Blog

Updates and insights from the FabrCore project.

FabrCore 1.7.1: Build Agents That Keep Working—Safely

The Agent Harness, Surface squads, a five-rung compaction ladder, authenticated durable WebSockets, versioned Skills, and production hardening give .NET developers a complete foundation for long-running agent work.

Eric Brasher August 10, 2026 at 7:00 AM

The v1.7.1 Build Journal

Five days of engineering notes leading to the August 10 release.

Engineering

When "Notify the User" Meant "Notify the Tab They Already Had Open"

August 18, 2026 at 8:20 AM • 6 min read

An explicit PrincipalDeliveryTarget channel now means external-routing intent, and a channel-only target picks the newest eligible endpoint.

Release

FabrCore 1.7.1: Build Agents That Keep Working—Safely

August 10, 2026 at 7:00 AM • 8 min read

Agent Harness, Surface squads, bounded context, WebSocket v2, versioned Skills, and production hardening in one release.

Engineering

Release Hardening Lives in the Details

August 7, 2026 at 2:30 PM • 5 min read

Dedicated Cloud long-poll behavior, clean Microsoft 365 completion, consistent discovery, and an aligned dependency baseline.

Engineering

Less Registration, Better Boundaries

August 7, 2026 at 11:15 AM • 5 min read

Automatic referenced-assembly discovery and a clear boundary between in-process model resolution and remote administration.

Engineering

Versioned Harness Skills

August 7, 2026 at 8:00 AM • 6 min read

Immutable, exact-version instruction packages let principals teach Harness agents without rebuilding them.

Engineering

The WebSocket Client We Wanted Applications to Have

August 6, 2026 at 2:15 PM • 5 min read

A typed .NET client owns tickets, retries, operations, deliveries, checkpoints, and resynchronization.

Engineering

A Reconnect Should Not Erase the Conversation

August 6, 2026 at 11:00 AM • 6 min read

Ordered at-least-once delivery adds acknowledgements, replay, stable cursors, and explicit gap recovery.

Engineering

WebSocket v2 Starts with Identity

August 6, 2026 at 7:45 AM • 5 min read

Short-lived single-use tickets replace query-string identity, with typed operations and an explicit hello handshake.

Engineering

Run Safety with Diagnostics

August 5, 2026 at 2:00 PM • 5 min read

Per-prompt and per-turn budgets stop runaway work at an explainable, observable boundary.

Engineering

Context and History Are Not the Same Thing

August 5, 2026 at 10:45 AM • 5 min read

Reversible per-run context reduction and durable history compaction solve different token problems.

Engineering

The Five-Rung Compaction Ladder

August 5, 2026 at 7:30 AM • 6 min read

Evict, truncate, summarize, fuse, then stop: the cheapest and most reversible safety action always comes first.

Engineering

Delegation Without Team Sprawl

August 4, 2026 at 1:45 PM • 5 min read

Harness agents delegate to durable workers or create private specialists for focused, ephemeral reasoning.

Engineering

Plan, Execute, Recover

August 4, 2026 at 10:30 AM • 5 min read

Task plans and execution snapshots survive ordinary Orleans deactivation and recovery.

Engineering

A Native Harness for Agents That Need to Finish

August 4, 2026 at 7:15 AM • 6 min read

Compose model-managed todos, iteration, persistence, and delegation onto an existing agent.

Engineering

Blueprints Become Contracts for Complete Teams

August 3, 2026 at 1:30 PM • 5 min read

Top-level squads make complete agent teams idempotent, reviewable deployment resources.

Engineering

Surface Squads: Two Operating Models

August 3, 2026 at 10:15 AM • 5 min read

Orchestrator squads and task squads describe two fundamentally different ways for agent teams to work.

Engineering

Retiring Swarm for Operational Truth

August 3, 2026 at 7:00 AM • 5 min read

Why durable runtime behavior and Surface-owned composition replace the experimental Swarm layer.

Earlier Articles

Release

Azure Storage Mode and a Modular Host

July 20, 2026 at 9:40 AM • 6 min read

Run the host on Azure tables, blobs, and queues with auto-provisioned resources — and a modular host where SqlServer and AzureStorage modes ship as their own NuGet packages.

Release

Your FabrCore Agents, Now in Microsoft 365 Copilot

July 13, 2026 at 7:55 AM • 7 min read

Surface FabrCore agents in Copilot and Teams as custom engine agents: /api/messages hosting, Entra identity mapping, per-user agents, SSO/OBO, and app package generation.

Release

Blueprints: A Predictable Baseline for Every Principal's Agents

July 10, 2026 at 11:10 AM • 7 min read

A developer and administrator guide to idempotent baseline agent provisioning, safe reconfiguration, and principal-scoped operations.

Engineering

We Built Our Own Accounting System. Then We Put Agents Inside It.

July 9, 2026 • 5 min read

How Vulcan365 built Impact, our in-house accounting system, then embedded ReconAgent directly into reconciliation with FabrCore and FabrCore Surface.

