diff --git a/docs/installation.md b/docs/installation.md
index 38c4d7966..75da703cf 100644
--- a/docs/installation.md
+++ b/docs/installation.md
@@ -129,6 +129,150 @@ Setup pins package-runner MCP registrations to the exact installed REA version,
 installs the matching skill and on-demand references in the same plan, and adds
 `startup_timeout_sec = 30` for Codex and Grok Build.
 
+## Limit REA to one project or agent profile
+
+Setup registers REA for the whole client. For Claude Code it writes
+`mcpServers.rea` in `~/.claude.json` and installs the bundled skill under
+`~/.claude/skills`, so every project that Claude Code opens can call REA. To
+offer REA's tools only where they're wanted, use one of the routes below.
+
+Both routes control which sessions discover REA's MCP server and skill. They
+leave shell commands, filesystem access and network access available. An agent
+under the same OS account can run `rea` from `PATH` or `npx` and read other
+profiles and REA output. For clean-room separation, use an implementation
+environment with filesystem and network restrictions that prevent reading or
+fetching REA, the target and analysis output, including through shared
+installations and package registries. A separate account or container must
+enforce those restrictions.
+
+For Claude Code, check existing default-profile state before choosing either
+route. Setup is additive: a previous user-level REA registration and personal
+skill remain active in other projects. Back up the default configuration and
+REA skill first, then, with `CLAUDE_CONFIG_DIR` unset, remove the REA user
+registration with `claude mcp remove --scope user rea` and remove the known
+REA-installed `~/.claude/skills/reverse-engineer-anything` directory. Preserve
+unrelated registrations and skills. `rea uninstall` applies to other clients
+as well, so it is broader than this Claude-only migration.
+
+**A separate Claude Code profile.** Claude Code keeps settings, skills and session
+history under `CLAUDE_CONFIG_DIR`. Setup follows the same
+variable: it writes the registration to `$CLAUDE_CONFIG_DIR/.claude.json` and
+the skill to `$CLAUDE_CONFIG_DIR/skills`.
+
+```bash
+CLAUDE_CONFIG_DIR=~/.claude-rea npx rea-agents setup --client claude_code
+CLAUDE_CONFIG_DIR=~/.claude-rea claude
+```
+
+A new profile may need authentication. Console sign-ins without an API key are
+stored outside `CLAUDE_CONFIG_DIR`; see
+[Claude Code authentication](https://code.claude.com/docs/en/authentication#log-in-with-multiple-accounts).
+Sessions started without the variable use the default profile's registration,
+skill and history.
+
+Inline assignments apply only to that command. Keep the same prefix for every
+profile check, setup rerun, update, or removal; bare commands use the current
+environment and can otherwise inspect or recreate default-profile state:
+
+```bash
+CLAUDE_CONFIG_DIR=~/.claude-rea claude mcp list
+CLAUDE_CONFIG_DIR=~/.claude-rea npx rea-agents doctor --client claude_code --skill --json
+CLAUDE_CONFIG_DIR=~/.claude-rea npx -y rea-agents@latest setup --client claude_code --dry-run
+```
+
+After reviewing an update plan, rerun that same prefixed setup command without
+`--dry-run` and approve its exact changes. Profile removal likewise needs the
+prefix on `claude mcp remove --scope user rea` and any `rea uninstall` command;
+keep the broader client scope of uninstall in mind. Restart the selected
+profile after changing its pinned registration.
+
+`claude mcp remove` removes only the registration. To remove REA from this
+profile without running the broader uninstall flow, first back up the profile's
+REA-managed skill directory, then remove
+`$CLAUDE_CONFIG_DIR/skills/reverse-engineer-anything` as well. Keep other skills
+in the profile intact.
+
+The commands above use POSIX shell assignment syntax. In native Windows
+PowerShell, select the profile for the whole setup/launch/check session and
+restore the previous selection afterward:
+
+```powershell
+$previousClaudeConfigDir = $env:CLAUDE_CONFIG_DIR
+try {
+  $env:CLAUDE_CONFIG_DIR = Join-Path $HOME ".claude-rea"
+  npx rea-agents setup --client claude_code
+  claude mcp list
+  npx rea-agents doctor --client claude_code --skill --json
+  npx -y rea-agents@latest setup --client claude_code --dry-run
+  # After reviewing the plan, repeat setup without --dry-run and approve it.
+  claude
+  # Profile removal, when intended, also belongs inside this selected scope:
+  # claude mcp remove --scope user rea
+} finally {
+  if ($null -eq $previousClaudeConfigDir) {
+    Remove-Item Env:CLAUDE_CONFIG_DIR -ErrorAction SilentlyContinue
+  } else {
+    $env:CLAUDE_CONFIG_DIR = $previousClaudeConfigDir
+  }
+}
+```
+
+Use PowerShell for these Windows examples rather than pasting POSIX assignments
+into cmd.exe. Keep profile updates, readiness checks and removal inside the
+same selected environment; the `finally` block restores the previous profile
+or unsets the variable when it was absent.
+
+**One project.** Install without configuring Claude Code: use the curl
+installer's `--no-setup`, or run setup only for other clients. Then register
+REA from the project directory at Claude Code's local scope.
+
+This route uses the default Claude profile. Keep `CLAUDE_CONFIG_DIR` unset for
+the entire local lifecycle: registration, backup, listing, version replacement
+and removal. In POSIX shells run `unset CLAUDE_CONFIG_DIR`; in PowerShell run
+`Remove-Item Env:CLAUDE_CONFIG_DIR -ErrorAction SilentlyContinue` before these
+commands. Record an existing selection first if you intend to restore it after
+finishing. The configuration path below is the default profile's
+`~/.claude.json`; a different active profile uses its own config root instead.
+
+Register with the variable unset:
+
+<!-- x-release-please-start-version -->
+
+```bash
+claude mcp add --scope local rea -- npx -y rea-agents@6.4.0 mcp
+```
+
+On native Windows, use the same project directory and wrap the package-runner
+shim so the stdio client can launch it:
+
+```powershell
+claude mcp add --scope local rea -- cmd.exe /d /c npx -y rea-agents@6.4.0 mcp
+```
+
+<!-- x-release-please-end -->
+
+Local scope stores the entry under that directory's path in `~/.claude.json`,
+so other projects don't load it. This route doesn't install the bundled skill.
+Avoid `--scope project`, which writes `.mcp.json` into the repository where it
+can be committed or copied. `rea doctor` and `rea uninstall` read only the
+user-level entry, so they don't report or remove a local-scope registration;
+remove it with `claude mcp remove --scope local rea` from the same directory.
+`rea update` doesn't refresh it either, so it stays on the version it names.
+To move it to a newer release, first back up the project entry in
+`~/.claude.json` and record its environment and other metadata. In particular,
+preserve caller-selected overrides such as `REA_MCP_INPUT_SCHEMA_PROFILE` and
+`REA_MCP_MAX_RESPONSE_BYTES`. Run `claude mcp remove --scope local rea` from the
+same directory, then recreate it with the platform-appropriate command above
+and the new version. Reapply every recorded environment value with Claude
+Code's `mcp add --env NAME=value` options and restore any other retained entry
+metadata before restarting the project session. Removal and re-addition do not
+preserve these values automatically. Running setup for Claude Code instead
+would add a user-level entry for every project.
+
+Check the separate profile with the prefixed `claude mcp list` above and compare
+with the default profile with `CLAUDE_CONFIG_DIR` unset. For local scope, run
+`claude mcp list` from the selected project and again from another project.
+
 ## Check readiness for your task
 
 Run `rea doctor` when you need diagnosis. It reads host prerequisites and agent