diff --git a/packages/core/src/__tests__/db-migrate.test.ts b/packages/core/src/__tests__/db-migrate.test.ts
index 8a989400d8..b36c04e128 100644
--- a/packages/core/src/__tests__/db-migrate.test.ts
+++ b/packages/core/src/__tests__/db-migrate.test.ts
@@ -715,7 +715,7 @@ describe("schema migration", () => {
 
     const row = db.prepare("SELECT deletedAt FROM tasks WHERE id = 'FN-legacy'").get() as { deletedAt: string | null };
     expect(row.deletedAt).toBeNull();
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     db.close();
   });
@@ -748,7 +748,7 @@ describe("schema migration", () => {
       { id: "WS-001", mode: "prompt", gateMode: "advisory" },
       { id: "WS-002", mode: "script", gateMode: "advisory" },
     ]);
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     db.close();
   });
@@ -798,7 +798,7 @@ describe("schema migration", () => {
       reviewerContextRetryCount: 0,
       reviewerFallbackRetryCount: 0,
     });
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     db.close();
   });
@@ -827,7 +827,7 @@ describe("schema migration", () => {
 
     const columns = db.prepare("PRAGMA table_info(milestones)").all() as Array<{ name: string }>;
     expect(columns.map((column) => column.name)).toContain("acceptanceCriteria");
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     db.close();
   });
@@ -868,7 +868,7 @@ describe("schema migration", () => {
     const missionColumns = db.prepare("PRAGMA table_info(missions)").all() as Array<{ name: string }>;
     expect(missionColumns.map((column) => column.name)).toContain("autoMerge");
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
     db.close();
   });
 
@@ -902,7 +902,7 @@ describe("schema migration", () => {
       { id: "WS-002", mode: "script", enabled: 1, gateMode: "advisory" },
       { id: "WS-003", mode: "prompt", enabled: 0, gateMode: "advisory" },
     ]);
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     db.close();
   });
@@ -939,8 +939,68 @@ describe("schema migration", () => {
 
     const indexes = db.prepare("PRAGMA index_list(mission_goals)").all() as Array<{ name: string }>;
     expect(indexes.some((index) => index.name === "idxMissionGoalsGoalId")).toBe(true);
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     db.close();
   });
+
+  it("adds workflow_run_step_instances table + tasks.customFields when migrating from schema version 107", () => {
+    const db = new Database(fusionDir);
+    db.exec("CREATE TABLE IF NOT EXISTS __meta (key TEXT PRIMARY KEY, value TEXT)");
+    db.exec("INSERT INTO __meta (key, value) VALUES ('schemaVersion', '107')");
+    db.exec("INSERT INTO __meta (key, value) VALUES ('lastModified', '1000')");
+    db.exec(`
+      CREATE TABLE IF NOT EXISTS tasks (
+        id TEXT PRIMARY KEY,
+        description TEXT NOT NULL,
+        "column" TEXT NOT NULL,
+        createdAt TEXT NOT NULL,
+        updatedAt TEXT NOT NULL
+      )
+    `);
+
+    db.init();
+
+    // The new per-step-instance run-state table exists with its index.
+    const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table'").all() as Array<{ name: string }>;
+    expect(tables.map((row) => row.name)).toContain("workflow_run_step_instances");
+
+    const stepInstanceColumns = db
+      .prepare("PRAGMA table_info(workflow_run_step_instances)")
+      .all() as Array<{ name: string }>;
+    expect(stepInstanceColumns.map((column) => column.name)).toEqual([
+      "taskId",
+      "runId",
+      "foreachNodeId",
+      "stepIndex",
+      "pinnedStepCount",
+      "currentNodeId",
+      "status",
+      "baselineSha",
+      "checkpointId",
+      "reworkCount",
+      "branchName",
+      "integratedAt",
+      "updatedAt",
+    ]);
+
+    const stepInstanceIndexes = db
+      .prepare("PRAGMA index_list(workflow_run_step_instances)")
+      .all() as Array<{ name: string }>;
+    expect(
+      stepInstanceIndexes.some((index) => index.name === "idx_workflow_run_step_instances_task_run"),
+    ).toBe(true);
+
+    // tasks.customFields column is added with a default-'{}' definition.
+    const taskColumns = db.prepare("PRAGMA table_info(tasks)").all() as Array<{
+      name: string;
+      dflt_value: string | null;
+    }>;
+    const customFieldsColumn = taskColumns.find((column) => column.name === "customFields");
+    expect(customFieldsColumn).toBeDefined();
+    expect(customFieldsColumn?.dflt_value).toBe("'{}'");
+
+    expect(db.getSchemaVersion()).toBe(108);
+    db.close();
+  });
 });
diff --git a/packages/core/src/__tests__/db.test.ts b/packages/core/src/__tests__/db.test.ts
index 7ef8601b31..8a618bd583 100644
--- a/packages/core/src/__tests__/db.test.ts
+++ b/packages/core/src/__tests__/db.test.ts
@@ -334,7 +334,7 @@ describe("Database", () => {
     });
 
     it("seeds schema version", () => {
-      expect(db.getSchemaVersion()).toBe(107);
+      expect(db.getSchemaVersion()).toBe(108);
     });
 
     it("includes tokenUsageCacheWriteTokens on freshly initialized tasks table", () => {
@@ -393,7 +393,7 @@ describe("Database", () => {
 
     it("is idempotent - calling init() twice does not fail", () => {
       expect(() => db.init()).not.toThrow();
-      expect(db.getSchemaVersion()).toBe(107);
+      expect(db.getSchemaVersion()).toBe(108);
     });
     it("does not overwrite existing config on re-init", () => {
       // Update the config
@@ -1463,7 +1463,7 @@ describe("schema migrations", () => {
     db.init();
 
     // Verify version bumped to 29 (includes v1→v2 through v26→v29)
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     // Verify new columns exist and existing data is intact
     const cols = db.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
@@ -1488,11 +1488,11 @@ describe("schema migrations", () => {
     const db = new Database(fusionDir);
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     // Re-init should not fail
     db.init();
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     db.close();
   });
@@ -1527,7 +1527,7 @@ describe("schema migrations", () => {
 
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     const cols = db.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
     expect(cols.map((col) => col.name)).toContain("priority");
@@ -1568,7 +1568,7 @@ describe("schema migrations", () => {
 
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     const cols = db.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
     const colNames = cols.map((col) => col.name);
@@ -1640,7 +1640,7 @@ describe("schema migrations", () => {
 
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     const cols = db.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
     const colNames = cols.map((col) => col.name);
@@ -1880,7 +1880,7 @@ describe("schema migrations", () => {
 
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     const cols = db.prepare("PRAGMA table_info(chat_messages)").all() as Array<{ name: string }>;
     expect(cols.map((col) => col.name)).toContain("attachments");
@@ -1954,7 +1954,7 @@ describe("schema migrations", () => {
 
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name = 'agentRatings'").all() as Array<{ name: string }>;
     expect(tables).toEqual([{ name: "agentRatings" }]);
@@ -1978,7 +1978,7 @@ describe("schema migrations", () => {
 
