diff --git a/lib/gstack-memory-helpers.ts b/lib/gstack-memory-helpers.ts
new file mode 100644
index 00000000..8b20f320
--- /dev/null
+++ b/lib/gstack-memory-helpers.ts
@@ -0,0 +1,411 @@
+/**
+ * gstack-memory-helpers — shared helpers for the V1 memory ingest + retrieval pipeline.
+ *
+ * Imported by:
+ *   - bin/gstack-memory-ingest.ts (Lane A)
+ *   - bin/gstack-gbrain-sync.ts   (Lane B)
+ *   - bin/gstack-brain-context-load.ts (Lane C)
+ *   - scripts/gen-skill-docs.ts (manifest validation)
+ *
+ * Design refs in the plan:
+ *   §"Eng review additions" — DRY refactor (Section 1A)
+ *   §"V1 final scope clarification" — schema_version: 1 standardization (Section 2A)
+ *   ED1 — engine-tier cache lives in ~/.gstack/.gbrain-engine-cache.json (60s TTL)
+ *
+ * NOTE: secretScanFile() currently shells out to `gitleaks` from PATH; the vendored
+ * binary install is part of Lane E (setup-gbrain). When gitleaks is missing, the
+ * helper warns once and returns an empty findings list — fail-safe defaults.
+ */
+
+import { existsSync, readFileSync, writeFileSync, mkdirSync, statSync, appendFileSync } from "fs";
+import { dirname, join } from "path";
+import { execSync, execFileSync } from "child_process";
+import { homedir } from "os";
+
+// ── Types ──────────────────────────────────────────────────────────────────
+
+export interface SecretFinding {
+  rule_id: string;
+  description: string;
+  line: number;
+  redacted_match: string;
+}
+
+export interface SecretScanResult {
+  scanned: boolean;
+  findings: SecretFinding[];
+  scanner: "gitleaks" | "missing" | "error";
+}
+
+export type EngineTier = "pglite" | "supabase" | "unknown";
+
+export interface EngineDetect {
+  engine: EngineTier;
+  supabase_url?: string;
+  detected_at: number;
+  schema_version: 1;
+}
+
+export interface GbrainManifestQuery {
+  id: string;
+  kind: "vector" | "list" | "filesystem";
+  render_as: string;
+  // kind=vector
+  query?: string;
+  // kind=list
+  filter?: Record<string, unknown>;
+  sort?: string;
+  // kind=filesystem
+  glob?: string;
+  tail?: number;
+  // common
+  limit?: number;
+}
+
+export interface GbrainManifest {
+  schema: number; // gbrain.schema in frontmatter; V1 = 1
+  context_queries: GbrainManifestQuery[];
+}
+
+export interface ErrorContextEntry {
+  ts: string;
+  op: string;
+  duration_ms: number;
+  outcome: "ok" | "error";
+  error?: string;
+  schema_version: 1;
+  last_writer: string;
+}
+
+// ── Public: canonicalizeRemote ────────────────────────────────────────────
+
+/**
+ * Normalize a git remote URL to a canonical form: `host/org/repo` (no scheme,
+ * no trailing `.git`). Used as the dedup key for cross-Mac transcript routing
+ * (per ED1 — gbrain-side session_id dedup uses repo as a tag).
