feat(runtime)!: action params are enforced by default, and the opt-in is gone (#3438)

ADR-0104 D2 landed warn-first behind OS_ACTION_PARAMS_STRICT_ENABLED. The
2026-07-30 addendum decided that window closes in 17.0 rather than 18.0, so
this executes it:

- actionParamsStrict() becomes laxActionParams(): enforcement is the default
  and OS_ALLOW_LAX_ACTION_PARAMS=1 is the only knob — spelled OS_ALLOW_* per
  PD #9 and ADR-0110 D6, which this change also removes the sole cited
  exception from. The opt-in name never reached `latest` (RC-only), so it is
  deleted outright rather than deprecated for a release.
- The escape-hatch path still warns once per action, so opting out tolerates
  the drift instead of hiding it again.
- Dogfood duals are inverted: the DEFAULT path is now what the gate proves,
  and the hatch — the branch nobody sets — is what gets a test so it cannot
  rot unnoticed.

Also corrects three docs the flip falsifies, plus two the earlier #3681 media
work had already left self-contradictory in the v17 notes (the section said
hard rejection arrives only via OS_DATA_VALUE_SHAPE_STRICT_ENABLED two
paragraphs before saying media enforces per verified deployment; the upgrade
checklist prescribed the env var as the way to get there, which would opt in
every value class including the ones with no migration behind them).

Verified: runtime 951, spec 7147, dogfood 425 (+3 skipped) all green; the D2
contract dogfood passes with the inverted duals; all ten spec artifact gates
pass. Swept examples and packages for callers posting param bags — the todo
MCP e2e invokes only param-less actions, showcase tests call handlers
directly.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016zgA8CQMJeJbFEjnbib1Uv

Author: claude

.changeset/adr-0104-d2-strict-by-default.md

@@ -0,0 +1,53 @@
+---
+"@objectstack/runtime": major
+---
+
+feat(runtime)!: action params are enforced by default, and the opt-in is gone (#3438, ADR-0104 D2)
+
+A request bag that violates an action's declared `params[]` — a missing
+`required` param, a value outside its `options`, a scalar where `multiple`
+declares an array, a non-id where a `reference` declares one, or a key the
+action never declared — is now **rejected before the handler runs**:
+`400 VALIDATION_FAILED` on REST, a thrown error on MCP. It used to be logged
+and passed through.
+
+```diff
+- OS_ACTION_PARAMS_STRICT_ENABLED=1   # removed — enforcement is the default
++ OS_ALLOW_LAX_ACTION_PARAMS=1        # escape hatch: warn and pass, as before
+```
+
+**What breaks.** Only calls that were *already* wrong. The declaration was a
+complete contract that informed nothing but the client dialog, so a bag the
+server accepted could still have been silently ignored by the handler — which
+is exactly how a correctly-intended `reference: 'sys_user'` degraded into a
+paste-a-UUID box (#3405) with a success envelope on top. Those calls now fail
+loudly instead of quietly. Actions declaring no `params` are untouched, and the
+dispatcher's own `recordId` / `objectName` are allowlisted
+(`ACTION_PARAM_BUILTIN_KEYS`), so the keys dispatch itself merges in were never
+candidates for the unknown-key error.
+
+**Fixing a rejection** takes one edit at the call site: the message names the
+offending param and the declared list. If an integration you cannot reach in
+time is affected, set `OS_ALLOW_LAX_ACTION_PARAMS=1` to restore the old
+pass-through — the violation still logs once per action, so the drift stays
+visible rather than becoming invisible again.
+
+**Why 17.0 rather than a warn window in 17 and the flip in 18.** R3 asked for
+warn-then-error, and ADR-0104's 2026-07-30 addendum declined it on the merits
+rather than postponing. What a violation strands is a **caller**, not data: the
+rejection reaches a developer or an agent who can fix it in one edit, no stored
+row is made unwritable, and the escape hatch makes it reversible in a restart.
+Deferring that by a major would have charged every deployment a second upgrade
+ceremony — 16→17 is already a substantial, tested migration — to postpone a
+break that costs one edited call. v17 already carries harsher zero-window
+flips (`allowExport` unset now means denied; an undeclared action handler 404s
+with no opt-out at all), so holding the milder change to a stricter standard
+would have been inconsistent rather than cautious.
+
+For AI and MCP callers specifically — the population D2 was built for — a 400
+is corrective feedback consumed in-loop, while a server-side warning is
+feedback nobody ever reads.
+
+D1's value-shape half went the opposite way for the opposite reason: it rejects
+on the basis of **stored data**, which an author cannot edit their way out of,
+so it stays gated per deployment on that deployment's own migration evidence.

