2026-09-26 21:22:53 +02:00
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---
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title: Progressive Enhancement
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status: draft
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maturity: hypothesis
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families: [quality, execution, affordance]
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scales: [L3, L6]
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admission: research-candidate-only
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---
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# Progressive Enhancement
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Context: essential reading/navigation or submission should work before optional
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scripts arrive. Problem: delayed or failed client execution can block a usable
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server-delivered interface. Resilience competes with interaction richness and the
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cost of maintaining equivalent behavior across paths.
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Proposed solution: give the essential task a usable HTML/link/form contract first;
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add client behavior that preserves its meaning and authoritative validation.
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Define which controls are essential and what enhanced behavior adds. Test absent,
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late and partially failing scripts separately. Server-rendered text alone does not
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establish a functional no-script task.
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For enhanced navigation, preserve route, history, loading/error feedback and focus
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semantics. For writes, avoid duplicate submission when falling back after an
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uncertain response: reconcile the original operation before resubmitting it.
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Keyboard operation, labels, status announcements and recovery focus need explicit
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verification in both paths. Native elements help but are not an accessibility proof.
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Consequences: initial tasks depend on fewer client capabilities, while parity and
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failure recovery add design work. No-script support is not offline support. A
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client-only rich editor may deliberately require scripts; name that requirement
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instead of promising a fallback that cannot perform the task.
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Evidence: [navigation review](../reviews/NavigationRenderingEvidence.md) N03–N05
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locates htmx and SvelteKit mechanisms with specific link/form/action prerequisites.
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These are two documentation families, not two verified deployments of this complete
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contract. Full-pattern recurrence and decision benefit remain unknown. This develops
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an existing seed; hypothesis only, no canonical identity or admitted relations.
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Proposed connections: [URL-addressable State](URLAddressableState.md) supports shared
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view selection; [Mutation Outcome Tracking](MutationOutcomeTracking.md) matters when
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an enhanced write becomes uncertain. Neither is a universal dependency.
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[VC-03](../walkthroughs/VC03-ContentPublication.md) explores a read-only core.
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2026-09-27 00:11:21 +02:00
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## Prospective runtime corroboration — 2026-09-27
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Native links and GET filtering remain usable with JavaScript disabled or htmx
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loading failed. An enhanced 503 keeps the old URL/view, and an explicitly provided
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native recovery link navigates successfully. This does not establish automatic fallback,
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late-script safety, accessible focus/announcements or offline availability.
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See [NH01–NH06](../reviews/NavigationHistoryExperiment.md). One authored application
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with a real package, not independent deployed recurrence. Hypothesis retained.
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2026-09-27 00:22:14 +02:00
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## Keyboard continuation and feedback — 2026-09-27
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[Navigation focus experiment](../reviews/NavigationFocusExperiment.md) NF01–NF06
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distinguishes successful route continuation, failed navigation, history restoration
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and background updates. In the raw fixture, a replacement link retains focus but
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fragment navigation leaves the old title and failures produce no visible status.
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The authored policy updates title/status, selects a heading for direct continuation
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and preserves a surviving control when the user has moved focus during the request.
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Choose a continuation policy for the task; do not universally focus a heading or
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return to the invoker. Check ownership when the response is applied, not only when
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it is requested. Failure feedback need not move focus. Same-ID restoration is not
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proof of semantic continuity. DOM/ARIA checks here do not establish spoken feedback;
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AT, delayed history and overlapping-request behavior remain unverified.
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2026-09-27 00:45:54 +02:00
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## Separate completion and focus ownership — 2026-09-27
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[Competing navigation](../reviews/NavigationOwnershipExperiment.md) NO01–NO06 exposes
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2026-09-27 00:56:50 +02:00
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limits of the preceding single-response policy. Validate applicability for each intended result
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effect, including old errors and history restoration, not only before moving focus.
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2026-09-27 00:45:54 +02:00
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A current response may update content/title/status while the user has moved focus
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to another surviving task; an obsolete response may own none of those effects.
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The latest-intent policy tested here does not revive older success when newer intent
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fails. Ignoring completion does not abort or undo server work.
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A scoped navigation generation and separate focus-change check meet the tested
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obligations. Their history adapter depends on pinned htmx internals; multiple history
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misses, nonzero swap delays, redirects, lifecycle teardown and AT validation remain
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open. Do not apply this navigation policy indiscriminately to unrelated background work.
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2026-09-27 00:56:50 +02:00
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## Effect-specific applicability contrast — 2026-09-27
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[Zulip source study](../reviews/ZulipNavigationSourceStudy.md) ZN02–ZN04 shows a useful
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contrast: noncurrent fetches may update cached data, while selected-view continuations
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check list identity. Shared connection feedback and view-specific errors have different
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scopes. Do not turn the earlier generation guard into a blanket discard rule for
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every result from a view the user has left. Define data/cache acceptance separately
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from current-view, feedback and focus effects, with their own consistency contracts.
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This is static support for an asynchronous-navigation obligation, not evidence that
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Zulip supplies the native/no-script path required by this whole candidate. Some
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auxiliary continuations lack a visible matching guard in the inspected code; runtime
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behavior and transport/caller limits remain unknown. Hypothesis retained.
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