Handling Unique Constraint Conflicts in Logical Replication
Authors: Ashutosh Sharma, Senior Software Engineer, and Gauri Kasar, Product Manager Logical replication can keep your PostgreSQL environments in sync, helping replicate selected tables with minimal impact on the primary workload. But what happens when your subscriber hits a duplicate key error and replication grinds to a halt? If you’ve seen a unique‑constraint violation while replicating between Azure Database for PostgreSQL servers, you’re not alone. This blog covers common causes, prevention tips, and practical recovery options. In PostgreSQL logical replication, the subscriber can fail with a unique-constraint error when it tries to apply a change that would create a duplicate key. duplicate key value violates unique constraint Understanding why this happens? When an INSERT or UPDATE would create a value that already exists in a column (or set of columns) protected by a UNIQUE constraint (including a PRIMARY KEY). In logical replication, this most commonly occurs because of local writes on the subscriber or if the table is being subscribed from multiple publishers. These conflicts are resolved on the subscriber side. Local writes on the subscriber: a row with the same primary key/unique key is inserted on the subscriber before the apply worker processes the corresponding change from the publisher. Multi-origin / multi-master without conflict-free keys: two origins generate (or replicate) the same unique key. Initial data synchronization issues: the subscriber already contains data when the subscription is created with initial copy enabled, resulting in duplicate inserts during the initial table sync. How to avoid this? Avoid local writes on subscribed tables (treat the subscriber as read-only for replicated relations). Avoid subscribing to the same table from multiple publishers unless you have explicit conflict handling and a conflict-free key design. Enabling server logs can help you identify and troubleshoot unique‑constraint conflicts more effectively. Refer to the official documentation to configure and access PostgreSQL logs. How to handle conflicts (recovery options) Option 1: Delete the conflicting row on the subscriber Use the subscriber logs to identify the key (or row) causing the conflict, then delete the row on the subscriber with a DELETE statement. Resume apply and repeat if more conflicts appear. Option 2: Use conflict logs and skip the conflicting transaction (PostgreSQL 17+) Starting with PostgreSQL 17, logical replication provides detailed conflict logging on the subscriber, making it easier to understand why replication stopped and which transaction caused the failure. When a replicated INSERT would violate a non‑deferrable unique constraint on the subscriber for example, when a row with the same key already exists the apply worker detects this as an insert_exists conflict and stops replication. In this case, PostgreSQL logs the conflict along with the transaction’s finish LSN, which uniquely identifies the failing transaction. ERROR: conflict detected on relation "public.t2": conflict=insert_exists ... in transaction 754, finished at 0/034F4090 ALTER SUBSCRIPTION <subscription_name> SKIP (lsn = '0/034F4090'); Option 3: Rebuild (re-sync) the table Rebuilding (re‑syncing) a table is the safest and most deterministic way to resolve logical replication conflicts caused by pre‑existing data differences or local writes on the subscriber. This approach is especially useful when a table repeatedly fails with unique‑constraint violations and it is unclear which rows are out of sync. Step 1 (subscriber): Disable the subscription. ALTER SUBSCRIPTION <subscription_name> DISABLE; Step 2 (subscriber): Remove the local copy of the table so it can be re-copied. TRUNCATE TABLE <conflicting_table>; Step 3 (publisher): Ensure the publication will (re)send the table (one approach is to recreate the publication entry for that table). ALTER PUBLICATION <pub_with_conflicting_table> DROP TABLE <conflicting_table>; CREATE PUBLICATION <pub_with_conflicting_table_rebuild> FOR TABLE <conflicting_table>; Step 4 (subscriber): Create a new subscription (or refresh the existing one) to re-copy the table. CREATE SUBSCRIPTION <sub_rebuild> CONNECTION '<connection_string>' PUBLICATION <pub_with_conflicting_table_rebuild>; Step 5 (subscriber): Re-enable the original subscription (if applicable). ALTER SUBSCRIPTION <subscription_name> ENABLE; Conclusion In most cases, these conflicts occur due to local changes on the subscriber or differences in data that existed before logical replication was fully synchronized. It is recommended to avoid direct modifications on subscribed tables and ensure that the replication setup is properly planned, especially when working with tables that have unique constraints.Build a Fully Offline AI App with Foundry Local and CAG
A hands-on guide to building an on-device AI support agent using Context-Augmented Generation, JavaScript, and Foundry Local. You have probably heard the AI pitch: "just call our API." But what happens when your application needs to work without an internet connection? Perhaps your users are field engineers standing next to a pipeline in the middle of nowhere, or your organisation has strict data privacy requirements, or you simply want to build something that works without a cloud bill. This post walks you through how to build a fully offline, on-device AI application using Foundry Local and a pattern called Context-Augmented Generation (CAG). By the end, you will have a clear understanding of what CAG is, how it compares to RAG, and the practical steps to build your own solution. The finished application: a browser-based AI support agent that runs entirely on your machine. What Is Context-Augmented Generation? Context-Augmented Generation (CAG) is a pattern for making AI models useful with your own domain-specific content. Instead of hoping the model "knows" the answer from its training data, you pre-load your entire knowledge base into the model's context window at startup. Every query the model handles has access to all of your documents, all of the time. The flow is straightforward: Load your documents into memory when the application starts. Inject the most relevant documents into the prompt alongside the user's question. Generate a response grounded in your content. There is no retrieval pipeline, no vector database, and no embedding model. Your documents are read from disc, held in memory, and selected per query using simple keyword scoring. The model generates answers grounded in your content rather than relying on what it learnt during training. CAG vs RAG: Understanding the Trade-offs If you have explored AI application patterns before, you have likely encountered Retrieval-Augmented Generation (RAG). Both CAG and RAG solve the same core problem: grounding an AI model's answers in your own content. They take different approaches, and each has genuine strengths and limitations. CAG (Context-Augmented Generation) How it works: All documents are loaded at startup. The most relevant ones are selected per query using keyword scoring and injected into the prompt. Strengths: Drastically simpler architecture with no vector database, no embeddings, and no retrieval pipeline Works fully offline with no external services Minimal dependencies (just two npm packages in this sample) Near-instant document selection with no embedding latency Easy to set up, debug, and reason about Limitations: Constrained by the model's context window size Best suited to small, curated document sets (tens of documents, not thousands) Keyword scoring is less precise than semantic similarity for ambiguous queries Adding documents requires an application restart RAG (Retrieval-Augmented Generation) How it works: Documents are chunked, embedded into vectors, and stored in a database. At query time, the most semantically similar chunks are retrieved and injected into the prompt. Strengths: Scales to thousands or millions of documents Semantic search finds relevant content even when the user's wording differs from the source material Documents can be added or updated dynamically without restarting Fine-grained retrieval (chunk-level) can be more token-efficient for large collections Limitations: More complex architecture: requires an embedding model, a vector database, and a chunking strategy Retrieval quality depends heavily on chunking, embedding model choice, and tuning Additional latency from the embedding and search steps More dependencies and infrastructure to manage Want to compare these patterns hands-on? There is a RAG-based implementation of the same gas field scenario using vector search and embeddings. Clone both repositories, run them side by side, and see how the architectures differ in practice. When Should You Choose Which? Consideration Choose CAG Choose RAG Document count Tens of documents Hundreds or thousands Offline requirement Essential Optional (can run locally too) Setup complexity Minimal Moderate to high Document updates Infrequent (restart to reload) Frequent or dynamic Query precision Good for keyword-matchable content Better for semantically diverse queries Infrastructure None beyond the runtime Vector database, embedding model For the sample application in this post (20 gas engineering procedure documents on a local machine), CAG is the clear winner. If your use case grows to hundreds of documents or requires real-time ingestion, RAG becomes the better choice. Both patterns can run offline using Foundry Local. Foundry Local: Your On-Device AI Runtime Foundry Local is a lightweight runtime from Microsoft that downloads, manages, and serves language models entirely on your device. No cloud account, no API keys, no outbound network calls (after the initial model download). In this sample, your application is responsible for deciding which model to use, and it does that through the foundry-local-sdk . The app creates a FoundryLocalManager , asks the SDK for the local model catalogue, and then runs a small selection policy from src/modelSelector.js . That policy looks at the machine's available RAM, filters out models that are too large, ranks the remaining chat models by preference, and then returns the best fit for that device. Why does it work this way? Because shipping one fixed model would either exclude lower-spec machines or underuse more capable ones. A 14B model may be perfectly reasonable on a 32 GB workstation, but the same choice would be slow or unusable on an 8 GB laptop. By selecting at runtime, the same codebase can run across a wider range of developer machines without manual tuning. What makes it particularly useful for developers: No GPU required — runs on CPU or NPU, making it accessible on standard laptops and desktops Native SDK bindings — in-process inference via the foundry-local-sdk npm package, with no HTTP round-trips to a local server Automatic model management — downloads, caches, and loads models automatically Dynamic model selection — the SDK can evaluate your device's available RAM and pick the best model from the catalogue Real-time progress callbacks — ideal for building loading UIs that show download and initialisation progress The integration code is refreshingly minimal. Here is the core pattern: import { FoundryLocalManager } from "foundry-local-sdk"; // Create a manager and get the model catalogue const manager = FoundryLocalManager.create({ appName: "my-app" }); // Auto-select the best model for this device based on available RAM const models = await manager.catalog.getModels(); const model = selectBestModel(models); // Download if not cached, then load into memory if (!model.isCached) { await model.download((progress) => { console.log(`Download: ${progress.toFixed(0)}%`); }); } await model.load(); // Create a chat client for direct in-process inference const chatClient = model.createChatClient(); const response = await chatClient.completeChat([ { role: "system", content: "You are a helpful assistant." }, { role: "user", content: "How do I detect a gas leak?" } ]); That is it. No server configuration, no authentication tokens, no cloud provisioning. The model runs in the same process as your application. The download step matters for a simple reason: offline inference only works once the model files exist locally. The SDK checks whether the chosen model is already cached on the machine. If it is not, the application asks Foundry Local to download it once, store it locally, and then load it into memory. After that first run, the cached model can be reused, which is why subsequent launches are much faster and can operate without any network dependency. Put another way, there are two cooperating pieces here. Your application chooses which model is appropriate for the device and the scenario. Foundry Local and its SDK handle the