feat(http-client-python): make SSE reconnection opt-in

[Libba Lawrence (l0lawrence)]

mock api test failing bc typespec-azure doesnt recognize the flag and that we have it set to false

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npm i https://pkg.pr.new/@typespec/http-client-python@12150

commit: b440a26

[github-actions]

All changed packages have been documented.

• ✅ @typespec/http-client-python

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@typespec/http-client-python - feature ✏️

Make automatic SSE reconnection opt-in with the enable-sse-reconnect emitter option, which defaults to false. Without this option, SSE streams end at EOF without reconnect callbacks, retry delays, or Last-Event-ID request plumbing. SSE parsing, event ID and retry metadata (including metadata-only blocks), terminal events, and stream cleanup remain available.,> ,> Enable reconnection when generating the client:,> ,> yaml,> emit:,> - "@typespec/http-client-python",> options:,> "@typespec/http-client-python":,> enable-sse-reconnect: true,>

[azure-sdk-automation]

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension

[github-actions]

Python emitter diff

Baseline gh:79ca62c01a9736ee89e5f32c2f3c744f1ae21f89 vs this PR.

Diff summary: 79 file(s), +15437 / -230

Rendered diff: inline on the run summary, or the emitter-diff-html artifact.

Informational check (eng/emitter-diff); does not block the PR.

[Copilot]

🟡 Changes recommended

Non-reconnecting streams lose metadata-only SSE state, and the breaking default change is incorrectly categorized as a feature.

2 open findings

• Preserve decoder metadata before synchronous no-reconnect exit · New
• Mark default SSE reconnection removal as a breaking change · New

What changed in this PR

Makes Python SSE reconnection opt-in while preserving SSE metadata and stream cleanup.

Changes:

• Adds the enable-sse-reconnect emitter option, defaulting to false.
• Conditionally generates reconnection runtime code and imports.
• Adds unit, emitter, and mock API coverage plus documentation.

File	Description
.chronus/​changes/​python-sse-reconnect-option.md	Adds the release note.
cspell.yaml	Allows the new test namespace.
packages/​http-client-python/​README.md	Documents the option.
packages/​http-client-python/​emitter/​src/​emitter.ts	Applies the default.
packages/​http-client-python/​emitter/​src/​lib.ts	Defines the option schema.
packages/​http-client-python/​emitter/​test/​emitter.test.ts	Tests validation and propagation.
packages/​http-client-python/​emitter/​test/​test-host.ts	Exposes command arguments to tests.
packages/​http-client-python/​eng/​scripts/​ci/​regenerate-common.ts	Generates reconnecting and non-reconnecting clients.
packages/​http-client-python/​generator/​pygen/​__init__.py	Adds generator validation and default.
packages/​http-client-python/​generator/​pygen/​codegen/​models/​response.py	Gates reconnect imports.
packages/​http-client-python/​generator/​pygen/​codegen/​serializers/​builder_serializer.py	Gates reconnect request generation.
packages/​http-client-python/​generator/​pygen/​codegen/​templates/​streaming_base.py.jinja2	Conditionally emits reconnect runtime behavior.
packages/​http-client-python/​tests/​mock_api/​shared/​asynctests/​test_streaming_sse_async.py	Tests async default behavior.
packages/​http-client-python/​tests/​mock_api/​shared/​test_streaming_sse.py	Tests sync default behavior.
packages/​http-client-python/​tests/​unit/​test_options_dict.py	Tests option parsing and validation.
packages/​http-client-python/​tests/​unit/​test_sse_reconnect_option.py	Tests generated runtime variants.
packages/​http-client-python/​tests/​unit/​test_sse_streaming.py	Extends serializer coverage.
website/​src/​content/​docs/​docs/​emitters/​clients/​http-client-python/​reference/​emitter.md	Documents the emitter option.

🧠 Review effort: Balanced

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[Copilot]

🔵 Needs a closer look

The changelog classifies a runtime-breaking default change as a feature.

1 open finding

• Mark default SSE reconnection removal as a breaking change

1 resolved since last review

• Preserve decoder metadata before synchronous no-reconnect exit

Previously missed (1)

In code that hasn't changed since last review

Classify changed SSE client EOF behavior as a breaking change

.chronus/​changes/​python-sse-reconnect-option.md:2

This changes existing generated SSE clients from reconnecting at EOF to stopping by default, so the output is not semantically equivalent and existing runtime behavior changes. Per website/src/content/docs/docs/handbook/breaking-change-policy.mdx:19-20,79-81 and .chronus/config.yaml:19-32, classify this entry as breaking rather than feature.

🧠 Review effort: Balanced