Implement progressive query admission, session boundaries and event-driven Studio observations

src/capability-language/assembly.ts

@@ -3,6 +3,7 @@ import path from "node:path";
 import { profile } from "./profile.js";
 import { loadQxSources, resolveQxSources } from "./source-loader.js";
 import { compileQuery, compileRepositoryQuery } from "../query/compile.js";
+import { queryTreeProjections } from "../query/tree.js";
 import type { QueryDeclaration } from "../query/types.js";
 import { compileQueryComposition, type QueryComposition } from "../query/composition.js";
 import { checkQueryTemplate } from "../query/templates.js";
@@ -390,6 +391,13 @@ const createResourceGraphResolver = (
             };
             pkg.checkedQueries = [];
             for (const query of pkg.queries!) pkg.checkedQueries.push(await compile(query.id));
+            const projections = pkg.checkedQueries.flatMap(queryTreeProjections);
+            for (const projection of projections) {
+              if (pkg.queries!.some((query) => query.id === projection.declaration.id))
+                throw new Error(`Generated Query Tree projection conflicts with ${projection.declaration.id}`);
+              pkg.queries!.push(projection.declaration);
+              pkg.checkedQueries.push(projection);
+            }
           }
           if (generated?.compositions?.length) {
             const pkg = compiled.resource.revision;

src/capability-language/workspace-cli.ts

@@ -118,7 +118,9 @@ const main = async () => {
   if (options.executionPlanOut || options.buildContextsOut) {
     const executionStarted = performance.now();
     const plan = compileExecutionPlan(assembled.workspace);
-    if (options.executionPlanOut) await writeFile(options.executionPlanOut, `${JSON.stringify(plan, null, 2)}\n`);
+    // Machine-consumed immutable metadata should not spend its bounded input
+    // reservation on indentation. Its parsed allocation is charged separately.
+    if (options.executionPlanOut) await writeFile(options.executionPlanOut, `${JSON.stringify(plan)}\n`);
     if (options.buildContextsOut)
       await writeFile(options.buildContextsOut, JSON.stringify(packageBuildContexts(plan.definition.bindingSchema)));
     profile("execution-plan-and-contexts", executionStarted);

src/execution-world/candidate.ts

@@ -15,7 +15,10 @@ import {
 } from "./metadata.js";
 const rootPattern = /^\/nix\/store\/[a-z0-9]{32}-[^/\s]+$/;
 async function readJson(root: string, file: string, scope: CandidateMetadataScope) {
-  const input = await readCandidateMetadata(join(root, file), scope, 32 * 1024 * 1024);
+  // Query Trees add checked projections to an already large application plan.
+  // The Reader now exceeds 32 MiB even without indentation. This file bound
+  // does not replace the stricter aggregate/owner parse-allocation budgets.
+  const input = await readCandidateMetadata(join(root, file), scope, 64 * 1024 * 1024);
   try {
     return {
       value: JSON.parse(new TextDecoder("utf-8", { fatal: true }).decode(input.bytes)),

src/execution-world/client-contracts.ts

@@ -11,6 +11,7 @@ import type { BindingSchema } from "../bindings/index.js";
 import type { PackageBuildContract } from "./build-contract.js";
 import { preparationArtifact, type ReactPreparationArtifact } from "../react-build/declarations.js";
 import { moduleTypeContext } from "./module-contracts.js";
+import { queryTreeBlueprint, queryTreeType } from "./query-trees.js";
 
