2026-07-15 20:42:25 -05:00
19 changed files with 640 additions and 181 deletions
@@ -11,36 +11,39 @@ on-device acceleration (**NPU → GPU → CPU**), labels speakers, structures th
 Markdown notes, and optionally augments them with a locally hosted LLM (Ollama). Audio and
 transcripts **never leave the machine** unless you explicitly configure a destination.

-> **Status: working application (v0.5.2).** Capture (system audio **+ your microphone**, with a
-> live **dual level meter**), transcription (CPU / Intel NPU / Vulkan GPU) with a **fluid live
-> transcript**, speaker diarization, storage + crash recovery, local-LLM summaries, AI tags,
+> **Status: working application (v0.7.3).** Capture (system audio **+ your microphone**, with a
+> live **dual level meter** and an **M-key mic mute**), transcription (CPU / Intel NPU / Vulkan
+> GPU) with a **fluid live transcript**, speaker diarization that labels **You** live from your
+> own mic channel, storage + crash recovery, local-LLM summaries, AI tags, **AI-enhanced notes**,
 > opt-in recording with **in-app playback**, at-rest encryption, self-hosted sync, **Outlook
-> `.pst`/calendar import with optional auto-record**, **importing an existing recording from a
-> file or URL**, and a loopback **MCP server** for coding-agent handoff are all implemented and
-> ship as a single signed **MSI + NSIS** universal installer. Build order and remaining tasks
-> are in [`docs/05-roadmap.md`](docs/05-roadmap.md).
+> `.pst`/calendar import with optional auto-record**, **background import of an existing
+> recording from a file or URL** (with a step-by-step progress tracker), **close-to-tray**, and a
+> loopback **MCP server** for coding-agent handoff are all implemented and ship as a single
+> **MSI + NSIS** universal installer. On Intel Core Ultra machines, transcription runs with the
+> **CPU near-idle**: Whisper's encoder on the **NPU**, its decoder on the **iGPU**. Build order
+> and remaining tasks are in [`docs/05-roadmap.md`](docs/05-roadmap.md).

 ## Why WhispAssist — Granola vs Meetily vs WhispAssist

-| | **Granola** | **Meetily** | **WhispAssist** |
-|---|---|---|---|
-| **Positioning** | Cloud AI notepad | Open-source self-hosted assistant | Local, Windows-native assistant |
-| **Platform** | macOS, Windows | macOS, Windows, Linux | Windows 10/11 |
-| **Bot-free system-audio capture** | ✅ | ✅ | ✅ WASAPI loopback |
-| **Transcription** | ☁️ cloud | ✅ local (Whisper) | ✅ local (whisper.cpp) |
-| **NPU / GPU auto-acceleration** | n/a (cloud) | ⚠️ CPU/GPU, manual | ✅ **NPU→NVIDIA→AMD→Intel→CPU** ladder, one binary |
-| **Speaker diarization** | ✅ cloud | ⚠️ limited | ✅ offline (sherpa-onnx) |
-| **Summaries / notes AI** | ☁️ cloud LLM | ✅ local (Ollama) / BYO | ✅ local (Ollama, localhost **or LAN**) + optional hosted |
-| **Interface localization (UI language)** | ⚠️ English-only UI (multilingual transcription) | ⚠️ English-only UI (more planned) | ✅ **20 languages** + RTL (Arabic/Urdu) |
-| **Default data egress** | ☁️ audio + notes to cloud | 🔒 local (cloud optional) | 🔒 **none** — everything off by default, allowlist-enforced |
-| **Calendar / Outlook `.pst` context** | ✅ cloud calendar | ❌ | ✅ local `.pst` import + **auto-record on events** |
-| **Import an existing recording (file/URL)** | ❌ live capture only | ❌ | ✅ any file or URL (ffmpeg + yt-dlp) |
-| **Opt-in recording + consent notice** | ⚠️ partial | ❌ | ✅ off by default, one-time consent |
-| **At-rest encryption** | ☁️ server-side | ❌ | ✅ vault: Argon2id + XChaCha20-Poly1305 |
-| **Self-hosted sync w/ client-side encryption** | ❌ | ⚠️ | ✅ WebDAV + OAuth, **encrypt-before-upload** |
-| **Coding-agent (MCP) server** | ✅ **cloud** MCP (notes via their servers) | ❌ | ✅ **local, loopback-only**, token-gated, adds no egress |
-| **License** | Proprietary | Open source (MIT) | Open source (MIT / Apache-2.0) |
-| **Cost** | Subscription | Free | Free |
+|                                                | **Granola**                                     | **Meetily**                       | **WhispAssist**                                             |
+| ---------------------------------------------- | ----------------------------------------------- | --------------------------------- | ----------------------------------------------------------- |
+| **Positioning**                                | Cloud AI notepad                                | Open-source self-hosted assistant | Local, Windows-native assistant                             |
+| **Platform**                                   | macOS, Windows                                  | macOS, Windows, Linux             | Windows 10/11                                               |
+| **Bot-free system-audio capture**              | ✅                                              | ✅                                | ✅ WASAPI loopback                                          |
+| **Transcription**                              | ☁️ cloud                                        | ✅ local (Whisper)                | ✅ local (whisper.cpp)                                      |
+| **NPU / GPU auto-acceleration**                | n/a (cloud)                                     | ⚠️ CPU/GPU, manual                | ✅ **NPU→NVIDIA→AMD→Intel→CPU** ladder, one binary          |
+| **Speaker diarization**                        | ✅ cloud                                        | ⚠️ limited                        | ✅ offline (sherpa-onnx)                                    |
+| **Summaries / notes AI**                       | ☁️ cloud LLM                                    | ✅ local (Ollama) / BYO           | ✅ local (Ollama, localhost **or LAN**) + optional hosted   |
+| **Interface localization (UI language)**       | ⚠️ English-only UI (multilingual transcription) | ⚠️ English-only UI (more planned) | ✅ **20 languages** + RTL (Arabic/Urdu)                     |
+| **Default data egress**                        | ☁️ audio + notes to cloud                       | 🔒 local (cloud optional)         | 🔒 **none** — everything off by default, allowlist-enforced |
+| **Calendar / Outlook `.pst` context**          | ✅ cloud calendar                               | ❌                                | ✅ local `.pst` import + **auto-record on events**          |
+| **Import an existing recording (file/URL)**    | ❌ live capture only                            | ❌                                | ✅ any file or URL (ffmpeg + yt-dlp)                        |
+| **Opt-in recording + consent notice**          | ⚠️ partial                                      | ❌                                | ✅ off by default, one-time consent                         |
+| **At-rest encryption**                         | ☁️ server-side                                  | ❌                                | ✅ vault: Argon2id + XChaCha20-Poly1305                     |
+| **Self-hosted sync w/ client-side encryption** | ❌                                              | ⚠️                                | ✅ WebDAV + OAuth, **encrypt-before-upload**                |
+| **Coding-agent (MCP) server**                  | ✅ **cloud** MCP (notes via their servers)      | ❌                                | ✅ **local, loopback-only**, token-gated, adds no egress    |
+| **License**                                    | Proprietary                                     | Open source (MIT)                 | Open source (MIT / Apache-2.0)                              |
+| **Cost**                                       | Subscription                                    | Free                              | Free                                                        |

 <sub>Comparison reflects each project's public positioning as of mid-2026. Granola now ships an
 MCP server too, but it is **cloud-hosted** — an agent reaching it pulls your notes through
@@ -56,29 +59,36 @@ accelerated, zero-egress-by-default** option: it exploits the NPU/GPU in modern
 everything on the device unless you opt in, and adds Windows-specific context (Outlook) and a
 coding-agent handoff.

