diff --git a/packages/ui/src/components/alert-dialog.tsx b/packages/ui/src/components/alert-dialog.tsx
index 7dc7b73f..fce38bad 100644
--- a/packages/ui/src/components/alert-dialog.tsx
+++ b/packages/ui/src/components/alert-dialog.tsx
@@ -1,5 +1,5 @@
 import { Dialog } from "@kobalte/core/dialog"
-import { Component, Show, createEffect } from "solid-js"
+import { Component, Show, createEffect, createSignal } from "solid-js"
 import { alertDialogState, dismissAlertDialog } from "../stores/alerts"
 import type { AlertVariant, AlertDialogState } from "../stores/alerts"
 
@@ -27,8 +27,9 @@ const variantAccent: Record<AlertVariant, { badgeBg: string; badgeBorder: string
   },
 }
 
-function dismiss(confirmed: boolean, payload?: AlertDialogState | null) {
+function dismiss(confirmed: boolean, payload?: AlertDialogState | null, promptValue?: string) {
   const current = payload ?? alertDialogState()
+
   if (current?.type === "confirm") {
     if (confirmed) {
       current.onConfirm?.()
@@ -36,7 +37,23 @@ function dismiss(confirmed: boolean, payload?: AlertDialogState | null) {
       current.onCancel?.()
     }
     current.resolve?.(confirmed)
-  } else if (confirmed) {
+    dismissAlertDialog()
+    return
+  }
+
+  if (current?.type === "prompt") {
+    if (confirmed) {
+      current.onConfirm?.()
+      current.resolvePrompt?.(promptValue ?? "")
+    } else {
+      current.onCancel?.()
+      current.resolvePrompt?.(null)
+    }
+    dismissAlertDialog()
+    return
+  }
+
+  if (confirmed) {
     current?.onConfirm?.()
   }
   dismissAlertDialog()
@@ -60,9 +77,12 @@ const AlertDialog: Component = () => {
         const accent = variantAccent[variant]
         const title = payload.title || accent.fallbackTitle
         const isConfirm = payload.type === "confirm"
-        const confirmLabel = payload.confirmLabel || (isConfirm ? "Confirm" : "OK")
+        const isPrompt = payload.type === "prompt"
+        const confirmLabel = payload.confirmLabel || (isConfirm ? "Confirm" : isPrompt ? "Run" : "OK")
         const cancelLabel = payload.cancelLabel || "Cancel"
 
+        const [inputValue, setInputValue] = createSignal(payload.inputDefaultValue ?? "")
+
         return (
           <Dialog
             open
@@ -98,27 +118,47 @@ const AlertDialog: Component = () => {
                     </div>
                   </div>
 
