fix(coding-agent): backported pi-mono changes (1feccfed..b21b42d0)

packages/ai:
- feat: expose provider responseId on AssistantMessage
- feat: lazy-load provider modules for faster startup
- fix: hash foreign Responses API tool call IDs exceeding 64-char limit
- fix: ignore null chunks in openai-completions streams
- fix: keep image tool results inline for Gemini 3+ and Antigravity
- fix: correct Bedrock Claude 4.6 context window to 200k
- fix: support prompt caching for Bedrock application inference profiles
- fix: add OpenRouter reasoning payload format
- fix: ignore placeholder Vertex API keys
- fix: skip AJV validation in restricted runtimes
- fix: Anthropic OAuth client injection and responseId extraction
- fix: Codex incomplete/failed response status handling

packages/agent:
- fix: defer steering until after tool execution completes

packages/tui:
- feat: namespaced keybinding IDs with KeybindingsManager conflict detection
- feat: configurable select list column sizing (#2154 by @markusylisiurunen)
- fix: stream truncateToWidth for large strings
- fix: skip Termux height redraws
- fix: stop evicting unrelated default keybindings
- fix: resolve raw backspace ambiguity on Windows Terminal
- fix: clear stale scrollback on session switch (#2155 by @Perlence)
- fix: remove trailing markdown block spacing (#2152 by @markusylisiurunen)

packages/coding-agent:
- feat: add resizable share sidebar (#2435 by @dmmulroy)
- feat: emit OSC 133 command-executed marker
- feat: reload custom themes from disk watcher
- feat: add --fork session flag
- feat: file mutation queue for serialized writes
- feat: initial message consolidation utility
- fix: keybindings migrated to namespaced IDs
- fix: resolve waitForRetry() race when auto-retry produces tool calls
- fix: handle slash-delimited /model refs
- fix: refresh active model after provider updates
- fix: extended transient error patterns for retry

packages/coding-agent/src/export/html/template.css

@@ -2,6 +2,10 @@
 
     :root {
       --line-height: 18px; /* 12px font * 1.5 */
+      --sidebar-width: 400px;
+      --sidebar-min-width: 240px;
+      --sidebar-max-width: 840px;
+      --sidebar-resizer-width: 6px;
     }
 
     body {
@@ -12,6 +16,11 @@
       background: var(--body-bg);
     }
 
+    body.sidebar-resizing {
+      cursor: col-resize;
+      user-select: none;
+    }
+
     #app {
       display: flex;
       min-height: 100vh;
@@ -19,7 +28,9 @@
 
     /* Sidebar */
     #sidebar {
-      width: 400px;
+      width: var(--sidebar-width);
+      min-width: var(--sidebar-width);
+      max-width: var(--sidebar-width);
       background: var(--container-bg);
       flex-shrink: 0;
       display: flex;
@@ -203,8 +214,28 @@
       flex-shrink: 0;
     }
 
+    #sidebar-resizer {
+      width: var(--sidebar-resizer-width);
+      flex-shrink: 0;
+      position: sticky;
+      top: 0;
+      height: 100vh;
+      cursor: col-resize;
+      touch-action: none;
+      background: transparent;
+      border-right: 1px solid transparent;
+    }
+
+    #sidebar-resizer:hover,
+    body.sidebar-resizing #sidebar-resizer {
+      background: var(--selectedBg);
+      border-right-color: var(--dim);
+    }
+
     /* Main content */
     #content {
+      flex: 1;
+      min-width: 0;
       flex: 1;
       overflow-y: auto;
       padding: var(--line-height) calc(var(--line-height) * 2);
@@ -841,17 +872,19 @@
     @media (max-width: 900px) {
       #sidebar {
         position: fixed;
-        left: -400px;
-        width: 400px;
+        transform: translateX(-100%);
+        width: min(var(--sidebar-width), 100vw);
+        min-width: 0;
+        max-width: 100vw;
         top: 0;
         bottom: 0;
         height: 100vh;
         z-index: 99;
-        transition: left 0.3s;
+        transition: transform 0.3s;
       }
 
       #sidebar.open {
-        left: 0;
+        transform: translateX(0);
       }
 
       #sidebar-overlay.open {
@@ -866,6 +899,10 @@
         display: block;
       }
 
+      #sidebar-resizer {
+        display: none;
+      }
+
       #content {
         padding: var(--line-height) 16px;
       }
@@ -875,15 +912,8 @@
       }
     }
 
-    @media (max-width: 500px) {
-      #sidebar {
-        width: 100vw;
-        left: -100vw;
-      }
-    }
-
     @media print {
-      #sidebar, #sidebar-toggle { display: none !important; }
+      #sidebar, #sidebar-toggle, #sidebar-resizer { display: none !important; }
       body { background: white; color: black; }
       #content { max-width: none; }
     }