MCP server for the sessions Drydock hosts: review-comment loop, bounded worktree fan-out, workspace awareness

README.md

@@ -19,6 +19,12 @@ activity, Git status, and your changes without leaving the app.
   terminal tabs, one per session, with session activity surfaced in the UI.
 - **Git & GitHub awareness** — repository status, review, and search surfaces
   built around the repos you register.
+- **MCP tools for your sessions** — sessions Drydock starts can call back into
+  the app: read the review comments you left on a diff and reply to them,
+  create worktrees and open sessions in them (bounded, and a session an agent
+  started cannot spawn further ones), and list your registered repositories
+  and running sessions. Local sessions only; remote SSH sessions do not get
+  these tools.
 - **Persistent state** — registered repositories and window layout persist
   across restarts.
 - **Remote repositories over SSH** — register a repo on a remote host via

app/src/main/java/app/drydock/DrydockApplication.java

@@ -17,6 +17,11 @@
 import app.drydock.git.WorktreeService;
 import app.drydock.github.GitHubService;
 import app.drydock.launcher.DockIcon;
+import app.drydock.mcp.McpConfigWriter;
+import app.drydock.mcp.McpServer;
+import app.drydock.mcp.McpSessionRegistry;
+import app.drydock.mcp.McpToolRouter;
+import app.drydock.mcp.WorkspaceMcpSessionContext;
 import app.drydock.review.AnnotationStore;
 import app.drydock.search.SessionSearchService;
 import app.drydock.state.JsonApplicationStateRepository;
@@ -61,7 +66,6 @@
 import java.util.Base64;
 import java.util.Optional;
 import java.util.function.Supplier;
-import java.util.concurrent.TimeUnit;
 
 /**
  * The main window: a {@link SplitPane} with the repository sidebar (plan
@@ -121,6 +125,7 @@ public final class DrydockApplication extends Application {
     private AppShell appShell;
     private GitHubService gitHubService;
     private AnnotationStore annotationStore;
+    private McpServer mcpServer;
 
     private boolean shutdownConfirmed;
 
@@ -200,6 +205,7 @@ private void startOnFxThread(Stage primaryStage) {
                         mainWorkspace, viewModel);
 
         installSessionActivityHooks(activityDir);
+        startMcpServer(stateDir);
 
         appShell = new AppShell(primaryStage, WINDOW_TITLE, sidebar, mainWorkspace,
                 repositoryManager.state().ui().sidebarWidth(),
@@ -800,6 +806,17 @@ public void stop() {
         if (gitHubService != null) {
             closeQuietly("GitHubService", gitHubService::close);
         }
+        // Before EVERY service a tool call can reach -- AnnotationStore and
+        // SessionManager both are -- because once the listener socket is gone
+        // and the in-flight handlers have drained, no tool call can arrive
+        // mid-teardown and touch a half-closed service. Closing
+        // AnnotationStore first (as an earlier revision did) let an in-flight
+        // review_reply reach AnnotationStore.persistAsync after its save
+        // executor had shut down, surfacing to the agent as a bare
+        // RejectedExecutionException wrapped in "Internal error".
+        if (mcpServer != null) {
+            closeQuietly("McpServer", mcpServer::close);
+        }
         if (annotationStore != null) {
             closeQuietly("AnnotationStore", annotationStore::close);
         }
@@ -869,6 +886,59 @@ private void installSessionActivityHooks(Path activityDirectory) {
                 });
     }
 
