[rekram1-node]

Problem

When a Cohere stream got cut off before message-end, the step just failed. Every other provider retries in that case.

Cohere had its own end-of-stream check that ran before the shared one and failed with a plain "Cohere stream ended without message-end" error. That error has no incomplete-stream classification, so AIError.isRetryable returned false.

 stream ends without a finish event
-  cohere onHalt -> "Cohere stream ended without message-end"   (not retryable)
+  shared requireTerminalEvent -> "The provider response ended unexpectedly."
+                                 classification: incomplete-stream (retryable)

Change

I removed Cohere's onHalt. Cohere's message-end step already emits a finish event, so the shared client check passes for complete streams and gives cut-off streams the same retryable error as everyone else.

I kept the finished state field even though nothing reads it now, because it shows up in the exported CohereChat.protocol type. The emitted .d.ts is identical before and after.

Verification

• bun run test in packages/ai (includes recorded fixtures): 2030 pass, 0 fail
• bun typecheck and bun run typecheck:tsc in packages/ai
• tsc -p tsconfig.build.json --emitDeclarationOnly before and after: no diff
• bun run check from the root

[opencodejr]

The change looks good. Removing Cohere's own onHalt lets the shared requireTerminalEvent check handle cut-off streams. Cohere's message-end step already emits finish through Lifecycle.finish, so complete streams still pass. Streams cut off before that now fail with the incomplete-stream error, which can be retried, the same as other providers.

I reproduced the problem on the base: the updated test fails there with the old error, which can't be retried. With this change it passes. The full packages/ai suite passes (2058 tests, 0 fail), and so does typecheck:tsc.

Public API: unchanged.

No concerns.