diff --git a/packages/opencode/src/cli/cmd/tui/component/prompt/autocomplete.tsx b/packages/opencode/src/cli/cmd/tui/component/prompt/autocomplete.tsx
index 2bda73cff7..476b52a5e0 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/autocomplete.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/autocomplete.tsx
@@ -543,8 +543,22 @@ export function Autocomplete(props: {
     ),
   )
 
+  function insertSlashCommand(name: string) {
+    const newText = `/${name} `
+    const cursor = props.input().logicalCursor
+    props.input().deleteRange(0, 0, cursor.row, cursor.col)
+    props.input().insertText(newText)
+    props.input().cursorOffset = Bun.stringWidth(newText)
+  }
+
   const commands = createMemo((): AutocompleteOption[] => {
-    const results: AutocompleteOption[] = [...slashes()]
+    const results: AutocompleteOption[] = slashes().map((command) => {
+      if (!command.input) return command
+      return {
+        ...command,
+        onSelect: () => insertSlashCommand(command.name),
+      }
+    })
 
     for (const serverCommand of sync.data.command) {
       if (serverCommand.source === "skill") continue
@@ -552,13 +566,7 @@ export function Autocomplete(props: {
       results.push({
         display: "/" + serverCommand.name + label,
         description: serverCommand.description,
-        onSelect: () => {
-          const newText = "/" + serverCommand.name + " "
-          const cursor = props.input().logicalCursor
-          props.input().deleteRange(0, 0, cursor.row, cursor.col)
-          props.input().insertText(newText)
-          props.input().cursorOffset = Bun.stringWidth(newText)
-        },
+        onSelect: () => insertSlashCommand(serverCommand.name),
       })
     }
 
diff --git a/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx b/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
index f4b11fa465..4461c3a893 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
@@ -59,7 +59,14 @@ import { DialogWorkspaceUnavailable } from "../dialog-workspace-unavailable"
 import { useArgs } from "@tui/context/args"
 import { Flag } from "@opencode-ai/core/flag/flag"
 import { type WorkspaceStatus } from "../workspace-label"
-import { OPENCODE_BASE_MODE, useBindings, useCommandShortcut, useLeaderActive, useOpencodeKeymap } from "../../keymap"
+import {
+  OPENCODE_BASE_MODE,
+  useBindings,
+  useCommandShortcut,
+  useCommandSlashes,
+  useLeaderActive,
+  useOpencodeKeymap,
+} from "../../keymap"
 import { useTuiConfig } from "../../context/tui-config"
 
 export type PromptProps = {
@@ -151,6 +158,7 @@ export function Prompt(props: PromptProps) {
   const history = usePromptHistory()
   const stash = usePromptStash()
   const keymap = useOpencodeKeymap()
+  const slashCommands = useCommandSlashes()
   const agentShortcut = useCommandShortcut("agent.cycle")
   const paletteShortcut = useCommandShortcut("command.palette.show")
   const renderer = useRenderer()
@@ -1132,6 +1140,8 @@ export function Prompt(props: PromptProps) {
           ]
         : []
 
