Convert a Tableau datasource or workbook into a Sigma data model and matching dashboard. Use when the user has a Tableau datasource, TDS file, or Tableau workbook and wants to recreate it in Sigma. Discovery, calc-field translation, data model + workbook creation via REST API, layout generation, and parity verification — driven by `scripts/*.rb`.
Installation
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name
tableau-to-sigma
description
Convert a Tableau datasource or workbook into a Sigma data model and matching dashboard. Use when the user has a Tableau datasource, TDS file, or Tableau workbook and wants to recreate it in Sigma. Discovery, calc-field translation, data model + workbook creation via REST API, layout generation, and parity verification — driven by `scripts/*.rb`.
user-invocable
true
Tableau → Sigma Conversion
Convert a Tableau datasource into a Sigma data model, then build a Sigma workbook
that mirrors the Tableau dashboard layout as closely as possible.
Read ALL of the following before replying or taking any action. Do not make assumptions about skill conventions, prompts, or global instructions — read the files.
refs/column-gotchas.md — column naming rules and special-character landmines
refs/data-model-spec.md — data model JSON schema, element format, relationship format
For canonical workbook spec shape (element kinds, source kinds, controls, formulas, formatting), defer to the companion sigma-workbooks skill, which ships as the sigma-authoring plugin in this same marketplace — install it alongside this converter (it's the canonical Sigma workbook spec reference, and this converter assumes it is present). This skill restates only the Tableau-conversion-specific patterns; everything else (KPI fields, color channel, pivot-table shape, manual sources, container styling, YAML default, etc.) lives there. Read its reference/specification/ whenever you need the current spec surface.
One command (orchestrated path)
eval"$(scripts/get-token.sh)"# PASS 1 — discover → gap gate → DM-reuse scan → DM → workbook → layout → parity plan
ruby scripts/migrate-tableau.rb \
--workbook "<name>" --connection <SIGMA_CONNECTION_ID> --folder <SIGMA_FOLDER_ID> \
[--db CSA --schema TJ] [--name '<prefix>'] [--row-scale 1.5] \
[--reuse-dm [ID]] [--force] [--yes]
# … pass 1 auto-fills <workdir>/parity-actuals.json via the pooled CSV-export# collector (collect-parity-actuals.rb); run the printed mcp-v2 queries for# the REMAINING charts only (pivot grids) and merge them in …# PASS 2 — finalize: phase6 verify + cleanup-orphans + census-aware hard gate
ruby scripts/migrate-tableau.rb --workbook "<name>" \
--finalize --actuals <workdir>/parity-actuals.json [--allow-missing-tiles N]
Converter backend — LOCAL by default, never upload customer data silently. The
mechanical path needs the Tableau→Sigma converter. It runs locally when
TABLEAU_MCP_BUILD points at a build/tableau.js (or a locally-run sigma-data-model
MCP) — nothing leaves the machine, which is required for customers who can't send
.twb contents (schema/SQL/formulas) off-box. The hosted converter
(https://sigma-data-model-mcp.onrender.com/mcp) is used only with explicit consent
(--converter hosted or SIGMA_CONVERTER_ALLOW_HOSTED=1) because it uploads the .twb
to a third-party server. With neither, pass 1 STOPS and prints both options — it never
falls back to hosted on its own. See QUICKSTART "the data-model converter backend".
Parity is EXACT for warehouse-backed migrations — never blame "drift." Sigma
queries the same warehouse the Tableau source reads, so a value gap is a real
bug (a missing view filter / NULL bucket, an ungrouped table, a wrong aggregate),
NOT data freshness. The drift-tolerance path (extract-mode) is only valid for
hasExtracts=true workbooks (frozen .hyper snapshots) and must be explicitly
flagged. Do not attribute a gap to drift on a live-warehouse source, and do not
declare GREEN while a table renders base-row-count detail or a chart shows a
NULL-dominant bucket — run scripts/lib/preflight_lint.rb on the spec first.
Chains the scripted spine (discover → scan-workbook-gaps → discover-columns →
find-or-pick-dm → DM build/validate/post → build-charts-from-signals → workbook
post-and-readback → build-dashboard-layout + put-layout → phase6-parity →
cleanup-orphan-workbooks + assert-phase6-ran) and STOPS with exact instructions
wherever agent judgment is genuinely required. Phase 1 is interleaved:
Tableau discovery + gap scan run as a background lane while the pure-Sigma-side
read-only phases (1.6 DM-reuse scan, 2 warehouse columns) run concurrently; the
lanes join before anything consumes discovery output, so every designed
stop/gate fires exactly as in the serial flow. A PHASE TIMINGS summary line
prints at every terminal exit so the speedup stays visible. Exit codes: 10 = OPEN QUESTIONS
(re-run with --yes/--answers), 11 = ❌-unhandled gap-scan features (close via
gap-scout or --force), 12 = pass 1 done, parity PENDING (collect mcp-v2 actuals,
then --finalize), 4 = DM posted but the workbook layer needs the agent path,
3 = a gate failed, 14 = migration GREEN + Phase E proposals pending
acceptance, 0 = ALL gates green (only reachable via --finalize).
DM-reuse is reuse-first — auto-reuses an existing DM that covers all the
workbook's source tables (collapsing duplicate-DM sprawl, skipping the POST);
--reuse-dm <id> pins one, --skip-reuse-scan forces build-new.
Optional --enhance [--enhance-accept <ids|all-low-risk>] runs Phase E
(opt-in) after all gates are green — see the Phase E section below.
Still manual by design (the orchestrator stops and tells you):
Parity actuals (pivot grids only) — pass 1 now collects actuals for every
exportable chart itself: collect-parity-actuals.rb pools the element CSV
exports (POST /v2/workbooks/{wb}/export → poll → download, 5-wide, under
sigma_rest's auto-refresh) straight into parity-actuals.json. Only
pivot-tables stay agent-mediated (their CSV export is the WIDE grid, not the
long row/col/value tuples the plan compares) — pass 1 prints exactly those
mcp__sigma-mcp-v2__query calls; merge their rows into the same file.
Empty-view-CSV recovery — a view that exports an empty CSV produces no
chart; surfaced at the OPEN-QUESTIONS checkpoint AND by the tile census at
--finalize (exit 7 → rebuild the chart manually or explain with
--allow-missing-tiles, naming the zones in your report).
Master-level calc overrides — when the workbook layer exits 4 naming a
field like master/ship speed category, translate the Tableau calc (see
calc-fields.json) and re-run the same command with
--master-col 'Name=<Sigma formula>'.
Shared relative-date filters — a dashboard-wide filter like
'Order Date ' = this year only surfaces as a uniform parity DIVERGE (every
Sigma value too big). Fix: expose the date key on the DM if the converter
consumed it, add a master boolean (e.g. [Order Year] = Year(Today())) plus a
master filters: [{id, columnId, kind: list, mode: include, values: [true]}]
entry — it propagates to every chart sourcing the master — then re-query and
re---finalize. (Validated live on Orders Conversion Test, 2026-06-10.)
❌-unhandled gap features — gap-scout subagent or --force (degraded).
DM-reuse shape preflight — when --reuse-dm hits a differently-shaped DM
the workbook gate exits 4; run Phase 1.5b (inspect-dm-shape.rb) and the
agent path against the reused DM.
Scripts
The conversion is driven by scripts/*.rb. Each script encapsulates one mechanical
phase. You compose them; the agent's role is judgment (which DM/workbook shape,
which calc translation, which layout) — not orchestration.
