| Filename | Latest commit message | Latest commit date |
|---|---|---|
e5e8f117e8Registers a sending middleware on each inner server that intercepts all outgoing messages and routes them through the front session using a session-swapped request wrapper. Replaces the previous proxy client handler approach which dropped log messages in stateless mode. ## Motivation and Context Tool handlers in variant servers use req.Session (the inner session) to send notifications. Previously, log messages were silently dropped in stateless mode because the inner session is not aware of the front session. This change injects the sendingMethodHandler from the frontSession into the context and adds a sending middleware to redirect all sending requests to the frontSession handler directly. A few considerations in this implementation: * Having frontSession in the context allows notifications to be sent to the correct frontSession, when the same backend session could be used by multiple front sessions. * This solution will work for synchronous notifications that happen within the same context (progress, log, sampling, elicitation) but not working for asynchronous notifications (tool list changed, resource updated etc), because asynchronous notifications are sent with a new context. * All the operations before the sending method will still happen in the backend. Most notable impact is in stateless mode, requests from one client could change the log level for other clients. For this reason, I default the logging level to debug for now. * This implementation relies on the MCP Go SDK sendingMethodHandler taking a generic `Request` not one that tied to specific function. Based on the current SDK implementation this is unlikely to change. * The same generic method forwarding mechanism could work for receiving methods too, but with some caveat. That can be addressed in separate PR. ## How Has This Been Tested? TestNotificationDelivery — verifies progress and log messages arrive at the front clients with multiple clients making concurrent request. New tests added for context preservation that was added in https://github.com/modelcontextprotocol/experimental-ext-variants/pull/6. Context preservation is required to make the notification forwarding work anyway. Since we use the context to carry frontSession handler to the backend session. All existing tests pass ## Breaking Changes None. Tool handlers continue to use req.Session normally. ## Types of changes Bug fix (non-breaking change which fixes an issue) |
||
| .. | ||
| main.go | ||
| README.md | ||
| tools.go | ||
Research Assistant
A variant-aware MCP server that manages context budget by providing the same research tools (search_papers, get_paper, summarize) at different verbosity levels.
Each tool sends progress notifications and log messages as it works, simulating a deep-research workflow where the client can observe each step (e.g. "Searching arXiv", "Resolving references", "Generating summary").
Patterns demonstrated: Context budget management with description verbosity control, notification streaming.
Variants
| Variant | Verbosity | Status | Use Case |
|---|---|---|---|
deep-research |
Multi-paragraph with usage examples | Stable | Literature reviews, large context windows |
quick-lookup |
Single-sentence descriptions | Stable | Fast Q&A, limited token budgets |
synthesis |
Balanced, moderate detail | Experimental | Report generation workflows |
All three variants expose the same three tools with the same behavior — only the description detail level differs.
Custom Ranking
Clients send a "contextSize" hint ("verbose", "compact", or "standard"). The ranking function matches the hint to the appropriate variant, falling back to priority order.
Run
go run ./examples/server/research
The server listens on http://localhost:8080.