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+export * as OpenCodeTools from "./opencode.js"
+
+import { SystemPart, ToolFailure } from "@opencode/ai"
+import type { Context } from "@opencode/plugin/effect/plugin"
+import type { SessionHooks } from "@opencode/plugin/effect/session"
+import { Model } from "@opencode/schema/model"
+import { AbsolutePath } from "@opencode/schema/schema"
+import { Session } from "@opencode/schema/session"
+import { Effect, Schema } from "effect"
+import { FileAccess } from "../../file-access.js"
+import { Git } from "../../git.js"
+import { Permission } from "../../permission.js"
+import { Worktree } from "../../worktree.js"
+
+export const RenameInput = Schema.Struct({
+  sessionID: Schema.optionalKey(Session.ID).annotate({ description: "Omit to rename the current session." }),
+  title: Schema.String.check(Schema.isMinLength(1)).annotate({ description: "New session title." }),
+})
+
+const RenameOutput = Schema.Struct({ sessionID: Session.ID, title: Schema.String })
+
+export const MoveInput = Schema.Struct({
+  sessionID: Schema.optionalKey(Session.ID).annotate({ description: "Omit to move the current session." }),
+  directory: AbsolutePath.check(Schema.isMinLength(1)).annotate({
+    description: "Destination directory, relative to the target session's directory or absolute. Supports ~.",
+  }),
+})
+
+const MoveOutput = Schema.Struct({ sessionID: Session.ID, directory: AbsolutePath })
+
+export const WorktreeCreateInput = Schema.Struct({
+  name: Schema.Trim.check(Schema.isNonEmpty()).annotate({ description: "Worktree name." }),
+})
+
+export const WorktreeRemoveInput = Schema.Struct({
+  directory: AbsolutePath.check(Schema.isMinLength(1)).annotate({
+    description: "Absolute path of the worktree to remove.",
+  }),
+  force: Schema.optionalKey(Schema.Boolean).annotate({
+    description: "Discard modified and untracked files. Only set this when the user has confirmed forced removal.",
+  }),
+})
+
+const WorktreeRemoveOutput = Schema.Struct({ directory: AbsolutePath, removed: Schema.Boolean })
+
+export const ModelsInput = Schema.Struct({
+  query: Schema.optionalKey(Schema.String).annotate({
+    description: "Text to search for in model names and IDs.",
+  }),
+  provider: Schema.optionalKey(Schema.String).annotate({
+    description: "Provider ID or name to filter by. Try your own provider first.",
+  }),
+  all: Schema.optionalKey(Schema.Boolean).annotate({
+    description: "Include older versions of each model family. By default only the newest version is listed.",
+  }),
+  limit: Schema.optionalKey(Schema.Int.check(Schema.isBetween({ minimum: 1, maximum: 100 }))).annotate({
+    description: "Maximum number of models to return. Defaults to 20.",
+  }),
+  offset: Schema.optionalKey(Schema.Int.check(Schema.isGreaterThanOrEqualTo(0))).annotate({
+    description: "Number of models to skip, for paging through results.",
+  }),
+})
+
+const ModelEntry = Schema.Struct({
+  id: Schema.String.annotate({ description: "providerID/modelID" }),
+  name: Schema.String,
+  released: Model.Info.fields.time.fields.released.annotate({
+    description: "Release date as a Unix timestamp in milliseconds, or 0 when unknown.",
+  }),
+  variants: Schema.Array(Model.VariantID),
+  cost: Model.Info.fields.cost.annotate({ description: "Pricing in USD per million tokens." }),
+  status: Model.Info.fields.status,
+})
+
+const ModelsOutput = Schema.Struct({
+  providers: Schema.Array(
+    Schema.Struct({
+      id: Schema.String,
+      name: Schema.String,
+      models: Schema.Array(ModelEntry).annotate({ description: "Newest first." }),
+    }),
+  ).annotate({ description: "Matching models grouped by provider. Your own provider comes first." }),
+  total: Schema.Int.annotate({ description: "Number of matching models across all pages." }),
+  next: Schema.NullOr(Schema.Int).annotate({ description: "Offset of the next page, or null on the last page." }),
+})
+
+export const Plugin = {
+  id: "opencode.tools",
+  effect: Effect.fn("OpenCodeTools.Plugin")(function* (ctx: Context) {
+    const access = yield* FileAccess.Service
+    const permission = yield* Permission.Service
+    const hook = (event: SessionHooks["context"]) =>
+      Effect.sync(() => {
+        event.system.push(
+          SystemPart.make(
+            "When you create a worktree outside the current working directory and intend to use it as your primary working directory, consider using `execute` to call `tools.opencode.session_move` and make the worktree the session's working directory.",
