From ec02f4bc877604c726f07dc790f182df2a1df61a Mon Sep 17 00:00:00 2001
From: Jeremy lewi <jeremy@lewi.us>
Date: Fri, 13 Feb 2026 06:51:47 -0800
Subject: [PATCH 1/3] Hide empty observable output panel until content exists

Signed-off-by: Jeremy lewi <jeremy@lewi.us>
---
 app/src/components/Actions/WebContainer.tsx | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/app/src/components/Actions/WebContainer.tsx b/app/src/components/Actions/WebContainer.tsx
index 5891e4a..b951459 100644
--- a/app/src/components/Actions/WebContainer.tsx
+++ b/app/src/components/Actions/WebContainer.tsx
@@ -46,6 +46,7 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
   const [stdout, setStdout] = useState<string>("");
   const [stderr, setStderr] = useState<string>("");
   const [lastRunId, setLastRunId] = useState<number>(0);
+  const [hasRenderableOutput, setHasRenderableOutput] = useState<boolean>(false);
   const activeRunIdRef = useRef<number | null>(null);
 
   const runCode = useCallback(async () => {
@@ -60,6 +61,7 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
     setLastRunId(runId);
     setStdout("");
     setStderr("");
+    setHasRenderableOutput(false);
     container.innerHTML = "";
     onPid(null);
 
@@ -140,6 +142,11 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
 
     const stdoutText = logBuffer.join("\n");
     const stderrText = errorBuffer.join("\n");
+    const renderedText = container.textContent?.trim() ?? "";
+    const renderedElements = container.querySelectorAll("*").length;
+    const hasRenderedContent = renderedElements > 0 || renderedText.length > 0;
+    const hasTerminalOutput =
+      stdoutText.trim().length > 0 || stderrText.trim().length > 0;
 
     const updatedCell = create(parser_pb.CellSchema, cell);
     updatedCell.outputs = createCellOutputs(
@@ -161,6 +168,7 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
 
     setStdout(stdoutText);
     setStderr(stderrText);
+    setHasRenderableOutput(hasRenderedContent || hasTerminalOutput);
     onExitCode(exitCode);
   }, [cell, notebookData, onExitCode, onPid]);
 
@@ -185,7 +193,7 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
     return stdout.trim().length > 0 || stderr.trim().length > 0;
   }, [stderr, stdout]);
 
-  return (
+  return hasRenderableOutput ? (
     <div className="mt-2 rounded-md border border-nb-cell-border bg-white p-2 text-xs text-nb-text">
       <div className="mb-1 font-mono text-[10px] uppercase tracking-wide text-nb-text-faint">
         Observable Output{" "}
@@ -198,7 +206,7 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
         className="mb-2 min-h-[240px] w-full overflow-auto rounded border border-dashed border-nb-cell-border bg-nb-surface-2"
       />
 
-      {hasStdIO ? (
+      {hasStdIO && (
         <div className="space-y-2 font-mono">
           {stdout.trim().length > 0 && (
             <div>
@@ -221,12 +229,10 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
             </div>
           )}
         </div>
-      ) : (
-        <div className="font-mono text-[11px] italic text-nb-text-faint">
-          Use d3 (or aisre.render) to draw into the panel above.
-        </div>
       )}
     </div>
+  ) : (
+    <div ref={containerRef} className="hidden" aria-hidden="true" />
   );
 };
 

From 1dc8da08fd879405b281ec1208151da00e694270 Mon Sep 17 00:00:00 2001
From: Jeremy Lewi <jeremy+github@lewi.us>
Date: Sat, 14 Feb 2026 17:50:28 -0800
Subject: [PATCH 2/3] Fix output panel visibility across cell types

Signed-off-by: Codex <codex@openai.com>
---
 app/src/components/Actions/Actions.tsx        |  3 +-
 .../components/Actions/WebContainer.test.tsx  | 57 +++++++++++++++++++
 app/src/components/Actions/WebContainer.tsx   | 22 +++----
 .../Actions/outputVisibility.test.ts          | 43 ++++++++++++++
 .../components/Actions/outputVisibility.ts    | 30 ++++++++++
 5 files changed, 144 insertions(+), 11 deletions(-)
 create mode 100644 app/src/components/Actions/WebContainer.test.tsx
 create mode 100644 app/src/components/Actions/outputVisibility.test.ts
 create mode 100644 app/src/components/Actions/outputVisibility.ts

