diff --git a/flake.nix b/flake.nix
index 54daab3..80677c9 100644
--- a/flake.nix
+++ b/flake.nix
@@ -81,11 +81,13 @@
                           install -Dm644 nix/checked-package.nix "$out/share/checked-package.nix"
                           install -Dm644 nix/checked-artifacts.nix "$out/share/checked-artifacts.nix"
                           install -Dm644 nix/package-context.nix "$out/share/package-context.nix"
+                          install -Dm644 nix/lock-source.nix "$out/share/lock-source.nix"
                           install -Dm644 nix/package-context.mjs "$out/share/package-context.mjs"
                           install -Dm644 nix/check-package.mjs "$out/share/check-package.mjs"
                           install -Dm644 nix/check-execution.mjs "$out/share/check-execution.mjs"
                           substitute nix/checked-candidate.nix "$out/share/checked-candidate.nix" \
-                            --replace-fail '@nixpkgs@' '${pkgs.path}'
+                            --replace-fail '@nixpkgs@' '${pkgs.path}' \
+                            --replace-fail '@nixpkgsNarHash@' '${nixpkgs.narHash}'
                           cp --reflink=auto --recursive grammar "$out/grammar"
                           cp --reflink=auto --recursive proto "$out/proto"
                           cp --reflink=auto --recursive dist "$out/dist"
diff --git a/nix/checked-candidate.nix b/nix/checked-candidate.nix
index 2cebdd7..d657ca0 100644
--- a/nix/checked-candidate.nix
+++ b/nix/checked-candidate.nix
@@ -9,7 +9,11 @@
   system ? builtins.currentSystem,
 }:
 let
-  pkgs = import (/. + "@nixpkgs@") { inherit system; };
+  pkgs = import (/. + "@nixpkgs@") {
+    inherit system;
+    config = { };
+    overlays = [ ];
+  };
   protocol = builtins.storePath generator;
   sourceKey = source: "${source.kind}:${source.repository}@${source.commit}";
   fetch =
@@ -26,8 +30,9 @@ let
     source:
     let
       directory = fetch source;
+      lockSource = import ./lock-source.nix { source = directory; };
       lockFile = pkgs.runCommand "qx-source-lock.json" { } ''
-        ${protocol}/bin/quixos-lock-check ${directory}/quixos.lock > "$out"
+        ${protocol}/bin/quixos-lock-check ${lockSource}/quixos.lock > "$out"
       '';
       lock = builtins.fromJSON (builtins.readFile lockFile);
     in
@@ -124,15 +129,40 @@ let
         }) (builtins.filter (entry: entry.kind != "workspace") (resourceClosure true node));
       }
     );
-  compile =
+  # Each resource is checked once per exact source/closure/frontend/toolchain.
+  # Composition imports these compiler outputs; authoring receipts are never
+  # build inputs. Missing entries in ordinary CLI use take the full check path.
+  compiledNodes = builtins.mapAttrs (_: node: compileNode node) nodeTable;
+  compile = node: compiledNodes.${sourceKey node};
+  checkedResources =
     node:
-    pkgs.runCommand "qx-${node.kind}-contract" { } ''
+    pkgs.writeText "qx-checked-resources.json" (
+      builtins.toJSON (
+        map
+          (dependency: {
+            inherit (dependency) kind repository commit;
+            artifact = compile dependency;
+          })
+          (
+            builtins.filter (
+              dependency:
+              dependency.kind != "workspace"
+              && dependency.kind != "build"
+              && sourceKey dependency != sourceKey node
+            ) (resourceClosure true node)
+          )
+      )
+    );
+  compileNode =
+    node:
+    pkgs.runCommand "qx-${node.kind}-contract" { QUIXOS_TRACE_PROFILE = "1"; } ''
       mkdir -p "$out"
       ${
         if node.kind == "workspace" then
           ''
             ${protocol}/bin/quixos-workspace-compile --root ${node.directory} \
-              ${queryGeneratorFlags node} \
+              ${queryGeneratorFlags root} \
+              --checked-resources ${checkedResources node} \
               --source-root-commit ${pkgs.lib.escapeShellArg node.commit} \
               --checkout-root "$TMPDIR/checkouts" --snapshot-map ${snapshots node} \
               --graph-out "$out/graph.json" --schemas-out "$out/package-schemas.json" \
@@ -144,7 +174,8 @@ let
         else
           ''
             ${protocol}/bin/quixos-resource-compile --root ${node.directory} \
-              ${queryGeneratorFlags node} \
+              ${queryGeneratorFlags root} \
+              --checked-resources ${checkedResources node} \
               --kind ${node.kind} --repository ${pkgs.lib.escapeShellArg node.repository} \
               --commit ${pkgs.lib.escapeShellArg node.commit} \
               --checkout-root "$TMPDIR/checkouts" --snapshot-map ${snapshots node} --snapshot-only true \
@@ -153,6 +184,18 @@ let
       }
     '';
   contract = compile root;
+  # Parse shared workspace outputs once. Repeating fromJSON in every package
+  # makes composition quadratic in package count and in the serialized world.
+  workspacePackages = builtins.listToAttrs (
+    map
+      (pkg: {
+        name = sourceKey (pkg.source // { kind = "package"; });
+        value = pkg;
+      })
+      (builtins.fromJSON (builtins.readFile "${contract}/execution-plan.json"))
+      .definition.bindingSchema.packages
+  );
+  workspaceContexts = builtins.fromJSON (builtins.readFile "${contract}/build-contexts.json");
   buildDependencies =
     node:
     builtins.listToAttrs (
@@ -218,17 +261,19 @@ let
         if execution && kind == "workspace" then
           {
             revision =
-              pkgs.lib.findFirst
-                (pkg: pkg.source.repository == node.repository && pkg.source.commit == node.commit)
-                (throw "Source package missing from workspace compilation: ${node.repository}")
-                (builtins.fromJSON (builtins.readFile "${contract}/execution-plan.json"))
-                .definition.bindingSchema.packages;
+              workspacePackages.${sourceKey node}
+              or (throw "Source package missing from workspace compilation: ${node.repository}");
           }
         else
           builtins.fromJSON (builtins.readFile "${compiled}/candidate.json");
       buildContext = import ./package-context.nix {
         inherit pkgs protocol;
         contexts = if kind == "workspace" then "${contract}/build-contexts.json" else null;
+        contextData =
+          if execution && kind == "workspace" then
+            workspaceContexts.${candidate.revision.revisionId}
+          else
+            null;
         plan = "${compiled}/bindings.json";
         packageRevisionId = candidate.revision.revisionId;
       };
@@ -254,6 +299,11 @@ let
             typescript = runtimePackages.camino-replica-core.dependencies;
             packageRevisionId = candidate.revision.revisionId;
             dependencies = buildDependencies node;
+            buildEnvironment = {
+              inherit pkgs system;
+              nixpkgsSource = toString pkgs.path;
+              narHash = "@nixpkgsNarHash@";
+            };
           }
           // pkgs.lib.optionalAttrs (componentEntries != [ ]) {
             react = {
@@ -310,7 +360,7 @@ in
 pkgs.runCommand (if contractOnly then "qx-contract" else "qx-checked-candidate") { } ''
   mkdir -p "$out"
   cp ${
-    pkgs.writeText "qx-candidate-source.json" (builtins.toJSON { inherit repository commit kind; })
+    builtins.toFile "qx-candidate-source.json" (builtins.toJSON { inherit repository commit kind; })
   } "$out/source.json"
   cp ${contract}/candidate.json "$out/candidate.json"
   cp ${contract}/graph.json "$out/graph.json"
diff --git a/nix/lock-source.nix b/nix/lock-source.nix
new file mode 100644
index 0000000..bceef63
--- /dev/null
+++ b/nix/lock-source.nix
@@ -0,0 +1,16 @@
+# Lock parsing only reads this one file when no import token can occur. A
+# conservative substring probe also sends comments/URLs containing "import"
+# through the complete-source path. Fragment names may have any extension.
