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2026-04-14 | 🔗 Fixing Link Insertion for Auto Blogs 🧩

🐛 The Bug

🔍 Every day, the Haskell automation generates blog posts for several auto blog series, like The Noise, Auto Blog Zero, and Chickie Loo. 📝 After writing each post, it inserts a wikilink into the day’s reflection note so the user can navigate from their daily reflection to that day’s generated content.

😤 But those links were wrong. 🏷️ Instead of showing the full display title with date and series icon emojis, like “2026-04-14 | 📰 My Post Title 📰”, the links showed just the raw title text, like “My Post Title”. 🔧 The user was correcting these links manually every single day.

🔬 Root Cause Analysis: Five Whys

🔢 Why number one: Why were emojis missing from auto blog post links in daily reflections? 🎯 Because the function that inserts links into reflections received a raw sanitized title instead of the full display title.

🔢 Why number two: Why was the raw title passed instead of the display title? 📝 Because the call site in RunScheduled.hs computed the display title for writing the post header, but then passed the original raw title to the reflection-linking function.

🔢 Why number three: Why was there a separate raw title and display title? 🧠 Because the AI generates just the creative title, and the system wraps it with the date and series icon emojis. The display title was computed at line 289 but the reflection link at line 327 used the pre-wrapped version.

🔢 Why number four: Why was this mismatch not caught? 🤖 The AI blog path (a different code path) reads titles from frontmatter, which already contains the full display title. So AI blog links in reflections looked correct. Only the blog series generation path had this bug.

🔢 Why number five: Why were there two separate code paths for the same operation? 🔀 The codebase evolved incrementally. The AI blog link path and the blog series link path grew independently, with duplicated link-building functions in different modules.

🔧 The Fix

🎯 The one-line fix was changing RunScheduled.hs to pass displayTitle instead of title to the updateDailyReflection function.

🧹 But the deeper fix was consolidating all the duplicated wikilink formatting logic into a single shared module.

🧩 The Shared Wikilink Module

📦 A new Automation.Wikilink module now provides formatWikilink, buildBackLink, and buildForwardLink as the single source of truth for all wikilink construction. Every module that constructs wikilinks now delegates to this shared module.

🔗 buildBackLink and buildForwardLink were moved from BlogPrompt (which is about AI prompt construction, not navigation) to Wikilink, their domain-appropriate home. AiBlogLinks, BlogSeries, BlogPrompt, and RunScheduled all import them from Wikilink now.

🗑️ AiBlogLinks had duplicate buildAiBlogBackLink and buildAiBlogForwardLink functions. These were removed entirely, replaced by direct calls to the shared functions.

📝 DailyReflection’s buildPostLink, buildSeriesSectionHeading, buildReflectionContent, and addForwardLink all delegate to the shared formatWikilink.

🔎 InternalLinking’s CandidateDiscovery module renamed its formatWikilink to formatContentEntryWikilink, which extracts the path and title from a ContentEntry and delegates to the shared formatWikilink.

🏷️ Domain Types Over Primitives

🔒 After the initial fix, a follow-up review pointed out that passing raw Text for the title parameter invites the same class of bug to recur. 📐 The solution: change updateDailyReflection, insertPostLink, and buildPostLink to take Title (a validated newtype from Automation.Title) instead of raw Text.

🧱 This pushes validation to the boundary. The blog series path wraps the display title via mkTitle before calling updateDailyReflection. The AI blog path validates titles inside buildReflectionLinks, filtering out any entries with invalid titles at the source.

🎯 Now, if someone tries to pass a raw Text where a Title is required, the compiler catches it. The type system prevents the bug from recurring.

🧪 Testing

📊 The final test count is 1758. ✅ Thirteen new tests cover the shared Wikilink module: six unit tests for formatWikilink, four unit tests for buildBackLink and buildForwardLink, and three property tests. ➕ Two tests in DailyReflectionTest verify emoji preservation. All existing tests were updated to use the Title type via the testTitle helper.

🧹 Zero hlint hints, zero compiler warnings.

💡 Lessons Learned

🧠 When the same operation exists in multiple code paths, small divergences accumulate. 🔗 One path reads the title from frontmatter (correct), another computes it and passes the wrong intermediate value (incorrect). 🏗️ The fix is not just patching the one-line bug, but extracting the shared abstraction so divergence cannot recur.

📐 The Unix philosophy applies here: do one thing and do it well. 🧩 A single formatWikilink function that every module delegates to is easier to reason about than five different inline string concatenations.

📚 Book Recommendations

📖 Similar

• A Philosophy of Software Design by John Ousterhout is relevant because it discusses how complexity accumulates through tactical programming, exactly the pattern that created duplicated link-building functions across modules
• Refactoring: Improving the Design of Existing Code by Martin Fowler is relevant because the core fix involved extracting a shared method from duplicated implementations, one of the most fundamental refactoring patterns

↔️ Contrasting

• Release It! by Michael T. Nygard offers a perspective focused on runtime failures and stability patterns rather than code-level duplication, showing that not all bugs come from shared abstractions

🔗 Related

• Domain-Driven Design by Eric Evans is relevant because the fix followed DDD principles: identifying that wikilink formatting is a domain concept that deserves its own module rather than being scattered across feature modules
• The Pragmatic Programmer by David Thomas and Andrew Hunt is relevant because the DRY principle (Don’t Repeat Yourself) is exactly what this refactoring enforced across the codebase