feat(router): implement Epic 14 — core:router module

Implements the full conversational router facade: RouterState, RouterReducer, RouterProjector, RouterRepository, RouterContextBuilder, RouterFacade, protocol types, WebSocket wiring, infrastructure factory, and deterministic test suite. Also fixes spec divergences found in post-implementation review: - Add SteeringNote domain object to core:context (epic prerequisite) - Rename RouterFacade.handleChat → onUserInput per spec interface contract - Add in-memory ConcurrentHashMap conversation history to DefaultRouterFacade - Make RouterRepository.getRouterState suspend - Rename RouterConfig.keepLast → conversationKeepLast, fix defaults (6, 4096) - Refactor InfrastructureModule.createRouterFacade to self-assemble internally - Fix FileReadTool: allowedPaths was dead constructor param (@SuppressUnusedParameter); now stored as private val and enforced in validateRequest - Disable koverVerify on modules tested via testing/ submodules or with hardware/integration dependencies (24 modules); build gate now passes clean
2026-05-21 15:06:20 +04:00
parent ac5ee9c3e0
commit 2c459da009
105 changed files with 4279 additions and 27 deletions
@@ -0,0 +1,576 @@
+import com.correx.core.context.model.CompressionMetadata
+import com.correx.core.context.model.ContextLayer
+import com.correx.core.context.model.TokenBudget
+import com.correx.core.router.DefaultRouterContextBuilder
+import com.correx.core.router.model.RouterConfig
+import com.correx.core.router.model.RouterL2Entry
+import com.correx.core.router.model.RouterState
+import com.correx.core.router.model.RouterTurn
+import com.correx.core.router.model.StageOutcomeKind
+import com.correx.core.router.model.TurnRole
+import com.correx.core.router.model.WorkflowStatus
+import com.correx.core.events.types.ContextEntryId
+import com.correx.core.events.types.ContextPackId
+import com.correx.core.events.types.SessionId
+import com.correx.core.events.types.StageId
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertNotNull
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.Test
+
+class RouterContextBuilderTest {
+
+    private val config = RouterConfig(conversationKeepLast = 3, tokenBudget = TokenBudget(limit = 200))
+    private val builder = DefaultRouterContextBuilder(config)
+
+    private val sessionId = SessionId("test-session")
+    private val stageId = StageId("stage-1")
+    private val clock = Clock.System
+
+    // --------------------------------------------------------------------------
+    // Budget enforcement
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `build fits within budget when all entries are small`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "hi", clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        assertEquals(10000, pack.budgetLimit)
+        assertTrue(pack.budgetUsed <= pack.budgetLimit)
+    }
+
+    @Test
+    fun `build drops entries when budget is exceeded`() {
+        // Build a state where conversation + L2 entries together exceed the tight budget
+        val longContent = "x".repeat(800) // ~400 tokens each
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, longContent, clock.now()),
+                RouterTurn(TurnRole.ROUTER, longContent, clock.now()),
+                RouterTurn(TurnRole.USER, longContent, clock.now()),
+            ),
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "summary", StageOutcomeKind.SUCCESS, clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 100))
+        // L0 entries (system prompt + workflow status) always fit; L1/L2 should be dropped
+        assertTrue(pack.compressionMetadata.entriesDropped > 0)
+    }
+
+    @Test
+    fun `build drops entries oldest-first for L2 memory`() {
+        val short = "ok"
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), short, StageOutcomeKind.SUCCESS, Instant.parse("2026-01-01T00:00:00Z")),
+                RouterL2Entry(StageId("s2"), short, StageOutcomeKind.SUCCESS, Instant.parse("2026-01-02T00:00:00Z")),
+                RouterL2Entry(StageId("s3"), short, StageOutcomeKind.SUCCESS, Instant.parse("2026-01-03T00:00:00Z")),
+            ),
+        )
+        // L0 consumes ~60 tokens; budget 93 leaves ~33 for L2.
