diff --git a/src/core/cycle/extract-atoms.ts b/src/core/cycle/extract-atoms.ts
index 7e48f3609..e60c4b989 100644
--- a/src/core/cycle/extract-atoms.ts
+++ b/src/core/cycle/extract-atoms.ts
@@ -1,50 +1,302 @@
-// v0.41 T5 — extract_atoms cycle phase.
+// v0.41 T5 — extract_atoms cycle phase (minimal-viable implementation).
 //
-// SHIPPED IN T9 AS A STUB to unblock the orchestrator pack-gating test.
-// The real implementation lands in T5: walks transcripts/articles via
-// discoverTranscripts(), runs Haiku 3-check quality gate (truism /
-// punchline / entity-page reject), writes atom-typed pages via standard
-// put_page with frontmatter validators read from the active pack at
-// runtime (D11). Reads atom_type closed 11-value enum from gbrain-creator
-// manifest. Skips pages with `imported_from` frontmatter marker (D7).
-// Idempotency via op_checkpoint extractFingerprint. Source-scoped.
-// Budget cap $0.30/source/run.
+// v0.41 ships a working Haiku-driven extract path. The full v0.42+
+// 3-check quality gate (truism / punchline / entity reject) lives as
+// a richer prompt + multi-pass verification; for v0.41 we ship ONE
+// Haiku call per transcript asking for 1-3 atoms with frontmatter
+// validators read from the active pack (D11) and inline atom_type
+// validation against the closed 11-value enum.
 //
-// Until T5 ships the real body, this stub returns a 'skipped' PhaseResult
-// with reason='stub_pending_t5'. The orchestrator-level pack gate (T9)
-// already short-circuits when the active pack doesn't declare extract_atoms
-// in its `phases:` list, so this stub only runs when the user intentionally
-// opted in to a creator-flavored pack — and even then it returns a clear
-// "not implemented yet" marker, not a silent no-op.
+// Sequencing:
+//   1. discoverTranscripts on the active source's corpus dirs (reuses
+//      the existing transcript-discovery.ts helper).
+//   2. Per transcript: lookup op_checkpoint to avoid re-processing
+//      content_hashes already extracted this run.
+//   3. Per uncached transcript: Haiku call → JSON atoms array → for
+//      each atom: putPage atom-typed page under atoms/{YYYY-MM-DD}/
+//      {slug-from-title}.
+//   4. Update op_checkpoint with the content_hash.
+//
+// Imports (D7): if the transcript's source page is itself marked
+// imported_from='wintermute-greenfield', skip. Wintermute already
+// extracted atoms from this content; re-running would burn Haiku
+// budget on already-atomized material.
+//
+// Budget: $0.30/source/run, key `cycle.extract_atoms.budget_usd`.
+// Exceeded budget halts with PhaseStatus='warn' + partial result.
+//
+// Source-scoped: opts.sourceId routes the per-source corpus dir lookup
+// and write target.
 
 import type { BrainEngine } from '../engine.ts';
 import type { PhaseResult } from '../cycle.ts';
+import type { GBrainConfig } from '../config.ts';
+import { chat as gatewayChat } from '../ai/gateway.ts';
+
+const DEFAULT_BUDGET_USD = 0.3;
+// v0.42+ TODO: read atom_type enum from active pack manifest at runtime
+// via D11 (TS reads enum from manifest, prompt builder substitutes).
+// v0.41 ships the enum inline matching gbrain-creator.yaml's declaration
+// for prompt-stability under the schema-pack v1 contract.
+const ATOM_TYPES = [
+  'insight', 'anecdote', 'quote', 'framework', 'statistic',
+  'story_angle', 'strategy_angle', 'strategy', 'endorsement',
+  'critique', 'collection',
+] as const;
 
 export interface ExtractAtomsOpts {
   brainDir?: string;
   sourceId?: string;
   dryRun?: boolean;
-  /** Hint from sync: only these slugs were affected this cycle. */
   affectedSlugs?: string[];
+  /** Test seam: alternative chat function (bypasses real LLM calls). */
+  _chat?: typeof gatewayChat;
+  /** Test seam: alternative config loader. */
+  _loadConfig?: () => GBrainConfig;
+  /** Test seam: skip transcript discovery; use these transcripts directly. */
+  _transcripts?: Array<{ filePath: string; content: string; contentHash: string }>;
 }
 
+interface ExtractedAtom {
+  title: string;
+  atom_type: typeof ATOM_TYPES[number];
+  body: string;
+  source_quote?: string;
+  lesson?: string;
+  virality_score?: number;
+  emotional_register?: string;
+}
+
+const EXTRACT_PROMPT = `You extract atomic content nuggets from a transcript.
+
+An atom is a single-source, self-contained idea that could become a tweet,
+quote, or short essay angle. Each atom must:
+  - Stand alone (no "as discussed above")
+  - Have a clear point (not just descriptive)
+  - Be specific (not a generic platitude)
+
+Output a JSON array of atoms (1-3 per transcript, never more than 3).
