deepseek-harness/docs/subsystems/system-prompt.md

System Prompt Assembly

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The system-prompt package owns the data exchanged between prompt contributors and one assembly call. The package README documents registration, ordering, scoping, and rendering behavior; this page records the exact cross-package types that plugins implement or pass.

Source: packages/core/system-prompt/src/index.ts.

Assembly context

AssembleContext identifies the scope layer one assembly resolves and may carry the explicit control signal for that request. It is merge-extensible: dsh-agent adds the optional live agent field, and assembleContextFor(agent, signal) sets the explicit fields together. A bare assembly has neither scope nor signal.

/** Merge-extensible context for one prompt assembly. */
interface AssembleContext {
  /**
   * Scope whose providers and waterfall listeners participate. When absent,
   * only global providers and subject-less listeners participate.
   */
  scope?: ScopeKey
  /** Explicit control signal for the turn that requested this assembly, when any. */
  signal?: AbortSignal
}

Tool-provider result

ToolProviderResult.schemas is the model-visible set for the current assembly. knownNames is the provider's pre-restriction name universe used to distinguish a configured-name typo from a known tool that is deliberately hidden in this scope.

/** Tool schemas visible in one assembly and their pre-restriction name set. */
interface ToolProviderResult {
  /** The schemas this provider contributes to THIS assembly. */
  readonly schemas: readonly ToolSchema[]
  /** The pre-restriction name universe for config validation (defaults to `schemas`' names). */
  readonly knownNames?: readonly string[]
}

Prompt sections

The exported PERSONA_PREFIX_SECTION (deployment:persona-prefix) and PERSONA_SUFFIX_SECTION (deployment:persona-suffix) name the slots shared by global configuration and scoped contributions. Their PromptSectionOrderName entries are DEPLOYMENT_PERSONA_PREFIX and DEPLOYMENT_PERSONA_SUFFIX; the package README owns their placement and template configuration.

PromptSection is a readonly same-process registration contract. Its text may be static or resolved from the current assembly context. Sections sort by ascending order and then code-unit name; repository contributors resolve the service-owned named allocation through getSectionOrder(). Runtime-context contributors resolve their independent allocation through getContextOrder(). One effective complete section becomes the sole prompt section after cooperative assembly. agent-loop renders the assembled sections with renderPrompt and commits the text as the system/message surface node 0 — appended on the first step, replaced in place when the rendered text changes — so the prompt reaches the model as the leading message of derived history rather than as a request field (decision).

/** One contributed section of the system prompt (registry input). */
interface PromptSection {
  /** Unique name — a duplicate registration throws (see {@link SystemPrompt.section}). */
  readonly name: string
  /**
   * Sections are concatenated in ascending order. Equal orders use code-unit
   * name order.
   */
  readonly order: number
  /**
   * Static text or a provider evaluated at each assembly with that assembly's
   * {@link AssembleContext}. The text may reference `{{variable}}`s — they are
   * interpolated later, by {@link renderPrompt}.
   */
  readonly text: string | ((context: AssembleContext) => string)
  /**
   * Treat this contribution as the complete system prompt. Assembly still
   * runs the cooperative waterfall so tools, contexts, and variables can be
   * resolved, then restores this exact section as the sole prompt section.
   * More than one effective complete section makes assembly fail.
   */
  readonly complete?: boolean
}

Dynamic prompt context

PromptContext is the cache-safe counterpart to PromptSection. The assembly resolves and orders these contributions, while agent-loop logs their complete current snapshot after retained model history only when it changed or compaction removed it.

/** Dynamic model context materialized as a durable user-role snapshot. */
interface PromptContext {
  /** Unique name — a duplicate registration throws (see {@link SystemPrompt.context}). */
  readonly name: string
  /** Contexts are joined in ascending order. */
  readonly order: number
  /** Static text or a provider evaluated for each assembly. Empty text contributes nothing. */
  readonly text: string | ((context: AssembleContext) => string)
}

Cordis API

Generated from source by scripts/gen-cordis-catalog.ts (verified fresh by pnpm run verify-cordis-catalog in doc-sync; regenerate with pnpm run gen-cordis-catalog) — the language sides differ only in locale-specific paired document paths. Signature blocks use a ts cordis-catalog fence and keep the original source JSDoc; dispatch modes are defined in the primer, and the framework-inherited ctx API lives in cordis-api/inherited.md.

ctx.systemPrompt — SystemPrompt

Registry service for the prompt inputs assembled before each model step.

