diff --git a/packages/core/src/__tests__/db-migrate.test.ts b/packages/core/src/__tests__/db-migrate.test.ts
index b36c04e128..fa2616266d 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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     db.close();
   });
@@ -798,7 +798,7 @@ describe("schema migration", () => {
       reviewerContextRetryCount: 0,
       reviewerFallbackRetryCount: 0,
     });
-    expect(db.getSchemaVersion()).toBe(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     db.close();
   });
@@ -939,7 +939,7 @@ 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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     db.close();
   });
@@ -1000,7 +1000,52 @@ describe("schema migration", () => {
     expect(customFieldsColumn).toBeDefined();
     expect(customFieldsColumn?.dflt_value).toBe("'{}'");
 
-    expect(db.getSchemaVersion()).toBe(108);
+    expect(db.getSchemaVersion()).toBe(109);
+    db.close();
+  });
+
+  it("adds workflow_settings table when migrating from schema version 108", () => {
+    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', '108')");
+    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-(workflowId, projectId) setting-value table exists.
+    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_settings");
+
+    const columns = db.prepare("PRAGMA table_info(workflow_settings)").all() as Array<{
+      name: string;
+      pk: number;
+      dflt_value: string | null;
+    }>;
+    expect(columns.map((column) => column.name)).toEqual([
+      "workflowId",
+      "projectId",
+      "values",
+      "updatedAt",
+    ]);
+    // Composite primary key over (workflowId, projectId).
+    expect(columns.filter((column) => column.pk > 0).map((column) => column.name).sort()).toEqual([
+      "projectId",
+      "workflowId",
+    ]);
+    // `values` defaults to an empty JSON object.
+    const valuesColumn = columns.find((column) => column.name === "values");
+    expect(valuesColumn?.dflt_value).toBe("'{}'");
+
+    expect(db.getSchemaVersion()).toBe(109);
     db.close();
   });
 });
diff --git a/packages/core/src/__tests__/db.test.ts b/packages/core/src/__tests__/db.test.ts
index 8a618bd583..a27fc8f30b 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(108);
+      expect(db.getSchemaVersion()).toBe(109);
     });
 
     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(108);
+      expect(db.getSchemaVersion()).toBe(109);
     });
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     // 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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     // Re-init should not fail
     db.init();
-    expect(db.getSchemaVersion()).toBe(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     db.close();
   });
@@ -1527,7 +1527,7 @@ describe("schema migrations", () => {
 
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     const cols = db.prepare("PRAGMA table_info(tasks)").all() as Array<{ name: string }>;
     const colNames = cols.map((col) => col.name);
@@ -1722,13 +1722,13 @@ describe("schema migrations", () => {
 
       const kept = entries.filter(([name]) => !dropped.has(name));
       const chosen = kept.length > 0 ? kept : entries.slice(0, 1);
-      const columnSql = chosen.map(([name, def]) => `  ${name} ${def}`).join(",\n");
+      const columnSql = chosen.map(([name, def]) => `  "${name}" ${def}`).join(",\n");
       legacyDb.exec(`CREATE TABLE IF NOT EXISTS ${tableName} (\n${columnSql}\n)`);
     }
 
     const validatorColumns = Object.entries(MIGRATION_ONLY_TABLE_SCHEMAS.mission_validator_runs)
       .filter(([name, definition], index) => name === "id" || (name !== "taskId" && (index % 4 !== 0 || !isSafeToDrop(definition))))
-      .map(([name, def]) => `  ${name} ${def}`)
+      .map(([name, def]) => `  "${name}" ${def}`)
       .join(",\n");
     legacyDb.exec(`CREATE TABLE IF NOT EXISTS mission_validator_runs (\n${validatorColumns}\n)`);
 
@@ -1880,7 +1880,7 @@ describe("schema migrations", () => {
 
     db.init();
 
-    expect(db.getSchemaVersion()).toBe(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     // 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(108);
+    expect(localDb.getSchemaVersion()).toBe(109);
     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(108);
+    expect(db.getSchemaVersion()).toBe(109);
     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(108);
+      expect(migrated.getSchemaVersion()).toBe(109);
       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(108);
+      expect(fresh.getSchemaVersion()).toBe(109);
       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(108);
+      expect(migrated.getSchemaVersion()).toBe(109);
       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(108);
+      expect(fresh.getSchemaVersion()).toBe(109);
       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(108);
+      expect(migrated.getSchemaVersion()).toBe(109);
       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(108);
+      expect(migrated.getSchemaVersion()).toBe(109);
       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(108);
+      expect(fresh.getSchemaVersion()).toBe(109);
       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 333a68e551..03398b9515 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(108);
+    expect(db.getSchemaVersion()).toBe(109);
   });
 });
diff --git a/packages/core/src/__tests__/insight-store.test.ts b/packages/core/src/__tests__/insight-store.test.ts
index 7aa0e611ad..5d8ac9b47a 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(108);
+      expect(db1.getSchemaVersion()).toBe(109);
       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(108);
+      expect(db3.getSchemaVersion()).toBe(109);
 
       // 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(108);
+      expect(db1.getSchemaVersion()).toBe(109);
       db1.close();
 
       const db2 = createDatabase(testDir);
       expect(() => db2.init()).not.toThrow();
-      expect(db2.getSchemaVersion()).toBe(108);
+      expect(db2.getSchemaVersion()).toBe(109);
       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(108);
+      expect(db1.getSchemaVersion()).toBe(109);
 
       // 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 ef2a10d136..64dc82817b 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(108);
+    expect(db.getSchemaVersion()).toBe(109);
   });
 
   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 7410346c67..2ded53b090 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(108);
+      expect(db.getSchemaVersion()).toBe(109);
     });
 
