Hydrate for GitHub Copilot — install in five minutes

After this page: the @hydrate participant is available in Copilot Chat, the hydrate_recall and hydrate_compress language model tools are auto-invoked by Copilot when relevant, and memory from your Claude Code and Codex sessions is accessible inside VS Code.

Prerequisites

• Hydrate installed (hydrate doctor all-green). See Free install.
• VS Code 1.90+ with the GitHub Copilot extension installed and active.

Install

hydrate install-vscode

This runs code --install-extension <vsix> using the hydrate.vsix that ships with the Hydrate release. Output:

✓ VS Code extension installed: sedasoft.hydrate

Alternatively, install manually from within VS Code: open the Extensions panel, search for Hydrate, install sedasoft.hydrate.

After installation, reload VS Code (or run Developer: Reload Window from the command palette).

Verify

Open a Copilot Chat panel and type:

@hydrate /recall auth middleware

Expected: a response drawing from your Hydrate memory — prior decisions, facts, and session summaries related to auth middleware. If you have no sessions captured yet, the response will say so; run a Claude Code session first.

To confirm the extension is active:

1. Open the command palette (Cmd+Shift+P / Ctrl+Shift+P).
2. Run Hydrate: Open Dashboard — your local dashboard should open in a browser tab.

What you get

@hydrate chat participant

A dedicated Copilot Chat participant with three commands:

Use @hydrate /recall when you remember you worked on something before but do not remember the details. Example:

@hydrate /recall why we chose postgres over sqlite for the session store

Language model tools (auto-invoked)

Two tools are registered as LM tools, meaning Copilot can invoke them automatically without you using @hydrate:

hydrate_recall — invoked when Copilot detects you are referencing past work. Input: a short topic phrase. Output: relevant facts and session summaries from your Hydrate store. Copilot uses this when you ask things like "what did we decide about X?" or "why is Y configured this way?"

hydrate_compress — invoked when Copilot needs to read a large document (README, ARCHITECTURE.md, vendor page) that would exceed the context window. Hydrate compresses it to a dense semantic summary first. Returns the compressed form with an estimate of tokens saved.

hydrate_read_file — reads a workspace file, automatically routing through hydrate_compress when the file is large. Copilot uses this instead of reading large files directly.

VS Code commands

Accessible from the command palette (Cmd+Shift+P):

Cross-runtime memory

Facts from your Claude Code and Codex sessions are immediately available in Copilot. No sync step needed — all three runtimes read from the same ~/.hydrate/data.db.

Example flow:

1. In a Claude Code session, pin a fact: hydrate canon add "always use structured logging, never fmt.Println".
2. Open VS Code with the same project.
3. In Copilot Chat, ask Copilot about logging. It auto-invokes hydrate_recall and injects the pinned fact before responding.

Copilot Chat vs inline completions

Hydrate integrates with Copilot Chat (the panel-based assistant), not with inline completions. VS Code does not expose third-party APIs for inline completion context. The token savings from hydrate_compress apply to Chat turns where Copilot would otherwise send a large document as raw context.

Measured token savings

In two measurement passes (Hydrate's own repo and an unrelated codebase):

Methodology and raw data: docs/measurement/2026-04-21-copilot-savings.md.

Environment variables

The extension reads the same variables as the CLI:

For enterprise installs where the server is not on localhost, set HYDRATE_CONTEXT_API in VS Code's settings.json:

{
  "hydrate.serverUrl": "http://192.168.1.100:8095"
}

What changed on your machine

The extension communicates with the already-running hydrate-server — no new daemon is started.

Troubleshooting

Next steps

• Claude Code integration — the memory substrate Copilot draws from
• Codex integration — another client sharing the same facts
• Pro install — unlock Hydration Packs to export/import project memory