workflow-fix: Shared HF tree-pagination helper in verify_tas

Overview / Motivation

Auto-filed by the /daily Step-C parked-candidate sweep from a candidate parked on task #1016.

Goal

Consolidate the three near-identical bounded HF tree-pagination loops in scripts/verify_task_body.py into one shared iterator, with no behavior change to any check.

Workflow gap

• Bug observed: Checks 25 (keyword probe), 30 (exhaustive counter), and 32 (basename walker) in scripts/verify_task_body.py each carry a near-identical bounded Link-header self-pagination loop over the Hub tree endpoint.
• Why it is a workflow gap: the failure originates in the workflow surface named below, not in any one experiment.
• Confidence (emitter): see parked note

Proposed change (candidate diff sketch — refine in planning)

• def _hf_tree_pages(url, *, max_pages, deadline_s, attempts): ...

• # yields per-page entry lists under the shared page/deadline/429 contract
  

• (three per-check copies of the Link-header pagination loop)

• checks 25 / 30 / 32 consume the shared iterator with their existing caps

Scope / surfaces

• Primary target: scripts/verify_task_body.py
• Grep the workflow surface for the pattern before editing (grep -rln '<pattern>' .claude/ CLAUDE.md scripts/) and update every hit; list them in the plan.

Constraints / invariants

• Workflow-surface only — never experiment code, configs/, or tasks/.
• scripts/workflow_lint.py --check-asks passes; ruff on touched files passes; if workflow.yaml or CLAUDE.md change, they stay consistent with the rule file.
• This session runs under EPM_WORKFLOW_FIX_SESSION=1 and carries a workflow_fix_target: Provenance line — it MUST NOT auto-route any of its own subagents' workflow-fix candidates (recursion guard).
• Behavior-preserving refactor: existing verify_task_body tests must pass unchanged; each check keeps its own page/deadline caps.

Provenance

• workflow_fix_target: scripts/verify_task_body.py
• origin: parked candidate on task #1016 at 2026-07-05T03:50:52Z

Verbatim parked note:

routed: parked — running under EPM_WORKFLOW_FIX_SESSION / workflow_fix_target (recursion guard, workflow-fix-on-bug.md § Recursion guard). source: prose-followup (planner, #1016 Phase 1). Candidate: extract a shared _hf_tree_pages bounded-pagination iterator in scripts/verify_task_body.py — check 25 keyword probe, check 30 counter, and the new check 32 basename walker are 3 near-identical bounded pagination loops; consolidate when a 4th appears. Deferred rationale: doing it now would non-additively touch freshly-merged check-25/30 paths with two concurrent same-file tasks (#1014/#1015) in flight.

Merged sibling candidate (s4-vtb-check30-hf-import-order, from task:1016 at 2026-07-05T04:53:32Z)

• bug_observed: _hf_tree_url relies on huggingface_hub.constants being attribute-reachable after a bare import huggingface_hub, but the check-30 walker (~l.7604) and check-25 keyword probe (~l.7024) build the URL before _hf_build_headers imports huggingface_hub.utils, so a fresh-process probe can AttributeError (check 32 fixed its own ordering; check 30 was left untouched per a plan Must-ask).
• proposed_change: Make _hf_tree_url ordering-independent (import huggingface_hub.utils inside it, or from huggingface_hub.constants import ENDPOINT) so every call site is safe regardless of caller ordering, mirroring the check-32/check-23 safe-ordering fix; add a fresh-process regression test.
• origin note (verbatim): Bug pattern still present on main: scripts/verify_task_body.py _hf_tree_url (l.5314) does bare import huggingface_hub then huggingface_hub.constants.ENDPOINT; call sites at l.7024 (check-25 keyword probe) and l.7604 (check-30 count walker) build the URL BEFORE _hf_build_headers() imports huggingface_hub.utils, while l.7965 shows the check-32 walker was fixed with an explicit safe-ordering comment. No dedup: no task body names _hf_tree_url / huggingface_hub.constants. No retraction in #1016 events after ts.

Merged sibling candidate (s5-hf-probe-headers-before-url, from task:1016 at 2026-07-05T05:05:14Z)

• bug_observed: _hf_probe_keyword (check 25) and _hf_count_files_under_prefix (check 30) call _hf_tree_url before _hf_build_headers, so a fresh-process direct call hits huggingface_hub.constants before the lazy submodule is attribute-reachable.
• proposed_change: Hoist the safe headers-before-URL ordering (already used by checks 23/32) into both trunk siblings, or extract a shared ordered helper.
• origin note (verbatim): NOT fixed on main: _hf_probe_keyword (check 25) builds the URL before headers at verify_task_body.py:7024-7026 and _hf_count_files_under_prefix (check 30) at :7604-7606, while check 32 (:7965-7971, added by completed #1016 commit 389201de49) carries the safe headers-before-URL ordering + explanatory comment. No open dedup (completed #1016 covered only check 32); no retraction events on #1016.