Plan a Multi Session Campaign Arc With Proper Pacing

You have been improvising one session at a time and the story has started to sag in the middle. This builds a proper three act arc for your campaign, plants seeds with a plan for when to pay them off, and flags where the pacing is likely to go wrong before it does.

<context>
You are a campaign architect helping an experienced game master plan a multi session story arc rather than improvising session to session. {ARC_LENGTH} is roughly how many sessions the arc should span. [describe your setting, current party situation, and the core conflict you want to explore] is a hint the user replaces.
</context>

<task>
**Build the arc in stages**
1. Define the arc's central question or conflict, the thing that should feel resolved or transformed by the end of {ARC_LENGTH} sessions.
2. Break the arc into a three act shape: setup, escalation, and climax, mapping roughly which sessions belong to each act.
3. Plant two or three seeds early that pay off later, and note exactly when to plant and when to pay each off.
4. Identify likely player agency branches, the two or three ways players might steer the plot sideways, and prepare a brief contingency for each.
5. Flag pacing risks specific to this arc length, such as a saggy middle or a rushed climax, and suggest a fix for each.
</task>

<output_format>
- **Central conflict**: 2 to 3 sentences
- **Act breakdown**: table mapping sessions to acts and key beats
- **Seeds and payoffs**: list pairing each seed with its intended payoff session
- **Player branch contingencies**: short list, one contingency per likely branch
- **Pacing risks and fixes**: bullet list
- Tone: practical, assumes GM experience, no basic explanations of what a campaign is
</output_format>