Epic: agent hot path optimization #621
Description
Summary
Core agent loop has SQLite contention (no WAL), O(n) token scans per tool iteration, per-chunk allocations, and unnecessary string copies in hot paths.
Child Issues
- Enable SQLite WAL mode and SYNCHRONOUS=NORMAL #639 Enable SQLite WAL mode + SYNCHRONOUS=NORMAL
- Replace O(n*iterations) token scan with incremental counter #640 Replace O(n*iterations) token scan with incremental counter
- Defer maybe_redact to flush_chunks() boundary #641 Defer maybe_redact to flush_chunks() boundary
- Replace format_tool_output allocation with Write-into-buffer #642 Replace format_tool_output allocation with Write-into-buffer
- Use serde_json::Map directly for tool call params #643 Use serde_json::Map directly for tool call params
- Pre-join static system prompt sections into LazyLock #644 Pre-join static system prompt sections into LazyLock
- Replace doom-loop string storage with content hash #645 Replace doom-loop string storage with content hash
- Return &'static str from detect_image_mime #646 Return &'static str from detect_image_mime
- Replace block_on in history persist with spawn_blocking #647 Replace block_on in history persist with spawn_blocking