feat: post-review backlog hardening (cancel/parser/stall/history/9502)

Five independent items from the post-review backlog. F1: Stop on an external
agent task now aborts the running child via a per-task AbortController registry
reachable from the cancel route, and finalizes the assistant message as
cancelled (fixing two latent bugs — catch blocks left the message streaming,
and warm success-paths wrote complete on an aborted turn); warm pools/worktrees
are preserved and the native path is unchanged. F2/F3: prune the tool-call
parser to its two load-bearing exports (unexport eight zero-caller symbols, add
a gate test for the <invoke>-as-text fallback) and route placeholder-rejection
logging through pino. F6: a 90s per-chunk stall-timeout wraps native inference's
fullStream via AbortSignal.any so a hung stream finalizes the message instead of
hanging — no retry (a pure classifyStreamError helper is added). F7: a read-only
view_session_history MCP tool (newest-N, chronological). F9: retire the unused
apps/coder/web :9502 fallback SPA, keeping every API/WS/health/MCP route.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/components/ChatInput.tsx

@@ -49,6 +49,9 @@ interface Props {
   // queues while busy). Omitting onStop falls back to a (disabled) Send button.
   generating?: boolean;
   onStop?: () => void | Promise<void>;
+  // F1: disable the Stop button while a cancel request is already in flight, so a
+  // rapid second click can't fire a duplicate Stop. Optional — BooChat omits it.
+  stopDisabled?: boolean;
   // Batch 9.6: slash-command dispatch. When the input parses to a known skill,
   // ChatInput calls this with the skill name + the post-name args (possibly
   // empty). Callers wire this to api.chats.skillInvoke. Omitting the prop
@@ -76,7 +79,7 @@ interface Props {
   modelContextLimit?: number | null;
 }
 
-export function ChatInput({ disabled, projectId, agentId, onAgentChange, sessionId, webSearchEnabled, onSend, onForceSend, generating, onStop, onSlashCommand, slashGroups, chatId, chatLabel, messages, modelContextLimit }: Props) {
+export function ChatInput({ disabled, projectId, agentId, onAgentChange, sessionId, webSearchEnabled, onSend, onForceSend, generating, onStop, stopDisabled, onSlashCommand, slashGroups, chatId, chatLabel, messages, modelContextLimit }: Props) {
   const { isMobile } = useViewport();
   const [value, setValue] = useState('');
   const [busy, setBusy] = useState(false);
@@ -701,10 +704,11 @@ export function ChatInput({ disabled, projectId, agentId, onAgentChange, session
                 return (
                   <Button
                     onClick={() => void onStop()}
+                    disabled={stopDisabled}
                     size="icon"
                     variant="outline"
                     aria-label="Stop generating"
-                    title="Stop generating"
+                    title={stopDisabled ? 'Stopping…' : 'Stop generating'}
                   >
                     <Square className="fill-current size-3.5" />
                   </Button>

apps/web/src/components/MessageBubble.tsx

@@ -780,6 +780,10 @@ export const MessageBubble = memo(function MessageBubble({
 
   const isStreaming = message.status === 'streaming';
   const failed = message.status === 'failed';
+  // F1 (D-10): a user Stop finalizes the turn as 'cancelled' — surface a muted
+  // "Stopped" label (not the red "message failed" — a deliberate Stop is not a
+  // failure), keeping whatever streamed before the abort.
+  const cancelled = message.status === 'cancelled';
   // v1.13.7: match the MessageList.flatten trim guard so a whitespace-only
   // assistant turn doesn't render an empty bubble + dangling ActionRow.
   const hasContent = message.content.trim().length > 0;
@@ -826,6 +830,7 @@ export const MessageBubble = memo(function MessageBubble({
           )}
         </div>
       )}
+      {cancelled && <div className="text-xs text-muted-foreground">Stopped</div>}
       {!isStreaming && (modelLabel || null) && (
         <span
           className="inline-flex w-fit items-center rounded-full border border-primary/25 bg-primary/10 px-2 py-0.5 text-[10px] font-mono text-primary/90"

