*`opentf test`: The previously experimental `opentf test` command has been moved out of experimental. This comes with a significant change in how OpenTF tests are written and executed.
OpenTF tests are written within `.tftest.hcl` files, controlled by a series of `run` blocks. Each `run` block will execute an OpenTF plan or apply command against the OpenTF configuration under test and can execute conditions against the resultant plan and state.
* config: OpenTF can now track some additional detail about values that won't be known until the apply step, such as the range of possible lengths for a collection or whether an unknown value can possibly be null. When this information is available, Terraform can potentially generate known results for some operations on unknown values. This doesn't mean that Terraform can immediately track that detail in all cases, but the type system now contains the facility for that and so over time we will improve the level of detail generated by built-in functions, language operators, Terraform providers, etc. ([#33234](https://github.com/hashicorp/terraform/issues/33234))
* jsonplan: Added `errored` field to JSON plan output, indicating whether a plan errored. ([#33372](https://github.com/hashicorp/terraform/issues/33372))
* cloud: Remote plans on cloud backends can now be saved using the `-out` flag, referenced in the `show` command, and applied by specifying the plan file name. ([#33492](https://github.com/hashicorp/terraform/issues/33492))
* config: The `import` block `id` field now accepts an expression referencing other values such as resource attributes, as long as the value is a string known at plan time. ([#33618](https://github.com/hashicorp/terraform/issues/33618))
* The upstream dependency that OpenTF uses for service discovery of OpenTF-native services such as cloud backend state storage was previously not concurrency-safe, but OpenTF was treating it as if it was in situations like when a configuration has multiple `terraform_remote_state` blocks all using the "remote" backend. OpenTF is now using a newer version of that library which updates its internal caches in a concurrency-safe way. ([#33364](https://github.com/hashicorp/terraform/issues/33364))
* Transitive dependencies were lost during apply when the referenced resource expanded into zero instances ([#33403](https://github.com/hashicorp/terraform/issues/33403))
* OpenTF will no longer override SSH settings in local git configuration when installing modules. ([#33592](https://github.com/hashicorp/terraform/issues/33592))
