Molar Trace — forensic test replay
Molar Trace vs Playwright Trace Viewer
Short answer: Playwright Trace Viewer is the official free tool for opening local trace.zip files. Molar Trace is a CI-native forensic debugger — five parallel ribbons, Layer 2 replay, agent thought traces, share links, and MCP — so teams stop downloading artifacts to debug red builds.
01 — SummaryViewer vs forensic record
Playwright's trace viewer (trace.playwright.dev) is excellent for single-developer debugging: snapshots, network, console, and video for one run. Gaps appear in team workflows — sharing traces, correlating clone activity, seeing agent planner reasoning, and re-running a fixed step without the full suite.
Trace treats every failure as a debugger session: video, DOM, network, console, and planner ribbons stay in sync. Layer 2 replay lets you patch a test step and validate the fix against the captured world state. Guard failures flow here automatically; Mender can draft fix PRs from the same record.
02 — TableSide-by-side
| Molar Trace | Playwright Trace Viewer | |
|---|---|---|
| Deployment | CI auto-upload + dashboard | Local zip open in browser |
| Timeline model | Five parallel forensic ribbons | Step snapshots + attachments |
| Sharing | Share links for QA ↔ dev | Send zip files |
| Layer 2 replay | Re-run step with fix, same state | Re-run full test locally |
| Agent runs | Planner thought ribbon | Not applicable |
| Clone activity | Stripe/email/S3 in same trace | Not integrated |
| MCP | Agents query trace as tools | Official Playwright MCP separate |
| Frameworks | Playwright, Cypress, agent runs | Playwright (primary) |
| Price | Part of Molar suite | Free (OSS viewer) |
03 — FitWhen teams pick Trace
Choose Trace when CI trace downloads slow triage, flakes eat eng hours, agentic test runs are opaque, or you want failures linked to Guard gates and Mender fix PRs. Keep Playwright Trace Viewer for quick local repro — many teams use both.
Related: Trace landing, Guard (failure → trace), Molar vs Playwright.