[reference-impl-sync] Reference Implementation sync: 3 new commits (2026-05-16)

[github-actions]

Automated Reference Implementation Sync

There are 3 new commits in the official Copilot SDK since the last merge.

• Last merged commit: e20f5bef125860accb30c60d1b35109371a77f16
• Reference Implementation HEAD: d0eb531e9ff58ea61f406caa9426f498f6485026

Recent reference implementation commits

d0eb531 feat: add model field to CustomAgentConfig across all SDKs (#1309)
38f38ff Update `@github/copilot` to 1.0.49-1 (#1307)
215676e Update `@github/copilot` to 1.0.49-0 (#1305)

Instructions

You MUST follow these steps in order. Do NOT improvise or skip scripts.

1. ✅✅Read .github/prompts/agentic-merge-reference-impl.prompt.md in full before starting✅✅

❌❌Do NOT clone the reference implementation manually — the start script does this.❌❌
❌❌Do NOT update .lastmerge manually — the finish script does this.❌❌
❌❌Do NOT skip the finish script — it syncs codegen versions and updates .lastmerge.❌❌

Generated by Reference Implementation Sync · ● 208.9K · ◷

• expires on May 22, 2026, 4:32 PM UTC

[github-actions]

Superseded by a newer reference implementation sync check.