+{ source }:
+let
+  regular = ((builtins.readDir source)."quixos.lock" or null) == "regular";
+  text = if regular then builtins.readFile (source + "/quixos.lock") else "import";
+in
+if builtins.replaceStrings [ "import" ] [ "" ] text != text then
+  source
+else
+  builtins.path {
+    path = source;
+    name = "qx-lock-source";
+    filter = filename: _: filename == toString source || filename == "${source}/quixos.lock";
+  }
diff --git a/nix/lock-source.test.nix b/nix/lock-source.test.nix
new file mode 100644
index 0000000..c1669f4
--- /dev/null
+++ b/nix/lock-source.test.nix
@@ -0,0 +1,42 @@
+{ pkgs, protocol }:
+let
+  base = ''quixos-lock version 1 { quixos source { repository "https://example.test/quixos.git"; commit "1111111111111111111111111111111111111111"; } }'';
+  fixture =
+    extra: lock:
+    pkgs.runCommand "qx-lock-source-fixture" { } ''
+      mkdir -p "$out/nested"
+      printf '%s' ${pkgs.lib.escapeShellArg lock} > "$out/quixos.lock"
+      printf '%s' ${pkgs.lib.escapeShellArg extra} > "$out/implementation.ts"
+      printf '%s' 'quixos-lock fragment version 1 {}' > "$out/nested/dependencies.txt"
+    '';
+  first = fixture "first implementation" base;
+  edited = fixture "edited implementation" base;
+  changed = fixture "first implementation" (
+    builtins.replaceStrings
+      [ "1111111111111111111111111111111111111111" ]
+      [ "2222222222222222222222222222222222222222" ]
+      base
+  );
+  fragments = fixture "first implementation" (
+    builtins.replaceStrings [ "quixos source" ] [ ''import "nested/dependencies.txt"; quixos source'' ]
+      base
+  );
+  conservative = fixture "first implementation" (base + "\n// import in a comment\n");
+  slice = source: import ./lock-source.nix { inherit source; };
+  parse =
+    source:
+    pkgs.runCommand "qx-source-lock.json" { } ''
+      ${protocol}/bin/quixos-lock-check ${slice source}/quixos.lock > "$out"
+    '';
+in
+assert slice first == slice edited;
+assert (parse first).drvPath == (parse edited).drvPath;
+assert slice first != slice changed;
+pkgs.runCommand "qx-lock-source-check" { } ''
+  ${protocol}/bin/quixos-lock-check ${slice first}/quixos.lock > first.json
+  ${protocol}/bin/quixos-lock-check ${slice edited}/quixos.lock > edited.json
+  cmp first.json edited.json
+  ${protocol}/bin/quixos-lock-check ${slice conservative}/quixos.lock > comment.json
+  cmp first.json comment.json
+  ${protocol}/bin/quixos-lock-check ${slice fragments}/quixos.lock > "$out"
+''
diff --git a/nix/package-context.nix b/nix/package-context.nix
index 7317379..ef20489 100644
--- a/nix/package-context.nix
+++ b/nix/package-context.nix
@@ -5,6 +5,7 @@
   protocol,
   plan ? null,
   contexts ? null,
+  contextData ? null,
   packageRevisionId,
 }:
 let
@@ -14,7 +15,9 @@ let
       ${pkgs.lib.escapeShellArg packageRevisionId} > "$out"
   '';
   context =
-    if contexts == null then
+    if contextData != null then
+      contextData
+    else if contexts == null then
       builtins.fromJSON (builtins.readFile projected)
     else
       (builtins.fromJSON (builtins.readFile contexts)).${packageRevisionId};
diff --git a/src/capability-language/assembly.ts b/src/capability-language/assembly.ts
index 332bca0..6236e1d 100644
--- a/src/capability-language/assembly.ts
+++ b/src/capability-language/assembly.ts
@@ -1,5 +1,6 @@
 import { readFile, realpath } from "node:fs/promises";
 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 type { QueryDeclaration } from "../query/types.js";
@@ -43,6 +44,15 @@ export type CapabilityRepositoryResolver = (
   kind: LockedResource["kind"],
 ) => Promise<CapabilityRepositorySnapshot>;
 
+/** Already checked outputs of this compiler, composed by the Nix build DAG.
+ * Source capture/check reports never grant this authority. */
+export type CheckedResourceResolver = (
+  kind: LockedResource["kind"],
+  source: GitSource,
+  lock: QuixosRepositoryLock,
+  dependencies: ReadonlyMap<string, ResolvedCapabilityResource>,
+) => Promise<CapabilityResource | undefined>;
+
 /** An explicitly selected build frontend supplies ordinary query sources. The
  * assembler never chooses a frontend by inspecting an interface/contract ID.