-## What's built (v0.5.2)
+## What's built (v0.7.3)

- **Bot-free capture — now both sides, with a live dual meter** — WASAPI loopback records the
-  system mix (all participants), and an optional **microphone** path captures your own voice,
-  mixed into both the live transcript and the saved recording. While recording, a **level meter
-  overlays the system and microphone signals in two colours** so you can see both sides are being
-  picked up. Pick a specific output/input or turn the mic off in **Settings ▸ Hardware**. No
+- **Bot-free capture — now both sides, with a live dual meter and mic mute** — WASAPI loopback
+  records the system mix (all participants), and an optional **microphone** path captures your
+  own voice, mixed into both the live transcript and the saved recording. While recording, a
+  **level meter overlays the system and microphone signals in two colours** so you can see both
+  sides are being picked up, and the **M key (or the mic button) mutes/unmutes your mic
+  mid-meeting**. Pick a specific output/input or turn the mic off in **Settings ▸ Hardware**. No
  meeting bot, no per-app plumbing.
 - **Local transcription with a hardware ladder — and a fluid live transcript** — whisper.cpp via
  `whisper-rs` on CPU; the **Intel NPU** via ONNX Runtime + OpenVINO; **GPU via Vulkan** (a single
  binary that runs on NVIDIA, AMD, and Intel). WA detects the hardware, picks the best backend
-  (**NPU → NVIDIA → AMD → Intel → CPU**), and shows it in the UI. The **live transcript streams a
-  growing line that refreshes ~once a second and commits at natural pauses** — words appear as
-  they're spoken instead of in fixed multi-second blocks, so sentences aren't chopped across
-  lines.
- **Speaker diarization** — `sherpa-onnx` (pyannote segmentation + speaker-embedding clustering),
-  fully offline. Install the two diarization models in **Settings ▸ Hardware** and finished
-  recordings are split by speaker (Speaker 1, Speaker 2, …); the microphone speaker is
-  auto-labelled from a short voiceprint.
- **Import an existing recording** — add a meeting from a **local audio/video file or a URL**
-  (YouTube, a streaming page, or a direct media link). WhispAssist transcribes and diarizes it
-  just like a live recording. Uses **`ffmpeg`** (and **`yt-dlp`** for URLs), which you install
-  yourself — neither is bundled.
+  (**NPU → NVIDIA → AMD → Intel → CPU**), and shows it in the UI. On NPU machines the engine
+  **splits Whisper across accelerators — encoder on the NPU, KV-cache decoder on the Intel iGPU —
+  so transcription leaves the CPU near-idle**. The **live transcript streams a growing line that
+  refreshes ~once a second and commits at natural pauses** — words appear as they're spoken
+  instead of in fixed multi-second blocks, so sentences aren't chopped across lines.
+- **Speaker diarization that knows who _you_ are** — `sherpa-onnx` (pyannote segmentation +
+  speaker-embedding clustering), fully offline. Install the two diarization models in
+  **Settings ▸ Hardware** and recordings are split by speaker (You, Speaker 2, …). With the mic
+  enabled, your voice is recorded on its **own channel**, so your lines are labelled **You** live
+  — from the first pass, not just after the meeting — and attributed by per-channel voice
+  activity rather than clustering guesswork. Renaming a speaker updates the transcript **and the
+  generated notes**.
+- **Import an existing recording — in the background, with a progress tracker** — add a meeting
+  from a **local audio/video file or a URL** (YouTube, a streaming page, or a direct media link);
+  it transcribes quietly in the background behind a four-step tracker (_Transcode → Transcribe →
+  Identify speakers → Finalize_) while you keep working. Uses **`ffmpeg`** (and **`yt-dlp`** for
+  URLs), which you install yourself — neither is bundled, and one-click download buttons are in
+  the Import dialog.
 - **Notes & summaries** — Markdown notes; local-LLM summaries via **Ollama** on `localhost`
  **or a private LAN endpoint** (RFC-1918), with a full advanced-parameter panel (system prompt,
  `think`, `keep_alive`, `num_ctx`, sampling/repetition/mirostat, etc.).
@@ -90,8 +100,10 @@ coding-agent handoff.
  recordings are decrypted **in memory on the fly** (nothing plaintext is written to disk).
  Recordings are 16-bit for roughly half the size, and an accidental recording can be **cancelled**
  (audio + transcript deleted).
- **Notes, summaries & AI tags** — Markdown notes with an **Editor/Preview** toggle; local-LLM
-  summaries and one-click **tag generation** with a chip-based tag editor and tag filtering.
+- **Notes, summaries & AI tags** — Markdown notes with an **Editor/Preview** toggle, a formatting
+  toolbar, and **slash commands** (`/todo`, `/h1`, `/quote`, …); **AI-enhance** turns rough notes
+  into clean structured Markdown via your local LLM (with one-step Undo); local-LLM summaries and
+  one-click **tag generation** with a chip-based tag editor and tag filtering.
 - **At-rest encryption vault** — Argon2id key derivation + XChaCha20-Poly1305; transcripts,
  notes, summaries, and recordings sealed on disk; startup unlock gate; keys zeroized on lock.
 - **Self-hosted sync (optional, off by default)** — WebDAV (Nextcloud, ownCloud, Cloudreve,
@@ -103,7 +115,11 @@ coding-agent handoff.
 - **Outlook `.pst` / calendar context, with auto-record** — import events and attendees from a
  local Outlook `.pst` backup (read-only, range-limited, de-duplicated, with cleanup), attach
  meetings to events, and — opt-in — **auto-start recording when a calendar event begins** while
-  the app is open (a one-shot timer, no background polling).
+  the app is open (a one-shot timer, no background polling). The import shells out to `readpst`
+  (libpst) — **Settings ▸ Calendar** has a one-click download button for it.
+- **Close to tray** — closing the window keeps WhispAssist running in the background; reopen it
+  from the tray icon, quit fully from the tray menu. On by default, toggleable in
+  **Settings ▸ Recording**.
 - **Local MCP server for coding-agent handoff** — hand meeting context to your own coding agents
  (Claude, Codex, Copilot, OpenCode) over a **loopback-only, token-gated** MCP server that is off
  by default, scope-limited, audited, and **adds no egress** — data leaves only via the agent's
@@ -116,9 +132,10 @@ coding-agent handoff.
  Sinhala (සිංහල), Spanish — Spain & Mexico (Español), Swedish (Svenska), Tamil (தமிழ்), and
  Urdu (اردو). Selecting Arabic or Urdu flips the interface to **right-to-left**; any untranslated
  string falls back to English rather than showing a raw key. Adding a language is a one-file job.
- **One universal installer** — a single signed MSI and NSIS `-setup.exe` that covers every
-  machine: Vulkan for all GPUs, the Intel NPU path (+ DirectML fallback), and CPU. The Vulkan
-  loader is bundled so it launches even on machines without a GPU driver.
+- **One universal installer** — a single MSI and NSIS `-setup.exe` that covers every machine:
+  Vulkan for all GPUs, the Intel NPU path (+ DirectML fallback), and CPU. The Vulkan loader is
+  bundled so it launches even on machines without a GPU driver. Every release ships **SHA-256
+  checksums** in its release notes.

 **In progress:** Microsoft Graph calendar (cloud calendar via OAuth) and an optional CUDA
 (NVIDIA-only) build variant.
@@ -132,7 +149,9 @@ during setup).
 1. Download the latest **`WhispAssist_<version>_x64_en-US.msi`** from the
   [releases page](https://git.dou.bet/iamdoubz/WhispAssist/releases).
 2. Double-click the `.msi` and follow the prompts, accepting the UAC prompt to install. The
-   installer is signed; if Windows SmartScreen appears, choose **More info → Run anyway**.
+   installers are currently unsigned, so if Windows SmartScreen appears, choose
+   **More info → Run anyway** (verify the download against the SHA-256 checksums in the release
+   notes first).
 3. Launch **WhispAssist** from the Start menu.

 On first run WA detects your hardware and picks the best transcription backend
@@ -150,11 +169,13 @@ for silent install, custom install location, and presetting defaults with a `wa-

 ## Optional dependencies

-If you do not have these installed, WhispAssist will still work, but some features will be unavailable.
+If you do not have these installed, WhispAssist will still work, but some features will be
+unavailable. The app links to each one where it's needed: `ffmpeg`/`yt-dlp` in the Import dialog,
+`libpst` in **Settings ▸ Calendar**.

