factcheck — do the sources say that?

/factcheck <path | URL> — audit a document's claims against its sources /factcheck <path> focus <section/topic> — audit only part of a long document

Answer one question: for each claim this document makes, is there a source that actually asserts it? The documented failure mode of cited writing — human and agent alike — is not missing links; it's links that resolve to pages that don't say that. A working URL is the weakest form of evidence there is. This audit replaces "it has citations" with "here is the passage."

Step 0 — Scope the audit

Read the document (WebFetch if a URL; ask for a paste if it's paywalled). Then size the job and say which tier you picked:

• Small (≤ ~10 checkable claims): verify inline, no sub-agents — the fan-out below would cost more than it saves.
• Standard: fan out, batching ~5–8 claims per verifier.
• Focused: the user named a section or topic → extract only there, note in the audit header that the rest was not examined.

If the document has no citations at all, say so up front — the audit's question shifts from "does the cited source say this" to "does support for this exist anywhere", and UNSUPPORTED becomes the default grade to beat.

Step 1 — Extract the checkable claims

Walk the document and number every checkable claim: factual, specific, and in principle verifiable — statistics, quotes, "X said/announced Y", version numbers, benchmark results, historical facts, "studies show".

For each claim record: a short restatement, its locator (section heading or line), the cited source if any, and whether it's date-sensitive (anything with "currently", "latest", a version, or a number that drifts).

Skip pure opinion and analysis — but flag opinion dressed as fact ("it is widely known that...") as a finding in its own right, ungraded.

Step 2 — Adversarial verification (fan out)

Spawn verifier sub-agents (subagent_type: "Explore"), each with a batch of claims and the same standing instruction: try to refute each claim, not confirm it — a verifier hunting for agreement finds it whether it exists or not. Per claim:

1. Fetch the cited source. Find the exact passage that supports or contradicts the claim — and quote it verbatim. No passage, no verification, regardless of how relevant the page looks.
2. Trace laundered sources. If the citation is a secondary write-up (a blog post about a paper, a news story about an announcement), follow it to the source that owns the claim — the paper, the changelog, the transcript. Grade against the owner; note the laundering.
3. Check the date. For date-sensitive claims, one search pass for newer, superseding evidence — a claim can be faithfully cited and still be wrong today.
4. Uncited claims: one honest search for a supporting primary source. Found → grade normally and record the found source. Not found → UNSUPPORTED, with the search noted.

Grades (exactly one per claim):

Lossless hand-off: each verifier writes full findings (quotes, URLs, search trails) to out/factcheck/.work/<batch>.md and returns a compact summary; build the audit from the files, not the summaries — a quote flattened by a relay is no longer evidence.

Step 3 — The audit

Render in chat, then save. Findings first, worst first:

# Factcheck: <document title> — <YYYY-MM-DD>

**Document:** <path/URL> · **Claims examined:** N (of M total; scope note if focused)
**Score:** X VERIFIED · X MISATTRIBUTED · X UNSUPPORTED · X STALE · X UNCHECKABLE

## Findings that matter most
1–3 sentences: the riskiest problems (misattributions and unsupported
central claims outrank stale trivia), any laundering pattern, any cluster.

## Claim-by-claim
| # | Claim | Locator | Cited source | Grade | Evidence |
|---|---|---|---|---|---|
(evidence column = the quoted passage or the reason, always)

## Laundered sources
citation → owning source, per case (omit section if none)

## Date-sensitive claims
what to re-check and when (omit if none)

Save to out/factcheck/<slug>-<YYYY-MM-DD>.md (<slug> from the document title; date via date +%F — never guessed). Create the folder if needed; committing the audit is the user's call. Then offer — never do unasked — the follow-ups: annotate the original with inline flags, or draft corrected text for the failing claims.

Guardrails

• A resolving link proves nothing. Verification is a quoted passage or it didn't happen.
• Refute-first. Every verifier hunts for the disconfirming reading; when a grade is genuinely arguable, take the lower one and say why.
• Primary sources own claims. A write-up of a paper is not the paper; grade against the owner.
• Unknowns stay UNCHECKABLE. Never guessed, averaged, or rounded up to VERIFIED — an honest "couldn't check" is a finding, not a failure.
• Advisory, not editorial. The audit grades; the human decides what to do about it. Never edit the audited document without being asked.
• This repo's outputs are fair game. Auditing a pulse or verdict brief with fresh-context verifiers is the intended use, not an insult — the writer of a claim is the worst-placed agent to check it.