Release

FabrCore's New ACL: Principals, Roles, Groups, and Real Agent-to-Agent Security

July 2, 2026 at 10:05 AM • 8 min read

Permission grants in 3-dot notation, deny-by-default cross-principal agent messaging, fan-out auditing, enforcement modes, and app-defined permissions.

Release

PrincipalGrain: Standardizing Identity-Scoped Agent Tracking

July 1, 2026 at 9:25 AM • 5 min read

ClientGrain is now PrincipalGrain, FabrCore.Client is removed, and identity-scoped tracking now uses principal terminology.

Release

Verifiable Agent Execution: Turning Agent Activity into Signed Evidence

June 25, 2026 at 9:20 AM • 9 min read

Signed, tamper-evident timelines for messages, events, LLM calls, tools, plugins, and external effects.

Engineering

Testing FabrCore Agents — Test Harness, Fake Chat Clients, and LLM Evaluation

April 15, 2026 at 9:00 AM • 7 min read

In-memory test hosts, deterministic fake chat clients, and LLM evaluation with Microsoft.Extensions.AI.Evaluation.

Release

Talk to FabrCore Agents with Any OpenAI-Compatible Client

April 14, 2026 at 11:30 AM • 6 min read

New OpenAI-compatible Chat Completions endpoint lets any system that speaks the OpenAI protocol talk to your agents.

Engineering

Introducing FabrCore Swarm — Distributed Multi-Agent Task Orchestration

April 9, 2026 at 3:15 PM • 12 min read

An experimental multi-agent orchestration layer that plans, delegates, and recovers across distributed client agents — without clients changing a line of code.

Engineering

The FabrCore Agent Proxy — Client-Side Busy-State Interleaving

April 9, 2026 at 2:00 PM • 6 min read

A client-side proxy pattern that manages busy-state interleaving for better UX during long-running agent operations.

Release

Microsoft.Agents.Ai Hits 1.0 — What It Means for FabrCore

April 7, 2026 at 9:00 AM • 5 min read

The Microsoft Agent Framework reaches GA — what the 1.0 release means for stability and FabrCore's integration.

Engineering

Auto-Discovery of Agents, Plugins, and Tools

April 2, 2026 at 10:15 AM • 6 min read

Enhanced registry with capabilities, hidden, and note attributes for richer metadata and collision detection.

Engineering

From Monolith to Modules — Restructuring Developer Tooling

March 31, 2026 at 8:30 AM • 5 min read

How FabrCore restructured from monolithic documentation to modular plugins and tools.

Engineering

Zero-Config Orleans Persistence — Auto-Provisioning SQL Server Tables

March 26, 2026 at 11:00 AM • 5 min read

OrleansSqlServerInitializer auto-creates all clustering, persistence, reminders, and streaming tables.

Engineering

Explicit Over Implicit — Why We Reverted Stream Inference

March 24, 2026 at 9:45 AM • 5 min read

A lessons-learned post about reverting implicit stream inference back to explicit handle resolution.

Engineering

How FabrCore Keeps Agents Talking Forever — Automatic Chat Compaction

March 19, 2026 at 3:30 PM • 6 min read

Configurable compaction thresholds, models, retention policies, and the OnCompaction override.

Engineering

Observability for AI Agents — Monitoring Every Message and LLM Call

March 17, 2026 at 10:00 AM • 7 min read

IAgentMessageMonitor, captured data types, configurable LLM capture, and custom monitor implementations.

Engineering

Know What Your Agents Cost — Built-in LLM Token Tracking

March 12, 2026 at 2:15 PM • 6 min read

TokenTrackingChatClient, LlmUsageScope, and per-call metadata capture for understanding agent costs.

Engineering

Multi-Tenant AI Agents — FabrCore's New ACL System

March 10, 2026 at 9:00 AM • 6 min read

IAclProvider, allow/deny rules, principal-based access control, and cross-principal messaging gated by ACL checks.

Engineering

Standards-First Messaging — FabrCore Adopts CloudEvents

March 5, 2026 at 11:20 AM • 5 min read

The new EventMessage class follows the CloudEvents spec for interoperable agent-to-agent communication.

Release

FabrCore Goes Multi-Model — Grok, Gemini, OpenAI, and Azure

March 3, 2026 at 8:45 AM • 5 min read

Four LLM backends in one runtime — configure each provider in fabrcore.json and let agents choose models per task.

Release

ChatDock 2.0 — A Drop-in Blazor Chat Panel for AI Agents

February 27, 2026 at 10:30 AM • 7 min read

Sizing options, drag-and-drop uploads, agent reset, plugins rendered in chat, and cross-principal messaging.

Engineering

Managing Agent Lifecycles at Scale with Orleans Grains

February 25, 2026 at 9:15 AM • 6 min read

FabrCoreAgentService manages agent lifecycles — grain activation, OnInitialize, OnMessage, health monitoring.