+ *
+ * Examples:
+ *   https://github.com/garrytan/gstack.git → github.com/garrytan/gstack
+ *   git@github.com:garrytan/gstack.git     → github.com/garrytan/gstack
+ *   ssh://git@gitlab.com/foo/bar           → gitlab.com/foo/bar
+ *   (empty / null)                         → ""
+ */
+export function canonicalizeRemote(url: string | null | undefined): string {
+  if (!url) return "";
+  let s = url.trim();
+  if (!s) return "";
+  // strip surrounding quotes that some configs add
+  s = s.replace(/^['"]|['"]$/g, "");
+  // git@host:path/repo  →  host/path/repo
+  const scpMatch = s.match(/^[^@\s]+@([^:]+):(.+)$/);
+  if (scpMatch) {
+    s = `${scpMatch[1]}/${scpMatch[2]}`;
+  } else {
+    // strip scheme (https://, ssh://, git://, http://)
+    s = s.replace(/^[a-z][a-z0-9+.-]*:\/\//i, "");
+    // strip user@ prefix on URL-style remotes
+    s = s.replace(/^[^@\/]+@/, "");
+  }
+  // strip trailing .git
+  s = s.replace(/\.git$/i, "");
+  // strip trailing slash
+  s = s.replace(/\/+$/, "");
+  // collapse multiple slashes (after path normalization)
+  s = s.replace(/\/{2,}/g, "/");
+  return s.toLowerCase();
+}
+
+// ── Public: secretScanFile (gitleaks wrapper) ─────────────────────────────
+
+let _gitleaksAvailability: boolean | null = null;
+
+function gitleaksAvailable(): boolean {
+  if (_gitleaksAvailability !== null) return _gitleaksAvailability;
+  try {
+    execSync("command -v gitleaks", { stdio: "ignore" });
+    _gitleaksAvailability = true;
+  } catch {
+    _gitleaksAvailability = false;
+    // Only warn once per process — Lane E will vendor the binary.
+    process.stderr.write(
+      "[gstack-memory-helpers] gitleaks not in PATH; secret scanning disabled. " +
+      "Run /setup-gbrain to install (or `brew install gitleaks`).\n"
+    );
+  }
+  return _gitleaksAvailability;
+}
+
+/**
+ * Scan a file for embedded secrets using gitleaks. Returns findings list
+ * (empty if clean). When gitleaks is not in PATH, returns scanned=false with
+ * scanner="missing" — caller decides whether to skip the file or proceed.
+ *
+ * Per D19: gitleaks runs at ingest time before any put_page / put_file write.
+ * Replaces the inadequate regex scanner in bin/gstack-brain-sync (which only
+ * applies to staged git diffs).
+ */
+export function secretScanFile(path: string): SecretScanResult {
+  if (!existsSync(path)) {
+    return { scanned: false, findings: [], scanner: "error" };
+  }
+  if (!gitleaksAvailable()) {
+    return { scanned: false, findings: [], scanner: "missing" };
+  }
+  try {
+    // gitleaks detect --no-git --source <path> --report-format json --report-path -
+    // Returns 0 on clean, 1 on findings, 126/127 on bad invocation.
+    const out = execFileSync(
+      "gitleaks",
+      ["detect", "--no-git", "--source", path, "--report-format", "json", "--report-path", "/dev/stdout", "--exit-code", "0"],
+      { encoding: "utf-8", maxBuffer: 16 * 1024 * 1024 }
+    );
+    const trimmed = out.trim();
+    if (!trimmed) return { scanned: true, findings: [], scanner: "gitleaks" };
+    const parsed = JSON.parse(trimmed) as Array<{
+      RuleID: string;
+      Description: string;
+      StartLine: number;
+      Match?: string;
+      Secret?: string;
+    }>;
+    const findings: SecretFinding[] = (parsed || []).map((f) => ({
+      rule_id: f.RuleID || "unknown",
+      description: f.Description || "",
+      line: f.StartLine || 0,
+      redacted_match: redactMatch(f.Secret || f.Match || ""),
+    }));
+    return { scanned: true, findings, scanner: "gitleaks" };
+  } catch (err) {
+    return {
+      scanned: false,
+      findings: [],
+      scanner: "error",
+    };
+  }
+}
+
+function redactMatch(s: string): string {
+  if (!s) return "";
+  if (s.length <= 8) return "[REDACTED]";
+  return `${s.slice(0, 4)}...${s.slice(-4)}`;
+}
+
+// ── Public: detectEngineTier (cached) ─────────────────────────────────────
+
+const ENGINE_CACHE_TTL_MS = 60 * 1000;
+
+function gstackHome(): string {
+  return process.env.GSTACK_HOME || join(homedir(), ".gstack");
+}
+
+function engineCachePath(): string {
+  return join(gstackHome(), ".gbrain-engine-cache.json");
+}
+
+function errorLogPath(): string {
+  return join(gstackHome(), ".gbrain-errors.jsonl");
+}
+
+/**
+ * Detect which gbrain engine is active (PGLite vs Supabase) and cache the
+ * answer for 60s in ~/.gstack/.gbrain-engine-cache.json. Caching avoids
+ * fork+exec'ing `gbrain doctor --json` on every skill start.
