From b26821ead97b986f886065b20d3dbde8283daa64 Mon Sep 17 00:00:00 2001
From: Adam Malczewski <github@tradam.dev>
Date: Wed, 3 Jun 2026 01:26:16 +0900
Subject: feat(compaction): add UI-driven conversation compaction
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Summarize a conversation's older "head" into a structured anchored Markdown
summary while preserving the most recent turns verbatim, shrinking context size
while keeping the information needed to continue coherently. Triggered by a
"Compact conversation" button in Chat Settings (not an agent tool).

Approach informed by OpenCode's session/compaction.ts:
- Ported SUMMARY_TEMPLATE (Goal / Constraints / Progress / Key Decisions /
  Next Steps / Critical Context / Relevant Files) and the anchored-summary
  buildPrompt (re-summarizes a prior summary when present).
- Ported the TOOL_OUTPUT_MAX_CHARS (2000) cap on tool results in the summary
  request.
- Simplified tail selection to a fixed recent-turn count (DEFAULT_TAIL_TURNS=2)
  instead of OpenCode's token-budget splitTurn.

core:
- New src/compaction/ module (pure, DB-free): template, prompt builder,
  head/tail selection, transcript renderer with tool-output capping, prior
  summary extraction. Generic over ChatMessage so callers keep turnId/seq.
- db/chunks.ts: rekeyChunks(from,to) relocates a tab's full history to a
  backup tab (reversible — nothing is deleted).
- AgentEvent: compaction-started / -complete / -error variants.

api:
- AgentManager.compactTab(tempTabId, sourceTabId): side-effect-free
  resolveConnection() for the compactor model (configured compaction_model_*,
  else the source tab's own key+model), one-shot tool-less summary generation
  via a transient Agent, then relocate full history to a fresh backup tab and
  re-seed the canonical source id with [summary turn + preserved tail]. Source
  tab is locked (messages queue) during the run; queue drains afterward.
- Routes: POST /tabs/:id/compact, GET/PUT /tabs/settings/compaction-model.

frontend:
- "Compact conversation" button in ModelSelector (Chat Settings), between
  Working Directory and the agent toggle; idle-gated.
- Compaction-model key+model selector in Settings, beside the title model.
- Transient placeholder tab shows a large, non-faded "Please wait, compacting
  conversation…" screen; closing it cancels. Source input locked while running.
- Handle compaction-* events: reload compacted source, insert backup tab,
  refocus source, discard placeholder.

tests: core compaction unit tests, rekeyChunks DB test, AgentManager.compactTab
orchestration tests, and compaction route tests. All green (713 tests), biome
clean, all typechecks pass, frontend builds.
---
 packages/core/src/db/chunks.ts | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'packages/core/src/db')

diff --git a/packages/core/src/db/chunks.ts b/packages/core/src/db/chunks.ts
index e0aadf3..b434a47 100644
--- a/packages/core/src/db/chunks.ts
+++ b/packages/core/src/db/chunks.ts
@@ -225,3 +225,22 @@ export function clearChunksForTab(tabId: string): void {
 	const db = getDatabase();
 	db.query("DELETE FROM chunks WHERE tab_id = $tabId").run({ $tabId: tabId });
 }
+
+/**
+ * Relocate every chunk row from one tab to another (compaction backup path).
+ *
+ * Used by conversation compaction to move the FULL pre-compaction history off
+ * the canonical tab id (`fromTabId`) onto a freshly-created backup tab id
+ * (`toTabId`), leaving the canonical id free to be re-seeded with the summary +
+ * preserved tail. `seq` values are preserved (they remain per-tab monotonic for
+ * the destination since it starts empty), as are turn ids, so the relocated
+ * history groups identically under its new tab. Returns the number of rows
+ * moved.
+ */
+export function rekeyChunks(fromTabId: string, toTabId: string): number {
+	const db = getDatabase();
+	const result = db
+		.query("UPDATE chunks SET tab_id = $to WHERE tab_id = $from")
+		.run({ $from: fromTabId, $to: toTabId });
+	return Number(result.changes ?? 0);
+}
-- 
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