import { PermissionV1 } from "@codilore/core/v1/permission"
import path from "path"
import { SessionV1 } from "@codilore/core/v1/session"
import os from "os"
import { SessionID, MessageID, PartID } from "./schema"
import { MessageV2 } from "./message-v2"
import { Log } from "@codilore/core/util/log"
import { SessionRevert } from "./revert"
import { Session } from "./session"
import { Agent } from "../agent/agent"
import { Provider } from "@/provider/provider"

import { type Tool as AITool, tool, jsonSchema } from "ai"
import type { JSONSchema7 } from "@ai-sdk/provider"
import { SessionCompaction } from "./compaction"
import { SystemPrompt } from "./system"
import { Instruction } from "./instruction"
import { Plugin } from "../plugin"
import MAX_STEPS from "../session/prompt/max-steps.txt"
import { ToolRegistry } from "@/tool/registry"
import { MCP } from "../mcp"
import { LSP } from "@/lsp/lsp"
import { ulid } from "ulid"
import { ChildProcess, ChildProcessSpawner } from "effect/unstable/process"
import { CrossSpawnSpawner } from "@codilore/core/cross-spawn-spawner"
import * as Stream from "effect/Stream"
import { Command } from "../command"
import { pathToFileURL, fileURLToPath } from "url"
import { Config } from "@/config/config"
import { ConfigMarkdown } from "@/config/markdown"
import { SessionSummary } from "./summary"
import { NamedError } from "@codilore/core/util/error"
import { SessionProcessor } from "./processor"
import { Tool } from "@/tool/tool"
import { Permission } from "@/permission"
import { SessionStatus } from "./status"
import { LLM } from "./llm"
import { Shell } from "@/shell/shell"
import { ShellID } from "@/tool/shell/id"
import { FSUtil } from "@codilore/core/fs-util"
import { Truncate } from "@/tool/truncate"
import { Image } from "@/image/image"
import { decodeDataUrl } from "@/util/data-url"
import { Process } from "@/util/process"
import { Cause, Effect, Exit, Latch, Layer, Option, Scope, Context, Schema, Types } from "effect"
import * as EffectLogger from "@codilore/core/effect/logger"
import { InstanceState } from "@/effect/instance-state"
import { TaskTool, type TaskPromptOps } from "@/tool/task"
import { SessionRunState } from "./run-state"
import { RuntimeFlags } from "@/effect/runtime-flags"
import { EventV2Bridge } from "@/event-v2-bridge"
import { Database } from "@codilore/core/database/database"
import { SessionEvent } from "@codilore/core/session/event"
import { ModelV2 } from "@codilore/core/model"
import { ProviderV2 } from "@codilore/core/provider"
import { AgentAttachment, FileAttachment, Prompt, ReferenceAttachment, Source } from "@codilore/core/session/prompt"
import { Reference } from "@/reference/reference"
import * as DateTime from "effect/DateTime"
import { eq } from "drizzle-orm"
import { SessionTable } from "@codilore/core/session/sql"
import { referencePromptMetadata, referenceTextPart } from "./prompt/reference"
import { SessionReminders } from "./reminders"
import { SessionTools } from "./tools"
import { LLMEvent } from "@codilore/llm"

// @ts-ignore
globalThis.AI_SDK_LOG_WARNINGS = false

const decodeMessageInfo = Schema.decodeUnknownExit(SessionV1.Info)
const decodeMessagePart = Schema.decodeUnknownExit(SessionV1.Part)

const STRUCTURED_OUTPUT_DESCRIPTION = `Use this tool to return your final response in the requested structured format.

IMPORTANT:
- You MUST call this tool exactly once at the end of your response
- The input must be valid JSON matching the required schema
- Complete all necessary research and tool calls BEFORE calling this tool
- This tool provides your final answer - no further actions are taken after calling it`

const STRUCTURED_OUTPUT_SYSTEM_PROMPT = `IMPORTANT: The user has requested structured output. You MUST use the StructuredOutput tool to provide your final response. Do NOT respond with plain text - you MUST call the StructuredOutput tool with your answer formatted according to the schema.`

const log = Log.create({ service: "session.prompt" })
const elog = EffectLogger.create({ service: "session.prompt" })

function isOrphanedInterruptedTool(part: SessionV1.ToolPart) {
  // cleanup() marks abandoned tool_use blocks this way after retries/aborts.
  // They are not pending work and must not trigger an assistant-prefill request.
  return part.state.status === "error" && part.state.metadata?.interrupted === true
}

export interface Interface {
  readonly cancel: (sessionID: SessionID) => Effect.Effect<void>
  readonly prompt: (input: PromptInput) => Effect.Effect<SessionV1.WithParts, Image.Error>
  readonly loop: (input: LoopInput) => Effect.Effect<SessionV1.WithParts>
  readonly shell: (input: ShellInput) => Effect.Effect<SessionV1.WithParts, Session.BusyError>
  readonly command: (input: CommandInput) => Effect.Effect<SessionV1.WithParts, Image.Error>
  readonly resolvePromptParts: (template: string) => Effect.Effect<PromptInput["parts"]>
}

export class Service extends Context.Service<Service, Interface>()("@Codilore/SessionPrompt") {}

export const layer = Layer.effect(
  Service,
  Effect.gen(function* () {
    const status = yield* SessionStatus.Service
    const sessions = yield* Session.Service
    const agents = yield* Agent.Service
    const provider = yield* Provider.Service
    const processor = yield* SessionProcessor.Service
    const compaction = yield* SessionCompaction.Service
    const plugin = yield* Plugin.Service
    const commands = yield* Command.Service
    const config = yield* Config.Service
    const permission = yield* Permission.Service
    const fsys = yield* FSUtil.Service
    const mcp = yield* MCP.Service
    const lsp = yield* LSP.Service
    const registry = yield* ToolRegistry.Service
    const truncate = yield* Truncate.Service
    const image = yield* Image.Service
    const spawner = yield* ChildProcessSpawner.ChildProcessSpawner
    const scope = yield* Scope.Scope
    const instruction = yield* Instruction.Service
    const state = yield* SessionRunState.Service
    const revert = yield* SessionRevert.Service
    const summary = yield* SessionSummary.Service
    const sys = yield* SystemPrompt.Service
    const llm = yield* LLM.Service
    const references = yield* Reference.Service
    const events = yield* EventV2Bridge.Service
    const flags = yield* RuntimeFlags.Service
    const database = yield* Database.Service
    const { db } = database
    const ops = Effect.fn("SessionPrompt.ops")(function* () {
      return {
        cancel: (sessionID: SessionID) => cancel(sessionID),
        resolvePromptParts: (template: string) => resolvePromptParts(template),
        prompt: (input: PromptInput) => prompt(input).pipe(Effect.catch(Effect.die)),
      } satisfies TaskPromptOps
    })

    const cancel = Effect.fn("SessionPrompt.cancel")(function* (sessionID: SessionID) {
      yield* elog.info("cancel", { sessionID })
      yield* state.cancel(sessionID)
    })

    const resolvePromptParts = Effect.fn("SessionPrompt.resolvePromptParts")(function* (template: string) {
      const ctx = yield* InstanceState.context
      const parts: Types.DeepMutable<PromptInput["parts"]> = [{ type: "text", text: template }]
      const files = ConfigMarkdown.files(template)
      const seen = new Set<string>()
      yield* Effect.forEach(
        files,
        Effect.fnUntraced(function* (match) {
          const name = match[1]
          if (!name) return
          if (seen.has(name)) return
          seen.add(name)

