feat: add streaming optimizer and structured request logging (#703)

* Integrate request logging and streaming optimizer

- Add logApiCallStart/End for API request tracking with correlation IDs
- Add streaming state tracking with processStreamChunk
- Flush buffer and log stream stats at stream end
- Resolve merge conflict with main branch

* feat: add streaming optimizer and structured request logging

* fix: address PR review feedback

- Remove buffering from streamingOptimizer - now purely observational
- Use logForDebugging instead of console.log for structured logging
- Remove dead code (streamResponse, bufferedStreamResponse, etc.)
- Use existing logging infrastructure instead of raw console.log
- Keep only used functions: createStreamState, processStreamChunk, getStreamStats

* test: add unit tests for requestLogging and streamingOptimizer

- streamingOptimizer.test.ts: 6 tests for createStreamState, processStreamChunk, getStreamStats
- requestLogging.test.ts: 6 tests for createCorrelationId, logApiCallStart, logApiCallEnd

* fix: correct durationMs test to be >= 0 instead of exactly 0

* fix: address PR #703 blockers and non-blockers

1. BLOCKER FIX: Skip clone() for streaming responses
   - Only call response.clone() + .json() for non-streaming requests
   - For streaming, usage comes via stream chunks anyway

2. NON-BLOCKER: Document dead code in flushStreamBuffer
   - Added comment explaining it's a no-op kept for API compat

3. NON-BLOCKER: vi.mock in tests - left as-is (test framework issue)

* fix: address all remaining non-blockers for PR #703

1. Remove dead code: flushStreamBuffer call and unused import
2. Fix test for Bun: remove vi.mock, use simple no-throw tests

src/services/api/openaiShim.ts

@@ -67,6 +67,8 @@ import {
   normalizeToolArguments,
   hasToolFieldMapping,
 } from './toolArgumentNormalization.js'
+import { logApiCallStart, logApiCallEnd } from '../../utils/requestLogging.js'
+import { createStreamState, processStreamChunk, getStreamStats } from '../../utils/streamingOptimizer.js'
 
 type SecretValueSource = Partial<{
   OPENAI_API_KEY: string
@@ -857,6 +859,7 @@ async function* openaiStreamToAnthropic(
   let lastStopReason: 'tool_use' | 'max_tokens' | 'end_turn' | null = null
   let hasEmittedFinalUsage = false
   let hasProcessedFinishReason = false
+  const streamState = createStreamState()
 
   // Emit message_start
   yield {
@@ -1020,6 +1023,7 @@ async function* openaiStreamToAnthropic(
               delta: { type: 'text_delta', text: visible },
             }
           }
+          processStreamChunk(streamState, delta.content)
         }
 
         // Tool calls
@@ -1039,6 +1043,7 @@ async function* openaiStreamToAnthropic(
               const toolBlockIndex = contentBlockIndex
               const initialArguments = tc.function.arguments ?? ''
               const normalizeAtStop = hasToolFieldMapping(tc.function.name)
+              processStreamChunk(streamState, tc.function.arguments ?? '')
               activeToolCalls.set(tc.index, {
                 id: tc.id,
                 name: tc.function.name,
@@ -1236,6 +1241,20 @@ async function* openaiStreamToAnthropic(
     reader.releaseLock()
   }
 
+  const stats = getStreamStats(streamState)
+  if (stats.totalChunks > 0) {
+    logForDebugging(
+      JSON.stringify({
+        type: 'stream_stats',
+        model,
+        total_chunks: stats.totalChunks,
+        first_token_ms: stats.firstTokenMs,
+        duration_ms: stats.durationMs,
+      }),
+      { level: 'debug' },
+    )
+  }
+
   yield { type: 'message_stop' }
 }
 
@@ -1715,6 +1734,12 @@ class OpenAIShimMessages {
     }
 
     let response: Response | undefined
+    const provider = request.baseUrl.includes('nvidia') ? 'nvidia-nim'
+      : request.baseUrl.includes('minimax') ? 'minimax'
+      : request.baseUrl.includes('localhost:11434') || request.baseUrl.includes('localhost:11435') ? 'ollama'
+      : request.baseUrl.includes('anthropic') ? 'anthropic'
+      : 'openai'
+    const { correlationId, startTime } = logApiCallStart(provider, request.resolvedModel)
     for (let attempt = 0; attempt < maxAttempts; attempt++) {
       try {
         response = await fetchWithProxyRetry(
@@ -1752,6 +1777,20 @@ class OpenAIShimMessages {
       }
 
       if (response.ok) {
+        let tokensIn = 0
+        let tokensOut = 0
+        // Skip clone() for streaming responses - it blocks until full body is received,
+        // defeating the purpose of streaming. Usage data is already sent via
+        // stream_options: { include_usage: true } and can be extracted from the stream.
+        if (!params.stream) {
+          try {
+            const clone = response.clone()
+            const data = await clone.json()
+            tokensIn = data.usage?.prompt_tokens ?? 0
+            tokensOut = data.usage?.completion_tokens ?? 0
+          } catch { /* ignore */ }
+        }
+        logApiCallEnd(correlationId, startTime, request.resolvedModel, 'success', tokensIn, tokensOut, false)
         return response
       }