From ca28dd02ec8eb98a7ad8afea83fdbc3105c48453 Mon Sep 17 00:00:00 2001
From: Aiden Cline <63023139+rekram1-node@users.noreply.github.com>
Date: Tue, 12 May 2026 15:33:16 -0500
Subject: [PATCH] fix(compaction): restore tail turns after summarization
(#27145)
---
packages/opencode/src/config/config.ts | 4 +-
packages/opencode/src/session/compaction.ts | 60 ++++++++-----------
packages/opencode/src/session/message-v2.ts | 44 ++++++++++++--
.../opencode/test/session/compaction.test.ts | 50 +++++++---------
.../test/session/messages-pagination.test.ts | 16 ++---
5 files changed, 96 insertions(+), 78 deletions(-)
diff --git a/packages/opencode/src/config/config.ts b/packages/opencode/src/config/config.ts
index d00c97f463..545e48e64d 100644
--- a/packages/opencode/src/config/config.ts
+++ b/packages/opencode/src/config/config.ts
@@ -261,10 +261,10 @@ export const Info = Schema.Struct({
}),
tail_turns: Schema.optional(NonNegativeInt).annotate({
description:
- "Number of recent user turns, including their following assistant/tool responses, to serialize into the compaction summary (default: 2)",
+ "Number of recent user turns, including their following assistant/tool responses, to keep verbatim during compaction (default: 2)",
}),
preserve_recent_tokens: Schema.optional(NonNegativeInt).annotate({
- description: "Maximum number of tokens from recent turns to serialize into the compaction summary",
+ description: "Maximum number of tokens from recent turns to preserve verbatim after compaction",
}),
reserved: Schema.optional(NonNegativeInt).annotate({
description: "Token buffer for compaction. Leaves enough window to avoid overflow during compaction.",
diff --git a/packages/opencode/src/session/compaction.ts b/packages/opencode/src/session/compaction.ts
index 3ca4f074f9..4eafbdf749 100644
--- a/packages/opencode/src/session/compaction.ts
+++ b/packages/opencode/src/session/compaction.ts
@@ -79,10 +79,12 @@ Rules:
type Turn = {
start: number
end: number
+ id: MessageID
}
type Tail = {
start: number
+ id: MessageID
}
type CompletedCompaction = {
@@ -119,41 +121,19 @@ function completedCompactions(messages: MessageV2.WithParts[]) {
})
}
-function buildPrompt(input: { previousSummary?: string; context: string[]; tail?: string }) {
- const source = input.tail
- ? "the conversation history above and the serialized recent conversation tail below"
- : "the conversation history above"
+function buildPrompt(input: { previousSummary?: string; context: string[] }) {
const anchor = input.previousSummary
? [
- `Update the anchored summary below using ${source}.`,
+ "Update the anchored summary below using the conversation history above.",
"Preserve still-true details, remove stale details, and merge in the new facts.",
"",
input.previousSummary,
"",
].join("\n")
- : `Create a new anchored summary from ${source}.`
- const tail = input.tail
- ? [
- "Fold this serialized recent conversation tail into the summary; it is not provider message history.",
- "",
- input.tail,
- "",
- ].join("\n")
- : undefined
- return [anchor, ...(tail ? [tail] : []), SUMMARY_TEMPLATE, ...input.context].join("\n\n")
+ : "Create a new anchored summary from the conversation history above."
+ return [anchor, SUMMARY_TEMPLATE, ...input.context].join("\n\n")
}
-const serialize = Effect.fn("SessionCompaction.serialize")(function* (input: {
- messages: MessageV2.WithParts[]
- model: Provider.Model
-}) {
- const messages = yield* MessageV2.toModelMessagesEffect(input.messages, input.model, {
- stripMedia: true,
- toolOutputMaxChars: TOOL_OUTPUT_MAX_CHARS,
- })
- return messages.length ? JSON.stringify(messages, null, 2) : undefined
-})
-
function preserveRecentBudget(input: { cfg: Config.Info; model: Provider.Model }) {
return (
input.cfg.compaction?.preserve_recent_tokens ??
