Discovery Rule
The discovery rule defers the start of limitations until the claimant knew or should have known of the injury. Texas applies it narrowly. It reaches only injuries that are inherently undiscoverable and objectively verifiable, and the question is asked category by category, so what matters is whether that type of injury is typically discoverable.
Limitations normally run from the day the wrongful act causes a legal injury, whether or not anyone knows about it. The discovery rule is an exception, and Texas treats it as a genuine exception rather than a general fairness principle.
The two-part test
Computer Associates International, Inc. v. Altai, Inc., 918 S.W.2d 453 (Tex. 1996), and S.V. v. R.V., 933 S.W.2d 1 (Tex. 1996), set the standard. The rule applies only where the nature of the injury is inherently undiscoverable and the injury itself is objectively verifiable. Both parts do work. The first asks whether an injury of that type is by its nature unlikely to be discovered within the limitations period despite due diligence. The second asks whether there is evidence of the injury and of the defendant's conduct that does not rest on the claimant's own account.
The analysis is categorical. Courts ask whether the class of injury is generally discoverable, not whether this particular claimant could have found out. A plaintiff who says he personally had no way of knowing has not answered the question the court is asking. Childs v. Haussecker, 974 S.W.2d 31 (Tex. 1998), and HECI Exploration Co. v. Neel, 982 S.W.2d 881 (Tex. 1998), develop the point.
Where it does and does not apply
Fiduciary relationships are the most reliable ground. A beneficiary is not expected to police a trustee and a minority member is not expected to audit a manager, so breaches of fiduciary duty are often treated as inherently undiscoverable. Fraud and fraudulent concealment operate on a related but distinct basis, since concealment estops the defendant from relying on limitations. That is a different doctrine and it should be pleaded separately.
Ordinary contract claims are the hard case. Texas has been reluctant to apply the rule to commercial contract disputes, reasoning that a contracting party can protect itself by inspecting performance and has a duty to exercise diligence in enforcing its own rights. Do not assume the rule rescues a late breach of contract claim just because the breach was quiet.
Pleading and burden
The discovery rule must be pleaded. A plaintiff who does not plead it in response to a limitations defense has waived it, and appellate courts enforce that. On summary judgment the sequence is specific. A defendant moving on limitations must negate the discovery rule where it has been pleaded, which usually means conclusively establishing when the plaintiff knew or should have known of the injury.
In commercial litigation the rule most often decides cases involving long-running fiduciary breaches inside closely held companies, where the wrongdoing was recorded in books the plaintiff did not control. The evidence that establishes objective verifiability is generally the same evidence that proves the breach, so the two arguments get built together.
Related doctrines are sometimes confused with it. The legal injury rule fixes accrual at the date of injury regardless of the amount of damage. Fraudulent concealment is an estoppel rather than an accrual rule. The continuing tort doctrine addresses repeated conduct rather than delayed discovery. Each carries its own pleading requirements, and a limitations response that runs them together invites a ruling on the weakest of them.