-                  <div class="mt-6 flex justify-end gap-3">
-                    {isConfirm && (
-                      <button
-                        type="button"
-                        class="button-secondary"
-                        onClick={() => dismiss(false, payload)}
-                      >
-                        {cancelLabel}
-                      </button>
-                    )}
-                    <button
-                      type="button"
-                      class="button-primary"
-                      ref={(el) => {
-                        primaryButtonRef = el
-                      }}
-                      onClick={() => dismiss(true, payload)}
-                    >
-                      {confirmLabel}
-                    </button>
-                  </div>
+                   <Show when={isPrompt}>
+                     <div class="mt-4">
+                       <label class="text-xs font-medium text-muted uppercase tracking-wide">
+                         {payload.inputLabel || "Arguments"}
+                       </label>
+                       <input
+                         class="modal-search-input mt-2"
+                         value={inputValue()}
+                         placeholder={payload.inputPlaceholder || ""}
+                         onInput={(e) => setInputValue(e.currentTarget.value)}
+                         onKeyDown={(e) => {
+                           if (e.key === "Enter") {
+                             e.preventDefault()
+                             dismiss(true, payload, inputValue())
+                           }
+                         }}
+                       />
+                     </div>
+                   </Show>
+
+                   <div class="mt-6 flex justify-end gap-3">
+                     {(isConfirm || isPrompt) && (
+                       <button
+                         type="button"
+                         class="button-secondary"
+                         onClick={() => dismiss(false, payload)}
+                       >
+                         {cancelLabel}
+                       </button>
+                     )}
+                     <button
+                       type="button"
+                       class="button-primary"
+                       ref={(el) => {
+                         primaryButtonRef = el
+                       }}
+                       onClick={() => dismiss(true, payload, inputValue())}
+                     >
+                       {confirmLabel}
+                     </button>
+                   </div>
                 </Dialog.Content>
               </div>
             </Dialog.Portal>
diff --git a/packages/ui/src/components/prompt-input.tsx b/packages/ui/src/components/prompt-input.tsx
index f0f621a1..22fc1f7c 100644
--- a/packages/ui/src/components/prompt-input.tsx
+++ b/packages/ui/src/components/prompt-input.tsx
@@ -9,7 +9,8 @@ import type { Attachment } from "../types/attachment"
 import type { Agent } from "../types/session"
 import Kbd from "./kbd"
 import { getActiveInstance } from "../stores/instances"
-import { agents, getSessionDraftPrompt, setSessionDraftPrompt, clearSessionDraftPrompt } from "../stores/sessions"
+import { agents, getSessionDraftPrompt, setSessionDraftPrompt, clearSessionDraftPrompt, executeCustomCommand } from "../stores/sessions"
+import { getCommands } from "../stores/commands"
 import { showAlertDialog } from "../stores/alerts"
 import { getLogger } from "../lib/logger"
 const log = getLogger("actions")
@@ -36,6 +37,7 @@ export default function PromptInput(props: PromptInputProps) {
   const [historyDraft, setHistoryDraft] = createSignal<string | null>(null)
   const [, setIsFocused] = createSignal(false)
   const [showPicker, setShowPicker] = createSignal(false)
+  const [pickerMode, setPickerMode] = createSignal<"mention" | "command">("mention")
   const [searchQuery, setSearchQuery] = createSignal("")
   const [atPosition, setAtPosition] = createSignal<number | null>(null)
   const [isDragging, setIsDragging] = createSignal(false)
@@ -560,14 +562,28 @@ export default function PromptInput(props: PromptInputProps) {
     const currentAttachments = attachments()
     if (props.disabled || (!text && currentAttachments.length === 0)) return
 
-    const resolvedPrompt = resolvePastedPlaceholders(text, currentAttachments)
     const isShellMode = mode() === "shell"
 
+    // Slash command routing (match OpenCode TUI): only run if the command exists.
+    const isSlashCandidate = !isShellMode && text.startsWith("/")
+    const firstSpace = isSlashCandidate ? text.indexOf(" ") : -1
+    const commandToken = isSlashCandidate ? (firstSpace === -1 ? text : text.slice(0, firstSpace)) : ""
+    const commandName = isSlashCandidate ? commandToken.slice(1) : ""
+    const commandArgs = isSlashCandidate ? (firstSpace === -1 ? "" : text.slice(firstSpace + 1).trimStart()) : ""
+
+    const isKnownSlashCommand =
+      isSlashCandidate &&
+      commandName.length > 0 &&
+      getCommands(props.instanceId).some((cmd) => cmd.name === commandName)
+
+    const resolvedPrompt = isKnownSlashCommand ? text : resolvePastedPlaceholders(text, currentAttachments)
+    const historyEntry = resolvedPrompt
+
     const refreshHistory = async () => {
       try {
-        await addToHistory(props.instanceFolder, resolvedPrompt)
+        await addToHistory(props.instanceFolder, historyEntry)
         setHistory((prev) => {
-          const next = [resolvedPrompt, ...prev]
+          const next = [historyEntry, ...prev]
           if (next.length > HISTORY_LIMIT) {
             next.length = HISTORY_LIMIT
           }
@@ -580,10 +596,18 @@ export default function PromptInput(props: PromptInputProps) {
     }
 
