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 cefef208de4..fcd66ec5958 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
@@ -37,6 +37,7 @@ export type PromptProps = {
   sessionID?: string
   visible?: boolean
   disabled?: boolean
+  maxHeight?: number
   onSubmit?: () => void
   ref?: (ref: PromptRef) => void
   hint?: JSX.Element
@@ -821,7 +822,7 @@ export function Prompt(props: PromptProps) {
               textColor={keybind.leader ? theme.textMuted : theme.text}
               focusedTextColor={keybind.leader ? theme.textMuted : theme.text}
               minHeight={1}
-              maxHeight={6}
+              maxHeight={props.maxHeight ?? 6}
               onContentChange={() => {
                 const value = input.plainText
                 setStore("prompt", "input", value)
diff --git a/packages/opencode/src/cli/cmd/tui/routes/home.tsx b/packages/opencode/src/cli/cmd/tui/routes/home.tsx
index c011f6c6246..0210b28eb33 100644
--- a/packages/opencode/src/cli/cmd/tui/routes/home.tsx
+++ b/packages/opencode/src/cli/cmd/tui/routes/home.tsx
@@ -2,6 +2,7 @@ import { Prompt, type PromptRef } from "@tui/component/prompt"
 import { createMemo, Match, onMount, Show, Switch } from "solid-js"
 import { useTheme } from "@tui/context/theme"
 import { useKeybind } from "@tui/context/keybind"
+import { useTerminalDimensions } from "@opentui/solid"
 import { Logo } from "../component/logo"
 import { Tips } from "../component/tips"
 import { Locale } from "@/util/locale"
@@ -22,6 +23,7 @@ export function Home() {
   const sync = useSync()
   const kv = useKV()
   const { theme } = useTheme()
+  const terminal = useTerminalDimensions()
   const route = useRouteData("home")
   const promptRef = usePromptRef()
   const command = useCommandDialog()
@@ -91,29 +93,85 @@ export function Home() {
 
   const keybind = useKeybind()
 
+  const initialPrompt = createMemo(() => sync.data.config.tui?.initial_prompt)
+  const size = createMemo(() => initialPrompt()?.size ?? "compact")
+  const width = createMemo(() => {
+    const value = initialPrompt()?.width_percent
+    if (value) return Math.max(40, Math.min(100, value))
+    if (size() === "medium") return 80
+    if (size() === "large") return 90
+    return 75
+  })
+  const maxWidth = createMemo(() => {
+    if (size() === "compact" && !initialPrompt()?.width_percent) return 75
+    const available = Math.max(50, terminal().width - 8)
+    return Math.max(50, Math.min(available, Math.floor((terminal().width * width()) / 100)))
+  })
+  const height = createMemo(() => {
+    const value = initialPrompt()?.height_percent
+    if (value) return Math.max(10, Math.min(60, value))
+    if (size() === "medium") return 25
+    if (size() === "large") return 35
+    return 0
+  })
+  const maxHeight = createMemo(() => {
+    if (size() === "compact" && !initialPrompt()?.height_percent) return 6
+    const available = Math.max(6, terminal().height - 18)
+    return Math.max(6, Math.min(available, Math.floor((terminal().height * height()) / 100)))
+  })
+  const top = createMemo(() => {
+    if (size() === "medium") return 2
+    if (size() === "large") return 1
+    return 4
+  })
+  const tipsHeight = createMemo(() => {
+    if (size() === "medium") return 3
+    if (size() === "large") return 2
+    return 4
+  })
+  const tipsPadding = createMemo(() => {
+    if (size() === "compact") return 3
+    if (size() === "medium") return 2
+    return 1
+  })
+
   return (
     <>
       <box flexGrow={1} alignItems="center" paddingLeft={2} paddingRight={2}>
         <box flexGrow={1} minHeight={0} />
-        <box height={4} minHeight={0} flexShrink={1} />
+        <box height={top()} minHeight={0} flexShrink={1} />
         <box flexShrink={0}>
           <Logo />
         </box>
         <box height={1} minHeight={0} flexShrink={1} />
-        <box width="100%" maxWidth={75} zIndex={1000} paddingTop={1} flexShrink={0}>