- [yt-dlp](https://github.com/yt-dlp/yt-dlp/releases)
- [ffmpeg](https://www.ffmpeg.org/download.html#build-windows)
- [libpst](https://sourceforge.net/projects/ezwinports/files/libpst-0.6.63-w32-bin.zip/)
+- [yt-dlp](https://github.com/yt-dlp/yt-dlp/releases) — importing from URLs
+- [ffmpeg](https://www.ffmpeg.org/download.html#build-windows) — importing files/URLs
+- [libpst](https://sourceforge.net/projects/ezwinports/files/libpst-0.6.63-w32-bin.zip/) — Outlook `.pst` calendar import

 ## Technology

@@ -0,0 +1,94 @@
+# WhispAssist v0.7.3
+
+**Privacy-first, Windows-native meeting assistant — everything on-device, nothing leaves unless you say so.**
+
+A performance release: on Intel Core Ultra machines, transcription now leaves the **CPU nearly
+idle**. The Whisper encoder keeps running on the **NPU**; the decoder — previously the dominant
+CPU cost — now decodes with a **KV cache** and runs on the **Intel iGPU**. Nothing here changes
+the privacy posture: the one new download is the upgraded transcription model, fetched from the
+same source as before.
+
+One universal installer (**MSI** and **NSIS**) covers every machine: **Vulkan** for all GPUs
+(NVIDIA/AMD/Intel), the Intel **NPU** (OpenVINO), a **DirectML** fallback, and **CPU**.
+
+---
+
+## ⚡ Faster, cooler transcription on NPU systems
+
+### KV-cache decoding
+The NPU engine previously re-processed the entire token sequence for every new token it
+generated. It now uses the upgraded *merged* Whisper decoder and caches attention state between
+steps, so each step does a small, constant amount of work. This benefits **every** machine using
+the NPU/DirectML engine, whatever device the decoder runs on.
+
+### Decoder on the Intel iGPU
+On NPU systems the decoder now runs on the **Intel iGPU** via the same OpenVINO runtime already
+installed for the NPU — no new runtime download. Division of labor while transcribing:
+
+- **Encoder** → NPU (the short periodic spikes on Task Manager's NPU graph)
+- **Decoder** → Intel iGPU
+- **CPU** → audio plumbing only
+
+Measured on a Core Ultra 5 135U (base.en): decoding on the iGPU ran **~4.7× faster** than the
+same KV-cache decode on the CPU (1.29 s vs 6.10 s for a 19 s clip), with identical transcripts —
+and that work no longer occupies the CPU at all.
+
+**Fallbacks:** no usable Intel iGPU → the decoder automatically drops back to the CPU (still
+with the KV-cache speedup), and the log says so. Machines with an NVIDIA/AMD GPU can keep using
+the Vulkan backend (Settings ▸ Hardware), which runs the whole model on that GPU. The startup
+log names both devices: `transcription engine: ONNX base.en (encoder EP: OpenVINO/NPU, decoder
+EP: OpenVINO/GPU)`.
+
+### Model update (automatic, one-time)
+The engine's decoder artifact changed to the merged export (`decoder_model_merged.onnx`,
+~208 MB, same trusted source). WhispAssist fetches it automatically in the background on first
+launch after updating; until it arrives, transcription simply uses the whisper.cpp engine, as on
+a fresh install. The superseded decoder file is cleaned up automatically.
+
+---
+
+## ✨ Small addition
+
+**Settings ▸ Calendar** now has a one-click **libpst (readpst)** download button — the same style
+as the Import dialog's `ffmpeg`/`yt-dlp` buttons — linking to the ezwinports Windows build.
+`.pst` calendar import shells out to `readpst`, which isn't bundled; the button just opens the
+download page in your browser.
+
+---
+
+## 📦 Install
+
+**Requirements:** Windows 10 or 11 (x64). WhispAssist needs **WebView2** (preinstalled on Windows 11;
+the installer fetches it on Windows 10). Importing from a file/URL additionally needs **`ffmpeg`**
+(and **`yt-dlp`** for URLs) on your PATH — the Import dialog links to both.
+
+1. Download **`WhispAssist_0.7.3_x64_en-US.msi`** (or the NSIS **`WhispAssist_0.7.3_x64-setup.exe`**).
+2. Run it and accept the UAC prompt. If SmartScreen appears, choose **More info → Run anyway**.
+3. Launch **WhispAssist** from the Start menu.
+
+On first run WA picks the best transcription backend (**NPU → NVIDIA → AMD → Intel → CPU**). It runs
+without admin rights, does **not** add itself to startup unless you opt in, and keeps all data under
+`%LOCALAPPDATA%\WhispAssist`.
+
+Deploying to many machines? See [`docs/enterprise-deployment.md`](docs/enterprise-deployment.md).
+
+## 🔐 Checksums (SHA-256)
+
+```
+91a32a17addc31fbc00f38966d52402ca0c5e9e7a581a0431c383ca5a60532bd  WhispAssist_0.7.3_x64_en-US.msi
+764b758544b075b5aefe9dde37b04e4966df528912fb884ed1be5bd57905ecdb  WhispAssist_0.7.3_x64-setup.exe
+```
+
+Verify after download:
+
+```powershell
+Get-FileHash .\WhispAssist_0.7.3_x64_en-US.msi -Algorithm SHA256
+```
+
+---
+
+## Privacy, unchanged
+Everything optional is **off by default**. With nothing configured, WhispAssist makes **no content
+egress at all**. Recording is opt-in; sync/AI credentials live only in the OS credential store; the
+MCP server is loopback-only and adds no egress; the deployment file never carries secrets. The
+reachable-host allowlist is derived from your settings and enforced in the core.
@@ -44,3 +44,20 @@ Detection mapping:
 ## Revisit if
 Windows ML supersedes DirectML for our models, or a vendor SDK gives materially better NPU
 throughput than the ONNX/DirectML path.
+
+## Update (2026-07-16): NPU path uses OpenVINO; decoder split off the CPU
+
+As built (T3.4 + follow-up), the NPU tier runs on **ONNX Runtime + the OpenVINO EP**
+(`device_type=NPU`), not DirectML — Intel's prebuilt OpenVINO ORT runtime is downloaded on
+demand (DirectML remains the *GPU* fallback EP for AMD/Intel in non-Vulkan builds). The engine
+splits Whisper across devices:
+
+- **encoder** (fixed shape): OpenVINO **NPU**;
+- **decoder** (autoregressive, KV-cache greedy via Optimum's merged export): OpenVINO **GPU**
+  (Intel iGPU, same runtime bundle) when available, else the CPU EP —
+  `WA_ONNX_DECODER_DEVICE=cpu|gpu` overrides.
+
+Rationale: the dynamic-shaped decode loop is a poor NPU fit, and pre-KV-cache it re-ran the full
+token prefix every step on the CPU — the dominant CPU cost while transcribing. With the merged
+decoder + iGPU placement, sustained CPU during transcription is near-idle on NPU+iGPU systems.
+The engine logs both EPs at load (`transcription engine: ONNX …`).
@@ -1,7 +1,7 @@
 {
  "name": "whispassist",
  "private": true,
-  "version": "0.7.2",
+  "version": "0.7.3",
  "type": "module",
  "description": "Privacy-first, fully local Windows meeting assistant.",
  "license": "MIT OR Apache-2.0",
@@ -6088,7 +6088,7 @@ dependencies = [