.changeset/adr-0104-d2-typed-action-handlers.md

@@ -25,12 +25,13 @@ read an untyped bag. D2 makes the declaration enforced and typed.
   required presence, per-type value shape, and unknown keys (the dispatcher's
   own `recordId` / `objectName` are allowlisted).
 
-**Warn-first rollout (ADR-0104 R3).** A violation is **logged and passes** by
-default — params that were silently wrong before keep working while the drift
-becomes visible. Set `OS_ACTION_PARAMS_STRICT_ENABLED=1` to reject with a
-`400 VALIDATION` (REST) / an error (MCP). Actions that declare no `params` are
-untouched (nothing to validate against). The flip to strict-by-default rides a
-later minor once telemetry is quiet.
+**Enforced by default.** A violation is rejected with a `400 VALIDATION_FAILED`
+(REST) / an error (MCP) before the handler runs. Actions that declare no
+`params` are untouched — there is nothing to validate against. This landed
+warn-first behind an `OS_ACTION_PARAMS_STRICT_ENABLED` opt-in during the 17.0
+RC line; that variable does **not** exist in 17.0 — see the companion entry
+"action params are enforced by default, and the opt-in is gone" for the
+reasoning and the `OS_ALLOW_LAX_ACTION_PARAMS` escape hatch.
 
 Not included: file/image params becoming `sys_file` references — that depends
 on file-as-reference (ADR-0104 D3). Per-name static typing of `ctx.params` from

content/docs/releases/v17.mdx

@@ -216,6 +216,47 @@ need no changes, other than gaining enforcement of the `requiredPermissions`
 they already declared. Callers that hard-coded a `target` in an action URL
 switch to the action's `name`.
 
+### An action's declared params are enforced at dispatch (ADR-0104 D2, #3438)
+
+An action's `params[]` (`required`, `options`, `multiple`, `reference`) was a
+complete contract that informed **only the client dialog**. The server passed
+`reqBody.params` to the handler unvalidated on both the REST and MCP paths, so
+a wrong bag could return a success envelope while the handler quietly ignored
+it — the #3405 shape, one layer out. It is now checked before the handler runs;
+a violation is `400 VALIDATION_FAILED` (REST) or a thrown error (MCP).
+
+| Violation | Example |
+|---|---|
+| missing `required` param | declared `p_text` absent from the bag |
+| value outside `options` | `p_priority: 'NOT_AN_OPTION'` |
+| `multiple` shape | a bare string where an array is declared |
+| `reference` shape | a non-id where `reference: 'sys_user'` is declared |
+| undeclared key | `bogus: 123` |
+
+```diff
+- OS_ACTION_PARAMS_STRICT_ENABLED=1   # removed — enforcement is the default
++ OS_ALLOW_LAX_ACTION_PARAMS=1        # escape hatch: warn and pass, as before
+```
+
+**Only already-wrong calls break**, and each rejection names the offending param
+and the declared list, so the fix is one edit at the call site. Actions
+declaring no `params` are untouched — there is nothing to validate against —
+and the dispatcher's own `recordId` / `objectName` are allowlisted, so keys
+dispatch merges in are never unknown-key errors. If an integration you cannot
+reach in time is affected, `OS_ALLOW_LAX_ACTION_PARAMS=1` restores the old
+pass-through in one restart; the violation still logs once per action, so the
+drift stays visible rather than becoming invisible again.
+
+The RC line carried this warn-first behind an `OS_ACTION_PARAMS_STRICT_ENABLED`
+opt-in. **That variable does not exist in 17.0.** The window was closed on
+purpose rather than deferred to 18.0: what a violation strands is a *caller*,
+not data — no stored row becomes unwritable, the party who sees the error is
+the party who can fix it, and the hatch makes it reversible. Deferring would
+have charged every deployment a second upgrade ceremony to postpone a break
+that costs one edited call. The value-shape half of the same ADR went the other
+way for the opposite reason: it rejects on the basis of data already at rest,
+so it stays gated per deployment (see *Files become platform records* below).
+
 ### A flow run with no trigger user may not touch data (#3760)
 
