diff --git a/cmd/cu/checkout.go b/cmd/cu/checkout.go
index b5dac2fc..7ceb3a5c 100644
--- a/cmd/cu/checkout.go
+++ b/cmd/cu/checkout.go
@@ -8,8 +8,8 @@ import (
 )
 
 var checkoutCmd = &cobra.Command{
-	Use:               "checkout <env>",
-	Short:             "Switch to an environment's branch locally",
+	Use:   "checkout <env>",
+	Short: "Switch to an environment's branch locally",
 	Long: `Bring an environment's work into your local git workspace.
 This creates a local branch from the environment's state so you can
 explore files in your IDE, make changes, or continue development.`,
@@ -48,4 +48,4 @@ cu checkout fancy-mallard -b my-review-branch`,
 func init() {
 	checkoutCmd.Flags().StringP("branch", "b", "", "Local branch name to use")
 	rootCmd.AddCommand(checkoutCmd)
-}
\ No newline at end of file
+}
diff --git a/cmd/cu/delete.go b/cmd/cu/delete.go
index 0d987173..a54aeb3c 100644
--- a/cmd/cu/delete.go
+++ b/cmd/cu/delete.go
@@ -8,8 +8,8 @@ import (
 )
 
 var deleteCmd = &cobra.Command{
-	Use:               "delete [<env>...]",
-	Short:             "Delete environments and start fresh",
+	Use:   "delete [<env>...]",
+	Short: "Delete environments and start fresh",
 	Long: `Delete one or more environments and their associated resources.
 This permanently removes the environment's branch and container state.
 Use this when starting over with a different approach.
@@ -80,4 +80,4 @@ cu delete --all`,
 func init() {
 	rootCmd.AddCommand(deleteCmd)
 	deleteCmd.Flags().Bool("all", false, "Delete all environments")
-}
\ No newline at end of file
+}
diff --git a/cmd/cu/diff.go b/cmd/cu/diff.go
index 99500c01..e0b39462 100644
--- a/cmd/cu/diff.go
+++ b/cmd/cu/diff.go
@@ -8,17 +8,21 @@ import (
 )
 
 var diffCmd = &cobra.Command{
-	Use:               "diff <env>",
-	Short:             "Show what files an agent changed",
+	Use:   "diff <env>",
+	Short: "Show what files an agent changed",
 	Long: `Display the code changes made by an agent in an environment.
-Shows a git diff between the environment's state and your current branch.`,
+Shows a git diff of all changes made since the environment was created.
+Use -b to compare against a specific branch instead of showing full diff.`,
 	Args:              cobra.ExactArgs(1),
 	ValidArgsFunction: suggestEnvironments,
-	Example: `# See what changes the agent made
+	Example: `# See what changes the agent made (full diff)
 cu diff fancy-mallard
 
+# Compare against main branch
+cu diff fancy-mallard -b main
+
 # Quick assessment before merging
-cu diff backend-api`,
+cu diff backend-api -b main`,
 	RunE: func(app *cobra.Command, args []string) error {
 		ctx := app.Context()
 
@@ -28,10 +32,13 @@ cu diff backend-api`,
 			return err
 		}
 
-		return repo.Diff(ctx, args[0], os.Stdout)
+		branch, _ := app.Flags().GetString("branch")
+
+		return repo.Diff(ctx, args[0], branch, os.Stdout)
 	},
 }
 
 func init() {
+	diffCmd.Flags().StringP("branch", "b", "", "Compare against specified branch (uses merge-base)")
 	rootCmd.AddCommand(diffCmd)
 }
\ No newline at end of file
diff --git a/cmd/cu/list.go b/cmd/cu/list.go
index 34cad09a..896cbbb5 100644
--- a/cmd/cu/list.go
+++ b/cmd/cu/list.go
@@ -57,4 +57,4 @@ func init() {
 	listCmd.Flags().BoolP("quiet", "q", false, "Display only environment IDs")
 	listCmd.Flags().BoolP("no-trunc", "", false, "Don't truncate output")
 	rootCmd.AddCommand(listCmd)
-}
\ No newline at end of file
+}
diff --git a/cmd/cu/log.go b/cmd/cu/log.go
index 4fadf8a3..c4e14337 100644
--- a/cmd/cu/log.go
+++ b/cmd/cu/log.go
@@ -8,18 +8,25 @@ import (
 )
 