+    const slash = parseSlashCommand(inputText)
+
     if (store.mode === "shell") {
       void sdk.client.session.shell({
         sessionID,
@@ -1143,25 +1153,13 @@ export function Prompt(props: PromptProps) {
         command: inputText,
       })
       setStore("mode", "normal")
-    } else if (
-      inputText.startsWith("/") &&
-      iife(() => {
-        const firstLine = inputText.split("\n")[0]
-        const command = firstLine.split(" ")[0].slice(1)
-        return sync.data.command.some((x) => x.name === command)
-      })
-    ) {
-      // Parse command from first line, preserve multi-line content in arguments
-      const firstLineEnd = inputText.indexOf("\n")
-      const firstLine = firstLineEnd === -1 ? inputText : inputText.slice(0, firstLineEnd)
-      const [command, ...firstLineArgs] = firstLine.split(" ")
-      const restOfInput = firstLineEnd === -1 ? "" : inputText.slice(firstLineEnd + 1)
-      const args = firstLineArgs.join(" ") + (restOfInput ? "\n" + restOfInput : "")
-
+    } else if (slash && slashCommand(slash.name)?.input) {
+      slashCommand(slash.name)?.onSelect()
+    } else if (slash && sync.data.command.some((x) => x.name === slash.name)) {
       void sdk.client.session.command({
         sessionID,
-        command: command.slice(1),
-        arguments: args,
+        command: slash.name,
+        arguments: slash.arguments,
         agent: agent.name,
         model: `${selectedModel.providerID}/${selectedModel.modelID}`,
         messageID,
@@ -1220,6 +1218,22 @@ export function Prompt(props: PromptProps) {
     input.clear()
     return true
   }
+
+  function parseSlashCommand(text: string) {
+    if (!text.startsWith("/")) return
+    const firstLineEnd = text.indexOf("\n")
+    const firstLine = firstLineEnd === -1 ? text : text.slice(0, firstLineEnd)
+    const [command, ...firstLineArgs] = firstLine.split(" ")
+    const restOfInput = firstLineEnd === -1 ? "" : text.slice(firstLineEnd + 1)
+    return {
+      name: command.slice(1),
+      arguments: firstLineArgs.join(" ") + (restOfInput ? "\n" + restOfInput : ""),
+    }
+  }
+
+  function slashCommand(name: string) {
+    return slashCommands().find((item) => item.name === name || item.aliases?.includes(`/${name}`))
+  }
   const exit = useExit()
 
   function pasteText(text: string, virtualText: string) {
diff --git a/packages/opencode/src/cli/cmd/tui/keymap.tsx b/packages/opencode/src/cli/cmd/tui/keymap.tsx
index d8489fd2f7..eea0ff74cb 100644
--- a/packages/opencode/src/cli/cmd/tui/keymap.tsx
+++ b/packages/opencode/src/cli/cmd/tui/keymap.tsx
@@ -25,9 +25,11 @@ export { useBindings, useKeymapSelector }
 export type OpenTuiKeymap = ReturnType<typeof useKeymap>
 type OpencodeModeStack = ReturnType<typeof createOpencodeModeStack>
 type CommandSlashEntry = {
+  name: string
   display: string
   description?: string
   aliases?: string[]
+  input?: boolean
   onSelect: () => void
 }
 type Command = ReturnType<OpenTuiKeymap["getCommands"]>[number]
@@ -256,6 +258,7 @@ export function useCommandSlashes(): Accessor<readonly CommandSlashEntry[]> {
       if (typeof slashName !== "string" || !slashName) return []
       const slashAliases = entry.command.slashAliases
       return {
+        name: slashName,
         display: `/${slashName}`,
         description:
           typeof entry.command.desc === "string"
@@ -266,6 +269,7 @@ export function useCommandSlashes(): Accessor<readonly CommandSlashEntry[]> {
         aliases: Array.isArray(slashAliases)
           ? slashAliases.filter((alias): alias is string => typeof alias === "string").map((alias) => `/${alias}`)
           : undefined,
+        input: entry.command.slashInput === true,
         onSelect: () => keymap.dispatchCommand(entry.command.name),
       }
     }),
diff --git a/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx b/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
index 245a7296b5..260bd5fe1b 100644
--- a/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
+++ b/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
@@ -314,6 +314,17 @@ export function Session() {
   const dialog = useDialog()
   const renderer = useRenderer()
 
