weft-debugging

# Debugging a run ## Reading a run Each verb below prints one compact line per run or per event and has a flag that opens the part you want, so a forty-node run reads without loading the whole journal. You read in this order and stop when you hold the failing node and the wrong value. - **If you want to know what ran, or whether your trigger fired since the change**: `weft runs --limit 10 --phase fire` (`--node <trigger>` for one trigger's runs, `--since 10m` for the recent ones, `--status failed` for the ones that broke). One line per run: run id, status (`running`, `waiting_for_input`, `completed`, `failed`, `cancelled`), phase, the start time in UTC, the project id, the entry node (the trigger that fired), the tags. An activate, a resync or an infra start creates setup runs, phases `trigger_setup` and `infra_setup`; `--phase fire` hides them. `--project <id>` narrows to one project. A run whose trigger has `recorded: false` is listed only if it failed (with the node that failed and why, nothing before it) or reported a cost or asked weft for something on its behalf, so a route that answered and left nothing here may simply be unrecorded: `weft status` shows how many runs each trigger started in the last minute or two and how many failed, which is how you confirm its runs happen. - **If a run failed and you want the reason**: `weft logs <run-id>`. It prints what the run's nodes wrote and every failure the journal recorded, as `error` and `warn` lines. A line about one node names it (and the loop iteration, `llm#3:`); a line about the run itself (the run failing, a cancel) names none: `[2026-09-02 21:36:47] error llm: node failed: the service answered 401 ...`. It is the last 1000 lines and says so when the run wrote more; `--limit` raises that up to 20000, higher is refused. For most failures this is enough and you never open the events. `(no logs: ...)` means the run wrote nothing and recorded no failure: it did not fail, so you check its status. - **If you want the values on the wires**: `weft events <run-id>`. One line per event: UTC time, kind, node, then everything the row carries as `key=value`, each cut to a screen's width (`input=` on `node_started`, `output=` on `node_completed`, `error=` on `node_failed`, `reason=` on a skip or a cancel, `token=` on a suspension, and so on). You narrow before you read: `--kind failed` for the failures (a substring matches, so this catches `node_failed` and `run_failed`), `--kind node_skipped` for what did not run and why, `--node <id>` for every event on one node, `--iteration 3` for the fourth time round a loop (counted from 0; `3.0` is the first iteration of a loop inside it, outermost first). - **If a value on one of those lines is cut off**: it was cut to fit the screen, not stored short. `weft events <run-id> --node <id> --full` prints it whole, and `--json` gives you the replay rows for `grep` or `jq` (their field names are camelCase, like `runId` and `atUnix`, and a kind is a snake_case value, like `node_skipped`). No value a run recorded is unreadable, so you never report one as unreadable. - **If a client says it missed part of a stream or a socket's messages**: `weft events <run-id> --kind caller` is the conversation with its caller. A `caller_window` line carrying `dropped=12,13 (the caller read too slowly and never received these messages)` means the trigger's `whenCallerIsSlow` let them go; under `block` that never happens. A `caller_disconnected` line carrying `dropped=...` names what was still waiting to go out when the exchange ended. The numbers are the messages' offsets, the same `offset` the window lines carry, so `--full` shows what each one held. A `caller_errored` line saying `a chunk was dropped and the exchange went on` is a message the program could not make, skipped because `whenChunkFails` is `drop_chunk`; the rest of the line says why. Every other message the program sent went out to the caller, so if none of these names the missing one, the program never sent it: walk back to the node that should have. - **If a node did not run**: its `node_skipped` line carries the reason. `did_not_flow`: the node's `_should_flow` said no. `flow_closed`: nothing ever answered its `_should_flow`, so walk to whatever drives that wire. `required_input_closed` names the input that arrived closed, so walk to that node's line. `every_input_closed` and `one_of_group_closed` are the same story for a node with no required inputs and for a `@require_one_of` group. `scope_skipped` names the group or loop that did not run, taking this node with it: walk to that container, whose own reason is its gate saying no, or `every_input_closed` when every wire into it closed with nothing on it. (One