Cost & two-tier models

Cost per PR is inline’s primary design constraint. A team opens a lot of pull requests; a naive “send the whole diff to the best model” review costs around $0.25 each. inline targets ~$0.03–0.07 per PR blended, and gets there by stacking five levers in order of impact.

The rule of thumb: filter what you can for free, diff only what changed, cache what repeats, compress what’s left, and spend the expensive model only where judgment is actually required.

# The levers, in order

# 1. Path filters (free)

The cheapest token is the one never sent. Before anything else, inline drops files that never deserve a review:

lockfiles · build output (dist, build, out, bin, obj) · dependencies (node_modules, vendor)
generated code · minified JS · migrations · snapshots
images · fonts · PDFs · source maps · data files · fixtures

Filtered files cost nothing — no triage, no review. The defaults are combined with per-repo and per-workspace globs you set in review config.

# 2. Incremental diffs

inline reviews only what’s new since it last looked. The last completed review’s head becomes the comparison base, so the third push to a PR reviews only the third push — deduped against everything already flagged. A PR with ten pushes doesn’t pay to re-read the first nine.

# 3. Prompt caching

inline uses prompt caching aggressively, with three cache breakpoints:

• The system prompt (role + guideline pack) is byte-identical per repo and cached at a long TTL, so it survives the gaps between a repo’s PRs.
• The first user message (diff + manifest) is cached.
• The last message rolls forward each agent step, so accumulating tool-result history stays cached across the loop.

Cached reads cost a small fraction of fresh input. Keeping per-PR content out of the system prompt is a deliberate discipline — anything that changes per review would bust the cache.

# 4. Diff compression

What survives the filters is ranked by change volume, enormous files are de-prioritized, and the diff sent to the model is clipped. Omitted files are noted so the review agent can pull exactly what it needs with its file-reading tools instead of paying for everything up front.

# 5. Two model tiers

The biggest structural saving is never running the expensive model when it isn’t warranted:

A fast model triages every PR cheaply; the frontier model only runs on the ~40–60% classified substantive. Within a deep review, the token-heavy breadth work is delegated to fast explorer subagents at a fraction of the frontier model’s input price, leaving the deep model to do the reasoning. inline is powered by Claude across every tier.

# Cost accounting

inline accounts for every review’s cost from live token usage, tracking input, output, and cached-read and cached-write tokens separately so cached tokens are never double-billed. Each review stores a per-model breakdown (triage, review, explore) you can inspect in the portal.

# Monthly budgets

Every workspace has a monthly budget. inline fires a one-time alert at 80% of the cap. Past the cap, with budget-degrade enabled, reviews stop at the cheap triage stage and are marked incomplete — which excludes them from the incremental base, so a PR that got a degraded review this month gets a full one next month rather than being silently skipped. Configure the cap and degrade behavior in review config.

# What you can tune

In the portal you can adjust, per repo or per workspace:

• Path filters — additional globs to exclude.
• Reasoning effort — how hard the deep model thinks (low through max).
• Severity threshold and confidence floor — see noise control.
• Monthly budget and budget-degrade behavior.

See review config for the full list.