claude-code

The experimental /rubber-duck command in VS Code 1.135 hands the agent's plan, code, and tests to a model from another family for review. GPT-5.4 critiques Claude, and the cross-family choice is the whole point.

Agent Plugins 1.0.0 standardizes exactly two component types: skills and MCP servers. Slash commands, hooks, subagents, rules, LSP servers, permission config and secrets all stay vendor-specific. Here is the field-by-field matrix across Claude Code, Cursor, Copilot and Codex, and which layout to author in.

Claude Code 2.1.251 adds PreModelSwitch and PostModelSwitch hook events. The matcher fires on the canonical name of the model you are switching to, and exit code 2 cancels the switch.

A symlink swapped after the check, deny rules that stopped applying through a symlinked search path, a marketplace command pointing outside its plugin, and a workflow script read before approval. Four fixes in one release, all the same bug.

A server that vanished from /mcp with no error is almost always an allowlist. Run claude mcp add on the same server: the add path prints the reason the load path swallows.

A headersHelper field on url marketplaces and catalog entries runs a local command that prints HTTP headers, so an internal plugin catalog behind S3 or an artifact repo can authenticate with a short-lived token. Here is the schema, the consent prompt, and the header names Claude Code drops.

MCP error -32022 means your client opened at 2025-11-25 but the server only serves 2026-07-28. Make one side dual-era instead of pinning a version.

Claude Code and GitHub Copilot both ship allowedMcpServers and deniedMcpServers, but the matchers behave differently. serverName is a fallback that a single serverCommand entry silently disables, deny is a union while allow is not, and an invalid allowlist locks everything out.

Agent Plugins 1.0 says plugin.json at the root and mcp.json beside it. Claude Code 2.1.x wants .claude-plugin/plugin.json and .mcp.json. Here is what each client actually loads, tested against a real plugin, and the dual-layout directory that satisfies both.

Tightening a team's default permission mode to Manual is a one-line settings change interactively and a silent outage in CI, because headless runs turn every ask into a deny and still report success. Measured on Claude Code 2.1.224, including the trust gate that drops your allowlist but keeps your mode.