fix(#804): reject unknown installer arguments

README.md

@@ -349,6 +349,8 @@ bash tools/install.sh --yes             # Non-interactive, accept all defaults
 bash tools/install.sh --no-auto-launch  # Skip auto-launch of wizard
 ```
 
+The installer rejects unrecognized flags or positional arguments before making changes and prints the supported-option usage.
+
 ## Contributing
 
 ```bash

docs/guides/user-guide.md

@@ -183,6 +183,8 @@ non-interactive use:
 --no-auto-launch    # Skip auto-launch of wizard after install
 ```
 
+Unrecognized flags or positional arguments fail before installation starts and print the supported-option usage.
+
 Or if installed globally:
 
 ```bash

docs/scratchpads/804-install-unknown-flags.md

@@ -43,12 +43,44 @@ Implement Part 1 of Gitea issue #804 only: `tools/install.sh` must reject every
 - 2026-07-17: Confirmed the parser has no legitimate positional arguments and currently drops all unmatched input via `*) shift ;;`.
 - 2026-07-17: Installed locked workspace dependencies with a worktree-local pnpm store; no lockfile changes.
 - 2026-07-17: Added the process-level unknown-argument regression with an isolated `$HOME` and npm shim.
+- 2026-07-17: Replaced the silent catch-all with STDERR error + usage output and exit 2 before preflight or installation.
+- 2026-07-17: Initial Codex code review found an unknown option could still be consumed as the `--ref` value. Added a second RED reproducer, then rejected option-shaped/missing `--ref` values without changing valid `--ref <branch>` behavior. The review's launcher-state note is handled by excluding both `.mosaic/orchestrator/` files from commits.
+- 2026-07-17: Updated README, user guide, and packaged framework README with the fail-closed argument contract. No API, auth, admin, sitemap/navigation, or publishing surface changed.
 
 ## Verification
 
 - RED: `pnpm --filter @mosaicstack/mosaic exec vitest run src/commands/install-arguments.spec.ts` — expected failure: installer exited `0` instead of nonzero at the exit-status assertion; confirms the test reproduces the silent-drop defect before production changes.
+- Remediation RED: the added `--cli --ref --bogus` case exited `0`, proving `--ref` could swallow an unknown option before the guard was added.
+- GREEN: `pnpm --filter @mosaicstack/mosaic exec vitest run src/commands/install-arguments.spec.ts src/commands/install-heading.spec.ts` — 2 files, 3 tests passed.
+- Situational process check: unknown positional input exited 2, named the input on STDERR, printed usage, and did not call the npm shim.
+- `bash -n tools/install.sh` — passed.
+- Bare `--ref` process check — exited 2 with `Missing value for --ref` and usage.
+- `pnpm --filter @mosaicstack/mosaic test` — 69 files, 1,287 tests passed; framework shell checks passed. The first attempt lacked generated `dist/cli.js`; `pnpm --filter @mosaicstack/mosaic build` restored the required test precondition and the full rerun passed.
+- `pnpm lint` — 23/23 tasks passed.
+- `pnpm typecheck` — 42/42 tasks passed.
+- `pnpm format:check` — passed.
+- Codex code re-review against `origin/main` — `approve`, 0 blockers/should-fix/suggestions.
+- Codex security re-review against `origin/main` — risk `none`, 0 findings.
+
+## Acceptance evidence
+
+| Criterion | Evidence |
+| --- | --- |
+| Unknown input is named on STDERR | Process-level Vitest assertions for `--bogus`, including after `--ref` |
+| Short usage hint is printed on STDERR | Vitest usage regex + manual process output |
+| Exit is nonzero | Vitest status assertions and manual exit 2 |
+| Installation does not proceed | Isolated npm shim marker remains absent |
+| Recognized behavior is preserved | Parser cases are unchanged except validation of malformed `--ref`; full Mosaic package suite passed |
+| Part 2 is excluded | No `--next`, `MOSAIC_NEXT`, dist-tag, or prerelease routing changes |
+
+## Documentation checklist
+
+- Current canonical `docs/PRD.md` remains unchanged; issue #804 and the coordinator brief supply this bounded defect's acceptance contract.
+- Updated installer behavior in root README, user guide, and packaged framework README in the same logical change set.
+- API/OpenAPI, auth/permissions, admin operations, developer architecture, sitemap/navigation, and external publishing are not affected.
+- Scratchpad remains under `docs/scratchpads/`; no root-hygiene changes.
 
