diff --git a/packages/core/src/process.ts b/packages/core/src/process.ts
new file mode 100644
index 0000000000..f855459b2c
--- /dev/null
+++ b/packages/core/src/process.ts
@@ -0,0 +1,207 @@
+import { Context, Duration, Effect, Fiber, Layer, Schema, Stream } from "effect"
+import type { PlatformError } from "effect/PlatformError"
+import { ChildProcess } from "effect/unstable/process"
+import { ChildProcessSpawner } from "effect/unstable/process/ChildProcessSpawner"
+import { CrossSpawnSpawner } from "./cross-spawn-spawner"
+
+export class AppProcessError extends Schema.TaggedErrorClass<AppProcessError>()("AppProcessError", {
+  command: Schema.String,
+  exitCode: Schema.optional(Schema.Number),
+  stderr: Schema.optional(Schema.String),
+  cause: Schema.optional(Schema.Defect),
+}) {}
+
+export interface RunOptions {
+  readonly maxOutputBytes?: number
+  readonly maxErrorBytes?: number
+  readonly signal?: AbortSignal
+  readonly timeout?: Duration.Input
+}
+
+export interface RunStreamOptions {
+  readonly signal?: AbortSignal
+  readonly includeStderr?: boolean
+  readonly okExitCodes?: ReadonlyArray<number>
+  readonly maxErrorBytes?: number
+}
+
+export interface RunResult {
+  readonly command: string
+  readonly exitCode: number
+  readonly stdout: Buffer
+  readonly stderr: Buffer
+  readonly truncated: boolean
+}
+
+export type Interface = ChildProcessSpawner["Service"] & {
+  readonly run: (command: ChildProcess.Command, options?: RunOptions) => Effect.Effect<RunResult, AppProcessError>
+  readonly runStream: (
+    command: ChildProcess.Command,
+    options?: RunStreamOptions,
+  ) => Stream.Stream<string, AppProcessError>
+}
+
+export class Service extends Context.Service<Service, Interface>()("@opencode/AppProcess") {}
+
+export const requireSuccess = (result: RunResult): Effect.Effect<RunResult, AppProcessError> =>
+  result.exitCode === 0
+    ? Effect.succeed(result)
+    : Effect.fail(
+        new AppProcessError({
+          command: result.command,
+          exitCode: result.exitCode,
+          stderr: result.stderr.toString("utf8"),
+        }),
+      )
+
+export const requireExitIn =
+  (codes: ReadonlyArray<number>) =>
+  (result: RunResult): Effect.Effect<RunResult, AppProcessError> =>
+    codes.includes(result.exitCode)
+      ? Effect.succeed(result)
+      : Effect.fail(
+          new AppProcessError({
+            command: result.command,
+            exitCode: result.exitCode,
+            stderr: result.stderr.toString("utf8"),
+          }),
+        )
+
+const describeCommand = (command: ChildProcess.Command): string => {
+  if (command._tag === "StandardCommand") {
+    return command.args.length ? `${command.command} ${command.args.join(" ")}` : command.command
+  }
+  return `${describeCommand(command.left)} | ${describeCommand(command.right)}`
+}
+
+const wrapError = (description: string, cause: unknown): AppProcessError =>
+  cause instanceof AppProcessError ? cause : new AppProcessError({ command: description, cause })
+
+const abortError = (signal: AbortSignal): Error => {
+  const reason = signal.reason
+  if (reason instanceof Error) return reason
+  const err = new Error("Aborted")
+  err.name = "AbortError"
+  return err
+}
+
+const waitForAbort = (signal: AbortSignal) =>
+  Effect.callback<never, Error>((resume) => {
+    if (signal.aborted) {
+      resume(Effect.fail(abortError(signal)))
+      return
+    }
+    const onabort = () => resume(Effect.fail(abortError(signal)))
+    signal.addEventListener("abort", onabort, { once: true })
+    return Effect.sync(() => signal.removeEventListener("abort", onabort))
+  })
+
+const collectStream = (stream: Stream.Stream<Uint8Array, PlatformError>, maxOutputBytes: number | undefined) =>
+  Stream.runFold(
+    stream,
+    () => ({ chunks: [] as Uint8Array[], bytes: 0, truncated: false }),