+  function slashArguments(name: string) {
+    const input = prompt?.current.input
+    if (!input?.startsWith("/")) return
+    const firstLineEnd = input.indexOf("\n")
+    const firstLine = firstLineEnd === -1 ? input : input.slice(0, firstLineEnd)
+    const [command, ...firstLineArgs] = firstLine.split(" ")
+    if (command !== `/${name}`) return
+    const restOfInput = firstLineEnd === -1 ? "" : input.slice(firstLineEnd + 1)
+    return firstLineArgs.join(" ") + (restOfInput ? "\n" + restOfInput : "")
+  }
+
   event.on("session.status", (evt) => {
     if (evt.properties.sessionID !== route.sessionID) return
     if (evt.properties.status.type !== "retry") return
@@ -546,6 +557,7 @@ export function Session() {
       slash: {
         name: "compact",
         aliases: ["summarize"],
+        input: true,
       },
       run: () => {
         const selectedModel = local.model.current()
@@ -557,11 +569,14 @@ export function Session() {
           })
           return
         }
-        void sdk.client.session.summarize({
+        const instructions = slashArguments("compact") ?? slashArguments("summarize")
+        const payload = {
           sessionID: route.sessionID,
           modelID: selectedModel.modelID,
           providerID: selectedModel.providerID,
-        })
+          ...(instructions?.trim() ? { $body_instructions: instructions.trim() } : {}),
+        } satisfies Parameters<typeof sdk.client.session.summarize>[0] & { $body_instructions?: string }
+        void sdk.client.session.summarize(payload)
         dialog.clear()
       },
     },
@@ -1046,6 +1061,7 @@ export function Session() {
       desc: "description" in command ? command.description : undefined,
       slashName: "slash" in command ? command.slash?.name : undefined,
       slashAliases: "slash" in command ? command.slash?.aliases : undefined,
+      slashInput: "slash" in command ? command.slash?.input : undefined,
       ...command,
     })),
   )
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/session.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/session.ts
index b8c8a142be..314aaba6b2 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/session.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/session.ts
@@ -62,6 +62,7 @@ export const SummarizePayload = Schema.Struct({
   providerID: ProviderID,
   modelID: ModelID,
   auto: Schema.optional(Schema.Boolean),
+  instructions: Schema.optional(Schema.String),
 })
 export const PromptPayload = Schema.Struct(Struct.omit(SessionPrompt.PromptInput.fields, ["sessionID"]))
 export const CommandPayload = Schema.Struct(Struct.omit(SessionPrompt.CommandInput.fields, ["sessionID"]))
diff --git a/packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts b/packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts
index 2e3617d146..8096dcb470 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts
@@ -277,6 +277,7 @@ export const sessionHandlers = HttpApiBuilder.group(InstanceHttpApi, "session",
           modelID: ctx.payload.modelID,
         },
         auto: ctx.payload.auto ?? false,
+        instructions: ctx.payload.instructions,
       })
       yield* promptSvc.loop({ sessionID: ctx.params.sessionID })
       return true
diff --git a/packages/opencode/src/session/compaction.ts b/packages/opencode/src/session/compaction.ts
index ef007fe74d..b6028e8770 100644
--- a/packages/opencode/src/session/compaction.ts
+++ b/packages/opencode/src/session/compaction.ts
@@ -133,6 +133,12 @@ function buildPrompt(input: { previousSummary?: string; context: string[] }) {
   return [anchor, SUMMARY_TEMPLATE, ...input.context].join("\n\n")
 }
 
+function appendInstructions(prompt: string, instructions: string | undefined) {
+  const trimmed = instructions?.trim()
+  if (!trimmed) return prompt
+  return [prompt, "Additional user instructions for this compaction:", trimmed].join("\n\n")
+}
+
 function preserveRecentBudget(input: { cfg: Config.Info; model: Provider.Model }) {
   return (
     input.cfg.compaction?.preserve_recent_tokens ??
@@ -202,6 +208,7 @@ export interface Interface {
     model: { providerID: ProviderID; modelID: ModelID }
     auto: boolean
     overflow?: boolean
+    instructions?: string
   }) => Effect.Effect<void>
 }
 