diff --git a/app/src/components/Actions/Actions.tsx b/app/src/components/Actions/Actions.tsx
index 43324be..762f081 100644
--- a/app/src/components/Actions/Actions.tsx
+++ b/app/src/components/Actions/Actions.tsx
@@ -37,6 +37,7 @@ import { useCurrentDoc } from "../../contexts/CurrentDocContext";
 import { useRunners } from "../../contexts/RunnersContext";
 import { DEFAULT_RUNNER_PLACEHOLDER } from "../../lib/runtime/runnersManager";
 import React from "react";
+import { hasVisibleCellOutput } from "./outputVisibility";
 
 type TabPanelProps = React.HTMLAttributes<HTMLDivElement> & {
   "data-state"?: "active" | "inactive";
@@ -472,7 +473,7 @@ export function Action({ cellData, isFirst }: { cellData: CellData; isFirst: boo
     //   return rendered;
     // }
 
-    if (!runID && (cell?.outputs?.length ?? 0) === 0) {
+    if (!runID && !hasVisibleCellOutput(cell?.outputs)) {
       return null;
     }
 
diff --git a/app/src/components/Actions/WebContainer.test.tsx b/app/src/components/Actions/WebContainer.test.tsx
new file mode 100644
index 0000000..3e59e8e
--- /dev/null
+++ b/app/src/components/Actions/WebContainer.test.tsx
@@ -0,0 +1,57 @@
+// @vitest-environment jsdom
+import { act, render, screen } from "@testing-library/react";
+import { create } from "@bufbuild/protobuf";
+import { describe, expect, it, vi } from "vitest";
+
+import { parser_pb } from "../../runme/client";
+import WebContainer from "./WebContainer";
+
+const updateCell = vi.fn();
+
+vi.mock("../../contexts/NotebookContext", () => ({
+  useNotebookContext: () => ({
+    getNotebookData: () => ({ updateCell }),
+  }),
+}));
+
+vi.mock("../../contexts/CurrentDocContext", () => ({
+  useCurrentDoc: () => ({
+    getCurrentDoc: () => "notebook://test",
+  }),
+}));
+
+vi.mock("../../lib/useAisreClient", () => ({
+  useBaseUrl: () => "http://localhost:3000",
+}));
+
+describe("WebContainer", () => {
+  it("keeps the render container mounted while toggling visibility", async () => {
+    const cell = create(parser_pb.CellSchema, {
+      refId: "cell-wc",
+      value: "await aisre.render((selection) => { selection.append('div').text('chart-ready'); });",
+      metadata: {},
+      outputs: [],
+    });
+
+    render(<WebContainer cell={cell} onExitCode={vi.fn()} onPid={vi.fn()} />);
+
+    const shell = document.getElementById("webcontainer-output-shell-cell-wc");
+    const before = document.getElementById("webcontainer-output-content-cell-wc");
+    expect(shell).toBeTruthy();
+    expect(shell?.className).toContain("hidden");
+    expect(before).toBeTruthy();
+
+    await act(async () => {
+      window.dispatchEvent(
+        new CustomEvent("runCodeCell", { detail: { cellId: "cell-wc" } }),
+      );
+      await Promise.resolve();
+    });
+
+    const after = document.getElementById("webcontainer-output-content-cell-wc");
+    expect(after).toBe(before);
+    expect(shell?.className).not.toContain("hidden");
+    expect(screen.getByText("chart-ready")).toBeTruthy();
+    expect(updateCell).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/app/src/components/Actions/WebContainer.tsx b/app/src/components/Actions/WebContainer.tsx
index b951459..cc3311f 100644
--- a/app/src/components/Actions/WebContainer.tsx
+++ b/app/src/components/Actions/WebContainer.tsx
@@ -28,7 +28,7 @@ const toPrintable = (value: unknown) => {
   }
   try {
     return JSON.stringify(value);
-  } catch (err) {
+  } catch {
     return String(value);
   }
 };
@@ -81,19 +81,19 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
 
     const mockedConsole = {
       log: (...args: unknown[]) => {
-        originalConsole.log(...(args as any[]));
+        originalConsole.log(...args);
         append(logBuffer, args);
       },
       info: (...args: unknown[]) => {
-        originalConsole.info(...(args as any[]));
+        originalConsole.info(...args);
         append(logBuffer, args);
       },
       warn: (...args: unknown[]) => {
-        originalConsole.warn(...(args as any[]));
+        originalConsole.warn(...args);
         append(errorBuffer, args);
       },
       error: (...args: unknown[]) => {
-        originalConsole.error(...(args as any[]));
+        originalConsole.error(...args);
         append(errorBuffer, args);
       },
     };
@@ -122,7 +122,6 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
     let exitCode = 0;
 
     try {
-      // eslint-disable-next-line @typescript-eslint/no-implied-eval
       const runner = new Function(
         // Inject the libraries/objects we want to expose to the cell code
         "d3",
@@ -193,8 +192,12 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
     return stdout.trim().length > 0 || stderr.trim().length > 0;
   }, [stderr, stdout]);
 