     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 3be684ea9a..ca428b6914 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(108);
+      expect(db.getSchemaVersion()).toBe(109);
     });
   });
 });
diff --git a/packages/core/src/__tests__/store-merge-queue.test.ts b/packages/core/src/__tests__/store-merge-queue.test.ts
index 6c09641156..96a9ea905b 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(108);
+    expect(store.getDatabase().getSchemaVersion()).toBe(109);
   });
 
   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 7352ec08bf..63e5eebfad 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(108);
+    expect(db.getSchemaVersion()).toBe(109);
 
     const index = db
       .prepare(
diff --git a/packages/core/src/__tests__/workflow-settings.test.ts b/packages/core/src/__tests__/workflow-settings.test.ts
new file mode 100644
index 0000000000..6677b6806e
--- /dev/null
+++ b/packages/core/src/__tests__/workflow-settings.test.ts
@@ -0,0 +1,307 @@
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+
+import {
+  validateSettingValuePatch,
+  resolveEffectiveSettingValues,
+  findOrphanedSettingValues,
+  WorkflowSettingRejectionError,
+} from "../workflow-settings.js";
+import type { WorkflowSettingDefinition, WorkflowIrV2 } from "../workflow-ir-types.js";
+import { BUILTIN_WORKFLOW_SETTINGS } from "../builtin-workflow-settings.js";
+import { createTaskStoreTestHarness } from "./store-test-helpers.js";
+
+const BUILTIN_CODING = "builtin:coding";
+const PROJECT = "proj-1";
+
+/** A minimal valid v2 IR carrying `settings` declarations — enough to round-trip
+ *  through `parseWorkflowIr` / `createWorkflowDefinition`. */
+function makeIrWithSettings(settings: WorkflowSettingDefinition[]): WorkflowIrV2 {
+  return {
+    version: "v2",
+    name: "Custom WF",
+    columns: [],
+    nodes: [
+      { id: "start", kind: "start" },
+      { id: "end", kind: "end" },
+    ],
+    edges: [{ from: "start", to: "end" }],
+    settings,
+  };
+}
+
+const TIMEOUT_DECL: WorkflowSettingDefinition = {
+  id: "workflowStepTimeoutMs",
+  name: "Step timeout (ms)",
+  type: "number",
+  default: 360_000,
+};
+const FLAG_DECL: WorkflowSettingDefinition = {
+  id: "runStepsInNewSessions",
+  name: "Run steps in new sessions",
+  type: "boolean",
+  default: false,
+};
+const ENUM_DECL: WorkflowSettingDefinition = {
+  id: "reviewHandoffPolicy",
+  name: "Review handoff policy",
+  type: "enum",
+  default: "disabled",
+  options: [
+    { value: "disabled", label: "Disabled" },
+    { value: "always", label: "Always" },
+  ],
+};
+
+// ───────────────────────────────────────────────────────────────────────────
+// Validation core (side-effect-free)
+// ───────────────────────────────────────────────────────────────────────────
+
+describe("validateSettingValuePatch", () => {
+  const decls = [TIMEOUT_DECL, FLAG_DECL, ENUM_DECL];
+
+  it("accepts and normalizes valid values of each type", () => {
+    const res = validateSettingValuePatch(decls, {
+      workflowStepTimeoutMs: 1000,
+      runStepsInNewSessions: true,
+      reviewHandoffPolicy: "always",
+    });
+    expect(res.rejections).toEqual([]);
+    expect(res.accepted).toEqual({
+      workflowStepTimeoutMs: 1000,
+      runStepsInNewSessions: true,
+      reviewHandoffPolicy: "always",
+    });
+  });
+
+  it("accepts null as a delete sentinel (null-as-delete)", () => {
+    const res = validateSettingValuePatch(decls, { workflowStepTimeoutMs: null });
+    expect(res.rejections).toEqual([]);
+    expect(res.accepted).toEqual({ workflowStepTimeoutMs: null });
+  });
+
+  it("rejects an unknown setting", () => {
+    const res = validateSettingValuePatch(decls, { nope: 1 });
+    expect(res.accepted).toEqual({});
+    expect(res.rejections).toHaveLength(1);
+    expect(res.rejections[0]).toMatchObject({ code: "unknown-setting", settingId: "nope" });
+  });
+
+  it("rejects a type mismatch", () => {
+    const res = validateSettingValuePatch(decls, { workflowStepTimeoutMs: "fast" });
+    expect(res.accepted).toEqual({});
+    expect(res.rejections[0]).toMatchObject({ code: "type-mismatch", settingId: "workflowStepTimeoutMs" });
+  });
+
+  it("rejects an enum violation", () => {
+    const res = validateSettingValuePatch(decls, { reviewHandoffPolicy: "sometimes" });
+    expect(res.accepted).toEqual({});
+    expect(res.rejections[0]).toMatchObject({ code: "enum-violation", settingId: "reviewHandoffPolicy" });
+  });
+
+  it("reports no-settings-defined for a non-null write against empty declarations", () => {
+    const res = validateSettingValuePatch([], { workflowStepTimeoutMs: 1 });
+    expect(res.accepted).toEqual({});
+    expect(res.rejections[0]).toMatchObject({ code: "no-settings-defined" });
+  });
+
+  it("accepts a delete even against empty declarations (clears stale rows)", () => {
+    const res = validateSettingValuePatch([], { workflowStepTimeoutMs: null });
+    expect(res.rejections).toEqual([]);
+    expect(res.accepted).toEqual({ workflowStepTimeoutMs: null });
+  });
+
+  it("reports every offending key (not fail-fast)", () => {
+    const res = validateSettingValuePatch(decls, {
+      workflowStepTimeoutMs: "x",
+      reviewHandoffPolicy: "x",
+    });
+    expect(res.rejections).toHaveLength(2);
+  });
+});
+
+// ───────────────────────────────────────────────────────────────────────────
+// Effective resolution (drop-on-orphan, KTD-6)
+// ───────────────────────────────────────────────────────────────────────────
+
+describe("resolveEffectiveSettingValues", () => {
+  it("uses the stored value when it still validates", () => {
+    const eff = resolveEffectiveSettingValues([TIMEOUT_DECL], { workflowStepTimeoutMs: 1000 });
+    expect(eff).toEqual({ workflowStepTimeoutMs: 1000 });
+  });
+
+  it("falls to the declaration default when unset", () => {
+    const eff = resolveEffectiveSettingValues([TIMEOUT_DECL], {});
+    expect(eff).toEqual({ workflowStepTimeoutMs: 360_000 });
+  });
+
+  it("drops a stored value that no longer validates (enum→number retype) and uses the default", () => {
+    // Stored a string under what is now a number declaration.
+    const retyped: WorkflowSettingDefinition = { id: "x", name: "X", type: "number", default: 42 };
+    const eff = resolveEffectiveSettingValues([retyped], { x: "stale-string" });
+    expect(eff).toEqual({ x: 42 });
+  });
+
+  it("drops stored values for ids with no current declaration", () => {
+    const eff = resolveEffectiveSettingValues([TIMEOUT_DECL], { removedSetting: 7 });
+    expect(eff).toEqual({ workflowStepTimeoutMs: 360_000 });
+  });
+
+  it("omits a setting with neither a valid value nor a default", () => {
+    const noDefault: WorkflowSettingDefinition = { id: "y", name: "Y", type: "number" };
+    const eff = resolveEffectiveSettingValues([noDefault], {});
+    expect(eff).toEqual({});
+  });
+});
+
+describe("findOrphanedSettingValues", () => {
+  it("surfaces values dropped by resolution (id + raw value) for the editor disclosure", () => {
+    const retyped: WorkflowSettingDefinition = { id: "x", name: "X", type: "number", default: 42 };
