Lamprey Debugging Playbook

When to use / when not

• Use when the app or a test is misbehaving and you need triage: what to check first, what the likely causes are, and the experiment that discriminates between them.
• Don't use for the full history of an already-solved defect (see lamprey-failure-archaeology), loop deep-work (see lamprey-loop-reliability-campaign), or building measurement tooling (see lamprey-diagnostics-and-tooling).

TL;DR triage table

Symptom	First check	Likely causes (ranked)	Discriminating experiment
Every chat send fails with a SQL error ("no column named …", "no such table")	DB schema version (see below)	1. A migration never ran because init threw earlier 2. New code references a column its migration didn't add 3. Stale cached DB handle	Open %APPDATA%\Lamprey\lamprey.db read-only, run PRAGMA user_version — if it's behind LATEST_VERSION in electron/services/db-migrations.ts, init is aborting before migrations. Find the throw in initLegacySchema (electron/services/schema-init.ts).
Turn hangs, spinner forever	Whether the stream ever started (streaming vitals pill / chat:streaming-vitals)	1. Pre-stream throw not settling the turn (historically JM-8) 2. SSE stall past streamInactivityMs 3. MCP tool call past mcpCallTimeoutMs 4. Abort controller never resolved	If no first chunk ever arrived → pre-stream path; check main-process console for a throw in runHeadlessTurn before chatStream. If chunks stopped mid-stream → watchdog should abort at 60s default; if it didn't, check streamInactivityMs in settings.json (0 disables it).
Conversation shows nothing after a turn ("ghost reply")	messages table for a role='system' notice row	1. Turn failed and the ghost-reply guard fired (working as designed — read the notice) 2. Research pipeline hit NoSourcesError and fell through 3. Guard itself failed (regression)	The guard (electron/services/ghost-reply-guard.ts) persists a system notice on any failed turn with no visible reply; user cancels are exempt. If a failed turn left NO system row and NO assistant row, that's a guard regression — check ghost-reply-regression.test.ts still passes.
Loop never fires / fires twice / never stops	loopsEnabled in settings.json, then the loop tables	1. Master toggle off (gates every entry point) 2. Ceiling already tripped (loops row status + reason) 3. Historical class: overlap/watchdog bugs (fixed v0.16.0)	SELECT id,status,iteration,active_ms FROM loops; and SELECT status,fire_at FROM loop_wakeups ORDER BY fire_at DESC LIMIT 10; — see lamprey-loop-reliability-campaign for the full protocol and expected values.
Provider returns HTTP 400 on a model that used to work	The model id against RETIRED_MODEL_MAP (electron/services/providers/registry.ts)	1. Provider retired the model (DeepSeek did this v0.15.6) 2. Malformed request from a capability flag mismatch 3. Bad custom-model entry	If the id is in the retired map it should remap silently — a 400 means the id bypassed resolveModel. Grep the id: grep -rn "<model-id>" electron/ src/.
Provider 401 / key rejected	settings:testProviderKey path / Settings → API Keys test button	1. Wrong or expired key 2. keys.json was corrupt and preserved aside	Look for keys.json.corrupt-<timestamp> next to %APPDATA%\Lamprey\keys.json — if present, a torn file was preserved and the live file may be empty. Re-enter keys; the corrupt copy is kept for forensics.
429s / rate limiting	Retry behavior in chatStream	Normal: up to 3 retries with backoff for 429 and connection errors	Only escalate if retries exhaust; persistent 429 = provider quota, not a code bug.
Tool call executes with empty args, or model "calls tools" in prose	The tool_calls table + whether the model is on the fallback path	1. Token exhaustion producing empty params (detected, corrective result returned) 2. Model doesn't support native tools → FC-6 fallback JSON contract 3. Capability downgrade engaged (3 mismatches)	Fallback call ids are prefixed fb_. SELECT id,tool_name,status FROM tool_calls ORDER BY rowid DESC LIMIT 20; — fb_ prefixes mean the fallback parser produced them, which also disables persisted "always allow".
tool_search spam / model flailing on lazy surface	Whether the conversation got downgraded to the full catalog	Threshold is MALFORMED_SEARCH_DOWNGRADE_THRESHOLD = 3 in electron/services/tool-unlock-state.ts	Note: lazy surface is opt-in (toolSurface: 'lazy'); era default is 'full'. If flailing occurs on defaults, something re-enabled lazy.
Tests "pass" but a DB test never ran	Native-binding skip accounting	better-sqlite3 ABI vs the Node running vitest	npm run verify:proof -- --list-native-skips prints the guarded cohort and whether the binding loads. Since Electron 43 / Node 22 the ABIs match and these tests RUN — any skip reappearing is an event, not noise. See the v0.9.2 story in lamprey-failure-archaeology.
Settings or keys vanished	Corrupt-file preservation	Atomic-write layer (electron/services/atomic-json.ts) preserves parse-failing files as <file>.corrupt-<timestamp> and never heals to {}	If values are gone AND no .corrupt-* file exists, the loss predates v0.16.0 or something bypassed writeJsonAtomic — grep for raw writeFileSync on those paths.
Input locked app-wide during streaming, or stream text lands in the wrong conversation	Renderer streaming state	Historical class (fixed JM-21/22): conversation switches now clear streaming state; staleness guards added	If reproducible on ≥ v0.16.0, capture exact repro; this class was closed and a recurrence is a regression worth a DEVLOG entry.
Approval dialogs replacing each other / lost approvals	Approval queue in src/App.tsx	Historical class (fixed JM-23): queue replaced modal clobbering	Reproduce with two slow concurrent tool calls needing approval; second should queue, not clobber.
npm run dev exits instantly	ELECTRON_EXEC_PATH	The dev server on this machine needs the explicit Electron binary path	ELECTRON_EXEC_PATH="<repo>/node_modules/electron/dist/electron.exe" npx electron-vite dev — see lamprey-build-and-env.
vitest fails to even start / esbuild error	AV quarantine of esbuild.exe	Windows Defender or third-party AV blocking node_modules/esbuild/bin/esbuild.exe	Remedies in CONTRIBUTING.md: AV exclusion for node_modules/esbuild, or run node node_modules/esbuild/bin/esbuild --version once, or reinstall after exclusion.

