Fix Qiskit Runtime Session Creation Failure

Aug 7, 2025 by Pedro Alvarez 44 views

Qiskit Runtime Session Creation Failure: No API Client Found Error

Hey guys! Ever run into that frustrating error when trying to create a Qiskit Runtime session? Specifically, the dreaded qiskit_ibm_runtime.exceptions.IBMInputValueError: 'No API client found for given instance: <my-crn>? Yeah, it's a pain, but let's break it down and figure out what's going on and how to fix it. This article dives deep into this issue, providing a comprehensive guide for anyone facing this problem.

Understanding the Bug

The core issue revolves around the Qiskit Runtime library, particularly version 0.41.0. Users have reported that they're unable to create sessions, leading to the "No API client found" error. This typically surfaces when trying to initialize a Session object within a Qiskit Runtime program. Let's explore the steps to reproduce this bug and the expected behavior to fully grasp the situation.

Reproducing the Error

To reproduce the error, follow these steps:

First, ensure you have the latest version of the runtime library installed. You can do this using pip:
```
pip install qiskit-ibm-runtime==0.41.0
```

Next, execute the following Python snippet:

from qiskit_ibm_runtime import QiskitRuntimeService, Session, EstimatorV2 as Estimator

service = QiskitRuntimeService()
backend = service.least_busy(operational=True, simulator=False)

with Session(backend=backend) as session:
    estimator = Estimator(mode=session)
    print("test")

If you encounter the bug, you'll see an error message similar to the following:

Traceback (most recent call last):
  File "/home/paulschw/ai/qiskit-studio/coderun-agent/demos/test.py", line 7, in <module>
    with Session(backend=backend) as session:
         ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/paulschw/ai/qiskit-studio/coderun-agent/demos/venv/lib64/python3.12/site-packages/qiskit_ibm_runtime/session.py", line 132, in __init__
    self._session_id = self._create_session(create_new=create_new)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/paulschw/ai/qiskit-studio/coderun-agent/demos/venv/lib64/python3.12/site-packages/qiskit_ibm_runtime/session.py", line 137, in _create_session
    session = self._service._get_api_client(self._instance).create_session(
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/paulschw/ai/qiskit-studio/coderun-agent/demos/venv/lib64/python3.12/site-packages/qiskit_ibm_runtime/qiskit_runtime_service.py", line 390, in _get_api_client
    raise IBMInputValueError(f"No API client found for given instance: {instance}")
qiskit_ibm_runtime.exceptions.IBMInputValueError: 'No API client found for given instance: <my-crn>'

Expected Behavior

In contrast, if the code runs correctly, it should execute without errors and print "test" to the console. This is what happens with version 0.40.1 of the qiskit-ibm-runtime library. To illustrate:

$ python test.py
test

The discrepancy between versions highlights a potential issue introduced in version 0.41.0, making it crucial to understand the underlying cause and find a resolution. This detailed explanation of the bug and its reproduction helps users quickly identify if they are facing the same problem and sets the stage for exploring solutions.

Diving Deeper: Root Cause Analysis

Okay, so we know the bug exists in version 0.41.0, but why? Let's put on our detective hats and dig into the potential root causes. Understanding the cause is half the battle, guys! By pinpointing the exact changes that triggered this issue, we can better address it and prevent similar problems in the future.

Investigating Changes Since v0.40.1

A good starting point is to compare the changes between version 0.40.1 and 0.41.0. Thankfully, the Qiskit team maintains a public repository on GitHub, making it easy to see the differences. A quick look at the comparison (https://github.com/Qiskit/qiskit-ibm-runtime/compare/0.40.1...0.41.0) reveals a number of commits. We need to sift through these changes, looking for anything that might affect API client initialization or session creation.

Potential Culprits

Several areas could be the source of the problem. Here are a few possibilities:

API Client Initialization: The way the QiskitRuntimeService initializes and manages API clients might have changed. A faulty initialization process could explain why the client isn't found when creating a session.
Session Creation Logic: The Session class's internal logic for creating sessions, particularly the _create_session method, is another area to scrutinize. If this method is failing to properly connect to the API, it would lead to the observed error.
Instance Handling: The way the service handles different instances (specified by the <my-crn> in the error message) might be problematic. If the service can't correctly identify or access the specified instance, it won't be able to create an API client for it.
Authentication Mechanisms: Changes in authentication methods or the handling of credentials could also be a factor. If the service can't authenticate properly, it won't be able to establish an API client.

