- Added `cwd` and `env` optional parameters to kernel execution API for runtime working directory and environment variable control.
- Implemented runtime environment setup in Python runner with `_apply_request_runtime()` to apply cwd and env from request before code execution.
- Enhanced SIGINT handler management with `active_executions` counter and `_begin_exec_sigint()` / `_end_exec_sigint()` functions to prevent state mutation during concurrent execution.
- Changed `SearchRenderArgs.paths` parameter type from `string[]` to `string | string[]` to accept single string paths.
- Added comprehensive test coverage for kernel cwd updates, timeout interruption safety, and SystemExit handling in shared executor sessions.
- Removed per-session run queues from JS and Python backends, allowing async cells on the same session id to interleave.
- Introduced `getEvalSessionId` on ToolSession so subagents spawned via `task` inherit the parent's executor id and share JS VM and Python kernel state.
- Switched JS runtime state from module-level fields to AsyncLocalStorage so concurrent runs route output and tool calls to their own context.
- Changed Python runner to an asyncio event loop with per-request tasks and ContextVar-based run id tracking for concurrent execution.
- Added mtime-based module cache eviction to preserve singleton state across re-imports of unchanged local files.
- Added a persistent asyncio event loop and coroutine-aware compiled-code execution for runner cells.
- Enabled compiling notebook cells with top-level await flags and awaiting coroutine results before rendering.
- Added an integration test confirming top-level await works across kernel cells with preserved state.
- Replaced Python execution with a local `python -u runner.py` subprocess and NDJSON stdin/stdout framing.
- Removed shared-gateway architecture, including coordinator lifecycle APIs, `useSharedGateway` wiring, and `jupyter` CLI/actions.
- Simplified setup checks to a plain Python 3 availability probe and removed automatic dependency-install fallbacks.
- Updated kernel cancellation and display processing to use status frames, SIGINT/SIGTERM escalation, and normalized output coercion.
- Added `python-runner` integration and display tests while deleting legacy websocket and kernel lifecycle test suites.
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