Capture baselines of SEO-critical elements, detect changes

SEO Drift Monitor (April 2026)

Git for your SEO. Capture baselines, detect regressions, track changes over time.

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Commands

Command	Purpose
/seo drift baseline <url>	Capture current SEO state as a "known good" snapshot
/seo drift compare <url>	Compare current page state to stored baseline
/seo drift history <url>	Show change history and past comparisons

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What It Captures

Every baseline records these SEO-critical elements:

Element	Field	Source
Title tag	title	parse_html.py
Meta description	meta_description	parse_html.py
Canonical URL	canonical	parse_html.py
Robots directives	meta_robots	parse_html.py
H1 headings	h1 (array)	parse_html.py
H2 headings	h2 (array)	parse_html.py
H3 headings	h3 (array)	parse_html.py
JSON-LD schema	schema (array)	parse_html.py
Open Graph tags	open_graph (dict)	parse_html.py
Core Web Vitals	cwv (dict)	pagespeed_check.py
HTTP status code	status_code	fetch_page.py
HTML content hash	html_hash (SHA-256)	Computed
Schema content hash	schema_hash (SHA-256)	Computed

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How Comparison Works

The comparison engine applies 17 rules across 3 severity levels. Load references/comparison-rules.md for the full rule set with thresholds, recommended actions, and cross-skill references.

Severity Levels

Level	Meaning	Response Time
CRITICAL	SEO-breaking change, likely traffic loss	Immediate
WARNING	Potential impact, needs investigation	Within 1 week
INFO	Awareness only, may be intentional	Review at convenience

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Storage

All data is stored locally in SQLite:

~/.cache/claude-seo/drift/baselines.db

Tables

• baselines: Captured snapshots with all SEO elements
• comparisons: Diff results with triggered rules and severities

URL normalization ensures consistent matching: lowercase scheme/host, strip default ports (80/443), sort query parameters, remove UTM parameters, strip trailing slashes.

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Command: baseline

Captures the current state of a page and stores it.

Steps:

1. Validate URL (SSRF protection via google_auth.validate_url())
2. Fetch page via "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run fetch_page.py <URL>
3. Parse HTML via "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run parse_html.py <URL>
4. Optionally fetch CWV via "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run pagespeed_check.py <URL> (use --skip-cwv to skip)
5. Hash HTML body and schema content (SHA-256)
6. Store snapshot in SQLite

Execution:

"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run drift_baseline.py <url>
"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run drift_baseline.py <url> --skip-cwv

Output: JSON with baseline ID, timestamp, URL, and summary of captured elements.

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Command: compare

Fetches the current page state and diffs it against the most recent baseline.

Steps:

1. Validate URL
2. Load most recent baseline from SQLite (or specific --baseline-id)
3. Fetch and parse current page state
4. Run all 17 comparison rules
5. Classify findings by severity
6. Store comparison result
7. Output JSON diff report

Execution:

"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run drift_compare.py <url>
"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run drift_compare.py <url> --baseline-id 5
"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run drift_compare.py <url> --skip-cwv

Output: JSON with all triggered rules, old/new values, severity, and actions.

After comparison, offer to generate an HTML report:

"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run drift_report.py <comparison_json_file> --output drift-report.html

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Command: history

Shows all baselines and comparisons for a URL.

Execution:

"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run drift_history.py <url>
"${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run drift_history.py <url> --limit 10

Output: JSON array of baselines (newest first) with timestamps and comparison summaries.

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Cross-Skill Integration

When drift is detected, recommend the appropriate specialized skill:

Finding	Recommendation
Schema removed or modified	Run /seo schema <url> for full validation
CWV regression	Run /seo technical <url> for performance audit
Title or meta description changed	Run /seo page <url> for content analysis
Canonical changed or removed	Run /seo technical <url> for indexability check
Noindex added	Run /seo technical <url> for crawlability audit
H1/heading structure changed	Run /seo content <url> for E-E-A-T review
OG tags removed	Run /seo page <url> for social sharing analysis
Status code changed to error	Run /seo technical <url> for full diagnostics

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Error Handling

Scenario	Action
URL unreachable	Report error from fetch_page.py. Do not guess state. Suggest user verify URL.
No baseline exists for URL	Inform user and suggest running baseline first.
SSRF blocked (private IP)	Report validate_url() rejection. Never bypass.
SQLite database missing	Auto-create on first use. No error.
CWV fetch fails (no API key)	Store null for CWV fields. Skip CWV rules during comparison.
Page returns 4xx/5xx	Still capture as baseline (status code IS a tracked field).
Multiple baselines exist	Use most recent unless --baseline-id specified.

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Security

• All URL fetching goes through "${CLAUDE_PLUGIN_ROOT}/scripts/claude-seo" run fetch_page.py, which enforces SSRF protection (blocks private IPs, loopback, reserved ranges, GCP metadata endpoints)
• No curl, no subprocess HTTP calls -- only the project's validated fetch pipeline
• All SQLite queries use parameterized placeholders (?), never string interpolation
• TLS always verified -- no verify=False anywhere in the pipeline

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Typical Workflows

Pre/Post Deployment Check

/seo drift baseline https://example.com     # Before deploy
# ... deploy happens ...
/seo drift compare https://example.com      # After deploy

Ongoing Monitoring

/seo drift baseline https://example.com     # Initial capture
# ... weeks later ...
/seo drift compare https://example.com      # Check for drift
/seo drift history https://example.com      # Review all changes

Investigating a Traffic Drop

/seo drift compare https://example.com      # What changed?
/seo drift history https://example.com      # When did it change?