group input arriving closed while another brings a value is not this: it passes through to the nodes inside that read it, and they carry their own reason.) `wait_skipped`: the node was waiting on a person (a form, a question) and they skipped it, so it ends with nothing sent on and what reads it skips: not a bug to chase. - **If a `Debug` shows `output=` empty**: correct, a `Debug` has no outputs. Its value is on its `node_started` line as `input=`, or `weft events <run-id> --node <debug id>`. - **If a past run shows no values at all**: a run's rows say what happened, not what it meant; the editor works out every input and output by replaying those rows against the code the run ran, so a run whose code [the daemon] no longer holds shows every node with no values, and the run itself says why. The empty graph is not "the node produced nothing" and not a viewer bug. The code is kept as long as any run points at it, so this is rare. If the files are still on disk, `weft build` puts the program back under the hash the run names and the run reads as it did. If not, the run is readable only as its shape, and `weft clean <run-id>` removes it. - In VS Code with the weft extension: the Runs view, "View in Graph" replays the run in the graph, values on every wire; `Debug` nodes render their latest value inline. For the full editor surface (inspector, action bar, targets, everything clickable), go and read the `weft-editor` skill. ## The debugging playbook 1. **It does not compile.** Read the diagnostics: `line:column message`, a stable slug, and the message names the fix. You fix what it names; you never route around a diagnostic. `weft validate --file src/main.weft < src/main.weft` re-checks without building. A diagnostic naming the catalog (an enrichment error, an unknown field, "a stale base_catalog copy") means the stdlib copy lags the installed weft: `weft catalog update`, then re-check, before anything else. A command refused with `it needs parts of the program that do not compile:` lists each broken part with its file and line, and only those stand between you and the run: fix them, or cut the run so it does not reach them. A part reading `package '<name>' didn't compile: <first error>; its full errors are in the build log: <url>` is a node package the worker was built without: the log at that address has the whole compiler output. 2. **A run failed.** `weft logs <run-id>` names the node and the error. If that is not enough, `weft events <run-id> --node <that node>` shows the values that reached it, on its `node_started` line. For the compiler error slugs, go and read the `weft-language` skill. A node's own error text is written by the node's author. A run, an activate or a resync is refused before it starts while a connection it needs is not picked, naming the `weft connect` that picks it, and a node error saying it has no connection picked is the same [the runtime tier] gap, not a source bug: you pick a stored connection yourself (`weft connect --node <id> --grant <grant>`) or send the user to the node's Connect button / `weft connect` in their terminal, then run again. A failure saying `the worker running '<node>' went away while it was running` means the worker of a durable run died while that node was running: weft does not run a node again once its start is on record, because what it did may have partly happened. Check what it did outside (the email, the row, the post), then, if it has to happen again, start a run at that node by hand: `weft run --from <node>=<inputs>`, with the inputs from `weft events <run-id> --node <node> --full`. If the message says `went away while it was reading a stream` instead, the items it read are gone from the stream, so `--from` cannot hand them back: check what it did, then run the whole run again. A run that cannot pause and held a wait for the trigger's whole `holdSecs` fails too, with the waiting node saying it gave up; a caller still on the line was answered `504`. A queued run (a `weft run`, a resume) that ended with `its worker refused it 3 times: <error>`, `the platform refused weft's calls for it 3 times: <error>` or `its project's worker settings kept it from any worker 3 times: <error>` never got going. The `<error>` says why, and item 8 says whether the workers are still out of reach. 3. **A value is wrong, not failed.** Work upstream from the output: open the run, look at the top-level groups, find the first whose output is already wrong, descend, repeat. When you hold the concrete failing case, iterate on that one node (build, run, look) and feed the earlier stages' passing examples through again. 4. **Suspended.