add read tool formatters

lib/roast/cogs/agent/providers/pi/messages/tool_call_message.rb

@@ -63,6 +63,40 @@ def format_bash
                 command.empty? ? "BASH" : "BASH #{command}"
               end
 
+              # Formats a read tool call.
+              #
+              # Input fields:
+              #   :path   (String)  – file to read              [required]
+              #   :offset (Integer) – 1-indexed first line       [optional]
+              #   :limit  (Integer) – maximum number of lines    [optional]
+              #
+              # Output: "READ <path>", with a line range appended when :offset and/or
+              # :limit is given:
+              #   :limit >= 1  → " (lines <start>–<end>)", start = :offset (default 1),
+              #                  end = start + :limit - 1
+              #   :offset only → " (from line <offset>)" (reads to end of file); also the
+              #                  fallback when :limit <= 0, which has no sensible range
+              # With neither, the bare "READ <path>". A missing path renders "READ".
+              #
+              # Examples:
+              #   READ lib/roast.rb (lines 30–80)
+              #   READ lib/roast.rb (from line 30)
+              #   READ lib/roast.rb
+              #
+              #: () -> String
+              def format_read
+                path, offset, limit = arguments.values_at(:path, :offset, :limit)
+                path = path.to_s
+                details = if limit&.positive?
+                  offset ||= 1
+                  "lines #{offset}–#{offset + limit - 1}"
+                elsif offset
+                  "from line #{offset}"
+                end
+                label = path.empty? ? "READ" : "READ #{path}"
+                details ? "#{label} (#{details})" : label
+              end
+
               # Formats a tool call for which Roast has no dedicated formatter.
               #
               # Output: "<NAME> <key>: <value>, ..." – the upcased tool name, then each

lib/roast/cogs/agent/providers/pi/messages/tool_result_message.rb

@@ -76,6 +76,26 @@ def format_bash
                 ok_line("#{count} #{"line".pluralize(count)}", preview)
               end
 
+              # Formats a read tool result.
+              #
+              # Content: the file's text.
+              #
+              # Output: "READ OK <n> <line|lines>" – <n> is the file's line count
+              # (pluralized). Blank lines are counted: this is the file's own length, so
+              # it deliberately differs from entry-listing tools (find/ls), which drop
+              # blanks because a blank isn't an entry.
+              #
+              # Examples:
+              #   READ OK 42 lines
+              #   READ OK 1 line
+              #   READ OK 0 lines
+              #
+              #: () -> String
+              def format_read
+                count = content.to_s.lines.length
+                ok_line("#{count} #{"line".pluralize(count)}")
+              end
+
               # Formats a result for which Roast has no dedicated formatter.
               #
               # Content: the tool's output text.

test/roast/cogs/agent/providers/pi/messages/tool_call_message_test.rb

@@ -26,6 +26,41 @@ class ToolCallMessageTest < ActiveSupport::TestCase
           assert_equal "BASH #{"x" * (ToolCallMessage::TRUNCATE_LIMIT - 3)}...", msg.format
         end
 
+        test "format renders READ with the path" do
+          msg = ToolCallMessage.new(id: "1", name: "read", arguments: { path: "lib/roast.rb" })
+          assert_equal "READ lib/roast.rb", msg.format
+        end
+
+        test "format renders a bare READ when the path is missing" do
+          msg = ToolCallMessage.new(id: "1", name: "read", arguments: {})
+          assert_equal "READ", msg.format
+        end
+
+        test "format renders READ with a closed line range when offset and limit are set" do
+          msg = ToolCallMessage.new(id: "1", name: "read", arguments: { path: "lib/roast.rb", offset: 30, limit: 51 })
+          assert_equal "READ lib/roast.rb (lines 30–80)", msg.format
+        end
+
+        test "format defaults the read offset to 1 when only limit is given" do
+          msg = ToolCallMessage.new(id: "1", name: "read", arguments: { path: "lib/roast.rb", limit: 50 })
+          assert_equal "READ lib/roast.rb (lines 1–50)", msg.format
+        end
+
+        test "format renders an open-ended read range from offset when limit is absent" do
+          msg = ToolCallMessage.new(id: "1", name: "read", arguments: { path: "lib/roast.rb", offset: 30 })
+          assert_equal "READ lib/roast.rb (from line 30)", msg.format
+        end
+
+        test "format falls back to the open-ended range when read limit is non-positive" do
+          msg = ToolCallMessage.new(id: "1", name: "read", arguments: { path: "lib/roast.rb", offset: 30, limit: 0 })
+          assert_equal "READ lib/roast.rb (from line 30)", msg.format
+        end
+
+        test "format omits the range entirely when read limit is non-positive and no offset is given" do
+          msg = ToolCallMessage.new(id: "1", name: "read", arguments: { path: "lib/roast.rb", limit: 0 })
+          assert_equal "READ lib/roast.rb", msg.format
+        end
+
         test "format renders an unhandled tool as NAME key: value, ..." do
           msg = ToolCallMessage.new(
             id: "1",

test/roast/cogs/agent/providers/pi/messages/tool_result_message_test.rb

@@ -43,6 +43,39 @@ def setup
           assert_equal "BASH OK 0 lines", msg.format(@context)
         end
 
+        test "format summarizes read output with a line count" do
+          msg = ToolResultMessage.new(
+            tool_call_id: "1",
+            tool_name: "read",
+            content: "line one\nline two\nline three",
+            is_error: false,
+          )
+
+          assert_equal "READ OK 3 lines", msg.format(@context)
+        end
+
+        test "format pluralizes a single line of read output" do
+          msg = ToolResultMessage.new(
+            tool_call_id: "1",
+            tool_name: "read",
+            content: "just one line",
+            is_error: false,
+          )
+
+          assert_equal "READ OK 1 line", msg.format(@context)
+        end
+
+        test "format reports zero lines when the file is empty" do
+          msg = ToolResultMessage.new(
+            tool_call_id: "1",
+            tool_name: "read",
+            content: nil,
+            is_error: false,
+          )
+
+          assert_equal "READ OK 0 lines", msg.format(@context)
+        end
+
         test "format renders NAME ERROR with the message for an error result" do
           msg = ToolResultMessage.new(
             tool_call_id: "1",