fix(opencode): improve tool robustness and session loop stability

packages/opencode/src/session/prompt.ts

@@ -274,13 +274,13 @@ export namespace SessionPrompt {
       let msgs = await MessageV2.filterCompacted(MessageV2.stream(sessionID))
 
       let lastUser: MessageV2.User | undefined
-      let lastAssistant: MessageV2.Assistant | undefined
+      let lastAssistant: MessageV2.WithParts | undefined
       let lastFinished: MessageV2.Assistant | undefined
       let tasks: (MessageV2.CompactionPart | MessageV2.SubtaskPart)[] = []
       for (let i = msgs.length - 1; i >= 0; i--) {
         const msg = msgs[i]
         if (!lastUser && msg.info.role === "user") lastUser = msg.info as MessageV2.User
-        if (!lastAssistant && msg.info.role === "assistant") lastAssistant = msg.info as MessageV2.Assistant
+        if (!lastAssistant && msg.info.role === "assistant") lastAssistant = msg
         if (!lastFinished && msg.info.role === "assistant" && msg.info.finish)
           lastFinished = msg.info as MessageV2.Assistant
         if (lastUser && lastFinished) break
@@ -292,12 +292,33 @@ export namespace SessionPrompt {
 
       if (!lastUser) throw new Error("No user message found in stream. This should never happen.")
       if (
-        lastAssistant?.finish &&
-        !["tool-calls", "unknown"].includes(lastAssistant.finish) &&
-        lastUser.id < lastAssistant.id
+        lastAssistant?.info.role === "assistant" &&
+        lastAssistant.info.finish &&
+        !["tool-calls", "unknown"].includes(lastAssistant.info.finish) &&
+        lastUser.id < lastAssistant.info.id
       ) {
-        log.info("exiting loop", { sessionID })
-        break
+        // Only exit if the last assistant message actually has text content or no tool calls
+        const hasText = lastAssistant.parts.some((p) => p.type === "text" && !p.synthetic)
+        const hasToolCalls = lastAssistant.parts.some((p) => p.type === "tool")
+
+        if (hasText || !hasToolCalls) {
+          log.info("exiting loop", {
+            sessionID,
+            finish: lastAssistant.info.finish,
+            lastUserID: lastUser.id,
+            lastAssistantID: lastAssistant.info.id,
+            hasText,
+            hasToolCalls,
+          })
+          break
+        }
+
+        log.info("continuing loop despite finish reason", {
+          sessionID,
+          finish: lastAssistant.info.finish,
+          hasText,
+          hasToolCalls,
+        })
       }
 
       step++

packages/opencode/src/tool/bash.ts

@@ -72,10 +72,20 @@ export const BashTool = Tool.define("bash", async () => {
         .string()
         .describe(
           "Clear, concise description of what this command does in 5-10 words. Examples:\nInput: ls\nOutput: Lists files in current directory\n\nInput: git status\nOutput: Shows working tree status\n\nInput: npm install\nOutput: Installs package dependencies\n\nInput: mkdir foo\nOutput: Creates directory 'foo'",
-        ),
+        )
+        .optional(),
     }),
+    formatValidationError(error) {
+      if (error instanceof z.ZodError) {
+        return `Invalid parameters for tool 'bash':\n${(error as any).errors
+          .map((e: z.ZodIssue) => `- ${e.path.join(".")}: ${e.message}`)
+          .join("\n")}\n\nMake sure to provide 'command' and a concise 'description' of what the command does.`
+      }
+      return `Invalid parameters for tool 'bash': ${error}`
+    },
     async execute(params, ctx) {
       const cwd = params.workdir || Instance.directory
+      const description = params.description || params.command
       if (params.timeout !== undefined && params.timeout < 0) {
         throw new Error(`Invalid timeout value: ${params.timeout}. Timeout must be a positive number.`)
       }
@@ -170,7 +180,7 @@ export const BashTool = Tool.define("bash", async () => {
       ctx.metadata({
         metadata: {
           output: "",
-          description: params.description,
+          description,
         },
       })
 
@@ -180,7 +190,7 @@ export const BashTool = Tool.define("bash", async () => {
           metadata: {
             // truncate the metadata to avoid GIANT blobs of data (has nothing to do w/ what agent can access)
             output: output.length > MAX_METADATA_LENGTH ? output.slice(0, MAX_METADATA_LENGTH) + "\n\n..." : output,
-            description: params.description,
+            description,
           },
         })
       }
@@ -244,14 +254,16 @@ export const BashTool = Tool.define("bash", async () => {
         output += "\n\n<bash_metadata>\n" + resultMetadata.join("\n") + "\n</bash_metadata>"
       }
 