+        <box width="100%" maxWidth={maxWidth()} zIndex={1000} paddingTop={1} flexShrink={0}>
           <Prompt
             ref={(r) => {
               prompt = r
               promptRef.set(r)
             }}
             hint={Hint}
+            maxHeight={maxHeight()}
           />
         </box>
-        <box height={4} minHeight={0} width="100%" maxWidth={75} alignItems="center" paddingTop={3} flexShrink={1}>
+        <box
+          height={tipsHeight()}
+          minHeight={0}
+          width="100%"
+          maxWidth={maxWidth()}
+          alignItems="center"
+          paddingTop={tipsPadding()}
+          flexShrink={1}
+        >
           <Show when={showTips()}>
             <Tips />
           </Show>
         </box>
+        <Show when={size() !== "compact"}>
+          <box width="100%" maxWidth={maxWidth()} alignItems="center" paddingTop={1}>
+            <text fg={theme.textMuted}>home prompt size: {size()}</text>
+          </box>
+        </Show>
         <box flexGrow={1} minHeight={0} />
         <Toast />
       </box>
diff --git a/packages/opencode/src/config/config.ts b/packages/opencode/src/config/config.ts
index 261731b8b0a..3f4b2f50985 100644
--- a/packages/opencode/src/config/config.ts
+++ b/packages/opencode/src/config/config.ts
@@ -930,6 +930,29 @@ export namespace Config {
       .enum(["auto", "stacked"])
       .optional()
       .describe("Control diff rendering style: 'auto' adapts to terminal width, 'stacked' always shows single column"),
+    initial_prompt: z
+      .object({
+        size: z
+          .enum(["compact", "medium", "large"])
+          .optional()
+          .describe("Preset size for the opening home-screen prompt composer"),
+        width_percent: z
+          .number()
+          .int()
+          .min(40)
+          .max(100)
+          .optional()
+          .describe("Override opening home-screen prompt width as terminal percentage (40-100)"),
+        height_percent: z
+          .number()
+          .int()
+          .min(10)
+          .max(60)
+          .optional()
+          .describe("Override opening home-screen prompt max input height as terminal percentage (10-60)"),
+      })
+      .optional()
+      .describe("Opening home-screen prompt sizing preferences"),
   })
 
   export const Server = z
diff --git a/packages/opencode/test/config/config.test.ts b/packages/opencode/test/config/config.test.ts
index 91b87f6498c..00695e6e6b6 100644
--- a/packages/opencode/test/config/config.test.ts
+++ b/packages/opencode/test/config/config.test.ts
@@ -333,6 +333,78 @@ test("handles command configuration", async () => {
   })
 })
 
+test("handles tui initial prompt configuration", async () => {
+  await using tmp = await tmpdir({
+    init: async (dir) => {
+      await writeConfig(dir, {
+        $schema: "https://opencode.ai/config.json",
+        tui: {
+          initial_prompt: {
+            size: "large",
+            width_percent: 92,
+            height_percent: 38,
+          },
+        },
+      })
+    },
+  })
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const config = await Config.get()
+      expect(config.tui?.initial_prompt).toEqual({
+        size: "large",
+        width_percent: 92,
+        height_percent: 38,
+      })
+    },
+  })
+})
+
+test("rejects invalid tui initial prompt size", async () => {
+  await using tmp = await tmpdir({
+    init: async (dir) => {
+      await writeConfig(dir, {
+        $schema: "https://opencode.ai/config.json",
+        tui: {
+          initial_prompt: {
+            size: "huge",
+          },
+        },
+      })
+    },
+  })
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      await expect(Config.get()).rejects.toThrow()
+    },
+  })
+})
+
+test("rejects invalid tui initial prompt percentages", async () => {
+  await using tmp = await tmpdir({
+    init: async (dir) => {
+      await writeConfig(dir, {