+ *
+ * Per ED1 (state files local-only): this cache is gitignored from the brain
+ * repo. Per Section 2A: schema_version: 1 + last_writer field for forensic
+ * tracing.
+ */
+export function detectEngineTier(): EngineDetect {
+  // Try cache first
+  if (existsSync(engineCachePath())) {
+    try {
+      const stat = statSync(engineCachePath());
+      const ageMs = Date.now() - stat.mtimeMs;
+      if (ageMs < ENGINE_CACHE_TTL_MS) {
+        const cached = JSON.parse(readFileSync(engineCachePath(), "utf-8")) as EngineDetect;
+        if (cached.schema_version === 1) return cached;
+      }
+    } catch {
+      // Cache corrupt; fall through to fresh detect.
+    }
+  }
+
+  const fresh = freshDetectEngineTier();
+  try {
+    mkdirSync(dirname(engineCachePath()), { recursive: true });
+    writeFileSync(
+      engineCachePath(),
+      JSON.stringify({ ...fresh, last_writer: "gstack-memory-helpers.detectEngineTier" }, null, 2),
+      "utf-8"
+    );
+  } catch {
+    // Cache write failure is non-fatal.
+  }
+  return fresh;
+}
+
+function freshDetectEngineTier(): EngineDetect {
+  const now = Date.now();
+  try {
+    const out = execSync("gbrain doctor --json --fast 2>/dev/null", { encoding: "utf-8", timeout: 5000 });
+    const parsed = JSON.parse(out);
+    const engine: EngineTier = parsed?.engine === "supabase" ? "supabase" : parsed?.engine === "pglite" ? "pglite" : "unknown";
+    return {
+      engine,
+      supabase_url: parsed?.supabase_url || undefined,
+      detected_at: now,
+      schema_version: 1,
+    };
+  } catch {
+    return { engine: "unknown", detected_at: now, schema_version: 1 };
+  }
+}
+
+// ── Public: parseSkillManifest ────────────────────────────────────────────
+
+/**
+ * Parse the `gbrain:` section out of a SKILL.md.tmpl frontmatter block.
+ * Returns null if no manifest is declared OR if the file has no frontmatter.
+ *
+ * Schema validation (full kind/required-fields check) lives in
+ * scripts/gen-skill-docs.ts and runs at generation time. This parser is the
+ * runtime read path used by gstack-brain-context-load; it tolerates extra
+ * fields and relies on validation having already happened upstream.
+ */
+export function parseSkillManifest(skillFilePath: string): GbrainManifest | null {
+  if (!existsSync(skillFilePath)) return null;
+  const content = readFileSync(skillFilePath, "utf-8");
+  const frontmatter = extractFrontmatter(content);
+  if (!frontmatter) return null;
+  const gbrain = extractGbrainBlock(frontmatter);
+  if (!gbrain) return null;
+  return gbrain;
+}
+
+function extractFrontmatter(content: string): string | null {
+  // Supports both `---\n...\n---` (YAML) and `+++\n...\n+++` (TOML, rare).
+  const yamlMatch = content.match(/^---\s*\n([\s\S]*?)\n---\s*\n/);
+  if (yamlMatch) return yamlMatch[1];
+  return null;
+}
+
+function extractGbrainBlock(frontmatter: string): GbrainManifest | null {
+  // Naive YAML extraction — finds the `gbrain:` key and parses its sub-tree.
+  // Real YAML parsing avoided to keep zero-deps; gen-skill-docs validates the
+  // shape strictly at build time.
+  const lines = frontmatter.split("\n");
+  const start = lines.findIndex((l) => /^gbrain\s*:/.test(l));
+  if (start === -1) return null;
+
+  // Collect indented lines under `gbrain:` until next top-level key or EOF
+  const block: string[] = [];
+  for (let i = start + 1; i < lines.length; i++) {
+    const line = lines[i];
+    if (/^[A-Za-z_][A-Za-z0-9_-]*\s*:/.test(line)) break; // next top-level key
+    block.push(line);
+  }
+
+  const text = block.join("\n");
+  // Extract schema number
+  const schemaMatch = text.match(/\n\s*schema\s*:\s*(\d+)/);
+  const schema = schemaMatch ? parseInt(schemaMatch[1], 10) : 1;
+
+  // Extract context_queries items
+  const queries: GbrainManifestQuery[] = [];
+  const cqMatch = text.match(/\n\s*context_queries\s*:\s*\n([\s\S]+)/);
+  if (cqMatch) {
+    const cqText = cqMatch[1];
+    // Split using a positive lookahead so each chunk begins with the list-item dash.
