feat(mosaic): claudex isolated config + env-inject + yolo wiring (P2–P4 of #790) (#806)

packages/mosaic/README.md

@@ -47,6 +47,61 @@ export MOSAIC_ADMIN_PASSWORD="securepass123"
 mosaic gateway install
 ```
 
+## Runtime launchers
+
+```bash
+mosaic claude            # Launch Claude Code with Mosaic injection
+mosaic yolo claude       # …with --dangerously-skip-permissions
+mosaic codex | opencode | pi
+```
+
+### `mosaic claudex` (EXPERIMENTAL)
+
+Runs GPT models **inside the Claude Code harness** by pointing Claude Code at a
+local [`claude-code-proxy`](https://github.com/raine/claude-code-proxy) that
+translates the Anthropic Messages API to a ChatGPT-subscription (Codex OAuth)
+backend. This is **not Anthropic Claude** — model behavior, tool use, and output
+quality may differ. Intended for evaluation, not production delivery.
+
+```bash
+mosaic claudex           # launch (prompts through the proxy readiness gate)
+mosaic yolo claudex      # …with --dangerously-skip-permissions
+mosaic claudex --print "hello"   # trailing args are forwarded to Claude Code
+```
+
+**Prerequisite:** the `claude-code-proxy` binary must be installed and
+authenticated (`claude-code-proxy codex auth …`). `mosaic claudex` runs a
+preflight that verifies the binary, the OAuth state (triggering a device re-auth
+if needed), and a trusted local listener before launching; it **fails closed**
+if the proxy cannot be brought up with a verified identity.
+
+**Isolation (never touches your real Claude state).** claudex always launches
+against an isolated `CLAUDE_CONFIG_DIR` (default `~/.config/mosaic/claudex/home`).
+The ambient `CLAUDE_CONFIG_DIR` is deliberately ignored, and a guard proves the
+resolved dir can never be — or live under — the real `~/.claude`. A claudex
+session therefore cannot mutate your normal Claude Code config.
+
+**No token leakage.** claudex never reads the proxy's credential file. Claude
+Code is handed only `ANTHROPIC_AUTH_TOKEN=unused` pointed at the loopback proxy;
+the entire credential-bearing env family (`ANTHROPIC_*`, `AWS_*`, `GOOGLE_CLOUD_*`,
+`GOOGLE_APPLICATION_CREDENTIALS`, `*_TOKEN`, `*_KEY`, `*_SECRET`, …) is stripped
+from the composed environment. The Bedrock/Vertex routing switches
+(`CLAUDE_CODE_USE_BEDROCK`, `CLAUDE_CODE_USE_VERTEX`, and the `_SKIP_*_AUTH`
+pair) are force-removed regardless of value — otherwise their mere presence
+would route Claude Code to the real Anthropic API via AWS/GCP and bypass the
+proxy. The proxy holds the real OAuth credential.
+
+**Model tiers (override via env).**
+
+| Tier                  | Env var                      | Default        |
+| --------------------- | ---------------------------- | -------------- |
+| primary (opus/sonnet) | `ANTHROPIC_MODEL`            | `gpt-5.6-sol`  |
+| small/fast (haiku)    | `ANTHROPIC_SMALL_FAST_MODEL` | `gpt-5.6-luna` |
+
+Operator-provided values win over the defaults. Additional overrides:
+`MOSAIC_CLAUDEX_CONFIG_DIR` (isolated config dir), `ANTHROPIC_BASE_URL` (proxy
+endpoint).
+
 ## Hooks management
 
 After running `mosaic wizard`, Claude hooks are installed in `~/.claude/hooks-config.json`.