final updates

MainContext.md

@@ -244,3 +244,23 @@ Documentation has been completely rewritten matching the strict, structural form
 - `docs/guide_architecture.md`: Details the Python implementation algorithms, queue management for UI rendering, the specific AST heuristics used for context aggregation, and the distinct algorithms for trimming Anthropic history vs Gemini state caching.
 - `docs/Readme.md`: The core interface manual.
 - `docs/guide_tools.md`: Security architecture for `_is_allowed` paths and definitions of the read-only vs destructive tool pipeline.
+
+## Branch Analysis: master vs not_sure (2026-02-22)
+
+### Summary
+The `not_sure` branch introduces a static/dynamic context split in the `send()` API signature, separating files+screenshots (cacheable, stable) from discussion history (changes every turn). This improves cache hit rates for both Anthropic and Gemini.
+
+### Current master branch API correctness
+- **Anthropic**: Correct. System blocks with cache_control, SDK content block serialisation, history repair, stale file refresh stripping all work properly.
+- **Gemini**: Correct after `patch_gemini_history.py` was applied. Uses `_get_gemini_history_list()` for safe SDK access, drops history in pairs to maintain alternating roles, explicit caching via `caches.create()`.
+
+### not_sure branch improvements
+- **Anthropic**: Puts discussion history as a separate uncached system block after the cached static context. Better cache hit rates when discussion changes between turns.
+- **Gemini**: Wraps discussion in `<discussion>` tags in user messages and strips old ones from history via regex. Prevents discussion duplication across turns.
+
+### not_sure branch bugs (not merged from master)
+- Uses `_gemini_chat.history` directly instead of `_get_gemini_history_list()` — will crash on newer google-genai SDK versions where `.history` was removed.
+- Missing the pair-wise history dropping fix (drops single messages, breaking Gemini's alternating role requirement).
+
+### Recommended merge path
+Cherry-pick the static/dynamic split from `not_sure` into `master` while keeping master's SDK safety fixes (`_get_gemini_history_list`, pair-wise dropping, `_content_block_to_dict`).