Core Context

This repository prototypes the path from shared Cursor extensions to native Cursor plugins with versioned context packs and semantic MCP indexing. Available extensions are defined in installer/extensions.json, their committed Cursor primitives and context files live in installer/payload, and machine-installed state is tracked separately in ~/.extensions/extensions.json.

The catalog and installed registry intentionally have different lifecycles:

• pulling a commit can add or change available payloads without installing them
• installing or uninstalling changes only the current machine's registry
• the installed set persists over time and is reconciled into each configured clone
• updating applies newer committed payload files only to extensions already installed

Cursor plugin migration

Extensions are precursors to Cursor plugins: both package agents, commands, hooks, rules, and skills, but extensions additionally own versioned CONTEXT/ files that are installed, linked, and indexed alongside those primitives.

The intended next step is migration to native Cursor plugins once the design for linking a plugin to its corresponding context pack—and keeping that pack's semantic index current—is settled. Until then, the extension catalog, installed registry, and context MCP service make that relationship explicit and testable.

Architecture and roadmap

This project deliberately separates version-controlled extension availability from machine-local installation. That distinction, the deployed filesystem layout, and the Context MCP runtime are documented in Architecture.

The Roadmap describes the milestones needed to harden the prototype and evaluate a migration to native Cursor plugins. It presents several design approaches rather than treating the native-plugin integration as a pre-decided implementation.

Setup

Prerequisites:

• POSIX shell utilities (cp, find, ln, mv)
• Python 3.11+ and uv
• Docker Engine with Docker Compose v2
• Cursor's agent CLI, used by setup to enable the user-level MCP registration

From a clone, run:

./installer/setup.sh
uv sync --all-groups

The setup script installs CORE, reconciles extensions already recorded in the machine registry, builds and starts the local core-context container, and registers http://127.0.0.1:8989/mcp in ~/.cursor/mcp.json. It preserves unrelated user-level MCP registrations and enables core-context with agent mcp enable core-context. It does not automatically install every available payload. Restart Cursor or reload its MCP servers after the first registration so the IDE connects to the new user-level server. Consequently, a newly cloned project picks up the machine's existing extension set, while a new catalog entry remains available until explicitly installed.

The installer synchronizes ~/CORE in place so the running container retains its bind mount and the watcher can reindex changes without a restart. It backs up managed symlinks and replaced extension payloads beneath ~/.local/state/cursor-symlink-ext-context-mcp/backups/<timestamp>/. Preview changes without writing anything:

./installer/setup.sh --dry-run

For an isolated setup, pass both locations explicitly:

./installer/setup.sh --home /tmp/symlink-home --project-root "$PWD"

Installed layout

installer/setup.sh deploys:

• installer/payload/CORE to ~/CORE
• CONTEXT in the repository as a symlink to ~/CORE/CONTEXT
• previously installed extensions from the machine registry, when reconciling a new clone

It also creates the CORE and extension .cursor symlinks. The sole hook configuration is ~/CORE/.cursor/hooks.json, exposed to the project as .cursor/hooks.json; installed extension hooks are assembled from the catalog.

Inspect catalog and machine state at any time:

python3 installer/manage_extensions.py list --status all
python3 installer/manage_extensions.py list --status available
python3 installer/manage_extensions.py list --status installed

These commands derive their output from the current catalog and machine registry; the documentation does not define a fixed extension list.

Extension lifecycle

Use /extension-list to inspect every catalog payload and whether it is installed on the current machine.

Use /extension-create to add only committed catalog metadata and payload files. It does not modify the home directory, project symlinks, ignore files, or installed registry.

Use /extension-install to select an available payload through AskQuestion. Installation:

• copies it to ~/.extensions/extensions/<NAME>
• records it in ~/.extensions/extensions.json
• creates .cursor/*/ext/<NAME> and CONTEXT/ext/<NAME> symlinks
• adds managed blocks to .gitignore and .cursorignore
• rebuilds the single installed hook configuration
• signals the running context index to refresh

Use /extension-uninstall to select an installed extension through AskQuestion. It removes the managed links and ignore blocks, backs up the home-directory extension, updates the registry and hooks, and leaves the committed payload intact.

Use /extension-update after pulling committed payload changes. It only copies the payloads for currently installed extensions into their existing home directories and signals the context index. It does not change installation state, links, ignore files, or registry entries.

