feat: add --context flag to set model context window

AGENTS.md

@@ -21,7 +21,7 @@ Run a single test: `go test -run TestWriteConfig_Idempotent ./...`
 ## Layout
 
 - `main.go` — CLI: command dispatch (`add`/`remove`/`list`), flag parsing (`parseSelection` registers both long and short flags against the same vars), and user-facing output.
-- `catalog.go` — the embedded provider catalogue (`//go:embed providers.yaml`), its types, and `buildProviderBlock`, which turns a provider+family+model selection into an opencode provider block. The catalogue can be overridden at runtime via the `--providers`/`-c` flag or `OC_CONFIG_PROVIDERS` env var (flag > env > embedded; see `resolveCatalogPath`/`loadCatalogFrom`).
+- `catalog.go` — the embedded provider catalogue (`//go:embed providers.yaml`), its types, and `buildProviderBlock`, which turns a provider+family+model selection into an opencode provider block. The catalogue can be overridden at runtime via the `--providers` flag or `OC_CONFIG_PROVIDERS` env var (flag > env > embedded; see `resolveCatalogPath`/`loadCatalogFrom`).
 - `config.go` — opencode config IO: JSONC read/merge/write, env/key resolution, JSON-Pointer helpers.
 - `providers.yaml` — externalised provider/model-family data (URLs, model ids, key env vars). **Add providers/models here, not in Go.** Embedded at build time but kept external for maintenance.
 - `*_test.go` — `catalog_test.go` (catalogue integrity + `buildProviderBlock`), `config_test.go` (merge/remove/IO), `main_test.go` (CLI layer).

README.md

@@ -56,11 +56,11 @@ Then just run `opencode`.
 
 ```sh
 oc-config list
-oc-config add    --provider <name> [--model-family <family>] [--model <id>] [--base-url <url>]
+oc-config add    --provider <name> [--model-family <family>] [--model <id>] [--context <size>] [--base-url <url>]
 oc-config remove --provider <name> [--model-family <family>] [--model <id>]
 ```
 
-Short flags: `-p` (provider), `-f` (model-family), `-m` (model), `-b` (base-url).
+Short flags: `-p` (provider), `-f` (model-family), `-m` (model), `-c` (context), `-b` (base-url).
 
 ### Examples
 
@@ -78,6 +78,10 @@ OPENAI_API_KEY=sk-... \
 # Pin a specific default model
 oc-config add -p openrouter -f deepseek-v4 -m deepseek/deepseek-v4-pro
 
+# Set the context window — human suffixes or an absolute count, both fine
+oc-config add -p llamacpp -m my-model -c 128k
+oc-config add -p llamacpp -m my-model --context 200000
+
 # Take a provider back out
 oc-config remove -p ollama
 
@@ -88,6 +92,10 @@ oc-config remove -p openrouter -f deepseek-v4
 `add` sets the chosen model as opencode's default. `remove` clears the default
 if it pointed at something you removed.
 
+`--context`/`-c` records each added model's context window. Parsing is
+forgiving: `128k`, `1m`, `1.5m`, `200000`, `128,000`, even `128 K tokens` all
+land where you'd expect (`k`/`m`/`g` are decimal — `128k` is 128,000 tokens).
+
 ## Keys and endpoints
 
 Each provider declares which environment variable holds its key (`oc-config
@@ -125,7 +133,7 @@ Don't want to rebuild? Point `oc-config` at your own catalogue at runtime — th
 flag wins, then the env var, then the built-in default:
 
 ```sh
-oc-config list --providers ./my-providers.yaml   # or: -c
+oc-config list --providers ./my-providers.yaml
 OC_CONFIG_PROVIDERS=./my-providers.yaml oc-config list
 ```
 

context.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// parseContextSize parses a human-friendly context window size into a token
+// count. It is deliberately lenient: surrounding whitespace, commas, and
+// underscores are ignored, an optional k/m/g/t suffix is honoured
+// (case-insensitive, decimal — k=1e3, m=1e6, g/b=1e9, t=1e12), a fractional
+// value may precede a suffix (e.g. "1.5m"), and a trailing "tokens"/"tok" word
+// is tolerated. So "128k", "128,000", "128_000", "  128 K tokens ", and
+// "0.128m" all parse to 128000.
+func parseContextSize(s string) (int, error) {
+	orig := s
+	// Normalise: drop separators, lowercase, strip a trailing "tokens" word.
+	s = strings.ToLower(strings.TrimSpace(s))
+	s = strings.NewReplacer(",", "", "_", "", " ", "").Replace(s)
+	for _, suf := range []string{"tokens", "token", "toks", "tok"} {
+		if strings.HasSuffix(s, suf) {
+			s = strings.TrimSuffix(s, suf)
+			break
+		}
+	}
+
+	mult := 1.0
+	if n := len(s); n > 0 {
+		switch s[n-1] {
+		case 'k':
+			mult, s = 1e3, s[:n-1]
+		case 'm':
+			mult, s = 1e6, s[:n-1]
+		case 'g', 'b':
+			mult, s = 1e9, s[:n-1]
+		case 't':
+			mult, s = 1e12, s[:n-1]
+		}
+	}
+
+	if s == "" {
+		return 0, fmt.Errorf("invalid context size %q", orig)
+	}
+	val, err := strconv.ParseFloat(s, 64)
+	if err != nil {
+		return 0, fmt.Errorf("invalid context size %q", orig)
+	}
+	tokens := val * mult
+	if tokens < 1 {
+		return 0, fmt.Errorf("context size %q must be at least 1 token", orig)
+	}
+	return int(tokens), nil
+}
+
+// applyContextSize sets limit.context on every model in models, merging into
+// any existing limit map rather than replacing it. The model values are the
+// map[string]any entries produced by buildProviderBlock.
+func applyContextSize(models map[string]any, ctx int) {
+	for k, v := range models {
+		m, ok := v.(map[string]any)
+		if !ok {
+			m = map[string]any{}
+		}
+		limit, ok := m["limit"].(map[string]any)
+		if !ok {
+			limit = map[string]any{}
+		}
+		limit["context"] = ctx
+		m["limit"] = limit
+		models[k] = m
+	}
+}

