taodengandClaude Opus 4.7 (noreply@anthropic.com) 5960486542 feat(phase-1): land fallback engine (D9)
Phase 1 Day 6 — the architectural milestone of Phase 1. OLP is no longer
a single-provider proxy with cache; it is now a multi-provider router
with idempotent-failure-safe fallback. ADR 0004 ratified in v0.1 governance
is fully implemented for D9 scope. Configuration-driven chains activate
when a user populates ~/.olp/config.json routing.chains; at v0.1 default
(empty chains), behaviour is single-hop pass-through identical to D5.

Files:
  NEW:  lib/fallback/engine.mjs (~470 lines) — Trigger taxonomy, chain
        advancement, first-chunk safety, observability annotation.
  MOD:  server.mjs (+80 lines net) — wires executeWithFallback between IR
        construction and provider.spawn. Per-hop cache key isolation
        (ADR 0005 § Cross-provider fallback). Test seams added:
        __setFallbackConfig, __resetFallbackConfig, __clearCache.
  MOD:  test-features.mjs (+845 lines, 6 new suites = +55 tests).

Authority citations:
  ADR 0004 § Decision § Trigger taxonomy — Hard / Soft / Deterministic
    (deferred) / Cost-aware (deferred) implemented exactly per spec.
  ADR 0004 § Decision § Fallback safety — first-chunk rule satisfied at
    D9 by buffering composition (executeHopFn = collectAllChunks; server
    writes to res only after engine returns).
  ADR 0004 § Decision § Chain advancement — one-at-a-time iteration;
    originalError preserved from FIRST hop (not last) on exhaustion.
  ADR 0004 § Decision § No fallback for client-side errors — HTTP 400/
    401/403/404/422 stop the chain immediately; AUTH_MISSING also stops
    immediately (user-config failure, not provider-quota).
  ADR 0004 § Decision § Observability headers — X-OLP-Fallback-Hops set
    from engine return value; X-OLP-Fallback-Exhausted lists tried
    providers on exhaustion.
  ADR 0005 § Cross-provider fallback cache behavior — each fallback hop
    computes a fresh cache key with the hop's (provider, model) tuple;
    primary's cache entries cannot leak to secondary's hop.

Reviewer chain (Iron Rule 10):
  Implementer: sonnet (general-purpose).
  Fresh-context reviewer: opus. Verdict APPROVE_WITH_MINOR.
  Reviewer ran npm test (277/277 pass), read ADR 0004 + ADR 0005 end-
    to-end, verified first-chunk-safety composition, checked all
    trigger taxonomy mappings.

Reviewer non-blocking findings folded in this commit:
  1. Test label at test-features.mjs:3756 clarified. Original title
     "client error (400) → does NOT fall back" was misleading because
     the test actually exercises both-fail SPAWN_FAILED → exhausted
     path (400-no-fallback semantic is covered at unit level instead).
     Renamed + commented to match actual behaviour.
  2. triedProviders semantic (includes soft-skipped) documented in
     engine.mjs comment near the soft-trigger branch.
  3. SOFT_TRIGGER synthetic code documented in engine.mjs as engine-
     internal, NOT a member of base.mjs PROVIDER_ERROR_CODES.

Reviewer non-blocking suggestions deferred (open D-later questions):
  - Q1 cacheStatus on fallback hops: conservative 'miss', acceptable
    per ADR 0005 § Per-model isolation.
  - Q2 X-OLP-Fallback-Exhausted only when triedProviders > 1:
    acceptable per ADR 0004 spec.
  - Q3 soft-trigger quotaSnapshot always null at D9: acceptable per
    ADR 0004 § Consequences/Negative graceful-degrade clause. Phase 2
    will add quota poll-worker.
  - Q4 loadFallbackConfigSync sync-only: acceptable for bounded
    startup I/O.

Test count: 222 (D8) → 277 (D9). 6 new test suites cover trigger
taxonomy, engine chain advancement (including the load-bearing
originalError-from-FIRST-hop property), HTTP integration through
real server.mjs, soft trigger pre-fetch path, exhausted-chain
header emission.

Verification:
  node --check on all touched files: clean.
  npm test on Node 25.8.0: 277/277 pass in 266ms.
  Hygiene grep: zero personal-name/path/token hits.
  No new external npm deps.

Co-Authored-By: Claude Opus 4.7 (noreply@anthropic.com)
2026-05-23 22:09:39 +10:00

OLP — Open LLM Proxy

A personal- and family-scale multi-provider LLM proxy. One HTTP endpoint, many subscriptions behind it, automatic routing, automatic fallback, content-addressed caching — so your IDEs and family clients keep working as long as any of your subscriptions has quota left.

