Seren Loci
Keyed, deterministic coding/logic memory for GitHub Copilot. Seren Loci connects Copilot to a locally-hosted left brain - addressable facts that survive across sessions, with exactly one live value per key - without sending anything to a third party.
Where Seren Memory is the right brain (fuzzy, episodic recall), Seren Loci is the left brain: you ask for an address, you get the thing.
How it works
Seren Loci runs a small Python service on your machine (or your team's internal server) backed by a single SQLite file - no daemon, no second process, runs on a 4GB laptop. The extension registers a set of Copilot language model tools that Copilot calls automatically to read and write facts during normal conversations. Everything lives in a local database you own.
The facts model
Every fact is an addressable locus:
{ project, key, value, why }
| Concept |
What it means |
| key |
The address - a dotted identifier like posh.brace_style or cuda.no_vmm. |
| value |
The fact itself. |
| why |
The hard-won reason it's shaped this way. Searchable - "that CUDA thing" finds a fact whose reason mentions CUDA. |
| project |
Scope. * = fundamentals (cross-project truths like camelCase is life); a concrete name = a per-project convention. |
Strict supersede. Set a new value for a key and the old one is superseded - kept as history, never blended. The database physically enforces one live value per (project, key). A fact you replace doesn't get vibed together with the old one; it cleanly takes over, and the old value stays as an audit trail.
Three ways in, cheapest first
- Exact - you know the key, you get the live value deterministically.
- Lexical - FTS5 full-text over key/value/why when you sort of remember the words. No GPU, no embeddings.
- Vector (optional) - a semantic finder for the associative jump, lit up only when an embedder is configured (
pip install 'seren-loci[vector]').
Requirements
- GitHub Copilot (Chat) - the extension registers Copilot language model tools; Copilot Chat is required to use them.
- SerenLoci service - the Python backend, from the SerenLoci repository.
Quick start
1. Install the SerenLoci service
pip install 'seren-loci[mcp]' # add ,vector for the semantic finder
The floor (exact + lexical) needs no extras and no torch.
2. Configure the extension
Open Settings (Ctrl+Shift+P → Open User Settings) and set:
| Setting |
Default |
Description |
serenLoci.endpoint |
http://localhost:7422 |
Base URL of the SerenLoci service |
serenLoci.startCommand |
python -m seren_loci |
Command used by Start Service |
serenLoci.suppressStartPrompt |
false |
Suppress the startup "not reachable" prompt |
3. Set your bearer token (if auth is enabled)
Run Ctrl+Shift+P → Seren Loci: Set Bearer Token. The token is stored in the OS keychain, never in settings files.
4. Check the status bar
The $(database) Loci item in the bottom-right shows service health at a glance: Loci ✓ reachable, Loci ✗ not (click to retry).
Once the service is running, Copilot can use these automatically. You can also reference them directly in chat with #serenSetFact, #serenSearch, etc.
| Tool |
Reference |
What it does |
| Set Fact |
#serenSetFact |
Set or replace a fact. Strict supersede - the old value becomes history, never blended. Always include why. |
| Get Fact |
#serenGetFact |
The live value for a (project, key), deterministically. Returns found: false for a never-set or retired key. |
| Search Loci |
#serenSearch |
Find facts when you don't know the exact key. Exact match leads at score 1.0; otherwise the finder (vector or lexical) runs. |
| Forget Fact |
#serenForgetFact |
Retire a key's live value - a flag, not a scalpel. Kept as history, key free to set again. |
| Fact History |
#serenHistory |
Every value a key has ever held, newest first - "what did we used to think, and why did it change". |
| List Facts |
#serenListFacts |
Survey a whole scope - a project, or everything. |
There's no consolidator, draft gate, or tiers here - that's the right brain. Loci is deterministic facts, full stop.
Commands
Open the Command Palette (Ctrl+Shift+P) and search Seren Loci:
| Command |
What it does |
| Seren Loci: Set Bearer Token |
Store your auth token in the OS keychain |
| Seren Loci: Check Service Health |
Ping the service and update the status bar |
| Seren Loci: Start Service |
Launch the service using serenLoci.startCommand |
MCP transport (optional)
The service also exposes an MCP HTTP endpoint at /mcp/ (install with the [mcp] extra). This lets a model connect directly via the VS Code or Visual Studio MCP client config without the extension, or use both at once.
.vscode/mcp.json (VS Code):
{
"servers": {
"seren-loci": {
"type": "http",
"url": "http://localhost:7422/mcp/",
"headers": {
"Authorization": "Bearer YOUR_TOKEN"
}
}
}
}
Omit the headers block if you didn't set a bearer token. The endpoint exposes the same six tools: set_fact, get_fact, search_loci, forget_fact, fact_history, list_facts.
Source & issues
github.com/ChadRoesler/SerenLoci
