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Sethu traces OpenAPI changes into a consumer application, repairs the affected code, and records evidence that an independent checker can validate.

Three tools share the work. Each one owns a distinct step.

Tool	Role	Example
Vimanam	Creates the contract diff from two specs	Reports that POST /search/random changed its success response
Bob IDE	Changes consumer code through /api-upgrade	Gives random search its own parser and leaves the shared parser alone
Sethu	Checks facts and evidence around the change	Refuses to close the paging decision without a recorded human choice

One concrete change

Immich v1.117.0 changes POST /search/random. Its success response moves from SearchResponseDto (with assets.items) to an array of AssetResponseDto.

Vimanam creates this diff. Bob IDE changes the consumer. Sethu commands check the evidence.

Key terms

Contract diff. Vimanam output that lists every change between two specs. Example: the diff lists 27 required changes across 4 operations for the pinned Immich pair.

Change record. One entry in that diff, with a stable ID and severity. Example: the random search response change carries an operation origin, because the old component still serves other operations.

Migration attempt. One bound run of sethu init for a spec pair, a consumer commit, and a scope. Example: an attempt binds the v1.116.2 to v1.117.0 pair to the picker checkout.

First steps

1. Install the tools by following Install and first run.
2. Confirm the setup with the capability command:

   sethu capabilities

3. Read the Immich walkthrough to see the full sequence from init to report.
4. Look up any flag in the Command reference.

The workflow page explains ledgers, verification runs, and the difference between accounting and readiness.