fix compression context usage accounting (#924)

tests/server/run-chat-usage.test.ts

@@ -1,6 +1,10 @@
-import { describe, expect, it } from 'vitest'
+import { describe, expect, it, vi } from 'vitest'
 import { countTokens } from '../../packages/server/src/lib/context-compressor'
-import { estimateUsageTokensFromMessages } from '../../packages/server/src/services/hermes/run-chat/usage'
+import {
+  contextTokensWithCachedOverhead,
+  estimateUsageTokensFromMessages,
+  updateMessageContextTokenUsage,
+} from '../../packages/server/src/services/hermes/run-chat/usage'
 
 describe('run-chat usage token estimates', () => {
   it('counts message content instead of serialized message payloads', () => {
@@ -30,4 +34,58 @@ describe('run-chat usage token estimates', () => {
     expect(usage.inputTokens).toBe(0)
     expect(usage.outputTokens).toBe(countTokens('calling tool') + countTokens(String(messages[0].tool_calls || '')))
   })
+
+  it('adds cached bridge fixed context when updating full context usage', () => {
+    const emit = vi.fn()
+    const state = {
+      messages: [],
+      isWorking: false,
+      events: [],
+      queue: [],
+      bridgeContext: { fixedContextTokens: 20_000 },
+    } as any
+
+    const contextTokens = updateMessageContextTokenUsage(
+      'session-1',
+      state,
+      emit,
+      1_569,
+      { inputTokens: 1_200, outputTokens: 369 },
+    )
+
+    expect(contextTokens).toBe(21_569)
+    expect(state.contextTokens).toBe(21_569)
+    expect(emit).toHaveBeenCalledWith('usage.updated', expect.objectContaining({
+      session_id: 'session-1',
+      inputTokens: 1_200,
+      outputTokens: 369,
+      contextTokens: 21_569,
+    }))
+  })
+
+  it('falls back to message tokens when bridge fixed context is missing', () => {
+    const emit = vi.fn()
+    const state = {
+      messages: [],
+      isWorking: false,
+      events: [],
+      queue: [],
+    } as any
+
+    expect(contextTokensWithCachedOverhead(state, 1_569)).toBe(1_569)
+
+    const contextTokens = updateMessageContextTokenUsage(
+      'session-1',
+      state,
+      emit,
+      1_569,
+      { inputTokens: 1_200, outputTokens: 369 },
+    )
+
+    expect(contextTokens).toBe(1_569)
+    expect(state.contextTokens).toBe(1_569)
+    expect(emit).toHaveBeenCalledWith('usage.updated', expect.objectContaining({
+      contextTokens: 1_569,
+    }))
+  })
 })