          const slash = name.indexOf("/")
          const alias = slash === -1 ? name : name.slice(0, slash)
          const reference = yield* references.get(alias)
          if (reference) {
            const start = match.index ?? 0
            const source = { value: match[0], start, end: start + match[0].length }
            if (reference.kind === "invalid") {
              parts.push(
                referenceTextPart({ reference, source, target: slash === -1 ? undefined : name.slice(slash + 1) }),
              )
              return
            }

            yield* references.ensure(reference.path)
            if (slash === -1) {
              parts.push(referenceTextPart({ reference, source }))
              return
            }

            const target = name.slice(slash + 1)
            const targetPath = path.resolve(reference.path, target)
            if (!FSUtil.contains(reference.path, targetPath)) {
              parts.push(
                referenceTextPart({
                  reference,
                  source,
                  target,
                  targetPath,
                  problem: `Path escapes configured reference @${alias}: ${target}`,
                }),
              )
              return
            }

            const info = yield* fsys.stat(targetPath).pipe(Effect.option)
            if (Option.isNone(info)) {
              parts.push(
                referenceTextPart({
                  reference,
                  source,
                  target,
                  targetPath,
                  problem: `Path does not exist inside configured reference @${alias}: ${target}`,
                }),
              )
              return
            }

            parts.push({
              type: "file",
              url: pathToFileURL(targetPath).href,
              filename: name,
              mime: info.value.type === "Directory" ? "application/x-directory" : "text/plain",
            })
            return
          }

          const filepath = name.startsWith("~/")
            ? path.join(os.homedir(), name.slice(2))
            : path.resolve(ctx.worktree, name)

          const info = yield* fsys.stat(filepath).pipe(Effect.option)
          if (Option.isNone(info)) {
            const found = yield* agents.get(name)
            if (found) parts.push({ type: "agent", name: found.name })
            return
          }
          const stat = info.value
          parts.push({
            type: "file",
            url: pathToFileURL(filepath).href,
            filename: name,
            mime: stat.type === "Directory" ? "application/x-directory" : "text/plain",
          })
        }),
        { concurrency: "unbounded", discard: true },
      )
      return parts
    })

    const title = Effect.fn("SessionPrompt.ensureTitle")(function* (input: {
      session: Session.Info
      history: SessionV1.WithParts[]
      providerID: ProviderV2.ID
      modelID: ProviderV2.ModelID
    }) {
      if (input.session.parentID) return
      if (!Session.isDefaultTitle(input.session.title)) return

      const real = (m: SessionV1.WithParts) =>
        m.info.role === "user" && !m.parts.every((p) => "synthetic" in p && p.synthetic)
      const idx = input.history.findIndex(real)
      if (idx === -1) return
      if (input.history.filter(real).length !== 1) return

      const context = input.history.slice(0, idx + 1)
      const firstUser = context[idx]
      if (!firstUser || firstUser.info.role !== "user") return
      const firstInfo = firstUser.info

      const subtasks = firstUser.parts.filter((p): p is SessionV1.SubtaskPart => p.type === "subtask")
      const onlySubtasks = subtasks.length > 0 && firstUser.parts.every((p) => p.type === "subtask")

      const ag = yield* agents.get("title")
      if (!ag) return
      const mdl = ag.model
        ? yield* provider.getModel(ag.model.providerID, ag.model.modelID)
        : ((yield* provider.getSmallModel(input.providerID)) ??
          (yield* provider.getModel(input.providerID, input.modelID)))
      const msgs = onlySubtasks
        ? [{ role: "user" as const, content: subtasks.map((p) => p.prompt).join("\n") }]
        : yield* MessageV2.toModelMessagesEffect(context, mdl)
      const text = yield* llm
        .stream({
          agent: ag,
          user: firstInfo,
          system: [],
          small: true,
          tools: {},
          model: mdl,
          sessionID: input.session.id,
          retries: 2,
          messages: [{ role: "user", content: "Generate a title for this conversation:\n" }, ...msgs],
        })
        .pipe(
          Stream.filter(LLMEvent.is.textDelta),
          Stream.map((e) => e.text),
          Stream.mkString,
          Effect.orDie,
        )
      const cleaned = text
        .replace(/<think>[\s\S]*?<\/think>\s*/g, "")
        .split("\n")
        .map((line) => line.trim())
        .find((line) => line.length > 0)
      if (!cleaned) return
      const t = cleaned.length > 100 ? cleaned.substring(0, 97) + "..." : cleaned
      yield* sessions
        .setTitle({ sessionID: input.session.id, title: t })
        .pipe(Effect.catchCause((cause) => elog.error("failed to generate title", { error: Cause.squash(cause) })))
    })

    const handleSubtask = Effect.fn("SessionPrompt.handleSubtask")(function* (input: {
      task: SessionV1.SubtaskPart
      model: Provider.Model
      lastUser: SessionV1.User
      sessionID: SessionID
      session: Session.Info
      msgs: SessionV1.WithParts[]
    }) {
      const { task, model, lastUser, sessionID, session, msgs } = input
      const ctx = yield* InstanceState.context
      const promptOps = yield* ops()
      const { task: taskTool } = yield* registry.named()
      const taskModel = task.model ? yield* getModel(task.model.providerID, task.model.modelID, sessionID) : model
      const assistantMessage: SessionV1.Assistant = yield* sessions.updateMessage({
        id: MessageID.ascending(),
        role: "assistant",
        parentID: lastUser.id,
        sessionID,
        mode: task.agent,
        agent: task.agent,
        variant: lastUser.model.variant,
        path: { cwd: ctx.directory, root: ctx.worktree },
        cost: 0,
        tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
        modelID: taskModel.id,
        providerID: taskModel.providerID,
        time: { created: Date.now() },
      })
      let part: SessionV1.ToolPart = yield* sessions.updatePart({
        id: PartID.ascending(),
        messageID: assistantMessage.id,
        sessionID: assistantMessage.sessionID,
        type: "tool",
        callID: ulid(),
        tool: TaskTool.id,
        state: {
          status: "running",
          input: {
            prompt: task.prompt,
            description: task.description,
            subagent_type: task.agent,
            command: task.command,
          },
          time: { start: Date.now() },
        },
      })
      const taskArgs = {
        prompt: task.prompt,
        description: task.description,
        subagent_type: task.agent,
        command: task.command,
      }
      yield* plugin.trigger(
        "tool.execute.before",
        { tool: TaskTool.id, sessionID, callID: part.id },
        { args: taskArgs },
      )

      const taskAgent = yield* agents.get(task.agent)
      if (!taskAgent) {
        const available = (yield* agents.list()).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}` })
        yield* events.publish(Session.Event.Error, { sessionID, error: error.toObject() })
        throw error
      }

      let error: Error | undefined
      const taskAbort = new AbortController()
      const result = yield* taskTool
        .execute(taskArgs, {
          agent: task.agent,
          messageID: assistantMessage.id,
          sessionID,
          abort: taskAbort.signal,
          callID: part.callID,
          extra: { bypassAgentCheck: true, promptOps },
          messages: msgs,
          metadata: (val: { title?: string; metadata?: Record<string, any> }) =>
            Effect.gen(function* () {
              part = yield* sessions.updatePart({
                ...part,
                type: "tool",
                state: { ...part.state, ...val },
              } satisfies SessionV1.ToolPart)
            }),
          ask: (req: any) =>
            permission
              .ask({
                ...req,
                sessionID,
                ruleset: Permission.merge(taskAgent.permission, session.permission ?? []),
              })
              .pipe(Effect.orDie),
        })
        .pipe(
          Effect.catchCause((cause) => {
            const defect = Cause.squash(cause)
            error = defect instanceof Error ? defect : new Error(String(defect))
            log.error("subtask execution failed", { error, agent: task.agent, description: task.description })
            return Effect.void
          }),
          Effect.onInterrupt(() =>
            Effect.gen(function* () {
              taskAbort.abort()
              assistantMessage.finish = "tool-calls"
              assistantMessage.time.completed = Date.now()
              yield* sessions.updateMessage(assistantMessage)
              if (part.state.status === "running") {
                yield* sessions.updatePart({
                  ...part,
                  state: {
                    status: "error",
                    error: "Cancelled",
                    time: { start: part.state.time.start, end: Date.now() },
                    metadata: part.state.metadata,
                    input: part.state.input,
                  },
                } satisfies SessionV1.ToolPart)
              }
            }),
          ),
        )

