Copilot chat erro: `stream.usage is not a function`

[kv9898]

System details:

Windows 11

Positron and OS details:

Version: Positron Version: 2026.06.0 (system setup) build 8
Code - OSS Version: 1.111.0
Commit: 164c170
Date: 2026-04-30T13:52:32-07:00
Commit: 39.6.0
Date: 142.0.7444.265
Electron: 22.22.0
ElectronBuildId: 14.2.231.22-electron.0
Chromium: Windows_NT x64 10.0.26200
Node.js: undefined
V8: undefined
OS: undefined

Session details:

Python 3.13.7

Describe the issue:

Every time I start a copilot agent chat, I got:

Steps to reproduce the issue:

1. Choose a GitHub Copilot model from chat pane
2. Start a conversation

Expected or desired behavior:

No error should appear

Were there any error messages in the UI, Output panel, or Developer Tools console?

stream.usage is not a function

GitHub Copilot Chat output channel:

2026-05-03 00:57:43.255 [info] Logged in as kv9898
2026-05-03 00:57:43.514 [info] Got Copilot token for kv9898
2026-05-03 00:57:43.514 [info] Copilot Chat: 0.39.2, VS Code: 1.111.0
2026-05-03 00:57:43.537 [info] AuthenticationService: firing onDidAuthenticationChange from handleAuthChangeEvent. Has token: true
2026-05-03 00:57:43.537 [info] copilot token sku: free_educational_quota
2026-05-03 00:57:43.537 [info] ConversationFeature: onDidAuthenticationChange has token: true
2026-05-03 00:57:43.537 [info] [code-referencing] Public code references are enabled.
2026-05-03 00:57:43.747 [info] Fetched model metadata in 529ms a010702b-406d-4767-9ecf-dd91389097da
2026-05-03 00:57:43.831 [info] ccreq:4ac58b3a.copilotmd | markdown
2026-05-03 00:57:44.412 [info] message 0 returned. finish reason: [stop]
2026-05-03 00:57:44.414 [info] request done: requestId: [b50c941d-9bf3-4d03-a731-fe9e1333231e] model deployment ID: []
2026-05-03 00:57:44.414 [info] ccreq:6ed08d5b.copilotmd | success | gpt-4o-mini-2024-07-18 | 409ms | [title]
2026-05-03 00:57:51.623 [info] ccreq:01a49083.copilotmd | success | gpt-5-mini -> capi-cus-ptuc-h100-ib-gpt-5-mini-2025-08-07 | 7398ms | [panel/editAgent]
2026-05-03 00:57:51.631 [error] TypeError: stream.usage is not a function
    at _ChatResponseStreamImpl._usage (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:464812:16)
    at _ChatResponseStreamImpl.usage (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:464975:12)
    at _ChatResponseStreamImpl._usage (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:464812:16)
    at _ChatResponseStreamImpl.usage (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:464975:12)
    at DefaultToolCallingLoop.runOne (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:466162:14)
    at DefaultToolCallingLoop._runLoop (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:465847:24)
    at d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:465787:26
    at DefaultIntentRequestHandler.runWithToolCalling (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:502391:22)
    at DefaultIntentRequestHandler.getResult (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:502202:29)
    at EditIntentRequestHandler.getResult (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:503309:20)
    at ChatParticipantRequestHandler.getResult (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:505903:18)
    at ExtHostChatAgent._requestHandler (d:\positron\resources\app\extensions\positron-copilot-chat\dist\extension.js:683620:14)
    at _ExtHostChatAgents2.$invokeAgent (file:///d:/positron/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:74055:14)
2026-05-03 00:57:51.702 [info] message 0 returned. finish reason: [stop]
2026-05-03 00:57:51.703 [info] request done: requestId: [7c8ffb6e-f121-47e8-8480-f17530cd5ddb] model deployment ID: []