diff --git a/wasm/dist-repl/repl.css b/wasm/dist-repl/repl.css
index 7ea2382..66ca2d4 100644
--- a/wasm/dist-repl/repl.css
+++ b/wasm/dist-repl/repl.css
@@ -310,6 +310,12 @@ body.repl {
   color: var(--green);
   font-weight: 600;
   font-size: 0.95em;
+  /* Top-align so multi-line input keeps λ> on the first line instead
+   * of drifting to vertical-center as the textarea grows. The padding
+   * matches the textarea's padding-top so the sigil sits on the same
+   * baseline as the first character. */
+  align-self: start;
+  padding-top: 0.4rem;
 }
 .prompt-bar textarea {
   resize: none;
diff --git a/wasm/dist-repl/repl.js b/wasm/dist-repl/repl.js
index da5f681..623a2ce 100644
--- a/wasm/dist-repl/repl.js
+++ b/wasm/dist-repl/repl.js
@@ -534,6 +534,7 @@ function historyPrev() {
     }
     inputEl.value = entries[history.idx];
     inputEl.setSelectionRange(inputEl.value.length, inputEl.value.length);
+    autosizeInput();
 }
 
 function historyNext() {
@@ -548,6 +549,7 @@ function historyNext() {
         inputEl.value = entries[history.idx];
     }
     inputEl.setSelectionRange(inputEl.value.length, inputEl.value.length);
+    autosizeInput();
 }
 
 function resetHistory() {
@@ -555,6 +557,16 @@ function resetHistory() {
     history.draft = "";
 }
 
+// Auto-grow the textarea to fit its content (up to the max-height the
+// CSS pins it at, after which the textarea scrolls internally). Paste
+// a 40-line program and the prompt-bar expands instead of leaving you
+// editing the program through a one-line keyhole. Fires on every input
+// event and every programmatic value set (sendInput, history, etc.).
+function autosizeInput() {
+    inputEl.style.height = "auto";
+    inputEl.style.height = inputEl.scrollHeight + "px";
+}
+
 // ─── Input handling ─────────────────────────────────────────────────
 async function sendInput() {
     const src = inputEl.value.trim();
@@ -577,6 +589,7 @@ async function sendInput() {
     };
     tab.transcript.push(entry);
     inputEl.value = "";
+    autosizeInput();
     resetHistory();
     sendBtn.disabled = true;
     cancelBtn.disabled = false;
@@ -737,6 +750,7 @@ inputEl.addEventListener("keydown", (e) => {
     }
 });
 inputEl.addEventListener("input", () => {
+    autosizeInput();
     // Any keystroke that isn't an arrow drops history navigation —
     // edits are now the user's own draft, not the historical entry.
     if (history.idx !== null && document.activeElement === inputEl) {
diff --git a/wasm/repl/repl.css b/wasm/repl/repl.css
index 7ea2382..66ca2d4 100644
--- a/wasm/repl/repl.css
+++ b/wasm/repl/repl.css
@@ -310,6 +310,12 @@ body.repl {
   color: var(--green);
   font-weight: 600;
   font-size: 0.95em;
+  /* Top-align so multi-line input keeps λ> on the first line instead
+   * of drifting to vertical-center as the textarea grows. The padding
+   * matches the textarea's padding-top so the sigil sits on the same
+   * baseline as the first character. */
+  align-self: start;
+  padding-top: 0.4rem;
 }
 .prompt-bar textarea {
   resize: none;
diff --git a/wasm/repl/repl.js b/wasm/repl/repl.js
index da5f681..623a2ce 100644
--- a/wasm/repl/repl.js
+++ b/wasm/repl/repl.js
@@ -534,6 +534,7 @@ function historyPrev() {
     }
     inputEl.value = entries[history.idx];
     inputEl.setSelectionRange(inputEl.value.length, inputEl.value.length);
+    autosizeInput();
 }
 
 function historyNext() {
@@ -548,6 +549,7 @@ function historyNext() {
         inputEl.value = entries[history.idx];
     }
     inputEl.setSelectionRange(inputEl.value.length, inputEl.value.length);
+    autosizeInput();
 }
 
 function resetHistory() {
@@ -555,6 +557,16 @@ function resetHistory() {
     history.draft = "";
 }
 
