diff --git a/apps/api/src/llm/router.ts b/apps/api/src/llm/router.ts
index ba27eb9..7794bbb 100644
--- a/apps/api/src/llm/router.ts
+++ b/apps/api/src/llm/router.ts
@@ -38,6 +38,24 @@ export class LLMRouter {
     return (response.content[0] as { text: string }).text;
   }
 
+  async *stream(
+    messages: Array<{ role: 'user' | 'assistant'; content: string }>,
+    contextBlock: string
+  ): AsyncIterable<string> {
+    const system = `${SHORT_RESPONSE_CONTRACT}\n\n## Prior context\n\n${contextBlock}`;
+    const stream = this.claude.messages.stream({
+      model: 'claude-sonnet-4-6',
+      max_tokens: 1024,
+      system,
+      messages,
+    });
+    for await (const chunk of stream) {
+      if (chunk.type === 'content_block_delta' && chunk.delta.type === 'text_delta') {
+        yield chunk.delta.text;
+      }
+    }
+  }
+
   async summarise(content: string): Promise<string> {
     const result = await this.flashModel.generateContent(
       `Write a 2-3 sentence session summary of this conversation. Be specific about decisions made and next steps.\n\n${content}`
diff --git a/apps/api/src/routes/chat.test.ts b/apps/api/src/routes/chat.test.ts
index 805e97c..de7315d 100644
--- a/apps/api/src/routes/chat.test.ts
+++ b/apps/api/src/routes/chat.test.ts
@@ -8,8 +8,13 @@ const mockCache = {
   all: vi.fn().mockReturnValue([]),
 } as unknown as IndexCache;
 
+async function* mockStream() {
+  yield 'assistant ';
+  yield 'reply';
+}
+
 const mockLlm = {
-  chat: vi.fn().mockResolvedValue('assistant reply'),
+  stream: vi.fn().mockImplementation(mockStream),
   summarise: vi.fn().mockResolvedValue('session summary'),
   generateFrontmatter: vi.fn().mockResolvedValue({ tags: ['a'], summary: 'a summary' }),
 } as unknown as LLMRouter;
@@ -52,21 +57,30 @@ describe('POST /api/chat', () => {
     expect(res.status).toBe(400);
   });
 
-  it('returns reply and context on valid request', async () => {
+  it('streams reply tokens and context event', async () => {
     const res = await authedPost(app, sessionCookie, '/api/chat', { messages: validMessages });
     expect(res.status).toBe(200);
-    const data = (await res.json()) as { reply: string; context: unknown[] };
-    expect(data.reply).toBe('assistant reply');
-    expect(Array.isArray(data.context)).toBe(true);
+    expect(res.headers.get('content-type')).toContain('text/event-stream');
+    const text = await res.text();
+    expect(text).toContain('event: context');
+    expect(text).toContain('data: assistant ');
+    expect(text).toContain('data: reply');
+    expect(text).toContain('data: [DONE]');
   });
 
-  it('propagates LLM error as 500 via global error handler', async () => {
-    vi.mocked(mockLlm.chat).mockRejectedValueOnce(new Error('LLM timeout'));
+  it('closes stream gracefully on LLM error', async () => {
+    const failingIterable: AsyncIterable<string> = {
+      [Symbol.asyncIterator]: () => ({
+        next: () => Promise.reject(new Error('LLM timeout')),
+        return: () => Promise.resolve({ value: undefined, done: true as const }),
+      }),
+    };
+    vi.mocked(mockLlm.stream).mockReturnValueOnce(failingIterable);
     const res = await authedPost(app, sessionCookie, '/api/chat', { messages: validMessages });
-    expect(res.status).toBe(500);
-    const data = (await res.json()) as { error: string };
-    expect(data.error).toBe('Internal server error');
-    expect(data.error).not.toContain('LLM timeout');
+    // SSE always returns 200 once headers are sent; stream closes on error without [DONE]
+    expect(res.status).toBe(200);
+    const text = await res.text();
+    expect(text).not.toContain('data: [DONE]');
   });
 });
 
diff --git a/apps/api/src/routes/chat.ts b/apps/api/src/routes/chat.ts
index e5bb363..b0cc549 100644
--- a/apps/api/src/routes/chat.ts
+++ b/apps/api/src/routes/chat.ts
@@ -34,8 +34,20 @@ export function chatRoutes(llm: LLMRouter, cache: IndexCache) {
     const { messages, query, relatedToId } = c.req.valid('json');
     const contextEntries = assembleContext(cache.all(), query, relatedToId);
     const contextBlock = formatContextBlock(contextEntries);
-    const reply = await llm.chat(messages, contextBlock);
-    return c.json({ reply, context: contextEntries.map((e) => ({ id: e.id, title: e.title })) });
+    const { streamSSE } = await import('hono/streaming');
+    return streamSSE(c, async (stream) => {
+      // First event: context metadata
+      await stream.writeSSE({
+        event: 'context',
+        data: JSON.stringify(contextEntries.map((e) => ({ id: e.id, title: e.title }))),
+      });
+      // Stream tokens
+      for await (const chunk of llm.stream(messages, contextBlock)) {
+        await stream.writeSSE({ data: chunk });
+      }
+      // Done sentinel
+      await stream.writeSSE({ data: '[DONE]' });
+    });
   });
 
