Telemetry moves onto the plugin hook system, with a built-in cc-plugin-otlp and new rules for plugin telemetry hooks

What

OpenTelemetry is the standard Claude Code uses to send usage data to a collector you set up. Plugins can register hooks, small pieces of code that run when certain events happen. Telemetry now runs through that same hook system.

• New built-in plugin cc-plugin-otlp, registered next to "sec-default", "agents-md" and "telemetry". It registers a telemetry.log hook on the "collector" stream and sends each record from core or built-in origins to the OpenTelemetry log exporter. When it is loaded and hooks telemetry.log, Claude Code's own event records go through that hook; otherwise they take the old path.
• It is available only when CLAUDE_CODE_ENABLE_TELEMETRY is set, a further check is false, and the gate tengu_basalt_plover passes. That gate's built-in fallback is off, and nothing has been read about it for this release.
• Plugins get a telemetry interface: $.telemetry.log takes an entry { to?, event, props? } or a collector record, and $.telemetry.mark takes { feature, kind, reason?, props? }. Calls run through the handler chain and can be denied. telemetry.log and telemetry.mark become hookable events, and a hook's return value must have a value key.
• A telemetry hook's to must be a plain string, or list of them, from "anthropic" and "collector". Anything else is rejected with a message naming what was written (for example "a template string" or "the variable x"). A hook that changes to is rejected as "a changed to (pinned)".
• A hook with no to stands on every stream. The "anthropic" stream is reserved for plugins built into the CLI: a non-built-in plugin on it is refused and told to write on("telemetry.log", { to: "collector" }, hook).
• Wildcard hook patterns from non-built-in plugins no longer match telemetry.* events unless the pattern itself starts with telemetry..

Why

Plugin authors who write telemetry hooks must now add { to: "collector" }, and third-party plugins cannot tap Anthropic's telemetry stream through a broad wildcard. The built-in plugin shows telemetry export becoming a plugin rather than fixed code, though it only runs when its gate passes.