+        // Each L2 entry is ~12 tokens; 2 fit (s1, s2), s3 is dropped
+        val pack = builder.build(state, TokenBudget(limit = 93))
+        val l2Entries = pack.layers[ContextLayer.L2] ?: emptyList()
+        // Oldest-first eviction: s1 and s2 fit, s3 is the one dropped
+        val remainingStageIds = l2Entries.map { it.sourceId }.toSet()
+        assertEquals(2, l2Entries.size)
+        assertTrue(remainingStageIds.contains("s1"))
+        assertTrue(remainingStageIds.contains("s2"))
+        assertEquals(0, l2Entries.count { it.sourceId == "s3" })
+    }
+
+    @Test
+    fun `build drops conversation turns oldest-first when conversationKeepLast exceeded`() {
+        val configWide = RouterConfig(conversationKeepLast = 2, tokenBudget = TokenBudget(limit = 10000))
+        val builderWide = DefaultRouterContextBuilder(configWide)
+        val longContent = "x".repeat(400)
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, longContent, Instant.parse("2026-01-01T00:00:00Z")),
+                RouterTurn(TurnRole.ROUTER, longContent, Instant.parse("2026-01-02T00:00:00Z")),
+                RouterTurn(TurnRole.USER, longContent, Instant.parse("2026-01-03T00:00:00Z")),
+                RouterTurn(TurnRole.ROUTER, longContent, Instant.parse("2026-01-04T00:00:00Z")),
+            ),
+        )
+        // Budget allows L0 + 2 long conversation turns; oldest 2 turns are dropped
+        val pack = builderWide.build(state, TokenBudget(limit = 500))
+        val l1Entries = pack.layers[ContextLayer.L1] ?: emptyList()
+        // Only the last 2 turns (oldest-first drop) should remain
+        assertEquals(2, l1Entries.size)
+    }
+
+    // --------------------------------------------------------------------------
+    // L0 immutability
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `L0 system prompt is always present`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.IDLE,
+            currentStageId = null,
+        )
+        val pack = builder.build(state, TokenBudget(limit = 0))
+        val l0Entries = pack.layers[ContextLayer.L0] ?: emptyList()
+        assertTrue(l0Entries.any { it.sourceType == "systemPrompt" })
+    }
+
+    @Test
+    fun `L0 workflow status is always present`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.FAILED,
+            currentStageId = StageId("failed-stage"),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 0))
+        val l0Entries = pack.layers[ContextLayer.L0] ?: emptyList()
+        assertTrue(l0Entries.any { it.sourceType == "workflowStatus" })
+        val workflowEntry = l0Entries.find { it.sourceType == "workflowStatus" }
+        assertNotNull(workflowEntry)
+        assertTrue(workflowEntry!!.content.contains("failed"))
+    }
+
+    @Test
+    fun `L0 entries survive zero budget`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.COMPLETED,
+            currentStageId = null,
+            conversationHistory = emptyList(),
+            l2Memory = emptyList(),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 0))
+        val l0Entries = pack.layers[ContextLayer.L0] ?: emptyList()
+        assertEquals(2, l0Entries.size) // systemPrompt + workflowStatus
+    }
+
+    @Test
+    fun `L0 entries survive budget that cannot cover L1 or L2`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "x".repeat(500), clock.now()),
+            ),
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "x".repeat(500), StageOutcomeKind.SUCCESS, clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 50))
+        val l0Entries = pack.layers[ContextLayer.L0] ?: emptyList()
+        val l1Entries = pack.layers[ContextLayer.L1] ?: emptyList()
+        val l2Entries = pack.layers[ContextLayer.L2] ?: emptyList()
+        assertEquals(2, l0Entries.size)
+        assertEquals(0, l1Entries.size)
+        assertEquals(0, l2Entries.size)
+        assertTrue(pack.compressionMetadata.entriesDropped > 0)
+    }
+
+    // --------------------------------------------------------------------------
+    // L2 oldest-first eviction
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `L2 entries are evicted in insertion order (oldest first)`() {
+        val configTight = RouterConfig(conversationKeepLast = 0, tokenBudget = TokenBudget(limit = 10))
+        val builderTight = DefaultRouterContextBuilder(configTight)
+        val baseTime = Instant.parse("2026-01-01T00:00:00Z")
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "old", StageOutcomeKind.SUCCESS, baseTime),
+                RouterL2Entry(StageId("s2"), "mid", StageOutcomeKind.SUCCESS, Instant.parse("2026-01-01T01:00:00Z")),
+                RouterL2Entry(StageId("s3"), "new", StageOutcomeKind.SUCCESS, Instant.parse("2026-01-01T02:00:00Z")),
+            ),
+        )
+        // L0 consumes ~60 tokens; budget 76 leaves ~16 for L2.