mechanics of making that model available locally, caching it, loading it, and exposing a chat client for inference. That separation keeps the application logic clear whilst letting the runtime handle the heavy lifting. The Technology Stack The sample application is deliberately simple. No frameworks, no build steps, no Docker: Layer Technology Purpose AI Model Foundry Local + auto-selected model Runs locally via native SDK bindings; best model chosen for your device Back end Node.js + Express Lightweight HTTP server, everyone knows it Context Markdown files pre-loaded at startup No vector database, no embeddings, no retrieval step Front end Single HTML file with inline CSS No build step, mobile-responsive, field-ready The total dependency footprint is two npm packages: express and foundry-local-sdk . Architecture Overview The four-layer architecture, all running on a single machine. The system has four layers, all running in a single process on your device: Client layer: a single HTML file served by Express, with quick-action buttons and a responsive chat interface Server layer: Express.js starts immediately and serves the UI plus an SSE status endpoint; API routes handle chat (streaming and non-streaming), context listing, and health checks CAG engine: loads all domain documents at startup, selects the most relevant ones per query using keyword scoring, and injects them into the prompt AI layer: Foundry Local runs the auto-selected model on CPU/NPU via native SDK bindings (in-process inference, no HTTP round-trips) Building the Solution Step by Step Prerequisites You need two things installed on your machine: Node.js 20 or later: download from nodejs.org Foundry Local: Microsoft's on-device AI runtime: winget install Microsoft.FoundryLocal Foundry Local will automatically select and download the best model for your device the first time you run the application. You can override this by setting the FOUNDRY_MODEL environment variable to a specific model alias. Getting the Code Running # Clone the repository git clone https://github.com/leestott/local-cag.git cd local-cag # Install dependencies npm install # Start the server npm start Open http://127.0.0.1:3000 in your browser. You will see a loading overlay with a progress bar whilst the model downloads (first run only) and loads into memory. Once the model is ready, the overlay fades away and you can start chatting. Desktop view Mobile view How the CAG Pipeline Works Let us trace what happens when a user asks: "How do I detect a gas leak?" The query flow from browser to model and back. 1 Server starts and loads documents When you run npm start , the Express server starts on port 3000. All .md files in the docs/ folder are read, parsed (with optional YAML front-matter for title, category, and ID), and grouped by category. A document index is built listing all available topics. 2 Model is selected and loaded The model selector evaluates your system's available RAM and picks the best model from the Foundry Local catalogue. If the model is not already cached, it downloads it (with progress streamed to the browser via SSE). The model is then loaded into memory for in-process inference. 3 User sends a question The question arrives at the Express server. The chat engine selects the top 3 most relevant documents using keyword scoring. 4 Prompt is constructed The engine builds a messages array containing: the system prompt (with safety-first instructions), the document index (so the model knows all available topics), the 3 selected documents (approximately 6,000 characters), the conversation history, and the user's question. 5 Model generates a grounded response The prompt is sent to the locally loaded model via the Foundry Local SDK's native bindings. The response streams back token by token through Server-Sent Events to the browser. A response with safety warnings and step-by-step guidance The sources panel shows which documents were used Key Code Walkthrough Loading Documents (the Context Module) The context module reads all markdown files from the docs/ folder at startup. Each document can have optional YAML front-matter for metadata: // src/context.js export function loadDocuments() { const files = fs.readdirSync(config.docsDir) .filter(f => f.endsWith(".md")) .sort(); const docs = []; for (const file of files) { const raw = fs.readFileSync(path.join(config.docsDir, file), "utf-8"); const { meta, body } = parseFrontMatter(raw); docs.push({ id: meta.id || path.basename(file, ".md"), title: meta.title || file, category: meta.category || "General", content: body.trim(), }); } return docs; } There is no chunking, no vector computation, and no database. The documents are held in memory as plain text. Dynamic Model Selection Rather than hard-coding a model, the application evaluates your system at runtime: // src/modelSelector.js const totalRamMb = os.totalmem() / (1024 * 1024); const budgetMb = totalRamMb * 0.6; // Use up to 60% of system RAM // Filter to models that fit, rank by quality, boost cached models const candidates = allModels.filter(m => m.task === "chat-completion" && m.fileSizeMb <= budgetMb ); // Returns the best model: e.g. phi-4 on a 32 GB machine, // or phi-3.5-mini on a laptop with 8 GB RAM This means the same application runs on a powerful workstation (selecting a 14B parameter model) or a constrained laptop (selecting a 3.8B model), with no code changes required. This is worth calling out because it is one of the most practical parts of the sample. Developers do not have to decide up front which single model every user should run. The application makes that decision at startup based on the hardware budget you set, then asks Foundry Local to fetch the model if it is missing. The result is a smoother first-run experience and fewer support headaches when the same app is used on mixed hardware. The System Prompt For safety-critical domains, the system prompt is engineered to prioritise safety, prevent hallucination, and enforce structured responses: // src/prompts.js export const SYSTEM_PROMPT = `You are a local, offline support agent for gas field inspection and maintenance engineers. Behaviour Rules: - Always prioritise safety. If a procedure involves risk, explicitly call it out. - Do not hallucinate procedures, measurements, or tolerances. - If the answer is not in the provided context, say: "This information is not available in the local knowledge base." Response Format: - Summary (1-2 lines) - Safety Warnings (if applicable) - Step-by-step Guidance - Reference (document name + section)`; This pattern is transferable to any safety-critical domain: medical devices, electrical work, aviation maintenance, or chemical handling. Adapting This for Your Own Domain The sample project is designed to be forked and adapted. Here is how to make it yours in three steps: 1. Replace the documents Delete the gas engineering documents in docs/ and add your own markdown files. The context module handles any markdown content with optional YAML front-matter: --- title: Troubleshooting Widget Errors category: Support id: KB-001 --- # Troubleshooting Widget Errors ...your content here... 2. Edit the system prompt Open src/prompts.js and rewrite the system prompt for your domain. Keep the structure (summary, safety, steps, reference) and update the language to match your users' expectations. 3. Override the model (optional) By default the application auto-selects the best model. To force a specific model: # See available models foundry model list # Force a smaller, faster model FOUNDRY_MODEL=phi-3.5-mini npm start # Or a larger, higher-quality model FOUNDRY_MODEL=phi-4 npm start Smaller models give faster responses on constrained devices. Larger models give better quality. The auto-selector picks the largest model that fits within 60% of your system RAM. Building a Field-Ready UI The front end is a single HTML file with inline CSS. No React, no build tooling, no bundler. This keeps the project accessible to beginners and easy to deploy. Design decisions that matter for field use: Dark, high-contrast theme with 18px base font size for readability in bright sunlight Large touch targets (minimum 48px) for operation with gloves or PPE Quick-action buttons for common questions, so engineers do not need to type on a phone Responsive layout that works from 320px to 1920px+ screen widths Streaming responses via SSE, so the user sees tokens arriving in real time The mobile chat experience, optimised for field use. Visual Startup Progress with SSE A standout feature of this application is the loading experience. When the user opens the browser, they see a progress overlay showing exactly what the application is doing: Loading domain documents Initialising the Foundry Local SDK Selecting the best model for the device Downloading the model (with a percentage progress bar, first run only) Loading the model into memory This works because the Express server starts before the model finishes loading. The browser connects immediately and receives real-time status updates via Server-Sent Events. Chat endpoints return 503 whilst the model is loading, so the UI cannot send queries prematurely. // Server-side: broadcast status to all connected browsers function broadcastStatus(state) { initState = state; const payload = `data: ${JSON.stringify(state)}\n\n`; for (const client of statusClients) { client.write(payload); } } // During initialisation: broadcastStatus({ stage: "downloading", message: "Downloading phi-4...", progress: 42 }); This pattern is worth adopting in any application where model loading takes more than a few seconds. Users should never stare at a blank screen wondering whether something is broken. Testing The project includes unit tests using the built-in Node.js test runner, with no extra test framework needed: # Run all tests npm test Tests cover configuration, server endpoints, and document loading. Use them as a starting point when you adapt the project for your own domain. Ideas for Extending the Project Once you have the basics running, there are plenty of directions to explore: Conversation memory: persist chat history across sessions using local storage or a lightweight database Hybrid CAG + RAG: add a vector retrieval step for larger document collections that exceed the context window Multi-modal support: add image-based queries (photographing a fault code, for example) PWA packaging: make it installable as a standalone offline application on mobile devices Custom model fine-tuning: fine-tune a model on your domain data for even better answers Ready to Build Your Own? Clone the CAG sample, swap in your own documents, and have an offline AI agent running in minutes. Or compare it with the RAG approach to see which pattern suits your use case best. Get the CAG Sample Get the RAG Sample Summary Building a local AI application does not require a PhD in machine learning or a cloud budget. With Foundry Local, Node.js, and a set of domain documents, you can create a fully offline, mobile-responsive AI agent that answers questions grounded in your own content. The key takeaways: CAG is ideal for small, curated document sets where simplicity and offline capability matter most. No vector database, no embeddings, no retrieval pipeline. RAG scales further when you have hundreds or thousands of documents, or need semantic search for ambiguous queries. See the local-rag sample to compare. Foundry Local makes on-device AI accessible: native SDK bindings, in-process inference, automatic model selection, and no GPU required. The architecture is transferable. Replace the gas engineering documents with your own content, update the system prompt, and you have a domain-specific AI agent for any field. Start simple, iterate outwards. Begin with CAG and a handful of documents. If your needs outgrow the context window, graduate to RAG. Both patterns can run entirely offline. Clone the repository, swap in your own documents, and start building. The best way to learn is to get your hands on the code. This project is open source under the MIT licence. It is a scenario sample for learning and experimentation, not production medical or safety advice. local-cag on GitHub · local-rag on GitHub · Foundry LocalBuilding a Smart Building HVAC Digital Twin with AI Copilot Using Foundry Local
