Show usage stats in context window for BYOK#315394
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Pull request overview
This PR fixes missing token/usage reporting for BYOK models in the Chat “Context Window” by propagating APIUsage through the VS Code Language Model streaming channel (as a custom LanguageModelDataPart) and decoding it back into the ChatResponse.usage returned to the chat layer.
Changes:
- Introduce
CustomDataPartMimeTypes.Usagefor streaming token usage as aLanguageModelDataPart. - Emit usage data parts from BYOK providers (Anthropic/Gemini) and from
CopilotLanguageModelWrapper. - Decode usage data parts in
ExtensionContributedChatEndpointand use them instead of hardcoded zero usage.
Show a summary per file
| File | Description |
|---|---|
| extensions/copilot/src/platform/endpoint/vscode-node/extChatEndpoint.ts | Collect Usage data parts from the response stream and populate ChatResponse.usage (fallback remains zeros). |
| extensions/copilot/src/platform/endpoint/common/endpointTypes.ts | Add CustomDataPartMimeTypes.Usage constant. |
| extensions/copilot/src/extension/conversation/vscode-node/languageModelAccess.ts | Have CopilotLanguageModelWrapper return APIUsage and emit it as a Usage LanguageModelDataPart. |
| extensions/copilot/src/extension/byok/vscode-node/geminiNativeProvider.ts | Emit Gemini BYOK usage as a Usage LanguageModelDataPart. |
| extensions/copilot/src/extension/byok/vscode-node/anthropicProvider.ts | Emit Anthropic BYOK usage as a Usage LanguageModelDataPart. |
Copilot's findings
- Files reviewed: 5/5 changed files
- Comments generated: 4
Contributor
blocks-ci screenshots changedReplace the contents of Updated blocks-ci-screenshots.md<!-- auto-generated by CI — do not edit manually -->
#### editor/codeEditor/CodeEditor/Dark
#### editor/codeEditor/CodeEditor/Light
#### editor/inlineChatZoneWidget/InlineChatZoneWidget/Dark
#### editor/inlineChatZoneWidget/InlineChatZoneWidget/Light
#### editor/inlineChatZoneWidget/InlineChatZoneWidgetTerminated/Dark
#### editor/inlineChatZoneWidget/InlineChatZoneWidgetTerminated/Light
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dmitrivMS
approved these changes
May 8, 2026
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Fixes #291100
The Context Window widget in chat shows
0%and zero token counts for all BYOK models. The root cause is inExtensionContributedChatEndpoint.makeChatRequest2— the success response hardcoded usage to all zeros.Fix:
Mirror the existing ContextManagement / StatefulMarker pattern by introducing a new CustomDataPartMimeTypes.Usage data part. BYOK providers emit token usage into the response stream as a LanguageModelDataPart, and ExtensionContributedChatEndpoint decodes it into the APIUsage returned to the chat layer.