diff --git a/packages/opencode/src/server/server.ts b/packages/opencode/src/server/server.ts
index b096f20f5..173ecbac9 100644
--- a/packages/opencode/src/server/server.ts
+++ b/packages/opencode/src/server/server.ts
@@ -720,12 +720,7 @@ export namespace Server {
             },
           },
         }),
-        zValidator(
-          "json",
-          z.object({
-            text: z.string(),
-          }),
-        ),
+        zValidator("json", Session.ChatInput.pick({ parts: true })),
         async (c) => c.json(await callTui(c)),
       )
       .post(
diff --git a/packages/opencode/src/session/index.ts b/packages/opencode/src/session/index.ts
index 5f090137a..ac0658758 100644
--- a/packages/opencode/src/session/index.ts
+++ b/packages/opencode/src/session/index.ts
@@ -330,14 +330,8 @@ export namespace Session {
     return part
   }
 
-  export const ChatInput = z.object({
-    sessionID: Identifier.schema("session"),
-    messageID: Identifier.schema("message").optional(),
-    providerID: z.string(),
-    modelID: z.string(),
-    mode: z.string().optional(),
-    tools: z.record(z.boolean()).optional(),
-    parts: z.array(
+  export const PartsInput = z
+    .array(
       z.discriminatedUnion("type", [
         MessageV2.TextPart.omit({
           messageID: true,
@@ -360,7 +354,19 @@ export namespace Session {
             ref: "FilePartInput",
           }),
       ]),
-    ),
+    )
+    .openapi({
+      ref: "PartsInput",
+    })
+
+  export const ChatInput = z.object({
+    sessionID: Identifier.schema("session"),
+    messageID: Identifier.schema("message").optional(),
+    providerID: z.string(),
+    modelID: z.string(),
+    mode: z.string().optional(),
+    tools: z.record(z.boolean()).optional(),
+    parts: PartsInput,
   })
   export type ChatInput = z.infer<typeof ChatInput>
 
diff --git a/packages/sdk/.stats.yml b/packages/sdk/.stats.yml
index f9f86831f..d4064bf8b 100644
--- a/packages/sdk/.stats.yml
+++ b/packages/sdk/.stats.yml
@@ -1,4 +1,4 @@
 configured_endpoints: 24
-openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/opencode%2Fopencode-9574184bd9e916aa69eae8e26e0679556038d3fcfb4009a445c97c6cc3e4f3ee.yml
-openapi_spec_hash: 93ba1215ab0dc853a1691b049cc47d75
-config_hash: 09e4835d57ec7ed0b2d316c6815bcf0a
+openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/opencode%2Fopencode-305a02cb514ed54609aa9daae92410230435b7f886f04f790b1db828cd20e524.yml
+openapi_spec_hash: b207cc749da156457a2b48c9337aa690
+config_hash: 14ba54419d8428bd5440fd20eba04f99
diff --git a/packages/sdk/api.md b/packages/sdk/api.md
index 7cbaaf6c5..ff10ca128 100644
--- a/packages/sdk/api.md
+++ b/packages/sdk/api.md
@@ -92,6 +92,7 @@ Types:
 - <code><a href="./src/resources/session.ts">FileSource</a></code>
 - <code><a href="./src/resources/session.ts">Message</a></code>
 - <code><a href="./src/resources/session.ts">Part</a></code>
+- <code><a href="./src/resources/session.ts">PartsInput</a></code>
 - <code><a href="./src/resources/session.ts">Session</a></code>
 - <code><a href="./src/resources/session.ts">SnapshotPart</a></code>
 - <code><a href="./src/resources/session.ts">StepFinishPart</a></code>
diff --git a/packages/sdk/src/client.ts b/packages/sdk/src/client.ts
index c514ca877..30f2a5443 100644
--- a/packages/sdk/src/client.ts
+++ b/packages/sdk/src/client.ts
@@ -58,6 +58,7 @@ import {
   FileSource,
   Message,
   Part,
+  PartsInput,
   Session,
   SessionAbortResponse,
   SessionChatParams,
@@ -825,6 +826,7 @@ export declare namespace Opencode {
     type FileSource as FileSource,
     type Message as Message,
     type Part as Part,
+    type PartsInput as PartsInput,
     type Session as Session,
     type SnapshotPart as SnapshotPart,
     type StepFinishPart as StepFinishPart,
diff --git a/packages/sdk/src/resources/config.ts b/packages/sdk/src/resources/config.ts
index e1fc09de5..0c8c1c9f4 100644
--- a/packages/sdk/src/resources/config.ts
+++ b/packages/sdk/src/resources/config.ts
@@ -147,7 +147,7 @@ export namespace Config {
 
     npm?: string;
 
