Feature/agent compaction by Pradeesh333 · Pull Request #68 · xynehq/jaf

Pradeesh333 · 2026-04-22T14:49:12Z

deterministic compaction when tokens exceeds 180_000 by trimming old tool pairs

codecov-commenter · 2026-04-22T14:58:35Z

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Codecov Report

❌ Patch coverage is 23.25581% with 66 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/core/compaction.ts	22.66%	57 Missing and 1 partial ⚠️
src/core/engine.ts	27.27%	8 Missing ⚠️

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Copilot

Pull request overview

Adds deterministic, token-threshold-based message compaction to prevent oversized runs by trimming older tool-call/tool-result pairs once the message history exceeds ~180k estimated tokens.

Changes:

Introduces src/core/compaction.ts with token estimation and tool-group trimming logic plus a trace event helper.
Hooks compaction into runInternal in src/core/engine.ts and emits a memory_operation trace event for compaction.
Extends TraceEvent['memory_operation'] to support operation: 'compact' and optional metadata.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 5 comments.

File	Description
src/core/types.ts	Extends trace event typing for compaction metadata.
src/core/engine.ts	Triggers compaction before agent execution and emits a compaction trace event.
src/core/compaction.ts	Implements token estimation + deterministic trimming of tool interaction groups.
package-lock.json	Updates lockfile dependency set (includes `cfb`).

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Copilot · 2026-04-22T15:01:58Z

+    safeConsole.log(`[JAF:ENGINE] Compaction complete: removed ${result.removedCount} messages, reduced from ${result.originalTokens} to ${result.compactedTokens} tokens`);
+
+    // Emit compaction event
+    config.onEvent?.(createCompactionEvent(result, state.runId as string, state.traceId as string));


shouldCompact can be true even when there are no removable tool groups (e.g., long user/assistant text history), in which case compactState returns removedCount === 0 and token counts don’t change. The current logs and createCompactionEvent emission still claim compaction completed; consider guarding the “complete” log + event behind result.removedCount > 0, and emitting a distinct “compaction skipped/no-op” message if nothing could be removed.

Suggested change

safeConsole.log(`[JAF:ENGINE] Compaction complete: removed ${result.removedCount} messages, reduced from ${result.originalTokens} to ${result.compactedTokens} tokens`);

// Emit compaction event

config.onEvent?.(createCompactionEvent(result, state.runId as string, state.traceId as string));

if (result.removedCount > 0) {

safeConsole.log(`[JAF:ENGINE] Compaction complete: removed ${result.removedCount} messages, reduced from ${result.originalTokens} to ${result.compactedTokens} tokens`);

// Emit compaction event

config.onEvent?.(createCompactionEvent(result, state.runId as string, state.traceId as string));

} else {

safeConsole.log(`[JAF:ENGINE] Compaction skipped: no removable messages found; token count remains ${result.originalTokens}`);

}

Copilot · 2026-04-22T15:01:59Z

@@ -0,0 +1,243 @@
+import { Message, RunState, TraceEvent, getTextContent } from './types.js';


getTextContent is imported but never used in this module. This will fail lint/typecheck in repos that enforce no-unused-vars; remove the import or use it as part of token estimation.

Suggested change

import { Message, RunState, TraceEvent, getTextContent } from './types.js';

import { Message, RunState, TraceEvent } from './types.js';

This is relevant

Copilot · 2026-04-22T15:01:59Z

+      // Calculate tokens for the entire group
+      let groupTokens = 0;
+      const groupIndices: number[] = [];
+
+      for (let j = i; j < messages.length; j++) {
+        if (toolGroups.get(j) === groupId) {
+          groupTokens += estimateMessageTokens(messages[j]);
+          groupIndices.push(j);
+        }
+      }


trimToolMessages computes each tool-group’s token total by scanning from the current index to the end of the message list. In the compaction-triggered scenario (very large histories) this becomes O(n²) and can add significant latency. Consider precomputing a map of groupId -> {indices, tokens} in a single pass and then trimming groups from the front using that precomputed structure.

Copilot · 2026-04-22T15:02:00Z

+  traceId: string
+): TraceEvent {
+  return {
+    type: 'memory_operation',
+    data: {
+      operation: 'compact',
+      conversationId: runId,


createCompactionEvent sets conversationId to runId, but elsewhere the engine/memory integration treats conversationId as config.conversationId (the persisted conversation key). Using runId here makes this event ambiguous and can break consumers correlating memory operations by conversation. Consider passing the actual conversation id (e.g., config.conversationId when available) and, if absent, falling back to runId explicitly so semantics are clear.

Suggested change

traceId: string

): TraceEvent {

return {

type: 'memory_operation',

data: {

operation: 'compact',

conversationId: runId,

traceId: string,

conversationId?: string

): TraceEvent {

return {

type: 'memory_operation',

data: {

operation: 'compact',

conversationId: conversationId ?? runId,

Copilot · 2026-04-22T15:02:00Z

+  // Token-based compaction: check and trim if messages exceed limit
+  let compactionState = state;
+  if (shouldCompact(state.messages, defaultCompactionConfig)) {
+    const currentTokens = estimateTotalTokens(state.messages);
+    safeConsole.log(`[JAF:ENGINE] Compaction triggered: ${currentTokens} tokens exceed ${defaultCompactionConfig.maxTokenLimit} limit`);
+
+    const { state: compactedState, result } = compactState(state, defaultCompactionConfig);
+    compactionState = compactedState;
+
+    safeConsole.log(`[JAF:ENGINE] Compaction complete: removed ${result.removedCount} messages, reduced from ${result.originalTokens} to ${result.compactedTokens} tokens`);
+
+    // Emit compaction event
+    config.onEvent?.(createCompactionEvent(result, state.runId as string, state.traceId as string));
+  }
+
+  const currentAgent = config.agentRegistry.get(compactionState.currentAgentName);
  if (!currentAgent) {


Compaction updates are computed into compactionState, but the function continues to use the original state for subsequent processing (events, messageCount, and presumably the LLM prompt later). As a result, the compaction has no effect on token usage and the emitted agent_processing event still reports the pre-compaction message list. Consider reassigning state to the compacted state (or consistently use compactionState for all downstream reads) so the trimmed message history is actually used.

nishant49-code · 2026-04-22T15:38:12Z


+  // Token-based compaction: check and trim if messages exceed limit
+  let compactionState = state;
+  if (shouldCompact(state.messages, defaultCompactionConfig)) {


We are always checking here whether to compact or not based on default hardcoded config , but ideally we should provide the developer consuming this framework to pass the values for this configuration, whether to enable of disable compaction and what limits to set , and the hardcoded values can be used as fallback

Pradeesh S added 2 commits April 22, 2026 20:08

feat: added token level compaction in agent loop

dc4d454

fix: pair wise removal

2675a80

nishant49-code requested a review from Copilot April 22, 2026 14:57

Copilot started reviewing on behalf of nishant49-code April 22, 2026 14:57 View session

Copilot AI reviewed Apr 22, 2026

View reviewed changes

fix: comments resolved

5374553

nishant49-code reviewed Apr 22, 2026

View reviewed changes

feat: added compaction config

4577291

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Feature/agent compaction#68

Feature/agent compaction#68
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		@@ -0,0 +1,243 @@
		import { Message, RunState, TraceEvent, getTextContent } from './types.js';

	import { Message, RunState, TraceEvent, getTextContent } from './types.js';
	import { Message, RunState, TraceEvent } from './types.js';

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