tandemlisted

# Tandem — Collaborative Document Editor > **Scope:** This skill teaches Claude Code how to use Tandem effectively. Tandem's integration contract is MCP, and **Claude is the default integration** per [ADR-038](https://github.com/bloknayrb/tandem/blob/master/docs/decisions.md#adr-038-mcp-first-integration-policy-claude-as-default-integration). This skill is a Claude-Code-specific resource shipped via the npm `skills/` folder; other MCP clients receive the tool descriptions directly through MCP and don't need this file. Tandem lets you annotate and edit documents alongside the user in real time. The user sees your changes in the editor; you interact via the tandem_* MCP tool suite. ## Hard Rules These prevent the most common failures. Follow them always. 1. **Resolve before mutating.** Call `tandem_resolveRange` (or `tandem_search`) to get offsets before calling `tandem_edit` or `tandem_comment`. Never compute offsets by counting characters in previously-read text — they go stale when the user edits, and they are not characters: offsets are **UTF-16 code units**, so every emoji or other non-BMP character in the document puts a hand-count off by one more, even on text you just read. An offset that lands between the two halves of a surrogate pair is refused with `INVALID_RANGE` and `details.reason: "surrogate"`. 2. **Pass `textSnapshot`.** Include the matched text as `textSnapshot` on mutations and annotations. If the text moved, the server returns `RANGE_MOVED` with relocat