     clearPrompt()
-    clearAttachments(props.instanceId, props.sessionId)
-    setIgnoredAtPositions(new Set<number>())
-    setPasteCount(0)
-    setImageCount(0)
+
+    // Ignore attachments for slash commands, but keep them for next prompt.
+    if (!isKnownSlashCommand) {
+      clearAttachments(props.instanceId, props.sessionId)
+      setPasteCount(0)
+      setImageCount(0)
+      setIgnoredAtPositions(new Set<number>())
+    } else {
+      syncAttachmentCounters("", currentAttachments)
+      setIgnoredAtPositions(new Set<number>())
+    }
+
     setHistoryDraft(null)
 
     try {
@@ -593,6 +617,8 @@ export default function PromptInput(props: PromptInputProps) {
         } else {
           await props.onSend(resolvedPrompt, [])
         }
+      } else if (isKnownSlashCommand) {
+        await executeCustomCommand(props.instanceId, props.sessionId, commandName, commandArgs)
       } else {
         await props.onSend(resolvedPrompt, currentAttachments)
       }
@@ -677,11 +703,27 @@ export default function PromptInput(props: PromptInputProps) {
     setHistoryDraft(null)
 
     const cursorPos = target.selectionStart
+
+    // Slash command picker (only when editing the command token: "/<query>")
+    if (value.startsWith("/") && cursorPos >= 1) {
+      const firstWhitespaceIndex = value.slice(1).search(/\s/)
+      const tokenEnd = firstWhitespaceIndex === -1 ? value.length : firstWhitespaceIndex + 1
+
+      if (cursorPos <= tokenEnd) {
+        setPickerMode("command")
+        setAtPosition(0)
+        setSearchQuery(value.substring(1, cursorPos))
+        setShowPicker(true)
+        return
+      }
+    }
+
     const textBeforeCursor = value.substring(0, cursorPos)
     const lastAtIndex = textBeforeCursor.lastIndexOf("@")
 
     const previousAtPosition = atPosition()
 
+
     if (lastAtIndex === -1) {
       setIgnoredAtPositions(new Set<number>())
     } else if (previousAtPosition !== null && lastAtIndex !== previousAtPosition) {
@@ -698,6 +740,7 @@ export default function PromptInput(props: PromptInputProps) {
 
       if (!hasSpace && cursorPos === lastAtIndex + textAfterAt.length + 1) {
         if (!ignoredAtPositions().has(lastAtIndex)) {
+          setPickerMode("mention")
           setAtPosition(lastAtIndex)
           setSearchQuery(textAfterAt)
           setShowPicker(true)
@@ -716,9 +759,30 @@ export default function PromptInput(props: PromptInputProps) {
       | {
           type: "file"
           file: { path: string; relativePath?: string; isGitFile: boolean; isDirectory?: boolean }
-        },
+        }
+      | { type: "command"; command: { name: string; description?: string } },
   ) {
-    if (item.type === "agent") {
+    if (item.type === "command") {
+      const name = item.command.name
+      const currentPrompt = prompt()
+
+      const afterSlash = currentPrompt.slice(1)
+      const firstWhitespaceIndex = afterSlash.search(/\s/)
+      const tokenEnd = firstWhitespaceIndex === -1 ? currentPrompt.length : firstWhitespaceIndex + 1
+
+      const before = ""
+      const after = currentPrompt.substring(tokenEnd)
+      const newPrompt = before + `/${name} ` + after
+      setPrompt(newPrompt)
+
+      setTimeout(() => {
+        if (textareaRef) {
+          const newCursorPos = `/${name} `.length
+          textareaRef.setSelectionRange(newCursorPos, newCursorPos)
+          textareaRef.focus()
+        }
+      }, 0)
+    } else if (item.type === "agent") {
       const agentName = item.agent.name
       const existingAttachments = attachments()
       const alreadyAttached = existingAttachments.some(
@@ -822,7 +886,7 @@ export default function PromptInput(props: PromptInputProps) {
 
