The Principia Machina/Diagrams/03 Digest gate and recovery

The Principia Machina: map
Reading the diagrams Structure key Process key Definition of terms Roles
Reading by audience Start here: the walk through The operator's guide Tutorial: create a UUID Workspace Container (UWC) Public Recorder inputs Sponsors: your first agent
The specification Contents: parts, tables, diagrams TPS 0.5.0 (declared 2026-10-03, revision 8; machine-optimized text) Decisions (the foundations record, one line each)

Structural diagram 3 of 12. Part of the TPM hub.

• KIND: process
• LANGUAGE: Mermaid
• GENERATED FROM: static, TPS 2.5
• STATUS: hand-authored at TPS 0.1.0; superseded by TPX at its first build
• SOURCE SHA-256: 4be2e6c404af62401bd2e9e150494b524fe136aae72463f7c617a49bf7fc9b35

Rendered live from the source, which is the text equivalent and is shown under the drawing. The key to the shapes is in the panel.

Source (the text equivalent; Mermaid)

%% 03 Digest gate and recovery. process/Mermaid flow. Static, TPS 2.5.
%% One line per label: the wiki renderer clips a second line.
flowchart TD
  W[write requested] --> R[TPX rematches D-TFK, TPS 2.5.8]
  R -- match --> OK[write proceeds]
  R -- mismatch --> H[write halted, zone named]
  H --> D[/human declares RESTORE or FORK/]
  D -- RESTORE --> RS[kernel pages back to that revision]
  RS --> R2[digest re-verified]
  R2 -- match --> OK
  D -- FORK --> F[COPY-FORWARD under a new TFK]

  classDef task fill:#eaecf0,stroke:#a2a9b1,color:#202122
  classDef human fill:#eaf3ff,stroke:#36c,color:#202122
  classDef data fill:#fef6e7,stroke:#ac6600,color:#202122
  classDef bad fill:#fee7e6,stroke:#d33,color:#202122
  classDef good fill:#d5fdf4,stroke:#14866d,color:#202122
  class W,R,RS,R2,F task
  class D human
  class OK good
  class H bad

Text equivalent

Before every write TPX recomputes D(TFK) and matches it against the certificate (2.5.8). A match lets the write proceed. A mismatch halts the write and names the zone (2.5.5, 2.5.6); recovery is a human declaration: RESTORE returns the TFK pages to the revision whose content hash matches the chain and writes resume only after the digest matches; FORK copies forward under a newly declared TFK (2.5.7, 3.4).