fix: support GA transcription-type sessions in POST /v1/realtime/client_secrets

[Shaik-Sirajuddin]

Summary

POST /v1/realtime/client_secrets mints both full realtime sessions and GA transcription-only sessions (session.type: "transcription"), but model extraction only checked session.model — the transcription schema has no such field, only session.audio.input.transcription.model. Every transcription-type request 400'd; confirmed live against real OpenAI.

Changes

• ExtractRealtimeClientSecretModel falls back to the nested transcription model when session.model is absent.
• Added schemas.IsGATranscriptionSessionBody, a single classifier shared by extraction and both normalization layers (handler + provider), so they can't disagree on the same body. Explicit session.type wins when present; otherwise session.model/legacy root model beat the structural fallback, so a full session with transcription enabled as a sibling feature is never misclassified.
• Writes the model into the correct nested slot for transcription sessions instead of a bogus top-level session.model; the alias-resolution rewrite does the same.
• A first pass introduced its own classification bugs, caught by codex --yolo review and fixed in a follow-up commit.

Type of change

• Bug fix

How to test

cd core && go test ./schemas/... ./providers/openai/... ./providers/azure/...
cd ../transports/bifrost-http && go test ./handlers/...

Also live-verified against real OpenAI's platform API using the openai Python SDK (and curl): minted a real GA transcription-session client_secret, and confirmed the regression scenario (full session + transcription sibling) keeps type: "realtime" and the correct model.

Breaking changes

• No

[coderabbitai]

📝 Walkthrough

Walkthrough

GA transcription-only realtime sessions now extract and rewrite models from session.audio.input.transcription.model. Full realtime sessions retain root-model behavior, while OpenAI normalization defaults and removes session fields according to the detected session shape.

Changes

GA transcription session handling

Layer / File(s)	Summary
Session classification and model extraction core/schemas/realtime_client_secrets.go, core/schemas/realtime_client_secrets_test.go	Adds GA transcription-shape detection and nested model extraction with explicit handling for null, legacy, and full realtime session fields.
Handler model resolution and nested rewriting transports/bifrost-http/handlers/realtime_client_secrets.go, transports/bifrost-http/handlers/realtime_client_secrets_test.go	Resolves nested transcription models and rewrites them during alias normalization while preserving root models for full realtime sessions.
OpenAI provider normalization core/providers/openai/realtime.go, core/providers/openai/realtime_test.go	Writes normalized models into nested transcription configuration, removes stale top-level session models, and applies transcription or realtime defaults by session shape.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Client
  participant HTTPHandler
  participant RealtimeSchemas
  participant OpenAIProvider
  Client->>HTTPHandler: Submit realtime client-secret request
  HTTPHandler->>RealtimeSchemas: Classify session and extract model
  RealtimeSchemas-->>HTTPHandler: Resolved provider and model
  HTTPHandler->>HTTPHandler: Rewrite nested transcription model
  HTTPHandler->>OpenAIProvider: Normalize session request
  OpenAIProvider-->>HTTPHandler: Normalized realtime session

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Possibly related PRs

• maximhq/bifrost#3334: Both changes modify OpenAI realtime client-secret normalization around nested transcription model handling.

Suggested reviewers: akshaydeo, danpiths, roroghost17, Pratham-Mishra04

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title is concise and accurately summarizes the main change: GA transcription-type session support for POST /v1/realtime/client_secrets.
Description check	✅ Passed	The description covers the main summary, changes, type, testing, and breaking-changes sections; only some optional template sections are omitted.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[greptile-apps]

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.
• The classifier is shared across the parsing and normalization paths.
• The tests cover the main shape conflicts between full realtime sessions and transcription-only sessions.

Important Files Changed

Filename	Overview
core/schemas/realtime_client_secrets.go	Adds nested GA transcription model extraction and a shared session-shape classifier.
core/providers/openai/realtime.go	Updates provider normalization to preserve the transcription-session wire shape and write the model into the nested transcription field.
transports/bifrost-http/handlers/realtime_client_secrets.go	Updates handler normalization and alias rewrites to use the shared classifier and nested transcription model path.
core/providers/openai/realtime_test.go	Adds provider normalization coverage for GA transcription sessions and full realtime sessions with transcription sibling config.
core/schemas/realtime_client_secrets_test.go	Adds extraction and classification coverage for GA transcription and full realtime request shapes.
transports/bifrost-http/handlers/realtime_client_secrets_test.go	Adds handler and two-pass normalization tests for transcription sessions and alias rewrites.

_{Reviews (1): Last reviewed commit: "fix: correct GA transcription-session cl..." | Re-trigger Greptile}