diff --git a/plugins/orchestrator/dist/server.js b/plugins/orchestrator/dist/server.js
index 6b6141f..1b60687 100644
--- a/plugins/orchestrator/dist/server.js
+++ b/plugins/orchestrator/dist/server.js
@@ -6519,7 +6519,7 @@ var require_dist = __commonJS((exports, module) => {
 
 // mcp/server.ts
 import { resolve, join as join5 } from "path";
-import { existsSync as existsSync6, readFileSync as readFileSync3, writeFileSync } from "fs";
+import { existsSync as existsSync6, readFileSync as readFileSync3, readdirSync as readdirSync2, unlinkSync as unlinkSync2, writeFileSync } from "fs";
 import { execSync } from "child_process";
 
 // node_modules/zod/v3/external.js
@@ -24629,22 +24629,22 @@ async function startSidecar() {
     }
   } catch {}
   try {
-    const { unlinkSync: unlinkSync2 } = await import("fs");
-    unlinkSync2(portFile);
+    const { unlinkSync: unlinkSync3 } = await import("fs");
+    unlinkSync3(portFile);
   } catch {}
   const baseArgs = ["--port", "0", "--port-file", portFile];
   let result = await trySpawn(["uvx", "--with-requirements", requirementsPath, "python", sidecarPath, ...baseArgs], portFile, "uvx", 60000);
   if (!result) {
     try {
-      const { unlinkSync: unlinkSync2 } = await import("fs");
-      unlinkSync2(portFile);
+      const { unlinkSync: unlinkSync3 } = await import("fs");
+      unlinkSync3(portFile);
     } catch {}
     result = await trySpawn(["python", sidecarPath, ...baseArgs], portFile, "python", 30000);
   }
   if (!result) {
     try {
-      const { unlinkSync: unlinkSync2 } = await import("fs");
-      unlinkSync2(portFile);
+      const { unlinkSync: unlinkSync3 } = await import("fs");
+      unlinkSync3(portFile);
     } catch {}
     result = await trySpawn(["python3", sidecarPath, ...baseArgs], portFile, "python3", 30000);
   }
@@ -26357,6 +26357,99 @@ foreach ($s in $siblings) {
 `);
   }
 }
+function reapStaleActiveSessionFiles(stateDir) {
+  if (!existsSync6(stateDir))
+    return;
+  let reaped = 0;
+  try {
+    const entries = readdirSync2(stateDir);
+    for (const entry of entries) {
+      const m = entry.match(/^active-session-(\d+)$/);
+      if (!m)
+        continue;
+      const pid = Number(m[1]);
+      if (!Number.isFinite(pid) || pid <= 0)
+        continue;
+      let alive = false;
+      try {
+        process.kill(pid, 0);
+        alive = true;
+      } catch {
+        alive = false;
+      }
+      if (!alive) {
+        try {
+          unlinkSync2(join5(stateDir, entry));
+          reaped++;
+        } catch {}
+      }
+    }
+  } catch {}
+  if (reaped > 0) {
+    process.stderr.write(`[orchestrator] startup hygiene: reaped ${reaped} stale active-session-<pid> file(s) in ${stateDir}
+`);
+  }
+}
+function warnAboutLikelyOrphanSiblings() {
+  if (process.platform !== "linux")
+    return;
+  const myPid = process.pid;
+  const distMarker = "orchestrator/dist/server.js";
+  let procDirs;
+  try {
+    procDirs = readdirSync2("/proc").filter((n) => /^\d+$/.test(n));
+  } catch {
+    return;
+  }
+  const orphanPids = [];
+  for (const pidStr of procDirs) {
+    const pid = Number(pidStr);
+    if (pid === myPid)
+      continue;
+    let isSiblingMcp = false;
+    try {
+      const cmdline = readFileSync3(`/proc/${pid}/cmdline`, "utf8");
+      isSiblingMcp = cmdline.includes(distMarker);
+    } catch {
+      continue;
+    }
+    if (!isSiblingMcp)
+      continue;
+    let walk = pid;
+    let foundClaude = false;
+    for (let depth = 0;depth < 8; depth++) {
+      try {
+        const stat = readFileSync3(`/proc/${walk}/stat`, "utf8");
+        const rparen = stat.lastIndexOf(")");
+        if (rparen < 0)
+          break;
+        const name = stat.slice(stat.indexOf("(") + 1, rparen).toLowerCase();
+        if (name === "claude" || name === "claude.exe") {
+          foundClaude = true;
+          break;
+        }
+        const fields = stat.slice(rparen + 2).split(/\s+/);
+        const ppid = parseInt(fields[1] ?? "0", 10);
+        if (!ppid || ppid === walk || ppid === 1)
+          break;
+        walk = ppid;
+      } catch {
+        break;
+      }
+    }
+    if (!foundClaude)
+      orphanPids.push(pid);
+  }
+  if (orphanPids.length > 0) {
+    process.stderr.write(`[orchestrator] startup hygiene: detected ${orphanPids.length} likely-orphan sibling MCP process(es): pid=${orphanPids.join(",")}. Their parent claude is no longer in the process tree, suggesting they outlived their owning session and may be running stale bytecode whose watchdog never fired. Diagnose with 'pstree -ps <pid>'; clean up with 'kill -9 <pid>' if confirmed orphan.
