diff --git a/cli/node/src/config.ts b/cli/node/src/config.ts
index 91cb76d94..5077d6a61 100644
--- a/cli/node/src/config.ts
+++ b/cli/node/src/config.ts
@@ -143,6 +143,20 @@ export function saveConfig(config: Mem0Config): void {
 
 	fs.writeFileSync(CONFIG_FILE, JSON.stringify(data, null, 2));
 	fs.chmodSync(CONFIG_FILE, 0o600);
+
+	// Propagate api_key to ecosystem touchpoints (Claude plugin env injection,
+	// shell rc exports). Idempotent — updates only EXISTING entries; never
+	// creates new ones. Best-effort: errors swallowed so config.json is
+	// always authoritative, never blocked by plugin-state issues.
+	if (config.platform.apiKey) {
+		try {
+			// eslint-disable-next-line @typescript-eslint/no-require-imports
+			const { syncApiKey } = require("./plugin-sync.js");
+			syncApiKey(config.platform.apiKey);
+		} catch {
+			/* swallow */
+		}
+	}
 }
 
 export function redactKey(key: string): string {
diff --git a/cli/node/src/plugin-sync.ts b/cli/node/src/plugin-sync.ts
new file mode 100644
index 000000000..4c98eabfd
--- /dev/null
+++ b/cli/node/src/plugin-sync.ts
@@ -0,0 +1,115 @@
+/**
+ * Sync the active Mem0 API key into other ecosystem touchpoints.
+ *
+ * Why: the CLI canonical state is ~/.mem0/config.json. MCP servers
+ * (Claude Code plugin, Codex plugin) read MEM0_API_KEY from env or
+ * their own config files. Without a sync, agent-mode bootstrap mints a
+ * new key into config.json but the plugin's MCP keeps using the old
+ * key from env — silent surprise.
+ *
+ * Design:
+ *  - Update ONLY entries that already exist; never create new ones
+ *  - Preserve surrounding content, formatting, other keys
+ *  - Atomic writes (tmp + rename) so a crash mid-write doesn't corrupt
+ *  - Idempotent — re-running with the same key is a no-op
+ *
+ * Targets:
+ *  - ~/.claude/settings.json::env::MEM0_API_KEY (Claude Code env injection)
+ *  - ~/.zshrc / ~/.bashrc `export MEM0_API_KEY="..."` lines
+ *
+ * Out of scope: Codex / Cursor MCP configs and the plugin's own
+ * <plugin-dir>/.api_key file (plugin-managed, different schema).
+ */
+
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+const CLAUDE_SETTINGS = path.join(os.homedir(), ".claude", "settings.json");
+const SHELL_RCS = [
+	path.join(os.homedir(), ".zshrc"),
+	path.join(os.homedir(), ".bashrc"),
+	path.join(os.homedir(), ".bash_profile"),
+];
+
+// Use [ \t]* (not \s*) so a trailing newline at end-of-file is preserved
+// when the MEM0_API_KEY export is the last line of the rc file.
