fix(server): force Claude 200k context when selected/(default)

apps/server/src/provider/Layers/ClaudeAdapter.test.ts

@@ -156,6 +156,7 @@ function makeHarness(config?: {
   readonly baseDir?: string;
   readonly claudeConfig?: Partial<ClaudeSettings>;
   readonly instanceId?: ProviderInstanceId;
+  readonly environment?: NodeJS.ProcessEnv;
 }) {
   const query = new FakeClaudeQuery();
   let createInput:
@@ -167,6 +168,7 @@ function makeHarness(config?: {
 
   const adapterOptions: ClaudeAdapterLiveOptions = {
     ...(config?.instanceId ? { instanceId: config.instanceId } : {}),
+    ...(config?.environment ? { environment: config.environment } : {}),
     createQuery: (input) => {
       createInput = input;
       return query;
@@ -380,6 +382,79 @@ describe("ClaudeAdapterLive", () => {
     );
   });
 
+  it.effect("disables Claude Code automatic 1M context when Claude context window is 200k", () => {
+    const harness = makeHarness();
+    return Effect.gen(function* () {
+      const adapter = yield* ClaudeAdapter;
+      yield* adapter.startSession({
+        threadId: THREAD_ID,
+        provider: ProviderDriverKind.make("claudeAgent"),
+        modelSelection: createModelSelection(
+          ProviderInstanceId.make("claudeAgent"),
+          "claude-opus-4-6",
+          [{ id: "contextWindow", value: "200k" }],
+        ),
+        runtimeMode: "full-access",
+      });
+
+      const createInput = harness.getLastCreateQueryInput();
+      assert.equal(createInput?.options.model, "claude-opus-4-6");
+      assert.equal(createInput?.options.env?.CLAUDE_CODE_DISABLE_1M_CONTEXT, "1");
+    }).pipe(
+      Effect.provideService(Random.Random, makeDeterministicRandomService()),
+      Effect.provide(harness.layer),
+    );
+  });
+
+  it.effect("uses 200k as T3 Code's default Claude context window", () => {
+    const harness = makeHarness();
+    return Effect.gen(function* () {
+      const adapter = yield* ClaudeAdapter;
+      yield* adapter.startSession({
+        threadId: THREAD_ID,
+        provider: ProviderDriverKind.make("claudeAgent"),
+        modelSelection: createModelSelection(
+          ProviderInstanceId.make("claudeAgent"),
+          "claude-opus-4-6",
+        ),
+        runtimeMode: "full-access",
+      });
+
+      const createInput = harness.getLastCreateQueryInput();
+      assert.equal(createInput?.options.model, "claude-opus-4-6");
+      assert.equal(createInput?.options.env?.CLAUDE_CODE_DISABLE_1M_CONTEXT, "1");
+    }).pipe(
+      Effect.provideService(Random.Random, makeDeterministicRandomService()),
+      Effect.provide(harness.layer),
+    );
+  });
+
+  it.effect("allows explicit Claude 1M context even when the process env disables it", () => {
+    const harness = makeHarness({
+      environment: { CLAUDE_CODE_DISABLE_1M_CONTEXT: "1" },
+    });
+    return Effect.gen(function* () {
+      const adapter = yield* ClaudeAdapter;
+      yield* adapter.startSession({
+        threadId: THREAD_ID,
+        provider: ProviderDriverKind.make("claudeAgent"),
+        modelSelection: createModelSelection(
+          ProviderInstanceId.make("claudeAgent"),
+          "claude-opus-4-6",
+          [{ id: "contextWindow", value: "1m" }],
+        ),
+        runtimeMode: "full-access",
+      });
+
+      const createInput = harness.getLastCreateQueryInput();
+      assert.equal(createInput?.options.model, "claude-opus-4-6[1m]");
+      assert.equal(createInput?.options.env?.CLAUDE_CODE_DISABLE_1M_CONTEXT, undefined);
+    }).pipe(
+      Effect.provideService(Random.Random, makeDeterministicRandomService()),
+      Effect.provide(harness.layer),
+    );
+  });
+
   it.effect("runs Claude SDK sessions with the configured Claude HOME", () => {
     const harness = makeHarness({ claudeConfig: { homePath: "~/.claude-work" } });
     return Effect.gen(function* () {

