analyze-vtt-docs

name	analyze-vtt-docs
description	Generates EXHAUSTIVE WebVTT specification summary from web sources with complete rule coverage, all tags/settings/entities, and self-validation.

analyze-vtt-docs

What this skill does

Generates comprehensive, exhaustive WebVTT specification (vtt_specs_summary.md) as single source of truth for compliance checking.

Outputs:

1. 50+ RULE-XXX specifications with unique IDs and test patterns
2. 12+ IMPL-XXX requirements (generic, no pycaption references)
3. All 8 markup tags individually documented (c, i, b, u, v, lang, ruby, timestamp)
4. All 8 cue settings individually documented (vertical, line, position, size, align, region, etc.)
5. All required HTML entities (&, <, >,  , ‎, ‏)
6. Region specifications complete (REGION block properties)
7. STYLE/NOTE blocks documented
8. Self-validation report (rule counts, completeness check)
9. Source attribution per rule

Key: Ensures NO requirements missed - exhaustive coverage from W3C spec + MDN + web search.

Pre-flight: Read .claude/skills/gotchas.md before generating specs. Pay special attention to gotcha #3 (W3C license attribution required).

Post-run: If you discover a new gotcha during spec generation (a copyright/licensing trap, a W3C attribution pattern that should be avoided, a web source that returns misleading data, or a spec structure issue that could cause downstream compliance check failures), append it to .claude/skills/gotchas.md with the same numbered format.

Usage:

/analyze-vtt-docs

Single command - fetches web sources, performs comprehensive analysis, generates complete spec.

---

Implementation

Step 0: Check Existing Sources

Read existing documentation:

# Check what we already have
ls -la ai_artifacts/specs/vtt/
cat ai_artifacts/specs/vtt/vtt_web_sources.md

If vtt_specs_summary.md exists:

• Read it to assess completeness
• Identify gaps using completeness checklist (Step 2)
• Only fetch new sources if gaps exist

Step 1: Fetch Known Web Sources (WebFetch Tool Required)

IMPORTANT: This step requires the WebFetch tool to be loaded first.

Check if WebFetch is available, load if needed:

# WebFetch is a deferred tool - load it before use
# Use ToolSearch to load WebFetch

Read URLs from ai_artifacts/specs/vtt/vtt_web_sources.md:

import re

with open("ai_artifacts/specs/vtt/vtt_web_sources.md") as _f:
    sources_content = _f.read()

# Extract URLs from markdown links: [Text](URL)
url_pattern = r'\[([^\]]+)\]\(([^)]+)\)'
existing_sources = []

for match in re.findall(url_pattern, sources_content):
    title, url = match
    existing_sources.append({'title': title, 'url': url})

print(f"Found {len(existing_sources)} existing sources")
for s in existing_sources:
    print(f"   - {s['title']}")

Fetch W3C WebVTT Specification (Primary Source):

# Fetch W3C spec - most authoritative source
w3c_url = 'https://www.w3.org/TR/webvtt1/'
print("Fetching W3C WebVTT Specification...")

# Use the WebFetch tool to fetch w3c_url
# Store result in a variable for processing
# w3c_content = <result from WebFetch tool>

Fetch MDN Documentation (Supplementary):

# MDN provides practical examples and browser compatibility info
mdn_url = 'https://developer.mozilla.org/en-US/docs/Web/API/WebVTT_API'
print("Fetching MDN WebVTT Documentation...")