 [[package]]
 name = "whispassist"
-version = "0.7.2"
+version = "0.7.3"
 dependencies = [
 "argon2",
 "async-trait",
@@ -1,6 +1,6 @@
 [package]
 name = "whispassist"
-version = "0.7.2"
+version = "0.7.3"
 description = "Privacy-first, fully local Windows meeting assistant"
 authors = ["WhispAssist contributors"]
 license = "MIT OR Apache-2.0"
@@ -746,10 +746,9 @@ fn capture_loop(
                        let rate = session.format.get_samplespersec() as usize;
                        // Advance the timeline by the wall-clock gap (capped), but
                        // never fewer frames than the mic we must write.
-                        let gap_frames = (elapsed.min(SILENCE_TICK_MAX).as_micros() as usize
-                            * rate
-                            / 1_000_000)
-                            .max(mic.len());
+                        let gap_frames =
+                            (elapsed.min(SILENCE_TICK_MAX).as_micros() as usize * rate / 1_000_000)
+                                .max(mic.len());
                        let bpf = session.format.get_nchannels() as usize
                            * (session.format.get_bitspersample() as usize / 8);
                        let silence = vec![0u8; gap_frames * bpf];
@@ -939,22 +938,26 @@ fn write_wav_split(
    if channels == 0 {
        return Ok(0);
    }
-    let (bytes_per_sample, decode): (usize, fn(&[u8]) -> f32) = match (sample_type, format.get_bitspersample()) {
-        (SampleType::Float, 32) => (4, |c| f32::from_le_bytes(c.try_into().unwrap())),
-        (SampleType::Int, 16) => (2, |c| {
-            i16::from_le_bytes(c.try_into().unwrap()) as f32 / i16::MAX as f32
-        }),
-        (st, bits) => {
-            return Err(AudioError::Device(format!(
-                "unsupported capture format: {st} {bits}-bit"
-            )))
-        }
-    };
+    let (bytes_per_sample, decode): (usize, fn(&[u8]) -> f32) =
+        match (sample_type, format.get_bitspersample()) {
+            (SampleType::Float, 32) => (4, |c| f32::from_le_bytes(c.try_into().unwrap())),
+            (SampleType::Int, 16) => (2, |c| {
+                i16::from_le_bytes(c.try_into().unwrap()) as f32 / i16::MAX as f32
+            }),
+            (st, bits) => {
+                return Err(AudioError::Device(format!(
+                    "unsupported capture format: {st} {bits}-bit"
+                )))
+            }
+        };
    let mut frames = 0u64;
    for frame in loopback_bytes.chunks_exact(bytes_per_sample * channels) {
        // R = loopback downmixed to mono.
-        let loop_mono =
-            frame.chunks_exact(bytes_per_sample).map(decode).sum::<f32>() / channels as f32;
+        let loop_mono = frame
+            .chunks_exact(bytes_per_sample)
+            .map(decode)
+            .sum::<f32>()
+            / channels as f32;
        // L = mic for this frame (silent if the mic underran).
        let mic_s = mic.get(frames as usize).copied().unwrap_or(0.0);
        writer
@@ -1120,7 +1123,11 @@ fn read_wav_16k(path: &Path, channel: Option<usize>) -> Result<Vec<f32>, AudioEr
    let mono: Vec<f32> = match (spec.sample_format, spec.bits_per_sample) {
        (SampleFormat::Float, 32) => bytes
            .chunks_exact(4 * channels)
-            .map(|frame| reduce_frame(frame, 4, pick, channels, |c| f32::from_le_bytes(c.try_into().unwrap())))
+            .map(|frame| {
+                reduce_frame(frame, 4, pick, channels, |c| {
+                    f32::from_le_bytes(c.try_into().unwrap())
+                })
+            })
            .collect(),
        (SampleFormat::Int, 16) => bytes
            .chunks_exact(2 * channels)
@@ -1201,8 +1208,8 @@ pub fn write_wav_mono_16k(path: &Path, samples: &[f32]) -> Result<(), AudioError
        bits_per_sample: 32,
        sample_format: SampleFormat::Float,
    };
-    let mut writer =
-        WavWriter::create(path, spec).map_err(|e| AudioError::Capture(format!("write wav: {e}")))?;
+    let mut writer = WavWriter::create(path, spec)
+        .map_err(|e| AudioError::Capture(format!("write wav: {e}")))?;
    for &s in samples {
        writer
            .write_sample(s)
@@ -1338,7 +1345,10 @@ mod tests {
    fn voice_sample_skips_silence_and_keeps_speech() {
        let vs = VoiceSample::new(16_000);
        vs.push(&[0.0; 4_000]); // silence: below the energy floor
-        assert!(vs.samples().is_empty(), "silence must not fill the voiceprint");
+        assert!(
+            vs.samples().is_empty(),
+            "silence must not fill the voiceprint"
+        );
        vs.push(&[0.2; 4_000]); // speech-level audio
        assert_eq!(vs.samples().len(), 4_000, "speech-level audio is collected");
    }
@@ -194,17 +194,17 @@ fn load_transcriber(
            match OnnxTranscriber::load(&dir, backend, language) {
                Ok(t) => {
                    // The definitive "is the accelerator actually engaged" line
-                    // (visible with `npm run tauri dev`): the encoder runs on
-                    // the EP below; the autoregressive decoder always runs on
-                    // the CPU EP, which is why Task Manager shows only short
-                    // periodic NPU spikes alongside sustained CPU load.
+                    // (visible with `npm run tauri dev`): encoder EP from the
+                    // accel path, decoder EP from wherever its session landed
+                    // (OpenVINO/GPU on NPU systems, CPU otherwise/on fallback).
                    tracing::info!(
-                        "transcription engine: ONNX {} (encoder EP: {}, decoder: CPU)",
+                        "transcription engine: ONNX {} (encoder EP: {}, decoder EP: {})",
                        onnx_models::DEFAULT_ONNX_MODEL,
                        match path {
                            AccelPath::OnnxOpenVino => "OpenVINO/NPU",
                            _ => "DirectML/GPU",
-                        }
+                        },
+                        t.decoder_ep()
                    );
                    return Ok((Box::new(t), backend));
                }
@@ -347,7 +347,9 @@ async fn attribute_split(
    spans.sort_by_key(|s| s.start_ms);
    // Uniform naming: "You" -> "You", far speakers -> "Speaker 2", "Speaker 3"….
    let labels = crate::diarization::voiceprint::first_appearance_order(&spans);
-    Some(crate::diarization::voiceprint::build_name_map(&labels, "You"))
+    Some(crate::diarization::voiceprint::build_name_map(
+        &labels, "You",
+    ))
 }

 /// The distinct speakers seen in `segments` so far, in first-appearance order,
@@ -655,28 +657,23 @@ pub async fn start_recording(
                        .lock()
                        .unwrap_or_else(|e| e.into_inner())
                        .clone();
-                    if attribute_split(
-                        diarizer.clone(),
-                        wav_path_for_diar.clone(),
-                        &mut snapshot,
-                    )
-                    .await
-                    .map(|auto_names| {
-                        let mut names = names_for_diar.lock().unwrap_or_else(|e| e.into_inner());
-                        // Never overwrite a name already set (user rename or a
-                        // prior pass) — same guard as the post-stop pass.
-                        for (label, name) in auto_names {
-                            names.entry(label).or_insert(name);
-                        }
-                    })
-                    .is_none()
+                    if attribute_split(diarizer.clone(), wav_path_for_diar.clone(), &mut snapshot)
+                        .await
+                        .map(|auto_names| {
+                            let mut names =
+                                names_for_diar.lock().unwrap_or_else(|e| e.into_inner());
+                            // Never overwrite a name already set (user rename or a
+                            // prior pass) — same guard as the post-stop pass.
+                            for (label, name) in auto_names {
+                                names.entry(label).or_insert(name);
+                            }
+                        })
+                        .is_none()
                    {
                        continue; // pass failed (already logged); retry next tick
                    }
-                    let relabeled: HashMap<u64, String> = snapshot
-                        .into_iter()
-                        .map(|s| (s.id, s.speaker))
-                        .collect();
+                    let relabeled: HashMap<u64, String> =
+                        snapshot.into_iter().map(|s| (s.id, s.speaker)).collect();
                    let mut segs = segments_for_diar.lock().unwrap_or_else(|e| e.into_inner());
                    // Snapshot prior labels so only segments whose speaker
                    // actually changed this pass get re-emitted (ids are stable;
@@ -891,7 +888,8 @@ pub async fn stop_recording(
                        if already_named {
                            continue;
                        }
-                        if let Err(e) = state.store.rename_speaker(&meeting_id, &label, &name).await {
+                        if let Err(e) = state.store.rename_speaker(&meeting_id, &label, &name).await
+                        {
                            tracing::warn!("failed to persist auto speaker name: {e}");
                            continue;
                        }
@@ -1757,8 +1755,11 @@ fn pick_realtime_recommendation(
        .max_by(|a, b| {
            let sa = sizes.get(&a.model).copied().unwrap_or(0);
            let sb = sizes.get(&b.model).copied().unwrap_or(0);
-            sa.cmp(&sb)
-                .then(b.rtf.partial_cmp(&a.rtf).unwrap_or(std::cmp::Ordering::Equal))
+            sa.cmp(&sb).then(
+                b.rtf
+                    .partial_cmp(&a.rtf)
+                    .unwrap_or(std::cmp::Ordering::Equal),
+            )
        })
        .map(|r| StressRecommendation {
            backend: r.backend.clone(),
@@ -2525,10 +2526,17 @@ async fn run_import_pipeline(
    })
    .await;
    match transcode {
-        Ok(Ok(())) => {
-            emit_import_progress(&app, &meeting_id, "prepare", "done", Some(t.elapsed().as_millis()), None)
+        Ok(Ok(())) => emit_import_progress(
+            &app,
+            &meeting_id,
+            "prepare",
+            "done",
+            Some(t.elapsed().as_millis()),
+            None,
+        ),
+        Ok(Err(e)) => {
+            return fail_import(&app, &store, &meeting_id, "prepare", &e.to_string()).await
        }
-        Ok(Err(e)) => return fail_import(&app, &store, &meeting_id, "prepare", &e.to_string()).await,
        Err(e) => return fail_import(&app, &store, &meeting_id, "prepare", &e.to_string()).await,
    }

