feat(cli): install command auto-writes ~/.claude.json MCP entry

The previous flow printed a \`claude mcp add ...\` command and asked
users to paste it. That's 2 steps, a typo surface, and a point of
user dropoff. Replace with direct read-modify-write of ~/.claude.json.

install:
- preflights bun on PATH (clear error + Bun.com link if missing)
- verifies the MCP entry file exists on disk
- reads ~/.claude.json (empty object if absent)
- adds/updates mcpServers.claudemesh with resolved absolute path
- writes back with 0600 perms, creates parent dir if needed
- read-back verification (bails loudly if post-write state is wrong)
- idempotent: re-running returns "unchanged" if entry already matches
- preserves existing mcpServers entries + other top-level config keys

uninstall:
- removes the claudemesh entry if present
- no-ops cleanly when entry or config file doesn't exist
- doesn't touch anything else

Both print a clear post-action hint: "Restart Claude Code to load
the MCP server. Then join a mesh with claudemesh join <invite-link>".

verified locally with HOME=/tmp/fake-home:
- fresh install → ✓ added, config emitted correctly
- re-install → ✓ unchanged (idempotent)
- install alongside existing "other-mcp" entry → both preserved,
  plus unrelated top-level keys kept verbatim
- uninstall → ✓ removed, claudemesh gone, other entries intact
- uninstall again → · not present (no error)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/cli/src/commands/install.ts

@@ -1,36 +1,173 @@
 /**
- * `claudemesh install` — print Claude Code MCP registration instructions.
+ * `claudemesh install` / `uninstall` — manage Claude Code MCP registration.
  *
- * In the v1 flow, users copy-paste a `claude mcp add ...` command.
- * Later we'll auto-write the MCP entry to ~/.claude.json and hooks
- * to ~/.claude/settings.json (mirroring claude-intercom's installer).
+ * install:
+ *   1. Preflight: bun is on PATH, this package's MCP entry is on disk.
+ *   2. Read ~/.claude.json (or empty object if absent).
+ *   3. Add/update `mcpServers.claudemesh` with the resolved entry path.
+ *   4. Write back with 0600 perms.
+ *   5. Verify via read-back, print success.
+ *
+ * uninstall:
+ *   1. Read ~/.claude.json (bail if missing).
+ *   2. Delete `mcpServers.claudemesh` if present.
+ *   3. Write back.
+ *
+ * Both are idempotent — re-running install is a no-op if the entry is
+ * already correct, and uninstall is a no-op if no entry exists.
  */
 
+import {
+  chmodSync,
+  existsSync,
+  mkdirSync,
+  readFileSync,
+  writeFileSync,
+} from "node:fs";
+import { homedir, platform } from "node:os";
+import { dirname, join, resolve } from "node:path";
 import { fileURLToPath } from "node:url";
-import { dirname, resolve } from "node:path";
+
+const MCP_NAME = "claudemesh";
+const CLAUDE_CONFIG = join(homedir(), ".claude.json");
+
+type McpEntry = {
+  command: string;
+  args?: string[];
+  env?: Record<string, string>;
+};
+
+function readClaudeConfig(): Record<string, unknown> {
+  if (!existsSync(CLAUDE_CONFIG)) return {};
+  const text = readFileSync(CLAUDE_CONFIG, "utf-8").trim();
+  if (!text) return {};
+  try {
+    return JSON.parse(text) as Record<string, unknown>;
+  } catch (e) {
+    throw new Error(
+      `failed to parse ${CLAUDE_CONFIG}: ${e instanceof Error ? e.message : String(e)}`,
+    );
+  }
+}
+
+function writeClaudeConfig(obj: Record<string, unknown>): void {
+  mkdirSync(dirname(CLAUDE_CONFIG), { recursive: true });
+  writeFileSync(
+    CLAUDE_CONFIG,
+    JSON.stringify(obj, null, 2) + "\n",
+    "utf-8",
+  );
+  try {
+    chmodSync(CLAUDE_CONFIG, 0o600);
+  } catch {
+    /* windows has no chmod */
+  }
+}
+
+/** Check `bun` is on PATH — OS-agnostic. */
+function bunAvailable(): boolean {
+  const which =
+    platform() === "win32"
+      ? Bun.spawnSync(["where", "bun"])
+      : Bun.spawnSync(["sh", "-c", "command -v bun"]);
+  return which.exitCode === 0;
+}
+
+/** Absolute path to this CLI's entry file. */
+function resolveEntry(): string {
+  const here = fileURLToPath(import.meta.url);
+  return resolve(dirname(here), "..", "index.ts");
+}
+
+function buildMcpEntry(entryPath: string): McpEntry {
+  return {
+    command: "bun",
+    args: [entryPath, "mcp"],
+  };
+}
+
+function entriesEqual(a: McpEntry, b: McpEntry): boolean {
+  return (
+    a.command === b.command &&
+    JSON.stringify(a.args ?? []) === JSON.stringify(b.args ?? [])
+  );
+}
 
 export function runInstall(): void {
-  // Resolve the path to this package's own index.ts so the generated
-  // command points at the right binary even when installed globally.
-  const here = fileURLToPath(import.meta.url);
-  const entry = resolve(dirname(here), "..", "index.ts");
+  console.log("claudemesh install");
+  console.log("------------------");
 
