feat: restrict task invocation by caller

SPECIFICATION.md

@@ -581,6 +581,43 @@ expand: false
 ---
 ```
 
+#### 5.2.13 `allowed_surfaces` (optional)
+- **Type:** Array of strings
+- **Purpose:** Restrict task execution to matching invocation surfaces
+- **Default:** Unrestricted when omitted or empty
+- **Matching:** Case-insensitive OR logic across entries
+
+```yaml
+---
+allowed_surfaces:
+  - jira
+  - github
+---
+```
+
+The caller must configure its invocation surface with `WithSurface` or the
+`-surface` CLI flag. A restricted task rejects invocations with a missing or
+non-matching surface before task content is assembled.
+
+#### 5.2.14 `allowed_requesters` (optional)
+- **Type:** Array of strings
+- **Purpose:** Restrict task execution to matching requester usernames or email addresses
+- **Default:** Unrestricted when omitted or empty
+- **Matching:** Case-insensitive OR logic across entries
+
+```yaml
+---
+allowed_requesters:
+  - alice
+  - alice@example.com
+---
+```
+
+The caller must configure a requester with `WithCaller` or the `-caller` and
+`-caller-email` CLI flags. A username or email match permits the requester.
+When both `allowed_surfaces` and `allowed_requesters` are present, both
+restrictions must match.
+
 ### 5.3 Standard Rule Fields
 
 #### 5.3.1 `id` (optional)
@@ -1554,6 +1591,16 @@ Potential future additions while maintaining backward compatibility:
       "description": "Enable/disable parameter expansion",
       "default": true
     },
+    "allowed_surfaces": {
+      "type": "array",
+      "items": {"type": "string"},
+      "description": "Invocation surfaces permitted to run a task"
+    },
+    "allowed_requesters": {
+      "type": "array",
+      "items": {"type": "string"},
+      "description": "Requester usernames or email addresses permitted to run a task"
+    },
     "selectors": {
       "type": "object",
       "description": "Auto-filter rules",
@@ -1634,6 +1681,8 @@ Potential future additions while maintaining backward compatibility:
 | `timeout` | string | No | Timeout duration |
 | `selectors` | object | No | Auto-filter rules |
 | `expand` | boolean | No | Parameter expansion control |
+| `allowed_surfaces` | array | No | Permitted invocation surfaces |
+| `allowed_requesters` | array | No | Permitted requester usernames or email addresses |
 
 ### Rule Fields
 

docs/how-to/create-tasks.md

@@ -169,6 +169,45 @@ coding-context -s priority=high implement-feature
 
 **Note:** Language values should be lowercase (e.g., `go`, `python`, `javascript`).
 
+## Restricting Task Invocation
+
+Use `allowed_surfaces` and `allowed_requesters` to limit who may run a task and
+where the invocation may originate:
+
+```markdown
+---
+allowed_surfaces:
+  - jira
+  - github
+allowed_requesters:
+  - alice
+  - alice@example.com
+---
+# Deploy Service
+
+Deploy the requested service update.
+```
+
+Values within each list use case-insensitive OR logic. When both fields are
+present, the invocation must match both restrictions. Omitting a field or
+setting it to an empty list leaves that dimension unrestricted.
+
+Library callers provide trusted invocation data with `WithSurface` and
+`WithCaller`. Direct CLI callers use `-surface`, `-caller`, and optionally
+`-caller-email`:
+
+```bash
+coding-context \
+  -surface jira \
+  -caller alice \
+  -caller-email alice@example.com \
+  deploy-service
+```
+
+Restricted tasks reject missing or non-matching invocation data before task
+content is assembled. Linting validates the task file without enforcing
+invocation restrictions.
+
 ## Task Frontmatter
 
 Task frontmatter is used for filtering and metadata purposes but is **NOT included in the output**. The frontmatter controls behavior (like auto-filtering rules via the `selectors` field) but only the task content below the frontmatter delimiters is included in the assembled context.

docs/reference/cli.md

@@ -184,7 +184,7 @@ coding-context \
 
 ### `-a <agent>`
 
-**Type:** String  
+**Type:** String
 **Default:** (empty)
 
 Specify the target agent being used. This is currently used for:
@@ -216,6 +216,41 @@ coding-context -a copilot -w implement-feature
 
 **See also:** [Targeting a Specific Agent](../../README.md#targeting-a-specific-agent) in README
 
+### `-surface <surface>`
+
+**Type:** String
+**Default:** (empty)
+
+Set the invocation surface used to authorize a task that declares
+`allowed_surfaces`. Matching is case-insensitive. A restricted task rejects an
+empty or non-matching surface.
