tak

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Configuration ​

credit ​

  • Type: bool
  • Default: true
  • Since: 0.0.4
  • Set with: --no-credit, TAK_CREDIT, config report.credit

Whether generated reports end with a line naming tak.

On by default. A report that appears in someone's pull request should say what put it there — a reader who has never heard of tak needs a way to find out, and a maintainer evaluating the comment needs to know what to turn off.

Turn it off with --no-credit, TAK_CREDIT=0, or credit = false under [report]. Nothing else about the report changes.

tak compare origin/main --no-credit
TAK_CREDIT=0 tak compare origin/main

env_allow ​

  • Type: list<string>
  • Since: 0.0.3
  • Set with: --env-allow, TAK_ENV_ALLOW, config env.allow

Environment variables kept even though env_deny lists them.

Subtracted from env_deny, so a project can opt one variable back in without restating the whole default list. A CLI whose measured path genuinely requires a token — a client that cannot start unauthenticated, say — needs this.

Doing so makes the measurement depend on something outside the repository. That is a real cost, not a formality: the numbers become conditional on the environment the run happened to have, and a token expiring will read as a performance change.

Listing a variable here that env_deny does not mention has no effect. This setting removes entries from the deny list; it does not add anything to the environment.

tak run --env-deny GITHUB_TOKEN --env-allow GITHUB_TOKEN

env_deny ​

  • Type: list<string>
  • Default: GITHUB_TOKEN, GH_TOKEN
  • Since: 0.0.3
  • Set with: --env-deny, TAK_ENV_DENY, config env.deny

Environment variables removed from every command tak measures.

Two reasons this defaults to a non-empty list rather than to nothing.

Determinism. A CLI that finds a forge token in its environment often does more with it than without — authenticating, fetching, checking rate limits. A measurement that moves depending on whether CI happened to export a token is not a measurement of the code under test. It lands in the series as an unexplained step change on the day someone edits an unrelated workflow.

This is not a credential sandbox. The listed variables are absent from the child's direct environment, but a hostile binary can still inspect accessible same-user processes and files. In particular, tak backfill downloads and executes release binaries; run it on an isolated credential-free machine when those assets are not fully trusted.

Setting this replaces the default list rather than adding to it. To keep the defaults and remove more, list them alongside. To keep the defaults and remove fewer, use env_allow — it is subtracted from this list, so the two compose without either having to restate the other.

Names are matched exactly. There is no globbing: a benchmark whose behaviour depends on which variables happen to match a pattern is the problem this setting exists to avoid.

tak's own network calls are unaffected. backfill authenticates with curl directly rather than through the measurement path.

tak run --env-deny AWS_PROFILE --env-deny AWS_REGION
TAK_ENV_DENY=GITHUB_TOKEN,GH_TOKEN,NPM_TOKEN tak run

gate_pct ​

  • Type: float
  • Default: 1.0
  • Since: 0.0.4
  • Set with: --gate-pct, TAK_GATE_PCT, config gate.pct

How much an instruction count may rise before tak compare fails.

A percentage of the base measurement. Only instruction counts are gated. Wall clock is reported and never gated: on the same hardware it moves 4-20% run to run, so a threshold tight enough to catch a real regression would fire constantly, and one loose enough to stay quiet would catch nothing.

The default of 1% is about fifty times the ~0.02% instruction counting reproduces to, leaving room for the small differences a compiler or dependency bump can produce without turning the gate into noise.

Raise it to report without effectively failing. Setting it to zero fails on any increase at all, which sounds appealing and is not: one extra instruction on a startup path is not worth blocking a pull request over.

tak compare origin/main --gate-pct 0.5
TAK_GATE_PCT=5 tak compare origin/main

runner_class ​

  • Type: string
  • Default: derived from the machine
  • Since: 0.0.6
  • Set with: --runner, TAK_RUNNER, config runner.class

The machine class a measurement is recorded under, and compared within.

Empty means derive it: gha-<os>-<arch> under GitHub Actions, local-<os>-<arch> otherwise. That is right until something about the machine changes without the name changing.

Series are partitioned on this, and must be. Absolute instruction counts shift between machine types by more than a real regression does, so tak will not compare across classes — it reports the old series as removed and the new one as added rather than inventing a step change.

Set it when the environment changes in a way the derived name cannot see. The common case is a toolchain bump: a hosted runner image or a compiler upgrade between the base measurement and this one is attributed to the code otherwise, and on a one-percent gate that is a false failure. Encoding the compiler version into the class starts a fresh series at the bump, which is honest — the numbers either side genuinely are not comparable.

tak cannot detect this for you. It measures programs, not build systems, and has no way to know what produced the binary it is timing.

TAK_RUNNER=gha-linux-x64-rust1.85 tak run --record
tak run --runner gha-linux-x64-glibc2.39