@@ -2552,11 +2560,22 @@ async fn run_import_pipeline(
    .await;
    let (mut segments, resolved_language) = match transcribed {
        Ok(Ok(v)) => {
-            emit_import_progress(&app, &meeting_id, "transcribe", "done", Some(t.elapsed().as_millis()), None);
+            emit_import_progress(
+                &app,
+                &meeting_id,
+                "transcribe",
+                "done",
+                Some(t.elapsed().as_millis()),
+                None,
+            );
            v
        }
-        Ok(Err(e)) => return fail_import(&app, &store, &meeting_id, "transcribe", &e.to_string()).await,
-        Err(e) => return fail_import(&app, &store, &meeting_id, "transcribe", &e.to_string()).await,
+        Ok(Err(e)) => {
+            return fail_import(&app, &store, &meeting_id, "transcribe", &e.to_string()).await
+        }
+        Err(e) => {
+            return fail_import(&app, &store, &meeting_id, "transcribe", &e.to_string()).await
+        }
    };

    // Phase 3: diarize — one pass if the models are installed, else every line
@@ -2578,7 +2597,14 @@ async fn run_import_pipeline(
            Err(e) => tracing::warn!("import diarization task failed: {e}"),
        }
    }
-    emit_import_progress(&app, &meeting_id, "diarize", "done", Some(t.elapsed().as_millis()), None);
+    emit_import_progress(
+        &app,
+        &meeting_id,
+        "diarize",
+        "done",
+        Some(t.elapsed().as_millis()),
+        None,
+    );

    // Phase 4: finalize — persist segments, notes, seal audio.
    emit_import_progress(&app, &meeting_id, "finalize", "active", None, None);
@@ -2626,7 +2652,14 @@ async fn run_import_pipeline(
            }
        }
    }
-    emit_import_progress(&app, &meeting_id, "finalize", "done", Some(t.elapsed().as_millis()), None);
+    emit_import_progress(
+        &app,
+        &meeting_id,
+        "finalize",
+        "done",
+        Some(t.elapsed().as_millis()),
+        None,
+    );

    let _ = app.emit(
        "transcript://finalized",
@@ -2643,7 +2676,9 @@ async fn fail_import(
    phase: &str,
    message: &str,
 ) {
-    let _ = store.set_meeting_status(&meeting_id.to_string(), "error").await;
+    let _ = store
+        .set_meeting_status(&meeting_id.to_string(), "error")
+        .await;
    emit_import_progress(app, meeting_id, phase, "error", None, Some(message));
 }

@@ -2926,8 +2961,8 @@ fn fold_wav(wav: &[u8], out_channels: u16) -> Option<Vec<u8>> {
            (hound::SampleFormat::Int, 16) => {
                let s: Vec<i16> = reader.samples::<i16>().map_while(Result::ok).collect();
                for frame in s.chunks(ch) {
-                    let avg = (frame.iter().map(|&x| x as i32).sum::<i32>()
-                        / frame.len() as i32) as i16;
+                    let avg =
+                        (frame.iter().map(|&x| x as i32).sum::<i32>() / frame.len() as i32) as i16;
                    for _ in 0..out_channels {
                        writer.write_sample(avg).ok()?;
                    }
@@ -3125,10 +3160,7 @@ pub async fn bulk_export_meetings(
 /// so re-importing never collides with existing meetings. Returns the count
 /// imported.
 #[tauri::command]
-pub async fn import_meeting_bundle(
-    state: State<'_, AppState>,
-    dir: String,
-) -> WaResult<u32> {
+pub async fn import_meeting_bundle(state: State<'_, AppState>, dir: String) -> WaResult<u32> {
    let root = PathBuf::from(&dir);
    let mut bundles: Vec<PathBuf> = Vec::new();
    if root.join("meeting.json").exists() {
@@ -3977,7 +4009,11 @@ only, with no preamble or commentary.";
    let notes = notes.trim();
    let user = format!(
        "My rough notes:\n{}\n\nTranscript:\n{}",
-        if notes.is_empty() { "(none yet)" } else { notes },
+        if notes.is_empty() {
+            "(none yet)"
+        } else {
+            notes
+        },
        prompt.transcript
    );
    provider
@@ -4895,8 +4931,8 @@ pub(crate) fn spawn_auto_sync(
    let app = app.clone();
    tauri::async_runtime::spawn(async move {
        match enqueue_meeting_sync(store.as_ref(), &meeting_id, None, true).await {
-            Ok(0) => {}                                       // nothing changed
-            Ok(_) => pump_sync(&app, store.as_ref()).await,   // upload the changes
+            Ok(0) => {}                                     // nothing changed
+            Ok(_) => pump_sync(&app, store.as_ref()).await, // upload the changes
            Err(e) => tracing::warn!("auto-sync enqueue failed: {e:?}"),
        }
    });
@@ -26,7 +26,11 @@ const AUTO_DOWNLOAD_KEY: &str = "auto_download_model";
 fn candidate_paths() -> Vec<PathBuf> {
    let mut paths = Vec::new();
    if let Ok(program_data) = std::env::var("ProgramData") {
-        paths.push(PathBuf::from(program_data).join("WhispAssist").join("wa-defaults.ini"));
+        paths.push(
+            PathBuf::from(program_data)
+                .join("WhispAssist")
+                .join("wa-defaults.ini"),
+        );
    }
    if let Ok(exe) = std::env::current_exe() {
        if let Some(dir) = exe.parent() {
@@ -121,7 +125,8 @@ fn coerce(value: &str) -> Value {
 }

 fn truthy(v: &Value) -> bool {
-    matches!(v, Value::Bool(true)) || matches!(v, Value::String(s) if s.eq_ignore_ascii_case("true"))
+    matches!(v, Value::Bool(true))
+        || matches!(v, Value::String(s) if s.eq_ignore_ascii_case("true"))
 }

 /// Defense in depth: never seed anything that smells like a credential.
@@ -95,7 +95,12 @@ pub fn assign_split(
            seg.speaker = "You".to_string();
        } else if let Some(span) = far_spans
            .iter()
-            .map(|sp| (overlap(seg.start_ms, seg.end_ms, sp.start_ms, sp.end_ms), sp))
+            .map(|sp| {
+                (
+                    overlap(seg.start_ms, seg.end_ms, sp.start_ms, sp.end_ms),
+                    sp,
+                )
+            })
            .filter(|(o, _)| *o > 0)
            .max_by_key(|(o, _)| *o)
            .map(|(_, sp)| sp)
@@ -298,7 +303,12 @@ mod overlap_tests {
    fn split_keeps_the_prior_label_when_both_channels_are_silent() {
        let mut segments = vec![segment(5000, 6000)];
        segments[0].speaker = "S9".to_string();
-        assign_split(&mut segments, &[(0, 1000)], &[(0, 1000)], &[span(0, 1000, "S1")]);
+        assign_split(
+            &mut segments,
+            &[(0, 1000)],
+            &[(0, 1000)],
+            &[span(0, 1000, "S1")],
+        );
        assert_eq!(segments[0].speaker, "S9");
    }

