Terraform Drift Skill

Detect infrastructure drift via Terraform plan, propose .tf code alignment diffs, get batch approval, re-verify with terraform fmt/validate/plan, and commit verified aligned code. This skill covers drift detection and resolution only — applying infrastructure changes (recreating remotely-deleted resources) is handled by /terraform:apply.

Tools Used

• AskUserQuestion: Module selection when multiple modules are found, destructive drift A/B choice per resource, and batch approval gate before applying code edits.
• Bash: Git commit after a clean re-verification plan confirms zero changes.

Workflow

Step 1: Discover Modules

If the user invoked the skill with a path argument (e.g., /terraform:drift modules/vpc), skip discovery and use that path resolved to an absolute path as absolute_module_path directly. Proceed to Step 2.

Otherwise:

Read plugins/terraform/agents/terraform-engineer.md and follow its Module Discovery algorithm (Section 2), executing all Glob, Bash, and MCP tool calls in the current session. Do NOT spawn a subagent. Return: sorted list of relative module paths (relative to git root), or the message "No Terraform root modules found in this repository." if none exist.

Based on the agent's response:

If 0 modules found:

Show:

No Terraform modules found. Run terraform init in your module directory first.

Stop.

If 1 module found:

Show:

Found 1 module: {relative_path} — running drift detection...

Resolve the absolute path (git_root + "/" + relative_path). Proceed to Step 2.

If 2+ modules found:

Present the numbered list via AskUserQuestion:

Found {N} Terraform modules:

  1. {relative_path_1}
  2. {relative_path_2}
  ...

Which module? (1-{N}):

Wait for the user to type a number. If the input is not a valid number between 1 and N, re-show the list with:

Please enter a number between 1 and {N}.

Resolve the selected absolute path (git_root + "/" + selected_relative_path). Proceed to Step 2.

Step 2: Run Plan and Detect Drift

Read plugins/terraform/agents/terraform-engineer.md and follow its Plan Execution (Section 1) and Safety Categorization (Section 3) instructions, executing all MCP tool calls in the current session. Do NOT spawn a subagent. Working directory: {absolute_module_path} Return: categorized resource list (SAFE/RISKY/DESTRUCTIVE), one-line impact description per resource in plain operational English, total counts per category, and a "No changes" signal if infrastructure matches configuration.

If plan fails with init required:

Auto-run: Read plugins/terraform/agents/terraform-engineer.md and follow its Plan Execution instructions (Section 1) to run terraform init -backend=false for the module at {absolute_module_path}, then re-run terraform plan, executing all MCP tool calls in the current session. Do NOT spawn a subagent. Do NOT use the -upgrade flag. Return: categorized resource list as above, or the error output if init or plan fails.

If init fails, surface the error and tell the user:

Run `terraform init -backend=false` in `{module_path}` manually and re-run /terraform:drift.

Stop.

If plan fails with any other error:

Show the raw error output from the agent. Append:

Fix the error above and re-run /terraform:drift.

Stop.

If plan returns no changes:

Show:

No drift detected — remote state matches your code.

Stop.

If plan returns changes, classify each resource:

• DESTRUCTIVE drift: resource exists in .tf code AND plan shows will be destroyed — meaning the resource no longer exists in remote state (remote deleted it). Cross-check: confirm the resource block exists in the .tf files. If it does AND plan shows destruction → DESTRUCTIVE drift.
• Normal drift: attribute-level mismatches (remote state has values that differ from code — updates, in-place changes).

Show summary header:

{N} resources drifted: {resource1}, {resource2}, ...

(List all drifted resources, both destructive and normal.)

Proceed to Step 3 if any DESTRUCTIVE drift resources exist; otherwise skip to Step 4.

Step 3: DESTRUCTIVE Drift Gate

This step MUST complete for all destructive resources before Step 4 begins.

For each destructive resource, show the hard gate block:

DESTRUCTIVE DRIFT: {resource_name}

This resource exists in your .tf code but was deleted from remote infrastructure.

Possible causes:
  - Intentionally deleted via AWS Console or CLI
  - Terminated by another automation or lifecycle policy
  - Removed by another Terraform run outside this codebase

Choose an action:
  (A) Remove from .tf code — aligns code with remote state (resource stays deleted)
  (B) Recreate via terraform apply — restores the resource to match your code

Ask via AskUserQuestion: "Enter A or B for {resource_name}:"

If user chooses A: Note this resource for inclusion in the Step 4 diff batch as a deletion diff (remove the entire resource block from the .tf file). Continue to next destructive resource.

If user chooses B: Show:

To recreate {resource_name}, run /terraform:apply after this drift session.

Exclude this resource from code alignment. Continue to next destructive resource.

Edge case — all drift was destructive and user chose B for all of them:

No code changes to commit. Run /terraform:apply to recreate the deleted resources.