 An effective `runAs: 'user'` run that resolved **no trigger user** used to
@@ -893,10 +934,10 @@ For media fields specifically:
   toward an explicit `url` field, so "managed file" and "external link" stop
   being the same declaration).
 
-**Value-shape checking is warn-first.** A not-yet-backfilled row still writes and
-the author gets a warning naming the field. Hard rejection arrives only when a
-deployment opts into `OS_DATA_VALUE_SHAPE_STRICT_ENABLED` — which it should do
-*after* running the backfill and confirming reconciliation:
+**Value-shape checking follows your own migration, not the version number.** A
+not-yet-backfilled row still writes, and the author gets a warning naming the
+field. Media fields start *rejecting* malformed values only once **this
+deployment** has run the migration and passed its self-check:
 
 ```bash
 os migrate files-to-references           # dry run: reports, writes nothing
@@ -906,9 +947,18 @@ os migrate files-to-references --apply   # converts, verifies, records the flag
 The run backfills legacy file-field values (inline metadata blobs, own-resolver
 URLs, `data:` URIs) into owned `sys_file` references and reconciles the ownership
 ledger against what records actually hold. The **deployment-level flag it
-records** — never the platform version — is what may later authorise
-irreversible behaviour, and media value shapes enforce only once *this*
-deployment has verified its own migration.
+records** — never the platform version — is what authorises both strict media
+value shapes and, later, irreversible file collection. Upgrading changes
+neither; running the migration does.
+
+Two knobs sit either side of that flag. `OS_ALLOW_LAX_MEDIA_VALUES=1` returns a
+verified deployment to warnings, for an operator who hits an unforeseen
+rejection and needs writes flowing while they diagnose. `OS_DATA_VALUE_SHAPE_STRICT_ENABLED=1`
+goes the other way and opts *every* value class into strict immediately —
+including the reference (`lookup`/`user`/…) and structured-JSON
+(`location`/`address`/…) types, whose own per-deployment gate is still being
+built (#3438). Those stay warn-only by default until it lands, because unlike
+media they have no migration standing behind them yet.
 
 ### Approvals: dynamic approver routing (#3447)
 
@@ -1195,9 +1245,16 @@ objectui commits on top of the pin 16.1.0 shipped.
 - **Auth:** plan for the better-auth 1.7 account-identity backfill — check the
   boot log for federated accounts whose IdP is no longer registered, and stamp or
   remove those rows.
+- **Actions:** check any programmatic caller that posts `params` — a bag the
+  server used to accept silently now 400s if it misses a `required` param,
+  breaks `options`/`multiple`/`reference`, or carries an undeclared key. The
+  error names the param and the declared list. `OS_ALLOW_LAX_ACTION_PARAMS=1`
+  buys time for an integration you cannot reach today.
 - **Files:** run `os migrate files-to-references` (dry run first, then
-  `--apply`), reconcile, and only then set
-  `OS_DATA_VALUE_SHAPE_STRICT_ENABLED`.
+  `--apply`) and reconcile — passing its self-check is what turns strict media
+  value shapes on for this deployment. Do **not** reach for
+  `OS_DATA_VALUE_SHAPE_STRICT_ENABLED` to get there: it opts every value class
+  in at once, including ones with no migration behind them.
 - **Datasources:** verify every declared datasource connects in every
   environment — a bound datasource that cannot connect now fails the boot
   instead of failing every later query.

