fix(agent): fall back to an available project agent

src/agent/manager.ts

@@ -40,6 +40,40 @@ export async function getAvailableAgents(): Promise<AgentInfo[]> {
 
 const DEFAULT_AGENT = "build";
 
+function pickFallbackAgent(agents: AgentInfo[]): string {
+  const defaultAgent = agents.find((agent) => agent.name === DEFAULT_AGENT);
+  if (defaultAgent) {
+    return defaultAgent.name;
+  }
+
+  return agents[0]?.name ?? DEFAULT_AGENT;
+}
+
+export async function resolveProjectAgent(preferredAgent?: string): Promise<string> {
+  const requestedAgent = preferredAgent ?? getCurrentAgent() ?? DEFAULT_AGENT;
+  const project = getCurrentProject();
+
+  if (!project) {
+    return requestedAgent;
+  }
+
+  const agents = await getAvailableAgents();
+  if (agents.length === 0) {
+    return requestedAgent;
+  }
+
+  if (agents.some((agent) => agent.name === requestedAgent)) {
+    return requestedAgent;
+  }
+
+  const fallbackAgent = pickFallbackAgent(agents);
+  logger.warn(
+    `[AgentManager] Agent "${requestedAgent}" is not available for project ${project.worktree}. Falling back to "${fallbackAgent}".`,
+  );
+  setCurrentAgent(fallbackAgent);
+  return fallbackAgent;
+}
+
 /**
  * Get current agent from last session message or settings.
  * Falls back to "build" if nothing is stored.
@@ -50,11 +84,15 @@ export async function fetchCurrentAgent(): Promise<string> {
   const session = getCurrentSession();
   const project = getCurrentProject();
 
-  if (!session || !project) {
-    // No active session, return stored agent from settings
+  if (!project) {
+    // No active project, return stored agent from settings
     return storedAgent ?? DEFAULT_AGENT;
   }
 
+  if (!session) {
+    return resolveProjectAgent(storedAgent ?? DEFAULT_AGENT);
+  }
+
   try {
     const { data: messages, error } = await opencodeClient.session.messages({
       sessionID: session.id,
@@ -64,7 +102,7 @@ export async function fetchCurrentAgent(): Promise<string> {
 
     if (error || !messages || messages.length === 0) {
       logger.debug("[AgentManager] No messages found, using stored agent");
-      return storedAgent ?? DEFAULT_AGENT;
+      return resolveProjectAgent(storedAgent ?? DEFAULT_AGENT);
     }
 
     const lastAgent = messages[0].info.agent;
@@ -76,18 +114,18 @@ export async function fetchCurrentAgent(): Promise<string> {
       logger.debug(
         `[AgentManager] Using stored agent "${storedAgent}" instead of session agent "${lastAgent}"`,
       );
-      return storedAgent;
+      return resolveProjectAgent(storedAgent);
     }
 
     // No stored agent yet: sync from session history
     if (lastAgent && lastAgent !== storedAgent) {
       setCurrentAgent(lastAgent);
     }
 
-    return lastAgent || storedAgent || DEFAULT_AGENT;
+    return resolveProjectAgent(lastAgent || storedAgent || DEFAULT_AGENT);
   } catch (err) {
     logger.error("[AgentManager] Error fetching current agent:", err);
-    return storedAgent ?? DEFAULT_AGENT;
+    return resolveProjectAgent(storedAgent ?? DEFAULT_AGENT);
   }
 }
 

src/bot/commands/commands.ts

@@ -11,7 +11,7 @@ import { ingestSessionInfoForCache } from "../../session/cache-manager.js";
 import { interactionManager } from "../../interaction/manager.js";
 import type { InteractionState } from "../../interaction/types.js";
 import { summaryAggregator } from "../../summary/aggregator.js";
-import { getStoredAgent } from "../../agent/manager.js";
+import { getStoredAgent, resolveProjectAgent } from "../../agent/manager.js";
 import { getStoredModel } from "../../model/manager.js";
 import { safeBackgroundTask } from "../../utils/safe-background-task.js";
 import { logger } from "../../utils/logger.js";
@@ -426,7 +426,7 @@ async function executeCommand(
     return;
   }
 
-  const currentAgent = getStoredAgent();
+  const currentAgent = await resolveProjectAgent(getStoredAgent());
   const storedModel = getStoredModel();
   const model =
     storedModel.providerID && storedModel.modelID

src/bot/commands/new.ts

@@ -7,7 +7,7 @@ import { clearAllInteractionState } from "../../interaction/cleanup.js";
 import { summaryAggregator } from "../../summary/aggregator.js";
 import { pinnedMessageManager } from "../../pinned/manager.js";
 import { keyboardManager } from "../../keyboard/manager.js";
-import { getStoredAgent } from "../../agent/manager.js";
+import { getStoredAgent, resolveProjectAgent } from "../../agent/manager.js";
 import { getStoredModel } from "../../model/manager.js";
 import { formatVariantForButton } from "../../variant/manager.js";
 import { createMainKeyboard } from "../utils/keyboard.js";
@@ -68,10 +68,11 @@ export async function newCommand(ctx: CommandContext<Context>) {
     }
 