 /** Public shape only: no slot inventory, implementation binding, or workspace identity. */
 export interface PublicOperationContract {
@@ -76,6 +77,7 @@ export interface PublicQueryContract {
   sourceQuery?: string;
   input: unknown;
   output: unknown;
+  tree?: ReturnType<typeof queryTreeBlueprint>;
 }
 export function publicQueryContract(pkg: PackageRevision, queryId: string): PublicQueryContract {
   const query = pkg.checkedQueries?.find((q) => q.declaration.id === queryId);
@@ -88,9 +90,10 @@ export function publicQueryContract(pkg: PackageRevision, queryId: string): Publ
     definitionDigest: query.definitionDigest,
     root: query.declaration.root,
     placement: placement?.kind ?? "server",
-    ...(placement?.kind === "local" ? { sourceQuery: placement.sourceQueryId } : {}),
+    ...(placement?.kind === "local" ? { sourceQuery: query.treeProjection?.tree ?? placement.sourceQueryId } : {}),
     input: portableValueSchema(query.variables),
     output: portableValueSchema(query.output),
+    ...(query.tree ? { tree: queryTreeBlueprint(pkg.revisionId, query) } : {}),
   };
 }
 export function linkPackageQuery(plan: ExecutionPlan, contract: PublicQueryContract) {
@@ -156,10 +159,10 @@ export function generatePackageQueryClientBindings(
     checkedQueries: pkg.checkedQueries?.filter((query) => !internal.includes(query.declaration.id)),
   };
   const queries = (pkg.checkedQueries ?? [])
-    .filter((query) => !query.declaration.fragment)
+    .filter((query) => !query.declaration.fragment && !query.treeProjection)
     .map(
       (query) =>
-        `${JSON.stringify(query.declaration.displayName)}: definePackageQuery<${tsType(query.variables)}, ${tsType(query.output)}, ${JSON.stringify(publicQueryContract(pkg, query.declaration.id).placement)}>(${JSON.stringify(publicQueryContract(pkg, query.declaration.id))})`,
+        `${JSON.stringify(query.declaration.displayName)}: ${query.tree ? `definePackageQueryTree<${tsType(query.variables)}, ${queryTreeType(query)}, ${JSON.stringify(query.declaration.root.interface)}>` : `definePackageQuery<${tsType(query.variables)}, ${tsType(query.output)}, ${JSON.stringify(publicQueryContract(pkg, query.declaration.id).placement)}>`}(${JSON.stringify(publicQueryContract(pkg, query.declaration.id))})`,
     );
   const emitFragment = (provider: PackageRevision, id: string) => {
     const query = provider.checkedQueries?.find((query) => query.declaration.id === id);
@@ -210,7 +213,7 @@ export function generatePackageQueryClientBindings(
     fragments.push(
       `${JSON.stringify(alias)}: {${[...entries].map(([name, value]) => `${JSON.stringify(name)}: ${value}`).join(",")}}`,
     );
-  return `// Generated from checked package query contracts. Regenerate; do not edit.\nimport { definePackageQuery, definePackageFragment, type ManagedReference } from ${JSON.stringify(runtimeModule)};\nexport const queries = {${queries.join(",\n")}} as const;\nexport const fragments = {${fragments.join(",\n")}} as const;\n`;
+  return `// Generated from checked package query contracts. Regenerate; do not edit.\nimport { definePackageQuery, definePackageFragment, ${queries.some((query) => query.includes("definePackageQueryTree<")) ? "definePackageQueryTree, type QueryTreeShape, type QueryTreeOccurrence, " : ""}type ManagedReference } from ${JSON.stringify(runtimeModule)};\nexport const queries = {${queries.join(",\n")}} as const;\nexport const fragments = {${fragments.join(",\n")}} as const;\n`;
 }
 
 /** Receipt-covered bindings expose the package's imports, component subjects and
@@ -279,7 +282,7 @@ export function generatePackageComponentBindings(
     .join("\n");
   return (
     interfaces +
-    '\nimport {createObjectRenderer,definePackageQuery,definePackageFragment,type ComponentType,type ComponentProps,type PresentationHandle} from "@quixos/camino-react";\n' +
+    '\nimport {createObjectRenderer,definePackageQuery,definePackageFragment,definePackageQueryTree,type QueryTreeShape,type QueryTreeOccurrence,type QueryTreeHandle,type ComponentType,type ComponentProps,type PresentationHandle} from "@quixos/camino-react";\n' +
     subjectBindings +
     "\n" +
     queries +
@@ -319,7 +322,13 @@ export function generatePackageComponentBindings(
           const handle = `PresentationHandle<${JSON.stringify(child.subject)}, ${extra}>`;
           return `readonly ${JSON.stringify(child.name)}: ${child.each ? `readonly ${handle}[]` : child.with || child.when ? `${handle} | null` : handle}`;
         });
-        const input = `${tsType(preparation.input ?? composition.output)} & {readonly children: {${children.join(";")}}}`;
+        const trees = (preparation.trees ?? []).map((tree) => {
+          const query = pkg.checkedQueries?.find((query) => query.declaration.id === tree.query);
+          if (!query?.tree)
+            throw new ExecutionPlanError("MISSING_QUERY_TREE", tree.query, "Expected a checked Query Tree");
+          return `readonly ${JSON.stringify(tree.name)}: QueryTreeHandle<${queryTreeType(query)}>`;
+        });
+        const input = `${tsType(preparation.input ?? composition.output)} & {readonly children: {${children.join(";")}}${trees.length ? `;readonly trees:{${trees.join(";")}}` : ""}}`;
         return `${JSON.stringify(component.displayName)}: ComponentType<ComponentProps<${JSON.stringify(component.subject)}, ${JSON.stringify(module.contract)}, ${moduleArguments(find(module.interfaceRevisionId))}, ${input}> & ExtraModuleProps<${JSON.stringify(key)}>>;`;
       })
       .join("\n") +

src/execution-world/metadata.ts

@@ -10,10 +10,10 @@ export class CandidateMetadataBudget {
   private scopes = 0;
   private readonly owners = new Map<string, number>();
   // A cutover holds both the serving and proposed installation plus transient
-  // parsing space. The 57-repository reader retains ~133 MiB per installation;
-  // a 256 MiB owner ceiling cannot admit its ordinary atomic replacement.
+  // parsing space. The Reader with checked Query Trees retains ~176 MiB per
+  // installation; its replacement also needs transient parse/index space.
   // Keep the aggregate ceiling independent and leave room for parsing overlap.
-  constructor(limits = { bytes: 512 * 1024 * 1024, ownerBytes: 384 * 1024 * 1024, candidates: 128 }) {
+  constructor(limits = { bytes: 768 * 1024 * 1024, ownerBytes: 512 * 1024 * 1024, candidates: 128 }) {
     for (const value of Object.values(limits))
       if (!Number.isSafeInteger(value) || value < 1) throw Error("INVALID_CANDIDATE_METADATA_BUDGET");
     if (limits.ownerBytes > limits.bytes) throw Error("INVALID_CANDIDATE_METADATA_BUDGET");