+        $schema: "https://opencode.ai/config.json",
+        tui: {
+          initial_prompt: {
+            size: "medium",
+            width_percent: 120,
+            height_percent: 5,
+          },
+        },
+      })
+    },
+  })
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      await expect(Config.get()).rejects.toThrow()
+    },
+  })
+})
+
 test("migrates autoshare to share field", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
diff --git a/packages/sdk/js/src/v2/gen/types.gen.ts b/packages/sdk/js/src/v2/gen/types.gen.ts
index efb7e202e12..e558189c9c4 100644
--- a/packages/sdk/js/src/v2/gen/types.gen.ts
+++ b/packages/sdk/js/src/v2/gen/types.gen.ts
@@ -1699,6 +1699,23 @@ export type Config = {
      * Control diff rendering style: 'auto' adapts to terminal width, 'stacked' always shows single column
      */
     diff_style?: "auto" | "stacked"
+    /**
+     * Opening home-screen prompt sizing preferences
+     */
+    initial_prompt?: {
+      /**
+       * Preset size for the opening home-screen prompt composer
+       */
+      size?: "compact" | "medium" | "large"
+      /**
+       * Override opening home-screen prompt width as terminal percentage (40-100)
+       */
+      width_percent?: number
+      /**
+       * Override opening home-screen prompt max input height as terminal percentage (10-60)
+       */
+      height_percent?: number
+    }
   }
   server?: ServerConfig
   /**
diff --git a/packages/sdk/openapi.json b/packages/sdk/openapi.json
index 85a1af9d70c..68d9d226ea0 100644
--- a/packages/sdk/openapi.json
+++ b/packages/sdk/openapi.json
@@ -9655,6 +9655,29 @@
                 "description": "Control diff rendering style: 'auto' adapts to terminal width, 'stacked' always shows single column",
                 "type": "string",
                 "enum": ["auto", "stacked"]
+              },
+              "initial_prompt": {
+                "description": "Opening home-screen prompt sizing preferences",
+                "type": "object",
+                "properties": {
+                  "size": {
+                    "description": "Preset size for the opening home-screen prompt composer",
+                    "type": "string",
+                    "enum": ["compact", "medium", "large"]
+                  },
+                  "width_percent": {
+                    "description": "Override opening home-screen prompt width as terminal percentage (40-100)",
+                    "type": "integer",
+                    "minimum": 40,
+                    "maximum": 100
+                  },
+                  "height_percent": {
+                    "description": "Override opening home-screen prompt max input height as terminal percentage (10-60)",
+                    "type": "integer",
+                    "minimum": 10,
+                    "maximum": 60
+                  }
+                }
               }
             }
           },
diff --git a/packages/web/src/content/docs/config.mdx b/packages/web/src/content/docs/config.mdx
index eeccde2f791..f07b24df4c8 100644
--- a/packages/web/src/content/docs/config.mdx
+++ b/packages/web/src/content/docs/config.mdx
@@ -164,7 +164,12 @@ You can configure TUI-specific settings through the `tui` option.
     "scroll_acceleration": {
       "enabled": true
     },
-    "diff_style": "auto"
+    "diff_style": "auto",
+    "initial_prompt": {
+      "size": "medium",
+      "width_percent": 80,
+      "height_percent": 25
+    }
   }
 }
 ```
@@ -174,6 +179,11 @@ Available options:
 - `scroll_acceleration.enabled` - Enable macOS-style scroll acceleration. **Takes precedence over `scroll_speed`.**
 - `scroll_speed` - Custom scroll speed multiplier (default: `3`, minimum: `1`). Ignored if `scroll_acceleration.enabled` is `true`.
 - `diff_style` - Control diff rendering. `"auto"` adapts to terminal width, `"stacked"` always shows single column.
