diff --git a/lib/llm-summarize.ts b/lib/llm-summarize.ts
new file mode 100644
index 00000000..03c0d7fb
--- /dev/null
+++ b/lib/llm-summarize.ts
@@ -0,0 +1,125 @@
+/**
+ * LLM session summarization via raw fetch() to Anthropic Messages API.
+ *
+ * No SDK dependency — matches the Supabase raw-fetch pattern.
+ * Uses eval-cache for SHA-based caching (reruns are instant).
+ *
+ * Retry strategy (per Anthropic docs):
+ *   429: read retry-after header, wait that duration, max 2 retries
+ *   5xx: exponential backoff (1s, 2s), max 2 retries
+ *   All other errors: return null immediately
+ */
+
+import { computeCacheKey, cacheRead, cacheWrite } from './eval-cache';
+
+const ANTHROPIC_API_URL = 'https://api.anthropic.com/v1/messages';
+const MODEL = 'claude-haiku-4-5-20251001';
+const MAX_RETRIES = 2;
+const TIMEOUT_MS = 10_000;
+
+/**
+ * Generate a 1-sentence summary of a Claude Code session.
+ * Returns null if: no API key, API error, or malformed response.
+ */
+export async function summarizeSession(
+  messages: Array<{ display: string; timestamp: number }>,
+  toolsUsed: string[] | null,
+): Promise<string | null> {
+  const apiKey = process.env.ANTHROPIC_API_KEY;
+  if (!apiKey) return null;
+  if (messages.length === 0) return null;
+
+  // Build cache key from session content
+  const contentForHash = messages.map(m => m.display).join('\n').slice(0, 10_000);
+  const toolsStr = toolsUsed ? toolsUsed.join(',') : '';
+  const cacheKey = computeCacheKey([], `summary:${MODEL}:${contentForHash}:${toolsStr}`);
+
+  const cached = cacheRead('transcript-summaries', cacheKey);
+  if (cached !== null && typeof cached === 'string') return cached;
+
+  const promptLines = messages.slice(0, 50).map(m =>
+    m.display.length > 200 ? m.display.slice(0, 200) + '...' : m.display,
+  );
+  const toolInfo = toolsUsed && toolsUsed.length > 0
+    ? `\nTools used: ${toolsUsed.join(', ')}`
+    : '';
+
+  const userPrompt = `Summarize this Claude Code session in exactly one sentence. Focus on what the user accomplished, not the process. Be specific and concise.
+
+User prompts (${messages.length} turns):
+${promptLines.join('\n')}
+${toolInfo}
+
+Respond with ONLY the summary sentence, nothing else.`;
+
+  const body = JSON.stringify({
+    model: MODEL,
+    max_tokens: 150,
+    messages: [{ role: 'user', content: userPrompt }],
+  });
+
+  const summary = await fetchWithRetry(apiKey, body);
+  if (summary) {
+    cacheWrite('transcript-summaries', cacheKey, summary, { model: MODEL });
+  }
+  return summary;
+}
+
+async function fetchWithRetry(apiKey: string, body: string): Promise<string | null> {
+  for (let attempt = 0; attempt <= MAX_RETRIES; attempt++) {
+    try {
+      const controller = new AbortController();
+      const timeout = setTimeout(() => controller.abort(), TIMEOUT_MS);
+
+      const res = await fetch(ANTHROPIC_API_URL, {
+        method: 'POST',
+        signal: controller.signal,
+        headers: {
+          'Content-Type': 'application/json',
+          'x-api-key': apiKey,
+          'anthropic-version': '2023-06-01',
+        },
+        body,
+      });
+
+      clearTimeout(timeout);
+
+      if (res.ok) {
+        const data = await res.json() as Record<string, unknown>;
+        const content = (data.content as any[])?.[0];
+        if (content?.type === 'text' && typeof content.text === 'string') {
+          return content.text.trim().slice(0, 500);
+        }
+        return null;
+      }
+
+      // 429: use retry-after header
+      if (res.status === 429 && attempt < MAX_RETRIES) {
+        const retryAfter = parseInt(res.headers.get('retry-after') || '2', 10);
+        await sleep(retryAfter * 1000);
+        continue;
+      }
+
+      // 5xx: exponential backoff
+      if (res.status >= 500 && attempt < MAX_RETRIES) {
+        await sleep(1000 * Math.pow(2, attempt));
+        continue;
+      }
+
+      // 4xx (not 429): don't retry
+      return null;
+    } catch {
