Link Tasks (Set Predecessors)

What this does

• link A → B: The second selected task (B) gets a predecessor pointing to the first selected task (A). Scheduling will enforce a Finish-to-Start constraint so B starts on the next business day after A finishes.
• business-day aware: All date math respects business days/hours (start 8am, finish 5pm), consistent with Duration and Critical Path docs.
• no duplicates / no self-links: If the link already exists it isn't duplicated. A task can't reference itself.

How to use it

1. Select two tasks in the Plan grid

• Click the checkbox for the first task (this is A, the predecessor)
• Click the checkbox for the second task (this is B, the successor)

2. Click Link A → B in the toolbar

• The action appears when exactly two tasks are selected and you have edit permissions.
• After linking, B's Predecessors cell will include A's task ID (e.g., 3).

3. Review the schedule

• B's start will shift to the next valid business day/time after A's effective finish.
• If A is a parent (group) task, the link uses the parent's rolled‑up latest child finish.
• The Critical Path will recompute; enable Highlight critical or Show critical only to visualize impacts.

Keyboard

• Optional keyboard shortcut: L will link the last two selected tasks (if exactly two are selected).

Unlinking

• Clear the Predecessors cell on B (e.g., delete 3).
• The schedule will reflow immediately; CPM recalculates automatically.

Behavior details

• Selection order: The order of your clicks determines direction. The first clicked is A (predecessor), the second clicked is B (successor). If order cannot be inferred, the grid falls back to the visible row order.
• Duplicates: Linking avoids adding duplicate predecessor tokens to B.
• Cycles: Self‑dependency is blocked. If a cycle would be created (A → … → B and you try to link B → A), you'll see a warning and the link won't be applied.
• Cycles: Self‑dependency is blocked. Complex cycles are not automatically detected yet; avoid creating circular references.
• Parents and milestones:
  • Linking to a parent uses the parent's rolled‑up child latest finish.
  • Milestones (0‑day) are valid predecessors and successors.
• ID tokens: The Predecessors cell uses task IDs as tokens (e.g., 1, 3, 8). IDs are automatically renumbered when you reorder rows; predecessor tokens are remapped safely.

FAQs

Can I link more than two at once?

Yes. Select 2 or more tasks, then click Link A → B to create a sequential chain. See Task Chaining for details on chaining multiple tasks.

Does this support lag or different dependency types?

Link A → B creates Finish‑to‑Start (FS) relationships by default. After linking, you can edit the Predecessors cell to add lag (e.g., 1FS+2 for 2-day delay) or change the relationship type (e.g., 1SS for Start-to-Start). See Predecessor Relationships for details on all relationship types and lag/lead time.

Where is this visible in the Gantt?

Dependency constraints affect task bar positions and start dates. Critical tasks are highlighted when Highlight critical is enabled. Dependency lines are not rendered yet.

Notes for administrators

• The Plan grid persists the predecessors string; saves occur on incremental edits (triggered by the Link action) and on full snapshots. The backend writes dependency edges based on those values.
• Parent/child structure is derived from indent levels; automatic parent linking is preserved.
• Dependency safety rules: For a given successor, existing edges are cleared only when (a) the client explicitly sends an empty predecessors string for that row, or (b) at least one predecessor code in the update resolves. Otherwise, existing links are preserved.

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Last updated: 2025‑10‑04