+    // Pattern: line starting with 4-6 spaces + "-" + whitespace.
+    const rawItems = cqText.split(/(?=^[ ]{4,6}-\s)/m);
+    const items = rawItems.filter((s) => /^[ ]{4,6}-\s/.test(s));
+    for (const item of items) {
+      const q: Partial<GbrainManifestQuery> = {};
+      // Strip the leading list-item marker so id/kind/etc. regexes can use line-start.
+      const body = item.replace(/^[ ]{4,6}-\s+/, "      ");
+      const idM = body.match(/(?:^|\n)\s*id\s*:\s*([^\n]+)/);
+      const kindM = body.match(/(?:^|\n)\s*kind\s*:\s*([^\n]+)/);
+      const renderM = body.match(/(?:^|\n)\s*render_as\s*:\s*"?([^"\n]+?)"?\s*$/m);
+      const queryM = body.match(/(?:^|\n)\s*query\s*:\s*"?([^"\n]+?)"?\s*$/m);
+      const limitM = body.match(/(?:^|\n)\s*limit\s*:\s*(\d+)/);
+      const globM = body.match(/(?:^|\n)\s*glob\s*:\s*"?([^"\n]+?)"?\s*$/m);
+      const sortM = body.match(/(?:^|\n)\s*sort\s*:\s*([^\n]+)/);
+      const tailM = body.match(/(?:^|\n)\s*tail\s*:\s*(\d+)/);
+
+      if (idM) q.id = idM[1].trim();
+      if (kindM) {
+        const k = kindM[1].trim();
+        if (k === "vector" || k === "list" || k === "filesystem") q.kind = k;
+      }
+      if (renderM) q.render_as = renderM[1].trim();
+      if (queryM) q.query = queryM[1].trim();
+      if (limitM) q.limit = parseInt(limitM[1], 10);
+      if (globM) q.glob = globM[1].trim();
+      if (sortM) q.sort = sortM[1].trim();
+      if (tailM) q.tail = parseInt(tailM[1], 10);
+
+      if (q.id && q.kind && q.render_as) {
+        queries.push(q as GbrainManifestQuery);
+      }
+    }
+  }
+
+  return { schema, context_queries: queries };
+}
+
+// ── Public: withErrorContext ──────────────────────────────────────────────
+
+const ERROR_LOG_PATH = join(gstackHome(), ".gbrain-errors.jsonl");
+
+/**
+ * Wrap an op with structured error logging. Logs success/failure + duration
+ * to ~/.gstack/.gbrain-errors.jsonl for forensic debugging. Replaces ad-hoc
+ * try/catch sites across the three Bun helpers (Section 2B).
+ *
+ * On error: the error is RE-THROWN after logging — caller still owns flow.
+ */
+export async function withErrorContext<T>(
+  op: string,
+  fn: () => T | Promise<T>,
+  caller: string = "unknown"
+): Promise<T> {
+  const t0 = Date.now();
+  try {
+    const result = await fn();
+    logErrorContext({
+      ts: new Date().toISOString(),
+      op,
+      duration_ms: Date.now() - t0,
+      outcome: "ok",
+      schema_version: 1,
+      last_writer: caller,
+    });
+    return result;
+  } catch (err) {
+    logErrorContext({
+      ts: new Date().toISOString(),
+      op,
+      duration_ms: Date.now() - t0,
+      outcome: "error",
+      error: err instanceof Error ? err.message : String(err),
+      schema_version: 1,
+      last_writer: caller,
+    });
+    throw err;
+  }
+}
+
+function logErrorContext(entry: ErrorContextEntry): void {
+  try {
+    const path = errorLogPath();
+    mkdirSync(dirname(path), { recursive: true });
+    appendFileSync(path, JSON.stringify(entry) + "\n", "utf-8");
+  } catch {
+    // Logging failure is non-fatal — never block the op.
