diff --git a/packages/extension/package.json b/packages/extension/package.json
index 993a5d15..400d28b9 100644
--- a/packages/extension/package.json
+++ b/packages/extension/package.json
@@ -99,6 +99,11 @@
           "type": "string",
           "default": "",
           "description": "Runs root the inspector watches. Empty = ~/.amico/runs/default (must match where amico-run writes)."
+        },
+        "amicode.labToml": {
+          "type": "string",
+          "default": "",
+          "description": "Path to the lab.toml hardware profile, validated on load. Empty = ~/.amico/lab.toml (where install.sh writes the starter)."
         }
       }
     }
diff --git a/packages/extension/scripts/lab.toml.example b/packages/extension/scripts/lab.toml.example
index df482a22..da264532 100644
--- a/packages/extension/scripts/lab.toml.example
+++ b/packages/extension/scripts/lab.toml.example
@@ -1,5 +1,9 @@
 # Amicode starter lab config (one lab). Representative single-transmon params;
-# the agent / template may read these. (lab.toml schema lands in Phase 2.)
+# the agent / template reads these. Validated on extension load against the shared
+# @amicode/schema lab schema — a malformed value surfaces a field-precise error
+# rather than silently solving against the wrong hardware.
+schema_version = "1"
+
 [lab]
 name = "demo-lab"
 
diff --git a/packages/extension/src/extension.ts b/packages/extension/src/extension.ts
index 6cf97b10..a10f0c71 100644
--- a/packages/extension/src/extension.ts
+++ b/packages/extension/src/extension.ts
@@ -9,6 +9,7 @@ import { registerTrees } from "./trees";
 import { StatusBarManager } from "./status_bar";
 import { prepareOpencodeProject, resolveJuliaProject, buildOpencodeConfigContent } from "./opencode_config";
 import { resolveAmicoRunBinDir, resolveRunsRoot } from "./opencode_paths";
+import { resolveLabTomlPath, checkLabToml } from "./lab_config";
 import { OpencodeEventClient } from "./sse_client";
 import { RunsRootWatcher } from "./file_watcher";
 import { stageDemoRun } from "./demo_replay";
@@ -50,6 +51,23 @@ export async function activate(ctx: vscode.ExtensionContext): Promise<void> {
   watcher.start();
   ctx.subscriptions.push(watcher);
 
+  // Validate lab.toml on load (0.1b / S17). A malformed hardware profile would
+  // otherwise silently solve against the wrong hardware or fail opaquely mid-solve.
+  // Field-precise: the error names the offending key + path. Non-fatal — the rest
+  // of the extension still activates; a partner can fix the config and reload.
+  const labPath = resolveLabTomlPath(vscode.workspace.getConfiguration("amicode").get<string>("labToml", ""));
+  const lab = checkLabToml(labPath);
+  if (lab.state === "invalid") {
+    runsChannel.appendLine(`[lab] ${lab.path} is INVALID:`);
+    for (const e of lab.errors) runsChannel.appendLine(`  ${e}`);
+    void vscode.window.showErrorMessage(
+      `Amicode: lab.toml is invalid — ${lab.errors[0]}` +
+        (lab.errors.length > 1 ? ` (+${lab.errors.length - 1} more; see "Amicode — runs" output)` : ""),
+    );
+  } else if (lab.state === "valid") {
+    runsChannel.appendLine(`[lab] validated ${lab.path}`);
+  }
+
   // 3. opencode project bootstrap
   const amicoRunBinDir = resolveAmicoRunBinDir(ctx.extensionPath);
   const opencodeProject = prepareOpencodeProject({
diff --git a/packages/extension/src/lab_config.ts b/packages/extension/src/lab_config.ts
new file mode 100644
index 00000000..efb3efbf
--- /dev/null
+++ b/packages/extension/src/lab_config.ts
@@ -0,0 +1,38 @@
+import * as fs from "node:fs";
+import * as path from "node:path";
+import * as os from "node:os";
+import { validateFile, type Validation } from "@amicode/schema";
+
+// ============================================================================
+// lab.toml load-time validation (0.1b / S17). A partner lab's lab.toml is the
+// only place hardware params enter a solve; validating it on extension load
+// turns a malformed/mistyped config into a field-precise error (offending key +
+// path) instead of a silent solve against the wrong hardware or an opaque
+// mid-solve failure. The schema itself lives in the shared @amicode/schema
+// package (0.1a) — this is only the resolve-path + load + surface seam.