src/execution-world/queries.ts

@@ -4,6 +4,7 @@ import { portableValueSchema } from "../bindings/portable.js";
 import { ExecutionPlanError, hexDigest, type ExecutionPlan } from "./plan.js";
 import type { ValueType } from "../capability-model/types.js";
 import { compileQueryComposition } from "../query/composition.js";
+import { queryTreeBlueprint } from "./query-trees.js";
 
 const lowerTypes = (value: unknown): unknown =>
   JSON.parse(
@@ -59,6 +60,12 @@ export function compileQueryProgram(plan: ExecutionPlan): unknown {
     codec: "camino-query-program-v1",
     plan: (compileKernelProgram(plan) as { plan: string }).plan,
     ...(compositions.length ? { compositions } : {}),
+    trees: plan.definition.queries
+      .filter((entry) => entry.query.checked.tree)
+      .map((entry) => ({
+        id: entry.id,
+        ...queryTreeBlueprint(entry.query.packageRevisionId, entry.query.checked),
+      })),
     queries: [
       ...compileInspectionTemplates(plan).queries,
       ...plan.definition.queries.map((entry) => queryProgramEntry(plan, entry)),
@@ -85,7 +92,10 @@ export function queryProgramEntry(plan: ExecutionPlan, entry: import("./plan.js"
     placement: checked.declaration.placement?.kind ?? "remote",
     source:
       checked.declaration.placement?.kind === "local"
-        ? JSON.stringify([query.packageRevisionId, checked.declaration.placement.sourceQueryId])
+        ? JSON.stringify([
+            query.packageRevisionId,
+            checked.treeProjection?.tree ?? checked.declaration.placement.sourceQueryId,
+          ])
         : null,
     root: checked.declaration.root,
     atoms: query.rootAtoms,
@@ -105,6 +115,19 @@ export function queryProgramEntry(plan: ExecutionPlan, entry: import("./plan.js"
         operation: JSON.stringify([field.atomId, field.interfaceRevisionId, field.getter]),
       };
     }),
-    admittedOperations,
+    admittedOperations: checked.tree
+      ? [
+          ...new Set([
+            ...admittedOperations,
+            ...plan.definition.queries
+              .filter(
+                (entry) =>
+                  entry.query.packageRevisionId === query.packageRevisionId &&
+                  entry.query.checked.treeProjection?.tree === checked.declaration.id,
+              )
+              .flatMap((entry) => entry.operations),
+          ]),
+        ].sort()
+      : admittedOperations,
   };
 }

src/execution-world/query-trees.ts

@@ -0,0 +1,94 @@
+import type { CheckedQuery, QueryTreeNode } from "../query/types.js";
+import type { ValueType } from "../capability-model/types.js";
+import { treeProjectionQuery } from "../query/tree.js";
+import { tsType } from "../bindings/portable.js";
+
+export function queryTreeBlueprint(packageId: string, query: CheckedQuery) {
+  const tree = query.tree!;
+  const projection = (id: string) =>
+    JSON.stringify([packageId, treeProjectionQuery(query.declaration.id, id, "local")]);
+  const admission = (id: string) =>
+    JSON.stringify([packageId, treeProjectionQuery(query.declaration.id, id, "replica")]);
+  return {
+    root: tree.root,
+    maxOccurrences: tree.maxOccurrences,
+    nodes: tree.nodes.map((node) => ({
+      ...node,
+      projection: projection(node.projection),
+      admission: admission(node.projection),
+      bindings: node.bindings.map((binding) => ({
+        ...binding,
+        projection: projection(binding.projection),
+        admission: admission(binding.projection),
+      })),
+    })),
+  };
+}
+
+/** Emit the shape of owned handles separately from graph result codecs. */
+export function queryTreeType(query: CheckedQuery): string {
+  const tree = query.tree!;
+  const nodes = new Map(tree.nodes.map((node) => [node.id, node]));
+  const projections = new Map(tree.projections.map((projection) => [projection.id, projection]));
+  const rootOutput = (id: string) => {
+    const shape = projections.get(id)!.output;
+    if (shape.kind !== "record" || !shape.fields.root) throw Error("Unchecked Query Tree projection");
+    return shape.fields.root;
+  };
+  const shape = (id: string): string => {
+    const node = nodes.get(id)!;
+    return `QueryTreeShape<${tsType(rootOutput(node.projection))}, {${node.boundaries
+      .map(
+        (boundary) =>
+          `readonly ${JSON.stringify(boundary.name)}${boundary.conditions.length ? "?" : ""}: ${shape(boundary.node)}`,
+      )
+      .join(";")}}, {readonly root: {${node.bindings
+      .map(
+        (binding) =>
+          `readonly ${JSON.stringify(binding.name)}: ${bindingType(rootOutput(binding.projection), binding.targets, [binding.name])}`,
+      )
+      .join(";")}}}>`;
+  };
+  const bindingType = (
+    type: ValueType,
+    targets: QueryTreeNode["bindings"][number]["targets"],
+    prefix: string[],
+  ): string => {
+    const at = (type: ValueType, targets: QueryTreeNode["bindings"][number]["targets"]): string => {
+      if (type.kind === "optional") return `(${at(type.value, targets)} | null)`;
+      if (type.kind === "list")
+        return `ReadonlyArray<${at(
+          type.value,
+          targets.map((target) => ({ ...target, path: target.path.slice(1) })),
+        )}>`;
+      const target = targets.find((target) => !target.path.length);
+      if (target) {
+        if (type.kind !== "record" || type.fields._camino?.kind !== "record" || !type.fields._camino.fields.ref)
+          throw Error("Unchecked binding identity");
+        return `QueryTreeOccurrence<${tsType(type.fields._camino.fields.ref)}, ${shape(target.node)}>`;
+      }
+      if (type.kind !== "record") return tsType(type);
+      return `{${Object.entries(type.fields)
+        .map(
+          ([key, value]) =>
+            `readonly ${JSON.stringify(key)}: ${at(
+              value,
+              targets
+                .filter((target) => target.path[0] === key)
+                .map((target) => ({ ...target, path: target.path.slice(1) })),
+            )}`,
+        )
+        .join(";")}}`;
+    };
+    let selected = type;
+    for (const key of prefix) {
+      if (selected.kind !== "record" || !selected.fields[key]) throw Error("Unchecked binding field");
+      selected = selected.fields[key];
+    }
+    return at(
+      selected,
+      targets.map((target) => ({ ...target, path: target.path.slice(prefix.length) })),
+    );
+  };
+  return shape(tree.root);
+}

