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Jangwook Kim

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Joined Joined on  Personal website https://effloow.com
Zero Failures Tabbing Down, 16 Tabbing Up: The Sticky Header Problem
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Zero Failures Tabbing Down, 16 Tabbing Up: The Sticky Header Problem

#a11y #wcag #keyboard #css
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12 min read
Your Last Deploy Reset Every Cache Validator on the Site
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Your Last Deploy Reset Every Cache Validator on the Site

#seo #crawling #httpcaching #statichosting
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14 min read
What a 26-page WCAG-EM sample missed across 1,342 built pages
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What a 26-page WCAG-EM sample missed across 1,342 built pages

#a11y #wcag #webdev #auditing
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12 min read
I Authored Six of the Seven Places My Title Is Declared
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I Authored Six of the Seven Places My Title Is Declared

#seo #a11y #anchortext #structureddata
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12 min read
24,948 of My 46,382 Internal Links Pointed at a 301
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24,948 of My 46,382 Internal Links Pointed at a 301

#seo #internallinking #redirects #canonical
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9 min read
I removed one archive page and 296 posts became unreachable
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I removed one archive page and 296 posts became unreachable

#seo #internallinking #crawlability #informationarchitecture
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10 min read
What a div grid quietly loses: measuring the a11y tree and text extraction on the same table
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What a div grid quietly loses: measuring the a11y tree and text extraction on the same table

#a11y #semantichtml #geo #wcag
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10 min read
OpenAI Spend Limits Return 429: Your Retry Logic Will Make It Worse
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OpenAI Spend Limits Return 429: Your Retry Logic Will Make It Worse

#openai #apireliability #costcontrol #errors
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11 min read
Why Prerendered LCP Reads 6.2s Without activationStart
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Why Prerendered LCP Reads 6.2s Without activationStart

#performance #corewebvitals #webdev #chrome
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9 min read
Why I Re-Run My Injection Tests Every Time I Bump the Model
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Why I Re-Run My Injection Tests Every Time I Bump the Model

#security #llm #webdev #cicd
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11 min read
Your AI Gateway Blocked the Request. Did You Still Pay?
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Your AI Gateway Blocked the Request. Did You Still Pay?

#openrouter #aigateway #finops #governance
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9 min read
WebMCP's Origin Trial: provideContext Is Already Gone
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WebMCP's Origin Trial: provideContext Is Already Gone

#webmcp #agents #chrome #webdev
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8 min read
FAQ Rich Results Are Dead. Don't Delete the Q&A Markup
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FAQ Rich Results Are Dead. Don't Delete the Q&A Markup

#seo #structureddata #jsonld #geo
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7 min read
WebSockets No Longer Block bfcache? Chrome 150 Still Said 'websocket'
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WebSockets No Longer Block bfcache? Chrome 150 Still Said 'websocket'

#performance #corewebvitals #webdev #chrome
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9 min read
OpenAI Output Moderation: What the Scores Actually Catch
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OpenAI Output Moderation: What the Scores Actually Catch

#openai #contentmoderation #aisafety #responsesapi
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8 min read
aria-modal="true" Blocked Nothing: Modal Focus Escape, Measured
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aria-modal="true" Blocked Nothing: Modal Focus Escape, Measured

#a11y #wcag #webdev
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7 min read
Restaurant JSON-LD: Nobody Catches opens: "eleven"
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Restaurant JSON-LD: Nobody Catches opens: "eleven"

#seo #structureddata #localseo #jsonld
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9 min read
One listener costs you the back button: six bfcache probes
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One listener costs you the back button: six bfcache probes

#performance #corewebvitals #webdev #chrome
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9 min read
1,248 Feed Items, Four Languages, Zero Language Metadata
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1,248 Feed Items, Four Languages, Zero Language Metadata

#i18n #w3c #webdev
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12 min read
GPT-5.6 Prompt Caching: The 24-Hour Cache Is Gone
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GPT-5.6 Prompt Caching: The 24-Hour Cache Is Gone

#openai #promptcaching #gpt56 #apicost
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10 min read
WCAG 2.2 Minimum Target Size: the AA Failure Hiding Behind a Green 92
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WCAG 2.2 Minimum Target Size: the AA Failure Hiding Behind a Green 92

#a11y #wcag #webdev
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9 min read
The meta Line That Decides If AI Overviews Can Quote You
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The meta Line That Decides If AI Overviews Can Quote You

#seo #geo #aioverview #structureddata
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8 min read
content-visibility Measured: One CSS Line, 15x Less Forced Layout
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content-visibility Measured: One CSS Line, 15x Less Forced Layout

#corewebvitals #css #webperf #rendering
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8 min read
When an AI Agent Bungles a Tool Call, Does It Fix Itself?
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When an AI Agent Bungles a Tool Call, Does It Fix Itself?

