fix(native): name the model choice when a provider rejects the model on a turn

Claude (ACPX) opens the provider session and then rejects an unknown
model on the first turn. The run is native_provider_model_rejected, but
its recovery action told the board to "explicitly resolve the ambiguous
session state", because the startup choose-model action applied only
when no provider session was established. Give a rejected model the
choose-model next action in that case too.

Co-Authored-By: Claude <noreply@anthropic.com>

server/src/services/native-runtime/native-session-executor.ts

@@ -8210,6 +8210,11 @@ const NATIVE_PROVIDER_STATE_INCOMPATIBLE_ACTION =
 const NATIVE_STARTUP_MODEL_REJECTED_ACTION =
   "The provider could not start the selected model before any provider work began. Choose a supported model for this agent, then retry the task. Automatic retries are stopped.";
 
+// The provider session opened, then the provider refused the selected model on
+// the turn. The task needs a model choice, not a reconciliation of session state.
+const NATIVE_TURN_MODEL_REJECTED_ACTION =
+  "The provider rejected the selected model. Choose a supported model for this agent, then retry the task. Automatic retries are stopped.";
+
 const NATIVE_CLEANUP_OPERATOR_RECOVERY_MESSAGE =
   "Send a new message to continue after Paperclip verifies that the previous provider and its tools have stopped. Clearing a task session does not resolve this quarantine. Automatic retries are stopped.";
 
@@ -11913,6 +11918,8 @@ async function executePaperclipNativeSessionAttempt(
                     ? "The work and waiting state are saved. Confirm shutdown of the retained execution and settle that same handoff without repeating provider work."
                   : sourceFailureCode === "native_provider_model_rejected" && !recoveryEvidence.providerSessionEstablished
                     ? NATIVE_STARTUP_MODEL_REJECTED_ACTION
+                  : sourceFailureCode === "native_provider_model_rejected"
+                    ? NATIVE_TURN_MODEL_REJECTED_ACTION
                   : sourceFailureCode === NATIVE_PROVIDER_STATE_INCOMPATIBLE
                     ? NATIVE_PROVIDER_STATE_INCOMPATIBLE_ACTION
                   : sourceFailureCode === NATIVE_PROVIDER_SIDE_EFFECT_PENDING
@@ -12170,6 +12177,8 @@ async function executePaperclipNativeSessionAttempt(
                 ? "Verify that the failed provider stopped and reconcile its action outcomes. A linked continuation can proceed only after these checks succeed."
               : sourceFailureCode === "native_provider_model_rejected" && !recoveryEvidence.providerSessionEstablished
                 ? NATIVE_STARTUP_MODEL_REJECTED_ACTION
+              : sourceFailureCode === "native_provider_model_rejected"
+                ? NATIVE_TURN_MODEL_REJECTED_ACTION
               : sourceFailureCode === NATIVE_PROVIDER_STATE_INCOMPATIBLE
                 ? NATIVE_PROVIDER_STATE_INCOMPATIBLE_ACTION
               : sourceFailureCode === NATIVE_PROVIDER_SIDE_EFFECT_PENDING

server/src/services/native-runtime/native-startup-retry.integration.test.ts

@@ -33,7 +33,7 @@ import { executePaperclipNativeSession, prepareNativeSessionOpenTimeoutRetry, sc
 import { buildNativeCompletionContract } from "./completion-contracts.js";
 import { prepareNativeHeartbeatRun } from "./prepare-native-run.js";
 import { claimNativeSessionResumptions } from "./native-finalization-reconciler.js";
-import { DurablePrpControlPlane } from "../../vendor/paperclip-runner/index.js";
+import { DurablePrpControlPlane, NativeProviderTerminalFailure } from "../../vendor/paperclip-runner/index.js";
 import { createNativeRunnerExecutionDriver } from "./native-runner-execution-driver.js";
 import { currentNativeControllerIdentity } from "./native-restart-recovery.js";
 import { loadNativeRunnerCheckpoint } from "./native-runner-checkpoint.js";
@@ -785,6 +785,41 @@ describe("native provider startup retry", () => {
     },
   );
 
+  it("asks for a model choice when the provider rejects the model on an opened session's turn (Claude ACPX)", async () => {
+    const seeded = await seedRun(await createAgent());
+    provider.execute.mockReset().mockImplementation(async () => {
+      await db.insert(heartbeatRunEvents).values({
+        companyId, runId: seeded.runId, agentId: seeded.agentId, seq: 900,
+        eventType: "turn.started", stream: "system",
+      });
+      // What the native runtime throws for Claude's AIR "selected model" request failure.
+      throw new NativeProviderTerminalFailure("RUNTIME", false,
+        "native_provider_model_rejected: ACP agent reported a terminal request failure.");
+    });
+    await expect(executePaperclipNativeSession({
+      db, execution: seeded.execution, runnerInstanceId: seeded.runnerInstanceId,
+      backend: {
+        descriptor: async () => { throw new Error("Unexpected provider descriptor call"); },
+        openSession: async () => { throw new Error("Unexpected provider session call"); },
+      },
+    })).rejects.toThrow("native_provider_model_rejected");
+
+    const state = await read(seeded);
+    expect(state.coordinator).toMatchObject({
+      phase: "terminal_failure",
+      failureCode: "native_provider_model_rejected",
+      nextAttemptAt: null,
+      failureDetail: expect.objectContaining({ providerSessionEstablished: true }),
+    });
+    expect(String(state.coordinator.failureDetail?.nextAction)).toContain("Choose a supported model");
+    expect(String(state.coordinator.failureDetail?.nextAction)).not.toContain("ambiguous");
+    expect(state.run).toMatchObject({ status: "failed", errorCode: "native_provider_model_rejected" });
+    expect(state.issue.status).toBe("blocked");
+    expect(state.action).toMatchObject({ ownerType: "board", cause: "native_provider_model_rejected", wakePolicy: null });
+    expect(state.action!.nextAction).toContain("Choose a supported model");
+    expect(state.action!.nextAction).not.toContain("ambiguous");
+  });
+
   it("blocks with a clear reason once the bounded startup budget is exhausted", async () => {
     const seeded = await seedRun(await createAgent());
     await failStartup(seeded, sessionOpenFailure());