  * Generated sources go through the same query and imported-fragment checks. */
@@ -221,7 +231,12 @@ const createResourceGraphResolver = (
   quixosCommit: string,
   resolveResource: CapabilityRepositoryResolver,
   generateQueries?: PackageQueryGenerator,
+  checkedResource?: CheckedResourceResolver,
 ) => {
+  const graphStarted = performance.now();
+  let checkedResources = 0,
+    reusedResources = 0,
+    checkedQueries = 0;
   const resolved = new Map<string, Promise<ResolvedCapabilityResource>>();
   const active: string[] = [];
 
@@ -275,6 +290,30 @@ const createResourceGraphResolver = (
           };
         }
         const dependencyClosure = resourceClosure(directPairs.map(([, node]) => node));
+        const dependencies = new Map(
+          directPairs.map(([dependency, node]) => [bindingKey(dependency.kind, dependency.binding), node]),
+        );
+        const checked = await checkedResource?.(locked.kind, locked.source, lockResult.lock, dependencies);
+        if (checked) {
+          if (
+            checked.kind !== locked.kind ||
+            checked.revision.source.repository !== locked.source.repository ||
+            checked.revision.source.commit !== locked.source.commit
+          )
+            throw new Error("Checked resource identity mismatch");
+          assertImportsMatchLock("Checked resource", checked.imports, lockResult.lock.resources);
+          reusedResources++;
+          return {
+            key,
+            kind: locked.kind,
+            source: locked.source,
+            directory: snapshot.directory,
+            lock: lockResult.lock,
+            resource: structuredClone(checked),
+            dependencies,
+          };
+        }
+        const checkStarted = performance.now();
         const environment = environmentFor(directPairs, dependencyClosure);
         const manifestName = locked.kind === "interface" ? "interface.qx" : "package.qx";
         const manifestPath = path.join(snapshot.directory, manifestName);
@@ -399,6 +438,15 @@ const createResourceGraphResolver = (
             compiled.resource.revision.migrationCatalog = catalog;
           }
         }
+        checkedResources++;
+        const queries =
+          compiled.resource.kind === "package" ? (compiled.resource.revision.checkedQueries?.length ?? 0) : 0;
+        checkedQueries += queries;
+        profile("resource-check", checkStarted, {
+          kind: locked.kind,
+          resource: compiled.resource.revision.displayName,
+          queries,
+        });
         return {
           key,
           kind: locked.kind,
@@ -420,7 +468,11 @@ const createResourceGraphResolver = (
 
   return {
     visit,
-    nodes: async () => await Promise.all(resolved.values()),
+    nodes: async () => {
+      const nodes = await Promise.all(resolved.values());
+      profile("resource-graph", graphStarted, { checkedResources, reusedResources, checkedQueries });
+      return nodes;
+    },
   };
 };
 
@@ -430,6 +482,7 @@ export const compileCapabilityResourceRepository = async (options: {
   source: GitSource;
   resolveResource: CapabilityRepositoryResolver;
   generateQueries?: PackageQueryGenerator;
+  checkedResource?: CheckedResourceResolver;
 }): Promise<CompiledCapabilityResourceRepository> => {
   const lockResult = await loadQuixosLock(path.join(options.rootDirectory, "quixos.lock"));
   if (!lockResult.ok) {
@@ -439,6 +492,7 @@ export const compileCapabilityResourceRepository = async (options: {
     lockResult.lock.quixos.commit,
     options.resolveResource,
     options.generateQueries,
+    options.checkedResource,
   );
   const root = await resolver.visit(
     {
@@ -466,6 +520,7 @@ export const compileWorkspaceRepository = async (options: {
   /** An editor's proposed source snapshot; locks and dependency revisions remain exact. */
   readSource?: (name: string) => Promise<string>;
   generateQueries?: PackageQueryGenerator;
+  checkedResource?: CheckedResourceResolver;
 }): Promise<CompiledWorkspaceRepository> => {
   const rootLockResult = await loadQuixosLock(path.join(options.rootDirectory, "quixos.lock"));
   if (!rootLockResult.ok) {
@@ -476,6 +531,7 @@ export const compileWorkspaceRepository = async (options: {
     rootLock.quixos.commit,
     options.resolveResource,
     options.generateQueries,
+    options.checkedResource,
   );
 
   const directPairs: Array<[LockedResource, ResolvedCapabilityResource]> = [];
diff --git a/src/capability-language/authoring-check.ts b/src/capability-language/authoring-check.ts
index 5f65355..b378075 100644
--- a/src/capability-language/authoring-check.ts
+++ b/src/capability-language/authoring-check.ts
@@ -64,7 +64,7 @@ export async function checkAuthoring(
     // Repository-scoped agents can check separate immutable candidates in parallel.
     const capture = promisify(callback)("quixos-qx", ["converge", context.workbench, directory], {
       maxBuffer: 4 * 1024 * 1024,
-      env: { ...process.env, QUIXOS_JJ_NO_CHECKPOINT: "1", QUIXOS_TRACE_CAPTURE: "1" },
+      env: { ...process.env, QUIXOS_JJ_NO_CHECKPOINT: "1", QUIXOS_TRACE_CAPTURE: "1", QUIXOS_TRACE_PROFILE: "1" },
     });
     console.error(`Capture details: ${path.join(output, "capture.log")}`);
     capture.child.stderr?.on("data", (chunk) => appendFileSync(path.join(output, "capture.log"), chunk));
@@ -94,6 +94,9 @@ export async function checkAuthoring(
         resource.kind,
         path.join(output, "nix.log"),
         options.contractOnly,
+        (phase, ms) => {
+          timings[phase] = ms;
+        },
       );
     } finally {
       timings.immutableCheckMs = Math.round(performance.now() - buildStarted);
diff --git a/src/capability-language/authoring-converge.ts b/src/capability-language/authoring-converge.ts
index c410152..cba7d94 100644
--- a/src/capability-language/authoring-converge.ts
+++ b/src/capability-language/authoring-converge.ts
@@ -5,6 +5,7 @@ import { promisify } from "node:util";
 import { randomUUID } from "node:crypto";
 import { authoringContext } from "./authoring-context.js";
 import { snapshotCommit } from "./checked-build.js";
+import { profile } from "./profile.js";
 import {
   loadQuixosLock,
   parseQuixosLockDocument,
@@ -14,6 +15,42 @@ import {
 } from "../resource-lock/index.js";
 
 const execFile = promisify(callback);
+// Bound independent repository operations. One visit owns each repository;
+// all visits finish before the final concurrent-edit validation pass.
