fix(health-freshness): revalidate every poll — CF browser-TTL rewrite oscillates synthesized-OK sources to stale (#4910) by koala73 · Pull Request #4912 · koala73/worldmonitor

koala73 · 2026-07-05T17:52:35Z

Fixes #4910. Post-deploy follow-up to #4907 / PR #4908.

Problem

Live probing after #4908 deployed showed the Cloudflare zone's Browser Cache TTL override rewrites the compact health endpoint's Cache-Control: public, max-age=0, must-revalidate to public, max-age=1800, must-revalidate — browsers cache the body for up to 30 minutes. Since PR #4905, healthy checks are synthesized as OK-as-of-checkedAt and compared against the 15-min FRESH_THRESHOLD, so a tab reading a 15–30-min-old cached body computes age > threshold and flips every healthy source badge to stale, then back to fresh when the browser cache window rolls — oscillating ~30-min waves.

(The CDN side works as intended: CDN-Cache-Control: public, s-maxage=60 is respected — cf-cache-status: HIT + x-vercel-cache: HIT observed, origin collapse confirmed.)

Fix

cache: 'no-cache' on the client health fetch: the browser revalidates every poll, Cloudflare answers from its 60s edge cache, so the #4907 origin collapse is intact and checkedAt stays ≤ ~60s + poll interval old — far under threshold. This is also the correct standing declaration for a freshness poller and is robust against future CF browser-TTL config drift.

Verification

New failing-first test pins cache: 'no-cache' on the fetch init; 14/14 pass in tests/data-freshness-health.test.mts.
npm run typecheck clean; tiered pre-push gate green.

https://claude.ai/code/session_01YKrVoDp8TfEKLYXo83kPFV

… would oscillate synthesized-OK sources to stale (#4910) Cloudflare's zone Browser-Cache-TTL override rewrites the compact health endpoint's max-age=0 to 30min (observed live post-#4908). Synthesized-OK sources compute freshness from checkedAt against the 15-min FRESH_THRESHOLD, so a browser-cached body 15-30min old flips every healthy badge to stale, then back on the next cache window — oscillating ~30min waves. fetch cache: 'no-cache' forces revalidation on every poll; Cloudflare answers from its 60s edge cache, so the #4907 origin collapse is intact and checkedAt stays well under threshold. Fixes #4910 Claude-Session: https://claude.ai/code/session_01YKrVoDp8TfEKLYXo83kPFV

vercel · 2026-07-05T17:52:41Z

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Project	Deployment	Actions	Updated (UTC)
worldmonitor	Ready	Preview, Comment	Jul 5, 2026 5:55pm

greptile-apps · 2026-07-05T17:54:28Z

Greptile Summary

Adds cache: 'no-cache' to the browser fetch call inside refreshDataFreshnessFromHealth to force revalidation on every poll, bypassing the Cloudflare Browser-Cache-TTL override that was rewriting the origin's max-age=0 to 30 minutes and causing synthesized-OK source badges to oscillate between fresh and stale.

src/services/health-freshness.ts: Single-line addition of cache: 'no-cache' to the fetchFn init object, with an inline comment anchoring it to issues perf(health): collapse health polling cost — CDN-cache compact health (s-maxage=60), 5-min client cadence, idle-deferred first hydration #4907 and fix(health-freshness): Cloudflare browser-TTL rewrite (max-age=1800) makes synthesized-OK sources oscillate to stale — client must fetch with cache:'no-cache' #4910. No logic changes.
tests/data-freshness-health.test.mts: New test 'forces browser revalidation on every poll (cache: no-cache)' that captures the RequestInit passed to the mock fetchFn and asserts seenInit?.cache === 'no-cache', giving the fix a failing-first regression guard.

Confidence Score: 5/5

Safe to merge — a one-line fetch option addition with a direct regression test and no changes to business logic.

The change is minimal and precisely targeted: cache: 'no-cache' added to the fetch init in one file, guarded by a new test that captures the exact RequestInit passed to the poller. The comment ties it to the verified production symptom. No logic paths, data structures, or error handling are altered, and the existing 13-test suite remains intact.

No files require special attention.