# Use the WebFetch tool to fetch mdn_url
# mdn_content = <result from WebFetch tool>

Context optimization:

• Fetch sources sequentially, not in parallel (avoid context overflow)
• Extract text content only, discard HTML tags
• Focus on specification sections
• Save to temp files, don't hold in memory

Step 2: Comprehensive Web Search for Missing Details

Perform targeted web searches to fill gaps:

# Define search queries for comprehensive coverage
search_queries = [
    "WebVTT specification complete W3C",
    "WebVTT cue settings all options",
    "WebVTT markup tags complete list",
    "WebVTT HTML entities supported",
    "WebVTT REGION block specification",
    "WebVTT STYLE block CSS",
    "WebVTT NOTE comment syntax",
    "WebVTT timestamp format validation",
    "WebVTT best practices implementation",
    "WebVTT validation rules MUST SHOULD",
]

# Execute searches and collect results
search_results = []
for query in search_queries:
    print(f"Searching: {query}")
    # Use the WebSearch tool for each query
    results = []  # populated by WebSearch tool
    search_results.append({
        'query': query,
        'results': results
    })
    # Brief delay to avoid rate limiting

Identify high-value sources from search results:

import re

# Re-read existing sources (each block is independent)
with open("ai_artifacts/specs/vtt/vtt_web_sources.md") as _f:
    _sources_content = _f.read()
existing_sources = [
    {'title': m[0], 'url': m[1]}
    for m in re.findall(r'\[([^\]]+)\]\(([^)]+)\)', _sources_content)
]

# Agent: for each URL found in the search step above, check if it is
# authoritative (w3.org, developer.mozilla.org, github.com/w3c) and not
# already in existing_sources. Collect matches into new_sources list:
_existing_urls = {s['url'] for s in existing_sources}
new_sources = []  # Agent fills this from search results
# new_sources.append({'title': <title>, 'url': <url>, 'query': <query>})

print(f"\nFound {len(new_sources)} new authoritative sources")

Fetch new sources:

# Agent: for each source in new_sources (up to 5), use WebFetch to
# retrieve the content. new_sources was built in the filtering step above.
# for source in new_sources[:5]:
#     print(f"Fetching: {source['title']}")
#     # Use the WebFetch tool with url=source['url']

Step 3: Exhaustive Completeness Verification

CRITICAL: Verify ALL these areas covered in fetched content (100% coverage required):

File Format:

• Header: "WEBVTT" exact match (case-sensitive), optional space + comment
• UTF-8 encoding requirement (MUST)
• Optional UTF-8 BOM handling
• Line endings: CR, LF, CRLF all valid
• Blank line after header before first cue

Timestamp Format:

• Format: [HH:]MM:SS.mmm (hours optional if < 1 hour)
• Milliseconds required (3 digits)
• Separator: --> (spaces required)
• Start time <= end time (MUST)
• Sequential ordering (SHOULD)
• Valid ranges: HH (00-99), MM (00-59), SS (00-59), mmm (000-999)

Cue Structure:

• Optional cue identifier (any text except "-->", "NOTE", or looks like timestamp)
• Required: start --> end [optional settings]
• Cue payload (can span multiple lines)
• Blank line terminates cue

Cue Settings:

• vertical: rl, lr (text direction)
• line: N or N% (vertical position, can be negative)
• position: N% (horizontal position 0-100)
• size: N% (cue box width 0-100)
• align: start, center, end, left, right
• region: region_id (reference to defined region)

Tags (Markup):

• Class spans: <c.classname>text</c> (multiple classes: <c.class1.class2>)
• Italics: <i>text</i>
• Bold: <b>text</b>
• Underline: <u>text</u>
• Ruby: <ruby>base<rt>annotation</rt></ruby>
• Voice: <v Speaker>text</v> (optional annotation)
• Language: <lang code>text</lang>
• Internal timestamps: <00:01:23.456> (karaoke-style)
• Tag nesting rules and restrictions
• Escape sequences: & < >   ‎ ‏

Regions (Optional Feature):

• REGION block definition before cues
• Properties: id, width, lines, regionanchor, viewportanchor, scroll
• Association with cues via region:id setting

Special Blocks:

• NOTE blocks (comments, ignored by parser)
• STYLE blocks (CSS for cue pseudo-elements)
• Syntax and placement rules

Validation Requirements:

• All MUST requirements from W3C spec
• All SHOULD requirements
• All MAY optional features
• All MUST NOT forbidden patterns
• Error handling strategies