+// ============================================================================
+
+/** Resolve the lab.toml the extension validates on load. Empty config →
+ *  ~/.amico/lab.toml (where install.sh writes the starter). A leading ~ is
+ *  expanded, mirroring resolveRunsRoot / resolveJuliaProject. */
+export function resolveLabTomlPath(configValue: string): string {
+  const v = (configValue ?? "").trim();
+  if (v === "") return path.join(os.homedir(), ".amico", "lab.toml");
+  if (v === "~") return os.homedir();
+  if (v.startsWith("~/")) return path.join(os.homedir(), v.slice(2));
+  return v;
+}
+
+export type LabCheck =
+  | { state: "absent"; path: string }
+  | { state: "valid"; path: string }
+  | { state: "invalid"; path: string; errors: string[] };
+
+/** Validate the lab.toml at `labPath` against the shared lab schema. A missing
+ *  file is `absent` (not an error — a lab may be provisioned later); a present
+ *  file is validated field-precise via the single @amicode/schema validator. */
+export function checkLabToml(labPath: string): LabCheck {
+  if (!fs.existsSync(labPath)) return { state: "absent", path: labPath };
+  const v: Validation = validateFile(labPath, "lab");
+  return v.ok ? { state: "valid", path: labPath } : { state: "invalid", path: labPath, errors: v.errors };
+}
diff --git a/packages/extension/test/lab_config.test.ts b/packages/extension/test/lab_config.test.ts
new file mode 100644
index 00000000..176d4f47
--- /dev/null
+++ b/packages/extension/test/lab_config.test.ts
@@ -0,0 +1,91 @@
+import { describe, it, expect } from "vitest";
+import { mkdtempSync, writeFileSync } from "node:fs";
+import { tmpdir, homedir } from "node:os";
+import { join } from "node:path";
+import { validateFile } from "@amicode/schema";
+import { resolveLabTomlPath, checkLabToml } from "../src/lab_config";
+
+const VALID =
+  'schema_version = "1"\n[lab]\nname = "demo-lab"\n' +
+  "[transmon]\nomega_GHz = 5.0\ndelta_GHz = 0.2\nlevels = 3\ndrive_max_GHz = 0.2\n";
+
+function writeLab(content: string): string {
+  const p = join(mkdtempSync(join(tmpdir(), "lab-")), "lab.toml");
+  writeFileSync(p, content);
+  return p;
+}
+function errs(content: string): string[] {
+  const c = checkLabToml(writeLab(content));
+  return c.state === "invalid" ? c.errors : [];
+}
+const has = (es: string[], needle: string) => es.some((e) => e.includes(needle));
+
+describe("resolveLabTomlPath", () => {
+  it("defaults to ~/.amico/lab.toml", () =>
+    expect(resolveLabTomlPath("")).toBe(join(homedir(), ".amico", "lab.toml")));
+  it("expands a leading ~", () => {
+    expect(resolveLabTomlPath("~")).toBe(homedir());
+    expect(resolveLabTomlPath("~/x/lab.toml")).toBe(join(homedir(), "x", "lab.toml"));
+  });
+  it("uses an explicit path, trimmed", () =>
+    expect(resolveLabTomlPath("  /a/lab.toml ")).toBe("/a/lab.toml"));
+});
+
+describe("checkLabToml", () => {
+  it("a missing file is `absent`, not an error (a lab may be provisioned later)", () =>
+    expect(checkLabToml(join(tmpdir(), "definitely-absent-lab-dir", "lab.toml")).state).toBe("absent"));
+  it("a conforming lab.toml is `valid`", () =>
+    expect(checkLabToml(writeLab(VALID)).state).toBe("valid"));
+
+  // field-precise negative matrix (#16 ACs / S17)
+  it("missing required key → names the absent key + path", () =>
+    expect(has(errs(VALID.replace("drive_max_GHz = 0.2\n", "")), 'missing required key "drive_max_GHz"')).toBe(true));
