feat: add session reload command (#63)

Author: benvinegar

README.md

@@ -158,13 +158,17 @@ Use explicit session targeting with either a live `<session-id>` or `--repo <pat
 hunk session list
 hunk session context --repo .
 hunk session navigate --repo . --file README.md --hunk 2
+hunk session reload --repo . -- diff
+hunk session reload --repo . -- show HEAD~1 -- README.md
 hunk session comment add --repo . --file README.md --new-line 103 --summary "Frame this as MCP-first"
 hunk session comment list --repo .
 hunk session comment rm --repo . mcp:1234
 hunk session comment clear --repo . --file README.md --yes
 ```
 
-The session CLI works against live session comments only. It does not edit `.hunk/latest.json`.
+`hunk session reload ... -- <hunk command>` swaps the live session to a new `diff`, `show`, or other reviewable Hunk input without opening a new TUI window.
+
+The session CLI can inspect, navigate, annotate, and reload a live session, but it does not edit `.hunk/latest.json`.
 
 ## Performance notes
 

src/core/cli.ts

@@ -2,6 +2,7 @@ import { existsSync, readFileSync, statSync } from "node:fs";
 import { dirname, resolve } from "node:path";
 import { Command } from "commander";
 import type {
+  CliInput,
   CommonOptions,
   HelpCommandInput,
   LayoutMode,
@@ -398,6 +399,24 @@ async function parseDifftoolCommand(tokens: string[], argv: string[]): Promise<P
   };
 }
 
+function requireReloadableCliInput(input: ParsedCliInput): CliInput {
+  if (input.kind === "help" || input.kind === "pager" || input.kind === "mcp-serve") {
+    throw new Error(
+      "Session reload requires a Hunk review command after --, such as `diff` or `show`.",
+    );
+  }
+
+  if (input.kind === "session") {
+    throw new Error("Session reload cannot invoke another session command.");
+  }
+
+  if (input.kind === "patch" && (!input.file || input.file === "-")) {
+    throw new Error("Session reload does not support `patch -` or stdin-backed patch input.");
+  }
+
+  return input;
+}
+
 /** Parse `hunk session ...` as live-session daemon-backed commands. */
 async function parseSessionCommand(tokens: string[]): Promise<ParsedCliInput> {
   const [subcommand, ...rest] = tokens;
@@ -417,6 +436,8 @@ async function parseSessionCommand(tokens: string[]): Promise<ParsedCliInput> {
           "  hunk session context <session-id>",
           "  hunk session context --repo <path>",
           "  hunk session navigate <session-id> --file <path> (--hunk <n> | --old-line <n> | --new-line <n>)",
+          "  hunk session reload <session-id> -- diff [ref] [-- <pathspec...>]",
+          "  hunk session reload <session-id> -- show [ref] [-- <pathspec...>]",
           "  hunk session comment add <session-id> --file <path> (--old-line <n> | --new-line <n>) --summary <text>",
           "  hunk session comment list <session-id>",
           "  hunk session comment rm <session-id> <comment-id>",
@@ -551,6 +572,64 @@ async function parseSessionCommand(tokens: string[]): Promise<ParsedCliInput> {
     };
   }
 
+  if (subcommand === "reload") {
+    const separatorIndex = rest.indexOf("--");
+    const outerTokens = separatorIndex === -1 ? rest : rest.slice(0, separatorIndex);
+
+    const command = new Command("session reload")
+      .description("replace the contents of one live Hunk session")
+      .argument("[sessionId]")
+      .option("--repo <path>", "target the live session whose repo root matches this path")
+      .option("--json", "emit structured JSON");
+
+    let parsedSessionId: string | undefined;
+    let parsedOptions: { repo?: string; json?: boolean } = {};
+
+    command.action((sessionId: string | undefined, options: { repo?: string; json?: boolean }) => {
+      parsedSessionId = sessionId;
+      parsedOptions = options;
+    });
+
+    if (outerTokens.includes("--help") || outerTokens.includes("-h")) {
+      return {
+        kind: "help",
+        text:
+          `${command.helpInformation().trimEnd()}\n\n` +
+          [
+            "Examples:",
+            "  hunk session reload --repo . -- diff",
+            "  hunk session reload --repo . -- diff main...feature -- src/ui",
+            "  hunk session reload --repo . -- show HEAD~1 -- README.md",
+          ].join("\n") +
+          "\n",
+      };
+    }
+
+    if (separatorIndex === -1) {
+      throw new Error(
+        "Pass the replacement Hunk command after `--`, for example `hunk session reload <session-id> -- diff`.",
+      );
