Implement ADR-0007

docs/adr/0006-separate-output-cache-and-debug-state.md

@@ -1,6 +1,6 @@
 # ADR-0006: Separate output, cache, and debug state
 
-**Status:** Accepted
+**Status:** Superseded by [ADR-0007](0007-separate-checkpoint-recording-from-reuse.md)
 **Date:** 2026-07-17
 
 ## Context

docs/adr/0007-separate-checkpoint-recording-from-reuse.md

@@ -0,0 +1,50 @@
+# ADR-0007: Separate checkpoint recording from reuse
+
+**Status:** Accepted
+**Date:** 2026-07-19
+
+## Context
+
+ADR-0006 made checkpoint I/O conditional on an explicit `--resume` invocation.
+That policy requires an operator to anticipate the need for recovery before a
+run begins. A failed ordinary run cannot reuse completed work because it did not
+record checkpoints.
+
+Recording reconstructible state and authorizing reuse are separate operational
+decisions. Recording consumes storage and retains sensitive derived application
+data, while reuse may change which module operations execute during a run.
+
+## Decision
+
+ADR-0006's separation of output, cache, and debug surfaces remains in effect;
+this decision supersedes only its checkpoint invocation policy.
+
+Checkpoint recording is controlled by an explicit persistent Boolean
+configuration setting and remains disabled by default. When recording is
+enabled, every run records checkpoint transitions and reusable approved stage
+results.
+
+Checkpoint loading remains an invocation policy. Only a run with `--resume`
+loads and reuses compatible completed work. A recording-enabled run without
+`--resume` executes every stage normally and never loads checkpoints. A resume
+request while recording is disabled is rejected.
+
+The existing checkpoint identities, compatibility rules, payload format,
+filesystem root behavior, and pipeline collaborator contracts remain unchanged.
+
+## Alternatives considered
+
+- Continue coupling reads and writes to `--resume`. This is safe by default but
+  prevents recovery unless resume was anticipated on the earlier run.
+- Always record checkpoints. This maximizes recovery but creates potentially
+  sensitive state without explicit operator consent.
+- Add a multi-value recording policy. This preserves the old behavior as an
+  option but adds configuration complexity without a current need.
+
+## Consequences
+
+Operators can opt into recovery-ready runs while keeping checkpoint reuse
+explicit. Enabled successful, rejected, and failed runs may all leave sensitive
+checkpoint state, so operators remain responsible for access and retention.
+Disabled configurations perform no checkpoint I/O, and `--resume` requires the
+operator to enable recording first.