apps/server/src/provider/Layers/ClaudeAdapter.ts

@@ -47,6 +47,7 @@ import {
 import {
   applyClaudePromptEffortPrefix,
   getModelSelectionBooleanOptionValue,
+  getProviderOptionCurrentValue,
   getModelSelectionStringOptionValue,
   getProviderOptionDescriptors,
   resolvePromptInjectedEffort,
@@ -260,6 +261,35 @@ function getEffectiveClaudeAgentEffort(effort: string | null | undefined): Claud
   return normalized ? (normalized as ClaudeSdkEffort) : null;
 }
 
+function resolveClaudeOneMillionContextDisabled(
+  descriptors: ReadonlyArray<ReturnType<typeof getProviderOptionDescriptors>[number]>,
+): boolean | undefined {
+  const contextWindowDescriptor = descriptors.find(
+    (descriptor) => descriptor.type === "select" && descriptor.id === "contextWindow",
+  );
+  if (!contextWindowDescriptor) {
+    return undefined;
+  }
+  return getProviderOptionCurrentValue(contextWindowDescriptor) !== "1m";
+}
+
+function withClaudeContextWindowEnvironment(
+  env: NodeJS.ProcessEnv,
+  oneMillionContextDisabled: boolean | undefined,
+): NodeJS.ProcessEnv {
+  if (oneMillionContextDisabled === true) {
+    return {
+      ...env,
+      CLAUDE_CODE_DISABLE_1M_CONTEXT: "1",
+    };
+  }
+  if (oneMillionContextDisabled === false) {
+    const { CLAUDE_CODE_DISABLE_1M_CONTEXT: _unused, ...rest } = env;
+    return rest;
+  }
+  return env;
+}
+
 function isClaudeInterruptedMessage(message: string): boolean {
   const normalized = message.toLowerCase();
   return (
@@ -2871,10 +2901,14 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
       const modelSelection =
         input.modelSelection?.instanceId === boundInstanceId ? input.modelSelection : undefined;
       const caps = getClaudeModelCapabilities(modelSelection?.model);
-      const descriptors = getProviderOptionDescriptors({ caps });
+      const descriptors = getProviderOptionDescriptors({
+        caps,
+        selections: modelSelection?.options,
+      });
       const apiModelId = modelSelection ? resolveClaudeApiModelId(modelSelection) : undefined;
       const rawEffort = getModelSelectionStringOptionValue(modelSelection, "effort");
       const effort = resolveClaudeEffort(caps, rawEffort) ?? null;
+      const oneMillionContextDisabled = resolveClaudeOneMillionContextDisabled(descriptors);
       const fastModeSupported = descriptors.some(
         (descriptor) => descriptor.type === "boolean" && descriptor.id === "fastMode",
       );
@@ -2919,7 +2953,7 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
         ...(newSessionId ? { sessionId: newSessionId } : {}),
         includePartialMessages: true,
         canUseTool,
-        env: claudeEnvironment,
+        env: withClaudeContextWindowEnvironment(claudeEnvironment, oneMillionContextDisabled),
         ...(input.cwd ? { additionalDirectories: [input.cwd] } : {}),
         ...(Object.keys(extraArgs).length > 0 ? { extraArgs } : {}),
       };
@@ -2946,6 +2980,7 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
         "claude.query.setting_sources": [...CLAUDE_SETTING_SOURCES],
         "claude.query.settings_json": encodeJsonStringForDiagnostics(settings) ?? "",
         "claude.query.extra_args_json": encodeJsonStringForDiagnostics(extraArgs) ?? "",
+        "claude.query.one_million_context_disabled": oneMillionContextDisabled ?? "",
         "claude.query.path_to_executable": claudeBinaryPath,
       });