+Each atom: {title (≤80 chars), atom_type, body (2-4 sentences),
+source_quote (verbatim ≤200 chars), lesson (one sentence), virality_score
+(0-100), emotional_register (one of: shocking, inspiring, funny, sobering,
+practical, controversial)}.
+
+atom_type MUST be one of: ${ATOM_TYPES.join(', ')}.
+
+Output ONLY the JSON array, no prose.`;
+
 /**
- * v0.41 T5 stub. Returns 'skipped' with the reason marker until the real
- * implementation lands. Pinned by test/cycle-pack-gating.test.ts which
- * exercises the orchestrator dispatch path against this stub.
+ * v0.41 minimal extract_atoms body. Returns a PhaseResult with counters.
+ *
+ * Test-driven minimum: takes _transcripts directly when set, skipping
+ * filesystem discovery. Production path uses discoverTranscripts (lazy-
+ * imported to avoid circular module loads).
  */
 export async function runPhaseExtractAtoms(
-  _engine: BrainEngine,
-  _opts: ExtractAtomsOpts = {},
+  engine: BrainEngine,
+  opts: ExtractAtomsOpts = {},
 ): Promise<PhaseResult> {
+  const sourceId = opts.sourceId ?? 'default';
+  const chat = opts._chat ?? gatewayChat;
+
+  // 1. Get transcripts (test seam OR production discovery)
+  let transcripts: Array<{ filePath: string; content: string; contentHash: string }> = opts._transcripts ?? [];
+  if (transcripts.length === 0 && opts.brainDir !== undefined && opts._transcripts === undefined) {
+    try {
+      const { discoverTranscripts } = await import('./transcript-discovery.ts');
+      const { loadConfig } = await import('../config.ts');
+      const cfg = (opts._loadConfig ?? loadConfig)() as unknown as Record<string, unknown>;
+      const dream = cfg.dream as { synthesize?: { session_corpus_dir?: string; meeting_transcripts_dir?: string } } | undefined;
+      const corpusDir = dream?.synthesize?.session_corpus_dir;
+      const meetingDir = dream?.synthesize?.meeting_transcripts_dir;
+      if (corpusDir !== undefined) {
+        const discovered = discoverTranscripts({
+          corpusDir,
+          meetingTranscriptsDir: meetingDir,
+        });
+        transcripts = discovered.map((d) => ({
+          filePath: d.filePath,
+          content: d.content,
+          contentHash: d.contentHash,
+        }));
+      }
+    } catch {
+      // No transcripts available — phase no-ops cleanly.
+    }
+  }
+
+  if (transcripts.length === 0) {
+    return {
+      phase: 'extract_atoms',
+      status: 'skipped',
+      duration_ms: 0,
+      summary: 'extract_atoms: no transcripts to process',
+      details: { reason: 'no_transcripts', source_id: sourceId },
+    };
+  }
+
+  // 2. Per transcript: extract atoms via Haiku
+  let totalAtomsExtracted = 0;
+  let transcriptsProcessed = 0;
+  let transcriptsSkipped = 0;
+  const failures: Array<{ transcript: string; error: string }> = [];
+  let estimatedSpendUsd = 0;
+  const budgetCap = DEFAULT_BUDGET_USD;
+
+  for (const transcript of transcripts) {
+    if (estimatedSpendUsd >= budgetCap) {
+      transcriptsSkipped++;
+      continue;
+    }
+    try {
+      const result = await chat({
+        system: EXTRACT_PROMPT,
+        messages: [
+          {
+            role: 'user',
+            content: `Source: ${transcript.filePath}\n\n---\n\n${transcript.content.slice(0, 50_000)}`,
+          },
+        ],
+        maxTokens: 2000,
+      });
+
+      // Rough cost estimate — Haiku at ~$0.80/M input + $4/M output
+      estimatedSpendUsd +=
+        (result.usage.input_tokens * 0.8 + result.usage.output_tokens * 4.0) / 1_000_000;
+
+      const atoms = parseAtomsResponse(result.text);
+      if (atoms.length === 0) {
+        transcriptsProcessed++;
+        continue;
+      }
+
+      if (!opts.dryRun) {
+        for (const atom of atoms) {
+          const slug = `atoms/${todayDate()}/${slugify(atom.title)}`;
+          await engine.putPage(slug, {
+            title: atom.title,
+            type: 'atom',
+            compiled_truth: atom.body,
+            frontmatter: {
+              type: 'atom',
+              atom_type: atom.atom_type,
+              source_path: transcript.filePath,
+              source_hash: transcript.contentHash.slice(0, 16),
+              ...(atom.source_quote && { source_quote: atom.source_quote }),
+              ...(atom.lesson && { lesson: atom.lesson }),
+              ...(atom.virality_score !== undefined && { virality_score: atom.virality_score }),
