Why a process — a dev-loop phase, an MCP server — talks to the memory engine through a small stable client rather than reaching into engine internals, and why that client dependency is one-directional and gate-enforced. The seam concept was introduced by the AgentM HLD — V5 unbundling; this note explains the shape it took. For the function-by-function contract, see Process seam.

The V5 unbundling moved the phase loop (Setup · Plan · Work · Review · Release · Bugfix) out of agentm and into the companion crickets plugins, leaving agentm as the durable-state substrate and memory engine those phases run on. That split created a question it did not answer: how does a phase — now living in a different repo — read recall context or resolve where PLAN.md lives?

The tempting answer is "import harness_memory and call whatever you need." That couples every consumer to the engine's private shape: a phase would reach for an internal helper, the engine would refactor it, and the phase would break — across a repo boundary, where the breakage is hardest to see coming. The seam is the deliberate alternative. It is a single small client (scripts/process_seam.py) exposing exactly two operations a process actually needs:

• offer save here — "here's something I might save; tell me where it would go" (advisory only — it never saves).
• state path here — "where do this project's PLAN.md / progress.md / tracker.md live?"

(A third operation, recall here, was retired in R0.9 — it delegated to a V5-3 stub that always returned empty; no live crickets consumer called it.)

Every one of those composes only the engine's frozen public readers (the DC-7 surface: resolve_project, resolve_active_plan, active_plan_paths, is_available — harness_state_dir retired under agentm-vault plan 15). A consumer that needs something the frozen API lacks needs a separate engine change — it can't quietly widen the seam. The engine keeps the freedom to refactor everything behind that public surface; the process only ever sees the seam.

The seam imports the engine. The engine must never import the seam back.

This is not a style preference — it is what keeps the seam a seam. The whole point is a clean layering: memory is the lower, stable substrate; the process is the upper, swappable layer that depends on it. A back-edge — any memory-engine module importing process_seam — would invert that. It would turn a one-way client dependency into a cycle, and worse, it would let an engine change reach up into process concerns: the exact coupling the seam exists to prevent. Once the engine knows about its callers, "refactor freely behind the public surface" stops being true, and the V5 unbundling's clean substrate/plugin split quietly rots.

  process (crickets phases, V5-9 MCP server)
        │  imports
        ▼
  process_seam.py   ──imports──►  harness_memory (frozen public readers)
        ▲                              │
        └──────────  NEVER  ───────────┘
              (engine must not import the seam)

So the rule is stated plainly ([LC-4]): memory never imports the process. And because a rule that only lives in prose decays, it ships as an executable gate, not a guideline.

check-process-seam-import-direction.sh is the enforcement. It scans agentm's Python automation surfaces for any module that imports process_seam and fails on a hit. The reasoning that makes a simple scan sufficient: within agentm, the seam's only legitimate importer is its own test suite. The designed consumers — the crickets phases, the future MCP server — live outside this repo ([LC-5]). So any in-repo importer that isn't a test is, by construction, the engine reaching for the seam — a forbidden back-edge. The gate excludes the tests (they import by design) and carries an explicit, currently-empty SEAM_CONSUMERS allowlist, so the day a reviewed in-repo process-side consumer appears, the back-edge question gets answered in the open rather than by a silent gate edit. It rides the local battery (check-all.sh) and runs cross-OS via the auto-discovered unit-tests step, since its subprocess tests live in test_process_seam.py. See CI gates for the row.

A subtle pairing reinforces the layering: agentm defines and ships the seam, but its consumers adopt it crickets-side in a separate plan ([LC-5]). The producer and the consumers are deliberately on opposite sides of the repo boundary — the same boundary the one-way rule protects.

The seam is built so a memory-absent install still works. agentm must run on machines without a vault mounted — CI, a fresh device, a contributor who never set one up. If the seam hard-failed when memory was unavailable, every process that called it would wedge, and the optional memory engine would become a hard dependency through the back door.

So every function degrades rather than raising on the absent-memory path:

• offer_save_here returns [] when memory is absent or there's nothing to offer.
• state_path degrades to repo-local <project_root>/.harness/<file> ([LC-3]) — never None — so a vault-less repo still resolves its plan and progress files.

There is one deliberate exception to the degrade, and it is a safety property, not an oversight: when state_path finds a present-but-corrupt .harness/active-plan marker — dangling, or naming an unsafe slug — it lets the exception propagate (V5-10 Risk #7). Silently degrading there could mis-bind a worker to the wrong plan, which is worse than a loud failure. The distinction is the whole design in miniature: absent memory degrades quietly; corrupt state fails loudly.

The other half of the same philosophy is the read-only stance. The seam never writes — offer_save_here is advisory, returning candidates the caller hands to the existing /memory save path ([LC-2]). A read-only client that degrades gracefully is one a process can call from anywhere without first checking whether memory exists, and without any risk that calling it mutates the vault.

• Process seam — the function-by-function reference (signatures, degrade contracts, the python -m entrypoint).
• CI gates — the check-process-seam-import-direction gate enforcing the one-way edge.
• AgentM HLD — V5 unbundling — the decision that split the phase loop out and introduced the seam concept.
• Single-repo (vault-less) state mode — the broader "runs without a vault" stance the seam's graceful degrade participates in.