TruthCast: multi-agent fact-checking with on-chain provenance

By Suryansh Sijwali · · 2 min read · Engineering, Hackathon, Multi-agent

What it does

TruthCast is a fully autonomous fact-checking pipeline that does more than return true-or-false. A claim goes through five stages:

  1. Ingest. Accept text or a URL, decompose into atomic sub-claims using the HiSS method.
  2. Research. Retrieve evidence via Gemini 2.0 Flash with google_search grounding.
  3. Score credibility. Use the MBFC dataset (about 4,000 expert-rated domains) so contradictory but low-credibility evidence is down-weighted, not just counted.
  4. Debate (sometimes). If inter-agent agreement falls below 80%, an adversarial pro/con debate fires before the verdict.
  5. Publish. Emit one of seven verdicts (TRUE, MOSTLY_TRUE, MISLEADING, MOSTLY_FALSE, FALSE, CONFLICTING, UNVERIFIABLE), write it to a Solana memo on devnet so the result is permanent and tamper-evident, and generate a voice summary via ElevenLabs TTS.

The frontend streams pipeline progress in real time over SSE so the user watches the reasoning happen.

Why the design choices

Seven verdicts, not boolean. The boolean fact-check is what makes most fact-checkers feel adversarial. “Half true” is a real category of claim. CONFLICTING and UNVERIFIABLE are honest states; they are not the same as MOSTLY_FALSE.

Source credibility instead of vote count. Three low-credibility sources that agree shouldn’t outweigh one high-credibility source that disagrees. MBFC’s per-domain ratings are the cheapest weight to apply that gets the directional answer right most of the time.

Debate gates on agreement, not always. Debating every claim is expensive and slow. Debating only when the researchers disagree (under 80% agreement) is where the marginal cost buys real information.

Solana memo, not a custom contract. The point is provenance, not on-chain logic. Writing a memo to devnet costs nothing, is permanent, and is enough.

Stack

Next.js 14, TypeScript, Gemini 2.0 Flash, Solana (devnet), ElevenLabs TTS, Turso/SQLite, MBFC dataset, Sentry.

Recognition

HackPSU Spring 2026, Solana track winner.

Built in a weekend. Not actively maintained, but the live demo still runs against devnet.