terraform-knowledge-patch

Terraform Knowledge Patch

Baseline: Terraform through 1.6.x, including tests, import and check blocks, HCL, providers, state, modules, workspaces, and the OpenTofu 1.6 fork; covered range: Terraform 1.7–1.15, OpenTofu 1.7–1.12, current Stacks/HCP behavior, and Plugin Framework v1.5–v1.19.

Reference index

Reference	Topics
language-and-modules.md	Expressions, functions, validation, sensitivity, ephemeral values, modules, provider configuration
state-import-and-refactoring.md	State compatibility, removal, moves, imports, identities, plans, locking
backends-encryption-and-security.md	Backends, authentication, encryption, artifact installation, security and platform boundaries
cli-automation-and-output.md	CLI changes, JSON, console, plan rendering, query, actions, automation flags
testing.md	Terraform Test and OpenTofu Test, mocks, overrides, variables, concurrency, cleanup, JUnit
stacks-and-hcp.md	Stacks components and deployments, HCP execution, migration, governance, registries
provider-plugin-framework.md	Provider functions, moves, schema types, ephemeral/write-only/identity/list/action APIs, Go floors

Upgrade blockers and deprecations

S3 backend migrations

• Terraform 1.7 changed the S3 credential search order. Its temporary use_legacy_workflow = true escape hatch is deprecated; OpenTofu 1.8 removes that argument entirely.
• Terraform 1.10 removes deprecated flat assume-role attributes: use the assume_role block.
• Native S3 lock files use use_lockfile. Terraform 1.11 deprecates DynamoDB locking arguments; when both mechanisms are configured on Terraform 1.10, both locks are acquired.
• Terraform 1.15 validates AWS_USE_FIPS_ENDPOINT and AWS_USE_DUALSTACK_ENDPOINT strictly as true or false.

Configuration and state compatibility

• Terraform 1.7 writes input validations into state. Readers on the 1.3, 1.4, or 1.5 lines need at least 1.3.10, 1.4.7, or 1.5.7 respectively; pre-1.3 and 1.6+ readers are unaffected.
• Terraform 1.9 rejects provider version constraints inside .tftest.hcl; put them in the main required_providers configuration.
• Terraform 1.10 deprecates -state on plan, apply, and refresh; configure backend "local" { path = ... }.
• Reserved resource type names in Terraform 1.10 moved blocks require resource.<type>.<name>.
• OpenTofu 1.10's PostgreSQL locking is incompatible with older OpenTofu processes sharing the same database; mixing them risks data loss.
• OpenTofu 1.11 ignores deprecated AzureRM endpoint/ARM_ENDPOINT and msi_endpoint/ARM_MSI_ENDPOINT; reinitialize with tofu init -reconfigure.

Platform boundaries

• Terraform 1.12 and OpenTofu 1.10 require Linux kernel 3.2+.
• OpenTofu 1.10 requires macOS 11+, OpenTofu 1.11 requires macOS 12+, and OpenTofu 1.12 is the last planned macOS 12 line.
• Building Terraform 1.14 requires macOS Monterey or later.
• OpenTofu 1.12 deprecates WinRM provisioner connections for removal in 1.13; migrate Windows targets to SSH.

Ephemeral and write-only data

Terraform 1.10 introduces phase-scoped ephemeral resources and ephemeral = true variables/outputs. Their values exist only during one operation phase, are not stored in plan or state, and may differ between plan and apply. Provider support is per resource type.

ephemeral "aws_secretsmanager_secret_version" "db" {
  secret_id = var.secret_id
}

variable "session_token" {
  type      = string
  ephemeral = true
}

Terraform 1.11 adds provider-declared write-only managed-resource arguments. A _wo value is sent every operation but produces no diff and is never persisted. Pair it with a stored provider-specific version/trigger argument to make rotation visible.

resource "aws_db_instance" "db" {
  password_wo         = ephemeral.random_password.db.result
  password_wo_version = var.password_version
}

Unknown ephemeral inputs can defer opening an ephemeral resource until apply. OpenTofu gains ephemeral resources, variables, outputs, and write-only attributes in 1.11. See the language and provider-framework references for mark propagation, partial ephemeral values, schema rules, and lifecycle APIs.

