fix: treat missing slash commands as warning

integration_test.go

@@ -2006,3 +2006,26 @@ task_name: whitespace-task
 		})
 	}
 }
+
+// TestNonExistentSlashCommandPassesThrough verifies that a task referencing a
+// slash command that does not exist passes through the text as-is instead of erroring.
+func TestNonExistentSlashCommandPassesThrough(t *testing.T) {
+	t.Parallel()
+	dirs := setupTestDirs(t)
+
+	// Create a task that references a non-existent slash command
+	taskContent := `# My Task with a File Path
+
+	/home/coder/.config should be ignored
+	`
+	taskFile := filepath.Join(dirs.tasksDir, "bad-command-task.md")
+	if err := os.WriteFile(taskFile, []byte(taskContent), 0o600); err != nil {
+		t.Fatalf("failed to write task file: %v", err)
+	}
+
+	output := runTool(t, "-C", dirs.tmpDir, "bad-command-task")
+
+	if !strings.Contains(output, "/home/coder/.config should be ignored") {
+		t.Errorf("expected non-existent slash command to pass through as-is, got: %s", output)
+	}
+}

pkg/codingcontext/context.go

@@ -465,11 +465,16 @@ func (cc *Context) processTaskBlock(block taskparser.Block, path string, expandP
 	if block.SlashCommand != nil {
 		commandContent, err := cc.findCommand(block.SlashCommand.Name, block.SlashCommand.Params())
 		if err != nil {
-			if cc.lintMode && errors.Is(err, ErrCommandNotFound) {
-				cc.lintCollector.recordError(path, LintErrorKindMissingCommand,
-					"command not found: "+block.SlashCommand.Name)
+			if errors.Is(err, ErrCommandNotFound) {
+				if cc.lintMode {
+					cc.lintCollector.recordError(path, LintErrorKindMissingCommand,
+						"command not found: "+block.SlashCommand.Name)
+				} else {
+					cc.logger.Warn("Command not found, passing through as-is",
+						"command", block.SlashCommand.Name)
+				}
 
-				return "/" + block.SlashCommand.Name, nil
+				return block.SlashCommand.String(), nil
 			}
 
 			return "", fmt.Errorf("failed to find command %s: %w", block.SlashCommand.Name, err)

pkg/codingcontext/context_test.go

@@ -957,14 +957,19 @@ func TestContext_Run_Commands(t *testing.T) {
 			check:    checkTaskNotEmpty,
 		},
 		{
-			name: "command not found returns error",
+			name: "command not found passes through as-is",
 			setup: func(t *testing.T, dir string) {
 				t.Helper()
 				createTask(t, dir, "missing-cmd", "", "/nonexistent")
 			},
-			taskName:    "missing-cmd",
-			wantErr:     true,
-			errContains: "command not found",
+			taskName: "missing-cmd",
+			wantErr:  false,
+			check: func(t *testing.T, result *Result) {
+				t.Helper()
+				if !strings.Contains(result.Prompt, "/nonexistent") {
+					t.Errorf("expected pass-through of /nonexistent, got %q", result.Prompt)
+				}
+			},
 		},
 		{
 			name: "command parameter overrides context parameter",
@@ -1249,16 +1254,22 @@ func TestContext_Run_Errors(t *testing.T) {
 		taskName    string
 		wantErr     bool
 		errContains string
+		check       func(t *testing.T, result *Result)
 	}{
 		{
-			name: "command not found in task",
+			name: "command not found in task passes through as-is",
 			setup: func(t *testing.T, dir string) {
 				t.Helper()
 				createTask(t, dir, "bad-cmd", "", "/missing-command\n")
 			},
-			taskName:    "bad-cmd",
-			wantErr:     true,
-			errContains: "command not found",
+			taskName: "bad-cmd",
+			wantErr:  false,
+			check: func(t *testing.T, result *Result) {
+				t.Helper()
+				if !strings.Contains(result.Prompt, "/missing-command") {
+					t.Errorf("expected pass-through of /missing-command, got %q", result.Prompt)
+				}
+			},
 		},
 		{
 			name: "invalid agent in task frontmatter",
@@ -1298,6 +1309,10 @@ func TestContext_Run_Errors(t *testing.T) {
 					t.Errorf("expected error to contain %q, got %v", tt.errContains, err)
 				}
 			}
+
+			if !tt.wantErr && tt.check != nil {
+				tt.check(t, result)
+			}
 		})
 	}
 }
@@ -1839,17 +1854,22 @@ func TestUserPrompt(t *testing.T) {
 			check:    checkTaskContains("${issue_number}"), // expand:false applies to user_prompt too
 		},
 		{
-			name: "user_prompt with invalid slash command",
+			name: "user_prompt with invalid slash command passes through as-is",
 			setup: func(t *testing.T, dir string) {
 				t.Helper()
 				createTask(t, dir, "invalid", "", "Task content\n")
 			},
 			opts: []Option{
 				WithUserPrompt("/nonexistent-command\n"),
 			},
-			taskName:    "invalid",
-			wantErr:     true,
-			errContains: "command not found",
+			taskName: "invalid",
+			wantErr:  false,
+			check: func(t *testing.T, result *Result) {
+				t.Helper()
+				if !strings.Contains(result.Prompt, "/nonexistent-command") {
+					t.Errorf("expected pass-through of /nonexistent-command, got %q", result.Prompt)
+				}
+			},
 		},
 		{
 			name: "both task prompt and user prompt parse correctly",