"Agile" and "fixed price" get framed as philosophy; they are actually risk allocation. Time-and-materials puts scope risk on you and flexibility in your hands; fixed price puts delivery risk on the vendor and discipline on the scope. Neither is virtuous — the question is which risk you can afford to hold. Here is the honest map.
What each model really means
Agile / time-and-materials: you buy a team's weeks and direct them sprint by sprint. Scope evolves freely; you pay for whatever it becomes. Works beautifully when you can product-manage — prioritize ruthlessly, accept increments, kill features. Fails expensively when you cannot: an undirected T&M engagement is a taxi with the meter running and no destination.
Fixed price: a defined scope at a committed number (acceptance criteria make it real). The vendor absorbs estimation misses; you absorb the discipline of deciding upfront and paying for changes explicitly (change control). Works when scope is definable; fails when nobody can define it and the contract becomes a fight about interpretations.
The decision, honestly
| Your situation | Model |
|---|---|
| Bounded outcome (MVP, migration, defined product) | Fixed price |
| Continuous evolution with in-house product leadership | Agile/T&M (or a dedicated team) |
| Cannot write scope yet | Paid discovery first, then fixed price |
| Non-technical buyer, first project | Fixed price — the acceptance criteria protect you |
The myths, both directions
"Fixed price means waterfall" — false: inside a fixed scope, good vendors still build iteratively with weekly demos; the contract is fixed, not the method. "Agile means no commitments" — also false as practiced honestly: sprint goals, velocity transparency, and budget caps are commitments; their absence is not agile, it is drift with ceremonies.
The hybrid that serves SMBs best
Fixed-price milestones inside a phased roadmap. Phase one scoped and priced firmly; learnings reprice phase two; both sides re-commit or part cleanly at each gate. You get price certainty per phase and evolution between phases — the MVP-then-iterate rhythm with contracts that match it.
We work fixed-price by default because most of our clients should not have to carry estimation risk — and we put the discipline where it belongs, in discovery and acceptance criteria. Bring us a scope conversation and we will tell you which model your project actually wants.
Frequently asked questions
Should I choose agile or fixed price for my software project?
Fixed price for bounded outcomes (MVPs, migrations, defined products) and first-time non-technical buyers — acceptance criteria protect you. Time-and-materials for continuous evolution with in-house product leadership. Can't write scope yet? Paid discovery first.
Does fixed price mean waterfall development?
No — the contract is fixed, not the method. Good vendors build iteratively with weekly demos inside a fixed scope. Conversely, honest agile still commits to sprint goals and budget caps; commitment-free 'agile' is drift with ceremonies.
What is the hybrid contract model?
Fixed-price milestones inside a phased roadmap: phase one priced firmly, learnings reprice phase two, both sides re-commit at each gate. Price certainty per phase plus evolution between phases — the MVP-then-iterate rhythm in contract form.
Who carries the risk in each contract model?
Time-and-materials: you carry scope and delivery risk — the meter runs regardless. Fixed price: the vendor absorbs estimation misses; you carry upfront decision discipline and pay explicitly for changes. Pick the risk you can afford to hold.