+    /**
+     * Brings up the localhost MCP server and points subsequently launched
+     * sessions at a per-session {@code --mcp-config} file, so the sessions
+     * Drydock hosts can call back into it (see {@code app.drydock.mcp}).
+     *
+     * <p>Runs off the FX thread: {@link McpConfigWriter#purgeStale()} and
+     * {@link McpServer#start()} both do I/O. A failure is logged and swallowed
+     * -- exactly like {@link #installSessionActivityHooks} -- because a
+     * session without Drydock tools is strictly better than one that will not
+     * launch. {@link SessionManager#useMcpConfig} is called inside {@link
+     * Platform#runLater} for the same reason the hook install's
+     * {@code useActivitySettings} is.</p>
+     *
+     * <p>Never logs the port or a token: the endpoint URL carries the port,
+     * and the per-session token is written only into its owner-readable
+     * config file.</p>
+     */
+    private void startMcpServer(Path stateDirectory) {
+        McpSessionRegistry registry = new McpSessionRegistry();
+        McpConfigWriter configWriter = new McpConfigWriter(stateDirectory);
+        WorkspaceMcpSessionContext context = new WorkspaceMcpSessionContext(
+                sessionManager::sessions,
+                repositoryManager::repositories,
+                annotationStore,
+                gitStatusService,
+                worktreeService,
+                UserConfig::load,
+                (worktree, prompt) -> mainWorkspace.startAgentSession(worktree, prompt));
+        McpServer server = new McpServer(registry, new McpToolRouter(context, registry));
+        // Published before start() so a shutdown racing startup still reaches
+        // it. Publication alone would not be enough -- a close() that wins the
+        // race would find nothing bound yet and no-op -- which is why
+        // McpServer.close() also latches a flag that start() honours.
+        mcpServer = server;
+
+        Thread.ofVirtual().name("drydock-mcp-start").start(() -> {
+            try {
+                // Every config file left by a previous run is stale by
+                // definition: no terminal process survives a restart.
+                configWriter.purgeStale();
+                server.start();
+            } catch (IOException | RuntimeException e) {
+                LOG.log(Level.WARNING, "MCP server unavailable; sessions will run without Drydock tools", e);
+                server.close();
+                return;
+            }
+            Platform.runLater(() -> {
+                sessionManager.useMcpConfig(configWriter, registry, server.endpointUrl());
+                LOG.log(Level.INFO, "MCP server started on loopback");
+            });
+        });
+    }
+
     /**
      * Waits briefly for {@link #installSessionActivityHooks}'s file writes, so
      * shutdown cannot race a half-written hook script (AGENTS.md: background

app/src/main/java/app/drydock/agent/api/CreateContext.java

@@ -10,13 +10,18 @@
  * Inputs a provider needs to build a create command. {@code sessionId} is the
  * app-generated id for {@code PRESET} providers; {@code DISCOVERED} providers
  * ignore it. {@code remote}, when present, means launch over SSH.
+ *
+ * <p>{@code mcpConfig} is the per-session MCP config file when one was minted
+ * for this launch, empty otherwise; providers that do not support it (see
+ * {@code AgentProvider.supportsMcpConfig}) ignore it.</p>
  */
 public record CreateContext(String displayName, String sessionId, Path workingDirectory,
-                            Optional<SshRemote> remote) {
+                            Optional<SshRemote> remote, Optional<Path> mcpConfig) {
     public CreateContext {
         Objects.requireNonNull(displayName, "displayName");
         Objects.requireNonNull(sessionId, "sessionId");
         Objects.requireNonNull(workingDirectory, "workingDirectory");
         Objects.requireNonNull(remote, "remote");
+        Objects.requireNonNull(mcpConfig, "mcpConfig");
     }
 }

app/src/main/java/app/drydock/agent/api/ResumeContext.java

@@ -6,13 +6,20 @@
 import java.util.Objects;
 import java.util.Optional;
 
