diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 93af96a9..89bd5349 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -30,8 +30,13 @@ jobs:
         with:
           python-version: "3.11"
 
+      # enable-cache persists ~/.cache/uv across runs, keyed on uv.lock —
+      # turns `uv sync` from ~45 s cold to ~5 s warm.
       - name: Install uv
         uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: true
+          cache-dependency-glob: "uv.lock"
 
       # Node 22 is needed for --experimental-strip-types so node:test can
       # import .ts files directly from frontend/src/api/*.
@@ -43,10 +48,12 @@ jobs:
       - name: Setup Bun
         uses: oven-sh/setup-bun@v1
 
+      # apt install ffmpeg is ~30 s every run; cache the resolved .debs.
       - name: System deps (ffmpeg)
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y ffmpeg
+        uses: awalsh128/cache-apt-pkgs-action@latest
+        with:
+          packages: ffmpeg
+          version: 1.0
 
       - name: Install Python deps
         run: uv sync
@@ -54,6 +61,16 @@ jobs:
       - name: Run pytest
         run: uv run pytest tests/ -q --tb=short
 
+      # Cache ~/.bun/install/cache keyed on bun.lock — `bun install` drops
+      # from ~15 s cold to near-instant on warm cache.
+      - name: Cache bun deps
+        uses: actions/cache@v4
+        with:
+          path: ~/.bun/install/cache
+          key: ${{ runner.os }}-bun-${{ hashFiles('frontend/bun.lock', 'bun.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-bun-
+
       - name: Install frontend deps
         working-directory: frontend
         run: bun install
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 8144d7b0..fe043f4f 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -50,8 +50,12 @@ jobs:
         with:
           python-version: "3.11"
 
+      # enable-cache persists ~/.cache/uv keyed on uv.lock.
       - name: Install uv
         uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: true
+          cache-dependency-glob: "uv.lock"
 
       # Node 22 is needed for --experimental-strip-types so node:test can
       # import .ts files directly from frontend/src/api/*.
@@ -63,13 +67,13 @@ jobs:
       - name: Setup Bun
         uses: oven-sh/setup-bun@v1
 
-      # Backend tests need ffmpeg (subprocess calls in fixtures) + the minimal
-      # apt deps pydub/imageio pull in. Model weights are mocked so no HF
-      # downloads happen.
+      # Backend tests need ffmpeg (subprocess calls in fixtures). Cache the
+      # resolved .debs so warm runs skip the apt-get update + install.
       - name: System deps (ffmpeg)
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y ffmpeg
+        uses: awalsh128/cache-apt-pkgs-action@latest
+        with:
+          packages: ffmpeg
+          version: 1.0
 
       - name: Install Python deps
         run: uv sync
@@ -77,6 +81,14 @@ jobs:
       - name: Run pytest
         run: uv run pytest tests/ -q --tb=short
 
+      - name: Cache bun deps
+        uses: actions/cache@v4
+        with:
+          path: ~/.bun/install/cache
+          key: ${{ runner.os }}-bun-${{ hashFiles('frontend/bun.lock', 'bun.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-bun-
+
       - name: Install frontend deps
         working-directory: frontend
         run: bun install
@@ -170,6 +182,14 @@ jobs:
             libasound2-dev ffmpeg
 
       # ── Frontend build ─────────────────────────────────────────────────
+      - name: Cache bun deps
+        uses: actions/cache@v4
+        with:
+          path: ~/.bun/install/cache
+          key: ${{ runner.os }}-bun-${{ hashFiles('frontend/bun.lock', 'bun.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-bun-
+
       - name: Install frontend deps
         working-directory: frontend
         run: bun install
diff --git a/backend/main.py b/backend/main.py
index efbaa9ac..773c668a 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -157,7 +157,7 @@ async def global_exception_handler(request: Request, exc: Exception):
 
