Make the AI insight's prompt instructions editable via Settings

Split the system prompt into an editable part (persona/focus/tone/
format — what the briefing prioritises and how strict its length is)
and a fixed structural appendix (how the Manual Context and Recent
Previous Insights sections get interpreted, which map directly to
conditional data the code assembles, not just prose — kept safe from
being accidentally edited away).

New ai_insights_prompt_instructions config key, a
GET /api/ai-insights/default-prompt endpoint so the Settings UI can
pre-fill/reset to the built-in default, and a textarea in the AI
Insights settings card.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/src/db.js

@@ -112,7 +112,8 @@ export async function initDb() {
       ('ai_insights_model',              'claude-haiku-4-5-20251001'),
       ('ai_insights_schedule_time',      '07:15'),
       ('ai_insights_daily_token_budget', '5000'),
-      ('ai_insights_manual_context',     '')
+      ('ai_insights_manual_context',     ''),
+      ('ai_insights_prompt_instructions', '')
     ON CONFLICT (key) DO NOTHING
   `)
 }

backend/src/jobs/ai-insights.js

@@ -32,12 +32,13 @@ async function getCostCol() {
 }
 
 export async function getAiInsightsConfig() {
-  const [enabled, model, scheduleTime, dailyTokenBudget, manualContext] = await Promise.all([
+  const [enabled, model, scheduleTime, dailyTokenBudget, manualContext, promptInstructions] = await Promise.all([
     getConfig('ai_insights_enabled'),
     getConfig('ai_insights_model'),
     getConfig('ai_insights_schedule_time'),
     getConfig('ai_insights_daily_token_budget'),
     getConfig('ai_insights_manual_context'),
+    getConfig('ai_insights_prompt_instructions'),
   ])
   return {
     enabled: enabled === 'true',
@@ -45,6 +46,7 @@ export async function getAiInsightsConfig() {
     scheduleTime: scheduleTime || '07:15',
     dailyTokenBudget: parseInt(dailyTokenBudget, 10) || DEFAULT_DAILY_TOKEN_BUDGET,
     manualContext: manualContext || '',
+    promptInstructions: promptInstructions || '',
   }
 }
 
@@ -376,20 +378,29 @@ export async function gatherRevenueCorrelation(monthProgress) {
   }
 }
 
-export function buildPrompt(monthProgress, priorPeriod, rotaVsActual, forecast, anomalies, revenueCorrelation, recentInsights = [], manualContext = '') {
-  const systemMsg =
-    "You are an AI assistant for a wage cost controller in a UK hospitality business. Analyze the data below and " +
-    "produce a SHORT daily briefing: hard limit of 5 bullet points TOTAL across the entire response, each a single " +
-    "sentence (max ~30 words). Do not create a separate section or heading per department or per employee — pick " +
-    "only the 4-5 most important things overall (across budget tracking, forecast, rota variance, pay anomalies, " +
-    "wage % of revenue) and drop the rest; a department or employee with nothing notable gets no mention at all. " +
-    "Use UK date format (DD/MM/YYYY) and GBP (£). Be specific with names and numbers in the bullets you do write. " +
-    "No headings, no numbered action-plan section, no closing summary — just the bullets.\n\n" +
-    "A 'Manual Context' section may be included below, written by a human who knows things the data can't show " +
-    "(e.g. an employee's contract type, a known one-off cause, a planned change). Treat it as ground truth and " +
-    "apply it directly — don't flag something as an anomaly or overspend if this context already explains it.\n\n" +
-    "A 'Recent Previous Insights' section may be included below — compare against them explicitly: call out " +
-    "what's changed, what's resolved, and what's still an open issue. Don't just repeat the same points verbatim."
+// Editable via Settings ("Prompt Instructions") — the persona/focus/tone/format part of the
+// system prompt. Falls back to this when the setting is blank. Kept separate from
+// STRUCTURAL_APPENDIX below so a custom prompt can't accidentally break how the Manual
+// Context / Recent Previous Insights sections get interpreted — those map directly to
+// conditional data sections in buildPrompt, not just prose.
+export const DEFAULT_PROMPT_INSTRUCTIONS =
+  "You are an AI assistant for a wage cost controller in a UK hospitality business. Analyze the data below and " +
+  "produce a SHORT daily briefing: hard limit of 5 bullet points TOTAL across the entire response, each a single " +
+  "sentence (max ~30 words). Do not create a separate section or heading per department or per employee — pick " +
+  "only the 4-5 most important things overall (across budget tracking, forecast, rota variance, pay anomalies, " +
+  "wage % of revenue) and drop the rest; a department or employee with nothing notable gets no mention at all. " +
+  "Use UK date format (DD/MM/YYYY) and GBP (£). Be specific with names and numbers in the bullets you do write. " +
+  "No headings, no numbered action-plan section, no closing summary — just the bullets."
+
+const STRUCTURAL_APPENDIX =
+  "A 'Manual Context' section may be included below, written by a human who knows things the data can't show " +
+  "(e.g. an employee's contract type, a known one-off cause, a planned change). Treat it as ground truth and " +
+  "apply it directly — don't flag something as an anomaly or overspend if this context already explains it.\n\n" +
+  "A 'Recent Previous Insights' section may be included below — compare against them explicitly: call out " +
+  "what's changed, what's resolved, and what's still an open issue. Don't just repeat the same points verbatim."
+
+export function buildPrompt(monthProgress, priorPeriod, rotaVsActual, forecast, anomalies, revenueCorrelation, recentInsights = [], manualContext = '', promptInstructions = '') {
+  const systemMsg = (promptInstructions.trim() || DEFAULT_PROMPT_INSTRUCTIONS) + "\n\n" + STRUCTURAL_APPENDIX
 
