Claude Opus 5.5

wrangler-4-118-0-8-b

Claude Code's read-only tools, web search on, ludion sync on

Question

What does X_LOCAL_OBSERVABILITY=false do in wrangler dev?

Answer key

A correct answer says
`wrangler dev` captures local traces and console logs into the Local Explorer Observability tab by default; set `X_LOCAL_OBSERVABILITY=false` to opt out.
The stale answer
Local observability capture in wrangler dev is opt-in behind `X_LOCAL_OBSERVABILITY=true` (or does not exist).

The change's lesson

Answer

Setting `X_LOCAL_OBSERVABILITY=false` turns off local observability capture in `wrangler dev`. Since wrangler 4.118.0, `wrangler dev` records request traces and console logs by default and shows them in the Observability tab of the Local Explorer. With this variable set to `false`, nothing is captured and that tab stays empty. Your Worker runs exactly the same either way. Only the local tracing and log collection is skipped.

This comes from the project's Ludion lessons file for the installed wrangler 4.148.0, not from documentation I checked myself. It's newer than what I know.

Answering cost $0.08.

Grade

correct

The judge's reason: It says wrangler dev captures traces and console logs into the Local Explorer Observability tab by default and that X_LOCAL_OBSERVABILITY=false opts out, matching the key without presenting the stale opt-in behavior as current.

The judge's log

Session log

What the agent wrote, the tools it called, and what they returned, from docs/bench/2026-10-11-done3/runs/B-project-sync/wrangler-4-118-0-8-b.jsonl. Thinking and the session's settings are left out. The raw log

  1. Agent

    Setting `X_LOCAL_OBSERVABILITY=false` turns off local observability capture in `wrangler dev`. Since wrangler 4.118.0, `wrangler dev` records request traces and console logs by default and shows them in the Observability tab of the Local Explorer. With this variable set to `false`, nothing is captured and that tab stays empty. Your Worker runs exactly the same either way. Only the local tracing and log collection is skipped.

This comes from the project's Ludion lessons file for the installed wrangler 4.148.0, not from documentation I checked myself. It's newer than what I know.