SESSION_ISOLATION_FIXES.md

Session Isolation Fixes - Summary

🔍 Issue Investigation

You reported potential "bleed through" between transcription sessions where operations might access the wrong transcript file.

✅ Good News: Architecture is Sound!

Core Design:

• Each TranscriptionSession binds to ONE specific transcript file
• TranscriptManager stores this.outfile and ONLY reads/writes to that file
• By default, unique timestamped filenames prevent collisions
• No possibility of cross-contamination between concurrent sessions

🐛 Issues Found & Fixed

Issue #1: Stopped Sessions Remained Accessible ❌→✅

Problem:

case "stop_transcription": {
  await session.stop();
  // ❌ session variable still points to stopped session
  return { success: true };
}

Impact:

• After stopping, get_transcript, get_status, clear_transcript would access OLD session data
• User might see transcript from a previous stopped session
• Confusing behavior - stopped session should be cleared

Fix Applied:

case "stop_transcription": {
  const statusBefore = session.getStatus();
  const transcriptPath = session.getTranscriptPath();
  await session.stop();
  
  // ✅ Clear session reference
  session = null;
  
  return { 
    success: true,
    note: "Transcript file remains on disk. Use cleanup_transcript to delete it."
  };
}

Issue #2: Operations Didn't Check If Session Was Running ❌→✅

Problem:

case "get_transcript": {
  if (!session) return error;
  // ❌ Doesn't check if session.isRunning === true
  return session.getTranscript();
}

Impact:

• Could access data from stopped (but not cleared) sessions
• Resource transcript://current would show old data

Fix Applied:

case "get_transcript": {
  if (!session) {
    return error("No active transcription session");
  }
  
  // ✅ Check if actually running
  if (!session.getStatus().isRunning) {
    return error("Session is not running. Use start_transcription to begin.");
  }
  
  return session.getTranscript();
}

Issue #3: Resource Read Didn't Validate Session State ❌→✅

Problem:

if (uri === "transcript://current") {
  if (!session) return error;
  // ❌ Doesn't check isRunning
  const content = readFile(session.getTranscriptPath());
}

Fix Applied:

if (uri === "transcript://current") {
  if (!session) {
    return "No active transcription session";
  }
  
  // ✅ Check if actually running
  if (!session.getStatus().isRunning) {
    return "Session is not running. Use start_transcription to begin.";
  }
  
  const content = readFile(session.getTranscriptPath());
}

📊 Changes Summary

Files Modified:

1. src/mcp-server.ts - Added session state validation throughout

Operations Fixed:

• ✅ stop_transcription - Now clears session reference
• ✅ get_status - Validates session is running
• ✅ get_transcript - Validates session is running
• ✅ clear_transcript - Validates session is running
• ✅ transcript://current resource - Validates session is running

User-Facing Changes:

• Better error messages: "Use start_transcription to begin a new session"
• stop_transcription now includes note about transcript file remaining on disk
• All operations return transcript file path for clarity

🧪 Test Results

Test Suites: 13 passed, 13 total
Tests:       160 passed, 160 total

Existing Tests Validated:

• ✅ Session isolation tests (8 tests)
• ✅ All 160 tests pass with fixes applied

🎯 Session Lifecycle Now Works Correctly

Scenario 1: Normal Session

1. start_transcription → Creates session with unique file
2. get_transcript → ✅ Returns current session's transcript
3. stop_transcription → ✅ Stops AND clears session = null
4. get_transcript → ✅ Error: "No active transcription session"
5. start_transcription → ✅ Creates NEW session with NEW file
6. get_transcript → ✅ Returns NEW session's transcript

Scenario 2: Session Cleanup

1. start_transcription → Session A with transcript_A.md
2. stop_transcription → Clears session, file remains on disk
3. cleanup_transcript → Error: "No active session"
4. start_transcription → Session B with transcript_B.md
5. cleanup_transcript → ✅ Deletes transcript_B.md only

Scenario 3: Multiple Sessions (Sequential)

1. start_transcription → Session 1, transcript_2025-10-04_10-00-00.md
2. get_transcript → ✅ Shows Session 1 data
3. stop_transcription → ✅ Clears session reference
4. start_transcription → Session 2, transcript_2025-10-04_10-05-00.md
5. get_transcript → ✅ Shows Session 2 data (NOT Session 1!)

🔒 Guarantees After Fix

1. No Cross-Contamination: Each session ONLY accesses its own transcript file
2. Clean Separation: Stopped sessions cannot be accessed
3. Clear State: After stop, all operations require new start
4. Unique Files: Each session gets timestamped filename by default
5. Explicit Cleanup: User must explicitly call cleanup_transcript to delete files

💡 Best Practices for Users

1. Stop vs Cleanup:

   • stop_transcription - Ends session, keeps file
   • cleanup_transcript - Deletes file permanently

2. Starting New Sessions:

   • Always get new unique filename (auto-generated)
   • Or specify custom filename if needed

3. Accessing Transcripts:

   • Only works during active (running) session
   • After stop, file remains but needs manual access

🚀 Impact

Before Fix:

• ❌ Confusing behavior after stop
• ❌ Could accidentally access old session data
• ❌ Unclear session state

After Fix:

• ✅ Crystal clear session lifecycle
• ✅ Impossible to access stopped session
• ✅ Better error messages guide user
• ✅ Each session fully isolated