+      // Network error, timeout, abort — retry with backoff
+      if (attempt < MAX_RETRIES) {
+        await sleep(1000 * Math.pow(2, attempt));
+        continue;
+      }
+      return null;
+    }
+  }
+  return null;
+}
+
+function sleep(ms: number): Promise<void> {
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
diff --git a/lib/sync.ts b/lib/sync.ts
index ca7f5c6b..72e63c2b 100644
--- a/lib/sync.ts
+++ b/lib/sync.ts
@@ -213,6 +213,11 @@ export function pushHeartbeat(): Promise<boolean> {
   return pushWithSync('sync_heartbeats', { hostname: os.hostname() }, { addRepoSlug: false });
 }
 
+/** Push a session transcript to Supabase. repo_slug is in the data (from getRemoteSlugForPath). */
+export function pushTranscript(data: Record<string, unknown>): Promise<boolean> {
+  return pushWithSync('session_transcripts', data, { addRepoSlug: false });
+}
+
 // --- Pull operations ---
 
 /**
@@ -277,6 +282,18 @@ export async function pullRetros(opts?: { repoSlug?: string; limit?: number }):
   return pullTable('retro_snapshots', parts.join('&'));
 }
 
+/** Pull team session transcripts. */
+export async function pullTranscripts(opts?: { repoSlug?: string; limit?: number }): Promise<Record<string, unknown>[]> {
+  const config = resolveSyncConfig();
+  if (!config) return [];
+
+  const parts = [`team_id=eq.${config.auth.team_id}`, 'order=started_at.desc'];
+  if (opts?.repoSlug) parts.push(`repo_slug=eq.${opts.repoSlug}`);
+  parts.push(`limit=${opts?.limit || 50}`);
+
+  return pullTable('session_transcripts', parts.join('&'));
+}
+
 // --- Offline queue ---
 
 function enqueue(entry: QueueEntry): void {
diff --git a/lib/transcript-sync.ts b/lib/transcript-sync.ts
new file mode 100644
index 00000000..1ae5d37e
--- /dev/null
+++ b/lib/transcript-sync.ts
@@ -0,0 +1,395 @@
+/**
+ * Transcript sync — parse Claude Code session history, enrich with
+ * tool usage and LLM summaries, push to Supabase.
+ *
+ * Data sources:
+ *   ~/.claude/history.jsonl          — user prompts (always available)
+ *   ~/.claude/projects/{hash}/{sid}.jsonl — full transcript (when available, ~19%)
+ *
+ * Degradation cascade:
+ *   history.jsonl only                → user prompts, turn count, duration
+ *   + session file                    → + tools_used, full turn count
+ *   + ANTHROPIC_API_KEY               → + 1-sentence LLM summary
+ *
+ * All operations are non-fatal. If any step fails, we degrade gracefully.
+ */
+
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+import { readJSON, atomicWriteJSON, GSTACK_STATE_DIR } from './util';
+import { resolveSyncConfig } from './sync-config';
+import { pushTranscript } from './sync';
+import { summarizeSession } from './llm-summarize';
+
+const HISTORY_FILE = path.join(os.homedir(), '.claude', 'history.jsonl');
+const CLAUDE_PROJECTS_DIR = path.join(os.homedir(), '.claude', 'projects');
+const MARKER_FILE = path.join(GSTACK_STATE_DIR, 'transcript-sync-marker.json');
+const MAX_HISTORY_SIZE = 50 * 1024 * 1024; // 50MB warn threshold
+const MAX_SESSION_FILE_SIZE = 10 * 1024 * 1024; // 10MB skip threshold
+const PUSH_CONCURRENCY = 10;
+const SUMMARY_CONCURRENCY = 5;
+
+// --- Types ---
+
+export interface HistoryEntry {
+  display: string;
+  pastedContents: Record<string, unknown>;
+  timestamp: number;
+  project: string;
+  sessionId: string;
+}
+
+export interface TranscriptSyncMarker {
+  pushed_sessions: Record<string, { turns_pushed: number; last_push: string }>;
+  last_file_size: number;
+  updated_at: string;
+}
+
+export interface SessionFileData {
+  tools_used: string[];
+  totalTurns: number;
+}
+
+export interface TranscriptData {
+  session_id: string;
+  repo_slug: string;
+  messages: Array<{ display: string; timestamp: number }>;
+  total_turns: number;
+  tools_used: string[] | null;
+  summary: string | null;
+  started_at: string;
+  ended_at: string;
+}
+
+// --- History parsing ---
+
+/**
+ * Parse ~/.claude/history.jsonl into HistoryEntry[].
