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Use this review before planning a gateway cutover. It focuses on the behaviors that can change even when both platforms accept OpenAI-compatible requests.

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1. Inventory the integration boundary

Record every place the current gateway appears:
  • base URLs and API key environment variables
  • SDK initialization and custom headers
  • model IDs and fallback models
  • provider ordering, allowlists, and privacy requirements
  • streaming, tool-calling, and structured-output code
  • batch jobs, files, webhooks, and async status polling
  • request attribution and user or session metadata
Keep this inventory beside the rollout plan so reviewers can verify that the migration does not leave a second, hidden configuration path behind.

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2. Classify each capability

For each production behavior, assign one status: Use the Migration Feature Checklist to cover core requests, routing, attribution, async work, and operations.

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3. Validate representative traffic

Build a small test set from real workload patterns without copying sensitive production data. Test:
  1. One normal request for every endpoint in use.
  2. Streaming through the same client path used in production.
  3. Tool calls and structured outputs with realistic schemas.
  4. Every provider or privacy constraint.
  5. Invalid keys, invalid models, rate limits, and unavailable-provider failures.
  6. Batch or async jobs through terminal success, failure, and cancellation states.
Compare output quality, latency, token usage, selected provider, and final cost. Record the request ID for each result so it can be inspected in Gateway usage.

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4. Preserve attribution and observability

Keep app attribution headers when they describe the calling application. Phaseo supports stable app IDs, names, URLs, and categories; removing them during migration makes cost and usage comparisons harder. See App Attribution for the supported headers and category values.

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5. Roll out with a reversible switch

Start with development and internal traffic. Move a small production percentage only after the test set passes, and keep rollback limited to endpoint and credential configuration until results are stable. Do not combine the initial cutover with unrelated prompt, model, or routing optimization. Make those changes after the gateway boundary is verified.

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Platform-specific guides

Last modified on August 23, 2026