Change-detectors, tautologies, source-reading tests, redundant duplicates,
mock-echo tests and dead/unrunnable tests. Per-test rationale in the lane
ledger (category + reason for every removal).
Squash of the three commits on PR #96768 (net diff is tests-only: the
mid-series production hunk in agent/transports/codex.py was reverted
within the PR after review). Pins the cache-scope isolation invariant
for hosts that mint one physical session per response, plus the
system-prompt write-path lifecycle under a per-response session (#96570).
/simplify-code finding: turn_context evaluated resolve_prompt_cache_scope()
inside set_runtime_main's argument list under the umbrella try/except — a
resolution failure would silently skip the ENTIRE runtime binding
(provider/model/base_url/api_key/session_id for all aux calls that turn),
not just the cache scope.
- prompt_cache_scope: add resolve_prompt_cache_scope_safe() (never raises,
returns None on failure/empty).
- turn_context: resolve the scope into a local via the safe variant BEFORE
the set_runtime_main call, so a failure can only lose the scope.
- chat_completion_helpers: _prompt_cache_scope_for_agent delegates to the
shared safe variant (guarded import retained).
- tests: +1 (hostile-property agent -> None; normal/empty passthrough).
- prompt_cache_scope: memo key now includes DB presence (a lazily attached
_session_db re-resolves instead of staying pinned to the physical id);
_persist_disabled agents (background-review forks that never get a DB row)
memoize the fallback instead of re-querying the lineage per API call;
module docstring cross-references get_conversation_root and why the two
lineage resolvers must not be deduplicated.
- chat_completion_helpers: hoist the triplicated
_prompt_cache_scope_for_agent(agent) call to a single local above the
OpenAI-wire dispatch (after the anthropic/bedrock early returns, which
don't use prompt_cache_key).
- codex transport docstring: x-client-request-id mirrors the derived body
key, not the raw scope id.
- turn_context comment: acknowledge the first-turn pre-persist fallback.
- tests: +2 (persist-disabled memoization; lazy DB attach re-resolution).
Legacy compaction mode (compression.in_place: false) rotates the physical
session_id mid-conversation. The prompt-cache scope introduced in #79161 was
derived from that physical id, so every rotation moved the same conversation
into a fresh cache bucket - the prompt cache went cold at every rotation
boundary (#79017).
Fix: resolve a rotation-stable logical scope - the compression-lineage ROOT
of the current session (SessionDB.get_compression_lineage, fork-aware
post-#79193) - once per turn, memoized per transcript segment, and prefer it
over the physical session_id at every prompt_cache_key derivation site:
- agent/prompt_cache_scope.py (new): resolve_prompt_cache_scope(agent) -
lineage-root walk with per-segment memo; falls back to the physical id
when no DB is attached or the walk fails, degrading to pre-fix behavior.
- transports/codex.py: build_kwargs accepts cache_scope_id and prefers it
for the body prompt_cache_key, the xAI x-grok-conv-id header, and the
Codex x-client-request-id routing header. The Codex session_id header
keeps the raw physical id (transcript identity, #57012 contract).
- transports/chat_completions.py: _add_prompt_cache_key accepts
cache_scope_id with the same precedence.
- chat_completion_helpers.py: build_api_kwargs threads the resolved scope
into all three build_kwargs call sites (codex, profile, legacy).
- auxiliary_client.py: set_runtime_main carries cache_scope; the aux
Responses cache-key site prefers it over the physical session_id.
- turn_context.py: resolves the scope once per turn and threads it through
set_runtime_main (no DB walk on the per-API-call hot path).
Scope semantics preserved from #79161: /new starts a fresh scope (new
lineage), /branch children, delegate subagents, and tool children stay
isolated (explicit-fork exclusion in get_compression_lineage), unrelated
sessions keep distinct buckets, and cron per-fire timestamps still
normalize via _cache_scope_from_session_id.
Default installs compact in place (session_id never rotates), so they hit
the memo and produce byte-identical keys to before.
Fixes#79017
