fix: improve plugin system robustness — agent/command resolution, async errors, hook timing, two-phase init

packages/opencode/src/plugin/index.ts

@@ -136,7 +136,11 @@ export namespace Plugin {
 
             // Notify plugins of current config
             for (const hook of hooks) {
-              await (hook as any).config?.(cfg)
+              try {
+                await (hook as any).config?.(cfg)
+              } catch (err) {
+                log.error("plugin config hook failed", { error: err })
+              }
             }
           })
 

packages/opencode/src/server/routes/session.ts

@@ -19,6 +19,8 @@ import { PermissionID } from "@/permission/schema"
 import { ModelID, ProviderID } from "@/provider/schema"
 import { errors } from "../error"
 import { lazy } from "../../util/lazy"
+import { Bus } from "../../bus"
+import { NamedError } from "@opencode-ai/util/error"
 
 const log = Log.create({ service: "server" })
 
@@ -846,7 +848,13 @@ export const SessionRoutes = lazy(() =>
         return stream(c, async () => {
           const sessionID = c.req.valid("param").sessionID
           const body = c.req.valid("json")
-          SessionPrompt.prompt({ ...body, sessionID })
+          SessionPrompt.prompt({ ...body, sessionID }).catch((err) => {
+            log.error("prompt_async failed", { sessionID, error: err })
+            Bus.publish(Session.Event.Error, {
+              sessionID,
+              error: new NamedError.Unknown({ message: err instanceof Error ? err.message : String(err) }).toObject(),
+            })
+          })
         })
       },
     )

packages/opencode/src/session/prompt.ts

@@ -418,6 +418,16 @@ export namespace SessionPrompt {
         )
         let executionError: Error | undefined
         const taskAgent = await Agent.get(task.agent)
+        if (!taskAgent) {
+          const available = await Agent.list().then((agents) => agents.filter((a) => !a.hidden).map((a) => a.name))
+          const hint = available.length ? ` Available agents: ${available.join(", ")}` : ""
+          const error = new NamedError.Unknown({ message: `Agent not found: "${task.agent}".${hint}` })
+          Bus.publish(Session.Event.Error, {
+            sessionID,
+            error: error.toObject(),
+          })
+          throw error
+        }
         const taskCtx: Tool.Context = {
           agent: task.agent,
           messageID: assistantMessage.id,
@@ -560,6 +570,16 @@ export namespace SessionPrompt {
 
       // normal processing
       const agent = await Agent.get(lastUser.agent)
+      if (!agent) {
+        const available = await Agent.list().then((agents) => agents.filter((a) => !a.hidden).map((a) => a.name))
+        const hint = available.length ? ` Available agents: ${available.join(", ")}` : ""
+        const error = new NamedError.Unknown({ message: `Agent not found: "${lastUser.agent}".${hint}` })
+        Bus.publish(Session.Event.Error, {
+          sessionID,
+          error: error.toObject(),
+        })
+        throw error
+      }
       const maxSteps = agent.steps ?? Infinity
       const isLastStep = step >= maxSteps
       msgs = await insertReminders({
@@ -964,7 +984,18 @@ export namespace SessionPrompt {
   }
 
   async function createUserMessage(input: PromptInput) {
-    const agent = await Agent.get(input.agent ?? (await Agent.defaultAgent()))
+    const agentName = input.agent || (await Agent.defaultAgent())
+    const agent = await Agent.get(agentName)
+    if (!agent) {
+      const available = await Agent.list().then((agents) => agents.filter((a) => !a.hidden).map((a) => a.name))
+      const hint = available.length ? ` Available agents: ${available.join(", ")}` : ""
+      const error = new NamedError.Unknown({ message: `Agent not found: "${agentName}".${hint}` })
+      Bus.publish(Session.Event.Error, {
+        sessionID: input.sessionID,
+        error: error.toObject(),
+      })
+      throw error
+    }
 
     const model = input.model ?? agent.model ?? (await lastModel(input.sessionID))
     const full =
@@ -1531,6 +1562,16 @@ NOTE: At any point in time through this workflow you should feel free to ask the
       await SessionRevert.cleanup(session)
     }
     const agent = await Agent.get(input.agent)
+    if (!agent) {
+      const available = await Agent.list().then((agents) => agents.filter((a) => !a.hidden).map((a) => a.name))
+      const hint = available.length ? ` Available agents: ${available.join(", ")}` : ""
+      const error = new NamedError.Unknown({ message: `Agent not found: "${input.agent}".${hint}` })
+      Bus.publish(Session.Event.Error, {
+        sessionID: input.sessionID,
+        error: error.toObject(),
+      })
+      throw error
+    }
     const model = input.model ?? agent.model ?? (await lastModel(input.sessionID))
     const userMsg: MessageV2.User = {
       id: MessageID.ascending(),
@@ -1783,7 +1824,14 @@ NOTE: At any point in time through this workflow you should feel free to ask the
     log.info("command", input)
     const command = await Command.get(input.command)
     if (!command) {
-      throw new NamedError.Unknown({ message: `Command not found: "${input.command}"` })
+      const available = await Command.list().then((cmds) => cmds.map((c) => c.name))
+      const hint = available.length ? ` Available commands: ${available.join(", ")}` : ""
+      const error = new NamedError.Unknown({ message: `Command not found: "${input.command}".${hint}` })
+      Bus.publish(Session.Event.Error, {
+        sessionID: input.sessionID,
+        error: error.toObject(),
+      })
+      throw error
     }
     const agentName = command.agent ?? input.agent ?? (await Agent.defaultAgent())
 