context_test.go

@@ -0,0 +1,94 @@
+package main
+
+import "testing"
+
+func TestParseContextSize_Lenient(t *testing.T) {
+	// Each input must parse to the same 128000-token window, exercising the
+	// suffix, separator, whitespace, fraction, and trailing-word leniency.
+	for _, in := range []string{
+		"128000",
+		"128,000",
+		"128_000",
+		"128k",
+		"128K",
+		"  128 k ",
+		"128 K tokens",
+		"128ktok",
+		"0.128m",
+	} {
+		got, err := parseContextSize(in)
+		if err != nil {
+			t.Errorf("parseContextSize(%q) errored: %v", in, err)
+			continue
+		}
+		if got != 128000 {
+			t.Errorf("parseContextSize(%q) = %d, want 128000", in, got)
+		}
+	}
+}
+
+func TestParseContextSize_Suffixes(t *testing.T) {
+	cases := map[string]int{
+		"200000": 200000,
+		"1m":     1_000_000,
+		"1M":     1_000_000,
+		"1.5m":   1_500_000,
+		"2g":     2_000_000_000,
+		"3b":     3_000_000_000,
+		"1t":     1_000_000_000_000,
+		"32k":    32_000,
+	}
+	for in, want := range cases {
+		got, err := parseContextSize(in)
+		if err != nil {
+			t.Errorf("parseContextSize(%q) errored: %v", in, err)
+			continue
+		}
+		if got != want {
+			t.Errorf("parseContextSize(%q) = %d, want %d", in, got, want)
+		}
+	}
+}
+
+func TestParseContextSize_Invalid(t *testing.T) {
+	for _, in := range []string{
+		"",        // empty
+		"   ",     // blank
+		"abc",     // not a number
+		"k",       // suffix only, no value
+		"12x",     // unknown suffix folds into the number and fails
+		"0",       // below one token
+		"-5k",     // negative
+		"0.0001k", // rounds below one token
+	} {
+		if got, err := parseContextSize(in); err == nil {
+			t.Errorf("parseContextSize(%q) = %d, want error", in, got)
+		}
+	}
+}
+
+func TestApplyContextSize(t *testing.T) {
+	// A model with an existing limit must keep sibling limit keys.
+	models := map[string]any{
+		"a": map[string]any{"name": "A"},
+		"b": map[string]any{"name": "B", "limit": map[string]any{"output": 8192}},
+		"c": "not-a-map", // hardened against unexpected shapes
+	}
+	applyContextSize(models, 200000)
+
+	a := models["a"].(map[string]any)["limit"].(map[string]any)
+	if a["context"] != 200000 {
+		t.Errorf("model a context = %v, want 200000", a["context"])
+	}
+	b := models["b"].(map[string]any)["limit"].(map[string]any)
+	if b["context"] != 200000 {
+		t.Errorf("model b context = %v, want 200000", b["context"])
+	}
+	if b["output"] != 8192 {
+		t.Errorf("model b output limit not preserved: %v", b["output"])
+	}
+	c := models["c"].(map[string]any)["limit"].(map[string]any)
+	if c["context"] != 200000 {
+		t.Errorf("non-map model c was not normalised: %v", c)
+	}
+}

docs/llamacpp/gemma4.md

@@ -118,6 +118,13 @@ oc-config add -p llamacpp -m gemma-4-12b-it
 The model name is just a label — `llama-server` serves whichever model it has
 loaded regardless of what's requested — so call it whatever you find readable.
 
+Match opencode's context window to the `--ctx-size` you launched the server
+with, so it doesn't overshoot what `llama-server` will accept:
+
+```sh
+oc-config add -p llamacpp -m gemma-4-12b-it --context 32k
+```
+
 Running on a non-default host or port? Point the provider at it with the
 `--base-url`/`-b` flag (or `LLAMACPP_BASE_URL`):
 

docs/llamacpp/qwen3.6.md

@@ -93,6 +93,13 @@ oc-config add -p llamacpp -m qwen3.6-35b-a3b
 The model name is just a label — `llama-server` serves whichever model it has
 loaded regardless of what's requested — so call it whatever you find readable.
 
