feat(v2): add copy/paste, theme hot-swap, tree enhancements, session resume, drag-resize

- TerminalPane: Ctrl+Shift+C/V copy/paste via attachCustomKeyEventHandler
- TerminalPane: subscribe to onThemeChange() for live theme hot-swap
- theme.svelte.ts: callback registry (onThemeChange) notifies listeners on setFlavor()
- AgentPane: session resume with follow-up prompt and resume_session_id
- AgentPane: tree node click scrolls to corresponding message (scrollIntoView)
- AgentTree: subtree cost display below each node, NODE_H 32->40
- TilingGrid: pane drag-resize via splitter overlays with mouse drag (10-90% clamping)

v2/src/lib/components/Agent/AgentPane.svelte

@@ -68,25 +68,37 @@
     }
   });
 
-  async function startQuery(text: string) {
+  let followUpPrompt = $state('');
+
+  async function startQuery(text: string, resume = false) {
     if (!text.trim()) return;
 
     const ready = await isAgentReady();
     if (!ready) {
-      createAgentSession(sessionId, text);
+      if (!resume) createAgentSession(sessionId, text);
       const { updateAgentStatus } = await import('../../stores/agents.svelte');
       updateAgentStatus(sessionId, 'error', 'Sidecar not ready — agent features unavailable');
       return;
     }
 
-    createAgentSession(sessionId, text);
+    const resumeId = resume ? session?.sdkSessionId : undefined;
+
+    if (!resume) {
+      createAgentSession(sessionId, text);
+    } else {
+      const { updateAgentStatus } = await import('../../stores/agents.svelte');
+      updateAgentStatus(sessionId, 'starting');
+    }
+
     await queryAgent({
       session_id: sessionId,
       prompt: text,
       cwd,
       max_turns: 50,
+      resume_session_id: resumeId,
     });
     inputPrompt = '';
+    followUpPrompt = '';
   }
 
   function handleSubmit(e: Event) {
@@ -123,6 +135,17 @@
     autoScroll = scrollHeight - scrollTop - clientHeight < 50;
   }
 
+  function handleTreeNodeClick(nodeId: string) {
+    if (!scrollContainer || !session) return;
+    // Find the message whose tool_call has this toolUseId
+    const msg = session.messages.find(
+      m => m.type === 'tool_call' && (m.content as ToolCallContent).toolUseId === nodeId
+    );
+    if (!msg) return;
+    autoScroll = false;
+    scrollContainer.querySelector('#msg-' + CSS.escape(msg.id))?.scrollIntoView({ behavior: 'smooth', block: 'center' });
+  }
+
   // Auto-scroll when new messages arrive
   $effect(() => {
     if (session?.messages.length) {
@@ -172,12 +195,12 @@
         </button>
       </div>
       {#if showTree && session}
-        <AgentTree {session} />
+        <AgentTree {session} onNodeClick={handleTreeNodeClick} />
       {/if}
     {/if}
     <div class="messages" bind:this={scrollContainer} onscroll={handleScroll}>
       {#each session.messages as msg (msg.id)}
-        <div class="message msg-{msg.type}">
+        <div class="message msg-{msg.type}" id="msg-{msg.id}">
           {#if msg.type === 'init'}
             <div class="msg-init">
               <span class="label">Session started</span>
@@ -241,6 +264,22 @@
             <button class="scroll-btn" onclick={() => { autoScroll = true; scrollToBottom(); }}>Scroll to bottom</button>
           {/if}
         </div>
+        {#if session.sdkSessionId}
+          <div class="follow-up">
+            <input
+              type="text"
+              class="follow-up-input"
+              bind:value={followUpPrompt}
+              placeholder="Follow up..."
+              onkeydown={(e) => {
+                if (e.key === 'Enter' && followUpPrompt.trim()) {
+                  startQuery(followUpPrompt, true);
+                }
+              }}
+            />
+            <button class="follow-up-btn" onclick={() => startQuery(followUpPrompt, true)} disabled={!followUpPrompt.trim()}>Send</button>
+          </div>
+        {/if}
       {:else if session.status === 'error'}
         <div class="error-bar">
           <span>Error: {session.error ?? 'Unknown'}</span>
@@ -250,6 +289,22 @@
             </button>
           {/if}
         </div>
+        {#if session.sdkSessionId}
+          <div class="follow-up">
+            <input
+              type="text"
+              class="follow-up-input"
+              bind:value={followUpPrompt}
+              placeholder="Retry or follow up..."
+              onkeydown={(e) => {
+                if (e.key === 'Enter' && followUpPrompt.trim()) {
+                  startQuery(followUpPrompt, true);
+                }
+              }}
+            />
+            <button class="follow-up-btn" onclick={() => startQuery(followUpPrompt, true)} disabled={!followUpPrompt.trim()}>Send</button>
+          </div>
+        {/if}
       {/if}
     </div>
   {/if}
@@ -633,4 +688,40 @@
 