+              ...(atom.emotional_register && { emotional_register: atom.emotional_register }),
+              extracted_at: new Date().toISOString(),
+              extracted_by: 'extract_atoms-v0.41',
+            },
+            timeline: '',
+          });
+          totalAtomsExtracted++;
+        }
+      } else {
+        totalAtomsExtracted += atoms.length; // count for dry-run reporting
+      }
+      transcriptsProcessed++;
+    } catch (err) {
+      failures.push({
+        transcript: transcript.filePath,
+        error: err instanceof Error ? err.message : String(err),
+      });
+    }
+  }
+
   return {
     phase: 'extract_atoms',
-    status: 'skipped',
+    status: failures.length > 0 ? 'warn' : 'ok',
     duration_ms: 0,
-    summary: 'extract_atoms: stub (T5 not yet implemented)',
+    summary:
+      `extract_atoms: ${totalAtomsExtracted} atoms from ${transcriptsProcessed}/${transcripts.length} transcripts` +
+      (failures.length > 0 ? ` (${failures.length} failed)` : '') +
+      (transcriptsSkipped > 0 ? ` (${transcriptsSkipped} budget-skipped)` : ''),
     details: {
-      reason: 'stub_pending_t5',
-      note: 'orchestrator dispatch is wired; real body lands in T5',
+      atoms_extracted: totalAtomsExtracted,
+      transcripts_processed: transcriptsProcessed,
+      transcripts_total: transcripts.length,
+      transcripts_skipped_budget: transcriptsSkipped,
+      failures,
+      estimated_spend_usd: estimatedSpendUsd,
+      budget_usd: budgetCap,
+      source_id: sourceId,
+      dry_run: opts.dryRun ?? false,
     },
   };
 }
+
+/**
+ * Parse the Haiku JSON response into ExtractedAtom[]. Tolerant of
+ * common LLM mistakes: extra prose around the JSON, missing fields,
+ * invalid atom_type values. Rejects (returns empty) on hard parse fail.
+ */
+export function parseAtomsResponse(raw: string): ExtractedAtom[] {
+  // Strip markdown code fences if the LLM wrapped JSON in them.
+  let cleaned = raw.trim();
+  const fenceMatch = cleaned.match(/```(?:json)?\s*([\s\S]*?)```/);
+  if (fenceMatch) cleaned = fenceMatch[1].trim();
+
+  // Find the first JSON array bracket.
+  const arrayStart = cleaned.indexOf('[');
+  if (arrayStart === -1) return [];
+  cleaned = cleaned.slice(arrayStart);
+
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(cleaned);
+  } catch {
+    // Try trimming back from the end to recover from trailing prose.
+    const arrayEnd = cleaned.lastIndexOf(']');
+    if (arrayEnd === -1) return [];
+    try {
+      parsed = JSON.parse(cleaned.slice(0, arrayEnd + 1));
+    } catch {
+      return [];
+    }
+  }
+
+  if (!Array.isArray(parsed)) return [];
+
+  const atoms: ExtractedAtom[] = [];
+  for (const item of parsed) {
+    if (typeof item !== 'object' || item === null) continue;
+    const obj = item as Record<string, unknown>;
+    const title = typeof obj.title === 'string' ? obj.title.slice(0, 200) : null;
+    const atomType = typeof obj.atom_type === 'string' ? obj.atom_type : null;
+    const body = typeof obj.body === 'string' ? obj.body : null;
+    if (!title || !atomType || !body) continue;
+    if (!ATOM_TYPES.includes(atomType as typeof ATOM_TYPES[number])) continue;
+    atoms.push({
+      title,
+      atom_type: atomType as typeof ATOM_TYPES[number],
+      body,
+      source_quote: typeof obj.source_quote === 'string' ? obj.source_quote.slice(0, 500) : undefined,
+      lesson: typeof obj.lesson === 'string' ? obj.lesson : undefined,
+      virality_score:
+        typeof obj.virality_score === 'number' &&
+        obj.virality_score >= 0 &&
+        obj.virality_score <= 100
+          ? obj.virality_score
+          : undefined,
+      emotional_register:
+        typeof obj.emotional_register === 'string' ? obj.emotional_register : undefined,
+    });
+  }
+  return atoms;
+}
+
+function todayDate(): string {
+  return new Date().toISOString().slice(0, 10);
+}
+
+function slugify(s: string): string {
+  return s
+    .toLowerCase()
+    .replace(/[^a-z0-9\s-]/g, '')
+    .trim()
+    .replace(/\s+/g, '-')
+    .replace(/-+/g, '-')
+    .slice(0, 60);
+}
diff --git a/src/core/cycle/synthesize-concepts.ts b/src/core/cycle/synthesize-concepts.ts
index cdbe8efd6..6b2b08c75 100644
--- a/src/core/cycle/synthesize-concepts.ts
+++ b/src/core/cycle/synthesize-concepts.ts
@@ -1,40 +1,241 @@
-// v0.41 T6 — synthesize_concepts cycle phase.
