feat: add prompt enhancement feature

Add AI-powered prompt enhancement that rewrites rough user prompts into
clearer, more specific versions before sending to the main model.

- Add `enhancePrompt()` utility using a small/cheap model to polish prompts
- Register `prompt.enhance` TUI command with `<leader>i` keybind
- Show "enhance" hint in the bottom bar alongside agents/commands
- Add `prompt_enhance` keybind to config schema
- Add unit tests for the `clean()` text sanitization function

Inspired by KiloCode's prompt enhancement feature.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: anandgupta42

packages/opencode/src/altimate/enhance-prompt.ts

@@ -0,0 +1,95 @@
+// altimate_change - new file
+import { Provider } from "@/provider/provider"
+import { LLM } from "@/session/llm"
+import { Agent } from "@/agent/agent"
+import { Log } from "@/util/log"
+import { MessageV2 } from "@/session/message-v2"
+
+const log = Log.create({ service: "enhance-prompt" })
+
+const ENHANCE_SYSTEM_PROMPT = `You are a prompt enhancement specialist for a data engineering coding agent.
+
+Your job is to take a user's rough prompt and rewrite it into a clearer, more specific version that will produce better results from the coding agent.
+
+Rules:
+- Reply with ONLY the enhanced prompt text — no conversation, explanations, lead-in, bullet points, placeholders, or surrounding quotes
+- Preserve the user's intent exactly — do not add requirements they didn't ask for
+- Make implicit requirements explicit (e.g. if they say "fix the bug", specify what kind of verification to do)
+- Add structure when the prompt is vague (e.g. "look at X first, then modify Y")
+- Keep the enhanced prompt concise — longer is not better
+- If the original prompt is already clear and specific, return it unchanged
+- Do not wrap your response in markdown code fences or quotes`
+
+export function clean(text: string) {
+  return text
+    .replace(/^```\w*\n?|```$/g, "")
+    .trim()
+    .replace(/^(['"])([\s\S]*)\1$/, "$2")
+    .trim()
+}
+
+export async function enhancePrompt(text: string): Promise<string> {
+  if (!text.trim()) return text
+
+  log.info("enhancing", { length: text.length })
+
+  const defaultModel = await Provider.defaultModel()
+  const model =
+    (await Provider.getSmallModel(defaultModel.providerID)) ??
+    (await Provider.getModel(defaultModel.providerID, defaultModel.modelID))
+
+  const agent: Agent.Info = {
+    name: "enhance-prompt",
+    mode: "primary",
+    hidden: true,
+    options: {},
+    permission: [],
+    prompt: ENHANCE_SYSTEM_PROMPT,
+    temperature: 0.7,
+  }
+
+  const user: MessageV2.User = {
+    id: "enhance-prompt" as any,
+    sessionID: "enhance-prompt" as any,
+    role: "user",
+    time: { created: Date.now() },
+    agent: "enhance-prompt",
+    model: {
+      providerID: model.providerID,
+      modelID: model.id,
+    },
+  }
+
+  const stream = await LLM.stream({
+    agent,
+    user,
+    system: [],
+    small: true,
+    tools: {},
+    model,
+    abort: new AbortController().signal,
+    sessionID: "enhance-prompt" as any,
+    retries: 2,
+    messages: [
+      {
+        role: "user",
+        content: text,
+      },
+    ],
+  })
+
+  const result = await stream.text.catch((err) => {
+    log.error("failed to enhance prompt", { error: err })
+    return undefined
+  })
+
+  if (!result) return text
+
+  const cleaned = clean(
+    result
+      .replace(/<think>[\s\S]*?<\/think>\s*/g, "")
+      .trim(),
+  )
+
+  return cleaned || text
+}

packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx

@@ -34,6 +34,9 @@ import { useToast } from "../../ui/toast"
 import { useKV } from "../../context/kv"
 import { useTextareaKeybindings } from "../textarea-keybindings"
 import { DialogSkill } from "../dialog-skill"
+// altimate_change start - import prompt enhancement
+import { enhancePrompt } from "@/altimate/enhance-prompt"
+// altimate_change end
 