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name = 'mission_events'").all() as Array<{ name: string }>;
     expect(tables).toEqual([{ name: "mission_events" }]);
@@ -2082,7 +2082,7 @@ describe("schema migrations", () => {
     db.init();
 
     // Verify version bumped to 29
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     // Verify new columns exist and existing data is intact
     const cols = db.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
@@ -2301,7 +2301,7 @@ describe("schema migrations", () => {
 
     localDb.init();
 
-    expect(localDb.getSchemaVersion()).toBe(107);
+    expect(localDb.getSchemaVersion()).toBe(108);
     const columns = localDb.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
     expect(columns.map((column) => column.name)).toContain("tokenUsageCacheWriteTokens");
 
@@ -2612,7 +2612,7 @@ describe("createDatabase factory", () => {
     const db = createDatabase(fusionDir);
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
     expect(db.getLastModified()).toBeGreaterThan(0);
 
     db.close();
@@ -2766,7 +2766,7 @@ describe("migration v77 task token budget columns", () => {
 
       migrated = new Database(fusion);
       migrated.init();
-      expect(migrated.getSchemaVersion()).toBe(107);
+      expect(migrated.getSchemaVersion()).toBe(108);
       const rows = migrated.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
       const names = new Set(rows.map((row) => row.name));
       expect(names.has("tokenBudgetSoftAlertedAt")).toBe(true);
@@ -2797,7 +2797,7 @@ describe("migration v106 adds tasks.transitionPending (FN-1417)", () => {
     const fresh = new Database(fusion);
     try {
       fresh.init();
-      expect(fresh.getSchemaVersion()).toBe(107);
+      expect(fresh.getSchemaVersion()).toBe(108);
       const names = new Set(
         (fresh.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>).map((r) => r.name),
       );
@@ -2825,7 +2825,7 @@ describe("migration v106 adds tasks.transitionPending (FN-1417)", () => {
 
       migrated = new Database(fusion);
       migrated.init();
-      expect(migrated.getSchemaVersion()).toBe(107);
+      expect(migrated.getSchemaVersion()).toBe(108);
       const names = new Set(
         (migrated.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>).map((r) => r.name),
       );
@@ -2851,7 +2851,7 @@ describe("migration v107 adds workflow_run_branches + index (FN-1417)", () => {
     const fresh = new Database(fusion);
     try {
       fresh.init();
-      expect(fresh.getSchemaVersion()).toBe(107);
+      expect(fresh.getSchemaVersion()).toBe(108);
       const table = fresh
         .prepare("SELECT name FROM sqlite_master WHERE type='table' AND name = 'workflow_run_branches'")
         .get() as { name: string } | undefined;
@@ -2885,7 +2885,7 @@ describe("migration v107 adds workflow_run_branches + index (FN-1417)", () => {
 
       migrated = new Database(fusion);
       migrated.init();
-      expect(migrated.getSchemaVersion()).toBe(107);
+      expect(migrated.getSchemaVersion()).toBe(108);
       const table = migrated
         .prepare("SELECT name FROM sqlite_master WHERE type='table' AND name = 'workflow_run_branches'")
         .get() as { name: string } | undefined;
@@ -2926,7 +2926,7 @@ describe("migration v67 drops orphan project auth tables", () => {
 
       migrated = new Database(fusion);
       migrated.init();
-      expect(migrated.getSchemaVersion()).toBe(107);
+      expect(migrated.getSchemaVersion()).toBe(108);
       const tables = migrated
         .prepare("SELECT name FROM sqlite_master WHERE type='table' AND name LIKE 'project_auth_%'")
         .all() as Array<{ name: string }>;
@@ -2953,7 +2953,7 @@ describe("migration v67 drops orphan project auth tables", () => {
 
     try {
       fresh.init();
-      expect(fresh.getSchemaVersion()).toBe(107);
+      expect(fresh.getSchemaVersion()).toBe(108);
       const tables = fresh
         .prepare("SELECT name FROM sqlite_master WHERE type='table' AND name LIKE 'project_auth_%'")
         .all() as Array<{ name: string }>;
diff --git a/packages/core/src/__tests__/goals-schema.test.ts b/packages/core/src/__tests__/goals-schema.test.ts
index 1e449be32b..333a68e551 100644
--- a/packages/core/src/__tests__/goals-schema.test.ts
+++ b/packages/core/src/__tests__/goals-schema.test.ts
@@ -91,6 +91,6 @@ describe("goals schema", () => {
   });
 
   it("reports schema version 101", () => {
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
   });
 });
diff --git a/packages/core/src/__tests__/insight-store.test.ts b/packages/core/src/__tests__/insight-store.test.ts
index 447411ad52..7aa0e611ad 100644
--- a/packages/core/src/__tests__/insight-store.test.ts
+++ b/packages/core/src/__tests__/insight-store.test.ts
@@ -1000,7 +1000,7 @@ describe("Migration: pre-33 DB upgrade", () => {
       // Step 1: Create a fresh database at v33 (runs all migrations up to 33)
       const db1 = createDatabase(legacyDir);
       db1.init();
-      expect(db1.getSchemaVersion()).toBe(107);
+      expect(db1.getSchemaVersion()).toBe(108);
       db1.close();
 
       // Step 2: Manually downgrade to version 32 and drop insight tables
@@ -1035,7 +1035,7 @@ describe("Migration: pre-33 DB upgrade", () => {
       expect(tableNamesBefore).not.toContain("project_insight_runs");
       // Now run init — this triggers the v32→v33 migration
       db3.init();
-      expect(db3.getSchemaVersion()).toBe(107);
+      expect(db3.getSchemaVersion()).toBe(108);
 
       // Step 4: Verify insight tables exist after migration
       const tablesAfter = db3.prepare(
@@ -1066,12 +1066,12 @@ describe("Migration: pre-33 DB upgrade", () => {
     try {
       const db1 = createDatabase(testDir);
       db1.init();
-      expect(db1.getSchemaVersion()).toBe(107);
+      expect(db1.getSchemaVersion()).toBe(108);
       db1.close();
 
       const db2 = createDatabase(testDir);
       expect(() => db2.init()).not.toThrow();
-      expect(db2.getSchemaVersion()).toBe(107);
+      expect(db2.getSchemaVersion()).toBe(108);
       db2.close();
     } finally {
       rmSync(testDir, { recursive: true, force: true });
@@ -1085,7 +1085,7 @@ describe("Migration: pre-33 DB upgrade", () => {
       // Step 1: Create a fresh DB and run migrations
       const db1 = createDatabase(compatDir);
       db1.init();
-      expect(db1.getSchemaVersion()).toBe(107);
+      expect(db1.getSchemaVersion()).toBe(108);
 
