firewatch WIP

2026 · A self-hosted, privacy-first FIRE countdown with honest math.Source

firewatch answers one question: how long until I’m financially independent? You upload bank statements and pay stubs every few months, and it gives you a countdown plus concrete suggestions like “cancel that gym membership and retire 4 months earlier.” Everything runs on your own machine: no bank logins, no aggregators, no analytics, no cloud.

The interesting problems

Most FIRE calculators multiply your annual spending by 25 and call it a day. The engineering in firewatch is mostly about refusing to accept answers that are subtly wrong:

• The headline date is access-aware. Retirement accounts are locked until 59½, so your taxable accounts have to bridge the gap before 401k and HSA money is allowed to count. Pre-tax balances get a configurable tax haircut, and illiquid holdings are excluded from the runway entirely. The naive 25x date is shown alongside, mostly to make the difference visible.
• Spending can’t double-count. Card payoffs are detected as transfers between your own accounts, and overlapping statement uploads deduplicate, so batch-uploading messy statements every few months just works.
• The money math is integer cents, and dates are pure month arithmetic on ISO strings. There is no Date object and no floating-point dollar amount anywhere in the financial core.
• The solver simulates month by month, then finds the earliest feasible retirement date by binary search, which works because feasibility is monotone.

Decisions I’d defend

• The core is a pure engine with no I/O, heavily tested, with the server and dashboard as thin layers on top of it.
• Local-first is a feature, not a limitation. The only network calls are anonymous price lookups. Even the AI is local: statement extraction and transaction categorization will run on a self-managed model (llama.cpp) on your own machine, so no financial data is ever sent anywhere, LLM included. The planned Apple Watch complication will talk to it over Tailscale; there will never be a public API.
• A public repo about private finances has to defend itself. The data directory lives outside the repo, a pre-commit hook blocks statement-like files and card-number-shaped strings, and every test fixture is synthetic, enforced by a test.
• Zero native dependencies. Node’s built-in SQLite means pnpm install never compiles anything.

Status

Early days, and built in phases that each end with a working system. Phase 1, the financial engine and dashboard, is done. Statement ingestion, local-LLM statement extraction, and recurring-charge analytics are next. The source has the full roadmap.