diff --git a/packages/console/app/public/theme.json b/packages/console/app/public/theme.json
index b3e97f7ca897..d0715536c22b 100644
--- a/packages/console/app/public/theme.json
+++ b/packages/console/app/public/theme.json
@@ -46,6 +46,7 @@
         "info": { "$ref": "#/definitions/colorValue" },
         "text": { "$ref": "#/definitions/colorValue" },
         "textMuted": { "$ref": "#/definitions/colorValue" },
+        "placeholderText": { "$ref": "#/definitions/colorValue" },
         "background": { "$ref": "#/definitions/colorValue" },
         "backgroundPanel": { "$ref": "#/definitions/colorValue" },
         "backgroundElement": { "$ref": "#/definitions/colorValue" },
diff --git a/packages/opencode/src/cli/cmd/session.ts b/packages/opencode/src/cli/cmd/session.ts
index c8b5b0336607..01d028c8d505 100644
--- a/packages/opencode/src/cli/cmd/session.ts
+++ b/packages/opencode/src/cli/cmd/session.ts
@@ -5,11 +5,14 @@ import { bootstrap } from "../bootstrap"
 import { UI } from "../ui"
 import { Locale } from "../../util/locale"
 import { EOL } from "os"
+import { createOpencodeClient } from "@opencode-ai/sdk"
+import { Server } from "../../server/server"
+import { tui } from "./tui/app"
 
 export const SessionCommand = cmd({
   command: "session",
   describe: "manage sessions",
-  builder: (yargs: Argv) => yargs.command(SessionListCommand).demandCommand(),
+  builder: (yargs: Argv) => yargs.command(SessionListCommand).command(SessionForkCommand).demandCommand(),
   async handler() {},
 })
 
@@ -104,3 +107,57 @@ function formatSessionJSON(sessions: Session.Info[]): string {
   }))
   return JSON.stringify(jsonData, null, 2)
 }
+
+export const SessionForkCommand = cmd({
+  command: "fork",
+  describe: "fork a session to explore parallel conversation branches",
+  builder: (yargs: Argv) => {
+    return yargs
+      .option("session", {
+        alias: "s",
+        describe: "session ID to fork",
+        type: "string",
+        demandOption: true,
+      })
+      .option("message", {
+        alias: "m",
+        describe: "fork up to this message ID",
+        type: "string",
+      })
+  },
+  handler: async (args) => {
+    await bootstrap(process.cwd(), async () => {
+      const server = Server.listen({ port: 0, hostname: "127.0.0.1" })
+      const sdk = createOpencodeClient({ baseUrl: `http://${server.hostname}:${server.port}` })
+
+      const result = await sdk.session
+        .fork({
+          path: { id: args.session },
+          body: { messageID: args.message },
+        })
+        .catch((error) => {
+          server.stop()
+          const errorMessage = error.message || String(error)
+          UI.error(`Failed to fork session: ${errorMessage}`)
+          process.exit(1)
+        })
+
+      if (!result.data) {
+        server.stop()
+        UI.error("Failed to fork session")
+        process.exit(1)
+      }
+
+      const forkedSessionID = result.data.id
+      UI.println(UI.Style.TEXT_INFO_BOLD + `Forked session: ${forkedSessionID}`)
+      UI.println()
+
+      await tui({
+        url: `http://${server.hostname}:${server.port}`,
+        args: { sessionID: forkedSessionID },
+      })
+
+      server.stop()
+    })
+  },
+})
diff --git a/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx b/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
index 7d5bbb9f06a0..1b13264df8dd 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
@@ -656,7 +656,7 @@ export function Prompt(props: PromptProps) {
             flexGrow={1}
           >
             <textarea