+const concurrency = 4;
+async function mapConcurrent<T, R>(values: readonly T[], action: (value: T) => Promise<R>): Promise<R[]> {
+  const results = new Array<R>(values.length);
+  let next = 0;
+  await Promise.all(
+    Array.from({ length: Math.min(concurrency, values.length) }, async () => {
+      while (next < values.length) {
+        const index = next++;
+        results[index] = await action(values[index]);
+      }
+    }),
+  );
+  return results;
+}
+const limiter = () => {
+  let running = 0;
+  const waiting: Array<() => void> = [];
+  return async <T>(action: () => Promise<T>): Promise<T> => {
+    await new Promise<void>((resolve) => {
+      if (running < concurrency) {
+        running++;
+        resolve();
+      } else waiting.push(resolve);
+    });
+    try {
+      return await action();
+    } finally {
+      const next = waiting.shift();
+      if (next) next();
+      else running--;
+    }
+  };
+};
+
 const command = async (cwd: string, executable: string, args: string[]) => {
   const start = performance.now();
   // Do not log arguments: transports may contain credentials. Source identities
@@ -44,13 +81,14 @@ export type AuthoringBlocker = {
  * worklist grants typechecking, semantic review or activation approval.
  * Caller serializes coordinators; package authors may still be editing. */
 export async function convergeAuthoring(start: string, target = "root") {
+  const started = performance.now();
   const context = await authoringContext(start);
   const graphFile = path.join(context.workbench, ".quixos/resource-graph.json");
   const graphBefore = await readFile(graphFile, "utf8");
   const blockers: AuthoringBlocker[] = [];
   const nodes = new Map<string, { directory: string; kind: string; source: GitSource; dependencies: string[] }>();
   const selected = new Map<string, string>();
-  for (const entry of context.resources) {
+  const inventory = await mapConcurrent(context.resources, async (entry) => {
     const root = path.join(context.workbench, entry.directory);
     let repository = entry.source?.repository;
     try {
@@ -64,6 +102,9 @@ export async function convergeAuthoring(start: string, target = "root") {
       blockers.push({ directory: entry.directory, phase: "source", message: String(error).slice(0, 2000) });
       if (!repository) throw error; // The root has no separate registered source.
     }
+    return { ...entry, repository };
+  });
+  for (const { repository, ...entry } of inventory) {
     const key = identity(entry.kind, repository);
     if (selected.has(key)) throw new Error(`More than one editable checkout for ${repository}`);
     selected.set(key, entry.directory);
@@ -73,7 +114,7 @@ export async function convergeAuthoring(start: string, target = "root") {
       dependencies: [],
     });
   }
-  for (const node of nodes.values()) {
+  await mapConcurrent([...nodes.values()], async (node) => {
     try {
       const lock = await loadQuixosLock(path.join(context.workbench, node.directory, "quixos.lock"));
       if (!lock.ok) throw new Error(lock.diagnostics.map((d) => `${d.fileName}: ${d.message}`).join("\n"));
@@ -88,97 +129,122 @@ export async function convergeAuthoring(start: string, target = "root") {
     } catch (error) {
       blockers.push({ directory: node.directory, phase: "resolution", message: String(error) });
     }
-  }
-  const complete = new Map<string, GitSource>(),
-    active = new Set<string>();
-  const visited = new Set<string>();
-  if (!nodes.has(target)) throw new Error(`Not a registered repository: ${target}`);
-  const visit = async (directory: string): Promise<boolean> => {
-    visited.add(directory);
-    if (complete.has(directory)) return true;
-    if (blockers.some((entry) => entry.directory === directory)) return false;
-    if (active.has(directory)) {
+  });
+  // Detect cycles before starting concurrent futures: two roots awaiting each
+  // other must fail clearly rather than deadlocking on their cached promises.
+  const scanned = new Set<string>();
+  const detectCycles = (directory: string, parents: string[] = []) => {
+    if (parents.includes(directory)) {
       blockers.push({
         directory,
         phase: "dependency",
-        message: `Source dependency cycle: ${[...active, directory].join(" -> ")}`,
+        message: `Source dependency cycle: ${[...parents, directory].join(" -> ")}`,
       });
-      return false;
+      return;
     }
-    active.add(directory);
-    const node = nodes.get(directory)!;
-    for (const dependency of node.dependencies)
-      if (!(await visit(dependency))) {
-        blockers.push({ directory, phase: "dependency", message: `Waiting for ${dependency}` });
-        active.delete(directory);
+    if (scanned.has(directory)) return;
+    for (const dependency of nodes.get(directory)!.dependencies) detectCycles(dependency, [...parents, directory]);
+    scanned.add(directory);
+  };
+  for (const directory of nodes.keys()) detectCycles(directory);
+  const complete = new Map<string, GitSource>();
+  const pending = new Map<string, Promise<boolean>>();
+  const capture = limiter();
+  const visited = new Set<string>();
+  if (!nodes.has(target)) throw new Error(`Not a registered repository: ${target}`);
+  const visit = (directory: string): Promise<boolean> => {
+    visited.add(directory);
+    const existing = pending.get(directory);
+    if (existing) return existing;
+    const result = (async () => {
+      if (blockers.some((entry) => entry.directory === directory)) return false;
+      const node = nodes.get(directory)!;
+      const ready = await Promise.all(node.dependencies.map(visit));
+      const unavailable = node.dependencies.find((_, index) => !ready[index]);
+      if (unavailable) {
+        blockers.push({ directory, phase: "dependency", message: `Waiting for ${unavailable}` });
         return false;
       }
-    const root = path.join(context.workbench, directory);
-    let phase: AuthoringBlocker["phase"] = "source";
-    try {
-      const lock = await loadQuixosLock(path.join(root, "quixos.lock"));
-      if (!lock.ok) throw new Error("Lock changed during convergence; retry after joining writers");
-      for (const file of lock.lock.sourceFiles ?? ["quixos.lock"]) {
-        const filename = path.join(root, file),
-          before = await readFile(filename, "utf8");
-        const parsed = parseQuixosLockDocument(before, file);
-        if (!parsed.ok) throw new Error(`Invalid lock ${file}`);
-        let changed = false;
-        for (const dependency of parsed.document.resources) {
-          const target = selected.get(identity(dependency.kind, dependency.source.repository));
-          const source = target ? complete.get(target) : undefined;
-          if (target && !source)
-            throw new Error(`Dependencies changed during convergence (${dependency.binding}); join writers and retry`);
-          if (source && source.commit !== dependency.source.commit) {
-            dependency.source = source;
-            changed = true;
+      return await capture(async () => {
+        const root = path.join(context.workbench, directory);
+        let phase: AuthoringBlocker["phase"] = "source";
+        try {
+          const lock = await loadQuixosLock(path.join(root, "quixos.lock"));