-  console.log("claudemesh — MCP registration");
-  console.log("------------------------------");
+  if (!bunAvailable()) {
+    console.error(
+      "✗ `bun` is not on PATH. Install Bun first: https://bun.com",
+    );
+    process.exit(1);
+  }
+
+  const entry = resolveEntry();
+  if (!existsSync(entry)) {
+    console.error(`✗ MCP entry not found at ${entry}`);
+    process.exit(1);
+  }
+
+  const cfg = readClaudeConfig();
+  const servers =
+    ((cfg.mcpServers ??= {}) as Record<string, McpEntry>) ?? {};
+  const desired = buildMcpEntry(entry);
+  const existing = servers[MCP_NAME];
+  let action: "added" | "updated" | "unchanged";
+  if (!existing) {
+    servers[MCP_NAME] = desired;
+    action = "added";
+  } else if (entriesEqual(existing, desired)) {
+    action = "unchanged";
+  } else {
+    servers[MCP_NAME] = desired;
+    action = "updated";
+  }
+  cfg.mcpServers = servers;
+
+  writeClaudeConfig(cfg);
+
+  // Read-back verification.
+  const verify = readClaudeConfig();
+  const verifyServers = (verify.mcpServers ?? {}) as Record<string, McpEntry>;
+  const stored = verifyServers[MCP_NAME];
+  if (!stored || !entriesEqual(stored, desired)) {
+    console.error(
+      `✗ post-write verification failed — ${CLAUDE_CONFIG} may be corrupt`,
+    );
+    process.exit(1);
+  }
+
+  console.log(`✓ MCP server "${MCP_NAME}" ${action}`);
+  console.log(`  config:  ${CLAUDE_CONFIG}`);
+  console.log(`  command: bun ${entry} mcp`);
   console.log("");
-  console.log("Register the MCP server with Claude Code:");
-  console.log("");
-  console.log(`  claude mcp add claudemesh --scope user -- bun ${entry} mcp`);
-  console.log("");
-  console.log("Or if installed globally:");
-  console.log("");
-  console.log(`  claude mcp add claudemesh --scope user -- claudemesh mcp`);
-  console.log("");
-  console.log(
-    "After registering, restart Claude Code. Then join a mesh with:",
-  );
+  console.log("Restart Claude Code to load the MCP server.");
+  console.log("Then join a mesh:");
   console.log("");
   console.log("  claudemesh join <invite-link>");
-  console.log("");
-  console.log("(Auto-install of hooks + MCP entry will ship in a later step.)");
+}
+
+export function runUninstall(): void {
+  console.log("claudemesh uninstall");
+  console.log("--------------------");
+  if (!existsSync(CLAUDE_CONFIG)) {
+    console.log(`· no ${CLAUDE_CONFIG} — nothing to remove`);
+    return;
+  }
+  const cfg = readClaudeConfig();
+  const servers = cfg.mcpServers as
+    | Record<string, McpEntry>
+    | undefined;
+  if (!servers || !(MCP_NAME in servers)) {
+    console.log(`· MCP server "${MCP_NAME}" not present — nothing to remove`);
+    return;
+  }
+  delete servers[MCP_NAME];
+  cfg.mcpServers = servers;
+  writeClaudeConfig(cfg);
+  console.log(`✓ MCP server "${MCP_NAME}" removed`);
+  console.log("Restart Claude Code to drop the MCP connection.");
 }

apps/cli/src/index.ts

@@ -10,7 +10,7 @@
  */
 
 import { startMcpServer } from "./mcp/server";
-import { runInstall } from "./commands/install";
+import { runInstall, runUninstall } from "./commands/install";
 import { runJoin } from "./commands/join";
 import { runList } from "./commands/list";
 import { runLeave } from "./commands/leave";
@@ -22,7 +22,8 @@ Usage:
   claudemesh <command> [args]
 
 Commands:
-  install         Print Claude Code MCP registration instructions
+  install         Register claudemesh as a Claude Code MCP server
+  uninstall       Remove claudemesh MCP server registration
   join <link>     Join a mesh via invite link (ic://join/...)
   list            Show all joined meshes
   leave <slug>    Leave a joined mesh
@@ -47,6 +48,9 @@ async function main(): Promise<void> {
     case "install":
       runInstall();
       return;
+    case "uninstall":
+      runUninstall();
+      return;
     case "join":
       await runJoin(args);
       return;