-              placeholder={props.sessionID ? undefined : `Ask anything... "${PLACEHOLDERS[store.placeholder]}"`}
+              placeholder={props.sessionID ? undefined : t`${fg(theme.placeholderText)(`Ask anything... "${PLACEHOLDERS[store.placeholder]}"`)}`}
               textColor={theme.text}
               focusedTextColor={theme.text}
               minHeight={1}
diff --git a/packages/opencode/src/cli/cmd/tui/context/theme.tsx b/packages/opencode/src/cli/cmd/tui/context/theme.tsx
index 5f3a0ad4adf7..66d7f6a26764 100644
--- a/packages/opencode/src/cli/cmd/tui/context/theme.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/theme.tsx
@@ -47,6 +47,7 @@ type ThemeColors = {
   info: RGBA
   text: RGBA
   textMuted: RGBA
+  placeholderText: RGBA
   selectedListItemText: RGBA
   background: RGBA
   backgroundPanel: RGBA
@@ -124,10 +125,11 @@ type ColorValue = HexColor | RefName | Variant | RGBA
 type ThemeJson = {
   $schema?: string
   defs?: Record<string, HexColor | RefName>
-  theme: Omit<Record<keyof ThemeColors, ColorValue>, "selectedListItemText" | "backgroundMenu"> & {
+  theme: Omit<Record<keyof ThemeColors, ColorValue>, "selectedListItemText" | "backgroundMenu" | "placeholderText"> & {
     selectedListItemText?: ColorValue
     backgroundMenu?: ColorValue
     thinkingOpacity?: number
+    placeholderText?: ColorValue
   }
 }
 
@@ -187,7 +189,7 @@ function resolveTheme(theme: ThemeJson, mode: "dark" | "light") {
 
   const resolved = Object.fromEntries(
     Object.entries(theme.theme)
-      .filter(([key]) => key !== "selectedListItemText" && key !== "backgroundMenu" && key !== "thinkingOpacity")
+      .filter(([key]) => key !== "selectedListItemText" && key !== "backgroundMenu" && key !== "thinkingOpacity" && key !== "placeholderText")
       .map(([key, value]) => {
         return [key, resolveColor(value as ColorValue)]
       }),
@@ -212,6 +214,12 @@ function resolveTheme(theme: ThemeJson, mode: "dark" | "light") {
 
   // Handle thinkingOpacity - optional with default of 0.6
   const thinkingOpacity = theme.theme.thinkingOpacity ?? 0.6
+  // Handle placeholderText - optional with fallback to textMuted
+  if (theme.theme.placeholderText !== undefined) {
+    resolved.placeholderText = resolveColor(theme.theme.placeholderText)
+  } else {
+    resolved.placeholderText = resolved.textMuted
+  }
 
   return {
     ...resolved,
@@ -402,6 +410,7 @@ function generateSystem(colors: TerminalColors, mode: "dark" | "light"): ThemeJs
       // Text colors
       text: fg,
       textMuted,
+      placeholderText: textMuted,
       selectedListItemText: bg,
 
       // Background colors
diff --git a/packages/opencode/src/cli/cmd/tui/routes/session/dialog-message.tsx b/packages/opencode/src/cli/cmd/tui/routes/session/dialog-message.tsx
index b9e6632ac8a1..c1a0d4c620d2 100644
--- a/packages/opencode/src/cli/cmd/tui/routes/session/dialog-message.tsx
+++ b/packages/opencode/src/cli/cmd/tui/routes/session/dialog-message.tsx
@@ -87,6 +87,16 @@ export function DialogMessage(props: {
             dialog.clear()
           },
         },
+        {
+          title: "Copy Fork Command",
+          value: "session.copy-fork-command",
+          description: "to fork in a new terminal",
+          onSelect: async (dialog) => {
+            const command = `opencode session fork --session ${props.sessionID} --message ${props.messageID}`
+            await Clipboard.copy(command)
+            dialog.clear()
+          },
+        },
       ]}
     />
   )
diff --git a/packages/opencode/src/cli/cmd/tui/ui/dialog-prompt.tsx b/packages/opencode/src/cli/cmd/tui/ui/dialog-prompt.tsx
