feat: cost-per-call transparency + week-over-week activity in ROI dialog (#2)

- Read instance cost_per_call_usd and show 'Cost per avoided call' in ROI Summary
- Compute week-over-week activity client-side from the insights 30-day trend
- Bump 0.3.2 → 0.3.3 + changelog

Co-authored-by: Claude <noreply@anthropic.com>

Author: HeinrichNebula

CHANGELOG.md

@@ -2,6 +2,20 @@
 
 ---
 
+## [0.3.3] – 2026-06-13
+
+### Added
+- **Cost per avoided call** — the Brain Health dialog's ROI Summary now shows the
+  per-call price used for savings estimates, read from the instance's configured
+  `cost_per_call_usd` (falls back to the $0.002 default), so the dollar figures
+  reflect your real bill.
+- **Week-over-week activity** — a new ROI row compares this week's Brain activity
+  to the prior week (computed client-side from the insights 30-day trend) with a
+  ▲/▼ indicator and percentage change. Shows a "no baseline yet" hint until two
+  weeks of data exist.
+
+---
+
 ## [0.3.2] – 2026-06-06
 
 ### Added

build.gradle.kts

@@ -5,7 +5,7 @@ plugins {
 }
 
 group = "dev.cachly"
-version = "0.3.2"
+version = "0.3.3"
 
 repositories {
     mavenCentral()

src/main/kotlin/dev/cachly/brain/CachlyApiClient.kt

@@ -40,6 +40,14 @@ data class MemoryResponse(
 data class InstanceResponse(
     val tier: String? = null,
     val status: String? = null,
+    @SerializedName("cost_per_call_usd") val costPerCallUsd: Double = 0.0,
+)
+
+/** One day of activity from the insights 30-day trend array. */
+data class TrendBucket(
+    val date: String = "",
+    val events: Int = 0,
+    val fixes: Int = 0,
 )
 
 data class InsightsResponse(
@@ -51,8 +59,23 @@ data class InsightsResponse(
     @SerializedName("ttfr_p90_sec") val ttfrP90Sec: Double = -1.0,
     val currency: String = "EUR",
     @SerializedName("hourly_rate") val hourlyRate: Double = 75.0,
+    val trend: List<TrendBucket> = emptyList(),
 )
 
+/** Week-over-week activity from the trend array: last 7 days vs the prior 7. */
+data class WeekOverWeek(val thisWeek: Int, val lastWeek: Int, val pct: Double?)
+
+/** pct is null when there is no prior-week baseline to compare against. */
+fun computeWoW(trend: List<TrendBucket>): WeekOverWeek {
+    if (trend.isEmpty()) return WeekOverWeek(0, 0, null)
+    val sorted = trend.sortedBy { it.date }
+    val thisWeek = sorted.takeLast(7).sumOf { it.events }
+    val prior = sorted.dropLast(7).takeLast(7)
+    val lastWeek = prior.sumOf { it.events }
+    val pct = if (lastWeek > 0) (thisWeek - lastWeek).toDouble() / lastWeek * 100 else null
+    return WeekOverWeek(thisWeek, lastWeek, pct)
+}
+
 data class BrainHealth(
     val lessons: Int = 0,
     val contexts: Int = 0,
@@ -75,6 +98,8 @@ data class BrainHealth(
     val recallLimit: Int = -1,
     /** ROI aggregates from /api/v1/insights — null if endpoint unavailable. */
     val insights: InsightsResponse? = null,
+    /** Configured per-avoided-call price for ROI; 0 = use the $0.002 default. */
+    val costPerCallUsd: Double = 0.0,
 ) {
     companion object {
         /** Average tokens saved per recall — reuses known solution instead of re-researching. */
@@ -133,6 +158,7 @@ object CachlyApiClient {
             pendingLessons = pendingCount,
             recallLimit = mem.recallLimit,
             insights = insights,
+            costPerCallUsd = inst.costPerCallUsd,
         )
     }
 

src/main/kotlin/dev/cachly/brain/ShowBrainHealthAction.kt

@@ -82,13 +82,29 @@ private class BrainHealthDialog(
         val insightsHtml = health.insights?.let { ins ->
             val curr = if (ins.currency == "EUR") "€" else ins.currency
             val ttfr = if (ins.ttfrP50Sec > 0) "${"%.0f".format(ins.ttfrP50Sec)}s" else "—"
+            // Cost-per-avoided-call: prefer the instance's configured price, else the $0.002 default.
+            val cpc = if (health.costPerCallUsd > 0) health.costPerCallUsd else 0.002
+            val cpcNote = if (health.costPerCallUsd > 0) "your configured rate" else "default — set it on the instance page"
+            // Week-over-week activity from the 30-day trend array.
+            val wow = computeWoW(ins.trend)
+            val wowPct = wow.pct
+            val wowRow = if (wowPct == null) {
+                "<tr><td><b>This week's activity:</b></td><td><b>${wow.thisWeek}</b> events <i>(no prior-week baseline yet)</i></td></tr>"
+            } else {
+                val arrow = if (wowPct > 0) "▲" else if (wowPct < 0) "▼" else "—"
+                val color = if (wowPct > 0) "#3fb950" else if (wowPct < 0) "#f85149" else "inherit"
+                val sign = if (wowPct > 0) "+" else ""
+                "<tr><td><b>Week-over-week activity:</b></td><td><b>${wow.thisWeek}</b> vs ${wow.lastWeek} last week &nbsp;<font color='$color'>$arrow $sign${"%.0f".format(wowPct)}%</font></td></tr>"
+            }
             """
             <h2>💰 ROI Summary</h2>
             <table cellpadding="4">
               <tr><td><b>Developer time saved:</b></td><td><b>${"%.0f".format(ins.minutesSaved)} min</b></td></tr>
               <tr><td><b>Cost saved:</b></td><td><b>$curr${"%.2f".format(ins.dollarsSaved)}</b> <i>(at $curr${ins.hourlyRate}/h)</i></td></tr>
+              <tr><td><b>Cost per avoided call:</b></td><td><b>$$cpc</b> <i>($cpcNote)</i></td></tr>
               <tr><td><b>Knowledge reuse:</b></td><td><b>${"%.1f".format(ins.reusePct)}%</b> of recalls cross-author</td></tr>
               <tr><td><b>Time-to-first-recall (p50):</b></td><td>$ttfr</td></tr>
+              $wowRow
             </table>
             """
         } ?: ""