bug(host): one hand-edited diagnostics line without a level throws the whole report #2591

Written-by: Chief-audit

At main 8126953894f5d9b649605e98f39f9bcadb63f563.

core/src/host/diagnostics.js:62 (entryLine) trusts every field of a line it is handed:

return `${new Date(entry.time).toISOString()} ${entry.level.toUpperCase()} ${entry.source}${where ? ` (${where})` : ''}${code} ${entry.text}`

The line before it, the reader of the same logs/diagnostics.jsonl (diagnostics.js:147-153), keeps a line when it parses and carries a numeric time and a string text — it never checks level or source:

try {
  const entry = JSON.parse(line)
  return typeof entry?.time === 'number' && typeof entry.text === 'string' ? [entry] : []
} catch { return [] }

Corrupt input

One line in logs/diagnostics.jsonl from an earlier run, hand-edited (or written by an older build) without a level:

{"time":1700000000000,"text":"an earlier run line"}

It passes the reader's two checks, joins the list, and then report() (diagnostics.js:417-425) calls reportMarkdown(), which maps every entry through entryLine. The first such line throws Cannot read properties of undefined (reading 'toUpperCase'), so the whole report is thrown away — the Diagnostics panel's report endpoint rejects and the Download (logText()) rejects too.

Red output

node --test against a test that boots the diagnostics host over a home whose log holds that one line:

not ok 1 - a hand-edited diagnostics line without a level does not kill the report
  error: "Cannot read properties of undefined (reading 'toUpperCase')"
  stack: |-
    entryLine (core/src/host/diagnostics.js:62:63)
    Array.map (<anonymous>)
    reportMarkdown (core/src/host/diagnostics.js:101:52)
    Object.report (core/src/host/diagnostics.js:425:17)

The same shape also throws for "time":1e400 (parses as Infinity, passes the typeof === 'number' check, and new Date(Infinity).toISOString() throws RangeError).

Sibling readers that already tolerate it

• sanitizeClientEntries (diagnostics.js:423) defaults a browser entry's missing/unknown level to 'error' instead of refusing the entry.
• The log reader above skips a line it cannot parse one by one, so a half-written line does not lose the rest; only the field-level shape is unchecked.
• store.js:572 and decisions.js:128 treat an unreadable timestamp as a fallback (Number(entry.at) || Date.now()) rather than aborting their list.

Expected behaviour

One corrupt log line must not cost the whole report: entryLine should default what the reader does not guarantee (level -> error, source -> host) and render an unparseable time as no time, the way the browser-entry reader already defaults a missing level. Alternatively the earlier filter can require level and source strings, dropping the line like any other unusable one.

Docs-not-needed: internal diagnostics formatting, no architecture change.