🧭 Customer-safe answer: Use Optimization when the future campaign setup will look much like the reference period. Use Forecast when the future period may have a different campaign mix, especially when the current spend amounts and campaign mix are not representative of the planning period. Spend Flexibility then sets how far each line may move from its baseline, and it scales with whatever budget is entered.

The 30-second decision

optimization-forecast-adaptive-decision-guide.html

Why there are two planning methods

Optimization and Forecast answer different questions. They are not a “basic” and “advanced” version of the same plan.

This difference is reflected in the current product and planning libraries: Optimization builds a campaign-level problem with campaign curves, locks, and campaign spend bounds. Forecast uses aggregate tactic planning curves, then applies future seasonal and holiday pacing. (Using Media Forecaster: Optimization, Forecast, and Reference Periods, Helenus Seasonal Forecast — Architecture and Serving Contract)

Optimization: use it for a campaign plan you can act on

Choose Optimization when:

• the planning period is near term;
• most of the campaigns that will receive budget already exist;
• the reference period contains a useful version of those campaigns;
• the client wants detailed campaign allocations; and
• campaign minimums, maximums, or fixed amounts matter.

Optimization respects campaign-level guardrails. That makes it useful for execution, but it also means the campaign list matters. If a campaign is missing from the planning setup, Optimization cannot invent it.

CSM talk track

“Optimization is best when we are deciding how to allocate budget across campaigns that already exist and are likely to remain in place.”

Forecast: use it when the future media structure may change

Choose Forecast when:

• the client is planning a future quarter or seasonal event;
• the number or mix of campaigns will change;
• the exact future campaigns do not exist yet;
• the client wants to compare future budget scenarios; or
• tactic-level guidance is more useful than campaign-by-campaign instructions.

Forecast plans at a broader tactic level. That is what makes it useful before the final campaign roster exists.

CSM talk track

“Forecast is the better choice when we know the broader media tactics, but the exact campaigns for the future period are not all live yet.”

The Q4 example to remember

A client is in Q3 and has 5 active campaigns. In Q4, the client normally runs about 20 campaigns and expects to double total spend.

If we use Optimization:

1. The plan starts with the 5 campaigns in the reference setup.
2. Each campaign has a spend range and a modeled response curve.
3. Trying to place twice the budget into only those 5 campaigns can push them to their maximums or into diminishing returns.
4. The other 15 future campaigns are not present, so Optimization cannot allocate budget to them.

The result may be impossible to run or may be technically possible but not useful for the client.

If we use Forecast:

1. The plan works at the broader tactic level.
2. The future budget can be divided across tactics without pretending today's 5 campaigns are the complete Q4 campaign roster.
3. Seasonal and holiday timing can shape the expected response across Q4.
4. When the Q4 campaigns are live and the client is ready to execute, the CSM can run Optimization for detailed campaign allocations.

How Spend Flexibility works

Spend Flexibility sets how far the plan may move each line away from its baseline. A line's baseline is its share of reference-period spend, applied to the plan budget. This is the same Baseline shown on the plan's results.

In plain language:

“Medium (0.5× to 1.5×) means each line can go as low as half its baseline or as high as one and a half times it, whatever the total budget is.”

Because the limits scale with the budget, a budget much larger or smaller than usual fits without any special setting. Fixed, Min spend and Max spend amounts are respected first. The other lines' baselines share what remains.

Spend Flexibility does

• keep each line within the chosen multiple of its Baseline;
• scale automatically with the budget entered;
• keep fixed campaign, tactic, and channel amounts fixed; and
• work with either Optimization or Forecast.

Spend Flexibility does not

• add campaigns that do not exist in the plan;
• remove saturation or diminishing returns;
• make an unrealistic campaign mix realistic;
• choose the customer's total budget;
• replace the need for a sensible reference period; or
• guarantee a revenue, ROAS, CAC, or customer result.

Target and required-spend plans work differently. When the plan finds the spend needed to reach a goal, the budget is only a ceiling, so the limits stay around reference-period spend.

The one-rule version for a call

“Spend Flexibility is how far each line can move from its Baseline. If the real issue is that Q4 will have a different campaign roster, use Forecast.”

Planning period vs. reference period

These dates do different jobs.

A reference period is an anchor, not a promise and not a copy command. It does not recreate last year's campaigns. The future dates still determine the seasonal planning context. (Understanding the Seasonal Forecast Curve)

Choosing a reference period

For Optimization, prefer a recent or representative period when the campaigns being planned were active and the spend mix was usable.

For Forecast, prefer a period with a useful tactic mix. Last year's same season can be helpful when it resembles the expected Q4 strategy, but it is not required. If the client already knows the future budget, enter that budget directly; the reference period still anchors the starting mix and bounds.

Avoid choosing a period only because the dates are close. Q3 may be recent but still be a poor reference for Q4 if campaign count, promotions, tactics, or spend change sharply.

Concrete client examples

CSM call flow

1. Ask about structure: “Will the future campaign list look mostly like the reference period?”
2. Choose the method: Same structure → Optimization. Different or not-yet-built structure → Forecast.
3. Ask about flexibility: “How far are you comfortable moving each line from its usual share?”
4. Choose Spend Flexibility: Low, Medium, or High. The limits scale with the budget automatically.
5. Check fixed amounts: Confirm fixed channel, tactic, and campaign amounts leave budget available for the flexible items.
6. Set expectations: The plan is a modeled scenario, not a guarantee. Large moves deserve more business review.

Quick troubleshooting

• Plan cannot use the full budget: Check fixed amounts and Max spend limits. With every line capped, the caps may add up to less than the budget.
• Q4 result puts too much money into today's few campaigns: Switch from Optimization to Forecast. Wider campaign bounds are not the right fix.
• Forecast still cannot fit the budget: Check tactic locks and fixed amounts.
• Customer wants exact campaign instructions for campaigns that are not live: Explain that Forecast is for the broader plan; run Optimization after the campaigns exist.
• Customer asks whether seasonality solves campaign capacity: No. Seasonality changes expected response over future dates. It does not add campaign inventory.

Recommended CSM wording

Say

• “Optimization is for detailed campaign allocation.”
• “Forecast is for a future period where the campaign mix may change.”
• “The reference period gives the plan a sensible starting point.”
• “Spend Flexibility is how far each line can move from its Baseline.”
• “Wider limits do not create campaigns or remove diminishing returns.”

Avoid

• “You need a special setting for a big budget.”
• “Wider bounds solve saturation.”
• “Forecast predicts the exact campaigns you will run.”
• “The reference period copies last year.”
• “The plan guarantees this result.”

Key takeaway

Choose Optimization or Forecast based on the future media structure. Choose Spend Flexibility based on how far each line may move from its Baseline, which scales with any budget. For Q4 with many more campaigns than today, start with Forecast.