Introduction Building operations teams face a constant challenge: optimizing HVAC systems for energy efficiency while maintaining occupant comfort and air quality. Traditional building management systems display raw sensor data, temperatures, pressures, CO₂ levels—but translating this into actionable insights requires deep HVAC expertise. What if operators could simply ask "Why is the third floor so warm?" and get an intelligent answer grounded in real building state? This article demonstrates building a sample smart building digital twin with an AI-powered operations copilot, implemented using DigitalTwin, React, Three.js, and Microsoft Foundry Local. You'll learn how to architect physics-based simulators that model thermal dynamics, implement 3D visualizations of building systems, integrate natural language AI control, and design fault injection systems for testing and training. Whether you're building IoT platforms for commercial real estate, designing energy management systems, or implementing predictive maintenance for building automation, this sample provides proven patterns for intelligent facility operations. Why Digital Twins Matter for Building Operations Physical buildings generate enormous operational data but lack intelligent interpretation layers. A 50,000 square foot office building might have 500+ sensors streaming metrics every minute, zone temperatures, humidity levels, equipment runtimes, energy consumption. Traditional BMS (Building Management Systems) visualize this data as charts and gauges, but operators must manually correlate patterns, diagnose issues, and predict failures. Digital twins solve this through physics-based simulation coupled with AI interpretation. Instead of just displaying current temperature readings, a digital twin models thermal dynamics, heat transfer rates, HVAC response characteristics, occupancy impacts. When conditions deviate from expectations, the twin compares observed versus predicted states, identifying root causes. Layer AI on top, and operators get natural language explanations: "The conference room is 3 degrees too warm because the VAV damper is stuck at 40% open, reducing airflow by 60%." This application focuses on HVAC, the largest building energy consumer, typically 40-50% of total usage. Optimizing HVAC by just 10% through better controls can save thousands of dollars monthly while improving occupant satisfaction. The digital twin enables "what-if" scenarios before making changes: "What happens to energy consumption and comfort if we raise the cooling setpoint by 2 degrees during peak demand response events?" Architecture: Three-Tier Digital Twin System The application implements a clean three-tier architecture separating visualization, simulation, and state management: The frontend uses React with Three.js for 3D visualization. Users see an interactive 3D model of the three-floor building with color-coded zones indicating temperature and CO₂ levels. Click any equipment, AHUs, VAVs, chillers, to see detailed telemetry. The control panel enables adjusting setpoints, running simulation steps, and activating demand response scenarios. Real-time charts display KPIs: energy consumption, comfort compliance, air quality levels. The backend Node.js/Express server orchestrates simulation and state management. It maintains the digital twin state as JSON, the single source of truth for all equipment, zones, and telemetry. REST API endpoints handle control requests, simulation steps, and AI copilot queries. WebSocket connections push real-time updates to the frontend for live monitoring. The HVAC simulator implements physics-based models: 1R1C thermal models for zones, affinity laws for fan power, chiller COP calculations, CO₂ mass balance equations. Foundry Local provides AI copilot capabilities. The backend uses foundry-local-sdk to query locally running models. Natural language queries ("How's the lobby temperature?") get answered with building state context. The copilot can explain anomalies, suggest optimizations, and even execute commands when explicitly requested. Implementing Physics-Based HVAC Simulation Accurate simulation requires modeling actual HVAC physics. The simulator implements several established building energy models: // backend/src/simulator/thermal-model.js class ZoneThermalModel { // 1R1C (one resistance, one capacitance) thermal model static calculateTemperatureChange(zone, delta_t_seconds) { const C_thermal = zone.volume * 1.2 * 1000; // Heat capacity (J/K) const R_thermal = zone.r_value * zone.envelope_area; // Thermal resistance // Internal heat gains (occupancy, equipment, lighting) const Q_internal = zone.occupancy * 100 + // 100W per person zone.equipment_load + zone.lighting_load; // Cooling/heating from HVAC const airflow_kg_s = zone.vav.airflow_cfm * 0.0004719; // CFM to kg/s const c_p_air = 1006; // Specific heat of air (J/kg·K) const Q_hvac = airflow_kg_s * c_p_air * (zone.vav.supply_temp - zone.temperature); // Envelope losses const Q_envelope = (zone.outdoor_temp - zone.temperature) / R_thermal; // Net energy balance const Q_net = Q_internal + Q_hvac + Q_envelope; // Temperature change: Q = C * dT/dt const dT = (Q_net / C_thermal) * delta_t_seconds; return zone.temperature + dT; } } This model captures essential thermal dynamics while remaining computationally fast enough for real-time simulation. It accounts for internal heat generation from occupants and equipment, HVAC cooling/heating contributions, and heat loss through the building envelope. The CO₂ model uses mass balance equations: class AirQualityModel { static calculateCO2Change(zone, delta_t_seconds) { // CO₂ generation from occupants const G_co2 = zone.occupancy * 0.0052; // L/s per person at rest // Outdoor air ventilation rate const V_oa = zone.vav.outdoor_air_cfm * 0.000471947; // CFM to m³/s // CO₂ concentration difference (indoor - outdoor) const delta_CO2 = zone.co2_ppm - 400; // Outdoor ~400ppm // Mass balance: dC/dt = (G - V*ΔC) / Volume const dCO2_dt = (G_co2 - V_oa * delta_CO2) / zone.volume; return zone.co2_ppm + (dCO2_dt * delta_t_seconds); } } These models execute every simulation step, updating the entire building state: async function simulateStep(twin, timestep_minutes) { const delta_t = timestep_minutes * 60; // Convert to seconds // Update each zone for (const zone of twin.zones) { zone.temperature = ZoneThermalModel.calculateTemperatureChange(zone, delta_t); zone.co2_ppm = AirQualityModel.calculateCO2Change(zone, delta_t); } // Update equipment based on zone demands for (const vav of twin.vavs) { updateVAVOperation(vav, twin.zones); } for (const ahu of twin.ahus) { updateAHUOperation(ahu, twin.vavs); } updateChillerOperation(twin.chiller, twin.ahus); updateBoilerOperation(twin.boiler, twin.ahus); // Calculate system KPIs twin.kpis = calculateSystemKPIs(twin); // Detect alerts twin.alerts = detectAnomalies(twin); // Persist updated state await saveTwinState(twin); return twin; } 3D Visualization with React and Three.js The frontend renders an interactive 3D building view that updates in real-time as conditions change. Using React Three Fiber simplifies Three.js integration with React's component model: // frontend/src/components/BuildingView3D.jsx import { Canvas } from '@react-three/fiber'; import { OrbitControls } from '@react-three/drei'; export function BuildingView3D({ twinState }) { return ( {/* Render building floors */} {twinState.zones.map(zone => ( selectZone(zone.id)} /> ))} {/* Render equipment */} {twinState.ahus.map(ahu => ( ))} ); } function ZoneMesh({ zone, onClick }) { const color = getTemperatureColor(zone.temperature, zone.setpoint); return ( ); } function getTemperatureColor(current, setpoint) { const deviation = current - setpoint; if (Math.abs(deviation) < 1) return '#00ff00'; // Green: comfortable if (Math.abs(deviation) < 3) return '#ffff00'; // Yellow: acceptable return '#ff0000'; // Red: uncomfortable } This visualization immediately shows building state at a glance, operators see "hot spots" in red, comfortable zones in green, and can click any area for detailed metrics. Integrating AI Copilot for Natural Language Control The AI copilot transforms building data into conversational insights. Instead of navigating multiple screens, operators simply ask questions: // backend/src/routes/copilot.js import { FoundryLocalClient } from 'foundry-local-sdk'; const foundry = new FoundryLocalClient({ endpoint: process.env.FOUNDRY_LOCAL_ENDPOINT }); router.post('/api/copilot/chat', async (req, res) => { const { message } = req.body; // Load current building state const twin = await loadTwinState(); // Build context for AI const context = buildBuildingContext(twin); const completion = await foundry.chat.completions.create({ model: 'phi-4', messages: [ { role: 'system', content: `You are an HVAC operations assistant for a 3-floor office building. Current Building State: ${context} Answer questions about equipment status, comfort conditions, and energy usage. Provide specific, actionable information based on the current data. Do not speculate beyond provided information.` }, { role: 'user', content: message } ], temperature: 0.3, max_tokens: 300 }); res.json({ response: completion.choices[0].message.content, model: 'phi-4', timestamp: new Date().toISOString() }); }); function buildBuildingContext(twin) { const alerts = twin.alerts.filter(a => a.active); const zoneStatus = twin.zones.map(z => `${z.name}: ${z.temperature.toFixed(1)}°F (setpoint: ${z.setpoint}°F), CO₂: ${z.co2_ppm}ppm, ${z.occupancy} people` ); return ` Zones: ${zoneStatus.join('\n')} Active Alerts: ${alerts.length} ${alerts.map(a => `- ${a.severity}: ${a.message}`).join('\n')} Energy: ${twin.kpis.total_power_kw.toFixed(1)} kW Chiller: ${twin.chiller.percent_load}% load, ${twin.chiller.cop.toFixed(2)} COP `.trim(); } Example interactions: User: "Why is the third floor conference room warm?" AI: "The Executive Suite on Floor 3 is currently 75.2°F, 3 degrees above the 72°F setpoint. This is due to high occupancy (8 people) and VAV-F3-EXEC operating at reduced airflow (285 CFM vs 450 CFM capacity). AHU-2 is supplying adequate cool air at 55°F. Recommend checking VAV damper position—it may be partially stuck." User: "What's our current energy usage?" AI: "Total building power consumption is 47.3 kW. Breakdown: Chiller (24.1 kW, 51%), AHU fans (12.8 kW, 27%), Pumps (7.2 kW, 15%), Other (3.2 kW, 7%). Chiller is operating at 62% load with a COP of 4.8, which is efficient for current conditions." User: "Activate demand response level 2" AI: "I cannot directly control building systems for safety reasons. To activate DR Level 2, use the Control Panel and click 'Demand Response' → 'Level 2'. This will raise cooling setpoints by 3°F and reduce auxiliary loads, targeting 15% energy reduction." The AI provides grounded, specific answers citing actual equipment IDs and metrics. It refuses to directly execute control commands, instead guiding operators to explicit control interfaces, a critical safety pattern for building systems. Fault Injection for Testing and Training Real building operations experience equipment failures, stuck dampers, sensor drift, communication losses. The digital twin includes comprehensive fault injection capabilities to train operators and test control logic: // backend/src/simulator/fault-injector.js const FAULT_CATALOG = { chillerFailure: { description: 'Chiller compressor failure', apply: (twin) => { twin.chiller.status = 'FAULT'; twin.chiller.cooling_output = 0; twin.alerts.push({ id: 'chiller-fault', severity: 'CRITICAL', message: 'Chiller compressor failure - no cooling available', equipment: 'CHILLER-01' }); } }, stuckVAVDamper: { description: 'VAV damper stuck at current position', apply: (twin, vavId) => { const vav = twin.vavs.find(v => v.id === vavId); vav.damper_stuck = true; vav.damper_position_fixed = vav.damper_position; twin.alerts.push({ id: `vav-stuck-${vavId}`, severity: 'HIGH', message: `VAV ${vavId} damper stuck at ${vav.damper_position}%`, equipment: vavId }); } }, sensorDrift: { description: 'Temperature sensor reading 5°F high', apply: (twin, zoneId) => { const zone = twin.zones.find(z => z.id === zoneId); zone.sensor_drift = 5.0; zone.temperature_measured = zone.temperature_actual + 5.0; } }, communicationLoss: { description: 'Equipment communication timeout', apply: (twin, equipmentId) => { const equipment = findEquipmentById(twin, equipmentId); equipment.comm_status = 'OFFLINE'; equipment.stale_data = true; twin.alerts.push({ id: `comm-loss-${equipmentId}`, severity: 'MEDIUM', message: `Lost communication with ${equipmentId}`, equipment: equipmentId }); } } }; router.post('/api/twin/fault', async (req, res) => { const { faultType, targetEquipment } = req.body; const twin = await loadTwinState(); const fault = FAULT_CATALOG[faultType]; if (!fault) { return res.status(400).json({ error: 'Unknown fault type' }); } fault.apply(twin, targetEquipment); await saveTwinState(twin); res.json({ message: `Applied fault: ${fault.description}`, affectedEquipment: targetEquipment, timestamp: new Date().toISOString() }); }); Operators can inject faults to practice diagnosis and response. Training scenarios might include: "The chiller just failed during a heat wave, how do you maintain comfort?" or "Multiple VAV dampers are stuck, which zones need immediate attention?" Key Takeaways and Production Deployment Building a physics-based digital twin with AI capabilities requires balancing simulation accuracy with computational performance, providing intuitive visualization while maintaining technical depth, and enabling AI assistance without compromising safety. Key architectural lessons: Physics models enable prediction: Comparing predicted vs observed behavior identifies anomalies that simple thresholds miss 3D visualization improves spatial understanding: Operators immediately see which floors or zones need attention AI copilots accelerate diagnosis: Natural language queries get answers in seconds vs. minutes of manual data examination Fault injection validates readiness: Testing failure scenarios prepares operators for real incidents JSON state enables integration: Simple file-based state makes connecting to real BMS systems straightforward For production deployment, connect the twin to actual building systems via BACnet, Modbus, or MQTT integrations. Replace simulated telemetry with real sensor streams. Calibrate model parameters against historical building performance. Implement continuous learning where the twin's predictions improve as it observes actual building behavior. The complete implementation with simulation engine, 3D visualization, AI copilot, and fault injection system is available at github.com/leestott/DigitalTwin. Clone the repository and run the startup scripts to explore the digital twin, no building hardware required. Resources and Further Reading Smart Building HVAC Digital Twin Repository - Complete source code and simulation engine Setup and Quick Start Guide - Installation instructions and usage examples Microsoft Foundry Local Documentation - AI integration reference HVAC Simulation Documentation - Physics model details and calibration Three.js Documentation - 3D visualization framework ASHRAE Standards - Building energy modeling standardsWhy Windows Should Adopt ReFS as a Bootable Filesystem
