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seo-mobile (M7b)

Google indexes mobile-first: the mobile rendering of a page is the canonical one for ranking. This module checks that a page is usable on a small viewport. Layout problems that hurt mobile usability often surface as CLS — cross-check references/cwv-thresholds.md.

Inputs

Work from the PageSnapshot named in your dispatch envelope: read parsed from <run_dir>/pages/<slug>.json (metas[] for the viewport tag) and parsed_rendered when render.used is not none (layout/geometry checks need it); Grep pages/<slug>.html for verbatim evidence; site artifacts live in <run_dir>/site/{robots.json,sitemaps.json,discovery.json}. Deterministic findings already emitted by audit.mjs are listed in <run_dir>/findings.deterministic.json — do not re-emit those ids; add model-judged findings only. If invoked directly with a URL/path and no snapshot exists, first run node "${CLAUDE_PLUGIN_ROOT}/scripts/snapshot.mjs" <target> --out "${CLAUDE_PLUGIN_DATA}/runs" and use the printed snapshot path.

Audits

Working from the PageSnapshot (parsed_rendered when render.used is not none, else parsed):

1. Viewport meta: a <meta name="viewport"> exists with width=device-width and initial-scale=1. Flag missing, fixed-width (width=1024), or zoom-blocking (user-scalable=no, maximum-scale=1) values — the last also harms accessibility.
2. No horizontal scroll: detect fixed-width containers / large absolute widths that force the viewport wider than the device (content overflowing a ~360 px small viewport).
3. Tap-target size: interactive elements (links, buttons, form controls) should be large enough and spaced so adjacent targets are not easily mis-tapped.
4. Legible base font: body text rendered at a readable base size, not a desktop-only small size that forces pinch-zoom on mobile.
5. Content parity: the mobile DOM must contain the same primary content, headings, structured data, and links as desktop — mobile-first indexing ranks what is in the mobile render, so hidden/stripped mobile content is a ranking risk.

Fixes

• AUTO (fixable: auto): inject <meta name="viewport" content="width=device-width, initial-scale=1"> into <head> when absent. Deterministic, additive, verifiable — emitted as a diff for fix.
• ADVISORY (fixable: advisory): fixed-width/overflow layouts, tap-target sizing, base-font, and parity gaps depend on CSS, design system, and JS — high breakage risk. The tool diagnoses and prioritizes but does not auto-edit layout code. Never invent breakpoint values or pixel sizes — report observed values or leave a clearly-marked TODO for the user.

Verification

• Method dom_assert: assert against the snapshot (viewport meta presence/content, computed widths, target geometry).
• Reproduce the deterministic part (viewport meta presence/content) offline: node "${CLAUDE_PLUGIN_ROOT}/scripts/parse-html.mjs" --snapshot <pages/<slug>.json> (or --url <u> / --file <path>) — inspect head_hygiene.viewport. Tap-target/overflow geometry is a manual_review pass over the rendered snapshot.
• Tap-target and overflow checks need the rendered snapshot (computed layout). When only raw_html_path is available and layout cannot be resolved, status is needs_api, never a false pass.

Findings

Emit findings per schema/finding.schema.json. Examples:

• M7b.viewport.missing — no viewport meta (status fail, severity 3, fixable: auto, axis search, confidence established).
• M7b.viewport.user_scalable_no — viewport disables zoom (status warn, severity 3, fixable: advisory, axis search, confidence established).
• M7b.layout.horizontal_scroll — content overflows the small viewport (status fail, severity 3, fixable: advisory, axis search, confidence directional).
• M7b.taptarget.too_small — interactive targets too small/close (status warn, severity 3, fixable: advisory, axis search, confidence directional).

Each finding: evidence.observed quotes the page (the meta tag string, the overflowing selector/width, the target geometry); verification.reproduce is the runnable command above; expected_impact is banded + confidence-tagged (no naked %).

Honesty

• Mobile-friendliness is a usability baseline, not a strong positive ranking lever — a fast, well-built desktop-only site does not get a ranking boost for adding a viewport tag; it removes a usability liability. Frame fixes as removing risk, not gaining rank.
• Google retired the standalone "Mobile-Friendly Test" tool and the page-experience badge; there is no single mobile-friendly ranking flag to "win." Don't ship that myth.
• A present viewport meta does not prove the layout is actually responsive — confirm with the rendered snapshot, don't infer responsiveness from the tag alone.