feat(ios): iOS build pipeline + XCFramework, fix K/Native source bugs

Modules: chart-realtime (commonMain, iosMain), root, .paul

- chart-realtime/build.gradle.kts: applyDefaultHierarchyTemplate() + XCFramework("ChartRealtime") over iosX64/iosArm64/iosSimulatorArm64, baseName CamelCase
- commonMain RealtimeChartState/CircularBuffer: switch to kotlin.concurrent.Volatile, add kotlin.jvm.JvmName import (OptionalExpectation)
- commonMain AxisRenderer: replace JVM-only String.format with multiplatform formatFixed/formatScientific/pow10 helpers
- iosMain Platform.ios.kt: NSDate() + timeIntervalSinceReferenceDate + 978_307_200s 1970-epoch offset (K/Native binding has no direct timeIntervalSince1970)
- gradle.properties: remove Linux JDK pin (rely on JAVA_HOME)
- .paul: phases plan, STATE+ROADMAP updates

Acceptance: A1 compile 3 iOS targets, A2 linkDebugFrameworkIosSimulatorArm64, A3 iosSimulatorArm64Test (33 tests, 0 failures), A4 assembleChartRealtimeXCFramework (ios-arm64 + ios-arm64_x86_64-simulator slices), A5 Android assembleRelease/publishToMavenLocal --dry-run.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.paul/ROADMAP.md

@@ -10,7 +10,8 @@ KMP real-time chart library. Six phases v0.1.0 MVP shipped; v0.2.0 polish shippe
 |-----------|---------|--------|-----------|
 | v0.1.0 MVP | 0.1.0 | ✓ Shipped | 2026-05-20 |
 | v0.2.0 Polish | 0.5.0-SNAPSHOT | ✓ Shipped | 2026-05-21 |
-| v0.3.0 (TBD) | - | Not started | - |
+| v0.3.0 iOS Build Pipeline | 0.5.0-SNAPSHOT | ✓ Shipped | 2026-05-21 |
+| v0.4.0 (TBD) | - | Not started | - |
 
 ---
 
@@ -56,16 +57,37 @@ Summary: .paul/phases/v0.2.0-plan-SUMMARY.md
 
 ---
 
-## v0.3.0 — Potential Scope (TBD)
+## v0.3.0 — iOS Build Pipeline (SHIPPED)
+
+Status: ✓ Complete
+Plan: .paul/phases/v0.3.0-ios-build-plan.md
+
+### Delivered
+
+- 3 iOS targets compile green (iosX64, iosArm64, iosSimulatorArm64)
+- `applyDefaultHierarchyTemplate()` wires iosMain/iosTest across targets
+- `linkDebugFrameworkIosSimulatorArm64` green
+- `iosSimulatorArm64Test` green — 33 tests, 0 failures
+- XCFramework `ChartRealtime` produced (debug + release): ios-arm64 + ios-arm64_x86_64-simulator slices
+- Pre-existing compile bugs fixed:
+  - `@Volatile` → `kotlin.concurrent.Volatile` import
+  - `@JvmName` → `kotlin.jvm.JvmName` import (OptionalExpectation)
+  - `String.format` in AxisRenderer → manual `formatFixed`/`formatScientific`/`pow10` helpers
+  - `NSDate.date()` → `NSDate()` + `timeIntervalSinceReferenceDate` + 1970 epoch offset
+- Android non-regression confirmed (`assembleRelease`, `publishToMavenLocal --dry-run`)
+- Local Mac config: removed Linux JDK pin from `gradle.properties`, added `local.properties` for Android SDK
+
+---
+
+## v0.4.0 — Potential Scope (TBD)
 
 | Item | Effort | Priority |
 |------|--------|----------|
-| Dirty flag render (skip frame if no new data) | S | High — thermal |
+| Publish to Maven Central / GitHub Packages | M | Medium |
-| targetFps=30 default | S | High — thermal |
+| iOS demo app (SwiftUI) | L | Medium |
-| KDoc on public API surface | M | Medium |
+| CI workflow GitHub Actions (Android + iOS) | M | Medium |
-| README with integration example | S | Medium |
+| Compose compiler stability annotation on SignalConfig | S | Low |
-| Publish to Maven Central / GitHub Packages | M | Low |
+| CocoaPods / SPM publication | M | Low |
-| iOS expect/actual (beyond currentTimeMs) | L | Future |
 
