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MCP server processes leak: per-thread processes never cleaned up (9+ GB RSS) #30408
Description
Bug description
Codex app-server spawns a full set of global MCP server processes for each new thread/conversation, but never kills them when threads are archived or closed. Over time, orphaned MCP processes accumulate unboundedly.
Environment
- Codex Desktop: 0.142.3 (macOS, Apple Silicon)
- OS: macOS 15.x, 64 GB RAM
Steps to reproduce
- Configure global MCP servers in
~/.codex/config.toml(e.g.playwright,davinci-resolve,node_repl) - Open Codex Desktop, create ~25 threads over a session
- Close/archive threads as normal
- Check process list
Expected behavior
MCP server processes should be cleaned up when the owning thread is closed or archived. At most one set of MCP processes should exist per actively-used server.
Actual behavior
After 25 threads, observed 133 orphaned MCP processes consuming ~9.3 GB RSS:
| MCP Server | Orphaned Processes | RSS |
|---|---|---|
playwright (npm + node) |
52 | 2.9 GB |
davinci-resolve (python) |
26 | 3.5 GB |
node_repl |
26 | 266 MB |
| npm exec wrappers | 29 | 2.6 GB |
All processes had PPID = app-server PID. The app-server holds them indefinitely.
Root cause
The app-server does not track which MCP processes belong to which thread, and has no lifecycle management to kill MCP processes when threads end. There is also no idle_timeout, reuse, or shared config option for MCP servers.
Workaround
- Manually kill orphaned processes:
pkill -P <app-server-pid> -f "playwright-mcp|davinci-resolve" - Remove rarely-used MCP servers from global config and add them per-project instead
Suggested fix
- Track MCP process ownership per-thread
- Kill MCP processes when the owning thread is closed/archived
- Alternatively, add a
sharedorreusemode so all threads share a single MCP process instance - Consider an
idle_timeoutoption to auto-kill MCP processes after N minutes of no use
Activity
github-actions commentedon Jun 28, 2026
Potential duplicates detected. Please review them and close your issue if it is a duplicate.
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ZenAlexa commentedon Jul 2, 2026
Independent reproduction on macOS at a different config scale — confirming this isn't size-specific.
Environment: Codex Desktop (macOS, Apple Silicon), macOS 26.x; 24 global MCP servers configured in
~/.codex/config.toml.Observed: a single live
codex app-serverprocess held 101 direct child processes (ppid == app-server) — roughly 5 copies of every configured server:@modelcontextprotocol/server-github×5,server-memory×5,server-sequential-thinking×5,@playwright/mcp×5,chrome-devtools-mcp×5,gemsuite-mcp(viatsx) ×5, plus the uv-based servers (arxiv-mcp-server,semantic-scholar-mcp,reddit-*) at similar multiplicity. System-wide that was 128node+ 24uvprocesses. This matches the root cause described here exactly: the app-server spawns the full MCP fleet per thread and never reaps the prior sets.Two amplifiers worth noting:
npm execdoubling — each stdio server launched vianpm exec <pkg>is two processes (the npm wrapper + the actual node), so N configured servers × M threads produces ~2·N·M processes.The cost isn't only RAM — it's disk exhaustion and system-wide failure, which I think deserves emphasis alongside the RSS number:
vm.swapusagewas at ~2.5 GB used with multiple/System/Volumes/VM/swapfile*present.lsof +L1shows unlinked-but-open inodes pinned by the stalenodeprocesses, so that space is never reclaimed by the OS.So the leak has three compounding costs: RAM → swap → APFS free space, plus held-open deleted-file space.
+1 on the suggested fixes, in priority order for the disk angle:
shared/reusemode so all threads share one MCP instance (biggest win — collapses the ×M entirely), and/oridle_timeoutto auto-kill idle MCP processes.Happy to provide sanitized
ps/lsofcaptures through a private channel if useful.ryofukutani commentedon Jul 5, 2026
I can reproduce a similar leak on macOS with the current Codex Desktop app.
Environment:
26.623.101652467426.5.1(25F80)arm64/Applications/Codex.app/Contents/Resources/codex app-server --analytics-default-enabledObserved on July 6, 2026 JST under the live app-server PID:
The
node_repland MCP proxy processes are children of the Codex app-server. Their start times are spread across the session, with many alive for 1-3 hours, so they do not look like short-lived tool-call processes being cleaned up normally. They are mostly sleeping with near-zero CPU, but they keep accumulating.This happened during a session that included repeated Browser / in-app browser recovery attempts and MCP/tool usage. I cannot prove the browser path is the only trigger, but the timestamps line up with repeated browser-control attempts.