+    }
+
+    const nestedTokens = rest.slice(separatorIndex + 1);
+    if (nestedTokens.length === 0) {
+      throw new Error(
+        "Pass the replacement Hunk command after `--`, for example `hunk session reload <session-id> -- diff`.",
+      );
+    }
+
+    await parseStandaloneCommand(command, outerTokens);
+    const nextInput = requireReloadableCliInput(await parseCli(["bun", "hunk", ...nestedTokens]));
+
+    return {
+      kind: "session",
+      action: "reload",
+      output: resolveJsonOutput(parsedOptions),
+      selector: resolveExplicitSessionSelector(parsedSessionId, parsedOptions.repo),
+      nextInput,
+    };
+  }
+
   if (subcommand === "comment") {
     const [commentSubcommand, ...commentRest] = rest;
     if (!commentSubcommand || commentSubcommand === "--help" || commentSubcommand === "-h") {

src/core/types.ts

@@ -115,6 +115,14 @@ export interface SessionNavigateCommandInput {
   line?: number;
 }
 
+export interface SessionReloadCommandInput {
+  kind: "session";
+  action: "reload";
+  output: SessionCommandOutput;
+  selector: SessionSelectorInput;
+  nextInput: CliInput;
+}
+
 export interface SessionCommentAddCommandInput {
   kind: "session";
   action: "comment-add";
@@ -158,6 +166,7 @@ export type SessionCommandInput =
   | SessionListCommandInput
   | SessionGetCommandInput
   | SessionNavigateCommandInput
+  | SessionReloadCommandInput
   | SessionCommentAddCommandInput
   | SessionCommentListCommandInput
   | SessionCommentRemoveCommandInput

src/mcp/client.ts

@@ -4,6 +4,7 @@ import type {
   HunkSessionRegistration,
   HunkSessionSnapshot,
   NavigatedSelectionResult,
+  ReloadedSessionResult,
   RemovedCommentResult,
   SessionClientMessage,
   SessionCommandResult,
@@ -33,6 +34,9 @@ interface HunkAppBridge {
   navigateToHunk: (
     message: Extract<SessionServerMessage, { command: "navigate_to_hunk" }>,
   ) => Promise<NavigatedSelectionResult>;
+  reloadSession: (
+    message: Extract<SessionServerMessage, { command: "reload_session" }>,
+  ) => Promise<ReloadedSessionResult>;
   removeComment: (
     message: Extract<SessionServerMessage, { command: "remove_comment" }>,
   ) => Promise<RemovedCommentResult>;
@@ -54,7 +58,7 @@ export class HunkHostClient {
   private lastConnectionWarning: string | null = null;
 
   constructor(
-    private readonly registration: HunkSessionRegistration,
+    private registration: HunkSessionRegistration,
     private snapshot: HunkSessionSnapshot,
   ) {}
 
@@ -93,6 +97,20 @@ export class HunkHostClient {
     this.websocket = null;
   }
 
+  getRegistration() {
+    return this.registration;
+  }
+
+  replaceSession(registration: HunkSessionRegistration, snapshot: HunkSessionSnapshot) {
+    this.registration = registration;
+    this.snapshot = snapshot;
+    this.send({
+      type: "register",
+      registration,
+      snapshot,
+    });
+  }
+
   private resolveConfig() {
     return resolveHunkMcpConfig();
   }
@@ -281,6 +299,8 @@ export class HunkHostClient {
         return this.bridge.applyComment(message);
       case "navigate_to_hunk":
         return this.bridge.navigateToHunk(message);
+      case "reload_session":
+        return this.bridge.reloadSession(message);
       case "remove_comment":
         return this.bridge.removeComment(message);
       case "clear_comments":

src/mcp/daemonState.ts

@@ -9,6 +9,8 @@ import type {
   ListedSession,
   NavigateToHunkToolInput,
   NavigatedSelectionResult,
+  ReloadSessionToolInput,
+  ReloadedSessionResult,
   RemoveCommentToolInput,
   RemovedCommentResult,
   SelectedSessionContext,
@@ -267,6 +269,16 @@ export class HunkDaemonState {
     );
   }
 
+  sendReloadSession(input: ReloadSessionToolInput) {
+    return this.sendCommand<ReloadedSessionResult, "reload_session">(
+      { sessionId: input.sessionId, repoRoot: input.repoRoot },
+      "reload_session",
+      input,
+      "Timed out waiting for the Hunk session to reload the requested contents.",
+      30_000,
+    );
+  }
+
   sendRemoveComment(input: RemoveCommentToolInput) {
     return this.sendCommand<RemovedCommentResult, "remove_comment">(
       { sessionId: input.sessionId, repoRoot: input.repoRoot },
@@ -326,6 +338,7 @@ export class HunkDaemonState {
     command: CommandName,
     input: Extract<SessionServerMessage, { command: CommandName }>["input"],
     timeoutMessage: string,
+    timeoutMs = 15_000,
   ) {
     const session = resolveSessionTarget(this.listSessions(), selector);
