diff --git a/.ameba.yml b/.ameba.yml
new file mode 100644
index 0000000..74885d6
--- /dev/null
+++ b/.ameba.yml
@@ -0,0 +1,30 @@
+# Ameba configuration for cjules.
+# https://github.com/crystal-ameba/ameba
+#
+# Only rules that conflict with deliberate, documented project conventions are
+# disabled here; everything else runs with ameba defaults and is expected to
+# stay clean.
+
+# Locals and instance vars intentionally mirror the Jules REST API JSON field
+# names verbatim (createTime, gitPatch, planGenerated, nextPageToken, ...) so the
+# code maps 1:1 onto the upstream API. snake_case would obscure that mapping.
+Naming/VariableNames:
+  Enabled: false
+
+# Short block parameter names (s, a, l, j, ...) are used idiomatically throughout
+# the command and serialization layers.
+Naming/BlockParameterName:
+  Enabled: false
+
+# The CLI dispatcher and per-command OptionParser flag handlers are inherently
+# branch-heavy; high cyclomatic complexity is expected for argument parsing here
+# and does not indicate a refactor is needed.
+Metrics/CyclomaticComplexity:
+  Enabled: false
+
+# not_nil! is used deliberately: flag values are captured inside OptionParser
+# blocks (closures), so Crystal's flow typing cannot narrow them and not_nil! is
+# the idiomatic guard; specs also use it over decoded JSON fixtures whose shape is
+# guaranteed by the fixture.
+Lint/NotNil:
+  Enabled: false
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b74d266..fd2af30 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -47,8 +47,15 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
+      - uses: crystal-lang/install-crystal@v1
+        with:
+          crystal: 1.20.0
+      - name: Install dependencies
+        run: shards install
+      # Use the ameba version pinned in shard.lock (respects .ameba.yml) so local
+      # `just lint` and CI agree and an upstream rule change can't break CI silently.
       - name: Run Ameba linter
-        uses: crystal-ameba/github-action@master
+        run: bin/ameba
   build-snapcraft:
     if: github.event_name == 'push' && github.ref == 'refs/heads/main' || github.event_name == 'workflow_dispatch'
     runs-on: ubuntu-latest
diff --git a/justfile b/justfile
index ea25c0c..25aedc4 100644
--- a/justfile
+++ b/justfile
@@ -36,10 +36,11 @@ check:
     crystal tool format --check
 
 # Run ameba static linter (requires shards install first).
+# Rule configuration lives in .ameba.yml so local and CI stay in sync.
 [group('development')]
 lint:
-    @[ -f lib/ameba/src/ameba.cr ] || shards install
-    crystal lib/ameba/src/ameba.cr src spec --except Metrics/CyclomaticComplexity --except Metrics/MethodLength
+    @[ -f bin/ameba ] || shards install
+    bin/ameba
 
 # Run all tests.
 [group('development')]
diff --git a/shard.lock b/shard.lock
index f612c4d..26eb0c5 100644
--- a/shard.lock
+++ b/shard.lock
@@ -4,3 +4,7 @@ shards:
     git: https://github.com/crystal-ameba/ameba.git
     version: 1.6.4
 
+  webmock:
+    git: https://github.com/manastech/webmock.cr.git
+    version: 0.14.0
+
diff --git a/shard.yml b/shard.yml
index c3c41b4..d777146 100644
--- a/shard.yml
+++ b/shard.yml
@@ -20,3 +20,6 @@ development_dependencies:
   ameba:
     github: crystal-ameba/ameba
     version: "~> 1.6"
+  webmock:
+    github: manastech/webmock.cr
+    version: "~> 0.14"
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
index e469081..19ebe76 100644
--- a/spec/spec_helper.cr
+++ b/spec/spec_helper.cr
@@ -2,18 +2,13 @@ require "spec"
 require "file_utils"
 require "../src/cjules"
 
-# WebMock is vendored under lib/webmock (committed in tree) to enable hermetic
-# HTTP tests for Client, API, and command layers without a production dependency.
-require "../lib/webmock/src/webmock"
-
-def require_webmock!
-  # always available in this project
-end
+# WebMock is a development_dependency used to enable hermetic HTTP tests for the
+# Client, API, and command layers without adding a production dependency.
+require "webmock"
 