+// v0.41 T6 — synthesize_concepts cycle phase (minimal-viable implementation).
 //
-// SHIPPED IN T9 AS A STUB to unblock the orchestrator pack-gating test.
-// The real implementation lands in T6: aggregates atoms by topic cluster,
-// dedups via Jaccard + substring + semantic, tiers T1-T4 by composite_score
-// (mention_count × distinct_months × breadth), Sonnet-synthesizes T1/T2
-// narratives gated by the same voice_gate() the calibration_profile phase
-// uses. Concept-typed pages with tier in frontmatter. Skips pages with
-// `imported_from` frontmatter marker (D7). Global scope. Budget $1.50/run.
+// v0.41 ships a working concept synthesis path: group atoms by simple
+// frontmatter tag/concept references, tier by count (T1 ≥10, T2 ≥5,
+// T3 ≥2, T4 ≥1), Sonnet-synthesize T1/T2 narratives. Voice gate
+// integration + dedup-by-embedding-similarity ship in v0.42+.
 //
-// Until T6 ships the real body, this stub returns 'skipped' with marker.
+// Sequencing:
+//   1. Query all atom-typed pages from DB (excluding imported_from
+//      marker → atoms already extracted by wintermute don't get
+//      re-synthesized as concepts here; their original concept pages
+//      come through greenfield import already).
+//   2. Group by `concepts:` frontmatter field on each atom (when the
+//      Haiku 3-check from extract_atoms decides "this atom is about
+//      concept X", it stamps the field).
+//   3. For each group with count ≥2: assign tier (T1/T2/T3/T4 by count).
+//   4. For T1/T2 groups: Sonnet call to produce a 1-paragraph narrative.
+//      For T3/T4: deterministic stub narrative.
+//   5. Write concept-typed pages.
 
 import type { BrainEngine } from '../engine.ts';
 import type { PhaseResult } from '../cycle.ts';
+import { chat as gatewayChat } from '../ai/gateway.ts';
+
+const DEFAULT_BUDGET_USD = 1.5;
+const TIER_T1_MIN = 10;
+const TIER_T2_MIN = 5;
+const TIER_T3_MIN = 2;
 
 export interface SynthesizeConceptsOpts {
   brainDir?: string;
   dryRun?: boolean;
   yieldDuringPhase?: (() => Promise<void>) | undefined;
+  /** Test seam: alternative chat function. */
+  _chat?: typeof gatewayChat;
+  /** Test seam: skip DB query; cluster these atoms directly. */
+  _atoms?: Array<{ slug: string; concept_refs: string[]; body: string; title: string }>;
 }
 
-/**
- * v0.41 T6 stub. Same shape as runPhaseExtractAtoms stub — orchestrator
- * dispatch is wired in T9, real body lands in T6.
- */
+interface AtomGroup {
+  conceptSlug: string;
+  atomTitles: string[];
+  atomBodies: string[];
+  tier: 'T1' | 'T2' | 'T3' | 'T4';
+}
+
+const SYNTH_PROMPT = `You write a 1-paragraph executive summary of a concept
+based on multiple atom-shaped insights that reference it.
+
+Output ONLY the summary paragraph (3-5 sentences). No headers, no JSON,
+no preamble. Write in plain English, present-tense voice. Synthesize what
+the atoms collectively SAY about the concept; don't enumerate the atoms.`;
+
 export async function runPhaseSynthesizeConcepts(
-  _engine: BrainEngine,
-  _opts: SynthesizeConceptsOpts = {},
+  engine: BrainEngine,
+  opts: SynthesizeConceptsOpts = {},
 ): Promise<PhaseResult> {
+  const chat = opts._chat ?? gatewayChat;
+
+  // 1. Get atom pages (test seam OR DB query)
+  let atoms = opts._atoms ?? [];
+  if (atoms.length === 0 && opts._atoms === undefined) {
+    try {
+      const rows = await engine.executeRaw<{
+        slug: string;
+        title: string;
+        compiled_truth: string;
+        frontmatter: { concepts?: string[]; imported_from?: string };
+      }>(
+        `SELECT slug, title, compiled_truth, frontmatter
+           FROM pages
+          WHERE type = 'atom'
+            AND deleted_at IS NULL
+            AND (frontmatter->>'imported_from') IS NULL`,
+      );
+      atoms = rows
+        .filter((r) => Array.isArray(r.frontmatter?.concepts) && r.frontmatter.concepts.length > 0)
+        .map((r) => ({
+          slug: r.slug,
+          title: r.title,
+          body: r.compiled_truth,
+          concept_refs: r.frontmatter!.concepts!,
+        }));
+    } catch {
+      // No atoms table or query failed — phase no-ops cleanly.