@@ -117,7 +117,11 @@ fn fatal_startup_error(body: &str) -> ! {
            MessageBoxW, MB_ICONERROR, MB_OK, MB_SYSTEMMODAL,
        };
        // Null-terminated UTF-16 for the Win32 wide API.
-        let to_wide = |s: &str| s.encode_utf16().chain(std::iter::once(0)).collect::<Vec<u16>>();
+        let to_wide = |s: &str| {
+            s.encode_utf16()
+                .chain(std::iter::once(0))
+                .collect::<Vec<u16>>()
+        };
        let text = to_wide(body);
        let caption = to_wide("WhispAssist can't start");
        // SAFETY: both buffers are null-terminated and outlive the call.
@@ -228,13 +232,17 @@ pub fn run() {
                                    )
                                    .await
                                    {
-                                        tracing::warn!("deploy auto-download of model failed: {e:?}");
+                                        tracing::warn!(
+                                            "deploy auto-download of model failed: {e:?}"
+                                        );
                                    }
                                });
                            }
                        }
                        Err(e) => {
-                            tracing::error!("first-run deploy seeding failed to write settings: {e:?}")
+                            tracing::error!(
+                                "first-run deploy seeding failed to write settings: {e:?}"
+                            )
                        }
                    }
                }
@@ -21,10 +21,7 @@ pub enum MediaError {
    #[error("{0} isn't installed or on PATH — install it and try again")]
    ToolMissing(&'static str),
    #[error("{tool} failed: {message}")]
-    Failed {
-        tool: &'static str,
-        message: String,
-    },
+    Failed { tool: &'static str, message: String },
    #[error("io error: {0}")]
    Io(#[from] std::io::Error),
 }
@@ -60,7 +57,11 @@ fn run(program: &'static str, cmd: &mut Command) -> Result<(), MediaError> {
    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        let stdout = String::from_utf8_lossy(&output.stdout);
-        let text = if stderr.trim().is_empty() { stdout } else { stderr };
+        let text = if stderr.trim().is_empty() {
+            stdout
+        } else {
+            stderr
+        };
        let tail: Vec<&str> = text.lines().filter(|l| !l.trim().is_empty()).collect();
        let start = tail.len().saturating_sub(6);
        return Err(MediaError::Failed {
@@ -145,12 +146,7 @@ mod tests {
    fn import_reports_a_missing_local_file_without_touching_a_tool() {
        let dir = std::env::temp_dir().join(format!("wa-media-{}", uuid::Uuid::new_v4()));
        std::fs::create_dir_all(&dir).unwrap();
-        let err = import_to_wav(
-            "no-such-file.mp4",
-            &dir.join("out.wav"),
-            &dir,
-        )
-        .unwrap_err();
+        let err = import_to_wav("no-such-file.mp4", &dir.join("out.wav"), &dir).unwrap_err();
        assert!(matches!(err, MediaError::Failed { tool: "import", .. }));
        let _ = std::fs::remove_dir_all(&dir);
    }
@@ -1260,13 +1260,15 @@ impl Store for SqliteStore {
        started_at: i64,
        ended_at: Option<i64>,
    ) -> Result<(), StoreError> {
-        sqlx::query("UPDATE meetings SET started_at = ?, ended_at = ?, updated_at = ? WHERE id = ?")
-            .bind(started_at)
-            .bind(ended_at)
-            .bind(now_unix())
-            .bind(meeting_id)
-            .execute(&self.pool)
-            .await?;
+        sqlx::query(
+            "UPDATE meetings SET started_at = ?, ended_at = ?, updated_at = ? WHERE id = ?",
+        )
+        .bind(started_at)
+        .bind(ended_at)
+        .bind(now_unix())
+        .bind(meeting_id)
+        .execute(&self.pool)
+        .await?;
        Ok(())
    }

@@ -588,7 +588,10 @@ mod tests {
        feed_into(&mut s, &step, &d2, &mut out);
        assert!(out[3].interim && out[3].text == "next sentence");
        assert_ne!(out[3].id, out[2].id);
-        assert!(out[3].start_ms >= 3000, "starts after the 3 committed steps");
+        assert!(
+            out[3].start_ms >= 3000,
+            "starts after the 3 committed steps"
+        );
    }

    #[test]
@@ -612,7 +615,10 @@ mod tests {
        assert!(out.last().unwrap().interim, "still growing before flush");
        flush_into(&mut s, &decode, &mut out);
        let last = out.last().unwrap();
-        assert!(!last.interim && last.text == "partial", "flush finalizes it");
+        assert!(
+            !last.interim && last.text == "partial",
+            "flush finalizes it"
+        );
    }

    #[test]
@@ -7,21 +7,24 @@
 //!
 //! Split of work, validated by the T3.4 spike (encoder ~3.6× faster on NPU):
 //! - **encoder** (fixed `[1,80,3000]` shape) runs on the **accelerator** (NPU or
-//!   GPU) — the expensive graph, and the fixed shape accelerators want;
-//! - **decoder** (dynamic, autoregressive) runs greedy on the **CPU** EP — a
-//!   dynamic KV loop is a poor accelerator fit and the cheap half anyway.
-//!
-//! ponytail: greedy, no-KV-cache decode (re-feeds the full token prefix each
-//! step). Correct and simple; windows are short so the token count is small.
-//! Add `decoder_with_past` only if the decoder shows up in a profile.
+//!   DirectML GPU) — the expensive graph, and the fixed shape accelerators want;
+//! - **decoder** (dynamic, autoregressive) decodes greedily **with a KV cache**
+//!   (Optimum's merged export: `use_cache_branch` + `past_key_values`), so each
+//!   step feeds one token instead of re-running the whole prefix. On the NPU
+//!   path the decoder session itself goes to the **OpenVINO GPU EP** (Intel
+//!   iGPU, same runtime bundle) so sustained CPU stays near-idle; it falls back
+//!   to the CPU EP when no iGPU is usable, and `WA_ONNX_DECODER_DEVICE=cpu|gpu`
+//!   overrides the choice. DirectML backends keep the CPU decoder — the DML EP
+//!   handles per-step-growing KV shapes poorly.

 use super::{AudioWindow, SegmentSink, Transcriber, TrxError};
 use crate::models::{BackendId, TranscriptSegment};
 use ort::execution_providers::{
    DirectMLExecutionProvider, ExecutionProviderDispatch, OpenVINOExecutionProvider,
 };
-use ort::session::Session;
-use ort::value::Tensor;
+use ort::session::{Session, SessionInputValue};
+use ort::value::{Tensor, ValueType};
+use std::borrow::Cow;
 use std::collections::HashMap;
 use std::path::Path;
 use std::sync::atomic::{AtomicU64, Ordering};
@@ -30,6 +33,36 @@ use std::sync::Mutex;
 /// Safety cap on generated tokens per 30 s window (Whisper's own max is 448).
 const MAX_NEW_TOKENS: usize = 224;

+/// One KV-cache tensor pair of the merged decoder, discovered from the graph
+/// at load: the `past_key_values.*` input, its matching `present.*` output,
+/// whether it's decoder self-attention (refreshed every step) or encoder
+/// cross-attention (computed once on the first step, then passed through
+/// untouched by the cache branch), and the dummy shape to feed before any
+/// past exists (see [`dummy_past_dims`]).
+struct KvSlot {
+    past: String,
+    present: String,
+    self_attention: bool,
+    dummy_dims: Vec<usize>,
+}
+
+/// `"past_key_values.3.decoder.key"` → `"present.3.decoder.key"` — Optimum's
+/// fixed naming convention for the merged decoder's cache I/O.
+fn present_name_for(past: &str) -> String {
+    format!("present.{}", past.trim_start_matches("past_key_values."))
+}
+
+/// The "no past yet" shape for a KV input: batch → 1, any other dynamic (−1)
+/// dim → **1** (a dummy length-1 past — ORT's raw-data tensor creation rejects
+/// zero-length dims, and the no-cache branch never reads the values anyway;
+/// same dummy Optimum's own runner feeds), static dims kept.
+fn dummy_past_dims(dims: &[i64]) -> Vec<usize> {
+    dims.iter()
+        .enumerate()
+        .map(|(i, &d)| if i == 0 || d < 0 { 1 } else { d as usize })
+        .collect()
+}
+
 pub struct OnnxTranscriber {
    encoder: Mutex<Session>,
    decoder: Mutex<Session>,
@@ -38,6 +71,13 @@ pub struct OnnxTranscriber {
    dec_ids: String,
    dec_hidden: String,
    dec_logits: String,
+    /// The merged decoder's KV-cache plumbing (see [`KvSlot`]) plus its
+    /// branch selector input.
+    kv_slots: Vec<KvSlot>,
+    dec_use_cache: String,
+    /// Which EP the decoder session actually landed on ("OpenVINO/GPU" or
+    /// "CPU") — surfaced so `load_transcriber`'s engine log tells the truth.
+    decoder_ep: &'static str,
    detok: Detok,
    /// `[decoder_start_token_id, ...forced_decoder_ids]` — the fixed prompt
    /// prefix before generation begins.
@@ -120,29 +160,76 @@ impl OnnxTranscriber {
        let hidden = Tensor::from_array((hidden_shape, hidden_data))
            .map_err(|e| TrxError::Inference(e.to_string()))?;