Edge Cases & Common Pitfalls:

• Extra text on first line after "WEBVTT"
• Missing milliseconds in timestamps
• Missing spaces around -->
• Invalid cue settings
• Unclosed tags
• Un-escaped special characters
• Percentage out of range (0-100)
• Start > end time
• Invalid UTF-8 sequences

Implementation Requirements:

• Parser requirements (UTF-8 decoder, timestamp parser, tag parser, settings parser)
• Writer requirements (UTF-8 encoder, escaping, formatting)
• Error handling strategies
• Performance considerations

Browser Compatibility:

• Feature support across browsers
• Cue settings support
• Region support (limited)
• STYLE block support (varies)
• Graceful degradation

Completeness Checklist (MUST achieve 100%):

# TEMPLATE: All values start as False. Update each to True as you confirm
# coverage during spec generation. Re-run this block to check progress.
completeness_check = {
    'file_format': {
        'header': False,  # WEBVTT signature
        'encoding': False,  # UTF-8
        'bom': False,  # BOM handling
        'line_endings': False,  # CR/LF/CRLF
        'blank_line': False,  # After header
    },
    'timestamps': {
        'format': False,  # [HH:]MM:SS.mmm
        'validation': False,  # Start <= end
        'ranges': False,  # MM/SS 00-59
        'milliseconds': False,  # Exactly 3 digits
        'separator': False,  # ` --> `
    },
    'cue_settings': {
        'vertical': False,  # rl/lr
        'line': False,  # N or N%
        'position': False,  # N%
        'size': False,  # N%
        'align': False,  
        : ,  
    },
    : {
        : ,  
        : ,  
        : ,  
        : ,  
        : ,  
        : ,  
        : ,  
        : ,  
    },
    : {
        : ,  
        : ,  
    },
    : {
        : ,  
        : ,  
    },
    : {
        : ,  
        : ,  
    },
    : {
        : ,  
        : ,  
        : ,  
    },
}


total_items = ((v)  v  completeness_check.values())
covered_items = ((v.values())  v  completeness_check.values())
completeness = (covered_items / total_items) * 

()

 completeness < :
    ()
    
     category, items  completeness_check.items():
        missing = [k  k, v  items.items()   v]
         missing:
            ()

If new sources found during search, update vtt_web_sources.md:

# Agent: if you discovered new sources during the search/filter steps,
# append them to vtt_web_sources.md now. For each new source URL not
# already in the file, add a markdown link line.
import re as _re, os
_sources_path = "ai_artifacts/specs/vtt/vtt_web_sources.md"
if os.path.exists(_sources_path):
    with open(_sources_path) as _f:
        _current = _f.read()
    _known_urls = {m[1] for m in _re.findall(r'\[([^\]]+)\]\(([^)]+)\)', _current)}
    # Agent: for each new source discovered above, if url not in _known_urls:
    #   _current += f"- [{title}]({url})\n"
    # Then write back:
    # with open(_sources_path, "w") as _f:
    #     _f.write(_current)
    print("Source file update complete")
else:
    print(f"WARNING: {_sources_path} not found — skipping source update")

Step 4: Generate Exhaustive Specification

Create ai_artifacts/specs/vtt/vtt_specs_summary.md using the rule format below.

Key differences from old approach:

• Rule-based format with unique IDs (RULE-FMT-###, RULE-TIME-###, etc.)
• Generic IMPL-### rules (no pycaption-specific code references)
• Test patterns for automated validation
• Level indicators (MUST/SHOULD/MAY/MUST NOT)
• Source attribution per rule

Rule Format:

**[RULE-XXX-###]** Brief requirement
- **Requirement:** What must be true
- **Level:** MUST | SHOULD | MAY | MUST NOT
- **Validation:** How to check
- **Test Pattern:** Regex or algorithm
- **Sources:** [Attribution]

Implementation Rule Format (GENERIC):

