[stigdreyer]

Summary

fetch_tags()'s GHCR branch requests n=10000 but never follows the registry's Link: rel="next" pagination header — it just takes whatever the first response contains. GHCR silently caps the actual page size below the requested n for tag-heavy images, so any image with more tags than that cap loses everything past the first page, with no error or warning.

How this was found

check-image-updates.sh produced a PR against a downstream repo proposing to change ghcr.io/home-assistant/home-assistant from 2026.7.0 (the live-running version) to 2023.3.6 — a 3+ year downgrade masquerading as an "update".

Confirmed directly against the registry:

$ curl -s -D - -o /dev/null -H "Authorization: Bearer $TOKEN" \
    "https://ghcr.io/v2/home-assistant/home-assistant/tags/list?n=10000" | grep -i link
link: </v2/home-assistant/home-assistant/tags/list?last=2023.4.0b2&n=10000>; rel="next"

Despite requesting n=10000, GHCR returned exactly 1000 tags and a Link header pointing at the rest. Tags come back in lexicographic order, so this isn't a random subset — it's a full page of the earliest-sorting tags (up to 2023.4.0b2) with a hard stop, and 2026.x releases exist entirely past that cutoff, unseen.

Fix

• GHCR: follow Link: rel="next" in a loop until absent, accumulating tags across all pages.
• Docker Hub: same class of bug existed (the response's next field was ignored) — hardened the same way, though I haven't observed it bite in practice since that endpoint orders by last_updated rather than lexicographically. Same silent-truncation risk for any image with enough tags, though.

Tested

Extracted fetch_tags() and ran it directly against the real registries:

• ghcr.io/home-assistant/home-assistant: now returns 4327 tags (vs. 1000 before), correctly including 2026.7.0, 2026.7.1, 2026.7.2
• Ran the full script end-to-end against a throwaway compose fixture with homeassistant:2026.7.0 as the "current" tag: now correctly computes Latest: 2026.7.2 (previously would have computed 2023.3.6, per the actual downstream PR this surfaced from)
• ghcr.io/music-assistant/server (small image, genuinely single page, no Link header): unaffected, no regression — loop terminates immediately as before

Did not modify tag_pattern() or the sort -V comparison logic — those were already correct; the only issue was the tag list being incomplete before it ever reached them.

Calling repositories now receive all matching image tags. fetch_tags() follows GHCR Link: rel="next" headers and Docker Hub next URLs. This prevents stale updates when the first page omits newer tags.

tag_pattern() and sort -V remain unchanged. Repositories pinned to an older workflow commit must update the pin to receive this fix.

Reported validation finds 4,327 Home Assistant tags, including 2026.7.0–2026.7.2, and selects 2026.7.2 from the 2026.7.0 fixture.

[stigdreyer]

This bit us again today: a fresh `check-updates.yml` run proposed downgrading Home Assistant from `2026.7.2` to `2023.3.6` — the identical bug, since this fix hasn't merged yet. Second time we've had to manually correct a downstream PR because of it.

One more thing worth noting for whenever this does land: downstream consumers that pin this workflow to a fixed commit SHA (rather than tracking main) will need to bump that pin afterward to actually pick up the fix — ours does (ziganka-containers's check-updates.yml pins @e7da767...), so the bug will keep recurring there even after merge until that's updated too.

[coderabbitai]

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📝 Walkthrough

The fetch_tags function now follows pagination links from GHCR and Docker Hub to retrieve tags from all available response pages.

Changes: Registry tag retrieval

Layer / File(s)	Summary
Paginate registry tag responses scripts/check-image-updates.sh	fetch_tags follows GHCR Link: rel="next" headers and Docker Hub next URLs. Tag extraction and registry selection remain unchanged.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: mairas

Merge Risk: 🟡 Moderate · up to 85034

Pagination fixes the old 1,000-tag cap. However, if any later GHCR page request fails, the script can treat the earlier pages as the full tag list. It can then propose an older image version, the same kind of downgrade this change is meant to prevent. Fail when a page request fails before merging.

Pre-merge checks: 3

Check name	Status	Explanation
Title check		The title accurately identifies the primary change: fixing GHCR tag pagination. It does not mention Docker Hub pagination, but the title need not cover every change.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

---

• 🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @scripts/check-image-updates.sh:
- Line 90: Update the GHCR page-fetch loop in fetch_tags to explicitly check the
combined curl and JSON-parse pipeline; on failure, remove the current headers
file and return nonzero immediately, while preserving the existing pagination
and cleanup behavior for successful pages.

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[mairas]

@stigdreyer Sorry this sat unnoticed for three months, especially after you reported that it bit you a second time. That's on us. Thanks for tracking the problem down to the registry's Link header and for the detailed write-up. I've reviewed it now and am pushing fixes to your branch; the details are in the next comment.

