# System Prompt Assembly
English | [中文](system-prompt.zh.md)
The [system-prompt package](../../packages/core/system-prompt) owns the data exchanged between prompt contributors and one assembly call. The package [README](../../packages/core/system-prompt/README.md) 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`](../../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.
```ts type-equiv
/** 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.
```ts type-equiv
/** 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
`PromptSection` is a readonly same-process registration contract. Its text may be static or resolved from the current assembly context.
```ts type-equiv
/** 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. Convention: `-100` is the
* harness identity, `0` the deployment persona, tool guidance uses 100–199;
* other negative orders also render before the persona.
*/
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)
}
```
## 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.
```ts type-equiv
/** 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 surface
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`) — this section is byte-identical in both language sides of the page. Signature blocks use a `ts cordis-catalog` fence and keep the original source JSDoc; dispatch modes are defined in the [primer](../cordis-primer.md#dispatch-modes), and the framework-inherited `ctx` surface lives in [cordis-api/inherited.md](../cordis-api/inherited.md).
### `ctx.systemPrompt` — `SystemPrompt`
Registry service for the prompt inputs assembled before each model step.
```ts cordis-catalog
/**
* 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
/**
* 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
/**
* 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.
* @param context - the optional scope and plugin-defined assembly fields.
* @returns the authoritative post-waterfall assembly.
*/
async assemble(context: AssembleContext = {}): Promise
```
Source: [`packages/core/system-prompt/src/index.ts:325`](../../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.
```ts cordis-catalog
/**
* 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.
* @param assembly - the mutable assembly built from registered providers.
* @param context - the caller's per-assembly context.
* @mode waterfall
*/
'system-prompt/assemble'(this: Scoped, assembly: PromptAssembly, context: AssembleContext, next: () => Promise): Promise
```
Types: [Scoped](scope.md)
Source: [`packages/core/system-prompt/src/index.ts:29`](../../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.
```ts cordis-catalog
/**
* 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:35`](../../packages/core/system-prompt/src/index.ts)