 var logCmd = &cobra.Command{
-	Use:               "log <env>",
-	Short:             "View what an agent did step-by-step",
+	Use:   "log <env>",
+	Short: "View what an agent did step-by-step",
 	Long: `Display the complete development history for an environment.
 Shows all commits made by the agent plus command execution notes.
-Use -p to include code patches in the output.`,
+Use -p to include code patches in the output.
+Use -b to compare against a specific branch instead of showing full history.`,
 	Args:              cobra.ExactArgs(1),
 	ValidArgsFunction: suggestEnvironments,
-	Example: `# See what agent did
+	Example: `# See what agent did (full history)
 cu log fancy-mallard
 
 # Include code changes
-cu log fancy-mallard -p`,
+cu log fancy-mallard -p
+
+# Compare against main branch
+cu log fancy-mallard -b main
+
+# Compare against main with patches
+cu log fancy-mallard -b main -p`,
 	RunE: func(app *cobra.Command, args []string) error {
 		ctx := app.Context()
 
@@ -30,12 +37,14 @@ cu log fancy-mallard -p`,
 		}
 
 		patch, _ := app.Flags().GetBool("patch")
+		branch, _ := app.Flags().GetString("branch")
 
-		return repo.Log(ctx, args[0], patch, os.Stdout)
+		return repo.Log(ctx, args[0], patch, branch, os.Stdout)
 	},
 }
 
 func init() {
 	logCmd.Flags().BoolP("patch", "p", false, "Generate patch")
+	logCmd.Flags().StringP("branch", "b", "", "Compare against specified branch (uses merge-base)")
 	rootCmd.AddCommand(logCmd)
 }
\ No newline at end of file
diff --git a/cmd/cu/watch.go b/cmd/cu/watch.go
index 2207ae82..fa9d5096 100644
--- a/cmd/cu/watch.go
+++ b/cmd/cu/watch.go
@@ -35,4 +35,4 @@ cu watch`,
 
 func init() {
 	rootCmd.AddCommand(watchCmd)
-}
\ No newline at end of file
+}
diff --git a/environment/integration/repository_test.go b/environment/integration/repository_test.go
index 9fef47f9..8418a15f 100644
--- a/environment/integration/repository_test.go
+++ b/environment/integration/repository_test.go
@@ -142,7 +142,7 @@ func TestRepositoryLog(t *testing.T) {
 
 		// Get commit log without patches
 		var logBuf bytes.Buffer
-		err := repo.Log(ctx, env.ID, false, &logBuf)
+		err := repo.Log(ctx, env.ID, false, "", &logBuf)
 		logOutput := logBuf.String()
 		require.NoError(t, err, logOutput)
 
@@ -153,7 +153,7 @@ func TestRepositoryLog(t *testing.T) {
 
 		// Get commit log with patches
 		logBuf.Reset()
-		err = repo.Log(ctx, env.ID, true, &logBuf)
+		err = repo.Log(ctx, env.ID, true, "", &logBuf)
 		logWithPatchOutput := logBuf.String()
 		require.NoError(t, err, logWithPatchOutput)
 
@@ -162,7 +162,7 @@ func TestRepositoryLog(t *testing.T) {
 		assert.Contains(t, logWithPatchOutput, "+updated content")
 
 		// Test log for non-existent environment
-		err = repo.Log(ctx, "non-existent-env", false, &logBuf)
+		err = repo.Log(ctx, "non-existent-env", false, "", &logBuf)
 		assert.Error(t, err)
 	})
 }
@@ -184,7 +184,7 @@ func TestRepositoryDiff(t *testing.T) {
 
