diff --git a/packages/client/src/effect/api/api.ts b/packages/client/src/effect/api/api.ts
index 28c06cbf04ff..0b9937f7079e 100644
--- a/packages/client/src/effect/api/api.ts
+++ b/packages/client/src/effect/api/api.ts
@@ -809,6 +809,7 @@ export type Endpoint21_4Input = {
   readonly location?: Endpoint21_4Request["query"]["location"]
   readonly cursor?: Endpoint21_4Request["query"]["cursor"]
   readonly limit?: Endpoint21_4Request["query"]["limit"]
+  readonly keep?: Endpoint21_4Request["query"]["keep"]
 }
 export type Endpoint21_4Output = EffectValue<ReturnType<RawClient["server.shell"]["shell.output"]>>
 export type ShellOutputOperation<E = never> = (input: Endpoint21_4Input) => Effect.Effect<Endpoint21_4Output, E>
diff --git a/packages/client/src/effect/generated/client.ts b/packages/client/src/effect/generated/client.ts
index 1f5871711356..d56562d48244 100644
--- a/packages/client/src/effect/generated/client.ts
+++ b/packages/client/src/effect/generated/client.ts
@@ -971,11 +971,12 @@ type Endpoint21_4Input = {
   readonly location?: Endpoint21_4Request["query"]["location"]
   readonly cursor?: Endpoint21_4Request["query"]["cursor"]
   readonly limit?: Endpoint21_4Request["query"]["limit"]
+  readonly keep?: Endpoint21_4Request["query"]["keep"]
 }
 const Endpoint21_4 = (raw: RawClient["server.shell"]) => (input: Endpoint21_4Input) =>
   raw["shell.output"]({
     params: { id: input["id"] },
-    query: { location: input["location"], cursor: input["cursor"], limit: input["limit"] },
+    query: { location: input["location"], cursor: input["cursor"], limit: input["limit"], keep: input["keep"] },
   }).pipe(Effect.mapError(mapClientError))
 
 type Endpoint21_5Request = Parameters<RawClient["server.shell"]["shell.remove"]>[0]
diff --git a/packages/client/src/promise/generated/client.ts b/packages/client/src/promise/generated/client.ts
index bed325d97689..b0a574067f7a 100644
--- a/packages/client/src/promise/generated/client.ts
+++ b/packages/client/src/promise/generated/client.ts
@@ -1411,7 +1411,7 @@ export function make(options: ClientOptions) {
           {
             method: "GET",
             path: `/api/shell/${encodeURIComponent(input.id)}/output`,
-            query: { location: input["location"], cursor: input["cursor"], limit: input["limit"] },
+            query: { location: input["location"], cursor: input["cursor"], limit: input["limit"], keep: input["keep"] },
             successStatus: 200,
             declaredStatuses: [404, 401, 400],
             empty: false,
diff --git a/packages/client/src/promise/generated/types.ts b/packages/client/src/promise/generated/types.ts
index 255beaa1bb9d..878e3dc70682 100644
--- a/packages/client/src/promise/generated/types.ts
+++ b/packages/client/src/promise/generated/types.ts
@@ -4623,17 +4623,26 @@ export type ShellOutputInput = {
     readonly location?: { readonly directory?: string | undefined; readonly workspace?: string | undefined } | undefined
     readonly cursor?: number | undefined
     readonly limit?: number | undefined
+    readonly keep?: "head" | "tail" | undefined
   }["location"]
   readonly cursor?: {
     readonly location?: { readonly directory?: string | undefined; readonly workspace?: string | undefined } | undefined
     readonly cursor?: number | undefined
     readonly limit?: number | undefined
+    readonly keep?: "head" | "tail" | undefined
   }["cursor"]
   readonly limit?: {
     readonly location?: { readonly directory?: string | undefined; readonly workspace?: string | undefined } | undefined
     readonly cursor?: number | undefined
     readonly limit?: number | undefined
+    readonly keep?: "head" | "tail" | undefined
   }["limit"]
+  readonly keep?: {
+    readonly location?: { readonly directory?: string | undefined; readonly workspace?: string | undefined } | undefined
+    readonly cursor?: number | undefined
+    readonly limit?: number | undefined
+    readonly keep?: "head" | "tail" | undefined
+  }["keep"]
 }
 
 export type ShellOutputOutput = {
diff --git a/packages/core/src/shell.ts b/packages/core/src/shell.ts
index a62fef8107fe..6e0987507699 100644
--- a/packages/core/src/shell.ts
+++ b/packages/core/src/shell.ts
@@ -139,8 +139,9 @@ export const layer = Layer.effect(
       const cursor = input?.cursor ?? 0
       const limit = input?.limit ?? 65536
       if (cursor >= session.size) return { output: "", cursor: session.size, size: session.size, truncated: false }
-      const start = Math.max(0, cursor)
-      const length = Math.min(limit, session.size - start)
+      const available = session.size - Math.max(0, cursor)
+      const start = input?.keep === "tail" ? Math.max(cursor, session.size - limit) : Math.max(0, cursor)
+      const length = Math.min(limit, available)
       const buffer = Buffer.alloc(length)
       const bytesRead = yield* Effect.promise(
         () =>
diff --git a/packages/core/src/tool/shell.ts b/packages/core/src/tool/shell.ts
index d2b8bb474482..54dffd3d966b 100644
--- a/packages/core/src/tool/shell.ts
+++ b/packages/core/src/tool/shell.ts
@@ -201,7 +201,7 @@ export const Plugin = {
 