@@ -170,6 +150,7 @@ function turns(messages: MessageV2.WithParts[]) {
result.push({
start: i,
end: messages.length,
+ id: msg.info.id,
})
}
for (let i = 0; i < result.length - 1; i++) {
@@ -196,6 +177,7 @@ function splitTurn(input: {
if (size > input.budget) continue
return {
start,
+ id: input.messages[start]!.info.id,
} satisfies Tail
}
return undefined
@@ -262,7 +244,8 @@ export const layer: Layer.Layer<
messages: MessageV2.WithParts[]
model: Provider.Model
}) {
- return Token.estimate((yield* serialize(input)) ?? "")
+ const msgs = yield* MessageV2.toModelMessagesEffect(input.messages, input.model)
+ return Token.estimate(JSON.stringify(msgs))
})
const select = Effect.fn("SessionCompaction.select")(function* (input: {
@@ -271,10 +254,10 @@ export const layer: Layer.Layer<
model: Provider.Model
}) {
const limit = input.cfg.compaction?.tail_turns ?? DEFAULT_TAIL_TURNS
- if (limit <= 0) return { head: input.messages, tail: [] }
+ if (limit <= 0) return { head: input.messages, tail_start_id: undefined }
const budget = preserveRecentBudget({ cfg: input.cfg, model: input.model })
const all = turns(input.messages)
- if (!all.length) return { head: input.messages, tail: [] }
+ if (!all.length) return { head: input.messages, tail_start_id: undefined }
const recent = all.slice(-limit)
const sizes = yield* Effect.forEach(
recent,
@@ -293,7 +276,7 @@ export const layer: Layer.Layer<
const size = sizes[i]
if (total + size <= budget) {
total += size
- keep = { start: turn.start }
+ keep = { start: turn.start, id: turn.id }
continue
}
const remaining = budget - total
@@ -309,10 +292,10 @@ export const layer: Layer.Layer<
break
}
- if (!keep) return { head: input.messages, tail: [] }
+ if (!keep || keep.start === 0) return { head: input.messages, tail_start_id: undefined }
return {
head: input.messages.slice(0, keep.start),
- tail: input.messages.slice(keep.start),
+ tail_start_id: keep.id,
}
})
@@ -423,10 +406,7 @@ export const layer: Layer.Layer<
{ sessionID: input.sessionID },
{ context: [], prompt: undefined },
)
- const tailMessages = structuredClone(selected.tail)
- yield* plugin.trigger("experimental.chat.messages.transform", {}, { messages: tailMessages })
- const tail = yield* serialize({ messages: tailMessages, model })
- const nextPrompt = compacting.prompt ?? buildPrompt({ previousSummary, context: compacting.context, tail })
+ const nextPrompt = compacting.prompt ?? buildPrompt({ previousSummary, context: compacting.context })
const msgs = structuredClone(selected.head)
yield* plugin.trigger("experimental.chat.messages.transform", {}, { messages: msgs })
const modelMessages = yield* MessageV2.toModelMessagesEffect(msgs, model, {
@@ -493,6 +473,13 @@ export const layer: Layer.Layer<
return "stop"
}
+ if (compactionPart && selected.tail_start_id && compactionPart.tail_start_id !== selected.tail_start_id) {
+ yield* session.updatePart({
+ ...compactionPart,
+ tail_start_id: selected.tail_start_id,
+ })
+ }
+
if (result === "continue" && input.auto) {
if (replay) {
const original = replay.info
@@ -588,6 +575,7 @@ export const layer: Layer.Layer<
sessionID: input.sessionID,
timestamp: DateTime.makeUnsafe(Date.now()),
text: summary ?? "",
+ include: selected.tail_start_id,
})
}
yield* bus.publish(Event.Compacted, { sessionID: input.sessionID })
diff --git a/packages/opencode/src/session/message-v2.ts b/packages/opencode/src/session/message-v2.ts
index 626261d0f6..e6ee40e953 100644
--- a/packages/opencode/src/session/message-v2.ts
+++ b/packages/opencode/src/session/message-v2.ts
@@ -772,13 +772,12 @@ export const toModelMessagesEffect = Effect.fnUntraced(function* (
