feat(anthropic-auto-compact): Add tool output truncation recovery layer for token limit handling (#63)

- Add storage.ts: Functions to find and truncate largest tool results
- Add TruncateState and TRUNCATE_CONFIG for truncation tracking
- Implement truncate-first recovery: truncate largest output -> retry (10x) -> compact (2x) -> revert (3x)
- Move session error handling to immediate recovery instead of session.idle wait
- Add compactionInProgress tracking to prevent concurrent execution

This fixes GitHub issue #63: "prompt is too long" errors now trigger immediate recovery by truncating the largest tool outputs first before attempting compaction.

🤖 Generated with assistance of OhMyOpenCode (https://github.com/code-yeongyu/oh-my-opencode)

src/hooks/anthropic-auto-compact/executor.ts

@@ -1,5 +1,6 @@
-import type { AutoCompactState, FallbackState, RetryState } from "./types"
+import type { AutoCompactState, FallbackState, RetryState, TruncateState } from "./types"
-import { FALLBACK_CONFIG, RETRY_CONFIG } from "./types"
+import { FALLBACK_CONFIG, RETRY_CONFIG, TRUNCATE_CONFIG } from "./types"
+import { findLargestToolResult, truncateToolResult } from "./storage"
 
 type Client = {
   session: {
@@ -23,16 +24,6 @@ type Client = {
   }
 }
 
-function calculateRetryDelay(attempt: number): number {
-  const delay = RETRY_CONFIG.initialDelayMs * Math.pow(RETRY_CONFIG.backoffFactor, attempt - 1)
-  return Math.min(delay, RETRY_CONFIG.maxDelayMs)
-}
-
-function shouldRetry(retryState: RetryState | undefined): boolean {
-  if (!retryState) return true
-  return retryState.attempt < RETRY_CONFIG.maxAttempts
-}
-
 function getOrCreateRetryState(
   autoCompactState: AutoCompactState,
   sessionID: string
@@ -57,6 +48,18 @@ function getOrCreateFallbackState(
   return state
 }
 
+function getOrCreateTruncateState(
+  autoCompactState: AutoCompactState,
+  sessionID: string
+): TruncateState {
+  let state = autoCompactState.truncateStateBySession.get(sessionID)
+  if (!state) {
+    state = { truncateAttempt: 0 }
+    autoCompactState.truncateStateBySession.set(sessionID, state)
+  }
+  return state
+}
+
 async function getLastMessagePair(
   sessionID: string,
   client: Client,
@@ -104,61 +107,10 @@ async function getLastMessagePair(
   }
 }
 
-async function executeRevertFallback(
+function formatBytes(bytes: number): string {
-  sessionID: string,
+  if (bytes < 1024) return `${bytes}B`
-  autoCompactState: AutoCompactState,
+  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)}KB`
-  client: Client,
+  return `${(bytes / (1024 * 1024)).toFixed(1)}MB`
-  directory: string
-): Promise<boolean> {
-  const fallbackState = getOrCreateFallbackState(autoCompactState, sessionID)
-
-  if (fallbackState.revertAttempt >= FALLBACK_CONFIG.maxRevertAttempts) {
-    return false
-  }
-
-  const pair = await getLastMessagePair(sessionID, client, directory)
-  if (!pair) {
-    return false
-  }
-
-  await client.tui
-    .showToast({
-      body: {
-        title: "⚠️ Emergency Recovery",
-        message: `Context too large. Removing last message pair to recover session...`,
-        variant: "warning",
-        duration: 4000,
-      },
-    })
-    .catch(() => {})
-
-  try {
-    if (pair.assistantMessageID) {
-      await client.session.revert({
-        path: { id: sessionID },
-        body: { messageID: pair.assistantMessageID },
-        query: { directory },
-      })
-    }
-
-    await client.session.revert({
-      path: { id: sessionID },
-      body: { messageID: pair.userMessageID },
-      query: { directory },
-    })
-
-    fallbackState.revertAttempt++
-    fallbackState.lastRevertedMessageID = pair.userMessageID
-
-    const retryState = autoCompactState.retryStateBySession.get(sessionID)
-    if (retryState) {
-      retryState.attempt = 0
-    }
-
-    return true
-  } catch {
-    return false
-  }
 }
 