** Expected for human-in-the-loop: nothing is wrong. A suspended run is alive and costs nothing: the `HumanQuery` parks, the worker exits, and the answer resumes it. The person answers in the browser extension (built with `./setup.sh --browser --no-sign`). If nobody should have been asked, the bug is the `_should_flow` that routed into the person. A run waiting on an outside job (a render, a crawl) is suspended the same way, and `weft node-state <run-id> <node>` prints the last answer its wait read from the service (`last answer: ...`), which the editor also shows on the waiting node while you follow the run. 5. **Cancelled.** Read the reason on `run_cancelled`. `Cancelled by user` is a person or a take-down: the Stop button, `weft stop`, a take-down that cancelled the runs going (`--running cancel`) or dropped the paused ones (`--held drop`), `weft rm`, or a cancel through a signal token. A run the infra health check stopped says so (`the infra health check found 'db' broken and took down the triggers that read it, stopping their runs`), and `Stopped by run <run-id>, which took its triggers down` means a program's own run took those triggers down: look at that run. `Stopped by run <run-id> (tag <tag>)` means another run asked the engine to stop everything carrying that tag: look at **that** run, and if no sibling was supposed to stop this one, the bug is in whichever node tagged and stopped it (`weft runs` shows each run's tags, so you see which runs shared it). `Caller disconnected` means the live caller this run was answering went away: it hung up, closed its socket (or never opened it), missed its heartbeat, or sent a message the connection refused. `the worker running this run went away; a fast run lives in its worker's memory, so it is not run again` means a fast run lost its worker (a crash, a machine gone): check what it did outside, then start it again (let the trigger fire again, or fire it by hand: `weft bake`, then `weft run --fire <trigger>=<payload>`, with the `payload` on the trigger's `node_kicked` line in `weft events <run-id>`), and if the trigger's runs have to carry on after a worker dies, set `durable: true` on it. A durable run whose worker stops or dies is never cancelled: another worker picks it up from its record, and only the node that was running fails (item 2). `the run had to leave the copy of the program running it (...), and it cannot be suspended: <why>` means its worker was stopping and this run could not move to another one; the `<why>` names the reason: its trigger has `recorded: false`, its route does not have `outlivesCaller`, or a bus between its nodes was open. Check what it did outside, then start it again the same way as a fast run that lost its worker. A run cut by a platform limit on a cloud install (its hour, or its worker's connection to weft about to be cut while every run on it only waited) carries the cause kind `limit` (`{"kind": "limit", "detail": "..."}` in `--json`, `(a time limit: <detail>)` in `weft tree`). A caller still connected was answered `504`, and the detail names the way out (a pause, a reconnect). A run whose caller's session reached the route's or socket's `maxSessionSecs` is a time limit too, on any install: `run <id> stopped when its caller's session reached the <n> second limit its trigger sets (maxSessionSecs), and the caller was told it was a time limit (a 504, or close code 1011 on a socket). A session meant to last longer raises maxSessionSecs, or sets it to 0 for no limit`. `its worker refused it 3 times: <error>`, `the platform refused weft's calls for it 3 times: <error>` and `its project's worker settings kept it from any worker 3 times: <error>` mean a queued run (a `weft run`, a resume) was answered no three times, 5 s and then 20 s apart, the reason names who said the last no, and `<error>` is that answer: fix what it names, then start the run again (item 8 has what counts as a refusal). Anything else is the runtime's own reason, printed as words. 6. **Stuck.** The engine proved nothing can proceed; that is a graph-shape bug (a wire the compiler could not catch). The `run_failed` line names every firing left holding a pulse and the wired ports it never received (`theirs has value, still waiting on go`): walk to whatever should have driven the missing port. 7. **Nothing ran.** Nothing reached the branch: check that the trigger that should have fired is on, then walk from it down to the first `_should_flow` or required input that closed. If the trigger is off, `weft status` says on its line whether it was taken down with its infra or by the health check, and adds `held back: <why>` when it cannot come back yet; one that only reads `off` was turned off by hand. The `weft-running` skill, "Taking triggers down, and bringing them back", says what brings each one back. 8. **The trigger fired, or you ran it, and no run starts (or the [infra] does not move).