diff --git a/src/components/code-composer.tsx b/src/components/code-composer.tsx
new file mode 100644
index 000000000..638fe9fba
--- /dev/null
+++ b/src/components/code-composer.tsx
@@ -0,0 +1,135 @@
+"use client";
+
+/**
+ * CodeComposer — the workbench's "Ask for follow-up changes" box (cave-k0ua):
+ * sends a prompt to the SELECTED session's agent through the sanctioned
+ * client LLM path (streamFamiliarText → /api/chat/send with sessionId, the
+ * same resume the chat surface uses) and shows a compact tail of the reply
+ * as it streams. The full transcript stays in Chat — Open in Chat jumps
+ * there. Stop cancels the run via /api/chat/stop with the send's runId.
+ */
+
+import { useRef, useState } from "react";
+import { Button } from "@/components/ui/button";
+import { streamFamiliarText } from "@/lib/familiar-stream";
+import { codeSessionWorkRoot } from "@/lib/code-surface";
+import type { SessionRow } from "@/lib/types";
+
+type Phase = { kind: "idle" } | { kind: "streaming"; runId: string } | { kind: "done" } | { kind: "error"; message: string };
+
+/** Last few lines of the streamed reply — a peek, not a transcript. */
+function replyTail(text: string, lines = 3): string {
+  const all = text.trimEnd().split("\n");
+  return all.slice(-lines).join("\n");
+}
+
+export function CodeComposer({
+  row,
+  onJumpToSession,
+}: {
+  row: SessionRow;
+  onJumpToSession: (sessionId: string, familiarId?: string | null) => void;
+}) {
+  const [prompt, setPrompt] = useState("");
+  const [phase, setPhase] = useState<Phase>({ kind: "idle" });
+  const [reply, setReply] = useState("");
+  const abortRef = useRef<AbortController | null>(null);
+  const busy = phase.kind === "streaming";
+
+  async function send() {
+    const trimmed = prompt.trim();
+    if (!trimmed || busy || !row.familiarId) return;
+    const runId = `code-composer-${Date.now().toString(36)}`;
+    const controller = new AbortController();
+    abortRef.current = controller;
+    setPhase({ kind: "streaming", runId });
+    setReply("");
+    setPrompt("");
+    const result = await streamFamiliarText({
+      familiarId: row.familiarId,
+      sessionId: row.id,
+      prompt: trimmed,
+      projectRoot: codeSessionWorkRoot(row),
+      runId,
+      signal: controller.signal,
+      onText: setReply,
+    });
+    abortRef.current = null;
+    if (controller.signal.aborted) {
+      setPhase({ kind: "done" });
+      return;
+    }
+    if (result.error && !result.text) {
+      setPhase({ kind: "error", message: result.error });
+      setPrompt(trimmed); // let the user retry without retyping
+      return;
+    }
+    setReply(result.text);
+    setPhase({ kind: "done" });
+  }
+
+  async function stop() {
+    if (phase.kind !== "streaming") return;
+    // Ask the bridge to stop the run, then drop the stream client-side too.