+ * Returns [] on ENOENT, EBUSY, EACCES, or any error. Skips malformed lines.
+ */
+export function parseHistoryFile(historyPath: string = HISTORY_FILE): HistoryEntry[] {
+  try {
+    const stat = fs.statSync(historyPath);
+    if (stat.size > MAX_HISTORY_SIZE) {
+      console.error(`Warning: history.jsonl is ${(stat.size / 1024 / 1024).toFixed(1)}MB — parsing may be slow.`);
+    }
+    const content = fs.readFileSync(historyPath, 'utf-8');
+    const entries: HistoryEntry[] = [];
+    for (const line of content.split('\n')) {
+      if (!line.trim()) continue;
+      try {
+        const d = JSON.parse(line);
+        if (d.sessionId && d.timestamp && d.project) {
+          entries.push({
+            display: typeof d.display === 'string' ? d.display : '',
+            pastedContents: d.pastedContents || {},
+            timestamp: d.timestamp,
+            project: d.project,
+            sessionId: d.sessionId,
+          });
+        }
+      } catch { /* skip malformed line */ }
+    }
+    return entries;
+  } catch {
+    return [];
+  }
+}
+
+/**
+ * Group history entries by sessionId.
+ */
+export function groupBySession(entries: HistoryEntry[]): Map<string, HistoryEntry[]> {
+  const map = new Map<string, HistoryEntry[]>();
+  for (const entry of entries) {
+    const group = map.get(entry.sessionId);
+    if (group) {
+      group.push(entry);
+    } else {
+      map.set(entry.sessionId, [entry]);
+    }
+  }
+  return map;
+}
+
+// --- Session file enrichment ---
+
+/**
+ * Find the rich session file for a given sessionId and project path.
+ * Returns the file path or null if not found.
+ *
+ * Claude Code stores session files at:
+ *   ~/.claude/projects/-{project.replaceAll('/', '-')}/{sessionId}.jsonl
+ */
+export function findSessionFile(sessionId: string, projectPath: string): string | null {
+  try {
+    const projectHash = '-' + projectPath.replace(/\//g, '-');
+    const sessionFile = path.join(CLAUDE_PROJECTS_DIR, projectHash, `${sessionId}.jsonl`);
+
+    // Security: validate the resolved path stays within ~/.claude/projects/
+    const resolved = path.resolve(sessionFile);
+    if (!resolved.startsWith(path.resolve(CLAUDE_PROJECTS_DIR))) return null;
+
+    if (!fs.existsSync(sessionFile)) return null;
+
+    const stat = fs.statSync(sessionFile);
+    if (stat.size > MAX_SESSION_FILE_SIZE) return null; // Skip large files
+    if (stat.size === 0) return null;
+
+    return sessionFile;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Parse a session JSONL file to extract tool usage and turn counts.
+ */
+export function parseSessionFile(sessionFilePath: string): SessionFileData | null {
+  try {
+    const content = fs.readFileSync(sessionFilePath, 'utf-8');
+    const toolSet = new Set<string>();
+    let totalTurns = 0;
+
+    for (const line of content.split('\n')) {
+      if (!line.trim()) continue;
+      try {
+        const d = JSON.parse(line);
+        const type = d.type;
+        if (type === 'user' || type === 'assistant') {
+          totalTurns++;
+        }
+        if (type === 'assistant') {
+          const content = d.message?.content;
+          if (Array.isArray(content)) {
+            for (const block of content) {
+              if (block?.type === 'tool_use' && typeof block.name === 'string') {
+                toolSet.add(block.name);
+              }
+            }
+          }
+        }
+      } catch { /* skip malformed line */ }
+    }
+
+    return {
+      tools_used: Array.from(toolSet).sort(),
+      totalTurns,
+    };
+  } catch {
+    return null;
+  }
+}
+
+// --- Repo slug resolution ---
+
+const slugCache = new Map<string, string>();
+
+/**
+ * Get the repo slug for a project path. Memoized.