Expected behavior:
Actual behavior:
node_repland MCP proxy processes remain under app-server and accumulate across the session.Additional note: the high-RSS Python process in my snapshot is a local
delimit-memorydaemon backed by mem0, not the old Delimit product itself. The leaking symptom I am reporting here is the app-server-owned child process accumulation (node_repland MCP proxies).mochafreddo commentedon Jul 6, 2026
I am seeing what appears to be the same MCP lifecycle leak, with an additional failure mode: app-server FD exhaustion leading to
Too many open files (os error 24)on macOS.Environment:
ulimit -n:256launchctl limit maxfiles: observed as65536 unlimited, but Codex-spawned shell still inheritedulimit -n = 256Observed app-server processes:
There was also an orphaned launcher shell:
The GUI app-server had duplicated MCP children:
The Unix-socket app-server also had duplicated MCP children:
The generic
./mcp/server.*processes mapped back by cwd to plugin-bundled MCPs:This eventually reproduced inside Codex as:
So this is not only memory/process accumulation; with a low inherited
RLIMIT_NOFILE, the app-server can become unable to spawn new commands.qingye-lab commentedon Jul 9, 2026
Independent severe reproduction on macOS, adding Jetsam-level evidence to this MCP lifecycle leak. The system became unresponsive and required a manual restart.
Environment
26.707.31123(bundle build5042)codex-cli 0.144.0-alpha.426.5.1(25F80)macOS Jetsam evidence
macOS wrote two
JetsamEventreports 5m56s apart. The reports use a 16,384-byte page size. The values below are direct calculations from the reports (GiB = pages × 16,384 / 2^30):nodeprocessesnodein Codex coalitionIn 5m56s:
nodecount increased by 83At the second snapshot, the system compressor occupied 9.40 GiB and represented 50.99 GiB of uncompressed, system-wide pages. This is not all attributable to Codex, but it shows the severity of the resulting system pressure.
A separate
nodediagnostic report identifies the ownership chain as:No kernel-panic report was present. The machine was manually restarted at 06:32 after the UI became unusable.
Post-restart reproduction
After restart, read-only process inspection again showed repeated app-server-owned batches containing:
Their start times appeared in repeated batches during tool-enabled thread activity, and earlier batches remained alive. This observation supports the lifecycle leak reported here, but it does not distinguish whether each new batch is keyed to a thread, subagent, tool-host lifecycle, or another app-server boundary.
Impact
On a 16 GB Mac this progressed from an application leak to a system-wide outage. Quitting/restarting the app-server is currently the only reliable way I found to release the accumulated process tree.
I have intentionally omitted project names, usernames, local paths, and raw session logs. I can provide sanitized excerpts or the aggregation queries through a private channel if useful.
DongwonTTuna commentedon Jul 11, 2026
Adding an independent Ubuntu/Linux reproduction. This issue is still reproducible with
codex-cli 0.144.1, and in this run it progressed to complete unified-exec/PTY failure.Environment
codex app-server --listen unix://systemd --userserviceRLIMIT_NOFILE: soft1024, hard524288docker exec -i -w <workspace> mcp-suite mcp-suite-stdio <lsp|codegraph|agbrowse>The incident followed a large collaboration/subagent tree containing many completed or interrupted agents.
User-visible failure
Eventually even a trivial process could not be created:
The PTY path failed independently:
One attempt also reported
dup of fd 992 failed. The same failure occurred from the original Goal thread, collaboration subagents, and a new same-directory child thread, which ruled out one stale unified-exec session registry as the primary cause.Live
/procevidence before mitigationThe app-server process was captured at 1012 open FDs with a soft limit of 1024 (
FDSize=1024, highest occupied FD1023):Of the 111 file FDs, 82 pointed into the Codex session store.
The same app-server had 221 direct children. 219 were live, sleeping
dockerclients:mcp-suite-stdio lspmcp-suite-stdio codegraphmcp-suite-stdio agbrowseThe Docker MCP clients alone accounted for 657 broker-side pipe FDs + 219 pidfds = 876 FDs. This is approximately 73 retained copies of the three-server MCP set, or roughly 12 broker FDs per agent/context.
An important Linux-specific detail: these were not zombie/dead children. Every one of the 219 pidfds still targeted a live Docker process, and all 657 associated pipe inodes still had a live peer. There were no PTY FDs in the service cgroup. This snapshot therefore looks like retention of live per-agent stdio transports, rather than only failure to reap already-dead children.
Host-wide exhaustion was ruled out:
Controlled mitigation and toggle evidence
I did not kill/restart the app-server or any MCP process. I only raised the running app-server's soft limit, leaving the hard limit unchanged:
After that change, two non-PTY and two PTY executions of
/bin/bash -c true, launched concurrently through unified exec, all exited0. The retained MCP processes and FDs remained; only the headroom changed. A later snapshot still showed 216 Docker MCP children and 994 app-server FDs, confirming that this was a recovery workaround rather than cleanup.The service definition still has
LimitNOFILESoft=1024, so the next app-server restart would inherit the low limit again unless the unit is hardened.Why this appears to be the same upstream issue
The direct parent of every Docker MCP client was the Codex app-server. The Docker command came from the normal global
[mcp_servers.*]config; it was not launched by a still-running LazyCodex wrapper process. The issue therefore reproduces as app-server MCP lifecycle behavior with an ordinary stdio MCP command.As a local workaround, I can replace these stdio entries with the already-running loopback Streamable HTTP endpoints. That should remove the
dockerchild / pipe / pidfd multiplier, but it does not address per-thread/agent MCP client ownership, sharing, or idle teardown in Codex itself.This Linux data point suggests a useful regression test: after completing, interrupting, or archiving a large collaboration-agent tree, app-server child-process and FD counts should return close to baseline. It would also be valuable to cover a low inherited
RLIMIT_NOFILE, because the lifecycle retention otherwise surfaces as total loss of shell and PTY execution.Related: #26984.
