v1.17.7: GitHub Copilot API missing X-GitHub-Api-Version header — GPT-5.5 and latest models not shown #32627

Summary

v1.17.7 does not send the X-GitHub-Api-Version header when calling the GitHub Copilot /models endpoint. As a result, the API returns only legacy models (20 models), omitting GPT-5.5, GPT-5.4, Claude Opus 4.7, Claude Sonnet 4.6, etc.

Impact

• Model selector (TUI and /model command) only shows old models (claude-opus-4.5, gpt-4o, etc.)
• GPT-5.5, GPT-5.4, Claude Opus 4.7, Claude Sonnet 4.6 are missing
• Users cannot select the latest premium models

Root Cause

GitHub Copilot API now requires the X-GitHub-Api-Version header to return the full model list:

Evidence

# Without header — only legacy models
curl -s -H "Authorization: Bearer $TOKEN" \
  "https://api.githubcopilot.com/models" | jq '.data | length'
# Returns: 20

# With header — full model list
curl -s -H "Authorization: Bearer $TOKEN" \
  -H "X-GitHub-Api-Version: 2024-12-15" \
  "https://api.githubcopilot.com/models" | jq '.data | length'
# Returns: 30

Workaround

Downgrade to v1.17.6:

opencode upgrade 1.17.6

Environment

• OpenCode version: 1.17.7 (broken), 1.17.6 (works)
• Platform: macOS (arm64)
• Provider: GitHub Copilot (Business plan, organization: selta-dev)
• Auth: OAuth (non-enterprise, github.com)

Suggested Fix

Add X-GitHub-Api-Version: 2024-12-15 header to all GitHub Copilot API requests, especially the /models endpoint.