ADR 0004 § Decision § Chain advancement step 4 promised a per-hop
failure detail debug header `X-OLP-Fallback-Detail`. From D9 through
D39 the engine logged per-hop events (D28 added correlation fields)
but never surfaced the failure trail on the response. D40 fulfills
the promise via Option A — ungated v0.1 emission. Phase 2 will
re-introduce owner-vs-non-owner gating when `lib/keys.mjs` lands.
**Per-hop tuple collection** (lib/fallback/engine.mjs)
executeWithFallback now collects `fallbackDetail` — an array of per-hop
tuples — and returns it on EVERY return shape (success / client-error /
AUTH_MISSING / non-trigger / chain-exhausted). Soft-trigger skipped
hops are also recorded with `trigger_type: 'soft'` (currently dead-
code-by-config per ADR 0004 Amendment 2; shape forward-compatible).
Tuple shape (reuses D28 log-event field shapes so logs and the header
pivot on the same keys):
```
{
hop: <0-indexed hop number>,
provider: <provider name>,
model: <model name from IR>,
code: <ProviderError code, engine-synthetic SOFT_TRIGGER, or 'UNKNOWN'>,
error_message: <truncated to 200 chars with ellipsis on overflow>,
trigger_type: 'hard' | 'soft' | 'client_error' | 'auth_missing' | 'unclassified'
}
```
**Header serialiser** (server.mjs)
- `FALLBACK_DETAIL_BYTE_CAP = 4096` (UTF-8 bytes).
- `serializeFallbackDetailHeader(fallbackDetail)` exported. Returns
`null` for empty/null/undefined → caller omits the header.
- `jsonStringifyAscii` escapes every non-ASCII code point as `\uXXXX`
to satisfy RFC 7230 §3.2.6 field-vchar (Node's HTTP header validator
rejects multi-byte UTF-8). The D38 CONCURRENCY_LIMIT synthesised
message contains a U+2014 em dash — without this escape, every
CONCURRENCY_LIMIT response crashed at writeHead with
"Invalid character in header content". The regression test pins
this exact string.
- 4KB cap algorithm: builds candidates as `[...slice(0, kept), sentinel]`
and measures the FULL serialised length (including sentinel) before
comparing against the cap, so the result is guaranteed under cap.
Tail tuples dropped one at a time. Sentinel form:
`{ truncated: true, omitted_hops: N }`.
**Header emission** (server.mjs)
- `withFallbackDetailHeader(base, fallbackDetail)` wraps the base
header object; emits the header only when serialiser returns
non-null.
- Emitted on chain-exhausted, non-trigger-error, client-error,
AUTH_MISSING, and success-with-prior-failure paths.
- ABSENT on clean primary success — verified by a dedicated HTTP
integration test.
**Tests** (test-features.mjs): 452 → 468 (+16):
- Engine-level tuple shape: 2-hop/exhausted, 2-hop/success-with-prior-
failure, 1-hop/success (empty array), 1-hop/fail, non-ProviderError-
yields-UNKNOWN, 500-char-message → 200-char-with-ellipsis, client
error → 1 tuple + client_error trigger type
- Serialiser: empty/null → null, small array round-trip, >4KB cap
with `{truncated:true,omitted_hops:N}` sentinel, RFC 7230 newline/CR
escaping, non-ASCII escaping (em dash regression guard for the D38
CONCURRENCY_LIMIT synthesised message)
- HTTP integration: clean-1-hop-success (header absent), 2-hop-
exhausted (2 tuples on the wire), 2-hop-success-with-prior-failure
(1 tuple on the wire)
Pre-commit fold-in (per evidence-first checkpoint #4):
- **Reviewer Suggestion #2**: `jsonStringifyAscii` regex character
class `[U+0080-U+FFFF]` contains an invisible U+0080 boundary marker
that editors render as nothing, making the line easy to misread as
the empty class `[-...]`. Folded in a 5-line comment block above
the function body explaining the literal byte range and citing
RFC 7230 §3.2.6.
Two reviewer suggestions not folded:
- **Suggestion #1**: AUTH_MISSING tuple path lacks a dedicated D40
test. Code is structurally correct (tuple pushed before early-
return); low priority. Future polish.
- **Suggestion #3**: defensive `err.code != null` guard. Extremely
low priority — PROVIDER_ERROR_CODES is a closed enum with no
falsy values.
**ADR amendments** (docs/adr/0004-fallback-engine.md)
- Amendment 5 added at top of amendments stack — full tuple schema,
cap behavior, RFC 7230 hygiene, ungated v0.1 rationale, Phase 2
follow-up.
