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Evasive Mode paces per host. Each host gets its own sensor and controller, so a strict host is slowed without dragging down a permissive one.

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The sensor

A sliding window of recent observations (status codes, latency, challenge and reset signals) produces one of three readings: Only 429 (Too Many Requests) and 503 (Service Unavailable) count as blocks. Ordinary answers like 401, 403, 404 or 405 are treated as clean samples, so per-URL results never falsely trip the brakes. Challenge pages (“just a moment”, “attention required”, CAPTCHA, Cloudflare) and connection resets also register as blocks.

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The state machine

Each host moves through states as its signals change:
1

Normal

Healthy. The rate climbs on every clean interval (additive increase).
2

Throttle

Straining. The rate holds and the client identity (User-Agent) switches to a browser string.
3

Blocked, then Cooldown

A block triggers a multiplicative back-off (rate is halved, down to a floor), the egress lane escalates (direct to Tor), and the host pauses for a cooldown window.
4

Resume

After the cooldown, the host resumes at its rate floor and ramps back up only after several clean intervals in a row.
5

Parked

If a host blocks repeatedly (several cooldown cycles), it is parked: it keeps running at the floor rate rather than being abandoned, so the engagement still makes progress.

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The rate model (AIMD)

The rate follows additive increase, multiplicative decrease, the same principle that keeps TCP stable:
  • Clean interval: rate = min(rate + step, ceiling), climb gently.
  • Block: rate = max(rate x backoff, floor), drop sharply (balanced halves it).
The exact start, step, ceiling, floor, back-off and cooldown values come from the chosen intensity. Balanced, for example, starts at 8 req/s, steps by 2, ceils at 30, floors at 1 and halves on a block.

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Honoring Retry-After

If a target sends an explicit Retry-After, Evasive Mode honors it, but caps the wait at 180 seconds so a hostile or misconfigured header can never stall the run indefinitely.
Because pacing is per host and additive, a single strict endpoint slows only itself. The rest of the surface keeps moving at the fastest rate each host allows.