#agentreliability #tooluse #businessautomation #apibackedlab
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8 min read
Measuring INP: one click cost 264ms, chunking it got 56ms
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Measuring INP: one click cost 264ms, chunking it got 56ms

#corewebvitals #inp #webperf
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10 min read
Cutting CLS from 0.559 to 0.014, measured
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Cutting CLS from 0.559 to 0.014, measured

#corewebvitals #cls #webperf #a11y
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8 min read
GPT-5.6 Programmatic Tool Calling: When It Cuts the Token Bill
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GPT-5.6 Programmatic Tool Calling: When It Cuts the Token Bill

#gpt56 #programmatictoolcalling #tokencost #aifinops
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8 min read
A 117KB hero with a 1.2s LCP: the browser found it too late
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A 117KB hero with a 1.2s LCP: the browser found it too late

#corewebvitals #lcp #webperf #rendering
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8 min read
Catch Broken JSON-LD in CI Before It Ships
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Catch Broken JSON-LD in CI Before It Ships

#structureddata #jsonld #ci #seo
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8 min read
Claude Programmatic Tool Calling: Measured Token Savings
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Claude Programmatic Tool Calling: Measured Token Savings

#claude #programmatictoolcalling #tokencost #aifinops
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9 min read
AI Consumer Research: Validation Priorities, Not Market Truth
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AI Consumer Research: Validation Priorities, Not Market Truth

#airesearch #marketresearch #syntheticpanels #productvalidation
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11 min read
Can an AI Agent Finish Orders When a Tool Fails?
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Can an AI Agent Finish Orders When a Tool Fails?

#agentreliability #businessautomation #proofstudio
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8 min read
Goose by Block: A Free, Open-Source AI Agent Review 2026
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Goose by Block: A Free, Open-Source AI Agent Review 2026

#opensource #agents #mcp #developertools
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13 min read
GitHub Copilot Agent Mode in JetBrains IDEs: 2026 Guide
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GitHub Copilot Agent Mode in JetBrains IDEs: 2026 Guide

#githubcopilot #jetbrains #agentmode #aicoding
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15 min read
What Automated Accessibility Checks Miss After the Green Light
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What Automated Accessibility Checks Miss After the Green Light

#a11y #wcag #webdev
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11 min read
JSON-LD vs Microdata vs RDFa: Which Structured Data Syntax, and Why
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JSON-LD vs Microdata vs RDFa: Which Structured Data Syntax, and Why

#structureddata #jsonld #seo #webdev
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8 min read
A wrong accessible name breaks voice control and AI agents
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A wrong accessible name breaks voice control and AI agents

#a11y #wcag #geo
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9 min read
Web-Search Agents Waste Tokens: We Measured How Much
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Web-Search Agents Waste Tokens: We Measured How Much

#agenticsearch #tokencost #aifinops #llmtools
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8 min read
AI Crawlers Don't Run Your JavaScript
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AI Crawlers Don't Run Your JavaScript

#geo #seo #ssr #aicrawler
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8 min read
In sitemap.xml, lastmod Is the Only Field Google Actually Reads
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In sitemap.xml, lastmod Is the Only Field Google Actually Reads

#seo #sitemaps #crawling #webdev
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8 min read
OpenAI Models on Bedrock: A Responses API Readiness Check
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OpenAI Models on Bedrock: A Responses API Readiness Check

#openai #amazonbedrock #responsesapi #gpt55
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9 min read
Why color-contrast Disappears When You Put axe-core in CI
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Why color-contrast Disappears When You Put axe-core in CI