return part.metadata?.anthropic?.signature != null
})
for (const part of msg.parts) {
- if (msg.info.summary && part.type !== "text") continue
if (part.type === "text") {
const text = part.text === "" && hasSignedReasoning ? " " : part.text
assistantMessage.parts.push({
type: "text",
text,
- ...(differentModel || msg.info.summary ? {} : { providerMetadata: part.metadata }),
+ ...(differentModel ? {} : { providerMetadata: part.metadata }),
})
}
if (part.type === "step-start")
@@ -1004,16 +1003,53 @@ export function get(input: { sessionID: SessionID; messageID: MessageID }): With
export function filterCompacted(msgs: Iterable) {
const result = [] as WithParts[]
const completed = new Set()
+ let retain: MessageID | undefined
for (const msg of msgs) {
result.push(msg)
- if (msg.info.role === "user" && completed.has(msg.info.id)) {
- if (msg.parts.some((item): item is CompactionPart => item.type === "compaction")) break
+ if (retain) {
+ if (msg.info.id === retain) break
continue
}
+ if (msg.info.role === "user" && completed.has(msg.info.id)) {
+ const part = msg.parts.find((item): item is CompactionPart => item.type === "compaction")
+ if (!part) continue
+ if (!part.tail_start_id) break
+ retain = part.tail_start_id
+ if (msg.info.id === retain) break
+ continue
+ }
+ if (msg.info.role === "user" && completed.has(msg.info.id) && msg.parts.some((part) => part.type === "compaction"))
+ break
if (msg.info.role === "assistant" && msg.info.summary && msg.info.finish && !msg.info.error)
completed.add(msg.info.parentID)
}
result.reverse()
+ const compactionIndex = result.findLastIndex(
+ (msg) =>
+ msg.info.role === "user" &&
+ msg.parts.some((item): item is CompactionPart => item.type === "compaction" && item.tail_start_id !== undefined),
+ )
+ const compaction = result[compactionIndex]
+ const part = compaction?.parts.find(
+ (item): item is CompactionPart => item.type === "compaction" && item.tail_start_id !== undefined,
+ )
+ const summaryIndex = compaction
+ ? result.findIndex(
+ (msg, index) =>
+ index > compactionIndex &&
+ msg.info.role === "assistant" &&
+ msg.info.summary &&
+ msg.info.parentID === compaction.info.id,
+ )
+ : -1
+ const tailIndex = part?.tail_start_id ? result.findIndex((msg) => msg.info.id === part.tail_start_id) : -1
+ if (tailIndex >= 0 && tailIndex < compactionIndex && summaryIndex > compactionIndex) {
+ return [
+ ...result.slice(compactionIndex, summaryIndex + 1),
+ ...result.slice(tailIndex, compactionIndex),
+ ...result.slice(summaryIndex + 1),
+ ]
+ }
return result
}
diff --git a/packages/opencode/test/session/compaction.test.ts b/packages/opencode/test/session/compaction.test.ts
index c7f349d5ce..1d329699f6 100644
--- a/packages/opencode/test/session/compaction.test.ts
+++ b/packages/opencode/test/session/compaction.test.ts
@@ -926,12 +926,12 @@ describe("session.compaction.process", () => {
)
itCompaction.instance(
- "does not persist tail_start_id for serialized recent turns",
+ "persists tail_start_id for retained recent turns",
Effect.gen(function* () {
const ssn = yield* SessionNs.Service
const session = yield* ssn.create({})
yield* createUserMessage(session.id, "first")
- yield* createUserMessage(session.id, "second")
+ const keep = yield* createUserMessage(session.id, "second")
yield* createUserMessage(session.id, "third")
yield* createSummaryCompaction(session.id)
@@ -947,18 +947,18 @@ describe("session.compaction.process", () => {
const part = yield* readCompactionPart(session.id)
expect(part?.type).toBe("compaction")
- expect(part?.tail_start_id).toBeUndefined()
