Signalcraft

A group adopts Scrap, a small salvaged robot who runs on signal. Every honest check-in from a member keeps him powered. Overnight, while nobody is watching, he writes a short log entry about the day in his own voice, and it is waiting in the morning.

The rule: Scrap is powered by honesty, not by happiness. A terrible day powers him exactly as much as a great one. He only runs low when nobody says anything at all. He never dies; with no signal he sleeps, and wakes the moment someone checks in.

Built solo in one weekend for the AWS Builder Center Weekend Creative Agent Challenge (Aug 21–24, 2026), on top of Undercurrent.

Live app: [TODO: Signalcraft Amplify URL — step 7] · Article: docs/article.md

What it does

• Check in once a day. A score and an optional note, anonymous by schema: the row with your score has no author, and the row with your name has no score.
• Scrap's power comes from who showed up, never from what they said. Five states (asleep, waking, low, steady, bright) computed from unique members in the rolling 24 hours, by a Lambda that reads a table with no mood column.
• Every night he writes. An EventBridge Scheduler wakes a Lambda that asks Claude Haiku 4.5 on Amazon Bedrock for three to five sentences in Scrap's voice and stores them keyed to the date, never overwritten.

Architecture in one line: React + Vite on Amplify Hosting; Amplify Gen 2 (Cognito groups, AppSync + DynamoDB with subscriptions); a Node Lambda on the PingReceipt stream for power; an EventBridge Scheduler driving a Python 3.12 Lambda that calls Bedrock and writes LogEntry rows. Scrap is SVG in React with named parts; Bedrock writes only what is around him.

Concept build, with an ending

This is a concept build with a seven-day life. It runs through Sun Aug 30, 2026. On Mon Aug 31: disable both EventBridge schedules (the nightly log and the hourly power tick), delete the Amplify app, confirm zero Bedrock invocations remain, delete the $5 budget, keep this repo public. An unattended nightly job is the failure mode for a hackathon project, so the date is here where future-me will see it.

Demo history is seeded. Log entries dated Aug 18–22 were generated by scripts/backfill-log.ts, which runs the same Bedrock generator against five days of synthetic aggregates so the archive looks lived-in from day one. The first autonomous entry is scheduled for 00:30 ET on Aug 24 (dayKey 2026-08-23); until it lands, every entry you can see is seeded and labeled.

Run it

npm install
npx ampx sandbox        # personal cloud backend; writes amplify_outputs.json (needs `aws login`)
npm run dev             # http://localhost:5173

Before pushing: npx tsc -p amplify/tsconfig.json && npm run build — the root build does not type-check amplify/.

Demo cast

Five demo accounts share one group (demoN@signalcraft.local, ask for the password): demo1 is ana, the lead; demo2–demo5 are kai, mira, theo, june. A sixth, dev@signalcraft.local, is in the dev group and gets the dev tab (forget today's check-ins, reset, cycle Scrap's states). They live in this app's own Cognito pool — scripts/create-cast.sh creates them.

Scripts

All npx tsx scripts/<name>.ts; set OUTPUTS=<path> to target another backend's amplify_outputs.json (defaults to the local sandbox).

Script	Env	What it proves / does
prove-log.ts	member creds	the scheduler tick → Python Lambda → Bedrock → a dated LogEntry lands; fails on fallback bodies
backfill-log.ts	AWS CLI session	five days of seeded log entries for the demo group (deterministic ids; reruns add nothing)
create-cast.sh	USER_POOL_ID, DEMO_PASSWORD	creates the demo cast in this app's user pool with groups (idempotent)
checkin-as.ts EMAIL SCORE [NOTE]	DEMO_PASSWORD	check in as any cast member from the terminal — how the demo reaches "bright"
show-robot.ts	member creds	prints the Robot row (power state, unique members)
prove-realtime.ts	TEST_EMAIL, TEST_PASSWORD	check-in → stream → Lambda → AppSync mutation → subscription event in 30s
seed-members.ts	DEMO_PASSWORD	names and poses for the five-member cast
reset-demo.ts	DEV_EMAIL, DEV_PASSWORD	forget today's check-ins / wipe / reseed

Docs

PLAN.md the weekend schedule · docs/MAP.md codebase map · NOTES.md the build log, every decision and bug as it happened · docs/learn/ the React + system-design journal · docs/marketing/ Scrap's voice guide and copy · docs/undercurrent/ what this is built on.