When a Contractor submits a target cost and this is approved and agreed with the provider. How long does this agreed Target Cost remain valid ? If the target is based on prices from a certain supply chain partner and by the time the work is actually instructed they are no longer available (and all alternative suppliers are significantly more expensive), is the provider within their rights to maintain that the original target cost still holders ?
The legal answer would be something like “a reasonable time given the context” which is not much use and why most of the time either the Client, when asking for a tender, or the Contractor, when giving it, state how long it is open for.
The typical time I see for construction contracts is 3 months from the date of submission if that helps.
When you say “agreed with the provider” does that mean you have signed the contract? Obviously at that point the Target is fixed and any change to that would be managed through the compensation event process - but only for things that are a compensation event. In this case it is unlikely to be a CE, unless the Scope specifically dictated the use of that material and/or supplier.
If you have not yet signed the contract, you are unlikely to sign a contract now you know you you can not meet the programme for or do it for that price. Whether they can
“make” you sign it at that point then becomes a legal issue, but I have never seen a Client take a Contractor to court for not signing up to a contract they now know before signing they can not achieve.