ReFS could become a bootable filesystem — it only needs a few missing layers. No need to copy NTFS, just implement what the Windows boot process requires. Key missing pieces: System‑level journaling (not only metadata) Full hardlink + extended attribute support EFS, ACLs, USN Journal for security + Windows Update Boot‑critical atomicity for safe system file updates Bootloader‑compatible APIs (BCD, BitLocker pre‑boot, WinRE, Secure Boot) Goals: Use NTFS as a reference map, add the missing capabilities to ReFS, and optimize them using ReFS features (copy‑on‑write, integrity streams, block cloning). Result: A modern, resilient filesystem that can finally boot Windows - without losing its benefits.Native Vulkan in Windows System Manifest
Vulkan’s been in Windows for ages as a loader and runtime, but the OS still doesn't use it as a native backend. It's wild because so many studios start with Vulkan now and only port to DirectX later, which just adds a ton of extra work for no reason. If Windows actually supported Vulkan natively, we’d get rid of those translation layers that cause CPU overhead and shaky frame times. In CPU-bound games, we’re talking 20–30% more performance just by cutting out the middleman. Plus, it would mean consistent performance across NVIDIA, AMD, and Intel. I really think Vulkan should be a priority in Windows, not just an add-on. What do you guys think? Is it worth pushing Microsoft on this, or are they too locked into DX12?" Community Call to Action If you believe Windows deserves a modern, efficient graphics backend — If you’ve ever seen performance lost to translation layers — If you want Vulkan to be treated as a first-class citizen inside Windows — Then speak up. Share your thoughts. Test, compare, and challenge the status quo. This isn’t just about games. It’s about the future of UI, recovery, and system performance. Let’s show Microsoft that the community is ready for native Vulkan. No translation. No compromise.System Windows Ram Problem Fix
You’ve probably seen this happen — you leave your desktop or laptop running, and after a while the system starts eating a huge chunk of your RAM, even on modern hardware. Today I’m bringing a fix that removes this issue permanently and gives Windows back the speed, stability, and clean behavior it should have. By disabling two legacy predictive mechanisms (SysMain + Prefetch), the system stops aggressively caching applications, idle RAM usage drops significantly, and micro‑lags disappear. The attached screenshots show the system before and after applying the fix. This solution works on both Windows 10 and Windows 11, and it’s safe, reversible, and the improvement is immediate. System Ram Before: System Ram After: Step‑by‑step guide (Windows 10 / 11 RAM issue fix) Note: This is a safe and fully reversible system tweak. You’re simply disabling two legacy predictive mechanisms that no longer make sense on modern hardware. 1️⃣ Disable the SysMain service Press Win + R Type services.msc → press Enter Find SysMain in the list Double‑click it Set Startup type to Disabled Click Stop if the service is running Confirm with Apply and OK 2️⃣ Disable Prefetch in the Registry Press Win + R Type regedit → press Enter Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters Find the value EnablePrefetcher Double‑click it and set the value to: 0 Confirm with OK 3️⃣ Restart your system After rebooting, your RAM usage in idle should drop noticeably, and the system will feel cleaner, faster, and more responsive. 4️⃣ How to revert (optional) If you ever want to undo the changes: SysMain: set Startup type back to Automatic and start the service EnablePrefetcher: set the value back to 3 (default) With my regular applications open, RAM usage dropped from 60–70% to just 33%. This is how Windows should have behaved from the beginning. On top of that, overall system responsiveness improved by roughly 50% — even weaker hardware feels noticeably faster almost immediately. This RAM regression has been around since Windows 7. After the kernel overhaul in Windows 8.1 it actually got worse, and it has followed every version of Windows all the way to today. RAM stability after - optimization results: RAM stability after 21 hours uptime – optimization results | Microsoft Community HubBuilding Your First Local RAG Application with Foundry Local
A developer's guide to building an offline, mobile-responsive AI support agent using Retrieval-Augmented Generation, the Foundry Local SDK, and JavaScript. Imagine you are a gas field engineer standing beside a pipeline in a remote location. There is no Wi-Fi, no mobile signal, and you need a safety procedure right now. What do you do? This is the exact problem that inspired this project: a fully offline RAG-powered support agent that runs entirely on your machine. No cloud. No API keys. No outbound network calls. Just a local language model, a local vector store, and your own documents, all accessible from a browser on any device. In this post, you will learn how it works, how to build your own, and the key architectural decisions behind it. If you have ever wanted to build an AI application that runs locally and answers questions grounded in your own data, this is the place to start. The finished application: a browser-based AI support agent that runs entirely on your machine. What Is Retrieval-Augmented Generation? Retrieval-Augmented Generation (RAG) is a pattern that makes AI models genuinely useful for domain-specific tasks. Rather than hoping the model "knows" the answer from its training data, you: Retrieve relevant chunks from your own documents using a vector store Augment the model's prompt with those chunks as context Generate a response grounded in your actual data The result is fewer hallucinations, traceable answers with source attribution, and an AI that works with your content rather than relying on general knowledge. If you are building internal tools, customer support bots, field manuals, or knowledge bases, RAG is the pattern you want. RAG vs CAG: Understanding the Trade-offs If you have explored AI application patterns before, you have likely encountered Context-Augmented Generation (CAG). Both RAG and CAG solve the same core problem: grounding an AI model's answers in your own content. They take different approaches, and each has genuine strengths and limitations. RAG (Retrieval-Augmented Generation) How it works: Documents are split into chunks, vectorised, and stored in a database. At query time, the most relevant chunks are retrieved and injected into the prompt. Strengths: Scales to thousands or millions of documents Fine-grained retrieval at chunk level with source attribution Documents can be added or updated dynamically without restarting Token-efficient: only relevant chunks are sent to the model Supports runtime document upload via the web UI Limitations: More complex architecture: requires a vector store and chunking strategy Retrieval quality depends on chunking parameters and scoring method May miss relevant content if the retrieval step does not surface it CAG (Context-Augmented Generation) How it works: All documents are loaded at startup. The most relevant ones are selected per query using keyword scoring and injected into the prompt. Strengths: Drastically simpler architecture with no vector database or embeddings All information is always available to the model Minimal dependencies and easy to set up Near-instant document selection Limitations: Constrained by the model's context window size Best suited to small, curated document sets (tens of documents) Adding documents requires an application restart Want to compare these patterns hands-on? There is a CAG-based implementation of the same gas field scenario using whole-document context injection. Clone both repositories, run them side by side, and see how the architectures differ in practice. When Should You Choose Which? Consideration Choose RAG Choose CAG Document count Hundreds or thousands Tens of documents Document updates Frequent or dynamic (runtime upload) Infrequent (restart to reload) Source attribution Per-chunk with relevance scores Per-document Setup complexity Moderate (ingestion step required) Minimal Query precision Better for large or diverse collections Good for keyword-matchable content Infrastructure SQLite vector store (single file) None beyond the runtime For the sample application in this post (20 gas engineering procedure documents with runtime upload), RAG is the clear winner. If your document set is small and static, CAG may be simpler. Both patterns run fully offline using Foundry Local. Foundry Local: Your On-Device AI Runtime Foundry Local is a lightweight runtime from Microsoft that downloads, manages, and serves language models entirely on your device. No cloud account, no API keys, no outbound network calls (after the initial model download). What makes it particularly useful for developers: No GPU required: runs on CPU or NPU, making it accessible on standard laptops and desktops Native SDK bindings: in-process inference via the foundry-local-sdk npm package, with no HTTP round-trips to a local server Automatic model management: downloads, caches, and loads models automatically Hardware-optimised variant selection: the SDK picks the best variant for your hardware (GPU, NPU, or CPU) Real-time progress callbacks: ideal for building loading UIs that show download and initialisation progress The integration code is refreshingly minimal: import { FoundryLocalManager } from "foundry-local-sdk"; // Create a manager and discover models via the catalogue const manager = FoundryLocalManager.create({ appName: "gas-field-local-rag" }); const model = await manager.catalog.getModel("phi-3.5-mini"); // Download if not cached, then load into memory if (!model.isCached) { await model.download((progress) => { console.log(`Download: ${Math.round(progress * 100)}%`); }); } await model.load(); // Create a chat client for direct in-process inference const chatClient = model.createChatClient(); const response = await chatClient.completeChat([ { role: "system", content: "You are a helpful assistant." }, { role: "user", content: "How do I detect a gas leak?" } ]); That is it. No server configuration, no authentication tokens, no cloud provisioning. The model runs in the same process as your application. The Technology Stack The sample application is deliberately simple. No frameworks, no build steps, no Docker: Layer Technology Purpose AI Model Foundry Local + Phi-3.5 Mini Runs locally via native SDK bindings, no GPU required Back end Node.js + Express Lightweight HTTP server, everyone knows it Vector Store SQLite (via better-sqlite3 ) Zero infrastructure, single file on disc Retrieval TF-IDF + cosine similarity No embedding model required, fully offline Front end Single HTML file with inline CSS No build step, mobile-responsive, field-ready The total dependency footprint is three npm packages: express , foundry-local-sdk , and better-sqlite3 . Architecture