+    (acc, chunk) => {
+      if (maxOutputBytes === undefined) {
+        acc.chunks.push(chunk)
+        acc.bytes += chunk.length
+        return acc
+      }
+      const remaining = maxOutputBytes - acc.bytes
+      if (remaining > 0) acc.chunks.push(remaining >= chunk.length ? chunk : chunk.slice(0, remaining))
+      acc.bytes += chunk.length
+      acc.truncated = acc.truncated || acc.bytes > maxOutputBytes
+      return acc
+    },
+  ).pipe(Effect.map((x) => ({ buffer: Buffer.concat(x.chunks), truncated: x.truncated })))
+
+export const layer = Layer.effect(
+  Service,
+  Effect.gen(function* () {
+    const spawner = yield* ChildProcessSpawner
+
+    const run = Effect.fn("AppProcess.run")(function* (command: ChildProcess.Command, options?: RunOptions) {
+      const description = describeCommand(command)
+      const collect = Effect.scoped(
+        Effect.gen(function* () {
+          const handle = yield* spawner.spawn(command)
+          const [stdout, stderr, exitCode] = yield* Effect.all(
+            [
+              collectStream(handle.stdout, options?.maxOutputBytes),
+              collectStream(handle.stderr, options?.maxErrorBytes),
+              handle.exitCode,
+            ],
+            { concurrency: "unbounded" },
+          )
+          return {
+            command: description,
+            exitCode,
+            stdout: stdout.buffer,
+            stderr: stderr.buffer,
+            truncated: stdout.truncated,
+          } satisfies RunResult
+        }),
+      )
+      const timed = options?.timeout
+        ? Effect.timeoutOrElse(collect, {
+            duration: options.timeout,
+            orElse: () =>
+              Effect.fail(new AppProcessError({ command: description, cause: new Error("Timed out") })),
+          })
+        : collect
+      const aborted = options?.signal
+        ? timed.pipe(
+            Effect.raceFirst(
+              waitForAbort(options.signal).pipe(Effect.mapError((cause) => wrapError(description, cause))),
+            ),
+          )
+        : timed
+      return yield* aborted.pipe(Effect.catch((cause) => Effect.fail(wrapError(description, cause))))
+    })
+
+    const runStream = (command: ChildProcess.Command, options?: RunStreamOptions): Stream.Stream<string, AppProcessError> => {
+      const description = describeCommand(command)
+      const okExitCodes = options?.okExitCodes
+      const built: Stream.Stream<string, AppProcessError | PlatformError> = Stream.unwrap(
+        Effect.gen(function* () {
+          const handle = yield* spawner.spawn(command)
+          const stderrFiber = yield* Effect.forkScoped(
+            collectStream(handle.stderr, options?.maxErrorBytes).pipe(
+              Effect.map((x) => x.buffer.toString("utf8")),
+            ),
+          )
+          const source = options?.includeStderr === true ? handle.all : handle.stdout
+          const lines = source.pipe(
+            Stream.decodeText,
+            Stream.splitLines,
+            Stream.filter((line) => line.length > 0),
+          )
+          const tail = Stream.unwrap(
+            Effect.gen(function* () {
+              const code = yield* handle.exitCode
+              if (okExitCodes && okExitCodes.length > 0 && !okExitCodes.includes(code)) {
+                const stderr = yield* Fiber.join(stderrFiber)
+                return Stream.fail(new AppProcessError({ command: description, exitCode: code, stderr }))
+              }
+              return Stream.empty
+            }),
+          )
+          return Stream.concat(lines, tail) as Stream.Stream<string, AppProcessError | PlatformError>
+        }),
+      )
+      const mapped = built.pipe(
+        Stream.catch((cause): Stream.Stream<string, AppProcessError> => Stream.fail(wrapError(description, cause))),
+      )
+      if (!options?.signal) return mapped