 ---
 *Roadmap updated: 2026-05-21*

.paul/STATE.md

@@ -5,25 +5,26 @@
 See: .paul/PROJECT.md (updated 2026-05-21)
 
 **Core value:** Android devs plot 200Hz+ multi-signal sensor data without frame drops
-**Current focus:** v0.3.0 IN PROGRESS — dirty flag render + targetFps=30 shipped
+**Current focus:** v0.3.0 iOS build pipeline SHIPPED — 33 tests pass on iOS sim, XCFramework produced
 
 ## Current Position
 
-Milestone: v0.2.0-polish
+Milestone: v0.3.0-ios-build
 Phase: 6 of 6 — Complete
-Plan: .paul/phases/v0.2.0-plan.md
+Plan: .paul/phases/v0.3.0-ios-build-plan.md
 Status: Complete
-Last activity: 2026-05-21 — dirty flag render, targetFps=30, 17 unit tests, KDoc, README, iOS targets (iosX64/iosArm64/iosSimulatorArm64) + Platform.ios.kt actual.
+Last activity: 2026-05-21 — iOS pipeline: compile 3 targets, link debug framework, iosSimulatorArm64Test green (33 tests, 0 failures), XCFramework "ChartRealtime" output (ios-arm64 + ios-arm64_x86_64-simulator slices). Android non-regression confirmed.
 
 Progress:
 - v0.1.0 milestone: [██████████] 100% SHIPPED
 - v0.2.0 milestone: [██████████] 100% SHIPPED
+- v0.3.0 milestone: [██████████] 100% SHIPPED
 
 ## Loop Position
 
 ```
 PLAN ──▶ APPLY ──▶ UNIFY
-  ✓        ✓        ✓     [v0.2.0 SHIPPED — v0.5.0-SNAPSHOT]
+  ✓        ✓        ✓     [v0.3.0 iOS build SHIPPED — v0.5.0-SNAPSHOT]
 ```
 
 ## Accumulated Context
@@ -41,6 +42,11 @@ PLAN ──▶ APPLY ──▶ UNIFY
 | Sensor cap 200Hz (5_000μs) | v0.2.0 | Thermal/battery optimization |
 | Package dev.dtrentin | v0.2.0 | Personal project, not company |
 | iOS targets shipped | v0.3.0 | iosX64/iosArm64/iosSimulatorArm64 + Platform.ios.kt |
+| iOS build pipeline green | v0.3.0 iOS | 33 tests pass on iOS sim, XCFramework "ChartRealtime" produced |
+| timeIntervalSinceReferenceDate + epoch offset | v0.3.0 iOS | K/Native binding doesn't expose timeIntervalSince1970; use 978_307_200s constant |
+| applyDefaultHierarchyTemplate() explicit | v0.3.0 iOS | iosMain/iosTest auto-wired across 3 iOS targets |
+| Manual format helpers in AxisRenderer | v0.3.0 iOS | String.format JVM-only; private formatFixed/formatScientific/pow10 |
+| kotlin.concurrent.Volatile + kotlin.jvm.JvmName imports | v0.3.0 iOS | Multiplatform replacements for JVM-default annotations |
 
 ### Deferred Issues
 
@@ -51,21 +57,27 @@ PLAN ──▶ APPLY ──▶ UNIFY
 | ~~iOS expect/actual beyond currentTimeMs~~ | Init | L | ✓ v0.3.0 |
 | ~~KDoc on public API surface~~ | v0.2.0 | M | ✓ v0.3.0 |
 | ~~README with integration example~~ | v0.2.0 | S | ✓ v0.3.0 |
-| Publish to Maven Central / GitHub Packages | v0.2.0 | M | v0.3.0 |
+| ~~iOS build/test pipeline (compile + iosTest + XCFramework)~~ | v0.3.0 plan | M | ✓ v0.3.0 iOS |
+| Publish to Maven Central / GitHub Packages | v0.2.0 | M | v0.4.0 |
+| iOS demo app (SwiftUI) | v0.3.0 iOS | L | v0.4.0 |
+| CI workflow for iOS build (GitHub Actions) | v0.3.0 iOS | M | v0.4.0 |
+| Compose compiler unstable warning on SignalConfig | v0.3.0 iOS | S | v0.4.0 |
 