      const attachments = result?.attachments?.map((attachment) => ({
        ...attachment,
        id: PartID.ascending(),
        sessionID,
        messageID: assistantMessage.id,
      }))

      yield* plugin.trigger(
        "tool.execute.after",
        { tool: TaskTool.id, sessionID, callID: part.id, args: taskArgs },
        result,
      )

      assistantMessage.finish = "tool-calls"
      assistantMessage.time.completed = Date.now()
      yield* sessions.updateMessage(assistantMessage)

      if (result && part.state.status === "running") {
        yield* sessions.updatePart({
          ...part,
          state: {
            status: "completed",
            input: part.state.input,
            title: result.title,
            metadata: result.metadata,
            output: result.output,
            attachments,
            time: { ...part.state.time, end: Date.now() },
          },
        } satisfies SessionV1.ToolPart)
      }

      if (!result) {
        yield* sessions.updatePart({
          ...part,
          state: {
            status: "error",
            error: error ? `Tool execution failed: ${error.message}` : "Tool execution failed",
            time: {
              start: part.state.status === "running" ? part.state.time.start : Date.now(),
              end: Date.now(),
            },
            metadata: part.state.status === "pending" ? undefined : part.state.metadata,
            input: part.state.input,
          },
        } satisfies SessionV1.ToolPart)
      }

      if (!task.command) return

      const summaryUserMsg: SessionV1.User = {
        id: MessageID.ascending(),
        sessionID,
        role: "user",
        time: { created: Date.now() },
        agent: lastUser.agent,
        model: lastUser.model,
      }
      yield* sessions.updateMessage(summaryUserMsg)
      yield* sessions.updatePart({
        id: PartID.ascending(),
        messageID: summaryUserMsg.id,
        sessionID,
        type: "text",
        text: "Summarize the task tool output above and continue with your task.",
        synthetic: true,
      } satisfies SessionV1.TextPart)
    })

    const shellImpl = Effect.fn("SessionPrompt.shellImpl")(function* (input: ShellInput, ready?: Latch.Latch) {
      return yield* Effect.uninterruptibleMask((restore) =>
        Effect.gen(function* () {
          const markReady = ready ? ready.open.pipe(Effect.asVoid) : Effect.void
          const { msg, part, cwd } = yield* Effect.gen(function* () {
            const ctx = yield* InstanceState.context
            const session = yield* sessions.get(input.sessionID).pipe(Effect.orDie)
            if (session.revert) {
              yield* revert.cleanup(session)
            }
            const agent = yield* agents.get(input.agent)
            if (!agent) {
              const available = (yield* agents.list()).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}` })
              yield* events.publish(Session.Event.Error, { sessionID: input.sessionID, error: error.toObject() })
              throw error
            }
            const model = input.model ?? agent.model ?? (yield* currentModel(input.sessionID))
            const userMsg: SessionV1.User = {
              id: input.messageID ?? MessageID.ascending(),
              sessionID: input.sessionID,
              time: { created: Date.now() },
              role: "user",
              agent: input.agent,
              model: { providerID: model.providerID, modelID: model.modelID },
            }
            yield* sessions.updateMessage(userMsg)
            const userPart: SessionV1.Part = {
              type: "text",
              id: PartID.ascending(),
              messageID: userMsg.id,
              sessionID: input.sessionID,
              text: "The following tool was executed by the user",
              synthetic: true,
            }
            yield* sessions.updatePart(userPart)

            const msg: SessionV1.Assistant = {
              id: MessageID.ascending(),
              sessionID: input.sessionID,
              parentID: userMsg.id,
              mode: input.agent,
              agent: input.agent,
              cost: 0,
              path: { cwd: ctx.directory, root: ctx.worktree },
              time: { created: Date.now() },
              role: "assistant",
              tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
              modelID: model.modelID,
              providerID: model.providerID,
            }
            yield* sessions.updateMessage(msg)
            const started = Date.now()
            const part: SessionV1.ToolPart = {
              type: "tool",
              id: PartID.ascending(),
              messageID: msg.id,
              sessionID: input.sessionID,
              tool: ShellID.ToolID,
              callID: ulid(),
              state: {
                status: "running",
                time: { start: started },
                input: { command: input.command },
              },
            }
            yield* sessions.updatePart(part)
            if (flags.experimentalEventSystem) {
              yield* events.publish(SessionEvent.Shell.Started, {
                sessionID: input.sessionID,
                timestamp: DateTime.makeUnsafe(started),
                callID: part.callID,
                command: input.command,
              })
            }
            return { msg, part, cwd: ctx.directory }
          }).pipe(Effect.ensuring(markReady))

          const cfg = yield* config.get()
          const sh = Shell.preferred(cfg.shell)
          const args = Shell.args(sh, input.command, cwd)
          let output = ""
          let aborted = false

          const finish = Effect.uninterruptible(
            Effect.gen(function* () {
              if (aborted) {
                output += "\n\n" + ["<metadata>", "User aborted the command", "</metadata>"].join("\n")
              }
              const completed = Date.now()
              if (flags.experimentalEventSystem) {
                yield* events.publish(SessionEvent.Shell.Ended, {
                  sessionID: input.sessionID,
                  timestamp: DateTime.makeUnsafe(completed),
                  callID: part.callID,
                  output,
                })
              }
              if (!msg.time.completed) {
                msg.time.completed = completed
                yield* sessions.updateMessage(msg)
              }
              if (part.state.status === "running") {
                part.state = {
                  status: "completed",
                  time: { ...part.state.time, end: completed },
                  input: part.state.input,
                  title: "",
                  metadata: { output, description: "" },
                  output,
                }
                yield* sessions.updatePart(part)
              }
            }),
          )

          const exit = yield* restore(
            Effect.gen(function* () {
              const shellEnv = yield* plugin.trigger(
                "shell.env",
                { cwd, sessionID: input.sessionID, callID: part.callID },
                { env: {} },
              )
              const cmd = ChildProcess.make(sh, args, {
                cwd,
                extendEnv: true,
                env: { ...shellEnv.env, TERM: "dumb" },
                stdin: "ignore",
                forceKillAfter: "3 seconds",
              })
              const handle = yield* spawner.spawn(cmd)
              yield* Stream.runForEach(Stream.decodeText(handle.all), (chunk) =>
                Effect.gen(function* () {
                  output += chunk
                  if (part.state.status === "running") {
                    part.state.metadata = { output, description: "" }
                    yield* sessions.updatePart(part)
                  }
                }),
              )
              yield* handle.exitCode
            }).pipe(Effect.scoped, Effect.orDie),
          ).pipe(Effect.exit)

          if (Exit.isFailure(exit) && Cause.hasInterrupts(exit.cause) && !Cause.hasDies(exit.cause)) {
            aborted = true
          }
          yield* finish