   app.post('/api/chat/summarise', requireAuth(), zValidator('json', summariseSchema), async (c) => {
diff --git a/apps/api/src/routes/content.ts b/apps/api/src/routes/content.ts
index 11baba6..fb418b5 100644
--- a/apps/api/src/routes/content.ts
+++ b/apps/api/src/routes/content.ts
@@ -7,7 +7,8 @@ import type { IndexCache } from '../store/index-cache.js';
 import { requireAuth } from './auth.js';
 
 const patchSchema = z.object({
-  session_summary: z.string().min(1).max(2000),
+  session_summary: z.string().min(1).max(2000).optional(),
+  body: z.string().max(50000).optional(),
 });
 
 export function contentRoutes(cache: IndexCache, github: GitHubClient) {
@@ -63,14 +64,17 @@ export function contentRoutes(cache: IndexCache, github: GitHubClient) {
     const id = c.req.param('id');
     const entry = cache.findById(id);
     if (!entry) return c.json({ error: 'not found' }, 404);
-    const { session_summary } = c.req.valid('json');
+    const input = c.req.valid('json');
 
     const { content, encoding, sha } = await github.getFile(entry.path, entry.branch ?? 'main');
     const decoded =
       encoding === 'base64' ? Buffer.from(content, 'base64').toString('utf-8') : content;
 
-    const { data, content: body } = matter(decoded);
-    const updated = matter.stringify(body, { ...data, session_summary });
+    const { data, content: existingBody } = matter(decoded);
+    const updated = matter.stringify(input.body ?? existingBody, {
+      ...data,
+      ...(input.session_summary ? { session_summary: input.session_summary } : {}),
+    });
 
     await github.upsertFile(
       entry.path,
diff --git a/apps/web/src/lib/api.ts b/apps/web/src/lib/api.ts
index 67236f7..a1092b7 100644
--- a/apps/web/src/lib/api.ts
+++ b/apps/web/src/lib/api.ts
@@ -58,7 +58,7 @@ export const api = {
       headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify(input),
     }),
-  patch: (id: string, body: { session_summary: string }) =>
+  patch: (id: string, body: { session_summary?: string; body?: string }) =>
     req<{ ok: boolean }>(`/api/content/${id}`, {
       method: 'PATCH',
       headers: { 'Content-Type': 'application/json' },
@@ -68,7 +68,7 @@ export const api = {
   park: (id: string) => req(`/api/content/${id}/park`, { method: 'POST' }),
   dismiss: (id: string) => req(`/api/content/${id}/dismiss`, { method: 'POST' }),
   discardPR: (pr: number) => req(`/api/inflight/${pr}/discard`, { method: 'POST' }),
-  promote: (id: string, title: string, summary: string) =>
+  promote: (id: string, title: string, summary: string, sessionSummary?: string) =>
     req<{ id: string; pr: number; branch: string }>('/api/capture', {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
@@ -78,7 +78,17 @@ export const api = {
         tags: [],
         summary,
         promoted_from: [id],
-        body: `## Goal\n${summary || title}\n\n## Steps\n- (to be refined)\n\n## Success criteria\n- (to be refined)`,
+        body: [
+          '## Goal',
+          summary || title,
+          '',
+          ...(sessionSummary ? ['## Context from idea session', sessionSummary, ''] : []),
+          '## Steps',
+          '- (to be refined)',
+          '',
+          '## Success criteria',
+          '- (to be refined)',
+        ].join('\n'),
       }),
     }),
   chat: (messages: unknown[], query?: string, relatedToId?: string) =>
diff --git a/apps/web/src/routes/chat/[id]/+page.svelte b/apps/web/src/routes/chat/[id]/+page.svelte
index 2c19c01..d569dd0 100644
--- a/apps/web/src/routes/chat/[id]/+page.svelte
+++ b/apps/web/src/routes/chat/[id]/+page.svelte
@@ -14,6 +14,8 @@ let parking = false;
 let promoting = false;
 let contextTitles: string[] = [];
 let error = '';
+let saving = false;
+let savedAt: Date | null = null;
 
 const idParam = $page.params.id;
 if (!idParam) throw new Error('Missing route param: id');
@@ -28,6 +30,19 @@ onMount(async () => {
   }
 });
 