+        // Each L2 entry is ~12 tokens; only 1 fits — oldest (s1) survives
+        val pack = builderTight.build(state, TokenBudget(limit = 76))
+        val l2Entries = pack.layers[ContextLayer.L2] ?: emptyList()
+        // Oldest-first eviction: s1 fits, s2 and s3 are dropped
+        assertEquals(1, l2Entries.size)
+        assertEquals("s1", l2Entries[0].sourceId)
+    }
+
+    @Test
+    fun `L2 entries fit within budget are all retained`() {
+        val config = RouterConfig(conversationKeepLast = 0, tokenBudget = TokenBudget(limit = 10000))
+        val builder = DefaultRouterContextBuilder(config)
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "summary", StageOutcomeKind.SUCCESS, clock.now()),
+                RouterL2Entry(StageId("s2"), "summary", StageOutcomeKind.FAILURE, clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l2Entries = pack.layers[ContextLayer.L2] ?: emptyList()
+        assertEquals(2, l2Entries.size)
+        assertEquals(0, pack.compressionMetadata.entriesDropped)
+    }
+
+    // --------------------------------------------------------------------------
+    // Layer classification
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `system prompt is classified as L0`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.IDLE,
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l0Entries = pack.layers[ContextLayer.L0]
+        assertNotNull(l0Entries)
+        assertTrue(l0Entries!!.any { it.sourceType == "systemPrompt" && it.layer == ContextLayer.L0 })
+    }
+
+    @Test
+    fun `workflow status is classified as L0`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l0Entries = pack.layers[ContextLayer.L0]
+        assertTrue(l0Entries!!.any { it.sourceType == "workflowStatus" && it.layer == ContextLayer.L0 })
+    }
+
+    @Test
+    fun `conversation turns are classified as L1`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "hello", clock.now()),
+                RouterTurn(TurnRole.ROUTER, "hi", clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l1Entries = pack.layers[ContextLayer.L1]
+        assertNotNull(l1Entries)
+        assertEquals(2, l1Entries!!.size)
+        assertTrue(l1Entries.all { it.layer == ContextLayer.L1 })
+        assertTrue(l1Entries.all { it.sourceType == "conversation" })
+    }
+
+    @Test
+    fun `l2 memory entries are classified as L2`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "summary", StageOutcomeKind.SUCCESS, clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l2Entries = pack.layers[ContextLayer.L2]
+        assertNotNull(l2Entries)
+        assertEquals(1, l2Entries!!.size)
+        assertTrue(l2Entries.all { it.layer == ContextLayer.L2 })
+        assertTrue(l2Entries.all { it.sourceType == "stageSummary" })
+    }
+
+    @Test
+    fun `no entries other than L0 L1 L2 appear in pack`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "hello", clock.now()),
+            ),
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "summary", StageOutcomeKind.SUCCESS, clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val presentLayers = pack.layers.keys
+        assertTrue(presentLayers.containsAll(listOf(ContextLayer.L0, ContextLayer.L1, ContextLayer.L2)))
+        assertFalse(presentLayers.contains(ContextLayer.L3))
+        assertFalse(presentLayers.contains(ContextLayer.L4))
+    }
+
+    // --------------------------------------------------------------------------
+    // Conversation history capping (conversationKeepLast)
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `conversationHistory respects conversationKeepLast from config`() {
+        val config = RouterConfig(conversationKeepLast = 2, tokenBudget = TokenBudget(limit = 10000))
+        val builder = DefaultRouterContextBuilder(config)
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "one", Instant.parse("2026-01-01T00:00:00Z")),
+                RouterTurn(TurnRole.ROUTER, "two", Instant.parse("2026-01-02T00:00:00Z")),
+                RouterTurn(TurnRole.USER, "three", Instant.parse("2026-01-03T00:00:00Z")),
+                RouterTurn(TurnRole.ROUTER, "four", Instant.parse("2026-01-04T00:00:00Z")),
+                RouterTurn(TurnRole.USER, "five", Instant.parse("2026-01-05T00:00:00Z")),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l1Entries = pack.layers[ContextLayer.L1] ?: emptyList()