+const RC_LINE_RE =
+	/^([ \t]*export[ \t]+MEM0_API_KEY[ \t]*=[ \t]*)(["']?)([^"'\n]*)(["']?)[ \t]*$/m;
+
+export function syncApiKey(apiKey: string): string[] {
+	if (!apiKey) return [];
+	const updated: string[] = [];
+	if (updateClaudeSettings(CLAUDE_SETTINGS, apiKey)) {
+		updated.push(CLAUDE_SETTINGS);
+	}
+	for (const rc of SHELL_RCS) {
+		if (updateShellRc(rc, apiKey)) updated.push(rc);
+	}
+	return updated;
+}
+
+function updateClaudeSettings(filePath: string, apiKey: string): boolean {
+	if (!fs.existsSync(filePath)) return false;
+	let raw: string;
+	let data: Record<string, unknown>;
+	try {
+		raw = fs.readFileSync(filePath, "utf-8");
+		data = JSON.parse(raw);
+	} catch {
+		return false;
+	}
+	const env = data.env;
+	if (!env || typeof env !== "object" || !("MEM0_API_KEY" in env)) {
+		return false; // no existing entry — don't create one
+	}
+	const envObj = env as Record<string, string>;
+	if (envObj.MEM0_API_KEY === apiKey) return false; // already in sync
+	envObj.MEM0_API_KEY = apiKey;
+	atomicWriteText(filePath, `${JSON.stringify(data, null, 2)}\n`);
+	return true;
+}
+
+function updateShellRc(filePath: string, apiKey: string): boolean {
+	if (!fs.existsSync(filePath)) return false;
+	let text: string;
+	try {
+		text = fs.readFileSync(filePath, "utf-8");
+	} catch {
+		return false;
+	}
+	const match = text.match(RC_LINE_RE);
+	if (!match) return false; // no existing line
+	if (match[3] === apiKey) return false;
+	const newText = text.replace(
+		RC_LINE_RE,
+		(_full, prefix) => `${prefix}"${apiKey}"`,
+	);
+	atomicWriteText(filePath, newText);
+	return true;
+}
+
+function atomicWriteText(filePath: string, content: string): void {
+	const dir = path.dirname(filePath);
+	const tmp = path.join(dir, `.${path.basename(filePath)}.${process.pid}.tmp`);
+	try {
+		fs.writeFileSync(tmp, content, "utf-8");
+		// Preserve permissions if original existed.
+		if (fs.existsSync(filePath)) {
+			try {
+				const mode = fs.statSync(filePath).mode & 0o777;
+				fs.chmodSync(tmp, mode);
+			} catch {
+				/* best-effort */
+			}
+		}
+		fs.renameSync(tmp, filePath);
+	} catch (err) {
+		try {
+			fs.unlinkSync(tmp);
+		} catch {
+			/* ignore */
+		}
+		throw err;
+	}
+}
diff --git a/cli/python/src/mem0_cli/config.py b/cli/python/src/mem0_cli/config.py
index caf231be7..a8f1285df 100644
--- a/cli/python/src/mem0_cli/config.py
+++ b/cli/python/src/mem0_cli/config.py
@@ -160,6 +160,19 @@ def save_config(config: Mem0Config) -> None:
 