+          ),
+        )
+      })
+    yield* ctx.session.hook("context", hook)
+    yield* ctx.session.hook("compaction", hook)
+    yield* ctx.session.hook("generate", hook)
+    yield* ctx.tool
+      .transform((draft) => {
+        draft.namespace({
+          name: "opencode",
+          description:
+            "Tools for managing OpenCode itself, such as working with sessions and worktrees, searching the available models, and reading MCP resources.",
+        })
+        draft.add({
+          name: "session_rename",
+          description:
+            "Rename a session, or omit sessionID to rename the current session. Use a short, specific title that summarizes the work being done.",
+          input: RenameInput,
+          output: RenameOutput,
+          options: { namespace: "opencode", codemode: true },
+          execute: (input, context) => {
+            const sessionID = input.sessionID ?? context.sessionID
+            const title = input.title.trim()
+            if (!title) return Effect.fail(new ToolFailure({ message: "Session title must not be empty" }))
+            return ctx.session.update({ sessionID, title }).pipe(
+              Effect.as({
+                output: { sessionID, title },
+                content: `Renamed session ${sessionID} to ${title}.`,
+              }),
+              Effect.mapError((error) => new ToolFailure({ message: `Unable to rename session ${sessionID}`, error })),
+            )
+          },
+        })
+        draft.add({
+          name: "session_move",
+          description:
+            "Move a session to another directory, or omit sessionID to move the current session. The current session moves at the next safe boundary; do not run destination-dependent tools in the same execute call.",
+          input: MoveInput,
+          output: MoveOutput,
+          options: { namespace: "opencode", codemode: true, pinned: true },
+          execute: (input, context) =>
+            Effect.gen(function* () {
+              const sessionID = input.sessionID ?? context.sessionID
+              yield* ctx.session.move({
+                sessionID,
+                directory: input.directory,
+                delivery: "steer",
+              })
+              return {
+                output: { sessionID, directory: input.directory },
+                content: `Moved session ${sessionID} to ${input.directory}.`,
+              }
+            }).pipe(
+              Effect.mapError(
+                (error) => new ToolFailure({ message: `Unable to move session to ${input.directory}`, error }),
+              ),
+            ),
+        })
+        draft.add({
+          name: "worktree_create",
+          description: "Create a named worktree. Returns its directory.",
+          input: WorktreeCreateInput,
+          output: Worktree.Info,
+          options: { namespace: "opencode", codemode: true, pinned: true },
+          execute: (input) =>
+            ctx.worktree.create({ projectID: ctx.location.project.id, name: input.name }).pipe(
+              Effect.map((output) => ({ output, content: `Created worktree in ${output.directory}.` })),
+              Effect.mapError(
+                (error) => new ToolFailure({ message: `Unable to create worktree ${input.name}`, error }),
+              ),
+            ),
+        })
+        draft.add({
+          name: "worktree_list",
+          description: "List a repository's worktrees.",
+          input: Schema.Struct({}),
+          output: Schema.Struct({ worktrees: Worktree.List }),
+          options: { namespace: "opencode", codemode: true, pinned: true },
+          execute: () =>
+            ctx.worktree.list({ projectID: ctx.location.project.id }).pipe(
+              Effect.map((worktrees) => ({ output: { worktrees } })),
+              Effect.mapError((error) => new ToolFailure({ message: "Unable to list worktrees", error })),
+            ),
+        })
+        draft.add({
+          name: "worktree_remove",
+          description:
+            "Remove a worktree. The repository location selects configuration; directory identifies the worktree to remove.",
+          input: WorktreeRemoveInput,
+          output: WorktreeRemoveOutput,
+          options: { namespace: "opencode", codemode: true, pinned: true, permission: "edit" },
+          execute: (input, context) =>
+            Effect.gen(function* () {
+              // Removing a worktree deletes files, so it requires the same approval as editing them.