+    try {
+      await fetch("/api/chat/stop", {
+        method: "POST",
+        headers: { "content-type": "application/json" },
+        body: JSON.stringify({ runId: phase.runId, sessionId: row.id }),
+      });
+    } catch {
+      /* the local abort below still ends the stream */
+    }
+    abortRef.current?.abort();
+  }
+
+  return (
+    <div className="shrink-0 border-t border-[var(--border-hairline)] px-4 py-3">
+      {reply && phase.kind !== "idle" ? (
+        <div className="mb-2 flex items-start justify-between gap-3 text-[length:var(--text-xs)]">
+          <pre className="min-w-0 flex-1 whitespace-pre-wrap break-words font-sans text-[var(--text-secondary)]">
+            {replyTail(reply)}
+          </pre>
+          <button
+            type="button"
+            className="focus-ring shrink-0 rounded px-1 text-[length:var(--text-2xs)] text-[var(--text-muted)] underline decoration-dotted underline-offset-2 hover:text-[var(--text-primary)]"
+            onClick={() => onJumpToSession(row.id, row.familiarId)}
+          >
+            Full thread in Chat
+          </button>
+        </div>
+      ) : null}
+      {phase.kind === "error" ? (
+        <p role="alert" className="mb-2 text-[length:var(--text-xs)] text-[var(--color-danger)]">
+          {phase.message}
+        </p>
+      ) : null}
+      <div className="flex items-end gap-2">
+        <textarea
+          className="focus-ring-inset min-h-9 w-full resize-y rounded border border-[var(--border-hairline)] bg-transparent px-2.5 py-1.5 text-[length:var(--text-xs)] text-[var(--text-primary)] placeholder:text-[var(--text-muted)]"
+          rows={2}
+          placeholder={busy ? "The familiar is working…" : "Ask for follow-up changes…"}
+          value={prompt}
+          onChange={(e) => setPrompt(e.target.value)}
+          onKeyDown={(e) => {
+            if ((e.metaKey || e.ctrlKey) && e.key === "Enter") {
+              e.preventDefault();
+              void send();
+            }
+          }}
+          disabled={busy}
+          aria-label="Ask for follow-up changes"
+        />
+        {busy ? (
+          <Button size="sm" variant="danger-ghost" onClick={() => void stop()}>
+            Stop
+          </Button>
+        ) : (
+          <Button size="sm" variant="primary" disabled={!prompt.trim() || !row.familiarId} onClick={() => void send()}>
+            Send
+          </Button>
+        )}
+      </div>
+    </div>
+  );
+}
diff --git a/src/components/code-new-session.tsx b/src/components/code-new-session.tsx
new file mode 100644
index 000000000..bba897128
--- /dev/null
+++ b/src/components/code-new-session.tsx
@@ -0,0 +1,214 @@
+"use client";
+
+/**
+ * CodeNewSession — the Code surface's "+ New session" flow (cave-k0ua):
+ * pick a project + familiar, optionally provision a FRESH worktree for a
+ * named branch (POST /api/changes action=create-worktree — .worktrees/<branch>
+ * off origin's default), write the kickoff prompt, and start the conversation
+ * through the sanctioned client LLM path (streamFamiliarText, no sessionId =
+ * new thread) rooted at the chosen cwd. The moment the bridge announces the
+ * backing session id we hand it to the rail and close — the stream keeps
+ * running server-side; the transcript lives in Chat.
+ */
+
+import { useEffect, useState } from "react";
+import { Modal } from "@/components/ui/modal";
+import { Button } from "@/components/ui/button";
+import { StandardSelect } from "@/components/ui/select";
+import { streamFamiliarText } from "@/lib/familiar-stream";
+import type { CaveProject } from "@/lib/cave-projects-types";
+import type { Familiar } from "@/lib/types";
+
+type Phase = { kind: "idle" } | { kind: "provisioning" } | { kind: "starting" } | { kind: "error"; message: string };
+
+export function CodeNewSession({
+  open,
+  onClose,
+  onCreated,
+}: {
+  open: boolean;
+  onClose: () => void;
+  /** Fired as soon as the bridge announces the new session id. */
+  onCreated: (sessionId: string) => void;
+}) {
+  const [projects, setProjects] = useState<CaveProject[]>([]);
+  const [familiars, setFamiliars] = useState<Familiar[]>([]);
+  const [projectId, setProjectId] = useState("");
+  const [familiarId, setFamiliarId] = useState("");
+  const [freshWorktree, setFreshWorktree] = useState(false);
+  const [branch, setBranch] = useState("");
+  const [prompt, setPrompt] = useState("");
+  const [phase, setPhase] = useState<Phase>({ kind: "idle" });
+  const busy = phase.kind === "provisioning" || phase.kind === "starting";
+
+  useEffect(() => {
+    if (!open) return;
+    let cancelled = false;
+    (async () => {
+      try {
+        const [projRes, famRes] = await Promise.all([
+          fetch("/api/projects", { cache: "no-store" }),
+          fetch("/api/familiars", { cache: "no-store" }),
+        ]);
+        const proj = (await projRes.json().catch(() => null)) as { ok?: boolean; projects?: CaveProject[] } | null;
+        const fam = (await famRes.json().catch(() => null)) as { ok?: boolean; familiars?: Familiar[] } | null;
+        if (cancelled) return;
+        const projectRows = proj?.ok && Array.isArray(proj.projects) ? proj.projects : [];
+        const familiarRows = fam?.ok && Array.isArray(fam.familiars) ? fam.familiars : [];