 		// Get diff output
 		var diffBuf bytes.Buffer
-		err := repo.Diff(ctx, env.ID, &diffBuf)
+		err := repo.Diff(ctx, env.ID, "", &diffBuf)
 		diffOutput := diffBuf.String()
 		require.NoError(t, err, diffOutput)
 
@@ -192,7 +192,7 @@ func TestRepositoryDiff(t *testing.T) {
 		assert.Contains(t, diffOutput, "+updated content")
 
 		// Test diff with non-existent environment
-		err = repo.Diff(ctx, "non-existent-env", &diffBuf)
+		err = repo.Diff(ctx, "non-existent-env", "", &diffBuf)
 		assert.Error(t, err)
 	})
 }
diff --git a/mcpserver/tools.go b/mcpserver/tools.go
index 6142cda2..b679e495 100644
--- a/mcpserver/tools.go
+++ b/mcpserver/tools.go
@@ -1,6 +1,7 @@
 package mcpserver
 
 import (
+	"bytes"
 	"context"
 	_ "embed"
 	"encoding/json"
@@ -115,6 +116,8 @@ func init() {
 		EnvironmentAddServiceTool,
 
 		EnvironmentCheckpointTool,
+		EnvironmentLogTool,
+		EnvironmentDiffTool,
 	)
 }
 
@@ -816,3 +819,80 @@ Supported schemas are:
 		return mcp.NewToolResultText(fmt.Sprintf("Service added and started successfully: %s", string(output))), nil
 	},
 }
+
+var EnvironmentLogTool = &Tool{
+	Definition: mcp.NewTool("environment_log",
+		mcp.WithDescription("View the development history of an environment, showing all commits made by the agent plus command execution notes."),
+		mcp.WithString("explanation",
+			mcp.Description("One sentence explanation for why this environment log is being viewed."),
+		),
+		mcp.WithString("environment_source",
+			mcp.Description("Absolute path to the source git repository for the environment."),
+			mcp.Required(),
+		),
+		mcp.WithString("environment_id",
+			mcp.Description("The ID of the environment to view the log for."),
+			mcp.Required(),
+		),
+		mcp.WithBoolean("patch",
+			mcp.Description("Include code patches in the output (default: false)."),
+		),
+	),
+	Handler: func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+		repo, err := openRepository(ctx, request)
+		if err != nil {
+			return mcp.NewToolResultErrorFromErr("unable to open the repository", err), nil
+		}
+
+		envID, err := request.RequireString("environment_id")
+		if err != nil {
+			return nil, err
+		}
+
+		patch := request.GetBool("patch", false)
+
+		var buf bytes.Buffer
+		// MCP tools always show full history (no branch comparison)
+		if err := repo.Log(ctx, envID, patch, "", &buf); err != nil {
+			return mcp.NewToolResultErrorFromErr("failed to get environment log", err), nil
+		}
+
+		return mcp.NewToolResultText(buf.String()), nil
+	},
+}
+
+var EnvironmentDiffTool = &Tool{
+	Definition: mcp.NewTool("environment_diff",
+		mcp.WithDescription("View the cumulative changes made in an environment from its creation point, showing all code modifications as a unified diff."),
+		mcp.WithString("explanation",
+			mcp.Description("One sentence explanation for why this environment diff is being viewed."),
+		),
+		mcp.WithString("environment_source",
+			mcp.Description("Absolute path to the source git repository for the environment."),
+			mcp.Required(),
+		),
+		mcp.WithString("environment_id",
+			mcp.Description("The ID of the environment to view the diff for."),
+			mcp.Required(),
+		),
+	),
+	Handler: func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+		repo, err := openRepository(ctx, request)
+		if err != nil {
+			return mcp.NewToolResultErrorFromErr("unable to open the repository", err), nil
+		}
+
+		envID, err := request.RequireString("environment_id")
+		if err != nil {
+			return nil, err
+		}
+
+		var buf bytes.Buffer
+		// MCP tools always show full diff (no branch comparison)
+		if err := repo.Diff(ctx, envID, "", &buf); err != nil {
+			return mcp.NewToolResultErrorFromErr("failed to get environment diff", err), nil
+		}
+
+		return mcp.NewToolResultText(buf.String()), nil
+	},
+}
\ No newline at end of file
diff --git a/repository/git.go b/repository/git.go
index 9f6aa52c..343cf583 100644
--- a/repository/git.go
+++ b/repository/git.go
@@ -239,26 +239,41 @@ func (r *Repository) currentUserBranch(ctx context.Context) (string, error) {
 	return RunGitCommand(ctx, r.userRepoPath, "branch", "--show-current")
 }
 