          if (Exit.isFailure(exit) && !aborted && !Cause.hasInterruptsOnly(exit.cause)) {
            return yield* Effect.failCause(exit.cause)
          }

          return { info: msg, parts: [part] }
        }),
      )
    })

    const getModel = Effect.fn("SessionPrompt.getModel")(function* (
      providerID: ProviderV2.ID,
      modelID: ProviderV2.ModelID,
      sessionID: SessionID,
    ) {
      const exit = yield* provider.getModel(providerID, modelID).pipe(Effect.exit)
      if (Exit.isSuccess(exit)) return exit.value
      const err = Cause.squash(exit.cause)
      if (Provider.ModelNotFoundError.isInstance(err)) {
        const hint = err.suggestions?.length ? ` Did you mean: ${err.suggestions.join(", ")}?` : ""
        yield* events.publish(Session.Event.Error, {
          sessionID,
          error: new NamedError.Unknown({
            message: `Model not found: ${err.providerID}/${err.modelID}.${hint}`,
          }).toObject(),
        })
      }
      return yield* Effect.die(err)
    })

    const currentModel = Effect.fnUntraced(function* (sessionID: SessionID) {
      const current = yield* db
        .select({ model: SessionTable.model })
        .from(SessionTable)
        .where(eq(SessionTable.id, sessionID))
        .get()
        .pipe(Effect.orDie)
      if (current?.model) {
        return {
          providerID: ProviderV2.ID.make(current.model.providerID),
          modelID: ProviderV2.ModelID.make(current.model.id),
          ...(current.model.variant && current.model.variant !== "default" ? { variant: current.model.variant } : {}),
        }
      }
      const match = yield* sessions
        .findMessage(sessionID, (m) => m.info.role === "user" && !!m.info.model)
        .pipe(Effect.orDie)
      if (Option.isSome(match) && match.value.info.role === "user") return match.value.info.model
      return yield* provider.defaultModel().pipe(Effect.orDie)
    })

    const createUserMessage = Effect.fn("SessionPrompt.createUserMessage")(function* (input: PromptInput) {
      const agentName = input.agent
      const ag = agentName ? yield* agents.get(agentName) : yield* agents.defaultInfo()
      if (!ag) {
        const available = (yield* agents.list()).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}` })
        yield* events.publish(Session.Event.Error, { sessionID: input.sessionID, error: error.toObject() })
        throw error
      }

      const current = yield* db
        .select({ agent: SessionTable.agent, model: SessionTable.model })
        .from(SessionTable)
        .where(eq(SessionTable.id, input.sessionID))
        .get()
        .pipe(Effect.orDie)
      const model = input.model ?? ag.model ?? (yield* currentModel(input.sessionID))
      const same = ag.model && model.providerID === ag.model.providerID && model.modelID === ag.model.modelID
      const full =
        !input.variant && ag.variant && same
          ? yield* provider
              .getModel(model.providerID, model.modelID)
              .pipe(Effect.catchIf(Provider.ModelNotFoundError.isInstance, () => Effect.succeed(undefined)))
          : undefined
      const variant = input.variant ?? (ag.variant && full?.variants?.[ag.variant] ? ag.variant : undefined)

      const info: SessionV1.User = {
        id: input.messageID ?? MessageID.ascending(),
        role: "user",
        sessionID: input.sessionID,
        time: { created: Date.now() },
        tools: input.tools,
        agent: ag.name,
        model: {
          providerID: model.providerID,
          modelID: model.modelID,
          variant,
        },
        system: input.system,
        format: input.format,
      }

      if (current?.agent !== info.agent) {
        yield* events.publish(SessionEvent.AgentSwitched, {
          sessionID: input.sessionID,
          timestamp: DateTime.makeUnsafe(info.time.created),
          agent: info.agent,
        })
      }
      if (
        current?.model?.providerID !== info.model.providerID ||
        current.model.id !== info.model.modelID ||
        (current.model.variant === "default" ? undefined : current.model.variant) !== info.model.variant
      ) {
        yield* events.publish(SessionEvent.ModelSwitched, {
          sessionID: input.sessionID,
          timestamp: DateTime.makeUnsafe(info.time.created),
          model: {
            id: ModelV2.ID.make(info.model.modelID),
            providerID: ProviderV2.ID.make(info.model.providerID),
            variant: ModelV2.VariantID.make(info.model.variant ?? "default"),
          },
        })
      }

      yield* Effect.addFinalizer(() => instruction.clear(info.id))

      type Draft<T> = T extends SessionV1.Part ? Omit<T, "id"> & { id?: string } : never
      const assign = (part: Draft<SessionV1.Part>): SessionV1.Part => ({
        ...part,
        id: part.id ? PartID.make(part.id) : PartID.ascending(),
      })

      const referenceContextFromFilePart = Effect.fnUntraced(function* (
        part: Extract<PromptInput["parts"][number], { type: "file" }>,
        filepath: string,
      ) {
        const name = part.filename?.replace(/#\d+(?:-\d*)?$/, "")
        if (!name) return
        const slash = name.indexOf("/")
        if (slash === -1) return

        const reference = yield* references.get(name.slice(0, slash))
        if (!reference || reference.kind === "invalid") return
        if (!FSUtil.contains(reference.path, filepath)) return

        const target = path.relative(reference.path, filepath).split(path.sep).join("/")
        if (!target || target.startsWith("../") || target === "..") return

        return referenceTextPart({
          reference,
          source: part.source?.text ?? { value: `@${name}`, start: 0, end: name.length + 1 },
          target,
          targetPath: filepath,
        })
      })

      const resolvePart: (part: PromptInput["parts"][number]) => Effect.Effect<Draft<SessionV1.Part>[]> = Effect.fn(
        "SessionPrompt.resolveUserPart",
      )(function* (part) {
        if (part.type === "file") {
          if (part.source?.type === "resource") {
            const { clientName, uri } = part.source
            log.info("mcp resource", { clientName, uri, mime: part.mime })
            const pieces: Draft<SessionV1.Part>[] = [
              {
                messageID: info.id,
                sessionID: input.sessionID,
                type: "text",
                synthetic: true,
                text: `Reading MCP resource: ${part.filename} (${uri})`,
              },
            ]
            const exit = yield* mcp.readResource(clientName, uri).pipe(Effect.exit)
            if (Exit.isSuccess(exit)) {
              const content = exit.value
              if (!content) throw new Error(`Resource not found: ${clientName}/${uri}`)
              const items = Array.isArray(content.contents) ? content.contents : [content.contents]
              for (const c of items) {
                if ("text" in c && c.text) {
                  pieces.push({
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: c.text,
                  })
                } else if ("blob" in c && c.blob) {
                  const mime = "mimeType" in c ? c.mimeType : part.mime
                  pieces.push({
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: `[Binary content: ${mime}]`,
                  })
                }
              }
              pieces.push({ ...part, messageID: info.id, sessionID: input.sessionID })
            } else {
              const error = Cause.squash(exit.cause)
              log.error("failed to read MCP resource", { error, clientName, uri })
              const message = error instanceof Error ? error.message : String(error)
              pieces.push({
                messageID: info.id,
                sessionID: input.sessionID,
                type: "text",
                synthetic: true,
                text: `Failed to read MCP resource ${part.filename}: ${message}`,
              })
            }
            return pieces
          }
          const url = new URL(part.url)
          switch (url.protocol) {
            case "data:":
              if (part.mime === "text/plain") {
                return [
                  {
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: `Called the Read tool with the following input: ${JSON.stringify({ filePath: part.filename })}`,
                  },
                  {
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: decodeDataUrl(part.url),
                  },
                  { ...part, messageID: info.id, sessionID: input.sessionID },
                ]
              }
              break
            case "file:": {
              log.info("file", { mime: part.mime })
              const filepath = fileURLToPath(part.url)
              const referenceContext = yield* referenceContextFromFilePart(part, filepath)
              const mime = (yield* fsys.isDir(filepath)) ? "application/x-directory" : part.mime