       // Step 2: Strip lifecycle and cancelledAt columns by recreating the
       // table without them. This simulates a DB that was created before the
diff --git a/packages/core/src/__tests__/merge-request-record.test.ts b/packages/core/src/__tests__/merge-request-record.test.ts
index fd508a69be..ef2a10d136 100644
--- a/packages/core/src/__tests__/merge-request-record.test.ts
+++ b/packages/core/src/__tests__/merge-request-record.test.ts
@@ -38,7 +38,7 @@ describe("TaskStore merge request record + completion handoff marker", () => {
       .all() as Array<{ name: string }>;
 
     expect(tableRows).toEqual([{ name: "completion_handoff_markers" }, { name: "merge_requests" }]);
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
   });
 
   it("upserts merge request records", async () => {
diff --git a/packages/core/src/__tests__/mission-store.test.ts b/packages/core/src/__tests__/mission-store.test.ts
index fbff57d141..7410346c67 100644
--- a/packages/core/src/__tests__/mission-store.test.ts
+++ b/packages/core/src/__tests__/mission-store.test.ts
@@ -3746,7 +3746,7 @@ describe("MissionStore", () => {
 
   describe("Loop State & Validator Run Schema (v31)", () => {
     it("schema version is 101 after migration", () => {
-      expect(db.getSchemaVersion()).toBe(107);
+      expect(db.getSchemaVersion()).toBe(108);
     });
 
     it("mission_features table has loop state columns", () => {
diff --git a/packages/core/src/__tests__/run-audit.test.ts b/packages/core/src/__tests__/run-audit.test.ts
index c64b9a50f3..3be684ea9a 100644
--- a/packages/core/src/__tests__/run-audit.test.ts
+++ b/packages/core/src/__tests__/run-audit.test.ts
@@ -584,7 +584,7 @@ describe("Run Audit", () => {
     });
 
     it("schema version is bumped to 40", () => {
-      expect(db.getSchemaVersion()).toBe(107);
+      expect(db.getSchemaVersion()).toBe(108);
     });
   });
 });
diff --git a/packages/core/src/__tests__/store-merge-queue.test.ts b/packages/core/src/__tests__/store-merge-queue.test.ts
index 6d2b141a97..6c09641156 100644
--- a/packages/core/src/__tests__/store-merge-queue.test.ts
+++ b/packages/core/src/__tests__/store-merge-queue.test.ts
@@ -60,7 +60,7 @@ describe("TaskStore merge queue", () => {
       expect.arrayContaining(["idx_mergeQueue_lease_ready", "idx_mergeQueue_leaseExpiresAt"]),
     );
 
-    expect(store.getDatabase().getSchemaVersion()).toBe(107);
+    expect(store.getDatabase().getSchemaVersion()).toBe(108);
   });
 
   it("migrates a legacy v88 database and preserves task rows", async () => {
diff --git a/packages/core/src/__tests__/task-documents.test.ts b/packages/core/src/__tests__/task-documents.test.ts
index ccde60a72e..7352ec08bf 100644
--- a/packages/core/src/__tests__/task-documents.test.ts
+++ b/packages/core/src/__tests__/task-documents.test.ts
@@ -51,7 +51,7 @@ describe("TaskStore task documents", () => {
 
     expect(tableNames.has("task_documents")).toBe(true);
     expect(tableNames.has("task_document_revisions")).toBe(true);
-    expect(db.getSchemaVersion()).toBe(107);
+    expect(db.getSchemaVersion()).toBe(108);
 