-func (r *Repository) mergeBase(ctx context.Context, env *environment.EnvironmentInfo) (string, error) {
-	currentBranch, err := r.currentUserBranch(ctx)
-	if err != nil {
-		return "", err
-	}
-	currentBranch = strings.TrimSpace(currentBranch)
+func (r *Repository) mergeBase(ctx context.Context, env *environment.EnvironmentInfo, branch string) (string, error) {
 	envGitRef := fmt.Sprintf("%s/%s", containerUseRemote, env.ID)
-	mergeBase, err := RunGitCommand(ctx, r.userRepoPath, "merge-base", currentBranch, envGitRef)
+	mergeBase, err := RunGitCommand(ctx, r.userRepoPath, "merge-base", branch, envGitRef)
 	if err != nil {
 		return "", err
 	}
 	return strings.TrimSpace(mergeBase), nil
 }
 
-func (r *Repository) revisionRange(ctx context.Context, env *environment.EnvironmentInfo) (string, error) {
-	mergeBase, err := r.mergeBase(ctx, env)
+// revisionRange determines the git revision range for log/diff operations.
+// If branch is provided, uses merge-base with that branch.
+// Otherwise, uses merge-base with the current user branch.
+func (r *Repository) revisionRange(ctx context.Context, env *environment.EnvironmentInfo, branch string) (string, error) {
+	envGitRef := fmt.Sprintf("%s/%s", containerUseRemote, env.ID)
+
+	if branch != "" {
+		// Use merge-base with specified branch
+		mergeBase, err := r.mergeBase(ctx, env, branch)
+		if err != nil {
+			return "", err
+		}
+		return fmt.Sprintf("%s..%s", mergeBase, envGitRef), nil
+	}
+
+	// Use merge-base with current user branch (original behavior)
+	currentBranch, err := r.currentUserBranch(ctx)
+	if err != nil {
+		return "", err
+	}
+	currentBranch = strings.TrimSpace(currentBranch)
+	
+	mergeBase, err := r.mergeBase(ctx, env, currentBranch)
 	if err != nil {
 		return "", err
 	}
-	envGitRef := fmt.Sprintf("%s/%s", containerUseRemote, env.ID)
 	return fmt.Sprintf("%s..%s", mergeBase, envGitRef), nil
 }
 
@@ -582,4 +597,4 @@ func matchesScpLike(url string) bool {
 func findScpLikeComponents(url string) (user, host, port, path string) {
 	m := scpLikeURLRegExp.FindStringSubmatch(url)
 	return m[1], m[2], m[3], m[4]
-}
+}
\ No newline at end of file
diff --git a/repository/repository.go b/repository/repository.go
index 695d0912..be9b3202 100644
--- a/repository/repository.go
+++ b/repository/repository.go
@@ -357,7 +357,10 @@ func (r *Repository) Checkout(ctx context.Context, id, branch string) (string, e
 	return branch, err
 }
 
-func (r *Repository) Log(ctx context.Context, id string, patch bool, w io.Writer) error {
+// Log displays the development history for an environment.
+// If branch is provided, shows log since merge-base with that branch.
+// Otherwise, shows log from environment creation.
+func (r *Repository) Log(ctx context.Context, id string, patch bool, branch string, w io.Writer) error {
 	envInfo, err := r.Info(ctx, id)
 	if err != nil {
 		return err
@@ -375,7 +378,7 @@ func (r *Repository) Log(ctx context.Context, id string, patch bool, w io.Writer
 		logArgs = append(logArgs, "--format=%C(yellow)%h%Creset  %s %Cgreen(%cr)%Creset %+N")
 	}
 