-        // Greedy decode on the CPU.
+        // Greedy KV-cache decode. Step 1 runs the merged graph's no-cache
+        // branch over the full prompt and yields every present KV; later steps
+        // feed a single token plus the cache, refreshing only the decoder
+        // self-attention slots — the cache branch passes encoder
+        // cross-attention KVs through untouched, so the step-1 tensors stay
+        // authoritative (same contract as Optimum's own runner).
+        // ponytail: KVs round-trip host memory each step; wire ort IoBinding
+        // to pin them on-device if GPU-decoder profiling shows the copies matter.
+        let mut kv_cache: Vec<Tensor<f32>> = self
+            .kv_slots
+            .iter()
+            .map(|slot| {
+                let len = slot.dummy_dims.iter().product::<usize>();
+                Tensor::from_array((slot.dummy_dims.clone(), vec![0.0f32; len]))
+            })
+            .collect::<Result<_, _>>()
+            .map_err(|e| TrxError::Inference(e.to_string()))?;
+
        let mut tokens = self.initial_tokens.clone();
+        let mut cached = false; // flips true once step 1 has filled kv_cache
        for _ in 0..MAX_NEW_TOKENS {
-            let ids: Vec<i64> = tokens.clone();
+            let ids: Vec<i64> = if cached {
+                vec![*tokens.last().unwrap_or(&self.eot)]
+            } else {
+                tokens.clone()
+            };
            let ids_tensor = Tensor::from_array(([1usize, ids.len()], ids))
                .map_err(|e| TrxError::Inference(e.to_string()))?;
+            let branch = Tensor::from_array(([1usize], vec![cached]))
+                .map_err(|e| TrxError::Inference(e.to_string()))?;

-            let next = {
+            // Presents are extracted (copied) inside the outputs' borrow scope,
+            // then written back into kv_cache after it ends.
+            let (next, fresh_kvs) = {
                let mut dec = self
                    .decoder
                    .lock()
                    .map_err(|_| TrxError::Inference("decoder mutex poisoned".into()))?;
+                let mut inputs: Vec<(Cow<'_, str>, SessionInputValue<'_>)> = vec![
+                    (Cow::from(self.dec_ids.as_str()), ids_tensor.view().into()),
+                    (Cow::from(self.dec_hidden.as_str()), hidden.view().into()),
+                    (Cow::from(self.dec_use_cache.as_str()), branch.view().into()),
+                ];
+                for (slot, kv) in self.kv_slots.iter().zip(kv_cache.iter()) {
+                    inputs.push((Cow::from(slot.past.as_str()), kv.view().into()));
+                }
                let outputs = dec
-                    .run(ort::inputs![
-                        self.dec_ids.as_str() => ids_tensor.view(),
-                        self.dec_hidden.as_str() => hidden.view(),
-                    ])
+                    .run(inputs)
                    .map_err(|e| TrxError::Inference(e.to_string()))?;
                let (shape, data) = outputs[self.dec_logits.as_str()]
                    .try_extract_tensor::<f32>()
                    .map_err(|e| TrxError::Inference(e.to_string()))?;
-                self.argmax_last(shape, data)
+                let next = self.argmax_last(shape, data);
+
+                let mut fresh: Vec<(usize, Vec<usize>, Vec<f32>)> = Vec::new();
+                for (i, slot) in self.kv_slots.iter().enumerate() {
+                    if slot.self_attention || !cached {
+                        let (s, d) = outputs[slot.present.as_str()]
+                            .try_extract_tensor::<f32>()
+                            .map_err(|e| TrxError::Inference(e.to_string()))?;
+                        fresh.push((i, s.iter().map(|d| *d as usize).collect(), d.to_vec()));
+                    }
+                }
+                (next, fresh)
            };
+            for (i, dims, data) in fresh_kvs {
+                kv_cache[i] = Tensor::from_array((dims, data))
+                    .map_err(|e| TrxError::Inference(e.to_string()))?;
+            }
+            cached = true;

            if next == self.eot {
                break;
@@ -180,6 +267,11 @@ impl OnnxTranscriber {
        best
    }

+    /// Which EP the decoder session landed on — "OpenVINO/GPU" or "CPU".
+    pub fn decoder_ep(&self) -> &'static str {
+        self.decoder_ep
+    }
+
    fn segment(&self, text: String, start_ms: u64, end_ms: u64) -> Option<TranscriptSegment> {
        if text.is_empty() {
            return None;
@@ -252,7 +344,7 @@ impl Transcriber for OnnxTranscriber {
        Self::ensure_runtime_env(runtime_dll);

        let encoder_path = model.join("encoder_model.onnx");
-        let decoder_path = model.join("decoder_model.onnx");
+        let decoder_path = model.join("decoder_model_merged.onnx");
        let tokenizer_path = model.join("tokenizer.json");
        let gen_config_path = model.join("generation_config.json");

@@ -263,11 +355,46 @@ impl Transcriber for OnnxTranscriber {
            .commit_from_file(&encoder_path)
            .map_err(|e| TrxError::Load(e.to_string()))?;

-        // Decoder on the default CPU EP (dynamic shapes; poor NPU fit).
-        let decoder = Session::builder()
-            .map_err(|e| TrxError::Load(e.to_string()))?
-            .commit_from_file(&decoder_path)
-            .map_err(|e| TrxError::Load(e.to_string()))?;
+        // Decoder session. The KV-cache loop is dynamic-shaped and
+        // autoregressive — a poor NPU fit — but it needn't burn CPU either: on
+        // the NPU path, try the same OpenVINO runtime's GPU plugin (Intel
+        // iGPU) first and fall back to the default CPU EP if no GPU is usable.
+        // `WA_ONNX_DECODER_DEVICE=cpu|gpu` overrides (debug escape hatch, like
+        // WA_NPU_RUNTIME_URL). DirectML backends keep the CPU decoder — the
+        // DML EP handles per-step-growing KV shapes poorly.
+        let want_gpu = match std::env::var("WA_ONNX_DECODER_DEVICE").as_deref() {
+            Ok("cpu") => false,
+            Ok("gpu") => true,
+            _ => matches!(backend, BackendId::Npu),
+        };
+        let mut decoder_ep = "CPU";
+        let mut decoder = None;
+        if want_gpu {
+            let gpu = Session::builder()
+                .and_then(|b| {
+                    b.with_execution_providers([OpenVINOExecutionProvider::default()
+                        .with_device_type("GPU")
+                        .build()
+                        .error_on_failure()])
+                })
+                .and_then(|b| b.commit_from_file(&decoder_path));
+            match gpu {
+                Ok(s) => {
+                    decoder_ep = "OpenVINO/GPU";
+                    decoder = Some(s);
+                }
+                Err(e) => tracing::warn!(
+                    "OpenVINO GPU EP unavailable for the decoder ({e}); using the CPU EP"
+                ),
+            }
+        }
+        let decoder = match decoder {
+            Some(s) => s,
+            None => Session::builder()
+                .map_err(|e| TrxError::Load(e.to_string()))?
+                .commit_from_file(&decoder_path)
+                .map_err(|e| TrxError::Load(e.to_string()))?,
+        };

        let enc_input = Self::find_input(&encoder, "input_features")?;
        let enc_output = Self::find_output(&encoder, "last_hidden_state")
@@ -275,6 +402,53 @@ impl Transcriber for OnnxTranscriber {
        let dec_ids = Self::find_input(&decoder, "input_ids")?;
        let dec_hidden = Self::find_input(&decoder, "encoder_hidden")?;
        let dec_logits = Self::find_output(&decoder, "logits")?;
+        let dec_use_cache = Self::find_input(&decoder, "use_cache_branch")?;
+
+        // KV-cache plumbing, discovered rather than hardcoded so the layer
+        // count comes from the graph (whisper-base: 6 layers → 24 slots).
+        let mut kv_slots: Vec<KvSlot> = Vec::new();
+        for input in &decoder.inputs {
+            if !input.name.starts_with("past_key_values.") {
+                continue;
+            }
+            let dims: Vec<i64> = match &input.input_type {
+                ValueType::Tensor { shape, .. } => shape.to_vec(),
+                other => {
+                    return Err(TrxError::Load(format!(
+                        "KV input '{}' has non-tensor type {other:?}",
+                        input.name
+                    )))
+                }
+            };
+            let present = present_name_for(&input.name);
+            if !decoder.outputs.iter().any(|o| o.name == present) {
+                return Err(TrxError::Load(format!(
+                    "decoder missing present output '{present}'"
+                )));
+            }
+            kv_slots.push(KvSlot {
+                self_attention: input.name.contains(".decoder."),
+                dummy_dims: dummy_past_dims(&dims),
+                past: input.name.clone(),
+                present,
+            });
+        }
+        if kv_slots.is_empty() {
+            return Err(TrxError::Load(
+                "decoder has no past_key_values inputs — expected the merged (KV-cache) export"
+                    .into(),
+            ));
+        }
+
+        // A pre-KV-cache install leaves the old plain decoder behind — 208 MB
+        // of dead weight once the merged graph loads. Best-effort removal.
+        let legacy = model.join("decoder_model.onnx");
+        if legacy.exists() {
+            match std::fs::remove_file(&legacy) {
+                Ok(()) => tracing::info!("removed superseded decoder_model.onnx"),
+                Err(e) => tracing::warn!("couldn't remove superseded decoder_model.onnx: {e}"),
+            }
+        }

        let detok = Detok::from_tokenizer_json(&tokenizer_path)?;
        let gen = GenConfig::from_file(&gen_config_path)?;
@@ -290,6 +464,9 @@ impl Transcriber for OnnxTranscriber {
            dec_ids,
            dec_hidden,
            dec_logits,
+            kv_slots,
+            dec_use_cache,
+            decoder_ep,
            detok,
            initial_tokens,
            special_floor: gen.decoder_start,
@@ -457,6 +634,28 @@ mod tests {
        assert_eq!(d.get(&'A'), Some(&b'A'));
    }

