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| 1 | +import { publisher } from './constants' |
| 2 | +import type { AgentDefinition, Message } from './types/agent-definition' |
| 3 | + |
| 4 | +const definition: AgentDefinition = { |
| 5 | + id: 'context-pruner', |
| 6 | + publisher, |
| 7 | + displayName: 'Context Pruner', |
| 8 | + model: 'openai/gpt-5-mini', |
| 9 | + |
| 10 | + toolNames: ['set_messages'], |
| 11 | + |
| 12 | + spawnerPrompt: `Spawn this agent between steps to prune context, starting with old tool results and then old messages.`, |
| 13 | + |
| 14 | + inputSchema: {}, |
| 15 | + |
| 16 | + includeMessageHistory: true, |
| 17 | + |
| 18 | + handleSteps: function* ({ agentState }) { |
| 19 | + const messages = agentState.messageHistory |
| 20 | + |
| 21 | + const countTokensJson = (obj: any): number => { |
| 22 | + // Very rough approximation |
| 23 | + return Math.ceil(JSON.stringify(obj).length / 3) |
| 24 | + } |
| 25 | + |
| 26 | + const maxMessageTokens = 200_000 |
| 27 | + const numTerminalCommandsToKeep = 5 |
| 28 | + |
| 29 | + // Remove the last assistant message if it contains the spawn call that invoked this context-pruner |
| 30 | + let currentMessages = [...messages] |
| 31 | + if (currentMessages.length > 0) { |
| 32 | + const lastMessage = currentMessages[currentMessages.length - 1] |
| 33 | + if ( |
| 34 | + lastMessage.role === 'assistant' && |
| 35 | + typeof lastMessage.content === 'string' |
| 36 | + ) { |
| 37 | + // Check if this message contains a spawn_agent_inline call for context-pruner |
| 38 | + if ( |
| 39 | + lastMessage.content.includes('spawn_agent_inline') && |
| 40 | + lastMessage.content.includes('context-pruner') |
| 41 | + ) { |
| 42 | + // Remove the entire message |
| 43 | + currentMessages.pop() |
| 44 | + } |
| 45 | + } |
| 46 | + } |
| 47 | + |
| 48 | + // Initial check - if already under limit, return (with inline agent tool call removed) |
| 49 | + const initialTokens = countTokensJson(currentMessages) |
| 50 | + if (initialTokens < maxMessageTokens) { |
| 51 | + yield { |
| 52 | + toolName: 'set_messages', |
| 53 | + input: { |
| 54 | + messages: currentMessages, |
| 55 | + }, |
| 56 | + } |
| 57 | + return |
| 58 | + } |
| 59 | + |
| 60 | + // PASS 1: Remove terminal command results (oldest first, preserve recent 5) |
| 61 | + let numKeptTerminalCommands = 0 |
| 62 | + const afterTerminalPass: Message[] = [] |
| 63 | + |
| 64 | + for (let i = currentMessages.length - 1; i >= 0; i--) { |
| 65 | + const message = currentMessages[i] |
| 66 | + let processedContent = |
| 67 | + typeof message.content === 'string' |
| 68 | + ? message.content |
| 69 | + : JSON.stringify(message.content) |
| 70 | + |
| 71 | + if (processedContent.includes('<tool>run_terminal_command</tool>')) { |
| 72 | + if (numKeptTerminalCommands < numTerminalCommandsToKeep) { |
| 73 | + numKeptTerminalCommands++ |
| 74 | + afterTerminalPass.unshift({ ...message, content: processedContent }) |
| 75 | + } else { |
| 76 | + // Simplify terminal command result |
| 77 | + processedContent = processedContent.replace( |
| 78 | + /<tool_result>\s*<tool>run_terminal_command<\/tool>\s*<result>[\s\S]*?<\/result>\s*<\/tool_result>/g, |
| 79 | + '<tool_result><tool>run_terminal_command</tool><result>[Output omitted]</result></tool_result>', |
| 80 | + ) |
| 81 | + afterTerminalPass.unshift({ ...message, content: processedContent }) |
| 82 | + } |
| 83 | + } else { |