+
+### `-caller <username>`
+
+**Type:** String
+**Default:** (empty)
+
+Set the requester username used to authorize a task that declares
+`allowed_requesters`.
+
+### `-caller-email <email>`
+
+**Type:** String
+**Default:** (empty)
+
+Set the requester email address used to authorize a task that declares
+`allowed_requesters`. Either the configured username or email may match an
+allowed requester.
+
+**Example:**
+```bash
+coding-context \
+  -surface jira \
+  -caller alice \
+  -caller-email alice@example.com \
+  deploy-service
+```
+
 ### `-r`
 
 **Type:** Boolean flag  

main.go

@@ -18,11 +18,11 @@ import (
 )
 
 var (
-	errInvalidUsage          = errors.New("invalid usage: expected one task name argument and optional user-prompt")
-	errWriteRulesNoAgent     = errors.New("-w flag requires an agent to be specified (via task 'agent' field or -a flag)")
-	errNoUserRulePath        = errors.New("no user rule path available for agent")
-	errRulesPathEscapesHome  = errors.New("rules path escapes home directory")
-	errAgentFlagsMutExcl     = errors.New("-a and -A flags are mutually exclusive")
+	errInvalidUsage         = errors.New("invalid usage: expected one task name argument and optional user-prompt")
+	errWriteRulesNoAgent    = errors.New("-w flag requires an agent to be specified (via task 'agent' field or -a flag)")
+	errNoUserRulePath       = errors.New("no user rule path available for agent")
+	errRulesPathEscapesHome = errors.New("rules path escapes home directory")
+	errAgentFlagsMutExcl    = errors.New("-a and -A flags are mutually exclusive")
 )
 
 type cliConfig struct {
@@ -37,6 +37,8 @@ type cliConfig struct {
 	searchPaths        []string
 	lenientSearchPaths []string
 	manifestURL        string
+	surface            string
+	caller             codingcontext.CallerIdentity
 	taskName           string
 	userPrompt         string
 }
@@ -81,6 +83,8 @@ func run(ctx context.Context, logger *slog.Logger) error {
 		codingcontext.WithUserPrompt(cfg.userPrompt),
 		codingcontext.WithAgent(cfg.agent),
 		codingcontext.WithLenientAgent(cfg.lenientAgent),
+		codingcontext.WithSurface(cfg.surface),
+		codingcontext.WithCaller(cfg.caller),
 	)
 
 	result, err := cc.Run(ctx, cfg.taskName)
@@ -156,6 +160,12 @@ func parseFlags(logger *slog.Logger) (*cliConfig, error) {
 		})
 	flag.StringVar(&cfg.manifestURL, "m", "",
 		"Go Getter URL to a manifest file containing search paths (one per line). Every line is included as-is.")
+	flag.StringVar(&cfg.surface, "surface", "",
+		"Invocation surface used to authorize tasks that declare allowed_surfaces.")
+	flag.StringVar(&cfg.caller.Username, "caller", "",
+		"Requester username used to authorize tasks that declare allowed_requesters.")
+	flag.StringVar(&cfg.caller.Email, "caller-email", "",
+		"Requester email used to authorize tasks that declare allowed_requesters.")
 
 	setupUsage(logger)
 	flag.Parse()

pkg/codingcontext/authorization.go

@@ -0,0 +1,47 @@
+package codingcontext
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/kitproj/coding-context-cli/pkg/codingcontext/markdown"
+)
+
+// CallerIdentity identifies the requester invoking a task.
+type CallerIdentity struct {
+	Username string
+	Email    string
+}
+
+func (cc *Context) authorizeTaskInvocation(frontMatter markdown.TaskFrontMatter) error {
+	if !isAllowed(frontMatter.AllowedSurfaces, cc.surface) {
+		return fmt.Errorf("%w: surface is not permitted", ErrCallerNotAllowed)
+	}
+
+	if !isAllowed(frontMatter.AllowedRequesters, cc.caller.Username, cc.caller.Email) {
+		return fmt.Errorf("%w: requester identity is not permitted", ErrCallerNotAllowed)
+	}
+
+	return nil
+}
+
+func isAllowed(allowlist []string, values ...string) bool {
+	if len(allowlist) == 0 {
+		return true
+	}
+
+	for _, value := range values {
+		value = strings.TrimSpace(value)
+		if value == "" {
+			continue
+		}
+
+		for _, allowed := range allowlist {
+			if strings.EqualFold(value, strings.TrimSpace(allowed)) {
+				return true
+			}
+		}
+	}
+
+	return false
+}