** `weft status` says what holds it. Under `triggers:`, a trigger whose fires are queued shows one line: - `2 fires wait until the infra the runs read is running again: <reason>` (or `until the instance's values change`, or `until the install picks the connections the runs need`): they go on by themselves once that happens, so the fix is whatever the `<reason>` names. - `1 fire stopped after failing to start a run, and holds the trigger's queue; ...`: handing it to a worker failed three times (tried again 5 s later, then 20 s after that), and every fire behind it waits in order. Fix the `<reason>`, then run `weft activate` (a new build or a change of the worker settings also tries again). A fire waiting for room (a limit reached) or for its trigger gets no line here. If it waits for room, it tries again by itself, waiting longer each time, up to 5 minutes. If it waits for its trigger to come back on, it is handed over when the trigger is activated again. Under `waiting on weft:`, each row is one of weft's own calls that keeps failing, as `<what> (failing for <span>, last tried <span> ago; <then>): <error>`, and it stays until the thing is resolved. The rows about weft's roles and jobs, the bucket and news rows, and the row about removed projects are install-wide, so every project shows them. - `weft's supervisor, which starts and stops infra, cannot be reached` (or the dispatcher, or another role): weft tries again on the next change that needs it. As with [the daemon] in item 11, you report the row to the user and restart nothing. - `this project's workers, which runs are handed to, cannot be reached or cannot take them`, followed by `a queued run refused 3 times ends, and one its workers could not be reached for 3 times waits until a worker of the project comes up or a build of it registers; one they keep answering busy (which spends no try) is tried again after a pause that grows to a minute, for as long as they do; changing the project's worker settings (more memory, for a worker that stays busy) tries every queued run afresh`. Only an answer that says no is a refusal: from the worker, any error but its busy `503`; from Cloud Run answering in its place, a `4xx` other than `404`, `408` or `429`; from Google Cloud asked to create the worker, a `400`, `401` or `403`, whose words end up in the `<error>`; from weft itself, worker settings that together are a shape no platform could run. A `404`, `408`, `429` or `5xx` from Cloud Run, and a `429`, `5xx` or timeout from Google Cloud, are no answer. A queued run (a `weft run`, a resume) that is refused is tried again 5 s later, then 20 s after that, and the third refusal ends it cancelled with a reason naming who said the last no: `its worker refused it 3 times: <error>`, `the platform refused weft's calls for it 3 times: <error>`, or `its project's worker settings kept it from any worker 3 times: <error>`. A worker answering busy makes the run wait without spending a try, for as long as the workers answer busy, each wait as long as it has been turned away so far (at least 5 s, at most a minute). Once that lasts longer than the install's alert delay (`alert_after_minutes`, 5 minutes by default), this row shows, its error reading ``this project's worker has answered busy for <time> (memory full); raise its memory (`weft workers set --memory <size>`)``, and a Google Cloud install emails an alert. A call that got no answer at all is tried again 5 s and then 20 s later too, but after a third with no answer the run is not ended: it waits, queued, until a worker of its project comes alive or a build of the project registers, and then its tries start over. A worker still starting is not a failure at all. Changing the project's worker settings (`weft workers set ...`) hands every run still queued to the workers again at once, its tries forgotten. The row goes once none of the project's queued runs still waits on its workers (answered busy, refused, or not reached) and a run of the project has since left the queue: the last one that waited (it reached a worker, ended, or was cancelled), or one started after the failure. A change of the project's worker settings takes it away too. - `weft's <role> could not <job>` (say, `hand queued runs to workers`), followed by `weft tried a few times and stopped; it tries again on the next change that concerns it`: this row appears only on a cloud install. A pass of one of weft's background jobs failed, was tried again 1 s, 5 s and 20 s later, and failed every time, so it stopped and wrote its error here; Google Cloud's queue does not keep calling it. The job runs again on the next change that concerns it, and