+      const signal = options.signal
+      return mapped.pipe(
+        Stream.interruptWhen(waitForAbort(signal).pipe(Effect.mapError((cause) => wrapError(description, cause)))),
+      )
+    }
+
+    return Service.of({ ...spawner, run, runStream })
+  }),
+)
+
+export const defaultLayer = layer.pipe(Layer.provide(CrossSpawnSpawner.defaultLayer))
+
+export * as AppProcess from "./process"
diff --git a/packages/core/test/process/process.test.ts b/packages/core/test/process/process.test.ts
new file mode 100644
index 0000000000..1b46c1f1e6
--- /dev/null
+++ b/packages/core/test/process/process.test.ts
@@ -0,0 +1,210 @@
+import { describe, expect } from "bun:test"
+import { Effect, Exit, Stream } from "effect"
+import { ChildProcess } from "effect/unstable/process"
+import { AppProcess } from "@opencode-ai/core/process"
+import { testEffect } from "../lib/effect"
+
+const it = testEffect(AppProcess.defaultLayer)
+
+const NODE = process.execPath
+const cmd = (...args: string[]) => ChildProcess.make(NODE, args)
+
+describe("AppProcess", () => {
+  describe("run", () => {
+    it.effect(
+      "captures stdout and exit code zero",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const result = yield* svc.run(cmd("-e", "process.stdout.write('hi\\n')"))
+        expect(result.exitCode).toBe(0)
+        expect(result.stdout.toString("utf8")).toBe("hi\n")
+        expect(result.truncated).toBe(false)
+      }),
+    )
+
+    it.effect(
+      "non-zero exit returns RunResult; caller can require success",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const result = yield* svc.run(cmd("-e", "process.exit(1)"))
+        expect(result.exitCode).toBe(1)
+      }),
+    )
+
+    it.effect(
+      "requireSuccess fails on non-zero exit",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const exit = yield* Effect.exit(svc.run(cmd("-e", "process.exit(1)")).pipe(Effect.flatMap(AppProcess.requireSuccess)))
+        expect(Exit.isFailure(exit)).toBe(true)
+        if (Exit.isFailure(exit)) {
+          const reason = exit.cause.reasons[0]
+          if (reason && reason._tag === "Fail") {
+            expect(reason.error).toBeInstanceOf(AppProcess.AppProcessError)
+            expect((reason.error as AppProcess.AppProcessError).exitCode).toBe(1)
+          } else {
+            throw new Error("expected fail reason")
+          }
+        }
+      }),
+    )
+
+    it.effect(
+      "requireSuccess succeeds on exit 0",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const result = yield* svc.run(cmd("-e", "process.exit(0)")).pipe(Effect.flatMap(AppProcess.requireSuccess))
+        expect(result.exitCode).toBe(0)
+      }),
+    )
+
+    it.effect(
+      "requireExitIn allowlists multiple exit codes",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const requireZeroOrOne = AppProcess.requireExitIn([0, 1])
+        const okZero = yield* svc.run(cmd("-e", "process.exit(0)")).pipe(Effect.flatMap(requireZeroOrOne))
+        expect(okZero.exitCode).toBe(0)
+        const okOne = yield* svc.run(cmd("-e", "process.exit(1)")).pipe(Effect.flatMap(requireZeroOrOne))
+        expect(okOne.exitCode).toBe(1)
+        const exit = yield* Effect.exit(
+          svc.run(cmd("-e", "process.exit(2)")).pipe(Effect.flatMap(requireZeroOrOne)),
+        )
+        expect(Exit.isFailure(exit)).toBe(true)
+        if (Exit.isFailure(exit)) {
+          const reason = exit.cause.reasons[0]
+          if (reason && reason._tag === "Fail") {
+            expect(reason.error).toBeInstanceOf(AppProcess.AppProcessError)
+            expect((reason.error as AppProcess.AppProcessError).exitCode).toBe(2)
+          }
+        }
+      }),
+    )
+
+    it.effect(
+      "truncates output when maxOutputBytes is set",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const result = yield* svc.run(cmd("-e", "process.stdout.write('0123456789')"), { maxOutputBytes: 5 })
