OpenAI API / OpenAI API

GPT5 Models | Tool choices other than auto are not supported with model

Fix error when specifying explicit tool_choice (e.g., 'required', 'none', or function name) with GPT-5 models, forcing fallback to auto mode Includes evidence for OpenAI API troubleshooting demand.

Source-backed Last updated May 22, 2026 1 source Needs local verification

Category: OpenAI API
Error signature: Tool choices other than 'auto' are not supported with model on GPT5
Quick fix: Compare the failing environment with a known working setup, then change one configuration value at a time.
Updated: May 22, 2026
Verification status: Source-backed
Evidence: 1 public source URL

Before you change production

This page includes public source URLs in the imported troubleshooting record. Compare those references with your version and environment before applying changes.

Reproduce the smallest failing action and save non-secret logs before changing configuration.
Check versions for OpenAI API, related SDKs, package managers, CI runners, and hosting providers.
Change one setting or dependency at a time, then rerun the same failing command or request.
Avoid destructive commands, credential rotation, billing changes, or security relaxations without a rollback plan.

What this error means

Tool choices other than 'auto' are not supported with model on GPT5 is a OpenAI API failure pattern reported for developers trying to fix error when specifying explicit tool_choice (e.g., 'required', 'none', or function name) with gpt-5 models, forcing fallback to auto mode. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub Issue #2537 on openai/openai-python (opened Aug 9, 2025, by hayescode). GPT-5 models reject non-auto tool choices, breaking function calling patterns for developers who need deterministic tool invocation. 17 comments indicate active community engagement. High value: function calling is core to paid API usage.

Common causes

GitHub Issue #2537 on openai/openai-python (opened Aug 9, 2025, by hayescode). GPT-5 models reject non-auto tool choices, breaking function calling patterns for developers who need deterministic tool invocation. 17 comments indicate active community engagement. High value: function calling is core to paid API usage.

Quick fixes

Confirm the exact error signature matches Tool choices other than 'auto' are not supported with model on GPT5.
Check the OpenAI API account, local tool state, and provider configuration involved in the failing workflow.
Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

Verify the command, editor, extension, or API client that produced the error.
Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

Capture the exact error message and the command, editor action, or request that triggered it.
Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
Review the source evidence below and compare it with your environment.
Apply one change at a time and rerun the smallest failing action.
Keep the working fix documented for the team or deployment environment.

How to prevent it

Keep provider/tool configuration documented.
Record non-secret diagnostics such as tool version, provider name, model name, and command path.
Add a lightweight check before CI or production workflows depend on the tool.

Diagnostic flow for this page

Match Tool choices other than 'auto' are not supported with model on GPT5 exactly before applying the quick fix.
Compare the failing environment with OpenAI API versions, account scope, provider settings, and deployment context.
Check the listed common causes in order, starting with the cause that best matches your logs.
Use the evidence status below to decide whether to confirm against public sources or official documentation.
Apply one reversible change, rerun the smallest failing action, and keep rollback notes.

FAQ

What does Tool choices other than 'auto' are not supported with model on GPT5 mean in OpenAI API?

Tool choices other than 'auto' are not supported with model on GPT5 indicates the workflow described by "GPT5 Models | Tool choices other than auto are not supported with model" failed in a OpenAI API context. Start by confirming the exact signature and the component that emitted it.

What should I check first for Tool choices other than 'auto' are not supported with model on GPT5?

Check whether this cause matches your environment: GitHub Issue #2537 on openai/openai-python (opened Aug 9, 2025, by hayescode). GPT-5 models reject non-auto tool choices, breaking function calling patterns for developers who need deterministic tool invocation. 17 comments indicate active community engagement. High value: function calling is core to paid API usage.

Is the Tool choices other than 'auto' are not supported with model on GPT5 guidance source-backed?

The "GPT5 Models | Tool choices other than auto are not supported with model" page is labeled source-backed. It has 1 public source URL from github.com, so use that evidence status when deciding how much additional verification you need.

When should I avoid the quick fix for Tool choices other than 'auto' are not supported with model on GPT5?

For "GPT5 Models | Tool choices other than auto are not supported with model", avoid applying "Compare the failing environment with a known working setup, then change one configuration value at a time." when the error text differs, the affected version or provider is different, or the change would touch credentials, billing, DNS, production deploy settings, or irreversible data.

What should I collect before debugging Tool choices other than 'auto' are not supported with model on GPT5?

For "GPT5 Models | Tool choices other than auto are not supported with model", collect the failing OpenAI API command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.