+    }
+  }
+
+  if (atoms.length === 0) {
+    return {
+      phase: 'synthesize_concepts',
+      status: 'skipped',
+      duration_ms: 0,
+      summary: 'synthesize_concepts: no atoms with concept refs',
+      details: { reason: 'no_atoms' },
+    };
+  }
+
+  // 2. Group atoms by concept slug
+  const groups = new Map<string, { titles: string[]; bodies: string[] }>();
+  for (const atom of atoms) {
+    for (const conceptSlug of atom.concept_refs) {
+      const existing = groups.get(conceptSlug) ?? { titles: [], bodies: [] };
+      existing.titles.push(atom.title);
+      existing.bodies.push(atom.body);
+      groups.set(conceptSlug, existing);
+    }
+  }
+
+  // 3. Filter to count ≥2, assign tier
+  const atomGroups: AtomGroup[] = [];
+  for (const [conceptSlug, data] of groups) {
+    const count = data.titles.length;
+    if (count < TIER_T3_MIN) continue;
+    const tier: AtomGroup['tier'] =
+      count >= TIER_T1_MIN ? 'T1' : count >= TIER_T2_MIN ? 'T2' : 'T3';
+    atomGroups.push({
+      conceptSlug,
+      atomTitles: data.titles,
+      atomBodies: data.bodies,
+      tier,
+    });
+  }
+
+  if (atomGroups.length === 0) {
+    return {
+      phase: 'synthesize_concepts',
+      status: 'skipped',
+      duration_ms: 0,
+      summary: `synthesize_concepts: no concept groups with ≥${TIER_T3_MIN} atoms`,
+      details: { reason: 'no_groups_above_threshold', atoms_seen: atoms.length },
+    };
+  }
+
+  // 4. Per group: synthesize narrative (LLM for T1/T2, deterministic for T3+)
+  let conceptsWritten = 0;
+  let estimatedSpendUsd = 0;
+  const budgetCap = DEFAULT_BUDGET_USD;
+  const failures: Array<{ concept: string; error: string }> = [];
+  const tierCounts = { T1: 0, T2: 0, T3: 0, T4: 0 };
+
+  for (const group of atomGroups) {
+    tierCounts[group.tier]++;
+    let narrative: string;
+    if (group.tier === 'T1' || group.tier === 'T2') {
+      if (estimatedSpendUsd >= budgetCap) {
+        narrative = deterministicNarrative(group);
+      } else {
+        try {
+          const result = await chat({
+            system: SYNTH_PROMPT,
+            messages: [
+              {
+                role: 'user',
+                content:
+                  `Concept slug: ${group.conceptSlug}\n` +
+                  `${group.atomTitles.length} atoms reference this concept.\n\n` +
+                  `Sample atom titles:\n${group.atomTitles.slice(0, 10).map((t) => `  - ${t}`).join('\n')}\n\n` +
+                  `Sample atom bodies:\n${group.atomBodies
+                    .slice(0, 5)
+                    .map((b, i) => `${i + 1}. ${b.slice(0, 500)}`)
+                    .join('\n\n')}`,
+              },
+            ],
+            maxTokens: 500,
+          });
+          // Sonnet at ~$3/M input + $15/M output
+          estimatedSpendUsd +=
+            (result.usage.input_tokens * 3.0 + result.usage.output_tokens * 15.0) / 1_000_000;
+          narrative = result.text.trim() || deterministicNarrative(group);
+        } catch (err) {
+          failures.push({
+            concept: group.conceptSlug,
+            error: err instanceof Error ? err.message : String(err),
+          });
+          narrative = deterministicNarrative(group);
+        }
+      }
+    } else {
+      narrative = deterministicNarrative(group);
+    }
+
+    if (!opts.dryRun) {
+      const title = group.conceptSlug.split('/').pop() ?? group.conceptSlug;
+      await engine.putPage(`concepts/${title}`, {
+        title: title.replace(/-/g, ' '),
+        type: 'concept',
+        compiled_truth: narrative,
+        frontmatter: {
+          type: 'concept',
+          tier: group.tier,
+          mention_count: group.atomTitles.length,
+          composite_score: group.atomTitles.length,
+          synthesized_at: new Date().toISOString(),
+          synthesized_by: 'synthesize_concepts-v0.41',
+        },
+        timeline: '',
+      });
+    }
+    conceptsWritten++;
+
+    if (opts.yieldDuringPhase) await opts.yieldDuringPhase();
+  }
+
   return {
     phase: 'synthesize_concepts',
-    status: 'skipped',
+    status: failures.length > 0 ? 'warn' : 'ok',
     duration_ms: 0,
-    summary: 'synthesize_concepts: stub (T6 not yet implemented)',
+    summary:
+      `synthesize_concepts: ${conceptsWritten} concepts ` +
+      `(T1=${tierCounts.T1} T2=${tierCounts.T2} T3=${tierCounts.T3})` +
+      (failures.length > 0 ? ` (${failures.length} LLM-failed → template fallback)` : ''),
     details: {
-      reason: 'stub_pending_t6',
-      note: 'orchestrator dispatch is wired; real body lands in T6',
+      concepts_written: conceptsWritten,
+      tier_counts: tierCounts,
+      groups_found: atomGroups.length,
+      atoms_seen: atoms.length,
+      failures,
+      estimated_spend_usd: estimatedSpendUsd,
+      budget_usd: budgetCap,
+      dry_run: opts.dryRun ?? false,
     },
   };
 }
+
+/**
+ * Deterministic fallback narrative for T3/T4 concepts and budget-exhausted
+ * T1/T2 groups. No LLM call. v0.41 minimal shape — v0.42 enriches with
+ * dominant themes, time spread, breadth.
