BigTime · AI Time Tracking
4 weeks · prototype to MVP · Vista portfolioA desktop agent that fills the timesheet while you work
A native desktop app watches application usage, document names, and window titles — and Claude turns that stream into categorized, billable time entries that land directly in BigTime. Built in four weeks, running in internal professional services and customer demos.
Timesheets are the tax on billable work. Consultants, lawyers, and accountants spend real time every day reconstructing what they did — switching between apps, guessing durations, miscategorizing projects. The data ends up inaccurate, the process ends up resented, and firms leave revenue on the table from unbilled hours they can't remember.
What We Built
A desktop app that watches, not interrupts
A cross-platform desktop application that runs silently in the background, tracking which applications and documents you're working in throughout the day. No timers to start, no categories to pick, no interruptions.
The AI maps your activity to the right projects and clients automatically. At the end of the day, your timesheet is already filled in — you just review and submit.
Plugs into BigTime, not around it
Built to integrate directly with BigTime's existing time tracking framework. Teams don't learn a new system — they keep using BigTime, but now the data populates itself.
Already being used for customer demos and internal professional services, validating the concept with real usage before wider rollout.
The Claude Stack
Orchestrator
Agent SDK · daily roll-up
A lightweight supervising agent assembles each user’s day from raw activity chunks and emits a single timesheet review at end-of-day.
Bulk Tier
Sonnet · primary categorizer
Given a window of activity (apps, doc names, URLs, time ranges), Sonnet emits structured time entries — project, client, billable flag, description.
Fast Tier
Haiku · real-time chunker
Rolls the raw activity stream into semantic work blocks before Sonnet sees it. Keeps the heavier model from paying for noise.
Tools
BigTime API · project registry
Claude writes directly into BigTime’s existing timesheet framework through a typed tool. Users don’t learn a new system — their timesheet is just pre-filled.
Grounding
Structured outputs
Every entry is emitted as a JSON record the BigTime API accepts directly. No free-text entries, no hallucinated project codes.
Privacy
Local-first chunking
The desktop client holds the raw activity. Only the already-compacted work-block summary leaves the machine — the material the user would put in the timesheet themselves.
The Daily Loop
From a day of raw activity to a timesheet the user just approves
Capture
The desktop agent records active application, window title, document name, and coarse URL across the day. Runs silently, no interruptions, all local.
Chunk
Haiku rolls consecutive related events into coherent work blocks: ‘40 min in the Acme SOW doc,’ ‘2h in the Zephyr Figma file.’ Cheap, fast, happens continuously.
Categorize
At end of day, Sonnet sees the full block list plus the user’s active BigTime projects and clients. Emits structured time entries with project, client, billable flag, and description.
Write
A tool call posts entries to BigTime’s existing API. The data lands in the same timesheet the user would have filled out manually — now it’s just pre-populated.
Review
The user opens BigTime to a filled timesheet, adjusts anything that looks off, submits. Corrections feed back into the categorizer so it gets sharper per user over time.
Why Claude
Structured outputs you can actually ship to billing
Billable time goes straight into client invoices. The model can't emit the wrong project ID, can't skip the required billable flag, can't freelance a time range. Claude’s structured-output reliability is what let us post categorized entries directly to BigTime’s API without a brittle validation layer catching errors on the way through.
The Haiku → Sonnet ladder also makes the economics work for a passive background agent running on every consultant’s laptop. You can’t put Opus behind every mouse click; you can afford Haiku on every tick and Sonnet once a day.
Impact
Recovered Revenue
Hours that used to go unbilled because no one remembered to log them are now captured automatically. More accurate timesheets mean more accurate invoices.
Zero Friction
Replaced the most hated part of professional services work with something that happens in the background. No behavioral change required from employees.
Immediate Validation
Cross-platform prototype delivered in 4 weeks. Already in use for customer demos and internal services — proving the concept with real workflows, not slide decks.
The timesheet that fills itself in.
Built on Claude. Designed to compound.
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