+- `initial_prompt.size` - Preset size for the opening home-screen prompt composer. Values: `"compact"` (current behavior), `"medium"`, `"large"`.
+- `initial_prompt.width_percent` - Optional opening-screen width override (percentage of terminal width, `40`-`100`).
+- `initial_prompt.height_percent` - Optional opening-screen max input height override (percentage of terminal height, `10`-`60`).
+
+`initial_prompt` only affects the opening home screen prompt. Session prompt behavior is unchanged.
 
 [Learn more about using the TUI here](/docs/tui).
 
diff --git a/packages/web/src/content/docs/tui.mdx b/packages/web/src/content/docs/tui.mdx
index 085eb6169f8..46763ec38a8 100644
--- a/packages/web/src/content/docs/tui.mdx
+++ b/packages/web/src/content/docs/tui.mdx
@@ -364,6 +364,11 @@ You can customize TUI behavior through your OpenCode config file.
     "scroll_speed": 3,
     "scroll_acceleration": {
       "enabled": true
+    },
+    "initial_prompt": {
+      "size": "medium",
+      "width_percent": 80,
+      "height_percent": 25
     }
   }
 }
@@ -373,6 +378,13 @@ You can customize TUI behavior through your OpenCode config file.
 
 - `scroll_acceleration` - Enable macOS-style scroll acceleration for smooth, natural scrolling. When enabled, scroll speed increases with rapid scrolling gestures and stays precise for slower movements. **This setting takes precedence over `scroll_speed` and overrides it when enabled.**
 - `scroll_speed` - Controls how fast the TUI scrolls when using scroll commands (minimum: `1`). Defaults to `3`. **Note: This is ignored if `scroll_acceleration.enabled` is set to `true`.**
+- `initial_prompt.size` - Preset opening-screen prompt size: `compact`, `medium`, or `large`.
+- `initial_prompt.width_percent` - Optional opening-screen width override as percent of terminal width (`40`-`100`).
+- `initial_prompt.height_percent` - Optional opening-screen input max-height override as percent of terminal height (`10`-`60`).
+
+`compact` preserves the current default opening prompt behavior.
+
+`initial_prompt` only affects the opening home screen prompt. Session prompt behavior is unchanged.
 
 ---
 
diff --git a/specs/bd-2lf-tui-home-prompt-sizing-plan.md b/specs/bd-2lf-tui-home-prompt-sizing-plan.md
new file mode 100644
index 00000000000..29ad0610c07
--- /dev/null
+++ b/specs/bd-2lf-tui-home-prompt-sizing-plan.md
@@ -0,0 +1,219 @@
+# bd-2lf - TUI Home Prompt Sizing + UX (Single PR)
+
+## Status
+
+| Scope                                            | Status    | Owner | Notes                                                            |
+| ------------------------------------------------ | --------- | ----- | ---------------------------------------------------------------- |
+| Epic A - Config contract + behavior              | completed | build | Add `tui.initial_prompt` schema, defaults, and resolution rules  |
+| Epic B - Home screen layout sizing               | completed | build | Replace fixed width/height on opening screen                     |
+| Epic C - UX quality improvements (same PR)       | completed | build | Better context visibility + clearer affordances on home composer |
+| Epic D - Validation + docs + generated artifacts | completed | build | Tests, docs, SDK/OpenAPI regeneration                            |
+| Epic E - Issue/PR packaging for `dev`            | planned   | build | Single PR with rationale, verification, and UX notes             |
+
+Current branch/worktree for WT flow:
+
+- Branch: `opencode-initial-prompt-sizing`
+- Worktree: `../opencode-initial-prompt-sizing`
+- Tracking issue: `bd-2lf`
+
+## Problem Statement
+
+The opening (home) prompt area in the TUI is too constrained for longer planning prompts.
+
+Observed hard constraints in code:
+
+- Home prompt container width is fixed to `maxWidth={75}` in `packages/opencode/src/cli/cmd/tui/routes/home.tsx`.
