What exact interface or behavior do I need?

Backstop exposes a repository-oriented CLI, YAML artifacts, JSON-capable output, and process exit codes. A runtime integration must invoke the pinned binary from the intended working directory and propagate blocking exits. That proves operability; artifact order and role separation require additional harness behavior.

A harness can invoke Backstop, but operability alone does not preserve artifact ordering, review separation, or enforcement of a blocking verdict.

Invocation proves that the binary runs. A trustworthy integration separately proves that the harness preserves lifecycle order and stops on failure.

Runtime-neutral does not mean runtime-guaranteed. Backstop cannot make a harness respect a result it chooses to discard.

Artifact schemas live under artifacts/<kind>/v1/schema.json. The CLI reserves IDs, scaffolds valid records, validates references and state, and excludes terminal historical artifacts where policy declares that behavior.

The repository root contains backstop.yml. Its project, packs, and enforcement.policy fields declare versioned standards and policy levels. The lock under .backstop/ binds resolved pack bytes.

Backstop commands return 0 for success, 1 for blocking violations or broken promises, and 2 for configuration failure. The global --json flag selects structured output where supported, while backstop commands provides machine-readable command discovery.

backstop doctor diagnoses configuration discovery and loading, Git repository state, installed packs, build identity, toolchain execution, engine-tool availability, and artifact layout. A failing check returns 1; an unknown check identifier is a configuration error.

backstop gate evaluates changed files by default. backstop gate --file <path> bounds verification explicitly, while backstop gate --all runs the repository-wide kill chain. Exit zero means every blocking step passed; a nonzero exit is a verdict to preserve, not suppress.

Use backstop pack install, backstop pack list, backstop pack update, and backstop pack relock to manage declared versions and resolved locks. Inspect findings before accepting an update.

A pack declares identity, version, claims, engines, fixtures, tools, applicability, and findings. Commands are direct argv contracts; tool pins are trust declarations rather than installers.

Closing an issue requires a ## Resolution section and at most one traceability field: delivered_by names a completed plan, while resolved-by names a direct typed artifact reference, commit SHA, or pull-request URL when no plan lineage applies.

A gate result is useful evidence only when its command, prerequisites, and captured artifact are named.

A literal Liquid-shaped {{ ... }} expression is currently interpreted as an undeclared recipe parameter and rejected before any write; ISSUE-182 tracks the missing literal-escape capability.

Linux CI exposed a contracts-pack fixture false negative, and commit f8b3846fe5d4c2bc6465efc6eb5e4594e1b591da repaired it with checked-in before-and-after evidence.

The command families cover initialization, diagnosis, gates, packs, artifacts, recipes, baselines, waivers, version reporting, and command discovery. Use --help on the pinned release for exact flags and --json where a command exposes structured output.