Sessions and Task DAGs

Persistent PTY Sessions

For commands requiring user interaction, REPLs, or live monitoring:

• shell_open: Spawns a persistent pseudoterminal (PTY) session inside the workspace.
• shell_io: Sends input (keystrokes, text) and reads streaming output.
• shell_close: Gracefully signals or terminates the process.

Task Graphs (DAGs) & Durable Task Engine

For detached builds, test suites, and multi-stage workflows:

• tasks_run: Submits a dependency-aware task graph (dependsOn). Task metadata, dependency DAGs, and status are persisted in SQLite, while output streams are written to 0600 log files on disk.
• tasks_status: Polls execution status, progress, and bounded log outputs.
• tasks_list: Lists all tasks associated with the workspace.
• tasks_cancel: Cancels running or pending task stages.
• tasks_graph: Inspects dependency topology for diagnosing blocked tasks.

Durability & Restart Reconciliation

• Durable State: Unlike interactive PTY sessions (which live in volatile memory only and are lost on runner restart), task records, dependency DAGs, and on-disk logs persist across runner restarts.
• Crash Reconciliation: In-flight tasks from a prior runner epoch transition to terminal failed status (status: "failed" with errorCode: "RUNNER_RESTARTED") upon restart and can be inspected via tasks_status/tasks_list.
• Artifact Spooling: When a workspace closes or expires, task log outputs are automatically spooled into retained artifact storage.

The official Model Context Protocol specification (Tasks Extension Overview, 2026-07-28 revision) defines task management as an optional protocol extension (io.modelcontextprotocol/tasks) with tasks/get, tasks/update, tasks/cancel, and progress notifications.

Host / Client	Extension Support Status	Capability Handshake	Decision
Claude Desktop	Absent from official matrix	Not verified	Maintain canonical tasks_* tools
Cursor	Absent from official matrix	Not verified	Maintain canonical tasks_* tools
Codex	Absent from official matrix	Not verified	Maintain canonical tasks_* tools
ChatGPT Web	Absent from official matrix	Not verified	Maintain canonical tasks_* tools
Generic Streamable HTTP	Absent from official matrix	Not verified	Maintain canonical tasks_* tools

Reference: Official Extension Client Matrix.

Decision: Cloud Harness MCP keeps its stable, verified tool contracts (tasks_run, tasks_status, tasks_list, tasks_cancel, tasks_graph) as canonical. Standard MCP Tasks facade integration remains evaluated and default-off to prevent protocol drift until official client host runtime support is verified across the ecosystem matrix.