+ expect(part?.tail_start_id).toBe(keep.id)
}).pipe(withCompaction({ config: cfg({ tail_turns: 2, preserve_recent_tokens: 10_000 }) })),
)
itCompaction.instance(
- "does not persist tail_start_id when shrinking serialized tail",
+ "shrinks retained tail to fit preserve token budget",
Effect.gen(function* () {
const ssn = yield* SessionNs.Service
const session = yield* ssn.create({})
yield* createUserMessage(session.id, "first")
yield* createUserMessage(session.id, "x".repeat(2_000))
- yield* createUserMessage(session.id, "tiny")
+ const keep = yield* createUserMessage(session.id, "tiny")
yield* createSummaryCompaction(session.id)
const msgs = yield* ssn.messages({ sessionID: session.id })
@@ -973,7 +973,7 @@ describe("session.compaction.process", () => {
const part = yield* readCompactionPart(session.id)
expect(part?.type).toBe("compaction")
- expect(part?.tail_start_id).toBeUndefined()
+ expect(part?.tail_start_id).toBe(keep.id)
}).pipe(withCompaction({ config: cfg({ tail_turns: 2, preserve_recent_tokens: 100 }) })),
)
@@ -1005,7 +1005,7 @@ describe("session.compaction.process", () => {
)
itCompaction.instance(
- "serializes retained tail media as text in the summary input",
+ "falls back to full summary when retained tail media exceeds preserve token budget",
() => {
const stub = llm()
let captured = ""
@@ -1078,16 +1078,15 @@ describe("session.compaction.process", () => {
const part = yield* readCompactionPart(session.id)
expect(part?.type).toBe("compaction")
- expect(part?.tail_start_id).toBeUndefined()
+ expect(part?.tail_start_id).toBe(keep.id)
expect(captured).toContain("zzzz")
- expect(captured).toContain("keep tail")
+ expect(captured).not.toContain("keep tail")
const filtered = MessageV2.filterCompacted(MessageV2.stream(session.id))
- expect(filtered.map((msg) => msg.info.id)).toEqual([parent!, expect.any(String)])
+ expect(filtered.map((msg) => msg.info.id).slice(0, 3)).toEqual([parent!, expect.any(String), keep.id])
expect(filtered[1]?.info.role).toBe("assistant")
expect(filtered[1]?.info.role === "assistant" ? filtered[1].info.summary : false).toBe(true)
expect(filtered.map((msg) => msg.info.id)).not.toContain(large.id)
- expect(filtered.map((msg) => msg.info.id)).not.toContain(keep.id)
}).pipe(withCompaction({ llm: stub.layer, config: cfg({ tail_turns: 1, preserve_recent_tokens: 100 }) }))
},
{ git: true },
@@ -1354,13 +1353,13 @@ describe("session.compaction.process", () => {
)
itCompaction.instance(
- "summarizes the head while serializing recent tail into summary input",
+ "summarizes only the head while keeping recent tail out of summary input",
() => {
const stub = llm()
- let captured: LLM.StreamInput["messages"] = []
+ let captured = ""
stub.push(
reply("summary", (input) => {
- captured = input.messages
+ captured = JSON.stringify(input.messages)
}),
)
return Effect.gen(function* () {
@@ -1381,15 +1380,10 @@ describe("session.compaction.process", () => {
auto: false,
})
- const head = JSON.stringify(captured.slice(0, -1))
- const prompt = JSON.stringify(captured.at(-1))
- expect(head).toContain("older context")
- expect(head).not.toContain("keep this turn")
- expect(head).not.toContain("and this one too")
- expect(prompt).toContain("keep this turn")
- expect(prompt).toContain("and this one too")
- expect(prompt).toContain("recent-conversation-tail")
- expect(prompt).not.toContain("What did we do so far?")
+ expect(captured).toContain("older context")
+ expect(captured).not.toContain("keep this turn")
+ expect(captured).not.toContain("and this one too")
+ expect(captured).not.toContain("What did we do so far?")
