[danielkov]

Summary

Expose sanitized provider retry progress to ACP v1/v2 clients and live subagent activity, including foreground and background compose execution. Preserve actual provider attempt counts, next delay, and cumulative completed backoff without introducing another model or tool outcome.

Resolves #45.

Technical details

Retry notices carry typed kit/providerRetry metadata containing route, status, attempts, reason category, next delay, and completed backoff milliseconds. Scheduled notices are limited to one per second of provider elapsed time and sixteen per logical request; the final retry observation clears activity and preserves exact accounting even when intermediate observations were suppressed.

ACP v1 emits or forwards this retry stream only when the parent advertises session.notices; nested Kit clients advertise that support. ACP v2 requires no notice capability, as specified by its notice contract.

The projection copies only allowlisted enums and numeric accounting. Provider payloads, prompts, credentials, endpoints, and customer identifiers are not included. Child notices retain their session ownership and are also projected into typed retry activity; centralized UI presentation remains separate.

[kit-code-agent]

The retry-notice stream needs to respect the client's negotiated notice capability.

_{Took 18 min}

[kit-code-agent]

The new v1 child notice advertisement can forward ordinary notices to parent clients that did not negotiate notice support.

_{Took 6 min 47 sec}

[kit-code-agent]

No issues found. The changes look good to merge.

_{Took 5 min 19 sec}