src/query/compile.ts

@@ -41,6 +41,7 @@ import { objectRow } from "./relational-schema.js";
 import { workspaceQueryRootId } from "./root.js";
 import { relationalCompiler } from "./relational-compile.js";
 import { fragmentSources, type FragmentResolver } from "./fragments.js";
+import { lowerQueryTree, stripQueryBoundaries } from "./tree.js";
 import {
   QueryCompileError,
   type QueryDeclaration,
@@ -158,7 +159,7 @@ export async function compileQuery(
       if (node.name.value.startsWith("__")) fail("QUERY_UNSUPPORTED_FEATURE", "Introspection is not supported", node);
     },
     Directive(node) {
-      if (!["include", "skip"].includes(node.name.value))
+      if (!["include", "skip", "boundary"].includes(node.name.value))
         fail("QUERY_UNSUPPORTED_FEATURE", `Unsupported directive ${node.name.value}`, node);
     },
   });
@@ -421,6 +422,7 @@ export async function compileQuery(
         for (const selection of set.selections) {
           if (++expandedFields > 10000) fail("QUERY_WORK_LIMIT", "Expanded query exceeds 10000 fields", selection);
           if (selection.kind === "FragmentSpread") {
+            if (selection.directives?.some((directive) => directive.name.value === "boundary")) continue;
             if (fragmentContracts.get(selection.name.value)?.mode === "reference") continue;
             add(
               fragments.get(selection.name.value)!.selectionSet,
@@ -519,7 +521,7 @@ export async function compileQuery(
   };
   const conditions = (directives: readonly DirectiveNode[] = []) =>
     directives
-      .filter((directive) => directive.name.value !== "live")
+      .filter((directive) => ["include", "skip"].includes(directive.name.value))
       .map((directive) => ({
         include: directive.name.value === "include",
         value: argument(directive.arguments!.find((entry) => entry.name.value === "if")!.value),
@@ -540,6 +542,52 @@ export async function compileQuery(
         const contract = fragmentContracts.get(node.name.value);
         if (contract && generated.byName.get(parent.name)?.revisionId !== contract.root)
           fail("FRAGMENT_ROOT_MISMATCH", "Imported fragment requires its exact nominal root interface", node);
+        const directive = node.directives?.find((directive) => directive.name.value === "boundary");
+        if (directive) {
+          const name = directive.arguments?.find((argument) => argument.name.value === "name")?.value;
+          if (name?.kind !== "StringValue" || !/^[A-Za-z_][A-Za-z0-9_]{0,63}$/.test(name.value))
+            return fail(
+              "QUERY_BOUNDARY_NAME",
+              "A boundary needs a literal identifier of at most 64 characters",
+              directive,
+            );
+          const root = generated.byName.get(parent.name)?.revisionId;
+          if (!root || root === workspaceQueryRootId)
+            return fail("QUERY_BOUNDARY_ROOT", "A boundary must select a nominal Graph Object", node);
+          if (contract?.mode === "reference")
+            fail("QUERY_BOUNDARY_REFERENCE", "Use an ordinary checked Fragment spread for a boundary", node);
+          const fragment = fragments.get(node.name.value)!;
+          const token = node.loc?.startToken;
+          return [
+            {
+              name: "$boundary",
+              key: "",
+              arguments: {},
+              conditions: inheritedConditions,
+              boundary: {
+                name: name.value,
+                root,
+                output: required(parent, fragment.selectionSet),
+                ...(token ? { location: { file: node.loc!.source.name, line: token.line, column: token.column } } : {}),
+              },
+              selection: [
+                ...(contract
+                  ? [
+                      {
+                        name: "$fragment",
+                        key: "",
+                        selection: [],
+                        arguments: {},
+                        conditions: [],
+                        fragmentSpread: contract,
+                      },
+                    ]
+                  : []),
+                ...selection(fragment.selectionSet, parent),
+              ],
+            },
+          ];
+        }
         return [
           ...(contract
             ? [
@@ -598,6 +646,13 @@ export async function compileQuery(
       ];
     });
     const contract = generated.byName.get(parent.name);
+    const names = new Set<string>();
+    for (const field of selections)
+      if (field.boundary) {
+        if (names.has(field.boundary.name))
+          fail("QUERY_BOUNDARY_DUPLICATE", `Duplicate boundary ${field.boundary.name}`);
+        names.add(field.boundary.name);
+      }
     if (!contract || contract.revisionId === workspaceQueryRootId) return selections;
     // Fragment expansion may repeat metadata. Combine its children so a later
     // implicit reference cannot overwrite an explicitly selected aggregate.
@@ -632,10 +687,11 @@ export async function compileQuery(
   const normalized = print(document),
     schema = printSchema(generated.schema);
   const selections = selection(operations[0]!.selectionSet, generated.schema.getQueryType()!);
+  const tree = lowerQueryTree(declaration, selections, result);
   const definitionDigest = createHash("sha256")
     .update(
       canonicalJson({
-        semantics: 6,
+        semantics: tree ? 7 : 6,
         declaration,
         normalized,
         fragmentContracts: Object.fromEntries(fragmentContracts),
@@ -667,7 +723,8 @@ export async function compileQuery(
     variables: { kind: "record", fields: variables },
     output: result,
     effects: [...effects.values()],
-    selection: selections,
+    selection: tree ? stripQueryBoundaries(selections) : selections,
+    ...(tree ? { tree } : {}),
     variableDefaults: Object.fromEntries(
       (operations[0]!.variableDefinitions ?? [])
         .filter((entry) => entry.defaultValue)