+        setProjects(projectRows);
+        setFamiliars(familiarRows);
+        setProjectId((prev) => prev || (projectRows[0]?.id ?? ""));
+        setFamiliarId((prev) => prev || (familiarRows[0]?.id ?? ""));
+      } catch {
+        if (!cancelled) setPhase({ kind: "error", message: "Couldn’t load projects/familiars." });
+      }
+    })();
+    return () => {
+      cancelled = true;
+    };
+  }, [open]);
+
+  const project = projects.find((p) => p.id === projectId) ?? null;
+  const canCreate = Boolean(project && familiarId && prompt.trim() && (!freshWorktree || branch.trim()) && !busy);
+
+  async function create() {
+    if (!project || !canCreate) return;
+    let cwd = project.root;
+
+    if (freshWorktree) {
+      setPhase({ kind: "provisioning" });
+      try {
+        const res = await fetch("/api/changes", {
+          method: "POST",
+          headers: { "content-type": "application/json" },
+          body: JSON.stringify({ projectRoot: project.root, action: "create-worktree", branch: branch.trim() }),
+        });
+        const json = (await res.json().catch(() => null)) as
+          | { ok?: boolean; worktree?: string; error?: string }
+          | null;
+        if (!res.ok || !json?.ok || !json.worktree) {
+          setPhase({ kind: "error", message: json?.error ?? "Couldn’t create the worktree." });
+          return;
+        }
+        cwd = json.worktree;
+      } catch (err) {
+        setPhase({ kind: "error", message: err instanceof Error ? err.message : "Couldn’t create the worktree." });
+        return;
+      }
+    }
+
+    setPhase({ kind: "starting" });
+    let announced = false;
+    // Fire-and-continue: the moment the session id arrives the rail can select
+    // it; the stream keeps flowing server-side and Chat shows the transcript.
+    void streamFamiliarText({
+      familiarId,
+      prompt: prompt.trim(),
+      projectRoot: cwd,
+      runId: `code-new-session-${Date.now().toString(36)}`,
+      onSession: (sessionId) => {
+        if (announced) return;
+        announced = true;
+        onCreated(sessionId);
+      },
+    }).then((result) => {
+      if (!announced && result.sessionId) {
+        announced = true;
+        onCreated(result.sessionId);
+      } else if (!announced && result.error) {
+        setPhase({ kind: "error", message: result.error });
+      }
+    });
+  }
+
+  function reset() {
+    setPhase({ kind: "idle" });
+    setPrompt("");
+    setBranch("");
+    setFreshWorktree(false);
+  }
+
+  return (
+    <Modal
+      open={open}
+      onClose={() => {
+        if (busy && phase.kind !== "starting") return; // don't abandon mid-provision
+        reset();
+        onClose();
+      }}
+      breadcrumb={["Code", "New session"]}
+      footerActions={
+        <>
+          <Button
+            size="sm"
+            variant="ghost"
+            onClick={() => {
+              reset();
+              onClose();
+            }}
+            disabled={phase.kind === "provisioning"}
+          >
+            Cancel
+          </Button>
+          <Button size="sm" variant="primary" disabled={!canCreate} onClick={() => void create()}>
+            {phase.kind === "provisioning"
+              ? "Creating worktree…"
+              : phase.kind === "starting"
+                ? "Starting session…"
+                : "Start session"}
+          </Button>
+        </>
+      }
+    >
+      <div className="flex flex-col gap-3">
+        <StandardSelect
+          label="Project"
+          value={projectId}
+          onChange={setProjectId}
+          options={projects.map((p) => ({ value: p.id, label: p.name || p.root }))}
+          disabled={busy || projects.length === 0}
+        />
+        <StandardSelect
+          label="Familiar"
+          value={familiarId}
+          onChange={setFamiliarId}
+          options={familiars.map((f) => ({ value: f.id, label: f.display_name }))}
+          disabled={busy || familiars.length === 0}
+        />
+        <label className="flex items-center gap-2 text-[length:var(--text-xs)] text-[var(--text-secondary)]">
+          <input
+            type="checkbox"
+            checked={freshWorktree}
+            onChange={(e) => setFreshWorktree(e.target.checked)}
+            disabled={busy}
+          />
+          Work in a fresh worktree
+        </label>
+        {freshWorktree ? (
+          <input
+            type="text"
+            className="focus-ring-inset w-full rounded border border-[var(--border-hairline)] bg-transparent px-2.5 py-1.5 font-mono text-[length:var(--text-xs)] text-[var(--text-primary)] placeholder:text-[var(--text-muted)]"
+            placeholder="branch name (e.g. feat/my-change)"
+            value={branch}
+            onChange={(e) => setBranch(e.target.value)}
+            disabled={busy}
+            aria-label="Worktree branch name"
+          />
+        ) : null}
+        <textarea
+          className="focus-ring-inset min-h-20 w-full resize-y rounded border border-[var(--border-hairline)] bg-transparent px-2.5 py-1.5 text-[length:var(--text-xs)] text-[var(--text-primary)] placeholder:text-[var(--text-muted)]"
+          placeholder="What should this session work on?"