**[IMPL-XXX-###]** Component MUST do X
- **Spec Rule:** RULE-XXX-###
- **Component:** Parser | Writer | Validator
- **Implementation Requirement:** What ANY compliant implementation must do
- **Expected Behavior:** Input → Output examples
- **Validation Criteria:** What to verify
- **Common Patterns:** Correct vs incorrect (generic)
- **Test Coverage:** Required test scenarios

Critical requirements (must be included as rules):

Part 1 (File Format): Header format, UTF-8, BOM handling, blank line after header
Part 2 (Timestamps): Format [HH:]MM:SS.mmm, ranges, start<=end, sequential
Part 3 (Cue Structure): Identifier restrictions, --> separator, blank line terminator
Part 4 (Cue Settings): vertical, line, position, size, align, region (6 settings)
Part 5 (Tags): c, i, b, u, v, lang, ruby, timestamp (8 tags), closing rules, escaping
Part 6 (Regions): REGION block, id/width/lines/regionanchor/viewportanchor/scroll
Part 7 (Special Blocks): NOTE (comments), STYLE (CSS)
Part 8 (Implementation): Generic IMPL-* rules for Parser/Writer/Validator
Part 9 (Validation Summary): Rule counts, self-validation report
Part 10 (Quick Reference): Tables for settings and tags

Target Rule Counts (Exhaustive):

• RULE-FMT-###: 5-7 file format rules (header, encoding, BOM, line endings, blank line)
• RULE-TIME-###: 7-10 timestamp rules (format, validation, ranges, separator, sequential)
• RULE-CUE-###: 5-8 cue structure rules (identifier, timing line, payload, blank line)
• RULE-SET-###: 8 cue setting rules (vertical, line, position, size, align, region, + constraints)
• RULE-TAG-###: 11-15 tag/markup rules (all 8 tags + closing rules + nesting + escaping)
• RULE-ENT-###: 3-5 HTML entity rules (&, <, >,  , ‎, ‏)
• RULE-REG-###: 5-8 region rules (REGION block, all properties, association)
• RULE-BLK-###: 3-5 special block rules (NOTE, STYLE, metadata)
• RULE-VAL-###: 5-8 validation rules (error handling, recovery, strict vs. lenient)
• IMPL-###: 12-15 implementation requirements (parser, writer, validator)
• Total: 60-80 rules (comprehensive coverage)

Level Distribution (Exhaustive):

• MUST: 30-40 rules (critical requirements)
• SHOULD: 15-20 rules (recommended practices)
• MAY: 5-10 rules (optional features)
• MUST NOT: 3-5 rules (forbidden patterns)

Critical Inclusions (MUST be documented):

All 8 Markup Tags (Individual Rules):

1. <c> / <c.class> - Class spans (RULE-TAG-001)
2. <i> - Italics (RULE-TAG-002)
3. <b> - Bold (RULE-TAG-003)
4. <u> - Underline (RULE-TAG-004)
5. <v> - Voice/speaker (RULE-TAG-005)
6. <lang> - Language (RULE-TAG-006)
7. <ruby><rt> - Ruby text (RULE-TAG-007)
8. <HH:MM:SS.mmm> - Internal timestamp (RULE-TAG-008)

All 6 Cue Settings (Individual Rules):

1. vertical: rl | lr (RULE-SET-001)
2. line: N | N% (RULE-SET-002)
3. position: N% (RULE-SET-003)
4. size: N% (RULE-SET-004)
5. align: start|center|end|left|right (RULE-SET-005)
6. region: id (RULE-SET-006)

All Required HTML Entities (Individual Rules):

1. & (ampersand) - RULE-ENT-001
2. < (less than) - RULE-ENT-002
3. > (greater than) - RULE-ENT-003
4.   (non-breaking space) - RULE-ENT-004
5. ‎ (left-to-right mark) - RULE-ENT-005
6. ‏ (right-to-left mark) - RULE-ENT-006

REGION Properties (Individual Rules):