| 84 | + afterTerminalPass.unshift({ ...message, content: processedContent }) |
| 85 | + } |
| 86 | + } |
| 87 | + |
| 88 | + // Check if terminal pass was enough |
| 89 | + const tokensAfterTerminal = countTokensJson(afterTerminalPass) |
| 90 | + if (tokensAfterTerminal < maxMessageTokens) { |
| 91 | + yield { |
| 92 | + toolName: 'set_messages', |
| 93 | + input: { |
| 94 | + messages: afterTerminalPass, |
| 95 | + }, |
| 96 | + } |
| 97 | + return |
| 98 | + } |
| 99 | + |
| 100 | + // PASS 2: Remove large tool results (any tool result > 1000 chars) |
| 101 | + const afterToolResultsPass: Message[] = afterTerminalPass.map((message) => { |
| 102 | + let processedContent = |
| 103 | + typeof message.content === 'string' |
| 104 | + ? message.content |
| 105 | + : JSON.stringify(message.content) |
| 106 | + |
| 107 | + if ( |
| 108 | + processedContent.includes('<tool_result>') && |
| 109 | + processedContent.length > 1000 |
| 110 | + ) { |
| 111 | + processedContent = processedContent.replace( |
| 112 | + /<result>[\s\S]*?<\/result>/g, |
| 113 | + '<result>[Large tool result omitted]</result>', |
| 114 | + ) |
| 115 | + } |
| 116 | + |
| 117 | + return { ...message, content: processedContent } |
| 118 | + }) |
| 119 | + |
| 120 | + // Check if tool results pass was enough |
| 121 | + const tokensAfterToolResults = countTokensJson(afterToolResultsPass) |
| 122 | + if (tokensAfterToolResults < maxMessageTokens) { |
| 123 | + yield { |
| 124 | + toolName: 'set_messages', |
| 125 | + input: { |
| 126 | + messages: afterToolResultsPass, |
| 127 | + }, |
| 128 | + } |
| 129 | + return |
| 130 | + } |
| 131 | + |
| 132 | + // PASS 3: Message-level pruning (like trimMessagesToFitTokenLimit) |
| 133 | + const shortenedMessageTokenFactor = 0.5 |
| 134 | + const replacementMessage: Message = { |
| 135 | + role: 'user', |
| 136 | + content: '<system>Previous message(s) omitted due to length</system>', |
| 137 | + } |
| 138 | + |
| 139 | + const requiredTokens = countTokensJson( |
| 140 | + afterToolResultsPass.filter((m: any) => m.keepDuringTruncation), |
| 141 | + ) |
| 142 | + let removedTokens = 0 |
| 143 | + const tokensToRemove = |
| 144 | + (maxMessageTokens - requiredTokens) * (1 - shortenedMessageTokenFactor) |
| 145 | + |
| 146 | + const placeholder = 'deleted' |
| 147 | + const filteredMessages: (Message | typeof placeholder)[] = [] |
| 148 | + |
| 149 | + for (const message of afterToolResultsPass) { |
| 150 | + if ( |
| 151 | + removedTokens >= tokensToRemove || |
| 152 | + (message as any).keepDuringTruncation |
| 153 | + ) { |
| 154 | + filteredMessages.push(message) |
| 155 | + continue |
| 156 | + } |
| 157 | + |
| 158 | + removedTokens += countTokensJson(message) |
| 159 | + if ( |
| 160 | + filteredMessages.length === 0 || |
| 161 | + filteredMessages[filteredMessages.length - 1] !== placeholder |
| 162 | + ) { |
| 163 | + filteredMessages.push(placeholder) |
| 164 | + removedTokens -= countTokensJson(replacementMessage) |
| 165 | + } |
| 166 | + } |
| 167 | + |
| 168 | + const finalMessages = filteredMessages.map((m) => |
| 169 | + m === placeholder ? replacementMessage : m, |
| 170 | + ) |
| 171 | + |
| 172 | + // Apply the final pruned message history |
| 173 | + yield { |
| 174 | + toolName: 'set_messages', |
| 175 | + input: { |
| 176 | + messages: finalMessages, |
| 177 | + }, |
| 178 | + } |
| 179 | + }, |
| 180 | +} |
| 181 | + |
| 182 | +export default definition |
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