index 4b4c635a5294..f44b4800d998 100644
--- a/packages/opencode/src/cli/cmd/tui/ui/dialog-prompt.tsx
+++ b/packages/opencode/src/cli/cmd/tui/ui/dialog-prompt.tsx
@@ -1,4 +1,4 @@
-import { TextareaRenderable, TextAttributes } from "@opentui/core"
+import { TextareaRenderable, TextAttributes, t, fg } from "@opentui/core"
 import { useTheme } from "../context/theme"
 import { useDialog, type DialogContext } from "./dialog"
 import { onMount, type JSX } from "solid-js"
@@ -48,7 +48,7 @@ export function DialogPrompt(props: DialogPromptProps) {
           keyBindings={[{ name: "return", action: "submit" }]}
           ref={(val: TextareaRenderable) => (textarea = val)}
           initialValue={props.value}
-          placeholder={props.placeholder ?? "Enter text"}
+          placeholder={t`${fg(theme.placeholderText)(props.placeholder ?? "Enter text")}`}
           textColor={theme.text}
           focusedTextColor={theme.text}
           cursorColor={theme.text}
diff --git a/packages/opencode/src/cli/cmd/tui/ui/dialog-select.tsx b/packages/opencode/src/cli/cmd/tui/ui/dialog-select.tsx
index b6c5b5f8b959..d72a980ba295 100644
--- a/packages/opencode/src/cli/cmd/tui/ui/dialog-select.tsx
+++ b/packages/opencode/src/cli/cmd/tui/ui/dialog-select.tsx
@@ -196,6 +196,7 @@ export function DialogSelect<T>(props: DialogSelectProps<T>) {
             focusedBackgroundColor={theme.backgroundPanel}
             cursorColor={theme.primary}
             focusedTextColor={theme.textMuted}
+            placeholderColor={theme.placeholderText}
             ref={(r) => {
               input = r
               setTimeout(() => input.focus(), 1)
diff --git a/packages/opencode/src/session/index.ts b/packages/opencode/src/session/index.ts
index b8b7af742ebb..af591c62a61d 100644
--- a/packages/opencode/src/session/index.ts
+++ b/packages/opencode/src/session/index.ts
@@ -141,23 +141,24 @@ export namespace Session {
       messageID: Identifier.schema("message").optional(),
     }),
     async (input) => {
+      const originalSession = await get(input.sessionID)
       const session = await createNext({
-        directory: Instance.directory,
+        directory: originalSession.directory,
+        parentID: input.sessionID,
       })
+
       const msgs = await messages({ sessionID: input.sessionID })
       for (const msg of msgs) {
-        if (input.messageID && msg.info.id >= input.messageID) break
-        const cloned = await updateMessage({
+        if (input.messageID && msg.info.id > input.messageID) break
+
+        await Storage.write(["message", session.id, msg.info.id], {
           ...msg.info,
           sessionID: session.id,
-          id: Identifier.ascending("message"),
         })
 
         for (const part of msg.parts) {
-          await updatePart({
+          await Storage.write(["part", msg.info.id, part.id], {
             ...part,
-            id: Identifier.ascending("part"),
-            messageID: cloned.id,
             sessionID: session.id,
           })
         }
diff --git a/packages/opencode/test/session/fork.test.ts b/packages/opencode/test/session/fork.test.ts
new file mode 100644
index 000000000000..23882dc23497
--- /dev/null
+++ b/packages/opencode/test/session/fork.test.ts
@@ -0,0 +1,258 @@
+import { describe, expect, test } from "bun:test"
+import path from "path"
+import { Session } from "../../src/session"
+import { Log } from "../../src/util/log"
+import { Instance } from "../../src/project/instance"
+import { Identifier } from "../../src/id/id"
+
+const projectRoot = path.join(__dirname, "../..")