+- Opening layout also uses fixed vertical spacing that contributes to the compact feel in `packages/opencode/src/cli/cmd/tui/routes/home.tsx`.
+- Prompt textarea max height is fixed to `maxHeight={6}` in `packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx`.
+
+This causes prompt authoring friction for large planning prompts where users need more visible context while typing.
+
+## Goals
+
+1. Make opening-screen prompt size configurable through user config.
+2. Provide presets: `compact`, `medium`, `large`.
+3. Keep `compact` behavior equal to current defaults.
+4. Allow optional percent overrides for width and height.
+5. Include UX improvements in the same PR (not a follow-up PR).
+6. Keep scope focused: apply sizing behavior to home/opening screen first.
+
+## Non-Goals (for this PR)
+
+- Do not change session prompt dock sizing behavior in web app.
+- Do not redesign the full TUI home page layout.
+- Do not add interactive runtime settings UI (command palette toggles can be follow-up).
+
+## Assumptions
+
+1. `compact` must remain visually equivalent to current behavior.
+2. Presets should work across small and large terminal sizes with clamped values.
+3. Configuration should be stable (under `tui`), not experimental.
+4. UX improvements should be low-risk and preserve established TUI visual language.
+5. Single PR should include code, tests, docs, and generated SDK/OpenAPI updates.
+
+## OpenCode Observed Standards (from this repo)
+
+1. Config schema is centralized in `packages/opencode/src/config/config.ts`.
+2. TUI settings currently live under `tui` (`scroll_speed`, `scroll_acceleration`, `diff_style`).
+3. Public config changes require generated artifacts updates:
+   - `packages/sdk/openapi.json`
+   - `packages/sdk/js/src/v2/gen/*`
+   - `packages/sdk/js/src/gen/*`
+4. Docs include both config and tui guides:
+   - `packages/web/src/content/docs/config.mdx`
+   - `packages/web/src/content/docs/tui.mdx`
+5. Config parsing/validation coverage is in `packages/opencode/test/config/config.test.ts`.
+
+## Proposed Config Contract
+
+```jsonc
+{
+  "$schema": "https://opencode.ai/config.json",
+  "tui": {
+    "initial_prompt": {
+      "size": "medium",
+      "width_percent": 80,
+      "height_percent": 25,
+    },
+  },
+}
+```
+
+### Presets
+
+- `compact` (current): width behaves like current `75` col cap, input max height behaves like current `6` rows.
+- `medium`: width `80%` of terminal, input max height `25%` of terminal.
+- `large`: width `90%` of terminal, input max height `35%` of terminal.
+
+### Resolution + Clamping Rules
+
+1. Start from preset defaults.
+2. Apply `width_percent`/`height_percent` overrides when provided.
+3. Clamp final values to safe bounds for small terminals.
+4. Preserve readable minimums so UX remains usable in narrow terminals.
+
+## Epic/Task Breakdown
+
+### Epic A - Config Contract + Resolution Logic
+
+Status: completed
+
+Tasks:
+
+- [x] A1. Add `tui.initial_prompt` schema in `packages/opencode/src/config/config.ts`.
+- [x] A2. Add enum + numeric bounds + descriptions for all fields.
+- [x] A3. Add small helper/resolver for preset + override + clamp logic (kept local to TUI route/component layer unless reused).
+- [x] A4. Ensure defaults map exactly to current behavior for `compact`.
+
+Acceptance criteria:
+
+- Config accepts all valid shapes and rejects invalid enum/range values.
+- `compact` produces same effective home prompt dimensions as today.
+
+### Epic B - Opening Screen Sizing Implementation
+
+Status: completed
+
+Tasks:
+
+- [x] B1. Update `packages/opencode/src/cli/cmd/tui/routes/home.tsx` to compute opening layout width from resolved size config.
+- [x] B2. Replace fixed home `maxWidth={75}` usage with resolved width behavior.
+- [x] B3. Update prompt component API (`packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx`) to accept optional max input height override.
