Copilot Weekly: Custom Agents, Semantic Codebase, and CLI BYOK

This week’s Copilot Weekly covers the April 1–7, 2026 release cycle across Visual Studio, VS Code, and Copilot CLI. The headline: custom agents are now a first-class feature you define in your repo, the #codebase tool went fully semantic in VS Code 1.114, org-wide custom instructions hit GA, and Copilot CLI gained full bring-your-own-key support with air-gapped mode.

Visual Studio — March 2026 Update

Announced April 2, 2026 · github.blog/changelog

Custom Agents via .agent.md

Developers can now define specialized Copilot agents as .agent.md files stored directly in the repository. Custom agents get full workspace awareness, code understanding, tool access, model selection, and MCP connections — and they appear in the agent picker for the entire team. No separate configuration service required; the file is the agent.

This is a meaningful shift toward treating AI agents as versioned, reviewable artifacts alongside your code.

Agent Skills

Agent skills are reusable instruction sets that teach agents how to perform specific tasks. Define them in a repository or user profile and Copilot auto-discovers them. Community-shared skills are available at awesome-copilot — a growing library of tasks you’d otherwise write custom prompts for every time.

find_symbol Tool for Agent Mode

A new find_symbol tool gives agents language-aware symbol navigation: all references, type metadata, declarations, and scope. Supported languages include C++, C#, Razor, TypeScript, and any language with an LSP extension. Agents that previously had to infer symbol relationships from file content can now navigate the symbol graph directly.

Profile Tests with Copilot

A new “Profile with Copilot” command in Test Explorer runs a selected test through the Profiling Agent, which analyzes CPU and instrumentation data automatically and surfaces actionable performance insights. Beats staring at a flame graph and guessing.

PerfTips Powered by Live Profiling

Debug-time PerfTips now connect to the Profiler Agent. Click an inline performance signal while debugging and Copilot analyzes elapsed time, CPU usage, and memory behavior to suggest targeted optimizations — not just “this line took 200ms” but why and what to do about it.

Smart Watch Suggestions

Copilot now offers context-aware expression suggestions in Watch windows during debugging, surfacing the most meaningful runtime values faster. Small quality-of-life win, but welcome for anyone who’s typed the same nested property paths fifty times.

Fix NuGet Vulnerabilities with Copilot

When a NuGet package vulnerability is detected in Solution Explorer, Copilot can now recommend and apply targeted dependency updates via a “Fix with GitHub Copilot” link. Removes the manual CVE-to-package-version lookup step.

Enterprise MCP Governance

MCP server usage in Visual Studio now respects GitHub-managed allowlist policies, giving admins control over which MCP servers are permitted within their organizations. If you’ve been waiting for a governance story before rolling out MCP to developers, this is the answer.

VS Code 1.114 — Workspace Search Simplification

Released April 1, 2026 · code.visualstudio.com/updates/v1_114

The #codebase tool is now purely semantic — the previous fallback to fuzzy text search has been removed. The local vs. remote index distinction is also gone; VS Code now manages a single unified index automatically with no manual configuration.

This matters more than it sounds. Semantic-only means results are based on meaning, not substring matching — you stop getting noise from unrelated files that happen to share a keyword. The unified index means you stop having to reason about whether your code was indexed locally or remotely before attaching it as context.

Copilot Chat Updates

Released April 1, 2026 · code.visualstudio.com/updates/v1_114

/troubleshoot References Previous Sessions

The /troubleshoot skill can now reference any previous chat session when diagnosing chat issues — why custom instructions were ignored, why responses are slow, etc. Attach a prior session via /troubleshoot #session or through + Add Context > Sessions. No need to reproduce issues to investigate them.

Copy Final Response

A new “Copy Final Response” command copies only the last Markdown output after all tool calls have completed, excluding thinking steps and intermediate tool output. Useful for sharing clean responses without agent scaffolding cluttering the paste.

Organization Custom Instructions — Generally Available

April 2, 2026 · github.blog/changelog

Organization custom instructions for GitHub Copilot are now GA for Copilot Business and Enterprise admins. Set default instructions that shape Copilot’s behavior across all repositories — applied consistently in Copilot Chat on github.com, Copilot code review, and the Copilot cloud agent.

Configuration: Organization Settings → Copilot → Custom Instructions.

This closes a gap that mattered for enterprise governance: you could set custom instructions per-repo, but not enforce baseline behavior org-wide. Now you can.

Copilot CLI — BYOK and Local Model Support

April 7, 2026 · github.blog/changelog

Copilot CLI now supports Bring Your Own Key (BYOK) — configure it to use Azure OpenAI, Anthropic, or any OpenAI-compatible endpoint (including local models via Ollama, vLLM, and Foundry Local) through environment variables. A new COPILOT_OFFLINE=true mode disables all GitHub telemetry for fully air-gapped workflows.

GitHub authentication is now optional when using a custom provider, though signing in still unlocks features like /delegate, GitHub Code Search, and the GitHub MCP server.

For enterprise teams in regulated industries or sovereign cloud environments, this is a significant unlock. You get the Copilot CLI workflow without data leaving your boundary.

Sources: github.blog/changelog · code.visualstudio.com/updates · devblogs.microsoft.com/visualstudio