Recurring cron jobs were prompt-cache-cold on every fire. session_id is
built as cron_<job_id>_<timestamp>, and the Codex/Responses transport used
session_id directly as prompt_cache_key — so the timestamp changed the cache
key on every run and the static prefix (agent identity + tool schemas) was
re-paid each tick.
Derive prompt_cache_key from a SHA-256 of the static prefix (instructions +
sorted tool schemas) instead. Repeated fires of the same job share one
content-addressed key (pck_<hash>) and reuse the warm prefix within the
provider's cache TTL. The key changes exactly when the prefix changes —
edit the job's prompt or toolset and it re-keys; leave it alone and it stays
stable.
session_id is left untouched for transcript isolation, log correlation, and
the Codex/xAI session-scope routing headers (session_id, x-client-request-id,
x-grok-conv-id) — those are the per-fire identity, not the cache key. Only the
prompt_cache_key body field (standard OpenAI/Codex path and the xAI extra_body
field) is content-addressed.
Closes#51395.
Co-authored-by: spiky02plateau <spiky02plateau@users.noreply.github.com>
Co-authored-by: JoaoMarcos44 <JoaoMarcos44@users.noreply.github.com>
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