     const index = db
       .prepare(
diff --git a/packages/core/src/__tests__/workflow-step-instances.test.ts b/packages/core/src/__tests__/workflow-step-instances.test.ts
new file mode 100644
index 0000000000..1d301698b9
--- /dev/null
+++ b/packages/core/src/__tests__/workflow-step-instances.test.ts
@@ -0,0 +1,222 @@
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+
+import type { WorkflowRunStepInstance } from "../types.js";
+import { createTaskStoreTestHarness } from "./store-test-helpers.js";
+
+/**
+ * Step-inversion U4 (KTD-6/KTD-13): persistence groundwork for the foreach
+ * step-instance region. Covers the workflow_run_step_instances CRUD trio
+ * (save/load/clear) — upsert-on-conflict, per-run pruning, load ordering — plus
+ * the raw tasks.customFields JSON round-trip through create/update/get.
+ *
+ * The CRUD trio mirrors workflow_run_branches: a `save` is an idempotent UPSERT
+ * keyed by (taskId, runId, foreachNodeId, stepIndex); `load` returns the run's
+ * rows ordered by stepIndex; `clear` prunes either everything-but-a-kept-run
+ * (per-run prune) or, with no runId, every row for the task.
+ */
+
+describe("workflow_run_step_instances CRUD (U4, KTD-6)", () => {
+  const harness = createTaskStoreTestHarness();
+  let store: ReturnType<typeof harness.store>;
+
+  beforeEach(async () => {
+    await harness.beforeEach();
+    store = harness.store();
+  });
+  afterEach(async () => {
+    await harness.afterEach();
+  });
+
+  type StepInstanceStore = {
+    saveWorkflowRunStepInstance(state: WorkflowRunStepInstance): void;
+    loadWorkflowRunStepInstances(taskId: string, runId: string): WorkflowRunStepInstance[];
+    clearWorkflowRunStepInstances(taskId: string, keepRunId?: string): void;
+  };
+  const sis = (): StepInstanceStore => store as unknown as StepInstanceStore;
+
+  function rawCount(taskId: string): number {
+    const db = (store as unknown as { db: { prepare: (s: string) => { get: (...a: unknown[]) => unknown } } }).db;
+    const row = db
+      .prepare("SELECT COUNT(*) AS c FROM workflow_run_step_instances WHERE taskId = ?")
+      .get(taskId) as { c: number };
+    return row.c;
+  }
+
+  function makeInstance(overrides: Partial<WorkflowRunStepInstance> = {}): WorkflowRunStepInstance {
+    return {
+      taskId: "T-1",
+      runId: "r1",
+      foreachNodeId: "fe",
+      stepIndex: 0,
+      pinnedStepCount: 3,
+      currentNodeId: "n1",
+      status: "in-progress",
+      baselineSha: "abc123",
+      checkpointId: "ckpt-1",
+      reworkCount: 0,
+      branchName: null,
+      integratedAt: null,
+      updatedAt: "2026-06-04T00:00:00.000Z",
+      ...overrides,
+    };
+  }
+
+  it("round-trips a full instance row through save → load", async () => {
+    const t = await store.createTask({ description: "stepped" });
+    const inst = makeInstance({
+      taskId: t.id,
+      branchName: "step/0",
+      integratedAt: "2026-06-04T01:00:00.000Z",
+      status: "completed",
+      reworkCount: 2,
+    });
+    sis().saveWorkflowRunStepInstance(inst);
+
+    const [loaded] = sis().loadWorkflowRunStepInstances(t.id, "r1");
+    expect(loaded.taskId).toBe(t.id);
+    expect(loaded.runId).toBe("r1");
+    expect(loaded.foreachNodeId).toBe("fe");
+    expect(loaded.stepIndex).toBe(0);
+    expect(loaded.pinnedStepCount).toBe(3);
+    expect(loaded.currentNodeId).toBe("n1");
+    expect(loaded.status).toBe("completed");
+    expect(loaded.baselineSha).toBe("abc123");
+    expect(loaded.checkpointId).toBe("ckpt-1");
+    expect(loaded.reworkCount).toBe(2);
+    expect(loaded.branchName).toBe("step/0");
+    expect(loaded.integratedAt).toBe("2026-06-04T01:00:00.000Z");
+    expect(typeof loaded.updatedAt).toBe("string");
+  });
+
+  it("save UPSERTS on (taskId, runId, foreachNodeId, stepIndex) conflict", async () => {
+    const t = await store.createTask({ description: "upsert" });
+    sis().saveWorkflowRunStepInstance(
+      makeInstance({ taskId: t.id, stepIndex: 0, currentNodeId: "n1", status: "in-progress", reworkCount: 0 }),
+    );
+    // Same PK — overwrites in place, not a second row.
+    sis().saveWorkflowRunStepInstance(
+      makeInstance({ taskId: t.id, stepIndex: 0, currentNodeId: "n5", status: "completed", reworkCount: 1 }),
+    );
+    // Different stepIndex — a new row.
+    sis().saveWorkflowRunStepInstance(
+      makeInstance({ taskId: t.id, stepIndex: 1, currentNodeId: "n2", status: "pending" }),
+    );
+
+    expect(rawCount(t.id)).toBe(2);
+    const loaded = sis().loadWorkflowRunStepInstances(t.id, "r1");
+    const step0 = loaded.find((row) => row.stepIndex === 0);
+    expect(step0?.currentNodeId).toBe("n5");
+    expect(step0?.status).toBe("completed");
+    expect(step0?.reworkCount).toBe(1);
+  });
+
+  it("persists nullable anchors as null and reads them back as null", async () => {
+    const t = await store.createTask({ description: "nulls" });
+    sis().saveWorkflowRunStepInstance(
+      makeInstance({
+        taskId: t.id,
+        currentNodeId: null,
+        baselineSha: null,
+        checkpointId: null,
+        branchName: null,
+        integratedAt: null,
+        status: "pending",
+      }),
+    );
+    const [loaded] = sis().loadWorkflowRunStepInstances(t.id, "r1");
+    expect(loaded.currentNodeId).toBeNull();
+    expect(loaded.baselineSha).toBeNull();
+    expect(loaded.checkpointId).toBeNull();
+    expect(loaded.branchName).toBeNull();
+    expect(loaded.integratedAt).toBeNull();
+  });
+
+  it("loadWorkflowRunStepInstances returns the run ordered by stepIndex", async () => {
+    const t = await store.createTask({ description: "ordered" });
+    // Insert out of order.
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, stepIndex: 2, currentNodeId: "n2" }));
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, stepIndex: 0, currentNodeId: "n0" }));
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, stepIndex: 1, currentNodeId: "n1" }));
+
+    const loaded = sis().loadWorkflowRunStepInstances(t.id, "r1");
+    expect(loaded.map((row) => row.stepIndex)).toEqual([0, 1, 2]);
+  });
+
+  it("loadWorkflowRunStepInstances scopes to the requested run only", async () => {
+    const t = await store.createTask({ description: "scoped" });
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, runId: "r1", stepIndex: 0 }));
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, runId: "r2", stepIndex: 0 }));
+    expect(sis().loadWorkflowRunStepInstances(t.id, "r1").length).toBe(1);
+    expect(sis().loadWorkflowRunStepInstances(t.id, "r2").length).toBe(1);
+  });
+
+  it("clear with keepRunId prunes every other run, keeps the kept run", async () => {
+    const t = await store.createTask({ description: "prune" });
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, runId: "old", stepIndex: 0 }));
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, runId: "old", stepIndex: 1 }));
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, runId: "cur", stepIndex: 0 }));
+
+    sis().clearWorkflowRunStepInstances(t.id, "cur");
+
+    expect(rawCount(t.id)).toBe(1);
+    expect(sis().loadWorkflowRunStepInstances(t.id, "old").length).toBe(0);
+    expect(sis().loadWorkflowRunStepInstances(t.id, "cur").length).toBe(1);
+  });
+
+  it("clear with no keepRunId prunes all rows for the task", async () => {
+    const t = await store.createTask({ description: "wipe" });
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, runId: "r1", stepIndex: 0 }));
+    sis().saveWorkflowRunStepInstance(makeInstance({ taskId: t.id, runId: "r2", stepIndex: 0 }));
+
+    sis().clearWorkflowRunStepInstances(t.id);
+
+    expect(rawCount(t.id)).toBe(0);
+  });
+});
+
+describe("tasks.customFields raw JSON round-trip (U4 groundwork for KTD-13)", () => {
+  const harness = createTaskStoreTestHarness();
+  let store: ReturnType<typeof harness.store>;
+
+  beforeEach(async () => {
+    await harness.beforeEach();
+    store = harness.store();
+  });
+  afterEach(async () => {
+    await harness.afterEach();
+  });
+
+  it("a freshly created task has no customFields (legacy-shape default)", async () => {
+    const t = await store.createTask({ description: "no fields" });
+    const got = await store.getTask(t.id);
+    // Stored default is '{}' which parses to an empty object; the row→Task map
+    // surfaces that as an empty object, distinguishable from later writes.
+    expect(got?.customFields).toEqual({});
+  });
+
+  it("round-trips a customFields object through updateTask → getTask", async () => {
+    const t = await store.createTask({ description: "fielded" });
+    await store.updateTask(t.id, {
+      customFields: { severity: "high", points: 3, flagged: true, tags: ["a", "b"] },
+    });
+    const got = await store.getTask(t.id);
+    expect(got?.customFields).toEqual({ severity: "high", points: 3, flagged: true, tags: ["a", "b"] });
+  });
+
+  it("updateTask treats customFields as a whole-object opaque patch (replaces, not merges)", async () => {
+    const t = await store.createTask({ description: "replace" });
+    await store.updateTask(t.id, { customFields: { a: 1, b: 2 } });
+    await store.updateTask(t.id, { customFields: { a: 9 } });
+    const got = await store.getTask(t.id);
+    // Whole-object replacement: `b` is gone. (Merge/validation is a later unit.)
+    expect(got?.customFields).toEqual({ a: 9 });
+  });
+
+  it("leaves customFields untouched when an unrelated field is updated", async () => {
+    const t = await store.createTask({ description: "untouched" });
+    await store.updateTask(t.id, { customFields: { keep: "me" } });
+    await store.updateTask(t.id, { summary: "an unrelated change" });
+    const got = await store.getTask(t.id);
+    expect(got?.customFields).toEqual({ keep: "me" });
+  });
+});
diff --git a/packages/core/src/db.ts b/packages/core/src/db.ts
index 0b9d5a0dba..6403a186f1 100644
--- a/packages/core/src/db.ts
+++ b/packages/core/src/db.ts
@@ -149,7 +149,7 @@ export function probeFts5(db: DatabaseSync): boolean {
 
 // ── Schema Definition ────────────────────────────────────────────────
 
-const SCHEMA_VERSION = 107;
+const SCHEMA_VERSION = 108;
 
 export { SCHEMA_VERSION };
 
@@ -323,7 +323,8 @@ CREATE TABLE IF NOT EXISTS tasks (
   checkoutLeaseEpoch INTEGER DEFAULT 0,
   deletedAt TEXT,
   allowResurrection INTEGER DEFAULT 0,
-  transitionPending TEXT
+  transitionPending TEXT,
+  customFields TEXT DEFAULT '{}'
 );
 
