chore: Clarify ADR-0008's handling for cache headers in addition to query params

[JamieSinn]

This PR

This was an unclear gap that I ran into when implementing open-feature/flagd#2036

This basically states that the flagConfigEtag is the "winner", but only in the truth case of 200 vs 304. It must never downgrade a 200 to a 304 from any other cache control headers.

Related Issues

open-feature/flagd#2036

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• service/adrs/0008-sse-for-bulk-evaluation-changes.md

📝 Walkthrough

Walkthrough

The ADR adds provider guidance for SSE-triggered re-fetches. A differing flagConfigEtag must preserve a 200 response when HTTP cache headers would otherwise match and produce a 304.

Changes

SSE cache response handling

Layer / File(s)	Summary
Provider cache response guideline service/adrs/0008-sse-for-bulk-evaluation-changes.md	Adds guideline 9. Providers must not downgrade a 200 response caused by a differing flagConfigEtag to 304 because If-None-Match or another cache header matches.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: 🔵 Low · up to 15770

The ADR clarification still leaves it unclear that a 200 selected by a differing flagConfigEtag must remain 200 despite other cache validators, which could lead implementations to return 304 incorrectly. The PR is otherwise narrowly scoped and is mergeable after the precedence wording is made explicit.

Suggested reviewers: fabriziodemaria, jonathannorris, lukas-reining

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: clarifying ADR-0008 behavior for cache headers and query parameters.
Description check	✅ Passed	The description directly explains the ADR clarification and its relationship to cache headers, 200 versus 304 responses, and flagd pull request #2036.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)

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Actionable comments posted: 1

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Inline comments:
In `@service/adrs/0008-sse-for-bulk-evaluation-changes.md`:
- Line 166: Update the response-precedence rule in item 9 so a 200 selected
because the SSE flagConfigEtag differs remains 200 even when If-None-Match or
other cache headers would otherwise produce 304; state that normal
conditional-request handling applies when this condition does not occur.

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• service/adrs/0008-sse-for-bulk-evaluation-changes.md

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[toddbaert]

https://github.com/open-feature/protocol/pull/84/changes#r3873271525