+          if (!lock.ok) throw new Error("Lock changed during convergence; retry after joining writers");
+          for (const file of lock.lock.sourceFiles ?? ["quixos.lock"]) {
+            const filename = path.join(root, file),
+              before = await readFile(filename, "utf8");
+            const parsed = parseQuixosLockDocument(before, file);
+            if (!parsed.ok) throw new Error(`Invalid lock ${file}`);
+            let changed = false;
+            for (const dependency of parsed.document.resources) {
+              const target = selected.get(identity(dependency.kind, dependency.source.repository));
+              const source = target ? complete.get(target) : undefined;
+              if (target && !source)
+                throw new Error(
+                  `Dependencies changed during convergence (${dependency.binding}); join writers and retry`,
+                );
+              if (source && source.commit !== dependency.source.commit) {
+                dependency.source = source;
+                changed = true;
+              }
+            }
+            if (changed) {
+              const temporary = `${filename}.${randomUUID()}.tmp`;
+              try {
+                await writeFile(temporary, formatQuixosLockDocument(parsed.document), { flag: "wx" });
+                if ((await readFile(filename, "utf8")) !== before)
+                  throw new Error(`Concurrent edit to ${file}; retry after joining writers`);
+                await rename(temporary, filename);
+              } finally {
+                await rm(temporary, { force: true });
+              }
+            }
           }
-        }
-        if (changed) {
-          const temporary = `${filename}.${randomUUID()}.tmp`;
-          try {
-            await writeFile(temporary, formatQuixosLockDocument(parsed.document), { flag: "wx" });
-            if ((await readFile(filename, "utf8")) !== before)
-              throw new Error(`Concurrent edit to ${file}; retry after joining writers`);
-            await rename(temporary, filename);
-          } finally {
-            await rm(temporary, { force: true });
+          const snapshotStarted = performance.now();
+          const commit = await snapshotCommit(root);
+          if (process.env.QUIXOS_TRACE_CAPTURE === "1")
+            console.error(
+              `[${new Date().toISOString()}] Capture: ${directory} snapshot: ${Math.round(performance.now() - snapshotStarted)}ms`,
+            );
+          phase = "publication";
+          const ref = retentionTagForCommit(commit);
+          const remote = await command(root, "git", ["ls-remote", "--refs", node.source.repository, ref]);
+          if (remote && remote.split(/\s+/)[0] !== commit)
+            throw new Error(`Conflicting immutable retention ref ${ref}`);
+          if (!remote) {
+            await command(root, "git", ["push", node.source.repository, `${commit}:${ref}`]);
+            if (
+              (await command(root, "git", ["ls-remote", "--refs", node.source.repository, ref])).split(/\s+/)[0] !==
+              commit
+            )
+              throw new Error("Published source retention was not observed");
           }
+          complete.set(directory, { ...node.source, commit });
+        } catch (error) {
+          blockers.push({ directory, phase, message: String(error).slice(0, 4000) });
         }
-      }
-      const snapshotStarted = performance.now();
-      const commit = await snapshotCommit(root);
-      if (process.env.QUIXOS_TRACE_CAPTURE === "1")
-        console.error(
-          `[${new Date().toISOString()}] Capture: ${directory} snapshot: ${Math.round(performance.now() - snapshotStarted)}ms`,
-        );
-      phase = "publication";
-      const ref = retentionTagForCommit(commit);
-      const remote = await command(root, "git", ["ls-remote", "--refs", node.source.repository, ref]);
-      if (remote && remote.split(/\s+/)[0] !== commit) throw new Error(`Conflicting immutable retention ref ${ref}`);
-      if (!remote) await command(root, "git", ["push", node.source.repository, `${commit}:${ref}`]);
-      if ((await command(root, "git", ["ls-remote", "--refs", node.source.repository, ref])).split(/\s+/)[0] !== commit)
-        throw new Error("Published source retention was not observed");
-      complete.set(directory, { ...node.source, commit });
-    } catch (error) {
-      blockers.push({ directory, phase, message: String(error).slice(0, 4000) });
-    }
-    active.delete(directory);
-    return complete.has(directory);
+        return complete.has(directory);
+      });
+    })();
+    pending.set(directory, result);
+    return result;
   };
   // Include newly created, not-yet-imported resources, then the root.
-  if (target === "root") for (const directory of [...nodes.keys()].filter((d) => d !== "root")) await visit(directory);
+  if (target === "root") await Promise.all([...nodes.keys()].filter((d) => d !== "root").map(visit));
   await visit(target);
   for (let index = blockers.length - 1; index >= 0; index--)
     if (!visited.has(blockers[index].directory)) blockers.splice(index, 1);
-  for (const [directory, source] of complete) {
+  const recheckStarted = performance.now();
+  await mapConcurrent([...complete], async ([directory, source]) => {
     try {
       if ((await snapshotCommit(path.join(context.workbench, directory))) !== source.commit)
         throw new Error("Source advanced while converging; join writers and retry");
     } catch (error) {
       blockers.push({ directory, phase: "concurrent-edit", message: String(error) });
     }
-  }
+  });
+  profile("capture-recheck", recheckStarted, { repositories: complete.size });
   // Persist successful selections even if another repository is still broken.
   // Recovery must not depend on all parents succeeding in the same invocation.
   const graph = JSON.parse(graphBefore);
@@ -238,11 +304,14 @@ export async function convergeAuthoring(start: string, target = "root") {
       await rm(temporary, { force: true });
     }
   }
+  profile("capture", started, { repositories: nodes.size, snapshots: complete.size * 2, target });
   return {
     workbench: context.workbench,
     converged: blockers.length === 0,
     candidate: blockers.length ? null : (complete.get(target) ?? null),
-    retained: [...complete].map(([directory, source]) => ({ directory, source })),
+    retained: [...complete]
+      .sort(([left], [right]) => left.localeCompare(right))
+      .map(([directory, source]) => ({ directory, source })),
     worklist: blockers,
     verificationEvidence: false,
     activated: false,
diff --git a/src/capability-language/checked-build.ts b/src/capability-language/checked-build.ts
index ee04814..7e2e7fd 100644
--- a/src/capability-language/checked-build.ts
+++ b/src/capability-language/checked-build.ts
@@ -13,13 +13,14 @@ export const checkerIdentity = () =>
 export async function snapshotCommit(root: string): Promise<string> {
   const run = async (...args: string[]) =>
     (await execFile("jj", args, { cwd: root, env: environment() })).stdout.trim();
-  await run("status");
-  // jj resolve --list exits 1 on a clean revision. Query structured revision
-  // metadata instead of depending on diagnostic wording or swallowing errors.