Script
Purpose
scripts/migrate-tableau.rb
The one command — chains the whole scripted spine (gap gate → DM-reuse scan → DM → workbook → layout → two-pass parity → cleanup + census gate) and stops with exact instructions where agent judgment is required. See "One command" above.
scripts/setup.rb
One-time Sigma credential setup
scripts/get-token.sh
Exchange SIGMA_CLIENT_ID/SIGMA_CLIENT_SECRET for SIGMA_API_TOKEN (~1h TTL)
scripts/setup-tableau.rb
One-time Tableau PAT setup (only needed for PAT mode — see refs/tableau-rest.md)
PAT-mode Phase 1 discovery in one CLI: workbook + views + VDS metadata + GraphQL + .twb content. ONE unified fetch pool (default 5, --pool N, longest-job-first) with 429/timeout backoff + 401 re-mint; always writes per-task timings.json. Measured 61.8s → 13.7–18.9s on the 7-view reference workbook
scripts/scan-workbook-gaps.rb
Phase 0a (mandatory): scan a .twb and emit gaps-report.md + gaps.json categorising every feature into ✅ auto / ⚠️ hint / 🛠 manual / ❌ unhandled. Run BEFORE any other phase. Also detects multi-datasource data blends (secondary datasource-dependencies + linking fields) and writes blend-plan.json with a per-blend route — same-warehouse-repoint / materialize-via-vds / flag-unreachable (decision tree: refs/blending.md).
scripts/gap-scout.md
Phase 0a-scout: subagent prompt + protocol for resolving ❌ Unhandled gaps. Main agent spawns one scout per gap via the Agent tool.
scripts/validate-sigma-formula.rb
Scout primitive: POST a tiny test workbook with a candidate formula, read back column types, return JSON `{ status: ok
scripts/scout-validate-and-persist.rb
Scout wrapper: call validate-sigma-formula, on success append the rule to ~/.tableau-to-sigma/learned-rules.yaml (customer's HOME, never the skill repo), on failure write ~/.tableau-to-sigma/escalations/<ts>-<slug>.yaml AND return an opt-in escalate-gap.py command (confirm-before-file).
scripts/escalate-gap.py
Shared opt-in issue filer. Dry-run by default (drafts the issue + dedupes against open issues/beads); files only with --yes. Routes by gap category: converter→sigma-data-model-manager+sigma-data-model-mcp (mirrored), builder/skill→sigma-migration-skills.
scripts/learned-rules.rb
Loader module: reads ~/.tableau-to-sigma/learned-rules.yaml at startup. Customer-discovered rules apply BEFORE the built-in translators in build-charts-from-signals.rb.
scripts/parse-twb-layout.rb
Parse a .twb XML file into a per-dashboard zone list plus a sister *-meta.json (worksheets + shared_filters + parameters + column_aliases). Per chart zone surfaces: position (x/y/w/h%), chart_kind, mark_class, geo_role, sort, filters (with resolved column captions + member values + action-vs-value flag), aggregations, channels, formats (Tableau format strings → Sigma d3-format with paren-negative handling), calculations, dual_axis (synchronized-axes detection), ref_marks (reference lines/bands/trendlines), filter_column_caption. Detects Tableau stories (both <story> and storyboard-dashboard shapes): flags storyboard dashboards is_story: true and writes story-plan.json (story → ordered points with captions + captured sheets) — when present, run build-story-pages.rb. Bin calc columns surface bin_size/bin_peg.
Phase 1f: pull Custom SQL blocks behind a workbook via Metadata GraphQL + .twb XML fallback. Output → /tmp/<name>/custom-sql.json.
scripts/lib/tableau_rest.rb
Ruby wrapper for the Tableau REST endpoints the skill uses
scripts/estimate-cost.rb
Predict input/output token cost from workbook + datasource metadata
scripts/fetch-view-data.rb
Parse pre-fetched view CSVs into a signals manifest (distinct values, date min/max, agg hints)
scripts/discover-warehouse-columns.rb
Parallel-fetch Sigma column metadata for N table inodeIds
scripts/probe-custom-sql-columns.rb
Phase 1e.1: when discover-columns 404s (catalog miss), probe column names + types via a one-shot Custom-SQL probe workbook that SELECTs INFORMATION_SCHEMA, exports CSV, and self-destructs. ~6s end-to-end. Saves ~120s on every Custom-SQL fallback vs. POST-fail-cleanup column-name guessing.
scripts/find-prior-cache.rb
Phase 1d-cache (Phase -1): detect cached Tableau-discovery + Sigma-conversion artifacts from prior audit-run-* or converter-test runs so re-conversions skip discovery (~3 min saved).
scripts/remap-wb-spec-to-dm-ids.rb
When a DM is re-POSTed and element IDs churn, remaps a cached wb-spec.json to the new IDs via name-based matching. Optional --rename for renamed elements.
scripts/extract-calc-fields.rb
Phase 1e: pull every Tableau calc field (with formula) via Metadata API (POST /api/metadata/graphql); falls back to .twb XML when Metadata API is unavailable. Drops VDS dependency. Caches to <wb-dir>/calc-fields.json.
scripts/validate-spec.rb
DM or workbook spec validator. Accepts --type and --dm-context
scripts/post-and-readback.rb
POST a DM or workbook spec, parse YAML response, GET back the spec, emit element ID map. Also runs a universal column-type guard afterward: any column whose formula resolved to type error aborts the script with exit 2 and the failing formula. Catches silent-error columns the validator doesn't pattern-match (typo refs, IsIn, unsupported functions) without waiting for Phase 6. Then the shared layout lint (exit 3) and control lint (scripts/lib/control_lint.rb, exit 4 — dead controls / ghost targets / partial same-page reach; honors the <workdir>/control-scope.json sidecar, --skip-control-lint escape).
scripts/lib/preflight_lint.rb
MANDATORY before any workbook POST — static lint of the spec that catches the two EDNA-class failure modes with a precise message instead of the opaque Invalid kind: control / a silently-detail-rendered table: (T1) a table with aggregate columns + dimensions but no groupings → renders raw 9.6M detail rows; (T2) a grouping calculation that passes through an already-aggregated column → "multiple values"; (C1/C2/C3) a control missing id/controlId/controlType nesting value fields under a value object (must be FLAT top-level), carrying a non-double-nested source, or a list-type control wired to neither source nor filters (a filters-only list control is valid). ruby scripts/lib/preflight_lint.rb <spec.json> (exit 1 on violations). Fix all violations before POST. Verified shapes: sigma-workbookscontrols.md/tables.md.
scripts/put-layout.rb
Apply a layout XML to an existing workbook (strips read-only fields)
scripts/auto-parity-plan.rb
Phase 6a: auto-build a parity plan by matching Sigma chart elements to Tableau view CSVs (with --rename for renamed tiles). Output → /tmp/<name>/parity-plan.json wrapped as { extract, charts: [...] }
scripts/verify-parity.rb
Phase 6c: diff expected (Tableau) vs actual (Sigma) per chart. --extract-mode switches to structural comparison (bucket count + dim set + sort) with value-drift tolerance for hasExtracts=true workbooks
scripts/assert-phase6-ran.rb
Conversion hard gate (8 gates) — exits 0 only when ALL pass: (1) Phase 6 ran and parity-final.json shows status=PASS at the required rate, (2) no uncleaned orphan workbooks (posted-workbooks.jsonl has ≤1 entry OR cleanup-marker.json shows a successful non-dry-run cleanup), (3) the live workbook's /columns endpoint shows no column with type=error (catches circular refs / runtime errors introduced after the initial POST's column-type guard), (4) a non-empty top-level layout XML is applied (beads-sigma-bw3), (5) tile census — parity-final.json's tile_census shows no unexplained dashboard zones without a matching chart (catches the empty-view-CSV N-1-charts escape, bead gjhe; --allow-missing-tiles N for legitimately unbuildable zones), (6) layout lint, (7) control lint, (8) Phase 6f visual render — a valid Sigma render PNG exists in the workdir (sigma-render.png or a screenshots/_manifest.json entry), proving the mandatory full-dashboard visual comparison could run. Closes the "declared done on HTTP 200 / CSV-parity-only" regression where the workbook shipped without anyone rendering the PNG. Exits 1 for missing parity sentinel, 2 for parity FAIL / extract-mode-without-flag / charts_total==0, 4 for uncleaned orphans, 5 for live type=error columns, 6 for missing layout, 7 for census failure, 8 for layout-lint violations (lib/layout_lint.rb, --skip-layout-lint), 9 for control-lint violations (lib/control_lint.rb — dead controls / ghost targets / partial reach / control-scope coverage; --skip-control-lint, --control-scope PATH), 10 for missing visual render (--sigma-render PATH, escape hatch --skip-visual-gate "<reason>"). Subagent flows MUST call this as their final step.
scripts/probe-controls.rb
Phase 6 (optional) — control flip test: per control, export one in-closure element CSV with and without parameters:{controlId: <first non-default value>} (must differ) and, with --check-out-of-closure, one out-of-closure element (must NOT differ). Runtime proof the wiring works; the static check is gate 7. Shared, vendored byte-identical (md5 discipline). See refs/control-parity.md.