@@ -400,7 +407,10 @@ export const layer = Layer.effect(
         { sessionID: input.sessionID },
         { context: [], prompt: undefined },
       )
-      const nextPrompt = compacting.prompt ?? buildPrompt({ previousSummary, context: compacting.context })
+      const nextPrompt = appendInstructions(
+        compacting.prompt ?? buildPrompt({ previousSummary, context: compacting.context }),
+        compactionPart?.instructions,
+      )
       const msgs = structuredClone(selected.head)
       yield* plugin.trigger("experimental.chat.messages.transform", {}, { messages: msgs })
       const modelMessages = yield* MessageV2.toModelMessagesEffect(msgs, model, {
@@ -587,6 +597,7 @@ export const layer = Layer.effect(
       model: { providerID: ProviderID; modelID: ModelID }
       auto: boolean
       overflow?: boolean
+      instructions?: string
     }) {
       const msg = yield* session.updateMessage({
         id: MessageID.ascending(),
@@ -603,6 +614,7 @@ export const layer = Layer.effect(
         type: "compaction",
         auto: input.auto,
         overflow: input.overflow,
+        instructions: input.instructions,
       })
       if (flags.experimentalEventSystem) {
         yield* events.publish(SessionEvent.Compaction.Started, {
diff --git a/packages/opencode/src/session/message-v2.ts b/packages/opencode/src/session/message-v2.ts
index 2745ff4f45..827d761967 100644
--- a/packages/opencode/src/session/message-v2.ts
+++ b/packages/opencode/src/session/message-v2.ts
@@ -186,6 +186,7 @@ export const CompactionPart = Schema.Struct({
   type: Schema.Literal("compaction"),
   auto: Schema.Boolean,
   overflow: Schema.optional(Schema.Boolean),
+  instructions: Schema.optional(Schema.String),
   tail_start_id: Schema.optional(MessageID),
 }).annotate({ identifier: "CompactionPart" })
 export type CompactionPart = Types.DeepMutable<Schema.Schema.Type<typeof CompactionPart>>
diff --git a/packages/opencode/test/session/compaction.test.ts b/packages/opencode/test/session/compaction.test.ts
index 55ddc621ca..310712df4a 100644
--- a/packages/opencode/test/session/compaction.test.ts
+++ b/packages/opencode/test/session/compaction.test.ts
@@ -287,8 +287,8 @@ function compactionProcessLayer(options?: CompactionProcessOptions) {
   )
 }
 
-function createSummaryCompaction(sessionID: SessionID) {
-  return SessionCompaction.use.create({ sessionID, agent: "build", model: ref, auto: false })
+function createSummaryCompaction(sessionID: SessionID, instructions?: string) {
+  return SessionCompaction.use.create({ sessionID, agent: "build", model: ref, auto: false, instructions })
 }
 
 function readCompactionPart(sessionID: SessionID) {
@@ -959,6 +959,30 @@ describe("session.compaction.process", () => {
     }).pipe(withCompaction({ config: cfg({ tail_turns: 2, preserve_recent_tokens: 100 }) })),
   )
 
+  itCompaction.instance(
+    "appends stored instructions to compaction prompt",
+    () => {
+      const stub = llm()
+      let captured = ""
+      stub.push(reply("summary", (input) => (captured = JSON.stringify(input.messages))))
+      return Effect.gen(function* () {
+        const ssn = yield* SessionNs.Service
+        const session = yield* ssn.create({})
+        yield* createUserMessage(session.id, "first")
+        yield* createSummaryCompaction(session.id, "focus on unresolved TODOs")
+
+        const msgs = yield* ssn.messages({ sessionID: session.id })
+        const parent = msgs.at(-1)?.info.id
+        expect(parent).toBeTruthy()
+        yield* SessionCompaction.use.process({ parentID: parent!, messages: msgs, sessionID: session.id, auto: false })
+
+        expect(captured).toContain("Additional user instructions for this compaction")
+        expect(captured).toContain("focus on unresolved TODOs")
+      }).pipe(withCompaction({ llm: stub.layer }))
+    },
+    { git: true },
+  )
+
   itCompaction.instance(
     "falls back to full summary when even one recent turn exceeds preserve token budget",
     () => {