     const requestId = randomUUID();
@@ -334,7 +347,7 @@ export class HunkDaemonState {
       const timeout = setTimeout(() => {
         this.pendingCommands.delete(requestId);
         reject(new Error(timeoutMessage));
-      }, 15_000);
+      }, timeoutMs);
 
       this.pendingCommands.set(requestId, {
         sessionId: session.sessionId,

src/mcp/server.ts

@@ -19,6 +19,7 @@ const SUPPORTED_SESSION_ACTIONS: SessionDaemonAction[] = [
   "get",
   "context",
   "navigate",
+  "reload",
   "comment-add",
   "comment-list",
   "comment-rm",
@@ -99,6 +100,14 @@ async function handleSessionApiRequest(state: HunkDaemonState, request: Request)
         };
         break;
       }
+      case "reload":
+        response = {
+          result: await state.sendReloadSession({
+            ...input.selector,
+            nextInput: input.nextInput,
+          }),
+        };
+        break;
       case "comment-add":
         response = {
           result: await state.sendComment({

src/mcp/sessionRegistration.ts

@@ -1,7 +1,7 @@
 import { randomUUID } from "node:crypto";
 import type { AppBootstrap } from "../core/types";
 import { hunkLineRange } from "../core/liveComments";
-import type { HunkSessionRegistration, HunkSessionSnapshot } from "./types";
+import type { HunkSessionRegistration, HunkSessionSnapshot, SessionFileSummary } from "./types";
 
 function inferRepoRoot(bootstrap: AppBootstrap) {
   return bootstrap.input.kind === "git" ||
@@ -11,6 +11,17 @@ function inferRepoRoot(bootstrap: AppBootstrap) {
     : undefined;
 }
 
+function buildSessionFiles(bootstrap: AppBootstrap): SessionFileSummary[] {
+  return bootstrap.changeset.files.map((file) => ({
+    id: file.id,
+    path: file.path,
+    previousPath: file.previousPath,
+    additions: file.stats.additions,
+    deletions: file.stats.deletions,
+    hunkCount: file.metadata.hunks.length,
+  }));
+}
+
 /** Build the daemon-facing metadata for one live Hunk TUI session. */
 export function createSessionRegistration(bootstrap: AppBootstrap): HunkSessionRegistration {
   return {
@@ -22,14 +33,22 @@ export function createSessionRegistration(bootstrap: AppBootstrap): HunkSessionR
     title: bootstrap.changeset.title,
     sourceLabel: bootstrap.changeset.sourceLabel,
     launchedAt: new Date().toISOString(),
-    files: bootstrap.changeset.files.map((file) => ({
-      id: file.id,
-      path: file.path,
-      previousPath: file.previousPath,
-      additions: file.stats.additions,
-      deletions: file.stats.deletions,
-      hunkCount: file.metadata.hunks.length,
-    })),
+    files: buildSessionFiles(bootstrap),
+  };
+}
+
+/** Rebuild registration metadata after a live session reload while preserving session identity. */
+export function updateSessionRegistration(
+  current: HunkSessionRegistration,
+  bootstrap: AppBootstrap,
+): HunkSessionRegistration {
+  return {
+    ...current,
+    repoRoot: inferRepoRoot(bootstrap),
+    inputKind: bootstrap.input.kind,
+    title: bootstrap.changeset.title,
+    sourceLabel: bootstrap.changeset.sourceLabel,
+    files: buildSessionFiles(bootstrap),
   };
 }
 

src/mcp/types.ts

@@ -68,6 +68,10 @@ export interface NavigateToHunkToolInput extends SessionTargetInput {
   line?: number;
 }
 
+export interface ReloadSessionToolInput extends SessionTargetInput {
+  nextInput: CliInput;
+}
+
 export interface LiveComment extends AgentAnnotation {
   id: string;
   source: "mcp";
@@ -119,6 +123,16 @@ export interface ClearedCommentsResult {
   filePath?: string;
 }
 
+export interface ReloadedSessionResult {
+  sessionId: string;
+  inputKind: CliInput["kind"];
+  title: string;
+  sourceLabel: string;
+  fileCount: number;
+  selectedFilePath?: string;
+  selectedHunkIndex: number;
+}
+
 export interface ListedSessionFile extends SessionFileSummary {
   selected: boolean;
 }
@@ -139,7 +153,8 @@ export type SessionCommandResult =
   | AppliedCommentResult
   | NavigatedSelectionResult
   | RemovedCommentResult
-  | ClearedCommentsResult;
+  | ClearedCommentsResult
+  | ReloadedSessionResult;
 
 export type SessionClientMessage =
   | {
@@ -194,6 +209,12 @@ export type SessionServerMessage =
       command: "navigate_to_hunk";
       input: NavigateToHunkToolInput;
     }
+  | {
+      type: "command";
+      requestId: string;
+      command: "reload_session";
+      input: ReloadSessionToolInput;
+    }
   | {
       type: "command";
       requestId: string;