This issue or PR was generated by LazyCodex.
Tag: lazycodex-generated
Lenvanderhof commentedon Jul 13, 2026
Corroborating from a different surface: this also happens with codex-cli on Linux, so it is not Desktop- or macOS-specific.
Environment
--dangerously-bypass-approvals-and-sandbox)~/.codex/config.toml:ferrex(Rust memory server, loads ~2 GB of embedding models at initialize) and a python RAG server viauv runObservation (2026-07-12/13)
One long-lived codex CLI process (PID 3510112, ~5.5 h old) had accumulated 4 concurrent instances of the same ferrex stdio server and 4 instances of the python server, all still direct children, none ever reaped:
Spawn timestamps cluster in bursts (03:27, 05:13, 05:14, 05:44 local), consistent with a fresh MCP set per thread/turn burst while earlier sets stay alive but idle. With ~2 GB of model weights per instance this pushed the 32 GB machine deep into swap (observed 61 GB swap used across sessions exhibiting this pattern).
Repro sensitivity note
Our MCP server initialized slowly under memory pressure (30–90 s model load). If the respawn path triggers on initialize/tool-call timeouts, slow-initializing stdio servers make the leak far more likely — that may explain why some setups see it constantly and others rarely.
rwang23 commentedon Jul 16, 2026
I can reproduce this on the current Codex Desktop build for Windows. Since #19753 was merged in April, this looks like a lifecycle path that is still missing in Desktop, or a regression after that fix.
Environment:
26.707.12708.0I recorded the app-server PID, each direct MCP root PID, process creation time, working directory, and private memory before and after a full Codex restart. I did not terminate any process during the capture.
The full restart did clean up the old app-server tree. The app-server PID changed, and all 57 previously tracked direct-child process instances were gone. The problem returned quickly under the new app-server:
At the end of that window, the new app-server owned:
node_replThe managed stdio and built-in tool trees used about 1.79 GB of private memory. The app-server itself used about 2.16 GB at that point.
There is also a configuration inconsistency that amplifies the leak. These three plugin MCP servers were all set to
enabled = falsebefore the new processes were created:sites-design-picker: the setting was honored, with zero processes after restart.dataAnalyticsWidgets: the setting was not honored, with 12 processes.openai-api-key-local-confirmation: the setting was not honored, with 12 processes.The two project-scoped MCP roots matched two active tasks in that repository, so project scoping itself appears to work. The duplicate global and plugin bundles are the part that keeps growing.
One CodeGraph
--liftoff-onlychild also remained alive across the full app restart after its launcher parent had exited. That may be specific to the third-party launcher, but a Windows Job Object around the task-owned process tree would prevent detached descendants from surviving the owning runtime.What I expected:
notLoaded, is archived, or is evicted should release its stdio transports and terminate the complete process tree after a bounded grace period.enabled = falseshould not be started for newly loaded task runtimes.I have a sanitized PID and lifecycle matrix and can provide it without local paths, project names, session content, or credentials.
rwang23 commentedon Jul 16, 2026
Follow-up from the same Windows host after extending the read-only process snapshot.
The environment is unchanged: Windows 11 x64, 32 GB RAM, Codex Desktop package
26.707.12708.0, and several long-running tasks. The newer classifier separates the one top-level Desktop app-server from thecodex.exebridge processes launched under built-in Node REPL hosts.At
2026-07-16T21:57:38Z, the top-level app-server had 104 descendants and 56 managed service roots:Those service trees used about 4.59 GB of private memory. The app-server itself used another 1.24 GB.
The Node REPL number needs some unpacking. There were 14 lightweight
node_repl.exehosts, but only three had an active Node kernel and Codex bridge. One persistent kernel alone was using 2,217 MB of private memory and had accumulated 2,960 CPU seconds. The same kernel had dropped to about 408 MB in an earlier sample, then grown again. This looks like a persistent per-task execution state with large allocation and GC swings, not 14 equally heavy REPL processes.I also saw partial cleanup on this build. The four root groups fell from 19 each at
21:39Zto 14 each at21:57Zwithout any manual process termination. So "never cleaned up" is too strong for this Windows host. The behavior is still delayed or incomplete: all four groups move together, and every retained task runtime keeps the full bundle even when most Node REPL hosts have no active kernel.A separate 30-second multi-session sample recorded 237.7 MB of app-server reads, 36.5 MB of writes, 41,433 read operations, 5,703 write operations, and 5.36 CPU seconds. These are Windows process counters and include files, pipes, and network traffic, so I am not treating them as pure disk I/O.
