build-buy-partner

# build-buy-partner ## When to use - A capability gap exists and the question is whether to build internally, buy a vendor / acquisition, or partner. - An "obviously build" choice has crept in by default; the question is whether it survives a deliberate compare. - A vendor / partner relationship is up for renewal; the question is whether to keep buying, switch, or insource. - An acquisition has been floated; the question is whether the integration cost justifies the speed-to-capability. Do NOT use for vendor selection within a "buy" decision (different skill), market-entry beachhead choice (route to `market-entry-analysis` (P2)), or scenario-shape comparison (route to `scenario-modeling` (O4); P1 consumes O4's bundle). ## Cognition cluster - **Mental model 28 — Inversion.** *"What would force us to undo this choice in 18 months?"* Inversion surfaces the dependency-risk and integration-cost that the forward case understates. See [`mental-models.md`](../../../docs/contracts/mental-models.md) § 28. - **Mental model 21 — Second-order thinking.** Each option chains: build → ongoing maintenance + opportunity cost; buy → integration + lock-in; partner → dependency + boundary management. Single-order *"build is cheaper"* fails on the second-order. See `mental-models.md` § 21. - **Mental model 26 — Optionality.** Read each option by which choices it preserves (switch costs, re-build optionality, re-negotiation power) vs forecloses. The option with bounded foreclosure usually wins...