-    options?: { [key: string]: unknown };
+    options?: Provider.Options;
   }
 
   export namespace Provider {
@@ -190,6 +190,14 @@ export namespace Config {
         output: number;
       }
     }
+
+    export interface Options {
+      apiKey?: string;
+
+      baseURL?: string;
+
+      [k: string]: unknown;
+    }
   }
 }
 
diff --git a/packages/sdk/src/resources/index.ts b/packages/sdk/src/resources/index.ts
index 50df8ff46..e83acd79d 100644
--- a/packages/sdk/src/resources/index.ts
+++ b/packages/sdk/src/resources/index.ts
@@ -50,6 +50,7 @@ export {
   type FileSource,
   type Message,
   type Part,
+  type PartsInput,
   type Session,
   type SnapshotPart,
   type StepFinishPart,
diff --git a/packages/sdk/src/resources/session.ts b/packages/sdk/src/resources/session.ts
index 6e160321d..0e40cff6b 100644
--- a/packages/sdk/src/resources/session.ts
+++ b/packages/sdk/src/resources/session.ts
@@ -205,6 +205,8 @@ export type Message = UserMessage | AssistantMessage;
 
 export type Part = TextPart | FilePart | ToolPart | StepStartPart | StepFinishPart | SnapshotPart;
 
+export type PartsInput = Array<TextPartInput | FilePartInput>;
+
 export interface Session {
   id: string;
 
@@ -494,7 +496,7 @@ export type SessionSummarizeResponse = boolean;
 export interface SessionChatParams {
   modelID: string;
 
-  parts: Array<TextPartInput | FilePartInput>;
+  parts: PartsInput;
 
   providerID: string;
 
@@ -529,6 +531,7 @@ export declare namespace SessionResource {
     type FileSource as FileSource,
     type Message as Message,
     type Part as Part,
+    type PartsInput as PartsInput,
     type Session as Session,
     type SnapshotPart as SnapshotPart,
     type StepFinishPart as StepFinishPart,
diff --git a/packages/sdk/src/resources/tui.ts b/packages/sdk/src/resources/tui.ts
index c7efbdd6c..ca82002b8 100644
--- a/packages/sdk/src/resources/tui.ts
+++ b/packages/sdk/src/resources/tui.ts
@@ -1,6 +1,7 @@
 // File generated from our OpenAPI spec by Stainless. See CONTRIBUTING.md for details.
 
 import { APIResource } from '../core/resource';
+import * as SessionAPI from './session';
 import { APIPromise } from '../core/api-promise';
 import { RequestOptions } from '../internal/request-options';
 
@@ -25,7 +26,7 @@ export type TuiAppendPromptResponse = boolean;
 export type TuiOpenHelpResponse = boolean;
 
 export interface TuiAppendPromptParams {
-  text: string;
+  parts: SessionAPI.PartsInput;
 }
 
 export declare namespace Tui {
diff --git a/packages/sdk/tests/api-resources/tui.test.ts b/packages/sdk/tests/api-resources/tui.test.ts
index 8ac0d4359..b8767104b 100644
--- a/packages/sdk/tests/api-resources/tui.test.ts
+++ b/packages/sdk/tests/api-resources/tui.test.ts
@@ -7,7 +7,7 @@ const client = new Opencode({ baseURL: process.env['TEST_API_BASE_URL'] ?? 'http
 describe('resource tui', () => {
   // skipped: tests are disabled for the time being
   test.skip('appendPrompt: only required params', async () => {
-    const responsePromise = client.tui.appendPrompt({ text: 'text' });
+    const responsePromise = client.tui.appendPrompt({ parts: [{ text: 'text', type: 'text' }] });
     const rawResponse = await responsePromise.asResponse();
     expect(rawResponse).toBeInstanceOf(Response);
     const response = await responsePromise;
@@ -19,7 +19,9 @@ describe('resource tui', () => {
 