Status: v0.1 — bootstrap. Most of this README is a skeleton; sections marked placeholder land alongside the relevant phase of work (see phase plan).


Why OLP

On 2026-05-14, Anthropic announced (effective 2026-06-15) that claude -p, the Agent SDK, and third-party agent traffic move out of the Pro/Max subscription pool into a separate fixed monthly Agent SDK Credit pool. OCP, OLP's predecessor, was a proxy around a single CLI — its core assumption was "subscription = unlimited within rate limits". That assumption breaks for Anthropic on the effective date.

The structural response is to stop relying on one provider's subscription terms remaining favourable. OLP spreads risk across multiple providers whose subscriptions still include CLI/programmatic use, routes intelligently between them, and caches aggressively so every request that does spawn a CLI counts.

OLP is not: a commercial multi-tenant SaaS; an enterprise gateway competing with LiteLLM / OpenCode / CLIProxyAPI on breadth; a model-capability router ("route to the smartest model" — you pick the model); a conversation-state store (your client handles that).

See ALIGNMENT.md for OLP's constitution and docs/adr/ for the founding ADRs.


Quick Start

placeholder — lands with Phase 1.

Anticipated shape:

# install
npm install -g @dtzp555-max/olp

# run setup (writes ~/.olp/config.json, asks which providers to enable)
olp setup

# start the proxy (default port 3456 — same as OCP if you migrate)
olp start

# point your IDE at http://localhost:3456/v1/chat/completions with the OLP API key from `olp keys list`.

Supported Providers

Source of truth: models-registry.json. This table is regenerated from the registry per the release_kit overlay; do not edit it out of sync.

OLP distinguishes Candidate Providers (declared as intended, not yet pinned) from Enabled Providers (authority pin filled + plugin landed + Phase audit passed). The v0.1 founding commit ships zero Enabled Providers — enablement is a Phase audit deliverable, not a bootstrap claim. See ALIGNMENT.md § Provider Inventory for the transition gate.

Candidate Providers

Provider key CLI Subscription / auth Anticipated Tier Anticipated Phase
anthropic claude -p Pro / Max OAuth (pre-2026-06-15); Agent SDK Credit pool after D (re-eval post-2026-06-15) Phase 1
openai codex exec --json ChatGPT Pro OAuth or API key D Phase 2
mistral vibe --prompt --output json Le Chat Pro API key D Phase 3
grok grok -p --output-format streaming-json xAI Build xai-... API key C Phase 8+
kimi kimi -p --output-format stream-json Moonshot Kimi API key C Phase 8+
minimax TBD MiniMax Token Plan (¥29+/mo) B Phase 8+
glm TBD Zhipu Coding Plan ($10+/mo) B Phase 8+
qwen TBD Alibaba Coding Plan ($50/mo) B Phase 8+

Risk tier guide. D = permissive / safe (eligible for default-enabled); C = tightening signal, no enforcement history (opt-in); B = service-level key revocation risk (opt-in + consent); A = excluded by default (cannot be opt-in enabled). Tier B providers prompt for explicit consent on first enable and record consent in ~/.olp/config.json. See ALIGNMENT.md § Risk Tier Framework.

Excluded by default (Tier A — evidence-backed, pending primary-source pin). Google Antigravity. See ADR 0006 for the named-prohibition + no-cost-advantage + reinstatement-friction rationale, and for the primary-source pinning follow-up that may force a Tier reconsideration if the Google FAQ language cannot be sourced within 90 days of 2026-05-23.


Configuration

placeholder — full configuration reference lands with Phase 4 (fallback engine).

OLP reads its config from ~/.olp/config.json. The minimum useful shape:

{
  "routing": {
    "chains": {
      "<requested-model>": [
        { "provider": "<key>", "model": "<provider-model-id>" },
        { "provider": "<key>", "model": "<provider-model-id>" }
      ]
    },
    "soft_triggers": {
      "<provider-key>": { "<trigger>": <threshold> }
    }
  }
}

Trigger types, fallback safety, idempotency rules, and the full example config land here when Phase 4 ships. See ADR 0004 (Fallback Engine Semantics & Safety) for the design.


API Endpoints

placeholder — full table lands as each endpoint lands.

Endpoint Method Phase Description
/v1/chat/completions POST 1 OpenAI-compatible Chat Completions entry. Internally normalized to IR, dispatched to a provider plugin, response shape converted back.
/v1/models GET 1 Lists models from models-registry.json.
/health GET 1 Per-provider health snapshot (owner-only).
/cache/stats GET 5 Cache hit rate, by-provider breakdown.
/v0/management/quota GET 6 Per-provider quota / credit pool status (best-effort).
/dashboard GET 6 Owner-only dashboard (localhost-bound by default).

