## What changed
Add session options for client- or server-owned output truncation and optional `max_output_tokens` budgets for wait and terminate observations. Introduce `TerminateRequest` and update session implementations and callers to use it.
Extend the stdio and gRPC schemas with optional truncation settings and budgets, and define the `bounded-output-v1` capability. Existing sessions retain client-side truncation; providers reject server mode by default. This change defines the contracts without enabling server-side truncation.
## Testing
Extend protocol serialization coverage for `outputTruncation: "server"` while preserving existing wire shapes when optional fields are absent.
GitOrigin-RevId: 22145897ea16d385c5ba9e7549109f7a669fceb4
## Why
Callbacks from the shared stdio host need to retain each execution's trace context after it yields, without keeping the execution span open until its background cell closes.
## What changed
Capture a W3C trace-context snapshot for each execution and restore it as the parent of tool callback and notification spans. Instrument delegate invocation and its returned future so the context is available on entry and across awaits.
## Testing
Add an integration test with overlapping yielded cells completed in reverse order. Cover sampled, unsampled, and untraced callers, trace isolation, callback and notification parentage, and execution spans finishing while callbacks remain blocked.
GitOrigin-RevId: 57924123d2c2f31bcfaf725688d8bba775235fa0
Sean Huang