   // skipped: tests are disabled for the time being
   test.skip('appendPrompt: required and optional params', async () => {
-    const response = await client.tui.appendPrompt({ text: 'text' });
+    const response = await client.tui.appendPrompt({
+      parts: [{ text: 'text', type: 'text', id: 'id', synthetic: true, time: { start: 0, end: 0 } }],
+    });
   });
 
   // skipped: tests are disabled for the time being
diff --git a/packages/tui/internal/app/prompt.go b/packages/tui/internal/app/prompt.go
index 9176b7df5..2a7a5058c 100644
--- a/packages/tui/internal/app/prompt.go
+++ b/packages/tui/internal/app/prompt.go
@@ -1,8 +1,10 @@
 package app
 
 import (
+	"strings"
 	"time"
 
+	"github.com/google/uuid"
 	"github.com/sst/opencode-sdk-go"
 	"github.com/sst/opencode/internal/attachment"
 	"github.com/sst/opencode/internal/id"
@@ -109,8 +111,8 @@ func (p Prompt) ToMessage(
 	}
 }
 
-func (m Message) ToSessionChatParams() []opencode.SessionChatParamsPartUnion {
-	parts := []opencode.SessionChatParamsPartUnion{}
+func (m Message) ToSessionChatParams() opencode.PartsInputParam {
+	parts := []opencode.PartsInputItemUnionParam{}
 	for _, part := range m.Parts {
 		switch p := part.(type) {
 		case opencode.TextPart:
@@ -173,8 +175,8 @@ func (m Message) ToSessionChatParams() []opencode.SessionChatParamsPartUnion {
 	return parts
 }
 
-func (p Prompt) ToSessionChatParams() []opencode.SessionChatParamsPartUnion {
-	parts := []opencode.SessionChatParamsPartUnion{
+func (p Prompt) ToSessionChatParams() opencode.PartsInputParam {
+	parts := []opencode.PartsInputItemUnionParam{
 		opencode.TextPartInputParam{
 			Type: opencode.F(opencode.TextPartInputTypeText),
 			Text: opencode.F(p.Text),
@@ -233,3 +235,62 @@ func (p Prompt) ToSessionChatParams() []opencode.SessionChatParamsPartUnion {
 	}
 	return parts
 }
+
+func NewPromptFromParts(parts opencode.PartsInputParam) Prompt {
+	texts := []string{}
+	attachments := []*attachment.Attachment{}
+	for _, part := range parts {
+		switch p := part.(type) {
+		case opencode.TextPartInputParam:
+			texts = append(texts, p.Text.Value)
+		case opencode.FilePartInputParam:
+			switch source := p.Source.Value.(type) {
+			case opencode.FileSourceParam:
+				display := source.Text.Value.Value.Value
+				texts = append(texts, display)
+				attachments = append(attachments, &attachment.Attachment{
+					ID:         uuid.NewString(),
+					Type:       "file",
+					Display:    display,
+					URL:        p.URL.Value,
+					Filename:   p.Filename.Value,
+					MediaType:  p.Mime.Value,
+					StartIndex: int(source.Text.Value.Start.Value),
+					EndIndex:   int(source.Text.Value.End.Value),
+					Source:     attachment.FileSource{Path: source.Path.Value, Mime: p.Mime.Value},
+				})
+			case opencode.SymbolSourceParam:
+				display := source.Text.Value.Value.Value
+				texts = append(texts, display)
+				attachments = append(attachments, &attachment.Attachment{
+					ID:         uuid.NewString(),
+					Type:       "symbol",
+					Display:    display,
+					URL:        p.URL.Value,
+					Filename:   p.Filename.Value,
+					MediaType:  p.Mime.Value,
+					StartIndex: int(source.Text.Value.Start.Value),
+					EndIndex:   int(source.Text.Value.End.Value),
+					Source: attachment.SymbolSource{
+						Path: source.Path.Value,
+						Name: source.Name.Value,
+						Kind: int(source.Kind.Value),
+						Range: attachment.SymbolRange{
+							Start: attachment.Position{
+								Line: int(source.Range.Value.Start.Value.Line.Value),
+								Char: int(source.Range.Value.Start.Value.Character.Value),
+							},
+							End: attachment.Position{
+								Line: int(source.Range.Value.End.Value.Line.Value),
+								Char: int(source.Range.Value.End.Value.Character.Value),
+							},
+						}},
+				})
+			}
+		}
+	}
+	return Prompt{
+		Text:        strings.Join(texts, " "),
+		Attachments: attachments,
+	}
+}
diff --git a/packages/tui/internal/components/chat/editor.go b/packages/tui/internal/components/chat/editor.go
index cdae954e6..a629044f8 100644
--- a/packages/tui/internal/components/chat/editor.go
+++ b/packages/tui/internal/components/chat/editor.go
@@ -45,6 +45,7 @@ type EditorComponent interface {
 	SetInterruptKeyInDebounce(inDebounce bool)
 	SetExitKeyInDebounce(inDebounce bool)
 	RestoreFromHistory(index int)
+	AppendPrompt(prompt app.Prompt)
 }
 