              const { read } = yield* registry.named()
              const execRead = (args: Parameters<typeof read.execute>[0], extra?: Tool.Context["extra"]) => {
                const controller = new AbortController()
                return read
                  .execute(args, {
                    sessionID: input.sessionID,
                    abort: controller.signal,
                    agent: input.agent!,
                    messageID: info.id,
                    extra: { bypassCwdCheck: true, ...extra },
                    messages: [],
                    metadata: () => Effect.void,
                    ask: () => Effect.void,
                  })
                  .pipe(Effect.onInterrupt(() => Effect.sync(() => controller.abort())))
              }

              if (mime === "text/plain") {
                let offset: number | undefined
                let limit: number | undefined
                const range = { start: url.searchParams.get("start"), end: url.searchParams.get("end") }
                if (range.start != null) {
                  const filePathURI = part.url.split("?")[0]
                  let start = parseInt(range.start)
                  let end = range.end ? parseInt(range.end) : undefined
                  if (start === end) {
                    const symbols = yield* lsp.documentSymbol(filePathURI).pipe(Effect.catch(() => Effect.succeed([])))
                    for (const symbol of symbols) {
                      let r: LSP.Range | undefined
                      if ("range" in symbol) r = symbol.range
                      else if ("location" in symbol) r = symbol.location.range
                      if (r?.start?.line && r?.start?.line === start) {
                        start = r.start.line
                        end = r?.end?.line ?? start
                        break
                      }
                    }
                  }
                  offset = Math.max(start, 1)
                  if (end) limit = end - (offset - 1)
                }
                const args = { filePath: filepath, offset, limit }
                const pieces: Draft<SessionV1.Part>[] = [
                  ...(referenceContext
                    ? [{ ...referenceContext, messageID: info.id, sessionID: input.sessionID }]
                    : []),
                  {
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: `Called the Read tool with the following input: ${JSON.stringify(args)}`,
                  },
                ]
                const exit = yield* provider.getModel(info.model.providerID, info.model.modelID).pipe(
                  Effect.flatMap((mdl) => execRead(args, { model: mdl })),
                  Effect.exit,
                )
                if (Exit.isSuccess(exit)) {
                  const result = exit.value
                  pieces.push({
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: result.output,
                  })
                  if (result.attachments?.length) {
                    pieces.push(
                      ...result.attachments.map((a) => ({
                        ...a,
                        synthetic: true,
                        filename: a.filename ?? part.filename,
                        messageID: info.id,
                        sessionID: input.sessionID,
                      })),
                    )
                  } else {
                    pieces.push({ ...part, mime, messageID: info.id, sessionID: input.sessionID })
                  }
                } else {
                  const error = Cause.squash(exit.cause)
                  log.error("failed to read file", { error })
                  const message = error instanceof Error ? error.message : String(error)
                  yield* events.publish(Session.Event.Error, {
                    sessionID: input.sessionID,
                    error: new NamedError.Unknown({ message }).toObject(),
                  })
                  pieces.push({
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: `Read tool failed to read ${filepath} with the following error: ${message}`,
                  })
                }
                return pieces
              }

              if (mime === "application/x-directory") {
                const args = { filePath: filepath }
                const exit = yield* execRead(args).pipe(Effect.exit)
                if (Exit.isFailure(exit)) {
                  const error = Cause.squash(exit.cause)
                  log.error("failed to read directory", { error })
                  const message = error instanceof Error ? error.message : String(error)
                  yield* events.publish(Session.Event.Error, {
                    sessionID: input.sessionID,
                    error: new NamedError.Unknown({ message }).toObject(),
                  })
                  return [
                    ...(referenceContext
                      ? [{ ...referenceContext, messageID: info.id, sessionID: input.sessionID }]
                      : []),
                    {
                      messageID: info.id,
                      sessionID: input.sessionID,
                      type: "text",
                      synthetic: true,
                      text: `Read tool failed to read ${filepath} with the following error: ${message}`,
                    },
                  ]
                }
                return [
                  ...(referenceContext
                    ? [{ ...referenceContext, messageID: info.id, sessionID: input.sessionID }]
                    : []),
                  {
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: `Called the Read tool with the following input: ${JSON.stringify(args)}`,
                  },
                  {
                    messageID: info.id,
                    sessionID: input.sessionID,
                    type: "text",
                    synthetic: true,
                    text: exit.value.output,
                  },
                  { ...part, mime, messageID: info.id, sessionID: input.sessionID },
                ]
              }

              return [
                ...(referenceContext ? [{ ...referenceContext, messageID: info.id, sessionID: input.sessionID }] : []),
                {
                  messageID: info.id,
                  sessionID: input.sessionID,
                  type: "text",
                  synthetic: true,
                  text: `Called the Read tool with the following input: {"filePath":"${filepath}"}`,
                },
                {
                  id: part.id,
                  messageID: info.id,
                  sessionID: input.sessionID,
                  type: "file",
                  url:
                    `data:${mime};base64,` +
                    Buffer.from(yield* fsys.readFile(filepath).pipe(Effect.catch(Effect.die))).toString("base64"),
                  mime,
                  filename: part.filename!,
                  source: part.source,
                },
              ]
            }
          }
        }

        if (part.type === "agent") {
          const perm = Permission.evaluate("task", part.name, ag.permission)
          const hint = perm.action === "deny" ? " . Invoked by user; guaranteed to exist." : ""
          return [
            { ...part, messageID: info.id, sessionID: input.sessionID },
            {
              messageID: info.id,
              sessionID: input.sessionID,
              type: "text",
              synthetic: true,
              text:
                " Use the above message and context to generate a prompt and call the task tool with subagent: " +
                part.name +
                hint,
            },
          ]
        }

        return [{ ...part, messageID: info.id, sessionID: input.sessionID }]
      })

      const resolvedParts = yield* Effect.forEach(input.parts, resolvePart, { concurrency: "unbounded" }).pipe(
        Effect.map((x) => x.flat().map(assign)),
      )

      yield* plugin.trigger(
        "chat.message",
        {
          sessionID: input.sessionID,
          agent: input.agent,
          model: input.model,
          messageID: input.messageID,
          variant: input.variant,
        },
        { message: info, parts: resolvedParts },
      )

      const parts = yield* Effect.forEach(resolvedParts, (part) =>
        part.type === "file" && part.mime.startsWith("image/")
          ? image.normalize(part).pipe(
              Effect.catchIf(
                (error) => error instanceof Image.ResizerUnavailableError,
                () => Effect.succeed(part),
              ),
            )
          : Effect.succeed(part),
      )

      const parsed = decodeMessageInfo(info, { errors: "all", propertyOrder: "original" })
      if (Exit.isFailure(parsed)) {
        log.error("invalid user message before save", {
          sessionID: input.sessionID,
          messageID: info.id,
          agent: info.agent,
          model: info.model,
          cause: Cause.pretty(parsed.cause),
        })
      }
      parts.forEach((part, index) => {
        const p = decodeMessagePart(part, { errors: "all", propertyOrder: "original" })
        if (Exit.isSuccess(p)) return
        log.error("invalid user part before save", {
          sessionID: input.sessionID,
          messageID: info.id,
          partID: part.id,
          partType: part.type,
          index,
          cause: Cause.pretty(p.cause),
          part,
        })
      })