-	revisionRange, err := r.revisionRange(ctx, envInfo)
+	revisionRange, err := r.revisionRange(ctx, envInfo, branch)
 	if err != nil {
 		return err
 	}
@@ -391,7 +394,10 @@ func (r *Repository) Log(ctx context.Context, id string, patch bool, w io.Writer
 	return cmd.Run()
 }
 
-func (r *Repository) Diff(ctx context.Context, id string, w io.Writer) error {
+// Diff shows changes made in an environment.
+// If branch is provided, shows diff since merge-base with that branch.
+// Otherwise, shows diff from environment creation.
+func (r *Repository) Diff(ctx context.Context, id string, branch string, w io.Writer) error {
 	envInfo, err := r.Info(ctx, id)
 	if err != nil {
 		return err
@@ -402,7 +408,7 @@ func (r *Repository) Diff(ctx context.Context, id string, w io.Writer) error {
 		"diff",
 	}
 
-	revisionRange, err := r.revisionRange(ctx, envInfo)
+	revisionRange, err := r.revisionRange(ctx, envInfo, branch)
 	if err != nil {
 		return err
 	}
@@ -416,4 +422,4 @@ func (r *Repository) Diff(ctx context.Context, id string, w io.Writer) error {
 	cmd.Stderr = w
 
 	return cmd.Run()
-}
+}
\ No newline at end of file
diff --git a/repository/repository_test.go b/repository/repository_test.go
index 4a7b0577..2d2924b4 100644
--- a/repository/repository_test.go
+++ b/repository/repository_test.go
@@ -14,38 +14,38 @@ import (
 // TestRepositoryOpen tests the Open function which initializes a Repository
 func TestRepositoryOpen(t *testing.T) {
 	ctx := context.Background()
-	
+
 	t.Run("not_a_git_repository", func(t *testing.T) {
 		tempDir := t.TempDir()
 		_, err := Open(ctx, tempDir)
 		assert.Error(t, err)
 		assert.Contains(t, err.Error(), "you must be in a git repository")
 	})
-	
+
 	t.Run("valid_git_repository", func(t *testing.T) {
 		tempDir := t.TempDir()
 		configDir := t.TempDir() // Separate dir for container-use config
-		
+
 		// Initialize a git repo
 		_, err := RunGitCommand(ctx, tempDir, "init")
 		require.NoError(t, err)
-		
+
 		// Set git config
 		_, err = RunGitCommand(ctx, tempDir, "config", "user.email", "test@example.com")
 		require.NoError(t, err)
 		_, err = RunGitCommand(ctx, tempDir, "config", "user.name", "Test User")
 		require.NoError(t, err)
-		
+
 		// Make initial commit
 		testFile := filepath.Join(tempDir, "README.md")
 		err = os.WriteFile(testFile, []byte("# Test"), 0644)
 		require.NoError(t, err)
-		
+
 		_, err = RunGitCommand(ctx, tempDir, "add", ".")
 		require.NoError(t, err)
 		_, err = RunGitCommand(ctx, tempDir, "commit", "-m", "Initial commit")
 		require.NoError(t, err)
-		
+
 		// Open repository with isolated base path
 		repo, err := OpenWithBasePath(ctx, tempDir, configDir)
 		require.NoError(t, err)
@@ -55,16 +55,14 @@ func TestRepositoryOpen(t *testing.T) {
 		assert.NotEmpty(t, repo.userRepoPath)
 		assert.DirExists(t, repo.userRepoPath)
 		assert.NotEmpty(t, repo.forkRepoPath)
-		
+
 		// Verify fork was created
 		_, err = os.Stat(repo.forkRepoPath)
 		assert.NoError(t, err)
-		
+
 		// Verify remote was added
 		remote, err := RunGitCommand(ctx, tempDir, "remote", "get-url", "container-use")
 		require.NoError(t, err)
 		assert.Equal(t, repo.forkRepoPath, strings.TrimSpace(remote))
 	})
 }
-
-