Dependency link would create a loop (dependency_cycle)

• HTTP status: 409
• Problem type URI: https://nowgetitdone.com/docs/api/problems/dependency-cycle

What it means

The blocker you tried to record would close a loop: the task you named as the blocker already waits on the task you were linking it to, directly or through other tasks. Every task in such a ring would wait on itself forever, so the link is refused before it is written. The dependency graph a client reads is therefore always acyclic — you can follow blocked_by links without a visited set.

Likely causes

• Recording A is blocked by B when B is already blocked by A.
• A longer chain closing on itself: A → B → C, then linking C as a blocker of A.
• A bulk import replaying links in an order the source system never validated.

How to fix

• Read GET /v1/tasks/{task_id}/dependencies on both tasks and follow the chain — the detail names the two tasks whose existing path the link would close.
• Remove the existing link that points the other way (DELETE /v1/tasks/{task_id}/dependencies/{blocker_task_id}), then record the new one.
• If both directions genuinely matter, the work is not finish-to-start: split one of the tasks so each half has a single direction of dependency.

Example problem+json

{
    "type": "https://nowgetitdone.com/docs/api/problems/dependency-cycle",
    "title": "Dependency link would create a loop",
    "status": 409,
    "code": "dependency_cycle",
    "detail": "T-42 already blocks T-17 (directly or through other tasks), so T-17 cannot also block it.",
    "request_id": "req_a1b2c3d4"
}

Related

• API reference