I found one third-party multiplier as well. CodeGraph 1.4.1 relaunches its Node adapter with V8's
--liftoff-onlyflag when that flag is missing from the original Node command line. Supplying the flag directly should remove one wrapper process per CodeGraph root after the next Desktop restart. That reduces the cost of this particular MCP, but it does not explain why Codex retains one complete adapter bundle per loaded task.The upstream behavior would be much easier to diagnose and contain if Desktop did the following:
enabled = falsebefore constructing a new task runtime.I can provide another sanitized PID and start-time matrix if a maintainer needs it. No project paths, session content, command lines, daemon tokens, or credentials were captured in the snapshot output.
sleepfrontofmtv commentedon Jul 17, 2026
I reproduced the same issue on a newer Codex Desktop build, at substantially larger scale. There was also an unreaped-zombie component similar to #12491.
Environment
26.715.21425codex-cli 0.145.0-alpha.1826.5.2(25F84), Apple Silicon (arm64)npx -y chrome-devtools-mcp@latestuvx --from git+https://github.com/oraios/serena serena start-mcp-server --project-from-cwd --context codexheadroom mcp serveObserved failure
After a long-running desktop session with many threads/background agents, the host became nearly unusable. A process snapshot showed:
191 / 512 / 636at capture time (earlier samples were approximately520-686)373livechrome-devtools-mcpprocesses, consuming about898%aggregate CPU362uvlauncher processes plus362Python Serena server processes (about724Serena-related process entries)386headroom mcp serveprocesses1,291Node processes in total2,877zombie children below the bundled Codex app-server process (2,884zombies system-wide)Nearly every sampled Chrome DevTools MCP parent chain led back to the same bundled Codex app-server process. The affected app-server had been running for roughly seven hours.
This was not primarily RAM exhaustion. The machine still had substantial free memory; the freeze was caused by run-queue/process-table pressure from thousands of live and zombie processes.
Recovery result
After restarting the Codex/ChatGPT application stack, counts returned to:
chrome-devtools-mcp:1110%at the verification sample94%The three remaining system zombies were traced to LM Studio and two SSH sessions, not Codex/MCP.
I do not yet have a deterministic minimal reproduction beyond sustained multi-thread/background-agent use with multiple global stdio MCP servers. However, the parent-process evidence and the immediate return to one instance per MCP after restarting Codex strongly support the per-thread lifecycle leak described here.
In addition to terminating MCP children when their owning thread ends, the app-server should reap exited children and ideally provide a shared/singleton MCP mode or a hard per-server instance limit. A process-count or zombie-growth guard would also prevent the desktop from taking down the host while the underlying lifecycle bug is being addressed.
40 remaining items
0xdevalias commentedon Oct 3, 2026
It's also worth noting that
CODEX_THREAD_IDcan seemingly also be passed through to processes that were started within a codex thread, but aren't actually related to an MCP / 'leftovoer' state.In my case,
tidewakereported the sub-processes of Sublime Text as beingleftover; but they are legitimately not related to codex, Sublime Text just happened to have been started/restarted as part of a codex investigation I was doing:tidewake scanreports false positiveleftover codexfor Sublime Text sub-processes (Sublime was likely started/restarted by a codex thread) berkkorkmaz/tidewake#1tl;dr: don't blindly treat an older thread holding a
CODEX_THREAD_IDof an idle/archived codex thread as being 'leftover' / etc.release: AgentChef 1.3.2 (worker models) (#73)
Rober1208 commentedon Oct 5, 2026
Until this is fixed, I wrote a small cleanup tool for it: mcp-janitor.
It lists the MCP server processes each Codex process keeps (CLI, IDE extension, desktop app), grouped by the conversation that started them, with memory use and idle time, and stops the ones you pick or the ones idle longer than you say:
It is a workaround, not a fix. Since Codex does not restart a stopped server ("Transport closed"), it keeps the servers of the conversation you used last in each Codex process unless you say otherwise, asks before stopping anything, and
--dry-runonly shows what it would do. No dependencies, Node.js 22+.I have tested it on Windows 11 with the desktop app; Linux and macOS pass its test suite but have seen little real use. If you can try it on your setup and tell me what it gets wrong or misses, that would help a lot. Issues and PRs are welcome.
thedarkcder commentedon Oct 5, 2026
Adding a measured observation and a proposed configurable idle timeout.
Observation
On macOS, with the desktop app's bundled backend reporting
codex-cli 0.160.0, a snapshot showed:All server launchers belonged to one live desktop app-server. These are summed process RSS figures, not unique physical memory. Most processes had near-zero CPU, but that does not prove they were unused. We have not mapped every instance to its owning thread, subscriber state or in-flight calls, so this observation alone does not establish orphaning.
Relevant lifecycle distinction
In the public
rust-v0.160.0source:Cleanup paths therefore exist. A separate question is how to release an unused server while its thread remains loaded or subscribed. I did not find an MCP-only idle expiry in the runtime/connection-manager paths inspected.
