Error: Cycle (dependency cycle) Terraform Origin: Platform & cloud OSI layer 7 · Application Last updated 5 Nov 2026

Terraform: Error: Cycle: aws_security_group.a, aws_security_group.b

Resources reference each other (directly or indirectly), so Terraform can't order them.

Exact message you may see Error: Cycle: aws_security_group.a, aws_security_group.bError: Cycle: module.x.aws_y.z, module.w.aws_v.uError: Cycle:Terraform dependency cycle detectedError: Cycle: local.x, aws_instance.y
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Seen on: Terraform

Meaning

Break the loop: security groups referencing each other → use separate aws_security_group_rule resources; moves values to variables/locals; remove unnecessary depends_on; split modules. terraform graph | dot -Tpng visualises the cycle.

Common causes

  • Mutual references between resources (security groups)
  • depends_on creating loops
  • Module outputs feeding each other's inputs
  • Locals referencing resources referencing locals
  • Provisioners referencing self

⚡ Quick fix

  1. Use standalone rule resources (aws_security_group_rule) instead of inline blocks
  2. Remove circular depends_on/references
  3. Visualise with terraform graph

Detailed fix by platform

Terraform

  1. terraform graph | dot -Tsvg > graph.svg

How to diagnose

  1. Cycle — Which resources?
  2. Reference — Mutual?
  3. Fix — Separate rule resources?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Platform & cloud. Errors that are often confused with or caused by this one (click to open):

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