Uses 1M context window to ingest an entire codebase and output a file-by-file migration plan. Supports JS to TS, React class to hooks, framework migrations, and more. Generates migration-plan.md with file inventory, dependency graph, migration order, file-by-file changes, estimated effort, and risk assessment.
SkillScore82Maintained
Automatic
◆Coding pack
Last verified 8/24/2026
What it changes
Passed 16 of 20 test cases with the skill, and 12 of 20 without it.
Without skill59%
With skill82%
Checks it passed that the model alone missed
Applies a 20% buffer to base effort estimates.
Uses a 1 to 5 numerical scale for file risk scoring.
Outputs the refactored TypeScript code directly in the response.
and 2 more in the full report
5 fixed13 passed either way4 still failing0 broke
Pass-rate lift
+23 pp
Tokens
+4%
Agent turns
0%
Response time
-20%
Model gemini-3.6-flashMeasured 8/24/2026v118 of 22 cases passed with skill · 20 comparable
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 5 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 5
Prompt
Here is our legacy database client file `db.js` that needs to be converted to TypeScript with full type annotations for our project. Please write the complete refactored `db.ts` file directly in your response.
What was checked, without and with the skill
Checked
Without skill
With skill
Outputs the refactored TypeScript code directly in the response.
Missed
Passed
Does not create a repository migration-plan.md document.
Passed
Passed
case-04 · gemini-3.6-flash · 8/24/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md25 lines5 files
Full Codebase Migrator
Leverage the full 1M token context window to ingest an entire codebase, understand its architecture end-to-end, and produce a comprehensive, file-by-file migration plan that a team can execute sequentially without conflicts.
Contents
references/migration-types.md -- supported migration types; when to use and when not to use this skill.
references/ingestion.md -- architecture, glob patterns, metadata collection, read order, context budgeting, and dependency graph construction (Steps 0-2).
references/output-template.md -- migration-plan.md and migration-plan.json templates, edge cases, and the final quality checklist (Steps 7-8).
Workflow
Identify scope. Determine migration type, scope (full repo or directory), output location for migration-plan.md, and any exclusions or constraints. Infer from the user's prompt when already specified. See references/migration-types.md for supported types and fit.
Ingest the codebase. Glob all source files, collect metadata with Bash (line counts, package manifest, configs, git history, directory tree), then Read every source file. For 500+ file codebases, dispatch Agent sub-agents to read directory subtrees in parallel. See references/ingestion.md.
Build the dependency graph. Extract every import, build an adjacency list, classify each file into layers, detect circular dependencies, and classify external dependencies. See references/ingestion.md.
Assess each file. Produce a per-file migration assessment covering layer, complexity, patterns found, required changes, prerequisite dependencies, risk factors, and testing impact. See references/workflow-detail.md.
Calculate migration order. Run a topological sort by layer, apply practical adjustments (quick wins, high-risk-early, break cycles first), and group files into buildable, PR-sized phases. See references/workflow-detail.md.
Assess risk. Score each file 1-5 on complexity, centrality, volatility, test coverage, and external coupling. Build the migration-level risk matrix and rollback strategy. See references/workflow-detail.md.
Estimate effort. Derive per-file, per-phase, and total estimates with overhead and a 20% buffer, then translate into calendar time by team size. See references/workflow-detail.md and the effort calibration table in references/migration-types.md.
Generate the deliverable. Write migration-plan.md to the output location, and migration-plan.json when machine-readability helps. Verify against the quality checklist before delivering. See references/output-template.md.
Edge Cases
Codebases too large for context, monorepos, partially migrated codebases, and codebases without tests each need adjusted handling. See references/output-template.md.
Review pull requests for code quality, security issues, and best practices. Use when reviewing PRs, checking code changes, or analyzing diffs before merge.