+// Auto-grow the textarea to fit its content (up to the max-height the
+// CSS pins it at, after which the textarea scrolls internally). Paste
+// a 40-line program and the prompt-bar expands instead of leaving you
+// editing the program through a one-line keyhole. Fires on every input
+// event and every programmatic value set (sendInput, history, etc.).
+function autosizeInput() {
+    inputEl.style.height = "auto";
+    inputEl.style.height = inputEl.scrollHeight + "px";
+}
+
 // ─── Input handling ─────────────────────────────────────────────────
 async function sendInput() {
     const src = inputEl.value.trim();
@@ -577,6 +589,7 @@ async function sendInput() {
     };
     tab.transcript.push(entry);
     inputEl.value = "";
+    autosizeInput();
     resetHistory();
     sendBtn.disabled = true;
     cancelBtn.disabled = false;
@@ -737,6 +750,7 @@ inputEl.addEventListener("keydown", (e) => {
     }
 });
 inputEl.addEventListener("input", () => {
+    autosizeInput();
     // Any keystroke that isn't an arrow drops history navigation —
     // edits are now the user's own draft, not the historical entry.
     if (history.idx !== null && document.activeElement === inputEl) {
diff --git a/www/repl/repl.css b/www/repl/repl.css
index 7ea2382..66ca2d4 100644
--- a/www/repl/repl.css
+++ b/www/repl/repl.css
@@ -310,6 +310,12 @@ body.repl {
   color: var(--green);
   font-weight: 600;
   font-size: 0.95em;
+  /* Top-align so multi-line input keeps λ> on the first line instead
+   * of drifting to vertical-center as the textarea grows. The padding
+   * matches the textarea's padding-top so the sigil sits on the same
+   * baseline as the first character. */
+  align-self: start;
+  padding-top: 0.4rem;
 }
 .prompt-bar textarea {
   resize: none;
diff --git a/www/repl/repl.js b/www/repl/repl.js
index da5f681..623a2ce 100644
--- a/www/repl/repl.js
+++ b/www/repl/repl.js
@@ -534,6 +534,7 @@ function historyPrev() {
     }
     inputEl.value = entries[history.idx];
     inputEl.setSelectionRange(inputEl.value.length, inputEl.value.length);
+    autosizeInput();
 }
 
 function historyNext() {
@@ -548,6 +549,7 @@ function historyNext() {
         inputEl.value = entries[history.idx];
     }
     inputEl.setSelectionRange(inputEl.value.length, inputEl.value.length);
+    autosizeInput();
 }
 
 function resetHistory() {
@@ -555,6 +557,16 @@ function resetHistory() {
     history.draft = "";
 }
 
+// Auto-grow the textarea to fit its content (up to the max-height the
+// CSS pins it at, after which the textarea scrolls internally). Paste
+// a 40-line program and the prompt-bar expands instead of leaving you
+// editing the program through a one-line keyhole. Fires on every input
+// event and every programmatic value set (sendInput, history, etc.).
+function autosizeInput() {
+    inputEl.style.height = "auto";
+    inputEl.style.height = inputEl.scrollHeight + "px";
+}
+
 // ─── Input handling ─────────────────────────────────────────────────
 async function sendInput() {
     const src = inputEl.value.trim();
@@ -577,6 +589,7 @@ async function sendInput() {
     };
     tab.transcript.push(entry);
     inputEl.value = "";
+    autosizeInput();
     resetHistory();
     sendBtn.disabled = true;
     cancelBtn.disabled = false;
@@ -737,6 +750,7 @@ inputEl.addEventListener("keydown", (e) => {
     }
 });
 inputEl.addEventListener("input", () => {
+    autosizeInput();
     // Any keystroke that isn't an arrow drops history navigation —
     // edits are now the user's own draft, not the historical entry.
     if (history.idx !== null && document.activeElement === inputEl) {