Agent Changelog
Compile a chronological record of key decisions, architectural changes, and project evolution optimized for coding agent context-building.
Output
Write to AGENT_CHANGELOG.md in the project root. This file helps agents:
- •Understand key decisions and their rationale
- •Identify deprecated patterns/approaches to avoid
- •Grasp the trajectory from past to present to likely future
- •Detect stale documentation that contradicts current reality
Workflow
1. Gather Sources
Collect information from these sources in parallel:
Git history:
bash
git log --oneline --since="6 months ago" | head -100 git log --all --oneline --grep="BREAKING" --grep="deprecate" --grep="remove" --grep="migrate" -i git tag -l --sort=-creatordate | head -20
Documentation:
- •
.claude/plans/- implementation plans and decisions - •
CLAUDE.md- project instructions - •
README.md- project overview - •
docs/or similar documentation directories - •
CHANGELOG.mdif exists (traditional changelog)
Code signals:
- •
@deprecatedannotations - •
TODO,FIXME,HACKcomments with dates - •Migration files, upgrade scripts
2. Identify Key Events
Extract events that matter for agent understanding:
Always include:
- •Architectural decisions (new patterns, removed patterns)
- •Breaking changes and migrations
- •Deprecated features/approaches
- •Major dependency changes
- •Directory structure changes
- •API changes (internal or external)
Include if significant:
- •New features that change how agents should work
- •Bug fixes that reveal incorrect assumptions
- •Performance changes that affect approach recommendations
Skip:
- •Minor bug fixes
- •Cosmetic changes
- •Routine dependency updates
- •Individual feature additions (unless architectural)
3. Cross-Reference for Contradictions
For each significant event, check if existing documentation contradicts it:
code
Event: "Migrated from Redux to Zustand" (commit abc123, 2024-03) Check: Does any documentation still reference Redux patterns? - README.md mentions Redux? → Flag as STALE - CLAUDE.md suggests Redux approach? → Flag as STALE - Old tutorials in docs/? → Flag as STALE
Track contradictions in a "Stale Information Detected" section.
4. Write the Changelog
Structure the output file:
markdown
# Agent Changelog > This file helps coding agents understand project evolution, key decisions, > and deprecated patterns. Updated: [DATE] ## Current State Summary [2-3 sentences on where the project is NOW - the authoritative current architecture] ## Stale Information Detected [List any documentation that contradicts current reality - agents should ignore these until fixed] | Location | States | Reality | Since | |----------|--------|---------|-------| | docs/auth.md | "Uses JWT tokens" | Migrated to sessions | 2024-06 | ## Timeline ### [YEAR-MONTH] - [Brief Title] **What changed:** [Factual description] **Why:** [Decision rationale if known from plans/commits] **Agent impact:** [How this affects how agents should work in the codebase] **Deprecated:** [What approaches/patterns should agents avoid] --- [Repeat for each significant event, reverse chronological] ## Deprecated Patterns [Consolidated list of things agents should NOT do, with what to do instead] | Don't | Do Instead | Deprecated Since | |-------|------------|------------------| | Use `OldService` | Use `NewService` | 2024-08 | ## Trajectory [Brief note on where the project appears to be heading based on recent changes and plans]
5. Validate and Update
After writing:
- •Read existing
AGENT_CHANGELOG.mdif present and merge, don't duplicate - •Verify dates against git history
- •Ensure "Stale Information Detected" section is actionable
When to Proactively Run
Suggest running this skill when:
- •A major refactor or migration just completed
- •Plans in
.claude/plans/were recently executed - •Multiple architectural decisions happened in quick succession
- •Detected documentation that seems to contradict code reality
- •Starting work on a codebase after a long gap
- •Onboarding to an unfamiliar codebase
Guidelines
- •Prioritize accuracy over completeness—wrong history is worse than incomplete
- •Include rationale when available (commit messages, plan docs)
- •Be specific about what agents should avoid, not just what changed
- •Keep entries concise—this is reference material, not storytelling
- •Date everything to help agents judge relevance