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Bug: Cannot read properties of null (reading 'length') when using BYOK #3911
Description
Describe the bug
When using BYOK (Bring Your Own Key) in the Copilot CLI, I encounter the following error: Cannot read properties of null (reading 'length').
Affected version
GitHub Copilot CLI 1.0.64.
Steps to reproduce the behavior
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Open Copilot CLI with the following command:
COPILOT_PROVIDER_TYPE=openai COPILOT_PROVIDER_WIRE_API=completions COPILOT_PROVIDER_BASE_URL=https://api.mistral.ai/v1 COPILOT_PROVIDER_API_KEY=$MISTRAL_API_KEY COPILOT_MODEL=mistral-medium-latest COPILOT_PROVIDER_MAX_PROMPT_TOKENS=262144 COPILOT_PROVIDER_MAX_OUTPUT_TOKENS=262144 copilot --yolo --log-level all --log-dir logs/
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Send prompt
hi
Expected behavior
No error
Additional context
Reacted by Martim Matias
Activity
martimmatias commentedon Jun 30, 2026
I was having the same issue with the Python Copilot SDK. I believe this error occurs when the OpeanAI compatible API returns a null value for
tool_calls.According to the OpenAI API docs, this field is an optional array. Copilot should check if it is null before checking the array's length.
Seeing this error on github-copilot-sdk 1.0.4 with copilot-cli 1.0.65 and 1.0.66.
patniko commentedon Oct 26, 2026
Thanks for the report. We've shipped fixes in this area since this was filed (most recently in Copilot CLI v1.0.81), and we believe this may now be resolved. Could you retest on the latest release (Copilot CLI v1.0.103) and let us know whether you still see it? If we don't hear back in a couple of weeks, we may close this issue — you can always reopen it.
Triaged as part of a Copilot SDK backlog review, with help from GitHub Copilot.