 _allowed = os.environ.get(
     "OMNIVOICE_ALLOWED_ORIGINS",
-    "http://localhost:5173,http://127.0.0.1:5173,tauri://localhost,http://tauri.localhost",
+    "http://localhost:3901,http://127.0.0.1:3901,tauri://localhost,http://tauri.localhost",
 ).split(",")
 
 app.add_middleware(
@@ -191,8 +191,10 @@ if os.path.exists(frontend_path):
 else:
     @app.get("/")
     def _dev_fallback():
-        return RedirectResponse(url="http://localhost:5173")
+        return RedirectResponse(url="http://localhost:3901")
 
 if __name__ == "__main__":
     import uvicorn
-    uvicorn.run(app, host="0.0.0.0", port=8000)
+    # Port 3900 picked to dodge common 8000 conflicts (Django/Rails/Jupyter).
+    # Rust sidecar launcher in lib.rs::BACKEND_PORT must stay in sync.
+    uvicorn.run(app, host="0.0.0.0", port=3900)
diff --git a/frontend/src-tauri/src/lib.rs b/frontend/src-tauri/src/lib.rs
index ee3fabb7..6c12fdf3 100644
--- a/frontend/src-tauri/src/lib.rs
+++ b/frontend/src-tauri/src/lib.rs
@@ -7,7 +7,11 @@ use std::sync::Mutex;
 use std::time::Duration;
 use tauri::Manager;
 
-const BACKEND_PORT: u16 = 8000;
+// Unique port range (3900-3902) chosen to avoid common conflicts:
+// 8000 collides with Django/Rails/Jupyter/Airflow on most dev machines.
+// 3900 is the backend (FastAPI + uvicorn), 3901 is the Vite dev server,
+// 3902 is reserved for future IPC / websocket listeners.
+const BACKEND_PORT: u16 = 3900;
 
 // Version of the Astral `uv` binary we download at first run when no system
 // uv is on PATH. Pinned for reproducibility — bump alongside the uv.lock
diff --git a/frontend/src-tauri/tauri.conf.json b/frontend/src-tauri/tauri.conf.json
index 56242624..93a5bb0e 100644
--- a/frontend/src-tauri/tauri.conf.json
+++ b/frontend/src-tauri/tauri.conf.json
@@ -5,7 +5,7 @@
   "identifier": "com.debpalash.omnivoice-studio",
   "build": {
     "frontendDist": "../dist",
-    "devUrl": "http://localhost:5173",
+    "devUrl": "http://localhost:3901",
     "beforeDevCommand": "bun run dev",
     "beforeBuildCommand": "bun run build"
   },
diff --git a/frontend/src/App.jsx b/frontend/src/App.jsx
index ce119fd6..93c17c00 100644
--- a/frontend/src/App.jsx
+++ b/frontend/src/App.jsx
@@ -68,7 +68,7 @@ const doubleClickMaximize = () => {
  * We upload to the backend's /preview endpoint and serve via HTTP instead.
  * Falls back to createObjectURL for regular browsers.
  */
-const _PREVIEW_API = import.meta.env.VITE_OMNIVOICE_API || 'http://localhost:8000';
+const _PREVIEW_API = import.meta.env.VITE_OMNIVOICE_API || 'http://localhost:3900';
 const fileToMediaUrl = async (file, prevUrls) => {
   // Revoke previous blob URLs if they exist
   if (prevUrls?.videoUrl?.startsWith('blob:')) URL.revokeObjectURL(prevUrls.videoUrl);
diff --git a/frontend/src/api/client.ts b/frontend/src/api/client.ts
index 428b19fd..6c5dd74d 100644
--- a/frontend/src/api/client.ts
+++ b/frontend/src/api/client.ts
@@ -1,8 +1,9 @@
-// Backend always listens on localhost:8000 — both in dev (Vite @ 5173 talking
+// Backend always listens on localhost:3900 — both in dev (Vite @ 3901 talking
 // to a separate uvicorn) and in the built .app (Tauri webview @ tauri://localhost
-// talking to the bundled frozen backend sidecar). Relative fetches against
+// talking to the venv-bootstrapped sidecar). Relative fetches against
 // tauri://localhost don't reach the sidecar, so we hardcode the absolute host.
-export const API = 'http://localhost:8000';
+// Port 3900 chosen to avoid common 8000 conflicts (Django/Rails/Jupyter).
+export const API = 'http://localhost:3900';
 
 export class ApiError extends Error {
   status?: number;
diff --git a/frontend/vite.config.js b/frontend/vite.config.js
index f856cc27..582dd5b8 100644
--- a/frontend/vite.config.js
+++ b/frontend/vite.config.js
@@ -13,7 +13,7 @@ export default defineConfig({
     },
   },
   server: {
-    port: 5173,
+    port: 3901,
     strictPort: true,
     host: false,
     watch: {