-  if ((await run("--ignore-working-copy", "log", "--no-graph", "-r", "@", "-T", "conflict")) !== "false")
-    throw new Error("Resolve source conflicts before verification");
-  const commit = await run("--ignore-working-copy", "log", "--no-graph", "-r", "@", "-T", "commit_id");
-  if (!/^(?:[a-f0-9]{40}|[a-f0-9]{64})$/.test(commit)) throw new Error("Verification requires an exact jj commit");
+  // A single normal log snapshots the working copy and observes both values
+  // from that exact revision. Separate status/log processes add no evidence.
+  const [conflict, commit] = (await run("log", "--no-graph", "-r", "@", "-T", 'conflict ++ "\\n" ++ commit_id')).split(
+    "\n",
+  );
+  if (conflict !== "false") throw new Error("Resolve source conflicts before verification");
+  if (!commit || !/^(?:[a-f0-9]{40}|[a-f0-9]{64})$/.test(commit))
+    throw new Error("Verification requires an exact jj commit");
   await execFile("git", ["diff", "--exit-code", "--no-ext-diff", "--no-textconv", commit, "--"], {
     cwd: root,
     env: environment(),
@@ -110,6 +111,7 @@ export async function buildImmutableCandidate(
   kind: "workspace" | "interface" | "package" | "build",
   logFile: string,
   contractOnly = false,
+  observe?: (phase: "nixEvaluationMs" | "nixBuildMs", ms: number) => void,
 ): Promise<string> {
   if (!/^(?:[a-f0-9]{40}|[a-f0-9]{64})$/.test(source.commit))
     throw new Error("An immutable candidate requires an exact commit");
@@ -126,16 +128,52 @@ export async function buildImmutableCandidate(
     log.once("open", () => resolve());
     log.once("error", reject);
   });
-  return await new Promise((resolve, reject) => {
-    let output = "",
-      tail = "",
-      failure: Error | undefined;
-    const child = spawn(
-      "nix",
-      [
-        "build",
-        "--impure",
-        "--file",
+  const run = async (executable: string, args: string[]) =>
+    await new Promise<string>((resolve, reject) => {
+      let output = "",
+        tail = "",
+        failure: Error | undefined;
+      const child = spawn(executable, args, { env: environment(), stdio: ["ignore", "pipe", "pipe"] });
+      const failedLog = (error: Error) => {
+        failure = error;
+        child.kill();
+      };
+      log.on("error", failedLog);
+      child.stdout.on("data", (chunk) => {
+        output += chunk;
+      });
+      child.stderr.on("data", (chunk) => {
+        log.write(chunk);
+        tail = (tail + String(chunk)).slice(-6000);
+      });
+      child.on("error", (error) => {
+        failure = error;
+      });
+      child.on("close", (code) => {
+        log.off("error", failedLog);
+        if (failure) reject(failure);
+        else if (code !== 0) reject(new Error(`Candidate Nix check failed (${code}). Full log: ${logFile}\n${tail}`));
+        else resolve(output.trim());
+      });
+    });
+  const timed = async (phase: "nixEvaluationMs" | "nixBuildMs", action: () => Promise<string>) => {
+    const started = performance.now();
+    try {
+      return await action();
+    } finally {
+      observe?.(phase, Math.round(performance.now() - started));
+    }
+  };
+  let gcDirectory: string | undefined;
+  try {
+    // Evaluation includes import-from-derivation builds (locks and contracts).
+    // Build the resulting derivation directly, without evaluating the DAG twice.
+    // Keep the derivation alive across the two processes, including concurrent
+    // GC. This temporary root is removed on success and on verification failure.
+    gcDirectory = await fs.mkdtemp(path.join(path.dirname(logFile), ".gc-root-"));
+    const gcRoot = path.join(gcDirectory, "candidate");
+    const derivation = await timed("nixEvaluationMs", async () => {
+      await run("nix-instantiate", [
         builder,
         "--argstr",
         "repository",
@@ -152,33 +190,22 @@ export async function buildImmutableCandidate(
         "--arg",
         "contractOnly",
         contractOnly ? "true" : "false",
-        "--no-link",
-        "--print-out-paths",
-        "-L",
-      ],
-      { env: environment(), stdio: ["ignore", "pipe", "pipe"] },
+        "--add-root",
+        gcRoot,
+        "--indirect",
+      ]);
+      return await fs.readlink(gcRoot);
+    });
+    if (!/^\/nix\/store\/[a-z0-9]{32}-[^\s/]+\.drv$/.test(derivation))
+      throw new Error("Nix returned an invalid candidate derivation");
+    const artifact = await timed("nixBuildMs", () =>
+      run("nix", ["build", derivation + "^*", "--no-link", "--print-out-paths", "-L"]),
     );
-    log.on("error", (error) => {
-      failure = error;
-      child.kill();
-    });
-    child.stdout.on("data", (chunk) => {
-      output += chunk;
-    });
-    child.stderr.on("data", (chunk) => {
-      log.write(chunk);
-      tail = (tail + String(chunk)).slice(-6000);
-    });
-    child.on("error", (error) => {
-      failure = error;
-    });
-    child.on("close", (code) =>
-      log.end(() => {
-        if (failure) reject(failure);
-        else if (code !== 0 || !/^\/nix\/store\/[a-z0-9]{32}-[^\s/]+$/.test(output.trim()))
-          reject(new Error(`Candidate Nix check failed (${code}). Full log: ${logFile}\n${tail}`));
-        else resolve(output.trim());
-      }),
-    );
-  });
+    if (!/^\/nix\/store\/[a-z0-9]{32}-[^\s/]+$/.test(artifact))
+      throw new Error("Nix returned an invalid candidate artifact");
+    return artifact;
+  } finally {
+    await new Promise<void>((resolve) => log.end(resolve));
+    if (gcDirectory) await fs.rm(gcDirectory, { recursive: true, force: true });
+  }
 }
diff --git a/src/capability-language/checked-resources.ts b/src/capability-language/checked-resources.ts
new file mode 100644
index 0000000..1d258fa
--- /dev/null
+++ b/src/capability-language/checked-resources.ts
@@ -0,0 +1,40 @@
+import { readFile } from "node:fs/promises";
+import type { CheckedResourceResolver } from "./assembly.js";
+import type { CapabilityResource } from "./parser.js";
+
+/** Internal compiler inputs produced by checked-candidate.nix, not authoring
+ * receipts. The Nix composition owns their derivations and exact toolchain.