 ### Blockers/Concerns
 None.
 
 ## Session Continuity
 
-Last session: 2026-05-21
+Last session: 2026-05-21 (iOS build pipeline)
-Stopped at: v0.2.0 complete. All AC pass. Git pushed to remote.
+Stopped at: v0.3.0 iOS shipped. All 5 acceptance items pass (A1-A5). 33 tests green on iOS sim. ChartRealtime.xcframework at chart-realtime/build/XCFrameworks/release/.
-Next action: Define v0.3.0 scope (dirty flag render, targetFps=30, KDoc, publish)
+Next action: Define v0.4.0 scope (Maven Central publish, iOS demo app, CI)
 Resume context:
-- Library: AndroidCharts/chart-realtime, published dev.dtrentin:chart-realtime:0.5.0-SNAPSHOT to mavenLocal
+- Library: chart-realtime, published dev.dtrentin:chart-realtime:0.5.0-SNAPSHOT to mavenLocal
 - App: AndroidChartsApp consuming library, builds clean
 - Remote: ssh://git@3nt-git.duckdns.org:222/davide.trentin/KMPCharts.git
 - Package: dev.dtrentin.chart
+- iOS: 3 targets compile, link, test (33 tests). XCFramework name `ChartRealtime`, baseName CamelCase.
+- Local Mac setup: Xcode.app at /Applications/Xcode.app, iOS sim runtime installed (iPhone 17 family), local.properties points to ~/Library/Android/sdk, JDK 21 Temurin via JAVA_HOME.
 
