Three phases, one document running through all of them. The method is deliberately unglamorous, and its distinguishing feature is what we do in the first two weeks and the last four — the parts most partners skip.

Before any architecture is discussed
Typical first release, deliberately narrow
Reported to the accountable executive
The middle of a project — design, engineering, testing — is the part our industry has largely solved. Competent teams build competent software with reasonable predictability. The failures cluster at the two ends: a beginning where nobody established what the work was worth, and an ending where everybody left before it was worth anything.
So our method concentrates effort there. Two weeks at the front establishing the value model with the people who own the numbers, and a final phase that does not close until adoption is real and the first measurement has been reported. The engineering in between looks much like any good team's.
They spent two weeks before writing any code, and then finished faster than the vendor who started building on day one.
A typical first engagement. Longer builds extend phase two; the front and back ends stay the same.
Interviews with finance, operations and frontline staff. We ask to see the spreadsheets the business actually runs on, the reports nobody trusts, and the queue that never empties. We measure rather than accept described process.
Metric, baseline, target, owner, mechanism, review dates. We present it to your leadership and expect the baseline to be challenged, because a baseline your finance team will not defend is worthless.
Production, not prototype. Deliberately narrow scope aimed at the single highest-value decision or workflow, with the interface and integration required for someone to actually use it.
Enablement, workflow change, holdout setup and instrumentation. This is where most projects stop and where most value is won. We report the first number to the accountable executive before the engagement closes.

Two weeks with finance, operations and frontline teams. We measure the current state rather than accept the described one, then write the value model and argue about it until your own people will defend the baseline.

Production software, narrow scope, fortnightly demonstrations. We ship the smallest thing that can move the agreed metric, including the workflow and integration required for a real person to use it in real conditions.

Adoption work, holdout measurement, monthly value reporting and iteration against evidence. The engagement does not close on launch day; it closes when the number has been measured and reported.

We are direct about this in the first meeting, because engagements fail on the client side at least as often as on ours.
Written recommendations not to proceed
Median first release
Clients continuing after project one
Fixed fee, credited against anything that follows, and an honest verdict at the end — including the recommendation to stop.