scripts/cleanup-orphan-workbooks.rb
Delete orphan workbooks left by spec-iteration retries. Reads <workdir>/posted-workbooks.jsonl, keeps the most-recent ID, deletes the rest via DELETE /v2/files/{id}. Writes cleanup-marker.json so the hard gate can confirm cleanup ran (and wasn't --dry-run). Idempotent (404 on delete is treated as success). See beads-sigma-38a.
scripts/build-dashboard-layout.rb
MANDATORY in Phase 5d (dashboard-fidelity mode) — auto-build the Sigma layout XML from the parsed Tableau zone tree (dashboard-layout.json) + the workbook readback IDs (wb-ids.json). Positions each chart at the grid cell derived from its zone's x/y/w/h%. Without this step, the workbook PUTs without a top-level layout and Sigma renders elements as a single-column stack — see assert-phase6-ran.rb gate 4 (beads-sigma-bw3).
scripts/build-story-pages.rb
Story workbooks only — when parse-twb-layout.rb wrote story-plan.json, emit one Sigma page per story point: pass 1 (--spec/--out) appends caption-named pages (annotation text atop + cloned elements with fresh ids/controlIds) to the workbook spec pre-POST; pass 2 (--wb-ids/--layout-out) emits the banded per-page layout + container sidecar post-readback. See refs/story-points.md.
scripts/export-chart-png.rb
Phase 6d (visual) drill-down only — per-element PNGs for diagnosing a chart-level regression (dropped log scale, missing data labels, wrong kind, palette drift). NOT the primary visual gate: the mandatory check is full-dashboard ↔ full-dashboard — render the whole Sigma page with sigma-export-png.py --page <pageId> and compare it to the FULL source dashboard image (Tableau MCP get-view-image on the dashboard view, not each worksheet). Per-element screenshots miss layout/relationship defects (overlaps, dead zones, stranded controls, wrong relative sizing). See refs/layout-visual-qa.md; loop-fix-and-re-render until the full page matches the source — never declare done on HTTP 200.
scripts/pick-destination.rb
Phase 0b: list build destinations (list → workspaces + editable folders + My Documents) and create folders (create --name [--parent]). Drives the "where should this land?" prompt when no --folder/SIGMA_FOLDER_ID is given. folderId accepts a workspace id (workspace root) or a folder id. Shared across the migration skills.
scripts/find-or-pick-dm.rb
Phase 1.5: scan existing DMs in the org and recommend reuse when one already covers the workbook's columns. Score = 0.7·column-overlap + 0.2·table-overlap + 0.1·metric-overlap. Parallel-fetches DM specs (~2s for 50 DMs). Output: dm-match.json with ranked candidates + recommendation. Non-destructive. Reuse skips Phase 2 + 3 entirely. --auto-pick flag (with tie-window safety) skips the user-confirm step when there's a clear winner.
scripts/inspect-dm-shape.rb
Phase 1.5b (MANDATORY when reusing): inspect the reused DM's element graph and emit a denormalization plan classifying every column as fact (direct ref) or dim (needs Lookup). Output: dm-denorm-plan.json with the exact Lookup formula per dim column. Eliminates the 2–3 min spec-rework loop when the reused DM has separate dim elements (a non-pre-denormalized DM shape).
scripts/scan-customer-style.rb
Phase 0c: sample N recent workbooks in the customer's Sigma org and aggregate style signals (color palettes, number-format strings, layout grids, chart-kind mix, dataLabel preference, element naming case, density). Lets the converter emit specs that match house conventions instead of generic defaults.
scripts/dev/phase-timer.sh
Dev / profiling only — do NOT source in customer conversions. Source helper for phase timing when iterating on the skill itself; emits ▶/■ log lines per phase and a phase-timings.json summary. Only invoke when the user explicitly asks for timing data ("time it", "where did the minutes go", "profile"). Usage: phase_start "<name>" / phase_end around each phase, phase_report at the end. Across multiple Bash tool-call blocks, export PHASE_TIMINGS_TMP=<path> BEFORE the first source so the helper appends across blocks.
scripts/lib/layout.rb
Layout-XML helpers (gc, le, page_xml, assemble) — require'd by per-workbook layout configs
scripts/enhance-scan.rb
Phase E (opt-in) part 1 — SCAN (read-only). Source signals + built spec + live element exports → enhancements.json candidates {id, category, evidence, proposed, risk, verdict_hint, patch} + descoped propose-in-UI notes. Shared Phase-E engine, vendored byte-identical across plugins (md5 discipline).
scripts/enhance-apply.rb
Phase E (opt-in) part 2 — APPLY (accept-only, clone-first). Clones the parity workbook as "<name> — Enhanced" (1:1 artifact never written), applies ONLY --accept-ed candidates one at a time, each gated by an untouched-element clone-vs-original spot-check (auto-revert on shift). Writes enhance-report.json. Shared engine, byte-identical twin of the tableau/powerbi copy.
Prerequisites
Sigma credentials
Run the setup script once:
ruby scripts/setup.rb
It writes credentials to two places: ~/.claude/settings.json (which Claude
Code auto-loads) and ~/.sigma-migration/env (a neutral, sourceable file any
other agent or plain shell can use). The scripts fall back to the neutral file
automatically when the env vars aren't already set, so the skill works under
any agent.
On Claude Code, open a new session (or run ! source ~/.claude/settings.json)
so the env vars are live — no manual sourcing needed thereafter.
Required env vars:
SIGMA_BASE_URL — e.g. https://aws-api.sigmacomputing.com
SIGMA_CLIENT_ID
SIGMA_CLIENT_SECRET
Fetch a token at the start of each phase that needs one:
eval"$(scripts/get-token.sh)"
Tokens live ~1 hour. Re-run when a curl returns 401. Never use
TOKEN=$(eval "$(scripts/get-token.sh)") — $() creates a subshell where
the exported var dies immediately. Keep eval + curl in the same bash -c '...'
invocation.
Inline Python inside bash — DON'T. Triple-nested escapes (f"...{e.get(\\\"name\\\")}..." inside python3 -c "..." inside bash -c '...') silently break. Instead always write a .py file with Write and call it via python3 file.py. Same rule for any inline script over ~5 lines: write it to disk, then exec. It's not slower, it's deterministic, and the file becomes a reusable artifact. (Same applies to Ruby — prefer ruby file.rb over ruby -e '...'.)
Tableau access — two modes
The skill supports two transports for Tableau-side discovery. Prefer the
API/PAT path — it is dramatically faster (measured on "Orders Conversion
Test", 7 views: 61.8s serial → 13.7–18.9s with the unified fetch pool, zero
rate-limiting at pool 5). The MCP is the no-PAT fallback only (each MCP
fetch is a separate agent tool turn; the PAT CLI does everything in one
process).
Mode
When to use
Setup
PAT (REST) — preferred
A Tableau PAT is available (run setup-tableau.rb once). Also the only path to .twb content (layout-hint extraction, embedded datasources)
ruby scripts/setup-tableau.rb once, then eval "$(scripts/get-tableau-token.sh)" per session
MCP — fallback
No PAT can be provisioned, and mcp__tableau__* tools are loaded in the session
Produces the same artifacts as MCP-driven Phase 1 in a single run: get-workbook.json,
workbook-content.twb, ds-metadata.json + graphql-fields.json (VDS field list + GraphQL
formulas), views/*.csv, the dashboard PNG, and timings.json (per-task
start/duration/attempts — always written; it's the evidence trail for any future
"discovery is slow" report). Downstream scripts in Phases 2–6 are unchanged.
Full endpoint inventory and gotchas in refs/tableau-rest.md.
--datasource-name / --datasource-luid are optional — the script parses the
downloaded .twb for the first non-Parameters <datasource caption='X'> and looks it up
on the site automatically. Pass --no-auto-ds to disable, or --datasource-luid to force
a specific datasource when the workbook has multiple (--datasource-luid must be the
full UUID — the REST filter has no prefix matching).
