diff --git a/gitnexus/src/cli/analyze-config.ts b/gitnexus/src/cli/analyze-config.ts
index 8fbe40feb..09ca4682b 100644
--- a/gitnexus/src/cli/analyze-config.ts
+++ b/gitnexus/src/cli/analyze-config.ts
@@ -84,6 +84,7 @@ const KEY_SPECS: Record<string, KeySpec> = {
   skipContextFiles: { target: 'skipAgentsMd', kind: 'boolean' },
   skipAiContext: { target: 'skipAgentsMd', kind: 'boolean' },
   skipSkills: { target: 'skipSkills', kind: 'boolean' },
+  pdg: { target: 'pdg', kind: 'boolean' },
   indexOnly: { target: 'indexOnly', kind: 'boolean' },
   stats: { target: 'stats', kind: 'boolean' },
   noStats: { target: 'stats', kind: 'boolean-negate' },
diff --git a/gitnexus/src/cli/analyze.ts b/gitnexus/src/cli/analyze.ts
index 3f196b11d..08f69f64a 100644
--- a/gitnexus/src/cli/analyze.ts
+++ b/gitnexus/src/cli/analyze.ts
@@ -599,6 +599,12 @@ export interface AnalyzeOptions {
   verbose?: boolean;
   /** Skip AGENTS.md and CLAUDE.md gitnexus block updates. */
   skipAgentsMd?: boolean;
+  /**
+   * Build the control-flow-graph / PDG substrate (#2081 M1). Opt-in; off by
+   * default. Threaded to both the worker (CFG build) and scope-resolution
+   * (BasicBlock/CFG emit).
+   */
+  pdg?: boolean;
   /**
    * Stats inclusion in AGENTS.md and CLAUDE.md.
    *
@@ -1089,6 +1095,8 @@ const analyzeCommandImpl = async (
         skipGit: options.skipGit,
         skipAgentsMd,
         skipSkills,
+        // CFG/PDG substrate opt-in (#2081 M1) — threaded to both sinks downstream.
+        pdg: options.pdg === true,
         // Resolved default branch (CLI > .gitnexusrc > auto-detect > "main")
         // threaded into the generated regression-compare example (#243).
         defaultBranch: resolvedDefaultBranch,
diff --git a/gitnexus/src/cli/index.ts b/gitnexus/src/cli/index.ts
index a2a88bd83..d519496f2 100644
--- a/gitnexus/src/cli/index.ts
+++ b/gitnexus/src/cli/index.ts
@@ -44,6 +44,11 @@ program
       '(no-op when --index-only is also set).',
   )
   .option('--skip-agents-md', 'Skip updating the gitnexus section in AGENTS.md and CLAUDE.md')
+  .option(
+    '--pdg',
+    'Build the control-flow-graph / PDG substrate (BasicBlock nodes + CFG edges) ' +
+      'for TypeScript/JavaScript. Opt-in; off by default. (#2081 M1)',
+  )
   .option(
     '--default-branch <branch>',
     'Default branch used in the generated regression-compare example (base_ref). ' +
diff --git a/gitnexus/src/core/run-analyze.ts b/gitnexus/src/core/run-analyze.ts
index fd7fb1d3f..35702b67f 100644
--- a/gitnexus/src/core/run-analyze.ts
+++ b/gitnexus/src/core/run-analyze.ts
@@ -115,6 +115,12 @@ export interface AnalyzeOptions {
   noStats?: boolean;
   /** Skip installing standard GitNexus skill files to .claude/skills/gitnexus/. */
   skipSkills?: boolean;
+  /**
+   * Build the CFG/PDG substrate (#2081 M1). Forwarded to `PipelineOptions.pdg`,
+   * which threads to BOTH the worker (CFG build, via workerData) AND
+   * scope-resolution (BasicBlock/CFG emit gate). Off by default.
+   */
+  pdg?: boolean;
   /**
    * Default branch threaded into generated AGENTS.md / CLAUDE.md so the
    * regression-compare example uses the configured branch instead of a
@@ -506,6 +512,9 @@ export async function runFullAnalysis(
     {
       parseCache,
       workerPoolSize: options.workerPoolSize,
+      // CFG/PDG opt-in (#2081 M1). PipelineOptions.pdg fans out to the worker
+      // build gate (workerData.pdg) and the scope-resolution emit gate.