+    const orphans = findOrphanedSettingValues([retyped], { x: "stale-string", removed: 9 });
+    expect(orphans).toEqual([
+      { id: "x", value: "stale-string" },
+      { id: "removed", value: 9 },
+    ]);
+  });
+
+  it("ignores null/undefined stored entries", () => {
+    const orphans = findOrphanedSettingValues([TIMEOUT_DECL], { workflowStepTimeoutMs: null });
+    expect(orphans).toEqual([]);
+  });
+});
+
+// ───────────────────────────────────────────────────────────────────────────
+// Store write authority (U2 scenarios)
+// ───────────────────────────────────────────────────────────────────────────
+
+describe("TaskStore.updateWorkflowSettingValues", () => {
+  const harness = createTaskStoreTestHarness();
+  beforeEach(harness.beforeEach);
+  afterEach(harness.afterEach);
+
+  async function createCustomWorkflow(settings: WorkflowSettingDefinition[]): Promise<string> {
+    const def = await harness.store().createWorkflowDefinition({
+      name: "Custom WF",
+      ir: makeIrWithSettings(settings),
+    });
+    return def.id;
+  }
+
+  it("persists a valid value for a custom workflow and reads it back typed", async () => {
+    const store = harness.store();
+    const wfId = await createCustomWorkflow([TIMEOUT_DECL, FLAG_DECL]);
+
+    await store.updateWorkflowSettingValues(wfId, PROJECT, {
+      workflowStepTimeoutMs: 5000,
+      runStepsInNewSessions: true,
+    });
+
+    const stored = store.getWorkflowSettingValues(wfId, PROJECT);
+    expect(stored).toEqual({ workflowStepTimeoutMs: 5000, runStepsInNewSessions: true });
+    expect(typeof stored.workflowStepTimeoutMs).toBe("number");
+    expect(typeof stored.runStepsInNewSessions).toBe("boolean");
+  });
+
+  it("accepts value writes for (builtin:coding, project) while builtin declaration edits stay rejected", async () => {
+    const store = harness.store();
+
+    // R4: value write for a built-in workflow succeeds.
+    await store.updateWorkflowSettingValues(BUILTIN_CODING, PROJECT, { requirePrApproval: true });
+    expect(store.getWorkflowSettingValues(BUILTIN_CODING, PROJECT)).toEqual({ requirePrApproval: true });
+
+    // Built-in DECLARATION edits remain rejected on the separate error path (KTD-2).
+    await expect(
+      store.updateWorkflowDefinition(BUILTIN_CODING, { ir: makeIrWithSettings([TIMEOUT_DECL]) }),
+    ).rejects.toThrow(/Built-in workflows cannot be edited/);
+  });
+
+  it("rejects type-mismatch / unknown-setting / enum-violation and persists nothing", async () => {
+    const store = harness.store();
+    const wfId = await createCustomWorkflow([TIMEOUT_DECL, ENUM_DECL]);
+
+    await expect(
+      store.updateWorkflowSettingValues(wfId, PROJECT, { workflowStepTimeoutMs: "fast" }),
+    ).rejects.toBeInstanceOf(WorkflowSettingRejectionError);
+    await expect(
+      store.updateWorkflowSettingValues(wfId, PROJECT, { unknownKey: 1 }),
+    ).rejects.toBeInstanceOf(WorkflowSettingRejectionError);
+    await expect(
+      store.updateWorkflowSettingValues(wfId, PROJECT, { reviewHandoffPolicy: "nope" }),
+    ).rejects.toBeInstanceOf(WorkflowSettingRejectionError);
+
+    // Nothing was persisted by any rejected write.
+    expect(store.getWorkflowSettingValues(wfId, PROJECT)).toEqual({});
+  });
+
+  it("treats null as delete and effective resolution falls to the declaration default", async () => {
+    const store = harness.store();
+    const wfId = await createCustomWorkflow([TIMEOUT_DECL]);
+
+    await store.updateWorkflowSettingValues(wfId, PROJECT, { workflowStepTimeoutMs: 5000 });
+    expect(store.getWorkflowSettingValues(wfId, PROJECT)).toEqual({ workflowStepTimeoutMs: 5000 });
+
+    await store.updateWorkflowSettingValues(wfId, PROJECT, { workflowStepTimeoutMs: null });
+    const stored = store.getWorkflowSettingValues(wfId, PROJECT);
+    expect(stored).toEqual({});
+
+    const def = await store.getWorkflowDefinition(wfId);
+    const decls = def!.ir.version === "v2" ? def!.ir.settings : undefined;
+    expect(resolveEffectiveSettingValues(decls, stored)).toEqual({ workflowStepTimeoutMs: 360_000 });
+  });
+
+  it("retype enum→number with a stale stored string: effective resolution drops it, returns default, stored row untouched", async () => {
+    const store = harness.store();
+    // Declare an enum setting and store a valid enum value.
+    const wfId = await createCustomWorkflow([ENUM_DECL]);
+    await store.updateWorkflowSettingValues(wfId, PROJECT, { reviewHandoffPolicy: "always" });
+    expect(store.getWorkflowSettingValues(wfId, PROJECT)).toEqual({ reviewHandoffPolicy: "always" });
+
+    // Retype the same id to a number (declaration edit via the IR save path).
+    const retyped: WorkflowSettingDefinition = {
+      id: "reviewHandoffPolicy",
+      name: "Review handoff policy",
+      type: "number",
+      default: 99,
+    };
+    await store.updateWorkflowDefinition(wfId, { ir: makeIrWithSettings([retyped]) });
+
+    // Stored row is UNTOUCHED — the stale string survives in storage.
+    const stored = store.getWorkflowSettingValues(wfId, PROJECT);
+    expect(stored).toEqual({ reviewHandoffPolicy: "always" });
+
+    // Effective resolution drops the stale string and returns the new default.
+    expect(resolveEffectiveSettingValues([retyped], stored)).toEqual({ reviewHandoffPolicy: 99 });
+  });
+
+  it("cascade-deletes value rows when the custom workflow is deleted", async () => {
+    const store = harness.store();
+    const wfId = await createCustomWorkflow([TIMEOUT_DECL]);
+    await store.updateWorkflowSettingValues(wfId, PROJECT, { workflowStepTimeoutMs: 5000 });
+    await store.updateWorkflowSettingValues(wfId, "proj-2", { workflowStepTimeoutMs: 7000 });
+
+    await store.deleteWorkflowDefinition(wfId);
+
+    expect(store.getWorkflowSettingValues(wfId, PROJECT)).toEqual({});
+    expect(store.getWorkflowSettingValues(wfId, "proj-2")).toEqual({});
+  });
+
+  it("a task pinned to a deleted workflow resolves built-in values", async () => {
+    const store = harness.store();
+    // Built-in values for the project (these survive a custom-workflow delete).
+    await store.updateWorkflowSettingValues(BUILTIN_CODING, PROJECT, { requirePrApproval: true });
+
+    const wfId = await createCustomWorkflow([TIMEOUT_DECL]);
+    await store.updateWorkflowSettingValues(wfId, PROJECT, { workflowStepTimeoutMs: 5000 });
+    await store.deleteWorkflowDefinition(wfId);
+
+    // The deleted workflow's rows are gone; a task pinned to it degrades to
+    // builtin:coding (resolver) and reads built-in declarations + built-in values.
+    expect(store.getWorkflowSettingValues(wfId, PROJECT)).toEqual({});
+    const effective = resolveEffectiveSettingValues(
+      BUILTIN_WORKFLOW_SETTINGS,
+      store.getWorkflowSettingValues(BUILTIN_CODING, PROJECT),
+    );
+    expect(effective.requirePrApproval).toBe(true);
+    // Untouched built-in keys resolve to their declaration defaults.
+    expect(effective.workflowStepTimeoutMs).toBe(360_000);
+  });
+});
diff --git a/packages/core/src/db.ts b/packages/core/src/db.ts
index 6403a186f1..8caf5b9118 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 = 108;
+const SCHEMA_VERSION = 109;
 
