AI coding agents (Claude Code, Codex) hang for ~5 minutes between API calls in sandbox

[xianxu]

Environment

• OpenShell CLI + sandbox: 0.0.16
• Base image: community base (Ubuntu 24.04)
• Claude Code: 2.1.92 (Node.js 22.22.1)
• OpenAI Codex: 0.117.0
• macOS host, same account — works fine

Summary

Claude Code and OpenAI Codex interactive sessions experience a consistent ~290 second delay between every API round-trip when running inside an OpenShell sandbox. The agents make progress in ~5 second bursts separated by ~5 minute hangs, making them effectively unusable.

This does NOT happen when running the same agents on the host machine with the same account and prompts.

Observed behavior

Simplest repro: just "hello" twice

19:21:43  USER  "hello"
19:21:47  ASST  "Hello!"                          (4s — fast)
19:21:47  USER  "hello"
           ─── 292 second hang ─────────────────
19:26:43  ASST  "Hi!"                             (4s once unblocked)
19:26:43  USER  "hello again"
           ─── 297 second hang ─────────────────
19:31:44  ASST  "Hey!"                            (4s once unblocked)

Larger session (tool use)

API call	Request sent	Response	Gap before request
1st	19:00:02	19:00:08	0s (startup)
2nd	19:04:57	19:05:04	288s
3rd	19:09:58	19:10:02	292s
4th	19:14:58	19:15:01	295s

Each API call itself completes in ~4-8 seconds. The entire delay is before the request is sent — the agent's process makes zero network calls for ~290 seconds between rounds.

What the proxy logs show

At startup, Claude Code opens ~12 CONNECT tunnels in rapid succession for various purposes:

• API calls (api.anthropic.com)
• Telemetry (/api/event_logging/v2/batch)
• Plugin updates (downloads.claude.ai)
• Superpowers plugin git fetch (github.com/.../git-upload-pack)
• Update checks (storage.googleapis.com)
• Datadog logging (http-intake.logs.us5.datadoghq.com — denied by policy)

During the ~290s gaps, the proxy log shows zero CONNECT or HTTP_REQUEST entries from the agent's PID. The agent is idle — not blocked on the proxy, not waiting for a response. Something internal to the process is blocking.

One anomaly: during the first gap, an orphan CONNECT tunnel (port 44778) was opened 65s into the gap with no corresponding HTTP_REQUEST. This tunnel was established at the TCP level but no HTTP traffic was relayed through it.

What we ruled out

Hypothesis	Test	Result
Proxy cold start	curl through proxy	1.5s consistently
API server slowness	Proxy logs show no request sent during gap	Not server-side
HTTP/1.1 vs HTTP/2	curl tests with both	Both fast
Large payload	--print with 60k system prompt	Fast (~12s)
Telemetry blocking	DO_NOT_TRACK=1 no_proxy=datadoghq.com	Still slow
Node.js EnvHttpProxyAgent	NODE_USE_ENV_PROXY=	Still slow
--print mode	Same prompt via --print with tool use	Fast (~14s)
--print --resume	Resume same session non-interactively	Fast (~12s)
Tool use	Bug repros with just "hello" twice	Not needed

The issue only affects long-lived interactive sessions. --print mode (short-lived process, exits after response) is always fast. Piped input to interactive mode is also fast (process is short-lived).

Reproduction

Minimal (just "hello" twice)

1. make sandbox into an OpenShell sandbox with policy allowing api.anthropic.com
2. claude --permission-mode bypassPermissions (interactive mode)
3. Type hello — response arrives in ~4s
4. Type hello again — hangs for ~290s, then responds in ~4s
5. Every subsequent message repeats the ~290s hang

Not affected

• claude --print -p "hello" (non-interactive) — always fast, even with --resume
• Same interactive session on host (outside sandbox) — always fast

Impact

Both Claude Code and OpenAI Codex are unusable in interactive mode inside OpenShell sandboxes. This started within the last few days (possibly related to a base image update, though reverting the base image didn't fix it).

Repo with full setup and debug artifacts

https://github.com/xianxu/parley.nvim, sha: df98ad791f9403608b0ca10dbaeba2b937650113

• .openshell/ — sandbox setup scripts, policy.yaml, bootstrap
• debug-slowness/ — test scripts, evidence logs, findings
• issues/ - open issues being worked on

Notes

• During Gap 1, one CONNECT tunnel (port 44778 at 19:01:13) was opened with no corresponding HTTP_REQUEST in the proxy log. This was the only network activity from the agent during the 288s gap
• Prior proxy relay issues that may be related: bug(proxy): inference.local buffers entire streaming response, inflating TTFB #260 (SSE response buffering), bug(proxy): 60s reqwest total timeout kills streaming inference responses mid-generation #641 (60s total timeout on streaming), [Bug] Egress proxy fails to relay WebSocket frames after successful HTTP CONNECT + 101 Switching Protocols #652 (WebSocket frames dropped after CONNECT)

[xianxu]

After updating to the latest, this issue went away, so closing this.