## What changed
Add the disabled-by-default `code_mode_host_output_truncation` feature flag. When enabled, Core requests server-side output truncation for its built-in code-mode session providers over both stdio and gRPC. Injected providers retain control of their session settings, and explicit session options pass through unchanged.
## Testing
Add coverage for both transports verifying that the host's output-limit notice survives a zero-token observation budget. Extend the shared-provider test to exercise an injected provider with the new flag enabled.
GitOrigin-RevId: edbb65e930bf544e3d2f8384767037a6fb82d451
## Why
Host-side truncation can bound Code Mode output before it crosses the transport, including script errors that would otherwise exceed the frame limit.
## What changed
- Negotiate server-side output truncation for stdio and gRPC sessions, with client-side fallback for older hosts.
- Forward output budgets for execution, waiting, and termination when server-side truncation is selected. Avoid truncating host-formatted output or appending script errors a second time.
- Preserve the negotiated mode across reconnects and reject hosts that cannot maintain it.
## Testing
Add transport and integration coverage for output budgets, oversized script errors, reconnect compatibility, and preservation of output-limit notices with a zero-token budget.
GitOrigin-RevId: 2075101e4845eca64f45491c27a3b326788645c8
## What changed
- Add `GetProcessMetrics` and provider sampling APIs for process ID, start time, cumulative CPU time, and resident memory, exposed through `ThreadManager` without creating a thread or session.
- Distinguish unsupported collection, a locally absent host, and sampling failures. Process-owned providers never start or replace a host when sampling.
- Bound gRPC sampling to one second without retries or explicit connection resets. Run optional collectors on a detached worker with at most one collection in flight, so stalled collection cannot block the HTTP/2 driver or runtime shutdown.
## Testing
Add coverage for snapshots, collector errors and panics, deadlines, overload, and shutdown with a stuck collector. Extend lifecycle tests to check that sampling preserves session state and keepalive behavior without starting or restarting local hosts.
GitOrigin-RevId: eeafe275891d0464636f28a29345a87aed1a12dc
## Why
Automatic gRPC reconnection could spawn a replacement host while dispatching an RPC for an existing session. Host loss must remain visible so recovery can report lost state without replaying execution or completed external effects.
## What changed
- Bind each local host channel to one child process and allow only `OpenSession` to replace a dead host.
- Add caller-owned transport support to `GrpcCodeModeSessionProvider` and map local transport failures to `Unavailable` so initial connection failures use the existing bounded admission retries.
## Testing
Add regression coverage for child exit during initial connection and between channel selection and dispatch, concurrent session recovery, and child reaping after teardown. An integration test kills the host after a command completes and verifies that recovery reports the reset, clears stored state, and leaves the command's external effect unchanged.
Increase the remote MCP stalled-handshake test's initialization timeout and mock response delay to let requests reach the server on loaded CI workers.
GitOrigin-RevId: 4ffd810e4cfcfb7a56e606816aa867bc206a09b6
## What changed
- Add `grpc+stdio://` as a host transport and the disabled-by-default `code_mode_host_grpc` feature flag to select it.
- Share a lazy HTTP/2 channel and host process across code-mode sessions while keeping session state isolated.
- Use HTTP/2 keepalives to detect unresponsive hosts, kill and reap disconnected children, and spawn a fresh host on reconnect. Exit the host when its stdio connection closes.
## Testing
Add coverage for shared-host session isolation, host exit on stdin EOF, and recovery after an unresponsive host is reaped. Exercise nested tool calls with both legacy stdio and gRPC stdio, asserting that the feature flag selects the expected transport.
GitOrigin-RevId: 31389d8540de236b8e0571d3c24e29e117b75c4a
Sean Huang