diff --git a/packages/paperclip-runner/src/drivers/acpx/claude-effort.test.ts b/packages/paperclip-runner/src/drivers/acpx/claude-effort.test.ts
index 6c5a9b8fcf1..e21cd094851 100644
--- a/packages/paperclip-runner/src/drivers/acpx/claude-effort.test.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/claude-effort.test.ts
@@ -5,7 +5,7 @@ const response = (value: string, sessionId?: string) => ({ ...(sessionId ? { ses
 function loaded(method = "session/new") {
   const admission = createClaudeEffortAdmission("high");
   const guard = admission.createGuard();
-  guard("outbound", { id: 1, method, params: method === "session/load" ? { sessionId: "s" } : {} });
+  guard("outbound", { id: 1, method, params: method === "session/new" ? {} : { sessionId: "s" } });
   guard("inbound", { id: 1, result: response("medium", method === "session/new" ? "s" : undefined) });
   return { admission, guard };
 }
@@ -23,17 +23,37 @@ describe("Claude effort admission", () => {
     expect(() => resolveClaudeEffort("pi", "high")).toThrow("only supported");
     expect(() => admittedClaudeEffort("claude", "high", { claudeEffort: "high" }, { claudeEffort: "medium" })).toThrow("differs");
   });
-  it.each(["session/new", "session/load"])("requires acknowledged effort before prompting after %s", method => {
+  it.each(["session/new", "session/load", "session/resume"])("requires acknowledged effort before prompting after %s", method => {
     const { admission, guard } = loaded(method);
     expect(admission.isReady()).toBe(false);
     select(guard);
     expect(admission.isReady()).toBe(true);
     expect(() => guard("outbound", { id: 3, method: "session/prompt", params: { sessionId: "s" } })).not.toThrow();
   });
+
+  it("rejects a resumed session with missing effort configuration", () => {
+    const admission = createClaudeEffortAdmission("high");
+    const guard = admission.createGuard();
+    guard("outbound", { id: 1, method: "session/resume", params: { sessionId: "s" } });
+    expect(() => guard("inbound", { id: 1, result: {} })).toThrow("missing or ambiguous");
+  });
   it("blocks a prompt based only on a restored default", () => {
     const { guard } = loaded("session/load");
     expect(() => guard("outbound", { id: 3, method: "session/prompt", params: { sessionId: "s" } })).toThrow("does not acknowledge");
   });
+
+  it("requires the bound effort acknowledgement on each cold connection", () => {
+    const { admission, guard } = loaded();
+    select(guard);
+    const resumed = admission.createGuard();
+    resumed("outbound", { id: 4, method: "session/load", params: { sessionId: "s" } });
+    expect(() => resumed("outbound", { id: 5, method: "session/prompt", params: { sessionId: "s" } })).toThrow("does not acknowledge");
+    const fresh = loaded(); select(fresh.guard);
+    const acknowledged = fresh.admission.createGuard();
+    acknowledged("outbound", { id: 4, method: "session/load", params: { sessionId: "s" } });
+    acknowledged("inbound", { id: 4, result: response("high") });
+    expect(() => acknowledged("outbound", { id: 5, method: "session/prompt", params: { sessionId: "s" } })).not.toThrow();
+  });
   it("rejects a provider that ignores the requested effort", () => {
     const { guard } = loaded();
     expect(() => select(guard, "medium")).toThrow("did not apply");
diff --git a/packages/paperclip-runner/src/drivers/acpx/config-admission.ts b/packages/paperclip-runner/src/drivers/acpx/config-admission.ts
index dfe8806ae2a..be597f10e16 100644
--- a/packages/paperclip-runner/src/drivers/acpx/config-admission.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/config-admission.ts
@@ -41,11 +41,11 @@ export function createAcpxConfigAdmission(expected: string, options: { label: st
             if (method === "session/prompt") {
               assertReady();
               if (params.sessionId !== state.sessionId) throw failure("prompt belongs to a different session");
-            } else if (method === "session/new" || method === "session/load" || method === "session/set_config_option") {
+            } else if (method === "session/new" || method === "session/load" || method === "session/resume" || method === "session/set_config_option") {
               if (typeof message.id !== "string" && typeof message.id !== "number") throw failure("uncorrelated mode request");
               if (pending.has(message.id)) throw failure("duplicate mode request identity");
               if (pending.size) throw failure("overlapping native admission controls");
-              if (method === "session/new" || method === "session/load") {
+              if (method === "session/new" || method === "session/load" || method === "session/resume") {
                 if (pending.size) throw failure("overlapping session admission");
                 state.sessionId = null; state.mode = null;
               } else {
diff --git a/packages/paperclip-runner/src/drivers/acpx/runtime-sandbox.test.ts b/packages/paperclip-runner/src/drivers/acpx/runtime-sandbox.test.ts
