Bug tracking for Rails — session replay, console + HAR (2026)
Debug Rails Hotwire bugs — Turbo Frame "Content missing", Stimulus data-action not firing, Turbo Stream broadcasts, and Turbo 8 morphing — with rrweb replay, console, and
What Rails teams ship with BugMojo
Rails shipped its frontend as React for years, but that era is over. In the 2024 Ruby on Rails Community Survey of 2,709 developers, Stimulus (31%) overtook React (24%) as the most-used JavaScript library alongside Rails — which means the typical 2026 Rails frontend bug is a Hotwire bug, not a React bug. The failures your team now spends the most time on are a Turbo Frame that renders "Content missing", a Stimulus data-action that silently never fires, a Turbo Stream broadcast that updates the wrong element, and a Turbo 8 morph that resets scroll or JavaScript state. None of these throw a stack trace you can paste into an issue; all of them are decided by the exact DOM, console, and network state at the failure instant.
A useful bug report from a Rails-on-Hotwire app needs three things a screenshot cannot carry: the rendered DOM at the moment of the swap (did the response actually contain a <turbo-frame> with the matching id?), the captured network status (a frame that 404s fails differently from one that returns 200 with the wrong body), and the WebSocket frames for Action Cable (the literal <turbo-stream action target> payload that did or did not match an element on the page). BugMojo captures an rrweb replay, the browser console, and the full network HAR including WebSocket frames, so every one of those questions is answerable after the fact instead of "cannot reproduce".
Rails gotchas
Framework-specific failure modes engineers actually ship through. Each is hard to spot in a screenshot and obvious in a session replay.
Common Rails bugs
Real Rails bug patterns — the symptom you will see in a report and the fix that actually works.
Turbo Frame renders "Content missing" instead of swapping
Symptom: Clicking a link inside a <turbo-frame> shows a "Content missing" placeholder instead of the expected content, and the page does not navigate.
Fix: The server response did not contain a <turbo-frame> with the same id. Make the controller render a response that includes the matching frame, break out of the frame with data-turbo-frame="_top" (or target="_top"), or intercept turbo:frame-missing to follow the redirect. Check the captured network status first: if it 404s, turbo:frame-missing never fires (issue #670), so a status-based handler is the real fix.
// Intercept the missing-frame case and follow the real location
document.addEventListener("turbo:frame-missing", (event) => {
const { detail: { response, visit } } = event;
event.preventDefault();
visit(response.url);
});Stimulus action wired to a non-default element never runs
Symptom: A button-styled <div> with data-action="menu#toggle" does nothing on click. The controller is connected; no error appears in the console.
Fix: A bare "menu#toggle" relies on a default event, and a div has none (only a/button => click, form => submit, input => input, select => change). Write the full descriptor so the event is explicit. While debugging, read the exact data-action and data-controller attributes from the captured DOM and confirm in the console that the controller connect() actually ran.
<!-- ❌ no default event on a div, never fires -->
<div data-controller="menu" data-action="menu#toggle">Open</div>
<!-- ✅ explicit event descriptor -->
<div data-controller="menu" data-action="click->menu#toggle">Open</div>Turbo Stream broadcast updates nothing (or the wrong element)
Symptom: An Action Cable broadcast fires server-side, but the page never updates — or a different element changes than intended. No navigation, no console error.
Fix: A <turbo-stream> targets an element by DOM id and no-ops silently when that id is not on the page, when the client never subscribed to the channel, or when the stream wraps the wrong partial. Inspect the WebSocket frames in the captured network log to read the literal action and target, and use the DOM replay to confirm whether the target id existed when the frame arrived.
<!-- target id must exist in the live DOM or this is a silent no-op -->
<turbo-stream action="replace" target="message_42">
<template>
<div id="message_42">Updated body</div>
</template>
</turbo-stream>BugMojo vs alternatives
The honest comparison — where BugMojo wins, and where another tool might serve you better.
| Feature | BugMojo | Telescope / Sentry / DevTools |
|---|---|---|
| DOM session replay of the exact Turbo/Stimulus interaction | ✅ rrweb-based, shows the frame swap & morph | ⚠️ Sentry replay (sampled); DevTools lose it on reload |
| Network HAR with the frame's response status + WebSocket turbo-stream frames | ✅ shows 200 vs 404 and the action/target payload | ⚠️ server-side logs only; no client WebSocket view |
| Reads the exact data-controller / data-action attributes at failure | ✅ captured DOM, no instrumentation | ❌ not captured |
| MCP server: Claude Code / Cursor read the Rails report in the IDE | ✅ bug is a first-class AI assignee | ❌ none expose sessions to an AI agent over MCP |
| Always-on production error monitoring & aggregation | ❌ on-demand capture | ✅ Sentry / AppSignal / Honeybadger are more complete |
| Local request / query / job inspection in development | ❌ | ✅ Rails Telescope-style tools (local dev) |
| Console + network (HAR) capture | ✓ | Partial |
| Zero-setup Quick Capture | No project, no SDK | Account / SDK required |
BugMojo records the DOM, console, and network — then ships a one-click ticket with the full replay attached. No SDK, no setup.
Try BugMojo freeFrequently asked questions
Frequently asked questions
Sources
- Turbo Handbook — Frames (frame-missing behavior, target=_top scoping, eager/lazy src loading) — Hotwired (turbo.hotwired.dev, official docs) (2025)
- Stimulus Reference — Actions (event->controller#method descriptor, default-events-per-element table, identifier rules) — Hotwired (stimulus.hotwired.dev, official docs) (2025)
- 2024 Ruby on Rails Community Survey — Stimulus (31%) overtook React (24%) as the most-used JS library alongside Rails; 2,709 respondents — Ruby on Rails Community Survey / Planet Argon (2024)
- A happier happy path in Turbo with morphing (idiomorph, data-turbo-permanent, broadcast debounce) — 37signals Dev (Jorge Manrubia) (2023)
- turbo:frame-missing event not dispatched when response code is not 200 (#670) — hotwired/turbo GitHub Issues (2024)
- Smooth page refreshes with morphing — Turbo handbook page-refreshes (turbo-refresh-method morph) — Hotwired (turbo.hotwired.dev, official docs) (2025)