 type editorComponent struct {
@@ -630,21 +631,15 @@ func NewEditorComponent(app *app.App) EditorComponent {
 	return m
 }
 
-// RestoreFromHistory restores a message from history at the given index
-func (m *editorComponent) RestoreFromHistory(index int) {
-	if index < 0 || index >= len(m.app.State.MessageHistory) {
-		return
-	}
-
-	entry := m.app.State.MessageHistory[index]
-
-	m.textarea.Reset()
-	m.textarea.SetValue(entry.Text)
+func (m *editorComponent) AppendPrompt(prompt app.Prompt) {
+	length := m.Length()
+	m.textarea.MoveToEnd()
+	m.textarea.InsertRunesFromUserInput([]rune(prompt.Text))
 
 	// Sort attachments by start index in reverse order (process from end to beginning)
 	// This prevents index shifting issues
-	attachmentsCopy := make([]*attachment.Attachment, len(entry.Attachments))
-	copy(attachmentsCopy, entry.Attachments)
+	attachmentsCopy := make([]*attachment.Attachment, len(prompt.Attachments))
+	copy(attachmentsCopy, prompt.Attachments)
 
 	for i := 0; i < len(attachmentsCopy)-1; i++ {
 		for j := i + 1; j < len(attachmentsCopy); j++ {
@@ -655,12 +650,27 @@ func (m *editorComponent) RestoreFromHistory(index int) {
 	}
 
 	for _, att := range attachmentsCopy {
-		m.textarea.SetCursorColumn(att.StartIndex)
-		m.textarea.ReplaceRange(att.StartIndex, att.EndIndex, "")
+		m.textarea.SetCursorColumn(length + att.StartIndex)
+		m.textarea.ReplaceRange(length+att.StartIndex, length+att.EndIndex, "")
 		m.textarea.InsertAttachment(att)
 	}
 }
 