      yield* sessions.updateMessage(info)
      for (const part of parts) yield* sessions.updatePart(part)
      const nextPrompt = parts.reduce(
        (result, part) => {
          if (part.type === "text") {
            if (part.synthetic) result.synthetic.push(part.text)
            else result.text.push(part.text)
            const reference = referencePromptMetadata(part.metadata?.reference)
            if (reference) {
              result.references.push(
                new ReferenceAttachment({
                  name: reference.name,
                  kind: reference.kind,
                  uri: reference.path ? pathToFileURL(reference.path).href : undefined,
                  repository: reference.repository,
                  branch: reference.branch,
                  target: reference.target,
                  targetUri: reference.targetPath ? pathToFileURL(reference.targetPath).href : undefined,
                  problem: reference.problem,
                  source: new Source({
                    start: reference.source.start,
                    end: reference.source.end,
                    text: reference.source.value,
                  }),
                }),
              )
            }
          }
          if (part.type === "file") {
            result.files.push(
              new FileAttachment({
                uri: part.url,
                mime: part.mime,
                name: part.filename,
                source: part.source
                  ? new Source({
                      start: part.source.text.start,
                      end: part.source.text.end,
                      text: part.source.text.value,
                    })
                  : undefined,
              }),
            )
          }
          if (part.type === "agent") {
            result.agents.push(
              new AgentAttachment({
                name: part.name,
                source: part.source
                  ? new Source({
                      start: part.source.start,
                      end: part.source.end,
                      text: part.source.value,
                    })
                  : undefined,
              }),
            )
          }
          return result
        },
        {
          text: [] as string[],
          files: [] as FileAttachment[],
          agents: [] as AgentAttachment[],
          references: [] as ReferenceAttachment[],
          synthetic: [] as string[],
        },
      )
      // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
      if (flags.experimentalEventSystem) {
        yield* events.publish(SessionEvent.Prompted, {
          sessionID: input.sessionID,
          timestamp: DateTime.makeUnsafe(info.time.created),
          delivery: "steer",
          prompt: new Prompt({
            text: nextPrompt.text.join("\n"),
            files: nextPrompt.files,
            agents: nextPrompt.agents,
            references: nextPrompt.references,
          }),
        })
      }
      for (const text of nextPrompt.synthetic) {
        // TODO(v2): Temporary dual-write while migrating session messages to v2 events.
        if (flags.experimentalEventSystem) {
          yield* events.publish(SessionEvent.Synthetic, {
            sessionID: input.sessionID,
            timestamp: DateTime.makeUnsafe(info.time.created),
            text,
          })
        }
      }

      return { info, parts }
    }, Effect.scoped)

    const prompt: (input: PromptInput) => Effect.Effect<SessionV1.WithParts, Image.Error> = Effect.fn(
      "SessionPrompt.prompt",
    )(function* (input: PromptInput) {
      const session = yield* sessions.get(input.sessionID).pipe(Effect.orDie)
      yield* revert.cleanup(session)
      const message = yield* createUserMessage(input)
      yield* sessions.touch(input.sessionID)

      const permissions: PermissionV1.Rule[] = []
      for (const [t, enabled] of Object.entries(input.tools ?? {})) {
        permissions.push({ permission: t, action: enabled ? "allow" : "deny", pattern: "*" })
      }
      if (permissions.length > 0) {
        session.permission = permissions
        yield* sessions.setPermission({ sessionID: session.id, permission: permissions })
      }

      if (input.noReply === true) return message
      return yield* loop({ sessionID: input.sessionID })
    })

    const lastAssistant = Effect.fnUntraced(function* (sessionID: SessionID) {
      const match = yield* sessions.findMessage(sessionID, (m) => m.info.role !== "user").pipe(Effect.orDie)
      if (Option.isSome(match)) return match.value
      const msgs = yield* sessions.messages({ sessionID, limit: 1 }).pipe(Effect.orDie)
      if (msgs.length > 0) return msgs[0]
      throw new Error("Impossible")
    })

    const runLoop: (sessionID: SessionID) => Effect.Effect<SessionV1.WithParts> = Effect.fn("SessionPrompt.run")(
      function* (sessionID: SessionID) {
        const ctx = yield* InstanceState.context
        const slog = elog.with({ sessionID })
        let structured: unknown
        let step = 0
        const session = yield* sessions.get(sessionID).pipe(Effect.orDie)

        while (true) {
          yield* status.set(sessionID, { type: "busy" })
          yield* slog.info("loop", { step })

          let msgs = yield* MessageV2.filterCompactedEffect(sessionID).pipe(
            Effect.provideService(Database.Service, database),
          )

          const { user: lastUser, assistant: lastAssistant, finished: lastFinished, tasks } = MessageV2.latest(msgs)

          if (!lastUser) throw new Error("No user message found in stream. This should never happen.")

          const lastAssistantMsg = msgs.findLast(
            (msg) => msg.info.role === "assistant" && msg.info.id === lastAssistant?.id,
          )
          // Some providers return "stop" even when the assistant message contains
          // tool calls. Keep the loop running so tool results can be sent back to
          // the model, but ignore cleanup-marked interrupted orphans.
          const hasToolCalls =
            lastAssistantMsg?.parts.some(
              (part) => part.type === "tool" && !part.metadata?.providerExecuted && !isOrphanedInterruptedTool(part),
            ) ?? false

          if (
            lastAssistant?.finish &&
            !["tool-calls"].includes(lastAssistant.finish) &&
            !hasToolCalls &&
            lastUser.id < lastAssistant.id
          ) {
            const orphan = lastAssistantMsg?.parts.find(
              (part): part is SessionV1.ToolPart => part.type === "tool" && isOrphanedInterruptedTool(part),
            )
            if (orphan) {
              yield* slog.warn("loop exit with orphaned interrupted tool", {
                messageID: lastAssistant.id,
                tool: orphan.tool,
                callID: orphan.callID,
              })
            }
            yield* slog.info("exiting loop")
            break
          }

          step++
          if (step === 1)
            yield* title({
              session,
              modelID: lastUser.model.modelID,
              providerID: lastUser.model.providerID,
              history: msgs,
            }).pipe(Effect.ignore, Effect.forkIn(scope))

          const model = yield* getModel(lastUser.model.providerID, lastUser.model.modelID, sessionID)
          const task = tasks.pop()

          if (task?.type === "subtask") {
            yield* handleSubtask({ task, model, lastUser, sessionID, session, msgs })
            continue
          }

          if (task?.type === "compaction") {
            const result = yield* compaction.process({
              messages: msgs,
              parentID: lastUser.id,
              sessionID,
              auto: task.auto,
              overflow: task.overflow,
            })
            if (result === "stop") break
            continue
          }

          if (
            lastFinished &&
            lastFinished.summary !== true &&
            (yield* compaction.isOverflow({ tokens: lastFinished.tokens, model }))
          ) {
            yield* compaction.create({ sessionID, agent: lastUser.agent, model: lastUser.model, auto: true })
            continue
          }

          const agent = yield* agents.get(lastUser.agent)
          if (!agent) {
            const available = (yield* agents.list()).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}` })
            yield* events.publish(Session.Event.Error, { sessionID, error: error.toObject() })
            throw error
          }
          const maxSteps = agent.steps ?? Infinity
          const isLastStep = step >= maxSteps
          msgs = yield* SessionReminders.apply({ messages: msgs, agent, session }).pipe(
            Effect.provideService(RuntimeFlags.Service, flags),
            Effect.provideService(FSUtil.Service, fsys),
            Effect.provideService(Session.Service, sessions),
          )