 -- Config table (single row with project settings)
@@ -589,6 +590,32 @@ CREATE TABLE IF NOT EXISTS workflow_run_branches (
 );
 CREATE INDEX IF NOT EXISTS idx_workflow_run_branches_task_run ON workflow_run_branches(taskId, runId);
 
+-- Per-step-instance run state for the step-inversion foreach region (step-inversion
+-- U4, KTD-6). One row per expanded step instance inside a foreach region; resume
+-- reconstructs the instance set from pinnedStepCount + persisted currentNodeId/
+-- reworkCount without re-running completed instances. baselineSha/checkpointId
+-- persist the RETHINK reset anchors (previously in-memory, lost on restart).
+-- branchName/integratedAt and the "awaiting-integration" status serve parallel
+-- mode (KTD-11) and are null/unused at concurrency 1. Additive-only, reconstructible.
+-- status ∈ "pending" | "in-progress" | "awaiting-integration" | "completed" | "failed".
+CREATE TABLE IF NOT EXISTS workflow_run_step_instances (
+  taskId TEXT NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
+  runId TEXT NOT NULL,
+  foreachNodeId TEXT NOT NULL,
+  stepIndex INTEGER NOT NULL,
+  pinnedStepCount INTEGER NOT NULL,
+  currentNodeId TEXT,
+  status TEXT NOT NULL,
+  baselineSha TEXT,
+  checkpointId TEXT,
+  reworkCount INTEGER NOT NULL DEFAULT 0,
+  branchName TEXT,
+  integratedAt TEXT,
+  updatedAt TEXT NOT NULL,
+  PRIMARY KEY (taskId, runId, foreachNodeId, stepIndex)
+);
+CREATE INDEX IF NOT EXISTS idx_workflow_run_step_instances_task_run ON workflow_run_step_instances(taskId, runId);
+
 -- Task documents (key-value store per task with revision tracking)
 CREATE TABLE IF NOT EXISTS task_documents (
   id TEXT PRIMARY KEY,
@@ -4229,6 +4256,41 @@ export class Database {
       });
     }
 
+    // Migration 108: Step-inversion persistence (step-inversion U4, KTD-6/KTD-13).
+    // Adds workflow_run_step_instances — one row per expanded step instance inside a
+    // foreach region — so a crashed/restarted run reconstructs the instance set from
+    // pinnedStepCount + persisted currentNodeId/reworkCount, and the RETHINK reset
+    // anchors (baselineSha/checkpointId) survive restart (previously in-memory Maps).
+    // branchName/integratedAt + "awaiting-integration" status serve parallel mode
+    // (KTD-11; null/unused at concurrency 1). Also adds tasks.customFields (KTD-13),
+    // the JSON store for workflow-defined custom task field values. Additive-only,
+    // idempotent (table-exists / addColumnIfMissing guards); no backfill.
+    // status ∈ "pending" | "in-progress" | "awaiting-integration" | "completed" | "failed".
+    if (version < 108) {
+      this.applyMigration(108, () => {
+        this.db.exec(`
+          CREATE TABLE IF NOT EXISTS workflow_run_step_instances (
+            taskId TEXT NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
+            runId TEXT NOT NULL,
+            foreachNodeId TEXT NOT NULL,
+            stepIndex INTEGER NOT NULL,
+            pinnedStepCount INTEGER NOT NULL,
+            currentNodeId TEXT,
+            status TEXT NOT NULL,
+            baselineSha TEXT,
+            checkpointId TEXT,
+            reworkCount INTEGER NOT NULL DEFAULT 0,
+            branchName TEXT,
+            integratedAt TEXT,
+            updatedAt TEXT NOT NULL,
+            PRIMARY KEY (taskId, runId, foreachNodeId, stepIndex)
+          );
+          CREATE INDEX IF NOT EXISTS idx_workflow_run_step_instances_task_run ON workflow_run_step_instances(taskId, runId);
+        `);
+        this.addColumnIfMissing("tasks", "customFields", "TEXT DEFAULT '{}'");
+      });
+    }
+
   }
 