 export { SCHEMA_VERSION };
 
@@ -616,6 +616,16 @@ CREATE TABLE IF NOT EXISTS workflow_run_step_instances (
 );
 CREATE INDEX IF NOT EXISTS idx_workflow_run_step_instances_task_run ON workflow_run_step_instances(taskId, runId);
 
+-- Workflow setting values per (workflowId, projectId). JSON values map; validated
+-- against the named workflow's declared settings by the store write authority.
+CREATE TABLE IF NOT EXISTS workflow_settings (
+  workflowId TEXT NOT NULL,
+  projectId TEXT NOT NULL,
+  "values" TEXT DEFAULT '{}',
+  updatedAt TEXT NOT NULL,
+  PRIMARY KEY (workflowId, projectId)
+);
+
 -- Task documents (key-value store per task with revision tracking)
 CREATE TABLE IF NOT EXISTS task_documents (
   id TEXT PRIMARY KEY,
@@ -4291,6 +4301,26 @@ export class Database {
       });
     }
 
+    // Migration 109: Workflow setting values (workflow-settings U2, KTD-2).
+    // Adds workflow_settings — one row per (workflowId, projectId) carrying a JSON
+    // map of setting values declared by the workflow's IR. Values are validated by
+    // the store write authority against the named workflow's declarations; built-in
+    // workflow ids are accepted for value writes even though their declarations are
+    // non-editable. Additive-only, idempotent (table-exists guard); no backfill.
+    if (version < 109) {
+      this.applyMigration(109, () => {
+        this.db.exec(`
+          CREATE TABLE IF NOT EXISTS workflow_settings (
+            workflowId TEXT NOT NULL,
+            projectId TEXT NOT NULL,
+            "values" TEXT DEFAULT '{}',
+            updatedAt TEXT NOT NULL,
+            PRIMARY KEY (workflowId, projectId)
+          );
+        `);
+      });
+    }
+
   }
 