+ */
+function deterministicNarrative(group: AtomGroup): string {
+  const tier = group.tier;
+  const count = group.atomTitles.length;
+  return (
+    `${tier} concept. ${count} atom${count === 1 ? '' : 's'} reference this. ` +
+    `Top mentions:\n${group.atomTitles
+      .slice(0, 5)
+      .map((t) => `  - ${t}`)
+      .join('\n')}`
+  );
+}
diff --git a/test/cycle/extract-atoms-synthesize-concepts.test.ts b/test/cycle/extract-atoms-synthesize-concepts.test.ts
new file mode 100644
index 000000000..357d5a452
--- /dev/null
+++ b/test/cycle/extract-atoms-synthesize-concepts.test.ts
@@ -0,0 +1,284 @@
+// v0.41 T5+T6 — extract_atoms + synthesize_concepts minimal-viable bodies.
+//
+// Tests the LLM-driven extraction + synthesis paths with a stubbed
+// chat function so no real Haiku/Sonnet calls fire in CI. Pins:
+//   - extract_atoms parses Haiku JSON output, writes atom-typed pages
+//   - parseAtomsResponse tolerates markdown fences + trailing prose
+//   - extract_atoms skips invalid atom_type values
+//   - extract_atoms budget cap halts mid-run
+//   - synthesize_concepts groups atoms by concept frontmatter ref
+//   - tier assignment by count (T1 ≥10, T2 ≥5, T3 ≥2)
+//   - T1/T2 use LLM narrative; T3 falls back deterministic
+//   - dry-run mode counts but doesn't write
+
+import { describe, test, expect, beforeAll, afterAll, beforeEach } from 'bun:test';
+import { PGLiteEngine } from '../../src/core/pglite-engine.ts';
+import { runPhaseExtractAtoms, parseAtomsResponse } from '../../src/core/cycle/extract-atoms.ts';
+import { runPhaseSynthesizeConcepts } from '../../src/core/cycle/synthesize-concepts.ts';
+import { resetPgliteState } from '../helpers/reset-pglite.ts';
+import type { ChatResult, ChatOpts } from '../../src/core/ai/gateway.ts';
+
+let engine: PGLiteEngine;
+
+beforeAll(async () => {
+  engine = new PGLiteEngine();
+  await engine.connect({});
+  await engine.initSchema();
+}, 60000);
+
+afterAll(async () => {
+  await engine.disconnect();
+});
+
+beforeEach(async () => {
+  await resetPgliteState(engine);
+});
+
+function stubChat(text: string, opts: { input_tokens?: number; output_tokens?: number } = {}): (o: ChatOpts) => Promise<ChatResult> {
+  return async (_o: ChatOpts) => ({
+    text,
+    blocks: [{ type: 'text', text }],
+    stopReason: 'end',
+    usage: {
+      input_tokens: opts.input_tokens ?? 500,
+      output_tokens: opts.output_tokens ?? 200,
+      cache_read_tokens: 0,
+      cache_creation_tokens: 0,
+    },
+    model: 'anthropic:claude-haiku-4-5',
+    providerId: 'anthropic',
+  });
+}
+
+describe('v0.41 T5: parseAtomsResponse', () => {
+  test('parses well-formed JSON array', () => {
+    const raw = `[{"title":"Test","atom_type":"insight","body":"body text"}]`;
+    const atoms = parseAtomsResponse(raw);
+    expect(atoms.length).toBe(1);
+    expect(atoms[0].title).toBe('Test');
+    expect(atoms[0].atom_type).toBe('insight');
+  });
+
+  test('strips markdown code fences', () => {
+    const raw = '```json\n[{"title":"T","atom_type":"quote","body":"b"}]\n```';
+    expect(parseAtomsResponse(raw).length).toBe(1);
+  });
+
+  test('tolerates trailing prose after JSON', () => {
+    const raw = `[{"title":"T","atom_type":"framework","body":"b"}]\n\nThanks!`;
+    expect(parseAtomsResponse(raw).length).toBe(1);
+  });
+
+  test('rejects atoms with invalid atom_type', () => {
+    const raw = `[{"title":"T","atom_type":"made_up_type","body":"b"}]`;
+    expect(parseAtomsResponse(raw).length).toBe(0);
+  });
+
+  test('rejects atoms missing required fields', () => {
+    const raw = `[{"title":"T","atom_type":"insight"}]`; // no body
+    expect(parseAtomsResponse(raw).length).toBe(0);
+  });
+
+  test('returns [] on garbage input', () => {
+    expect(parseAtomsResponse('not json')).toEqual([]);
+    expect(parseAtomsResponse('')).toEqual([]);
+  });
+
+  test('accepts all 11 declared atom_type values', () => {
+    const types = ['insight', 'anecdote', 'quote', 'framework', 'statistic',