index ab14aa666f3..7225231f2aa 100644
--- a/packages/paperclip-runner/src/drivers/acpx/runtime-sandbox.test.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/runtime-sandbox.test.ts
@@ -119,6 +119,20 @@ describe("ACPX runtime sandbox", () => {
     }
   });
 
+  it("restores bound Claude effort in private settings across cold connections", async () => {
+    const fixture = await sandboxFixture("claude");
+    for (const claudeEffort of ["high", "xhigh", "max"] as const) {
+      const binding = { ...fixture.binding, claudeEffort };
+      for (let attempt = 0; attempt < 2; attempt += 1) {
+        const sandbox = await prepareAcpxRuntimeSandbox({ binding, agent: "claude" });
+        const settings = JSON.parse(await readFile(join(sandbox.agentHomeDirectory, "settings.json"), "utf8"));
+        expect(settings.effortLevel).toBe(claudeEffort);
+      }
+    }
+    const sandbox = await prepareAcpxRuntimeSandbox({ binding: fixture.binding, agent: "claude" });
+    expect(JSON.parse(await readFile(join(sandbox.agentHomeDirectory, "settings.json"), "utf8"))).not.toHaveProperty("effortLevel");
+  });
+
   it.each([
     ["pi", "OPENROUTER_API_KEY", "pi-home"],
     ["claude", "ANTHROPIC_API_KEY", "claude-home"],
diff --git a/packages/paperclip-runner/src/drivers/acpx/runtime-sandbox.ts b/packages/paperclip-runner/src/drivers/acpx/runtime-sandbox.ts
index 3e0e52d250d..d5ae8ce9e14 100644
--- a/packages/paperclip-runner/src/drivers/acpx/runtime-sandbox.ts
+++ b/packages/paperclip-runner/src/drivers/acpx/runtime-sandbox.ts
@@ -403,6 +403,10 @@ export async function prepareAcpxRuntimeSandbox(input: {
       `${JSON.stringify({
         model: input.binding.requestedModel,
         availableModels: [input.binding.requestedModel],
+        // Claude reloads effort from settings on a new ACP connection. Keep
+        // the bound choice available during model verification and resume;
+        // the protocol guard still requires a provider acknowledgement.
+        ...(input.binding.claudeEffort ? { effortLevel: input.binding.claudeEffort } : {}),
         ...((input.binding.permissionMode === "approve-reads" || input.binding.permissionMode === "approve-paperclip")
           ? { permissions: { allow: claudePaperclipPermissionRules(input.tools ?? [], input.binding.permissionMode) } }
           : {}),
diff --git a/server/src/adapters/registry.ts b/server/src/adapters/registry.ts
index 5789821b052..bf6a6dcd746 100644
--- a/server/src/adapters/registry.ts
+++ b/server/src/adapters/registry.ts
@@ -501,19 +501,19 @@ const paperclipRunnerAdapter: ServerAdapterModule = {
   models: [
     ...codexModels,
     { id: DEFAULT_OPENCODE_RUNNER_MODEL, label: "OpenRouter · DeepSeek V4 Flash 0731" },
-    { id: DEFAULT_ACPX_RUNNER_MODELS.claude, label: "Claude Sonnet 5" },
+    { id: DEFAULT_ACPX_RUNNER_MODELS.claude, label: "Claude Opus 5.5" },
     { id: "global.anthropic.claude-sonnet-4-6", label: "Amazon Bedrock · Claude Sonnet 4.6 (global)" },
   ],
   listModels: async () => [
     ...await listCodexModels(),
     { id: DEFAULT_OPENCODE_RUNNER_MODEL, label: "OpenRouter · DeepSeek V4 Flash 0731" },
-    { id: DEFAULT_ACPX_RUNNER_MODELS.claude, label: "Claude Sonnet 5" },
+    { id: DEFAULT_ACPX_RUNNER_MODELS.claude, label: "Claude Opus 5.5" },
     { id: "global.anthropic.claude-sonnet-4-6", label: "Amazon Bedrock · Claude Sonnet 4.6 (global)" },
   ],
   refreshModels: async () => [
     ...await refreshCodexModels(),
     { id: DEFAULT_OPENCODE_RUNNER_MODEL, label: "OpenRouter · DeepSeek V4 Flash 0731" },
-    { id: DEFAULT_ACPX_RUNNER_MODELS.claude, label: "Claude Sonnet 5" },
+    { id: DEFAULT_ACPX_RUNNER_MODELS.claude, label: "Claude Opus 5.5" },
     { id: "global.anthropic.claude-sonnet-4-6", label: "Amazon Bedrock · Claude Sonnet 4.6 (global)" },
   ],
   supportsLocalAgentJwt: false,
diff --git a/server/src/services/heartbeat/runtime-selection.ts b/server/src/services/heartbeat/runtime-selection.ts
index 804b983940a..5e5b41b940c 100644
--- a/server/src/services/heartbeat/runtime-selection.ts
+++ b/server/src/services/heartbeat/runtime-selection.ts
@@ -696,7 +696,7 @@ export async function selectHeartbeatRuntime(db: Db, input: HeartbeatRuntimeSele
       });
       getNativeFreshSessionHandoff = nativeReviewRequest ? undefined : getFreshSessionHandoff;
       const nativeProviderConfig = nativeRuntimeResolution.profile.backend === "codex_app_server"
-        || (nativeRuntimeResolution.profile.backend === "acpx_runtime" && nativeRuntimeResolution.profile.provider === "acpx" && nativeRuntimeResolution.profile.acpxAgent === "claude")
+        || (nativeRuntimeResolution.profile.backend === "acpx_runtime" && parseObject(agent.adapterConfig).provider === "acpx" && parseObject(agent.adapterConfig).acpxAgent === "claude")
         || nativeRuntimeResolution.profile.backend === "opencode_server"
         ? projectPaperclipRunnerTaskConfig(
             nativeRuntimeResolution.profile.backend,