# lsp/ - LSP capability family

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The language-server capability seam: an abstract LSP interface, a generic stdio provider, and the model-facing `lsp` tool. All **product** packages.

| Package | Role | ctx key |
|---|---|---|
| `lsp/` | Abstract LSP seam (provider registry by branded id + extension mapping, per-query selection, vocabulary, `LspError`) | `ctx.lsp` |
| `lsp-local/` | Generic multi-server local backend (spawn, JSON-RPC, transient-open queries) | (registers providers on `ctx.lsp`) |
| `tool-lsp/` | Model-facing `lsp` tool (four operations, one-based UTF-16 cursor coordinates) | (registers on `ctx.tools`) |

The interface lives at `lsp/lsp/`. The seam exposes exactly four semantic operations — `goToDefinition`, `findReferences`, `goToImplementation`, `hover` — and no generic JSON-RPC escape hatch, so a provider swap does not change how the model asks for navigation and no protocol payload or unreviewed mutation reaches the model contract. Providers register **capabilities**, not tools; `tool-lsp` is the only owner of the model-facing name, schema, prompt guidance, and presentation.

See the [LSP capability seam Agent Note](../../.agents/notes/implemented/architecture/2026-07-15-lsp-capability-seam.md) for the design rationale, including why documents open transiently per query, why the local host reads through Node APIs rather than `ctx.fs`, and why extension ownership is exclusive within one runtime.