+Log.init({ print: false })
+
+describe("Session.fork", () => {
+  test("should fork entire session without message ID", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const originalSession = await Session.create({
+          title: "Original Session",
+        })
+
+        await Session.updateMessage({
+          id: Identifier.ascending("message"),
+          role: "user",
+          sessionID: originalSession.id,
+          time: { created: Date.now() },
+          agent: "build",
+          model: { providerID: "opencode", modelID: "claude-3-5-sonnet-20241022" },
+        })
+
+        const forkedSession = await Session.fork({
+          sessionID: originalSession.id,
+        })
+
+        expect(forkedSession).toBeDefined()
+        expect(forkedSession.id).not.toBe(originalSession.id)
+        expect(forkedSession.directory).toBe(originalSession.directory)
+        expect(forkedSession.projectID).toBe(originalSession.projectID)
+
+        const originalMessages = await Session.messages({ sessionID: originalSession.id })
+        const forkedMessages = await Session.messages({ sessionID: forkedSession.id })
+
+        expect(forkedMessages.length).toBe(originalMessages.length)
+
+        await Session.remove(originalSession.id)
+        await Session.remove(forkedSession.id)
+      },
+    })
+  })
+
+  test("should fork session up to specific message", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const originalSession = await Session.create({
+          title: "Session with Multiple Messages",
+        })
+
+        const msg1 = await Session.updateMessage({
+          id: Identifier.ascending("message"),
+          role: "user",
+          sessionID: originalSession.id,
+          time: { created: Date.now() },
+          agent: "build",
+          model: { providerID: "opencode", modelID: "claude-3-5-sonnet-20241022" },
+        })
+
+        await Session.updateMessage({
+          id: Identifier.ascending("message"),
+          role: "user",
+          sessionID: originalSession.id,
+          time: { created: Date.now() },
+          agent: "build",
+          model: { providerID: "opencode", modelID: "claude-3-5-sonnet-20241022" },
+        })
+
+        await Session.updateMessage({
+          id: Identifier.ascending("message"),
+          role: "user",
+          sessionID: originalSession.id,
+          time: { created: Date.now() },
+          agent: "build",
+          model: { providerID: "opencode", modelID: "claude-3-5-sonnet-20241022" },
+        })
+
+        const forkedSession = await Session.fork({
+          sessionID: originalSession.id,
+          messageID: msg1.id,
+        })
+
+        const originalMessages = await Session.messages({ sessionID: originalSession.id })
+        const forkedMessages = await Session.messages({ sessionID: forkedSession.id })
+
+        expect(originalMessages.length).toBe(3)
+        expect(forkedMessages.length).toBe(1)
+
+        await Session.remove(originalSession.id)
+        await Session.remove(forkedSession.id)
+      },
+    })
+  })
+
+  test("should create independent forked session", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const originalSession = await Session.create({
+          title: "Original Independent",
+        })
+
+        await Session.updateMessage({
+          id: Identifier.ascending("message"),
+          role: "user",
+          sessionID: originalSession.id,
+          time: { created: Date.now() },
+          agent: "build",
+          model: { providerID: "opencode", modelID: "claude-3-5-sonnet-20241022" },
+        })
+
+        const forkedSession = await Session.fork({
+          sessionID: originalSession.id,
+        })
+
+        const newMsgInFork = await Session.updateMessage({
+          id: Identifier.ascending("message"),
+          role: "user",
+          sessionID: forkedSession.id,
+          time: { created: Date.now() },
+          agent: "build",
+          model: { providerID: "opencode", modelID: "claude-3-5-sonnet-20241022" },
+        })
+
+        const originalMessages = await Session.messages({ sessionID: originalSession.id })
+        const forkedMessages = await Session.messages({ sessionID: forkedSession.id })
+
+        expect(originalMessages.length).toBe(1)
+        expect(forkedMessages.length).toBe(2)
