Measured in-session: turn 2 of a session reported `cacheRead: 15042` of ~15.1K prompt
tokens. Separate `--print` runs never share a cache because the system prompt embeds the
per-session conversation log path about 2.6K characters in, which is under the 1024-token
minimum for the shared prefix.
## Rate limits
Model Studio limits are per account, per model, per minute (TPM) and per second (TPS =
TPM/60). A 429 reads `Allocated quota exceeded` and means TPM, not the 7-day plan quota.
The gateway sends no `Retry-After` and no `x-ratelimit-*` headers, so the only signal is
the failure itself.
Recovery is fast: in a measured session, 32 of 124 calls hit 429, never more than two in
a row, and the next successful call landed 2.6-3.1s later. Prime handles this with its
own retry, tuned in `~/.prime/agent/settings.json`:
```json
{ "retry": { "maxRetries": 5, "baseDelayMs": 1000 } }
```
That gives 1s, 2s, 4s, 8s, 16s. Sustained throughput in that session was 0.7-1.6M
tokens/minute with 129K-token prompts, which is what pushes it over the limit; prompt
caching does not help here, because cached tokens still count as prompt tokens.