src/query/schema.ts

@@ -11,6 +11,8 @@ import {
   GraphQLList,
   GraphQLNonNull,
   GraphQLSchema,
+  GraphQLDirective,
+  DirectiveLocation,
   specifiedDirectives,
   visit,
   type GraphQLOutputType,
@@ -294,7 +296,14 @@ export function querySchema(
     return result;
   };
   const schema = new GraphQLSchema({
-    directives: specifiedDirectives,
+    directives: [
+      ...specifiedDirectives,
+      new GraphQLDirective({
+        name: "boundary",
+        locations: [DirectiveLocation.FRAGMENT_SPREAD],
+        args: { name: { type: new GraphQLNonNull(GraphQLString) } },
+      }),
+    ],
     // Nominal projections can mention an interface not reached by a relation.
     types: (() => {
       const requested = new Set<string>();

src/query/tree.ts

@@ -0,0 +1,260 @@
+import { valueType, type InterfaceRevisionId, type ValueType } from "../capability-model/types.js";
+import {
+  QueryCompileError,
+  type QueryDeclaration,
+  type QuerySelection,
+  type QueryTreePlan,
+  type QueryTreeNode,
+} from "./types.js";
+import type { CheckedQuery } from "./types.js";
+import { createHash } from "node:crypto";
+import { canonicalJson } from "../capability-model/evolution.js";
+
+export const stripQueryBoundaries = (fields: readonly QuerySelection[]): QuerySelection[] =>
+  fields
+    .filter((field) => !field.boundary)
+    .map((field) => ({ ...field, selection: stripQueryBoundaries(field.selection) }));
+
+const containsBoundary = (fields: readonly QuerySelection[]): boolean =>
+  fields.some((field) => !!field.boundary || containsBoundary(field.selection));
+
+/** GraphQL repeated paths form one projection. Equivalent checked selections
+ * reuse their binding; differing windows/guards never silently share it. */
+function mergeTreeFields(fields: readonly QuerySelection[]): QuerySelection[] {
+  const result: QuerySelection[] = [];
+  for (const input of fields) {
+    const field = { ...input, selection: mergeTreeFields(input.selection) };
+    const previous = result.find(
+      (candidate) =>
+        !candidate.boundary &&
+        !field.boundary &&
+        !candidate.fragmentSpread &&
+        !field.fragmentSpread &&
+        candidate.key === field.key,
+    );
+    if (!previous) {
+      result.push(field);
+      continue;
+    }
+    const { selection: _left, ...left } = previous;
+    const { selection: _right, ...right } = field;
+    if (canonicalJson(left) !== canonicalJson(right)) {
+      if (containsBoundary(previous.selection) || containsBoundary(field.selection))
+        throw new QueryCompileError(
+          "QUERY_TREE_BINDING_CONFLICT",
+          `Alias differently guarded or parameterized paths selected as ${field.key}`,
+        );
+      result.push(field);
+      continue;
+    }
+    previous.selection = mergeTreeFields([...previous.selection, ...field.selection]);
+  }
+  const names = new Set<string>();
+  for (const field of result)
+    if (field.boundary) {
+      if (names.has(field.boundary.name))
+        throw new QueryCompileError("QUERY_BOUNDARY_DUPLICATE", `Duplicate boundary ${field.boundary.name}`);
+      names.add(field.boundary.name);
+    }
+  return result;
+}
+const required = (type: ValueType): ValueType =>
+  type.kind === "optional" || type.kind === "list" ? required(type.value) : type;
+const fieldType = (type: ValueType, key: string): ValueType => {
+  const shape = required(type);
+  if (shape.kind !== "record" || !shape.fields[key])
+    throw new QueryCompileError("QUERY_TREE_SHAPE", `Missing checked field ${key}`);
+  return shape.fields[key];
+};
+const objectInterface = (fields: readonly QuerySelection[]): InterfaceRevisionId | undefined =>
+  fields
+    .find((field) => field.name === "_camino" && field.key === "_camino")
+    ?.selection.find((field) => field.name === "ref")?.targetInterfaceRevisionId;
+const identity = (fields: readonly QuerySelection[]): QuerySelection[] =>
+  fields
+    .filter((field) => field.name === "_camino" && field.key === "_camino")
+    .map((field) => ({ ...field, conditions: [], selection: field.selection.filter((child) => child.name === "ref") }));
+function projectionType(type: ValueType, fields: readonly QuerySelection[]): ValueType {
+  if (type.kind === "optional") return valueType.optional(projectionType(type.value, fields));
+  if (type.kind === "list") return valueType.list(projectionType(type.value, fields));
+  if (type.kind !== "record") return type;
+  return {
+    kind: "record",
+    fields: Object.fromEntries(
+      fields
+        .filter((field) => !field.fragmentSpread)
+        .map((field) => {
+          const source = type.fields[field.key] ?? (field.key === "key" ? valueType.string : undefined);
+          if (!source) throw new QueryCompileError("QUERY_TREE_SHAPE", `Missing checked projection ${field.key}`);
+          return [field.key, projectionType(source, field.selection)];
+        }),
+    ),
+  };
+}
+const keyField = (): QuerySelection => ({ name: "key", key: "key", conditions: [], arguments: {}, selection: [] });
+
+/** Lower into complete projections and minimal binding projections. No runtime
+ * component inspection, executable client source, or graph handle value is involved.
+ * Each projection is rooted at its own nominal subject; lists retain entry keys.
+ */
+export function lowerQueryTree(
+  declaration: QueryDeclaration,
+  selection: QuerySelection[],
+  output: ValueType,
+): QueryTreePlan | undefined {
+  if (!containsBoundary(selection)) return;
+  selection = mergeTreeFields(selection);
+  if (declaration.placement?.kind !== "replica" || declaration.fragment)
+    throw new QueryCompileError(
+      "QUERY_TREE_PLACEMENT",
+      "Declare a Query Tree as a replica query; its checked projections supply local views",
+    );
+  const root = selection.find((field) => field.name === "root" && field.key === "root");
+  if (!root || selection.some((field) => field !== root))
+    throw new QueryCompileError("QUERY_TREE_ROOT", "A Query Tree requires one unaliased root selection");
+  const plan: QueryTreePlan = { root: "root", nodes: [], projections: [], maxOccurrences: 0 };
