Close the streaming HTTP body on the Anthropic and OpenAI-Responses streaming paths

[PratikDhanave]

What

The Anthropic Messages streaming path (anthropicprovider/agent.go) and the OpenAI Responses streaming paths (openaiprovider/responses.go) create an SSE stream via NewStreaming / GetStreaming and iterate it with for stream.Next(), but never call Close() on the stream. On early consumer termination (yield returns false when the caller breaks out of the range) or context cancellation, the closure returns without releasing the HTTP response body.

The SDK's Stream.Close() releases the body (Stream.Close -> decoder.Close -> ReadCloser.Close). Without it, the body is never returned to the connection pool and the underlying connection leaks.

This adds defer func() { _ = stream.Close() }() immediately after each streaming call:

• anthropicprovider/agent.go: after Messages.NewStreaming
• openaiprovider/responses.go: after Responses.GetStreaming (continuation-token resume) and after Responses.NewStreaming

Why

The sibling Chat Completions path (openaiprovider/chat.go) already does exactly this — stream := ...NewStreaming(...) immediately followed by defer func() { _ = stream.Close() }(). This change brings the Anthropic and Responses paths in line with it. It also matches the .NET and Python SDKs, which dispose the streaming response when enumeration ends early, so streaming lifecycle semantics are consistent across the SDK ports.

Testing

Added a black-box test to each package's canonical test file (agent_test.go, responses_test.go) that:

• serves a valid SSE stream from an httptest.Server,
• injects an http.Client whose RoundTripper wraps the response body in a Close-counting ReadCloser,
• drives the provider's streaming Run and breaks out of the range after the first update,
• asserts the body's Close() was invoked.

Each test fails before the fix (Close count 0) and passes after (count 1). go build ./..., go vet, and go test pass for both changed packages.

[Copilot]

Pull request overview

This pull request fixes a streaming resource-leak issue by ensuring SSE streams are explicitly closed in the Anthropic Messages and OpenAI Responses streaming implementations, aligning these paths with the existing OpenAI Chat Completions behavior and preventing HTTP connection leaks on early consumer termination or context cancellation.

Changes:

• Added defer ...Close() immediately after creating streaming SSE streams in anthropicprovider/agent.go and both streaming branches of openaiprovider/responses.go.
• Added black-box tests in each provider package to verify the underlying HTTP response body is closed when the consumer stops iteration early.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
provider/openaiprovider/responses.go	Ensures OpenAI Responses streaming streams are closed on all exit paths (including early consumer exit).
provider/openaiprovider/responses_test.go	Adds a transport/body wrapper test to assert the streaming response body is closed when iteration ends early.
provider/anthropicprovider/agent.go	Ensures Anthropic Messages streaming stream is closed via defer to avoid leaking the HTTP body.
provider/anthropicprovider/agent_test.go	Adds a transport/body wrapper test to assert the streaming response body is closed when iteration ends early.

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[github-actions]

Parity Review: No Issues Found

This PR fixes a streaming HTTP body leak by adding defer stream.Close() on the Anthropic and OpenAI-Responses streaming paths, aligning them with the existing OpenAI Chat Completions path.

Scope: Internal implementation fix only — no exported Go APIs were added, removed, or changed.

Cross-repo parity: This is a convergence fix that matches .NET and Python SDK behavior (both dispose/close streaming responses on early enumeration exit). No parity issues.

Labels: parity-approved is already present and correct. No public-api-change label warranted.

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