+`);
+  }
+}
+{
+  const startupProjectDir = process.env.ORCHESTRATOR_PROJECT_ROOT || process.env.CLAUDE_PROJECT_DIR || process.cwd();
+  reapStaleActiveSessionFiles(join5(startupProjectDir, ".orchestrator-state"));
+  warnAboutLikelyOrphanSiblings();
+}
 var initialParentClaudePid = findClaudeAncestorPid();
 var initialParentClaudeCreationTime = initialParentClaudePid !== null ? getProcessCreationTime(initialParentClaudePid) : null;
 if (initialParentClaudePid) {
diff --git a/plugins/orchestrator/mcp/server.ts b/plugins/orchestrator/mcp/server.ts
index 85eed16..a34e2c7 100644
--- a/plugins/orchestrator/mcp/server.ts
+++ b/plugins/orchestrator/mcp/server.ts
@@ -1,5 +1,5 @@
 import { resolve, join } from "node:path";
-import { existsSync, readFileSync, writeFileSync } from "node:fs";
+import { existsSync, readFileSync, readdirSync, unlinkSync, writeFileSync } from "node:fs";
 import { execSync } from "node:child_process";
 import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
 import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
@@ -2822,6 +2822,160 @@ foreach ($s in $siblings) {
   }
 }
 
+/**
+ * Startup hygiene: remove stale per-PID `active-session-<pid>` files
+ * whose owning claude process has exited. The per-PID file scheme
+ * (introduced in 0.30.19+) makes session_id lookup race-free for
+ * concurrent sessions, but nothing has been reaping these files when
+ * the claude process they belong to dies. On a developer machine with
+ * many short-lived sessions per day, they accumulate indefinitely.
+ *
+ * They are cosmetic - the legacy single `active-session` file remains
+ * the primary lookup - but a slow directory listing eventually becomes
+ * a real cost. This sweep runs once at MCP startup; it is cheap,
+ * idempotent, and race-safe (we only unlink files whose PID is verified
+ * gone via `process.kill(pid, 0)`).
+ */
+function reapStaleActiveSessionFiles(stateDir: string): void {
+  if (!existsSync(stateDir)) return;
+  let reaped = 0;
+  try {
+    const entries = readdirSync(stateDir);
+    for (const entry of entries) {
+      const m = entry.match(/^active-session-(\d+)$/);
+      if (!m) continue;
+      const pid = Number(m[1]);
+      if (!Number.isFinite(pid) || pid <= 0) continue;
+      // Liveness probe: process.kill(pid, 0) throws if the PID does
+      // not exist. ESRCH = dead PID (reap). EPERM = alive but not
+      // ours to signal (rare for own state files; treat as alive to
+      // be safe). We don't distinguish error codes here because the
+      // failure cost of a missed reap is one extra orphan file at
+      // worst - next startup will retry.
+      let alive = false;
+      try {
+        process.kill(pid, 0);
+        alive = true;
+      } catch {
+        alive = false;
+      }
+      if (!alive) {
+        try {
+          unlinkSync(join(stateDir, entry));
+          reaped++;
+        } catch {
+          // Lost a race with another session, or permission issue.
+          // Non-fatal; next startup will retry.
+        }
+      }
+    }
+  } catch {
+    // readdir failure - directory may not exist, or permission denied.
+    // Either way nothing to reap.
+  }
+  if (reaped > 0) {
+    process.stderr.write(
+      `[orchestrator] startup hygiene: reaped ${reaped} stale active-session-<pid> file(s) in ${stateDir}\n`,
+    );
+  }
+}
+
+/**
+ * Startup hygiene: detect sibling orchestrator MCP processes whose
+ * parent claude is no longer alive, suggesting they outlived their
+ * owning session and may be running stale bytecode whose orphan
+ * watchdog never fired.
