@local/dsh-system-prompt-mod

@local/dsh-system-prompt-mod

A DSH plugin that puts a Prompt control in the chat header: it shows the system prompt the model is actually receiving, lets you edit it, and applies the result on the next model request — no restart.

Русская версия: README.ru.md.

What it does

Half	Role
lib/index.js (host)	Owns the editable prompt section and the /api/system-prompt.mod route
lib/client.js (browser)	Registers the header control into the conversation.session.header.utilities slot and renders the editor dialog
$DSH_HOME/system-prompt-mod.json	State: { enabled, mode, text }

The section registers at order: 10300 — after every shipped section, including the deployment persona suffix (10200). Its text is a function re-evaluated at every prompt assembly, which is what makes a saved edit reach the next request without re-registering anything.

Modes

• Append (default) — the text is added after the deployment prompt.
• Replace — the text becomes the entire system prompt (the section registers with complete: true).

complete is read at registration time, so switching modes re-registers the section. When the mod is disabled, or the text is empty, no section is registered at all and the shipped prompt is untouched.

The {{variable}} guard

renderPrompt interpolates {{name}} strictly and throws on an unknown name, and DSH offers no escape syntax. Text containing a {{…}} group is therefore rejected on save (HTTP 400 with an explanation) — otherwise it would break every later request.

The read-only preview is tolerant: when the exact rendering is impossible (for example the scope-less assembly has no {{model}} value), the modal shows the prompt with the resolvable variables substituted, leaves the rest literal, and marks the preview as inexact (exact: false).

The live prompt

The prompt is assembled in the live agent's scope (ctx.agents.get(sessionId) → assemble({ agent, scope: agent })) — exactly what dsh-agent-loop does. That resolves {{model}}, {{cwd}} and preset layers, so the dialog shows what the model really gets.

With no live agent for the session, the preview falls back to the global layer and is marked inexact. Editing and saving keep working either way.

HTTP contract

GET  /api/system-prompt.mod?sessionId=
POST /api/system-prompt.mod   { enabled?, mode?, text?, sessionId? }

Response: { ok, enabled, mode, text, active, path, section, order, sessionId, scoped, baseAvailable, basePrompt, effectivePrompt, exact, error }.

• effectivePrompt — what the model receives right now.
• basePrompt — the same assembly without this mod's section, offered as the starting point for a replacement. Unavailable (baseAvailable: false) in replace mode, because the assembly then contains only this mod's section.

The route is registered through ctx.connection.fetch.register(...), the same authenticated /api channel the shipped plugins use.

Install

Use the repository installer — node tools/install.mjs — which copies this package into $DSH_HOME/profiles/node_modules/@local/ and adds the loader row:

- insert:
    - id: system-prompt-mod
      name: '@local/dsh-system-prompt-mod'

Reload the GUI afterwards.

Limitations

• The prompt override is deployment-wide: the section lives in the global layer, so it applies to every agent, subagents included.
• In replace mode the dialog cannot show the original prompt — it cannot be assembled without dropping complete — so the editor holds your version.
• No push events: the dialog reads state when it opens, because DSH does not forward system-prompt/change to the browser.