Tag: claude-code

OAuth succeeded but every MCP call gets 401 invalid_token? Make the PRM resource, the token's aud and your validator agree on one canonical server URL.

Claude Code 2.1.260 adds a likely-cause diagnosis to the Prompt cache (main) line in /usage and to the prompt_cache status line object. Instead of just counting misses, it tells you whether the tool set changed, the system prompt changed, or the TTL expired.

A skill's body loads on demand, but its name and description sit in a listing that is always in the prompt, capped at 1% of the context window. Claude Code 2.1.261 adds /skill-doctor to say which loaded skills never get used and what each one costs, so you can prune them before the budget starts evicting the skills you do use.

The cold start of a subagent is not what costs you money. Measured across 117 real Claude Code subagent transcripts, startup context was 0.6% to 18% of each agent's total spend. Depth is expensive because every layer runs its own agentic loop and hands the layer above a summary instead of evidence. Here is the compression test that tells you which layer to delete.

Until now the only way to hand every developer the same MCP servers was managed-mcp.json, a file at a system path that takes exclusive control of MCP. Claude Code 2.1.259 adds a managedMcpServers setting for HTTP and SSE servers, and quietly narrows what allowedMcpServers governs.

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.