fix(core): restore shell tool fallback

packages/core/src/shell.ts

@@ -54,7 +54,7 @@ type Active = {
 export interface Interface {
   readonly name: () => Effect.Effect<string>
   readonly create: <E = never, R = never>(
-    input: Shell.CreateInput,
+    input: CreateInput,
     before?: (input: ShellCreateBefore) => Effect.Effect<void, E, R>,
   ) => Effect.Effect<Shell.Info, E | AppProcess.AppProcessError, R>
   // Currently running commands only; exited shells are retained for get/output but excluded here.
@@ -69,6 +69,10 @@ export interface Interface {
   readonly remove: (id: Shell.ID) => Effect.Effect<void, NotFoundError>
 }
 
+type CreateInput = Shell.CreateInput & {
+  readonly shell?: string
+}
+
 export class Service extends Context.Service<Service, Interface>()("@opencode/Shell") {}
 
 export const cleanup = Effect.fn("Shell.cleanup")(function* () {
@@ -218,7 +222,7 @@ const layer = () =>
       })
 
       const create = Effect.fn("Shell.create")(function* <E = never, R = never>(
-        input: Shell.CreateInput,
+        input: CreateInput,
         before?: (input: ShellCreateBefore) => Effect.Effect<void, E, R>,
       ) {
         const sessionID = input.metadata?.sessionID
@@ -230,7 +234,7 @@ const layer = () =>
           command: input.command,
           cwd: input.cwd ?? location.directory,
           timeout: input.timeout,
-          shell: yield* shell.preferred(),
+          shell: input.shell ?? (yield* shell.preferred()),
           env: {
             ...(sessionEnvironment ?? process.env),
             TERM: "xterm-256color",

packages/core/src/shell/select.ts

@@ -43,6 +43,7 @@ export type Draft = {
 
 export interface Interface extends State.Transformable<Draft> {
   readonly preferred: () => Effect.Effect<string>
+  readonly acceptable: () => Effect.Effect<string>
 }
 
 export class Service extends Context.Service<Service, Interface>()("@opencode/ShellSelect") {}
@@ -217,6 +218,7 @@ const layer = (options?: Options) =>
         transform: state.transform,
         reload: state.reload,
         preferred: () => Effect.sync(() => preferred(state.get().shell, options, global.bin)),
+        acceptable: () => Effect.sync(() => acceptable(state.get().shell, options, global.bin)),
       })
     }),
   )

packages/core/src/tool/plugin/shell.ts

@@ -13,6 +13,7 @@ import { NonNegativeInt } from "../../schema.js"
 import { SessionSchema } from "../../session/schema.js"
 import { Shell } from "../../shell.js"
 import { ShellParse } from "../../shell/parse.js"
+import { ShellSelect } from "../../shell/select.js"
 import { ToolOutput } from "../../tool-output.js"
 
 export const name = "shell"
@@ -102,6 +103,7 @@ export const Plugin = {
     const environment = yield* Environment.Service
     const mutation = yield* LocationMutation.Service
     const shell = yield* Shell.Service
+    const shellSelect = yield* ShellSelect.Service
     const permission = yield* Permission.Service
     const config = yield* Config.Service
 
@@ -179,6 +181,7 @@ export const Plugin = {
                   cwd: input.workdir,
                   timeout,
                   metadata: { sessionID: context.sessionID },
+                  shell: yield* shellSelect.acceptable(),
                 },
                 (invocation) =>
                   Effect.gen(function* () {
@@ -343,7 +346,7 @@ export const Plugin = {
       Effect.gen(function* () {
         const tool = event.tools[name]
         if (!tool) return
-        tool.description = description(yield* shell.name())
+        tool.description = description(ShellSelect.name(yield* shellSelect.acceptable()))
       }),
     )
   }),

packages/core/test/tool-shell.test.ts

@@ -32,6 +32,7 @@ import { Permission } from "@opencode-ai/core/permission"
 import { PluginRuntime } from "@opencode-ai/core/plugin/runtime"
 import { PluginSupervisor } from "@opencode-ai/core/plugin/supervisor"
 import { Shell } from "@opencode-ai/core/shell"
+import { ShellSelect } from "@opencode-ai/core/shell/select"
 import { Shell as ShellSchema } from "@opencode-ai/schema/shell"
 import { ShellTool } from "@opencode-ai/core/tool/plugin/shell"
 import { ToolOutput } from "@opencode-ai/core/tool-output"
@@ -136,6 +137,7 @@ const shellPluginSupervisor = makeLocationNode({
     Permission.node,
     PluginRuntime.node,
     Shell.node,
+    ShellSelect.node,
     Tool.node,
   ],
 })
@@ -167,6 +169,7 @@ const call = (input: typeof ShellTool.Input.Type, id = "call-shell") => ({
 })
 
 const isWindows = process.platform === "win32"
+const terminalOnlyIt = isWindows ? productionIt.live.skip : productionIt.live
 const cwdCommand = isWindows ? "(Get-Location).Path; Start-Sleep -Milliseconds 100" : "pwd"
 const helloCommand = isWindows ? "[Console]::Out.Write('hello'); Start-Sleep -Milliseconds 100" : "printf hello"
 const stderrCommand = isWindows
@@ -214,6 +217,38 @@ const withSession = <A, E, R>(directory: string, body: (registry: Tool.Interface
   })
 
 describe("ShellTool", () => {
+  terminalOnlyIt("falls back from a terminal-only shell", () =>
+    Effect.acquireUseRelease(
+      Effect.promise(() => tmpdir()),
+      (tmp) => {
+        reset()
+        return withSession(tmp.path, (registry) =>
+          Effect.gen(function* () {
+            const shellSelect = yield* ShellSelect.Service
+            const shell = yield* Shell.Service
+            const configured = path.join(tmp.path, "fish")
+            const preferred = yield* shellSelect.preferred()
+            yield* Effect.promise(() => fs.symlink(preferred, configured))
+            yield* shellSelect.transform((draft) => draft.configure(configured))
+            const acceptable = yield* shellSelect.acceptable()
+            expect(yield* shellSelect.preferred()).toBe(configured)
+            expect(acceptable).not.toBe(configured)
+
+            const progress: Tool.Metadata[] = []
+            yield* executeTool(registry, {
+              ...call({ command: "printf tool" }),
+              progress: (update) => Effect.sync(() => progress.push(update)),
+            })
+            const shellID = progress[0]?.shellID
+            if (typeof shellID !== "string") yield* Effect.die(new Error("Missing shell ID"))
+            expect((yield* shell.get(ShellSchema.ID.make(shellID))).shell).toBe(acceptable)
+          }),
+        )
+      },
+      (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
+    ),
+  )
+
   productionIt.live(
     "registers and returns real successful output from the active Location",
     () =>