diff --git a/apps/server/src/provider/Layers/ClaudeAdapter.lazy.test.ts b/apps/server/src/provider/Layers/ClaudeAdapter.lazy.test.ts
new file mode 100644
index 000000000000..be50143d93d3
--- /dev/null
+++ b/apps/server/src/provider/Layers/ClaudeAdapter.lazy.test.ts
@@ -0,0 +1,13 @@
+import { describe, expect, it, vi } from "vite-plus/test";
+
+vi.mock("@anthropic-ai/claude-agent-sdk", () => {
+  throw new Error("Claude SDK loaded eagerly.");
+});
+
+describe("ClaudeAdapter module loading", () => {
+  it("does not load the Claude SDK while importing the adapter", async () => {
+    await expect(import("./ClaudeAdapter.ts")).resolves.toMatchObject({
+      makeClaudeAdapter: expect.any(Function),
+    });
+  });
+});
diff --git a/apps/server/src/provider/Layers/ClaudeAdapter.test.ts b/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
index a45eae6faf3e..ea6410b8b01c 100644
--- a/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
+++ b/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
@@ -23,6 +23,7 @@ import {
 } from "@t3tools/contracts";
 import { createModelSelection } from "@t3tools/shared/model";
 import { assert, describe, it } from "@effect/vitest";
+import { vi } from "vite-plus/test";
 import * as Context from "effect/Context";
 import * as Effect from "effect/Effect";
 import * as Fiber from "effect/Fiber";
@@ -40,6 +41,34 @@ import type { ClaudeAdapterShape } from "../Services/ClaudeAdapter.ts";
 import { makeClaudeAdapter, type ClaudeAdapterLiveOptions } from "./ClaudeAdapter.ts";
 const decodeClaudeSettings = Schema.decodeSync(ClaudeSettings);
 
+const lazyClaudeSdk = vi.hoisted(() => {
+  let markImportStarted!: () => void;
+  let markImportFinished!: () => void;
+  let releaseImport!: () => void;
+  return {
+    importFinished: new Promise<void>((resolve) => {
+      markImportFinished = resolve;
+    }),
+    importStarted: new Promise<void>((resolve) => {
+      markImportStarted = resolve;
+    }),
+    markImportFinished: () => markImportFinished(),
+    markImportStarted: () => markImportStarted(),
+    query: vi.fn(),
+    releaseImport: () => releaseImport(),
+    waitForRelease: new Promise<void>((resolve) => {
+      releaseImport = resolve;
+    }),
+  };
+});
+
+vi.mock("@anthropic-ai/claude-agent-sdk", async () => {
+  lazyClaudeSdk.markImportStarted();
+  await lazyClaudeSdk.waitForRelease;
+  lazyClaudeSdk.markImportFinished();
+  return { query: lazyClaudeSdk.query };
+});
+
 // Test-local service tag so the rest of the file can keep using `yield* ClaudeAdapter`.
 class ClaudeAdapter extends Context.Service<ClaudeAdapter, ClaudeAdapterShape>()(
   "t3/provider/Layers/ClaudeAdapter.test/ClaudeAdapter",
@@ -1662,6 +1691,41 @@ describe("ClaudeAdapterLive", () => {
     );
   });
 