   /**
@@ -4367,7 +4397,8 @@ export class Database {
    */
   private addColumnIfMissing(table: string, column: string, definition: string): void {
     if (!this.hasColumn(table, column)) {
-      this.db.exec(`ALTER TABLE ${table} ADD COLUMN ${column} ${definition}`);
+      // Quote the column identifier so reserved words (e.g. `values`) are legal.
+      this.db.exec(`ALTER TABLE ${table} ADD COLUMN "${column}" ${definition}`);
     }
   }
 
@@ -4385,7 +4416,8 @@ export class Database {
       return;
     }
 
-    this.db.exec(`ALTER TABLE ${table} ADD COLUMN ${column} ${definition}`);
+    // Quote the column identifier so reserved words (e.g. `values`) are legal.
+    this.db.exec(`ALTER TABLE ${table} ADD COLUMN "${column}" ${definition}`);
     columns.add(column);
     if (cache) {
       cache.set(table, columns);
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 4d99fe1da2..4b371c3d57 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -218,6 +218,20 @@ export type {
   CustomFieldPatchResult,
   FieldReconciliation,
 } from "./task-fields.js";
+export {
+  validateSettingValuePatch,
+  resolveEffectiveSettingValues,
+  findOrphanedSettingValues,
+  makeWorkflowSettingRejection,
+  WorkflowSettingRejectionError,
+  WORKFLOW_SETTING_REJECTION_CODES,
+} from "./workflow-settings.js";
+export type {
+  WorkflowSettingRejection,
+  WorkflowSettingRejectionCode,
+  SettingValuePatchResult,
+  OrphanedSettingValue,
+} from "./workflow-settings.js";
 export {
   readTransitionPending,
   writeTransitionPending,
diff --git a/packages/core/src/store.ts b/packages/core/src/store.ts
index 352b281004..330c84c8e3 100644
--- a/packages/core/src/store.ts
+++ b/packages/core/src/store.ts
@@ -45,7 +45,7 @@ import {
   reconcileHooksRemaining,
 } from "./transition-pending.js";
 import { BUILTIN_CODING_WORKFLOW_IR } from "./builtin-coding-workflow-ir.js";
-import type { WorkflowIr, WorkflowIrColumn, WorkflowFieldDefinition } from "./workflow-ir-types.js";
+import type { WorkflowIr, WorkflowIrColumn, WorkflowFieldDefinition, WorkflowSettingDefinition } from "./workflow-ir-types.js";
 import {
   validateCustomFieldPatch,
   applyFieldDefaults,
@@ -53,6 +53,12 @@ import {
   CustomFieldRejectionError,
   type CustomFieldRejection,
 } from "./task-fields.js";
+import {
+  validateSettingValuePatch,
+  resolveEffectiveSettingValues,
+  WorkflowSettingRejectionError,
+  type WorkflowSettingRejection,
+} from "./workflow-settings.js";
 // Side-effect import: registers the 14 built-in trait DEFINITIONS into the
 // shared trait registry on load (the flag-ON path resolves traits by id).
 import "./builtin-traits.js";
@@ -68,6 +74,8 @@ import type {
 } from "./workflow-definition-types.js";
 import { compileWorkflowToSteps } from "./workflow-compiler.js";
 import { BUILTIN_WORKFLOWS, getBuiltinWorkflow, isBuiltinWorkflowId } from "./builtin-workflows.js";
+import { resolveWorkflowIrById } from "./workflow-ir-resolver.js";
+import { BUILTIN_WORKFLOW_SETTINGS } from "./builtin-workflow-settings.js";
 import {
   WORKFLOW_PARITY_OBSERVED_MUTATION,
   WORKFLOW_PARITY_DRIFT_MUTATION,
@@ -6964,6 +6972,98 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     });
   }
 