     os.chmod(CONFIG_FILE, stat.S_IRUSR | stat.S_IWUSR)  # 0600
 
+    # Propagate the active api_key to ecosystem touchpoints (Claude Code
+    # plugin env injection, shell rc exports). Idempotent — only updates
+    # EXISTING entries; never creates new ones. Best-effort: any IOError
+    # in the sync is swallowed so config.json is always the authoritative
+    # write, never blocked by plugin-state issues.
+    if config.platform.api_key:
+        try:
+            from mem0_cli.plugin_sync import sync_api_key
+
+            sync_api_key(config.platform.api_key)
+        except Exception:
+            pass
+
 
 def redact_key(key: str) -> str:
     """Redact an API key for display: m0-xxx...xxx"""
diff --git a/cli/python/src/mem0_cli/plugin_sync.py b/cli/python/src/mem0_cli/plugin_sync.py
new file mode 100644
index 000000000..f984c8cd5
--- /dev/null
+++ b/cli/python/src/mem0_cli/plugin_sync.py
@@ -0,0 +1,117 @@
+"""Sync the active Mem0 API key into other ecosystem touchpoints.
+
+Why this exists:
+  The CLI canonical state lives in ``~/.mem0/config.json``. But MCP servers
+  (Claude Code plugin, Codex plugin, etc.) read ``MEM0_API_KEY`` from env
+  vars or their own config files. Without a sync, an agent-mode bootstrap
+  mints a new key into config.json but the plugin's MCP keeps using the
+  old key from env — silent surprise.
+
+Design:
+  - Update ONLY entries that already exist (never create new ones)
+  - Preserve all surrounding content / formatting / other keys
+  - Atomic writes (tmpfile + rename) so a crash mid-write doesn't corrupt
+  - Idempotent — re-running with the same key is a no-op
+  - Skip on dry_run
+
+Targets currently handled:
+  - ``~/.claude/settings.json::env::MEM0_API_KEY`` (Claude Code env injection)
+  - ``~/.zshrc`` / ``~/.bashrc`` ``export MEM0_API_KEY="..."`` lines
+
+Out of scope (deliberately not touched):
+  - Codex / Cursor MCP configs — would require schema-aware edits and
+    those tools don't have mem0 entries by default
+  - Plugin's own ``<plugin-dir>/.api_key`` file — plugin-managed
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import re
+import tempfile
+from pathlib import Path
+
+# Files we know how to update safely.
+_CLAUDE_SETTINGS = Path.home() / ".claude" / "settings.json"
+_SHELL_RCS = [Path.home() / ".zshrc", Path.home() / ".bashrc", Path.home() / ".bash_profile"]
+
+
+def sync_api_key(api_key: str) -> list[str]:
+    """Propagate ``api_key`` into known ecosystem touchpoints.
+
+    Returns the list of paths actually updated. Empty list means nothing
+    needed updating (either targets didn't exist or already had this value).
+    """
+    if not api_key:
+        return []
+    updated: list[str] = []
+    if _update_claude_settings(_CLAUDE_SETTINGS, api_key):
+        updated.append(str(_CLAUDE_SETTINGS))
+    for rc in _SHELL_RCS:
+        if _update_shell_rc(rc, api_key):
+            updated.append(str(rc))
+    return updated
+
+
+def _update_claude_settings(path: Path, api_key: str) -> bool:
+    """Update ``env.MEM0_API_KEY`` in path. Returns True if file was changed."""
+    if not path.is_file():
+        return False
+    try:
+        with path.open("r", encoding="utf-8") as f:
+            data = json.load(f)
+    except (json.JSONDecodeError, OSError):
+        return False
+    env = data.get("env")
+    if not isinstance(env, dict) or "MEM0_API_KEY" not in env:
+        # No existing entry — don't create one.
+        return False
+    if env["MEM0_API_KEY"] == api_key:
+        return False  # already in sync
+    env["MEM0_API_KEY"] = api_key
+    _atomic_write_text(path, json.dumps(data, indent=2, ensure_ascii=False) + "\n")
+    return True
+
+
+# Match `export MEM0_API_KEY="..."` (or single quotes, or no quotes).
+# Use [ \t]* (not \s*) for trailing whitespace so a trailing newline at
+# end-of-file is preserved when MEM0_API_KEY is the last line.
+_RC_LINE = re.compile(r'^([ \t]*export[ \t]+MEM0_API_KEY[ \t]*=[ \t]*)(["\']?)([^"\'\n]*)(["\']?)[ \t]*$', re.MULTILINE)
+
+
+def _update_shell_rc(path: Path, api_key: str) -> bool:
+    """Update an existing ``export MEM0_API_KEY=...`` line in path."""
+    if not path.is_file():
+        return False
+    try:
+        text = path.read_text(encoding="utf-8")
+    except OSError:
+        return False
+    match = _RC_LINE.search(text)
+    if not match:
+        return False  # no existing line
+    if match.group(3) == api_key:
+        return False
+    new_text = _RC_LINE.sub(lambda m: f'{m.group(1)}"{api_key}"', text, count=1)
+    _atomic_write_text(path, new_text)
+    return True
+
+
+def _atomic_write_text(path: Path, content: str) -> None:
+    """Write content to path atomically (temp + rename)."""
+    dirname = path.parent
+    fd, tmp_path = tempfile.mkstemp(prefix=f".{path.name}.", suffix=".tmp", dir=dirname)
+    try:
+        with os.fdopen(fd, "w", encoding="utf-8") as f:
+            f.write(content)
+        # Preserve mode if the original existed.
+        if path.exists():
+            os.chmod(tmp_path, path.stat().st_mode & 0o777)
+        os.replace(tmp_path, path)
+    except Exception:
+        try:
+            os.unlink(tmp_path)
+        except OSError:
+            pass
+        raise