   function handlePickerClose() {
     const pos = atPosition()
-    if (pos !== null) {
+    if (pickerMode() === "mention" && pos !== null) {
       setIgnoredAtPositions((prev) => new Set(prev).add(pos))
     }
     setShowPicker(false)
@@ -981,9 +1045,11 @@ export default function PromptInput(props: PromptInputProps) {
         <Show when={showPicker() && instance()}>
           <UnifiedPicker
             open={showPicker()}
+            mode={pickerMode()}
             onClose={handlePickerClose}
             onSelect={handlePickerSelect}
             agents={instanceAgents()}
+            commands={getCommands(props.instanceId)}
             instanceClient={instance()!.client}
             searchQuery={searchQuery()}
             textareaRef={textareaRef}
diff --git a/packages/ui/src/components/unified-picker.tsx b/packages/ui/src/components/unified-picker.tsx
index d12e9899..fab200c9 100644
--- a/packages/ui/src/components/unified-picker.tsx
+++ b/packages/ui/src/components/unified-picker.tsx
@@ -1,5 +1,6 @@
-import { Component, createSignal, createEffect, For, Show, onCleanup } from "solid-js"
+import { Component, createSignal, createEffect, createMemo, For, Show, onCleanup } from "solid-js"
 import type { Agent } from "../types/session"
+import type { Command as SDKCommand } from "@opencode-ai/sdk/v2"
 import type { OpencodeClient } from "@opencode-ai/sdk/v2/client"
 import { serverApi } from "../lib/api-client"
 import { getLogger } from "../lib/logger"
@@ -67,13 +68,18 @@ function mapEntriesToFileItems(entries: { path: string; type: "file" | "director
   })
 }
 
-type PickerItem = { type: "agent"; agent: Agent } | { type: "file"; file: FileItem }
+type PickerItem =
+  | { type: "agent"; agent: Agent }
+  | { type: "file"; file: FileItem }
+  | { type: "command"; command: SDKCommand }
 
 interface UnifiedPickerProps {
   open: boolean
+  mode?: "mention" | "command"
   onSelect: (item: PickerItem) => void
   onClose: () => void
   agents: Agent[]
+  commands?: SDKCommand[]
   instanceClient: OpencodeClient | null
   searchQuery: string
   textareaRef?: HTMLTextAreaElement
@@ -81,6 +87,8 @@ interface UnifiedPickerProps {
 }
 
 const UnifiedPicker: Component<UnifiedPickerProps> = (props) => {
+  const mode = () => props.mode ?? "mention"
+
   const [files, setFiles] = createSignal<FileItem[]>([])
   const [filteredAgents, setFilteredAgents] = createSignal<Agent[]>([])
   const [selectedIndex, setSelectedIndex] = createSignal(0)
@@ -246,6 +254,11 @@ const UnifiedPicker: Component<UnifiedPickerProps> = (props) => {
       return
     }
 
+    if (mode() !== "mention") {
+      // Command mode doesn't use file snapshots.
+      return
+    }
+
     const workspaceChanged = lastWorkspaceId !== props.workspaceId
     const queryChanged = lastQuery !== props.searchQuery
 
@@ -262,6 +275,7 @@ const UnifiedPicker: Component<UnifiedPickerProps> = (props) => {
 
   createEffect(() => {
     if (!props.open) return
+    if (mode() !== "mention") return
 
     const query = props.searchQuery.toLowerCase()
     const filtered = query
@@ -275,8 +289,25 @@ const UnifiedPicker: Component<UnifiedPickerProps> = (props) => {
     setFilteredAgents(filtered)
   })
 