State removal, moves, and imports

Use declarative removal when the change belongs in reviewable configuration:

removed {
  from = aws_instance.example
  lifecycle { destroy = false }
}

Terraform 1.7 supports removed blocks and for_each imports. Terraform 1.8 supports provider-approved cross-resource-type moved conversions. Terraform 1.9 adds destroy-time provisioners to removed; use 1.9.5+ for nested-module targets. Terraform 1.12 imports can use provider-defined identity instead of id, but not both.

OpenTofu 1.10 reaches cross-type moves and richer removals. OpenTofu 1.12 also permits dynamic prevent_destroy and lifecycle { destroy = false } directly on managed resources.

Dynamic modules and module contracts

Terraform 1.15 permits variables and locals in module source and version. OpenTofu has supported early-evaluated module and backend inputs since 1.8; values must be available before provider configuration. OpenTofu 1.12 can declare that contract explicitly:

variable "module_source" {
  type  = string
  const = true
}

Terraform 1.15 and OpenTofu 1.10 allow deprecated = "..." on module variables and outputs. Terraform 1.15 also adds output type constraints and convert(value, type).

Expressions and provider functions

• Provider-defined functions use provider::<name>::<function>(...) in Terraform 1.8+.
• templatestring(template, variables) renders dynamic template text in Terraform 1.9 and OpenTofu 1.7.
• Terraform 1.9 variable validations can refer to other variables, locals, and data sources.
• element accepts negative indices in Terraform 1.10 and OpenTofu 1.10; use Terraform 1.10.5+ for tuples.
• && and || short-circuit in Terraform 1.12 and OpenTofu 1.10.
• Terraform 1.15 adds convert; output blocks can declare a type.

Queries and actions

Terraform 1.14 adds list resources declared in *.tfquery.hcl, terraform query, optional generated imports, and offline terraform validate -query. Terraform 1.15 extends terraform fmt to query files.

Providers can also expose top-level actions for imperative operations. Actions can be lifecycle-triggered or invoked explicitly with -invoke; Terraform 1.14.1 fixes post-create/update ordering.

Testing essentials

• Terraform 1.7 adds provider mocks, resource/data/module-output overrides, test tfvars, functions in inputs, and references to variables or prior runs.
• Terraform 1.11 adds shared state_key, plan-time overrides through override_during = plan, and GA -junit-xml.
• Terraform 1.12 adds parallel run eligibility and terraform test -parallelism=n; Terraform 1.13 parallelizes eligible teardown.
• Terraform 1.13 test files can declare typed external variables and derive file variables from run outputs.
• Terraform 1.15 mock values can call functions. Alpha builds also expose retained test backends, skip_cleanup, and terraform test cleanup; do not rely on these in stable releases.

OpenTofu state encryption

OpenTofu 1.7 adds terraform.encryption and the overriding/merging TF_ENCRYPTION input for local/backend state and saved plans. Back up both state and keys first. Migrate by making the new method primary and the old/plaintext method a fallback; reads try fallbacks, but writes always use the primary method. Remove the fallback only after a successful rewrite.

Available 1.7 key sources include PBKDF2, AWS KMS, GCP KMS, and OpenBao Transit. Remote-state consumers configure decryption separately through remote_state_data_sources. OpenTofu 1.10 adds external programs and PBKDF2 chaining; OpenTofu 1.11 adds Azure Key Vault.

Experimental boundaries

Do not assume prerelease features exist in stable binaries. Terraform 1.13's -allow-deferral is alpha-only, as are Terraform 1.15's retained test backends, skip_cleanup, and terraform test cleanup. Plugin Framework deferred operations and state stores are experimental and carry no compatibility promise until their matching Terraform Core features stabilize.

Batch coverage

The detailed references incorporate content from every included batch, with overlaps deduplicated into shared topics:

Terraform	OpenTofu	Other
terraform-1.7.0-guide, terraform-1.7.0	opentofu-1.7.0	terraform-stacks-and-hcp
terraform-1.8.0-guide, terraform-1.8.0	opentofu-1.8.0	provider-plugin-framework
terraform-1.9.0-guide, terraform-1.9.0	opentofu-1.9.0
terraform-1.10.0-guide, terraform-1.10.0	opentofu-1.10.0
terraform-1.11.0-guide, terraform-1.11.0	opentofu-1.11.0
terraform-1.12.0	opentofu-1.12.0
terraform-1.13.0
terraform-1.14.0
terraform-1.15.0