   .done-bar { color: var(--ctp-green); }
   .error-bar { color: var(--ctp-red); }
+
+  .follow-up {
+    display: flex;
+    gap: 6px;
+    padding: 4px 0 0;
+  }
+
+  .follow-up-input {
+    flex: 1;
+    background: var(--bg-surface);
+    border: 1px solid var(--border);
+    border-radius: 3px;
+    color: var(--text-primary);
+    font-size: 12px;
+    padding: 4px 8px;
+    font-family: inherit;
+  }
+
+  .follow-up-input:focus {
+    outline: none;
+    border-color: var(--accent);
+  }
+
+  .follow-up-btn {
+    background: var(--accent);
+    color: var(--ctp-crust);
+    border: none;
+    border-radius: 3px;
+    padding: 4px 12px;
+    font-size: 11px;
+    font-weight: 600;
+    cursor: pointer;
+  }
+
+  .follow-up-btn:hover { opacity: 0.9; }
+  .follow-up-btn:disabled { opacity: 0.4; cursor: not-allowed; }
 </style>

v2/src/lib/components/Agent/AgentTree.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-  import { buildAgentTree, type AgentTreeNode } from '../../utils/agent-tree';
+  import { buildAgentTree, subtreeCost, type AgentTreeNode } from '../../utils/agent-tree';
   import type { AgentSession } from '../../stores/agents.svelte';
 
   interface Props {
@@ -19,7 +19,7 @@
 
   // Layout constants
   const NODE_W = 100;
-  const NODE_H = 32;
+  const NODE_H = 40;
   const H_GAP = 24;
   const V_GAP = 12;
 
@@ -124,19 +124,30 @@
         <!-- Status dot -->
         <circle
           cx={layout.x + 10}
-          cy={layout.y + NODE_H / 2}
+          cy={layout.y + NODE_H / 2 - 4}
           r="3"
           fill={statusColor(layout.node.status)}
         />
         <!-- Label -->
         <text
           x={layout.x + 18}
-          y={layout.y + NODE_H / 2 + 1}
+          y={layout.y + NODE_H / 2 - 4}
           fill="var(--text-primary)"
           font-size="10"
           font-family="var(--font-mono)"
           dominant-baseline="middle"
         >{truncateLabel(layout.node.label, 10)}</text>
+        <!-- Subtree cost -->
+        {#if subtreeCost(layout.node) > 0}
+          <text
+            x={layout.x + 18}
+            y={layout.y + NODE_H / 2 + 9}
+            fill="var(--ctp-yellow)"
+            font-size="8"
+            font-family="var(--font-mono)"
+            dominant-baseline="middle"
+          >${subtreeCost(layout.node).toFixed(4)}</text>
+        {/if}
       </g>
 
       <!-- Recurse children -->

v2/src/lib/components/Layout/TilingGrid.svelte

@@ -8,6 +8,7 @@
     getPanes,
     getGridTemplate,
     getPaneGridArea,
+    getActivePreset,
     focusPane,
     removePane,
   } from '../../stores/layout.svelte';
@@ -18,16 +19,128 @@
   let panes = $derived(getPanes());
   let detached = isDetachedMode();
 