+  const filteredCommands = createMemo(() => {
+    if (mode() !== "command") return []
+    const q = props.searchQuery.trim().toLowerCase()
+    const source = props.commands ?? []
+    if (!q) return source
+    return source.filter((cmd) => {
+      const nameMatch = cmd.name.toLowerCase().includes(q)
+      const descMatch = (cmd.description ?? "").toLowerCase().includes(q)
+      return nameMatch || descMatch
+    })
+  })
+
   const allItems = (): PickerItem[] => {
     const items: PickerItem[] = []
+    if (mode() === "command") {
+      filteredCommands().forEach((command) => items.push({ type: "command", command }))
+      return items
+    }
+
     filteredAgents().forEach((agent) => items.push({ type: "agent", agent }))
     files().forEach((file) => items.push({ type: "file", file }))
     return items
@@ -329,9 +360,10 @@ const UnifiedPicker: Component<UnifiedPickerProps> = (props) => {
     }
   })
 
+  const commandCount = () => filteredCommands().length
   const agentCount = () => filteredAgents().length
   const fileCount = () => files().length
-  const isLoading = () => loadingState() !== "idle"
+  const isLoading = () => mode() === "mention" && loadingState() !== "idle"
   const loadingMessage = () => {
     if (loadingState() === "search") {
       return "Searching..."
@@ -351,7 +383,9 @@ const UnifiedPicker: Component<UnifiedPickerProps> = (props) => {
       >
         <div class="dropdown-header">
           <div class="dropdown-header-title">
-            Select Agent or File
+            <Show when={mode() === "command"} fallback={"Select Agent or File"}>
+              Select Command
+            </Show>
             <Show when={isLoading()}>
               <span class="ml-2">{loadingMessage()}</span>
             </Show>
@@ -359,11 +393,41 @@ const UnifiedPicker: Component<UnifiedPickerProps> = (props) => {
         </div>
 
         <div ref={scrollContainerRef} class="dropdown-content max-h-60">
-          <Show when={agentCount() === 0 && fileCount() === 0}>
+          <Show when={(mode() === "command" ? commandCount() === 0 : agentCount() === 0 && fileCount() === 0)}>
             <div class="dropdown-empty">No results found</div>
           </Show>
 
-          <Show when={agentCount() > 0}>
+          <Show when={mode() === "command" && commandCount() > 0}>
+            <div class="dropdown-section-header">COMMANDS</div>
+            <For each={filteredCommands()}>
+              {(command) => {
+                const itemIndex = allItems().findIndex((item) => item.type === "command" && item.command.name === command.name)
+                return (
+                  <div
+                    class={`dropdown-item ${itemIndex === selectedIndex() ? "dropdown-item-highlight" : ""}`}
+                    data-picker-selected={itemIndex === selectedIndex()}
+                    onClick={() => handleSelect({ type: "command", command })}
+                  >
+                    <div class="flex items-start gap-2">
+                      <svg class="dropdown-icon-accent h-4 w-4 mt-0.5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M4 6h16M4 12h16M4 18h16" />
+                      </svg>
+                      <div class="flex-1">
+                        <div class="text-sm font-medium">/{command.name}</div>
+                        <Show when={command.description}>
+                          <div class="mt-0.5 text-xs" style="color: var(--text-muted)">
+                            {(command.description ?? "").length > 80 ? (command.description ?? "").slice(0, 80) + "..." : command.description}
+                          </div>
+                        </Show>
+                      </div>
+                    </div>
+                  </div>
+                )
+              }}
+            </For>
+          </Show>
+
+          <Show when={mode() === "mention" && agentCount() > 0}>
             <div class="dropdown-section-header">
               AGENTS
             </div>
@@ -418,7 +482,7 @@ const UnifiedPicker: Component<UnifiedPickerProps> = (props) => {
             </For>
           </Show>
 