How the pool works (and why 5): every fetch after the initial workbook GET
(.twb, VDS read-metadata, GraphQL fields, all view CSVs, dashboard PNG) goes
through ONE shared pool of 5 threads, enqueued longest-job-first — the PNG
render is the longest single fetch, so it starts at t≈0 and hides behind the
CSV batch. 5 is the measured sweet spot; 8 risks long-tail stragglers — at
8 threads a contended VizQL session parked one CSV fetch for ~40s (56s total
run vs. 13.7–18.9s at 5). The pool keeps 429/timeout exponential backoff and
single-flight 401 re-mint machinery as insurance even though neither fired at
pool 5 in validation. Also note Tableau's ~60s server-side render cache:
a view rendered within the last minute returns much faster, so back-to-back
runs land at the fast end of the range and cold-cache runs at the slow end —
don't read a 5s spread between runs as a regression.
One signin attempt only. Tableau Cloud invalidates a PAT after 4 consecutive failed
signins. get-tableau-token.sh runs exactly once; never wrap it in a retry loop.
Phase 0a — Scan the workbook for feature gaps (MANDATORY)
Run the gap scanner against the customer's .twbbefore anything else. It
inventories every workbook feature the skill currently handles vs. doesn't, so
the agent can plan around real translation gaps instead of discovering them
mid-conversion.
✅ Auto — translated end-to-end without intervention
⚠️ Hint — agent gets a copy-paste-ready Sigma formula in WARN lines
🛠 Manual — customer wires up post-publish (action filters, ref-marks)
❌ Unhandled — feature is used in the .twb but the skill does not yet
cover it; the agent should escalate via the gap-scout subagent OR file
an issue at github.com/twells89/sigma-skills-staging
Share the markdown report with the customer up front to set expectations.
Save the JSON for the subagent.
Phase 0b — Choose where to build (MANDATORY when no destination given)
Never silently dump the migrated data model + workbook into an auto-picked
folder. If the user did not supply a destination (no --folder <id> on
migrate-tableau.rb and no SIGMA_FOLDER_ID), ASK first:
Pass the chosen id to the migration as --folder <id> — it flows into both
the DM and workbook POSTs.
folderId accepts a workspace id (lands in the root) or a folder id. If the
user already passed --folder / SIGMA_FOLDER_ID, honor it silently — do NOT ask.
Data blending: when the scanner writes blend-plan.json, route each
blend BEFORE Phase 2 using its route field — (a) same-warehouse-repoint
→ one DM, both sources as elements + relationship on the linking fields
(deep-walk connectionId incl. joins[].left/right when repointing);
(b) materialize-via-vds → run the tableau-vds-to-cdw skill to land the
secondary in the primary's warehouse first; (c) flag-unreachable → keep
manual, report the linking fields. Full decision tree: refs/blending.md.
Story points: when parse-twb-layout.rb writes story-plan.json
(Phase 1d), plan one Sigma page per story point and run
scripts/build-story-pages.rb in Phase 5 (spec pass) and Phase 5d (layout
pass). Storyboard dashboards are flagged is_story: true in
dashboard-layout.json — do NOT build a regular page from the flipboard
chrome. See refs/story-points.md.
Phase 0a-scout — spawn the gap-scout subagent for unhandled features
MANDATORY, parallelizable. As soon as the gap scanner produces gaps.json,
read the detected_features array and spawn one gap-scout Agent per row
whose status is unhandled (and optionally for high-volume hint rows).
Use run_in_background: true so the scout runs in parallel with the rest of
conversion — by the time you reach Phase 5, the scout has either persisted a
rule or escalated. Don't read the gap report and proceed without doing this.
For every ❌ Unhandled row in the gap report (and for high-volume ⚠️ Hint
rows worth automating), spawn a gap-scout subagent via the Agent tool. Each
scout takes ONE gap, proposes a Sigma translation, validates against the
customer's Sigma site via scripts/validate-sigma-formula.rb, and:
on success → writes the rule to ~/.tableau-to-sigma/learned-rules.yaml
(the customer's home dir — git pull of the skill cannot clobber it).
All future workbook conversions on this machine pick up the rule via
scripts/learned-rules.rb automatically.
on failure → writes to ~/.tableau-to-sigma/escalations/ and returns an
opt-inescalate-gap.py command. Filing a tracking issue is never
automatic: run the returned escalation.dry_run_cmd to draft the issue
(shows target repo + dedupe), show the user, and only re-run with --yes
if they accept. Calc-field gaps route to the converter repos
(sigma-data-model-manager + sigma-data-model-mcp, mirrored) with a
cross-linked bead. See "Opt-in issue filing" in scripts/gap-scout.md.
The build script (build-charts-from-signals.rb) loads learned rules at
startup; matching rules apply before the built-in translators, so customer-
discovered translations override defaults. See scripts/gap-scout.md for the
full subagent prompt + procedure.
Customer-local files always live under ~/.tableau-to-sigma/:
escalations/*.yaml — gaps the scout couldn't solve
(override path for testing with TABLEAU_TO_SIGMA_HOME env var)
Phase 0b — Pick the conversion mode (MANDATORY, ask the customer)
Before building anything, ask the customer which mode they want. There is
no good default — picking the wrong one wastes the whole conversion.
Mode
When
Output
Dashboard fidelity (default for dashboard URLs like /views/<WB>/<Dashboard>)
Customer wants the source dashboard recreated 1:1 in Sigma
One Sigma page with all charts positioned in the same grid as Tableau; shared filters as page-level controls; layout XML mirrors the dashboard's zone tree
Page-per-worksheet (default for /sheets/<Sheet> URLs OR when the customer says "split it up")
Customer wants each worksheet adjustable independently, OR the dashboard is too dense to recreate cleanly
One Sigma page per Tableau worksheet; shared filters duplicated on each page
When the customer's URL is a dashboard URL and they haven't explicitly said
"split into pages," the agent MUST ask: "Want me to recreate the dashboard
1:1 (all 6 tiles on one page) or break each worksheet into its own Sigma
page?" Don't assume.
For dashboard mode, build-charts-from-signals.rb is invoked WITHOUT
--page-per-worksheet — that emits the legacy flat-array output. Then a
separate layout script positions the chart elements in a grid matching the
Tableau dashboard's zone x/y/w/h percentages (parse-twb-layout already
extracts these).
For page-per-worksheet mode, pass --page-per-worksheet.
Phase 0 — Estimate cost up front
Before committing to the conversion, predict the agent token cost. Useful for
quoting and for bucketing workbooks (small/medium/large/very-large) in a
multi-workbook migration.
The estimator emits a JSON record with features (dashboards, sheets, calc
fields, custom SQL bytes) and estimate (complexity bucket, input/output
token counts, USD cost). Coefficients are heuristic and should be calibrated
against ~10 measured conversions before use in customer quotes.
Phase 1 — Discover the Tableau datasource structure
1a. Resolve the name the customer gave you
The customer's name may be a datasource, a workbook, or a dashboard view inside a workbook. Tableau Cloud's search and list endpoints partition by content type, so you have to try each before declaring no match.
# Workbook by name
mcp__tableau__search-content terms="<name>" filter.contentTypes=["workbook"]
# Dashboard view by name — falls back to workbook owner via the view's response
mcp__tableau__list-views filter="name:eq:<name>"
# Datasource by name
mcp__tableau__search-content terms="<name>" filter.contentTypes=["datasource"]
mcp__tableau__list-datasources
If the workbook search returns nothing, try list-views next — the customer almost certainly named a dashboard sheet (e.g. "Orders Overview") that lives inside a differently-named workbook ("Orders Conversion Test"). The view response includes the parent workbook's LUID.
Check hasExtracts on the search result. When hasExtracts: true on a workbook
(and especially on its datasource), the Tableau view CSVs reflect a frozen snapshot
of the warehouse — not its current state. Sigma always reads the live warehouse, so the
absolute counts in Tableau views will diverge from Sigma values, even when the chart
structure (dimensions, aggregations, breakdowns) is identical.
1c. Get workbook views
mcp__tableau__get-workbook workbookId="<luid>"
Returns the list of views (sheets) with their id and name. Record all view IDs.
1d-cache. Reuse prior conversion artifacts when present (PHASE -1)
Before re-running tableau-discover / fetch-view-data / parse-twb-layout, check
for cached artifacts from a previous run. The standalone Workforce conversion
on 2026-05-22 found cached audit-run-1 artifacts in
/tmp/audit-run-1/workforce/ (views CSVs, view PNGs, signature, dm-spec,
wb-spec, dashboard layout meta) — re-running discovery cost ~3 minutes that
could have been zero.