Stop.

Step 4: Present Normal Drift Diffs and Batch Approval Gate

First, instruct the agent to generate diffs WITHOUT applying:

Read plugins/terraform/agents/terraform-engineer.md and follow its File Operations (Section 4) instructions, executing all Read and Grep tool calls in the current session. Do NOT spawn a subagent. For each drifted resource (including destructive resources where user chose A):

• Read the current .tf file content
• Compare with remote state values from the plan output
• Produce a before/after diff in .tf file syntax showing which lines would change

IMPORTANT: Do NOT apply any edits. Return the complete set of proposed diffs only.

Present all diffs as inline before/after blocks per resource:

Proposed code changes to align with remote state:

--- {relative_tf_file_path} ({resource_name})
- {old_line}
+ {new_line}

--- {relative_tf_file_path} ({resource_name_2})
+ {new_block_lines}

Then ask via AskUserQuestion:

Apply all {N} code changes above? [yes/no]

If user says no:

Changes not applied. Drift still exists on: {resource list}

Stop.

If user says yes: Instruct the agent to apply all proposed edits via File Operations (Section 4), using the same inline agent reference pattern:

Read plugins/terraform/agents/terraform-engineer.md and follow its File Operations (Section 4) instructions, executing all Edit tool calls in the current session. Do NOT spawn a subagent. Apply all proposed edits from the diff set above to the relevant .tf files.

Proceed to Step 5.

Step 5: Re-verify and Commit

After edits are applied, run in sequence:

1. terraform fmt

Read plugins/terraform/agents/terraform-engineer.md and follow its Plan Execution (Section 1) instructions to run terraform fmt for the module at {absolute_module_path}, executing all MCP tool calls in the current session. Do NOT spawn a subagent.

If ExecuteTerraformCommand does not support fmt, fall back to:

Bash: terraform fmt {absolute_module_path}

(fmt is low-risk; Bash fallback is acceptable here.)

If fmt fails: show the error. Tell user:

Fix the formatting issue and re-run /terraform:drift.

Stop.

2. terraform validate

Read plugins/terraform/agents/terraform-engineer.md and follow its Plan Execution (Section 1) instructions to run terraform validate for the module at {absolute_module_path}, executing all MCP tool calls in the current session. Do NOT spawn a subagent.

If validate fails: show the validation error. Tell user:

Fix the configuration error and re-run /terraform:drift.

Stop.

3. Re-run plan (re-verification)

Read plugins/terraform/agents/terraform-engineer.md and follow its Plan Execution (Section 1) and Safety Categorization (Section 3) instructions, executing all MCP tool calls in the current session. Do NOT spawn a subagent. Working directory: {absolute_module_path}

If plan shows zero changes:

Show:

✓ Drift resolved. Code is aligned with remote state.

Run via Bash:

git add {list of .tf files that were edited} && git commit -m "Align .tf code with remote state — resolved drift on: {resource list}"

(Use specific file paths — do NOT use git add -A or git add .)

Show:

Committed: {commit hash} — {commit message}

If plan still shows changes:

Show:

Re-verification failed — plan still shows {N} change(s) after code alignment.

Show the remaining categorized changes using the same format as Step 3 of the plan skill (DESTRUCTIVE → RISKY → SAFE sections with emoji headers).

Show:

Do not commit. Review the residual changes and re-run /terraform:drift.

Stop.

Error Handling

Situation	Action
No modules found	"No Terraform modules found. Run terraform init in your module directory first." Stop.
User types invalid module number	Re-show the numbered list via AskUserQuestion. Show "Please enter a number between 1 and {N}."
No drift detected	"No drift detected — remote state matches your code." Stop.
User rejects batch approval	"Changes not applied. Drift still exists on: {resource list}" Stop.
User chooses B for all destructive drift (no normal drift)	"No code changes to commit. Run /terraform:apply to recreate the deleted resources." Stop.
Plan fails during drift detection — init required	Auto-run terraform init -backend=false (no consent, no -upgrade). Retry plan.
Plan fails — other error	Show raw error. Append "Fix the error above and re-run /terraform:drift." Stop.
terraform fmt fails after edits	Show error. "Fix the formatting issue and re-run /terraform:drift." Stop.
terraform validate fails after edits	Show validation error. "Fix the configuration error and re-run /terraform:drift." Stop.
Re-verification plan not clean	Show residual changes categorized (DESTRUCTIVE → RISKY → SAFE). "Review and re-run /terraform:drift." Stop. Do NOT commit.
git commit fails	Show git error. Tell user to commit manually: git add {files} && git commit -m "Align .tf code with remote state — resolved drift on: {resource list}"
All destructive drift resolved via B (recreate) and no normal drift	"No code changes to commit. Run /terraform:apply to recreate the deleted resources." Stop.