 # Run a block with WebMock enabled (real net disabled, stubs required).
-# Automatically resets after the block. Skips/pends if webmock not vendored.
+# Automatically resets after the block.
 def with_webmock(&)
-  require_webmock!
   WebMock.wrap do
     yield
   end
@@ -22,7 +17,6 @@ end
 # Stub a successful Jules API response for common paths.
 # Usage: stub_jules(:get, "/v1alpha/sessions", body: json, status: 200)
 def stub_jules(method : Symbol, path : String, body : String = "", status : Int32 = 200, headers : HTTP::Headers? = nil)
-  require_webmock!
   url = "https://jules.googleapis.com#{path}"
   stub = WebMock.stub(method, url)
   stub.to_return(status: status, body: body, headers: headers || HTTP::Headers{"Content-Type" => "application/json"})
diff --git a/spec/unidiff_spec.cr b/spec/unidiff_spec.cr
index cbb3799..e77f4a8 100644
--- a/spec/unidiff_spec.cr
+++ b/spec/unidiff_spec.cr
@@ -16,8 +16,8 @@ describe Cjules::Unidiff do
     chunks = Cjules::Unidiff.chunks(patch)
     chunks.size.should eq(2)
     chunks[0].lines.first.should start_with("diff --git a/foo.txt b/foo.txt")
-    chunks[0].lines.any? { |l| l.starts_with?("@@ -0,0 +1,2 @@") }.should be_true
-    chunks[1].lines.any? { |l| l.starts_with?("@@ -10,0 +12,1 @@") }.should be_true
+    chunks[0].lines.any?(&.starts_with?("@@ -0,0 +1,2 @@")).should be_true
+    chunks[1].lines.any?(&.starts_with?("@@ -10,0 +12,1 @@")).should be_true
   end
 
   it "treats no-@@ sections as one chunk" do
@@ -28,7 +28,7 @@ describe Cjules::Unidiff do
     PATCH
     chunks = Cjules::Unidiff.chunks(patch)
     chunks.size.should eq(1)
-    chunks[0].lines.any? { |l| l.includes?("new mode") }.should be_true
+    chunks[0].lines.any?(&.includes?("new mode")).should be_true
   end
 end
 
@@ -91,7 +91,7 @@ describe Cjules::Unidiff::Interactive do
     PATCH
     result, _, _ = run_select.call(patch, "d\n")
     result.selected_patch.empty?.should be_true
-    result.quit_early.should be_false
+    result.quit_early?.should be_false
     result.skipped_chunks.should eq(2)
   end
 
@@ -106,6 +106,6 @@ describe Cjules::Unidiff::Interactive do
     PATCH
     result, _, _ = run_select.call(patch, "q\n")
     result.selected_patch.empty?.should be_true
-    result.quit_early.should be_true
+    result.quit_early?.should be_true
   end
 end
diff --git a/src/cjules/client.cr b/src/cjules/client.cr
index 64c6eb9..1304ce9 100644
--- a/src/cjules/client.cr
+++ b/src/cjules/client.cr
@@ -46,7 +46,7 @@ module Cjules
     end
 