   /**
diff --git a/packages/core/src/store.ts b/packages/core/src/store.ts
index a477d46f3e..f4ddcf46e7 100644
--- a/packages/core/src/store.ts
+++ b/packages/core/src/store.ts
@@ -207,6 +207,7 @@ interface TaskRow {
   executionCompletedAt: string | null;
   dependencies: string | null;
   steps: string | null;
+  customFields: string | null;
   log: string | null;
   attachments: string | null;
   steeringComments: string | null;
@@ -1778,6 +1779,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       executionCompletedAt: row.executionCompletedAt || undefined,
       dependencies: fromJson<string[]>(row.dependencies) || [],
       steps: fromJson<import("./types.js").TaskStep[]>(row.steps) || [],
+      customFields: fromJson<Record<string, unknown>>(row.customFields) ?? undefined,
       log: fromJson<import("./types.js").TaskLogEntry[]>(row.log) || [],
       tokenBudgetSoftAlertedAt: row.tokenBudgetSoftAlertedAt || undefined,
       tokenBudgetHardAlertedAt: row.tokenBudgetHardAlertedAt || undefined,
@@ -1925,6 +1927,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       dependencies: entry.dependencies ?? [],
       steps: entry.steps ?? [],
       currentStep: entry.currentStep ?? 0,
+      customFields: entry.customFields ?? undefined,
       size: entry.size,
       reviewLevel: entry.reviewLevel,
       prInfo: slim ? undefined : entry.prInfo,
@@ -2057,6 +2060,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       dependencies: task.dependencies,
       steps: task.steps,
       currentStep: task.currentStep,
+      customFields: task.customFields,
       size: task.size,
       reviewLevel: task.reviewLevel,
       prInfo: task.prInfo,
@@ -2265,7 +2269,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       "error", "summary", "thinkingLevel", "executionMode",
       "tokenUsageInputTokens", "tokenUsageOutputTokens", "tokenUsageCachedTokens", "tokenUsageCacheWriteTokens", "tokenUsageTotalTokens", "tokenUsageFirstUsedAt", "tokenUsageLastUsedAt", "tokenBudgetSoftAlertedAt", "tokenBudgetHardAlertedAt", "tokenBudgetOverride",
       "createdAt", "updatedAt", "columnMovedAt", "firstExecutionAt", "cumulativeActiveMs", "executionStartedAt", "executionCompletedAt",
-      "dependencies", "steps", "comments", "review", "reviewState", "workflowStepResults", "steeringComments",
+      "dependencies", "steps", "customFields", "comments", "review", "reviewState", "workflowStepResults", "steeringComments",
       "attachments", "prInfo", "prInfos", "issueInfo", "githubTracking", "sourceIssueProvider", "sourceIssueRepository", "sourceIssueExternalIssueId", "sourceIssueNumber", "sourceIssueUrl", "mergeDetails",
       "breakIntoSubtasks", "noCommitsExpected", "enabledWorkflowSteps", "modifiedFiles",
       "missionId", "sliceId", "scopeOverride", "scopeOverrideReason", "scopeAutoWiden", "assignedAgentId", "pausedByAgentId", "assigneeUserId", "nodeId", "effectiveNodeId", "effectiveNodeSource",
@@ -2314,7 +2318,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       "error", "summary", "thinkingLevel", "executionMode",
       "tokenUsageInputTokens", "tokenUsageOutputTokens", "tokenUsageCachedTokens", "tokenUsageCacheWriteTokens", "tokenUsageTotalTokens", "tokenUsageFirstUsedAt", "tokenUsageLastUsedAt", "tokenBudgetSoftAlertedAt", "tokenBudgetHardAlertedAt", "tokenBudgetOverride",
       "createdAt", "updatedAt", "columnMovedAt", "firstExecutionAt", "cumulativeActiveMs", "executionStartedAt", "executionCompletedAt",
-      "dependencies", "steps", "attachments", "steeringComments",
+      "dependencies", "steps", "customFields", "attachments", "steeringComments",
       "comments", "review", "reviewState", "workflowStepResults", "prInfo", "prInfos", "issueInfo", "githubTracking", "sourceIssueProvider", "sourceIssueRepository", "sourceIssueExternalIssueId", "sourceIssueNumber", "sourceIssueUrl", "mergeDetails",
       "breakIntoSubtasks", "noCommitsExpected", "enabledWorkflowSteps", "modifiedFiles",
       "missionId", "sliceId", "scopeOverride", "scopeOverrideReason", "scopeAutoWiden", "assignedAgentId", "pausedByAgentId", "assigneeUserId", "nodeId", "effectiveNodeId", "effectiveNodeSource",
@@ -2416,6 +2420,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       task.executionCompletedAt ?? null,
       toJson(task.dependencies || []),
       toJson(task.steps || []),
+      toJson(task.customFields ?? {}),
       toJson(task.log || []),
       toJson(task.attachments || []),
       toJson(task.steeringComments || []),
@@ -2483,7 +2488,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
         summary, thinkingLevel, executionMode, tokenUsageInputTokens, tokenUsageOutputTokens, tokenUsageCachedTokens,
         tokenUsageCacheWriteTokens, tokenUsageTotalTokens, tokenUsageFirstUsedAt, tokenUsageLastUsedAt, tokenBudgetSoftAlertedAt, tokenBudgetHardAlertedAt, tokenBudgetOverride, createdAt, updatedAt, columnMovedAt,
         firstExecutionAt, cumulativeActiveMs, executionStartedAt, executionCompletedAt,
-        dependencies, steps, log, attachments, steeringComments,
+        dependencies, steps, customFields, log, attachments, steeringComments,
         comments, review, reviewState, workflowStepResults, prInfo, prInfos, issueInfo, githubTracking,
         sourceIssueProvider, sourceIssueRepository, sourceIssueExternalIssueId, sourceIssueNumber, sourceIssueUrl,
         mergeDetails, breakIntoSubtasks, noCommitsExpected, autoMerge, enabledWorkflowSteps, modifiedFiles, missionId, sliceId, scopeOverride, scopeOverrideReason, scopeAutoWiden, assignedAgentId, pausedByAgentId, assigneeUserId, nodeId, effectiveNodeId, effectiveNodeSource, sourceType, sourceAgentId, sourceRunId, sourceSessionId, sourceMessageId, sourceParentTaskId, sourceMetadata, checkedOutBy, checkedOutAt, checkoutNodeId, checkoutRunId, checkoutLeaseRenewedAt, checkoutLeaseEpoch, deletedAt, allowResurrection
@@ -2510,7 +2515,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
         summary, thinkingLevel, executionMode, tokenUsageInputTokens, tokenUsageOutputTokens, tokenUsageCachedTokens,
         tokenUsageCacheWriteTokens, tokenUsageTotalTokens, tokenUsageFirstUsedAt, tokenUsageLastUsedAt, tokenBudgetSoftAlertedAt, tokenBudgetHardAlertedAt, tokenBudgetOverride, createdAt, updatedAt, columnMovedAt,
         firstExecutionAt, cumulativeActiveMs, executionStartedAt, executionCompletedAt,
-        dependencies, steps, log, attachments, steeringComments,
+        dependencies, steps, customFields, log, attachments, steeringComments,
         comments, review, reviewState, workflowStepResults, prInfo, prInfos, issueInfo, githubTracking,
         sourceIssueProvider, sourceIssueRepository, sourceIssueExternalIssueId, sourceIssueNumber, sourceIssueUrl,
         mergeDetails, breakIntoSubtasks, noCommitsExpected, autoMerge, enabledWorkflowSteps, modifiedFiles, missionId, sliceId, scopeOverride, scopeOverrideReason, scopeAutoWiden, assignedAgentId, pausedByAgentId, assigneeUserId, nodeId, effectiveNodeId, effectiveNodeSource, sourceType, sourceAgentId, sourceRunId, sourceSessionId, sourceMessageId, sourceParentTaskId, sourceMetadata, checkedOutBy, checkedOutAt, checkoutNodeId, checkoutRunId, checkoutLeaseRenewedAt, checkoutLeaseEpoch, deletedAt, allowResurrection
@@ -2585,6 +2590,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
         executionCompletedAt = excluded.executionCompletedAt,
         dependencies = excluded.dependencies,
         steps = excluded.steps,
+        customFields = excluded.customFields,
         log = excluded.log,
         attachments = excluded.attachments,
         steeringComments = excluded.steeringComments,
@@ -5295,6 +5301,103 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     }
   }
 