+async function save() {
+  if (messages.length === 0) return;
+  saving = true;
+  try {
+    const conversation = messages.map((m) => `${m.role}: ${m.content}`).join('\n');
+    const { summary } = await api.summarise(conversation);
+    await api.patch(id, { session_summary: summary });
+    savedAt = new Date();
+  } finally {
+    saving = false;
+  }
+}
+
 async function send() {
   if (!input.trim()) return;
   const userMsg = { role: 'user' as const, content: input };
@@ -35,12 +50,51 @@ async function send() {
   input = '';
   loading = true;
   error = '';
+  const BASE = import.meta.env.PUBLIC_API_URL ?? '';
+  const assistantMsg = { role: 'assistant' as const, content: '' };
+  messages = [...messages, assistantMsg];
   try {
-    const res = await api.chat(messages, item?.title, id);
-    messages = [...messages, { role: 'assistant', content: res.reply }];
-    contextTitles = res.context.map((c) => c.title);
+    const res = await fetch(`${BASE}/api/chat`, {
+      method: 'POST',
+      credentials: 'include',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        messages: messages.slice(0, -1),
+        query: item?.title,
+        relatedToId: id,
+      }),
+    });
+    if (!res.ok) throw new Error(`API error: ${res.status}`);
+    if (!res.body) throw new Error('No response body');
+    const reader = res.body.getReader();
+    const decoder = new TextDecoder();
+    let buffer = '';
+    while (true) {
+      const { done, value } = await reader.read();
+      if (done) break;
+      buffer += decoder.decode(value, { stream: true });
+      const parts = buffer.split('\n\n');
+      buffer = parts.pop() ?? '';
+      for (const part of parts) {
+        const eventLine = part.split('\n').find((l) => l.startsWith('event:'));
+        const dataLine = part.split('\n').find((l) => l.startsWith('data:'));
+        if (!dataLine) continue;
+        const data = dataLine.slice(5).trim();
+        if (eventLine?.includes('context')) {
+          try {
+            contextTitles = JSON.parse(data).map((e: { title: string }) => e.title);
+          } catch {
+            /* ignore */
+          }
+        } else if (data !== '[DONE]') {
+          assistantMsg.content += data;
+          messages = [...messages];
+        }
+      }
+    }
   } catch {
     error = 'Failed to send message. Please try again.';
+    messages = messages.slice(0, -1); // remove empty assistant message
   } finally {
     loading = false;
   }
@@ -50,6 +104,7 @@ async function park() {
   parking = true;
   error = '';
   try {
+    await save();
     await api.park(id);
     goto('/');
   } catch {
@@ -63,7 +118,7 @@ async function promote() {
   promoting = true;
   error = '';
   try {
-    const { id: planId } = await api.promote(id, item.title, item.summary);
+    const { id: planId } = await api.promote(id, item.title, item.summary, item.session_summary);
     goto(`/chat/${planId}`);
   } catch {
     error = 'Failed to promote. Please try again.';
@@ -97,6 +152,7 @@ async function finish() {
         <button on:click={promote} disabled={promoting || finishing} style="font-size:12px;background:#1a2a3a;color:#a78bfa;border:1px solid #a78bfa;padding:4px 10px;border-radius:6px;cursor:pointer">{promoting ? '...' : '→ Plan'}</button>
       {/if}
       <button on:click={park} disabled={parking || finishing} style="font-size:12px;background:#2a2a1a;color:#facc15;border:1px solid #facc15;padding:4px 10px;border-radius:6px;cursor:pointer">{parking ? '...' : 'Park'}</button>
+      <button on:click={save} disabled={saving || finishing || parking} style="font-size:12px;background:#1a1a2a;color:#94a3b8;border:1px solid #94a3b8;padding:4px 10px;border-radius:6px;cursor:pointer">{saving ? '...' : savedAt ? 'Saved ✓' : 'Save'}</button>
       {#if item.pr}
         <button on:click={finish} disabled={finishing || parking} style="font-size:12px;background:#1a3a1a;color:#4ade80;border:1px solid #4ade80;padding:4px 10px;border-radius:6px;cursor:pointer">{finishing ? '...' : 'Commit ✓'}</button>
       {/if}
@@ -115,11 +171,8 @@ async function finish() {
         align-self:{msg.role==='user'?'flex-end':'flex-start'};
         max-width:85%;background:{msg.role==='user'?'#1a3a5c':'#1a1a1a'};
         padding:10px 14px;border-radius:12px;font-size:14px;white-space:pre-wrap
-      ">{msg.content}</div>
+      ">{msg.content || (loading && msg.role === 'assistant' ? '…' : msg.content)}</div>
     {/each}
-    {#if loading}
-      <div style="align-self:flex-start;color:#666;font-size:14px">...</div>
-    {/if}
     {#if error}
       <p role="alert" style="color:#f87171;font-size:13px;padding:0 4px">{error}</p>
     {/if}