     private def full_path(path : String, query : Hash(String, String)? = nil) : String
-      return path unless query && !query.empty?
+      return path if query.nil? || query.empty?
       params = URI::Params.build do |form|
         query.each { |k, v| form.add(k, v) }
       end
diff --git a/src/cjules/commands/activity.cr b/src/cjules/commands/activity.cr
index be7e39c..e134b45 100644
--- a/src/cjules/commands/activity.cr
+++ b/src/cjules/commands/activity.cr
@@ -64,7 +64,7 @@ module Cjules
             (plan.steps || [] of Models::PlanStep).each do |s|
               puts "  #{(s.index || 0) + 1}. #{s.title || "(untitled)"}"
               if d = s.description
-                d.lines.each { |l| puts "     #{l.chomp}" } unless d.empty?
+                d.each_line { |l| puts "     #{l.chomp}" } unless d.empty?
               end
             end
           end
@@ -114,7 +114,7 @@ module Cjules
               puts Output::Colors.bold("#{label} (bashOutput):")
               puts "  $ #{bo.command}"
               if out = bo.output
-                out.lines.each { |l| puts "    #{l.chomp}" }
+                out.each_line { |l| puts "    #{l.chomp}" }
               end
               puts "  exit: #{bo.exitCode}"
             elsif med = art.media
diff --git a/src/cjules/commands/logs.cr b/src/cjules/commands/logs.cr
index bba829e..a9956b1 100644
--- a/src/cjules/commands/logs.cr
+++ b/src/cjules/commands/logs.cr
@@ -83,7 +83,7 @@ module Cjules
                 any = true
                 puts "$ #{bo.command}"
                 if out = bo.output
-                  out.lines.each { |l| puts l.chomp }
+                  out.each_line { |l| puts l.chomp }
                 end
                 puts "[exit #{bo.exitCode}]"
                 puts ""
@@ -103,7 +103,7 @@ module Cjules
             arts.each_with_index do |art, idx|
               if med = art.media
                 data = med.data
-                next unless data && !data.empty?
+                next if data.nil? || data.empty?
                 ext = ext_for(med.mimeType)
                 fname =
                   if aid = a.id
@@ -260,14 +260,22 @@ module Cjules
           n = pg.plan.try(&.steps).try(&.size) || 0
           return "plan generated (#{n} step(s))"
         end
-        return "plan #{a.planApproved.not_nil!.planId || "?"} approved" if a.planApproved
-        return "user> #{a.userMessaged.not_nil!.userMessage || ""}" if a.userMessaged
-        return "agent> #{a.agentMessaged.not_nil!.agentMessage || ""}" if a.agentMessaged
+        if pa = a.planApproved
+          return "plan #{pa.planId || "?"} approved"
+        end
+        if um = a.userMessaged
+          return "user> #{um.userMessage || ""}"
+        end
+        if am = a.agentMessaged
+          return "agent> #{am.agentMessage || ""}"
+        end
         if pu = a.progressUpdated
           parts = [pu.title, pu.description].compact.reject(&.empty?)
           return parts.join(" — ")
         end
-        return "failed: #{a.sessionFailed.not_nil!.reason || "(no reason)"}" if a.sessionFailed
+        if sf = a.sessionFailed
+          return "failed: #{sf.reason || "(no reason)"}"
+        end
         return "completed" if a.sessionCompleted
         ""
       end
diff --git a/src/cjules/commands/new.cr b/src/cjules/commands/new.cr
index 7c18c50..5fbb070 100644
--- a/src/cjules/commands/new.cr
+++ b/src/cjules/commands/new.cr
@@ -157,7 +157,7 @@ module Cjules
             else
               e.message || "unknown error"
             end
-          end.uniq
+          end.uniq!
           error_msgs.each { |msg| STDERR.puts "  - #{msg}" }
           return 1
         end
@@ -239,7 +239,7 @@ module Cjules
         JSON.build do |j|
           j.object do
             j.field "prompt", prompt
-            j.field "title", title.not_nil! if title
+            j.field "title", title if title
             j.field "requirePlanApproval", true if require_approval
             j.field "automationMode", "AUTO_CREATE_PR" if auto_pr
             if source && starting_branch
diff --git a/src/cjules/commands/patch.cr b/src/cjules/commands/patch.cr
index aab3b6c..0a8c261 100644
--- a/src/cjules/commands/patch.cr
+++ b/src/cjules/commands/patch.cr
@@ -95,7 +95,7 @@ module Cjules
             end
             result = Unidiff::Interactive.select(text, input: STDIN, output: STDERR, display: STDOUT)
             if result.selected_patch.empty?
-              if result.quit_early
+              if result.quit_early?
                 STDERR.puts "aborted"
                 return 1
               end
diff --git a/src/cjules/commands/pick.cr b/src/cjules/commands/pick.cr
index 7beb02a..9750be3 100644
--- a/src/cjules/commands/pick.cr
+++ b/src/cjules/commands/pick.cr
@@ -82,13 +82,11 @@ module Cjules
       end
 
       private def has_fzf? : Bool
-        begin
-          Process.run("which", ["fzf"],
-            output: Process::Redirect::Close,
-            error: Process::Redirect::Close).success?
-        rescue Exception
-          false
-        end
+        Process.run("which", ["fzf"],
+          output: Process::Redirect::Close,
+          error: Process::Redirect::Close).success?
+      rescue Exception
+        false
       end
 
       private def run_fzf(input : String) : String?
diff --git a/src/cjules/commands/plan.cr b/src/cjules/commands/plan.cr
index c01f845..2e8a3e5 100644
--- a/src/cjules/commands/plan.cr
+++ b/src/cjules/commands/plan.cr
@@ -76,7 +76,7 @@ module Cjules
           puts ""
           puts "  #{(s.index || 0) + 1}. #{Output::Colors.bold(s.title || "(untitled)")}"
           if d = s.description
-            d.lines.each { |l| puts "     #{l.chomp}" } unless d.empty?
+            d.each_line { |l| puts "     #{l.chomp}" } unless d.empty?
           end
         end
       end
diff --git a/src/cjules/commands/retry.cr b/src/cjules/commands/retry.cr
index 10b6721..bd1b070 100644
--- a/src/cjules/commands/retry.cr
+++ b/src/cjules/commands/retry.cr
@@ -98,7 +98,7 @@ module Cjules
         source = sc.try(&.source)
         starting_branch = branch_override || sc.try(&.githubRepoContext).try(&.startingBranch)
 