+  const project = (id: string, subject: InterfaceRevisionId, fields: QuerySelection[], shape: ValueType) => {
+    if (plan.projections.length >= 256)
+      throw new QueryCompileError("QUERY_TREE_LIMIT", "Query Tree exceeds 256 projections");
+    plan.projections.push({
+      id,
+      root: id === "root/value" ? declaration.root : { kind: "object", interface: subject },
+      selection: [{ name: "root", key: "root", arguments: {}, conditions: [], selection: fields }],
+      output: { kind: "record", fields: { root: shape } },
+    });
+    return id;
+  };
+  const node = (
+    id: string,
+    subject: InterfaceRevisionId,
+    fields: QuerySelection[],
+    shape: ValueType,
+    occurrences: number,
+  ): string => {
+    plan.maxOccurrences += occurrences;
+    if (!Number.isSafeInteger(plan.maxOccurrences) || plan.maxOccurrences > 256)
+      throw new QueryCompileError("QUERY_TREE_LIMIT", "Query Tree exceeds 256 bounded node occurrences");
+    const current: QueryTreeNode = {
+      id,
+      projection: project(id + "/value", subject, stripQueryBoundaries(fields), shape),
+      boundaries: [],
+      bindings: [],
+    };
+    plan.nodes.push(current);
+    for (const field of fields)
+      if (field.boundary) {
+        const child = field.boundary;
+        current.boundaries.push({
+          name: child.name,
+          conditions: field.conditions,
+          node: node(id + "/boundary/" + child.name, child.root, field.selection, child.output, occurrences),
+        });
+      }
+    for (const field of fields) {
+      if (field.boundary || !containsBoundary(field.selection)) continue;
+      const targets: { path: string[]; node: string }[] = [];
+      const prune = (fields: QuerySelection[], shape: ValueType, path: string[], bound: number): QuerySelection[] => {
+        if (shape.kind === "optional") return prune(fields, shape.value, path, bound);
+        if (shape.kind === "list") return prune(fields, shape.value, [...path, "[]"], bound * declaration.budgets.rows);
+        const target = objectInterface(fields);
+        if (target) {
+          targets.push({
+            path,
+            node: node(id + "/binding/" + path.map(encodeURIComponent).join("/"), target, fields, shape, bound),
+          });
+          return identity(fields);
+        }
+        const minimal = fields
+          .filter((field) => containsBoundary(field.selection))
+          .map((field) => ({
+            ...field,
+            selection: prune(field.selection, fieldType(shape, field.key), [...path, field.key], bound),
+          }));
+        // Relationship occurrence identity is its entry key, including duplicate
+        // target Objects. Never substitute list position or Object identity.
+        if (minimal.some((field) => field.name === "node") && !minimal.some((field) => field.name === "key"))
+          minimal.unshift(fields.find((field) => field.name === "key" && field.key === "key") ?? keyField());
+        return minimal;
+      };
+      const type = fieldType(shape, field.key);
+      const minimal = { ...field, selection: prune(field.selection, type, [field.key], occurrences) };
+      const selected = [...identity(fields), minimal];
+      current.bindings.push({
+        name: field.key,
+        targets,
+        projection: project(
+          id + "/bindings/" + encodeURIComponent(field.key),
+          subject,
+          selected,
+          projectionType(shape, selected),
+        ),
+      });
+    }
+    return id;
+  };
+  node("root", declaration.root.interface, root.selection, fieldType(output, "root"), 1);
+  return plan;
+}
+
+export const treeProjectionQuery = (tree: string, projection: string, role: "replica" | "local") =>
+  `${tree}/@tree/${projection}/${role}`;
+
+/** Checked synthetic queries remain ordinary nominal queries for linking,
+ * authority, native input acquisition and execution. Public trees own the plan;
+ * applications do not copy these projections into their source declarations. */
+export function queryTreeProjections(query: CheckedQuery): CheckedQuery[] {
+  if (!query.tree) return [];
+  const { tree: _tree, ...base } = query;
+  return query.tree.projections.flatMap((projection) => {
+    const selected = new Set<string>();
+    const walk = (fields: readonly QuerySelection[]) => {
+      for (const field of fields) {
+        if (field.interfaceRevisionId && field.memberId)
+          selected.add(JSON.stringify([field.interfaceRevisionId, field.memberId]));
+        walk(field.selection);
+      }
+    };
+    walk(projection.selection);
+    const effects = query.effects.filter(
+      (effect) =>
+        selected.has(JSON.stringify([effect.interfaceRevisionId, effect.memberId])) ||
+        effect.uses.some((use) => use !== "select"),
+    );
+    if (effects.some((effect) => effect.execution === "rpc-permitted"))
+      throw new QueryCompileError(
+        "QUERY_TREE_LOCAL_DEPENDENCY",
+        "A replica Query Tree requires locally executable snapshot projections",
+      );
+    return (["replica", "local"] as const).map((role): CheckedQuery => {
+      const id = treeProjectionQuery(query.declaration.id, projection.id, role);
+      const declaration: QueryDeclaration = {
+        ...query.declaration,
+        id,
+        displayName: id,
+        root: projection.root,
+        placement:
+          role === "replica"
+            ? { kind: "replica" }
+            : { kind: "local", sourceQueryId: treeProjectionQuery(query.declaration.id, projection.id, "replica") },
+      };
+      return {
+        ...base,
+        declaration,
+        effects,
+        selection: projection.selection,
+        output: projection.output,
+        treeProjection: { tree: query.declaration.id, projection: projection.id, role },
+        definitionDigest: createHash("sha256")
+          .update(
+            canonicalJson({
+              parent: query.definitionDigest,
+              declaration,
+              selection: projection.selection,
+              output: projection.output,
+            }),
+          )
+          .digest("hex"),
+      };
+    });
+  });
+}

