Move chat-history persistence to append-only JSONL - #2431
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SasinduDilshara wants to merge 4 commits into
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Move chat-history persistence to append-only JSONL#2431SasinduDilshara wants to merge 4 commits into
SasinduDilshara wants to merge 4 commits into
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Threads previously persisted as a single whole-file JSON snapshot (thread.json) that was re-serialized and rewritten on every mutation. Because the file grows with the conversation and the write is synchronous, per-turn cost scaled with total history (O(n²) over a session), causing noticeable lag in long chats. Switch to an append-only log (thread.jsonl): each mutation appends one record instead of rewriting everything, so adding a turn costs the same whether the conversation is 2 or 200 messages long. On load the records are replayed to rebuild the thread; the log is compacted (amortized, and on load) to reclaim superseded records. - file-utils: appendLineSync + readJsonlSync (tolerant of a torn trailing line for crash safety) - types: ThreadLogRecord union (head/meta/gen/del/trunc) - schema-migration: bump thread schema to v2 with an identity v1->v2 migration (data shape unchanged, storage format differs) - persistence-store: append API (appendGeneration/removeGenerationRecord/ truncateFromGeneration/updateThreadMeta), replay-based loadThread with one-time thread.json -> thread.jsonl migration + legacy delete, compacted saveThread, compactThread, amortized + on-load compaction - tests: full coverage of append/replay/tombstone/truncate/torn-line/ migration/compaction; existing suite updated for the new format Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
…writes (wso2#1861) Adversarial self-review follow-ups: - Amortized compaction is now size-proportional (compact after max(64, 3*liveGens) appends, not a fixed 100), so per-append cost stays genuinely O(1) amortized instead of growing with thread size — the O(n²) shape the issue targets is fully removed, not just reduced. - On-load compaction (compactOnLoadIfNeeded) and append-time compaction (noteAppend) now swallow write errors. loadThread became a writer on the happy path; an unguarded transient disk error there would have aborted restore of the entire workspace even though the thread was already replayed in memory. Compaction is a pure optimization and must never fail a load or an append. - loadThread falls back to a legacy thread.json when the jsonl exists but is empty/unrecoverable, instead of reporting the thread as gone. Tests: +3 (size-aware threshold, read-only-dir load resilience, empty-jsonl legacy fallback); 72 pass / 0 fail. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
) Follow-up to reviewer feedback: the previous design re-appended the whole generation (its entire, growing modelMessages) on every agent step and relied on compaction to clean up the duplicates — roughly O(S^2) bytes written per S-step turn, all synchronous. Switch to message-level records so each message is written exactly once: - `gen` — a lightweight generation header (everything except modelMessages), appended only when a header field actually changes. - `msg` — one model message, appended as it arrives. - `msgs` — replace a generation's whole message list (only when the messages are rewritten rather than extended, e.g. server-side compaction; detected cheaply via length/last-message change). appendGeneration now diffs against per-generation tracking and writes only the delta (new messages + header-if-changed), so a turn costs O(messages) to persist instead of O(messages^2). Replay groups `msg` records by genId in order; compaction/save emit one `msg` per message. The consumer (ChatStateStorage) is unchanged — it still calls appendGeneration with the full generation; the delta logic lives entirely in the store. Tests: +4 (message-once / no-duplication, header-only-on-change, msgs reset, headless message reconstruction); 75 pass / 0 fail. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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SasinduDilshara
marked this pull request as draft
July 27, 2026 14:43
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Solution
Moves Copilot chat-history persistence from full-file JSON rewrites to an append-only JSONL log in
copilot-utilities.appendGeneration/removeGenerationRecord/truncateFromGeneration); full rewrites are kept only for thread creation and one-time legacy migration.Fixes wso2/product-integrator#1861
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