-        if source && (starting_branch.nil? || starting_branch.not_nil!.empty?)
+        if source && (starting_branch.nil? || starting_branch.empty?)
           STDERR.puts "error: original session has no startingBranch; pass --branch BRANCH"
           return 2
         end
diff --git a/src/cjules/commands/templates.cr b/src/cjules/commands/templates.cr
index b87ea4b..fbba72d 100644
--- a/src/cjules/commands/templates.cr
+++ b/src/cjules/commands/templates.cr
@@ -35,7 +35,7 @@ module Cjules
             f
           end
         end
-        names.uniq.sort
+        names.uniq.sort!
       end
 
       def run(args : Array(String)) : Int32
diff --git a/src/cjules/template_renderer.cr b/src/cjules/template_renderer.cr
index bcdbdf4..1362e90 100644
--- a/src/cjules/template_renderer.cr
+++ b/src/cjules/template_renderer.cr
@@ -87,23 +87,21 @@ module Cjules
     end
 
     private def get_git_diff : String
-      begin
-        io = IO::Memory.new
-        status = Process.run("git", ["diff"], output: io, error: Process::Redirect::Close)
-
-        unless status.success?
-          return "[git diff failed]"
-        end
+      io = IO::Memory.new
+      status = Process.run("git", ["diff"], output: io, error: Process::Redirect::Close)
 
-        diff = io.to_s
-        if diff.empty?
-          return "[no git changes]"
-        end
+      unless status.success?
+        return "[git diff failed]"
+      end
 
-        diff
-      rescue e : Exception
-        "[error running git diff: #{e.message}]"
+      diff = io.to_s
+      if diff.empty?
+        return "[no git changes]"
       end
+
+      diff
+    rescue e : Exception
+      "[error running git diff: #{e.message}]"
     end
   end
 end
diff --git a/src/cjules/unidiff.cr b/src/cjules/unidiff.cr
index 5a06911..cd32de6 100644
--- a/src/cjules/unidiff.cr
+++ b/src/cjules/unidiff.cr
@@ -47,7 +47,7 @@ module Cjules
         getter selected_patch : String
         getter selected_chunks : Int32
         getter skipped_chunks : Int32
-        getter quit_early : Bool
+        getter? quit_early : Bool
 
         def initialize(@selected_patch : String, @selected_chunks : Int32, @skipped_chunks : Int32, @quit_early : Bool)
         end
@@ -131,7 +131,8 @@ module Cjules
       private def show_chunk(chunk : Chunk, idx : Int32, total : Int32, display : IO)
         display.puts "\n#{chunk.label} (hunk #{idx}/#{total})"
         display.puts "-" * 72
-        chunk.lines.each { |l| display.puts l }
+        # ameba:disable Performance/ExcessiveAllocations
+        chunk.lines.each { |l| display.puts l } # `lines` is an Array field, not a String
         display.puts "-" * 72
         display.flush
       end
@@ -280,17 +281,17 @@ module Cjules
     end
 
     private def section_label(section : Array(String)) : String
-      diff = section.find { |l| l.starts_with?("diff --git ") }
+      diff = section.find(&.starts_with?("diff --git "))
       if diff
         if m = diff.match(/^diff --git a\/(\S+)\s+b\/(\S+)$/)
           return m[2]
         end
       end
-      plus = section.find { |l| l.starts_with?("+++ ") }
+      plus = section.find(&.starts_with?("+++ "))
       if plus
         return plus.sub(/^\+\+\+\s+/, "")
       end
-      minus = section.find { |l| l.starts_with?("--- ") }
+      minus = section.find(&.starts_with?("--- "))
       if minus
         return minus.sub(/^---\s+/, "")
       end
diff --git a/src/cjules/util.cr b/src/cjules/util.cr
index f308010..423d11a 100644
--- a/src/cjules/util.cr
+++ b/src/cjules/util.cr
@@ -107,17 +107,15 @@ module Cjules
       end
 
       private def run(cmd : String, *args) : String?
-        begin
-          io = IO::Memory.new
-          status = Process.run(cmd, args.to_a,
-            output: io,
-            error: Process::Redirect::Close)
-          return nil unless status.success?
-          out = io.to_s.strip
-          out.empty? ? nil : out
-        rescue Exception
-          nil
-        end
+        io = IO::Memory.new
+        status = Process.run(cmd, args.to_a,
+          output: io,
+          error: Process::Redirect::Close)
+        return nil unless status.success?
+        out = io.to_s.strip
+        out.empty? ? nil : out
+      rescue Exception
+        nil
       end
     end