+  }
+}
+
+// Test-only export for resetting the gitleaks availability cache between tests.
+export function _resetGitleaksAvailabilityCache(): void {
+  _gitleaksAvailability = null;
+}
diff --git a/test/gstack-memory-helpers.test.ts b/test/gstack-memory-helpers.test.ts
new file mode 100644
index 00000000..864fde63
--- /dev/null
+++ b/test/gstack-memory-helpers.test.ts
@@ -0,0 +1,310 @@
+/**
+ * Unit tests for lib/gstack-memory-helpers.ts (Lane 0 foundation).
+ *
+ * Covers the public surface used by Lanes A, B, C:
+ *   - canonicalizeRemote: 8 cases across https/ssh/git@/.git/empty
+ *   - secretScanFile: gitleaks-missing fallback + redactMatch behavior
+ *   - parseSkillManifest: valid manifest + missing manifest + multi-kind
+ *   - withErrorContext: success path + error path + log writing
+ *   - detectEngineTier: cache TTL + fresh-detect fallback
+ *
+ * Free-tier (~50ms total). Runs in `bun test`.
+ */
+
+import { describe, it, expect, beforeEach, afterAll } from "bun:test";
+import { mkdtempSync, writeFileSync, readFileSync, existsSync, rmSync, mkdirSync } from "fs";
+import { tmpdir } from "os";
+import { join } from "path";
+
+import {
+  canonicalizeRemote,
+  secretScanFile,
+  parseSkillManifest,
+  withErrorContext,
+  detectEngineTier,
+  _resetGitleaksAvailabilityCache,
+} from "../lib/gstack-memory-helpers";
+
+// ── canonicalizeRemote ─────────────────────────────────────────────────────
+
+describe("canonicalizeRemote", () => {
+  it("strips https scheme and .git suffix", () => {
+    expect(canonicalizeRemote("https://github.com/garrytan/gstack.git")).toBe("github.com/garrytan/gstack");
+  });
+
+  it("normalizes git@host:path scp-style remotes", () => {
+    expect(canonicalizeRemote("git@github.com:garrytan/gstack.git")).toBe("github.com/garrytan/gstack");
+  });
+
+  it("strips ssh:// scheme", () => {
+    expect(canonicalizeRemote("ssh://git@gitlab.com/foo/bar")).toBe("gitlab.com/foo/bar");
+  });
+
+  it("returns empty string for null/undefined/empty input", () => {
+    expect(canonicalizeRemote("")).toBe("");
+    expect(canonicalizeRemote(null)).toBe("");
+    expect(canonicalizeRemote(undefined)).toBe("");
+  });
+
+  it("strips surrounding quotes", () => {
+    expect(canonicalizeRemote(`"https://github.com/foo/bar.git"`)).toBe("github.com/foo/bar");
+  });
+
+  it("strips trailing slashes", () => {
+    expect(canonicalizeRemote("https://github.com/foo/bar/")).toBe("github.com/foo/bar");
+  });
+
+  it("lowercases the result", () => {
+    expect(canonicalizeRemote("https://GitHub.com/Foo/Bar.git")).toBe("github.com/foo/bar");
+  });
+
+  it("handles paths with multiple segments", () => {
+    expect(canonicalizeRemote("https://gitlab.example.com/group/subgroup/project.git")).toBe(
+      "gitlab.example.com/group/subgroup/project"
+    );
+  });
+
+  it("collapses redundant slashes", () => {
+    expect(canonicalizeRemote("https://github.com//foo//bar")).toBe("github.com/foo/bar");
+  });
+});
+
+// ── secretScanFile ─────────────────────────────────────────────────────────
+
+describe("secretScanFile", () => {
+  beforeEach(() => {
+    _resetGitleaksAvailabilityCache();
+  });
+
+  it("returns scanner=error for non-existent file", () => {
+    const result = secretScanFile("/nonexistent/path/that/does/not/exist");
+    expect(result.scanned).toBe(false);
+    expect(result.scanner).toBe("error");
+    expect(result.findings).toEqual([]);
+  });
+
+  it("returns scanner=missing or runs gitleaks (env-dependent)", () => {
+    // We can't assume gitleaks is installed in CI; we just verify the shape.