#a11y #axecore #wcag #ci
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8 min read
I Ran a Technical SEO Audit for Five Days: the Gates Mattered More Than the Five Fixes
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I Ran a Technical SEO Audit for Five Days: the Gates Mattered More Than the Five Fixes

#technicalseo #webdev #hreflang #structureddata
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8 min read
OpenAI Assistants API Shutdown: Port Your Bot Before Aug 26
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OpenAI Assistants API Shutdown: Port Your Bot Before Aug 26

#openai #assistantsapi #responsesapi #migration
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9 min read
Tie Your JSON-LD Into One @graph — Turn Scattered Structured Data Into an Entity Model Search and AI Can Read
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Tie Your JSON-LD Into One @graph — Turn Scattered Structured Data Into an Entity Model Search and AI Can Read

#structureddata #jsonld #seo #geo
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9 min read
hreflang Has to Be Bidirectional — Auditing My Own 4-Language Blog Turned Up a Homepage Bug
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hreflang Has to Be Bidirectional — Auditing My Own 4-Language Blog Turned Up a Homepage Bug

#hreflang #seo #i18n #webdev
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9 min read
OpenAI Moderation Scores: A Safety-Routing Gate PoC
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OpenAI Moderation Scores: A Safety-Routing Gate PoC

#openai #contentmoderation #aisafety #responsesapi
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10 min read
OpenAI Agents SDK Sandboxes: Provider Readiness Checklist
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OpenAI Agents SDK Sandboxes: Provider Readiness Checklist

#agentinfrastructure #businessautomation #openaiagentssdk #sandbox
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9 min read
OpenAI's 24h Prompt Cache: We Measured the Real Discount
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OpenAI's 24h Prompt Cache: We Measured the Real Discount

#openai #promptcaching #apicost #gpt55
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9 min read
Controlling AI Crawlers with robots.txt — Block Training, Allow Citation (2026)
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Controlling AI Crawlers with robots.txt — Block Training, Allow Citation (2026)

#geo #aio #robotstxt #seo
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9 min read
Accessibility 55 to 100: Fixing Real WCAG Failures with Lighthouse
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Accessibility 55 to 100: Fixing Real WCAG Failures with Lighthouse

#a11y #wcag #lighthouse #webaccessibility
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7 min read
LocalBusiness Structured Data: JS Injection Works, but Server-Side Is Safer
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LocalBusiness Structured Data: JS Injection Works, but Server-Side Is Safer

#seo #structureddata #meo #jsonld
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4 min read
I Pointed 8 Agents at One Local LLM — Measuring Ollama Concurrency Throughput
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I Pointed 8 Agents at One Local LLM — Measuring Ollama Concurrency Throughput

#localllm #ollama #concurrency #aiagents
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7 min read
Does a Local Reasoning Model Earn Its Keep? Measuring thinking ON/OFF on gemma4:12b
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Does a Local Reasoning Model Earn Its Keep? Measuring thinking ON/OFF on gemma4:12b

#localllm #ollama #reasoningmodels #llmevaluation
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8 min read
Why My Local Agent Forgot Its System Prompt — Measuring Ollama num_ctx Silent Truncation
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Why My Local Agent Forgot Its System Prompt — Measuring Ollama num_ctx Silent Truncation

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8 min read
Why a local LLM''s first reply sometimes takes 10 seconds — I measured the cold start (load_duration)
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Why a local LLM''s first reply sometimes takes 10 seconds — I measured the cold start (load_duration)

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8 min read
Why a Local LLM Slows Down as the Conversation Grows — I Split Prefill From Generation
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Why a Local LLM Slows Down as the Conversation Grows — I Split Prefill From Generation

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9 min read
Same Article, 1.4x the Tokens in Korean: Measuring the Non-English Token Tax Across 285 of My Posts
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Same Article, 1.4x the Tokens in Korean: Measuring the Non-English Token Tax Across 285 of My Posts

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8 min read
Does a Local LLM Ever Repeat Itself? Measuring Output Reproducibility with Temperature and Seed
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Does a Local LLM Ever Repeat Itself? Measuring Output Reproducibility with Temperature and Seed

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9 min read
Stop Feeding Raw JSON to Your LLM — I Measured Token Cost Across 9 Data Formats
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Stop Feeding Raw JSON to Your LLM — I Measured Token Cost Across 9 Data Formats

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6 min read
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