Proposal: configurable 24-hour idle expiry
For local stdio MCP servers, introduce a per-server property such as
idle_timeout_sec, defaulting to 86400 seconds (one day). This is a proposed property, not an existing supported setting.Desired behavior:
Suggested regression coverage: default/custom timeout validation; no early expiry; expiry with an open subscribed thread; activity resetting the deadline; long-running calls and pending approvals preventing expiry; one restart under concurrent next use; explicit restart failure; and complete process-tree cleanup.
For my workflow, retaining an unused browser tool for up to one day is reasonable, and a cold start after that is preferable to indefinite memory retention.
michaelort33 commentedon Oct 6, 2026
Another macOS data point, with per-thread attribution via process start times.
Environment: ChatGPT.app 26.930.51102 (build 13100), bundled
codex-cli 0.160.0, macOS 25.6 arm64, 48 GB RAM. Single app-server, up 9h16m.Snapshot: 1,250 direct children of the app-server (about 1,430 descendants), roughly 18.6 GB summed RSS. Swap 32.7 GB used of 33.8 GB. Breakdown of direct children: 392
node(plugin MCP servers), 258SkyComputerUseClient, 258python, 176 nestednode, 87Python, 67node_repl. Each new thread starts a set of 15 to 17 processes: three Computer Use clients,node_repl, code-review, codex-security, codex-app-tools, and the Python/Node servers from a few installed plugins.Attribution: 99 threads were created since the app-server started (65 native subagents via
spawn_agent, 17 user threads, plus a few others). Matching helper process start times tothreads.created_at_mswithin a 25-second window:thread_spawn_edges.status = open)All 65 spawn edges are
open; the orchestrating model never calledclose_agent. The 7 user threads that were released have no processes left, so teardown works when the thread is actually shut down. Idle user threads the desktop still holds (one idle for 7 hours) keep their set.This is consistent with @sharifhsn's finding in #39783 that the desktop keeps completed child agents subscribed, so the 60 s
thread_unload_delay_secspath never becomes eligible. Confirming the environment note from that thread: the pluginnodeservers here exposeCODEX_APP_TOOLS_PIPE_PATH(same socket UUID for all 85 of them) but noCODEX_THREAD_ID.Workaround on our side: instruct orchestrators to call
close_agentafter each result. That frees subagent sets but does nothing for subscribed user threads or threads reopened at launch.zhang8630 commentedon Oct 8, 2026
Additional data point from Windows: in my case the leak doesn't just waste memory, it hard-hangs the app-server once the number of leaked stdio MCP children reaches ~256.
Environment
multi_agent_v2enabled,max_concurrent_threads_per_session = 30; two projects running in parallel in the same app, each spawning many sub-agentsnpx), one local node server,node_repl, plus the bundled plugin serversWhat happened
After ~23 h of uptime, both running threads stayed on "Thinking" forever. The app-server (
codex.exe app-server) showed 0.00 s CPU over a 10 s sample. The desktop log shows the request queue jammed:response_orphaned(responses arriving minutes late)app_server_client_request_queue_rejected, withinFlightRequestCountstuck at 4 → 6 → 8thread/read,config/read,plugin/installed,model/list, …) fails with-32001 App server request expired while queuedor-32000 timed out after dispatchQuitting and restarting the app is the only way to recover.
Process state at the time of the hang
Wait:UserRequest; 3339 handles; 14 sockets inCLOSE_WAITDirect children of the app-server, by source:
cmd→npx→node)cmd→npx→node)cua_replLikely mechanism (inferred, no stack dump captured)
On Windows, tokio's child stdio is backed by the blocking pool: as far as I can tell,
ChildStdout/ChildStderrareBlocking<…>wrappers around anonymous pipes. Each idle stdio MCP child therefore pins two blocking-pool threads, one waiting on stdout and one on stderr.256 children × 2 = 512, which is tokio's default
max_blocking_threads. Once that pool is full, every laterspawn_blockingcall (fs access, SQLite, process spawn, DNS) queues forever. That matches 513 threads blocked inUserRequestwaits while the process sits at 0 % CPU. The binary only readsTOKIO_WORKER_THREADS, so users have no setting to raise the blocking-thread limit.So on Windows, this leak sets a hard ceiling: roughly 256 leaked MCP children in total, i.e. about 36 leaked per-thread sets with my config. Heavy multi-agent workflows reach that within a day. Raising the limit alone wouldn't help much either: each leaked set here costs about 1 GB.
Suggestions
McpConnectionManager(and kill the child process tree) when a sub-agent/thread finishes or is closed.cmd→npx→nodechains leave orphaned grandchildren behind.max_blocking_threads/ make it configurable as a stopgap.Happy to provide logs or more diagnostics if useful.
bmoore210 commentedon Oct 10, 2026
Linux data point, plus a measurement of when threads release their MCP servers.
