Praetorium.Bridge

Turn an AI agent into a callable MCP tool — and let two agents have a real conversation through it.

Praetorium.Bridge is a .NET 10 server that publishes AI-agent-backed tools over the Model Context Protocol. You describe each tool in JSON — its inputs, its agent, its prompt — and the bridge spawns the agent, keeps its session alive across calls, and surfaces the whole thing in a live dashboard.

What sets it apart from a one-shot LLM call wrapped behind an MCP endpoint:

• Real-time agent-to-agent dialogue. A signaling tool inside the agent's session can park the caller, hand control back to the agent for follow-up, and resume — so an agent calling the bridge can ask clarifying questions, request more context, and respond, all in one logical exchange instead of a stateless request/response.
• Sessions that survive across calls. A code-review tool, for instance, holds the same agent through every clarification round of the same review (per-reference mode) — the model keeps its context, you don't pay to re-prime it, and the conversation actually progresses instead of restarting.

The goal is to make it boring to expose an agent as a tool: no glue code, no per-tool wiring, no redeploys.

Status: 0.1.0 — prerelease. Interfaces, schema, and UI are still moving.

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How it works

flowchart LR
    Caller[MCP caller<br/>e.g. another agent] -->|HTTP| Bridge[Praetorium.Bridge]
    Bridge --> Session[Pooled agent session]
    Session <-->|signaling tools| Bridge

A caller invokes a tool over HTTP. The bridge routes it to the right agent session — spawning a new one or reusing a pooled one based on the tool's session mode — and the agent runs until it hits a signaling tool. Non-blocking signaling tools stream a payload back and let the agent keep going; blocking ones park the agent's turn until the caller replies on the same MCP call, enabling a true back-and-forth without losing session state.

Everything that varies between tools — the agent backend, the prompt, the parameter schema, the session lifetime, the signaling contract — lives in praetorium-bridge.json and hot-reloads.

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Quick start

dotnet run --project src/Praetorium.Bridge.Web

dotnet run will print the bound URL (the launch profile defaults to http://localhost:5067); the dashboard is served at /, the MCP endpoint at /mcp. Override with ASPNETCORE_URLS or by editing Properties/launchSettings.json.

On first launch the bridge reads praetorium-bridge.json from:

OS	Path
Windows	%APPDATA%\PraetoriumBridge\
Linux / macOS	~/.config/PraetoriumBridge/

A working starter config lives in examples/PraetoriumBridge/ — copy it into the path above, then point any MCP client (Claude Desktop, Copilot, another bridge) at the endpoint.

Prerequisites: .NET 10 SDK, and access to a GitHub Copilot–compatible endpoint for the bundled provider.

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What's in the box

• Praetorium.Bridge — the core library: session lifecycle, signaling, tool dispatch, hot-reload
• Praetorium.Bridge.CopilotProvider — agent provider backed by the GitHub Copilot SDK
• Praetorium.Bridge.Web — Blazor dashboard with a configuration editor, prompt editor, live session view, and a Config Agent that edits the JSON for you

The core library is built around replaceable abstractions (IAgentProvider, IAgentSession, ISessionStore, ISignalRegistry, IConfigurationProvider, IBridgeHooks) so you can swap in a different LLM backend, persistent session store, or alternate config source.

The schema for praetorium-bridge.json is in praetorium-bridge.schema.json (drop it into your editor's JSON schema settings for autocomplete). The full design — session modes, signaling contracts, prompt templating, the lot — is in praetorium-bridge-design.md.

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Roadmap

For 0.2+:

• More IAgentProvider implementations (Anthropic, OpenAI, Azure OpenAI, local models)
• Dashboard authentication

Contributions, bug reports, and design feedback are welcome.

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License

See LICENSE.txt.