Environment Variables

placeholder — full table lands per-phase as variables are introduced.

Variable Default Description
OLP_PORT 3456 HTTP listener port.
OLP_HOME ~/.olp Config, providers, keys, cache, logs root.
OLP_LOG_LEVEL info One of error, warn, info, debug.

Further variables (per-provider auth path overrides, cache size limits, fallback-engine knobs) land with the relevant phase.


Response Headers

Every response served through OLP carries:

  • X-OLP-Provider-Used: <provider-key> — which provider's plugin served the request.
  • X-OLP-Model-Used: <model-id> — which model the served provider used.
  • X-OLP-Fallback-Hops: <n> — number of fallback hops (0 if served by the primary chain entry).
  • X-OLP-Cache: hit | miss | bypass — cache layer outcome.
  • X-OLP-Latency-Ms: <ms> — end-to-end latency observed at the proxy.

If a fallback chain is exhausted, X-OLP-Fallback-Exhausted lists the tried providers in order.


Architecture

OLP is a Node.js (ESM, .mjs) HTTP proxy with no build step and minimal dependencies. The high-level shape:

  • Entry surfaceserver.mjs handles /v1/chat/completions and the administrative endpoints. Governed by OpenAI's /v1/chat/completions specification as the wire authority. See ALIGNMENT.md § Authorities.
  • Intermediate Representation (IR)lib/ir/ normalizes between the entry surface and provider-native shapes. The IR is the lingua franca; any extension is an ADR 0003 amendment.
  • Provider pluginslib/providers/<name>.mjs. Each plugin implements the contract in ADR 0002 (Plugin Architecture for Providers), spawns its CLI, and translates between IR and provider-native IO.
  • Cache layerlib/cache/ is a content-addressed cache keyed on (provider, model, messages, tools, temperature, response_format, cache_control). Per-key isolation, prompt-caching bypass, chunked stream replay, and singleflight. See ADR 0005 (Cache Layer Cross-Provider Design).
  • Fallback enginelib/fallback/ advances a configured chain one provider at a time on configured triggers, never retrying after the first response chunk has been emitted to the client. See ADR 0004.
  • Multi-key authlib/keys.mjs carries OCP's per-OLP-key namespace isolation forward. Each OLP API key has independent quota, cache namespace, and audit log; each key declares which providers it can access.

Read the ADRs in docs/adr/ in order before proposing structural changes.


Phase plan

OLP lands in phases. Each phase has its own PR series and Iron-Rule-10 reviewer; this README's placeholders are filled per-phase via the release_kit overlay.

  • Phase 0 — Repo bootstrap, ALIGNMENT.md, founding ADRs, CI workflows, PR template. (current)
  • Phase 1 — server.mjs skeleton, IR, Anthropic plugin, cache D1+D4. Port from OCP.
  • Phase 2 — OpenAI Codex plugin.
  • Phase 3 — Mistral Vibe plugin.
  • Phase 4 — Fallback engine + routing chains config + quota poll worker.
  • Phase 5 — Cache cross-provider hardening (D2+D3).
  • Phase 6 — Dashboard + observability (/v0/management/quota).
  • Phase 7 — Release v0.1, OCP enters maintenance.
  • Phase 8+ — Optional Grok / Kimi / tier-2 plugins; provider-native protocol endpoints; deterministic triggers.

Full spec (decision rationale, open questions, risks): ~/.cc-rules/memory/projects/olp_v0_1_spec.md on the maintainer's workstations.


Migration from OCP

placeholder — scripts/migrate-from-ocp.mjs lands with Phase 7.

Anticipated user-facing flow (target: <5 minutes):

  1. Stop OCP (launchctl bootout the OCP service or ocp stop).
  2. Install OLP.
  3. Run olp migrate-from-ocp — copies ~/.ocp/keys/ to ~/.olp/keys/ and points provider plugins at OCP's existing auth artifacts where applicable.
  4. Start OLP. Clients pointing at port 3456 keep working; their existing OLP API keys remain valid.

OCP's cache directory is not migrated: OLP's cache key format includes provider+model and warms cold naturally. OCP enters maintenance mode (stability fixes only) when OLP v0.1 ships; new development happens in OLP.


License

MIT.


Acknowledgements

OLP evolved from OCP (Open Claude Proxy). OCP's per-key isolation model, cache-layer design (D1D4), dashboard, and alignment-constitution discipline are all carried forward. The structural generalization from single-CLI to multi-provider is what makes this a new project rather than an OCP minor version — see ALIGNMENT.md § Reference: How OCP's cli.js discipline maps to OLP.

Authors: project maintainer (with AI drafting assistance).

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