 export async function getLastAssistant(
@@ -194,6 +146,8 @@ function clearSessionState(autoCompactState: AutoCompactState, sessionID: string
   autoCompactState.errorDataBySession.delete(sessionID)
   autoCompactState.retryStateBySession.delete(sessionID)
   autoCompactState.fallbackStateBySession.delete(sessionID)
+  autoCompactState.truncateStateBySession.delete(sessionID)
+  autoCompactState.compactionInProgress.delete(sessionID)
 }
 
 export async function executeCompact(
@@ -204,91 +158,154 @@ export async function executeCompact(
   client: any,
   directory: string
 ): Promise<void> {
-  const retryState = getOrCreateRetryState(autoCompactState, sessionID)
+  if (autoCompactState.compactionInProgress.has(sessionID)) {
+    return
+  }
+  autoCompactState.compactionInProgress.add(sessionID)
 
-  if (!shouldRetry(retryState)) {
+  const truncateState = getOrCreateTruncateState(autoCompactState, sessionID)
-    const fallbackState = getOrCreateFallbackState(autoCompactState, sessionID)
 
-    if (fallbackState.revertAttempt < FALLBACK_CONFIG.maxRevertAttempts) {
+  if (truncateState.truncateAttempt < TRUNCATE_CONFIG.maxTruncateAttempts) {
-      const reverted = await executeRevertFallback(
+    const largest = findLargestToolResult(sessionID)
-        sessionID,
+
-        autoCompactState,
+    if (largest && largest.outputSize >= TRUNCATE_CONFIG.minOutputSizeToTruncate) {
-        client as Client,
+      const result = truncateToolResult(largest.partPath)
-        directory
+
-      )
+      if (result.success) {
+        truncateState.truncateAttempt++
+        truncateState.lastTruncatedPartId = largest.partId
 
-      if (reverted) {
         await (client as Client).tui
           .showToast({
             body: {
-              title: "Recovery Attempt",
+              title: "Truncating Large Output",
-              message: "Message removed. Retrying compaction...",
+              message: `Truncated ${result.toolName} (${formatBytes(result.originalSize ?? 0)}). Retrying...`,
-              variant: "info",
+              variant: "warning",
               duration: 3000,
             },
           })
           .catch(() => {})
 
-        setTimeout(() => {
+        autoCompactState.compactionInProgress.delete(sessionID)
-          executeCompact(sessionID, msg, autoCompactState, client, directory)
+
-        }, 1000)
+        setTimeout(async () => {
+          try {
+            await (client as Client).tui.submitPrompt({ query: { directory } })
+          } catch {}
+        }, 500)
         return
       }
     }
-
-    clearSessionState(autoCompactState, sessionID)
-
-    await (client as Client).tui
-      .showToast({
-        body: {
-          title: "Auto Compact Failed",
-          message: `Failed after ${RETRY_CONFIG.maxAttempts} retries and ${FALLBACK_CONFIG.maxRevertAttempts} message removals. Please start a new session.`,
-          variant: "error",
-          duration: 5000,
-        },
-      })
-      .catch(() => {})
-    return
   }
 
-  retryState.attempt++
+  const retryState = getOrCreateRetryState(autoCompactState, sessionID)
-  retryState.lastAttemptTime = Date.now()
+
+  if (retryState.attempt < RETRY_CONFIG.maxAttempts) {
+    retryState.attempt++
+    retryState.lastAttemptTime = Date.now()
 
-  try {
     const providerID = msg.providerID as string | undefined
     const modelID = msg.modelID as string | undefined
 
     if (providerID && modelID) {
-      await (client as Client).session.summarize({
+      try {
-        path: { id: sessionID },
+        await (client as Client).tui
-        body: { providerID, modelID },
+          .showToast({
-        query: { directory },
+            body: {
-      })
+              title: "Auto Compact",
+              message: `Summarizing session (attempt ${retryState.attempt}/${RETRY_CONFIG.maxAttempts})...`,
+              variant: "warning",
+              duration: 3000,
+            },
+          })
+          .catch(() => {})
 