The script searches /tmp/audit-run-*/<name>/, /tmp/converter-test/<name>/,
and /tmp/<name>/ for: views CSVs, views PNGs, workbook-content.twb,
gaps-report, dashboard-layout JSON, get-workbook.json, dm-spec.json /
wb-spec.json (and their ID maps), and the workbook signature. Output is a
JSON map of artifact name → absolute path (or null).
Use the cached artifacts as-is when they exist and the workbook hasn't
changed — copy them into your working directory (or symlink) and skip the
corresponding fetch step. The DM/wb specs become your reference for ID
mapping after a re-POST (see scripts/remap-wb-spec-to-dm-ids.rb).
1d. Retrieve view data and images
Two different fetches with very different cost profiles. Don't conflate them.
get-view-data (CSVs) — cheap, no VizQL session contention. Fire all view CSVs in parallel in a single batch.
get-view-image (PNGs) — expensive, hits VizQL session contention. Most 401s come from firing multiple image requests simultaneously (or alongside other view calls).
The output (signals.json) contains, per view, a columns map with kind
(dimension / numeric / date), distinct_count, sampled distinct values,
numeric ranges, and aggregation_hints parsed from CSV headers like
"Sum of Gross Revenue" or "Distinct count of Order Id".
The reliable fetch pattern:
Fire get-view-data calls in parallel batches, but cap each batch at ~4 concurrent calls. CSVs survive concurrency far better than image fetches, but 7-way batches have produced 6×401 from VizQL contention in the wild (verified 2026-05-22). For >4 views, split into back-to-back batches of 4 (e.g., 7 views → batch of 4, then batch of 3 in the next message).
This is the single biggest perf win in the whole conversion. Measured 2026-05-22: 7 view-CSVs sequentially = ~200s (~28s per call, range 19–40s). Same 7 calls fired in two batches of 4+3 = ~60-70s (vs. ~45s for an unrestricted batch when no contention hits — but unrestricted goes catastrophically slow once it does, because every 401 retry happens solo). Skipping parallelization entirely is responsible for ~2.5 min of the historical ~9-min conversion runtime. Send each batch as a single message with N mcp__tableau__get-view-data tool-call blocks side-by-side; do NOT send them in separate messages.
Fetch only the dashboard view's PNG with get-view-image. Solo — no other view calls in flight.
If a specific tile's dashboard title looks wrong or truncated, fetch that one sheet's PNG solo to disambiguate.
If get-view-data returns 401 for a view, retry that view solo (the contention almost always clears within a second or two); if it 401s on the solo retry, skip it.
Do not parallel-fire get-view-image calls. Even if the CSVs succeeded in parallel, concurrent image requests still 401 due to VizQL session contention. Images are always solo.
Reading the dashboard image is MANDATORY before writing the workbook spec in Phase 5. The CSV headers tell you a chart's dimensions and measures; they do NOT tell you (a) the chart's kind (a Category, Count CSV could back a bar OR a pie OR a donut), (b) any text annotations (titles, section headers, footnotes), or (c) the filter shelf. Skipping the image read is the most common Phase 5 mistake — you ship a workbook that has the right numbers but is missing tiles the source dashboard actually rendered.
Phase 1d checklist — confirm before moving on:
Opened the dashboard PNG and listed every tile, including non-chart tiles (text, filter shelves, legends, image placeholders)
Decided the chart kind of each tile from the image, not just the CSV header (bar / line / pie / donut / kpi / map / pivot-table / table)
For any text-mark / crosstab-looking tile, confirmed pivot vs flat: Tableau dims on BOTH the Rows AND Cols shelves ⇒ Sigma pivot-table (with rowsBy / columnsBy / values). Dims on Rows only ⇒ Sigma table. parse-twb-layout.rb sets is_crosstab: true and chart_kind: pivot-table automatically when shelves carry dims on both sides — trust that signal over the visual Square/Text mark which is the same for both.
Noted every text element on the dashboard surface (page title, section headers, free-text annotations)
Noted every dashboard-level filter or parameter control (date range, list, segmented buttons)
Use the dashboard image to understand:
How many KPIs are in the header row and what they measure
Which chart types are used (bar, line, scatter, map, small multiples, pie / donut)
The rough grid layout of each page (columns × rows) — count the rows; this is what your layout XML needs to match
Page titles, section headers, and any free-text annotations on the dashboard surface — these are real content (not metadata) and need to be recreated as text elements in the Sigma spec. The page tab name (page['name']) is not a substitute; it only appears in the tab bar, not on the canvas. If the Tableau dashboard shows a heading like "Orders Dashboard" at the top of the page, add a text element with body: "## Orders Dashboard" and reserve a row for it in the layout.
The filter shelf. Tableau dashboards usually have visible filter controls (a date range slider, a region list, a state list). These appear as control elements in the Sigma workbook — never just as Phase 2.5 element-level filters, because that strips the user-facing control surface.
Alternative / supplement: parse the .twb zone tree. If you have workbook-content.twb from PAT-mode Phase 1, run:
It emits a per-dashboard zone list with caption, view_ref, x/y/w/h in percent, and chart_kind extracted from each worksheet's <mark> element + Rows/Cols shelves (bar / line / pie / scatter / map-region / map-point / pivot-table / table / automatic / other). For text-mark worksheets, the parser disambiguates pivot-table (dims on both shelves — Tableau crosstab) from flat table (dims on one shelf — detail list) via the rows_shelf / cols_shelf summary; build-charts-from-signals.rb honors this and emits rowsBy / columnsBy / values for crosstabs. This is more reliable than inferring chart type from the view CSV — the CSV headers can't distinguish bar-vs-pie or pivot-vs-flat-table. Map every zone in the output to a Sigma element using the tables in refs/workbook-layout.md (Reading the .twb dashboard layout section).
Maps: if parse-twb-layout.rb emits chart_kind: map-region or chart_kind: map-point for any zone, do NOT build a bar chart. Use Sigma's region-map / point-map element kinds. The Tableau geographic role (semantic-role on the column) translates to Sigma's regionType via the table in refs/workbook-layout.md. Sigma's region types are US-only except for country — non-US state/county/ZIP data falls back to a sorted bar chart or, if lat/long is available, a point-map.
chart_kind: automatic: Tableau's "Automatic" mark picks a default for the encodings. It usually renders as a bar but is not deterministic. When you see automatic, fetch the dashboard PNG and look at that specific tile to decide the Sigma kind.
Common kind mistakes — all three are rejected by the API:
"kpi" → must be "kpi-chart"
"pie" → must be "pie-chart"
"donut" → must be "donut-chart"
The official Sigma example library shows kpi, pie, and donut — all three are wrong. The validator (scripts/validate-spec.rb) flags them, but do not rely on it: write the correct kind from the start.
Does not support via the spec API: bullet chart, gantt.
Maps are fully spec-supported. Use region-map for choropleths (US state / county / ZIP / CBSA / country fills) and point-map for lat/long bubble or symbol maps. See refs/workbook-layout.md "Map elements" for the field shape, the exact set of valid regionType values, and the color-channel rules.
Trellis (small multiples) is supported in Sigma but configured UI-only. Build the chart with the right dimensions via spec, then trellis it manually post-publish.
Log-scale axes round-trip through the spec.parse-twb-layout.rb extracts
axis_formats[].scale: "log" from each worksheet's <axes> block, and
build-charts-from-signals.rb emits it as
element.yAxis.format.scale = { type: "log", domain: {min, max} } whenever
range_type == "fixed". If you hand-write the workbook spec instead of
running build-charts-from-signals.rb, you MUST copy this manually —
otherwise the chart silently degrades to linear scale (OCT lost the Monthly
Trend log axis this way on 2026-05-24). Always grep
dashboard-layout-meta.json for "scale": "log" before declaring Phase 5
done.
Control types supported: list, date-range, text, text-area, segmented, number, number-range, slider, range-slider, top-n.
See refs/workbook-layout.md for full control element spec patterns.