+- [x] B4. Apply height override only when prompt is used on home route.
+
+Acceptance criteria:
+
+- Home prompt width/height responds to presets + overrides.
+- Session route prompt behavior is unchanged by default.
+
+### Epic C - UX Improvements in Same PR
+
+Status: completed
+
+Tasks:
+
+- [x] C1. Improve home composer readability for long prompts (vertical breathing room and clearer visibility of active typing area).
+- [x] C2. Ensure helper/tips/hint layout remains balanced at compact, medium, and large sizes.
+- [x] C3. Add subtle textual cue in home context about active size preset when not compact (if space allows).
+
+Acceptance criteria:
+
+- Users can keep more planning context in view without breaking home layout hierarchy.
+- UX remains clean and consistent with current TUI style.
+
+### Epic D - Validation, Docs, and Generated Artifacts
+
+Status: completed
+
+Tasks:
+
+- [x] D1. Add/adjust tests in `packages/opencode/test/config/config.test.ts` for schema validation and parsing.
+- [x] D2. Regenerate SDK/OpenAPI via `./packages/sdk/js/script/build.ts`.
+- [x] D3. Update docs:
+  - `packages/web/src/content/docs/config.mdx`
+  - `packages/web/src/content/docs/tui.mdx`
+- [x] D4. Validate formatting/lint/test commands from package directories (not repo root).
+
+Acceptance criteria:
+
+- Tests cover new config shape and guardrails.
+- Generated files include new config fields.
+- Docs describe presets, overrides, defaults, and scope (home screen).
+
+### Epic E - WT Flow E2E Delivery to `dev`
+
+Status: in_progress
+
+Tasks:
+
+- [x] E1. Create dedicated worktree + branch.
+- [x] E2. Create and set issue in progress (`bd-2lf`).
+- [x] E3. Implement Epics A-D on this worktree.
+- [x] E4. Run verification commands and capture outputs.
+- [ ] E5. Prepare issue text + PR text aligned with repo template.
+
+Acceptance criteria:
+
+- Single focused PR against `dev` includes implementation, docs, tests, and generated artifacts.
+- PR description explains why this improves planning UX and how behavior is preserved for compact users.
+
+## Validation Plan
+
+Run from package directories only:
+
+1. Config tests (targeted):
+   - `bun test test/config/config.test.ts` (from `packages/opencode`)
+2. TUI package checks:
+   - `bun run typecheck` (from `packages/opencode`)
+   - `bun run test` (from `packages/opencode`) if change set is broader than config-only
+3. SDK/OpenAPI regeneration:
+   - `./packages/sdk/js/script/build.ts` (from repo root)
+4. Docs build/lint check (if required by maintainers):
+   - Run docs validation command used by repo maintainers for `packages/web`.
+
+Manual UX validation:
+
+- Open TUI on multiple terminal sizes.
+- Verify `compact`, `medium`, `large` with and without percent overrides.
+- Confirm home screen remains usable with tips shown/hidden.
+- Confirm regular in-session prompt behavior remains unchanged.
+
+## Definition of Done (Repo-Culture Aligned)
+
+- [x] Behavior is configurable via stable `tui` config keys.
+- [x] Compact mode preserves current behavior.
+- [x] Medium/large materially improve long planning prompt authoring.
+- [x] No regression in non-home prompt flows.
+- [x] Tests pass for changed scope.
+- [x] Generated SDK/OpenAPI files are updated and committed.
+- [x] Docs updated with clear examples and precedence rules.
+- [ ] PR targets `dev`, explains why and how, and includes verification notes.
+
+## Risks and Mitigations
+
+- Risk: small terminals produce unusable layout.
+  - Mitigation: clamp width/height and preserve minimum readable values.
+- Risk: accidental behavior changes in session prompt.
+  - Mitigation: pass sizing overrides only from home route.
+- Risk: docs and generated artifacts drift.
+  - Mitigation: treat regeneration + docs updates as required gates.