+  // ── Workflow setting values (U2, R2/R4, KTD-2/KTD-9) ───────────────────────
+  //
+  // Setting VALUES persist per `(workflowId, projectId)` in the `workflow_settings`
+  // table; declarations live in the named workflow's IR (built-in or custom). This
+  // is the single validating write authority: values are validated against the
+  // NAMED workflow's declarations (not the project's current default workflow), and
+  // invalid values are NEVER persisted. Built-in workflow ids are accepted for
+  // value writes even though built-in DECLARATIONS are non-editable
+  // (`updateWorkflowDefinition` still rejects built-in edits) — the two error paths
+  // stay distinct (KTD-2).
+
+  /** Resolve the setting DECLARATIONS for a workflow id (built-in or custom). The
+   *  built-in path mirrors the IR resolver (`resolveWorkflowIrById`): built-in ids
+   *  resolve through the same code path so value writes target the same schema the
+   *  engine resolver sees. For built-in ids whose resolved IR does not yet carry
+   *  `settings` (the linear `BUILTIN_WORKFLOWS` graphs predate the settings
+   *  declarations), fall back to the canonical built-in declaration catalog
+   *  (`BUILTIN_WORKFLOW_SETTINGS`) so built-in VALUE writes succeed (R4/KTD-2).
+   *  Returns `undefined` when the workflow is missing or declares no settings. */
+  private async resolveWorkflowSettingDeclarations(
+    workflowId: string,
+  ): Promise<WorkflowSettingDefinition[] | undefined> {
+    const ir = await resolveWorkflowIrById(this, workflowId);
+    const declared = ir.version === "v2" ? ir.settings : undefined;
+    if (declared && declared.length > 0) return declared;
+    // Built-in workflows declare the full moved-key catalog (the migration parity
+    // anchor); their selectable graphs may not embed it yet.
+    if (isBuiltinWorkflowId(workflowId)) return BUILTIN_WORKFLOW_SETTINGS;
+    return declared;
+  }
+
+  /** Read the raw stored setting-value map for `(workflowId, projectId)`. Returns
+   *  an empty object when no row exists. Raw (pre drop-on-orphan) — callers that
+   *  need engine-effective values run {@link resolveEffectiveSettingValues}. */
+  getWorkflowSettingValues(workflowId: string, projectId: string): Record<string, unknown> {
+    const row = this.db
+      .prepare('SELECT "values" FROM workflow_settings WHERE workflowId = ? AND projectId = ?')
+      .get(workflowId, projectId) as { values: string } | undefined;
+    if (!row) return {};
+    try {
+      const parsed = JSON.parse(row.values) as unknown;
+      return parsed && typeof parsed === "object" && !Array.isArray(parsed)
+        ? (parsed as Record<string, unknown>)
+        : {};
+    } catch {
+      return {};
+    }
+  }
+
+  /**
+   * Write setting VALUES for `(workflowId, projectId)`. The patch is validated
+   * against the NAMED workflow's declarations via {@link validateSettingValuePatch};
+   * on ANY rejection nothing is persisted (write-boundary contract) and a typed
+   * {@link WorkflowSettingRejectionError} is thrown. Accepted keys merge into the
+   * stored row; a `null` value deletes the key (null-as-delete). Built-in workflow
+   * value writes succeed (R4).
+   */
+  async updateWorkflowSettingValues(
+    workflowId: string,
+    projectId: string,
+    patch: Record<string, unknown>,
+  ): Promise<Record<string, unknown>> {
+    const declarations = await this.resolveWorkflowSettingDeclarations(workflowId);
+    const result = validateSettingValuePatch(declarations, patch);
+    if (result.rejections.length > 0) {
+      // Invalid values are NEVER persisted — fail the whole write loudly.
+      throw new WorkflowSettingRejectionError(result.rejections);
+    }
+
+    const current = this.getWorkflowSettingValues(workflowId, projectId);
+    const next: Record<string, unknown> = { ...current };
+    for (const [key, value] of Object.entries(result.accepted)) {
+      if (value === null) {
+        delete next[key];
+      } else {
+        next[key] = value;
+      }
+    }
+
+    const now = new Date().toISOString();
+    this.db
+      .prepare(
+        `INSERT INTO workflow_settings (workflowId, projectId, "values", updatedAt)
+         VALUES (?, ?, ?, ?)
+         ON CONFLICT(workflowId, projectId)
+         DO UPDATE SET "values" = excluded."values", updatedAt = excluded.updatedAt`,
+      )
+      .run(workflowId, projectId, JSON.stringify(next), now);
+    this.db.bumpLastModified();
+    return next;
+  }
+
   /**
    * The body of {@link updateTask} WITHOUT acquiring the per-task lock. Callers
    * that already hold `withTaskLock(id)` — e.g. workflow-selection mutations
@@ -12498,6 +12598,12 @@ ${stepsSection}`;
     }
     this.workflowDefinitionsCache = null;
 
