Per-profile cost attribution¶

Once response-style profiles are in use, two surfaces answer "what did each profile actually cost?":

• bernstein cost --by profile - a live breakdown grouped by profile.
• bernstein cost profile-report - a content-addressed, audit-chain anchored report whose every figure recomputes from the ledger.

Every figure is derived strictly per ledger entry. Numbers that cannot be computed from recorded ledger rows are omitted, never estimated.

Source:

• src/bernstein/core/cost/profile_attribution.py - attribution logic
• src/bernstein/core/cost/profile_report.py - report builder
• src/bernstein/cli/commands/cost.py - cost group and profile-report

bernstein cost --by profile¶

Groups spend by the response_profile tag stamped onto each ledger entry by the spawn path.

bernstein cost --by profile
bernstein cost --by profile --last 7d
bernstein cost --by profile --json

When the ledger is present, attribution is per entry with transition exclusion (below). When it is missing, the command degrades to the response_profile tag on task records so older runs still show a breakdown.

Transition exclusion¶

A task started under profile A and re-spawned under profile B must not be credited to either profile. The spawn path records a profile-transition event when it overwrites a previously stamped profile, and every ledger entry of a transitioned task lands in a single excluded bucket. Attribution is all-or-nothing per task; spend is never split heuristically across profiles.

Transitions are read from profile_transitions.jsonl next to the ledger.

The honesty rule¶

No cross-profile savings claim is produced unless both profiles have at least MIN_COMPARABLE_TASKS (5) tasks sharing the same role and model. Below that bar the comparison list is empty and the output states insufficient comparable runs instead of a savings figure. This applies to bernstein cost (the per-profile comparison section prints only when two or more profiles appear in the window) and to the profile report.

bernstein cost profile-report¶

Emits a content-addressed per-profile cost report. The report is computed from recorded ledger entries only, hashed over canonical JSON with no timestamps in the payload, written as <sha256>.json, and appended to the audit chain. A third party holding the ledger can recompute it byte-identically.

bernstein cost profile-report
bernstein cost profile-report --last 7d
bernstein cost profile-report --json

The report carries, per profile: task count, output tokens, cost USD, mean output tokens per task, and (joined from metrics) the verification pass rate. Comparable cohorts that clear the honesty rule are listed separately.

Audit anchoring is mandatory¶

The report is only trustworthy once anchored. If the audit-chain append fails, the command exits non-zero rather than pretending the report is valid. The chain event type is cost.profile_report and it embeds the ledger line-hash range (first line, last line, count, digest) the report was computed from.

Evidence links¶

Cross-profile comparison rows link the newest eval ab comparison artifact for that pair (by artifact name and SHA-256) when one exists. These links are presentation metadata only; they live outside the report's hashed payload so byte-identical recomputability is untouched.

Related¶

• Response-style profiles
• Profile A/B harness
• Cost optimization