🪲 BUG-#19: Persist only new messages instead of rewriting the whole session - #54
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Storage backends need to tell an append-only save from one where existing history was replaced or reordered. replace_messages(), trim() (when it actually truncates), and _repair_dangling_tool_calls() (when it actually inserts a repair message) now set session.dirty, giving SqliteSessions a signal to fall back to a full rewrite instead of assuming everything before the last known count is unchanged.
…ession post() deleted and reinserted every MessageRecord on every call, even though Agent's on_message fires after each message including every tool result — a 20-tool-call turn on a 200-message session did 20 × (200 DELETE + 200 INSERT) writes. Now inserts only the messages appended since the last save (tracked via record.message_count), falling back to the previous full delete-and-reinsert when the session is new, a different Session object was posted for the same key (checked via identity — a count watermark alone can't tell an overwrite from an append), session.dirty is set, or the message count shrank.
FernandoCelmer
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Aug 15, 2026
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🔍 Code Review
Code issues found: 1
| # | Severity | Comment |
|---|---|---|
| 1 | [Suggestion] | session.dirty read without _lock in post() |
post() read session.dirty and session.messages unlocked while _repair_dangling_tool_calls() sets dirty under session._lock, letting a concurrent repair's synthetic messages be dropped silently. Snapshot both fields together under the lock before touching the DB.
This was referenced Aug 16, 2026
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Description
pycodeloop/core/session.py— Adds adirty: boolfield (defaultFalse) toSession.replace_messages(),trim()(when it actually truncates), and_repair_dangling_tool_calls()(when it inserts synthetic results) now setdirty = Trueto signal that history was mutated rather than appended.pycodeloop/store/sqlite_sessions.py—post()now appends only the messages added since the last save (tracked byrecord.message_count), falling back to a full delete-and-reinsert when the session is new, a different object was posted for the same key,session.dirtyis set, or the message count shrank. Adds_session_identitydict to detect object identity changes across calls. Clearssession.dirtyand records the identity after a successful commit.tests/core/test_session.py— NewTestSessionDirtyFlagsuite covering all dirty-marking paths and their no-op counterparts.tests/store/test_sqlite_sessions.py— New integration tests spy onQuery.deleteto prove the incremental path skips the rewrite, and that dirty/different-object/new-session cases fall back correctly.Motivation and Context
SqliteSessions.post()deleted and reinserted everyMessageRecordon every call, even thoughAgent.on_messagefires after each message including every tool result. For a 20-tool-call turn on a 200-message session that's 20 × (200 DELETE + 200 INSERT) = 8,000 row writes. Closes #19.Types of changes
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