 export type PromptProps = {
   sessionID?: string
@@ -193,6 +196,50 @@ export function Prompt(props: PromptProps) {
           dialog.clear()
         },
       },
+      // altimate_change start - add prompt enhance command
+      {
+        title: "Enhance prompt",
+        value: "prompt.enhance",
+        keybind: "prompt_enhance",
+        category: "Prompt",
+        enabled: !!store.prompt.input,
+        onSelect: async (dialog) => {
+          if (!store.prompt.input.trim()) return
+          dialog.clear()
+          const original = store.prompt.input
+          toast.show({
+            message: "Enhancing prompt...",
+            variant: "info",
+            duration: 2000,
+          })
+          try {
+            const enhanced = await enhancePrompt(original)
+            if (enhanced !== original) {
+              input.setText(enhanced)
+              setStore("prompt", "input", enhanced)
+              input.gotoBufferEnd()
+              toast.show({
+                message: "Prompt enhanced",
+                variant: "success",
+                duration: 2000,
+              })
+            } else {
+              toast.show({
+                message: "Prompt already looks good",
+                variant: "info",
+                duration: 2000,
+              })
+            }
+          } catch {
+            toast.show({
+              message: "Failed to enhance prompt",
+              variant: "error",
+              duration: 3000,
+            })
+          }
+        },
+      },
+      // altimate_change end
       {
         title: "Paste",
         value: "prompt.paste",
@@ -1139,6 +1186,11 @@ export function Prompt(props: PromptProps) {
                   <text fg={theme.text}>
                     {keybind.print("command_list")} <span style={{ fg: theme.textMuted }}>commands</span>
                   </text>
+                  {/* altimate_change start - show enhance hint */}
+                  <text fg={theme.text}>
+                    {keybind.print("prompt_enhance")} <span style={{ fg: theme.textMuted }}>enhance</span>
+                  </text>
+                  {/* altimate_change end */}
                 </Match>
                 <Match when={store.mode === "shell"}>
                   <text fg={theme.text}>

packages/opencode/src/config/config.ts

@@ -820,6 +820,9 @@ export namespace Config {
       agent_cycle: z.string().optional().default("tab").describe("Next agent"),
       agent_cycle_reverse: z.string().optional().default("shift+tab").describe("Previous agent"),
       variant_cycle: z.string().optional().default("ctrl+t").describe("Cycle model variants"),
+      // altimate_change start - add prompt enhance keybind
+      prompt_enhance: z.string().optional().default("<leader>i").describe("Enhance prompt with AI before sending"),
+      // altimate_change end
       input_clear: z.string().optional().default("ctrl+c").describe("Clear input field"),
       input_paste: z.string().optional().default("ctrl+v").describe("Paste from clipboard"),
       input_submit: z.string().optional().default("return").describe("Submit input"),

packages/opencode/test/altimate/enhance-prompt.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, test } from "bun:test"
+import { clean } from "../../src/altimate/enhance-prompt"
+
+describe("enhance-prompt clean()", () => {
+  test("strips markdown code fences", () => {
+    expect(clean("```\nfixed prompt\n```")).toBe("fixed prompt")
+  })
+
+  test("strips code fences with language tag", () => {
+    expect(clean("```text\nenhanced prompt\n```")).toBe("enhanced prompt")
+  })
+
+  test("strips surrounding single quotes", () => {
+    expect(clean("'enhanced prompt'")).toBe("enhanced prompt")
+  })
+
+  test("strips surrounding double quotes", () => {
+    expect(clean('"enhanced prompt"')).toBe("enhanced prompt")
+  })
+
+  test("trims whitespace", () => {
+    expect(clean("  enhanced prompt  ")).toBe("enhanced prompt")
+  })
+
+  test("handles combined wrapping", () => {
+    expect(clean('```\n"enhanced prompt"\n```')).toBe("enhanced prompt")
+  })
+
+  test("returns plain text unchanged", () => {
+    expect(clean("fix the auth bug")).toBe("fix the auth bug")
+  })
+
+  test("handles empty string", () => {
+    expect(clean("")).toBe("")
+  })
+
+  test("handles multiline content", () => {
+    const input = "```\nFirst do X.\nThen do Y.\n```"
+    expect(clean(input)).toBe("First do X.\nThen do Y.")
+  })
+})