Adapt a configuration and inspect the exact edit

Jump to the assistant task. Complete the setup below first if this is your first Guide.

Prerequisites and setup

You need Node.js, Git, and cub on your PATH. No account, credentials, cluster, registry, Docker, Helm, or target access is needed. GitHub access is needed to clone the reviewed source.

Missing a tool? Install Node.js, Git, and the cub CLI. The local steps in this Guide do not require signup or login. For the CLI version used in the retained local trials, choose the matching cub v0.4.4 release binary. Check node --version, git --version, and cub version in the terminal or assistant session you will use, then install the pinned plugin below.

If you already completed setup for another Guide, return to that pinned checkout and skip cloning and installation. Otherwise, start in a directory that does not already contain cub-workshop:

New to cub? Install the cub CLI first. Public catalog packages pull and render anonymously, and you sign in only once a command saves or changes ConfigHub data.

git clone https://github.com/confighub/cub-workshop.git
cd cub-workshop
git checkout 56e261a87dc3b060a86474bc796d379dd9bb7f3d
cub plugin install "$PWD"

For every new adapt trial, including when reusing that checkout, run the following from its root. Choose a fresh directory if this trial already exists.

mkdir adapt-demo
cp examples/adapt/prometheus-before.yaml adapt-demo/before.yaml
cp adapt-demo/before.yaml adapt-demo/after.yaml

Open adapt-demo/after.yaml and change only the Deployment spec.replicas value from 1 to 2. Keep before.yaml unchanged.

Run the direct review

cub config diff adapt-demo/before.yaml adapt-demo/after.yaml --json --out adapt-demo/diff.json

Expected exit code: 0. The JSON should identify Deployment monitoring/prometheus-server, one changed field at /spec/replicas, and the change from 1 to 2. It retains hashes for both input files. diff.json is review evidence; it is not approval and does not make the edit authoritative.

To use an exit status that distinguishes differences, run the same comparison with --exit-code and a new output filename:

cub config diff adapt-demo/before.yaml adapt-demo/after.yaml --json --exit-code --out adapt-demo/diff-with-exit.json

Expected exit code: 1 because a difference exists. Malformed input and other errors return 2. Existing output files are protected; choose a new filename when repeating the review.

Move the directory and rerun the comparison to check that the local files, hashes, and findings travel together:

mv adapt-demo adapt-demo-moved
cub config diff adapt-demo-moved/before.yaml adapt-demo-moved/after.yaml --json --out adapt-demo-moved/recheck.json

Keep unexpected edits visible

Make a separate candidate from the changed file:

cp adapt-demo-moved/after.yaml adapt-demo-moved/unexpected.yaml

In unexpected.yaml, change only the existing spec.revisionHistoryLimit from 10 to 5, then compare it with the unchanged baseline:

cub config diff adapt-demo-moved/before.yaml adapt-demo-moved/unexpected.yaml --json --out adapt-demo-moved/unexpected-diff.json

Expected exit code: 0, with two changed fields: /spec/replicas (1 to 2) and /spec/revisionHistoryLimit (10 to 5). Keep this candidate on review hold because it exceeds the requested replica edit. The tool reports the extra change; it does not automatically refuse or approve it.

If the result contains an unexpected field, keep that result for review and repeat from fresh copies after deciding which edit is authorized. A successful comparison means the files were compared; it does not authorize the change.

A task for an AI assistant

Return to the pinned cub-workshop checkout root. Prepare a separate trial:

mkdir adapt-ai
cp examples/adapt/prometheus-before.yaml adapt-ai/before.yaml
cp adapt-ai/before.yaml adapt-ai/after.yaml
cd adapt-ai

Open Claude Code or Codex in this directory and paste the task below. Use your normal tool approvals; do not disable them. Keep the resulting files and the assistant report together.

Use the prepared before.yaml and after.yaml in this directory. Using cub
config diff, inspect those local files. Change only the Deployment
monitoring/prometheus-server spec.replicas value in after.yaml from 1 to 2;
never change before.yaml. Save the JSON result to diff.json and report the exit
code, both input hashes, the changed JSON pointer, and its old and new values.
Repeat with --exit-code to diff-with-exit.json (expected exit 1). Move the
whole directory by running cd .., then mv adapt-ai adapt-ai-moved, then
cd adapt-ai-moved. Rerun there to recheck.json;
compare hashes and findings. Then copy after.yaml to unexpected.yaml, change only
spec.revisionHistoryLimit from 10 to 5 in that copy, and run a second diff
against the unchanged before.yaml to a fresh output file. Expect two field
changes and retain them for reviewer inspection; this is a review hold, not an
automatic refusal. Do not install, upload, publish, deploy, contact ConfigHub
or Kubernetes, or read credentials. Explain that this is a local comparison
and does not prove an upstream merge, schema validity, approval, or runtime
health.

The retained source metadata and input excerpt establish the local source scope. The excerpt is one Deployment, not a full Prometheus chart. Mapping and document order are ignored; array order, null, missing values, and duplicate identities remain meaningful. The result demonstrates source files and a materialized comparison only: ConfigHub creation and delivery are not run. Continue with the match guide for supplied target facts.

For a new field rather than a changed replica count, use Add a field and restore the source. It also explains why an exact local restoration is different from live rollback.