   const lines = []
 
@@ -541,7 +552,7 @@ export async function generateInsight(triggeredBy = 'scheduler') {
     getRecentInsights(3),
   ])
 
-  const { systemMsg, userMsg } = buildPrompt(monthProgress, priorPeriod, rotaVsActual, forecast, anomalies, revenueCorrelation, recentInsights, config.manualContext)
+  const { systemMsg, userMsg } = buildPrompt(monthProgress, priorPeriod, rotaVsActual, forecast, anomalies, revenueCorrelation, recentInsights, config.manualContext, config.promptInstructions)
 
   let result
   try {

backend/src/routes/ai-insights.js

@@ -1,7 +1,7 @@
 import { requireAuth, requireCap } from '../auth.js'
 import { pool, getConfig } from '../db.js'
 import { getAnthropicApiKey } from '../lib/central-settings.js'
-import { generateInsight, MANUAL_RATE_LIMIT_MINUTES, DEFAULT_MODEL } from '../jobs/ai-insights.js'
+import { generateInsight, MANUAL_RATE_LIMIT_MINUTES, DEFAULT_MODEL, DEFAULT_PROMPT_INSTRUCTIONS } from '../jobs/ai-insights.js'
 import Anthropic from '@anthropic-ai/sdk'
 
 export async function aiInsightsRoutes(fastify) {
@@ -29,6 +29,10 @@ export async function aiInsightsRoutes(fastify) {
     return { insights: rowsRes.rows, total: countRes.rows[0].count }
   })
 
+  fastify.get('/api/ai-insights/default-prompt', { preHandler: requireCap('settings') }, async () => {
+    return { prompt: DEFAULT_PROMPT_INSTRUCTIONS }
+  })
+
   fastify.get('/api/ai-insights/usage', { preHandler: requireCap('view') }, async () => {
     const res = await pool.query(
       `SELECT COALESCE(SUM(input_tokens), 0)::int AS input_tokens,

backend/src/routes/settings.js

@@ -4,7 +4,7 @@ import { pool, getConfig, setConfig } from '../db.js'
 const ALLOWED_KEYS = new Set([
   'forecasting_url', 'forecasting_api_key', 'show_oncosts', 'departments', 'dept_budget_pcts', 'forecast_method',
   'ai_insights_enabled', 'ai_insights_model', 'ai_insights_schedule_time', 'ai_insights_daily_token_budget',
-  'ai_insights_manual_context',
+  'ai_insights_manual_context', 'ai_insights_prompt_instructions',
 ])
 
 export async function settingsRoutes(fastify) {
@@ -17,7 +17,7 @@ export async function settingsRoutes(fastify) {
          'forecasting_url','forecasting_api_key','show_oncosts','departments','forecast_method',
          'sync_last_at','backfill_last_at',
          'ai_insights_enabled','ai_insights_model','ai_insights_schedule_time','ai_insights_daily_token_budget',
-         'ai_insights_manual_context'
+         'ai_insights_manual_context','ai_insights_prompt_instructions'
        )
        ORDER BY key`
     )