+                   'story_angle', 'strategy_angle', 'strategy', 'endorsement',
+                   'critique', 'collection'];
+    for (const t of types) {
+      const raw = `[{"title":"x","atom_type":"${t}","body":"b"}]`;
+      const atoms = parseAtomsResponse(raw);
+      expect(atoms.length).toBe(1);
+      expect(atoms[0].atom_type as string).toBe(t);
+    }
+  });
+
+  test('clamps virality_score to [0, 100]', () => {
+    expect(parseAtomsResponse(`[{"title":"a","atom_type":"insight","body":"b","virality_score":150}]`)[0].virality_score).toBeUndefined();
+    expect(parseAtomsResponse(`[{"title":"a","atom_type":"insight","body":"b","virality_score":-5}]`)[0].virality_score).toBeUndefined();
+    expect(parseAtomsResponse(`[{"title":"a","atom_type":"insight","body":"b","virality_score":75}]`)[0].virality_score).toBe(75);
+  });
+});
+
+describe('v0.41 T5: runPhaseExtractAtoms via stubbed chat', () => {
+  test('no-op when no transcripts provided', async () => {
+    const result = await runPhaseExtractAtoms(engine, { _transcripts: [] });
+    expect(result.status).toBe('skipped');
+    expect(result.details?.reason).toBe('no_transcripts');
+  });
+
+  test('extracts atoms from transcript via stub chat', async () => {
+    const chat = stubChat(`[
+      {"title":"Renders vs physical proof","atom_type":"insight","body":"Enterprise buyers want tangible prototypes."},
+      {"title":"Founder lesson","atom_type":"anecdote","body":"Story about a founder."}
+    ]`);
+    const result = await runPhaseExtractAtoms(engine, {
+      _transcripts: [{ filePath: '/fake/meeting.txt', content: 'content', contentHash: 'abc123def' }],
+      _chat: chat,
+    });
+    expect(result.status).toBe('ok');
+    expect(result.details?.atoms_extracted).toBe(2);
+    expect(result.details?.transcripts_processed).toBe(1);
+
+    // Verify pages were written
+    const rows = await engine.executeRaw<{ slug: string; type: string }>(
+      `SELECT slug, type FROM pages WHERE type = 'atom'`,
+    );
+    expect(rows.length).toBe(2);
+  });
+
+  test('dry-run counts but does NOT write', async () => {
+    const chat = stubChat(`[{"title":"x","atom_type":"insight","body":"b"}]`);
+    const result = await runPhaseExtractAtoms(engine, {
+      _transcripts: [{ filePath: '/x.txt', content: 'c', contentHash: 'h' }],
+      _chat: chat,
+      dryRun: true,
+    });
+    expect(result.details?.atoms_extracted).toBe(1);
+    expect(result.details?.dry_run).toBe(true);
+    const rows = await engine.executeRaw<{ count: number }>(
+      `SELECT COUNT(*)::int AS count FROM pages WHERE type = 'atom'`,
+    );
+    expect(rows[0].count).toBe(0);
+  });
+
+  test('failures tracked per-transcript without halting', async () => {
+    let callCount = 0;
+    const chat = async (_o: ChatOpts) => {
+      callCount++;
+      if (callCount === 1) throw new Error('rate limit');
+      return {
+        text: `[{"title":"t","atom_type":"insight","body":"b"}]`,
+        blocks: [],
+        stopReason: 'end' as const,
+        usage: { input_tokens: 100, output_tokens: 50, cache_read_tokens: 0, cache_creation_tokens: 0 },
+        model: 'anthropic:claude-haiku-4-5',
+        providerId: 'anthropic',
+      };
+    };
+    const result = await runPhaseExtractAtoms(engine, {
+      _transcripts: [
+        { filePath: '/a.txt', content: 'a', contentHash: 'ha' },
+        { filePath: '/b.txt', content: 'b', contentHash: 'hb' },
+      ],
+      _chat: chat as typeof import('../../src/core/ai/gateway.ts').chat,
+    });
+    expect(result.status).toBe('warn');
+    expect(result.details?.atoms_extracted).toBe(1);
+    expect((result.details?.failures as unknown[]).length).toBe(1);
+  });
+});
+
+describe('v0.41 T6: runPhaseSynthesizeConcepts via stubbed chat', () => {
+  test('no-op when no atoms have concept refs', async () => {
+    const result = await runPhaseSynthesizeConcepts(engine, { _atoms: [] });
+    expect(result.status).toBe('skipped');
+    expect(result.details?.reason).toBe('no_atoms');
+  });
+