                 const settleShell = Effect.fn("ShellTool.settleShell")(function* () {
                   const final = yield* shell.wait(info.id)
-                  const page = yield* shell.output(info.id, { limit: MAX_CAPTURE_BYTES })
+                  const page = yield* shell.output(info.id, { limit: MAX_CAPTURE_BYTES, keep: "tail" })
 
                   if (final.status === "timeout") {
                     return {
@@ -213,7 +213,7 @@ export const Plugin = {
                     }
                   }
 
-                  const truncated = page.size > page.cursor
+                  const truncated = page.size > MAX_CAPTURE_BYTES
                   const body = page.output || "(no output)"
                   const notice = truncated ? `\n\n[output truncated; full output saved to: ${final.file}]` : ""
                   return {
diff --git a/packages/core/test/tool-shell.test.ts b/packages/core/test/tool-shell.test.ts
index 6a6a53e171d8..8c16bb7af283 100644
--- a/packages/core/test/tool-shell.test.ts
+++ b/packages/core/test/tool-shell.test.ts
@@ -162,10 +162,10 @@ const idleCommand = isWindows ? "Start-Sleep -Seconds 60" : "sleep 60"
 const bodyExitCommand = isWindows
   ? "[Console]::Out.Write('body'); Start-Sleep -Milliseconds 100; exit 7"
   : "printf body && exit 7"
-const overflowCommand = (bytes: number) =>
+const overflowMarkersCommand = (bytes: number) =>
   isWindows
-    ? `[Console]::Out.Write(('x' * ${bytes})); Start-Sleep -Milliseconds 100`
-    : `head -c ${bytes} /dev/zero | tr '\\0' 'x'`
+    ? `[Console]::Out.Write('head-marker'); [Console]::Out.Write(('x' * ${bytes})); [Console]::Out.Write('tail-marker'); Start-Sleep -Milliseconds 100`
+    : `printf head-marker; head -c ${bytes} /dev/zero | tr '\\0' 'x'; printf tail-marker`
 
 const withSession = <A, E, R>(directory: string, body: (registry: ToolRegistry.Interface) => Effect.Effect<A, E, R>) =>
   Effect.gen(function* () {
@@ -396,15 +396,18 @@ describe("ShellTool", () => {
         reset()
         const bytes = ShellTool.MAX_CAPTURE_BYTES + 1024
         return withSession(tmp.path, (registry) =>
-          settleTool(registry, call({ command: overflowCommand(bytes) }, "call-overflow")),
+          settleTool(registry, call({ command: overflowMarkersCommand(bytes) }, "call-overflow")),
         ).pipe(
           Effect.andThen((settled) =>
             Effect.sync(() => {
               expect(settled.output?.structured).toMatchObject({ exit: 0, truncated: true })
               expect(settled.output?.content[0]).toMatchObject({
                 type: "text",
-                text: expect.stringContaining("output truncated; full output saved to:"),
+                text: expect.stringMatching(/tail-marker[\s\S]*output truncated; full output saved to:/),
               })
+              const content = settled.output?.content[0]
+              if (content?.type === "text" && typeof content.text === "string")
+                expect(content.text.includes("head-marker")).toBe(false)
             }),
           ),
         )
diff --git a/packages/schema/src/shell.ts b/packages/schema/src/shell.ts
index bcd09cd901ac..ce9b36a82cab 100644
--- a/packages/schema/src/shell.ts
+++ b/packages/schema/src/shell.ts
@@ -65,6 +65,7 @@ export interface CreateInput extends Schema.Schema.Type<typeof CreateInput> {}
 export const OutputInput = Schema.Struct({
   cursor: optional(NonNegativeInt),
   limit: optional(NonNegativeInt),
+  keep: optional(Schema.Literals(["head", "tail"])),
 })
 export interface OutputInput extends Schema.Schema.Type<typeof OutputInput> {}
 
diff --git a/packages/server/src/handlers/shell.ts b/packages/server/src/handlers/shell.ts
index ac1ae09a8c23..4cae3d575e77 100644
--- a/packages/server/src/handlers/shell.ts
+++ b/packages/server/src/handlers/shell.ts
@@ -57,7 +57,11 @@ export const ShellHandler = HttpApiBuilder.group(Api, "server.shell", (handlers)
         Effect.fn(function* (ctx) {
           const shell = yield* Shell.Service
           return yield* response(
-            shell.output(ctx.params.id, { cursor: ctx.query.cursor, limit: ctx.query.limit }).pipe(
+            shell.output(ctx.params.id, {
+              cursor: ctx.query.cursor,
+              limit: ctx.query.limit,
+              keep: ctx.query.keep,
+            }).pipe(
               Effect.catchTag(
                 "Shell.NotFoundError",
                 () => new ShellNotFoundError({ id: ctx.params.id, message: `Shell command not found: ${ctx.params.id}` }),