+  it.effect("does not start a Claude runtime after lazy loading is interrupted", () => {
+    const layer = Layer.effect(
+      ClaudeAdapter,
+      Effect.gen(function* () {
+        const claudeConfig = decodeClaudeSettings({});
+        return yield* makeClaudeAdapter(claudeConfig);
+      }),
+    ).pipe(
+      Layer.provideMerge(ServerConfig.layerTest("/tmp/claude-adapter-test", "/tmp")),
+      Layer.provideMerge(ServerSettingsService.layerTest()),
+      Layer.provideMerge(NodeServices.layer),
+    );
+
+    return Effect.gen(function* () {
+      const adapter = yield* ClaudeAdapter;
+      const startFiber = yield* Effect.forkChild(
+        adapter.startSession({
+          threadId: THREAD_ID,
+          provider: ProviderDriverKind.make("claudeAgent"),
+          runtimeMode: "full-access",
+        }),
+      );
+
+      yield* Effect.promise(() => lazyClaudeSdk.importStarted);
+      yield* Fiber.interrupt(startFiber);
+      lazyClaudeSdk.releaseImport();
+      yield* Effect.promise(() => lazyClaudeSdk.importFinished);
+
+      assert.equal(lazyClaudeSdk.query.mock.calls.length, 0);
+    }).pipe(
+      Effect.provideService(Random.Random, makeDeterministicRandomService()),
+      Effect.provide(layer),
+    );
+  });
+
   it.effect("keeps the session available when process close fails", () => {
     const harness = makeHarness();
     return Effect.gen(function* () {
diff --git a/apps/server/src/provider/Layers/ClaudeAdapter.ts b/apps/server/src/provider/Layers/ClaudeAdapter.ts
index d42049ebefc3..02b5ee43b9e7 100644
--- a/apps/server/src/provider/Layers/ClaudeAdapter.ts
+++ b/apps/server/src/provider/Layers/ClaudeAdapter.ts
@@ -6,19 +6,18 @@
  *
  * @module ClaudeAdapterLive
  */
-import {
-  type CanUseTool,
-  query,
-  type Options as ClaudeQueryOptions,
-  type PermissionMode,
-  type PermissionResult,
-  type PermissionUpdate,
-  type SDKMessage,
-  type SDKControlGetContextUsageResponse,
-  type SDKResultMessage,
-  type SettingSource,
-  type SDKUserMessage,
-  type ModelUsage,
+import type {
+  CanUseTool,
+  Options as ClaudeQueryOptions,
+  PermissionMode,
+  PermissionResult,
+  PermissionUpdate,
+  SDKMessage,
+  SDKControlGetContextUsageResponse,
+  SDKResultMessage,
+  SettingSource,
+  SDKUserMessage,
+  ModelUsage,
 } from "@anthropic-ai/claude-agent-sdk";
 import { parseCliArgs } from "@t3tools/shared/cliArgs";
 import {
@@ -1706,16 +1705,7 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
   const managedNativeEventLogger =
     options?.nativeEventLogger === undefined ? nativeEventLogger : undefined;
 
-  const createQuery =
-    options?.createQuery ??
-    ((input: {
-      readonly prompt: AsyncIterable<SDKUserMessage>;
-      readonly options: ClaudeQueryOptions;
-    }) =>
-      query({
-        prompt: input.prompt,
-        options: input.options,
-      }) as ClaudeQueryRuntime);
+  const createQuery = options?.createQuery;
 
   const sessions = new Map<ThreadId, ClaudeSessionContext>();
   const runtimeEventQueue = yield* Queue.unbounded<ProviderRuntimeEvent>();
@@ -4271,12 +4261,33 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
         "claude.query.path_to_executable": claudeBinaryPath,
       });
 
-      const queryRuntime = yield* Effect.try({
-        try: () =>
-          createQuery({
+      const queryRuntime = yield* Effect.tryPromise({
+        try: async (signal) => {
+          const query =
+            createQuery ??
+            (await import(/* @vite-ignore */ "@anthropic-ai/claude-agent-sdk")).query;
+          signal.throwIfAborted();
+          const runtime = query({
             prompt,
             options: queryOptions,
-          }),
+          }) as ClaudeQueryRuntime;
+          let closed = false;
+          const close = () => {
+            if (closed) return;
+            closed = true;
+            try {
+              runtime.close();
+            } catch {
+              // Interruption remains authoritative when late runtime cleanup fails.
+            }
+          };
+          signal.addEventListener("abort", close, { once: true });
+          if (signal.aborted) {
+            close();
+            signal.throwIfAborted();
+          }
+          return runtime;
+        },
         catch: (cause) =>
           new ProviderAdapterProcessError({
             provider: PROVIDER,
diff --git a/apps/server/src/provider/Layers/ClaudeProvider.ts b/apps/server/src/provider/Layers/ClaudeProvider.ts
index 806f7e19b905..5b6c7f54081a 100644
--- a/apps/server/src/provider/Layers/ClaudeProvider.ts
+++ b/apps/server/src/provider/Layers/ClaudeProvider.ts
@@ -20,12 +20,11 @@ import {
 } from "@t3tools/shared/model";
 import { resolveSpawnCommand } from "@t3tools/shared/shell";
 import { compareSemverVersions } from "@t3tools/shared/semver";
-import {
-  query as claudeQuery,
-  type Options as ClaudeQueryOptions,
-  type SlashCommand as ClaudeSlashCommand,
-  type SDKUserMessage,
-  type SettingSource,
+import type {
+  Options as ClaudeQueryOptions,
+  SlashCommand as ClaudeSlashCommand,
+  SDKUserMessage,
+  SettingSource,
 } from "@anthropic-ai/claude-agent-sdk";
 
 import {
@@ -742,6 +741,9 @@ const probeClaudeCapabilities = (
       claudeEnvironment,
     );
     return yield* Effect.tryPromise(async () => {
+      const { query: claudeQuery } = await import(
+        /* @vite-ignore */ "@anthropic-ai/claude-agent-sdk"
+      );
       const q = claudeQuery({
         // Never yield — we only need initialization data, not a conversation.
         // This prevents any prompt from reaching the Anthropic API.