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Cost Control: Model Routing and Effort Tiers
Harness Engineering90-120 minutes
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Step 1 of 4

Profile spend by call class

Find where the money actually goes before moving anything.

Prompt capsule

Profile my agent's model spend. Instrument every model call with: call class (main-loop reasoning, compaction summary, memory extraction, classification/routing, repair, sub-agent, embedding), model, tokens in/out, and computed cost. Run a representative day of tasks (or replay recent transcripts through the accounting). Produce the spend breakdown: cost share per class, average call size per class, and the top-3 cost concentrations. Typical finding worth checking: auxiliary calls (summaries, classifications) making up a large cost share while needing far less capability than they get.

Paste into Claude · Complete implementation prompt with explicit requirements

Expected after this step

A spend breakdown by call class with concentrations identified.

Should not happen

  • Premium models summarizing tool output at 20x the needed cost
  • Cheap models silently degrading main-task quality with no eval to notice
  • Routing logic duplicated across call sites, drifting independently
  • No escalation, so cheap-tier failures just become task failures

Verify before continuing

Do not move on until every check is true. The complete button stays locked until then.

Do not continue if…

  • !Premium models summarizing tool output at 20x the needed cost
  • !Cheap models silently degrading main-task quality with no eval to notice
  • !Routing logic duplicated across call sites, drifting independently
  • !No escalation, so cheap-tier failures just become task failures

If the AI messes this up

Use this when the AI fakes progress or breaks the feature. It forces a real fix.

Call sites are untagged and unmeasurable. Add the class tag to the single model-client wrapper (create one if calls are scattered - that wrapper is also where routing will live).

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