+  /**
+   * Persist (idempotent upsert) one step instance's run-state inside a foreach
+   * region (step-inversion U4, KTD-6). Keyed by (taskId, runId, foreachNodeId,
+   * stepIndex) — the table PK — so re-writing the same instance overwrites its
+   * single row with the latest currentNodeId/status/anchors. `updatedAt` is
+   * stamped server-side. Mirrors `saveWorkflowRunBranch`: additive, silently
+   * no-ops on a legacy/missing table.
+   */
+  saveWorkflowRunStepInstance(
+    state: import("./types.js").WorkflowRunStepInstance,
+  ): void {
+    try {
+      this.db
+        .prepare(
+          `INSERT INTO workflow_run_step_instances
+             (taskId, runId, foreachNodeId, stepIndex, pinnedStepCount, currentNodeId, status, baselineSha, checkpointId, reworkCount, branchName, integratedAt, updatedAt)
+           VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+           ON CONFLICT(taskId, runId, foreachNodeId, stepIndex) DO UPDATE SET
+             pinnedStepCount = excluded.pinnedStepCount,
+             currentNodeId = excluded.currentNodeId,
+             status = excluded.status,
+             baselineSha = excluded.baselineSha,
+             checkpointId = excluded.checkpointId,
+             reworkCount = excluded.reworkCount,
+             branchName = excluded.branchName,
+             integratedAt = excluded.integratedAt,
+             updatedAt = excluded.updatedAt`,
+        )
+        .run(
+          state.taskId,
+          state.runId,
+          state.foreachNodeId,
+          state.stepIndex,
+          state.pinnedStepCount,
+          state.currentNodeId ?? null,
+          state.status,
+          state.baselineSha ?? null,
+          state.checkpointId ?? null,
+          state.reworkCount ?? 0,
+          state.branchName ?? null,
+          state.integratedAt ?? null,
+          new Date().toISOString(),
+        );
+    } catch {
+      // Legacy/missing table — persistence is additive, so degrade silently.
+    }
+  }
+
+  /**
+   * Load persisted step-instance run-state for a run (crash-resume; KTD-6).
+   * Ordered by stepIndex so the executor can reconstruct the instance set in
+   * step order. Additive: returns [] on a legacy/missing table.
+   */
+  loadWorkflowRunStepInstances(
+    taskId: string,
+    runId: string,
+  ): import("./types.js").WorkflowRunStepInstance[] {
+    try {
+      const rows = this.db
+        .prepare(
+          `SELECT taskId, runId, foreachNodeId, stepIndex, pinnedStepCount, currentNodeId, status, baselineSha, checkpointId, reworkCount, branchName, integratedAt, updatedAt
+             FROM workflow_run_step_instances
+            WHERE taskId = ? AND runId = ?
+            ORDER BY stepIndex ASC`,
+        )
+        .all(taskId, runId) as import("./types.js").WorkflowRunStepInstance[];
+      return rows;
+    } catch {
+      return [];
+    }
+  }
+
+  /**
+   * Prune step-instance rows for a task (KTD-6, #1412 pattern). When `runId` is
+   * provided, deletes every row for `taskId` whose runId differs (bounding growth
+   * across a long-lived task's repeated runs — call on run start/completion).
+   * When `runId` is omitted, deletes all rows for the task (e.g. on archive).
+   * Additive: silently no-ops on a legacy/missing table.
+   */
+  clearWorkflowRunStepInstances(taskId: string, keepRunId?: string): void {
+    try {
+      if (keepRunId === undefined) {
+        this.db
+          .prepare(`DELETE FROM workflow_run_step_instances WHERE taskId = ?`)
+          .run(taskId);
+      } else {
+        this.db
+          .prepare(
+            `DELETE FROM workflow_run_step_instances WHERE taskId = ? AND runId != ?`,
+          )
+          .run(taskId, keepRunId);
+      }
+    } catch {
+      // Legacy/missing table — pruning is additive, so degrade silently.
+    }
+  }
+
   async listTasksForGithubTrackingReconcile(options?: { offset?: number; limit?: number }): Promise<{ tasks: Task[]; hasMore: boolean }> {
     const reconcileScanLimit = 200;
     const offset = Math.max(0, options?.offset ?? 0);
@@ -6865,7 +6968,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
 
   async updateTask(
     id: string,
-    updates: { title?: string; description?: string; priority?: TaskPriority | null; prompt?: string; worktree?: string | null; status?: string | null; dependencies?: string[]; steps?: import("./types.js").TaskStep[]; currentStep?: number; blockedBy?: string | null; overlapBlockedBy?: string | null; assignedAgentId?: string | null; pausedByAgentId?: string | null; pausedReason?: string | null; tokenBudgetSoftAlertedAt?: string | null; worktrunkFallbackAlertedAt?: string | null; worktrunkFailure?: import("./types.js").Task["worktrunkFailure"] | null; tokenBudgetHardAlertedAt?: string | null; tokenBudgetOverride?: import("./types.js").TaskTokenBudgetOverride | null; dispatchStormCount?: number | null; lastDispatchAt?: string | null; assigneeUserId?: string | null; scopeOverride?: boolean | null; scopeOverrideReason?: string | null; scopeAutoWiden?: string[] | null; nodeId?: string | null; effectiveNodeId?: string | null; effectiveNodeSource?: string | null; checkedOutBy?: string | null; checkedOutAt?: string | null; checkoutNodeId?: string | null; checkoutRunId?: string | null; checkoutLeaseRenewedAt?: string | null; checkoutLeaseEpoch?: number | null; paused?: boolean; baseBranch?: string | null; autoMerge?: boolean | null; branch?: string | null; executionStartBranch?: string | null; baseCommitSha?: string | null; size?: "S" | "M" | "L"; reviewLevel?: number; executionMode?: import("./types.js").ExecutionMode | null; mergeRetries?: number; workflowStepRetries?: number; stuckKillCount?: number | null; resumeLimboCount?: number | null; resumeLimboTipSha?: string | null; resumeLimboStepSignature?: string | null; postReviewFixCount?: number | null; recoveryRetryCount?: number | null; taskDoneRetryCount?: number | null; worktreeSessionRetryCount?: number | null; completionHandoffLimboRecoveryCount?: number | null; verificationFailureCount?: number | null; mergeConflictBounceCount?: number | null; mergeAuditBounceCount?: number | null; mergeTransientRetryCount?: number | null; branchConflictRecoveryCount?: number | null; reviewerContextRetryCount?: number | null; reviewerFallbackRetryCount?: number | null; nextRecoveryAt?: string | null; enabledWorkflowSteps?: string[]; noCommitsExpected?: boolean | null; modelProvider?: string | null; modelId?: string | null; validatorModelProvider?: string | null; validatorModelId?: string | null; planningModelProvider?: string | null; planningModelId?: string | null; thinkingLevel?: string | null; error?: string | null; summary?: string | null; sessionFile?: string | null; firstExecutionAt?: string | null; cumulativeActiveMs?: number | null; executionStartedAt?: string | null; executionCompletedAt?: string | null; review?: import("./types.js").TaskReview | null; reviewState?: import("./types.js").TaskReviewState | null; workflowStepResults?: import("./types.js").WorkflowStepResult[] | null; mergeDetails?: import("./types.js").MergeDetails | null; sourceIssue?: import("./types.js").TaskSourceIssue | null; sourceMetadataPatch?: Record<string, unknown> | null; githubTracking?: import("./types.js").TaskGithubTracking | null; tokenUsage?: import("./types.js").TaskTokenUsage | null; modifiedFiles?: string[] | null; missionId?: string | null; sliceId?: string | null },
+    updates: { title?: string; description?: string; priority?: TaskPriority | null; prompt?: string; worktree?: string | null; status?: string | null; dependencies?: string[]; steps?: import("./types.js").TaskStep[]; customFields?: Record<string, unknown>; currentStep?: number; blockedBy?: string | null; overlapBlockedBy?: string | null; assignedAgentId?: string | null; pausedByAgentId?: string | null; pausedReason?: string | null; tokenBudgetSoftAlertedAt?: string | null; worktrunkFallbackAlertedAt?: string | null; worktrunkFailure?: import("./types.js").Task["worktrunkFailure"] | null; tokenBudgetHardAlertedAt?: string | null; tokenBudgetOverride?: import("./types.js").TaskTokenBudgetOverride | null; dispatchStormCount?: number | null; lastDispatchAt?: string | null; assigneeUserId?: string | null; scopeOverride?: boolean | null; scopeOverrideReason?: string | null; scopeAutoWiden?: string[] | null; nodeId?: string | null; effectiveNodeId?: string | null; effectiveNodeSource?: string | null; checkedOutBy?: string | null; checkedOutAt?: string | null; checkoutNodeId?: string | null; checkoutRunId?: string | null; checkoutLeaseRenewedAt?: string | null; checkoutLeaseEpoch?: number | null; paused?: boolean; baseBranch?: string | null; autoMerge?: boolean | null; branch?: string | null; executionStartBranch?: string | null; baseCommitSha?: string | null; size?: "S" | "M" | "L"; reviewLevel?: number; executionMode?: import("./types.js").ExecutionMode | null; mergeRetries?: number; workflowStepRetries?: number; stuckKillCount?: number | null; resumeLimboCount?: number | null; resumeLimboTipSha?: string | null; resumeLimboStepSignature?: string | null; postReviewFixCount?: number | null; recoveryRetryCount?: number | null; taskDoneRetryCount?: number | null; worktreeSessionRetryCount?: number | null; completionHandoffLimboRecoveryCount?: number | null; verificationFailureCount?: number | null; mergeConflictBounceCount?: number | null; mergeAuditBounceCount?: number | null; mergeTransientRetryCount?: number | null; branchConflictRecoveryCount?: number | null; reviewerContextRetryCount?: number | null; reviewerFallbackRetryCount?: number | null; nextRecoveryAt?: string | null; enabledWorkflowSteps?: string[]; noCommitsExpected?: boolean | null; modelProvider?: string | null; modelId?: string | null; validatorModelProvider?: string | null; validatorModelId?: string | null; planningModelProvider?: string | null; planningModelId?: string | null; thinkingLevel?: string | null; error?: string | null; summary?: string | null; sessionFile?: string | null; firstExecutionAt?: string | null; cumulativeActiveMs?: number | null; executionStartedAt?: string | null; executionCompletedAt?: string | null; review?: import("./types.js").TaskReview | null; reviewState?: import("./types.js").TaskReviewState | null; workflowStepResults?: import("./types.js").WorkflowStepResult[] | null; mergeDetails?: import("./types.js").MergeDetails | null; sourceIssue?: import("./types.js").TaskSourceIssue | null; sourceMetadataPatch?: Record<string, unknown> | null; githubTracking?: import("./types.js").TaskGithubTracking | null; tokenUsage?: import("./types.js").TaskTokenUsage | null; modifiedFiles?: string[] | null; missionId?: string | null; sliceId?: string | null },
     runContext?: RunMutationContext,
   ): Promise<Task> {
     return this.withTaskLock(id, () => this.updateTaskUnlocked(id, updates, runContext));
@@ -6979,6 +7082,10 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
         }
       }
       if (updates.steps !== undefined) task.steps = updates.steps;
+      // U4/KTD-13 groundwork: round-trip customFields as an opaque whole-object
+      // patch. The typed validation/write authority (updateTaskCustomFields)
+      // lands in a later unit; for now updateTask just persists what it is given.
+      if (updates.customFields !== undefined) task.customFields = updates.customFields;
       if (updates.currentStep !== undefined) task.currentStep = updates.currentStep;
       if (updates.status === null) {
         task.status = undefined;
diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index fbf8f693da..a856b620fb 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -681,6 +681,59 @@ export interface WorkflowStepResult {
   completedAt?: string;
 }
 
