diff --git a/ui-tui-opentui-v2/eslint.config.mjs b/ui-tui-opentui-v2/eslint.config.mjs
index 88287cc2234..a98b35d61db 100644
--- a/ui-tui-opentui-v2/eslint.config.mjs
+++ b/ui-tui-opentui-v2/eslint.config.mjs
@@ -24,9 +24,10 @@ export default tseslint.config(
       "@typescript-eslint/no-explicit-any": "error",
       "@typescript-eslint/consistent-type-imports": ["error", { prefer: "type-imports" }],
       "@typescript-eslint/no-unused-vars": "off",
+      "@typescript-eslint/no-non-null-assertion": "error",
       "unused-imports/no-unused-imports": "error",
       "unused-imports/no-unused-vars": [
-        "warn",
+        "error",
         { vars: "all", varsIgnorePattern: "^_", args: "after-used", argsIgnorePattern: "^_" },
       ],
 
@@ -56,6 +57,13 @@ export default tseslint.config(
       "@typescript-eslint/require-await": "warn",
     },
   },
+  {
+    // Tests keep their `!` non-null assertions (fixtures with known-present data).
+    files: ["**/*.test.ts", "**/*.test.tsx"],
+    rules: {
+      "@typescript-eslint/no-non-null-assertion": "off",
+    },
+  },
   {
     // The eslint flat config is JS-only; the typed parser project service does not
     // cover it, so disable type-checking there to avoid parser errors.
diff --git a/ui-tui-opentui-v2/src/boundary/gateway/client.ts b/ui-tui-opentui-v2/src/boundary/gateway/client.ts
index dcb2dbbef91..b6831ce2376 100644
--- a/ui-tui-opentui-v2/src/boundary/gateway/client.ts
+++ b/ui-tui-opentui-v2/src/boundary/gateway/client.ts
@@ -170,8 +170,9 @@ export class RawGatewayClient {
     const frame = msg as { id?: unknown; method?: unknown; params?: unknown; result?: unknown; error?: unknown }
 
     // Response: has an id matching a pending request.
-    if (typeof frame.id === 'string' && this.pending.has(frame.id)) {
-      const p = this.pending.get(frame.id)!
+    const pending = typeof frame.id === 'string' ? this.pending.get(frame.id) : undefined
+    if (typeof frame.id === 'string' && pending) {
+      const p = pending
       this.pending.delete(frame.id)
       if (frame.error) {
         const err = frame.error as { code?: number; message?: string }
diff --git a/ui-tui-opentui-v2/src/logic/theme.ts b/ui-tui-opentui-v2/src/logic/theme.ts
index 5892a24d77d..e273a98f345 100644
--- a/ui-tui-opentui-v2/src/logic/theme.ts
+++ b/ui-tui-opentui-v2/src/logic/theme.ts
@@ -81,8 +81,9 @@ export interface GatewaySkin {
 
 function parseHex(h: string): [number, number, number] | null {
   const m = /^#?([0-9a-f]{6})$/i.exec(h)
-  if (!m) return null
-  const n = parseInt(m[1]!, 16)
+  const hex = m?.[1]
+  if (!hex) return null
+  const n = parseInt(hex, 16)
   return [(n >> 16) & 0xff, (n >> 8) & 0xff, n & 0xff]
 }
 