-  return hasRenderableOutput ? (
-    <div className="mt-2 rounded-md border border-nb-cell-border bg-white p-2 text-xs text-nb-text">
+  return (
+    <div
+      id={`webcontainer-output-shell-${cell.refId}`}
+      className={hasRenderableOutput ? "mt-2 rounded-md border border-nb-cell-border bg-white p-2 text-xs text-nb-text" : "hidden"}
+      aria-hidden={!hasRenderableOutput}
+    >
       <div className="mb-1 font-mono text-[10px] uppercase tracking-wide text-nb-text-faint">
         Observable Output{" "}
         {lastRunId
@@ -202,6 +205,7 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
           : ""}
       </div>
       <div
+        id={`webcontainer-output-content-${cell.refId}`}
         ref={containerRef}
         className="mb-2 min-h-[240px] w-full overflow-auto rounded border border-dashed border-nb-cell-border bg-nb-surface-2"
       />
@@ -231,8 +235,6 @@ const WebContainer = ({ cell, onExitCode, onPid }: ObservableOutputProps) => {
         </div>
       )}
     </div>
-  ) : (
-    <div ref={containerRef} className="hidden" aria-hidden="true" />
   );
 };
 
diff --git a/app/src/components/Actions/outputVisibility.test.ts b/app/src/components/Actions/outputVisibility.test.ts
new file mode 100644
index 0000000..ab17bb8
--- /dev/null
+++ b/app/src/components/Actions/outputVisibility.test.ts
@@ -0,0 +1,43 @@
+import { create } from "@bufbuild/protobuf";
+import { describe, expect, it } from "vitest";
+
+import { MimeType, parser_pb } from "../../runme/client";
+import { hasVisibleCellOutput } from "./outputVisibility";
+
+describe("hasVisibleCellOutput", () => {
+  it("returns false for empty output arrays", () => {
+    expect(hasVisibleCellOutput([])).toBe(false);
+  });
+
+  it("returns false for empty terminal placeholder items", () => {
+    const outputs = [
+      create(parser_pb.CellOutputSchema, {
+        items: [
+          create(parser_pb.CellOutputItemSchema, {
+            mime: MimeType.StatefulRunmeTerminal,
+            type: "Buffer",
+            data: new Uint8Array(),
+          }),
+        ],
+      }),
+    ];
+
+    expect(hasVisibleCellOutput(outputs)).toBe(false);
+  });
+
+  it("returns true when stdout has bytes", () => {
+    const outputs = [
+      create(parser_pb.CellOutputSchema, {
+        items: [
+          create(parser_pb.CellOutputItemSchema, {
+            mime: MimeType.VSCodeNotebookStdOut,
+            type: "Buffer",
+            data: new TextEncoder().encode("hello"),
+          }),
+        ],
+      }),
+    ];
+
+    expect(hasVisibleCellOutput(outputs)).toBe(true);
+  });
+});
diff --git a/app/src/components/Actions/outputVisibility.ts b/app/src/components/Actions/outputVisibility.ts
new file mode 100644
index 0000000..d15a392
--- /dev/null
+++ b/app/src/components/Actions/outputVisibility.ts
@@ -0,0 +1,30 @@
+import { MimeType, parser_pb } from "../../runme/client";
+
+const OUTPUT_VISIBILITY_IGNORE_MIMES = new Set<string>([
+  MimeType.StatefulRunmeTerminal,
+]);
+
+/**
+ * Determine whether a cell has user-visible output bytes.
+ *
+ * Cells may contain a placeholder terminal output item that allocates renderer
+ * state with an empty buffer. That placeholder should not force the output
+ * panel to render for idle cells.
+ */
+export function hasVisibleCellOutput(
+  outputs: parser_pb.CellOutput[] | undefined,
+): boolean {
+  if (!outputs || outputs.length === 0) {
+    return false;
+  }
+
+  return outputs.some((output) =>
+    (output.items ?? []).some((item) => {
+      if (!item || OUTPUT_VISIBILITY_IGNORE_MIMES.has(item.mime || "")) {
+        return false;
+      }
+      const data = item.data as Uint8Array | undefined;
+      return Boolean(data && data.length > 0);
+    }),
+  );
+}