packages/opencode/test/plugin/auth-override.test.ts

@@ -54,3 +54,19 @@ describe("plugin.auth-override", () => {
     expect(plainMethods[ProviderID.make("github-copilot")][0].label).not.toBe("Test Override Auth")
   }, 30000) // Increased timeout for plugin installation
 })
+
+const file = path.join(import.meta.dir, "../../src/plugin/index.ts")
+
+describe("plugin.config-hook-error-isolation", () => {
+  test("config hooks are individually error-isolated in the layer factory", async () => {
+    const src = await Bun.file(file).text()
+
+    // The config hook try/catch lives in the InstanceState factory (layer definition),
+    // not in init() which now just delegates to the Effect service.
+    expect(src).toContain("plugin config hook failed")
+
+    const pattern =
+      /for\s*\(const hook of hooks\)\s*\{[\s\S]*?try\s*\{[\s\S]*?\.config\?\.\([\s\S]*?\}\s*catch\s*\(err\)\s*\{[\s\S]*?plugin config hook failed[\s\S]*?\}/
+    expect(pattern.test(src)).toBe(true)
+  })
+})

packages/opencode/test/server/session-messages.test.ts

@@ -117,3 +117,16 @@ describe("session messages endpoint", () => {
     })
   })
 })
+
+describe("session.prompt_async error handling", () => {
+  test("prompt_async route has error handler for detached prompt call", async () => {
+    const src = await Bun.file(path.join(import.meta.dir, "../../src/server/routes/session.ts")).text()
+    const start = src.indexOf('"/:sessionID/prompt_async"')
+    const end = src.indexOf('"/:sessionID/command"', start)
+    expect(start).toBeGreaterThan(-1)
+    expect(end).toBeGreaterThan(start)
+    const route = src.slice(start, end)
+    expect(route).toContain(".catch(")
+    expect(route).toContain("Bus.publish(Session.Event.Error")
+  })
+})

packages/opencode/test/session/prompt.test.ts

@@ -1,5 +1,6 @@
 import path from "path"
 import { describe, expect, test } from "bun:test"
+import { NamedError } from "@opencode-ai/util/error"
 import { fileURLToPath } from "url"
 import { Instance } from "../../src/project/instance"
 import { ModelID, ProviderID } from "../../src/provider/schema"
@@ -210,3 +211,78 @@ describe("session.prompt agent variant", () => {
     }
   })
 })
+
+describe("session.agent-resolution", () => {
+  test("unknown agent throws typed error", async () => {
+    await using tmp = await tmpdir({ git: true })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const session = await Session.create({})
+        const err = await SessionPrompt.prompt({
+          sessionID: session.id,
+          agent: "nonexistent-agent-xyz",
+          noReply: true,
+          parts: [{ type: "text", text: "hello" }],
+        }).then(
+          () => undefined,
+          (e) => e,
+        )
+        expect(err).toBeDefined()
+        expect(err).not.toBeInstanceOf(TypeError)
+        expect(NamedError.Unknown.isInstance(err)).toBe(true)
+        if (NamedError.Unknown.isInstance(err)) {
+          expect(err.data.message).toContain('Agent not found: "nonexistent-agent-xyz"')
+        }
+      },
+    })
+  }, 30000)
+
+  test("unknown agent error includes available agent names", async () => {
+    await using tmp = await tmpdir({ git: true })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const session = await Session.create({})
+        const err = await SessionPrompt.prompt({
+          sessionID: session.id,
+          agent: "nonexistent-agent-xyz",
+          noReply: true,
+          parts: [{ type: "text", text: "hello" }],
+        }).then(
+          () => undefined,
+          (e) => e,
+        )
+        expect(NamedError.Unknown.isInstance(err)).toBe(true)
+        if (NamedError.Unknown.isInstance(err)) {
+          expect(err.data.message).toContain("build")
+        }
+      },
+    })
+  }, 30000)
+
+  test("unknown command throws typed error with available names", async () => {
+    await using tmp = await tmpdir({ git: true })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const session = await Session.create({})
+        const err = await SessionPrompt.command({
+          sessionID: session.id,
+          command: "nonexistent-command-xyz",
+          arguments: "",
+        }).then(
+          () => undefined,
+          (e) => e,
+        )
+        expect(err).toBeDefined()
+        expect(err).not.toBeInstanceOf(TypeError)
+        expect(NamedError.Unknown.isInstance(err)).toBe(true)
+        if (NamedError.Unknown.isInstance(err)) {
+          expect(err.data.message).toContain('Command not found: "nonexistent-command-xyz"')
+          expect(err.data.message).toContain("init")
+        }
+      },
+    })
+  }, 30000)
+})