+              const target = yield* access.resolve({ path: input.directory, kind: "directory" })
+              yield* permission.assert({
+                action: "edit",
+                resources: [target.resource],
+                save: ["*"],
+                sessionID: context.sessionID,
+                agent: context.agent,
+                source: { type: "tool", messageID: context.messageID, id: context.id },
+              })
+              yield* ctx.worktree
+                .remove({
+                  projectID: ctx.location.project.id,
+                  directory: target.absolute,
+                  force: input.force ?? false,
+                })
+                .pipe(Effect.mapError((error) => new ToolFailure({ message: removeFailure(target.absolute, error) })))
+              return {
+                output: { directory: target.absolute, removed: true },
+                content: `Removed worktree ${target.absolute}.`,
+              }
+            }).pipe(
+              Effect.mapError((error) =>
+                error instanceof ToolFailure
+                  ? error
+                  : new ToolFailure({ message: `Unable to remove worktree ${input.directory}`, error }),
+              ),
+            ),
+        })
+        draft.add({
+          name: "models",
+          description:
+            "Search the models available to use. Use this to turn a model name the user mentions into an exact reference before running a subagent on it. Check your own provider first.",
+          input: ModelsInput,
+          output: ModelsOutput,
+          options: { namespace: "opencode", codemode: true },
+          execute: (input, context) =>
+            Effect.gen(function* () {
+              const offset = input.offset ?? 0
+              const limit = input.limit ?? 20
+              const own = (yield* ctx.session.get({ sessionID: context.sessionID })).model?.providerID
+              const terms = input.query?.toLowerCase().split(/\s+/).filter(Boolean) ?? []
+              const names = new Map((yield* ctx.provider.list()).data.map((provider) => [provider.id, provider.name]))
+              const provider = input.provider?.toLowerCase()
+              const matching = (yield* ctx.model.list()).data
+                .filter(
+                  (model) =>
+                    provider === undefined ||
+                    model.providerID.toLowerCase() === provider ||
+                    names.get(model.providerID)?.toLowerCase() === provider,
+                )
+                .filter((model) => {
+                  const text = `${model.providerID}/${model.id} ${model.name}`.toLowerCase()
+                  return terms.every((term) => text.includes(term))
+                })
+                .toSorted(
+                  (left, right) =>
+                    Number(right.providerID === own) - Number(left.providerID === own) ||
+                    left.providerID.localeCompare(right.providerID) ||
+                    right.time.released - left.time.released,
+                )
+                .filter((model, index, sorted) => {
+                  if (input.all || model.family === undefined) return true
+                  return (
+                    sorted.findIndex(
+                      (other) => other.providerID === model.providerID && other.family === model.family,
+                    ) === index
+                  )
+                })
+              const page = matching.slice(offset, offset + limit)
+              const providers = Array.from(new Set(page.map((model) => model.providerID))).map((id) => ({
+                id,
+                name: names.get(id) ?? id,
+                models: page
+                  .filter((model) => model.providerID === id)
+                  .map((model) => ({
+                    id: `${model.providerID}/${model.id}`,
+                    name: model.name,
+                    released: model.time.released,
+                    variants: model.variants.map((variant) => variant.id),
+                    cost: model.cost,
+                    status: model.status,
+                  })),
+              }))
+              return {
+                output: {
+                  providers,
+                  total: matching.length,
+                  next: offset + limit < matching.length ? offset + limit : null,
+                },
+              }
+            }).pipe(Effect.mapError((error) => new ToolFailure({ message: "Unable to list models", error }))),
+        })
+      })
+      .pipe(Effect.orDie)
+  }),
+}
+
+// Worktree errors carry no model-facing message, and Git's own text suggests forcing removal.
+function removeFailure(directory: string, error: unknown) {
+  if (error instanceof Worktree.DirectoryUnavailableError)
+    return `Unable to remove worktree ${directory}: the directory does not exist or is not a directory.`
+  if (error instanceof Worktree.InvalidDirectoryError)
+    return `Unable to remove ${directory}: it is not a worktree of this project. Use worktree_list to see the project's worktrees.`
+  if (error instanceof Worktree.StrategyUnavailableError)
+    return `Unable to remove worktree ${directory}: its worktree strategy ${error.strategy} is not available.`
+  if ((error instanceof Git.WorktreeError || error instanceof Worktree.OperationError) && error.forceRequired)
+    return `Unable to remove worktree ${directory}: it has modified or untracked files.`
+  return `Unable to remove worktree ${directory}.`
+}