deepseek-harness/packages/host/runtime

@deepseek-ai/dsh-host-runtime

Host runtime assembly for dsh: bootHost composes the core plugin spine (LLM service + DeepSeek adapter, sessions with JSONL persistence, system prompt, tools, agents, agent loop, workspace instructions, local bash), createApiProxy implements the dsh-host-apiproxy contract over that composition, and startHost is the one-step shell seam returning { api, handler, defaults, ctx, dispose }.

Which plugins mount and with what defaults is decided only here — shells must not ctx.plugin to alter the assembly. RunningHost.ctx is a formal seam with exactly two sanctioned uses: mounting protocol front-door plugins (e.g. a future dsh acp) and headless session-event subscription; consuming clients must not bypass api through it.

Configuration

Key	Default	Contract
persistenceRoot	(required)	Root directory for JSONL session persistence.
workspaceContext	(required)	AGENTS.md/CLAUDE.md loader config with an explicit maxBytes, or false to disable it.
provider	'deepseek'	Default provider route injected as agentOptions on create/resume and reported by host.describe.
model	'deepseek-v4-flash'	Default model id, same single source as provider.

ApiProxy implementation notes

Unary methods take the narrow RpcRequest<P> and echo request.rpcId; a prompt's rpcId rides MessageSource into the user/message event so clients can promote optimistic echoes. history/prompt on a cold session implicitly resume it, deduplicating concurrent calls through an in-flight table; history paginates backwards on message boundaries (never mid-message). The mux stream replays a session/subscribed baseline per attached session on open; the host stream carries session lifecycle, running flips, and agent/error as the only outlet for live failures with no turn position.

Model Experience

Indirectly, through the model-facing plugins bootHost mounts and the provider/model defaults injected into created and resumed agents. When workspaceContext is enabled, each agent-loop instance freezes the applicable workspace instructions into its logged request prefix; the owning package documents the exact model-visible framing.

KV Cache effect

No direct invalidation; the mounted model-facing plugins own their request-prefix changes.

Known Limitations and Deferred Work

• respond is a stub — it always returns not-pending; the approval/question pending registry (stable-rpcId mint on accept, baseline replay on stream reopen, wire answerer) is the next host-side step.
• host.describe.version is a placeholder — it does not yet report the apps/cli package version.
• The assembly is fixed — per-deployment plugin selection (user profile, log sinks, alternative persistence) has a documented home here but no configuration surface yet.