+func (m *editorComponent) RestoreFromPrompt(prompt app.Prompt) {
+	m.textarea.Reset()
+	m.textarea.MoveToBegin()
+	m.AppendPrompt(prompt)
+}
+
+// RestoreFromHistory restores a message from history at the given index
+func (m *editorComponent) RestoreFromHistory(index int) {
+	if index < 0 || index >= len(m.app.State.MessageHistory) {
+		return
+	}
+	entry := m.app.State.MessageHistory[index]
+	m.RestoreFromPrompt(entry)
+}
+
 func getMediaTypeFromExtension(ext string) string {
 	switch strings.ToLower(ext) {
 	case ".jpg":
diff --git a/packages/tui/internal/tui/tui.go b/packages/tui/internal/tui/tui.go
index 752e805ea..4fc51e78b 100644
--- a/packages/tui/internal/tui/tui.go
+++ b/packages/tui/internal/tui/tui.go
@@ -511,15 +511,11 @@ func (a Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			a.modal = helpDialog
 		case "/tui/append-prompt":
 			var body struct {
-				Text string `json:"text"`
+				Parts opencode.PartsInputParam `json:"parts"`
 			}
 			json.Unmarshal((msg.Body), &body)
-			existing := a.editor.Value()
-			text := body.Text
-			if existing != "" && !strings.HasSuffix(existing, " ") {
-				text = " " + text
-			}
-			a.editor.SetValueWithAttachments(existing + text + " ")
+			prompt := app.NewPromptFromParts(body.Parts)
+			a.editor.AppendPrompt(prompt)
 		default:
 			break
 		}
diff --git a/packages/tui/sdk/.stats.yml b/packages/tui/sdk/.stats.yml
index f9f86831f..d4064bf8b 100644
--- a/packages/tui/sdk/.stats.yml
+++ b/packages/tui/sdk/.stats.yml
@@ -1,4 +1,4 @@
 configured_endpoints: 24
-openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/opencode%2Fopencode-9574184bd9e916aa69eae8e26e0679556038d3fcfb4009a445c97c6cc3e4f3ee.yml
-openapi_spec_hash: 93ba1215ab0dc853a1691b049cc47d75
-config_hash: 09e4835d57ec7ed0b2d316c6815bcf0a
+openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/opencode%2Fopencode-305a02cb514ed54609aa9daae92410230435b7f886f04f790b1db828cd20e524.yml
+openapi_spec_hash: b207cc749da156457a2b48c9337aa690
+config_hash: 14ba54419d8428bd5440fd20eba04f99
diff --git a/packages/tui/sdk/api.md b/packages/tui/sdk/api.md
index 1f5191cad..a72dc643c 100644
--- a/packages/tui/sdk/api.md
+++ b/packages/tui/sdk/api.md
@@ -79,6 +79,7 @@ Params Types:
 - <a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go">opencode</a>.<a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go#FilePartSourceUnionParam">FilePartSourceUnionParam</a>
 - <a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go">opencode</a>.<a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go#FilePartSourceTextParam">FilePartSourceTextParam</a>
 - <a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go">opencode</a>.<a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go#FileSourceParam">FileSourceParam</a>
+- <a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go">opencode</a>.<a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go#PartsInputParam">PartsInputParam</a>
 - <a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go">opencode</a>.<a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go#SymbolSourceParam">SymbolSourceParam</a>
 - <a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go">opencode</a>.<a href="https://pkg.go.dev/github.com/sst/opencode-sdk-go#TextPartInputParam">TextPartInputParam</a>
 
diff --git a/packages/tui/sdk/config.go b/packages/tui/sdk/config.go
index 0461cba87..e30a929a5 100644
--- a/packages/tui/sdk/config.go
+++ b/packages/tui/sdk/config.go
@@ -333,7 +333,7 @@ type ConfigProvider struct {
 	Env     []string                       `json:"env"`
 	Name    string                         `json:"name"`
 	Npm     string                         `json:"npm"`
-	Options map[string]interface{}         `json:"options"`
+	Options ConfigProviderOptions          `json:"options"`
 	JSON    configProviderJSON             `json:"-"`
 }
 
@@ -447,6 +447,30 @@ func (r configProviderModelsLimitJSON) RawJSON() string {
 	return r.raw
 }
 
+type ConfigProviderOptions struct {
+	APIKey      string                    `json:"apiKey"`
+	BaseURL     string                    `json:"baseURL"`
+	ExtraFields map[string]interface{}    `json:"-,extras"`
+	JSON        configProviderOptionsJSON `json:"-"`
+}
+
+// configProviderOptionsJSON contains the JSON metadata for the struct
+// [ConfigProviderOptions]
+type configProviderOptionsJSON struct {
+	APIKey      apijson.Field
+	BaseURL     apijson.Field
+	raw         string
+	ExtraFields map[string]apijson.Field
+}
+
+func (r *ConfigProviderOptions) UnmarshalJSON(data []byte) (err error) {
+	return apijson.UnmarshalRoot(data, r)
+}
+
+func (r configProviderOptionsJSON) RawJSON() string {
+	return r.raw
+}
+
 // Control sharing behavior:'manual' allows manual sharing via commands, 'auto'
 // enables automatic sharing, 'disabled' disables all sharing
 type ConfigShare string
diff --git a/packages/tui/sdk/session.go b/packages/tui/sdk/session.go
index 8426b64eb..5c78aefa2 100644
--- a/packages/tui/sdk/session.go
+++ b/packages/tui/sdk/session.go
@@ -496,7 +496,7 @@ func (r FilePartInputParam) MarshalJSON() (data []byte, err error) {
 	return apijson.MarshalRoot(r)
 }
 