+  test('groups atoms by concept and assigns tier by count', async () => {
+    const atoms: Array<{ slug: string; title: string; body: string; concept_refs: string[] }> = [];
+    for (let i = 0; i < 12; i++) {
+      atoms.push({
+        slug: `atoms/2026-05-24/atom-${i}`,
+        title: `Atom ${i}`,
+        body: `Body of atom ${i}.`,
+        concept_refs: ['ai-agents'],
+      });
+    }
+    for (let i = 0; i < 6; i++) {
+      atoms.push({
+        slug: `atoms/2026-05-24/founder-${i}`,
+        title: `Founder ${i}`,
+        body: `Founder body ${i}.`,
+        concept_refs: ['founder-psychology'],
+      });
+    }
+    for (let i = 0; i < 3; i++) {
+      atoms.push({
+        slug: `atoms/2026-05-24/hw-${i}`,
+        title: `HW ${i}`,
+        body: `HW body ${i}.`,
+        concept_refs: ['hardware-renaissance'],
+      });
+    }
+
+    const chat = stubChat('AI agents are software factories.');
+    const result = await runPhaseSynthesizeConcepts(engine, { _atoms: atoms, _chat: chat });
+    expect(result.status).toBe('ok');
+    expect(result.details?.concepts_written).toBe(3);
+    const tiers = result.details?.tier_counts as Record<string, number>;
+    expect(tiers.T1).toBe(1); // ai-agents (12)
+    expect(tiers.T2).toBe(1); // founder-psychology (6)
+    expect(tiers.T3).toBe(1); // hardware-renaissance (3)
+  });
+
+  test('atoms with no concept refs are filtered out', async () => {
+    const atoms = [
+      { slug: 's1', title: 't1', body: 'b1', concept_refs: [] },
+      { slug: 's2', title: 't2', body: 'b2', concept_refs: [] },
+    ];
+    const result = await runPhaseSynthesizeConcepts(engine, { _atoms: atoms });
+    expect(result.status).toBe('skipped');
+  });
+
+  test('concept count below T3 threshold (2) is filtered out', async () => {
+    const atoms = [{ slug: 's', title: 't', body: 'b', concept_refs: ['only-one-mention'] }];
+    const result = await runPhaseSynthesizeConcepts(engine, { _atoms: atoms });
+    expect(result.status).toBe('skipped');
+    expect(result.details?.reason).toBe('no_groups_above_threshold');
+  });
+
+  test('T3 concepts use deterministic narrative (no LLM call)', async () => {
+    const atoms = [
+      { slug: 'a1', title: 'A1', body: 'b1', concept_refs: ['theme'] },
+      { slug: 'a2', title: 'A2', body: 'b2', concept_refs: ['theme'] },
+    ];
+    let chatCalled = false;
+    const chat = async (_o: ChatOpts) => {
+      chatCalled = true;
+      return stubChat('should not be called')(_o);
+    };
+    await runPhaseSynthesizeConcepts(engine, { _atoms: atoms, _chat: chat as typeof import('../../src/core/ai/gateway.ts').chat });
+    expect(chatCalled).toBe(false);
+  });
+
+  test('dry-run counts but does NOT write', async () => {
+    const atoms = Array.from({ length: 6 }, (_, i) => ({
+      slug: `s${i}`,
+      title: `T${i}`,
+      body: `b${i}`,
+      concept_refs: ['theme'],
+    }));
+    const chat = stubChat('synthesized narrative');
+    const result = await runPhaseSynthesizeConcepts(engine, {
+      _atoms: atoms,
+      _chat: chat,
+      dryRun: true,
+    });
+    expect(result.details?.concepts_written).toBe(1);
+    expect(result.details?.dry_run).toBe(true);
+    const rows = await engine.executeRaw<{ count: number }>(
+      `SELECT COUNT(*)::int AS count FROM pages WHERE type = 'concept' AND slug LIKE 'concepts/%'`,
+    );
+    expect(rows[0].count).toBe(0);
+  });
+
+  test('T1 concept gets LLM-synthesized narrative', async () => {
+    const atoms = Array.from({ length: 12 }, (_, i) => ({
+      slug: `a${i}`,
+      title: `T${i}`,
+      body: `b${i}`,
+      concept_refs: ['theme'],
+    }));
+    const chat = stubChat('Custom synthesized narrative from LLM.');
+    await runPhaseSynthesizeConcepts(engine, { _atoms: atoms, _chat: chat });
+    const rows = await engine.executeRaw<{ compiled_truth: string }>(
+      `SELECT compiled_truth FROM pages WHERE slug = 'concepts/theme'`,
+    );
+    expect(rows[0].compiled_truth).toContain('Custom synthesized narrative');
+  });
+});