+ * Ordinary compiler callers omit this map and run all checks directly. */
+export async function loadCheckedResources(filename?: string): Promise<CheckedResourceResolver | undefined> {
+  if (!filename) return undefined;
+  const entries = JSON.parse(await readFile(filename, "utf8")) as Array<{
+    kind: string;
+    repository: string;
+    commit: string;
+    artifact: string;
+  }>;
+  const resources = new Map<string, string>();
+  for (const entry of entries) {
+    const key = `${entry.kind}\0${entry.repository}\0${entry.commit}`;
+    if (resources.has(key)) throw new Error("Repeated checked resource input");
+    if (!/^\/nix\/store\/[^/]+$/.test(entry.artifact))
+      throw new Error("Checked resources must be immutable Nix outputs");
+    resources.set(key, entry.artifact);
+  }
+  return async (kind, source, lock, dependencies) => {
+    const artifact = resources.get(`${kind}\0${source.repository}\0${source.commit}`);
+    if (!artifact) return undefined;
+    const graph = JSON.parse(await readFile(`${artifact}/graph.json`, "utf8"));
+    const expected = [...dependencies].map(([binding, node]) => ({ binding, resourceKey: node.key }));
+    if (
+      graph.quixos.commit !== lock.quixos.commit ||
+      graph.quixos.repository !== lock.quixos.repository ||
+      graph.root.kind !== kind ||
+      graph.root.source.repository !== source.repository ||
+      graph.root.source.commit !== source.commit ||
+      JSON.stringify(graph.root.dependencies) !== JSON.stringify(expected)
+    )
+      throw new Error("Checked resource input does not match its locked dependency graph");
+    return JSON.parse(await readFile(`${artifact}/candidate.json`, "utf8")) as CapabilityResource;
+  };
+}
diff --git a/src/capability-language/execution-scaffold.ts b/src/capability-language/execution-scaffold.ts
index e690ac8..226154e 100644
--- a/src/capability-language/execution-scaffold.ts
+++ b/src/capability-language/execution-scaffold.ts
@@ -80,6 +80,7 @@ export async function executionScaffold(
       devShells.default = (import (helpers + "/quixos-package-helpers.nix")).mkCaminoYarnShell { inherit pkgs; };
       quixosPackages.checkedArtifacts = context:
 let
+  pkgs = camino.packageSet { inherit nixpkgs system context; };
   contract = builtins.fromJSON (builtins.readFile context.buildContract);
   package = contract.definition.package;
   portable = builtins.filter (entry: entry.execution.kind != "remote") package.exports;
diff --git a/src/capability-language/profile.ts b/src/capability-language/profile.ts
new file mode 100644
index 0000000..5ff6c79
--- /dev/null
+++ b/src/capability-language/profile.ts
@@ -0,0 +1,5 @@
+/** Observations belong in logs, never in content-addressed compiler outputs. */
+export const profile = (phase: string, started: number, details: Record<string, unknown> = {}) => {
+  if (process.env.QUIXOS_TRACE_PROFILE === "1")
+    console.error(`[qx-profile] ${JSON.stringify({ phase, ms: Math.round(performance.now() - started), ...details })}`);
+};
diff --git a/src/capability-language/resource-cli.ts b/src/capability-language/resource-cli.ts
index 836419a..4f40494 100644
--- a/src/capability-language/resource-cli.ts
+++ b/src/capability-language/resource-cli.ts
@@ -6,11 +6,12 @@ import { bindingSchema } from "../bindings/index.js";
 import { compileCapabilityResourceRepository, type ResolvedCapabilityResource } from "./assembly.js";
 import { createGitCapabilityResolver } from "./git-resolver.js";
 import { loadQueryGenerator } from "./query-generator.js";
+import { loadCheckedResources } from "./checked-resources.js";
 
 const usage = `usage: quixos-resource-compile --root DIRECTORY --kind interface|package|build
        --repository URL --commit GIT_REV --checkout-root DIRECTORY
        [--snapshot-map PATH] [--snapshot-only true] [--graph-out PATH] [--schema-out PATH]
-       [--query-generator BUILD_MODULE_PATH]
+       [--query-generator BUILD_MODULE_PATH] [--checked-resources NIX_MAP]
 
 Resolves a standalone resource's recursive dependency-lock graph, validates
 its interface.qx or package.qx manifest, and emits the checked resource as JSON.`;
@@ -33,6 +34,7 @@ const parseArgs = (args: string[]) => {
         "--graph-out",
         "--schema-out",
         "--query-generator",
+        "--checked-resources",
       ].includes(key) ||
       values.has(key)
     )
@@ -69,6 +71,7 @@ const parseArgs = (args: string[]) => {
     graphOut: values.get("--graph-out"),
     schemaOut: values.get("--schema-out"),
     queryGenerator: values.get("--query-generator"),
+    checkedResources: values.get("--checked-resources"),
   } as const;
 };
 
@@ -111,6 +114,7 @@ const main = async () => {
     },
     resolveResource,
     generateQueries: await loadQueryGenerator(options.queryGenerator),
+    checkedResource: await loadCheckedResources(options.checkedResources),
   });
   if (options.graphOut) {
     await writeFile(
diff --git a/src/capability-language/workspace-cli.ts b/src/capability-language/workspace-cli.ts
index 18b2ec5..1159d8c 100644
--- a/src/capability-language/workspace-cli.ts
+++ b/src/capability-language/workspace-cli.ts
@@ -5,6 +5,8 @@ import process from "node:process";
 import { compileWorkspaceRepository } from "./assembly.js";
 import { createGitCapabilityResolver } from "./git-resolver.js";
 import { loadQueryGenerator } from "./query-generator.js";
+import { loadCheckedResources } from "./checked-resources.js";
+import { profile } from "./profile.js";
 import { compileExecutionPlan, packageBuildContexts } from "../execution-world/index.js";
 import { bindingSchema, specializeBindingSchema } from "../bindings/index.js";
 import {
@@ -18,7 +20,7 @@ const usage = `usage: quixos-workspace-compile --root DIRECTORY --checkout-root
        [--snapshot-map PATH] [--graph-out PATH] [--workspace-id ID] [--workspace-revision-id ID]
        [--source-root-commit GIT_REV] [--baseline PLAN_JSON] [--evolution-out PATH]
        [--reviews REVIEW_JSON] [--schemas-out PATH] [--execution-plan-out PATH] [--build-contexts-out PATH]
-       [--query-generator BUILD_MODULE_PATH]
+       [--query-generator BUILD_MODULE_PATH] [--checked-resources NIX_MAP]
 
 Resolves a workspace's recursive resource-lock graph, clones every exact
 resource revision, validates standalone interface/package manifests, and emits
@@ -50,6 +52,7 @@ const parseArgs = (args: string[]) => {
     evolutionOut: values.get("--evolution-out"),