1e. Discover calculated fields (Metadata API + .twb fallback)
Calculated field formulas are required to translate calc cols into Sigma DM
formula columns. The converter pulls them via the Tableau Metadata API
(GraphQL) as the primary path. Metadata API is independent of VDS — it
works even when VDS is disabled on the customer's site. VDS is NOT used for
calc discovery anymore.
eval"$(scripts/get-tableau-token.sh)"
ruby scripts/extract-calc-fields.rb \
--workbook-luid <luid> \
--out /tmp/<name>/calc-fields.json \
[--twb /tmp/<name>/workbook-content.twb] # used if metadata-api fails
The script caches its result to --out and reuses it (< 1h old) on subsequent
runs unless you pass --refresh. Downstream phases read from the cache.
Fallback order (--source auto is the default):
Metadata API (POST /api/metadata/graphql) — returns formula +
dependency graph + role + datatype + aggregation + isHidden.
.twb XML parse — returns formula only (no resolved field-name
dependency graph; depends_on is [] on this path). LOD formulas are
still captured because they live in the <calculation formula='...'/>
attribute verbatim.
Both produce the same JSON shape so downstream phases don't care which path
fired. Force a specific source with --source metadata or --source twb.
name, formula, role, data_type, aggregation, is_hidden — direct from Tableau
is_lod — true for {FIXED/INCLUDE/EXCLUDE} expressions
depends_on — referenced field names (metadata-api path only)
requires_custom_sql — true ONLY for the manual window residues
(WINDOW_MEDIAN/PERCENTILE/CORR/COVAR(P)/VAR(P)/STDEVP, PREVIOUS_VALUE,
SIZE, FIRST, LAST, RANK_UNIQUE/MODIFIED) and {INCLUDE/EXCLUDE}
LODs. The mainstream window/table-calc family (WINDOW_SUM/AVG/MIN/MAX/ COUNT/STDEV, RUNNING_*, RANK/RANK_DENSE/RANK_PERCENTILE, INDEX,
LOOKUP, TOTAL) is AUTO-TRANSLATED by build-charts-from-signals.rb
into Sigma-NATIVE window math emitted as CHART-element viz formulas on the
yAxis — single DM base element, zero Custom SQL (WINPROBE-validated
930/930 cells; full mapping table in refs/window-functions.md). The
functions still CANNOT be Sigma DM calc columns (silent error type) and
the *Over family is Unknown function everywhere — the chart yAxis is
the only valid placement.
translation_notes — common Tableau→Sigma gotchas to apply during the
Phase 3 DM build: IIF→If, COUNTD→CountDistinct, IF/ELSEIF chains
ending in literal need Coalesce wraps on nullable inputs (Tableau
collapses NULL into ELSE; Sigma If(NULL >= …, …) returns NULL), the
per-function window mapping (refs/window-functions.md), and the
Custom-SQL escalation for the manual window residues only.
If the workbook has > 1000 calcs on a single page or the GraphQL response
exceeds ~5 MB, the API may truncate. In that case re-run with
--source twb, which parses the cached .twb directly and is bounded only
by file size.
Translate the calc fields into the DM (Phase 3) using the original Tableau
formula as the source of truth, NOT the warehouse column the calc happens
to reference. Example: a Tableau "Customer Value Tier" calc that buckets
Lifetime Revenue must be re-derived in Sigma from LIFETIME_REVENUE, not
pulled from a same-named LOYALTY_TIER warehouse column.
1e.1. Warehouse-table source rejected? Fall back to Custom SQL
Verified 2026-05-24 against the tj-wells-1989 org during audit-run-1.
Two agents (Superstore, NASA) hit Source not found: warehouse table 'TJ.PUBLIC.XXX' on connection 'YYY' POSTing a DM element whose
source.kind: "warehouse-table" pointed at a table that physically existed
in the warehouse and was queryable via mcp__sigma-mcp-v2__query. This is
a Sigma static-catalog visibility issue: the warehouse-table source
path requires the table to be indexed in Sigma's internal catalog, which
does NOT auto-refresh after every warehouse-side landing (VDS write, dbt
run, manual CREATE TABLE). There is currently no public API to force a
catalog refresh; the UI's "Refresh schema" action on the connection page
is the only mechanism, and you usually can't drive it from the conversion
agent.
The fallback is to source the same table via Custom SQL:
{"id":"el-orders","kind":"table","name":"Orders","source":{"kind":"sql","connectionId":"<connection-id>","statement":"SELECT * FROM TJ.PUBLIC.NASA_GISS_LOTI"},"columns":[{"id":"c-year","name":"Year","formula":"[Custom SQL/YEAR]"},{"id":"c-temp","name":"Temp Anomaly","formula":"[Custom SQL/TEMP_ANOMALY]"}]}
This works because Custom SQL bypasses the catalog entirely — the connection
just executes the statement and Sigma reads whatever columns come back. The
trade-offs vs warehouse-table are:
Don't guess column names. Sigma's spec API does not expose the columns
of a SQL element until you've already declared them in the spec, which is a
chicken-and-egg problem during the fallback. Run
scripts/probe-custom-sql-columns.rb to resolve real column names + types
via an INFORMATION_SCHEMA query through a one-shot probe workbook (auto-
created, exported as CSV, deleted; ~6s end-to-end):
Validated 2026-05-24 against TJ.PUBLIC.SUPERSTORE_ORDERS — 19 columns
resolved in 7s. Saves ~120s on every Custom SQL fallback vs.
POST-fail-cleanup-retrying on column-name permutations (CUSTOMER_ID vs
CUST_ID vs ID vs RECORD_ID…). Don't skip this step.
column-level lineage is hidden (Sigma sees one opaque SQL statement)
per-column governance / CLS doesn't auto-apply
the warehouse-side query optimizer treats it as a sub-select
For a customer-facing conversion these trade-offs are acceptable; for a
"production" DM build, ask the customer to refresh the Sigma connection's
schema in the UI and retry with warehouse-table.
1f. Extract Custom SQL (PAT mode)
If the source workbook uses Custom SQL — either as the entire datasource or
mixed alongside warehouse tables — run:
Metadata GraphQL API for CustomSQLTable nodes downstream of the workbook (works for both published-datasource Custom SQL and embedded Custom SQL).
.twb XML fallback for embedded <relation type='text'> blocks (covers cases the Metadata API hasn't crawled yet).
Output is a JSON array, one entry per Custom SQL block, with query (the raw SQL text), connectionType, and downstream workbook/datasource pointers. If the array is non-empty, build the DM in Phase 3 with Custom SQL elements (kind: "sql") sourcing the actual SQL — not warehouse-table references.
MCP-mode caveat. This script needs PAT-mode env vars (TABLEAU_AUTH_TOKEN, etc.). If you only have MCP available, you cannot pull custom SQL — that's a real gap; switch to PAT mode for any workbook the customer says uses custom SQL.
Phase 1.5 — Check for an existing DM the workbook can reuse (DO THIS FIRST)
Before running Phase 2 (warehouse column discovery) and Phase 3 (DM build), check whether the customer's Sigma org already has a data model that satisfies the workbook's needs. Reusing an existing DM:
Avoids DM sprawl (customers complain when they end up with a 4th "Orders" DM)
Cuts Phase 2 + Phase 3 entirely on the reuse path — typically the heaviest 2–3 minutes of a conversion
The picker parallel-fetches DM specs (10 concurrent threads — ~2s for 50 DMs vs ~15s serial). Scoring weights: column overlap 0.7, source-table FQN 0.2, metric overlap 0.1. Output thresholds:
Score
Action
≥ 0.85
auto-reuse the recommended DM, skip Phase 2 + 3
0.6 – 0.85
ambiguous — ask the user before reusing; surface the candidates from dm-match.json
< 0.6
no usable match; proceed to Phase 2 + 3
Surface this in your conversation with the user:
"Found existing DM <name> covering N/M of the columns this workbook references. Reuse this DM? It would skip ~2–3 min of conversion time but the workbook will inherit X extra columns (sample: ...). Reply yes to reuse, no to build new, or show to see other candidates."
When reusing, jump straight from Phase 1.5 to Phase 5 — the workbook spec's table elements set source: { kind: data-model, dataModelId: <recommended_dm_id>, elementId: <chosen-element-id> } and use formula prefixes derived from the existing DM's element name (e.g. [Plugs Sales/Revenue]).