From 8e24cbd9a1271305e37d621f01b7c89f6d8ae544 Mon Sep 17 00:00:00 2001
From: Jeremy Lewi <jeremy+github@lewi.us>
Date: Sat, 14 Feb 2026 17:50:32 -0800
Subject: [PATCH 3/3] Add pre-run no-output CUJ verification and docs

Signed-off-by: Codex <codex@openai.com>
---
 app/test/browser/test-scenario-hello-world.ts | 30 +++++++++++++++++--
 docs-dev/cujs/hello-world-local-notebook.md   |  6 ++--
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/app/test/browser/test-scenario-hello-world.ts b/app/test/browser/test-scenario-hello-world.ts
index 2e85074..eb8fc03 100644
--- a/app/test/browser/test-scenario-hello-world.ts
+++ b/app/test/browser/test-scenario-hello-world.ts
@@ -92,6 +92,8 @@ for (const file of [
   "scenario-hello-world-04-before-open.txt",
   "scenario-hello-world-04b-after-expand.txt",
   "scenario-hello-world-05-opened-notebook.txt",
+  "scenario-hello-world-05-before-run.png",
+  "scenario-hello-world-05-before-run-output-check.txt",
   "scenario-hello-world-06-after-run.txt",
   "scenario-hello-world-06-after-run.png",
 ]) {
@@ -131,7 +133,7 @@ const seedResult = run(
         refId: 'cell_hello_world',
         kind: 2,
         languageId: 'bash',
-        value: 'echo \\\"hello world\\\"',
+        value: 'echo hello world',
         metadata: { runner: 'local' },
         outputs: []
       }
@@ -211,7 +213,31 @@ if (notebookRef) {
 
 snapshot = run("agent-browser snapshot -i").stdout;
 writeArtifact("scenario-hello-world-05-opened-notebook.txt", snapshot);
-let runRef = firstRef(snapshot, /Run cell/i) ?? firstRef(snapshot, /\bRun\b/i);
+run(`agent-browser screenshot ${join(OUTPUT_DIR, "scenario-hello-world-05-before-run.png")}`);
+
+const beforeRunOutputCheck = run(
+  `agent-browser eval "(() => {
+    const outputItems = document.querySelectorAll('[data-testid="cell-output-item"]');
+    const consoles = document.querySelectorAll('[data-testid="cell-console"]');
+    const webContainerShells = document.querySelectorAll('[id^="webcontainer-output-shell-"]:not(.hidden)');
+    return JSON.stringify({
+      outputItemCount: outputItems.length,
+      consoleCount: consoles.length,
+      visibleWebContainerOutputCount: webContainerShells.length,
+    });
+  })()"`,
+).stdout;
+writeArtifact("scenario-hello-world-05-before-run-output-check.txt", beforeRunOutputCheck);
+
+if (beforeRunOutputCheck.includes('"outputItemCount":0') &&
+    beforeRunOutputCheck.includes('"consoleCount":0') &&
+    beforeRunOutputCheck.includes('"visibleWebContainerOutputCount":0')) {
+  pass("Cell shows no output panel before execution");
+} else {
+  fail(`Unexpected visible output before execution: ${beforeRunOutputCheck.trim()}`);
+}
+
+const runRef = firstRef(snapshot, /Run cell/i) ?? firstRef(snapshot, /\bRun\b/i);
 if (runRef) {
   run(`agent-browser click ${runRef}`);
   run("agent-browser wait 3500");
diff --git a/docs-dev/cujs/hello-world-local-notebook.md b/docs-dev/cujs/hello-world-local-notebook.md
index 2ad8f32..d5c4578 100644
--- a/docs-dev/cujs/hello-world-local-notebook.md
+++ b/docs-dev/cujs/hello-world-local-notebook.md
@@ -17,8 +17,9 @@ cell end-to-end.
 3. Create a new local notebook with one bash cell: `echo "hello world"`.
 4. Use AppConsole to add a local runner endpoint.
 5. Open the local notebook.
-6. Execute the bash cell.
-7. Verify execution output contains `hello world`.
+6. Verify the notebook shows no output for the cell before it is executed.
+7. Execute the bash cell.
+8. Verify execution output contains `hello world`.
 
 ## Machine-verifiable acceptance criteria
 
@@ -26,5 +27,6 @@ cell end-to-end.
 - [ ] `aisreRunners.getDefault()` reports runner `local` after setting default.
 - [ ] The workspace tree shows notebook `scenario-hello-world.runme.md`.
 - [ ] Clicking the notebook opens a tab with the notebook name.
+- [ ] Before running, the first cell shows no rendered output panel.
 - [ ] Running the first cell completes without a blocking runner error.
 - [ ] The rendered output area includes `hello world`.