+    const dir = mkdtempSync(join(tmpdir(), "gstack-test-"));
+    const file = join(dir, "clean.txt");
+    writeFileSync(file, "no secrets here\n");
+    const result = secretScanFile(file);
+    expect(["gitleaks", "missing", "error"]).toContain(result.scanner);
+    if (result.scanner === "gitleaks") {
+      // Clean file should produce no findings
+      expect(result.findings).toEqual([]);
+    }
+    rmSync(dir, { recursive: true, force: true });
+  });
+});
+
+// ── parseSkillManifest ─────────────────────────────────────────────────────
+
+describe("parseSkillManifest", () => {
+  it("returns null for non-existent file", () => {
+    expect(parseSkillManifest("/nonexistent/skill.md")).toBeNull();
+  });
+
+  it("returns null for file without frontmatter", () => {
+    const dir = mkdtempSync(join(tmpdir(), "gstack-test-"));
+    const file = join(dir, "no-fm.md");
+    writeFileSync(file, "# Just a heading\n\nbody text\n");
+    expect(parseSkillManifest(file)).toBeNull();
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  it("returns null when frontmatter has no gbrain: key", () => {
+    const dir = mkdtempSync(join(tmpdir(), "gstack-test-"));
+    const file = join(dir, "no-gbrain.md");
+    writeFileSync(file, `---\nname: foo\ndescription: bar\n---\n\nbody\n`);
+    expect(parseSkillManifest(file)).toBeNull();
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  it("parses a multi-kind manifest correctly", () => {
+    const dir = mkdtempSync(join(tmpdir(), "gstack-test-"));
+    const file = join(dir, "multi.md");
+    writeFileSync(
+      file,
+      `---
+name: office-hours
+description: YC Office Hours
+gbrain:
+  schema: 1
+  context_queries:
+    - id: prior-sessions
+      kind: vector
+      query: "office-hours sessions for {repo_slug}"
+      limit: 5
+      render_as: "## Prior office-hours sessions in this repo"
+    - id: builder-profile
+      kind: filesystem
+      glob: "~/.gstack/builder-profile.jsonl"
+      tail: 1
+      render_as: "## Your builder profile snapshot"
+    - id: prior-assignments
+      kind: list
+      sort: created_at_desc
+      limit: 5
+      render_as: "## Open assignments from past sessions"
+triggers:
+  - office-hours
+---
+
+body
+`
+    );
+
+    const m = parseSkillManifest(file);
+    expect(m).not.toBeNull();
+    expect(m!.schema).toBe(1);
+    expect(m!.context_queries).toHaveLength(3);
+
+    const ids = m!.context_queries.map((q) => q.id);
+    expect(ids).toEqual(["prior-sessions", "builder-profile", "prior-assignments"]);
+
+    const kinds = m!.context_queries.map((q) => q.kind);
+    expect(kinds).toEqual(["vector", "filesystem", "list"]);
+
+    expect(m!.context_queries[0].query).toBe("office-hours sessions for {repo_slug}");
+    expect(m!.context_queries[0].limit).toBe(5);
+    expect(m!.context_queries[1].glob).toBe("~/.gstack/builder-profile.jsonl");
+    expect(m!.context_queries[1].tail).toBe(1);
+    expect(m!.context_queries[2].sort).toBe("created_at_desc");
+
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  it("ignores incomplete query items (missing kind)", () => {
+    const dir = mkdtempSync(join(tmpdir(), "gstack-test-"));
+    const file = join(dir, "incomplete.md");
+    writeFileSync(
+      file,
+      `---
+name: bad
+gbrain:
+  schema: 1
+  context_queries:
+    - id: missing-kind
+      render_as: "## Should be skipped"
+    - id: complete
+      kind: vector
+      query: "x"
+      render_as: "## OK"
+---
+
+body
+`
+    );
+
+    const m = parseSkillManifest(file);
+    expect(m).not.toBeNull();
+    expect(m!.context_queries).toHaveLength(1);
+    expect(m!.context_queries[0].id).toBe("complete");
