[BUG] Streaming stall: 150s gap mid-tool-call, no UI feedback during gap

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Subject: Streaming stall: 150s gap mid-tool-call, no UI feedback during gap

Environment:

Claude Code 2.1.126.d6f, claude-vscode entrypoint
VS Code native extension, Windows 11
Model: Opus 4.7

Symptom: Approval prompt for a long PowerShell tool call did not appear for ~2.5 minutes after the tool call was emitted. From the user's perspective, the UI looked frozen.

Log evidence (timestamps in UTC):

2026-05-02T19:51:24.858Z [DEBUG] [API REQUEST] /v1/messages
2026-05-02T19:51:26.570Z [DEBUG] Stream started - received first chunk
2026-05-02T19:53:58.158Z [WARN] Streaming stall detected: 150.0s gap between events (stall #1)
2026-05-02T19:53:58.160Z [WARN] Streaming completed with 1 stall(s), total stall time: 150.0s
2026-05-02T19:54:05.068Z [INFO] [Stall] tool_dispatch_start ... permissionDecisionMs=156921

Tool call payload: A single PowerShell command of ~600 chars invoking python.exe -c "import ast; ast.parse(...); ast.parse(...); print('OK')" to syntax-check two files.

Observations:

The streaming stall warning is firing as designed — good.
During the stall, no UI indication is shown to the user (no "still streaming…" or partial progress). The user reasonably interprets the silence as a freeze.
This is intermittent — other tool calls in the same session arrived in <2s.

Suggestions:

Surface the streaming stall to the user in the UI when it crosses a threshold (e.g., >30s), so they know waiting is the right action.
If possible, log whether the stall was server-side (API not sending) vs. network (client not receiving).

What Should Happen?

Minimal delay

Error Messages/Logs

2026-05-02 14:53:44.158 [info] Received message from webview: {"type":"request","requestId":"nofyo2316dq","request":{"type":"rename_tab","title":"Install Miniconda and mi…","hasPendingPermissions":true,"hasUnseenCompletion":false}}
2026-05-02 14:53:44.160 [info] Received message from webview: {"type":"request","requestId":"cmw9r7xecbi","request":{"type":"update_session_state","sessionId":"d5a5a7d1-17a1-46b5-83a1-6eb0e946cdd0","state":"waiting_input","title":"Install Miniconda and migrate from Anaconda 3"}}
2026-05-02 14:53:44.160 [info] Received message from webview: {"type":"request","requestId":"fkdrunf4s1n","request":{"type":"show_notification","message":"Claude is requesting permission to use PowerShell","severity":"info","buttons":["View"],"onlyIfNotVisible":true}}
2026-05-02 14:53:47.065 [info] Received message from webview: {"type":"request","requestId":"o0ot9i4w6y","request":{"type":"rename_tab","title":"Install Miniconda and mi…","hasPendingPermissions":false,"hasUnseenCompletion":false}}
2026-05-02 14:53:47.065 [info] Received message from webview: {"type":"request","requestId":"nb23r2ia7ah","request":{"type":"update_session_state","sessionId":"d5a5a7d1-17a1-46b5-83a1-6eb0e946cdd0","state":"running","title":"Install Miniconda and migrate from Anaconda 3"}}
2026-05-02 14:53:47.065 [info] Received message from webview: {"type":"request","requestId":"f11pqseq0cs","request":{"type":"rename_tab","title":"Install Miniconda and mi…","hasPendingPermissions":false,"hasUnseenCompletion":false}}
2026-05-02 14:53:47.066 [info] Received message from webview: {"type":"request","requestId":"1xerlzy3s1v","request":{"type":"update_session_state","sessionId":"d5a5a7d1-17a1-46b5-83a1-6eb0e946cdd0","state":"running","title":"Install Miniconda and migrate from Anaconda 3"}}
2026-05-02 14:53:47.069 [info] Received message from webview: {"type":"response","requestId":"c5509810532d5d6d3b35e76b35a93863","response":{"type":"tool_permission_response","result":{"behavior":"allow","updatedInput":{"command":"$pkgs = @('numpy','pandas','scipy','matplotlib','tqdm','xlwings','pywin32'); $freeze = Get-Content anaconda_pip_freeze.txt; foreach ($p in $pkgs) { $line = $freeze | Where-Object { $_ -match \"^$p==\" }; if ($line) { $line } else { \"$p : NOT FOUND in pip freeze\" } }","description":"Extract versions of project's third-party packages"},"updatedPermissions":[{"type":"addRules","rules":[{"toolName":"PowerShell","ruleContent":"$pkgs = @('numpy','pandas','scipy','matplotlib','tqdm','xlwings','pywin32'); $freeze = Get-Content anaconda_pip_freeze.txt; foreach ($p in $pkgs) { $line = $freeze | Where-Object { $_ -match \"^$p==\" }; if ($line) { $line } else { \"$p : NOT FOUND in pip freeze\" } }"}],"behavior":"allow","destination":"session"}]}}}
2026-05-02 14:53:47.081 [info] From claude: 2026-05-02T21:53:47.080Z [DEBUG] Applying permission update: Adding 1 allow rule(s) to destination 'session': ["PowerShell($pkgs = @\\('numpy','pandas','scipy','matplotlib','tqdm','xlwings','pywin32'\\); $freeze = Get-Content anaconda_pip_freeze.txt; foreach \\($p in $pkgs\\) { $line = $freeze | Where-Object { $_ -match \"^$p==\" }; if \\($line\\) { $line } else { \"$p : NOT FOUND in pip freeze\" } })"]

2026-05-02 14:53:47.082 [info] From claude: 2026-05-02T21:53:47.082Z [INFO] [Stall] tool_dispatch_start tool=PowerShell toolUseId=toolu_01SyE41Q2YSNLrjunnXNgWv9 permissionDecisionMs=153827

Steps to Reproduce

Claude trying to call a Powershell script with a long string.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.126 Claude Code

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_