-/** Inputs a provider needs to build a resume command. */
+/**
+ * Inputs a provider needs to build a resume command.
+ *
+ * <p>{@code mcpConfig} is the per-session MCP config file when one was minted
+ * for this launch, empty otherwise; providers that do not support it (see
+ * {@code AgentProvider.supportsMcpConfig}) ignore it.</p>
+ */
 public record ResumeContext(Optional<String> agentSessionId, Optional<String> agentSessionName,
-                            Path workingDirectory, Optional<SshRemote> remote) {
+                            Path workingDirectory, Optional<SshRemote> remote, Optional<Path> mcpConfig) {
     public ResumeContext {
         Objects.requireNonNull(agentSessionId, "agentSessionId");
         Objects.requireNonNull(agentSessionName, "agentSessionName");
         Objects.requireNonNull(workingDirectory, "workingDirectory");
         Objects.requireNonNull(remote, "remote");
+        Objects.requireNonNull(mcpConfig, "mcpConfig");
     }
 }

app/src/main/java/app/drydock/agent/providers/claude/ClaudeAgentProvider.java

@@ -86,6 +86,11 @@ public boolean supportsRemote() {
         return true;
     }
 
+    @Override
+    public boolean supportsMcpConfig() {
+        return true;
+    }
+
     @Override
     public LaunchPlan buildCreateCommand(CreateContext c) {
         if (c.remote().isPresent()) {
@@ -102,6 +107,7 @@ public LaunchPlan buildCreateCommand(CreateContext c) {
             sessionIdUsed = true;
         }
         command.append(activitySettingsFlag(caps));
+        command.append(mcpConfigFlag(caps, c.mcpConfig()));
         return LaunchPlan.of(command.toString(), sessionIdUsed);
     }
 
@@ -116,7 +122,8 @@ public LaunchPlan buildResumeCommand(ResumeContext r) {
             }
             return LaunchPlan.of(SshCommandBuilder.interactiveSessionCommand(r.remote().get(), exec), false);
         }
-        String suffix = activitySettingsFlag(detectCaps());
+        ClaudeCapabilities caps = detectCaps();
+        String suffix = activitySettingsFlag(caps) + mcpConfigFlag(caps, r.mcpConfig());
         if (r.agentSessionId().isPresent()) {
             return LaunchPlan.of(ENV_CLEANUP_PREFIX + "claude --resume " + AgentCommands.shellQuote(r.agentSessionId().get()) + suffix, false);
         }
@@ -152,7 +159,7 @@ private ClaudeCapabilities detectCaps() {
             return capabilityService.detectCapabilitiesBlocking();
         } catch (RuntimeException e) {
             // Fail conservatively: no name/session-id/settings support (matches NO_CAPABILITIES semantics).
-            return new ClaudeCapabilities(false, true, false, false, false, "unknown");
+            return new ClaudeCapabilities(false, true, false, false, false, false, "unknown");
         }
     }
 
@@ -164,4 +171,26 @@ private String activitySettingsFlag(ClaudeCapabilities caps) {
         return " --settings " + AgentCommands.shellQuote(settings.get().toString());
     }
 
+    /**
+     * Adds {@code --mcp-config <file>} so the session can call back into this
+     * app (see {@code app.drydock.mcp.McpServer}). Empty whenever the installed
+     * {@code claude} does not advertise the flag, or no per-session config file
+     * was minted for this launch -- a session without Drydock tools is strictly
+     * better than one that fails to launch.
+     *
+     * <p>No {@code --strict-mcp-config}: that would suppress the user's own MCP
+     * servers, and Drydock's tools are an addition to their setup, not a
+     * replacement.</p>
+     *
+     * <p>Only reached after each builder's remote early-return: {@code claude}
+     * runs on the remote host and cannot reach this machine's loopback
+     * address, so a remote session never receives a local config path.</p>
+     */
+    private static String mcpConfigFlag(ClaudeCapabilities caps, Optional<Path> mcpConfig) {
+        if (!caps.supportsMcpConfig() || mcpConfig.isEmpty()) {
+            return "";
+        }
+        return " --mcp-config " + AgentCommands.shellQuote(mcpConfig.get().toString());
+    }
+
 }

app/src/main/java/app/drydock/agent/providers/claude/internal/ClaudeCapabilities.java