}).pipe(withCompaction({ llm: stub.layer }))
},
{ git: true },
@@ -1437,7 +1431,7 @@ describe("session.compaction.process", () => {
{ git: true },
)
- itCompaction.instance("does not replay recent pre-compaction turns across repeated compactions", () => {
+ itCompaction.instance("keeps recent pre-compaction turns across repeated compactions", () => {
const stub = llm()
stub.push(reply("summary one"))
stub.push(reply("summary two"))
@@ -1468,8 +1462,8 @@ describe("session.compaction.process", () => {
expect(ids).not.toContain(u1.id)
expect(ids).not.toContain(u2.id)
- expect(ids).not.toContain(u3.id)
- expect(ids).not.toContain(u4.id)
+ expect(ids).toContain(u3.id)
+ expect(ids).toContain(u4.id)
expect(filtered.some((msg) => msg.info.role === "assistant" && msg.info.summary)).toBe(true)
expect(
filtered.some((msg) => msg.info.role === "user" && msg.parts.some((part) => part.type === "compaction")),
@@ -1478,7 +1472,7 @@ describe("session.compaction.process", () => {
})
itCompaction.instance(
- "ignores previous summaries when sizing the serialized tail",
+ "ignores previous summaries when sizing the retained tail",
Effect.gen(function* () {
const ssn = yield* SessionNs.Service
const test = yield* TestInstance
@@ -1517,7 +1511,7 @@ describe("session.compaction.process", () => {
const part = yield* readCompactionPart(session.id)
expect(part?.type).toBe("compaction")
- expect(part?.tail_start_id).toBeUndefined()
+ expect(part?.tail_start_id).toBe(keep.id)
}).pipe(withCompaction({ config: cfg({ tail_turns: 2, preserve_recent_tokens: 500 }) })),
)
})
diff --git a/packages/opencode/test/session/messages-pagination.test.ts b/packages/opencode/test/session/messages-pagination.test.ts
index e1714a9015..09e8d7b429 100644
--- a/packages/opencode/test/session/messages-pagination.test.ts
+++ b/packages/opencode/test/session/messages-pagination.test.ts
@@ -650,7 +650,7 @@ describe("MessageV2.filterCompacted", () => {
),
)
- it.instance("ignores original tail when compaction stores tail_start_id", () =>
+ it.instance("retains original tail when compaction stores tail_start_id", () =>
withSession(({ session, sessionID }) =>
Effect.gen(function* () {
const u1 = yield* addUser(sessionID, "first")
@@ -696,12 +696,12 @@ describe("MessageV2.filterCompacted", () => {
const result = MessageV2.filterCompacted(MessageV2.stream(sessionID))
- expect(result.map((item) => item.info.id)).toEqual([c1, s1, u3, a3])
+ expect(result.map((item) => item.info.id)).toEqual([c1, s1, u2, a2, u3, a3])
}),
),
)
- it.instance("fork keeps legacy tail_start_id without replaying the tail", () =>
+ it.instance("fork remaps compaction tail_start_id for filterCompacted", () =>
Effect.gen(function* () {
const session = yield* SessionNs.Service
const created = yield* session.create({})
@@ -748,7 +748,7 @@ describe("MessageV2.filterCompacted", () => {
})
const parentFiltered = MessageV2.filterCompacted(MessageV2.stream(created.id))
- expect(parentFiltered.map((item) => item.info.id)).toEqual([c1, s1, u3, a3])
+ expect(parentFiltered.map((item) => item.info.id)).toEqual([c1, s1, u2, a2, u3, a3])
const forked = yield* session.fork({ sessionID: created.id })
const childFiltered = MessageV2.filterCompacted(MessageV2.stream(forked.id))
@@ -758,14 +758,14 @@ describe("MessageV2.filterCompacted", () => {
expect(tailPart?.type).toBe("compaction")
if (!tailPart || tailPart.type !== "compaction") throw new Error("Expected forked compaction part")
expect(tailPart.tail_start_id).toBeDefined()
- expect(childFiltered.some((m) => m.info.id === tailPart.tail_start_id)).toBe(false)
+ expect(childFiltered.some((m) => m.info.id === tailPart.tail_start_id)).toBe(true)
yield* session.remove(forked.id)
yield* session.remove(created.id)
}),
)
- it.instance("does not replay an assistant tail when compaction starts inside a turn", () =>
+ it.instance("retains an assistant tail when compaction starts inside a turn", () =>
withSession(({ session, sessionID }) =>
Effect.gen(function* () {
const u1 = yield* addUser(sessionID, "first")
@@ -819,7 +819,7 @@ describe("MessageV2.filterCompacted", () => {
const result = MessageV2.filterCompacted(MessageV2.stream(sessionID))
- expect(result.map((item) => item.info.id)).toEqual([c1, s1, u3, a4])
+ expect(result.map((item) => item.info.id)).toEqual([c1, s1, a3, u3, a4])
}),
),
)
@@ -891,7 +891,7 @@ describe("MessageV2.filterCompacted", () => {
const result = MessageV2.filterCompacted(MessageV2.stream(sessionID))
- expect(result.map((item) => item.info.id)).toEqual([c2, s2, u4, a4])
+ expect(result.map((item) => item.info.id)).toEqual([c2, s2, u3, a3, u4, a4])
}),
),
)