex = 0
+        btn.focus()
+    }
+}
+
+// ─── Actions ──────────────────────────────────────────────────────────────
+
+function replaceMessage(text) {
+    emit('replace', text)
+    close()
+}
+
+function insertMessage(text) {
+    emit('insert', text)
+    close()
+}
+
+function replaceActive() {
+    const msg = messages.get(activeIndex.value)
+    if (msg?.text) replaceMessage(msg.text)
+}
+
+function insertActive() {
+    const msg = messages.get(activeIndex.value)
+    if (msg?.text) insertMessage(msg.text)
+}
+
+// ─── Item click (touch support) ──────────────────────────────────────────
+
+/**
+ * Handle click on an item row.
+ * First click: activate the item (shows action buttons).
+ * Second click (item already active): insert at cursor.
+ */
+function onItemClick(item) {
+    if (!item.text) return
+    if (item.index === confirmedIndex.value) {
+        // Already click-confirmed → insert (default action)
+        insertMessage(item.text)
+    } else {
+        // First click: activate and confirm
+        activeIndex.value = item.index
+        confirmedIndex.value = item.index
+    }
+}
+
+// ─── Navigate to index (with fetch if needed) ────────────────────────────
+
+function navigateTo(index) {
+    activeIndex.value = index
+    confirmedIndex.value = -1
+    scrollToIndex(index)
+    ensureVisible(index, index + 1)
+}
+
+// ─── Search input keyboard handler ────────────────────────────────────────
+
+function handleSearchKeydown(event) {
+    if (event.key === 'Escape') {
+        event.preventDefault()
+        event.stopPropagation()
+        close()
+        return
+    }
+    // Alt+PageDown: switch focus to list
+    if (event.altKey && event.key === 'PageDown') {
+        event.preventDefault()
+        focusTarget.value = 'list'
+        listRef.value?.focus()
+        return
+    }
+    if (event.key === 'ArrowDown') {
+        event.preventDefault()
+        if (totalCount.value > 0) {
+            if (activeIndex.value + 1 < totalCount.value) {
+                activeIndex.value++
+            }
+            focusTarget.value = 'list'
+            listRef.value?.focus()
+            scrollToIndex(activeIndex.value)
+        }
+        return
+    }
+    if (event.key === 'PageDown') {
+        event.preventDefault()
+        if (totalCount.value > 0) {
+            navigateTo(Math.min(activeIndex.value + 10, totalCount.value - 1))
+            focusTarget.value = 'list'
+            listRef.value?.focus()
+        }
+        return
+    }
+    if (event.key === 'Enter') {
+        event.preventDefault()
+        insertActive()
+        return
+    }
+}
+
+// ─── Action button keyboard handler ───────────────────────────────────────
+
+function handleActionKeydown(event, action) {
+    if (event.key === 'Enter') {
+        event.stopPropagation()
+        return
+    }
+    if (event.key === 'Escape') {
+        event.preventDefault()
+        event.stopPropagation()
+        close()
+        return
+    }
+    if (event.key === 'Tab') {
+        event.preventDefault()
+        event.stopPropagation()
+        if (action === 'insert') {
+            focusActionButton('replace')
+        } else {
+            focusTarget.value = 'list'
+            listRef.value?.focus()
+        }
+        return
+    }
+    if (event.key === 'ArrowUp' || event.key === 'ArrowDown') {
+        event.preventDefault()
+        event.stopPropagation()
+        focusTarget.value = 'list'
+        listRef.value?.focus()
+        if (event.key === 'ArrowUp' && activeIndex.value > 0) {
+            navigateTo(activeIndex.value - 1)
+        } else if (event.key === 'ArrowDown' && activeIndex.value < totalCount.value - 1) {
+            navigateTo(activeIndex.value + 1)
+        }
+        return
+    }
+}
+
+// ─── List keyboard handler ────────────────────────────────────────────────
+
+function handleListKeydown(event) {