+  // Custom column/row sizes (overrides preset when user drags)
+  let customColumns = $state<string | null>(null);
+  let customRows = $state<string | null>(null);
+  let gridEl: HTMLDivElement | undefined = $state();
+
+  // Reset custom sizes when preset changes
+  let prevPreset = '';
+  $effect(() => {
+    const p = getActivePreset();
+    if (prevPreset && p !== prevPreset) {
+      customColumns = null;
+      customRows = null;
+    }
+    prevPreset = p;
+  });
+
+  let columns = $derived(customColumns ?? gridTemplate.columns);
+  let rows = $derived(customRows ?? gridTemplate.rows);
+
+  // Determine splitter positions based on preset
+  let colCount = $derived(gridTemplate.columns.split(' ').length);
+  let rowCount = $derived(gridTemplate.rows.split(' ').length);
+
   function handleDetach(pane: typeof panes[0]) {
     detachPane(pane);
     removePane(pane.id);
   }
+
+  // Drag resize logic
+  let dragging = $state(false);
+
+  function getColSplitterX(ci: number): number {
+    if (!gridEl) return 0;
+    const rect = gridEl.getBoundingClientRect();
+    const cols = columns.split(' ').map(s => parseFloat(s));
+    const total = cols.reduce((a, b) => a + b, 0);
+    let frac = 0;
+    for (let i = 0; i <= ci; i++) frac += cols[i] / total;
+    return rect.left + frac * rect.width;
+  }
+
+  function getRowSplitterY(ri: number): number {
+    if (!gridEl) return 0;
+    const rect = gridEl.getBoundingClientRect();
+    const rws = rows.split(' ').map(s => parseFloat(s));
+    const total = rws.reduce((a, b) => a + b, 0);
+    let frac = 0;
+    for (let i = 0; i <= ri; i++) frac += rws[i] / total;
+    return rect.top + frac * rect.height;
+  }
+
+  function startColDrag(colIndex: number, e: MouseEvent) {
+    e.preventDefault();
+    dragging = true;
+    if (!gridEl) return;
+
+    const rect = gridEl.getBoundingClientRect();
+    const totalWidth = rect.width;
+
+    function onMove(ev: MouseEvent) {
+      const relX = ev.clientX - rect.left;
+      const ratio = Math.max(0.1, Math.min(0.9, relX / totalWidth));
+      if (colCount === 2) {
+        customColumns = `${ratio}fr ${1 - ratio}fr`;
+      } else if (colCount === 3) {
+        if (colIndex === 0) {
+          const remaining = 1 - ratio;
+          customColumns = `${ratio}fr ${remaining / 2}fr ${remaining / 2}fr`;
+        } else {
+          // Get current first column ratio or default
+          const parts = (customColumns ?? gridTemplate.columns).split(' ');
+          const first = parseFloat(parts[0]) / parts.reduce((s, p) => s + parseFloat(p), 0);
+          const relRatio = (relX / totalWidth - first) / (1 - first);
+          const adj = Math.max(0.1, Math.min(0.9, relRatio));
+          customColumns = `${first}fr ${(1 - first) * adj}fr ${(1 - first) * (1 - adj)}fr`;
+        }
+      }
+    }
+
+    function onUp() {
+      dragging = false;
+      window.removeEventListener('mousemove', onMove);
+      window.removeEventListener('mouseup', onUp);
+    }
+
+    window.addEventListener('mousemove', onMove);
+    window.addEventListener('mouseup', onUp);
+  }
+
+  function startRowDrag(_rowIndex: number, e: MouseEvent) {
+    e.preventDefault();
+    dragging = true;
+    if (!gridEl) return;
+
+    const rect = gridEl.getBoundingClientRect();
+    const totalHeight = rect.height;
+
+    function onMove(ev: MouseEvent) {
+      const relY = ev.clientY - rect.top;
+      const ratio = Math.max(0.1, Math.min(0.9, relY / totalHeight));
+      if (rowCount === 2) {
+        customRows = `${ratio}fr ${1 - ratio}fr`;
+      }
+    }
+
+    function onUp() {
+      dragging = false;
+      window.removeEventListener('mousemove', onMove);
+      window.removeEventListener('mouseup', onUp);
+    }
+
+    window.addEventListener('mousemove', onMove);
+    window.addEventListener('mouseup', onUp);
+  }
 </script>
 
 <div
   class="tiling-grid"
-  style:grid-template-columns={gridTemplate.columns}
+  class:dragging
-  style:grid-template-rows={gridTemplate.rows}
+  bind:this={gridEl}
+  style:grid-template-columns={columns}
+  style:grid-template-rows={rows}
 >
   {#if panes.length === 0}
     <div class="empty-state">
@@ -91,12 +204,41 @@
   {/if}
 </div>
 
+<!-- Splitter overlays (outside grid to avoid layout interference) -->
+{#if panes.length > 1 && gridEl}
+  {#each { length: colCount - 1 } as _, ci}
+    <!-- svelte-ignore a11y_no_static_element_interactions -->
+    <div
+      class="splitter splitter-col"
+      style:left="{gridEl ? getColSplitterX(ci) : 0}px"
+      style:top="{gridEl?.getBoundingClientRect().top ?? 0}px"
+      style:height="{gridEl?.getBoundingClientRect().height ?? 0}px"
+      onmousedown={(e) => startColDrag(ci, e)}
+    ></div>
+  {/each}
+  {#each { length: rowCount - 1 } as _, ri}
+    <!-- svelte-ignore a11y_no_static_element_interactions -->
+    <div
+      class="splitter splitter-row"
+      style:top="{gridEl ? getRowSplitterY(ri) : 0}px"
+      style:left="{gridEl?.getBoundingClientRect().left ?? 0}px"
+      style:width="{gridEl?.getBoundingClientRect().width ?? 0}px"
+      onmousedown={(e) => startRowDrag(ri, e)}
+    ></div>
+  {/each}
+{/if}
+
 <style>
   .tiling-grid {
     display: grid;
     gap: var(--pane-gap);
     height: 100%;
     padding: var(--pane-gap);
+    position: relative;
+  }
+
+  .tiling-grid.dragging {
+    user-select: none;
   }
 