The picker is non-destructive — it never modifies any DM. The downstream phase decides reuse vs build.
Phase 1.5b — DM-shape preflight (MANDATORY when reusing)
Before writing the workbook spec, inspect the reused DM's element graph. Skipping this is the single biggest source of conversion-time waste — a workbook POST that fails with Cannot resolve columns on table master: dependency not found: formula reference customer_dim/region forces 2–3 minutes of spec-rework.
The plan classifies every column on the DM as either:
location: "fact" — already on the fact element, reference directly as [Master/<col>]
location: "dim" — lives on a separate dim element, must use Lookup([<DimElement>/<col>], [Master/<FK>], [<DimElement>/<PK>])
For each dim column in dm-denorm-plan.json, the script provides the exact Lookup formula. When writing the workbook master table:
The primary master table sources from the fact element (use the fact_element.id from the plan).
For each dim element referenced by the workbook's worksheets, add a hidden master table sourcing that dim element (visibleAsSource: false).
Master-column formulas use the plan's column_resolution["<col>"].formula verbatim.
The plan also surfaces unmatched_dim_elements — dim elements with no detectable FK on the fact (often calendar tables). If a worksheet references columns from one of these, you'll need to manually identify the join key.
Measured 2026-05-22 against the same Tableau workbook in two consecutive conversions: the run that skipped this preflight rewound 130s (21.5% of total) on the failed-POST rework path. The plan computes in ~1s and eliminates that overhead.
Phase 2 — Discover actual warehouse column names
This step is mandatory. Do not skip it or infer column names from Tableau.Skip Phase 2 entirely if Phase 1.5 recommended a DM you reused.
Tableau display names ("Sub-Category", "Country/Region") are NOT the same as
warehouse column names ("SUB_CATEGORY", "COUNTRY_REGION" in Snowflake;
sub_category / country_region in lowercase-by-default Postgres / Databricks;
subCategory / countryRegion in case-preserved BigQuery). Using the
display name as the warehouse name produces "dependency not found" errors at
publish time.
Warehouse-agnostic discovery — use Sigma's REST API or MCP, NOT the
warehouse-specific CLI (snow sql DESCRIBE TABLE, bq show, databricks catalogs, etc.):
# 1. Find the connection ID (any warehouse — Snowflake / BigQuery / Databricks / etc.)
curl -sH "Authorization: Bearer $SIGMA_API_TOKEN" \
"$SIGMA_BASE_URL/v2/connections" | jq '.entries[] | {id, name, type}'# 2. Find the table inodeId (Sigma indexes warehouse tables in its catalog)
curl -sH "Authorization: Bearer $SIGMA_API_TOKEN" \
"$SIGMA_BASE_URL/v2/connections/<connectionId>/tables" | jq '.entries[] | {inodeId, path}'# 3. List columns — PER feedback_sigma_columns_api_endpoint, the endpoint is# /v2/connections/tables/<inodeId>/columns (no connectionId in the path).
curl -sH "Authorization: Bearer $SIGMA_API_TOKEN" \
"$SIGMA_BASE_URL/v2/connections/tables/<inodeId>/columns" | jq '.entries[] | {name, type}'
Or the equivalent MCP tools (preferred when available):
mcp__sigma-mcp-v2__describe on a connection table → returns column names + types
mcp__sigma-mcp-v2__search with entityTypes=["table"] to find inodeIds by name
The provided helper script wraps the REST call with parallel fan-out and the
"response key is entries, not columns" gotcha pre-handled. It works
against any Sigma connection regardless of underlying warehouse:
Convenience: for a single table by <db>.<schema>.<table> path (instead of
inodeId), use discover-columns.rb — it does the inode lookup automatically
and emits a JSON column list:
If discover-columns.rb returns 404 — meaning the table physically exists in
the warehouse but is not in Sigma's static catalog — the fallback is to source
via Custom SQL (see Phase 1e.1 "Warehouse-table source rejected? Fall back to
Custom SQL"). There is no public API today to force a Sigma catalog refresh;
only the UI's "Refresh schema" action on the connection page can do that.
The script:
runs all column-fetches in parallel,
handles the "response key is entries, not columns" gotcha,
writes one <inodeId>.json per table into the output dir.
The friendly names returned are the exact values to use in DM element formulas: [TABLE_NAME/Column Name].
parse-twb-layout.rb's *-meta.json — shared_filters (workbook-level filter shelf) and per-chart zone.filters (worksheet-level) carry resolved column captions, member-value lists, and an is_action flag distinguishing value filters from cross-chart action filters. build-charts-from-signals.rb --auto-controls translates list / relative-date / number-range shared filters into Sigma controls per page automatically.
View CSV ↔ warehouse diff (legacy fallback) — for .twbx-less workbooks or when the agent suspects the parser missed a filter, compare distinct values in the view CSV against the warehouse.
The diff method is still mandatory for any workbook where you don't have the .twb content. When you DO have it, trust the parser's filter output first — it carries member values that the CSV can't reveal.
For every dimension column on every view, compare:
SELECT DISTINCT <col> / SELECT MIN, MAX <date> via mcp__sigma-mcp-v2__query (type: "connection" with the table inodeId)
Any value present in the warehouse but missing from the CSV implies a filter on that column.
SELECTMIN("DATE") AS min_date, MAX("DATE") AS max_date,
COUNT(DISTINCT DATE_TRUNC('quarter', "DATE")) AS qtr_count
FROM "connection"."<table-inodeId>"
Common patterns
View CSV symptom
Likely Tableau filter
Sigma translation
Only some values of a categorical column appear
"Keep only" / dimension filter
list control with mode: "include", or element-level filter
Date min/max is narrower than warehouse
Date / relative-date filter
date-range control — mode: "current" + unit: "year"|"quarter"|... for relative; mode: "between" with explicit startDate/endDate for fixed
Numeric column is bounded
Range filter
number-range or range-slider control, or element-level filter
Only top N items by some measure
Top-N filter
top-n control or element-level top-n filter (see refs/workbook-layout.md)
Where to apply the filter
Prefer a workbook-level control filtering the master table — every chart that sources from master inherits the filter, matching how a Tableau dashboard filter works. Use element-level filters only when the filter is fixed and shouldn't be user-adjustable (a hard-coded slice).
A relative-date filter that "rolls forward" in Tableau ("this year", "last 30 days", "year to date") must be translated as a relative date-range control (mode: "current", unit: ...) — not a fixed start/end date. Hard-coding startDate/endDate freezes the filter to today's date and breaks tomorrow.
Phase 6 will not catch a missed filter on its own. Data parity in Phase 6 compares Sigma rows to Tableau rows for the dimensions you query — if your Sigma chart includes extra rows the CSV never had, the comparison only flags missing rows from Tableau, not extra rows in Sigma. Always sanity-check distinct values and date ranges side-by-side before declaring parity.
Phase 3 — Build the data model spec
Write the spec to /tmp/<name>/dm-spec.json. Full schema is in
refs/data-model-spec.md.
Critical rules
Endpoint: POST /v2/dataModels/spec — NOT /v2/workbooks/spec.
folderId is required. Find it via GET /v2/files?typeFilters=workbook — parentId on any of your workbooks.
Top-level shape uses pages: [{elements: [...]}], NOT a bare elements: [...] at root. The API rejects root-level elements with pages: Invalid array: undefined. Even if your DM only has one logical page (typical), still wrap the elements under a single page:
{"name":"Orders","folderId":"<folder>","schemaVersion":1,"pages":[{"id":"p-data","name":"Data","elements":[{/* warehouse-table or sql element */}]}]}
This is the same shape refs/data-model-spec.md documents; the abbreviated examples below show only the element body — wrap them in pages: [{elements: [...]}] before POSTing.
Column name special characters — read refs/column-gotchas.md. Rename any column whose name contains / ("Country/Region" → "Country", "State/Province" → "State").
Element name = formula prefix. The name field on a DM element (e.g. "Orders") becomes the prefix in all workbook formulas that reference it: [Orders/Sales]. Choose clean, stable names.
Relationships go on the source element, not the target. See refs/data-model-spec.md.
Column formulas use the warehouse table name as prefix: path ["CSA", "Tableau Test", "ORDERS"] → formula "[ORDERS/Column Name]".
