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keep recent turns during session compaction

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This commit is contained in:
Shoubhit Dash
2026-04-10 09:34:01 +05:30
parent 91786d2fc1
commit 6f5a3d30fd
6 changed files with 587 additions and 15 deletions
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90
packages/opencode/src/session/compaction.ts
View File

@@ -4,6 +4,7 @@ import { Session } from "."
import { SessionID, MessageID, PartID } from "./schema"
import { Instance } from "../project/instance"
import { Provider } from "../provider/provider"
import { ProviderTransform } from "../provider/transform"
import { MessageV2 } from "./message-v2"
import z from "zod"
import { Token } from "../util/token"
@@ -35,6 +36,24 @@ export namespace SessionCompaction {
export const PRUNE_MINIMUM = 20_000
export const PRUNE_PROTECT = 40_000
const PRUNE_PROTECTED_TOOLS = ["skill"]
const DEFAULT_TAIL_TURNS = 2
const MIN_TAIL_TOKENS = 2_000
const MAX_TAIL_TOKENS = 8_000
function usable(input: { cfg: Config.Info; model: Provider.Model }) {
const reserved =
input.cfg.compaction?.reserved ?? Math.min(20_000, ProviderTransform.maxOutputTokens(input.model))
return input.model.limit.input
? Math.max(0, input.model.limit.input - reserved)
: Math.max(0, input.model.limit.context - ProviderTransform.maxOutputTokens(input.model))
}
function tailBudget(input: { cfg: Config.Info; model: Provider.Model }) {
return (
input.cfg.compaction?.tail_tokens ??
Math.min(MAX_TAIL_TOKENS, Math.max(MIN_TAIL_TOKENS, Math.floor(usable(input) * 0.25)))
)
}
export interface Interface {
readonly isOverflow: (input: {
@@ -88,6 +107,55 @@ export namespace SessionCompaction {
return overflow({ cfg: yield* config.get(), tokens: input.tokens, model: input.model })
})
const estimate = Effect.fn("SessionCompaction.estimate")(function* (input: {
messages: MessageV2.WithParts[]
model: Provider.Model
}) {
const msgs = yield* MessageV2.toModelMessagesEffect(input.messages, input.model, { stripMedia: true })
return Token.estimate(JSON.stringify(msgs))
})
const select = Effect.fn("SessionCompaction.select")(function* (input: {
messages: MessageV2.WithParts[]
cfg: Config.Info
model: Provider.Model
}) {
const limit = input.cfg.compaction?.tail_turns ?? DEFAULT_TAIL_TURNS
if (limit <= 0) return { head: input.messages, tail_start_id: undefined }
const budget = tailBudget({ cfg: input.cfg, model: input.model })
const turns = input.messages.flatMap((msg, idx) =>
msg.info.role === "user" && !msg.parts.some((part) => part.type === "compaction") ? [idx] : [],
)
if (!turns.length) return { head: input.messages, tail_start_id: undefined }
let total = 0
let start = input.messages.length
let kept = 0
for (let i = turns.length - 1; i >= 0 && kept < limit; i--) {
const idx = turns[i]
const end = i + 1 < turns.length ? turns[i + 1] : input.messages.length
const size = yield* estimate({
messages: input.messages.slice(idx, end),
model: input.model,
})
if (kept === 0 && size > budget) {
log.info("tail fallback", { budget, size })
return { head: input.messages, tail_start_id: undefined }
}
if (total + size > budget) break
total += size
start = idx
kept++
}
if (kept === 0 || start === 0) return { head: input.messages, tail_start_id: undefined }
return {
head: input.messages.slice(0, start),
tail_start_id: input.messages[start]?.info.id,
}
})
// goes backwards through parts until there are PRUNE_PROTECT tokens worth of tool
// calls, then erases output of older tool calls to free context space
const prune = Effect.fn("SessionCompaction.prune")(function* (input: { sessionID: SessionID }) {
@@ -150,6 +218,7 @@ export namespace SessionCompaction {
throw new Error(`Compaction parent must be a user message: ${input.parentID}`)
}
const userMessage = parent.info
const compactionPart = parent.parts.find((part): part is MessageV2.CompactionPart => part.type === "compaction")
let messages = input.messages
let replay:
@@ -180,14 +249,22 @@ export namespace SessionCompaction {
const model = agent.model
? yield* provider.getModel(agent.model.providerID, agent.model.modelID)
: yield* provider.getModel(userMessage.model.providerID, userMessage.model.modelID)
const cfg = yield* config.get()
const history = compactionPart && messages.at(-1)?.info.id === input.parentID ? messages.slice(0, -1) : messages
const selected = yield* select({
messages: history,
cfg,
model,
})
// Allow plugins to inject context or replace compaction prompt.
const compacting = yield* plugin.trigger(
"experimental.session.compacting",
{ sessionID: input.sessionID },
{ context: [], prompt: undefined },
)
const defaultPrompt = `Provide a detailed prompt for continuing our conversation above.
Focus on information that would be helpful for continuing the conversation, including what we did, what we're doing, which files we're working on, and what we're going to do next.
const defaultPrompt = `Summarize the older conversation history so another agent can continue the work with the retained recent turns.
The most recent conversation turns will remain verbatim outside this summary, so focus on older context that is still needed to understand and continue the work.
Include what we did, what we're doing, which files we're working on, and what we're going to do next.
The summary that you construct will be used so that another agent can read it and continue the work.
Do not call any tools. Respond only with the summary text.
Respond in the same language as the user's messages in the conversation.
@@ -217,7 +294,7 @@ When constructing the summary, try to stick to this template:
---`
const prompt = compacting.prompt ?? [defaultPrompt, ...compacting.context].join("\n\n")
const msgs = structuredClone(messages)
const msgs = structuredClone(selected.head)
yield* plugin.trigger("experimental.chat.messages.transform", {}, { messages: msgs })
const modelMessages = yield* MessageV2.toModelMessagesEffect(msgs, model, { stripMedia: true })
const ctx = yield* InstanceState.context
@@ -280,6 +357,13 @@ When constructing the summary, try to stick to this template:
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

20
packages/opencode/src/session/message-v2.ts
View File

@@ -208,6 +208,7 @@ export namespace MessageV2 {
type: z.literal("compaction"),
auto: z.boolean(),
overflow: z.boolean().optional(),
tail_start_id: MessageID.zod.optional(),
}).meta({
ref: "CompactionPart",
})
@@ -926,14 +927,21 @@ export namespace MessageV2 {
export function filterCompacted(msgs: Iterable<MessageV2.WithParts>) {
const result = [] as MessageV2.WithParts[]
const completed = new Set<string>()
let retain: MessageID | undefined
for (const msg of msgs) {
result.push(msg)
if (
msg.info.role === "user" &&
completed.has(msg.info.id) &&
msg.parts.some((part) => part.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 MessageV2.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 === "assistant" && msg.info.summary && msg.info.finish && !msg.info.error)
completed.add(msg.info.parentID)
}