          const msg: SessionV1.Assistant = {
            id: MessageID.ascending(),
            parentID: lastUser.id,
            role: "assistant",
            mode: agent.name,
            agent: agent.name,
            variant: lastUser.model.variant,
            path: { cwd: ctx.directory, root: ctx.worktree },
            cost: 0,
            tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
            modelID: model.id,
            providerID: model.providerID,
            time: { created: Date.now() },
            sessionID,
          }
          yield* sessions.updateMessage(msg)

          const finalizeInterruptedAssistant = Effect.gen(function* () {
            if (msg.time.completed) return
            msg.error ??= MessageV2.fromError(new DOMException("Aborted", "AbortError"), {
              providerID: msg.providerID,
              aborted: true,
            })
            msg.time.completed = Date.now()
            yield* sessions.updateMessage(msg)
          })

          const handle = yield* processor
            .create({
              assistantMessage: msg,
              sessionID,
              model,
            })
            .pipe(Effect.onInterrupt(() => finalizeInterruptedAssistant))

          const outcome: "break" | "continue" = yield* Effect.gen(function* () {
            const lastUserMsg = msgs.findLast((m) => m.info.role === "user")
            const bypassAgentCheck = lastUserMsg?.parts.some((p) => p.type === "agent") ?? false
            const promptOps = yield* ops()

            const tools = yield* SessionTools.resolve({
              agent,
              session,
              model,
              processor: handle,
              bypassAgentCheck,
              messages: msgs,
              promptOps,
            }).pipe(
              Effect.provideService(Plugin.Service, plugin),
              Effect.provideService(Permission.Service, permission),
              Effect.provideService(ToolRegistry.Service, registry),
              Effect.provideService(MCP.Service, mcp),
              Effect.provideService(Truncate.Service, truncate),
            )

            if (lastUser.format?.type === "json_schema") {
              tools["StructuredOutput"] = createStructuredOutputTool({
                schema: lastUser.format.schema,
                onSuccess(output) {
                  structured = output
                },
              })
            }

            if (step === 1)
              yield* summary.summarize({ sessionID, messageID: lastUser.id }).pipe(Effect.ignore, Effect.forkIn(scope))

            if (step > 1 && lastFinished) {
              for (const m of msgs) {
                if (m.info.role !== "user" || m.info.id <= lastFinished.id) continue
                for (const p of m.parts) {
                  if (p.type !== "text" || p.ignored || p.synthetic) continue
                  if (!p.text.trim()) continue
                  p.text = [
                    "<system-reminder>",
                    "The user sent the following message:",
                    p.text,
                    "",
                    "Please address this message and continue with your tasks.",
                    "</system-reminder>",
                  ].join("\n")
                }
              }
            }

            yield* plugin.trigger("experimental.chat.messages.transform", {}, { messages: msgs })

            const [skills, env, instructions, modelMsgs] = yield* Effect.all([
              sys.skills(agent),
              sys.environment(model),
              instruction.system().pipe(Effect.orDie),
              MessageV2.toModelMessagesEffect(msgs, model),
            ])
            const system = [...env, ...instructions, ...(skills ? [skills] : [])]
            const format = lastUser.format ?? { type: "text" as const }
            if (format.type === "json_schema") system.push(STRUCTURED_OUTPUT_SYSTEM_PROMPT)
            const result = yield* handle.process({
              user: lastUser,
              agent,
              permission: session.permission,
              sessionID,
              parentSessionID: session.parentID,
              system,
              messages: [...modelMsgs, ...(isLastStep ? [{ role: "assistant" as const, content: MAX_STEPS }] : [])],
              tools,
              model,
              toolChoice: format.type === "json_schema" ? "required" : undefined,
            })

            if (structured !== undefined) {
              handle.message.structured = structured
              handle.message.finish = handle.message.finish ?? "stop"
              yield* sessions.updateMessage(handle.message)
              return "break" as const
            }

            const finished = handle.message.finish && !["tool-calls", "unknown"].includes(handle.message.finish)
            if (finished && !handle.message.error) {
              if (format.type === "json_schema") {
                handle.message.error = new SessionV1.StructuredOutputError({
                  message: "Model did not produce structured output",
                  retries: 0,
                }).toObject()
                yield* sessions.updateMessage(handle.message)
                return "break" as const
              }
            }

            if (result === "stop") return "break" as const
            if (result === "compact") {
              yield* compaction.create({
                sessionID,
                agent: lastUser.agent,
                model: lastUser.model,
                auto: true,
                overflow: !handle.message.finish,
              })
            }
            return "continue" as const
          }).pipe(
            Effect.ensuring(instruction.clear(handle.message.id)),
            Effect.onInterrupt(() => finalizeInterruptedAssistant),
          )
          if (outcome === "break") break
          continue
        }

        yield* compaction.prune({ sessionID }).pipe(Effect.ignore, Effect.forkIn(scope))
        return yield* lastAssistant(sessionID)
      },
    )

    const loop: (input: LoopInput) => Effect.Effect<SessionV1.WithParts> = Effect.fn("SessionPrompt.loop")(function* (
      input: LoopInput,
    ) {
      return yield* state.ensureRunning(input.sessionID, lastAssistant(input.sessionID), runLoop(input.sessionID))
    })

    const shell: (input: ShellInput) => Effect.Effect<SessionV1.WithParts, Session.BusyError> = Effect.fn(
      "SessionPrompt.shell",
    )(function* (input: ShellInput) {
      const ready = yield* Latch.make()
      return yield* state.startShell(input.sessionID, lastAssistant(input.sessionID), shellImpl(input, ready), ready)
    })

    const command = Effect.fn("SessionPrompt.command")(function* (input: CommandInput) {
      yield* elog.info("command", { sessionID: input.sessionID, command: input.command, agent: input.agent })
      const cmd = yield* commands.get(input.command)
      if (!cmd) {
        const available = (yield* commands.list()).map((c) => c.name)
        const hint = available.length ? ` Available commands: ${available.join(", ")}` : ""
        const error = new NamedError.Unknown({ message: `Command not found: "${input.command}".${hint}` })
        yield* events.publish(Session.Event.Error, { sessionID: input.sessionID, error: error.toObject() })
        throw error
      }
      const agentName = cmd.agent ?? input.agent

      const raw = input.arguments.match(argsRegex) ?? []
      const args = raw.map((arg) => arg.replace(quoteTrimRegex, ""))
      const templateCommand = yield* Effect.promise(async () => cmd.template)

      const placeholders = templateCommand.match(placeholderRegex) ?? []
      let last = 0
      for (const item of placeholders) {
        const value = Number(item.slice(1))
        if (value > last) last = value
      }

      const withArgs = templateCommand.replaceAll(placeholderRegex, (_, index) => {
        const position = Number(index)
        const argIndex = position - 1
        if (argIndex >= args.length) return ""
        if (position === last) return args.slice(argIndex).join(" ")
        return args[argIndex]
      })
      const usesArgumentsPlaceholder = templateCommand.includes("$ARGUMENTS")
      let template = withArgs.replaceAll("$ARGUMENTS", input.arguments)

      if (placeholders.length === 0 && !usesArgumentsPlaceholder && input.arguments.trim()) {
        template = template + "\n\n" + input.arguments
      }

