wiki: add troubleshooting articles from MajorTwin v8 cycle

Two articles surfaced during the v8 deploy + eval on 2026-04-25:

- Ollama: `ollama run` with piped stdin bypasses the chat template and
  SYSTEM prompt — output looks like raw base-model completion. Caught
  during initial v8 smoke test. Fix: use /api/chat HTTP endpoint.

- rsync over Tailscale can hang in TCP teardown after the data has
  fully transferred. Verify with md5sum, then kill the hung pipeline.
  Includes a watcher-threshold gotcha (set below true file size, not
  above) and prevention tips.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

05-troubleshooting/index.md

@@ -14,6 +14,7 @@ Practical fixes for common Linux, networking, and application problems.
 - [Mail Client Stops Receiving: Fail2ban IMAP Self-Ban](networking/fail2ban-imap-self-ban-mail-client.md)
 - [firewalld: Mail Ports Wiped After Reload](networking/firewalld-mail-ports-reset.md)
 - [Tailscale SSH: Unexpected Re-Authentication Prompt](networking/tailscale-ssh-reauth-prompt.md)
+- [rsync over Tailscale: Hung in TCP Teardown After Transfer Completes](networking/rsync-tailscale-teardown-stall.md)
 - [Windows OpenSSH: WSL Default Shell Breaks Remote Commands](networking/windows-openssh-wsl-default-shell-breaks-remote-commands.md)
 - [Pi-hole AI Blocklist Blocks Claude Desktop (ERR_CONNECTION_REFUSED)](networking/pihole-blocks-claude-desktop.md)
 - [ISP SNI Filtering & Caddy](isp-sni-filtering-caddy.md)
@@ -44,5 +45,6 @@ Practical fixes for common Linux, networking, and application problems.
 
 ## 🤖 AI / Local LLM
 - [Ollama Drops Off Tailscale When Mac Sleeps](ollama-macos-sleep-tailscale-disconnect.md)
+- [Ollama: `ollama run` with Piped Stdin Bypasses Chat Template + SYSTEM Prompt](ollama-chat-template-pipe-stdin-bypass.md)
 - [Windows OpenSSH Server (sshd) Stops After Reboot](networking/windows-sshd-stops-after-reboot.md)
 - [claude-mem Silently Fails with Claude Code 2.1+ (Empty `--setting-sources`)](claude-mem-setting-sources-empty-arg.md)