1. id (required) - RULE-REG-001
2. width (percentage) - RULE-REG-002
3. lines (integer) - RULE-REG-003
4. regionanchor (percentage pair) - RULE-REG-004
5. viewportanchor (percentage pair) - RULE-REG-005
6. scroll (up/none) - RULE-REG-006

Generate spec with incremental writing (context-efficient):

from datetime import datetime
import os

os.makedirs("ai_artifacts/specs/vtt", exist_ok=True)
spec_path = "ai_artifacts/specs/vtt/vtt_specs_summary.md"

# Write spec header
spec_content = f"""# WebVTT Specification - Complete Reference

**Generated**: {datetime.now().strftime("%Y-%m-%d")}
**Sources**: W3C WebVTT Specification (https://www.w3.org/TR/webvtt1/), MDN Web Docs
**Version**: W3C Candidate Recommendation
**Total Rules**: [TO BE CALCULATED]

---

"""

with open(spec_path, "w") as _f:
    _f.write(spec_content)

# Then generate and append each part section by section:
# Part 1: File Format rules
# Part 2: Timestamp rules
# ... continue for all parts (Parts 1-10)
# Append each part with: with open(spec_path, "a") as _f: _f.write(part)

Step 5: Exhaustive Quality Validation

Structure checks:

• All rule IDs unique
• Sequential numbering within each category
• Valid test patterns
• Level indicators present (MUST/SHOULD/MAY/MUST NOT)

Content checks (Exhaustive - 100% required):

• ✅ 60-80 total rules documented (RULE-* + IMPL-*)
• ✅ 30-40 MUST rules (all critical requirements)
• ✅ 15-20 SHOULD rules (best practices)
• ✅ 5-10 MAY rules (optional features)
• ✅ 12-15 IMPL-* rules (generic, no pycaption references)
• ✅ All 8 markup tags individually documented (c, i, b, u, v, lang, ruby, timestamp)
• ✅ All 6 cue settings individually documented (vertical, line, position, size, align, region)
• ✅ All 6 HTML entities individually documented (&, <, >,  , ‎, ‏)
• ✅ All 6 REGION properties individually documented (id, width, lines, regionanchor, viewportanchor, scroll)
• ✅ STYLE block specification complete
• ✅ NOTE block specification complete
• ✅ Timestamp validation rules complete (format, ranges, start<=end, sequential)
• ✅ Validation rules complete (error handling, recovery strategies)
• ✅ Best practices documented (interoperability, browser compatibility)

Generate exhaustive validation report in spec file:

## Part 10: Exhaustive Validation Summary

### Rule Counts by Category
- RULE-FMT-###: X file format rules (Target: 5-7)
- RULE-TIME-###: X timestamp rules (Target: 7-10)
- RULE-CUE-###: X cue structure rules (Target: 5-8)
- RULE-SET-###: X cue setting rules (Target: 8 - ALL settings)
- RULE-TAG-###: X tag/markup rules (Target: 11-15 - ALL 8 tags + rules)
- RULE-ENT-###: X HTML entity rules (Target: 3-5 - ALL 6 entities)
- RULE-REG-###: X region rules (Target: 5-8 - ALL 6 properties)
- RULE-BLK-###: X special block rules (Target: 3-5)
- RULE-VAL-###: X validation rules (Target: 5-8)
- IMPL-###: X implementation requirements (Target: 12-15)
- **Total: Y rules** (Target: 60-80 for exhaustive coverage)

### By Level (Exhaustive Distribution)
- MUST: X rules (Target: 30-40)
- SHOULD: X rules (Target: 15-20)
- MAY: X rules (Target: 5-10)
- MUST NOT: X rules (Target: 3-5)