+      pdg: options.pdg === true,
     },
   );
 
diff --git a/gitnexus/test/unit/analyze-config.test.ts b/gitnexus/test/unit/analyze-config.test.ts
index 07bbdbea1..0dab5e178 100644
--- a/gitnexus/test/unit/analyze-config.test.ts
+++ b/gitnexus/test/unit/analyze-config.test.ts
@@ -75,6 +75,17 @@ describe('analyze-config (.gitnexusrc support, #243)', () => {
     });
   });
 
+  it('normalizes the pdg opt-in (#2081) and rejects a non-boolean value', async () => {
+    await writeRc(JSON.stringify({ pdg: true }));
+    expect(loadAnalyzeConfig(dir)).toEqual({ pdg: true });
+
+    await writeRc(JSON.stringify({ pdg: false }));
+    expect(loadAnalyzeConfig(dir)).toEqual({ pdg: false });
+
+    await writeRc(JSON.stringify({ pdg: 'yes' }));
+    expect(() => loadAnalyzeConfig(dir)).toThrow(/must be a boolean/);
+  });
+
   it('parses the nested analyze form', async () => {
     await writeRc(JSON.stringify({ analyze: { defaultBranch: 'master', skipSkills: true } }));
     expect(loadAnalyzeConfig(dir)).toEqual({ defaultBranch: 'master', skipSkills: true });
diff --git a/gitnexus/test/unit/cfg/opt-in.test.ts b/gitnexus/test/unit/cfg/opt-in.test.ts
new file mode 100644
index 000000000..11a0d45fa
--- /dev/null
+++ b/gitnexus/test/unit/cfg/opt-in.test.ts
@@ -0,0 +1,39 @@
+import { describe, it, expect } from 'vitest';
+import { mergeAnalyzeOptions } from '../../../src/cli/analyze-config.js';
+import { computeChunkHash } from '../../../src/storage/parse-cache.js';
+
+// U5 — the `--pdg` opt-in plumbing (R7). The flag has TWO sinks downstream of
+// PipelineOptions.pdg: the parse worker (CFG build, gated on workerData.pdg)
+// and scope-resolution (BasicBlock/CFG emit, gated on the run input). These
+// tests pin the observable plumbing: the CLI/.gitnexusrc merge, and that the
+// flag perturbs the parse-cache/worker-dispatch key so a pdg run never reuses
+// a pdg-off shard. The full worker-build + main-emit round-trip is exercised
+// end-to-end by the U7 runPipelineFromRepo({ pdg: true }) integration test.
+
+describe('U5 — --pdg merges from CLI and .gitnexusrc', () => {
+  it('a CLI --pdg flag flows into the merged options', () => {
+    expect(mergeAnalyzeOptions({ pdg: true }, undefined).pdg).toBe(true);
+  });
+
+  it('a .gitnexusrc pdg value flows through when the CLI omits it', () => {
+    expect(mergeAnalyzeOptions({}, { pdg: true }).pdg).toBe(true);
+  });
+
+  it('the CLI flag wins over the file config', () => {
+    expect(mergeAnalyzeOptions({ pdg: true }, { pdg: false }).pdg).toBe(true);
+  });
+
+  it('absent everywhere ⇒ pdg is undefined (default off)', () => {
+    expect(mergeAnalyzeOptions({}, undefined).pdg).toBeUndefined();
+  });
+});
+
+describe('U5 — pdg perturbs the parse-cache / worker-dispatch key', () => {
+  // The chunk hash is what decides whether a chunk is re-dispatched to the
+  // workers (and thus whether the worker builds a CFG). Folding pdg in is the
+  // mechanism that makes the worker sink honor the flag across warm caches.
+  it('a pdg run computes a different chunk key than a pdg-off run', () => {
+    const entries = [{ filePath: 'a.ts', contentHash: 'h1' }];
+    expect(computeChunkHash(entries, true)).not.toBe(computeChunkHash(entries, false));
+  });
+});