feat: delegate compression

dcp.schema.json

@@ -169,17 +169,18 @@
                     ]
                 },
                 "minContextLimit": {
-                    "description": "Soft lower threshold for reminder nudges. Below this, turn/iteration reminders are off (compression is less likely). At or above this, reminders are on. Accepts number or \"X%\" of the model context window.",
-                    "default": 50000,
-                    "oneOf": [
-                        {
-                            "type": "number"
-                        },
-                        {
-                            "type": "string",
-                            "pattern": "^\\d+(?:\\.\\d+)?%$"
-                        }
-                    ]
+                    "type": ["number", "string"],
+                    "pattern": "^[0-9]+%$",
+                    "default": "45%",
+                    "description": "Lower threshold: contextual turn nudge stops appearing below this limit"
+                },
+                "model": {
+                    "type": "string",
+                    "description": "Provider/Model ID to use for generating compression summaries instead of the active model (e.g. 'anthropic/claude-3-haiku-20240307')"
+                },
+                "agent": {
+                    "type": "string",
+                    "description": "Agent to use when prompting the custom compression model (e.g. 'dcp-compressor')"
                 },
                 "modelMaxLimits": {
                     "description": "Per-model override for maxContextLimit by exact provider/model key. If set, this takes priority over the global maxContextLimit.",

lib/compress/message.ts

@@ -1,9 +1,10 @@
 import { tool } from "@opencode-ai/plugin"
 import type { ToolContext } from "./types"
 import { countTokens } from "../token-utils"
-import { MESSAGE_FORMAT_EXTENSION } from "../prompts/extensions/tool"
+import { getMessageFormatExtension } from "../prompts/extensions/tool"
 import { formatIssues, formatResult, resolveMessages, validateArgs } from "./message-utils"
-import { finalizeSession, prepareSession, type NotificationEntry } from "./pipeline"
+import { finalizeSession, prepareSession, generateDelegatedSummary, resolveCompressionDelegate, formatPartForDelegatedCompression, type NotificationEntry } from "./pipeline"
+import { INTERNAL_COMPRESSION_SYSTEM_PROMPT } from "../prompts/system"
 import { appendProtectedPromptInfo, appendProtectedTools } from "./protected-content"
 import {
     allocateBlockId,
@@ -31,6 +32,7 @@ function buildSchema() {
                         .describe("Short label (3-5 words) for this one message summary"),
                     summary: tool.schema
                         .string()
+                        .optional()
                         .describe("Complete technical summary replacing that one message"),
                 }),
             )
@@ -42,8 +44,10 @@ export function createCompressMessageTool(ctx: ToolContext): ReturnType<typeof t
     ctx.prompts.reload()
     const runtimePrompts = ctx.prompts.getRuntimePrompts()
 
+    const delegate = resolveCompressionDelegate(ctx.config)
+    const delegated = delegate.enabled
     return tool({
-        description: runtimePrompts.compressMessage + MESSAGE_FORMAT_EXTENSION,
+        description: runtimePrompts.compressMessage + getMessageFormatExtension(delegated),
         args: buildSchema(),
         async execute(args, toolCtx) {
             const input = args as CompressMessageToolArgs
@@ -77,8 +81,30 @@ export function createCompressMessageTool(ctx: ToolContext): ReturnType<typeof t
             }> = []
 
             for (const plan of plans) {
+                let initialSummary = plan.entry.summary || ""
+
+                if (delegated && delegate) {
+                    const rawText = plan.selection.messageIds
+                        .map((id) => {
+                            const msg = searchContext.rawMessagesById.get(id)
+                            return msg ? `[${msg.info.role}] ${msg.parts?.map(formatPartForDelegatedCompression).join("\n")}` : ""
+                        })
+                        .filter(Boolean)
+                        .join("\n\n")
+
+                    initialSummary = await generateDelegatedSummary(
+                        ctx.client,
+                        ctx.logger,
+                        delegate,
+                        INTERNAL_COMPRESSION_SYSTEM_PROMPT,
+                        `Please summarize the following messages:\n\n${rawText}`
+                    )
+                } else if (!initialSummary) {
+                    throw new Error("Summary is required when delegated compression is disabled.")
+                }
+
                 const summaryWithPromptInfo = appendProtectedPromptInfo(
-                    plan.entry.summary,
+                    initialSummary,
                     plan.selection,
                     searchContext,
                     ctx.state,