 ---
 *STATE.md — Updated after every significant action*

.paul/phases/v0.3.0-ios-build-plan.md

@@ -0,0 +1,109 @@
+# v0.3.0 — iOS Build & Test Pipeline Plan
+
+## Goal
+Wire `chart-realtime` for full iOS pipeline: compile all 3 iOS targets, link debug framework on `iosSimulatorArm64`, run `commonTest` on iOS sim, produce release `XCFramework`. Keep Android green. No new features, no demo app, no SPM/CocoaPods/CI.
+
+Acceptance:
+- A1: `./gradlew :chart-realtime:compileKotlinIosX64 compileKotlinIosArm64 compileKotlinIosSimulatorArm64` green
+- A2: `./gradlew :chart-realtime:linkDebugFrameworkIosSimulatorArm64` green
+- A3: `./gradlew :chart-realtime:iosSimulatorArm64Test` green, executes existing common tests
+- A4: `./gradlew :chart-realtime:assembleXCFramework` produces `chart-realtime/build/XCFrameworks/release/chart-realtime.xcframework`
+- A5: `./gradlew :chart-realtime:assemble` green (Android non-regression)
+
+## Locked decisions
+- T0: remove `org.gradle.java.home` pin (rely on JAVA_HOME)
+- XCFramework baseName: `ChartRealtime` (CamelCase iOS convention)
+- Include `iosX64` target in XCFramework
+- Local Mac dev only, no CI
+
+---
+
+## Tasks
+
+### T0 — Mac JDK / gradle.properties sanity
+- Goal: Unblock local Mac build. Current `gradle.properties` pins Linux JDK path. Pre-req for A1–A5.
+- Files: `gradle.properties`
+- Agent: `gradle-expert`
+- Action: remove line `org.gradle.java.home=/home/dtrentin/.local/share/JetBrains/Toolbox/apps/android-studio/jbr`. Keep other lines unchanged.
+- Deps: none
+- Verify: `./gradlew :chart-realtime:help`
+
+### T1+T2+T4 — Batched build.gradle.kts edit
+- Goal: iOS hierarchy explicit + XCFramework task.
+- Files: `chart-realtime/build.gradle.kts`
+- Agent: `gradle-expert` (single edit, single agent)
+- Actions:
+  - Apply default hierarchy template explicitly (`applyDefaultHierarchyTemplate()`)
+  - Configure each iOS target with `binaries.framework { baseName = "ChartRealtime"; xcf.add(this) }` using `XCFramework("ChartRealtime")` helper from `org.jetbrains.kotlin.gradle.plugin.mpp.apple.XCFramework`
+  - Keep `compose.material3` in `commonMain` (CMP 1.8.0 supports iOS native)
+  - Do not break Android target, publishing, or existing source-set deps
+- Deps: T0
+- Verify:
+  - `./gradlew :chart-realtime:compileKotlinIosX64`
+  - `./gradlew :chart-realtime:compileKotlinIosArm64`
+  - `./gradlew :chart-realtime:compileKotlinIosSimulatorArm64`
+  - `./gradlew :chart-realtime:linkDebugFrameworkIosSimulatorArm64`
+  - `./gradlew :chart-realtime:assembleXCFramework`
+
+### T3 — iosTest wiring
+- Goal: `iosTest` source set runs existing `commonTest` files on iOS sim.
+- Files: `chart-realtime/build.gradle.kts` (only if hierarchy template doesn't auto-wire)
+- Agent: `unit-test-writer`
+- Inputs: existing `commonTest.dependencies { implementation(libs.kotlin.test) }`. Default hierarchy template wires `iosTest → commonTest` automatically. Verify; add explicit block only if test discovery fails.
+- Deps: T1+T2+T4
+- Verify: `./gradlew :chart-realtime:iosSimulatorArm64Test`
+
+### T5 — Android non-regression guard
+- Goal: Confirm Android target/build/publish untouched.
+- Agent: `android-build-resolver`
+- Deps: T1+T2+T4
+- Verify: `./gradlew :chart-realtime:assembleRelease publishToMavenLocal --dry-run`
+
+### T6 — Smoke acceptance run
+- Goal: Sequential run of all 5 acceptance commands.
+- Agent: `general-purpose`
+- Deps: T3, T5
+- Verify: all 5 commands green
+
+---
+
+## Parallelism
+
+| Group | Tasks |
+|-------|-------|
+| P0 | T0 |
+| P1 | T1+T2+T4 (one batched agent call) |
+| P2 | T3, T5 (parallel) |
+| P3 | T6 |
+| P4 | Unify |
+
+---
+
+## Risks
+
+- R1: gradle.properties Linux JDK path — fixed in T0
+- R2: `compose.material3` iOS native — supported in 1.8.0; fallback = isolate to non-iOS if compile fails
+- R3: Hierarchy template silent inactivity — `applyDefaultHierarchyTemplate()` made explicit
+- R4: `commonTest` not seen by `iosTest` — same hierarchy fix
+- R5: XCFramework name collision — single `XCFramework("ChartRealtime")` registration
+- R6: Compose link errors on iOS — defer to v0.4.0 if hit
+- R7: Android regression — T5 final gate, revert if needed
+- R8: Sim runtime requirement — confirmed installed (iPhone 17 family available)
+
+## New Deps
+None. KGP + CMP 1.8.0 + Kotlin 2.1.0 cover everything.
+
+## Verification Commands
+
+```bash
+./gradlew :chart-realtime:help                                           # T0
+./gradlew :chart-realtime:compileKotlinIosX64                            # A1
+./gradlew :chart-realtime:compileKotlinIosArm64                          # A1
+./gradlew :chart-realtime:compileKotlinIosSimulatorArm64                 # A1
+./gradlew :chart-realtime:linkDebugFrameworkIosSimulatorArm64            # A2
+./gradlew :chart-realtime:iosSimulatorArm64Test                          # A3
+./gradlew :chart-realtime:assembleXCFramework                            # A4
+ls chart-realtime/build/XCFrameworks/release/ChartRealtime.xcframework   # A4
+./gradlew :chart-realtime:assembleRelease                                # A5
+./gradlew :chart-realtime:publishToMavenLocal --dry-run                  # T5
+```

chart-realtime/build.gradle.kts

@@ -1,3 +1,5 @@
+import org.jetbrains.kotlin.gradle.plugin.mpp.apple.XCFramework
+
 plugins {
     alias(libs.plugins.kotlin.multiplatform)
     alias(libs.plugins.android.library)
@@ -10,6 +12,8 @@ group = "dev.dtrentin"
 version = "0.5.0-SNAPSHOT"
 
 kotlin {
+    applyDefaultHierarchyTemplate()
+
     androidTarget {
         compilations.all {
             compileTaskProvider.configure {
@@ -21,9 +25,17 @@ kotlin {
         publishLibraryVariants("release")
     }
 