- § Chain advancement step 4 updated to remove TBD / not-yet-
implemented qualifiers and cross-reference Amendment 5.
- § Observability headers section gains the X-OLP-Fallback-Detail
schema as IMPLEMENTED at v0.1.
**CHANGELOG.md** — D40 sub-entry appended under existing D38/D39
entries in Unreleased section. No package.json bump per
phase_rolling_mode.
Authority:
- ADR 0004 § Decision § Chain advancement step 4 — D40 fulfils
the promise
- ADR 0004 Amendment 5 (this commit) — implementation contract
- ADR 0004 § Observability headers — updated to IMPLEMENTED state
- D18 (5 standard X-OLP-* headers) — D40 builds on this convention
- D28 (per-hop structured log fields) — D40 reuses the field shapes
- GitHub issue #7 — closed by this commit
- CC 开发铁律 v1.6 § 10.x — fresh-context opus reviewer independent
- CLAUDE.md release_kit_overlay phase_rolling_mode — no version bump
Reviewer (Iron Rule v1.6 § 10.x Mode A, fresh-context opus,
independent of drafter): APPROVE. Critical depth checks:
- Tuple pushed once per hop, BEFORE client-error / AUTH_MISSING
early-return branches — both paths include the failing tuple
- fallbackDetail returned on all 5 return paths (verified line by line)
- Cap algorithm measures FULL serialised length (with sentinel)
before comparing — no overshoot
- RFC 7230 compliance verified end-to-end: imported the function
in Node, confirmed em-dash → —, unescaped form throws
"Invalid character in header content"
- Serialiser handles null / undefined / [] gracefully → header
absent on clean primary success (HTTP test pins this)
- Hygiene: 0 hits for personal markers, home paths, tokens
- 468/468 tests pass in reviewer's independent npm test run
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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> }
}
}
}
Note:
routing.soft_triggersthresholds are parsed and stored but have no runtime effect at v0.1 — the quota polling path (quotaStatus()per hop) is deferred to v1.x per ADR 0004 Amendment 2. The evaluation logic exists and is tested; only the production data ingestion path is deferred.
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 | Status | Description |
|---|---|---|---|---|
/v1/chat/completions |
POST | 1 | ✅ Shipped | OpenAI-compatible Chat Completions entry. Internally normalized to IR, dispatched to a provider plugin, response shape converted back. |
/v1/models |
GET | 1 | ✅ Shipped | Lists models from models-registry.json. |
/health |
GET | 1 | ✅ Shipped | Per-provider health snapshot (owner-only). |
/cache/stats |
GET | 5 | 📋 Planned | Cache hit rate, by-provider breakdown. |
/v0/management/quota |
GET | 6 | 📋 Planned | Per-provider quota / credit pool status (best-effort). |
/dashboard |
GET | 6 | 📋 Planned | 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_CLAUDE_BIN |
claude (from PATH) |
Override path to the claude binary (Anthropic provider). Useful when multiple claude installs are present. |
OLP_CODEX_BIN |
codex (from PATH) |
Override path to the codex binary (OpenAI provider). |
OLP_VIBE_BIN |
vibe (from PATH) |
Override path to the vibe binary (Mistral provider). |
Per-provider auth env vars
These variables configure credential discovery for each provider plugin. Setting the correct one for your provider is usually required for OLP to make successful requests.
Anthropic (claude -p)
| Variable | Default behavior | Description |
|---|---|---|
CLAUDE_CODE_OAUTH_TOKEN |
Searches ~/.claude/.credentials.json first, then macOS keychain (darwin only) |
Directly supplies the OAuth access token. Highest-precedence override; bypasses all credential-discovery logic. Useful in CI/headless environments where the keychain is unavailable. |
OpenAI Codex (codex exec --json)
| Variable | Default behavior | Description |
|---|---|---|
OPENAI_CODEX_AUTH_PATH |
~/.codex/auth.json (or $CODEX_HOME/auth.json) |
Overrides the full path to the Codex auth artifact. When set, no other path is tried; missing or malformed file returns null (no auth). Useful for CI test fixtures. |
CODEX_HOME |
~/.codex |
Overrides the Codex home directory. $CODEX_HOME/auth.json becomes the default auth path. Ignored when OPENAI_CODEX_AUTH_PATH is set explicitly. |
Mistral Vibe (vibe --prompt)
| Variable | Default behavior | Description |
|---|---|---|
MISTRAL_API_KEY |
Reads $VIBE_HOME/.env (default ~/.vibe/.env) |
Directly supplies the Mistral API key. Highest-precedence override per DOCS-2; bypasses .env file lookup. |
MISTRAL_VIBE_AUTH_PATH |
~/.vibe/.env (or $VIBE_HOME/.env) |
Overrides the full path to the Vibe .env auth file. Evaluated only when MISTRAL_API_KEY is not set. When set, no other path is tried; missing or malformed file returns null (no auth). |
VIBE_HOME |
~/.vibe |
Overrides the Vibe home directory. $VIBE_HOME/.env becomes the default auth path. Ignored when MISTRAL_API_KEY or MISTRAL_VIBE_AUTH_PATH is set explicitly. |
📋 Planned (Phase 2) — not yet read by the codebase:
OLP_HOME(~/.olp) — Config, providers, keys, cache, logs root. Currently hardcoded to~/.olp/config.jsoninloadFallbackConfigSync; the env override path is a Phase 2 config-layer deliverable.OLP_LOG_LEVEL(info) — Log level filter (error/warn/info/debug).logEventcurrently writes unconditionally; level filtering is a Phase 2 observability deliverable.
