Grounded Progress

On long runs the failure mode isn't usually bad work — it's a report that drifts from the work: "tests passing" when they were never run, "deployed" when the command errored. The fix is an evidence rule applied at report time.

The evidence rule

Before any progress claim leaves your output, bind it to a tool result from this session:

• Completed → name the command/test/check whose output proves it.
• Failed → say so, and include the relevant output verbatim (trimmed, not paraphrased into optimism).
• Skipped or deferred → state it as skipped, with the reason.
• Not yet verified → label it explicitly as unverified; never round up to done.

A claim with no pointable evidence does not ship. Either produce the evidence (run the check now) or downgrade the claim.

Report shape for long runs

1. One line: overall state (on track / blocked / partially done).
2. Verified completions, each with its evidence pointer.
3. Failures and skips, stated plainly.
4. Unverified work-in-progress, labeled as such.
5. The single thing needed from the user, if anything.

Anti-patterns

• Hedged completions ("should be working now") — run the check instead.
• Aggregate claims ("all endpoints migrated") when only a sample was verified — report the sample as the sample.
• Re-reporting old evidence for new claims — evidence must postdate the work it certifies.

Receiving the updates (for the harness author, not the model)

Fable 5.1 writes fewer user-facing updates between tool calls than Fable 5, most noticeably at high effort in long tool chains. The updates it does write arrive as thinking blocks, which are empty under the default thinking.display of "omitted"; request "updates" (beta header thinking-display-updates-2026-08-18) and render each non-empty thinking block as a status line before concluding the model went silent. If your UI collapses or hides tool output, tell the model so in a turn-scoped system message; otherwise it may re-run commands to "show" output nobody sees.