-func (r FilePartInputParam) implementsSessionChatParamsPartUnion() {}
+func (r FilePartInputParam) implementsPartsInputItemUnionParam() {}
 
 type FilePartInputType string
 
@@ -932,6 +932,46 @@ func (r PartType) IsKnown() bool {
 	return false
 }
 
+type PartsInputParam []PartsInputItemUnionParam
+
+type PartsInputItemParam struct {
+	Type      param.Field[PartsInputItemType]       `json:"type,required"`
+	ID        param.Field[string]                   `json:"id"`
+	Filename  param.Field[string]                   `json:"filename"`
+	Mime      param.Field[string]                   `json:"mime"`
+	Source    param.Field[FilePartSourceUnionParam] `json:"source"`
+	Synthetic param.Field[bool]                     `json:"synthetic"`
+	Text      param.Field[string]                   `json:"text"`
+	Time      param.Field[interface{}]              `json:"time"`
+	URL       param.Field[string]                   `json:"url"`
+}
+
+func (r PartsInputItemParam) MarshalJSON() (data []byte, err error) {
+	return apijson.MarshalRoot(r)
+}
+
+func (r PartsInputItemParam) implementsPartsInputItemUnionParam() {}
+
+// Satisfied by [TextPartInputParam], [FilePartInputParam], [PartsInputItemParam].
+type PartsInputItemUnionParam interface {
+	implementsPartsInputItemUnionParam()
+}
+
+type PartsInputItemType string
+
+const (
+	PartsInputItemTypeText PartsInputItemType = "text"
+	PartsInputItemTypeFile PartsInputItemType = "file"
+)
+
+func (r PartsInputItemType) IsKnown() bool {
+	switch r {
+	case PartsInputItemTypeText, PartsInputItemTypeFile:
+		return true
+	}
+	return false
+}
+
 type Session struct {
 	ID       string        `json:"id,required"`
 	Time     SessionTime   `json:"time,required"`
@@ -1451,7 +1491,7 @@ func (r TextPartInputParam) MarshalJSON() (data []byte, err error) {
 	return apijson.MarshalRoot(r)
 }
 
-func (r TextPartInputParam) implementsSessionChatParamsPartUnion() {}
+func (r TextPartInputParam) implementsPartsInputItemUnionParam() {}
 
 type TextPartInputType string
 
@@ -1949,57 +1989,18 @@ func (r sessionMessagesResponseJSON) RawJSON() string {
 }
 
 type SessionChatParams struct {
-	ModelID    param.Field[string]                       `json:"modelID,required"`
-	Parts      param.Field[[]SessionChatParamsPartUnion] `json:"parts,required"`
-	ProviderID param.Field[string]                       `json:"providerID,required"`
-	MessageID  param.Field[string]                       `json:"messageID"`
-	Mode       param.Field[string]                       `json:"mode"`
-	Tools      param.Field[map[string]bool]              `json:"tools"`
+	ModelID    param.Field[string]          `json:"modelID,required"`
+	Parts      param.Field[PartsInputParam] `json:"parts,required"`
+	ProviderID param.Field[string]          `json:"providerID,required"`
+	MessageID  param.Field[string]          `json:"messageID"`
+	Mode       param.Field[string]          `json:"mode"`
+	Tools      param.Field[map[string]bool] `json:"tools"`
 }
 
 func (r SessionChatParams) MarshalJSON() (data []byte, err error) {
 	return apijson.MarshalRoot(r)
 }
 