The same operations are available directly:

python3 installer/manage_extensions.py list --status available
python3 installer/manage_extensions.py install <NAME>
python3 installer/manage_extensions.py uninstall <NAME>
python3 installer/manage_extensions.py update

Context MCP server

The local MCP server semantically searches Markdown in ~/CORE/CONTEXT and its extension context links. It uses FastMCP, sentence-transformers, and a persistent index at ~/.local/state/cursor-symlink-ext-context-mcp/context-index.json. It indexes only the installed home layout: ~/CORE/CONTEXT and ~/CORE/CONTEXT/ext/<NAME> symlinks into ~/.extensions/extensions/<NAME>/CONTEXT. Committed installer/payload/extensions/ directories are catalog sources and are never indexed directly.

core-context runs as a Docker Compose-managed Streamable HTTP service at http://127.0.0.1:8989/mcp. Docker restarts it with unless-stopped; the installer registers it once at the user level in ~/.cursor/mcp.json, so it is available to every Cursor workspace on this machine. The service binds only to loopback on the host. Cursor connects to the service but does not launch it. The container uses the CPU-only PyTorch distribution, limits embedding work to two CPU threads, and is capped at 2 GiB of memory, two CPUs, and 128 processes to keep the local service from monopolizing the machine. The service runs in stateful Streamable HTTP mode: FastMCP issues an Mcp-Session-Id during initialization and clients reuse it on later requests. The session is transport-managed and contains no persisted search history.

Use the installer-managed lifecycle script when needed:

./installer/context_mcp.sh status
./installer/context_mcp.sh logs
./installer/context_mcp.sh refresh
./installer/context_mcp.sh restart
./installer/context_mcp.sh rebuild

GET http://127.0.0.1:8989/health reports process liveness; /ready reports that the initial index and embedding model are ready. The initial connection may take longer while the default sentence-transformer model is downloaded into the Docker volume. Later changes to CORE or extension context files are re-indexed by the file watcher after a short debounce interval. Search, read, and status calls use the in-memory index and do not rescan the corpus. Extension install and uninstall update the CONTEXT/ext/<NAME> links; update refreshes the installed extension content. All three operations touch .index-refresh, which schedules a debounced rescan of the installed context set.

The server exposes:

• context_search(query, limit=5, source=None) for semantic search. source is an optional, case-insensitive exact source name such as CORE, PRODUCT, QA, or SUPPORT; it is not an extension category. Results contain path, source, title, score, and a snippet. When mixed results are closely ranked, an elicitation-capable client may offer an optional source or topic focus and rerun the search. Declining, cancelling, or lacking elicitation support returns the original ranked results.
• context_read(path) for an indexed document
• context_status() for indexed document count, sources, and active embedding model (all-MiniLM-L6-v2 by default), readiness, service URL, and session mode

Every MCP tool call is written to the container's stderr as a JSON Line tagged with server: "core-context" and containing complete arguments, responses, and errors. These audit logs can include full context documents and queries; treat ./installer/context_mcp.sh logs output as sensitive. Search records also include the clarification outcome (not_ambiguous, accepted, decline, cancel, or unavailable), which can reveal that a client was offered focus.

Use /context-search for an explicit shared-context lookup. The installed CORE context-search skill also applies automatically when a request depends on shared conventions or an installed extension's context. Both check context_status first, search with context_search, and use context_read only for a selected result's complete content.

Developing extensions

/extension-create writes new extension samples to installer/payload/extensions/<NAME> and adds metadata to installer/extensions.json. Run /extension-install when that payload should be materialized for the current machine and project. Existing installations do not change merely because a payload is added or committed.

Production hosting

The local container is intentionally loopback-only and is not a production deployment. For production, host Streamable HTTP behind TLS and authentication, then register Cursor with that remote URL. Keep the service's context corpus fresh by periodically reindexing and embedding changed documents; this is not model training.

Verification

uv run ruff check .
uv run python -m pytest
sh -n installer/setup.sh
sh -n installer/context_mcp.sh
python3 -m json.tool installer/extensions.json
HOST_HOME="$HOME" docker compose -f installer/docker/docker-compose.yml config

With core-context connected in Cursor, verify the live index and installed extension results by checking context_status, then searching for a known extension topic. For example, context_search("boundary cases quality tests") should return a QA result when QA is installed.