Overview The five-layer architecture, all running on a single machine. The system has five layers, all running on a single machine: Client layer: a single HTML file served by Express, with quick-action buttons and a responsive chat interface Server layer: Express.js starts immediately and serves the UI plus SSE status and chat endpoints RAG pipeline: the chat engine orchestrates retrieval and generation; the chunker handles TF-IDF vectorisation; the prompts module provides safety-first system instructions Data layer: SQLite stores document chunks and their TF-IDF vectors; documents live as .md files in the docs/ folder AI layer: Foundry Local runs Phi-3.5 Mini on CPU or NPU via native SDK bindings Building the Solution Step by Step Prerequisites You need two things installed on your machine: Node.js 20 or later: download from nodejs.org Foundry Local: Microsoft's on-device AI runtime: winget install Microsoft.FoundryLocal The SDK will automatically download the Phi-3.5 Mini model (approximately 2 GB) the first time you run the application. Getting the Code Running # Clone the repository git clone https://github.com/leestott/local-rag.git cd local-rag # Install dependencies npm install # Ingest the 20 gas engineering documents into the vector store npm run ingest # Start the server npm start Open http://127.0.0.1:3000 in your browser. You will see the status indicator whilst the model loads. Once the model is ready, the status changes to "Offline Ready" and you can start chatting. Desktop view Mobile view How the RAG Pipeline Works Let us trace what happens when a user asks: "How do I detect a gas leak?" The query flow from browser to model and back. 1 Documents are ingested and indexed When you run npm run ingest , every .md file in the docs/ folder is read, parsed (with optional YAML front-matter for title, category, and ID), split into overlapping chunks of approximately 200 tokens, and stored in SQLite with TF-IDF vectors. 2 Model is loaded via the SDK The Foundry Local SDK discovers the model in the local catalogue and loads it into memory. If the model is not already cached, it downloads it first (with progress streamed to the browser via SSE). 3 User sends a question The question arrives at the Express server. The chat engine converts it into a TF-IDF vector, uses an inverted index to find candidate chunks, and scores them using cosine similarity. The top 3 chunks are returned in under 1 ms. 4 Prompt is constructed The engine builds a messages array containing: the system prompt (with safety-first instructions), the retrieved chunks as context, the conversation history, and the user's question. 5 Model generates a grounded response The prompt is sent to the locally loaded model via the Foundry Local SDK's native chat client. The response streams back token by token through Server-Sent Events to the browser. Source references with relevance scores are included. A response with safety warnings and step-by-step guidance The sources panel shows which chunks were used and their relevance Key Code Walkthrough The Vector Store (TF-IDF + SQLite) The vector store uses SQLite to persist document chunks alongside their TF-IDF vectors. At query time, an inverted index finds candidate chunks that share terms with the query, then cosine similarity ranks them: // src/vectorStore.js search(query, topK = 5) { const queryTf = termFrequency(query); this._ensureCache(); // Build in-memory cache on first access // Use inverted index to find candidates sharing at least one term const candidateIndices = new Set(); for (const term of queryTf.keys()) { const indices = this._invertedIndex.get(term); if (indices) { for (const idx of indices) candidateIndices.add(idx); } } // Score only candidates, not all rows const scored = []; for (const idx of candidateIndices) { const row = this._rowCache[idx]; const score = cosineSimilarity(queryTf, row.tf); if (score > 0) scored.push({ ...row, score }); } scored.sort((a, b) => b.score - a.score); return scored.slice(0, topK); } The inverted index, in-memory row cache, and prepared SQL statements bring retrieval time to sub-millisecond for typical query loads. Why TF-IDF Instead of Embeddings? Most RAG tutorials use embedding models for retrieval. This project uses TF-IDF because: Fully offline: no embedding model to download or run Zero latency: vectorisation is instantaneous (it is just maths on word frequencies) Good enough: for 20 domain-specific documents, TF-IDF retrieves the right chunks reliably Transparent: you can inspect the vocabulary and weights, unlike neural embeddings For larger collections or when semantic similarity matters more than keyword overlap, you would swap in an embedding model. For this use case, TF-IDF keeps the stack simple and dependency-free. The System Prompt For safety-critical domains, the system prompt is engineered to prioritise safety, prevent hallucination, and enforce structured responses: // src/prompts.js export const SYSTEM_PROMPT = `You are a local, offline support agent for gas field inspection and maintenance engineers. Behaviour Rules: - Always prioritise safety. If a procedure involves risk, explicitly call it out. - Do not hallucinate procedures, measurements, or tolerances. - If the answer is not in the provided context, say: "This information is not available in the local knowledge base." Response Format: - Summary (1-2 lines) - Safety Warnings (if applicable) - Step-by-step Guidance - Reference (document name + section)`; This pattern is transferable to any safety-critical domain: medical devices, electrical work, aviation maintenance, or chemical handling. Runtime Document Upload Unlike the CAG approach, RAG supports adding documents without restarting the server. Click the upload button to add new .md or .txt files. They are chunked, vectorised, and indexed immediately. The upload modal with the complete list of indexed documents. Adapting This for Your Own Domain The sample project is designed to be forked and adapted. Here is how to make it yours in four steps: 1. Replace the documents Delete the gas engineering documents in docs/ and add your own markdown files. The ingestion pipeline handles any markdown content with optional YAML front-matter: --- title: Troubleshooting Widget Errors category: Support id: KB-001 --- # Troubleshooting Widget Errors ...your content here... 2. Edit the system prompt Open src/prompts.js and rewrite the system prompt for your domain. Keep the structure (summary, safety, steps, reference) and update the language to match your users' expectations. 3. Tune the retrieval In src/config.js : chunkSize: 200 : smaller chunks give more precise retrieval, less context per chunk chunkOverlap: 25 : prevents information falling between chunks topK: 3 : how many chunks to retrieve per query (more gives more context but slower generation) 4. Swap the model Change config.model in src/config.js to any model available in the Foundry Local catalogue. Smaller models give faster responses on constrained devices; larger models give better quality. Building a Field-Ready UI The front end is a single HTML file with inline CSS. No React, no build tooling, no bundler. This keeps the project accessible to beginners and easy to deploy. Design decisions that matter for field use: Dark, high-contrast theme with 18px base font size for readability in bright sunlight Large touch targets (minimum 44px) for operation with gloves or PPE Quick-action buttons that wrap on mobile so all options are visible without scrolling Responsive layout that works from 320px to 1920px+ screen widths Streaming responses via SSE, so the user sees tokens arriving in real time The mobile chat experience, optimised for field use. Testing The project includes unit tests using the built-in Node.js test runner, with no extra test framework needed: # Run all tests npm test Tests cover the chunker, vector store, configuration, and server endpoints. Use them as a starting point when you adapt the project for your own domain. Ideas for Extending the Project Once you have the basics running, there are plenty of directions to explore: Embedding-based retrieval: use a local embedding model for better semantic matching on diverse queries Conversation memory: persist chat history across sessions using local storage or a lightweight database Multi-modal support: add image-based queries (photographing a fault code, for example) PWA packaging: make it installable as a standalone offline application on mobile devices Hybrid retrieval: combine TF-IDF keyword search with semantic embeddings for best results Try the CAG approach: compare with the local-cag sample to see which pattern suits your use case Ready to Build Your Own? Clone the RAG sample, swap in your own documents, and have an offline AI agent running in minutes. Or compare it with the CAG approach to see which pattern suits your use case best. Get the RAG Sample Get the CAG Sample Summary Building a local RAG application does not require a PhD in machine learning or a cloud budget. With Foundry Local, Node.js, and SQLite, you can create a fully offline, mobile-responsive AI agent that answers questions grounded in your own documents. The key takeaways: RAG is ideal for scalable, dynamic document sets where you need fine-grained retrieval with source attribution. Documents can be added at runtime without restarting. CAG is simpler when you have a small, stable set of documents that fit in the context window. See the local-cag sample to compare. Foundry Local makes on-device AI accessible: native SDK bindings, in-process inference, automatic model selection, and no GPU required. TF-IDF + SQLite is a viable vector store for small-to-medium collections, with sub-millisecond retrieval thanks to inverted indexing and in-memory caching. Start simple, iterate outwards. Begin with RAG and a handful of documents. If your needs are simpler, try CAG. Both patterns run entirely offline. Clone the repository, swap in your own documents, and start building. The best way to learn is to get your hands on the code. This project is open source under the MIT licence. It is a scenario sample for learning and experimentation, not production medical or safety advice. local-rag on GitHub · local-cag on GitHub · Foundry LocalBuilding an Offline AI Interview Coach with Foundry Local, RAG, and SQLite
How to build a 100% offline, AI-powered interview preparation tool using Microsoft Foundry Local, Retrieval-Augmented Generation, and nothing but JavaScript. Foundry Local 100% Offline RAG + TF-IDF JavaScript / Node.js Contents Introduction What is RAG and Why Offline? Architecture Overview Setting Up Foundry Local Building the RAG Pipeline The Chat Engine Dual Interfaces: Web & CLI Testing Adapting for Your Own Use Case What I Learned Getting Started Introduction Imagine preparing for a job interview with an AI assistant that knows your CV inside and out, understands the job you're applying for, and generates tailored questions, all without ever sending your data to the cloud. That's exactly what Interview Doctor does. Interview Doctor's web UI, a polished, dark-themed interface running entirely on your local machine. In this post, I'll walk you through how I built an interview prep tool as a fully offline JavaScript application using: Foundry Local — Microsoft's on-device AI runtime SQLite — for storing document chunks and TF-IDF vectors RAG (Retrieval-Augmented Generation) — to ground the AI in your actual documents Express.js — for the web server Node.js built-in test runner — for testing with zero extra dependencies No cloud. No API keys. No internet required. Everything runs on your machine. What is RAG and Why Does It Matter? Retrieval-Augmented Generation (RAG) is a pattern that makes AI models dramatically more useful for domain-specific tasks. Instead of relying solely on what a model learned during training (which can be outdated or generic), RAG: Retrieves relevant chunks from your own documents Augments the model's prompt with those chunks as context Generates a response grounded in your actual data For Interview Doctor, this means the AI doesn't just ask generic interview questions, it asks questions specific to your CV, your experience, and the specific job you're applying for. Why Offline RAG? Privacy is the obvious benefit, your CV and job applications never leave your device. But there's more: No API costs — run as many queries as you want No rate limits — iterate rapidly during your prep Works anywhere — on a plane, in a café with bad Wi-Fi, anywhere Consistent performance — no cold starts, no API latency Architecture Overview Complete architecture showing all components and data flow. The application has two interfaces (CLI and Web) that share the same core engine: Document Ingestion — PDFs and markdown files are chunked and indexed Vector Store — SQLite stores chunks with TF-IDF vectors