src/query/types.ts

@@ -94,6 +94,9 @@ export class QueryCompileError extends Error {
   }
 }
 export interface CheckedQuery {
+  /** Checked decomposition; handles belong to a Client Session, never graph values. */
+  tree?: QueryTreePlan;
+  treeProjection?: { tree: string; projection: string; role: "replica" | "local" };
   fragmentContracts?: Record<string, NonNullable<QuerySelection["fragmentSpread"]>>;
   declaration: QueryDeclaration;
   definitionDigest: string;
@@ -115,6 +118,12 @@ export type QueryArgument =
   | { kind: "list"; values: QueryArgument[] }
   | { kind: "object"; fields: Record<string, QueryArgument> };
 export interface QuerySelection {
+  boundary?: {
+    name: string;
+    root: InterfaceRevisionId;
+    output: ValueType;
+    location?: QuerySourceLocation;
+  };
   /** A checked occurrence marker, not an output field or storage capability. */
   fragmentSpread?: {
     mode?: "reference";
@@ -135,3 +144,27 @@ export interface QuerySelection {
   relational?: import("./relational.js").QueryRelationalPlan;
   predicate?: import("./relational.js").QueryPredicate;
 }
+
+export interface QueryTreeProjection {
+  id: string;
+  root: QueryRoot;
+  selection: QuerySelection[];
+  output: ValueType;
+}
+export interface QueryTreeNode {
+  id: string;
+  projection: string;
+  boundaries: { name: string; conditions: QuerySelection["conditions"]; node: string }[];
+  bindings: {
+    name: string;
+    projection: string;
+    /** [] denotes an occurrence in a bounded list; its entry key owns identity. */
+    targets: { path: string[]; node: string }[];
+  }[];
+}
+export interface QueryTreePlan {
+  root: string;
+  nodes: QueryTreeNode[];
+  projections: QueryTreeProjection[];
+  maxOccurrences: number;
+}