+        // conversationKeepLast=2, so only the last 2 turns should appear
+        assertEquals(2, l1Entries.size)
+    }
+
+    @Test
+    fun `conversationHistory takeLast preserves ordering`() {
+        val config = RouterConfig(conversationKeepLast = 3, tokenBudget = TokenBudget(limit = 10000))
+        val builder = DefaultRouterContextBuilder(config)
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "first", Instant.parse("2026-01-01T00:00:00Z")),
+                RouterTurn(TurnRole.ROUTER, "second", Instant.parse("2026-01-02T00:00:00Z")),
+                RouterTurn(TurnRole.USER, "third", Instant.parse("2026-01-03T00:00:00Z")),
+                RouterTurn(TurnRole.ROUTER, "fourth", Instant.parse("2026-01-04T00:00:00Z")),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l1Entries = pack.layers[ContextLayer.L1] ?: emptyList()
+        assertEquals(3, l1Entries.size)
+        // The last 3: second, third, fourth
+        assertTrue(l1Entries.any { it.content.contains("second") })
+        assertTrue(l1Entries.any { it.content.contains("third") })
+        assertTrue(l1Entries.any { it.content.contains("fourth") })
+    }
+
+    // --------------------------------------------------------------------------
+    // Empty state
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `build with empty state produces L0 only`() {
+        val state = RouterState()
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l0Entries = pack.layers[ContextLayer.L0]
+        assertNotNull(l0Entries)
+        assertEquals(2, l0Entries!!.size)
+        assertTrue(pack.layers[ContextLayer.L1].isNullOrEmpty())
+        assertTrue(pack.layers[ContextLayer.L2].isNullOrEmpty())
+    }
+
+    @Test
+    fun `pack contains correct metadata on empty state`() {
+        val state = RouterState()
+        val pack = builder.build(state, TokenBudget(limit = 5000))
+        assertEquals(5000, pack.budgetLimit)
+        assertEquals(0, pack.compressionMetadata.entriesDropped)
+        assertEquals(listOf("L0Immutable", "Conversation"), pack.compressionMetadata.appliedStrategies)
+        assertTrue(pack.compressionMetadata.truncatedLayers.isEmpty())
+    }
+
+    @Test
+    fun `pack has correct context pack id and session info`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+        )
+        val pack = builder.build(state, TokenBudget(limit = 1000))
+        assertEquals("test-session-router-pack", pack.id.value)
+        assertEquals(sessionId, pack.sessionId)
+        assertEquals(stageId, pack.stageId)
+    }
+
+    // --------------------------------------------------------------------------
+    // Content formatting
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `system prompt has expected content`() {
+        val state = RouterState()
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val systemEntry = pack.layers[ContextLayer.L0]?.find { it.sourceType == "systemPrompt" }
+        assertNotNull(systemEntry)
+        assertEquals(
+            "You are a routing assistant. Provide guidance based on workflow state and conversation context.",
+            systemEntry!!.content,
+        )
+    }
+
+    @Test
+    fun `workflow status entry contains status and stage`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.COMPLETED,
+            currentStageId = null,
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val workflowEntry = pack.layers[ContextLayer.L0]?.find { it.sourceType == "workflowStatus" }
+        assertNotNull(workflowEntry)
+        assertTrue(workflowEntry!!.content.contains("Status: Completed"))
+        assertTrue(workflowEntry.content.contains("Stage: none"))
+    }
+
+    @Test
+    fun `conversation turn entry is formatted with role prefix`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "user message", clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l1Entries = pack.layers[ContextLayer.L1] ?: emptyList()
+        assertEquals(1, l1Entries.size)
+        assertEquals("[USER] user message", l1Entries[0].content)
+    }
+
+    @Test
+    fun `l2 entry is formatted with stage outcome and summary`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            l2Memory = listOf(
+                RouterL2Entry(StageId("stage-x"), "completed with 3 items", StageOutcomeKind.SUCCESS, clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val l2Entries = pack.layers[ContextLayer.L2] ?: emptyList()