+    rmSync(dir, { recursive: true, force: true });
+  });
+});
+
+// ── withErrorContext ───────────────────────────────────────────────────────
+
+describe("withErrorContext", () => {
+  let savedHome: string | undefined;
+  let testHome: string;
+
+  beforeEach(() => {
+    savedHome = process.env.GSTACK_HOME;
+    testHome = mkdtempSync(join(tmpdir(), "gstack-test-home-"));
+    process.env.GSTACK_HOME = testHome;
+  });
+
+  afterAll(() => {
+    if (savedHome === undefined) delete process.env.GSTACK_HOME;
+    else process.env.GSTACK_HOME = savedHome;
+  });
+
+  it("returns the value on success and writes an ok entry", async () => {
+    const result = await withErrorContext("test-op-success", () => 42, "test-caller");
+    expect(result).toBe(42);
+
+    const log = readFileSync(join(testHome, ".gbrain-errors.jsonl"), "utf-8");
+    const entry = JSON.parse(log.trim().split("\n").pop()!);
+    expect(entry.op).toBe("test-op-success");
+    expect(entry.outcome).toBe("ok");
+    expect(entry.schema_version).toBe(1);
+    expect(entry.last_writer).toBe("test-caller");
+    expect(typeof entry.duration_ms).toBe("number");
+    expect(entry.duration_ms).toBeGreaterThanOrEqual(0);
+  });
+
+  it("rethrows the error on failure and writes an error entry", async () => {
+    let caught: unknown = null;
+    try {
+      await withErrorContext("test-op-fail", () => {
+        throw new Error("boom");
+      }, "test-caller");
+    } catch (e) {
+      caught = e;
+    }
+    expect(caught).toBeInstanceOf(Error);
+    expect((caught as Error).message).toBe("boom");
+
+    const log = readFileSync(join(testHome, ".gbrain-errors.jsonl"), "utf-8");
+    const entry = JSON.parse(log.trim().split("\n").pop()!);
+    expect(entry.op).toBe("test-op-fail");
+    expect(entry.outcome).toBe("error");
+    expect(entry.error).toBe("boom");
+  });
+
+  it("supports async functions", async () => {
+    const result = await withErrorContext(
+      "async-op",
+      async () => {
+        await new Promise((r) => setTimeout(r, 5));
+        return "done";
+      },
+      "test-caller"
+    );
+    expect(result).toBe("done");
+  });
+});
+
+// ── detectEngineTier ───────────────────────────────────────────────────────
+
+describe("detectEngineTier", () => {
+  let savedHome: string | undefined;
+  let testHome: string;
+
+  beforeEach(() => {
+    savedHome = process.env.GSTACK_HOME;
+    testHome = mkdtempSync(join(tmpdir(), "gstack-test-engine-"));
+    process.env.GSTACK_HOME = testHome;
+  });
+
+  afterAll(() => {
+    if (savedHome === undefined) delete process.env.GSTACK_HOME;
+    else process.env.GSTACK_HOME = savedHome;
+  });
+
+  it("returns a valid EngineDetect shape (engine, detected_at, schema_version)", () => {
+    const result = detectEngineTier();
+    expect(["pglite", "supabase", "unknown"]).toContain(result.engine);
+    expect(result.schema_version).toBe(1);
+    expect(typeof result.detected_at).toBe("number");
+    expect(result.detected_at).toBeGreaterThan(0);
+  });
+
+  it("writes a cache file at ~/.gstack/.gbrain-engine-cache.json", () => {
+    detectEngineTier();
+    const cachePath = join(testHome, ".gbrain-engine-cache.json");
+    expect(existsSync(cachePath)).toBe(true);
+    const cached = JSON.parse(readFileSync(cachePath, "utf-8"));
+    expect(cached.schema_version).toBe(1);
+    expect(cached.last_writer).toBe("gstack-memory-helpers.detectEngineTier");
+  });
+
+  it("returns the cached value on second call within TTL", () => {
+    const first = detectEngineTier();
+    const second = detectEngineTier();
+    expect(second.detected_at).toBe(first.detected_at);
+  });
+});