@@ -19,6 +19,7 @@ public record ClaudeCapabilities(
         boolean supportsForkSession,
         boolean supportsSessionId,
         boolean supportsSettings,
+        boolean supportsMcpConfig,
         String version
 ) {
 

app/src/main/java/app/drydock/agent/providers/claude/internal/ClaudeCapabilityService.java

@@ -38,6 +38,9 @@ public final class ClaudeCapabilityService implements AutoCloseable {
     private static final Pattern FORK_SESSION_FLAG = Pattern.compile("--fork-session\\b");
     private static final Pattern SESSION_ID_FLAG = Pattern.compile("--session-id\\b");
     private static final Pattern SETTINGS_FLAG = Pattern.compile("--settings\\b");
+    // Not "--mcp-config\\b": '-' is a non-word character, so \b would also
+    // match "--mcp-config-verbose". Require a non-flag character after it.
+    private static final Pattern MCP_CONFIG_FLAG = Pattern.compile("--mcp-config(?![\\w-])");
 
     private final ClaudeExecutableLocator locator;
     private final ExecutorService executor;
@@ -94,9 +97,15 @@ public ClaudeCapabilities detectCapabilitiesBlocking() {
         boolean supportsForkSession = FORK_SESSION_FLAG.matcher(help).find();
         boolean supportsSessionId = SESSION_ID_FLAG.matcher(help).find();
         boolean supportsSettings = SETTINGS_FLAG.matcher(help).find();
+        boolean supportsMcpConfig = helpMentionsMcpConfig(help);
 
         return new ClaudeCapabilities(supportsName, supportsResume, supportsForkSession, supportsSessionId,
-                supportsSettings, version);
+                supportsSettings, supportsMcpConfig, version);
+    }
+
+    /** Package-private for tests: conservative presence check for {@code --mcp-config}. */
+    static boolean helpMentionsMcpConfig(String helpOutput) {
+        return MCP_CONFIG_FLAG.matcher(helpOutput).find();
     }
 
     private ProcessResult runAndRequireSuccess(Path claude, String arg) {

app/src/main/java/app/drydock/agent/providers/codex/CodexAgentProvider.java

@@ -82,6 +82,12 @@ public boolean supportsRemote() {
         return false;
     }
 
+    /** No {@code --mcp-config} equivalent: Drydock's per-session MCP file is Claude-specific. */
+    @Override
+    public boolean supportsMcpConfig() {
+        return false;
+    }
+
     @Override
     public LaunchPlan buildCreateCommand(CreateContext c) {
         if (c.remote().isPresent()) {

app/src/main/java/app/drydock/agent/providers/pi/PiAgentProvider.java

@@ -82,6 +82,12 @@ public boolean supportsRemote() {
         return false;
     }
 
+    /** No {@code --mcp-config} equivalent: Drydock's per-session MCP file is Claude-specific. */
+    @Override
+    public boolean supportsMcpConfig() {
+        return false;
+    }
+
     @Override
     public LaunchPlan buildCreateCommand(CreateContext c) {
         if (c.remote().isPresent()) {

app/src/main/java/app/drydock/agent/spi/AgentProvider.java

@@ -47,6 +47,20 @@ public interface AgentProvider {
      */
     boolean supportsRemote();
 
+    /**
+     * Whether this integration knows what to do with a per-session MCP config
+     * file (Claude's {@code --mcp-config}). A static fact about the integration,
+     * like {@link #supportsRemote()}, so implementations MUST make this CHEAP and
+     * non-blocking: no process spawns, no I/O. Safe on the JavaFX thread.
+     *
+     * <p>Distinct from any probed CLI flag: this says the integration can consume
+     * such a file at all, not that the installed binary accepts the option. The
+     * binary check stays provider-internal (Claude's {@code
+     * ClaudeCapabilities.supportsMcpConfig}), per this interface's rule that
+     * provider-internal flag detail is not exposed here.</p>
+     */
+    boolean supportsMcpConfig();
+
     LaunchPlan buildCreateCommand(CreateContext c);
 
     LaunchPlan buildResumeCommand(ResumeContext r);