Diary

An implementation diary captures the narrative of your work: what you did, why, what worked, what broke, what was tricky, and what needs review. The concept of "diary" activates existing behavioral patterns without requiring much engineering -- the model already knows what a diary is.

Working Loop

Follow this cycle for each meaningful unit of progress:

1. Implement -- make the code change
2. Update diary -- add or update the current step in the diary file
3. Commit -- commit the code and diary together

A "step" is a logical chunk of work, not necessarily a single commit. Examples: "wire up the API endpoint", "debug the flaky test", "research how the auth middleware works".

File Location

Diary files live at docs/diary/YYYY-MM-DD-<slug>.md relative to the project root.

• The date is when work on the task started
• The slug is free-form: a feature name, ticket reference, or whatever describes the task
• One file per task or feature -- if work spans multiple days, steps accumulate in the same file
• Create the docs/diary/ directory if it doesn't exist

Examples:

• docs/diary/2026-03-25-add-diary-skill.md
• docs/diary/2026-03-20-fix-auth-race-condition.md
• docs/diary/2026-03-18-PROJ-123.md

Diary File Structure

# Diary: <task description>

Brief description of the goal and context for this task.

## Step 1: <short description>

### Prompt Context

**Verbatim prompt:** <the exact user prompt that initiated this step>
**Interpretation:** <what the assistant understood from the prompt>
**Inferred intent:** <the underlying goal behind the prompt>

### What I did
<factual description of actions taken, files touched, commands run>

### Why
<connects the actions to the goal>

### What worked
<positive signals worth replicating>

### What didn't work
<failures recorded immediately with verbatim errors and commands>

### What I learned
<tacit knowledge that isn't obvious from the code>

### What was tricky
<friction points, hidden complexity, sharp edges>

### What warrants review
<tells a reviewer where to look and how to validate>

### Future work
<implied follow-ups that naturally fell out of the work, not a wishlist>

## Step 2: <short description>

...

Writing Rules

• Prose-first. The diary is a narrative, not a log dump. Technical details (paths, hashes, error messages) are included inline but wrapped in readable prose.
• All sections, every step. Never skip a section. If "What didn't work" is genuinely empty because everything went smoothly, say that explicitly.
• Failures are gold. Record them immediately with verbatim error messages and the exact commands that produced them. These are the most valuable parts of the diary.
• Absolute paths from project root. All file paths referenced in the diary are absolute relative to the project root (e.g., /src/handler.go).
• Prompt Context is verbatim. Copy the user's prompt exactly as given. Don't paraphrase the verbatim section.

When to Activate

This skill activates proactively during non-trivial implementation work:

• New features
• Bug fixes
• Refactors
• Research spikes

Do not activate for:

• One-line fixes
• Config tweaks
• Quick questions about the codebase
• Trivial changes that don't warrant narration