lib/compress/pipeline.ts

@@ -76,6 +76,193 @@ export async function prepareSession(
     }
 }
 
+const TOOL_PAYLOAD_LIMIT = 3000
+const TRUNCATION_MARKER = "\n...[truncated]...\n"
+
+function stringifyForCompression(value: unknown): string {
+    if (typeof value === "string") return value
+    if (value === undefined) return ""
+
+    try {
+        const seen = new WeakSet<object>()
+
+        return JSON.stringify(
+            value,
+            (_key, val) => {
+                if (typeof val === "bigint") return val.toString()
+                if (typeof val === "object" && val !== null) {
+                    if (seen.has(val)) return "[Circular]"
+                    seen.add(val)
+                }
+                return val
+            },
+            2,
+        )
+    } catch {
+        return String(value)
+    }
+}
+
+function truncateMiddle(value: string, limit = TOOL_PAYLOAD_LIMIT): string {
+    if (value.length <= limit) return value
+
+    const available = Math.max(0, limit - TRUNCATION_MARKER.length)
+    const headLength = Math.ceil(available / 2)
+    const tailLength = Math.floor(available / 2)
+
+    return `${value.slice(0, headLength)}${TRUNCATION_MARKER}${value.slice(value.length - tailLength)}`
+}
+
+export function formatPartForDelegatedCompression(part: any): string {
+    if (!part || typeof part !== "object") return ""
+
+    if (part.type === "text") {
+        return typeof part.text === "string" ? part.text : stringifyForCompression(part.text)
+    }
+
+    if (part.type === "tool") {
+        const state = part.state && typeof part.state === "object" ? part.state : {}
+        const status = typeof state.status === "string" ? state.status : "unknown"
+        const toolName = typeof part.tool === "string" ? part.tool : "unknown"
+        const args = stringifyForCompression(state.input ?? {})
+
+        if (status === "completed") {
+            return `[Tool: ${toolName} status=completed]\nargs: ${args}\noutput:\n${truncateMiddle(
+                stringifyForCompression(state.output),
+            )}`
+        }
+
+        if (status === "error") {
+            return `[Tool: ${toolName} status=error]\nargs: ${args}\nerror:\n${truncateMiddle(
+                stringifyForCompression(state.error),
+            )}`
+        }
+
+        return `[Tool: ${toolName} status=${status}]\nargs: ${args}`
+    }
+
+    if (typeof part.prompt === "string") {
+        return part.prompt
+    }
+
+    return ""
+}
+
+export type CompressionDelegate =
+    | {
+          enabled: false
+      }
+    | {
+          enabled: true
+          agent?: string
+          model?: {
+              providerID: string
+              modelID: string
+          }
+      }
+
+export function resolveCompressionDelegate(config: any): CompressionDelegate {
+    if (config.compress.agent) {
+        return {
+            enabled: true,
+            agent: config.compress.agent,
+            model: config.compress.model
+                ? {
+                      providerID: config.compress.model.split("/")[0],
+                      modelID: config.compress.model.split("/").slice(1).join("/"),
+                  }
+                : undefined,
+        }
+    }
+
+    if (config.compress.model) {
+        return {
+            enabled: true,
+            model: {
+                providerID: config.compress.model.split("/")[0],
+                modelID: config.compress.model.split("/").slice(1).join("/"),
+            },
+        }
+    }
+
+    return { enabled: false }
+}
+
+export async function generateDelegatedSummary(
+    client: any,
+    logger: any,
+    delegate: CompressionDelegate & { enabled: true },
+    systemPrompt: string,
+    rawText: string
+): Promise<string> {
+    let helperSession: any | undefined
+
+    try {
+        helperSession = await client.session.create({
+            body: { title: "DCP Compression helper" }
+        })
+
+        const internalSessionIdsModule = await import("../state")
+        internalSessionIdsModule.INTERNAL_SESSION_IDS.add(helperSession.data.id || helperSession.id)
+
+        const body: any = {
+            system: systemPrompt,
+            tools: {
+                compress: false,
+                bash: false,
+                edit: false,
+                write: false,
+                read: false,
+                webfetch: false,
+            },
+            parts: [{ type: "text", text: rawText }],
+        }
+
+        if (delegate.model) {
+            body.model = delegate.model
+        }
+        if (delegate.agent) {
+            body.agent = delegate.agent
+        }
+
+        const response = await client.session.prompt({
+            path: { id: helperSession.data.id || helperSession.id },
+            body,
+        })
+
+        if (!response?.data) {
+            throw new Error("No response data from compression model")
+        }
+
+        const info = response.data.info
+        if (info?.error) {
+            throw new Error(`Compression model error: ${JSON.stringify(info.error)}`)
+        }
+
+        const parts = response.data.parts || []
+        const textParts = parts.filter((p: any) => p.type === "text").map((p: any) => p.text)
+
+        if (textParts.length === 0) {
+            throw new Error("Compression model returned empty text")
+        }
+
+        return textParts.join("\n")
+    } finally {
+        if (helperSession) {
+            const helperId = helperSession.data?.id || helperSession.id
+            if (helperId) {
+                try {
+                    await client.session.delete({ path: { id: helperId } })
+                } catch (err: any) {
+                    logger.warn("Failed to delete DCP helper session", { error: err.message })
+                }
+                const internalSessionIdsModule = await import("../state")
+                internalSessionIdsModule.INTERNAL_SESSION_IDS.delete(helperId)
+            }
+        }
+    }
+}
+
 export async function finalizeSession(
     ctx: ToolContext,
     toolCtx: RunContext,