-      clearSessionState(autoCompactState, sessionID)
+        await (client as Client).session.summarize({
+          path: { id: sessionID },
+          body: { providerID, modelID },
+          query: { directory },
+        })
 
-      setTimeout(async () => {
+        clearSessionState(autoCompactState, sessionID)
-        try {
+
-          await (client as Client).tui.submitPrompt({ query: { directory } })
+        setTimeout(async () => {
-        } catch {}
+          try {
-      }, 500)
+            await (client as Client).tui.submitPrompt({ query: { directory } })
+          } catch {}
+        }, 500)
+        return
+      } catch {
+        autoCompactState.compactionInProgress.delete(sessionID)
+
+        const delay = RETRY_CONFIG.initialDelayMs * Math.pow(RETRY_CONFIG.backoffFactor, retryState.attempt - 1)
+        const cappedDelay = Math.min(delay, RETRY_CONFIG.maxDelayMs)
+
+        setTimeout(() => {
+          executeCompact(sessionID, msg, autoCompactState, client, directory)
+        }, cappedDelay)
+        return
+      }
     }
-  } catch {
-    const delay = calculateRetryDelay(retryState.attempt)
-
-    await (client as Client).tui
-      .showToast({
-        body: {
-          title: "Auto Compact Retry",
-          message: `Attempt ${retryState.attempt}/${RETRY_CONFIG.maxAttempts} failed. Retrying in ${Math.round(delay / 1000)}s...`,
-          variant: "warning",
-          duration: delay,
-        },
-      })
-      .catch(() => {})
-
-    setTimeout(() => {
-      executeCompact(sessionID, msg, autoCompactState, client, directory)
-    }, delay)
   }
+
+  const fallbackState = getOrCreateFallbackState(autoCompactState, sessionID)
+
+  if (fallbackState.revertAttempt < FALLBACK_CONFIG.maxRevertAttempts) {
+    const pair = await getLastMessagePair(sessionID, client as Client, directory)
+
+    if (pair) {
+      try {
+        await (client as Client).tui
+          .showToast({
+            body: {
+              title: "Emergency Recovery",
+              message: "Removing last message pair...",
+              variant: "warning",
+              duration: 3000,
+            },
+          })
+          .catch(() => {})
+
+        if (pair.assistantMessageID) {
+          await (client as Client).session.revert({
+            path: { id: sessionID },
+            body: { messageID: pair.assistantMessageID },
+            query: { directory },
+          })
+        }
+
+        await (client as Client).session.revert({
+          path: { id: sessionID },
+          body: { messageID: pair.userMessageID },
+          query: { directory },
+        })
+
+        fallbackState.revertAttempt++
+        fallbackState.lastRevertedMessageID = pair.userMessageID
+
+        retryState.attempt = 0
+        truncateState.truncateAttempt = 0
+
+        autoCompactState.compactionInProgress.delete(sessionID)
+
+        setTimeout(() => {
+          executeCompact(sessionID, msg, autoCompactState, client, directory)
+        }, 1000)
+        return
+      } catch {}
+    }
+  }
+
+  clearSessionState(autoCompactState, sessionID)
+
+  await (client as Client).tui
+    .showToast({
+      body: {
+        title: "Auto Compact Failed",
+        message: "All recovery attempts failed. Please start a new session.",
+        variant: "error",
+        duration: 5000,
+      },
+    })
+    .catch(() => {})
 }

src/hooks/anthropic-auto-compact/index.ts

@@ -9,6 +9,8 @@ function createAutoCompactState(): AutoCompactState {
     errorDataBySession: new Map<string, ParsedTokenLimitError>(),
     retryStateBySession: new Map(),
     fallbackStateBySession: new Map(),
+    truncateStateBySession: new Map(),
+    compactionInProgress: new Set<string>(),
   }
 }
 
