Similar wire shapes. Explicit boundaries.
A similar field name or endpoint is not evidence of support. This is a summary of the published matrix: PASS means the exact configuration passed on the named Flex build and client version. A result says nothing about builds after the one it names.
Tested coding agents.
Each agent has a setup page with the exact configuration it passed with. Results recorded 2026-09-26, each on the build shown. Re-run 2026-10-02 on build cce8ffca.
| Agent | Request shape | Status | Agent version | Passed on build | Re-verified on build | Setup |
|---|---|---|---|---|---|---|
| Claude Code | Anthropic Messages | PASS | 2.1.250 | 7819bd3b | cce8ffca | Claude Code setup |
| Codex CLI | Responses | PASS | 0.144.1 | 7819bd3b | cce8ffca | Codex CLI setup |
| opencode | Chat Completions | PASS | 1.18.31 | 7819bd3b | cce8ffca | opencode setup |
| Crush | Chat Completions | PASS | 0.96.1 | b823556b | cce8ffca | Crush setup |
Other agents are Pending: their setup pages are published once the configuration passes. A row is PASS only after authentication, a non-streamed reply with its request ID, a streamed reply, and one tool call with its result sent back all passed. “Not yet” under Re-verified means the row has not been run again on a later build; it is filled in when it has.
Request shapes.
One base URL answers three request shapes. Their direct SDK rows have not yet been run against the beta; the notes describe how the current build is designed to behave.
| Surface | Endpoint | Status | Notes |
|---|---|---|---|
| Chat Completions | POST /v1/chat/completions | Pending | Text, streaming, function tools and tool-result continuation. |
| Responses | POST /v1/responses | Pending | Stateless: send the full input, including function_call_output items, every turn. |
| Anthropic Messages | POST /v1/messages | Pending | Text, streaming, tool_use and tool_result, token counting. |
Excluded in the beta.
Flex intentionally does not offer these in the beta. Requests that use them are rejected with a clear error or, where the docs say so, ignored.
- Excluded: Stored responses, background responses and previous_response_id chaining
- Excluded: Hosted or server-side tools such as web search, file search or code execution
- Excluded: JSON mode and schema-constrained output
- Excluded: Image and audio input
- Excluded: n above 1, seed, logprobs, frequency and presence penalties
Field-by-field behavior and error codes are in the compatibility matrix and the API reference.