diff --git a/wasm/dist-repl/repl.js b/wasm/dist-repl/repl.js
index 51141e7..ab00233 100644
--- a/wasm/dist-repl/repl.js
+++ b/wasm/dist-repl/repl.js
@@ -146,13 +146,15 @@ function relock() {
 }
 
 // ─── Tabs ───────────────────────────────────────────────────────────
-function newTab(name) {
+async function newTab(name) {
     const id = state.nextTabId++;
     name = name || `session ${id}`;
     state.tabs.push({ id, name, tier: "c", transcript: [], inputDraft: "" });
-    state.activeTabId = id;
-    renderAll();
-    saveSoon();
+    // Route through setActiveTab so the outgoing tab's auto-pause
+    // fires and the toolbar buttons sync to the freshly-created
+    // (idle) tab. Without this, opening a new tab during an eval
+    // leaves the send button disabled and the eval orphaned.
+    await setActiveTab(id);
 }
 
 function closeTab(id) {
@@ -206,8 +208,19 @@ async function setActiveTab(id) {
         }
         state.activeTabId = id;
         renderAll();
-        saveSoon();
+        // Sync the global toolbar button states to the incoming tab —
+        // send/cancel/pause are not tab-scoped DOM elements, so a
+        // switch-away during one tab's eval would otherwise leave the
+        // newly-active (idle) tab with send disabled. The active tab
+        // is idle iff nothing in state.pending matches its id.
         const incoming = activeTab();
+        if (incoming) {
+            const evalRunning = isEvalInFlight(incoming);
+            sendBtn.disabled = evalRunning;
+            cancelBtn.disabled = !evalRunning;
+            pauseBtn.disabled = !evalRunning || !pauseFlagView;
+        }
+        saveSoon();
         if (incoming && incoming.autoPause) {
             await autoResumeTab(incoming);
         }
diff --git a/wasm/repl/repl.js b/wasm/repl/repl.js
index 51141e7..ab00233 100644
--- a/wasm/repl/repl.js
+++ b/wasm/repl/repl.js
@@ -146,13 +146,15 @@ function relock() {
 }
 
 // ─── Tabs ───────────────────────────────────────────────────────────
-function newTab(name) {
+async function newTab(name) {
     const id = state.nextTabId++;
     name = name || `session ${id}`;
     state.tabs.push({ id, name, tier: "c", transcript: [], inputDraft: "" });
-    state.activeTabId = id;
-    renderAll();
-    saveSoon();
+    // Route through setActiveTab so the outgoing tab's auto-pause
+    // fires and the toolbar buttons sync to the freshly-created
+    // (idle) tab. Without this, opening a new tab during an eval
+    // leaves the send button disabled and the eval orphaned.
+    await setActiveTab(id);
 }
 
 function closeTab(id) {
@@ -206,8 +208,19 @@ async function setActiveTab(id) {
         }
         state.activeTabId = id;
         renderAll();
-        saveSoon();
+        // Sync the global toolbar button states to the incoming tab —
+        // send/cancel/pause are not tab-scoped DOM elements, so a
+        // switch-away during one tab's eval would otherwise leave the
+        // newly-active (idle) tab with send disabled. The active tab
+        // is idle iff nothing in state.pending matches its id.
         const incoming = activeTab();
+        if (incoming) {
+            const evalRunning = isEvalInFlight(incoming);
+            sendBtn.disabled = evalRunning;
+            cancelBtn.disabled = !evalRunning;
+            pauseBtn.disabled = !evalRunning || !pauseFlagView;
+        }
+        saveSoon();
         if (incoming && incoming.autoPause) {
             await autoResumeTab(incoming);
         }
diff --git a/www/repl/repl.js b/www/repl/repl.js
index 51141e7..ab00233 100644
--- a/www/repl/repl.js
+++ b/www/repl/repl.js
@@ -146,13 +146,15 @@ function relock() {
 }
 
 // ─── Tabs ───────────────────────────────────────────────────────────
-function newTab(name) {
+async function newTab(name) {
     const id = state.nextTabId++;
     name = name || `session ${id}`;
     state.tabs.push({ id, name, tier: "c", transcript: [], inputDraft: "" });
-    state.activeTabId = id;
-    renderAll();
-    saveSoon();
+    // Route through setActiveTab so the outgoing tab's auto-pause
+    // fires and the toolbar buttons sync to the freshly-created
+    // (idle) tab. Without this, opening a new tab during an eval
+    // leaves the send button disabled and the eval orphaned.
+    await setActiveTab(id);
 }
 
 function closeTab(id) {
@@ -206,8 +208,19 @@ async function setActiveTab(id) {
         }
         state.activeTabId = id;
         renderAll();
-        saveSoon();
+        // Sync the global toolbar button states to the incoming tab —
+        // send/cancel/pause are not tab-scoped DOM elements, so a
+        // switch-away during one tab's eval would otherwise leave the
+        // newly-active (idle) tab with send disabled. The active tab
+        // is idle iff nothing in state.pending matches its id.
         const incoming = activeTab();
+        if (incoming) {
+            const evalRunning = isEvalInFlight(incoming);
+            sendBtn.disabled = evalRunning;
+            cancelBtn.disabled = !evalRunning;
+            pauseBtn.disabled = !evalRunning || !pauseFlagView;
+        }
+        saveSoon();
         if (incoming && incoming.autoPause) {
             await autoResumeTab(incoming);
         }