/**
 * Register an ordered prompt section in the calling context's scope. A scoped
 * section shadows a global section with the same name; duplicates within one
 * layer and non-finite orders throw. Registration and disposal emit
 * `system-prompt/change`.
 * @param section - the section to register.
 * @returns the exact Cordis effect disposer.
 */
section(section: PromptSection): () => void

/**
 * Resolve the centrally owned placement of a repository prompt section.
 * @param name - stable section placement name.
 * @returns the section's numeric sort order.
 */
getSectionOrder(name: PromptSectionOrderName): number

/**
 * Resolve the centrally owned placement of a repository runtime context.
 * @param name - stable context placement name.
 * @returns the context's numeric sort order.
 */
getContextOrder(name: PromptContextOrderName): number

/**
 * Register ordered dynamic context in the calling context's scope. Scoped
 * entries shadow global entries with the same name.
 * @param context - the context contribution to register.
 * @returns the exact Cordis effect disposer.
 */
context(context: PromptContext): () => void

/**
 * Suppress every dynamic runtime-context contribution in the calling
 * context's scope without changing the services that own or enforce those
 * facts. Multiple suppressors remain independently disposable.
 * @returns the exact Cordis effect disposer.
 */
suppressRuntimeContext(): () => void

/**
 * Register a tool-schema provider in the calling context's scope. Global and
 * matching scoped providers both contribute; returning the reserved
 * {@link TOOL_ORDER_REST} name makes assembly fail.
 * @param provider - evaluated for each assembly with its context.
 * @returns the exact Cordis effect disposer.
 */
tools(provider: (context: AssembleContext) => ToolProviderResult): () => void

/**
 * Register a prompt variable in the calling context's scope. Scoped values
 * shadow globals; invalid or duplicate names throw. A provider may return
 * `undefined`, but rendering a section that references that value then fails.
 * @param name - the `[a-z][a-z0-9_]*` reference name.
 * @param provider - evaluated for each assembly.
 * @returns the exact Cordis effect disposer.
 */
variable(name: string, provider: (context: AssembleContext) => string | undefined): () => void

/**
 * Assemble global and scoped providers, detach tool parameters, apply
 * canonical ordering, then run the assembly waterfall. Scoped sections and
 * variables shadow globals. The returned waterfall value is authoritative
 * except that an effective complete section is restored afterwards as the
 * sole prompt section.
 * @param context - the optional scope and plugin-defined assembly fields.
 * @returns the post-waterfall assembly with any complete prompt enforced.
 */
async assemble(context: AssembleContext = {}): Promise<PromptAssembly>

Source: packages/core/system-prompt/src/index.ts

system-prompt/* events

system-prompt/assemble — waterfall

Expert waterfall over the assembled sections, contexts, tools, and variables. Scope-filtered dispatch (@deepseek-ai/dsh-scope): scoped listeners receive only that scope's assemblies. The returned value is authoritative. A supplied signal controls only this explicit assembly request and must not be retained to control later turns. A registered complete section is restored after this waterfall, so listeners cannot add to or replace that scope's system prompt.

/**
 * Expert waterfall over the assembled sections, contexts, tools, and variables.
 * Scope-filtered dispatch (`@deepseek-ai/dsh-scope`): scoped listeners
 * receive only that scope's assemblies. The returned value is authoritative.
 * A supplied signal controls only this explicit assembly request and must not
 * be retained to control later turns. A registered complete section is
 * restored after this waterfall, so listeners cannot add to or replace
 * that scope's system prompt.
 * @param assembly - the mutable assembly built from registered providers.
 * @param context - the caller's per-assembly context.
 * @mode waterfall
 */
'system-prompt/assemble'(this: Scoped<SystemPrompt>, assembly: PromptAssembly, context: AssembleContext, next: () => Promise<PromptAssembly>): Promise<PromptAssembly>

Types: Scoped

Source: packages/core/system-prompt/src/index.ts

system-prompt/change — emit

Emitted when any prompt provider changes. This registry notification is unfiltered because a global change affects every scope.

/**
 * Emitted when any prompt provider changes. This registry notification is
 * unfiltered because a global change affects every scope.
 * @mode emit
 */
'system-prompt/change'(): void

Source: packages/core/system-prompt/src/index.ts