99a778d63f
Implement the continuable background subagents RFC: a durable child session with a series of Task-backed activations, each disposing its run before the Task settles. - dsh-subagent: rename SubagentRun.sendMessage to strict steer, drop run-level resume, add SubagentProvider.resume dispatch via SubagentService.resume, the continuation start field, and the versioned model-hidden subagent/descriptor session event. - dsh-subagent-inprocess/-spawn/-fork: publish the control-allocated child id, append the descriptor inside the initial turn, implement cold resume from the child's own transcript under the live parent scope, and strict running-only steer. - dsh-subagent-control (new): SubagentControlService owning stable child ids, descriptor snapshot/fold/authorization, Task-backed activation with settle-then-dispose ordering, the process-local active-run association, and steer-or-resume sendMessage routing. - dsh-tool-subagent: background route branches on the provider's resume capability (continuable via the control service; one-shot task for ACP), returning both child and task ids. - dsh-tool-subagent-control (new): the globally named send_message tool rendering steered/started routes. Keyless coverage spans Task ownership and disposal ordering, running delivery, cold follow-up, descriptor rejection and rollback, known-id reconstruction, kill during lookup, admission races, and a new subagent-continuable ACP snapshot scenario.
@deepseek-ai/dsh-subagent-fork
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The fork provider creates an in-process child seeded with the parent's completed conversation turns. It shares all run mechanics with spawn; the session seed is the only behavioral difference.
Seed boundary
The parent's current tool-calling turn is still open when a subagent starts: its log contains the assistant tool call but not the matching tool result or turn/end. Copying that raw log would give the child an invalid, unbalanced session.
Fork therefore computes the contiguous prefix ending at the last turn/end. The child sees all completed parent turns and none of the in-flight turn. If the parent has not completed a turn yet, the seed is empty and the child behaves like a fresh spawn.
The seed transfers conversation history only. The child still receives a fresh flat registration scope; it does not inherit the parent's tool restrictions or authority.
Start and capabilities
start(request) passes the completed-turn seed to startInProcessRun and awaits child publication. The shared driver owns cancellation, depth, customization, result reading, and disposal.
Fork advertises { outputSchema: true, depthLimit: true, toolFilter: true, persona: true }, identical to spawn.
Config
| Key | Meaning |
|---|---|
providerName |
Registry name on ctx.subagents (default fork). |
See dsh-subagent-spawn for the run lifecycle, model inheritance, and depth tracking — all shared. |
Model Experience
Child-agent history and envelope
What the model sees
The child receives the parent's balanced completed-turn surface prefix, then the new task content verbatim. A configured persona shadows prompt text in the child's fresh scope; a tool restriction filters its global wire schemas, executable lookup, and Code Mode SDK bindings but not standalone guidance. The parent's tool view and authority are not inherited. An optional structured-output request adds its child-only contract. The parent's current in-flight turn is excluded.
Token effect
Forking duplicates retained completed history into separate child requests; the child then accumulates its own tokens independently. Persona changes repeated prompt cost, filtering changes schema or generated SDK cost, and a first-turn fork has no inherited history.
KV Cache effect
The child may reuse the inherited byte-identical prefix under the same provider and model. Persona, tool-filter, generated-SDK, or route changes may invalidate reuse before inherited history; later child history is append-only.
Parent tool result, indirectly
What the model sees
The parent receives only the child's own final output through dsh-tool-subagent, not the inherited prefix or intermediate work.
Token effect
Parent input grows by one data-dependent final result retained until compaction.
KV Cache effect
Append-only; newly visible content follows the reusable request prefix and does not invalidate existing KV-cache entries.
Known Limitations and Deferred Work
- The seed is a one-time snapshot — the child sees the parent's completed turns as of the fork and nothing the parent logs afterwards; there is no live context sharing.