### Coverage Verification (100% Required)

**Markup Tags (8 total - ALL must be documented):**
- ✅/❌ `<c>` class spans (RULE-TAG-001)
- ✅/❌ `<i>` italics (RULE-TAG-002)
- ✅/❌ `<b>` bold (RULE-TAG-003)
- ✅/❌ `<u>` underline (RULE-TAG-004)
- ✅/❌ `<v>` voice (RULE-TAG-005)
- ✅/❌ `<lang>` language (RULE-TAG-006)
- ✅/❌ `<ruby><rt>` ruby text (RULE-TAG-007)
- ✅/❌ `<HH:MM:SS.mmm>` timestamp (RULE-TAG-008)
**Status: X/8 tags documented**

**Cue Settings (6 total - ALL must be documented):**
 ✅/❌ vertical: rl|lr (RULE-SET-001)
 ✅/❌ line: N|N% (RULE-SET-002)
 ✅/❌ position: N% (RULE-SET-003)
 ✅/❌ size: N% (RULE-SET-004)
 ✅/❌ align: start|center|end|left|right (RULE-SET-005)
 ✅/❌ region: id (RULE-SET-006)



 ✅/❌  ampersand (RULE-ENT-001)
 ✅/❌  less than (RULE-ENT-002)
 ✅/❌  greater than (RULE-ENT-003)
 ✅/❌  non-breaking space (RULE-ENT-004)
 ✅/❌  left-to-right mark (RULE-ENT-005)
 ✅/❌  right-to-left mark (RULE-ENT-006)



 ✅/❌ id (required) (RULE-REG-001)
 ✅/❌ width: N% (RULE-REG-002)
 ✅/❌ lines: N (RULE-REG-003)
 ✅/❌ regionanchor: X%,Y% (RULE-REG-004)
 ✅/❌ viewportanchor: X%,Y% (RULE-REG-005)
 ✅/❌ scroll: up|none (RULE-REG-006)



 ✅/❌ All rule IDs unique
 ✅/❌ Sequential numbering within categories
 ✅/❌ All 8 markup tags individually documented
 ✅/❌ All 6 cue settings individually documented
 ✅/❌ All 6 HTML entities individually documented
 ✅/❌ All 6 REGION properties individually documented
 ✅/❌ Generic IMPL rules (no pycaption-specific code)
 ✅/❌ Test patterns present for all rules
 ✅/❌ Source attribution present
 ✅/❌ 60-80 total rules (exhaustive coverage target)
 ✅/❌ 30-40 MUST rules documented


 : X% (100% required)
 : ✅ PASS | ❌ FAIL (requires fixes)

: Missing items listed above must be added before spec is complete.

If validation FAILS:

1. Identify missing rules/categories
2. Search additional sources for missing details
3. Add missing rules
4. Re-validate until PASS

Step 6: Source Attribution

Track sources for each rule:

• W3C WebVTT spec section (Primary)
• MDN docs (Confirms)
• Confidence: High/Medium/Low

Document conflicts and resolutions.

Step 7: Update Web Sources

Append new URLs (if any) to ai_artifacts/specs/vtt/vtt_web_sources.md:

- [New Source Title](https://url.example.com)

Step 8: Post-Generation Validation Against Master Checklist

CRITICAL: After generating the spec, run this validation script. If it reports FAIL, fix the spec and re-run until PASS.

import re

print("=" * 60)
print("POST-GENERATION VALIDATION: WebVTT")
print("Checking vtt_specs_summary.md against master_checklist.md")
print("=" * 60)

with open('ai_artifacts/specs/vtt/master_checklist.md') as _f:
    checklist = _f.read()
with open('ai_artifacts/specs/vtt/vtt_specs_summary.md') as _f:
    spec = _f.read()

failures = []
warnings = []

# 1. Check all required rule IDs
rule_ids = re.findall(r'^- ((?:RULE|IMPL)-[A-Z]+-\d{3})', checklist, re.M)
for rid in rule_ids:
    if rid not in spec:
        failures.append(f"MISSING RULE: {rid}")
found_rules = len(rule_ids) - len([f for f in failures if 'MISSING RULE' in f])
print(f"[1/6] Rule IDs: {found_rules}/{len(rule_ids)}")