+          value={prompt}
+          onChange={(e) => setPrompt(e.target.value)}
+          disabled={busy}
+          aria-label="Kickoff prompt"
+        />
+        {phase.kind === "error" ? (
+          <p role="alert" className="text-[length:var(--text-xs)] text-[var(--color-danger)]">
+            {phase.message}
+          </p>
+        ) : null}
+      </div>
+    </Modal>
+  );
+}
diff --git a/src/components/code-session-rail.tsx b/src/components/code-session-rail.tsx
index 976432d69..bad289fe1 100644
--- a/src/components/code-session-rail.tsx
+++ b/src/components/code-session-rail.tsx
@@ -51,21 +51,37 @@ export type CodeSessionRailProps = {
   sessions: SessionRow[];
   selectedId: string | null;
   onSelect: (sessionId: string) => void;
+  onNewSession?: () => void;
 };
 
-export function CodeSessionRail({ sessions, selectedId, onSelect }: CodeSessionRailProps) {
+export function CodeSessionRail({ sessions, selectedId, onSelect, onNewSession }: CodeSessionRailProps) {
   const groups = groupCodeRailSessions(sessions);
+  const newButton = onNewSession ? (
+    <div className="px-2 pb-1">
+      <button
+        type="button"
+        className="focus-ring flex w-full items-center gap-1.5 rounded px-2 py-1.5 text-[length:var(--text-xs)] text-[var(--text-secondary)] hover:bg-[var(--bg-hover)] hover:text-[var(--text-primary)]"
+        onClick={onNewSession}
+      >
+        <Icon name="ph:plus" width={12} height={12} />
+        New session
+      </button>
+    </div>
+  ) : null;
   if (groups.length === 0) {
     return (
-      <div className="px-3 py-6 text-[length:var(--text-xs)] text-[var(--text-muted)]">
-        No coding sessions yet. Start one from Chat — it will appear here with
-        its branch, diff, and PR context.
+      <div className="flex h-full flex-col py-2">
+        {newButton}
+        <div className="px-3 py-4 text-[length:var(--text-xs)] text-[var(--text-muted)]">
+          No coding sessions yet. Start one here — or from Chat — and it will
+          appear with its branch, diff, and PR context.