+    // Alt+PageUp: switch focus to search input
+    if (event.altKey && event.key === 'PageUp') {
+        event.preventDefault()
+        focusSearchInput()
+        return
+    }
+
+    const count = totalCount.value
+    if (!count) return
+
+    switch (event.key) {
+        case 'Tab': {
+            event.preventDefault()
+            focusActionButton('replace')
+            break
+        }
+
+        case 'ArrowDown': {
+            event.preventDefault()
+            if (activeIndex.value + 1 < count) {
+                navigateTo(activeIndex.value + 1)
+            }
+            break
+        }
+
+        case 'ArrowUp': {
+            event.preventDefault()
+            if (activeIndex.value <= 0) {
+                activeIndex.value = 0
+                focusSearchInput()
+            } else {
+                navigateTo(activeIndex.value - 1)
+            }
+            break
+        }
+
+        case 'Home': {
+            event.preventDefault()
+            navigateTo(0)
+            break
+        }
+
+        case 'End': {
+            event.preventDefault()
+            navigateTo(count - 1)
+            break
+        }
+
+        case 'PageDown': {
+            event.preventDefault()
+            navigateTo(Math.min(activeIndex.value + 10, count - 1))
+            break
+        }
+
+        case 'PageUp': {
+            event.preventDefault()
+            if (activeIndex.value <= 0) {
+                activeIndex.value = 0
+                focusSearchInput()
+            } else {
+                navigateTo(Math.max(activeIndex.value - 10, 0))
+            }
+            break
+        }
+
+        case 'Enter': {
+            event.preventDefault()
+            insertActive()
+            break
+        }
+
+        case 'Escape': {
+            event.preventDefault()
+            event.stopPropagation()
+            close()
+            break
+        }
+
+        default:
+            if (event.key.length === 1 && !event.ctrlKey && !event.metaKey) {
+                focusSearchInput()
+            }
+            return
+    }
+}
+
+// ─── Search debounce ──────────────────────────────────────────────────────
+
+let searchTimer = null
+
+watch(searchQuery, () => {
+    clearTimeout(searchTimer)
+    searchTimer = setTimeout(async () => {
+        resetData()
+        await fetchPage(0)
+        if (totalCount.value > 0) {
+            const lastPage = pageFor(totalCount.value - 1)
+            if (lastPage > 0) await fetchPage(lastPage)
+            activeIndex.value = totalCount.value - 1
+            await nextTick()
+            scrollToIndex(activeIndex.value)
+        } else {
+            activeIndex.value = 0
+        }
+    }, SEARCH_DEBOUNCE)
+})
+
+// ─── Click outside to close ───────────────────────────────────────────────
+
+function onDocumentClick(event) {
+    if (!isOpen.value) return
+    const popup = popupRef.value
+    if (!popup) return
+    if (popup.contains(event.target)) return
+    close()
+}
+
+watch(isOpen, (open) => {
+    if (open) {
+        setTimeout(() => {
+            document.addEventListener('click', onDocumentClick, true)
+        }, 0)
+    } else {
+        document.removeEventListener('click', onDocumentClick, true)
+    }
+})
+
+onBeforeUnmount(() => {
+    document.removeEventListener('click', onDocumentClick, true)
+    clearTimeout(searchTimer)
+})
+
+defineExpose({ open, close, isOpen, focusList })
+</script>
+
+<template>
+    <wa-popup
+        ref="popupRef"
+        :anchor="anchorId"
+        placement="top-start"
+        :active="isOpen"
+        :distance="4"
+        flip
+        shift
+        shift-padding="8"
+    >
+        <div class="picker-panel">
+            <!-- Search input -->
+            <div class="picker-search">
+                <wa-input
+                    ref="searchInputRef"
+                    :value="searchQuery"
+                    placeholder="Filter messages..."
