# Session Log — 2026-02-19

**Project**: PS_AI_Agent (Unreal Engine 5.5)
**Machine**: Desktop PC (j_foucher)
**Working directory**: `E:\ASTERION\GIT\PS_AI_Agent`

---

## Conversation Summary

### 1. Initial Request
User asked to create a plugin to use the ElevenLabs Conversational AI Agent in UE5.5.
Reference: existing Convai plugin (gRPC-based, more complex). Goal: simpler version using ElevenLabs.
Plugin name requested: `PS_AI_Agent_ElevenLabs`.

### 2. Codebase Exploration
Explored the Convai plugin source at `ConvAI/Convai/` to understand:
- Module/settings structure
- AudioCapture patterns
- HTTP proxy pattern
- gRPC streaming architecture (to know what to replace with WebSocket)
- Convai already had `EVoiceType::ElevenLabsVoices` — confirming the direction

### 3. Plugin Created
All source files written from scratch under:
`Unreal/PS_AI_Agent/Plugins/PS_AI_Agent_ElevenLabs/`

Files created:
- `PS_AI_Agent_ElevenLabs.uplugin`
- `PS_AI_Agent_ElevenLabs.Build.cs`
- `Public/PS_AI_Agent_ElevenLabs.h` — Module + `UElevenLabsSettings`
- `Public/ElevenLabsDefinitions.h` — Enums, structs, protocol constants
- `Public/ElevenLabsWebSocketProxy.h` + `.cpp` — WS session manager
- `Public/ElevenLabsConversationalAgentComponent.h` + `.cpp` — Main NPC component
- `Public/ElevenLabsMicrophoneCaptureComponent.h` + `.cpp` — Mic capture
- `PS_AI_Agent.uproject` — Plugin registered

Commit: `f0055e8`

### 4. Memory Files Created
To allow context recovery on any machine (including laptop):
- `.claude/MEMORY.md` — project structure + patterns (auto-loaded by Claude Code)
- `.claude/elevenlabs_plugin.md` — plugin file map + API protocol details
- `.claude/project_context.md` — original ask, intent, short/long-term goals
- Local copy also at `C:\Users\j_foucher\.claude\projects\...\memory\`

Commit: `f0055e8` (with plugin), updated in `4d6ae10`

### 5. .gitignore Updated
Added to existing ignores:
- `Unreal/PS_AI_Agent/Plugins/*/Binaries/`
- `Unreal/PS_AI_Agent/Plugins/*/Intermediate/`
- `Unreal/PS_AI_Agent/*.sln` / `*.suo`
- `.claude/settings.local.json`
- `generate_pptx.py`

Commit: `4d6ae10`, `b114ab0`

### 6. Compile — First Attempt (Errors Found)
Ran `Build.bat PS_AI_AgentEditor Win64 Development`. Errors:
- `WebSockets` listed in `.uplugin` — it's a module not a plugin → removed
- `OpenDefaultCaptureStream` doesn't exist in UE 5.5 → use `OpenAudioCaptureStream`
- `FOnAudioCaptureFunction` callback uses `const void*` not `const float*` → fixed cast
- `TArray::RemoveAt(0, N, false)` deprecated → use `EAllowShrinking::No`
- `AudioCapture` is a plugin and must be in `.uplugin` Plugins array → added

Commit: `bb1a857`

### 7. Compile — Success
Clean build, no warnings, no errors.
Output: `Plugins/PS_AI_Agent_ElevenLabs/Binaries/Win64/UnrealEditor-PS_AI_Agent_ElevenLabs.dll`

Memory updated with confirmed UE 5.5 API patterns. Commit: `3b98edc`

### 8. Documentation — Markdown
Full reference doc written to `.claude/PS_AI_Agent_ElevenLabs_Documentation.md`:
- Installation, Project Settings, Quick Start (BP + C++), Components Reference,
  Data Types, Turn Modes, Security/Signed URL, Audio Pipeline, Common Patterns, Troubleshooting.