+      const finalOutput = output.trim() || "(Command executed successfully with no output)"
+
       return {
-        title: params.description,
+        title: description,
         metadata: {
           output: output.length > MAX_METADATA_LENGTH ? output.slice(0, MAX_METADATA_LENGTH) + "\n\n..." : output,
           exit: proc.exitCode,
-          description: params.description,
+          description,
         },
-        output,
+        output: finalOutput,
       }
     },
   }

packages/opencode/src/tool/ls.ts

@@ -107,7 +107,8 @@ export const ListTool = Tool.define("list", {
       return output
     }
 
-    const output = `${searchPath}/\n` + renderDir(".", 0)
+    const output =
+      files.length > 0 ? `${searchPath}/\n` + renderDir(".", 0) : `(No files found in directory: ${searchPath})`
 
     return {
       title: path.relative(Instance.worktree, searchPath),

packages/opencode/src/tool/task.ts

@@ -13,7 +13,7 @@ import { Config } from "../config/config"
 import { PermissionNext } from "@/permission/next"
 
 const parameters = z.object({
-  description: z.string().describe("A short (3-5 words) description of the task"),
+  description: z.string().describe("A short (3-5 words) description of the task").optional(),
   prompt: z.string().describe("The task for the agent to perform"),
   subagent_type: z.string().describe("The type of specialized agent to use for this task"),
   session_id: z.string().describe("Existing Task session to continue").optional(),
@@ -38,8 +38,17 @@ export const TaskTool = Tool.define("task", async (ctx) => {
   return {
     description,
     parameters,
+    formatValidationError(error) {
+      if (error instanceof z.ZodError) {
+        return `Invalid parameters for tool 'task':\n${(error as any).errors
+          .map((e: z.ZodIssue) => `- ${e.path.join(".")}: ${e.message}`)
+          .join("\n")}\n\nMake sure to provide 'prompt', 'subagent_type' and a concise 'description'.`
+      }
+      return `Invalid parameters for tool 'task': ${error}`
+    },
     async execute(params: z.infer<typeof parameters>, ctx) {
       const config = await Config.get()
+      const taskDescription = params.description || "Task"
 
       // Skip permission check when user explicitly invoked via @ or command subtask
       if (!ctx.extra?.bypassAgentCheck) {
@@ -48,7 +57,7 @@ export const TaskTool = Tool.define("task", async (ctx) => {
           patterns: [params.subagent_type],
           always: ["*"],
           metadata: {
-            description: params.description,
+            description: taskDescription,
             subagent_type: params.subagent_type,
           },
         })
@@ -67,7 +76,7 @@ export const TaskTool = Tool.define("task", async (ctx) => {
 
         return await Session.create({
           parentID: ctx.sessionID,
-          title: params.description + ` (@${agent.name} subagent)`,
+          title: taskDescription + ` (@${agent.name} subagent)`,
           permission: [
             {
               permission: "todowrite",
@@ -100,7 +109,7 @@ export const TaskTool = Tool.define("task", async (ctx) => {
       if (msg.info.role !== "assistant") throw new Error("Not an assistant message")
 
       ctx.metadata({
-        title: params.description,
+        title: taskDescription,
         metadata: {
           sessionId: session.id,
         },
@@ -122,7 +131,7 @@ export const TaskTool = Tool.define("task", async (ctx) => {
           },
         }
         ctx.metadata({
-          title: params.description,
+          title: taskDescription,
           metadata: {
             summary: Object.values(parts).sort((a, b) => a.id.localeCompare(b.id)),
             sessionId: session.id,
@@ -176,7 +185,7 @@ export const TaskTool = Tool.define("task", async (ctx) => {
       const output = text + "\n\n" + ["<task_metadata>", `session_id: ${session.id}`, "</task_metadata>"].join("\n")
 
       return {
-        title: params.description,
+        title: taskDescription,
         metadata: {
           summary,
           sessionId: session.id,

packages/opencode/src/tool/write.ts

@@ -21,6 +21,14 @@ export const WriteTool = Tool.define("write", {
     content: z.string().describe("The content to write to the file"),
     filePath: z.string().describe("The absolute path to the file to write (must be absolute, not relative)"),
   }),
+  formatValidationError(error) {
+    if (error instanceof z.ZodError) {
+      return `Invalid parameters for tool 'write':\n${(error as any).errors
+        .map((e: z.ZodIssue) => `- ${e.path.join(".")}: ${e.message}`)
+        .join("\n")}\n\nMake sure to provide 'content' and 'filePath'.`
+    }
+    return `Invalid parameters for tool 'write': ${error}`
+  },
   async execute(params, ctx) {
     const filepath = path.isAbsolute(params.filePath) ? params.filePath : path.join(Instance.directory, params.filePath)
     await assertExternalDirectory(ctx, filepath)