     reviews: values.get("--reviews"),
     queryGenerator: values.get("--query-generator"),
+    checkedResources: values.get("--checked-resources"),
   };
 };
 
@@ -63,6 +66,7 @@ const main = async () => {
     checkoutRoot: options.checkoutRoot,
     snapshotMap: options.snapshotMap,
   });
+  const assemblyStarted = performance.now();
   const assembled = await compileWorkspaceRepository({
     rootDirectory: options.rootDirectory,
     workspaceId: options.workspaceId,
@@ -70,7 +74,9 @@ const main = async () => {
     sourceRootCommit: options.sourceRootCommit,
     resolveResource,
     generateQueries: await loadQueryGenerator(options.queryGenerator),
+    checkedResource: await loadCheckedResources(options.checkedResources),
   });
+  profile("workspace-assembly", assemblyStarted, { resources: assembled.resources.length });
 
   if (options.graphOut) {
     await writeFile(
@@ -110,12 +116,15 @@ const main = async () => {
   }
   const candidate = { ...assembled.workspace, executionContracts: runtimeContracts(assembled.workspace) };
   if (options.executionPlanOut || options.buildContextsOut) {
+    const executionStarted = performance.now();
     const plan = compileExecutionPlan(assembled.workspace);
     if (options.executionPlanOut) await writeFile(options.executionPlanOut, `${JSON.stringify(plan, null, 2)}\n`);
     if (options.buildContextsOut)
       await writeFile(options.buildContextsOut, JSON.stringify(packageBuildContexts(plan.definition.bindingSchema)));
+    profile("execution-plan-and-contexts", executionStarted);
   }
   if (options.schemasOut) {
+    const schemasStarted = performance.now();
     const schemas: Record<string, unknown> = {};
     for (const node of assembled.capabilityResources.filter((entry) => entry.kind === "package")) {
       const closure = new Map<string, typeof node>();
@@ -133,6 +142,7 @@ const main = async () => {
       );
     }
     await writeFile(options.schemasOut, JSON.stringify(schemas));
+    profile("package-schemas", schemasStarted);
   }
   if (options.evolutionOut) {
     const baseline = options.baseline
diff --git a/test/capability-assembly.test.ts b/test/capability-assembly.test.ts
index c147e19..33a16b1 100644
--- a/test/capability-assembly.test.ts
+++ b/test/capability-assembly.test.ts
@@ -107,6 +107,35 @@ package Runtime id "package:runtime" revision "package:runtime@1" {
   assert.equal(resource.resource.kind, "package");
   assert.equal(resource.resources.length, 2);
   assert.equal(resource.directResources.size, 1);
+
+  const checked = new Map(result.resources.map((node) => [node.key, node.resource]));
+  let generated = 0;
+  const reused = await compileWorkspaceRepository({
+    rootDirectory: root,
+    resolveResource: async (source, kind) => ({
+      directory: directories.get(`${kind}\0${source.repository}\0${source.commit}`)!,
+    }),
+    checkedResource: async (kind, source) => {
+      const value = checked.get(`${kind}\0${source.repository}\0${source.commit}`);
+      return value?.kind === "build" ? undefined : value;
+    },
+    generateQueries: async () => {
+      generated++;
+      return { queries: [], documents: new Map() };
+    },
+  });
+  assert.deepEqual(reused, result, "Nix-composed resource checks preserve full assembly results");
+  assert.equal(generated, 0, "unchanged checked packages do not run their query frontend again");
+  await assert.rejects(
+    compileWorkspaceRepository({
+      rootDirectory: root,
+      resolveResource: async (source, kind) => ({
+        directory: directories.get(`${kind}\0${source.repository}\0${source.commit}`)!,
+      }),
+      checkedResource: async () => (resource.resource.kind === "build" ? undefined : resource.resource),
+    }),
+    /Checked resource identity mismatch/,
+  );
 });
 
 test("resource repositories cannot own workspace Quixos selection policy", async (context) => {
@@ -249,19 +278,48 @@ test("resource-owned fragment imports compile through the locked package closure
  }`,
   );
   await writeFile(path.join(dirs.screen!, "screen.graphql"), "query Screen {root {...Row}}");
-  const result = await compileCapabilityResourceRepository({
+  const options = {
     rootDirectory: dirs.screen!,
-    kind: "package",
-    source: { resolver: "git", repository: "https://example.test/screen.git", commit: packageCommit },
-    resolveResource: async (source) => {
+    kind: "package" as const,
+    source: { resolver: "git" as const, repository: "https://example.test/screen.git", commit: packageCommit },
+    resolveResource: async (source: { repository: string }) => {
       const name = new URL(source.repository).pathname.slice(1, -4);
       assert.ok(dirs[name], name);
       return { directory: dirs[name]! };
     },
-  });
+  };
+  const result = await compileCapabilityResourceRepository(options);
   assert.equal(result.resource.kind, "package");
   if (result.resource.kind !== "package") throw Error("expected package");
   const view = result.resource.revision.checkedQueries!.find((q) => q.declaration.id === "view")!;
   assert.equal(view.selection[0]!.selection[0]!.fragmentSpread?.package, "rows@1");
   assert.equal(result.resources.length, 3);
+  const checked = new Map(result.resources.map((node) => [node.key, node.resource]));
+  let generated = 0;
+  const reused = await compileCapabilityResourceRepository({
+    ...options,
+    checkedResource: async (kind, source) => {
+      if (source.repository === options.source.repository) return undefined;
+      const resource = checked.get(`${kind}\0${source.repository}\0${source.commit}`);
+      return resource?.kind === "build" ? undefined : resource;
+    },
+    generateQueries: async () => {
+      generated++;
+      return { queries: [], documents: new Map() };
+    },
+  });
+  assert.deepEqual(reused, result, "cached imported fragments and full checking produce identical contracts");
+  assert.equal(generated, 1, "only the uncached package checks its queries");
+  await writeFile(path.join(dirs.screen!, "screen.graphql"), "query Screen {root {unknownField}}");
+  await assert.rejects(
+    compileCapabilityResourceRepository({
+      ...options,
+      source: { ...options.source, commit: "5".repeat(40) },
+      checkedResource: async (kind, source) => {
+        const resource = checked.get(`${kind}\0${source.repository}\0${source.commit}`);
+        return resource?.kind === "build" ? undefined : resource;
+      },
+    }),
+    /unknownField/,
+  );
 });