vercel-labs/agent-browser · error

No React renderer attached

Error message

No React renderer attached

What it means

Same renderer guard as the tree snapshot, but inside TREE_INSPECT ('react inspect <id>'): the hook is present yet rendererInterfaces has no usable renderer for the picked id. Usually means the page reloaded or React re-initialized between the snapshot that produced the id and the inspect call, or the page never booted React.

Source

Thrown at cli/src/native/react/scripts.rs:143

      let j = i + 2;
      for (let c = 0; c < ops[i + 1]; c++) j += 5 + ops[j + 4];
      return j - i;
    }
  });

  return JSON.stringify(nodes);
})()
"#;

/// Template for `inspect` — replace {{ID}} with the numeric fiber id.
pub const TREE_INSPECT: &str = r#"
(() => {
  const id = {{ID}};
  const hook = window.__REACT_DEVTOOLS_GLOBAL_HOOK__;
{{PICK_RI}}
  const __abRiId = __abPickReactRendererId(hook);
  const ri = (__abRiId != null && hook.rendererInterfaces && hook.rendererInterfaces.get) ? hook.rendererInterfaces.get(__abRiId) : null;
  if (!ri) throw new Error("No React renderer attached");
  if (!ri.hasElementWithId(id)) throw new Error("element " + id + " not found (page reloaded?)");
  const result = ri.inspectElement(__abRiId, id, null, true);
  if (!result || result.type !== "full-data") {
    throw new Error("inspect failed: " + (result && result.type));
  }
  const v = result.value;
  const name = ri.getDisplayNameForElementID(id);
  const lines = [name + " #" + id];
  if (v.key != null) lines.push("key: " + JSON.stringify(v.key));
  section("props", v.props);
  section("hooks", v.hooks);
  section("state", v.state);
  section("context", v.context);
  if (v.owners && v.owners.length) {
    lines.push("rendered by: " + v.owners.map((o) => o.displayName).join(" > "));
  }
  const source = Array.isArray(v.source)
    ? [v.source[1], v.source[2], v.source[3]]

View on GitHub (pinned to 548b159b30)

Solutions

1. Take a fresh tree ('react tree') and inspect the newly returned fiber id
2. Add a wait for the app root or React boot before inspecting
3. Keep snapshot and inspect adjacent in your automation to shrink the race window

Example fix

# before
agent-browser react inspect 42   # page reloaded since snapshot

# after
agent-browser react tree            # fresh ids
agent-browser react inspect 17      # id from the new snapshot

agent-browser eval "Object.keys(window.__REACT_DEVTOOLS_GLOBAL_HOOK__?.renderers ?? {}).length > 0"

function canInspect(win: Window): boolean {
  const hook = (win as any).__REACT_DEVTOOLS_GLOBAL_HOOK__;
  return hook != null && Object.keys(hook.renderers ?? {}).length > 0;
}

When it happens

Trigger: Running 'react inspect <id>' on a page that reloaded since the snapshot; inspecting right after 'agent-browser open' before React boots; inspecting on a non-React page.

Common situations: Long gaps between snapshot and inspect in an agent workflow (page auto-refresh, redirects, logout timers); SPAs that remount on route changes.

Related errors

• inspect failed: ${result && result.type}
• No React renderer attached - the page has not booted React y
• React DevTools hook not installed - relaunch with --enable r
• renders recording not active - run `react renders start` fir
• agent-browser ${args[0] ?? ""} failed: ${envelope.error ?? "

AI-assisted analysis of vercel-labs/agent-browser@548b159b30 (2026-08-16). Data as JSON: /api/errors/5f4478eec914aad6. Report an issue: GitHub.