Focusing on Key Changes

While a full code review is beyond the scope of this article, we can highlight some key areas to focus on:

Any changes to the QiskitRuntimeService._get_api_client method, as this is directly mentioned in the traceback.
Modifications to the Session._create_session method and related session management code.
Updates to the configuration and handling of instances, especially concerning the <my-crn> identifier.

By narrowing down the potential causes, we can better target our efforts in finding a solution. The next section will explore some concrete steps you can take to address this issue and get your Qiskit Runtime sessions up and running.

Solutions and Workarounds

Alright, let's get practical. We've identified the bug and explored potential causes. Now, what can you actually do about it? Here are some solutions and workarounds to get you back on track, coding those quantum circuits. These solutions range from simple fixes to more involved approaches, so you should be able to find something that works for your situation.

1. Downgrading to v0.40.1

The quickest and often most reliable workaround is to simply revert to the previous version of the qiskit-ibm-runtime library, where the issue doesn't exist. You can do this using pip:

pip install qiskit-ibm-runtime==0.40.1

This is a temporary fix, but it allows you to continue working while the underlying issue is being addressed. It's a good idea to keep an eye on future releases and patch notes to know when the bug is officially resolved.

2. Verifying Qiskit Runtime Service Configuration

Sometimes, the issue isn't a bug in the library itself, but rather a configuration problem. Double-check your QiskitRuntimeService setup to ensure everything is correctly configured. This includes:

Credentials: Make sure your IBM Quantum credentials are correctly set up. You might need to re-authenticate or check your API token.
Instance Configuration: Verify that the instance you're trying to use (the <my-crn> mentioned in the error) is correctly configured and accessible.
Service URL: Ensure that the service URL is correct and that you can reach the Qiskit Runtime service.

Here's a basic example of how you might configure the service:

from qiskit_ibm_runtime import QiskitRuntimeService

service = QiskitRuntimeService(
    channel="ibm_quantum",  # Or your specific channel
    instance="<your-instance-crn>",  # Replace with your instance CRN
    token="YOUR_API_TOKEN",  # Replace with your API token
)

Double-checking these configurations can often resolve the "No API client found" error.

3. Investigating Environment Variables

Qiskit Runtime often relies on environment variables for configuration. Make sure that any necessary environment variables, such as QISKIT_IBM_TOKEN or QISKIT_IBM_INSTANCE, are correctly set in your environment. Incorrect or missing environment variables can lead to the service failing to initialize the API client.

4. Checking for Conflicting Packages

In some cases, conflicts with other installed packages can cause unexpected behavior. Try creating a fresh virtual environment and installing only the necessary Qiskit packages. This can help isolate whether a conflict is the root cause.

python -m venv .venv
source .venv/bin/activate  # On Linux/macOS
.venv\Scripts\activate  # On Windows
pip install qiskit-ibm-runtime==0.41.0

If the error disappears in the new environment, it's likely a package conflict. You can then start adding back your other packages one by one to identify the culprit.

5. Reporting the Issue

If none of the above solutions work, it's crucial to report the issue to the Qiskit community. This helps the developers understand the problem and work on a fix. You can report the issue on the Qiskit GitHub repository (https://github.com/Qiskit/qiskit-ibm-runtime/issues).

When reporting, provide as much detail as possible, including:

Your Qiskit version
Python version
Operating system
The code snippet that reproduces the error
The full traceback
Any steps you've already taken to try to resolve the issue

By providing comprehensive information, you increase the chances of the developers quickly identifying and fixing the bug.

6. Monitoring Qiskit Release Notes

Keep an eye on the Qiskit release notes for updates and bug fixes. The Qiskit team is active in addressing issues, and a fix for this problem might be included in a future release. Regularly checking the release notes will help you know when to update your library.

These solutions and workarounds should give you a good starting point for tackling the "No API client found" error. Remember to systematically try each approach and provide detailed feedback if you encounter any issues. By working together, we can help make Qiskit Runtime a more robust and reliable platform for quantum computing.

Prevention and Best Practices

Prevention is always better than cure, right? So, let's talk about some best practices to minimize the chances of running into this