Law 08 · Reasoning & Planning
Branch When the First Step Matters
For decisions you can't take back, explore before you commit.
The principle
Tree-of-Thoughts turns linear reasoning into a search: generate several candidate thoughts, judge them, look ahead, and backtrack instead of being stuck going left to right. It matters most when an early choice is pivotal, which is exactly the spot where an agent's first irreversible action sets up everything downstream. Cheap, recoverable steps don't need it. Pivotal ones do.
Why it happens
Some first moves shape everything after them: a migration strategy, a contract interpretation, a tool with irreversible side effects. Linear reasoning commits early and then keeps going. Search-based methods such as Tree-of-Thoughts and LATS generate several candidate next moves, score them, and allow backtracking. That extra compute is not for every task. It pays when the first decision is high-leverage and hard to unwind. For cheap reversible work, branch less. For a pivotal commitment, explore before the path locks in.
Watch for
- The agent commits to a pivotal strategy on its first instinct, and everything downstream is locked to it.
- A wrong early choice forces an expensive redo of all the work that followed.
- There is no step where alternative plans are generated and compared before the irreversible move.
In practice
A migration agent picks a database cutover strategy on its first instinct, big-bang swap, and everything downstream (backfill, rollback plan, dual-write window) is now locked to that pivotal early choice that turns out wrong. Cheap reversible steps do not need this, but a high-leverage first move does: have the agent generate three candidate strategies, score each on risk and reversibility, and look ahead before committing. The branching cost is trivial next to re-running a botched cutover.
Apply it
- Reserve branching for early actions that are high-leverage or hard to reverse, not cheap recoverable ones.
- Have the agent generate several candidate plans and score each on risk and reversibility before picking.
- Look ahead and allow backtracking on the pivotal step instead of committing to the first path.
The takeaway
When an early action carries a lot of weight or can't be undone, have the agent generate and score a few candidate plans before it picks one. Don't let it commit to the first path.