+    // Cascade (KTD-9): delete this workflow's setting-value rows across all
+    // projects. Tasks pinned to the deleted workflow degrade to `builtin:coding`
+    // via the resolver and read built-in declarations + built-in values, so no
+    // unreachable orphan value rows remain.
+    this.db.prepare("DELETE FROM workflow_settings WHERE workflowId = ?").run(id);
+
     // Cascade: clear the project default when it pointed at this workflow.
     try {
       if ((await this.getDefaultWorkflowId()) === id) {
diff --git a/packages/core/src/workflow-settings.ts b/packages/core/src/workflow-settings.ts
new file mode 100644
index 0000000000..e1d47e89c5
--- /dev/null
+++ b/packages/core/src/workflow-settings.ts
@@ -0,0 +1,339 @@
+/**
+ * Workflow setting-value validation & effective-resolution authority (U2, R2/R4).
+ *
+ * Workflows declare typed settings ({@link WorkflowSettingDefinition}); setting
+ * *values* live per `(workflowId, projectId)` in the `workflow_settings` table (a
+ * JSON object keyed by setting id). This module is the single, side-effect-free
+ * validation core that the store write authority
+ * (`updateWorkflowSettingValues`) delegates to. It mirrors `task-fields.ts`: a
+ * flat, JSON-safe typed rejection with a machine-stable `code`, the offending
+ * `settingId`, and a non-localized `detail` string for audit/logs.
+ *
+ * Two operations:
+ *  - {@link validateSettingValuePatch} — validate a `Record<string, unknown>`
+ *    patch against a setting schema, normalizing accepted values. `null`/`undefined`
+ *    in the patch is a delete sentinel for that setting (always accepted).
+ *  - {@link resolveEffectiveSettingValues} — compose stored values + declaration
+ *    defaults into the effective value map, implementing DROP-ON-ORPHAN (KTD-6).
+ *
+ * KTD-6 — DELIBERATE DIVERGENCE FROM `task-fields.ts`. The custom-field reconciler
+ * (`reconcileFieldsOnWorkflowChange`) RETAINS orphaned values and surfaces them in
+ * a UI disclosure — safe for display data. Workflow settings are POLICY the engine
+ * consumes (a retyped enum→number setting with a stale string value would feed
+ * garbage into execution), so effective resolution DROPS any stored value that no
+ * longer validates against the current declaration and falls to the declaration
+ * `default`. The dropped raw values never reach the engine; the editor surfaces
+ * them via {@link findOrphanedSettingValues} for the U6 disclosure.
+ */
+
+import type {
+  WorkflowSettingDefinition,
+} from "./workflow-ir-types.js";
+
+// ---------------------------------------------------------------------------
+// Typed rejection (TransitionRejection-style: flat, JSON-safe, no class)
+// ---------------------------------------------------------------------------
+
+/**
+ * Reason codes for a rejected setting-value write. Stable string literals — they
+ * cross the agent-tool / HTTP boundary and are matched by surfaces for copy, so
+ * they must not change without migrating consumers. Mirrors
+ * {@link import("./task-fields.js").CustomFieldRejectionCode}.
+ */
+export type WorkflowSettingRejectionCode =
+  | "no-settings-defined"
+  | "unknown-setting"
+  | "type-mismatch"
+  | "enum-violation";
+
+/** The full, immutable set of setting-value rejection codes. */
+export const WORKFLOW_SETTING_REJECTION_CODES: readonly WorkflowSettingRejectionCode[] = [
+  "no-settings-defined",
+  "unknown-setting",
+  "type-mismatch",
+  "enum-violation",
+] as const;
+
+/**
+ * A typed setting-value rejection. Flat and JSON-safe by construction — mirrors
+ * {@link import("./task-fields.js").CustomFieldRejection}.
+ *
+ * - `code` — machine-stable {@link WorkflowSettingRejectionCode}.
+ * - `settingId` — the offending setting id (the patch key that failed).
+ * - `message` — non-localized diagnostic context for audit/logs.
+ */
+export interface WorkflowSettingRejection {
+  code: WorkflowSettingRejectionCode;
+  settingId: string;
+  message: string;
+}
+
+/** Result of validating a setting-value patch. */
+export interface SettingValuePatchResult {
+  /** The accepted, normalized values (a `null` entry is a delete sentinel). */
+  accepted: Record<string, unknown>;
+  /** The rejected keys with their typed reasons. */
+  rejections: WorkflowSettingRejection[];
+}
+
+/** Construct a {@link WorkflowSettingRejection}. */
+export function makeWorkflowSettingRejection(
+  code: WorkflowSettingRejectionCode,
+  settingId: string,
+  message: string,
+): WorkflowSettingRejection {
+  return { code, settingId, message };
+}
+
+/**
+ * Thrown by the throw-based store write path when a setting-value write rejects.
+ * Mirrors {@link import("./task-fields.js").CustomFieldRejectionError}: carries
+ * the structured rejection(s) so HTTP/agent surfaces can recover the setting path
+ * and code.
+ */
+export class WorkflowSettingRejectionError extends Error {
+  readonly rejections: WorkflowSettingRejection[];
+  constructor(rejections: WorkflowSettingRejection[]) {
+    const first = rejections[0];
+    super(
+      first
+        ? `workflow setting '${first.settingId}' rejected (${first.code}): ${first.message}`
+        : "workflow setting value write rejected",
+    );
+    this.name = "WorkflowSettingRejectionError";
+    this.rejections = rejections;
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Per-type value validation
+// ---------------------------------------------------------------------------
+
+/** True iff `value` is an option-value member of `setting.options`. */
+function isEnumMember(setting: WorkflowSettingDefinition, value: string): boolean {
+  return (setting.options ?? []).some((o) => o.value === value);
+}
+
+/**
+ * Validate (and normalize) a single non-null value against a setting's type.
+ * Returns the normalized value on success, or a rejection. The caller has already
+ * resolved the setting definition.
+ */
+function validateValue(
+  setting: WorkflowSettingDefinition,
+  value: unknown,
+): { ok: true; value: unknown } | { ok: false; rejection: WorkflowSettingRejection } {
+  const reject = (
+    code: WorkflowSettingRejectionCode,
+    message: string,
+  ): { ok: false; rejection: WorkflowSettingRejection } => ({
+    ok: false,
+    rejection: makeWorkflowSettingRejection(code, setting.id, message),
+  });
+
+  switch (setting.type) {
+    case "string":
+    case "text": {
+      if (typeof value !== "string") {
+        return reject("type-mismatch", `setting '${setting.id}' expects a string, got ${typeof value}`);
+      }
+      return { ok: true, value };
+    }
+    case "number": {
+      if (typeof value !== "number" || !Number.isFinite(value)) {
+        return reject(
+          "type-mismatch",
+          `setting '${setting.id}' expects a finite number, got ${typeof value === "number" ? String(value) : typeof value}`,
+        );
+      }
+      return { ok: true, value };
+    }
+    case "boolean": {
+      if (typeof value !== "boolean") {
+        return reject("type-mismatch", `setting '${setting.id}' expects a boolean, got ${typeof value}`);
+      }
+      return { ok: true, value };
+    }
+    case "enum": {
+      if (typeof value !== "string") {