Engineering

Batch Embeddings API — 1000x Fewer HTTP Calls

February 23, 2026 at 8:45 AM • 6 min read

Batch embedding requests, singleton client caching, and native batch in memory tools — collapsing thousands of HTTP round-trips into one call.

Engineering

ChatDock Message Filter Callback

February 23, 2026 at 7:50 AM • 5 min read

OnMessageReceived is now a Func<AgentMessage, Task<bool>> — return true to display, false to suppress. Migration guide and message type conventions.

Engineering

ChatDock Events & Subscriptions: Three Patterns for Agent-to-UI Communication

February 21, 2026 at 5:45 PM • 8 min read

EventCallback parameters, IClientContext events, and ChatDockManager state changes — three ways to get agent messages into your Blazor parent components.

Engineering

Health Monitoring Guide for FabrCore

February 21, 2026 at 11:49 AM • 5 min read

Use FabrCore's diagnostics endpoints with ASP.NET Core health checks for aggregated monitoring — no custom health agents needed.

Engineering

Structured Output with FabrCore

February 21, 2026 at 11:37 AM • 4 min read

Use Microsoft.Extensions.AI's structured output APIs for reliable JSON parsing from LLMs instead of building custom parsers.

Engineering

Security Best Practices for FabrCore Tools

February 21, 2026 at 11:21 AM • 5 min read

Input validation, allowlists, and sandboxing patterns for building secure FabrCore tools — security is your application's responsibility.

Engineering

Understanding the Actor Model in FabrCore

February 21, 2026 at 11:08 AM • 5 min read

Why FabrCore agents are isolated Orleans grains, and why sharing tools or state across agents contradicts the architecture.

Engineering

Tool Invocation Logging in FabrCore

February 21, 2026 at 10:52 AM • 4 min read

Use Microsoft.Extensions.AI's UseLogging() middleware to capture tool calls, arguments, and results through standard ILogger.

Engineering

Cross-Platform File Storage in FabrCore

February 21, 2026 at 10:45 AM • 4 min read

How to configure FileStorageSettings.StoragePath correctly for WSL and Linux environments to avoid hardcoded Windows paths.

Engineering

Configuration Validation Patterns in FabrCore

February 21, 2026 at 10:33 AM • 5 min read

A practical checklist for validating FabrCore configuration — catch missing API keys, empty models, and bad JSON before startup.

Engineering

Chat History Compaction Strategies

February 21, 2026 at 10:18 AM • 5 min read

How to use FabrCore's built-in CompactionService and TryCompactAsync to manage chat history growth before it hits context limits.

Engineering

Progress Notifications in FabrCore

February 21, 2026 at 10:07 AM • 4 min read

Implement real-time progress feedback using SendMessage with OneWay kind — no dedicated streaming API needed.

Engineering

Message Routing Patterns in FabrCore

February 21, 2026 at 9:55 AM • 5 min read

Use Channel, MessageType, and Kind fields for routing within OnMessage instead of building external routing infrastructure.

Engineering

Managing Plugin Resources in FabrCore

February 21, 2026 at 9:48 AM • 4 min read

Handle resource cleanup in FabrCore plugins using IDisposable and IAsyncDisposable — no custom lifecycle hooks needed.

Engineering

Agent Delegation Best Practices

February 21, 2026 at 9:42 AM • 5 min read

Build agent delegation workflows using FabrCore's health APIs and messaging primitives instead of custom orchestration layers.

Engineering

Working with Plugin Settings in FabrCore

February 21, 2026 at 9:31 AM • 4 min read

FabrCore's plugin settings convention through AgentConfiguration.Args — the GetPluginSetting pattern and best practices.

Engineering

Agent Discovery Patterns in FabrCore

February 21, 2026 at 9:23 AM • 5 min read

Understanding FabrCore's two-scope agent tracking architecture and how to query agents without custom merge services.

Engineering

Leveraging FabrCore's Built-in Discovery System

February 21, 2026 at 9:12 AM • 4 min read

FabrCore already includes assembly scanning for agents, plugins, and tools — use AdditionalAssemblies instead of custom discovery.

Engineering

Plugin Service Resolution in FabrCore

February 21, 2026 at 9:05 AM • 4 min read

How FabrCore resolves IFabrCoreAgentHost during InitializeAsync via PluginServiceProvider — and common pitfalls to avoid.

Release

MCP Server Support for FabrCore Agents

February 21, 2026 at 7:35 AM • 5 min read

Connect MCP servers to your agents for access to external tools like GitHub, filesystem, and databases — zero code changes required.

Engineering

Building a DelegateAgent on FabrCore

February 20, 2026 at 3:40 PM • 10 min read

Learn how to build an LLM-powered supervisor agent that routes user messages to the best specialist via a 4-step pipeline.

Announcement

Why We Renamed Fabr to FabrCore

February 20, 2026 at 2:10 PM • 3 min read

The story behind the rename — domain availability, naming doubts, and landing on a name that actually fits.