+        </div>
       </div>
     );
   }
   return (
     <nav aria-label="Coding sessions" className="flex h-full min-h-0 flex-col overflow-y-auto py-2">
-      {groups.map((group) => (
+      {newButton}      {groups.map((group) => (
         <section key={group.root || "(unknown)"} className="mb-2">
           <div
             className="truncate px-3 py-1 text-[length:var(--text-2xs)] font-semibold uppercase tracking-wider text-[var(--text-secondary)]"
diff --git a/src/components/code-surface-mode.test.ts b/src/components/code-surface-mode.test.ts
index e11be4b8a..b9b854b86 100644
--- a/src/components/code-surface-mode.test.ts
+++ b/src/components/code-surface-mode.test.ts
@@ -182,6 +182,59 @@ assert.match(
   "merge requires a second confirming click — no one-click merges",
 );
 
+// ── Composer + new-session flow ──────────────────────────────────────────────
+
+const composer = await readFile(new URL("./code-composer.tsx", import.meta.url), "utf8");
+const newSession = await readFile(new URL("./code-new-session.tsx", import.meta.url), "utf8");
+const rail = await readFile(new URL("./code-session-rail.tsx", import.meta.url), "utf8");
+
+assert.match(
+  composer,
+  /streamFamiliarText\(\{\s*familiarId: row\.familiarId,\s*sessionId: row\.id,/,
+  "the composer RESUMES the selected session (sessionId rides) — never forks a new thread",
+);
+assert.match(
+  composer,
+  /projectRoot: codeSessionWorkRoot\(row\),/,
+  "composer turns run in the session's work root (worktree over shared checkout, cave-9q24)",
+);
+assert.match(
+  composer,
+  /"\/api\/chat\/stop"[\s\S]*?runId: phase\.runId, sessionId: row\.id/,
+  "Stop cancels via /api/chat/stop with the send's runId before dropping the stream",
+);
+assert.match(
+  newSession,
+  /action: "create-worktree", branch: branch\.trim\(\)/,
+  "fresh-worktree option provisions through the existing /api/changes action",
+);
+const kickoff = newSession.match(/void streamFamiliarText\(\{[\s\S]*?\}\)\.then/)?.[0] ?? "";
+assert.ok(kickoff.length > 0, "the new-session kickoff send is present");
+assert.ok(
+  !kickoff.includes("sessionId:"),
+  "the kickoff send carries NO sessionId — a fresh thread, saved like any chat",
+);
+assert.match(
+  newSession,
+  /onSession: \(sessionId\) => \{/,
+  "the rail learns the new session id the moment the bridge announces it",
+);
+assert.match(
+  rail,
+  /onNewSession\?: \(\) => void;/,
+  "the rail exposes the + New session entry point",
+);
+assert.match(
+  codeView,
+  /pendingNewIdRef\.current === selectedId\) return;/,
+  "a just-created session's selection survives until /api/sessions/list catches up",
+);
+assert.match(
+  workbench,
+  /\{tab !== "terminal" \? <CodeComposer row=\{row\} onJumpToSession=\{onJumpToSession\} \/> : null\}/,
+  "the composer rides under every tab except Terminal (which owns its input)",
+);
+
 // ── Chat stays untouched this phase ──────────────────────────────────────────
 
 // Phase 1 builds the surface *behind the flag* without slimming Chat: the code
diff --git a/src/components/code-view.tsx b/src/components/code-view.tsx
index 93f8a3647..c5d5565ac 100644
--- a/src/components/code-view.tsx
+++ b/src/components/code-view.tsx
@@ -5,16 +5,16 @@
  * multi-session coding tab. Reverses the earlier Code-mode retirement on the
  * owner's request; gated by caveCodeSurface() (NEXT_PUBLIC_CAVE_CODE_SURFACE).
  *
- * Phase 2 (this shape): top-level Sessions/GitHub tabs, the session rail
- * grouped by project with git-attribution badges, and the per-session
- * workbench (Diff | Files | Terminal — see code-workbench.tsx). The PR tab,
- * inspector, composer, and new-session flow land in follow-up PRs; the
- * CODE_WORKBENCH_TABS vocabulary in src/lib/code-surface.ts already fixes
- * their deep-link names. GitHub mounts whole under the GitHub tab (its
- * sidebar row hides when the flag is on).
+ * Phase 3+ (this shape): top-level Sessions/GitHub tabs, the session rail
+ * (grouped by project, git-attribution badges, + New session) and the
+ * per-session workbench (Diff | Files | Terminal | PR) with the follow-up
+ * composer (code-composer.tsx). New sessions start via code-new-session.tsx —
+ * project + familiar + optional fresh worktree. The inspector and mobile
+ * layout land in follow-up PRs. GitHub mounts whole under the GitHub tab
+ * (its sidebar row hides when the flag is on).
