diff --git a/tests/commands/trekresearch-engine.test.mjs b/tests/commands/trekresearch-engine.test.mjs
new file mode 100644
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+++ b/tests/commands/trekresearch-engine.test.mjs
@@ -0,0 +1,35 @@
+// tests/commands/trekresearch-engine.test.mjs
+// Step 1 (deep-research-engine): pin the contract the `--engine deep-research`
+// adapter must hit. The adapted in-context `/deep-research` report, reduced into
+// the research-brief schema, must pass research-validator under the strict
+// default; and a brief missing a required section must fail. This is the one
+// genuinely automatable slice of SC2 (schema, not provenance).
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { validateResearchContent } from '../../lib/validators/research-validator.mjs';
+
+const HERE = dirname(fileURLToPath(import.meta.url));
+const ROOT = join(HERE, '..', '..');
+const FIXTURE = join(ROOT, 'tests', 'fixtures', 'research-deep-research-adapted.md');
+
+test('deep-research adapter output contract — valid brief passes, missing section fails', () => {
+  const text = readFileSync(FIXTURE, 'utf-8');
+
+  // (a) positive: the adapter's target output passes the validator (default = strict).
+  const okResult = validateResearchContent(text);
+  assert.equal(okResult.valid, true, JSON.stringify(okResult.errors));
+
+  // (b) negative: stripping a required section makes it fail with RESEARCH_MISSING_SECTION,
+  //     giving the contract teeth (a fixture that always passes proves nothing).
+  const mutated = text.replace('## Dimensions', '## Removed');
+  const badResult = validateResearchContent(mutated);
+  assert.equal(badResult.valid, false);
+  assert.ok(
+    badResult.errors.find(e => e.code === 'RESEARCH_MISSING_SECTION'),
+    'expected RESEARCH_MISSING_SECTION; got ' + JSON.stringify(badResult.errors),
+  );
+});
diff --git a/tests/fixtures/research-deep-research-adapted.md b/tests/fixtures/research-deep-research-adapted.md
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+---
+type: trekresearch-brief
+created: 2026-06-30
+question: "Should /trekresearch delegate its external phase to the built-in /deep-research workflow?"
+confidence: 0.8
+dimensions: 2
+mcp_servers_used: []
+local_agents_used: []
+external_agents_used:
+  - deep-research
+---
+
+# Deep-research engine adapter output
+
+> Fixture: a `/deep-research` in-context report reduced into the research-brief
+> schema by the `--engine deep-research` adapter (Step 4). Models the target the
+> adapter must hit; not real engine output.
+
+## Executive Summary
+
+Delegating the external phase to the built-in `/deep-research` workflow is a
+viable opt-in engine that supplies fan-out and cited claim-verification for free.
+Confidence is medium-high on the mechanism but lower on availability, because the
+workflow exposes no positive "is-enabled" probe. The load-bearing caveat is
+provenance: structural validity does not certify that the cited URLs are real, so
+a swarm fallback plus a human URL spot-check stay mandatory.
+
+## Dimensions
+
+### Engine mechanism -- Confidence: high
+
+**External findings:**
+- `/deep-research` is a built-in dynamic workflow reachable only by prose instruction, with no programmatic API (https://code.claude.com/docs/workflows).
+- Its report lands in-context with no on-disk artifact, so the adapter must transform what is already in the turn (https://code.claude.com/docs/commands).
+
+### Fallback ergonomics -- Confidence: high
+
+**External findings:**
+- There is no positive availability probe; only `disableWorkflows` / `CLAUDE_CODE_DISABLE_WORKFLOWS` off-switches and a 2.1.154 version floor are documented (https://code.claude.com/docs/skills).
+- Disabled-workflow behavior under `claude -p` is undocumented, so the post-hoc presence check must be robust to every failure manifestation (https://github.com/anthropics/claude-code/issues/52272).
+
+## Sources
+
+| # | Source | Type | Quality | Used in |
+|---|--------|------|---------|---------|
+| 1 | https://code.claude.com/docs/workflows | official | high | Engine mechanism |
+| 2 | https://code.claude.com/docs/commands | official | high | Engine mechanism |
+| 3 | https://code.claude.com/docs/skills | official | high | Fallback ergonomics |
+| 4 | https://github.com/anthropics/claude-code/issues/52272 | community | medium | Fallback ergonomics |