the row stays until a pass goes through. Report the row to the user as printed. - `weft's supervisor could not get through this project's infra`: the error says what the supervisor could not do (look at the project's health, delete what the host still holds for copies that are gone, or write down how a command ended). An error starting `could not list what the host holds to delete what its gone copies left` or `could not read what it owns to look at its health` means the whole pass failed, and every project the supervisor holds counts a failed pass. On the user's own machine the error ends `(tried again at the supervisor's next look)`, and the supervisor never gives up. On a cloud install the error ends with how many passes failed in a row and when it tries again (5 s after the first failure, 10 s after the second), or, at the third, ``(failed 3 times in a row, so the supervisor stopped trying; `weft infra look` tries again)``. A pass that goes through starts the count again from zero. A health rule whose action (taking down the triggers that reach a broken copy, or bringing them back) kept failing shows in this row too, as `its health rule '<name>' on <copy> failed <n> times: <error>`. Fix what the error names, then run `weft infra look`: it starts a fresh round of tries and gives every health rule that gave up another go. The row clears once a pass over the project goes through. - `weft's supervisor could not delete what the infra host still holds of removed projects (their disks included)`: the error names each removed project, what went wrong and what happens next: on the user's own machine `(tried again at the supervisor's next look)`; on a cloud install it is tried again 5 s, then 10 s later, and the third failure ends `(failed 3 times in a row, so the supervisor stopped trying; its next pass tries again)`. From then on every pass of the supervisor tries again, and `weft infra look` in any project starts one. The row clears once the host holds nothing of any removed project. - `weft's supervisor gave up infra commands of this project it could never finish`: a command (a start, a stop, an upgrade) was taken up 3 times and never ended, because its run or the write of how it ended kept failing. The error names the command and ends `so it gave the command up; issue it again`. Fix the cause, then issue the command again; the row clears once a later infra command of the project ends. - `weft could not repair work of this project whose holder went away`: weft tries again twice within half a minute, then whenever it next looks at lapsed work, and the error says what fixes it by hand. - `the listener still serves triggers of this project whose door stopped taking work, and what they pick up is refused`: the error names each node and why it was kept. weft tells the listener to let go of them again at the next change of a trigger. - `resync: stopped with triggers it took down still down: <error>. Next: <what comes next>`, a line of its own in `weft status`: the resync failed three times in one go (it tried again 5 s, then 20 s later; a busy database is waited out longer, 5, 15, 30 then 60 s, before it stops), and the error is the last failure. Builds are refused with `cannot build now` until it is settled, and one already compiling is not registered. If it stopped on infra those triggers read that was not running, on an activation still landing, or on a busy database, it goes on by itself once that infra runs, that activation has landed or the database has room again. Otherwise, once the cause is fixed, `weft resync --resume` takes it up again where it stopped (a plain `weft resync` is refused while it is held); `weft cancel-activate` on its own gives it up, leaves those triggers down for a `weft activate` later, and prints which ones, while `weft cancel-activate --trigger` or `--instance` is refused as long as the resync holds the project, because the resync covers every trigger of every owner. The editor's action bar shows the same as "Resync stopped", with Resync and Give up. - `a given-up resync left these triggers down: <whose triggers> (<names>)`: a resync was given up with `weft cancel-activate`, which printed the same triggers, and these are the ones still not on. `weft activate` turns them on, and the row clears once they are on again or the next resync begins. - `weft's broker could not remove stored files from the bucket`: the error counts the files and names up to five, which hold their tenant's quota until removed. They are tried again at the expiry loop's next pass, a wipe of their files, or the tenant's next upload. - `weft could not tell the install's news (a cancel or an answer reaching a run a worker drives); those runs hear of it late`: weft