@@ -25,6 +27,8 @@ export function createAnthropicAutoCompactHook(ctx: PluginInput) {
         autoCompactState.errorDataBySession.delete(sessionInfo.id)
         autoCompactState.retryStateBySession.delete(sessionInfo.id)
         autoCompactState.fallbackStateBySession.delete(sessionInfo.id)
+        autoCompactState.truncateStateBySession.delete(sessionInfo.id)
+        autoCompactState.compactionInProgress.delete(sessionInfo.id)
       }
       return
     }
@@ -37,6 +41,37 @@ export function createAnthropicAutoCompactHook(ctx: PluginInput) {
       if (parsed) {
         autoCompactState.pendingCompact.add(sessionID)
         autoCompactState.errorDataBySession.set(sessionID, parsed)
+
+        if (autoCompactState.compactionInProgress.has(sessionID)) {
+          return
+        }
+
+        const lastAssistant = await getLastAssistant(sessionID, ctx.client, ctx.directory)
+        const providerID = parsed.providerID ?? (lastAssistant?.providerID as string | undefined)
+        const modelID = parsed.modelID ?? (lastAssistant?.modelID as string | undefined)
+
+        if (providerID && modelID) {
+          await ctx.client.tui
+            .showToast({
+              body: {
+                title: "Context Limit Hit",
+                message: "Truncating large tool outputs and recovering...",
+                variant: "warning" as const,
+                duration: 3000,
+              },
+            })
+            .catch(() => {})
+
+          setTimeout(() => {
+            executeCompact(
+              sessionID,
+              { providerID, modelID },
+              autoCompactState,
+              ctx.client,
+              ctx.directory
+            )
+          }, 300)
+        }
       }
       return
     }
@@ -122,6 +157,6 @@ export function createAnthropicAutoCompactHook(ctx: PluginInput) {
   }
 }
 
-export type { AutoCompactState, FallbackState, ParsedTokenLimitError } from "./types"
+export type { AutoCompactState, FallbackState, ParsedTokenLimitError, TruncateState } from "./types"
 export { parseAnthropicTokenLimitError } from "./parser"
 export { executeCompact, getLastAssistant } from "./executor"