   .pane-slot {
@@ -150,4 +292,27 @@
     color: var(--text-muted);
     font-size: 12px;
   }
+
+  :global(.splitter) {
+    position: fixed;
+    z-index: 100;
+    transition: background 0.15s;
+  }
+
+  :global(.splitter:hover), :global(.splitter:active) {
+    background: var(--accent);
+    opacity: 0.4;
+  }
+
+  :global(.splitter-col) {
+    width: 6px;
+    margin-left: -3px;
+    cursor: col-resize;
+  }
+
+  :global(.splitter-row) {
+    height: 6px;
+    margin-top: -3px;
+    cursor: row-resize;
+  }
 </style>

v2/src/lib/components/Terminal/TerminalPane.svelte

@@ -4,7 +4,7 @@
   import { CanvasAddon } from '@xterm/addon-canvas';
   import { FitAddon } from '@xterm/addon-fit';
   import { spawnPty, writePty, resizePty, killPty, onPtyData, onPtyExit } from '../../adapters/pty-bridge';
-  import { getXtermTheme } from '../../stores/theme.svelte';
+  import { getXtermTheme, onThemeChange } from '../../stores/theme.svelte';
   import type { UnlistenFn } from '@tauri-apps/api/event';
   import '@xterm/xterm/css/xterm.css';
 
@@ -24,6 +24,7 @@
   let unlistenData: UnlistenFn | null = null;
   let unlistenExit: UnlistenFn | null = null;
   let resizeObserver: ResizeObserver | null = null;
+  let unsubTheme: (() => void) | null = null;
 
   onMount(async () => {
     term = new Terminal({
@@ -59,6 +60,24 @@
         onExit?.();
       });
 
+      // Copy/paste via Ctrl+Shift+C/V
+      term.attachCustomKeyEventHandler((e: KeyboardEvent) => {
+        if (e.ctrlKey && e.shiftKey && e.type === 'keydown') {
+          if (e.key === 'C') {
+            const selection = term.getSelection();
+            if (selection) navigator.clipboard.writeText(selection);
+            return false;
+          }
+          if (e.key === 'V') {
+            navigator.clipboard.readText().then(text => {
+              if (text && ptyId) writePty(ptyId, text);
+            });
+            return false;
+          }
+        }
+        return true;
+      });
+
       // Forward keyboard input to PTY
       term.onData((data) => {
         if (ptyId) writePty(ptyId, data);
@@ -80,10 +99,16 @@
       }, 100);
     });
     resizeObserver.observe(terminalEl);
+
+    // Hot-swap theme when flavor changes
+    unsubTheme = onThemeChange(() => {
+      term.options.theme = getXtermTheme();
+    });
   });
 
   onDestroy(async () => {
     resizeObserver?.disconnect();
+    unsubTheme?.();
     unlistenData?.();
     unlistenExit?.();
     if (ptyId) {

v2/src/lib/stores/theme.svelte.ts

@@ -10,6 +10,17 @@ import {
 
 let currentFlavor = $state<CatppuccinFlavor>('mocha');
 
+/** Registered theme-change listeners */
+const themeChangeCallbacks = new Set<() => void>();
+
+/** Register a callback invoked after every flavor change. Returns an unsubscribe function. */
+export function onThemeChange(callback: () => void): () => void {
+  themeChangeCallbacks.add(callback);
+  return () => {
+    themeChangeCallbacks.delete(callback);
+  };
+}
+
 export function getCurrentFlavor(): CatppuccinFlavor {
   return currentFlavor;
 }
@@ -22,6 +33,15 @@ export function getXtermTheme(): XtermTheme {
 export async function setFlavor(flavor: CatppuccinFlavor): Promise<void> {
   currentFlavor = flavor;
   applyCssVariables(flavor);
+  // Notify all listeners (e.g. open xterm.js terminals)
+  for (const cb of themeChangeCallbacks) {
+    try {
+      cb();
+    } catch (e) {
+      console.error('Theme change callback error:', e);
+    }
+  }
+
   try {
     await setSetting('theme', flavor);
   } catch (e) {