Retrieval — queries are matched against stored chunks using cosine similarity Generation — relevant chunks are injected into the prompt sent to the local LLM Step 1: Setting Up Foundry Local First, install Foundry Local: # Windows winget install Microsoft.FoundryLocal # macOS brew install microsoft/foundrylocal/foundrylocal The JavaScript SDK handles everything else — starting the service, downloading the model, and connecting: import { FoundryLocalManager } from "foundry-local-sdk"; import { OpenAI } from "openai"; const manager = new FoundryLocalManager(); const modelInfo = await manager.init("phi-3.5-mini"); // Foundry Local exposes an OpenAI-compatible API const openai = new OpenAI({ baseURL: manager.endpoint, // Dynamic port, discovered by SDK apiKey: manager.apiKey, }); ⚠️ Key Insight Foundry Local uses a dynamic port never hardcode localhost:5272 . Always use manager.endpoint which is discovered by the SDK at runtime. Step 2: Building the RAG Pipeline Document Chunking Documents are split into overlapping chunks of ~200 tokens. The overlap ensures important context isn't lost at chunk boundaries: export function chunkText(text, maxTokens = 200, overlapTokens = 25) { const words = text.split(/\s+/).filter(Boolean); if (words.length <= maxTokens) return [text.trim()]; const chunks = []; let start = 0; while (start < words.length) { const end = Math.min(start + maxTokens, words.length); chunks.push(words.slice(start, end).join(" ")); if (end >= words.length) break; start = end - overlapTokens; } return chunks; } Why 200 tokens with 25-token overlap? Small chunks keep retrieved context compact for the model's limited context window. Overlap prevents information loss at boundaries. And it's all pure string operations, no dependencies needed. TF-IDF Vectors Instead of using a separate embedding model (which would consume precious memory alongside the LLM), we use TF-IDF, a classic information retrieval technique: export function termFrequency(text) { const tf = new Map(); const tokens = text .toLowerCase() .replace(/[^a-z0-9\-']/g, " ") .split(/\s+/) .filter((t) => t.length > 1); for (const t of tokens) { tf.set(t, (tf.get(t) || 0) + 1); } return tf; } export function cosineSimilarity(a, b) { let dot = 0, normA = 0, normB = 0; for (const [term, freq] of a) { normA += freq * freq; if (b.has(term)) dot += freq * b.get(term); } for (const [, freq] of b) normB += freq * freq; if (normA === 0 || normB === 0) return 0; return dot / (Math.sqrt(normA) * Math.sqrt(normB)); } Each document chunk becomes a sparse vector of word frequencies. At query time, we compute cosine similarity between the query vector and all stored chunk vectors to find the most relevant matches. SQLite as a Vector Store Chunks and their TF-IDF vectors are stored in SQLite using sql.js (pure JavaScript — no native compilation needed): export class VectorStore { // Created via: const store = await VectorStore.create(dbPath) insert(docId, title, category, chunkIndex, content) { const tf = termFrequency(content); const tfJson = JSON.stringify([...tf]); this.db.run( "INSERT INTO chunks (...) VALUES (?, ?, ?, ?, ?, ?)", [docId, title, category, chunkIndex, content, tfJson] ); this.save(); } search(query, topK = 5) { const queryTf = termFrequency(query); // Score each chunk by cosine similarity, return top-K } } 💡 Why SQLite for Vectors? For a CV plus a few job descriptions (dozens of chunks), brute-force cosine similarity over SQLite rows is near-instant (~1ms). No need for Pinecone, Qdrant, or Chroma — just a single .db file on disk. Step 3: The RAG Chat Engine The chat engine ties retrieval and generation together: async *queryStream(userMessage, history = []) { // 1. Retrieve relevant CV/JD chunks const chunks = this.retrieve(userMessage); const context = this._buildContext(chunks); // 2. Build the prompt with retrieved context const messages = [ { role: "system", content: SYSTEM_PROMPT }, { role: "system", content: `Retrieved context:\n\n${context}` }, ...history, { role: "user", content: userMessage }, ]; // 3. Stream from the local model const stream = await this.openai.chat.completions.create({ model: this.modelId, messages, temperature: 0.3, stream: true, }); // 4. Yield chunks as they arrive for await (const chunk of stream) { const content = chunk.choices[0]?.delta?.content; if (content) yield { type: "text", data: content }; } } The flow is straightforward: vectorize the query, retrieve with cosine similarity, build a prompt with context, and stream from the local LLM. The temperature: 0.3 keeps responses focused — important for interview preparation where consistency matters. Step 4: Dual Interfaces — Web & CLI Web UI The web frontend is a single HTML file with inline CSS and JavaScript — no build step, no framework, no React or Vue. It communicates with the Express backend via REST and SSE: File upload via multipart/form-data Streaming chat via Server-Sent Events (SSE) Quick-action buttons for common follow-up queries (coaching tips, gap analysis, mock interview) The setup form with job title, seniority level, and a pasted job description — ready to generate tailored interview questions. CLI The CLI provides the same experience in the terminal with ANSI-coloured output: npm run cli It walks you through uploading your CV, entering the job details, and then generates streaming questions. Follow-up questions work interactively. Both interfaces share the same ChatEngine class, they're thin layers over identical logic. Edge Mode For constrained devices, toggle Edge mode to use a compact system prompt that fits within smaller context windows: Edge mode activated, uses a minimal prompt for devices with limited resources. Step 5: Testing Tests use the Node.js built-in test runner, no Jest, no Mocha, no extra dependencies: import { describe, it } from "node:test"; import assert from "node:assert/strict"; describe("chunkText", () => { it("returns single chunk for short text", () => { const chunks = chunkText("short text", 200, 25); assert.equal(chunks.length, 1); }); it("maintains overlap between chunks", () => { // Verifies overlapping tokens between consecutive chunks }); }); npm test Tests cover the chunker, vector store, config, prompts, and server API contract, all without needing Foundry Local running. Adapting for Your Own Use Case Interview Doctor is a pattern, not just a product. You can adapt it for any domain: What to Change How Domain documents Replace files in docs/ with your content System prompt Edit src/prompts.js Chunk sizes Adjust config.chunkSize and config.chunkOverlap Model Change config.model — run foundry model list UI Modify public/index.html — it's a single file Ideas for Adaptation Customer support bot — ingest your product docs and FAQs Code review assistant — ingest coding standards and best practices Study guide — ingest textbooks and lecture notes Compliance checker — ingest regulatory documents Onboarding assistant — ingest company handbooks and processes What I Learned Offline AI is production-ready. Foundry Local + small models like Phi-3.5 Mini are genuinely useful for focused tasks. You don't need vector databases for small collections. SQLite + TF-IDF is fast, simple, and has zero infrastructure overhead. RAG quality depends on chunking. Getting chunk sizes right for your use case is more impactful than the retrieval algorithm. The OpenAI-compatible API is a game-changer. Switching from cloud to local was mostly just changing the baseURL . Dual interfaces are easy when you share the engine. The CLI and Web UI are thin layers over the same ChatEngine class. ⚡ Performance Notes On a typical laptop (no GPU): ingestion takes under 1 second for ~20 documents, retrieval is ~1ms, and the first LLM token arrives in 2-5 seconds. Foundry Local automatically selects the best model variant for your hardware (CUDA GPU, NPU, or CPU). Getting Started git clone https://github.com/leestott/interview-doctor-js.git cd interview-doctor-js npm install npm run ingest npm start # Web UI at http://127.0.0.1:3000 # or npm run cli # Interactive terminal The full source code is on GitHub. Star it, fork it, adapt it — and good luck with your interviews! Resources Foundry Local — Microsoft's on-device AI runtime Foundry Local SDK (npm) — JavaScript SDK Foundry Local GitHub — Source, samples, and documentation Local RAG Reference — Reference RAG implementation Interview Doctor (JavaScript) — This project's source codeMicrosoft Foundry Labs: A Practical Fast Lane from Research to Real Developer Work
Why developers need a fast lane from research → prototypes AI engineering has a speed problem, but it is not a shortage of announcements. The hard part is turning research into a useful prototype before the next wave of models, tools, or agent patterns shows up. That gap matters. AI engineers want to compare quality, latency, and cost before they wire a model into a product. Full-stack teams want to test whether an agent workflow is real or just demo. Platform and operations teams want to know when an experiment can graduate into something observable and supportable. Microsoft makes that case directly in introducing Microsoft Foundry Labs: breakthroughs are arriving faster, and time from research to product has compressed from years to months. If you build real systems, the question is not "What is the coolest demo?" It is "Which experiments are worth my next hour, and how do I evaluate them without creating demo-ware?" That is where Microsoft Foundry Labs becomes interesting. What is Microsoft Foundry Labs? Microsoft Foundry Labs is a place to explore early-stage experiments and prototypes from Microsoft, with an explicit focus on research-driven innovation. The homepage describes it as a way to get a glimpse of potential future directions for AI through experimental technologies from Microsoft Research and more. The announcement adds the operating idea: Labs is a single access point for developers to experiment with new models from Microsoft, explore frameworks, and share feedback. That framing matters. Labs is not just a gallery of flashy ideas. It is a developer-facing exploration surface for projects that are still close to research: models, agent systems, UX ideas, and tool experiments. Here's some things you can do on Labs: Play with tomorrow’s AI, today: 30+ experimental projects—from models to agents—are openly available to fork and build upon, alongside direct access to breakthrough research from Microsoft. Go from prototype to production, fast: Seamless integration with Microsoft Foundry gives you access to 11,000+ models with built-in compute, safety, observability, and governance—so you can move from local experimentation to full-scale production without complex containerization or switching platforms. Build with the people shaping the future of AI: Join a thriving community of 25,000+ developers across Discord and GitHub with direct access to Microsoft researchers and engineers to share feedback and help shape the most promising technologies. What Labs is not: it is not a promise that every project has a production deployment path today, a long-term support commitment, or a hardened enterprise operating model. Spotlight: a few Labs experiments worth a developer's attention Phi-4-Reasoning-Vision-15B: A compact open-weight multimodal reasoning model that is interesting if you care about the quality-versus-efficiency tradeoff in smaller reasoning systems. BitNet: A native 1-bit large language model that is compelling for engineers who care about memory, compute, and energy efficiency. Fara-7B: An ultra-compact agentic small language model designed for computer use, which makes it relevant for builders exploring UI automation and on-device agents. OmniParser V2: A screen parsing module that turns interfaces into actionable elements, directly relevant to computer-use and UI-interaction agents. If you want to inspect actual code, the Labs project pages also expose official repository links for some of these experiments, including OmniParser, Magentic-UI, and BitNet. Labs vs. Foundry: how to think about the boundary The simplest mental model is this: Labs is the exploration edge; Foundry is the platform layer. The Microsoft Foundry documentation describes the broader platform as "the AI app and agent factory" to build, optimize, and govern AI apps and agents at scale. That is a different promise from Labs. Foundry is where you move from curiosity to implementation: model access, agent services, SDKs, observability, evaluation, monitoring, and governance. Labs helps you explore what might matter next. Foundry helps you build, optimize, and govern what matters now. Labs is where you test a research-shaped idea. Foundry is where you decide whether that idea can survive integration, evaluation, tracing, cost controls, and production scrutiny. That also means Labs is not a replacement for the broader