fix(guardrails): restore supported_decisions_providers on stable/1.104.x so Add Guardrail settings load

[devin-ai-integration]

TLDR

Problem this solves:

• The decisions backport (feat(decisions): backport the decisions and Jev follow-ups to stable/1.104.x and bump to 1.104.3 #45906) broke Add Provider Guardrail settings on stable/1.104.x
• GET /guardrails/ui/add_guardrail_settings returns 500 with an ImportError on every call
• The Admin UI guardrail wizard gets no providers, so nobody can add one from the dashboard

How it solves it:

• Imports the providers helper from litellm.decisions.call, where the backport moved it
• Restores its public name supported_decisions_providers, matching rc/1.105.0 and main
• Points the existing regression test at the same module

User Flow

Before: an admin opening the Add Provider Guardrail wizard on a stable/1.104.x proxy sees an empty provider list

1. They open http://localhost:4000/ui/?page=guardrails and click Add Guardrail
2. The dashboard calls GET http://localhost:4000/guardrails/ui/add_guardrail_settings
3. The proxy answers 500 Internal server error, so the wizard has no providers to pick

After: the same wizard loads its providers

1. They open http://localhost:4000/ui/?page=guardrails and click Add Guardrail
2. The same GET returns 200 with the guardrail settings, including the decision model providers
3. The wizard lists providers and the guardrail can be created

Affected release

Regression on stable/1.104.x since #45906

Pre-Submission checklist

• I have added meaningful tests
• The handful of test files covering my change pass locally, e.g. uv run pytest tests/unit/<your_test_file>.py -v. Leave the suites (make test-unit-*, make test-unit) to CI: it finishes in ~15 minutes where a laptop takes an hour or more
• My PR passes all required CI/CD checks (e.g., lint, schema.d.ts sync check, etc.)
• My PR's scope is as isolated as possible; it only solves 1 specific problem
• I have received a Greptile Confidence Score of at least 4/5 before requesting a maintainer review (Greptile reviews automatically once the PR is opened; only comment @greptileai to re-request a review after pushing changes)

Screenshots / Proof of Fix

Same config on both sides: model_list: [] and a master key from the environment, no database. Before runs the stable/1.104.x tip on port 4101 and After runs this branch on port 4102. The endpoint makes no provider call, so there is no provider spend

Before (0939a83)

1. curl -s -w '\nHTTP %{http_code}\n' -H "Authorization: Bearer $LITELLM_MASTER_KEY" http://localhost:4101/guardrails/ui/add_guardrail_settings
2. Output

{"error":{"message":"Internal server error","type":"internal_server_error"}}
HTTP 500

3. Proxy log

ImportError: cannot import name 'supported_decisions_providers' from 'litellm.decisions.main'

After (7cd5407)

1. The same curl against port 4102
2. Output is HTTP 200 with the full settings payload, and decision_model_providers reads

['openai', 'openrouter', 'azure_ai', 'perplexity', 'typesafe', 'strands_decider', 'cloudflare', 'hosted_vllm']

Type

🐛 Bug Fix

Final Attestation

• The tests check the right things, including the edge cases, and regressions in the respective real-world customer use-cases are not possible after this PR

---

Note

Low Risk
Narrow import-path and symbol rename fix for guardrail UI settings; no changes to auth, billing, or decision API runtime behavior beyond restoring the listing endpoint.

Overview
Fixes a stable/1.104.x regression where GET /guardrails/ui/add_guardrail_settings failed with an ImportError because the proxy still imported supported_decisions_providers from litellm.decisions.main after the decisions backport moved that logic.

supported_decisions_providers is now defined and exported from litellm.decisions.call (renamed from the private _supported_providers), and the guardrail UI endpoint plus its regression test import it from there. The Add Guardrail wizard can load decision_model_providers again instead of returning 500 with an empty provider list.

^{Reviewed by Cursor Bugbot for commit 7cd5407. Bugbot is set up for automated code reviews on this repo. Configure here.}

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring

[mateo-berri]

@litereview greptile code-review

[mateo-berri]

bugbot run

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 7cd5407. Configure here.}

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[mateo-berri]

@litereview greptile code-review

[mateo-berri]

LGTM