apps/web/src/components/panes/CoderMessageList.tsx

@@ -10,7 +10,8 @@ export interface CoderMessageWire {
   id: string;
   role: 'user' | 'assistant' | 'system';
   content: string;
-  status?: 'streaming' | 'complete' | 'failed';
+  // F1: 'cancelled' — a user Stop / stall finalized the turn (renders "Stopped").
+  status?: 'streaming' | 'complete' | 'failed' | 'cancelled';
   model?: string | null;
   reasoning_text?: string;
   tool_calls?: CoderToolCallWire[];

apps/web/src/components/panes/CoderPane.tsx

@@ -29,7 +29,8 @@ interface CoderMessage {
   id: string;
   role: 'user' | 'assistant' | 'system';
   content: string;
-  status?: 'streaming' | 'complete' | 'failed';
+  // F1: 'cancelled' — a user Stop / stall finalized the turn (renders "Stopped").
+  status?: 'streaming' | 'complete' | 'failed' | 'cancelled';
   // model-attribution: which model produced this assistant message (chip).
   model?: string | null;
   reasoning_text?: string;
@@ -296,7 +297,10 @@ function useCoderMessages(sessionId: string, chatId: string | undefined, handler
               m.id === frame.message_id && m.role !== 'tool'
                 ? {
                     ...m,
-                    status: 'complete' as const,
+                    // F1 (D-8): the terminal frame carries an optional status —
+                    // 'cancelled' on a Stop/stall, 'failed' on error. Absent on the
+                    // normal path → defaults to 'complete'.
+                    status: ((frame as any).status ?? 'complete') as CoderMessage['status'],
                     model: (frame as any).model ?? (m as any).model ?? null,
                     ctx_used: (frame as any).ctx_used ?? (m as any).ctx_used ?? null,
                     ctx_max: (frame as any).ctx_max ?? (m as any).ctx_max ?? null,
@@ -669,6 +673,9 @@ export function CoderPane({
     onAgentLabelChange?.(parts.join(' · '));
   }, [agentConfig.provider, agentConfig.model, onAgentLabelChange]);
   const [activeTaskId, setActiveTaskId] = useState<string | null>(null);
+  // F1: true while the Stop POST is in flight — disables the Stop button and makes
+  // a rapid double-click a no-op (the abort is idempotent server-side regardless).
+  const [stopping, setStopping] = useState(false);
   const [permissionPrompt, setPermissionPrompt] = useState<PermissionPrompt | null>(null);
   const [permissionBusy, setPermissionBusy] = useState(false);
   const [providerCommands, setProviderCommands] = useState<AgentCommand[]>([]);
@@ -986,14 +993,17 @@ export function CoderPane({
 
   const handleStop = useCallback(async () => {
     const taskId = activeTaskId;
-    if (!taskId) return;
+    if (!taskId || stopping) return; // ignore a second Stop while the POST is in flight
+    setStopping(true);
     try {
       await api.coder.cancelTask(taskId);
       setActiveTaskId(null); // optimistic; WS/poll terminal-state also clears it
     } catch (err) {
       toast.error(err instanceof Error ? err.message : 'stop failed');
+    } finally {
+      setStopping(false);
     }
-  }, [activeTaskId]);
+  }, [activeTaskId, stopping]);
 
   // write-edit-robustness #4: reset the worktree to a message's checkpoint and
   // trim the transcript past it. The confirm lives in MessageBubble's ActionRow
@@ -1125,6 +1135,7 @@ export function CoderPane({
           onSend={handleChatInputSend}
           generating={generating}
           onStop={handleStop}
+          stopDisabled={stopping}
           onSlashCommand={handleChatInputSlash}
           slashGroups={slashGroups}
           chatId={chatId ?? undefined}