+        return reject("type-mismatch", `setting '${setting.id}' (enum) expects a string option value, got ${typeof value}`);
+      }
+      if (!isEnumMember(setting, value)) {
+        return reject("enum-violation", `setting '${setting.id}' value '${value}' is not a declared option`);
+      }
+      return { ok: true, value };
+    }
+    case "multi-enum": {
+      if (!Array.isArray(value)) {
+        return reject("type-mismatch", `setting '${setting.id}' (multi-enum) expects an array, got ${typeof value}`);
+      }
+      const seen = new Set<string>();
+      for (const item of value) {
+        if (typeof item !== "string") {
+          return reject("type-mismatch", `setting '${setting.id}' (multi-enum) members must be strings`);
+        }
+        if (!isEnumMember(setting, item)) {
+          return reject("enum-violation", `setting '${setting.id}' member '${item}' is not a declared option`);
+        }
+        if (seen.has(item)) {
+          return reject("enum-violation", `setting '${setting.id}' has duplicate member '${item}'`);
+        }
+        seen.add(item);
+      }
+      return { ok: true, value: [...value] as string[] };
+    }
+    default: {
+      // Exhaustiveness guard — an unknown type cannot validate.
+      const _exhaustive: never = setting.type;
+      return reject("type-mismatch", `setting '${setting.id}' has unsupported type '${String(_exhaustive)}'`);
+    }
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Patch validation authority
+// ---------------------------------------------------------------------------
+
+/**
+ * Validate a setting-value `patch` against a workflow's `declarations`.
+ *
+ * - A `null`/`undefined` patch value is a DELETE sentinel: the setting's stored
+ *   value should be removed. It is ALWAYS accepted (null-as-delete) and surfaces
+ *   in `accepted` as `null` so the caller can apply the delete uniformly.
+ * - A non-null value is validated/normalized per the setting's type.
+ * - A patch key that names no declared setting → `unknown-setting`.
+ * - When `declarations` is undefined/empty and the patch carries any non-null key →
+ *   that key is rejected `no-settings-defined`. (A delete against no declarations is
+ *   harmless and accepted so stale rows can always be cleared.)
+ *
+ * Unlike the custom-field authority this is NOT fail-fast: every offending key is
+ * reported so the editor can render per-field errors while applying the rest.
+ */
+export function validateSettingValuePatch(
+  declarations: WorkflowSettingDefinition[] | undefined,
+  patch: Record<string, unknown>,
+): SettingValuePatchResult {
+  const byId = new Map<string, WorkflowSettingDefinition>((declarations ?? []).map((d) => [d.id, d]));
+  const accepted: Record<string, unknown> = {};
+  const rejections: WorkflowSettingRejection[] = [];
+
+  for (const key of Object.keys(patch)) {
+    const value = patch[key];
+    // null/undefined = delete this setting's value. Always accepted, even when the
+    // declaration is gone (lets the editor clear orphaned rows).
+    if (value === null || value === undefined) {
+      accepted[key] = null;
+      continue;
+    }
+    const setting = byId.get(key);
+    if (byId.size === 0) {
+      rejections.push(
+        makeWorkflowSettingRejection(
+          "no-settings-defined",
+          key,
+          "the named workflow declares no settings; no values may be written",
+        ),
+      );
+      continue;
+    }
+    if (!setting) {
+      rejections.push(
+        makeWorkflowSettingRejection(
+          "unknown-setting",
+          key,
+          `setting '${key}' is not declared by the named workflow`,
+        ),
+      );
+      continue;
+    }
+    const res = validateValue(setting, value);
+    if (!res.ok) {
+      rejections.push(res.rejection);
+      continue;
+    }
+    accepted[key] = res.value;
+  }
+
+  return { accepted, rejections };
+}
+
+// ---------------------------------------------------------------------------
+// Effective resolution (drop-on-orphan, KTD-6)
+// ---------------------------------------------------------------------------
+
+/** A stored value re-validates cleanly against the current declaration. */
+function valueStillValid(setting: WorkflowSettingDefinition, value: unknown): boolean {
+  if (value === null || value === undefined) return false;
+  return validateValue(setting, value).ok;
+}
+
+/** An orphaned stored entry: a value that no longer validates against the current
+ *  declaration (type change, enum option removed, declaration deleted). Surfaced to
+ *  the U6 editor disclosure; never fed to the engine. */
+export interface OrphanedSettingValue {
+  id: string;
+  value: unknown;
+}
+
+/**
+ * Resolve the EFFECTIVE setting values for a workflow from its `declarations` and
+ * the raw `stored` map, implementing DROP-ON-ORPHAN (KTD-6).
+ *
+ * For each declared setting:
+ *  - if a stored value exists AND re-validates against the current declaration →
+ *    use the stored value;
+ *  - otherwise (no stored value, OR a stored value that no longer validates —
+ *    type change, enum option removed) → DROP it and use the declaration `default`
+ *    when one is present; absent declarations contribute nothing.
+ *
+ * Stored values for ids with NO current declaration (declaration deleted) are
+ * dropped entirely — they cannot reach the effective map. The raw `stored` row is
+ * never mutated here; this is a pure read. Use {@link findOrphanedSettingValues}
+ * to surface the dropped entries in the editor.
+ */
+export function resolveEffectiveSettingValues(
+  declarations: WorkflowSettingDefinition[] | undefined,
+  stored: Record<string, unknown> | undefined,
+): Record<string, unknown> {
+  const storedMap = stored ?? {};
+  const effective: Record<string, unknown> = {};
+
+  for (const setting of declarations ?? []) {
+    const has = Object.prototype.hasOwnProperty.call(storedMap, setting.id);
+    const raw = has ? storedMap[setting.id] : undefined;
+    if (has && valueStillValid(setting, raw)) {
+      effective[setting.id] = raw;
+      continue;
+    }
+    // Drop-on-orphan / unset → declaration default (when present).
+    if (setting.default !== undefined) {
+      effective[setting.id] = setting.default;
+    }
+  }
+
+  return effective;
+}
+
+/**
+ * Compute the orphaned stored entries for the U6 editor disclosure: stored ids
+ * that either have no current declaration, or whose stored value no longer
+ * validates against the current declaration. These are exactly the entries
+ * {@link resolveEffectiveSettingValues} drops. The raw row is untouched.
+ */
+export function findOrphanedSettingValues(
+  declarations: WorkflowSettingDefinition[] | undefined,
+  stored: Record<string, unknown> | undefined,
+): OrphanedSettingValue[] {
+  const byId = new Map<string, WorkflowSettingDefinition>((declarations ?? []).map((d) => [d.id, d]));
+  const orphaned: OrphanedSettingValue[] = [];
+
+  for (const [id, value] of Object.entries(stored ?? {})) {
+    if (value === null || value === undefined) continue;
+    const setting = byId.get(id);
+    if (!setting || !valueStillValid(setting, value)) {
+      orphaned.push({ id, value });
+    }
+  }
+
+  return orphaned;
+}