+Match opencode's context window to the `--ctx-size` you launched the server
+with, so it doesn't overshoot what `llama-server` will accept:
+
+```sh
+oc-config add -p llamacpp -m qwen3.6-35b-a3b --context 32k
+```
+
 Running on a non-default host or port? Point the provider at it with the
 `--base-url`/`-b` flag (or `LLAMACPP_BASE_URL`):
 

main.go

@@ -12,7 +12,8 @@
 //	oc-config add    --provider <name> [--model-family <family>] [--model <id>]
 //	oc-config remove --provider <name> [--model-family <family>] [--model <id>]
 //
-// Short flags: -p (provider), -f (model-family), -m (model), -b (base-url).
+// Short flags: -p (provider), -f (model-family), -m (model), -c (context),
+// -b (base-url).
 //
 // The API base URL can be overridden for any provider with --base-url/-b or the
 // OC_CONFIG_BASE_URL environment variable; the flag wins over the env var, and
@@ -60,20 +61,23 @@ func usage() {
 
 Usage:
   oc-config list
-  oc-config add    --provider <name> [--model-family <family>] [--model <id>]
+  oc-config add    --provider <name> [--model-family <family>] [--model <id>] [--context <size>]
   oc-config remove --provider <name> [--model-family <family>] [--model <id>]
 
 Flags:
   -p, --provider       provider name (see `+"`oc-config list`"+`)
   -f, --model-family   model family to add or remove
   -m, --model          model id to set as default / to add or remove
+  -c, --context        context window size for the added model(s); accepts
+                       human suffixes (128k, 1m) or an absolute count (200000)
   -b, --base-url       override the provider API base URL
                        (or set OC_CONFIG_BASE_URL)
-  -c, --providers      path to a providers.yaml override
+      --providers      path to a providers.yaml override
                        (or set OC_CONFIG_PROVIDERS)
 
 add: deep-merges the provider into the opencode config, preserving everything
-     else. Specify a family and/or an explicit model.
+     else. Specify a family and/or an explicit model. --context sets the
+     model's limit.context window.
 remove: removes the provider, or just the named models when a family/model is
         given. Clears the default model if it pointed at something removed.
 `)
@@ -84,6 +88,7 @@ type selection struct {
 	provider  string
 	family    string
 	model     string
+	context   string
 	providers string
 	baseURL   string
 }
@@ -97,8 +102,9 @@ func parseSelection(name string, args []string) (selection, error) {
 	fs.StringVar(&s.family, "f", "", "model family (shorthand)")
 	fs.StringVar(&s.model, "model", "", "model id")
 	fs.StringVar(&s.model, "m", "", "model id (shorthand)")
+	fs.StringVar(&s.context, "context", "", "context window size (e.g. 128k, 1m, 200000)")
+	fs.StringVar(&s.context, "c", "", "context window size (shorthand)")
 	fs.StringVar(&s.providers, "providers", "", "path to a providers.yaml override")
-	fs.StringVar(&s.providers, "c", "", "providers.yaml override (shorthand)")
 	fs.StringVar(&s.baseURL, "base-url", "", "override the provider API base URL")
 	fs.StringVar(&s.baseURL, "b", "", "API base URL override (shorthand)")
 	if err := fs.Parse(args); err != nil {
@@ -133,6 +139,19 @@ func cmdAdd(args []string) error {
 		return err
 	}
 
+	var contextSize int
+	if sel.context != "" {
+		contextSize, err = parseContextSize(sel.context)
+		if err != nil {
+			return err
+		}
+		models, _ := block["models"].(map[string]any)
+		if len(models) == 0 {
+			return fmt.Errorf("--context/-c needs a model: specify --model-family/-f and/or --model/-m")
+		}
+		applyContextSize(models, contextSize)
+	}
+
 	configFile, err := resolveConfigFile()
 	if err != nil {
 		return err
@@ -150,6 +169,9 @@ func cmdAdd(args []string) error {
 	if defaultModel != "" {
 		fmt.Printf("Default model: %s\n", defaultModel)
 	}
+	if contextSize > 0 {
+		fmt.Printf("Context window: %d tokens\n", contextSize)
+	}
 	if opts, ok := block["options"].(map[string]any); ok {
 		if _, ok := opts["apiKey"]; ok {
 			fmt.Printf("API key injected from %s.\n", p.APIKeyEnv)
@@ -217,7 +239,6 @@ func cmdList(args []string) error {
 	fs := flag.NewFlagSet("list", flag.ContinueOnError)
 	var providers string
 	fs.StringVar(&providers, "providers", "", "path to a providers.yaml override")
-	fs.StringVar(&providers, "c", "", "providers.yaml override (shorthand)")
 	if err := fs.Parse(args); err != nil {
 		return err
 	}