diff --git a/packages/agent-core/src/agent/compaction/micro.ts b/packages/agent-core/src/agent/compaction/micro.ts
index da352db69..65a045a3d 100644
--- a/packages/agent-core/src/agent/compaction/micro.ts
+++ b/packages/agent-core/src/agent/compaction/micro.ts
@@ -2,7 +2,10 @@ import type { ContentPart } from '@moonshot-ai/kosong';
 
 import type { Agent } from '..';
 import type { ContextMessage } from '../context';
-import { estimateTokensForContentParts } from '../../utils/tokens';
+import {
+  estimateTokensForContentParts,
+  estimateTokensForMessages,
+} from '../../utils/tokens';
 
 export interface MicroCompactionConfig {
   keepRecentMessages: number;
@@ -65,9 +68,24 @@ export class MicroCompaction {
     this.apply(nextCutoff);
     if (previousCutoff !== nextCutoff) {
       const effect = this.measureEffect(history, nextCutoff);
-      this.agent.telemetry.track('micro_compaction_applied', {
+      const previousEffect = this.measureEffect(history, previousCutoff);
+      const rawContextTokens = estimateTokensForMessages(history);
+      // Whole-context length before/after this cutoff change, mirroring the
+      // `tokensBefore`/`tokensAfter` fields on `compaction_finished` so the
+      // two compaction paths can be compared on the same axis.
+      const tokensBefore =
+        rawContextTokens -
+        previousEffect.truncatedToolResultTokensBefore +
+        previousEffect.truncatedToolResultTokensAfter;
+      const tokensAfter =
+        rawContextTokens -
+        effect.truncatedToolResultTokensBefore +
+        effect.truncatedToolResultTokensAfter;
+      this.agent.telemetry.track('micro_compaction_finished', {
         ...config,
         ...effect,
+        tokensBefore,
+        tokensAfter,
         previous_cutoff: previousCutoff,
         cutoff: nextCutoff,
         message_count: history.length,
@@ -107,8 +125,8 @@ export class MicroCompaction {
   ) {
     let markerTokenCount: number | undefined;
     let truncatedToolResultCount = 0;
-    let beforeTokens = 0;
-    let afterTokens = 0;
+    let truncatedToolResultTokensBefore = 0;
+    let truncatedToolResultTokensAfter = 0;
     for (let i = 0; i < messages.length && i < cutoff; i++) {
       const message = messages[i];
       if (message?.role !== 'tool' || message.toolCallId === undefined) continue;
@@ -120,9 +138,13 @@ export class MicroCompaction {
         { type: 'text', text: this.config.truncatedMarker },
       ]);
       truncatedToolResultCount += 1;
-      beforeTokens += contentTokens;
-      afterTokens += markerTokenCount;
+      truncatedToolResultTokensBefore += contentTokens;
+      truncatedToolResultTokensAfter += markerTokenCount;
     }
-    return { truncatedToolResultCount, beforeTokens, afterTokens };
+    return {
+      truncatedToolResultCount,
+      truncatedToolResultTokensBefore,
+      truncatedToolResultTokensAfter,
+    };
   }
 }
diff --git a/packages/agent-core/test/agent/compaction/micro.test.ts b/packages/agent-core/test/agent/compaction/micro.test.ts
index bcdeb327e..34254d58c 100644
--- a/packages/agent-core/test/agent/compaction/micro.test.ts
+++ b/packages/agent-core/test/agent/compaction/micro.test.ts
@@ -469,7 +469,7 @@ describe('MicroCompaction', () => {
       'result three',
     ]);
 
-    const event = singleTelemetryEvent(records, 'micro_compaction_applied');
+    const event = singleTelemetryEvent(records, 'micro_compaction_finished');
     expect(event.properties).toMatchObject({
       ...microCompaction,
       truncatedMarker: DEFAULT_MARKER,
@@ -478,15 +478,64 @@ describe('MicroCompaction', () => {
       message_count: 9,
       cache_age_ms: 61 * MINUTE,
       truncatedToolResultCount: 2,
-      beforeTokens: expect.any(Number),
-      afterTokens: expect.any(Number),
+      truncatedToolResultTokensBefore: expect.any(Number),
+      truncatedToolResultTokensAfter: expect.any(Number),
+      tokensBefore: expect.any(Number),
+      tokensAfter: expect.any(Number),
     });
-    expect(numberProperty(event, 'beforeTokens')).toBeGreaterThan(
-      numberProperty(event, 'afterTokens'),
+    expect(numberProperty(event, 'truncatedToolResultTokensBefore')).toBeGreaterThan(
+      numberProperty(event, 'truncatedToolResultTokensAfter'),
+    );
+    expect(numberProperty(event, 'tokensBefore')).toBeGreaterThan(
+      numberProperty(event, 'tokensAfter'),
     );
 
     expect(ctx.agent.context.messages).toHaveLength(9);
-    expect(records.filter((record) => record.event === 'micro_compaction_applied')).toHaveLength(1);
+    expect(records.filter((record) => record.event === 'micro_compaction_finished')).toHaveLength(1);
+  });
+
+  it('reports context token deltas from the previously compacted projection', () => {
+    vi.useFakeTimers();
+    const records: TelemetryRecord[] = [];
+    const microCompaction = {
+      keepRecentMessages: 2,
+      minContentTokens: 1,
+      cacheMissedThresholdMs: 60 * MINUTE,
+      minContextUsageRatio: 0,
+    };
+    const ctx = testAgent({
+      telemetry: recordingTelemetry(records),
+      microCompaction,
+    });
+
+    vi.setSystemTime(0);
+    appendMicroToolExchange(ctx, 1, { output: 'result one '.repeat(20) });
+    appendMicroToolExchange(ctx, 2, { output: 'result two '.repeat(20) });
+
+    vi.setSystemTime(61 * MINUTE);
+    ctx.agent.microCompaction.detect();
+    expect(toolTexts(ctx.agent.context.messages)).toEqual([
+      DEFAULT_MARKER,
+      'result two '.repeat(20),
+    ]);
+
+    vi.setSystemTime(62 * MINUTE);
+    appendMicroToolExchange(ctx, 3, { output: 'result three' });
+    const expectedContextTokensBefore = estimateTokensForMessages(ctx.agent.context.messages);
+
+    vi.setSystemTime(123 * MINUTE);
+    ctx.agent.microCompaction.detect();
+
+    const events = records.filter((record) => record.event === 'micro_compaction_finished');
+    expect(events).toHaveLength(2);
+    const secondEvent = events[1]!;
+    expect(secondEvent.properties).toMatchObject({
+      previous_cutoff: 4,
+      cutoff: 7,
+      truncatedToolResultCount: 2,
+      tokensBefore: expectedContextTokensBefore,
+      tokensAfter: estimateTokensForMessages(ctx.agent.context.messages),
+    });
   });
 
   it('leaves context unchanged when the micro_compaction flag is disabled', () => {