docs(buglog): log worker signal and launch-type issues (bug-1954..bug-1956)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.wolf/bugs/bug-1956.md

@@ -0,0 +1,69 @@
+---
+id: "bug-1956"
+status: "investigating"
+status_updated: "2026-10-10"
+status_note: "suspected: confirm whether a job without launch type decodes to NULL at the worker"
+component: "worker"
+severity: "crash"
+timestamp: "2026-10-10T08:46:13Z"
+last_seen: "2026-10-10T08:46:13Z"
+occurrences: 1
+files: ["src/worker/src/controller_connector.c"]
+tags: ["worker", "crash", "launch-type"]
+related: []
+---
+
+# bug-1956: xcecd compares a NULL launch_type with strcmp when a job has no launch type (possible crash)
+
+## Description
+**Observed:** (source reading, 2026-10-10; suspected, not reproduced)
+`job_start_local_task()` stores NULL when the start info has no launch type
+and then dereferences it:
+```c
+if (d->start_info->launch_type) {
+    job_ctx->startinfo->launch_type = strdup(...);
+} else {
+    job_ctx->startinfo->launch_type = NULL;          /* :981-985 */
+}
+...
+if (strcmp(job_ctx->startinfo->launch_type, "openmpi") == 0   /* :994 */
+```
+`job_start_remote_task()` does the same without a check (`:753`). The apiserver
+sends no launch type when the user gives none (`cStringOrNil`,
+`backend/convert.go:339`). Jobs without a launch type do run in existing
+tests, so the decoder may deliver an empty string rather than NULL: not
+confirmed either way.
+
+**Expected:** a missing launch type means a plain (non-MPI) job; no NULL
+dereference.
+**Impact:** possible worker crash at job start for jobs without a launch
+type.
+**Found by:** review of the bug-1940/1942 fixes, 2026-10-10.
+## Environment
+- OS: no /etc/os-release; Docker container; NixOS kernel; kernel Linux 6.18.33 x86_64
+- libc: glibc 2.42-47 (interpreter /nix/store/wb6rhpznjfczwlwx23zmdrrw74bayxw4-glibc-2.42-47/lib/ld-linux-x86-64.so.2)
+- Toolchain: gcc (GCC) 15.2.0, meson 1.9.1
+- Build: asan (xce.build)
+- Code: scheduler-framework @ 8568c8ab-dirty
+- Deployment: real `xcecd` worker (systemd/dbus); multi-host for the remote-task case
+
+## Reproduction
+1. Decode a job start message whose start info has no launch type and run
+   `job_start_local_task()` (worker unit test), or submit a job without a
+   launch type through libxce/harness to a real `xcecd`.
+2. Check whether `startinfo->launch_type` is NULL at `:994`.
+- Frequency: deterministic by code reading (not yet run)
+- Evidence: the code quoted in Description; no logs kept.
+## Root cause
+TODO: required for fixed/partial
+
+## Fix
+TODO: required for fixed/partial
+
+## Verification
+- Test: TODO: name + file; RED before the fix, GREEN after
+- Suites: TODO: suite results and build profile
+- Live: TODO: soak/deploy run, or n/a and why
+
+## References
+- Related: none