Day 08Week 3 · Systems week

Day 8 — Local tools that work for you

Not everything belongs on the internet. Today you build a dashboard that lives on your machine, wire yesterday's loop to keep it fresh — and learn the pattern behind our lab's tools: local software that borrows your agent's intelligence through the subscription you already pay for.

Today's goal

Build a personal dashboard from your own data, connect it to your Day-7 loop so it updates itself, and start your capstone's first working version tonight.

You need: your laptop with both agents · any real data of yours (a CSV export, a notes folder — messy is fine) · your spec.md.

Block A A dashboard for an audience of one Local tools skip hosting entirely: the file lives on your machine, opens in your browser, and shows your data the way YOU want to see it. We build one on real data — expenses, clients, study hours, whatever you brought.

A dashboard is a page that answers your recurring questions at a glance: how much, how many, what's overdue, what's next. Companies pay real money for these. You'll commission yours in about twenty minutes — and because it never leaves your laptop, private data stays private.

1

Point Codex at your data — let it look first

New folder my-dashboard, copy your data file(s) in, and start with reconnaissance, not building:

PROMPT — copy & paste into Codex
Look at the data file(s) in this folder and tell me: what's in them, what's messy or inconsistent, and what three questions this data could answer at a glance. Don't build anything yet.

Step done when: you've picked the 3 questions your dashboard will answer (yours, not necessarily its suggestions).

2

Commission the dashboard

PROMPT — copy & paste into Codex
Build dashboard.html that reads my data file and answers these three questions at a glance:
1. [your question]
2. [your question]
3. [your question]

Big readable numbers on top, one simple chart, and a table below. Plain HTML/CSS/JS, everything local — the page must work by double-clicking the file, no internet needed.

Plan in 4 bullets first, wait for my OK.

Verify against your three questions — can you answer each in two seconds of looking? Tune what's slow to read (“make the overdue number red and twice as big”).

✦ Software with exactly one user is a luxury only agent-builders can afford. You just afforded it.

Step done when: all three questions answered at a glance, on your real data.

3

Fill it with synthetic data — see the dashboard under load

Ten real rows can't show you what December will look like. Ask for realistic fake data shaped exactly like yours:

PROMPT — copy & paste into Codex
Generate 200 realistic synthetic rows in my data file's exact format: same columns, believable values, spread over the last 12 months. Include realistic mess on purpose: two empty months, one huge outlier, a few near-duplicates.

Save it as a separate demo file and add a small switch to the dashboard: REAL / DEMO data.

Flip to DEMO and look hard: do the charts survive an empty month? Does the outlier crush the scale? Do 200 rows make the table unusable? Every weakness you find now is a bug real life won't get to show you later.

Step done when: DEMO mode shows 200 rows and you found at least one thing to fix at scale.

Block B Self-updating tools: loops + the Lens pattern Two upgrades: your Day-7 loop starts feeding the dashboard fresh data, and you see how a local tool can call an agent for intelligence — the pattern behind our lab's Prompt Lens — using your subscription instead of paid API keys.
4

Let your loop feed the dashboard

A dashboard you must update by hand dies in a week. But you own a scheduler now. In Hermes:

PROMPT — copy & paste into Hermes
New scheduled task "dashboard refresh", daily at 07:00: read [where your new data appears — a folder, an export file], update the data file inside my my-dashboard folder to include anything new, and send me a one-line Telegram report of what changed.

Guardrails: you may modify ONLY the data file inside my-dashboard; if the source is missing, report and change nothing. Dry-run now.

Step done when: the dry run updates the data correctly and your dashboard shows the change after a refresh.

5

The Lens pattern — intelligence on subscription

Open our lab's Prompt Lens experiment. Under the hood it's exactly what you've built this week, one step further: a local web tool that hands work to an agent through your subscription login — no separate paid API key. Upload an image, and the local app asks the agent to describe it as a reusable prompt.

The pattern, in course vocabulary: local tool for the interface · agent for the thinking · subscription for the fuel. Watch it in action once:

PROMPT — copy & paste into Codex (in my-dashboard)
Add a small "Insight" box to my dashboard: a button that, when I click it, shows three observations about the current data — trends, oddities, one suggestion.

Generate the observations yourself right now from the data file and store them in the page (we'll regenerate them on schedule later — for now the button just reveals them).

Then close the circle with one line to Hermes: “Extend the dashboard-refresh task: after updating the data, also rewrite the three observations in dashboard.html.” Now the intelligence refreshes on schedule too — an agent thinking about your data every morning, billed to the subscription you already pay.

✦ Interface local, thinking agentic, fuel by subscription — you now recognize this pattern everywhere, including in the tools of this course.

What a good Insight box says — expenses example
1. Taxi spending doubled in June (4,200 → 8,900 som) — almost all weekday mornings. 2. Three subscriptions charge within the same two days; aligning them with salary day would smooth the month. 3. Suggestion: "office lunches" is 40% of variable spending — a weekly cap of 1,500 som saves ~6,000/month.

Same pattern, other lives: a price list whose product descriptions rewrite themselves overnight; a folder where scanned documents name and file themselves; on Day 10 — a bot that drafts answers to customers. Always the same three roles: local interface, agent thinking, subscription fuel.

Step done when: the Insight box shows observations that are actually about YOUR data — as concrete as the example above.

Homework 30–45 minutes — capstone slice, flagged big
Tonight — capstone slice 1

Your tool stops being a spec: build the first working version, locally, ugly, tonight.

Time estimate: 30–45m
  1. Open the article →
Done when:
  • v0 opens and its one action works on your machine.
  • The screenshot is in Telegram.
  • You can explain what a server is (from the article) without saying “umm”.
Short on time? Build only the first screen with fake data — no working action yet — and post that. Tomorrow's session has slack to catch up.
Day complete?

Dashboard answers your 3 questions · loop feeds it · capstone v0 exists

Tick when the homework above is finished — it syncs to your account.

Self-checkAnswer first, then reveal

Three quick checks

When does a tool deserve to stay local instead of going on the internet?

When its only user is you — especially with private data. Local means no hosting, no accounts, no leaks: the file opens in your browser and the data never leaves the laptop. Publish when someone ELSE needs to open it; that's tomorrow.

Name the three roles in the Lens pattern.

Local tool = interface · agent = thinking · subscription = fuel. The tool collects input and shows output; the agent does the intelligent part; and it all runs on the plan you already pay for, not on separate API bills.

Why did the dashboard-refresh loop get “modify ONLY the data file” as a guardrail?

Because it runs unattended, and unattended writes need the smallest possible territory. If the loop misbehaves, the damage is one regenerable file — not your dashboard, not your project, not your Documents. Fences are sized to the worst case, not the best.

What you can do now
  • Turn any messy data file into a personal dashboard.
  • Chain a loop to a tool so it maintains itself.
  • Recognize and reuse the Lens pattern: local interface, agent thinking, subscription fuel.
  • Ship a capstone v0 — the spec is now software.
Next session: your capstone leaves the laptop, properly: save points you can restore, publishing that happens by itself on every change, and the two secrets rules that keep you out of trouble.