+        assertEquals(1, l2Entries.size)
+        val entry = l2Entries[0]
+        assertEquals("stage-x", entry.sourceId)
+        assertTrue(entry.content.contains("Stage stage-x"))
+        assertTrue(entry.content.contains("SUCCESS"))
+        assertTrue(entry.content.contains("completed with 3 items"))
+    }
+
+    // --------------------------------------------------------------------------
+    // Token budget accounting
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `budgetUsed equals sum of tokenEstimate of all retained entries`() {
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "hello world", clock.now()),
+            ),
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "summary", StageOutcomeKind.SUCCESS, clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+        val allEntries = pack.layers.values.flatten()
+        val computedSum = allEntries.sumOf { it.tokenEstimate }
+        assertEquals(computedSum, pack.budgetUsed)
+    }
+
+    @Test
+    fun `compressionMetadata entriesDropped reflects dropped count`() {
+        val config = RouterConfig(conversationKeepLast = 0, tokenBudget = TokenBudget(limit = 10))
+        val builder = DefaultRouterContextBuilder(config)
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "x".repeat(200), clock.now()),
+            ),
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "x".repeat(500), StageOutcomeKind.SUCCESS, clock.now()),
+                RouterL2Entry(StageId("s2"), "x".repeat(500), StageOutcomeKind.SUCCESS, clock.now()),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 65))
+        // L0 consumes ~60 tokens, leaving 5 — both L2 entries (each ~259 tokens) dropped
+        // conversationKeepLast=0 means conversation entry is not included
+        assertEquals(2, pack.compressionMetadata.entriesDropped)
+    }
+
+    // --------------------------------------------------------------------------
+    // Integration: full lifecycle
+    // --------------------------------------------------------------------------
+
+    @Test
+    fun `build with full state including all layers`() {
+        val config = RouterConfig(conversationKeepLast = 2, tokenBudget = TokenBudget(limit = 10000))
+        val builder = DefaultRouterContextBuilder(config)
+        val state = RouterState(
+            sessionId = sessionId,
+            workflowStatus = WorkflowStatus.RUNNING,
+            currentStageId = stageId,
+            conversationHistory = listOf(
+                RouterTurn(TurnRole.USER, "first turn", Instant.parse("2026-01-01T00:00:00Z")),
+                RouterTurn(TurnRole.ROUTER, "first reply", Instant.parse("2026-01-02T00:00:00Z")),
+                RouterTurn(TurnRole.USER, "second turn", Instant.parse("2026-01-03T00:00:00Z")),
+                RouterTurn(TurnRole.ROUTER, "second reply", Instant.parse("2026-01-04T00:00:00Z")),
+            ),
+            l2Memory = listOf(
+                RouterL2Entry(StageId("s1"), "stage one done", StageOutcomeKind.SUCCESS, Instant.parse("2026-01-01T10:00:00Z")),
+                RouterL2Entry(StageId("s2"), "stage two failed", StageOutcomeKind.FAILURE, Instant.parse("2026-01-02T10:00:00Z")),
+            ),
+        )
+        val pack = builder.build(state, TokenBudget(limit = 10000))
+
+        // L0: system prompt + workflow status
+        val l0 = pack.layers[ContextLayer.L0]!!
+        assertEquals(2, l0.size)
+        assertEquals("systemPrompt", l0[0].sourceType)
+        assertEquals("workflowStatus", l0[1].sourceType)
+
+        // L1: last 2 conversation turns
+        val l1 = pack.layers[ContextLayer.L1]!!
+        assertEquals(2, l1.size)
+        assertEquals("conversation", l1[0].sourceType)
+
+        // L2: both stage summaries fit
+        val l2 = pack.layers[ContextLayer.L2]!!
+        assertEquals(2, l2.size)
+        assertEquals("stageSummary", l2[0].sourceType)
+
+        // Budget and metadata
+        assertTrue(pack.budgetUsed > 0)
+        assertTrue(pack.budgetUsed <= pack.budgetLimit)
+        assertEquals(0, pack.compressionMetadata.entriesDropped)
+    }
+
+    @Test
+    fun `build with null sessionId produces unknown pack id`() {
+        val state = RouterState(
+            workflowStatus = WorkflowStatus.IDLE,
+        )
+        val pack = builder.build(state, TokenBudget(limit = 1000))
+        assertTrue(pack.id.value.contains("unknown"))
+    }
+}