+        expect(result.exitCode).toBe(0)
+        expect(result.truncated).toBe(true)
+        expect(result.stdout.length).toBe(5)
+        expect(result.stdout.toString("utf8")).toBe("01234")
+      }),
+    )
+
+    it.effect(
+      "result includes command description",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const result = yield* svc.run(cmd("-e", "process.stdout.write('hi')"))
+        expect(result.command).toBe(`${NODE} -e process.stdout.write('hi')`)
+      }),
+    )
+  })
+
+  describe("inherited platform methods", () => {
+    it.effect(
+      "string returns stdout as string",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const out = yield* svc.string(cmd("-e", "process.stdout.write('hi\\n')"))
+        expect(out).toBe("hi\n")
+      }),
+    )
+
+    it.effect(
+      "lines returns the platform's array of lines",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const out = yield* svc.lines(cmd("-e", "process.stdout.write('a\\nb\\n')"))
+        expect(Array.from(out)).toEqual(["a", "b"])
+      }),
+    )
+  })
+
+  describe("runStream", () => {
+    it.live(
+      "emits lines incrementally and ends cleanly on exit 0",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const result = yield* svc
+          .runStream(cmd("-e", "console.log('one'); console.log('two'); console.log('three')"))
+          .pipe(Stream.runCollect)
+        expect(Array.from(result)).toEqual(["one", "two", "three"])
+      }),
+    )
+
+    it.live(
+      "fails with AppProcessError when exit not in okExitCodes",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const exit = yield* Effect.exit(
+          svc
+            .runStream(cmd("-e", "console.log('a'); process.exit(2)"), { okExitCodes: [0] })
+            .pipe(Stream.runCollect),
+        )
+        expect(Exit.isFailure(exit)).toBe(true)
+        if (Exit.isFailure(exit)) {
+          const reason = exit.cause.reasons[0]
+          if (reason && reason._tag === "Fail") {
+            expect(reason.error).toBeInstanceOf(AppProcess.AppProcessError)
+          }
+        }
+      }),
+    )
+
+    it.live(
+      "okExitCodes allowlist treats non-zero as success",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const result = yield* svc
+          .runStream(cmd("-e", "console.log('only'); process.exit(1)"), { okExitCodes: [0, 1] })
+          .pipe(Stream.runCollect)
+        expect(Array.from(result)).toEqual(["only"])
+      }),
+    )
+
+    it.live(
+      "without okExitCodes, never fails on exit code",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const result = yield* svc
+          .runStream(cmd("-e", "console.log('only'); process.exit(7)"))
+          .pipe(Stream.runCollect)
+        expect(Array.from(result)).toEqual(["only"])
+      }),
+    )
+
+    it.live(
+      "AbortSignal interrupts the stream",
+      Effect.gen(function* () {
+        const svc = yield* AppProcess.Service
+        const controller = new AbortController()
+        setTimeout(() => controller.abort(), 50)
+        const exit = yield* Effect.exit(
+          svc
+            .runStream(cmd("-e", "setInterval(() => console.log('tick'), 100); setTimeout(() => {}, 60_000)"), {
+              signal: controller.signal,
+            })
+            .pipe(Stream.runCollect),
+        )
+        expect(Exit.isFailure(exit)).toBe(true)
+      }),
+    )
+  })
+
+  describe("spawn (inherited)", () => {
+    it.live(
+      "returns the platform ChildProcessHandle for advanced use",
+      Effect.scoped(
+        Effect.gen(function* () {
+          const svc = yield* AppProcess.Service
+          const handle = yield* svc.spawn(cmd("-e", "setInterval(() => {}, 1_000)"))
+          expect(yield* handle.isRunning).toBe(true)
+          yield* handle.kill()
+        }),
+      ),
+    )
+  })
+})