Foundry workflow. If an experiment catches your attention, the next question is not "Can I ship this tomorrow?" It is "What is the integration path, and how will I measure whether it deserves promotion?" What's real today vs. what's experimental Real today: Labs is live as an official exploration hub, and Foundry is the broader platform for building, evaluating, monitoring, and governing AI apps and agents. Experimental by design: Labs projects are presented as experiments and prototypes, so they still need validation for your use case. A developer's lens: Models, Agents, Observability What makes Labs useful is not that it shows new things. It is that it gives developers a way to inspect those things through the same three concerns that matter in every serious AI system: model choice, agent design, and observability. Diagram description: imagine a loop with three boxes in a row: Models, Agents, and Observability. A forward arrow runs across the row, and a feedback arrow loops from Observability back to Models. The point is that evaluation data should change both model choices and agent design, instead of arriving too late. Models: what to look for in Labs experiments If you are model-curious, Labs should trigger an evaluation mindset, not a fandom mindset. When you see something like Phi-4-Reasoning-Vision-15B or BitNet on the Labs homepage, ask three things: what capability is being demonstrated, what constraints are obvious, and what the integration path would look like. This is where the Microsoft Foundry Playgrounds mindset is useful even if you started in Labs. The documentation emphasizes model comparison, prompt iteration, parameter tuning, tools, safety guardrails, and code export. It also pushes the right pre-production questions: price-to-performance, latency, tool integration, and code readiness. That is how I would use Labs for models: not to choose winners, but to generate hypotheses worth testing. If a Labs experiment looks promising, move quickly into a small evaluation matrix around capability, latency, cost, and integration friction. Agents: what Labs unlocks for agent builders Labs is especially interesting for agent builders because many of the projects point toward orchestration and tool-use patterns that matter in practice. The official announcement highlights projects across models and agentic frameworks, including Magentic-One and OmniParser v2. On the homepage, projects such as Fara-7B, OmniParser V2, TypeAgent, and Magentic-UI point in a similar direction: agents get more useful when they can reason over tools, interfaces, plans, and human feedback loops. For working developers, that means Labs can act as a scouting surface for agent patterns rather than just agent demos. Look for UI or computer-use style agents when your system needs to act through an interface rather than an API. Look for planning or tool-selection patterns when orchestration matters more than raw model quality. My suggestion: when a Labs project looks relevant to agent work, do not ask "Can I copy this architecture?" Ask "Which agent pattern is being explored here, and under what constraints would it be useful in my system?" Observability: how to experiment responsibly and measure what matters Observability is where prototypes usually go to die, because teams postpone it until after they have something flashy. That is backwards. If you care about real systems, tracing, evaluation, monitoring, and governance should start during prototyping. The Microsoft Foundry documentation already puts that operating model in plain view through guidance for tracing applications, evaluating agentic workflows, and monitoring generative AI apps. The Microsoft Foundry Playgrounds page is also explicit that the agents playground supports tracing and evaluation through AgentOps. At the governance layer, the AI gateway in Azure API Management documentation reinforces why this matters beyond demos. It covers monitoring and logging AI interactions, tracking token metrics, logging prompts and completions, managing quotas, applying safety policies, and governing models, agents, and tools. You do not need every one of those controls on day one, but you do need the habit: if a prototype cannot tell you what it did, why it failed, and what it cost, it is not ready to influence a roadmap. "Pick one and try it": a 20-minute hands-on path Keep this lightweight and tool-agnostic. The point is not to memorize a product UI. The point is to run a disciplined experiment. Browse Labs and pick an experiment aligned to your work. Start at Microsoft Foundry Labs and choose one project that is adjacent to a real problem you have: model efficiency, multimodal reasoning, UI agents, debugging workflows, or human-in-the-loop design. Read the project page and jump to the repo or paper if available. Use the Labs entry to understand the claim being made. Then read the supporting material, not just the summary sentence. Define one small test task and explicit success criteria. Keep it concrete: latency budget, accuracy target, cost ceiling, acceptable safety behavior, or failure rate under a narrow scenario. Capture telemetry from the start. At minimum, keep prompts or inputs, outputs, intermediate decisions, and failures. If the experiment involves tools or agents, include tool choices and obvious reasons for failure or recovery. Make a hard call. Decide whether to keep exploring or wait for a stronger production-grade path. "Interesting" is not the same as "ready for integration." Minimal experiment logger (my suggestion): if you want a lightweight way to avoid demo-ware, even a local JSONL log is enough to capture prompts, outputs, decisions, failures, and latency while you compare ideas from Labs. import json import time from pathlib import Path LOG_PATH = Path("experiment-log.jsonl") def record_event(name, payload): # Append one event per line so runs are easy to diff and analyze later. with LOG_PATH.open("a", encoding="utf-8") as handle: handle.write(json.dumps({"event": name, **payload}) + "\n") def run_experiment(user_input): started = time.time() try: # Replace this stub with your real model or agent call. output = user_input.upper() decision = "keep exploring" if len(output) < 80 else "wait" record_event( "experiment_result", { "input": user_input, "output": output, "decision": decision, "latency_ms": round((time.time() - started) * 1000, 2), "failure": None, }, ) except Exception as error: record_event( "experiment_result", { "input": user_input, "output": None, "decision": "failed", "latency_ms": round((time.time() - started) * 1000, 2), "failure": str(error), }, ) raise if __name__ == "__main__": run_experiment("Summarize the constraints of this Labs project.") That script is intentionally boring. That is the point. It gives you a repeatable, runnable starting point for comparing experiments without pretending you already have a full observability stack. Practical tips: how I evaluate Labs experiments before betting a roadmap on them Separate the idea from the implementation path. A strong research direction can still have a weak near-term integration story. Test one workload, not ten. Pick a narrow task that resembles your production reality and see whether the experiment moves the needle. Track cost and latency as first-class metrics. A novel capability that breaks your budget or response-time envelope is still a failed fit. Treat agent demos skeptically unless you can inspect behavior. Tool calls, traces, failure cases, and recovery paths matter more than polished output. Common pitfalls are predictable here. Do not confuse a research win with a deployment path. Labs is for exploration, so you still need to validate integration, safety, and operations. Do not evaluate with vague prompts. Use a narrow task and explicit success criteria, or you will end up comparing vibes instead of outcomes. Do not skip telemetry because the prototype is small. If you cannot inspect failures early, the prototype will teach you very little. Do not ignore known limitations. For example, the Fara-7B project page explicitly notes challenges on more complex tasks, instruction-following mistakes, and hallucinations, which is exactly the kind of constraint you should carry into evaluation. What to explore next Azure AI Foundry Labs matters because it gives developers a practical way to explore research-shaped ideas before they harden into mainstream patterns. The smart move is to use Labs as an input into better platform decisions: explore in Labs, validate with the discipline encouraged by Foundry playgrounds, and then bring the learnings back into the broader Foundry workflow. Takeaway 1: Labs is an exploration surface for early-stage, research-driven experiments and prototypes, not a blanket promise of production readiness. Takeaway 2: The right workflow is Labs for discovery, then Microsoft Foundry for implementation, optimization, evaluation, monitoring, and governance. Takeaway 3: Tracing, evaluations, and telemetry should start during prototyping, because that is how you avoid confusing a compelling demo with a viable system. If you are curious, start with Microsoft Foundry Labs, read the official context in Introducing Microsoft Foundry Labs, and then map what you learn into the platform guidance in Microsoft Foundry documentation. Try this next Open Microsoft Foundry Labs and choose one experiment that matches a real workload you care about. Use the mindset from Microsoft Foundry Playgrounds to define a small validation task around quality, latency, cost, and safety. Write down the minimum telemetry you need before continuing: inputs, outputs, decisions, failures, and token or cost signals. Read the relevant operating guidance in AI gateway in Azure API Management if your experiment may eventually need monitoring, quotas, safety policies, or governance. Promote only the experiments that can explain their value clearly in a Foundry-shaped build, evaluation, and observability workflow.Building real-world AI automation with Foundry Local and the Microsoft Agent Framework
A hands-on guide to building real-world AI automation with Foundry Local, the Microsoft Agent Framework, and PyBullet. No cloud subscription, no API keys, no internet required. Why Developers Should Care About Offline AI Imagine telling a robot arm to "pick up the cube" and watching it execute the command in a physics simulator, all powered by a language model running on your laptop. No API calls leave your machine. No token costs accumulate. No internet connection is needed. That is what this project delivers, and every piece of it is open source and ready for you to fork, extend, and experiment with. Most AI demos today lean on cloud endpoints. That works for prototypes, but it introduces latency, ongoing costs, and data privacy concerns. For robotics and industrial automation, those trade-offs are unacceptable. You need inference that runs where the hardware is: on the factory floor, in the lab, or on your development machine. Foundry Local gives you an OpenAI-compatible endpoint running entirely on-device. Pair it with a multi-agent orchestration framework and a physics engine, and you have a complete pipeline that translates natural language into validated, safe robot actions. This post walks through how we built it, why the architecture works, and how you can start experimenting with your own offline AI simulators today. Architecture The system uses four specialised agents orchestrated by the Microsoft Agent Framework: Agent What It Does Speed PlannerAgent Sends user command to Foundry Local LLM → JSON action plan 4–45 s SafetyAgent Validates against workspace bounds + schema < 1 ms ExecutorAgent Dispatches actions to PyBullet (IK, gripper) < 2 s NarratorAgent Template summary (LLM opt-in via env var) < 1 ms User (text / voice) │ ▼ ┌──────────────┐ │ Orchestrator │ └──────┬───────┘ │ ┌────┴────┐ ▼ ▼ Planner Narrator │ ▼ Safety │ ▼ Executor │ ▼ PyBullet Setting Up Foundry Local from foundry_local import FoundryLocalManager import openai manager = FoundryLocalManager("qwen2.5-coder-0.5b") client = openai.OpenAI( base_url=manager.endpoint, api_key=manager.api_key, ) resp = client.chat.completions.create( model=manager.get_model_info("qwen2.5-coder-0.5b").id, messages=[{"role": "user", "content": "pick up the cube"}], max_tokens=128, stream=True, ) from foundry_local import FoundryLocalManager import openai manager = FoundryLocalManager("qwen2.5-coder-0.5b") client = openai.OpenAI( base_url=manager.endpoint, api_key=manager.api_key, ) resp = client.chat.completions.create( model=manager.get_model_info("qwen2.5-coder-0.5b").id, messages=[{"role": "user", "content": "pick up the cube"}], max_tokens=128, stream=True, ) The SDK auto-selects the best hardware backend (CUDA GPU → QNN NPU → CPU). No configuration needed. How the LLM Drives the Simulator Understanding