05-troubleshooting/networking/rsync-tailscale-teardown-stall.md

@@ -0,0 +1,89 @@
+---
+title: "rsync over Tailscale: Hung in TCP Teardown After Transfer Completes"
+domain: troubleshooting
+category: networking
+tags: [rsync, ssh, tailscale, hang, tcp-fin, hash-mismatch]
+status: published
+created: 2026-04-25
+updated: 2026-04-25
+---
+
+# rsync over Tailscale: Hung in TCP Teardown After Transfer Completes
+
+A long rsync transfer over Tailscale finishes — the destination file is at full size, rsync's own summary line is in the log — but the rsync, ssh client, and parent bash processes never exit. The `&&` chain that should run after rsync (e.g. `&& echo DONE`) never fires. Watcher scripts polling for completion can stall indefinitely.
+
+## The Short Answer
+
+The data is fine. Verify with `md5sum` (or `md5 -q` on macOS) against the source, then kill the hung pipeline.
+
+```bash
+# 1. confirm size matches rsync's reported total_size
+ls -lh ~/your-file.gguf
+tail ~/rsync.log    # look for "total size is N" line
+
+# 2. checksum end-to-end
+md5 -q ~/your-file.gguf                                                  # macOS
+ssh majorlinux@100.x.x.x 'md5sum /source/path/your-file.gguf'            # Linux source
+
+# 3. if hashes match, kill the hung pipeline by name
+pkill -f 'rsync.*your-file' || true
+pkill -f 'ssh .*rsync --server' || true
+```
+
+## How to Notice
+
+`ps aux | grep rsync` shows the rsync client, the spawned ssh, and the wrapping bash all in `S` state with **0 CPU activity** and timestamps from minutes-to-hours ago. The destination file already exists at the final (non-`.partial` / non-dotfile) path at full size. The trailing summary in the rsync log reads:
+
+```
+sent N bytes  received M bytes  ... bytes/sec
+total size is X  speedup is Y
+```
+
+…but the bash `&&` followup that depends on rsync's exit code never runs.
+
+## Why This Happens
+
+rsync's exit waits for the underlying ssh transport to close cleanly. Over Tailscale (especially after a long-running connection that bridged a sleep, reconnect, or NAT shuffle), the TCP FIN/ACK handshake from the remote sshd can be lost or delayed indefinitely. The local end has all the data, has finalized the file, has printed its summary — but it's still blocked in `read()` on a socket that will never close on its own.
+
+This is amplified when:
+- The transfer hits a hash-mismatch retry mid-flight (rsync re-pulls the temp file). Each retry re-establishes connection state that's more vulnerable to teardown weirdness.
+- The link briefly drops and reconnects via DERP relay during the transfer.
+- The source machine is on WSL2 — Windows network stack rewrites can defer FINs.
+
+The upshot: the data was transferred correctly long before the pipeline reports done. Don't wait — verify and move on.
+
+## Don't Just Kill — Verify First
+
+Killing a hung rsync **before the file is complete** can leave a partial file that looks complete by size alone. Always:
+
+1. Compare the on-disk size to the `total size is N` line in the rsync log
+2. md5 (or sha256) against the source to confirm bit-for-bit equality
+3. Only then kill the hung processes
+
+Skipping the checksum step risks silently corrupting downstream consumers of the file (Ollama blobs, archive pipelines, etc.).
+
+## Watcher Threshold Gotcha
+
+If you have a polling watcher script that fires a notification when the file reaches some threshold size, **set the threshold below the actual file size**, not above it. Example: a 4.68 GB GGUF transferred fine but the watcher's threshold was set to 4.7 GB (`4_700_000_000` bytes), so the threshold never triggered even though the transfer completed.
+
+```bash
+# bad — threshold above true size
+TARGET=4700000000  # 4.7 GB
+
+# good — threshold below true size
+TARGET=4600000000  # 4.6 GB, fires at ~98% complete
+```
+
+Or better: trust the rsync exit code / the `RSYNC_DONE` marker line your wrapper writes after `&&`, not file size.
+
+## Prevention
+
+- Wrap rsync in a watchdog. If rsync hasn't exited within `expected_runtime + 2 minutes`, snapshot status, md5-verify, and kill.
+- For very large files, use `rsync --partial-dir` so a fresh re-run resumes from the temp file instead of redoing the transfer.
+- Consider `rsync --inplace` for files that consumers will copy out of the destination anyway (Ollama blob copy step).
+- Add `ServerAliveInterval=30` / `ServerAliveCountMax=3` to your ssh config for the source host — kills the ssh transport if the remote stops responding to keepalives.
+
+## Related
+
+- [[tailscale-ssh-reauth-prompt]] — different Tailscale-over-ssh gotcha
+- [[../../02-selfhosting/storage-backup/rsync-backup-patterns|rsync backup patterns]] — general rsync usage in MajorInfrastructure