Commit: `c833ccd`

### 9. Documentation — PowerPoint
20-slide dark-themed PowerPoint generated via Python (python-pptx 1.0.2):
- File: `PS_AI_Agent_ElevenLabs_Documentation.pptx` in repo root
- Covers all sections with visual layout, code blocks, flow diagrams, colour-coded elements
- Generator script `generate_pptx.py` excluded from git via .gitignore

Commit: `1b72026`

---

## Session 2 — 2026-02-19 (continued context)

### 10. API vs Implementation Cross-Check (3 bugs found and fixed)
Cross-referenced `elevenlabs_api_reference.md` against plugin source. Found 3 protocol bugs:

**Bug 1 — Transcript fields wrong:**
- Type: `"transcript"` → `"user_transcript"`
- Event key: `"transcript_event"` → `"user_transcription_event"`
- Field: `"message"` → `"user_transcript"`

**Bug 2 — Pong format wrong:**
- `event_id` was nested in `pong_event{}` → must be top-level

**Bug 3 — Client turn mode messages don't exist:**
- `"user_turn_start"` / `"user_turn_end"` are not valid API types
- Replaced: start → `"user_activity"`, end → no-op (server detects silence)

Commit: `ae2c9b9`

### 11. SendTextMessage Added
User asked for text input to agent for testing (without mic).
Added `SendTextMessage(FString)` to `UElevenLabsWebSocketProxy` and `UElevenLabsConversationalAgentComponent`.
Sends `{"type":"user_message","text":"..."}` — agent replies with audio + text.

Commit: `b489d11`

### 12. Binary WebSocket Frame Fix
User reported: `"Received unexpected binary WebSocket frame"` warnings.
Root cause: ElevenLabs sends **ALL WebSocket frames as binary**, never text.
`OnMessage` (text handler) never fires. `OnRawMessage` must handle everything.

Fix: Implemented `OnWsBinaryMessage` with fragment reassembly (`BinaryFrameBuffer`).

Commit: `669c503`

### 13. JSON vs PCM Discrimination Fix
After binary fix: `"Failed to parse WebSocket message as JSON"` errors.
Root cause: Binary frames contain BOTH JSON control messages AND raw PCM audio.

Fix: Peek at byte[0] of assembled buffer:
- `'{'` (0x7B) → UTF-8 JSON → route to `OnWsMessage()`
- anything else → raw PCM audio → broadcast to `OnAudioReceived`

Commit: `4834567`

### 14. Documentation Updated to v1.1.0
Full rewrite of `.claude/PS_AI_Agent_ElevenLabs_Documentation.md`:
- Added Changelog section (v1.0.0 / v1.1.0)
- Updated audio pipeline (binary PCM path, not Base64 JSON)
- Added `SendTextMessage` to all function tables and examples
- Corrected turn mode docs, transcript docs, `OnAgentConnected` timing
- New troubleshooting entries

Commit: `e464cfe`

### 15. Test Blueprint Asset Updated
`test_AI_Actor.uasset` updated in UE Editor.

Commit: `99017f4`

---

## Git History (this session)

| Hash | Message |
|------|---------|
| `f0055e8` | Add PS_AI_Agent_ElevenLabs plugin (initial implementation) |
| `4d6ae10` | Update .gitignore: exclude plugin build artifacts and local Claude settings |
| `b114ab0` | Broaden .gitignore: use glob for all plugin Binaries/Intermediate |
| `bb1a857` | Fix compile errors in PS_AI_Agent_ElevenLabs plugin |
| `3b98edc` | Update memory: document confirmed UE 5.5 API patterns and plugin compile status |
| `c833ccd` | Add plugin documentation for PS_AI_Agent_ElevenLabs |
| `1b72026` | Add PowerPoint documentation and update .gitignore |
| `bbeb429` | ElevenLabs API reference doc |
| `dbd6161` | TestMap, test actor, DefaultEngine.ini, memory update |
| `ae2c9b9` | Fix 3 WebSocket protocol bugs |
| `b489d11` | Add SendTextMessage |
| `669c503` | Fix binary WebSocket frames |
| `4834567` | Fix JSON vs binary frame discrimination |
| `e464cfe` | Update documentation to v1.1.0 |
| `99017f4` | Update test_AI_Actor blueprint asset |