+ * Runs `git remote get-url origin` with cwd set to the project path.
+ * Falls back to path.basename() if git fails.
+ */
+export function getRemoteSlugForPath(projectPath: string): string {
+  const cached = slugCache.get(projectPath);
+  if (cached) return cached;
+
+  let slug = path.basename(projectPath);
+  try {
+    if (fs.existsSync(projectPath)) {
+      const { spawnSync } = require('child_process');
+      const result = spawnSync('git', ['remote', 'get-url', 'origin'], {
+        cwd: projectPath,
+        stdio: 'pipe',
+        timeout: 3_000,
+      });
+      if (result.status === 0 && result.stdout) {
+        const url = result.stdout.toString().trim();
+        // Parse "git@github.com:org/repo.git" or "https://github.com/org/repo.git"
+        const match = url.match(/[/:]([\w.-]+\/[\w.-]+?)(?:\.git)?$/);
+        if (match) slug = match[1];
+      }
+    }
+  } catch { /* fall back to basename */ }
+
+  slugCache.set(projectPath, slug);
+  return slug;
+}
+
+/** Clear the slug cache (for testing). */
+export function clearSlugCache(): void {
+  slugCache.clear();
+}
+
+// --- Transcript data assembly ---
+
+/**
+ * Convert a session's data into the shape expected by the session_transcripts table.
+ */
+export function sessionToTranscriptData(
+  sessionId: string,
+  historyEntries: HistoryEntry[],
+  sessionFileData: SessionFileData | null,
+  summary: string | null,
+): TranscriptData {
+  const messages = historyEntries.map(e => ({
+    display: e.display.length > 2000 ? e.display.slice(0, 2000) : e.display,
+    timestamp: e.timestamp,
+  }));
+
+  const timestamps = historyEntries.map(e => e.timestamp);
+  const startedAt = new Date(Math.min(...timestamps)).toISOString();
+  const endedAt = new Date(Math.max(...timestamps)).toISOString();
+
+  return {
+    session_id: sessionId,
+    repo_slug: getRemoteSlugForPath(historyEntries[0].project),
+    messages,
+    total_turns: sessionFileData?.totalTurns || historyEntries.length,
+    tools_used: sessionFileData?.tools_used || null,
+    summary,
+    started_at: startedAt,
+    ended_at: endedAt,
+  };
+}
+
+// --- Sync marker ---
+
+export function readSyncMarker(): TranscriptSyncMarker | null {
+  return readJSON<TranscriptSyncMarker>(MARKER_FILE);
+}
+
+export function writeSyncMarker(marker: TranscriptSyncMarker): void {
+  try {
+    fs.mkdirSync(GSTACK_STATE_DIR, { recursive: true });
+    atomicWriteJSON(MARKER_FILE, marker);
+  } catch { /* non-fatal */ }
+}
+
+// --- Orchestrator ---
+
+/**
+ * Main sync function. Parses history, enriches sessions, pushes to Supabase.
+ * Returns stats. All operations are non-fatal.