src/react-build/declarations.ts

@@ -20,6 +20,9 @@ export interface ReactModulePreparation {
   /** Public input type before workspace query lowering adds private projections. */
   input?: ValueType;
   children: ReactChildDeclaration[];
+  /** Binds roots/arguments only. The ordinary checked Query Tree owns every
+   * acquisition path; the React declaration does not repeat its descendants. */
+  trees?: Pick<QueryCompositionStep, "name" | "query" | "root" | "arguments">[];
 }
 export interface ReactPreparationArtifact {
   /** Frontend queries belong to installed preparation, not the authored client API. */
@@ -51,7 +54,7 @@ export function presentationDeclarations(
   };
   for (const [name, value] of Object.entries(modules)) {
     const declaration = object(value, `module ${name}`);
-    if (Object.keys(declaration).some((key) => !["inputs", "children"].includes(key)))
+    if (Object.keys(declaration).some((key) => !["inputs", "children", "trees"].includes(key)))
       throw Error(`${name}: unknown preparation field`);
     const module = pkg.modules?.find((entry) => entry.displayName === name);
     if (!module) throw Error(`React declaration: unknown module ${name}`);
@@ -129,7 +132,29 @@ export function presentationDeclarations(
         ...(role ? { role } : {}),
       };
     });
-    artifact.modules.push({ module: module.id, composition, children: parsed });
+    const trees = declaration.trees ?? [];
+    if (!Array.isArray(trees) || trees.length > 16) throw Error(`${name}: trees must be a bounded array`);
+    const treeNames = new Set<string>();
+    const preparedTrees = trees.map((value) => {
+      const tree = object(value, `${name} tree`) as unknown as NonNullable<ReactModulePreparation["trees"]>[number];
+      if (
+        Object.keys(tree).some((key) => !["name", "query", "root", "arguments"].includes(key)) ||
+        !/^[A-Za-z_][A-Za-z0-9_]*$/.test(tree.name) ||
+        treeNames.has(tree.name)
+      )
+        throw Error(`${name}: tree requires a unique name and checked root/arguments`);
+      treeNames.add(tree.name);
+      const query = pkg.queries?.find((entry) => entry.displayName === tree.query);
+      if (!query || query.placement?.kind !== "replica")
+        throw Error(`${name}.${tree.name}: requires a replica Query Tree`);
+      return { ...tree, query: query.id };
+    });
+    artifact.modules.push({
+      module: module.id,
+      composition,
+      children: parsed,
+      ...(preparedTrees.length ? { trees: preparedTrees } : {}),
+    });
   }
   for (const module of pkg.modules ?? []) {
     const contract = interfaces.find((entry) => entry.revisionId === module.interfaceRevisionId);

src/react-build/workspace.ts

@@ -1,7 +1,7 @@
 import type { WorkspaceRevision, ValueType } from "../capability-model/types.js";
 import { moduleContract } from "../capability-model/modules.js";
 import { canonicalJson } from "../capability-model/evolution.js";
-import { queryBindingType } from "../query/composition.js";
+import { queryBindingType, compileQueryComposition } from "../query/composition.js";
 import { moduleTypeContext } from "../execution-world/module-contracts.js";
 import { preparationArtifact, type ReactPreparationArtifact } from "./declarations.js";
 import { expandPresentationQueries } from "./expansion.js";
@@ -25,6 +25,17 @@ export async function completeWorkspace(workspace: WorkspaceRevision): Promise<v
     if (!composition || composition.output.kind !== "record")
       throw Error(`Missing checked inputs for ${parent.module.displayName}`);
     parent.preparation.input = structuredClone(composition.output);
+    const treeQueries = new Map((parent.pkg.checkedQueries ?? []).map((query) => [query.declaration.id, query]));
+    for (const tree of parent.preparation.trees ?? []) {
+      if (!treeQueries.get(tree.query)?.tree)
+        throw Error(`${parent.module.displayName}.${tree.name}: expected a checked Query Tree`);
+      // Reuse Camino's ordinary nominal/argument binder. Only input parameters
+      // are available; a tree cannot wait on a whole presentation result.
+      compileQueryComposition(
+        { id: `react:tree:${parent.module.id}:${tree.name}`, input: composition.input, steps: [tree], maxQueries: 1 },
+        treeQueries,
+      );
+    }
     const outputs = new Map(Object.entries(composition.output.fields));
     const dependencies: string[] = [];
     const children = parent.preparation.children.map((child) => {