     // Get current state for keyboard
-    const currentAgent = getStoredAgent();
+    const currentAgent = await resolveProjectAgent(getStoredAgent());
     const currentModel = getStoredModel();
     const contextInfo = pinnedMessageManager.getContextInfo();
     const variantName = formatVariantForButton(currentModel.variant || "default");
+    keyboardManager.updateAgent(currentAgent);
     const keyboard = createMainKeyboard(
       currentAgent,
       currentModel,

src/bot/commands/projects.ts

@@ -7,7 +7,7 @@ import { clearSession } from "../../session/manager.js";
 import { summaryAggregator } from "../../summary/aggregator.js";
 import { pinnedMessageManager } from "../../pinned/manager.js";
 import { keyboardManager } from "../../keyboard/manager.js";
-import { getStoredAgent } from "../../agent/manager.js";
+import { getStoredAgent, resolveProjectAgent } from "../../agent/manager.js";
 import { getStoredModel } from "../../model/manager.js";
 import { formatVariantForButton } from "../../variant/manager.js";
 import { clearAllInteractionState } from "../../interaction/cleanup.js";
@@ -286,10 +286,11 @@ export async function handleProjectSelect(ctx: Context): Promise<boolean> {
     keyboardManager.updateContext(0, contextLimit);
 
     // Get current state for keyboard (with context = 0)
-    const currentAgent = getStoredAgent();
+    const currentAgent = await resolveProjectAgent(getStoredAgent());
     const currentModel = getStoredModel();
     const contextInfo = { tokensUsed: 0, tokensLimit: contextLimit };
     const variantName = formatVariantForButton(currentModel.variant || "default");
+    keyboardManager.updateAgent(currentAgent);
     const keyboard = createMainKeyboard(currentAgent, currentModel, contextInfo, variantName);
 
     const projectName = selectedProject.name || selectedProject.worktree;

src/bot/handlers/model.ts

@@ -5,7 +5,7 @@ import type { FavoriteModel, ModelInfo, ModelSelectionLists } from "../../model/
 import { formatVariantForButton } from "../../variant/manager.js";
 import { logger } from "../../utils/logger.js";
 import { createMainKeyboard } from "../utils/keyboard.js";
-import { getStoredAgent } from "../../agent/manager.js";
+import { getStoredAgent, resolveProjectAgent } from "../../agent/manager.js";
 import { pinnedMessageManager } from "../../pinned/manager.js";
 import { keyboardManager } from "../../keyboard/manager.js";
 import {
@@ -83,13 +83,15 @@ export async function handleModelSelect(ctx: Context): Promise<boolean> {
     await pinnedMessageManager.refreshContextLimit();
 
     // Update Reply Keyboard with new model and context
-    const currentAgent = getStoredAgent();
+    const currentAgent = await resolveProjectAgent(getStoredAgent());
     const contextInfo =
       pinnedMessageManager.getContextInfo() ??
       (pinnedMessageManager.getContextLimit() > 0
         ? { tokensUsed: 0, tokensLimit: pinnedMessageManager.getContextLimit() }
         : null);
 
+    keyboardManager.updateAgent(currentAgent);
+
     if (contextInfo) {
       keyboardManager.updateContext(contextInfo.tokensUsed, contextInfo.tokensLimit);
     }

src/bot/handlers/prompt.ts

@@ -4,7 +4,7 @@ import { opencodeClient } from "../../opencode/client.js";
 import { clearSession, getCurrentSession, setCurrentSession } from "../../session/manager.js";
 import { ingestSessionInfoForCache } from "../../session/cache-manager.js";
 import { getCurrentProject } from "../../settings/manager.js";
-import { getStoredAgent } from "../../agent/manager.js";
+import { getStoredAgent, resolveProjectAgent } from "../../agent/manager.js";
 import { getStoredModel } from "../../model/manager.js";
 import { formatVariantForButton } from "../../variant/manager.js";
 import { createMainKeyboard } from "../utils/keyboard.js";
@@ -156,10 +156,11 @@ export async function processUserPrompt(
       logger.error("[Bot] Error creating pinned message for new session:", err);
     }
 
-    const currentAgent = getStoredAgent();
+    const currentAgent = await resolveProjectAgent(getStoredAgent());
     const currentModel = getStoredModel();
     const contextInfo = pinnedMessageManager.getContextInfo();
     const variantName = formatVariantForButton(currentModel.variant || "default");
+    keyboardManager.updateAgent(currentAgent);
     const keyboard = createMainKeyboard(
       currentAgent,
       currentModel,
@@ -198,7 +199,7 @@ export async function processUserPrompt(
   }
 
   try {
-    const currentAgent = getStoredAgent();
+    const currentAgent = await resolveProjectAgent(getStoredAgent());
     const storedModel = getStoredModel();
 
     // Build parts array with text and files

src/bot/handlers/variant.ts

@@ -7,7 +7,7 @@ import {
   formatVariantForButton,
 } from "../../variant/manager.js";
 import { getStoredModel } from "../../model/manager.js";
-import { getStoredAgent } from "../../agent/manager.js";
+import { getStoredAgent, resolveProjectAgent } from "../../agent/manager.js";
 import { logger } from "../../utils/logger.js";
 import { keyboardManager } from "../../keyboard/manager.js";
 import { pinnedMessageManager } from "../../pinned/manager.js";
@@ -70,13 +70,15 @@ export async function handleVariantSelect(ctx: Context): Promise<boolean> {
     keyboardManager.updateVariant(variantId);
 
     // Build keyboard with correct context info
-    const currentAgent = getStoredAgent();
+    const currentAgent = await resolveProjectAgent(getStoredAgent());
     const contextInfo =
       pinnedMessageManager.getContextInfo() ??
       (pinnedMessageManager.getContextLimit() > 0
         ? { tokensUsed: 0, tokensLimit: pinnedMessageManager.getContextLimit() }
         : null);
 
+    keyboardManager.updateAgent(currentAgent);
+
     if (contextInfo) {
       keyboardManager.updateContext(contextInfo.tokensUsed, contextInfo.tokensLimit);
     }