Two small tools for teams shipping with AI agents.
Free and open source. Each one runs from your terminal with npx. Below: what they do, the command, and real output.
Switch
Snapshot tests for AI model upgrades.
Run your real prompts on your current model and the one you want to switch to. Switch flags only consistent changes in which tools get called, and how.
npx switch-llm init
npx switch-llm compare
Switch claude-cli:sonnet -> claude-cli:haiku 7 cases x 3 samples? FLAKY search docs arg search_docs.limit (3/3 -> 2/3)~ CHANGE schedule past date asked-instead-of-acting: asked a clarifying question instead of calling create_calendar_event (acted 3/3 -> 1/3, asked 0/3 -> 2/3)✓ SAME schedule missing date✓ SAME email missing recipientResult: 0 regression, 1 change, 5 same, 1 flaky
Real output, abridged: Sonnet vs the cheaper Haiku on 7 tasks, 3 tries each. No regressions; Haiku questions a meeting date that has already passed.How Switch works →
Fusion
Claude writes, your tests check, Codex reviews.
One command, one repair round if needed. You get a tested, reviewed patch; your branch stays untouched until you apply it.
npx agent-fusion run "Fix slugify so all tests pass" --verify "npm test"
npx agent-fusion apply latest
Status READY: verify passed, codex approved. Your branch is untouched.Writer claude write succeeded 41sVerify PASS npm testReviewer codex APPROVE 0 blocking, 0 suggestion(s)Repairs 0 of 1 usedChanged 1 file(s), +6 -1
Real output, abridged: Claude fixed a failing test, npm test passed, Codex approved.How Fusion works →
Why they exist
Switch
Model upgrades quietly change what your agent does.
A cheaper or newer model can pick a different tool, or act when it should ask. Switch shows you before you switch.
Fusion
One agent writing and grading its own work misses things.
Fusion has your tests and a second vendor’s agent check each patch before it reaches your branch.
Early, free and open.
Maintained by Abenezer.
Both tools are Apache-2.0 and early (0.x). Both are on npm (agent-fusion, switch-llm) and run with npx.