ci: run tests on release-please PRs

README.md

@@ -182,13 +182,15 @@ for all 9 per-language benchmark deep dives.
 
 All configuration is via environment variables:
 
-| Variable                 | Default                  | Description                                |
-| ------------------------ | ------------------------ | ------------------------------------------ |
-| `LUMEN_EMBED_MODEL`      | see note ¹               | Embedding model (must be in registry)      |
-| `LUMEN_BACKEND`          | `ollama`                 | Embedding backend (`ollama` or `lmstudio`) |
-| `OLLAMA_HOST`            | `http://localhost:11434` | Ollama server URL                          |
-| `LM_STUDIO_HOST`         | `http://localhost:1234`  | LM Studio server URL                       |
-| `LUMEN_MAX_CHUNK_TOKENS` | `512`                    | Max tokens per chunk before splitting      |
+| Variable                 | Default                  | Description                                                   |
+| ------------------------ | ------------------------ | ------------------------------------------------------------- |
+| `LUMEN_EMBED_MODEL`      | see note ¹               | Embedding model; use with `LUMEN_EMBED_DIMS` for unlisted models |
+| `LUMEN_BACKEND`          | `ollama`                 | Embedding backend (`ollama` or `lmstudio`)                    |
+| `OLLAMA_HOST`            | `http://localhost:11434` | Ollama server URL                                             |
+| `LM_STUDIO_HOST`         | `http://localhost:1234`  | LM Studio server URL                                          |
+| `LUMEN_MAX_CHUNK_TOKENS` | `512`                    | Max tokens per chunk before splitting                         |
+| `LUMEN_EMBED_DIMS`       | —                        | Override embedding dimensions (required for unlisted models)  |
+| `LUMEN_EMBED_CTX`        | `8192` (unlisted models) | Override context window length                                |
 
 ¹ `ordis/jina-embeddings-v2-base-code` (Ollama),
 `nomic-ai/nomic-embed-code-GGUF` (LM Studio)
@@ -210,6 +212,22 @@ Dimensions and context length are configured automatically per model:
 Switching models creates a separate index automatically. The model name is part
 of the database path hash, so different models never collide.
 
+### Using a custom or unlisted model
+
+If your model is not in the registry above, set `LUMEN_EMBED_DIMS` to bypass the
+registry check. `LUMEN_EMBED_CTX` is optional and defaults to `8192`.
+
+Both variables can also override values for _known_ models — useful when running
+a model variant with a longer context window or different output dimensions.
+
+```sh
+LUMEN_BACKEND=lmstudio
+LM_STUDIO_HOST=http://localhost:8801
+LUMEN_EMBED_MODEL=mlx-community/Qwen3-Embedding-8B-4bit-DWQ
+LUMEN_EMBED_DIMS=4096
+LUMEN_EMBED_CTX=40960   # optional, defaults to 8192
+```
+
 ## Controlling what gets indexed
 
 Lumen filters files through six layers: built-in directory and lock file skips →

internal/config/config.go

@@ -59,21 +59,27 @@ func Load() (Config, error) {
 
 	model := EnvOrDefault("LUMEN_EMBED_MODEL", defaultModel)
 
-	// Allow fully custom models via LUMEN_EMBED_DIMS + LUMEN_EMBED_CTX,
-	// bypassing the KnownModels registry. Useful for any OpenAI-compat server.
-	var dims, ctxLength int
-	if d := EnvOrDefaultInt("LUMEN_EMBED_DIMS", 0); d > 0 {
-		dims = d
-		ctxLength = EnvOrDefaultInt("LUMEN_EMBED_CTX", 8192)
-	} else {
-		spec, ok := embedder.KnownModels[model]
-		if !ok {
-			return Config{}, fmt.Errorf("unknown embedding model %q: set LUMEN_EMBED_DIMS to use an unlisted model", model)
-		}
-		dims = spec.Dims
-		ctxLength = spec.CtxLength
+	overrideDims := EnvOrDefaultInt("LUMEN_EMBED_DIMS", 0)
+	overrideCtx := EnvOrDefaultInt("LUMEN_EMBED_CTX", 0)
+
+	spec, modelKnown := embedder.KnownModels[model]
+	if !modelKnown && overrideDims == 0 {
+		return Config{}, fmt.Errorf("unknown embedding model %q: set LUMEN_EMBED_DIMS to use an unlisted model", model)
 	}
 
+	dims := spec.Dims
+	ctxLength := spec.CtxLength
+
+	if overrideDims > 0 {
+		dims = overrideDims
+	}
+	if overrideCtx > 0 {
+		ctxLength = overrideCtx
+	} else if !modelKnown {
+		ctxLength = 8192
+	}
+
+
 	return Config{
 		Model:          model,
 		Dims:           dims,

internal/config/config_test.go

@@ -29,6 +29,102 @@ func TestEnvOrDefaultInt(t *testing.T) {
 	}
 }
 
+func TestLoad(t *testing.T) {
+	tests := []struct {
+		name        string
+		model       string
+		dims        string
+		ctx         string
+		wantDims    int
+		wantCtx     int
+		wantErr     bool
+	}{
+		{
+			name:     "known model no overrides",
+			model:    "ordis/jina-embeddings-v2-base-code",
+			wantDims: 768,
+			wantCtx:  8192,
+		},
+		{
+			name:     "unknown model with DIMS only",
+			model:    "custom-model",
+			dims:     "4096",
+			wantDims: 4096,
+			wantCtx:  8192,
+		},
+		{
+			name:     "unknown model with DIMS and CTX",
+			model:    "custom-model",
+			dims:     "4096",
+			ctx:      "40960",
+			wantDims: 4096,
+			wantCtx:  40960,
+		},
+		{
+			name:    "unknown model no DIMS",
+			model:   "custom-model",
+			wantErr: true,
+		},
+		{
+			name:    "unknown model CTX only no DIMS",
+			model:   "custom-model",
+			ctx:     "8192",
+			wantErr: true,
+		},
+		{
+			name:     "known model DIMS override",
+			model:    "ordis/jina-embeddings-v2-base-code",
+			dims:     "512",
+			wantDims: 512,
+			wantCtx:  8192,
+		},
+		{
+			name:     "known model CTX override",
+			model:    "ordis/jina-embeddings-v2-base-code",
+			ctx:      "16384",
+			wantDims: 768,
+			wantCtx:  16384,
+		},
+		{
+			name:     "known model both overrides",
+			model:    "ordis/jina-embeddings-v2-base-code",
+			dims:     "512",
+			ctx:      "4096",
+			wantDims: 512,
+			wantCtx:  4096,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Setenv("LUMEN_EMBED_MODEL", tc.model)
+			if tc.dims != "" {
+				t.Setenv("LUMEN_EMBED_DIMS", tc.dims)
+			}
+			if tc.ctx != "" {
+				t.Setenv("LUMEN_EMBED_CTX", tc.ctx)
+			}
+
+			cfg, err := Load()
+			if tc.wantErr {
+				if err == nil {
+					t.Fatal("expected error, got nil")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if cfg.Dims != tc.wantDims {
+				t.Errorf("Dims: got %d, want %d", cfg.Dims, tc.wantDims)
+			}
+			if cfg.CtxLength != tc.wantCtx {
+				t.Errorf("CtxLength: got %d, want %d", cfg.CtxLength, tc.wantCtx)
+			}
+		})
+	}
+}
+
 func TestDBPathForProject(t *testing.T) {
 	t.Run("deterministic", func(t *testing.T) {
 		p1 := DBPathForProject("/home/user/project", "model-a")