-          <Show when={fileCount() > 0}>
+          <Show when={mode() === "mention" && fileCount() > 0}>
             <div class="dropdown-section-header">
               FILES
             </div>
diff --git a/packages/ui/src/lib/command-utils.ts b/packages/ui/src/lib/command-utils.ts
index 992586d5..7152d5a3 100644
--- a/packages/ui/src/lib/command-utils.ts
+++ b/packages/ui/src/lib/command-utils.ts
@@ -1,6 +1,6 @@
 import type { Command } from "./commands"
 import type { Command as SDKCommand } from "@opencode-ai/sdk"
-import { showAlertDialog } from "../stores/alerts"
+import { showAlertDialog, showPromptDialog } from "../stores/alerts"
 import { activeSessionId, executeCustomCommand } from "../stores/sessions"
 import { getLogger } from "./logger"
 
@@ -11,15 +11,29 @@ export function commandRequiresArguments(template?: string): boolean {
   return /\$(?:\d+|ARGUMENTS)/.test(template)
 }
 
-export function promptForCommandArguments(command: SDKCommand): string | null {
+export async function promptForCommandArguments(command: SDKCommand): Promise<string | null> {
   if (!commandRequiresArguments(command.template)) {
     return ""
   }
-  const input = window.prompt(`Arguments for /${command.name}`, "")
-  if (input === null) {
+
+  try {
+    return await showPromptDialog(`Arguments for /${command.name}`, {
+      title: "Custom command",
+      variant: "info",
+      inputLabel: "Arguments",
+      inputPlaceholder: "e.g. foo bar",
+      inputDefaultValue: "",
+      confirmLabel: "Run",
+      cancelLabel: "Cancel",
+    })
+  } catch (error) {
+    log.error("Failed to prompt for command arguments", error)
+    showAlertDialog("Failed to open arguments prompt.", {
+      title: "Command arguments",
+      variant: "error",
+    })
     return null
   }
-  return input
 }
 
 function formatCommandLabel(name: string): string {
@@ -43,11 +57,11 @@ export function buildCustomCommandEntries(instanceId: string, commands: SDKComma
         })
         return
       }
-      const args = promptForCommandArguments(cmd)
-      if (args === null) {
-        return
-      }
       try {
+        const args = await promptForCommandArguments(cmd)
+        if (args === null) {
+          return
+        }
         await executeCustomCommand(instanceId, sessionId, cmd.name, args)
       } catch (error) {
         log.error("Failed to run custom command", error)
diff --git a/packages/ui/src/stores/alerts.ts b/packages/ui/src/stores/alerts.ts
index a3c7775b..720e0208 100644
--- a/packages/ui/src/stores/alerts.ts
+++ b/packages/ui/src/stores/alerts.ts
@@ -3,7 +3,7 @@ import { createSignal } from "solid-js"
 export type AlertVariant = "info" | "warning" | "error"
 
 export type AlertDialogState = {
-  type?: "alert" | "confirm"
+  type?: "alert" | "confirm" | "prompt"
   title?: string
   message: string
   detail?: string
@@ -12,7 +12,17 @@ export type AlertDialogState = {
   cancelLabel?: string
   onConfirm?: () => void
   onCancel?: () => void
+
+  // prompt-only
+  inputLabel?: string
+  inputPlaceholder?: string
+  inputDefaultValue?: string
+
+  // confirm-only
   resolve?: (value: boolean) => void
+
+  // prompt-only
+  resolvePrompt?: (value: string | null) => void
 }
 
 const [alertDialogState, setAlertDialogState] = createSignal<AlertDialogState | null>(null)
@@ -39,6 +49,23 @@ export function showConfirmDialog(message: string, options?: Omit<AlertDialogSta
   })
 }
 
+export function showPromptDialog(
+  message: string,
+  options?: Omit<AlertDialogState, "message" | "type" | "resolve" | "resolvePrompt">,
+): Promise<string | null> {
+  const activeElement = typeof document !== "undefined" ? (document.activeElement as HTMLElement | null) : null
+  activeElement?.blur()
+
+  return new Promise<string | null>((resolvePrompt) => {
+    setAlertDialogState({
+      type: "prompt",
+      message,
+      ...options,
+      resolvePrompt,
+    })
+  })
+}
+
 export function dismissAlertDialog() {
   setAlertDialogState(null)
 }