  */
 
-import React, { useEffect, useMemo, useState } from "react";
+import React, { useEffect, useMemo, useRef, useState } from "react";
 import dynamic from "next/dynamic";
 import { Icon } from "@/lib/icon";
 import {
@@ -24,6 +24,7 @@ import {
 } from "@/lib/code-surface";
 import { CodeSessionRail } from "@/components/code-session-rail";
 import { CodeWorkbench } from "@/components/code-workbench";
+import { CodeNewSession } from "@/components/code-new-session";
 import type { GitHubItemTarget } from "@/lib/github-item-url";
 import type { SessionRow } from "@/lib/types";
 
@@ -71,6 +72,10 @@ export function CodeView({
     githubTarget ? "github" : deepLink?.topTab ?? "sessions",
   );
   const [selectedId, setSelectedId] = useState<string | null>(deepLink?.sessionId ?? null);
+  const [newSessionOpen, setNewSessionOpen] = useState(false);
+  // A session created HERE isn't in the polled list yet; hold its selection
+  // until /api/sessions/list catches up instead of auto-picking the newest.
+  const pendingNewIdRef = useRef<string | null>(null);
 
   const groups = useMemo(() => groupCodeRailSessions(sessions), [sessions]);
   const selected = useMemo(() => {
@@ -85,10 +90,14 @@ export function CodeView({
   // Land on the newest session so the surface is immediately useful; keep the
   // user's explicit pick as long as that session is still visible.
   useEffect(() => {
-    if (selected) return;
+    if (selected) {
+      if (pendingNewIdRef.current === selected.id) pendingNewIdRef.current = null;
+      return;
+    }
+    if (selectedId && pendingNewIdRef.current === selectedId) return;
     const first = groups[0]?.sessions[0];
     if (first) setSelectedId(first.id);
-  }, [groups, selected]);
+  }, [groups, selected, selectedId]);
 
   return (
     <div className="flex h-full min-h-0 flex-col">
@@ -138,7 +147,12 @@ export function CodeView({
       ) : (
         <div className="flex min-h-0 flex-1">
           <div className="w-64 shrink-0 border-r border-[var(--border-hairline)]">
-            <CodeSessionRail sessions={sessions} selectedId={selectedId} onSelect={setSelectedId} />
+            <CodeSessionRail
+              sessions={sessions}
+              selectedId={selectedId}
+              onSelect={setSelectedId}
+              onNewSession={() => setNewSessionOpen(true)}
+            />
           </div>
           <div className="min-w-0 flex-1">
             {selected ? (
@@ -156,6 +170,15 @@ export function CodeView({
           </div>
         </div>
       )}
+      <CodeNewSession
+        open={newSessionOpen}
+        onClose={() => setNewSessionOpen(false)}
+        onCreated={(sessionId) => {
+          pendingNewIdRef.current = sessionId;
+          setSelectedId(sessionId);
+          setNewSessionOpen(false);
+        }}
+      />
     </div>
   );
 }
diff --git a/src/components/code-workbench.tsx b/src/components/code-workbench.tsx
index ca210dab2..8d00ea9a9 100644
--- a/src/components/code-workbench.tsx
+++ b/src/components/code-workbench.tsx
@@ -17,6 +17,9 @@
  *     xterm; stays mounted once opened so scrollback survives tab switches
  *   - PR → CodeSessionPrPanel (stage pipeline, checks, review threads,
  *     approve/merge via /api/github/*), dynamic() alongside its fetch hooks
+ *
+ * Below the tabs (except Terminal, which owns its input): the follow-up
+ * composer (code-composer.tsx) — sends to THIS session's agent.
  */
 
 import React, { useEffect, useState } from "react";
@@ -25,6 +28,7 @@ import { Icon } from "@/lib/icon";
 import { Button } from "@/components/ui/button";
 import { relativeTime } from "@/lib/relative-time";
 import { SessionChangesInner } from "@/components/session-changes-panel";
+import { CodeComposer } from "@/components/code-composer";
 import {
   codeSessionActivity,
   codeSessionBranch,
@@ -152,6 +156,7 @@ export function CodeWorkbench({
         ) : null}
         {tab === "pr" ? <LazyPrTab key={row.id} row={row} /> : null}
       </div>
+      {tab !== "terminal" ? <CodeComposer row={row} onJumpToSession={onJumpToSession} /> : null}
     </div>
   );
 }