Addresses Codex P2: the obfuscation fake in delta-split-obfuscation.test.ts
used an `as any` escape. RenderAdvisorDeltaChunksOptions.obfuscator is now
AdvisorObfuscator — a structural interface exposing only obfuscate() — so the
fake is typed without any, while a real SecretObfuscator stays assignable and
the production call site is unchanged. Also drops two leftover console.logs
from the test (matching the cleanup roboomp requested elsewhere).
The advisor sends its whole Session update as a single ever-growing user
message. Provider prompt caches are prefix-based: a single user message whose
text keeps growing invalidates the entire message on every turn, so cache_read
stays pinned at the instructions/tools boundary (observed 14491 tokens in
production, 11066 in tests) instead of growing with the session.
Split the update into multiple user messages — one per source message —
delivered via a single Agent.prompt(AgentMessage[]) call, so the provider
caches each appended message incrementally. Verified end-to-end: cache_read
grows 0 -> 11126 -> 11457 -> 11583 across turns with the split, versus pinned
11066 on the old single-message behavior.
- delta-split.ts: pure renderAdvisorDeltaChunks using chunked
formatSessionHistoryMarkdown (shared toolResultIndex/consumedToolCallIds/
watchedRoleState) so toolCall/result pairing and role collapsing stay
byte-identical to the old single-block render (equivalence-tested).
- session-history-format.ts: add HistoryFormatOptions.watchedRoleState so
chunked renders collapse consecutive same-role messages exactly like the
single-block render.
- runtime.ts: #prepareBatch does a single dedup+render pass; #drain delivers
agent.prompt(preparedMessages) (array), falling back to the string.
- Keep field-selective fingerprint (candidate 1) + wip-marker-at-tail
(candidate 3) as complementary wins.
Tests: advisor suite 209 pass / 0 fail; type check clean; lint clean.
Affected subsets (342 tests) green; full suite hits WSL EMFILE fd limit.
cuipengfei