Does an indemnity claim survive if the buyer later amalgamates the target into another company?

Generally yes. Under Ontario and federal corporate law, an amalgamation is treated as a continuation of the amalgamating corporations rather than the creation of a brand-new entity that starts with a clean slate, and the amalgamated corporation generally continues to hold the rights, and remains subject to the liabilities, that each predecessor corporation had immediately before the amalgamation took effect. On that basis, contractual rights the buyer held under the purchase agreement, including an indemnity claim, would generally continue to exist and be enforceable by, or through, the resulting amalgamated corporation.

That said, this depends on the buyer's own contractual rights actually being capable of continuing in that form, and on the purchase agreement not containing restrictions on assignment or on who may bring a claim that could complicate the picture after a later corporate restructuring. Because amalgamating the target is a common step buyers take for tax or administrative reasons after closing, it is worth confirming the purchase agreement's assignment language supports this before treating an existing indemnity claim as automatically unaffected.