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Reading a new release v2.1.251 Analysing changes · 2/5 Writing the entries · 2/4 steps 470 findings $18.91 so far

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.213 Home All releases olderv2.1.212 v2.1.214newer
Claude Code v2.1.213

Host OTLP Telemetry for SDK Integrations

What

SDK host integrations can now emit custom telemetry events into Claude Code's OTLP pipeline using a host.* namespace. The system includes rate limiting and deduplication of error messages to avoid log spam.

Details
  • Events must follow the naming pattern host.<lowercase.dotted.name>
  • Attributes must use snake_case keys with string values
  • Payload is validated and rejected if it uses reserved namespaces (claude_code.*) or has invalid shapes
  • Rate cap: 240 tokens, refilling over time
  • Error categories: bad_envelope, bad_event_name, bad_attributes_shape, too_many_attributes, bad_attribute_key, bad_attribute_value, payload_too_large, emit_failed
Evidence

OTLP routing implementation (search for "host OTLP event dropped", "host OTLP event route error", "host OTLP event emit failed")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.213 →