feat(issues): wire session resume through CLI and frontend handlers

Add --resume-sessions CLI arg to investigate subparser. Frontend reads
persisted session IDs from investigation_state.json and passes them to
the subprocess when resuming an interrupted investigation.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

apps/backend/runners/github/orchestrator.py

@@ -1519,6 +1519,7 @@ class GitHubOrchestrator:
         self,
         issue_number: int,
         project_root: Path | None = None,
+        resume_sessions: dict[str, str] | None = None,
     ) -> dict:
         """
         Run an AI investigation on a GitHub issue.
@@ -1531,6 +1532,8 @@ class GitHubOrchestrator:
             issue_number: The GitHub issue number to investigate
             project_root: Working directory for agents (e.g., worktree path).
                          Defaults to self.project_dir.
+            resume_sessions: Optional dict mapping specialist name to SDK
+                           session ID for resuming interrupted investigations.
 
         Returns:
             Dict with investigation results (InvestigationReport as dict)
@@ -1616,6 +1619,7 @@ class GitHubOrchestrator:
                 issue_labels=issue_labels,
                 issue_comments=issue_comments,
                 project_root=working_dir,
+                resume_sessions=resume_sessions,
             )
 
             # Update state to findings_ready

apps/backend/runners/github/runner.py

@@ -348,13 +348,25 @@ async def cmd_investigate(args) -> int:
         sys.stderr.reconfigure(line_buffering=True)
 
     config = get_config(args)
+
+    # Parse resume sessions if provided
+    resume_sessions = None
+    if getattr(args, "resume_sessions", None):
+        try:
+            resume_sessions = json.loads(args.resume_sessions)
+        except json.JSONDecodeError:
+            safe_print("Warning: Invalid --resume-sessions JSON, starting fresh")
+
     orchestrator = GitHubOrchestrator(
         project_dir=args.project,
         config=config,
         progress_callback=print_progress,
     )
 
-    result = await orchestrator.investigate_issue(args.issue_number)
+    result = await orchestrator.investigate_issue(
+        args.issue_number,
+        resume_sessions=resume_sessions,
+    )
 
     # Output JSON for the Electron frontend to parse
     safe_print("\nJSON Output")
@@ -830,6 +842,12 @@ def main():
     investigate_parser.add_argument(
         "issue_number", type=int, help="Issue number to investigate"
     )
+    investigate_parser.add_argument(
+        "--resume-sessions",
+        type=str,
+        default=None,
+        help="JSON dict of specialist_name:session_id for resuming interrupted investigations",
+    )
 
     # post-investigation command
     post_investigation_parser = subparsers.add_parser(

apps/backend/runners/github/services/issue_investigation_orchestrator.py

@@ -152,6 +152,7 @@ class IssueInvestigationOrchestrator(ParallelAgentOrchestrator):
         issue_labels: list[str] | None = None,
         issue_comments: list[str] | None = None,
         project_root: Path | None = None,
+        resume_sessions: dict[str, str] | None = None,
     ) -> InvestigationReport:
         """
         Run a full investigation on a GitHub issue.
@@ -217,6 +218,7 @@ class IssueInvestigationOrchestrator(ParallelAgentOrchestrator):
             model=model,
             thinking_budget=thinking_budget,
             issue_number=issue_number,
+            resume_sessions=resume_sessions,
         )
 
         self._report_progress(
@@ -331,6 +333,7 @@ Use Read, Grep, and Glob tools to explore the codebase.
         model: str,
         thinking_budget: int | None,
         issue_number: int | None = None,
+        resume_sessions: dict[str, str] | None = None,
     ) -> dict[str, dict[str, Any]]:
         """Run all investigation specialists in parallel.
 
@@ -340,6 +343,8 @@ Use Read, Grep, and Glob tools to explore the codebase.
             model: Model to use
             thinking_budget: Max thinking tokens
             issue_number: GitHub issue number (for session persistence)
+            resume_sessions: Optional dict mapping specialist name to SDK
+                           session ID for resuming interrupted sessions.
 
         Returns:
             Dict mapping specialist name → stream result dict
@@ -363,6 +368,10 @@ Use Read, Grep, and Glob tools to explore the codebase.
                     if thinking_budget
                     else None
                 )
+                # Look up resume session ID for this specialist
+                _resume_id = (
+                    resume_sessions.get(cfg.name) if resume_sessions else None
+                )
                 return self._run_specialist_session(
                     config=cfg,
                     prompt=_prompt,
@@ -373,6 +382,7 @@ Use Read, Grep, and Glob tools to explore the codebase.
                     agent_type="investigation_specialist",
                     context_name=f"Investigation:{cfg.name}",
                     max_messages=cfg.max_turns,
+                    resume_session_id=_resume_id,
                     on_thinking=lambda text, _name=cfg.name: emit_json_event(
                         "thinking",
                         _name,

apps/frontend/src/main/ipc-handlers/github/investigation-handlers.ts

@@ -977,13 +977,35 @@ async function runInvestigation(
         });
       }
 
-      const args = buildRunnerArgs(
-        getRunnerPath(backendPath),
-        project.path,
-        'investigate',
-        [String(issueNumber)],
-        { model, thinkingLevel },
-      );
+      // Read session IDs for interrupted investigation resume
+      let resumeSessionsArg: string[] = [];
+      try {
+        const stateFile = path.join(
+          project.path, '.auto-claude', 'issues', `${issueNumber}`, 'investigation_state.json'
+        );
+        if (fs.existsSync(stateFile)) {
+          const stateData = JSON.parse(fs.readFileSync(stateFile, 'utf-8'));
+          if (stateData.sessions && Object.keys(stateData.sessions).length > 0) {
+            // Only pass sessions if this is a resume (status was 'investigating')
+            if (stateData.status === 'investigating') {
+              resumeSessionsArg = ['--resume-sessions', JSON.stringify(stateData.sessions)];
+            }
+          }
+        }
+      } catch {
+        // Non-fatal: will start fresh
+      }
+
+      const args = [
+        ...buildRunnerArgs(
+          getRunnerPath(backendPath),
+          project.path,
+          'investigate',
+          [String(issueNumber)],
+          { model, thinkingLevel },
+        ),
+        ...resumeSessionsArg,
+      ];
 
       const startedAt = new Date().toISOString();