+/**
+ * Lifecycle status of one persisted step instance (step-inversion U4, KTD-6).
+ * - `pending` — expanded but not yet started.
+ * - `in-progress` — actively executing inside its foreach sub-walk.
+ * - `awaiting-integration` — work complete on a parallel-mode branch, waiting
+ *   for the ordered integration stage (KTD-11; unused at concurrency 1).
+ * - `completed` — terminal success (integrated in parallel mode).
+ * - `failed` — terminal failure.
+ */
+export type WorkflowRunStepInstanceStatus =
+  | "pending"
+  | "in-progress"
+  | "awaiting-integration"
+  | "completed"
+  | "failed";
+
+/**
+ * Persisted run-state for one expanded step instance inside a foreach region
+ * (step-inversion U4, KTD-6). One row per `(taskId, runId, foreachNodeId,
+ * stepIndex)`; mirrors the `workflow_run_branches` posture. Resume reconstructs
+ * the instance set from `pinnedStepCount` + per-instance `currentNodeId` /
+ * `reworkCount`. `baselineSha` / `checkpointId` are the RETHINK reset anchors
+ * (previously in-memory, lost on restart). `branchName` / `integratedAt` and the
+ * `awaiting-integration` status serve parallel mode (KTD-11); null/unused at
+ * concurrency 1. This is the core row shape; the engine-side instance model is
+ * separate and engine-owned.
+ */
+export interface WorkflowRunStepInstance {
+  taskId: string;
+  runId: string;
+  /** Node id of the foreach region that expanded this instance. */
+  foreachNodeId: string;
+  /** Zero-based index of the step this instance runs. */
+  stepIndex: number;
+  /** Step count pinned at expansion; resume fails on mismatch with live steps[]. */
+  pinnedStepCount: number;
+  /** Current sub-walk node id for the in-flight instance; null when not started. */
+  currentNodeId?: string | null;
+  status: WorkflowRunStepInstanceStatus;
+  /** Git sha the RETHINK reset rewinds to; null when no baseline captured. */
+  baselineSha?: string | null;
+  /** Session checkpoint to rewind to on RETHINK; null when none captured. */
+  checkpointId?: string | null;
+  /** Number of rework cycles consumed against the rework budget. */
+  reworkCount: number;
+  /** Per-instance branch name in worktree-isolation mode (KTD-11); null otherwise. */
+  branchName?: string | null;
+  /** ISO-8601 timestamp the instance branch was integrated (KTD-11); null otherwise. */
+  integratedAt?: string | null;
+  /** ISO-8601 timestamp of the last write to this row. */
+  updatedAt: string;
+}
+
 /** A built-in workflow step template for one-click creation. */
 export interface WorkflowStepTemplate {
   /** Unique template identifier (e.g., "documentation-review") */
@@ -1825,6 +1878,14 @@ export interface Task {
   worktree?: string;
   steps: TaskStep[];
   currentStep: number;
+  /**
+   * Workflow-defined custom task field values (KTD-13), keyed by field id.
+   * Persisted as the `tasks.customFields` JSON column. Treated as opaque by
+   * the core row⇄Task mapping and `updateTask`; the validation/write authority
+   * (type/enum/render checks against the workflow's field schema) lands in a
+   * later unit. Absent on legacy tasks.
+   */
+  customFields?: Record<string, unknown>;
   status?: string;
   /** ID of the in-progress task whose file scope overlaps with this task,
    *  causing the scheduler to defer it. Set when the scheduler queues
@@ -4037,6 +4098,8 @@ export interface ArchivedTaskEntry {
   dependencies: string[];
   steps: TaskStep[];
   currentStep: number;
+  /** Workflow-defined custom task field values (KTD-13) frozen at archive time. */
+  customFields?: Record<string, unknown>;
   size?: "S" | "M" | "L";
   reviewLevel?: number;
   /** Execution mode for task implementation at time of archival.