+                    size="small"
+                    with-clear
+                    class="picker-search-input"
+                    @input="searchQuery = $event.target.value"
+                    @keydown="handleSearchKeydown"
+                >
+                    <wa-icon slot="start" name="magnifying-glass"></wa-icon>
+                </wa-input>
+            </div>
+
+            <!-- Virtual-scrolled message list -->
+            <div
+                ref="listRef"
+                class="picker-list"
+                tabindex="0"
+                @scroll="onScroll"
+                @keydown="handleListKeydown"
+            >
+                <template v-if="loading">
+                    <div class="picker-status">
+                        <wa-spinner></wa-spinner>
+                    </div>
+                </template>
+                <template v-else-if="totalCount === 0">
+                    <div class="picker-status">
+                        {{ searchQuery ? 'No matching messages' : 'No messages in this session' }}
+                    </div>
+                </template>
+                <template v-else>
+                    <div class="virtual-viewport" :style="{ height: totalHeight + 'px' }">
+                        <div
+                            v-for="item in renderedItems"
+                            :key="item.index"
+                            :data-index="item.index"
+                            class="picker-item"
+                            :class="{ active: item.index === activeIndex }"
+                            :style="{ transform: `translateY(${item.index * ITEM_HEIGHT}px)` }"
+                            @mouseenter="activeIndex = item.index; confirmedIndex = -1"
+                            @click="onItemClick(item)"
+                        >
+                            <span class="item-num">{{ (item.original_index ?? item.index) + 1 }}</span>
+                            <div v-if="item.text" class="item-text">{{ item.text }}</div>
+                            <div v-else class="item-text item-placeholder">…</div>
+                            <div
+                                v-if="item.text"
+                                class="item-actions"
+                                :class="{ visible: item.index === activeIndex }"
+                            >
+                                <button
+                                    class="action-btn action-insert"
+                                    :class="{ 'pre-selected': item.index === activeIndex && focusTarget === 'list' }"
+                                    title="Insert (at cursor position) — Enter"
+                                    tabindex="-1"
+                                    @click.stop="insertMessage(item.text)"
+                                    @keydown="handleActionKeydown($event, 'insert')"
+                                >
+                                    <wa-icon name="right-to-bracket"></wa-icon>
+                                </button>
+                                <button
+                                    class="action-btn action-replace"
+                                    title="Replace (overwrite current text) — Tab+Enter"
+                                    tabindex="-1"
+                                    @click.stop="replaceMessage(item.text)"
+                                    @keydown="handleActionKeydown($event, 'replace')"
+                                >
+                                    <wa-icon name="right-left"></wa-icon>
+                                </button>
+                            </div>
+                        </div>
+                    </div>
+                </template>
+            </div>
+        </div>
+    </wa-popup>
+</template>
+
+<style scoped>
+.picker-panel {
+    width: min(40rem, calc(100vw - 1rem));
+    max-height: min(30rem, 80vh);
+    display: flex;
+    flex-direction: column;
+    background: var(--wa-color-surface-default);
+    border: 1px solid var(--wa-color-surface-border);
+    border-radius: var(--wa-border-radius-m);
+    box-shadow: var(--wa-shadow-l);
+    overflow: hidden;
+}
+
+/* ─── Search ──────────────────────────────────────────────────────────── */
+
+.picker-search {
+    padding: var(--wa-space-2xs);
+    border-bottom: 1px solid var(--wa-color-surface-border);
+    flex-shrink: 0;
+}
+
+.picker-search-input {
+    width: 100%;
+}
+
+/* ─── List ────────────────────────────────────────────────────────────── */
+
+.picker-list {
+    overflow-y: auto;
+    flex: 1;
+    min-height: 0;
+    outline: none;
+}
+
+.picker-status {
+    padding: var(--wa-space-m) var(--wa-space-s);
+    color: var(--wa-color-text-quiet);
+    font-size: var(--wa-font-size-s);
+    text-align: center;
+}
+
+/* ─── Virtual viewport ───────────────────────────────────────────────── */
+
+.virtual-viewport {