src/hooks/anthropic-auto-compact/storage.ts

@@ -0,0 +1,163 @@
+import { existsSync, readdirSync, readFileSync, writeFileSync } from "node:fs"
+import { join } from "node:path"
+import { xdgData } from "xdg-basedir"
+
+const OPENCODE_STORAGE = join(xdgData ?? "", "opencode", "storage")
+const MESSAGE_STORAGE = join(OPENCODE_STORAGE, "message")
+const PART_STORAGE = join(OPENCODE_STORAGE, "part")
+
+const TRUNCATION_MESSAGE =
+  "[TOOL RESULT TRUNCATED - Context limit exceeded. Original output was too large and has been truncated to recover the session. Please re-run this tool if you need the full output.]"
+
+interface StoredToolPart {
+  id: string
+  sessionID: string
+  messageID: string
+  type: "tool"
+  callID: string
+  tool: string
+  state: {
+    status: "pending" | "running" | "completed" | "error"
+    input: Record<string, unknown>
+    output?: string
+    error?: string
+  }
+  truncated?: boolean
+  originalSize?: number
+}
+
+export interface ToolResultInfo {
+  partPath: string
+  partId: string
+  messageID: string
+  toolName: string
+  outputSize: number
+}
+
+function getMessageDir(sessionID: string): string {
+  if (!existsSync(MESSAGE_STORAGE)) return ""
+
+  const directPath = join(MESSAGE_STORAGE, sessionID)
+  if (existsSync(directPath)) {
+    return directPath
+  }
+
+  for (const dir of readdirSync(MESSAGE_STORAGE)) {
+    const sessionPath = join(MESSAGE_STORAGE, dir, sessionID)
+    if (existsSync(sessionPath)) {
+      return sessionPath
+    }
+  }
+
+  return ""
+}
+
+function getMessageIds(sessionID: string): string[] {
+  const messageDir = getMessageDir(sessionID)
+  if (!messageDir || !existsSync(messageDir)) return []
+
+  const messageIds: string[] = []
+  for (const file of readdirSync(messageDir)) {
+    if (!file.endsWith(".json")) continue
+    const messageId = file.replace(".json", "")
+    messageIds.push(messageId)
+  }
+
+  return messageIds
+}
+
+export function findToolResultsBySize(sessionID: string): ToolResultInfo[] {
+  const messageIds = getMessageIds(sessionID)
+  const results: ToolResultInfo[] = []
+
+  for (const messageID of messageIds) {
+    const partDir = join(PART_STORAGE, messageID)
+    if (!existsSync(partDir)) continue
+
+    for (const file of readdirSync(partDir)) {
+      if (!file.endsWith(".json")) continue
+      try {
+        const partPath = join(partDir, file)
+        const content = readFileSync(partPath, "utf-8")
+        const part = JSON.parse(content) as StoredToolPart
+
+        if (part.type === "tool" && part.state?.output && !part.truncated) {
+          results.push({
+            partPath,
+            partId: part.id,
+            messageID,
+            toolName: part.tool,
+            outputSize: part.state.output.length,
+          })
+        }
+      } catch {
+        continue
+      }
+    }
+  }
+
+  return results.sort((a, b) => b.outputSize - a.outputSize)
+}
+
+export function findLargestToolResult(sessionID: string): ToolResultInfo | null {
+  const results = findToolResultsBySize(sessionID)
+  return results.length > 0 ? results[0] : null
+}
+
+export function truncateToolResult(partPath: string): {
+  success: boolean
+  toolName?: string
+  originalSize?: number
+} {
+  try {
+    const content = readFileSync(partPath, "utf-8")
+    const part = JSON.parse(content) as StoredToolPart
+
+    if (!part.state?.output) {
+      return { success: false }
+    }
+
+    const originalSize = part.state.output.length
+    const toolName = part.tool
+
+    part.truncated = true
+    part.originalSize = originalSize
+    part.state.output = TRUNCATION_MESSAGE
+
+    writeFileSync(partPath, JSON.stringify(part, null, 2))
+
+    return { success: true, toolName, originalSize }
+  } catch {
+    return { success: false }
+  }
+}
+
+export function getTotalToolOutputSize(sessionID: string): number {
+  const results = findToolResultsBySize(sessionID)
+  return results.reduce((sum, r) => sum + r.outputSize, 0)
+}
+
+export function countTruncatedResults(sessionID: string): number {
+  const messageIds = getMessageIds(sessionID)
+  let count = 0
+
+  for (const messageID of messageIds) {
+    const partDir = join(PART_STORAGE, messageID)
+    if (!existsSync(partDir)) continue
+
+    for (const file of readdirSync(partDir)) {
+      if (!file.endsWith(".json")) continue
+      try {
+        const content = readFileSync(join(partDir, file), "utf-8")
+        const part = JSON.parse(content)
+        if (part.truncated === true) {
+          count++
+        }
+      } catch {
+        continue
+      }
+    }
+  }
+
+  return count
+}

src/hooks/anthropic-auto-compact/types.ts

@@ -17,11 +17,18 @@ export interface FallbackState {
   lastRevertedMessageID?: string
 }
 
+export interface TruncateState {
+  truncateAttempt: number
+  lastTruncatedPartId?: string
+}
+
 export interface AutoCompactState {
   pendingCompact: Set<string>
   errorDataBySession: Map<string, ParsedTokenLimitError>
   retryStateBySession: Map<string, RetryState>
   fallbackStateBySession: Map<string, FallbackState>
+  truncateStateBySession: Map<string, TruncateState>
+  compactionInProgress: Set<string>
 }
 
 export const RETRY_CONFIG = {
@@ -35,3 +42,8 @@ export const FALLBACK_CONFIG = {
   maxRevertAttempts: 3,
   minMessagesRequired: 2,
 } as const
+
+export const TRUNCATE_CONFIG = {
+  maxTruncateAttempts: 10,
+  minOutputSizeToTruncate: 1000,
+} as const