+  it("wrong type → names the offending key", () =>
+    expect(has(errs(VALID.replace("levels = 3", 'levels = "three"')), "/transmon/levels: must be integer")).toBe(true));
+  it("out-of-range → names the offending key (distinct from wrong-type)", () =>
+    expect(has(errs(VALID.replace("levels = 3", "levels = 99")), "/transmon/levels: must be <= 10")).toBe(true));
+  it("unknown / misspelled key → names that key", () =>
+    expect(has(errs(VALID + "rogue = 1\n"), 'unknown key "rogue"')).toBe(true));
+  it("absent schema_version → field-precise required error", () =>
+    expect(has(errs(VALID.replace('schema_version = "1"\n', "")), 'missing required key "schema_version"')).toBe(true));
+  it("unrecognized schema_version → version-specific error", () =>
+    expect(has(errs(VALID.replace('schema_version = "1"', 'schema_version = "9"')), "/schema_version: unrecognized version")).toBe(true));
+
+  it("hardware range bounds are field-precise (#29: omega/drive_max/delta) + name minLength", () => {
+    expect(has(errs(VALID.replace("omega_GHz = 5.0", "omega_GHz = 999")), "/transmon/omega_GHz: must be <= 100")).toBe(true);
+    expect(has(errs(VALID.replace("drive_max_GHz = 0.2", "drive_max_GHz = 50")), "/transmon/drive_max_GHz: must be <= 10")).toBe(true);
+    expect(has(errs(VALID.replace("delta_GHz = 0.2", "delta_GHz = 25")), "/transmon/delta_GHz: must be <= 2")).toBe(true);   // garbage anharmonicity
+    expect(has(errs(VALID.replace('name = "demo-lab"', 'name = ""')), "/lab/name")).toBe(true);                              // minLength
+  });
+
+  it("parity over a corpus: checkLabToml === @amicode/schema.validateFile on every input (no second path) [#16]", () => {
+    const corpus = [
+      VALID,                                                  // valid
+      VALID.replace("drive_max_GHz = 0.2\n", ""),             // missing required
+      VALID.replace("levels = 3", 'levels = "three"'),        // wrong type
+      VALID.replace("levels = 3", "levels = 99"),             // out of range
+      VALID.replace("delta_GHz = 0.2", "delta_GHz = 25"),     // out of range (delta)
+      VALID + "rogue = 1\n",                                  // unknown key
+      VALID.replace('schema_version = "1"\n', ""),            // absent version
+      VALID.replace('schema_version = "1"', 'schema_version = "9"'), // unrecognized version
+    ];
+    for (const content of corpus) {
+      const p = writeLab(content);
+      const c = checkLabToml(p);
+      const direct = validateFile(p, "lab");
+      expect(c.state === "valid" ? [] : (c as { errors: string[] }).errors).toEqual(direct.errors);
+    }
+  });
+});
+
+describe("valid lab profiles conform (demo + Schuster)", () => {
+  it("scripts/lab.toml.example (the shipped starter) validates clean", () =>
+    expect(validateFile(join(__dirname, "..", "scripts", "lab.toml.example"), "lab").errors).toEqual([]));
+  it("a Schuster-profile lab (negative-convention δ, 4 levels) validates clean", () => {
+    // Distinct from demo-lab: negative anharmonicity convention + a 4-level model,
+    // exercising the schema's range tolerance on a second real-shaped profile.
+    const schuster = 'schema_version = "1"\n[lab]\nname = "schuster-transmon"\n' +
+      "[transmon]\nomega_GHz = 4.8\ndelta_GHz = -0.33\nlevels = 4\ndrive_max_GHz = 0.1\n";
+    expect(checkLabToml(writeLab(schuster)).state).toBe("valid");
+  });
+});