+    position: relative;
+}
+
+/* ─── Item (fixed height for virtual scroll) ─────────────────────────── */
+
+.picker-item {
+    position: absolute;
+    top: 0;
+    left: 0;
+    right: 0;
+    height: 52px; /* Must match ITEM_HEIGHT */
+    padding: var(--wa-space-2xs) var(--wa-space-s);
+    box-sizing: border-box;
+    display: flex;
+    align-items: center;
+    gap: var(--wa-space-xs);
+}
+
+.picker-item:hover {
+    background: var(--wa-color-surface-raised);
+}
+
+.picker-item.active {
+    background: var(--wa-color-surface-lowered);
+}
+
+.item-num {
+    flex-shrink: 0;
+    min-width: 1.5rem;
+    text-align: right;
+    color: var(--wa-color-text-quiet);
+    font-size: var(--wa-font-size-xs);
+    user-select: none;
+}
+
+.item-text {
+    flex: 1;
+    min-width: 0;
+    color: var(--wa-color-text-default);
+    font-size: var(--wa-font-size-s);
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+
+.item-placeholder {
+    color: var(--wa-color-text-quiet);
+    font-style: italic;
+}
+
+/* ─── Action buttons ─────────────────────────────────────────────────── */
+
+.item-actions {
+    display: flex;
+    gap: var(--wa-space-3xs);
+    flex-shrink: 0;
+    opacity: 0;
+    transition: opacity 0.1s;
+}
+
+.item-actions.visible,
+.picker-item:hover .item-actions {
+    opacity: 1;
+}
+
+.action-btn {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    width: 1.75rem;
+    height: 1.75rem;
+    border: 1px solid var(--wa-color-border-default);
+    border-radius: var(--wa-border-radius-s);
+    background: var(--wa-color-surface-default);
+    color: var(--wa-color-text-quiet);
+    cursor: pointer;
+    font-size: 0.8rem;
+    transition: background 0.1s, color 0.1s, border-color 0.1s;
+}
+
+.action-btn:hover {
+    background: var(--wa-color-surface-alt);
+    color: var(--wa-color-text-default);
+    border-color: var(--wa-color-border-hover);
+}
+
+.action-btn:focus-visible {
+    outline: 2px solid var(--wa-color-brand-default);
+    outline-offset: 1px;
+    color: var(--wa-color-text-default);
+}
+
+/* Pre-selected state: insert button is visually highlighted when list is focused */
+.action-btn.pre-selected {
+    background: var(--wa-color-surface-alt);
+    border-color: var(--wa-color-brand-default);
+    color: var(--wa-color-text-default);
+}
+</style>
diff --git a/src/twicc/urls.py b/src/twicc/urls.py
index 29c283b..6748dee 100644
--- a/src/twicc/urls.py
+++ b/src/twicc/urls.py
@@ -27,6 +27,7 @@
     path("api/projects/<str:project_id>/sessions/<str:session_id>/", views.session_detail),
     path("api/projects/<str:project_id>/sessions/<str:session_id>/items/", views.session_items),
     path("api/projects/<str:project_id>/sessions/<str:session_id>/items/metadata/", views.session_items_metadata),
+    path("api/projects/<str:project_id>/sessions/<str:session_id>/user-messages/", views.user_messages),
     path("api/projects/<str:project_id>/sessions/<str:session_id>/items/<int:line_num>/tool-results/<str:tool_id>/", views.tool_results),
     path("api/projects/<str:project_id>/sessions/<str:session_id>/subagents/", views.subagents_state),
     path("api/projects/<str:project_id>/sessions/<str:session_id>/tool-states/", views.tool_states),
@@ -34,6 +35,7 @@
     path("api/projects/<str:project_id>/sessions/<str:parent_session_id>/subagent/<str:session_id>/", views.session_detail),
     path("api/projects/<str:project_id>/sessions/<str:parent_session_id>/subagent/<str:session_id>/items/", views.session_items),
     path("api/projects/<str:project_id>/sessions/<str:parent_session_id>/subagent/<str:session_id>/items/metadata/", views.session_items_metadata),
+    path("api/projects/<str:project_id>/sessions/<str:parent_session_id>/subagent/<str:session_id>/user-messages/", views.user_messages),
     path("api/projects/<str:project_id>/sessions/<str:parent_session_id>/subagent/<str:session_id>/items/<int:line_num>/tool-results/<str:tool_id>/", views.tool_results),
     # Project-level git endpoints (for draft sessions)
     path("api/projects/<str:project_id>/git-log/", views.git_log),
diff --git a/src/twicc/views.py b/src/twicc/views.py
index 41c8b54..3992acd 100644
--- a/src/twicc/views.py
+++ b/src/twicc/views.py
@@ -11,7 +11,7 @@
 
 import orjson
 
-from twicc.compute import get_message_content_list
+from twicc.compute import get_message_content, get_message_content_list
 from twicc.core.models import AgentLink, DailyActivity, Project, Session, SessionItem, SessionType, SlashCommand, ToolResultLink, WeeklyActivity
 from twicc.core.serializers import (
     serialize_project,
@@ -489,6 +489,108 @@ def session_items_metadata(request, project_id, session_id, parent_session_id=No
     return JsonResponse(data, safe=False)
 
 
+def user_messages(request, project_id, session_id, parent_session_id=None):
+    """GET /api/projects/<id>/sessions/<session_id>/user-messages/ - Paginated user message texts.