-type SessionChatParamsPart struct {
-	Type      param.Field[SessionChatParamsPartsType] `json:"type,required"`
-	ID        param.Field[string]                     `json:"id"`
-	Filename  param.Field[string]                     `json:"filename"`
-	Mime      param.Field[string]                     `json:"mime"`
-	Source    param.Field[FilePartSourceUnionParam]   `json:"source"`
-	Synthetic param.Field[bool]                       `json:"synthetic"`
-	Text      param.Field[string]                     `json:"text"`
-	Time      param.Field[interface{}]                `json:"time"`
-	URL       param.Field[string]                     `json:"url"`
-}
-
-func (r SessionChatParamsPart) MarshalJSON() (data []byte, err error) {
-	return apijson.MarshalRoot(r)
-}
-
-func (r SessionChatParamsPart) implementsSessionChatParamsPartUnion() {}
-
-// Satisfied by [TextPartInputParam], [FilePartInputParam],
-// [SessionChatParamsPart].
-type SessionChatParamsPartUnion interface {
-	implementsSessionChatParamsPartUnion()
-}
-
-type SessionChatParamsPartsType string
-
-const (
-	SessionChatParamsPartsTypeText SessionChatParamsPartsType = "text"
-	SessionChatParamsPartsTypeFile SessionChatParamsPartsType = "file"
-)
-
-func (r SessionChatParamsPartsType) IsKnown() bool {
-	switch r {
-	case SessionChatParamsPartsTypeText, SessionChatParamsPartsTypeFile:
-		return true
-	}
-	return false
-}
-
 type SessionInitParams struct {
 	MessageID  param.Field[string] `json:"messageID,required"`
 	ModelID    param.Field[string] `json:"modelID,required"`
diff --git a/packages/tui/sdk/session_test.go b/packages/tui/sdk/session_test.go
index 5d7c55cad..59c28d01a 100644
--- a/packages/tui/sdk/session_test.go
+++ b/packages/tui/sdk/session_test.go
@@ -118,7 +118,7 @@ func TestSessionChatWithOptionalParams(t *testing.T) {
 		"id",
 		opencode.SessionChatParams{
 			ModelID: opencode.F("modelID"),
-			Parts: opencode.F([]opencode.SessionChatParamsPartUnion{opencode.TextPartInputParam{
+			Parts: opencode.F(opencode.PartsInputParam{opencode.TextPartInputParam{
 				Text:      opencode.F("text"),
 				Type:      opencode.F(opencode.TextPartInputTypeText),
 				ID:        opencode.F("id"),
diff --git a/packages/tui/sdk/tui.go b/packages/tui/sdk/tui.go
index d5243599f..74652f7fa 100644
--- a/packages/tui/sdk/tui.go
+++ b/packages/tui/sdk/tui.go
@@ -48,7 +48,7 @@ func (r *TuiService) OpenHelp(ctx context.Context, opts ...option.RequestOption)
 }
 
 type TuiAppendPromptParams struct {
-	Text param.Field[string] `json:"text,required"`
+	Parts param.Field[PartsInputParam] `json:"parts,required"`
 }
 
 func (r TuiAppendPromptParams) MarshalJSON() (data []byte, err error) {
diff --git a/packages/tui/sdk/tui_test.go b/packages/tui/sdk/tui_test.go
index 5283f37c5..f05e961fe 100644
--- a/packages/tui/sdk/tui_test.go
+++ b/packages/tui/sdk/tui_test.go
@@ -26,7 +26,16 @@ func TestTuiAppendPrompt(t *testing.T) {
 		option.WithBaseURL(baseURL),
 	)
 	_, err := client.Tui.AppendPrompt(context.TODO(), opencode.TuiAppendPromptParams{
-		Text: opencode.F("text"),
+		Parts: opencode.F(opencode.PartsInputParam{opencode.TextPartInputParam{
+			Text:      opencode.F("text"),
+			Type:      opencode.F(opencode.TextPartInputTypeText),
+			ID:        opencode.F("id"),
+			Synthetic: opencode.F(true),
+			Time: opencode.F(opencode.TextPartInputTimeParam{
+				Start: opencode.F(0.000000),
+				End:   opencode.F(0.000000),
+			}),
+		}}),
 	})
 	if err != nil {
 		var apierr *opencode.Error
diff --git a/sdks/vscode/src/extension.ts b/sdks/vscode/src/extension.ts
index 49a05f641..ebe42a147 100644
--- a/sdks/vscode/src/extension.ts
+++ b/sdks/vscode/src/extension.ts
@@ -77,7 +77,7 @@ async function appendPrompt(port: number, text: string) {
     headers: {
       "Content-Type": "application/json",
     },
-    body: JSON.stringify({ text }),
+    body: JSON.stringify({ parts: [{ type: "text", text }] }),
   })
 }
 
diff --git a/stainless.yml b/stainless.yml
index 317238438..f5275753f 100644
--- a/stainless.yml
+++ b/stainless.yml
@@ -90,6 +90,7 @@ resources:
       session: Session
       message: Message
       part: Part
+      partsInput: PartsInput
       textPart: TextPart
       textPartInput: TextPartInput
       filePart: FilePart