lib/compress/range.ts

@@ -1,8 +1,9 @@
 import { tool } from "@opencode-ai/plugin"
 import type { ToolContext } from "./types"
 import { countTokens } from "../token-utils"
-import { RANGE_FORMAT_EXTENSION } from "../prompts/extensions/tool"
-import { finalizeSession, prepareSession, type NotificationEntry } from "./pipeline"
+import { getRangeFormatExtension } from "../prompts/extensions/tool"
+import { finalizeSession, prepareSession, generateDelegatedSummary, resolveCompressionDelegate, formatPartForDelegatedCompression, type NotificationEntry } from "./pipeline"
+import { INTERNAL_COMPRESSION_SYSTEM_PROMPT } from "../prompts/system"
 import {
     appendProtectedPromptInfo,
     appendProtectedTools,
@@ -44,6 +45,7 @@ function buildSchema() {
                         .describe("Message or block ID marking the end of range (e.g. m0012, b5)"),
                     summary: tool.schema
                         .string()
+                        .optional()
                         .describe("Complete technical summary replacing all content in range"),
                 }),
             )
@@ -57,8 +59,10 @@ export function createCompressRangeTool(ctx: ToolContext): ReturnType<typeof too
     ctx.prompts.reload()
     const runtimePrompts = ctx.prompts.getRuntimePrompts()
 
+    const delegate = resolveCompressionDelegate(ctx.config)
+    const delegated = delegate.enabled
     return tool({
-        description: runtimePrompts.compressRange + RANGE_FORMAT_EXTENSION,
+        description: runtimePrompts.compressRange + getRangeFormatExtension(delegated),
         args: buildSchema(),
         async execute(args, toolCtx) {
             const input = args as CompressRangeToolArgs
@@ -87,7 +91,29 @@ export function createCompressRangeTool(ctx: ToolContext): ReturnType<typeof too
             let totalCompressedMessages = 0
 
             for (const plan of resolvedPlans) {
-                const parsedPlaceholders = parseBlockPlaceholders(plan.entry.summary)
+                let initialSummary = plan.entry.summary || ""
+
+                if (delegated && delegate) {
+                    const rawText = plan.selection.messageIds
+                        .map((id) => {
+                            const msg = searchContext.rawMessagesById.get(id)
+                            return msg ? `[${msg.info.role}] ${msg.parts?.map(formatPartForDelegatedCompression).join("\n")}` : ""
+                        })
+                        .filter(Boolean)
+                        .join("\n\n")
+
+                    initialSummary = await generateDelegatedSummary(
+                        ctx.client,
+                        ctx.logger,
+                        delegate,
+                        INTERNAL_COMPRESSION_SYSTEM_PROMPT,
+                        `Please summarize the following conversation range:\n\n${rawText}`
+                    )
+                } else if (!initialSummary) {
+                    throw new Error("Summary is required when delegated compression is disabled.")
+                }
+
+                const parsedPlaceholders = parseBlockPlaceholders(initialSummary)
                 const missingBlockIds = validateSummaryPlaceholders(
                     parsedPlaceholders,
                     plan.selection.requiredBlockIds,
@@ -97,7 +123,7 @@ export function createCompressRangeTool(ctx: ToolContext): ReturnType<typeof too
                 )
 
                 const injected = injectBlockPlaceholders(
-                    plan.entry.summary,
+                    initialSummary,
                     parsedPlaceholders,
                     searchContext.summaryByBlockId,
                     plan.selection.startReference,

lib/compress/types.ts

@@ -14,7 +14,7 @@ export interface ToolContext {
 export interface CompressRangeEntry {
     startId: string
     endId: string
-    summary: string
+    summary?: string
 }
 
 export interface CompressRangeToolArgs {
@@ -25,7 +25,7 @@ export interface CompressRangeToolArgs {
 export interface CompressMessageEntry {
     messageId: string
     topic: string
-    summary: string
+    summary?: string
 }
 
 export interface CompressMessageToolArgs {