See also the Implementation status table.
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 (0if 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.
Implementation status (as of 2026-05-24)
Phase 1 is in progress. This table reflects what is currently shipped vs. what is designed for later phases.
| File / artifact | Status | Notes |
|---|---|---|
server.mjs |
✅ Shipped | HTTP listener + dispatcher |
lib/ir/ |
✅ Shipped | IR definition + serializers (ADR 0003) |
lib/providers/anthropic.mjs |
✅ Shipped | claude -p spawn-binary plugin |
lib/providers/codex.mjs |
✅ Shipped | codex exec --json plugin |
lib/providers/mistral.mjs |
✅ Shipped | vibe --prompt plugin |
lib/cache/keys.mjs |
✅ Shipped | Content-addressed key computation |
lib/cache/store.mjs |
✅ Shipped | In-memory Map (file-backed layout: 📋 Phase 2 storage adapter) |
lib/fallback/engine.mjs |
✅ Shipped | Trigger evaluation + chain advancement (ADR 0004) |
Soft trigger data path (quotaStatus() polling) |
📋 Planned (v1.x) | Evaluation logic shipped + tested; data ingestion deferred per ADR 0004 Amendment 2 |
models-registry.json |
✅ Shipped | SPOT for (provider, model) metadata |
test-features.mjs |
✅ Shipped | Comprehensive test suite covering IR, cache, fallback, and integration paths (CI: test.yml) |
lib/keys.mjs |
📋 Planned (Phase 2) | Multi-key auth, per-key namespacing, audit log |
dashboard.html |
📋 Planned (Phase 6) | Owner-only multi-provider dashboard |
docs/provider-caveats.md |
📋 Planned (Phase 3+) | Lossy-translation reference; for now documented inline in each plugin header |
docs/openai-spec-pin.md |
✅ Shipped (D30) | OpenAI spec snapshot for annual audit; v0.1 baseline pinned 2026-05-24 |
docs/alignment-audits/ |
📋 Planned | Output directory for annual alignment audits (first audit: 2027-05-14) |
scripts/migrate-from-ocp.mjs |
📋 Planned (Phase 7) | OCP → OLP migration tool |
setup.mjs |
📋 Planned | Setup wizard / initial config |
Architecture
OLP is a Node.js (ESM, .mjs) HTTP proxy with no build step and minimal dependencies. The high-level shape:
- Entry surface —
server.mjshandles/v1/chat/completionsand the administrative endpoints. Governed by OpenAI's/v1/chat/completionsspecification as the wire authority. SeeALIGNMENT.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 plugins —
lib/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 layer —
lib/cache/is a content-addressed cache keyed on the 11-field tuple defined in ADR 0005 § "Cache key composition (v1.0)" (provider, model, messages, tools, temperature, response_format, cache_control, max_tokens, top_p, stop, tool_choice — as of Amendment 2/D15). Per-key isolation, prompt-caching bypass, chunked stream replay, and singleflight. See ADR 0005 (Cache Layer Cross-Provider Design). Current backing store is an in-memory Map; file-backed storage is planned for Phase 2. - Fallback engine —
lib/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 auth —
lib/keys.mjs(📋 planned, Phase 2) will carry OCP's per-OLP-key namespace isolation forward. Each OLP API key will have 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.mjsskeleton, 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 (📋 planned, not yet authored).
Anticipated user-facing flow (target: <5 minutes):
- Stop OCP (
launchctl bootoutthe OCP service orocp stop). - Install OLP.
- Run
olp migrate-from-ocp— copies~/.ocp/keys/to~/.olp/keys/and points provider plugins at OCP's existing auth artifacts where applicable. - 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 (D1–D4), 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).