the interaction between the language model and the physics simulator is central to the project. The two never communicate directly. Instead, a structured JSON contract forms the bridge between natural language and physical motion. From Words to JSON When a user says “pick up the cube”, the PlannerAgent sends the command to the Foundry Local LLM alongside a compact system prompt. The prompt lists every permitted tool and shows the expected JSON format. The LLM responds with a structured plan: { "type": "plan", "actions": [ {"tool": "describe_scene", "args": {}}, {"tool": "pick", "args": {"object": "cube_1"}} ] } The planner parses this response, validates it against the action schema, and retries once if the JSON is malformed. This constrained output format is what makes small models (0.5B parameters) viable: the response space is narrow enough that even a compact model can produce correct JSON reliably. From JSON to Motion Once the SafetyAgent approves the plan, the ExecutorAgent maps each action to concrete PyBullet calls: move_ee(target_xyz) : The target position in Cartesian coordinates is passed to PyBullet's inverse kinematics solver, which computes the seven joint angles needed to place the end-effector at that position. The robot then interpolates smoothly from its current joint state to the target, stepping the physics simulation at each increment. pick(object) : This triggers a multi-step grasp sequence. The controller looks up the object's position in the scene, moves the end-effector above the object, descends to grasp height, closes the gripper fingers with a configurable force, and lifts. At every step, PyBullet resolves contact forces and friction so that the object behaves realistically. place(target_xyz) : The reverse of a pick. The robot carries the grasped object to the target coordinates and opens the gripper, allowing the physics engine to drop the object naturally. describe_scene() : Rather than moving the robot, this action queries the simulation state and returns the position, orientation, and name of every object on the table, along with the current end-effector pose. The Abstraction Boundary The critical design choice is that the LLM knows nothing about joint angles, inverse kinematics, or physics. It operates purely at the level of high-level tool calls ( pick , move_ee ). The ActionExecutor translates those tool calls into the low-level API that PyBullet provides. This separation means the LLM prompt stays simple, the safety layer can validate plans without understanding kinematics, and the executor can be swapped out without retraining or re-prompting the model. Voice Input Pipeline Voice commands follow three stages: Browser capture: MediaRecorder captures audio, client-side resamples to 16 kHz mono WAV Server transcription: Foundry Local Whisper (ONNX, cached after first load) with automatic 30 s chunking Command execution: transcribed text goes through the same Planner → Safety → Executor pipeline The mic button (🎤) only appears when a Whisper model is cached or loaded. Whisper models are filtered out of the LLM dropdown. Web UI in Action Pick command Describe command Move command Reset command Performance: Model Choice Matters Model Params Inference Pipeline Total qwen2.5-coder-0.5b 0.5 B ~4 s ~5 s phi-4-mini 3.6 B ~35 s ~36 s qwen2.5-coder-7b 7 B ~45 s ~46 s For interactive robot control, qwen2.5-coder-0.5b is the clear winner: valid JSON for a 7-tool schema in under 5 seconds. The Simulator in Action Here is the Panda robot arm performing a pick-and-place sequence in PyBullet. Each frame is rendered by the simulator's built-in camera and streamed to the web UI in real time. Overview Reaching Above the cube Gripper detail Front interaction Side layout Get Running in Five Minutes You do not need a GPU, a cloud account, or any prior robotics experience. The entire stack runs on a standard development machine. # 1. Install Foundry Local winget install Microsoft.FoundryLocal # Windows brew install foundrylocal # macOS # 2. Download models (one-time, cached locally) foundry model run qwen2.5-coder-0.5b # Chat brain (~4 s inference) foundry model run whisper-base # Voice input (194 MB) # 3. Clone and set up the project git clone https://github.com/leestott/robot-simulator-foundrylocal cd robot-simulator-foundrylocal .\setup.ps1 # or ./setup.sh on macOS/Linux # 4. Launch the web UI python -m src.app --web --no-gui # → http://localhost:8080 Once the server starts, open your browser and try these commands in the chat box: "pick up the cube": the robot grasps the blue cube and lifts it "describe the scene": returns every object's name and position "move to 0.3 0.2 0.5": sends the end-effector to specific coordinates "reset": returns the arm to its neutral pose If you have a microphone connected, hold the mic button and speak your command instead of typing. Voice input uses a local Whisper model, so your audio never leaves the machine. Experiment and Build Your Own The project is deliberately simple so that you can modify it quickly. Here are some ideas to get started. Add a new robot action The robot currently understands seven tools. Adding an eighth takes four steps: Define the schema in TOOL_SCHEMAS ( src/brain/action_schema.py ). Write a _do_<tool> handler in src/executor/action_executor.py . Register it in ActionExecutor._dispatch . Add a test in tests/test_executor.py . For example, you could add a rotate_ee tool that spins the end-effector to a given roll/pitch/yaw without changing position. Add a new agent Every agent follows the same pattern: an async run(context) method that reads from and writes to a shared dictionary. Create a new file in src/agents/ , register it in orchestrator.py , and the pipeline will call it in sequence. Ideas for new agents: VisionAgent: analyse a camera frame to detect objects and update the scene state before planning. CostEstimatorAgent: predict how many simulation steps an action plan will take and warn the user if it is expensive. ExplanationAgent: generate a step-by-step natural language walkthrough of the plan before execution, allowing the user to approve or reject it. Swap the LLM python -m src.app --web --model phi-4-mini Or use the model dropdown in the web UI; no restart is needed. Try different models and compare accuracy against inference speed. Smaller models are faster but may produce malformed JSON more often. Larger models are more accurate but slower. The retry logic in the planner compensates for occasional failures, so even a small model works well in practice. Swap the simulator PyBullet is one option, but the architecture does not depend on it. You could replace the simulation layer with: MuJoCo: a high-fidelity physics engine popular in reinforcement learning research. Isaac Sim: NVIDIA's GPU-accelerated robotics simulator with photorealistic rendering. Gazebo: the standard ROS simulator, useful if you plan to move to real hardware through ROS 2. The only requirement is that your replacement implements the same interface as PandaRobot and GraspController . Build something completely different The pattern at the heart of this project (LLM produces structured JSON, safety layer validates, executor dispatches to a domain-specific engine) is not limited to robotics. You could apply the same architecture to: Home automation: "turn off the kitchen lights and set the thermostat to 19 degrees" translated into MQTT or Zigbee commands. Game AI: natural language control of characters in a game engine, with the safety agent preventing invalid moves. CAD automation: voice-driven 3D modelling where the LLM generates geometry commands for OpenSCAD or FreeCAD. Lab instrumentation: controlling scientific equipment (pumps, stages, spectrometers) via natural language, with the safety agent enforcing hardware limits. From Simulator to Real Robot One of the most common questions about projects like this is whether it could control a real robot. The answer is yes, and the architecture is designed to make that transition straightforward. What Stays the Same The entire upper half of the pipeline is hardware-agnostic: The LLM planner generates the same JSON action plans regardless of whether the target is simulated or physical. It has no knowledge of the underlying hardware. The safety agent validates workspace bounds and tool schemas. For a real robot, you would tighten the bounds to match the physical workspace and add checks for obstacle clearance using sensor data. The orchestrator coordinates agents in the same sequence. No changes are needed. The narrator reports what happened. It works with any result data the executor returns. What Changes The only component that must be replaced is the executor layer, specifically the PandaRobot class and the GraspController . In simulation, these call PyBullet's inverse kinematics solver and step the physics engine. On a real robot, they would instead call the hardware driver. For a Franka Emika Panda (the same robot modelled in the simulation), the replacement options include: libfranka: Franka's C++ real-time control library, which accepts joint position or torque commands at 1 kHz. ROS 2 with MoveIt: A robotics middleware stack that provides motion planning, collision avoidance, and hardware abstraction. The move_ee action would become a MoveIt goal, and the framework would handle trajectory planning and execution. Franka ROS 2 driver: Combines libfranka with ROS 2 for a drop-in replacement of the simulation controller. The ActionExecutor._dispatch method maps tool names to handler functions. Replacing _do_move_ee , _do_pick , and _do_place with calls to a real robot driver is the only code change required. Key Considerations for Real Hardware Safety: A simulated robot cannot cause physical harm; a real robot can. The safety agent would need to incorporate real-time collision checking against sensor data (point clouds from depth cameras, for example) rather than relying solely on static workspace bounds. Perception: In simulation, object positions are known exactly. On a real robot, you would need a perception system (cameras with object detection or fiducial markers) to locate objects before grasping. Calibration: The simulated robot's coordinate frame matches the URDF model perfectly. A real robot requires hand-eye calibration to align camera coordinates with the robot's base frame. Latency: Real actuators have physical response times. The executor would need to wait for motion completion signals from the hardware rather than stepping a simulation loop. Gripper feedback: In PyBullet, grasp success is determined by contact forces. A real gripper would provide force or torque feedback to confirm whether an object has been securely grasped. The Simulation as a Development Tool This is precisely why simulation-first development is valuable. You can iterate on the LLM prompts, agent logic, and command pipeline without risk to hardware. Once the pipeline reliably produces correct action plans in simulation, moving to a real robot is a matter of swapping the lowest layer of the stack. Key Takeaways for Developers On-device AI is production-ready. Foundry Local serves models through a standard OpenAI-compatible API. If your code already uses the OpenAI SDK, switching to local inference is a one-line change to base_url . Small models are surprisingly capable. A 0.5B parameter model produces valid JSON action plans in under 5 seconds. For constrained output schemas, you do not need a 70B model. Multi-agent pipelines are more reliable than monolithic prompts. Splitting planning, validation, execution, and narration across four agents makes each one simpler to test, debug, and replace. Simulation is the safest way to iterate. You can refine LLM prompts, agent logic, and tool schemas without risking real hardware. When the pipeline is reliable, swapping the executor for a real robot driver is the only change needed. The pattern generalises beyond robotics. Structured JSON output from an LLM, validated by a safety layer, dispatched to a domain-specific engine: that pattern works for home automation, game AI, CAD, lab equipment, and any other domain where you need safe, structured control. You can start building today. The entire project runs on a standard laptop with no GPU, no cloud account, and no API keys. Clone the repository, run the setup script, and you will have a working voice-controlled robot simulator in under five minutes. Ready to start building? Clone the repository, try the commands, and then start experimenting. Fork it, add your own agents, swap in a different simulator, or apply the pattern to an entirely different domain. The best way to learn how local AI can solve real-world problems is to build something yourself. Source code: github.com/leestott/robot-simulator-foundrylocal Built with Foundry Local, Microsoft Agent Framework, PyBullet, and FastAPI.
