Agent Handoff (vs compaction)

Almost every other agent stack handles "context window fills up" with compaction: throwing away or summarizing the older parts of the conversation. The result is the same in every case: the agent loses the thread, forgets early decisions, and starts to drift.

Syntax does Agent Handoff instead. When the context approaches its limit, the current agent writes a structured snapshot of the work so far, persists it, and a fresh agent picks it up.

Why this is structurally better

Compaction is lossy by construction:

• Summarize: the summary is wrong in subtle ways. The model is optimizing "shorter" without knowing what mattered.
• Truncate: the agent forgets exactly the thing it needs.
• Both: the new context is a mix of half-remembered earlier turns and full recent turns. The agent's behavior gets weird.

Handoff is an explicit checkpoint with a defined schema. The new agent gets:

• The original goal.
• The decisions made so far.
• The files touched and the intent of each change.
• The open questions.
• The next step.

…and nothing else. No turn-by-turn churn. No half-remembered context.

What you see

The user-visible effect: "the conversation feels like it just keeps going indefinitely". The technical effect: "every turn always has a clean context window".

For long-running agentic workflows, this is the difference between an agent that finishes its task and an agent that spirals after turn 30.

When to use compaction instead

Plain compaction is still available as a fallback if you want it for a specific session. Handoff is the default at the long-context threshold, but you can always force the simpler behavior.

Where this lives

• Concepts → Agent Handoff — the capability-level walkthrough.
• Concepts → Plan Mode — the front-end version of the same idea (separate planning context from execution context).