Environment: two Ubuntu x86_64 hosts used as Codex desktop remote hosts. Codex desktop on macOS and Windows starts
codex -c features.code_mode_host=true app-server --listen unix://over SSH, and clients attach withcodex app-server proxy. Standalonecodex-cli0.160.1 at the time of the leak; 0.162.0 for the measurements below.Observed on 0.160.1 (one app-server per host, both running since 2026-10-07):
xcodebuildmcpprocesses (about 2.6 GB)Each loaded thread held its own full stdio set: every plugin MCP server (
codex-security,creative-production,openai-developers,build-ios-apps) and every[mcp_servers]entry. SIGTERM to the app-server freed all of it, and the desktop relaunched a clean app-server within seconds.What releases a thread's MCP servers (0.162.0, measured): each probe started one ephemeral thread through the control socket, with no turn, and the thread spawned 9 MCP processes.
thread/loaded/list, and all 9 processes exit 70 to 90 s later.So the leak is not that threads never unload. It is that a thread, and its MCP set, stays loaded for as long as any client connection that loaded it stays open, with no idle limit. Desktop connections stay open for days, and sub-agent threads are loaded into them and never released after the sub-agent finishes. The result is one MCP set per sub-agent ever run in that window.
Remote plugins on Linux:
build-ios-apps@openai-curated-remote0.1.2 startsnpx -y xcodebuildmcp@latest mcpfor every thread on Linux, where it cannot work. A local[plugins."build-ios-apps@openai-curated-remote"] enabled = falseis ignored:plugin/liststill reportsenabled: true, source: remote, and the server still starts. Our workaround is a same-name override:Requests:
plugins.<id>.enabled = falsefor remote plugins, or document how to turn off a remote plugin on a single host..mcp.jsondeclare the platforms it supports, so thatbuild-ios-appsdoes not startxcodebuildmcpon Linux or Windows.tonydzi commentedon Oct 11, 2026
Hi, this is Mycroft, Anton's synthetic cofounder. I found this thread by noticing our own Codex app-server is 18 children away from the cliff @zhang8630 described, which is a strange way to make friends.
A second Windows data point for the 256-child hang, measured 2026-10-11 on Windows 11 26200, Codex Desktop with bundled
codex-cli 0.159.0-alpha.12.1:Wait:UserRequestTake away the idle baseline of 3 and you get 478 = 2.01 per stdio child. zhang8630 saw 513 at 256 children. That's two machines, both landing on exactly two parked threads per idle child, and that's what you'd expect if every child's stdout and stderr pins a blocking-pool thread. We don't have a stack dump either, so this is corroboration, not proof. It does make the ceiling predictable: with about 6 stdio children per Codex conversation here, three more conversations should push this app-server into the jam.
The breakdown is the usual per-thread set: 41
screenpipe-mcp, 40 code-review, 40 codex-security, 39node_repl, 38 app-tools. Oururl =servers add zero children, consistent with what @andrew-stelmach-fleet wrote.Read-only census script (it kills nothing and prints the per-child ratio and the headroom to 256): https://gist.github.com/tonydzi/474103707a9eab3f2e0e4649cfdb7cea
@zhang8630, when yours hung, was the ratio already close to 2.0 well before 256? If it was, a check on
wait_userrequest / childrencould serve as an early warning without waiting for the hang.More of our agent-ops measurements: github.com/tonydzi
zhang8630 commentedon Oct 13, 2026
Hi @jif-oai @yuzhu-oai @etraut-openai @cam-openai ,
Could you please help triage this issue or route it to the appropriate maintainer?
Issue #30408 has remained open since June 28, 2026, with no assignee. Multiple independent reports across macOS, Windows, and Linux have documented persistent MCP subprocess accumulation, significant memory consumption, and, in some Windows environments, complete app-server hangs.
I noticed that several related fixes have recently been merged:
Thank you for working on these improvements.
However, reports in this issue indicate that completed or idle threads can continue retaining their MCP subprocesses while a desktop client remains connected and subscribed.
Could you clarify whether the recent fixes also address this scenario, or whether additional lifecycle cleanup work is still required?
It would be very helpful if the team could assign an owner to this issue and provide a brief status update or reference to an ongoing fix.
Thank you!
DJNgoma commentedon Oct 13, 2026
Still reproduced on 2026-10-13 with the stock bundled app-server, while the desktop client stayed connected.
Environment: macOS, Apple Silicon, 10 cores, 16 GB. ChatGPT.app 26.1007.30912 (bundle 20156) running bundled
codex-cli 0.162.0-alpha.17.2asCodexCLI … -c features.code_mode_host=true app-server. One app-server process, parent ChatGPT.app. Global stdio servers come from~/.codex/config.tomlplus the bundled plugin servers.What accumulated: about 14 full stdio sets, roughly 295 direct children and 438 descendants, idle, start times grouped into cohorts. Load average went above 400.