      const shellMatches = ConfigMarkdown.shell(template)
      if (shellMatches.length > 0) {
        const cfg = yield* config.get()
        const sh = Shell.preferred(cfg.shell)
        const results = yield* Effect.promise(() =>
          Promise.all(
            shellMatches.map(async ([, cmd]) => (await Process.text([cmd], { shell: sh, nothrow: true })).text),
          ),
        )
        let index = 0
        template = template.replace(bashRegex, () => results[index++])
      }
      template = template.trim()

      const taskModel = yield* Effect.gen(function* () {
        if (cmd.model) return Provider.parseModel(cmd.model)
        if (cmd.agent) {
          const cmdAgent = yield* agents.get(cmd.agent)
          if (cmdAgent?.model) return cmdAgent.model
        }
        if (input.model) return Provider.parseModel(input.model)
        return yield* currentModel(input.sessionID)
      })

      yield* getModel(taskModel.providerID, taskModel.modelID, input.sessionID)

      const agent = agentName ? yield* agents.get(agentName) : yield* agents.defaultInfo()
      if (!agent) {
        const available = (yield* agents.list()).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}` })
        yield* events.publish(Session.Event.Error, { sessionID: input.sessionID, error: error.toObject() })
        throw error
      }

      const templateParts = yield* resolvePromptParts(template)
      const isSubtask = (agent.mode === "subagent" && cmd.subtask !== false) || cmd.subtask === true
      const parts = isSubtask
        ? [
            {
              type: "subtask" as const,
              agent: agent.name,
              description: cmd.description ?? "",
              command: input.command,
              model: { providerID: taskModel.providerID, modelID: taskModel.modelID },
              prompt: templateParts.find((y) => y.type === "text")?.text ?? "",
            },
          ]
        : [...templateParts, ...(input.parts ?? [])]

      const userAgent = isSubtask ? (input.agent ?? (yield* agents.defaultInfo()).name) : agent.name
      const userModel = isSubtask
        ? input.model
          ? Provider.parseModel(input.model)
          : yield* currentModel(input.sessionID)
        : taskModel

      yield* plugin.trigger(
        "command.execute.before",
        { command: input.command, sessionID: input.sessionID, arguments: input.arguments },
        { parts },
      )

      const result = yield* prompt({
        sessionID: input.sessionID,
        messageID: input.messageID,
        model: userModel,
        agent: userAgent,
        parts,
        variant: input.variant,
      })
      yield* events.publish(Command.Event.Executed, {
        name: input.command,
        sessionID: input.sessionID,
        arguments: input.arguments,
        messageID: result.info.id,
      })
      return result
    })

    return Service.of({
      cancel,
      prompt,
      loop,
      shell,
      command,
      resolvePromptParts,
    })
  }),
)

export const defaultLayer = Layer.suspend(() =>
  layer.pipe(
    Layer.provide(SessionRunState.defaultLayer),
    Layer.provide(SessionStatus.defaultLayer),
    Layer.provide(SessionCompaction.defaultLayer),
    Layer.provide(SessionProcessor.defaultLayer),
    Layer.provide(Command.defaultLayer),
    Layer.provide(Permission.defaultLayer),
    Layer.provide(MCP.defaultLayer),
    Layer.provide(LSP.defaultLayer),
    Layer.provide(ToolRegistry.defaultLayer),
    Layer.provide(Truncate.defaultLayer),
    Layer.provide(Provider.defaultLayer),
    Layer.provide(Config.defaultLayer),
    Layer.provide(Instruction.defaultLayer),
    Layer.provide(FSUtil.defaultLayer),
    Layer.provide(Plugin.defaultLayer),
    Layer.provide(Session.defaultLayer),
    Layer.provide(SessionRevert.defaultLayer),
    Layer.provide(SessionSummary.defaultLayer),
    Layer.provide(Image.defaultLayer),
    Layer.provide(
      Layer.mergeAll(
        Agent.defaultLayer,
        Database.defaultLayer,
        SystemPrompt.defaultLayer,
        LLM.defaultLayer,
        Reference.defaultLayer,
        CrossSpawnSpawner.defaultLayer,
        RuntimeFlags.defaultLayer,
        EventV2Bridge.defaultLayer,
      ),
    ),
  ),
)
const ModelRef = Schema.Struct({
  providerID: ProviderV2.ID,
  modelID: ProviderV2.ModelID,
})

export const PromptInput = Schema.Struct({
  sessionID: SessionID,
  messageID: Schema.optional(MessageID),
  model: Schema.optional(ModelRef),
  agent: Schema.optional(Schema.String),
  noReply: Schema.optional(Schema.Boolean),
  tools: Schema.optional(Schema.Record(Schema.String, Schema.Boolean)).annotate({
    description:
      "@deprecated tools and permissions have been merged, you can set permissions on the session itself now",
  }),
  format: Schema.optional(SessionV1.Format),
  system: Schema.optional(Schema.String),
  variant: Schema.optional(Schema.String),
  parts: Schema.Array(
    Schema.Union([
      SessionV1.TextPartInput,
      SessionV1.FilePartInput,
      SessionV1.AgentPartInput,
      SessionV1.SubtaskPartInput,
    ]).annotate({ discriminator: "type" }),
  ),
})
export type PromptInput = Schema.Schema.Type<typeof PromptInput>

export class LoopInput extends Schema.Class<LoopInput>("SessionPrompt.LoopInput")({
  sessionID: SessionID,
}) {}

export const ShellInput = Schema.Struct({
  sessionID: SessionID,
  messageID: Schema.optional(MessageID),
  agent: Schema.String,
  model: Schema.optional(ModelRef),
  command: Schema.String,
})
export type ShellInput = Schema.Schema.Type<typeof ShellInput>

export const CommandInput = Schema.Struct({
  messageID: Schema.optional(MessageID),
  sessionID: SessionID,
  agent: Schema.optional(Schema.String),
  model: Schema.optional(Schema.String),
  arguments: Schema.String,
  command: Schema.String,
  variant: Schema.optional(Schema.String),
  // Inlined (no identifier annotation) to keep the original SDK output — the
  // PromptInput call site below references FilePartInput by ref via the
  // Schema export in message-v2.ts.
  parts: Schema.optional(
    Schema.Array(
      Schema.Union([
        Schema.Struct({
          id: Schema.optional(PartID),
          type: Schema.Literal("file"),
          mime: Schema.String,
          filename: Schema.optional(Schema.String),
          url: Schema.String,
          source: Schema.optional(SessionV1.FilePartSource),
        }),
      ]).annotate({ discriminator: "type" }),
    ),
  ),
})
export type CommandInput = Schema.Schema.Type<typeof CommandInput>

/** @internal Exported for testing */
export function createStructuredOutputTool(input: {
  schema: Record<string, any>
  onSuccess: (output: unknown) => void
}): AITool {
  // Remove $schema property if present (not needed for tool input)
  const { $schema: _, ...toolSchema } = input.schema

  return tool({
    description: STRUCTURED_OUTPUT_DESCRIPTION,
    inputSchema: jsonSchema(toolSchema as JSONSchema7),
    async execute(args) {
      // AI SDK validates args against inputSchema before calling execute()
      input.onSuccess(args)
      return {
        output: "Structured output captured successfully.",
        title: "Structured Output",
        metadata: { valid: true },
      }
    },
    toModelOutput({ output }) {
      return {
        type: "text",
        value: output.output,
      }
    },
  })
}
const bashRegex = /!`([^`]+)`/g
// Match [Image N] as single token, quoted strings, or non-space sequences
const argsRegex = /(?:\[Image\s+\d+\]|"[^"]*"|'[^']*'|[^\s"']+)/gi
const placeholderRegex = /\$(\d+)/g
const quoteTrimRegex = /^["']|["']$/g

export * as SessionPrompt from "./prompt"