---

## Key Technical Decisions Made This Session

| Decision | Reason |
|----------|--------|
| WebSocket instead of gRPC | ElevenLabs Conversational AI uses WS/JSON; no ThirdParty libs needed |
| `AudioCapture` in `.uplugin` Plugins array | It's an engine plugin, not a module — UBT requires it declared |
| `WebSockets` in Build.cs only | It's a module (no `.uplugin` file), declaring it in `.uplugin` causes build error |
| `FOnAudioCaptureFunction` uses `const void*` | UE 5.3+ API change — must cast to `float*` inside callback |
| `EAllowShrinking::No` | Bool overload of `RemoveAt` deprecated in UE 5.5 |
| `USoundWaveProcedural` for playback | Allows pushing raw PCM bytes at runtime without file I/O |
| Silence threshold = 30 ticks | ~0.5s at 60fps heuristic to detect agent finished speaking |
| Binary frame handling | ElevenLabs sends ALL WS frames as binary; peek byte[0] to discriminate JSON vs PCM |
| `user_activity` for client turn | `user_turn_start`/`user_turn_end` don't exist in ElevenLabs API |

---

---

## Session 3 — 2026-02-19 (bug fixes from live testing)

### 16. Three Runtime Bugs Fixed (v1.2.0)

User reported after live testing:
1. **AI speaks twice** — every audio response played double
2. **Cannot speak** — mic capture didn't reach ElevenLabs
3. **Latency** — requested `enable_intermediate_response: true`

**Bug 1 Root Cause — Double Audio:**
UE's libwebsockets backend fires **both** `OnMessage()` (text callback) **and** `OnRawMessage()` (binary callback) for the same incoming frame.
We had bound both `WebSocket->OnMessage()` and `WebSocket->OnRawMessage()` in `Connect()`.
Result: every audio frame was decoded and enqueued twice → played twice.

Fix: **Remove `OnMessage` binding entirely.** `OnRawMessage` now handles all frames (JSON control messages peeked via first byte, raw PCM otherwise).

**Bug 2 Root Cause — Mic Silent:**
ElevenLabs requires a `conversation_initiation_client_data` message sent **immediately** after the WebSocket handshake completes. Without it, the server never enters a state where it will accept and process client audio chunks. This is a required session negotiation step, not optional.

Fix: Send `conversation_initiation_client_data` in `OnWsConnected()` before any other message.

**Bug 2 Secondary — Delegate Stacking:**
`StartListening()` called `Mic->OnAudioCaptured.AddUObject(this, ...)` without first removing existing bindings. If called more than once (e.g. after reconnect), delegates stack up and audio is sent multiple times per frame.

Fix: Add `Mic->OnAudioCaptured.RemoveAll(this)` before `AddUObject` in `StartListening()`.

**Bug 3 — Latency:**
Added `"enable_intermediate_response": true` inside `custom_llm_extra_body` of the `conversation_initiation_client_data` message. Also added `optimize_streaming_latency: 3` in `conversation_config_override.tts`.

**Files changed:**
- `ElevenLabsWebSocketProxy.cpp`:
  - `Connect()`: removed `OnMessage` binding
  - `OnWsConnected()`: now sends full `conversation_initiation_client_data` JSON
- `ElevenLabsConversationalAgentComponent.cpp`:
  - `StartListening()`: added `RemoveAll` guard before delegate binding

---

---

## Session 4 — 2026-02-19 (mic still silent — push-to-talk deeper investigation)

### 17. Two More Bugs Found and Fixed (v1.3.0)

User confirmed Bug 1 (double audio) was fixed. Bug 2 (cannot speak) persisted.

**Analysis of log:**
- Blueprint is correct: T Pressed → StartListening, T Released → StopListening (proper push-to-talk)
- Mic opens and closes correctly — audio capture IS happening
- Server never responds to mic input → audio reaching ElevenLabs but being ignored

**Bug A — TurnMode mismatch in conversation_initiation_client_data:**
`OnWsConnected()` hardcoded `"mode": "server_vad"` in the init message regardless of the
component's `TurnMode` setting. User's Blueprint uses Client turn mode (push-to-talk),
so the server was configured for server_vad while the client sent client_vad audio signals.

Fix: Read `TurnMode` field on the proxy (set from the component before `Connect()`).
Translate `EElevenLabsTurnMode::Client` → `"client_vad"`, Server → `"server_vad"`.

**Bug B — user_activity never sent continuously:**
In client VAD mode, ElevenLabs requires `user_activity` to be sent **continuously**
alongside every audio chunk to keep the server's VAD aware the user is speaking.
`SendUserTurnStart()` sent it once on key press, but never again during speech.
Server-side, without continuous `user_activity`, the server treated the audio as noise.

Fix: In `SendAudioChunk()`, automatically send `user_activity` before each audio chunk
when `TurnMode == Client`. This keeps the signal continuous for the full duration of speech.
When the user releases T, `StopListening()` stops the mic → audio stops → `user_activity`
stops → server detects silence and triggers the agent response.

