bug: implicit Big Pickle users (99% of the population) are never offered Altimate Base; silently rerouted to another free model

[anandgupta42]

Found while verifying the Big Pickle → Altimate Base migration end to end against the v0.11.1 binary (PTY-driven, isolated HOME) and cross-checking App Insights after the 0.11.0 GA.

What works (verified empirically, 0.11.1)

• A user whose persisted model.json has opencode/big-pickle in recent sees the "Big Pickle has been retired." disclosure on launch, explicit No + Enter persists altimate_base_big_pickle_migration_declined_v1 and opens the provider picker, Yes registers (one POST /register) and rewrites recents to altimate-free/altimate-base, an already-registered user is migrated silently, and a project provider allowlist suppresses the dialog.

The gap: implicit Big Pickle users are never offered Altimate Base

usesLegacyDefault() (packages/tui/src/context/local.tsx) only returns true when recent actually contains opencode/big-pickle. But recent is written only by a picker-driven selectModel(..., { recent: true }). A pre-0.11 user who never picked a model had Big Pickle purely as the server-side implicit default (Provider.defaultModel()), with an absent or empty recent. On 0.11.x that user:

• gets no migration dialog and no Altimate Base disclosure at all (verified: no model.json, and {"recent":[]}, both launch straight into chat), and
• is silently rerouted to whatever Provider.defaultModel() now resolves first, because big-pickle is excluded from the implicit scan. In the field that is opencode/nemotron-3.5-lightning-free; in the isolated test it was a Vertex model, i.e. catalog-order dependent.

Size of the population (App Insights, release builds, 2026-08-25 → 2026-09-09)

• 1,031 machines had sessions on big-pickle.
• Only 4 of them ever emitted provider_selected: big_pickle (an explicit pick). The other 1,027 are implicit-default users the migration cannot reach.
• Of the 4 Big Pickle machines already on 0.11.x, both with sessions since GA are running nemotron-3.5-lightning-free, not Altimate Base, and never saw a prompt.

This is the main reason Altimate Base has essentially no external traffic yet: the migration targets ~0.4% of the Big Pickle base, and the rest are moved to a different free Zen model without a disclosure.

Suggested fix

Treat "current model resolves to a retired implicit default and the user has no explicit selection" as migration-eligible: e.g. have the server report (or the TUI detect) that the pre-0.11 implicit default would have been opencode/big-pickle (no recent, no explicitDefault, no config model, no provider allowlist, and the opencode provider present without a key), and show the same origin="migration" disclosure. Keep the decline marker semantics.

Related UX nuance (same dialog)

Dismissing the migration dialog with Escape or Ctrl-C records the decline but leaves the user on Big Pickle with no picker, whereas explicit "No — pick something else" + Enter opens the provider picker. Escape is the likeliest "no thanks" gesture, so Escape users are stranded on the retired model with no visible next step other than /model.

Telemetry note

The migration dialog emits no events (consent events are gated on the first-run funnel), so prompts, accepts, and declines from the migration path are invisible in App Insights. Worth emitting altimate_base_confirm_shown / altimate_base_choice with origin: "migration".

[anandgupta42]

Fix is up in two PRs:

• fix: offer Altimate Base to every user on an implicit free Zen default #1302 — TUI: migration disclosure for any implicit free Zen default (not only Big Pickle), single startup decision, decline persisted in kv + model.json, Escape/mouse dismissal route to the picker, migration telemetry with origin. Server: registered Altimate Base outranks the keyless public Zen tier for the implicit default (headless and ACP), honouring a persisted decline and recents.
• AltimateAI/vscode-altimate-mcp-server#464 — proactive one-time Altimate Base consent prompt in the chat panel (reuses the fix: replace npm glob/minimatch with Bun.Glob — fixes 52 CI test failures #460 card), persisted decision, reset command. This is the path for the ~1,010 extension-driven machines.

Deliberately kept: an older picker-written Big Pickle recent without an explicit marker still migrates silently once Base is registered (the 0.11.0 behaviour); other free Zen recents get the disclosure instead.

[anandgupta42]

Resolved in v0.11.2: Altimate Base is now offered to every user on an implicit free default, with the dialog naming the model being replaced; declines are remembered across the TUI, headless, and ACP surfaces.