+ */
+export async function syncTranscripts(): Promise<{ pushed: number; skipped: number; errors: number }> {
+  const config = resolveSyncConfig();
+  if (!config || !config.syncTranscripts) {
+    return { pushed: 0, skipped: 0, errors: 0 };
+  }
+
+  // Quick check: file size unchanged = nothing new
+  let fileSize = 0;
+  try {
+    fileSize = fs.statSync(HISTORY_FILE).size;
+  } catch {
+    return { pushed: 0, skipped: 0, errors: 0 };
+  }
+
+  const marker = readSyncMarker() || {
+    pushed_sessions: {},
+    last_file_size: 0,
+    updated_at: '',
+  };
+
+  if (fileSize === marker.last_file_size) {
+    return { pushed: 0, skipped: 0, errors: 0 };
+  }
+
+  // Parse and group
+  const entries = parseHistoryFile();
+  if (entries.length === 0) return { pushed: 0, skipped: 0, errors: 0 };
+
+  const sessions = groupBySession(entries);
+
+  // Filter to sessions that need pushing
+  const toPush: Array<{ sessionId: string; entries: HistoryEntry[] }> = [];
+  let skipped = 0;
+  for (const [sessionId, sessionEntries] of sessions) {
+    const prev = marker.pushed_sessions[sessionId];
+    if (prev && prev.turns_pushed >= sessionEntries.length) {
+      skipped++;
+      continue;
+    }
+    toPush.push({ sessionId, entries: sessionEntries });
+  }
+
+  if (toPush.length === 0) {
+    // Update file size even if nothing to push (prevents re-parsing)
+    marker.last_file_size = fileSize;
+    marker.updated_at = new Date().toISOString();
+    writeSyncMarker(marker);
+    return { pushed: 0, skipped, errors: 0 };
+  }
+
+  // Enrich with session files
+  const enriched = toPush.map(({ sessionId, entries: sessionEntries }) => {
+    const sessionFile = findSessionFile(sessionId, sessionEntries[0].project);
+    const sessionFileData = sessionFile ? parseSessionFile(sessionFile) : null;
+    return { sessionId, entries: sessionEntries, sessionFileData };
+  });
+
+  // Summarize in batches (5-concurrent)
+  const withSummaries: Array<{
+    sessionId: string;
+    entries: HistoryEntry[];
+    sessionFileData: SessionFileData | null;
+    summary: string | null;
+  }> = [];
+
+  for (let i = 0; i < enriched.length; i += SUMMARY_CONCURRENCY) {
+    const batch = enriched.slice(i, i + SUMMARY_CONCURRENCY);
+    const summaries = await Promise.allSettled(
+      batch.map(({ entries: sessionEntries, sessionFileData }) => {
+        const messages = sessionEntries.map(e => ({
+          display: e.display.length > 200 ? e.display.slice(0, 200) : e.display,
+          timestamp: e.timestamp,
+        }));
+        return summarizeSession(messages, sessionFileData?.tools_used || null);
+      }),
+    );
+
+    batch.forEach((item, idx) => {
+      const result = summaries[idx];
+      withSummaries.push({
+        ...item,
+        summary: result.status === 'fulfilled' ? result.value : null,
+      });
+    });
+  }
+
+  // Push in batches (10-concurrent)
+  let pushed = 0;
+  let errors = 0;
+
+  for (let i = 0; i < withSummaries.length; i += PUSH_CONCURRENCY) {
+    const batch = withSummaries.slice(i, i + PUSH_CONCURRENCY);
+    const results = await Promise.allSettled(
+      batch.map(({ sessionId, entries: sessionEntries, sessionFileData, summary }) => {
+        const data = sessionToTranscriptData(sessionId, sessionEntries, sessionFileData, summary);
+        return pushTranscript(data as Record<string, unknown>);
+      }),
+    );
+
+    results.forEach((result, idx) => {
+      const item = batch[idx];
+      if (result.status === 'fulfilled' && result.value) {
+        pushed++;
+        marker.pushed_sessions[item.sessionId] = {
+          turns_pushed: item.entries.length,
+          last_push: new Date().toISOString(),
+        };
+      } else {
+        errors++;
+      }
+    });
+  }
+
+  // Update marker
+  marker.last_file_size = fileSize;
+  marker.updated_at = new Date().toISOString();
+  writeSyncMarker(marker);
+
+  return { pushed, skipped, errors };
+}
diff --git a/supabase/migrations/006_transcript_sync.sql b/supabase/migrations/006_transcript_sync.sql
new file mode 100644
index 00000000..1b8f9fa5
--- /dev/null
+++ b/supabase/migrations/006_transcript_sync.sql
@@ -0,0 +1,15 @@
+-- 006_transcript_sync.sql — Unique index for idempotent transcript upsert + RLS fix.
+
+-- Unique index on (team_id, session_id) for upsert via Prefer: resolution=merge-duplicates.
+-- session_id is a UUID from Claude Code — globally unique. No need for user_id in the key
+-- (which is nullable and breaks PostgreSQL unique index dedup on NULL values).
+create unique index if not exists idx_transcript_natural_key
+  on session_transcripts(team_id, session_id);
+
+-- Change transcript RLS from admin-only read to team-wide read.
+-- Matches the pattern used by eval_runs, retro_snapshots, qa_reports, ship_logs, greptile_triage.
+-- Opt-in transcript sync already requires user consent (sync_transcripts=true).
+drop policy if exists "admin_read" on session_transcripts;
+create policy "team_read" on session_transcripts for select using (
+  team_id in (select team_id from team_members where user_id = auth.uid())
+);