-    iosX64()
+    val xcf = XCFramework("ChartRealtime")
-    iosArm64()
+    listOf(
+        iosX64(),
+        iosArm64(),
         iosSimulatorArm64()
+    ).forEach { target ->
+        target.binaries.framework {
+            baseName = "ChartRealtime"
+            xcf.add(this)
+        }
+    }
 
     sourceSets {
         commonMain.dependencies {

chart-realtime/src/commonMain/kotlin/dev/dtrentin/chart/RealtimeChartState.kt

@@ -5,6 +5,8 @@ import dev.dtrentin.chart.buffer.TieredBuffer
 import dev.dtrentin.chart.model.ChartConfig
 import dev.dtrentin.chart.model.SignalConfig
 import dev.dtrentin.chart.model.T0
+import kotlin.concurrent.Volatile
+import kotlin.jvm.JvmName
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.Flow

chart-realtime/src/commonMain/kotlin/dev/dtrentin/chart/buffer/CircularBuffer.kt

@@ -1,5 +1,7 @@
 package dev.dtrentin.chart.buffer
 
+import kotlin.concurrent.Volatile
+
 /**
  * Lock-free circular buffer for (timestampMs, value) sensor samples.
  * Pre-allocated — zero allocations after construction.

chart-realtime/src/commonMain/kotlin/dev/dtrentin/chart/render/AxisRenderer.kt

@@ -164,15 +164,50 @@ internal object AxisRenderer {
 
     private fun formatAxisValue(value: Double, decimals: Int): String {
         val absVal = kotlin.math.abs(value)
-        return if (value == 0.0) {
+        return when {
-            "0"
+            value == 0.0 -> "0"
-        } else if (absVal < 0.01 || absVal >= 1e5) {
+            absVal < 0.01 || absVal >= 1e5 -> formatScientific(value, decimals)
-            "%.${decimals}e".format(value)
+            else -> formatFixed(value, decimals)
-        } else {
-            "%.${decimals}f".format(value)
         }
     }
 
+    private fun formatFixed(value: Double, decimals: Int): String {
+        val negative = value < 0.0
+        val absVal = kotlin.math.abs(value)
+        val factor = pow10(decimals)
+        val rounded = kotlin.math.round(absVal * factor)
+        val whole = (rounded / factor).toLong()
+        val frac = (rounded - whole * factor).toLong()
+        val sign = if (negative && (whole != 0L || frac != 0L)) "-" else ""
+        return if (decimals <= 0) {
+            "$sign$whole"
+        } else {
+            val fracStr = frac.toString().padStart(decimals, '0')
+            "$sign$whole.$fracStr"
+        }
+    }
+
+    private fun formatScientific(value: Double, decimals: Int): String {
+        if (value == 0.0) return formatFixed(0.0, decimals) + "e+00"
+        val negative = value < 0.0
+        val absVal = kotlin.math.abs(value)
+        val exp = kotlin.math.floor(kotlin.math.log10(absVal)).toInt()
+        val mantissa = absVal / pow10(exp)
+        val mantStr = formatFixed(mantissa, decimals)
+        val sign = if (negative) "-" else ""
+        val expSign = if (exp >= 0) "+" else "-"
+        val expAbs = kotlin.math.abs(exp).toString().padStart(2, '0')
+        return "$sign${mantStr}e$expSign$expAbs"
+    }
+
+    private fun pow10(n: Int): Double {
+        if (n == 0) return 1.0
+        var r = 1.0
+        val absN = kotlin.math.abs(n)
+        repeat(absN) { r *= 10.0 }
+        return if (n < 0) 1.0 / r else r
+    }
+
     private fun niceInterval(range: Double, targetTickCount: Int): Double {
         if (range <= 0) return 1.0
         val rough = range / targetTickCount

chart-realtime/src/iosMain/kotlin/dev/dtrentin/chart/Platform.ios.kt

@@ -2,4 +2,10 @@ package dev.dtrentin.chart
 
 import platform.Foundation.NSDate
 
-internal actual fun currentTimeMs(): Long = (NSDate.date().timeIntervalSince1970 * 1000).toLong()
+private const val REFERENCE_DATE_OFFSET_SEC = 978_307_200.0
+
+internal actual fun currentTimeMs(): Long {
+    val date = NSDate()
+    val secsSince1970 = date.timeIntervalSinceReferenceDate + REFERENCE_DATE_OFFSET_SEC
+    return (secsSince1970 * 1000).toLong()
+}

gradle.properties

@@ -1,4 +1,3 @@
-org.gradle.java.home=/home/dtrentin/.local/share/JetBrains/Toolbox/apps/android-studio/jbr
 org.gradle.parallel=true
 org.gradle.caching=true
 org.gradle.jvmargs=-Xmx4g -XX:+UseParallelGC