+
+        const msgExistsInFork = forkedMessages.some((m) => m.info.id === newMsgInFork.id)
+        const msgExistsInOriginal = originalMessages.some((m) => m.info.id === newMsgInFork.id)
+
+        expect(msgExistsInFork).toBe(true)
+        expect(msgExistsInOriginal).toBe(false)
+
+        await Session.remove(originalSession.id)
+        await Session.remove(forkedSession.id)
+      },
+    })
+  })
+
+  test("should copy message parts when forking", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const originalSession = await Session.create({
+          title: "Session with Parts",
+        })
+
+        const msg = await Session.updateMessage({
+          id: Identifier.ascending("message"),
+          role: "user",
+          sessionID: originalSession.id,
+          time: { created: Date.now() },
+          agent: "build",
+          model: { providerID: "opencode", modelID: "claude-3-5-sonnet-20241022" },
+        })
+
+        await Session.updatePart({
+          id: Identifier.ascending("part"),
+          messageID: msg.id,
+          sessionID: originalSession.id,
+          type: "text",
+          text: "Test message content",
+        })
+
+        const forkedSession = await Session.fork({
+          sessionID: originalSession.id,
+        })
+
+        const forkedMessages = await Session.messages({ sessionID: forkedSession.id })
+
+        expect(forkedMessages.length).toBe(1)
+        expect(forkedMessages[0].parts.length).toBe(1)
+        expect(forkedMessages[0].parts[0].type).toBe("text")
+
+        if (forkedMessages[0].parts[0].type === "text") {
+          expect(forkedMessages[0].parts[0].text).toBe("Test message content")
+        }
+
+        await Session.remove(originalSession.id)
+        await Session.remove(forkedSession.id)
+      },
+    })
+  })
+
+  test("should handle empty session fork", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const originalSession = await Session.create({
+          title: "Empty Session",
+        })
+
+        const forkedSession = await Session.fork({
+          sessionID: originalSession.id,
+        })
+
+        expect(forkedSession).toBeDefined()
+        expect(forkedSession.id).not.toBe(originalSession.id)
+
+        const forkedMessages = await Session.messages({ sessionID: forkedSession.id })
+        expect(forkedMessages.length).toBe(0)
+
+        await Session.remove(originalSession.id)
+        await Session.remove(forkedSession.id)
+      },
+    })
+  })
+
+  test("should throw error for non-existent session", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const nonExistentSessionID = "session_nonexistent123"
+
+        try {
+          await Session.fork({
+            sessionID: nonExistentSessionID,
+          })
+          expect(true).toBe(false)
+        } catch (error) {
+          expect(error).toBeDefined()
+        }
+      },
+    })
+  })
+
+  test("forked session should have different ID but same project", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const originalSession = await Session.create({
+          title: "Project Test",
+        })
+
+        const forkedSession = await Session.fork({
+          sessionID: originalSession.id,
+        })
+
+        expect(forkedSession.id).not.toBe(originalSession.id)
+        expect(forkedSession.projectID).toBe(originalSession.projectID)
+        expect(forkedSession.directory).toBe(originalSession.directory)
+        expect(forkedSession.version).toBe(originalSession.version)
+
+        await Session.remove(originalSession.id)
+        await Session.remove(forkedSession.id)
+      },
+    })
+  })
+})
diff --git a/packages/web/public/theme.json b/packages/web/public/theme.json
index 7c80776344fd..a38c96509346 100644
--- a/packages/web/public/theme.json
+++ b/packages/web/public/theme.json
@@ -46,6 +46,7 @@
         "info": { "$ref": "#/definitions/colorValue" },
         "text": { "$ref": "#/definitions/colorValue" },
         "textMuted": { "$ref": "#/definitions/colorValue" },
+        "placeholderText": { "$ref": "#/definitions/colorValue" },
         "selectedListItemText": { "$ref": "#/definitions/colorValue" },
         "background": { "$ref": "#/definitions/colorValue" },
         "backgroundPanel": { "$ref": "#/definitions/colorValue" },