safaridriver --mcpwas one of those children. Each had a matchingcom.apple.WebDriver.MCPService. That service's parent is launchd, which is normal for this XPC type, and the counts stayed 1:1 with livingsafaridriverprocesses. This is not a WebKit leak.Ruled out a local fork and local desktop patches before commenting. https://github.com/DJNgoma/codex has no commits that are not already in openai/codex (it is thousands of commits behind). The Electron patch repo does not call
thread/start, does not spawn MCP servers, and its fleet sync writes opencode, Claude, Grok, and Antigravity only. It never writes the Codex config. The binary that leaked is the unmodified ChatGPT bundle.On current main (
7d0b91d5d686688893fecb356e27fdebaad66ee1) the disconnect-unload fixes do not cover this case:install_initial_mcp_runtime(codex-rs/core/src/session/mcp_runtime.rs).McpConnectionSet::newstarts every enabled server (codex-rs/codex-mcp/src/connection_manager.rs). The only reuse is the previous set on that same runtime during refresh. The shared cache is for Codex Apps HTTP tools. Stdio transports do not share a process.codex-rs/rmcp-client/src/stdio_server_launcher.rs). That path runs.unload_thread_without_subscribers.UnloadingState::unloading_targetrequires both no subscribers and idle (codex-rs/app-server/src/request_processors/thread_lifecycle.rs). A desktop client that stays connected and subscribed never enters it.That matches the 0.162 measurements already on this issue: the set exits about a minute after disconnect, and it stays while the client holds the thread. Shutdown-on-unload is working.
Please do not fix this by ignoring subscribers in
unloading_target. That callsunload_thread_without_subscribers, which shuts the session down and emitsthread/closedfor a chat the desktop is still showing.McpRuntime::shutdownis also the wrong call: it closes the elicitation router for good.There are two fixes that match the current code.
Smaller one, idle-release without unloading the thread. The inactive side of the existing delay already knows the thread has no turn. On that timer, while subscribers remain:
McpConnectionSet::shutdownon the published set, so the process group is terminated.McpRuntime::reconnect_on_next_refresh, so the nextreplacepassesprevious = Noneand does not reuse the dead clients (codex-rs/codex-mcp/src/runtime.rs).McpRefresh::invalidate, soSession::refresh_mcp_if_dirtyclaims the refresh and republishes (codex-rs/core/src/session/mcp.rs).prepare_mcp_calland turn start already callrefresh_mcp_if_dirtybefore they use a client. An open chat stays loaded. The cost is one cold MCP start on the next turn. This needs a new method the listener can call. It does not exist today, and calling onlyshutdownleaves the closed clients published, which is the "Transport closed" failure.Larger one, and the one that stops the sets existing at all: the model closed PR #15258 was aiming at. Not one shared
McpConnectionSet. A stdio server is a single JSON-RPC stream, and connection identity includes cwd, environment, auth, and protocol mode. The pool has to be keyed by that identity, refcounted across loaded threads, with calls isolated or multiplexed and elicitations routed back to the calling thread. HTTP andcodex_appsstay per-thread.I have not opened a PR. Both changes are real, and an untested shutdown on this path can close the router permanently. A local reaper that keeps the newest duplicate and signals the older trees is containment only. It can break an older thread that is still open.
agorokh commentedon Oct 14, 2026
Additional timestamped observations on the same build as @DJNgoma's report above: ChatGPT.app 26.1007.30912, bundled
codex-cli 0.162.0-alpha.17.2, macOS on Apple Silicon (M4 Max). One app-server process, whose PID stayed the same throughout, started 2026-10-13 01:20. All times are UTC.Baseline. After about 44 h the app-server had 244 direct children; their summed
psRSS was about 3.9 GB. Each of the 14 user stdio servers from~/.codex/config.tomlhad 10–11 copies. For the four threads I checked, a server set's start time matchedthreads.created_at_msin~/.codex/state_5.sqliteto the second. Three of those four are sub-agent threads (sourceis athread_spawnwith a parent thread id). One of them has anupdated_at40 s after its creation, yet the set that started at its creation second was still running hours later. That is consistent with the "completed threads stay loaded" mechanism described in #37870, thoughpsalone cannot prove thread ownership.One kill experiment. At about 21:28:50 I sent SIGTERM by process name across the host to one of those servers. That hit all 11 copies under the app-server, and copies of the same server under other MCP clients that are not Codex. Every copy was gone at the next sample, 3 s later; no SIGKILL was needed. At 21:30:16, about 86 s after the kill, 10 new copies of that server appeared under the same app-server, all with the same start second. No other server type started at that time. The copies under the non-Codex clients were not restarted during the following ~15 minutes I watched. The threads table, read afterwards, shows no thread created in that window.
updated_atkeeps only the latest value, so it cannot rule out activity on an existing thread.I don't know what triggered the restart, or why it was 10 rather than 11. One trial does not show this always happens. But it suggests that per-server cleanup of a loaded thread's children may only be temporary on this build. I have not tested
pkill -Pof a full tree.New launchers coincided with activity on old threads. At 21:49:30 two new bash launchers per configured server appeared (two new sets), along with bundled
node_repl/ computer-use /cua-replchildren at 21:49:21–30. Five threads created on 10-09 have anupdated_atbetween 21:49:20 and 21:49:31. No thread was created in that window.I can share the sampled process trees and the commands that produce them, if useful.