@@ -124,10 +125,12 @@ function xtermEightBitRgb(colorNumber: number): [number, number, number] {
   }
   if (colorNumber >= 16) {
     const offset = colorNumber - 16
+    // Indices are `% 6`, always within XTERM_6_LEVELS' bounds; `?? 0` only
+    // satisfies noUncheckedIndexedAccess and is never actually reached.
     return [
-      XTERM_6_LEVELS[Math.floor(offset / 36) % 6]!,
-      XTERM_6_LEVELS[Math.floor(offset / 6) % 6]!,
-      XTERM_6_LEVELS[offset % 6]!
+      XTERM_6_LEVELS[Math.floor(offset / 36) % 6] ?? 0,
+      XTERM_6_LEVELS[Math.floor(offset / 6) % 6] ?? 0,
+      XTERM_6_LEVELS[offset % 6] ?? 0
     ]
   }
   return [0, 0, 0]
@@ -327,13 +330,20 @@ function backgroundLuminance(raw: string): null | number {
   const v = raw.trim().toLowerCase()
   if (!v) return null
   const hex = v.startsWith('#') ? v.slice(1) : v
-  const rgb = HEX_6_RE.test(hex)
-    ? [parseInt(hex.slice(0, 2), 16), parseInt(hex.slice(2, 4), 16), parseInt(hex.slice(4, 6), 16)]
-    : HEX_3_RE.test(hex)
-      ? [parseInt(hex[0]! + hex[0]!, 16), parseInt(hex[1]! + hex[1]!, 16), parseInt(hex[2]! + hex[2]!, 16)]
-      : null
+  let rgb: [number, number, number] | null = null
+  if (HEX_6_RE.test(hex)) {
+    rgb = [parseInt(hex.slice(0, 2), 16), parseInt(hex.slice(2, 4), 16), parseInt(hex.slice(4, 6), 16)]
+  } else if (HEX_3_RE.test(hex)) {
+    // `charAt` always returns a string (vs index access, which is `string |
+    // undefined` under noUncheckedIndexedAccess); the regex guarantees 3 chars.
+    const r = hex.charAt(0)
+    const g = hex.charAt(1)
+    const b = hex.charAt(2)
+    rgb = [parseInt(r + r, 16), parseInt(g + g, 16), parseInt(b + b, 16)]
+  }
   if (!rgb) return null
-  return (0.2126 * rgb[0]! + 0.7152 * rgb[1]! + 0.0722 * rgb[2]!) / 255
+  const [r, g, b] = rgb
+  return (0.2126 * r + 0.7152 * g + 0.0722 * b) / 255
 }
 
 /** Pick light vs dark with ordered, explainable env signals (mirror Ink). */
diff --git a/ui-tui-opentui-v2/src/view/homeHint.tsx b/ui-tui-opentui-v2/src/view/homeHint.tsx
index 482495b8370..76fdfae9582 100644
--- a/ui-tui-opentui-v2/src/view/homeHint.tsx
+++ b/ui-tui-opentui-v2/src/view/homeHint.tsx
@@ -101,18 +101,22 @@ export function HomeHint(props: { store: SessionStore }) {
       {/* session info block: model · Nous Research / dir / Session id */}
       <box style={{ flexDirection: 'column' }}>
         <Show when={info().model}>
-          <text selectable={false}>
-            <span style={{ fg: theme().color.accent }}>{shortModel(info().model!)}</span>
-            <span style={{ fg: theme().color.muted }}> · Nous Research</span>
-          </text>
+          {model => (
+            <text selectable={false}>
+              <span style={{ fg: theme().color.accent }}>{shortModel(model())}</span>
+              <span style={{ fg: theme().color.muted }}> · Nous Research</span>
+            </text>
+          )}
         </Show>
         <Show when={info().cwd}>
-          <text selectable={false}>
-            <span style={{ fg: theme().color.muted }}>{shortCwd(info().cwd!)}</span>
-            <Show when={info().branch}>
-              <span style={{ fg: theme().color.muted }}>{` (${info().branch})`}</span>
-            </Show>
-          </text>
+          {cwd => (
+            <text selectable={false}>
+              <span style={{ fg: theme().color.muted }}>{shortCwd(cwd())}</span>
+              <Show when={info().branch}>
+                <span style={{ fg: theme().color.muted }}>{` (${info().branch})`}</span>
+              </Show>
+            </text>
+          )}
         </Show>
         <Show when={props.store.state.sessionId}>
           <text selectable={false}>
diff --git a/ui-tui-opentui-v2/src/view/reasoningPart.tsx b/ui-tui-opentui-v2/src/view/reasoningPart.tsx
index a1690915d06..72f72f0e662 100644
--- a/ui-tui-opentui-v2/src/view/reasoningPart.tsx
+++ b/ui-tui-opentui-v2/src/view/reasoningPart.tsx
@@ -24,8 +24,8 @@ function reasoningSummary(text: string): { title?: string; body: string } {
   const s = (text ?? '').replace('[REDACTED]', '').trim()
   const m = s.match(/^\*\*([^*\n]+)\*\*(?:\r?\n\r?\n|$)/)
   const title = m?.[1]?.trim()
-  if (!title) return { body: s }
-  return { title, body: s.slice(m![0].length).trimStart() }
+  if (!m || !title) return { body: s }
+  return { title, body: s.slice(m[0].length).trimStart() }
 }
 
 export function ReasoningPart(props: { text: string; streaming?: boolean }) {
diff --git a/ui-tui-opentui-v2/src/view/statusBar.tsx b/ui-tui-opentui-v2/src/view/statusBar.tsx
index 1cc13c6c255..281ddabb37b 100644
--- a/ui-tui-opentui-v2/src/view/statusBar.tsx
+++ b/ui-tui-opentui-v2/src/view/statusBar.tsx
@@ -71,18 +71,25 @@ export function StatusBar(props: { store: SessionStore }) {
   const dotColor = () =>
     info().running ? theme().color.statusWarn : props.store.state.ready ? theme().color.statusGood : theme().color.muted
 
