Crate amberfork_attrib 

Counterfactual attribution: verify a fork by re-running the agent, not just observing it.

amberfork diff localizes the fork and labels attribution Static — a structural claim (“they diverge here, and it propagates downstream”) that no re-execution ever checked. This crate is the consumer the record/replay path was built for (epic #35): it patches the fork step with the good run’s behaviour, re-drives the agent through amberfork_replay against the patched cassette, and reports whether the run recovered — the difference between “they differ here” and “this is what broke it”.

It is the one crate that turns AttributionMode::Counterfactual — defined in the frozen model but produced nowhere — into real output.

Offline by default, opt-in to re-execute

Nothing here runs unless the CLI is invoked with --verify: default amberfork diff stays 100% offline and structural. Re-execution needs a live provider seam and a re-runnable agent command, both injected by the caller; the whole test suite substitutes an in-process stub for each, so cargo test --workspace stays offline and deterministic.

Shape of the pipeline

DiffResult + bad/good cassettes
  └─ patch_cassette        (pure) → the bad cassette with the fork step's response swapped
       └─ re-execute × N    (I/O) → each re-run's own cassette, via ReplayServer + the agent
            └─ recovery oracle (pure) → recovered / not recovered / inconclusive, per run
                 └─ consensus over N (pure) → Recovery tri-state → upgraded Attribution

verify is the entry that runs the whole pipeline; the CLI wires it behind diff --verify.

Enums

AgentError

Why the agent could not be driven.

ReexecError

Why a re-execution could not be carried out at all.

Traits

AgentDriver

Drives the agent under test once, pointed at a base URL, so a re-execution can capture what it does.

Functions

patch_cassette

Produce the patched bad cassette to re-execute, or None when the diff has no two-sided fork.

verify

Verify a diff’s fork by counterfactual re-execution, upgrading its attribution from Static to Counterfactual and refining its origin/propagation split.