[mairas]

Review

The GHCR Link pagination fixes the home-assistant truncation. The change also adds two regressions that need fixing before merge. Line numbers refer to scripts/check-image-updates.sh at 850340e.

Six reviewers covered correctness, testing, maintainability, project standards, reliability, and adversarial failure cases.

P1

	Line	Finding	Where it bites
1	101	Docker Hub refuses anonymous requests past 1000 results. Page 11 returns 403 with "pagination offset too large for anonymous requests; sign in to page further". The new loop always follows next into that page, so fetch_tags fails and the image is skipped with only a warning. Before this change, those images got their 100 most recently updated tags, and that set already includes the newest release.	traefik (2651 tags) and grafana/grafana (2017 tags), which halos-core-containers and halos-marine-containers ship, would stop getting update checks. Checked by hand: grafana page 10 returns 200 and page 11 returns 403.
2	95	The last command in the GHCR loop is rm -f "$headers", so fetch_tags always returns 0. If page 2 or later fails (429, 5xx, token expiry), the earlier pages come back as a complete list. GHCR sorts lexicographically, so the missing tags are the newest ones. If the token request or page 1 fails, the run logs "No tags matching pattern" where it used to log the fetch warning.	home-assistant needs 5 GHCR requests. With a fake curl that fails page 2, the script printed UPDATE: 2026.7.0 -> 2023.4.0, the same downgrade this PR fixes.

P2

	Line	Finding	Where it bites
3	72	No test covers either fetch loop. tests/*.test.sh with a fake binary on PATH, the pattern tests/lib/fake-gh uses, can cover multi-page, single-page and failed-page cases without network access.	Every check-image-updates.yml run goes through these loops.

P3

	Line	Finding
4	67–85	The function header tells the home-assistant story over nine lines, and lines 83–85 repeat the point about GHCR capping pages. The story is already in the PR description.
5	101	[ "$url" != "null" ] can never be true, because the Python extractor already prints '' for a null next.

Pre-existing

• Line 141 proposes an update whenever the computed latest tag differs from the current one, with no check that it is newer. That is why an incomplete tag list turns into a downgrade PR. Fixing here: the current tag is included in the comparison, so a short list can no longer produce an older tag.
• Digest-pinned images (busybox:1.37@sha256:…) are split at the last : and skipped on every run. Filed as check-image-updates: digest-pinned images are parsed into a bogus image and skipped #68, since it is unrelated to pagination.

Release follow-up

The workflow checks out scripts at the caller's pinned ref. Callers on v1.0.0-rc.1 or @v1 get this fix only after a release is cut at or after the merge. As already noted, SHA-pinned callers need to bump their pin too.

Fix plan (pushing to this branch)

1. Docker Hub: return to the single ordering=last_updated request. Its first page already holds the newest tags, and the PR reports no failure on that path. This also removes finding 5.
2. GHCR: a failed token request or a failed page makes fetch_tags return non-zero, so the caller skips the image with its existing warning instead of acting on a partial list.
3. Never propose a tag older than the current one (the line 141 item above).
4. Add tests/check-image-updates.test.sh with a fake curl. It covers two-page GHCR, single-page GHCR, a failed GHCR page 2, and a Docker Hub image.
5. Shorten the comments to the constraint they explain.

Dropped: no --max-time on curl, which predates this PR and has not been seen to hang. No page cap or repeated-cursor guard, since GHCR's Link targets always advance. The relative-path assumption in the Link parser, since GHCR returns relative paths today.

[mairas]

Fixes pushed

• 08215f7 scripts/check-image-updates.sh
  • Finding 1: Docker Hub is back to one ordering=last_updated request, so grafana and traefik get update checks again. This also removes finding 5.
  • Finding 2: a failed GHCR token request or page makes fetch_tags return 1, so the image is skipped with the existing warning.
  • Pre-existing: the current tag takes part in picking the latest, so an incomplete list cannot propose an older tag.
  • Finding 4: the comments are shortened.
• 4200918 adds tests/check-image-updates.test.sh with tests/lib/fake-curl for finding 3, and adds the fake to the shellcheck list in ci.yml. Seven cases: two-page GHCR, single-page GHCR, failed page 2, failed token, no downgrade, and Docker Hub with a next link that must not be followed.

Verification

• Before the fix, 5 of the 7 cases failed, one for each finding. All 7 pass after it, run in a Debian container. shellcheck -x is clean.
• The fixed fetch_tags against the real registries:

Image	Tags returned	Newest release
ghcr.io/home-assistant/home-assistant	4608	2026.10.2
grafana/grafana	100	13.2.4
traefik	100	v3.7.15
ghcr.io/music-assistant/server	991	2.10.7