framework: no-store cache for json responses & vary Accept

[gtn1024]

Problem

The same URL can return different representations depending on the request:
request.json is derived from the Accept header, so an XHR/fetch with
Accept: application/json gets raw JSON, while a normal navigation to the
same URL gets the rendered HTML page. However, JSON responses were sent
without any Cache-Control header and without Vary: Accept, so the
browser HTTP cache stored them keyed only by URL.

Concretely: open /p/:pid/config, let the frontend fetch it as JSON,
navigate to another page, then press the browser Back button — the browser
replays the cached JSON response for the navigation and the user is dumped
into a page of raw JSON instead of the UI.

Fix

• JSON responses now default to Cache-Control: no-store — added only
  when the response does not already set a Cache-Control header. JSON
  output often contains user-specific data and should not be stored by
  browsers or shared caches on its own. Responses with an ETag still get
  Cache-Control: public as before, and headers explicitly set by handlers
  are left untouched.
• All non-websocket responses now send Vary: Accept — since the same
  URL can return either HTML or JSON via content negotiation, caches must
  key on the Accept header. Otherwise a cached JSON representation can be
  wrongly served to a normal page navigation (or vice versa).

Summary by CodeRabbit

• Bug Fixes
  • JSON responses now default to Cache-Control: no-store when no caching policy is specified.
  • Non-websocket responses now vary by the Accept header for more accurate content negotiation.

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• framework/framework/base.ts

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Walkthrough

The base middleware now sets Cache-Control: no-store for application/json responses when no cache directive exists. It also adds Vary: Accept for non-websocket requests during final response handling.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Suggested reviewers: renbaoshuo

Merge Risk: ⚪ Minimal · up to 7a755

JSON responses now default to no-store when no policy is specified, while explicit policies remain unchanged and non-WebSocket responses vary by Accept. The prior response-ordering concern is resolved, so the change is mergeable.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main changes: default no-store caching for JSON responses and the Vary: Accept header for non-WebSocket responses.
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 1…
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.

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framework/framework/base.ts

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Actionable comments posted: 1

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Inline comments:
In `@framework/framework/base.ts`:
- Around line 105-107: Move the default Cache-Control check in the response
finalization flow to after final response typing and the ETag handling, using
the finalized response type so JSON error responses receive no-store. Add a
regression test covering a JSON request that returns 404 and assert its
Cache-Control header is no-store.

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Configuration used: Organization UI

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Run ID: 05354ed8-5eda-4dd9-851f-801052096d61

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Reviewing files that changed from the base of the PR and between 67b6053 and 6aaaeb6.

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• framework/framework/base.ts

Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review.