**Bug C — TurnMode not propagated to proxy:**
`UElevenLabsConversationalAgentComponent` never told the proxy what TurnMode to use.
Added `WebSocketProxy->TurnMode = TurnMode` before `Connect()` in `StartConversation()`.

**Files changed:**
- `ElevenLabsWebSocketProxy.h`: added `public TurnMode` field
- `ElevenLabsWebSocketProxy.cpp`:
  - `OnWsConnected()`: use `TurnMode` to set correct mode string in init message
  - `SendAudioChunk()`: auto-send `user_activity` before each chunk in Client mode
- `ElevenLabsConversationalAgentComponent.cpp`:
  - `StartConversation()`: set `WebSocketProxy->TurnMode = TurnMode` before `Connect()`

---

---

## Session 5 — 2026-02-19 (still can't speak — bAutoStartListening conflict)

### 18. Root Cause Found and Fixed (v1.4.0)

Log analysis revealed the true root cause:

**Exact sequence:**
```
OnConnected → bAutoStartListening=true → StartListening() → bIsListening=true, mic opens
OnAgentStoppedSpeaking → Blueprint calls StartListening() → bIsListening guard → no-op (already open)
User presses T → StartListening() → bIsListening guard → no-op
User releases T → StopListening() → bIsListening=false, mic CLOSES
User presses T → StartListening() → NOW opens mic (was closed)
User releases T → StopListening() → mic closes — but ElevenLabs never got audio
```

**Root cause:** `bAutoStartListening = true` opens the mic on connect and sets `bIsListening = true`.
In Client/push-to-talk mode, every T-press hits the `bIsListening` guard and does nothing.
Every T-release closes the auto-started mic. The mic was never open during actual speech.

**Fix:** `HandleConnected()` now only calls `StartListening()` when `TurnMode == Server`.
In Client mode, `bAutoStartListening` is ignored — the user controls listening via T key.

**File changed:**
- `ElevenLabsConversationalAgentComponent.cpp`:
  - `HandleConnected()`: guard `bAutoStartListening` with `TurnMode == Server` check

---

---

## Session 6 — 2026-02-19 (audio chunk size fix)

### 19. Mic Audio Chunk Accumulation (v1.5.0)

**Root cause (from diagnostic log in Session 5):**
Log showed hundreds of `SendAudioChunk: 158 bytes (TurnMode=Client)` lines with zero server responses.
- 158 bytes = 79 samples = ~5ms of audio at 16kHz 16-bit mono
- WASAPI (Windows Audio Session API) fires the `FAudioCapture` callback at its internal buffer period (~5ms)
- ElevenLabs requires a minimum chunk size for its VAD and STT to operate (~100ms / 3200 bytes)
- Tiny 5ms fragments arrived at the server but were silently ignored → agent never responded

**Fix applied:**
Added `MicAccumulationBuffer TArray<uint8>` to `UElevenLabsConversationalAgentComponent`.
`OnMicrophoneDataCaptured()` appends each callback's converted bytes and only calls `SendAudioChunk`
when `>= MicChunkMinBytes` (3200 bytes = 100ms) have accumulated.

`StopListening()` flushes any remaining bytes in the buffer before sending `SendUserTurnEnd()`,
so the last partial chunk of speech is never dropped.

`HandleDisconnected()` clears the buffer to prevent stale data on reconnect.

**Files changed:**
- `ElevenLabsConversationalAgentComponent.h`: added `MicAccumulationBuffer` + `MicChunkMinBytes = 3200`
- `ElevenLabsConversationalAgentComponent.cpp`:
  - `OnMicrophoneDataCaptured()`: accumulate → send when threshold reached
  - `StopListening()`: flush remainder before end-of-turn signal
  - `HandleDisconnected()`: clear accumulation buffer

Commit: `91cf5b1`

---

## Next Steps (not done yet)

- [ ] Test v1.5.0 in Editor — verify push-to-talk mic works end-to-end (should be the final fix)
- [ ] Test `USoundWaveProcedural` underflow behaviour in practice (check for audio glitches)
- [ ] Test `SendTextMessage` end-to-end in Blueprint
- [ ] Add lip-sync support (future)
- [ ] Add session memory / conversation history (future, matching Convai)
- [ ] Add environment/action context support (future)
- [ ] Consider Signed URL Mode backend implementation