When to use a Custom SQL element instead of a calc column
Sigma window functions silently fail in DM calc columns and in workbook master (grouping-table) calc columns — CumulativeSum, Rank, Lag, etc. POST successfully but resolve as error on GET, and the *Over family (SumOver/RankOver/MaxOver/...) is Unknown function in every spec context. But they are FIRST-CLASS as CHART-element viz formulas on the yAxis (WINPROBE-validated 2026-06-12, 930/930 cells): build-charts-from-signals.rb auto-emits the whole mainstream window/table-calc family that way — RUNNING_*→Cumulative*, bounded WINDOW_*→Moving*, share→PercentOfTotal(agg, "grand_total"), pareto→CumulativeSum(PercentOfTotal(...)), RANK*→Rank/RankDense/RankPercentile(agg, "desc"), INDEX()→RowNumber(), LOOKUP(±n)→Lag/Lead, unbounded WINDOW_MAX/MIN/SUM/TOTAL→hidden two-level grouped helper. Cumulative/rank formulas follow the chart's xAxis.sort (Tableau <computed-sort> is carried via a hidden companion measure) and auto-partition by the chart color dim. Full mapping table + the broadcast-down/week-anchor gotchas: refs/window-functions.md. The design rule stands: never write window functions as DM or master calc columns.
{FIXED ...} LODs are AUTO-TRANSLATED — no Custom SQL needed. When a
{FIXED [dims] : AGG([m])} calc is plotted as a chart/KPI measure,
build-charts-from-signals.rb emits a hidden TWO-LEVEL grouped helper
element on the Data page (visibleAsSource:false; inner grouping = the
FIXED dims computing the LOD aggregate, outer grouping = the chart's dims
computing the 2nd-stage aggregate over the inner GROUP values) and the chart
sources the helper, Max()-ing the outer calc (a chart re-aggregates a
grouped source at BASE grain with group calcs replicated per row — Max over
identical replicas is exact; verified live 2026-06-12). ⚠ Carried chart dims
must be functionally dependent on the FIXED dims (e.g. Customer Segment per
Customer Id) — the build emits a per-chart verify warning. The same helper
machinery handles grain-aware averages: Avg of a dim-table column
(Tableau relationship semantics evaluate it at the dim table's NATIVE grain,
including entities with no fact rows) sources the DM dim element directly.
NEVER write these as SumOver/CountOver master or DM calc columns — they
silently error.
Any Tableau calc whose requires_custom_sql: true (from Phase 1e) — that is, a manual window residue (WINDOW_MEDIAN/PERCENTILE/CORR/COVAR(P)/VAR(P)/STDEVP, PREVIOUS_VALUE, SIZE, FIRST, LAST, RANK_UNIQUE/MODIFIED, or a compute-using/addressing variant beyond Table(Across)/simple partitions) or an {INCLUDE/EXCLUDE} LOD (those need the chart-grouping context) — must be implemented as a Sigma Custom SQL data-model element. (The mainstream WINDOW_*/RUNNING_*/RANK*/INDEX/LOOKUP/TOTAL family no longer routes here — it is auto-emitted as Sigma-native chart formulas, refs/window-functions.md.)
{"id":"el-orders-windowed","kind":"table","name":"Orders With Window Calcs","source":{"connectionId":"<connection-id>","kind":"sql","statement":"SELECT o.ORDER_ID, o.REGION, o.SALES,\n SUM(o.SALES) OVER (PARTITION BY o.REGION) AS REGION_TOTAL_SALES,\n RANK() OVER (PARTITION BY o.REGION ORDER BY o.SALES DESC) AS SALES_RANK_IN_REGION,\n SUM(o.SALES) OVER (ORDER BY o.ORDER_DATE ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS RUNNING_SALES\nFROM ANALYTICS.PUBLIC.ORDERS o"},"columns":[{"id":"c-order-id","name":"Order Id","formula":"[Custom SQL/ORDER_ID]"},{"id":"c-region","name":"Region","formula":"[Custom SQL/REGION]"},{"id":"c-sales","name":"Sales","formula":"[Custom SQL/SALES]"},{"id":"c-region-total","name":"Region Total Sales","formula":"[Custom SQL/REGION_TOTAL_SALES]"},{"id":"c-sales-rank","name":"Sales Rank in Region","formula":"[Custom SQL/SALES_RANK_IN_REGION]"},{"id":"c-running-sales","name":"Running Sales","formula":"[Custom SQL/RUNNING_SALES]"}]}
Key points:
source.kind is "sql" (not "warehouse-table").
source.statement is the raw SQL text (the field name is statement, NOT sql). Use the warehouse dialect for the underlying connection (Snowflake, BigQuery, etc.).
Column formula prefix is [Custom SQL/<ALIAS_FROM_SELECT_LIST>]. The alias is whatever you wrote in the SELECT ... AS NAME clause. Use UPPERCASE aliases (matches Snowflake's default identifier casing); Sigma's column lookup is case-sensitive against the SQL output.
Every column you want to expose in the DM needs both a SELECT-list entry in the SQL AND a corresponding columns[] entry on the DM element.
Translation hints from extract-calc-fields.rb:
RUNNING_* / bounded WINDOW_* / RANK* / INDEX / LOOKUP / TOTAL — do NOT route here anymore: auto-emitted as Sigma-native chart viz formulas (refs/window-functions.md). The ANSI OVER(...) forms below are the fallback ONLY for the manual residues (WINDOW_MEDIAN/WINDOW_PERCENTILE/PREVIOUS_VALUE/SIZE/non-default addressing): e.g. WINDOW_MEDIAN(SUM([X])) → MEDIAN(X) OVER (<partition>), PREVIOUS_VALUE → recursive logic in SQL.
{FIXED [Dim] : SUM([X])} → SUM(X) OVER (PARTITION BY Dim) or a pre-aggregated subquery joined back — fallback only: when the LOD is plotted as a chart/KPI measure it is AUTO-TRANSLATED via the hidden two-level helper element (see the callout above), no Custom SQL needed
Nested LODs ({FIXED A : AVG({FIXED A, B : SUM([X])})}) → a helper-element CHAIN, not one formula: innermost LOD = helper element 1 (grouped by its dims, aggregate as Value), each outer level consumes [LOD Helper k/Value] via a relationship on the shared dims. build-charts-from-signals.rb decomposes these automatically into <out>-lod-chains.json (innermost first) — build one grouped element (or Custom SQL GROUP BY subquery) per level. Each outer level's source MUST carry groupingId pointing at the inner element's grouping — a plain {kind: table, elementId} source reads BASE-grain rows with the aggregate repeated per row, so outer Avg/Median/Count silently come out row-weighted (caught live: 969.82 row-weighted vs 687.81 correct on CSA.TJ.ORDER_FACT). Live-verified pattern (exact parity vs warehouse SQL), 2026-06-11.
When a workbook mixes plain calcs with window calcs, you can have BOTH kinds of DM elements in the same data model: one warehouse-table element for everything plain, plus one or more sql elements for the window/LOD calcs, related by key. Charts source from whichever element has the columns they need.
DM PUT reassigns element IDs. Combining a warehouse-table element with a sql element in the same DM works fine, but every PUT of the DM spec churns IDs — so plan to capture IDs once with post-and-readback.rb, build the workbook from those IDs, and avoid editing the DM in flight.
Translate Tableau calc fields here
Each calc from calc-fields.json (Phase 1e) becomes a DM calc column (or a workbook-level
calc on the master table, depending on grain). For calc columns that wrap a NULLABLE source
in an IF/ELSEIF chain, wrap with Coalesce to match Tableau's null-fallthrough behavior.
Example — Tableau:
IF [Lifetime Revenue] >= 5000 THEN "Platinum" ELSEIF >= 2000 THEN "Gold" ELSEIF >= 500 THEN "Silver" ELSE "Bronze" END
Sigma DM calc column on Order Fact (since the bucket depends on a joined dim):
Catches: formula prefix mismatches, bare refs not matching a sibling, kpi/pie/donut kind
mistakes, rgb(...) color strings (Cloudflare WAF blocks), missing yAxis on
bar/line/area/combo/scatter, missing color+value on pie/donut, donut holeValue.id matching
value.id (silent element drop), pivot-table missing rowsBy (single grand-total row), and
nested-If on date functions without IsNull guard.
