Cost preflight

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Cost preflight

Pre-send guard that estimates the dollar cost of a review and prompts/aborts when it exceeds the configured threshold. Catches "oops, I pasted a 50k-line generated file" before tokens are actually spent.

When it runs

Right after the cache lookup, before the provider call. The cache hit path skips it entirely (no provider call, no cost).

How the estimate is computed

estimated_input_tokens   = prompt.EstimatedTokens()    # chars/4 heuristic
estimated_output_tokens  = clamp(estimated_input / 4, 200, 1500)
estimated_cost           = provider.Pricing(model).Cost({
    InputTokens:  estimated_input_tokens,
    OutputTokens: estimated_output_tokens,
})

• Input tokens: chars-divided-by-4 — the well-known approximation.
• Output tokens: capped at 1500 (typical structured-finding review is 200–1500), floored at 200. Underestimating output matters: Opus output costs 5× the input, so a low estimate could hide the actual bill.
• Cost: applies the provider's pricing table (see each Provider page) including cached-input discounts where supported. Rates can be overridden per model via providers.<name>.pricing.<model> in config — see Configuration files (OQ-09).

The output-token heuristic intentionally errs high; if the user cares about precision, lower the cost threshold rather than reach for the heuristic.

Threshold

Config	Default	Meaning
cost.warn_threshold_usd	0.50	Estimated dollar cost above which the preflight fires.

0 or negative disables the check entirely. Bump it for scheduled jobs (a CI runner doing 100 reviews/day cares less about a single $1 review).

Behavior matrix

Estimated cost	Context	Outcome
<= threshold	any	Silent. Review proceeds.
> threshold	TTY, no --no-cost-check, no --yes	Prompt; default no → abort.
> threshold	TTY, --yes	Prompt still shows. --yes does NOT bypass since v0.9.1 (UC-06).
> threshold	Non-TTY, no --no-cost-check	Abort with Aborted (non-interactive); pass --no-cost-check or raise cost.warn_threshold_usd to override.
any	--no-cost-check	Skip the preflight entirely.

What the user sees

When the preflight fires (TTY):

⚠  Estimated cost: $0.8421 (threshold: $0.5000)

Proceed with the review?

  Yes  ▸ No        (←/→ to choose · Enter to confirm)

The confirmation is an arrow-key Yes/No toggle (huh), pre-selected on No. Picking No (or pressing Enter on the default) aborts with aborted: cost preflight. Non-TTY/piped input is unchanged: it falls back to the typed y/N line, and a non-TTY run aborts outright (see the matrix above).

Providers with zero pricing

Ollama, claude-cli, and gemini-cli return Pricing{} (all zero). The cost preflight short-circuits silently — estimated cost is always 0, never above the threshold, so the prompt never fires. The verbose footer shows — instead of a dollar figure in these cases.

Disabling

Per-invocation

commitbrief --staged --no-cost-check

Per-config (raise the threshold or disable entirely)

# Set a higher ceiling.
commitbrief config set cost.warn_threshold_usd 5.0

# Disable entirely.
commitbrief config set cost.warn_threshold_usd 0

Interaction with --yes

Important

Since v0.9.1 (UC-06), --yes no longer bypasses the cost preflight. Users routinely wire --yes into CI to skip the .commitbrief/ guard prompt, and we did not want that to also silently approve unbounded spend. Use --no-cost-check explicitly if you want bypass-on-CI semantics.

See also

• Review command — pipeline position.
• Configuration files — cost.warn_threshold_usd.
• Cache — cache hits skip the preflight entirely.