diff --git a/src/servers/sidecar/claude/claude-manager.ts b/src/servers/sidecar/claude/claude-manager.ts
index eb721668..d9cee15c 100644
--- a/src/servers/sidecar/claude/claude-manager.ts
+++ b/src/servers/sidecar/claude/claude-manager.ts
@@ -34,6 +34,39 @@ function resolveClaudeBin(): string {
 const CLAUDE_BIN = resolveClaudeBin();
 console.log(`[claude] CLI resolved to ${CLAUDE_BIN}`);
 
+/**
+ * Variables the `claude` CLI injects to describe ITS OWN session, which must never reach a `claude` we
+ * spawn ourselves.
+ *
+ * They arrive here by an ordinary accident: PM2 inherits the environment of whoever ran `pm2 start`, so
+ * restarting this sidecar from inside a Claude Code terminal — which is how it is restarted most of the
+ * time — bakes that terminal's session into the daemon. On 2026-08-14 this process was carrying
+ * `CLAUDE_CODE_MESSAGING_SOCKET` for an unrelated PID that had been alive for an hour and a half.
+ *
+ * Only three of these were stripped before (`CLAUDECODE`, `CLAUDE_CODE_ENTRYPOINT`, `CLAUDE_CODE_SSE_PORT`);
+ * the rest are newer and arrived with 2.x. Stripping them is hygiene rather than a fix — a spawn was
+ * verified to succeed with the whole set present — but the failure it prevents is a child attaching to a
+ * stranger's IPC socket, which would be extremely hard to recognise from the symptom.
+ */
+const NESTED_SESSION_ENV = [
+  'CLAUDECODE',
+  'CLAUDE_CODE_ENTRYPOINT',
+  'CLAUDE_CODE_SSE_PORT',
+  'CLAUDE_CODE_CHILD_SESSION',
+  'CLAUDE_CODE_MESSAGING_SOCKET',
+  'CLAUDE_CODE_MESSAGING_TOKEN',
+  'CLAUDE_CODE_SESSION_ID',
+  'CLAUDE_CODE_EXECPATH',
+  'CLAUDE_PID',
+] as const;
+
+/** `process.env` minus the parent session's fingerprint. */
+function envWithoutParentSession(): Record<string, string> {
+  const out: Record<string, string> = { ...process.env } as Record<string, string>;
+  for (const name of NESTED_SESSION_ENV) delete out[name];
+  return out;
+}
+
 // Capture original HOME before user-instance overrides it
 const HOST_HOME = process.env.HOME!;
 import { DATA_PATH } from '../../data-path';
@@ -404,7 +437,7 @@ function createSession(params: ClaudeSpawnStreamingParams, onEvent: (event: Chat
   };
 
   // Strip the nested-session guard vars so the SDK can spawn `claude` (mirrors the old spawn env clean).
-  const { CLAUDECODE: _c, CLAUDE_CODE_ENTRYPOINT: _e, CLAUDE_CODE_SSE_PORT: _s, ...cleanEnv } = process.env;
+  const cleanEnv = envWithoutParentSession();
 
   const resumeId = getClaudeSession(sessionKey, params.userId) ?? params.resumeSessionId;
   const subModel = params.model?.split('/')[1];