Change an existing repository

This guide follows one realistic change end to end: adding ISO week-date support to a date parser in an existing Python service, and delivering it as a draft pull request.

You will need: a connected repository with a working test command, and a policy that allows delivery_mode: draft_pr (or permission to open the pull request yourself).

Step by step#

Write the goal as an outcome#

Describe what should be true when the work is done, and name constraints Ysra cannot infer:

Goal

Make parse_date() accept ISO week dates such as 2026-W39-5 and 2026-W39.
Keep the public signature unchanged. Existing callers must not change.
Add tests for the week-date forms and for invalid weeks (W00, W54).

Acceptance criteria are yours to override

Ysra derives acceptance criteria from the goal. If you already have them — in a ticket, say — paste them in; explicit criteria are reviewed one by one against the final diff.

Set a budget that matches the change#

A focused change on a repository with a fast test suite usually needs a small budget. The session stops and asks before exceeding it, so an underestimate costs you a click, not a failed run.

Watch the first checkpoint#

Within a few minutes the session shows its plan and first checkpoint. This is the cheapest moment to correct course — steer now if the plan misreads the goal:

Use datetime.date.fromisocalendar rather than a hand-written week parser.

Review the evidence, not only the diff#

When the session completes, check three things before delivering:

Look at	Why
Checks	Which native commands ran, on which candidate, with what result.
Acceptance review	Each criterion, marked met or unmet against the exact diff.
Pre-existing failures	Anything already broken before the change, reported separately.

Deliver#

With delivery_mode: draft_pr, Ysra opens the draft pull request itself. With the default preserve_only, choose Open PR in the portal or the mobile app. Either way, the pull request links back to the session report.

When something goes wrong#

The session keeps failing the same test

Ysra stops after repeated identical outcomes and reports non-convergence. Read the last failure in the report: it is usually an environment need (a service, a secret, a fixture) the goal did not mention. Steer with that information and continue.

Ysra asks before installing a package

That is package_installs: ask. Approve it once in the session, or change the repository policy if the answer will always be yes.

See Troubleshooting for more.