+
+    Also handles subagent route:
+    GET /api/projects/<id>/sessions/<parent_session_id>/subagent/<session_id>/user-messages/
+
+    Returns user message texts in chronological order (oldest first), with pagination
+    and optional full-text search. Designed for the prompt history picker popup.
+
+    Query params:
+        offset (int): Number of messages to skip (default: 0)
+        limit (int): Maximum messages to return (default: 50, max: 200)
+        q (str): Optional search query (case-insensitive substring match)
+
+    Response:
+        {
+            "total": 312,
+            "total_unfiltered": 500,
+            "messages": [
+                {"index": 0, "original_index": 3, "text": "first matching message..."},
+                {"index": 1, "original_index": 7, "text": "second matching message..."},
+                ...
+            ]
+        }
+
+    Fields:
+        total: number of messages matching the current query (or all if no query)
+        total_unfiltered: total number of user messages (always the full count)
+        index: position within the filtered result set (0-based), for virtual scroll
+        original_index: chronological position among all user messages (for display)
+    """
+    try:
+        session = Session.objects.get(id=session_id, project_id=project_id)
+    except Session.DoesNotExist:
+        raise Http404("Session not found")
+
+    # Validate parent_session_id
+    if parent_session_id is not None:
+        if session.parent_session_id != parent_session_id:
+            raise Http404("Subagent not found for this parent session")
+    else:
+        if session.parent_session_id is not None:
+            raise Http404("Session not found")
+
+    # Parse pagination params
+    try:
+        offset = max(0, int(request.GET.get("offset", 0)))
+    except (ValueError, TypeError):
+        offset = 0
+    try:
+        limit = min(10000, max(1, int(request.GET.get("limit", 50))))
+    except (ValueError, TypeError):
+        limit = 50
+
+    query = request.GET.get("q", "").strip().lower()
+
+    # Fetch all user_message items (only content field needed), ordered by line_num
+    items = session.items.filter(kind="user_message").only("content").order_by("line_num")
+
+    # Extract text from each user message, tracking chronological position
+    # Each entry is (original_index, text) where original_index is the
+    # position among ALL user messages (regardless of filter).
+    filtered: list[tuple[int, str]] = []
+    msg_idx = 0
+    for item in items.iterator(chunk_size=500):
+        try:
+            parsed = orjson.loads(item.content)
+        except (orjson.JSONDecodeError, TypeError):
+            continue
+        content = get_message_content(parsed)
+        if not content:
+            continue
+        if isinstance(content, str):
+            text = content
+        elif isinstance(content, list):
+            # Find the first text block in the content array
+            text = ""
+            for block in content:
+                if isinstance(block, dict) and block.get("type") == "text" and block.get("text"):
+                    text = block["text"]
+                    break
+        else:
+            continue
+        if not text:
+            continue
+        if not query or query in text.lower():
+            filtered.append((msg_idx, text))
+        msg_idx += 1
+
+    total = len(filtered)
+    page = filtered[offset:offset + limit]
+
+    return JsonResponse({
+        "total": total,
+        "total_unfiltered": msg_idx,
+        "messages": [
+            {"index": offset + i, "original_index": orig_idx, "text": text}
+            for i, (orig_idx, text) in enumerate(page)
+        ],
+    })
+
+
 def tool_results(request, project_id, session_id, line_num, tool_id, parent_session_id=None):
     """GET /api/projects/<id>/sessions/<session_id>/items/<line_num>/tool-results/<tool_id>/