The traps that cost real time (with their stories)

The silent test skip (v0.9.2). The regression test that would have caught a fatal DDL error was skipping on every run — vitest's Node ABI didn't match the Electron-rebuilt better-sqlite3 binding, and describe.skipIf(!HAS_NATIVE_SQLITE) skipped quietly. The bug shipped; every chat send failed in production. Rule: a skipped test is a finding, not background noise. Always read the skip accounting in verify:proof output.

The half-initialized DB handle (v0.9.2 amplifier, fixed JM-16). getDb() cached its handle before initialization finished, so after an init throw, every later call returned a broken handle instead of retrying. If you see "impossible" schema states, ask whether init completed before anything cached.

Tests that assert the bug (v0.11.1). Two tests asserted the reviewer packet excluded the work product — the defect itself. When a behavior seems obviously wrong but tests are green, read what the tests actually assert before trusting them. Flip the suspicious assertion and see what breaks (recipe 7 in lamprey-proof-and-analysis-toolkit).

Unix-on-PowerShell loops (F7, v0.11.x era). Models repeated the same failing Unix-syntax shell command 3+ times on PowerShell. If a shell command fails on syntax, adapt after ONE failure — the primary dev machine is Windows; both PowerShell 7 and Git Bash exist, with different syntax.

Editing files through shell pipelines (F9). [System.IO.File]::WriteAllText and pipeline redirects caused silent UTF-8 corruption. Never edit source files via shell pipelines; use a proper editor/patch path.

The wake-up that never woke (LP-0 / G1). The original loop scaffold persisted a wake-up message and the renderer merely reloaded the message list — no turn ever ran. When a feature "runs" but has no visible effect, verify the actual execution path exists (documented-vs-wired audit, lamprey-proof-and-analysis-toolkit recipe 2).

Where evidence lives

• DB audit tables: events (structured event log), tool_calls (every call with status), loop_runs / loop_wakeups / loop_backlog, messages (incl. content_raw for pre-sanitization originals, reasoning for chain-of-thought). 90-day retention sweep applies to the audit families (JM-18).
• Streaming vitals: chat:streaming-vitals heartbeat (~2s) drives the "Ns since last chunk" pill — the fastest way to distinguish "model is thinking" from "stream is dead."
• Reasoning Trace viewer (right panel) + .md/.csv export — full per-turn reasoning audit.
• Debug trace: opt-in ONLY. It writes tool arguments to a plaintext log (lamprey-debug.log in userData) — it must never ship force-enabled (the JM-1 incident). Turn it off when done.
• Inspection scripts: lamprey-diagnostics-and-tooling ships read-only DB inspection scripts with interpretation guides.

General method

1. Reproduce once, capturing the exact error text.
2. Classify with the table above; run the discriminating experiment before touching code.
3. Check lamprey-failure-archaeology — most symptom classes here have a settled history; don't re-fight it.
4. Walk the causal chain to the FIRST cause, then ask what amplified it and why detection missed it (the v0.9.2 postmortem method — all three get fixed).
5. Route the fix through lamprey-change-control; add the test that would have caught it (often a source-lock test, see lamprey-validation-and-qa).

Provenance and maintenance

Based on source reads of ghost-reply-guard.ts, tool-unlock-state.ts, tool-result-spill.ts, providers/registry.ts, atomic-json.ts, loop-config.ts, hooks and DEVLOG incident entries, at v0.16.0 (2026-07-02).

Re-verify:

• Watchdog defaults: grep -n "DEFAULT_STREAM_INACTIVITY_MS\|MIN_STREAM_INACTIVITY_MS" electron/services/providers/registry.ts
• Downgrade threshold: grep -n "MALFORMED_SEARCH_DOWNGRADE_THRESHOLD" electron/services/tool-unlock-state.ts
• Spill threshold: grep -n "DEFAULT_SPILL_THRESHOLD" electron/services/tool-result-spill.ts
• Native-skip status: npm run verify:proof -- --list-native-skips