+ *
+ * Logs a warning naming the suspect PIDs - does NOT auto-kill, because
+ * killing a sibling MCP can disrupt infrastructure shared across live
+ * sessions (e.g. the python sidecar bound to .sidecar-port is
+ * deliberately shared - killing a sibling can take it down). Detection
+ * surfaces the issue; the operator decides whether to clean up.
+ *
+ * This complements the orphan-bun watchdog (which catches "parent dies
+ * while I'm alive" cases for processes loaded with the watchdog code).
+ * It does not help against orphans whose loaded bytecode predates the
+ * watchdog improvements - those need manual cleanup - but it makes
+ * such orphans visible at the next session's startup.
+ *
+ * Linux only. Windows already has killOlderDuplicateMcps for a related
+ * but different case (siblings sharing our parent claude); the orphan
+ * case on Windows is rare because parent death usually reaps children.
+ */
+function warnAboutLikelyOrphanSiblings(): void {
+  if (process.platform !== "linux") return;
+  const myPid = process.pid;
+  // Look for any other bun process whose cmdline references the
+  // orchestrator dist - that's the canonical sibling-MCP signature.
+  // We use a path suffix rather than an absolute marker so the check
+  // works regardless of where the plugin marketplace lives.
+  const distMarker = "orchestrator/dist/server.js";
+  let procDirs: string[];
+  try {
+    procDirs = readdirSync("/proc").filter((n) => /^\d+$/.test(n));
+  } catch {
+    return;
+  }
+  const orphanPids: number[] = [];
+  for (const pidStr of procDirs) {
+    const pid = Number(pidStr);
+    if (pid === myPid) continue;
+    let isSiblingMcp = false;
+    try {
+      const cmdline = readFileSync(`/proc/${pid}/cmdline`, "utf8");
+      isSiblingMcp = cmdline.includes(distMarker);
+    } catch {
+      continue;
+    }
+    if (!isSiblingMcp) continue;
+    // Walk this sibling's parent chain looking for a live claude
+    // process. If we never find one in 8 hops, the sibling has no
+    // claude ancestor in its current tree - likely orphaned.
+    let walk = pid;
+    let foundClaude = false;
+    for (let depth = 0; depth < 8; depth++) {
+      try {
+        const stat = readFileSync(`/proc/${walk}/stat`, "utf8");
+        const rparen = stat.lastIndexOf(")");
+        if (rparen < 0) break;
+        const name = stat
+          .slice(stat.indexOf("(") + 1, rparen)
+          .toLowerCase();
+        if (name === "claude" || name === "claude.exe") {
+          foundClaude = true;
+          break;
+        }
+        const fields = stat.slice(rparen + 2).split(/\s+/);
+        const ppid = parseInt(fields[1] ?? "0", 10);
+        if (!ppid || ppid === walk || ppid === 1) break;
+        walk = ppid;
+      } catch {
+        break;
+      }
+    }
+    if (!foundClaude) orphanPids.push(pid);
+  }
+  if (orphanPids.length > 0) {
+    process.stderr.write(
+      `[orchestrator] startup hygiene: detected ${orphanPids.length} likely-orphan sibling MCP process(es): pid=${orphanPids.join(",")}. ` +
+        `Their parent claude is no longer in the process tree, suggesting they outlived their owning session and may be running stale bytecode whose watchdog never fired. ` +
+        `Diagnose with 'pstree -ps <pid>'; clean up with 'kill -9 <pid>' if confirmed orphan.\n`,
+    );
+  }
+}
+
+// Startup hygiene runs unconditionally - it doesn't depend on parent
+// claude resolution and benefits future startups even if THIS one is
+// about to exit (no-claude-ancestor case below).
+{
+  const startupProjectDir =
+    process.env.ORCHESTRATOR_PROJECT_ROOT ||
+    process.env.CLAUDE_PROJECT_DIR ||
+    process.cwd();
+  reapStaleActiveSessionFiles(join(startupProjectDir, ".orchestrator-state"));
+  warnAboutLikelyOrphanSiblings();
+}
+
 const initialParentClaudePid = findClaudeAncestorPid();
 // 0.30.38: also capture parent claude.exe's creation time so the watchdog
 // can defend against PID reuse. Without this, when the user closes one