# 2. Check required tags
tags_section = re.search(r'## Required Tags.*?\n((?:- .+\n)+)', checklist)
if tags_section:
    tags = re.findall(r'^- `(.+?)`', tags_section.group(1), re.M)
    for tag in tags:
        # Search for the tag in spec (handle angle brackets)
        tag_clean = tag.replace(, ).replace(, ).split()[].split()[]
          re.search(, spec):
              re.search(re.escape(tag_clean), spec, re.I):
                failures.append()
    ()


settings_section = re.search(, checklist)
 settings_section:
    settings = re.findall(, settings_section.group(), re.M)
     setting  settings:
          re.search(, spec):
            failures.append()
    ()


entities_section = re.search(, checklist)
 entities_section:
    entities = re.findall(, entities_section.group(), re.M)
     entity  entities:
        entity_clean = entity.strip().split()[]
         entity_clean   spec:
              re.search(re.escape(entity_clean), spec):
                warnings.append()
    ()


enum_sections = re.findall(, checklist)
missing_enums = 
total_enums = 
 section_name, values_block  enum_sections:
    values = re.findall(, values_block, re.M)
     val  values:
        val_clean = val.strip()
        total_enums += 
         val_clean   spec:
              re.search(re.escape(val_clean), spec, re.I):
                missing_enums += 
                warnings.append()
()


severity_section = re.search(, checklist)
 severity_section:
       re.finditer(, severity_section.group()):
        level, minimum = .group(), (.group())
        actual = (re.findall(, spec))
         actual < minimum:
            failures.append()
        ()


( +  * )
 failures:
    ()
     f  failures:
        ()
     w  warnings[:]:
        ()
     (warnings) > :
        ()
    ()
:
    ()
     w  warnings[:]:
        ()
( * )

If FAIL: Fix the missing items in the spec, then re-run the validation script. Repeat until PASS.

---

Output Files

1. ai_artifacts/specs/vtt/vtt_specs_summary.md - Complete specification with 60-80 rules
2. ai_artifacts/specs/vtt/vtt_web_sources.md - Updated URL list (if new sources found)

---

Success Criteria (Exhaustive - 100% Required)

Master Checklist Validation (CRITICAL - must PASS):

• All rule IDs from master_checklist.md present in generated spec
• All 8 tags present
• All 6 settings present
• All 6 entities present
• All enum values present
• Severity distribution meets minimums

Completeness:

• 60-80 total rules documented (RULE-* + IMPL-*)
• All 8 markup tags individually documented with examples
• All 6 cue settings individually documented with validation
• All 6 HTML entities individually documented
• All 6 REGION properties individually documented
• Header, timestamp, cue structure, special blocks rules
• 12-15 IMPL rules (generic, no pycaption-specific code)

Quality:

• Unique rule IDs (no duplicates)
• Sequential numbering within categories
• Valid test patterns for all rules
• Source attribution (W3C section references)
• Generic IMPL rules (no pycaption-specific references)

Web Sources:

• W3C WebVTT spec fetched
• MDN documentation fetched
• All new sources added to vtt_web_sources.md

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Context Window Optimization

Token usage target: < 50K per invocation

Strategies:

1. Targeted web fetch - Extract text only, not full HTML
2. Incremental writing - Save spec file as rules are generated, not at end
3. On-demand web search - Only if completeness check finds gaps
4. Section-by-section - Process file format → timestamps → cues → tags → etc.
5. Rule metadata first - Extract rule IDs/levels, fetch details on-demand

Estimated token usage:

• Web source fetches: 10-15K tokens
• Rule generation (40-50 rules): 15-20K tokens
• Validation & tables: 5K tokens
• Total: ~35K tokens (30% safety margin)

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Error Handling

• vtt_web_sources.md not found: Create it with W3C spec URL
• No URLs in file: Proceed with web search
• Web fetch fails: Continue with available sources + web search
• Web search fails: Use built-in W3C WebVTT knowledge
• Cannot write output: Report error with path