Route Claude workflows through the Stacklok LLM gateway

[eleftherias]

Summary

• Centralizing LLM usage through Stacklok's internal gateway (instead of hitting the Anthropic API directly) requires each Claude Code Action workflow to authenticate with a gateway-issued key and point at the gateway endpoint.
• Replaced the shared ANTHROPIC_API_KEY secret with three per-workflow gateway keys, and set ANTHROPIC_BASE_URL so all Claude Code Action traffic routes through https://llm-gateway.stacklok.dev/anthropic:
  • claude.yml (Claude PR Assistant) now uses STACKLOK_GATEWAY_KEY_CLAUDE_TAG
  • issue-triage.yml now uses STACKLOK_GATEWAY_KEY_ISSUE_TRIAGE
  • release-notes.yml now uses STACKLOK_GATEWAY_KEY_RELEASE_NOTES

Type of change

• Other (describe): CI workflow configuration change (auth/routing only, no functional behavior change)

Test plan

• Manual testing (describe below)

Verified via grep that no workflow still references secrets.ANTHROPIC_API_KEY, and that each workflow sets exactly one STACKLOK_GATEWAY_KEY_* secret plus ANTHROPIC_BASE_URL. These are GitHub Actions YAML changes only — there is no local build/test path that exercises them; correctness will be confirmed by the next live trigger of each workflow.

Does this introduce a user-facing change?

No — internal CI/automation configuration only.

Special notes for reviewers

The three new secrets (STACKLOK_GATEWAY_KEY_RELEASE_NOTES, STACKLOK_GATEWAY_KEY_ISSUE_TRIAGE, STACKLOK_GATEWAY_KEY_CLAUDE_TAG) must exist in the repo/org secrets store before merge, or these workflows will fail on their next trigger. The old ANTHROPIC_API_KEY secret can be removed once this is merged and verified, if it's not used elsewhere.

Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.18%. Comparing base (2ad87a3) to head (c91ee10).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6498      +/-   ##
==========================================
- Coverage   78.19%   78.18%   -0.02%     
==========================================
  Files         769      769              
  Lines       75049    75049              
==========================================
- Hits        58684    58675       -9     
- Misses      16360    16369       +9     
  Partials        5        5              

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