SubScribe Field OS: A Local-First Voice OS for Construction Paperwork

This is a submission for the Hacktoberfest Open-Source AI Challenge Week 3: Slow and Steady

What I Built

SubScribe Field OS is a local-first, voice-controlled operating system engineered to automate construction field documentation entirely offline. On loud, chaotic job sites, tradespeople can speak a single sentence and instantly generate a signed, print-ready change order, daily log, or delay notice.
Small trade subcontractors (like electricians, plumbers, and HVAC technicians) lose thousands of dollars annually because out-of-scope work rarely gets documented on time. They are busy working on ladders, not sitting at desks. SubScribe allows them to translate plain spoken language—such as "We moved four electrical boxes eight feet due to a duct obstruction"—into a structured, contract-linked PDF in seconds.
Who benefits: Small trade contractors who need to safeguard their profit margins, eliminate manual paperwork, and secure faster payments for extra work. Recovering just one unbilled change order easily covers the system's value. The repository bundles the complete local stack: audio transcription, schema routing, contract RAG, a local SQLite audit trail, and a PDF generation engine.

How I Built It

The entire application runs locally on a standard laptop with zero API keys or per-document processing fees.
• Local Audio Transcription (faster-whisper): Audio is processed using an int8 quantized version of faster-whisper running directly on the local CPU. To overcome heavy job site background noise, a targeted trade-vocabulary prompt (loaded with terms like conduit, junction box, HVAC, rough-in, EMT) is injected into the model, ensuring highly accurate technical transcriptions.
• Schema-Enforced Routing (Gemma 2B + Ollama + Pydantic): Raw text transcripts are routed directly to Gemma 2B via Ollama using temperature=0.0 and format="json". Strict Pydantic schemas (ChangeOrderOutput, DailyLogOutput, DelayNoticeOutput, and an IntentClassification router) validate every model response. If a format mismatch occurs, the orchestrator instantly catches it and retries, creating an enterprise-grade financial tool.
• Offline Contract RAG (ChromaDB): Before finalizing a change order, the system searches a local ChromaDB instance populated from the subcontractor's original scope agreement PDF. The most relevant clauses are provided to Gemma as context, enabling the tool to automatically cite the exact contract sections backing up the financial claim.
• Local Audit Trail (SQLite): All finalized records are serialized via Pydantic and written to a local SQLite database across three dedicated tables (daily_logs, change_orders, delay_notices), bypassing external syncing or database conflicts.
• Printable PDF Engine (Jinja2 + WeasyPrint): A HTML template dynamically populates a professional invoice layout including company branding, out-of-scope descriptions, contract clause citations, material/labor cost breakdowns, and a physical signature block for the project supervisor. WeasyPrint compiles this into a clean PDF in under two seconds.
• Field UI (Streamlit/Gradio & FastAPI): Field users interact with a lightweight interface to record audio or upload .wav files, review the parsed JSON, and export PDFs. Off-site managers can track history via a FastAPI review dashboard.

Why Does Open Innovation Matter?

Open innovation is a mandatory requirement for this business model to protect users and control operational costs:

1. Privacy is the Product: Change orders contain sensitive labor rates, material margins, and confidential legal agreements. Uploading this data to third-party cloud APIs presents significant liabilities. Running Gemma 2B locally guarantees that proprietary contract data, audio files, and financials never leave the contractor’s physical hardware.
2. Zero Marginal Costs: Closed APIs levy charges per token. A contractor handling dozens of records daily would see usage fees cut into their profits. Local inference keeps runtime costs at zero, making the software highly affordable for solo operators.
3. True Offline Independence: Job sites and basements frequently lack reliable internet connections. A cloud-reliant tool breaks down right when a contractor needs to document an obstruction before their crew leaves the area. Local open weights ensure absolute operational reliability anywhere.
4. No Vendor Lock-In: Open-source architecture permits seamless model swapping. If a stronger open-weights model is released, or an older laptop demands a lighter footprint, the core system can adapt without breaking the application logic.

The Lazy Payoff

The system was put to the test by a solo contractor running SubScribe directly on a laptop. By simply dictating daily logs and change orders aloud, he was able to instantly compile polished, legal-ready PDFs without touching a keyboard. The immediate payoff convinced him that he would readily pay a $5–$10/month subscription—proving that a zero-marginal-cost architecture unlocks a highly competitive, accessible pricing model for trade professionals.

Prize Categories

• Best Use of Gemma — Gemma 2B serves as the local intelligence foundation, managing all intent classification, schema-enforced JSON extraction, and contract clause referencing via Ollama.
• Best Use of Render — The FastAPI review dashboard is hosted on Render's free tier, allowing office managers to view synchronized data logs seamlessly as soon as field devices reconnect to Wi-Fi.
To help fine-tune this submission, please let me know:
• Do you want to include any specific GitHub repository links or live deployment URLs?
• Would you like to add details about any additional open-weights models you might have tested alongside Gemma 2B?
• Should we expand the Lazy Payoff section with more concrete metrics from your friend's test run?