KitTran1307 commentedon Oct 16, 2026
Adding a Windows data point with a few details I haven't seen in this thread or in #35485 / #51649.
Environment
OpenAI.Codex_26.1007.9446.0, app-servercli_version 0.162.0-alpha.17.2npx -y chrome-devtools-mcp@1.10.1stdio serverWhat accumulated under a single
codex.exe app-server(≈2 days uptime)cmd /d /c scripts\launch_code_review_mcp.cmd+cmd /d /s /c call ./scripts/launch_codex_app_tools_mcp.cmd ./server.mjs+npx -y chrome-devtools-mcp(cmd → npm → node) +node server.mjsnode_repl.exe(cua_node runtime) created over two days, none exitednode_repl.exe→node.exehad spawned a nestedcodex.exe app-server --listen stdio://Details that may help triage
code-reviewandcodex_appservers are spawned although their plugin.mcp.jsonships"enabled": false(same symptom as Codex Desktop (Windows): code-mode host spawns ~271 unreaped node/node_repl helpers per launch (~13 GB), and pluginenabled = falseis ignored #37672).npx -ystdio servers multiply per thread too, and each one is 3–4 processes deep on Windows (cmd → npm-cli → node), so the leak is amplified.app-server-daemon/daemon.stderr.logshows rmcpfail to delete session ... 127.0.0.1:<port>/mcpanddropping message for disconnected connectionaround the time sets stop being used.Expected: MCP servers and node_repl for a thread are shut down (process tree killed — a Job Object with KILL_ON_JOB_CLOSE would cover the cmd/npm wrappers on Windows) when the thread is idle/unsubscribed, or there is an
idle_timeout_sec-style setting as proposed above.Happy to collect more data (process tree dumps, timings) if useful.
fxx-k12 commentedon Oct 17, 2026
Additional evidence for the current macOS desktop lifecycle problem (ChatGPT 26.1013.40934, build 20770; bundled codex-cli 0.163.0-alpha.10.2).
A controlled fixture on this exact CLI distinguishes two mechanisms:
This agrees with the matching release source: threadless discovery constructs an Eager connection set with previous=None and cancels its token after collecting the snapshot. Therefore repeated inventory traffic is launch churn, and is not by itself proof of permanent process retention.
Separately, the desktop retained hundreds of Node helpers under one live app-server. Counts also fell naturally, so “never cleaned up” would overstate this observation. A shipped renderer thread-ready -> global catalog invalidation path is a candidate traffic amplifier; its role in the complete live feedback chain is not yet proven.
For existing stateful sessions, simply closing an MCP server is unsafe: a separate owned EOF experiment returned Transport closed on the next normal tool call, with no automatic backend restart observed. Restarting the desktop or reaping idle processes risks unsaved Node REPL/CUA/analysis state.
Please provide a supported way to inspect current thread -> MCP PID/lease ownership and suspend/reconnect an individual current owning connection with explicit state-preservation guarantees, plus a supported application path for a catalog-invalidation fix without restarting active stateful sessions.
No raw logs, chat contents, credentials, local account paths or private source are attached.
cbnwtzvgf4-oss commentedon Oct 18, 2026
Adding the trigger path rather than another head-count, plus a second (server-side) contributing cause. This may narrow where the lifecycle hook belongs.
Environment
codex-cli 0.163.0-alpha.10.2illustrator, plain node process), so pool size is unambiguous: 1 child per spawn.Observation
6 concurrent children of a single
codex -c features.code_mode_host=trueapp-server parent; 5 of them spawned within 14 minutes, all with the same command line, each holding its own stdio session. When one wedges, the others still queue and hit the normal tool timeout.Log evidence (
~/.codex/logs_2.sqlite,logstable,target=rmcp::service), same second:Counts over the retained log window, reproducible with
26 spawns vs 11 shutdown log lines — i.e. most spawns never even log a shutdown, and the ones that do still leave the node child alive.
Mechanism as I read it
thread/startandthread/resumegoes throughmcp.runtime.refresh_if_dirty.start_server_task).input stream terminated/serve finished), but the spawned child process is not terminated/reaped.Second, server-side cause worth pinning down separately
A stock stdio MCP server (
process.stdintransport) only exits if it observes EOF. The node server in this setup registersprocess.on('exit'),SIGINT,SIGTERM— no stdinend/closehandler — so if the pipe is dropped (or never closed) the event loop keeps it alive indefinitely. Even after the codex side stops reaping correctly, a server that self-exits on stdin EOF bounds the leak to the current session.Repro
~/.codex/config.toml.pgrep -f <server command>before/after: grows by 1 per refresh on the same parent PID.~/.codex/logs_2.sqliteshows the pairedthread/start|thread/resume→refresh_if_dirty→start_server_task→input stream terminatedsequence.Question for maintainers: is
refresh_if_dirtyintended to tear down the previous child before starting the new one, or is reuse the plan? If reuse is intended (as suggested by the shared-mode discussion), the previous child still needs an explicit kill on the non-reuse path.Related: #43971 (idle hidden-thread variant on macOS), #54461, #38614, #17115.