 ## Risks and blockers
 
 - Part 2 remains owner-gated under #805 and is intentionally excluded.
-- Test harness must isolate `$HOME` and shim npm so the pre-fix installer cannot mutate operator state or contact the registry.
+- No implementation blocker remains. Independent coordinator RoR, CI, merge, and issue closure remain pending after worker handoff.

packages/mosaic/framework/defaults/README.md

@@ -177,6 +177,8 @@ bash tools/install.sh --cli         # npm CLI only (skip framework)
 bash tools/install.sh --ref v1.0    # Install from a specific git ref
 ```
 
+The installer rejects unrecognized flags or positional arguments before making changes and prints the supported-option usage.
+
 ## Universal Skills
 
 The installer syncs skills from `mosaic/agent-skills` into `~/.config/mosaic/skills/`, then links each skill into runtime directories.

packages/mosaic/src/commands/install-arguments.spec.ts

@@ -8,8 +8,11 @@ import { describe, expect, it } from 'vitest';
 
 const INSTALLER_PATH = fileURLToPath(new URL('../../../../tools/install.sh', import.meta.url));
 
-describe('installer arguments', () => {
-  it('rejects an unknown argument before installation starts', async () => {
+async function runInstaller(args: string[]): Promise<{
+  status: number | null;
+  stderr: string;
+  npmCalled: boolean;
+}> {
   const home = await mkdtemp(join(tmpdir(), 'mosaic-installer-args-'));
   const bin = join(home, 'bin');
   const npmMarker = join(home, 'npm-called');
@@ -20,7 +23,7 @@ describe('installer arguments', () => {
     await writeFile(npmShim, `#!/bin/sh\n: > "${npmMarker}"\n`);
     await chmod(npmShim, 0o755);
 
-      const result = spawnSync('bash', [INSTALLER_PATH, '--cli', '--bogus'], {
+    const result = spawnSync('bash', [INSTALLER_PATH, ...args], {
       encoding: 'utf8',
       env: {
         ...process.env,
@@ -30,12 +33,29 @@ describe('installer arguments', () => {
       },
     });
 
-      expect(result.status).not.toBe(0);
-      expect(result.stderr).toContain('Unknown argument: --bogus');
-      expect(result.stderr).toMatch(/Usage: .*install\.sh/);
-      expect(existsSync(npmMarker)).toBe(false);
+    return {
+      status: result.status,
+      stderr: result.stderr,
+      npmCalled: existsSync(npmMarker),
+    };
   } finally {
     await rm(home, { recursive: true, force: true });
   }
+}
+
+function expectUnknownArgument(result: Awaited<ReturnType<typeof runInstaller>>): void {
+  expect(result.status).not.toBe(0);
+  expect(result.stderr).toContain('Unknown argument: --bogus');
+  expect(result.stderr).toMatch(/Usage: .*install\.sh/);
+  expect(result.npmCalled).toBe(false);
+}
+
+describe('installer arguments', () => {
+  it('rejects an unknown argument before installation starts', async () => {
+    expectUnknownArgument(await runInstaller(['--cli', '--bogus']));
+  });
+
+  it('does not let --ref consume an unknown option', async () => {
+    expectUnknownArgument(await runInstaller(['--cli', '--ref', '--bogus']));
   });
 });

tools/install.sh

@@ -61,17 +61,38 @@ if [[ "${MOSAIC_DEV:-0}" == "1" ]]; then
   FLAG_DEV=true
 fi
 
+installer_usage() {
+  printf 'Usage: install.sh [--check] [--framework] [--cli] [--ref <branch>] [--dev] [--yes|-y] [--no-auto-launch] [--uninstall]\n' >&2
+}
+
 while [[ $# -gt 0 ]]; do
   case "$1" in
     --check)          FLAG_CHECK=true; shift ;;
     --framework)      FLAG_CLI=false; shift ;;
     --cli)            FLAG_FRAMEWORK=false; shift ;;
-    --ref)            GIT_REF="${2:-main}"; shift 2 ;;
+    --ref)
+      if [[ $# -lt 2 ]] || [[ -z "$2" ]]; then
+        printf 'Error: Missing value for --ref\n' >&2
+        installer_usage
+        exit 2
+      fi
+      if [[ "$2" == -* ]]; then
+        printf 'Error: Unknown argument: %s\n' "$2" >&2
+        installer_usage
+        exit 2
+      fi
+      GIT_REF="$2"
+      shift 2
+      ;;
     --dev)            FLAG_DEV=true; shift ;;
     --yes|-y)         FLAG_YES=true; shift ;;
     --no-auto-launch) FLAG_NO_AUTO_LAUNCH=true; shift ;;
     --uninstall)      FLAG_UNINSTALL=true; shift ;;
-    *)                shift ;;
+    *)
+      printf 'Error: Unknown argument: %s\n' "$1" >&2
+      installer_usage
+      exit 2
+      ;;
   esac
 done