Important Files Changed

Filename	Overview
src/services/health-freshness.ts	Adds `cache: 'no-cache'` to the health fetch init; one-line change with a well-anchored comment explaining the CF Browser-Cache-TTL interaction. No logic changes elsewhere.
tests/data-freshness-health.test.mts	New regression test captures the `RequestInit` from the injected `fetchFn` and asserts the `cache` field is `'no-cache'`; correctly calls `__resetHealthFreshnessForTests()` to clear auth suppression before the probe runs.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant Browser
    participant CF_Browser as CF Browser Cache
    participant CF_Edge as CF Edge Cache (60s TTL)
    participant Origin as Origin / Vercel

    Note over Browser,CF_Browser: Before fix — CF rewrites max-age=0 → 1800s
    Browser->>CF_Browser: "GET /api/health?compact=1"
    CF_Browser-->>Browser: Cached body (up to 30 min old)
    Note over Browser: checkedAt age > 15-min FRESH_THRESHOLD<br/>→ all synthesized-OK sources flip to stale

    Note over Browser,Origin: After fix — cache: 'no-cache' on every poll
    Browser->>CF_Browser: "GET /api/health?compact=1 + Cache-Control: no-cache"
    CF_Browser->>CF_Edge: Revalidate (browser cache bypassed)
    alt Edge cache hit (within 60s)
        CF_Edge-->>Browser: Fresh CDN-cached body
    else Edge cache miss
        CF_Edge->>Origin: Fetch from origin
        Origin-->>CF_Edge: "Response + CDN-Cache-Control: s-maxage=60"
        CF_Edge-->>Browser: Response (now cached at edge)
    end
    Note over Browser: checkedAt ≤ ~60s old → synthesized-OK sources stay fresh

%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
sequenceDiagram
    participant Browser
    participant CF_Browser as CF Browser Cache
    participant CF_Edge as CF Edge Cache (60s TTL)
    participant Origin as Origin / Vercel

    Note over Browser,CF_Browser: Before fix — CF rewrites max-age=0 → 1800s
    Browser->>CF_Browser: "GET /api/health?compact=1"
    CF_Browser-->>Browser: Cached body (up to 30 min old)
    Note over Browser: checkedAt age > 15-min FRESH_THRESHOLD<br/>→ all synthesized-OK sources flip to stale

    Note over Browser,Origin: After fix — cache: 'no-cache' on every poll
    Browser->>CF_Browser: "GET /api/health?compact=1 + Cache-Control: no-cache"
    CF_Browser->>CF_Edge: Revalidate (browser cache bypassed)
    alt Edge cache hit (within 60s)
        CF_Edge-->>Browser: Fresh CDN-cached body
    else Edge cache miss
        CF_Edge->>Origin: Fetch from origin
        Origin-->>CF_Edge: "Response + CDN-Cache-Control: s-maxage=60"
        CF_Edge-->>Browser: Response (now cached at edge)
    end
    Note over Browser: checkedAt ≤ ~60s old → synthesized-OK sources stay fresh

_{Reviews (1): Last reviewed commit: "fix(health-freshness): revalidate every ..." | Re-trigger Greptile}

koala73 enabled auto-merge (squash) July 5, 2026 17:52

vercel Bot deployed to Preview July 5, 2026 17:55 View deployment

koala73 merged commit eb426df into main Jul 5, 2026
26 checks passed

koala73 mentioned this pull request Jul 5, 2026

fix(summarization): anon dashboards dispatch premium summarize-article RPCs — 401 flood + 3-provider fan-out since #4687 (client caller never swept) #4913

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fix(health-freshness): revalidate every poll — CF browser-TTL rewrite oscillates synthesized-OK sources to stale (#4910)#4912

fix(health-freshness): revalidate every poll — CF browser-TTL rewrite oscillates synthesized-OK sources to stale (#4910)#4912
koala73 merged 1 commit into
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fix/4910-health-fetch-no-cache

koala73 commented Jul 5, 2026

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koala73 commented Jul 5, 2026

Problem

Fix

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greptile-apps Bot commented Jul 5, 2026

Greptile Summary

Confidence Score: 5/5

Important Files Changed

Sequence Diagram

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vercel Bot commented Jul 5, 2026 •

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