-  const model = () => (info().model ? shortModel(info().model!) : '')
+  const model = () => {
+    const m = info().model
+    return m ? shortModel(m) : ''
+  }
   const effort = () => effortSuffix(info().effort, info().fast)
   const pct = () => info().contextPercent
 
   // Progressive disclosure budget (the row is `width - 2` after the box padding).
   // left = dot+space+model+effort ; the context bar shows only when there's room.
   const showBar = createMemo(() => pct() !== undefined && dims().width >= 64)
-  const ctxText = () => (showBar() ? `${ctxBar(pct()!, CTX_BAR_CELLS)} ${pct()}%` : '')
+  const ctxText = () => {
+    const p = pct()
+    return showBar() && p !== undefined ? `${ctxBar(p, CTX_BAR_CELLS)} ${p}%` : ''
+  }
 
   // Right side: cwd (branch), left-truncated to whatever the left side leaves.
   const cwdFull = createMemo(() => {
-    const c = info().cwd ? shortCwd(info().cwd!) : ''
+    const cwd = info().cwd
+    const c = cwd ? shortCwd(cwd) : ''
     if (!c) return ''
     return info().branch ? `${c} (${info().branch})` : c
   })
@@ -111,9 +118,11 @@ export function StatusBar(props: { store: SessionStore }) {
             <span style={{ fg: theme().color.muted }}>{effort()}</span>
           </Show>
           <Show when={showBar()}>
-            {/* a dim divider segments the bar into scannable fields (item 8) */}
+            {/* a dim divider segments the bar into scannable fields (item 8).
+                showBar() already guarantees pct() is defined; `?? 0` only
+                satisfies the type and is never reached. */}
             <span style={{ fg: theme().color.border }}>{'  │  '}</span>
-            <span style={{ fg: ctxColor(pct()!) }}>{ctxBar(pct()!, CTX_BAR_CELLS)}</span>
+            <span style={{ fg: ctxColor(pct() ?? 0) }}>{ctxBar(pct() ?? 0, CTX_BAR_CELLS)}</span>
             <span style={{ fg: theme().color.statusFg }}>{` ${pct()}%`}</span>
           </Show>
         </text>
diff --git a/ui-tui-opentui-v2/src/view/toolPart.tsx b/ui-tui-opentui-v2/src/view/toolPart.tsx
index 5dc1a4c4d6f..bbdac8949a5 100644
--- a/ui-tui-opentui-v2/src/view/toolPart.tsx
+++ b/ui-tui-opentui-v2/src/view/toolPart.tsx
@@ -69,8 +69,9 @@ export function ToolPart(props: { part: ToolPartState }) {
     const e = argEntries()
     if (argsObj() === undefined) return !!props.part.argsText // unparsed → show raw
     if (e.length === 0) return false
-    if (e.length === 1) {
-      const v = e[0]![1]
+    const only = e.length === 1 ? e[0] : undefined
+    if (only) {
+      const v = only[1]
       const vs = (typeof v === 'string' ? v : JSON.stringify(v)).trim()
       return vs !== (props.part.argsPreview ?? '').trim()
     }
@@ -118,7 +119,7 @@ export function ToolPart(props: { part: ToolPartState }) {
               </span>
             </Show>
             <Show when={!running() && props.part.duration !== undefined}>
-              <span style={{ fg: theme().color.muted }}>{`  · ${fmtDuration(props.part.duration!)}`}</span>
+              <span style={{ fg: theme().color.muted }}>{`  · ${fmtDuration(props.part.duration ?? 0)}`}</span>
             </Show>
             <Show when={collapsible() && !expanded() && lines().length > 1}>
               <span style={{ fg: theme().color.muted }}>{`  (${lines().length} lines)`}</span>
diff --git a/ui-tui-opentui-v2/tsconfig.json b/ui-tui-opentui-v2/tsconfig.json
index b3b8db287ca..b0985fae5b6 100644
--- a/ui-tui-opentui-v2/tsconfig.json
+++ b/ui-tui-opentui-v2/tsconfig.json
@@ -13,6 +13,8 @@
     "noUncheckedIndexedAccess": true,
     "noFallthroughCasesInSwitch": true,
     "noImplicitOverride": true,
+    "noUnusedLocals": true,
+    "noImplicitReturns": true,
     "jsx": "preserve",
     "jsxImportSource": "@opentui/solid",
     "types": ["bun"],