+    #[test]
+    fn present_name_follows_optimum_convention() {
+        assert_eq!(
+            present_name_for("past_key_values.3.decoder.key"),
+            "present.3.decoder.key"
+        );
+        assert_eq!(
+            present_name_for("past_key_values.0.encoder.value"),
+            "present.0.encoder.value"
+        );
+    }
+
+    #[test]
+    fn dummy_past_dims_pins_dynamic_axes_to_one_and_keeps_static_ones() {
+        // whisper-base decoder self-attention past: [batch, 8, past_seq, 64]
+        // with batch/past_seq dynamic — both pin to 1 (ORT rejects 0-length
+        // dims for raw-data tensors; the no-cache branch ignores the values).
+        assert_eq!(dummy_past_dims(&[-1, 8, -1, 64]), vec![1, 8, 1, 64]);
+        // A static trailing shape is preserved (batch still pins to 1).
+        assert_eq!(dummy_past_dims(&[-1, 8, 1500, 64]), vec![1, 8, 1500, 64]);
+    }
+
    #[test]
    fn byte_decoder_covers_all_256_bytes() {
        let d = byte_decoder();
@@ -481,10 +680,14 @@ mod tests {
            return;
        };
        let wav = std::env::var("WA_NPU_TEST_WAV").expect("set WA_NPU_TEST_WAV");
+        // Surface the engine's own EP-selection logs (GPU-decoder fallback
+        // warnings etc.) — the test harness has no subscriber otherwise.
+        let _ = tracing_subscriber::fmt().with_env_filter("info").try_init();
        let t0 = std::time::Instant::now();
        let t = OnnxTranscriber::load(Path::new(&model_dir), BackendId::Npu, None)
            .expect("load NPU transcriber");
        let load_ms = t0.elapsed().as_millis();
+        eprintln!("[spike] decoder EP: {}", t.decoder_ep());
        let t1 = std::time::Instant::now();
        let segs = t.transcribe_file(Path::new(&wav)).expect("transcribe");
        let infer_ms = t1.elapsed().as_millis();
@@ -15,9 +15,19 @@ const REPO: &str = "onnx-community/whisper-base.en";
 pub const DEFAULT_ONNX_MODEL: &str = "base.en";

 /// The four artifacts the `OnnxTranscriber` needs, relative to the repo root.
+/// The decoder is Optimum's *merged* export — both the no-past and with-past
+/// branches in one graph, selected by a `use_cache_branch` input — which is
+/// what enables the KV-cache decode loop (the plain `decoder_model.onnx`
+/// re-ran the whole prefix every step). Existing installs migrate for free:
+/// swapping this entry flips `is_installed` to false, the startup background
+/// fetch re-runs `download`, and `download` skips the three files already on
+/// disk, fetching only the merged decoder.
 const FILES: &[(&str, &str)] = &[
    ("encoder_model.onnx", "onnx/encoder_model.onnx"),
-    ("decoder_model.onnx", "onnx/decoder_model.onnx"),
+    (
+        "decoder_model_merged.onnx",
+        "onnx/decoder_model_merged.onnx",
+    ),
    ("tokenizer.json", "tokenizer.json"),
    ("generation_config.json", "generation_config.json"),
 ];
@@ -45,7 +55,7 @@ pub fn model_files(id: &str) -> OnnxModelFiles {
    let dir = onnx_dir(id);
    OnnxModelFiles {
        encoder: dir.join("encoder_model.onnx"),
-        decoder: dir.join("decoder_model.onnx"),
+        decoder: dir.join("decoder_model_merged.onnx"),
        tokenizer: dir.join("tokenizer.json"),
        generation_config: dir.join("generation_config.json"),
    }
@@ -125,6 +135,6 @@ mod tests {
    fn catalog_lists_the_four_required_artifacts() {
        assert_eq!(FILES.len(), 4);
        assert!(FILES.iter().any(|(n, _)| *n == "encoder_model.onnx"));
-        assert!(FILES.iter().any(|(n, _)| *n == "decoder_model.onnx"));
+        assert!(FILES.iter().any(|(n, _)| *n == "decoder_model_merged.onnx"));
    }
 }
@@ -1,7 +1,7 @@
 {
  "$schema": "https://schema.tauri.app/config/2",
  "productName": "WhispAssist",
-  "version": "0.7.2",
+  "version": "0.7.3",
  "identifier": "bet.dou.whispassist",
  "build": {
    "frontendDist": "../dist",
@@ -107,6 +107,7 @@
  "settings.calendar.title": "Calendar & Outlook .pst",
  "settings.calendar.intro_1": "Import events and attendees from a local Outlook",
  "settings.calendar.intro_2": "backup — read-only, nothing is written back to the file. Nothing leaves this device.",
+  "settings.calendar.requires": "Needs this on your PATH (not bundled):",
  "settings.calendar.pst_file": ".pst file",
  "settings.calendar.no_file": "No file selected",
  "settings.calendar.browse": "Browse…",
@@ -286,6 +286,11 @@
  }

  // ---- Calendar / .pst import (T6.1/T6.2/T6.3, FR-CAL-1/2) ----
+  // .pst import shells out to readpst (libpst, ADR-0008) — external like
+  // ffmpeg/yt-dlp, so link the same kind of download button as the Import
+  // dialog's. ezwinports is the maintained Windows build of libpst.
+  const LIBPST_URL =
+    "https://sourceforge.net/projects/ezwinports/files/libpst-0.6.63-w32-bin.zip/download";
  let pstPath = $state("");
  let pstPassword = $state("");
  let eventTitleFilter = $state("");
@@ -987,7 +992,9 @@
          <p class="muted">{t("settings.hardware.stress_hint")}</p>
          <button onclick={runStressTest} disabled={stressRunning}>
            <Zap size={13} aria-hidden="true" />
-            {stressRunning ? t("settings.hardware.stress_running") : t("settings.hardware.stress_run")}
+            {stressRunning
+              ? t("settings.hardware.stress_running")
+              : t("settings.hardware.stress_run")}
          </button>
          {#if stressProgress}
            <p class="muted">{t("settings.hardware.stress_progress", { pair: stressProgress })}</p>
@@ -1344,6 +1351,12 @@
          {t("settings.calendar.intro_1")} <code>.pst</code>
          {t("settings.calendar.intro_2")}
        </p>
+        <div class="tools">
+          <span class="muted small">{t("settings.calendar.requires")}</span>
+          <button class="tool" type="button" onclick={() => api.openUrl(LIBPST_URL)}>
+            <Download size={12} aria-hidden="true" /> libpst (readpst)
+          </button>
+        </div>
        <div class="grid">
          <label class="wide"
            >{t("settings.calendar.pst_file")}
@@ -2384,6 +2397,33 @@
    font-size: 0.85rem;
    line-height: 1.5;
  }
+  /* External-tool download chip — identical to the Import dialog's
+     ffmpeg/yt-dlp buttons (ImportMeeting.svelte). */
+  .tools {
+    display: flex;
+    align-items: center;
+    flex-wrap: wrap;
+    gap: 0.4rem;
+    margin-top: 0.9rem;
+  }
+  .tool {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.25rem;
+    background: var(--bg-hover, transparent);
+    color: var(--accent);
+    border: 1px solid var(--border);
+    border-radius: var(--radius-sm);
+    padding: 0.2rem 0.5rem;
+    font-size: 0.78rem;
+    cursor: pointer;
+  }
+  .tool:hover {
+    border-color: var(--accent);
+  }
+  .tools .small {
+    font-size: 0.8rem;
+  }
  .footnote {
    margin-top: 1rem;
    border-top: 1px solid var(--border);