05-troubleshooting/ollama-chat-template-pipe-stdin-bypass.md

@@ -0,0 +1,88 @@
+---
+title: "Ollama: `ollama run` with Piped Stdin Bypasses Chat Template + SYSTEM Prompt"
+domain: troubleshooting
+category: ai-inference
+tags: [ollama, eval, chat-template, system-prompt, majortwin, gotcha]
+status: published
+created: 2026-04-25
+updated: 2026-04-25
+---
+
+# Ollama: `ollama run` with Piped Stdin Bypasses Chat Template + SYSTEM Prompt
+
+When eval'ing or smoke-testing an Ollama model, piping a prompt via stdin to `ollama run` skips the model's chat template **and** the SYSTEM prompt baked into the Modelfile. Output looks like raw base-model completion (often Mastodon-shaped or training-data-shaped), and you'll think the model is broken when it isn't.
+
+## The Short Answer
+
+For evals and any test where you want the model's actual chat behavior, **use the HTTP API at `/api/chat`** — never `ollama run` with `echo "..." | ollama run model`.
+
+```python
+import json, urllib.request
+body = json.dumps({
+    "model": "majortwin-v8",
+    "messages": [{"role": "user", "content": "What's your name?"}],
+    "stream": False,
+}).encode()
+req = urllib.request.Request(
+    "http://localhost:11434/api/chat",
+    data=body, headers={"Content-Type": "application/json"}, method="POST",
+)
+r = json.loads(urllib.request.urlopen(req).read())
+print(r["message"]["content"])
+```
+
+Or with curl piped through jq:
+
+```bash
+curl -s http://localhost:11434/api/chat -d '{
+  "model": "majortwin-v8",
+  "messages": [{"role": "user", "content": "What is your name?"}],
+  "stream": false
+}' | jq -r .message.content
+```
+
+## How to Notice
+
+Symptom: model responses are weirdly raw — Mastodon-style hashtag rants, news headlines, multiple unrelated thoughts strung together — even though the same model behaves normally in Open WebUI or via the chat API. This is the canonical fingerprint of a chat-template-bypassed call.
+
+## Why This Happens
+
+`ollama run` is the CLI's interactive REPL. When stdin is a TTY, it reads input as user turns and applies the chat template. When stdin is a **pipe** (`echo "..." | ollama run model`), the CLI treats stdin as raw text and forwards it to `/api/generate` (the completion endpoint), not `/api/chat`. `/api/generate` does **not** apply the chat template, and the SYSTEM prompt only takes effect when the chat template wraps it.
+
+The two endpoints serve different purposes:
+- `/api/generate` — raw completion, good for fill-in-the-blank or non-instruct base models
+- `/api/chat` — applies the model's chat template, includes SYSTEM, handles multi-turn message arrays
+
+For an instruct-tuned model (Qwen2.5-Instruct, Llama-3.1-Instruct, etc.), bypassing the chat template means the model never sees the `<|im_start|>system ... <|im_end|>` framing it was trained to expect, and its responses regress toward base-model behavior.
+
+## When You Actually Want `/api/generate`
+
+Almost never, for instruct models. The legitimate use case is base models without a chat template, or specific completion-style prompts where you want the model to continue a string verbatim. For evals of a fine-tuned Modelfile, always use `/api/chat`.
+
+## Reusable Eval Pattern
+
+A minimal stdlib-only eval harness used for MajorTwin evals lives at `~/MajorTwin/scripts/eval_v8.py`. The key call is the `chat()` helper:
+
+```python
+def chat(host, model, prompt, timeout=180):
+    body = json.dumps({
+        "model": model,
+        "messages": [{"role": "user", "content": prompt}],
+        "stream": False,
+    }).encode()
+    req = urllib.request.Request(
+        f"{host}/api/chat",
+        data=body,
+        headers={"Content-Type": "application/json"},
+        method="POST",
+    )
+    with urllib.request.urlopen(req, timeout=timeout) as r:
+        return json.loads(r.read())["message"]["content"].strip()
+```
+
+This applies the chat template and the SYSTEM prompt baked into the Modelfile. No need to re-specify SYSTEM per-call.
+
+## Related
+
+- [[ollama-macos-sleep-tailscale-disconnect]] — different Ollama gotcha (sleep + Tailscale)
+- [[20-Projects/MajorTwin/majortwin-v8-eval-report|MajorTwin v8 eval report]] — caught this issue during initial smoke test on 2026-04-25

SUMMARY.md

@@ -88,6 +88,8 @@ updated: 2026-04-22T19:58
     * [Windows OpenSSH: WSL Default Shell Breaks Remote Commands](05-troubleshooting/networking/windows-openssh-wsl-default-shell-breaks-remote-commands.md)
     * [Pi-hole AI Blocklist Blocks Claude Desktop (ERR_CONNECTION_REFUSED)](05-troubleshooting/networking/pihole-blocks-claude-desktop.md)
     * [Ollama Drops Off Tailscale When Mac Sleeps](05-troubleshooting/ollama-macos-sleep-tailscale-disconnect.md)
+    * [Ollama: `ollama run` with Piped Stdin Bypasses Chat Template + SYSTEM Prompt](05-troubleshooting/ollama-chat-template-pipe-stdin-bypass.md)
+    * [rsync over Tailscale: Hung in TCP Teardown After Transfer Completes](05-troubleshooting/networking/rsync-tailscale-teardown-stall.md)
     * [macOS: Repeating Alert Tone from Mirrored iPhone Notification](05-troubleshooting/macos-mirrored-notification-alert-loop.md)
     * [ClamAV CPU Spike: Safe Scheduling with nice/ionice](05-troubleshooting/security/clamscan-cpu-spike-nice-ionice.md)
     * [Ansible: Vault Password File Not Found](05-troubleshooting/ansible-vault-password-file-missing.md)