docs/adr/0104-field-runtime-value-shape-contract.md

@@ -414,7 +414,10 @@ rejects a targetless inline lookup param) — a build failure the AI must fix, n
 a runtime warning it never sees. The runtime **warn-first** posture (D1's
 `OS_DATA_VALUE_SHAPE_STRICT_ENABLED`, D2's `OS_ACTION_PARAMS_STRICT_ENABLED`)
 exists only to protect **already-deployed data** from stranding — it is not the
-authoring gate.
+authoring gate. *(D2's variable no longer exists: the 2026-07-30 addendum flips
+that half strict-by-default in 17.0, leaving only the `OS_ALLOW_LAX_ACTION_PARAMS`
+opt-out. The sentence's own logic is why — action params strand no deployed
+data, so the posture it justifies never applied to them.)*
 
 Therefore the target end-state is **two enforcement points, each with one job**:
 

docs/adr/0110-action-identity-and-declaration-admission.md

@@ -301,7 +301,7 @@ agent can act on.
 
 ### D6 — Security-gate strictness is opt-out, never opt-in
 
-`OS_ACTION_PARAMS_STRICT_ENABLED` (opt-**in** strict) is an acceptable
+`OS_ACTION_PARAMS_STRICT_ENABLED` (opt-**in** strict) was an acceptable
 shape for a *param-contract* ratchet (DX concern, warn-first). It is not an
 acceptable shape for an *authorization* gate: an enforcement that ships off
 for everyone who never read the release notes is not enforcement. A flag
@@ -310,6 +310,12 @@ where a security escape hatch is warranted at all; `OS_*_STRICT_ENABLED`
 (opt in to enforcement) is reserved for non-security contracts. Existing
 flags are not renamed by this ADR; new ones conform.
 
+*(Update, 2026-07-30: the one flag this section cited as tolerable no longer
+exists. ADR-0104's addendum flipped the param contract strict-by-default in
+17.0 and replaced the opt-in with the opt-out `OS_ALLOW_LAX_ACTION_PARAMS`
+(#3438), which the RC-only lifetime of the old name made free. The rule is
+unchanged; it simply has no remaining exception to point at.)*
+
 **The strongest form of this rule is no flag at all.** D3 originally carried
 an `OS_ALLOW_UNDECLARED_ACTIONS` opt-out — correctly *spelled* under this
 ruling, and still wrong, because what it opted out of was the gate itself

packages/qa/dogfood/test/action-params-contract.dogfood.test.ts

@@ -7,10 +7,17 @@
 // lookup `p_account`. Its body echoes the received param keys. We drive the
 // real `/actions/:object/:action` route to prove the declared contract is
 // enforced BEFORE the body runs:
-//   - warn-first (default): a malformed bag still passes (legacy callers keep
-//     working; the drift is logged, not fatal).
-//   - strict (OS_ACTION_PARAMS_STRICT_ENABLED=1): the same bag is rejected 400
+//   - default (strict since 17.0, #3438): a malformed bag is rejected 400
 //     before the handler runs; a conformant bag passes.
+//   - escape hatch (OS_ALLOW_LAX_ACTION_PARAMS=1): the same malformed bag is
+//     accepted again, for the operator who must keep an integration
+//     dispatching while they fix its caller.
+//
+// The duals are this way round on purpose. Under warn-first the strict path was
+// the one nobody reached without setting a variable; now the DEFAULT path is
+// what every caller hits, so it is what the gate must prove — and the hatch,
+// which is the branch nobody sets, is exactly the kind of thing that rots
+// unnoticed unless a test drives it.
 
 import { describe, it, expect, beforeAll, afterAll } from 'vitest';
 import showcaseStack from '@objectstack/example-showcase';
@@ -28,7 +35,7 @@ describe('dogfood: action param contract enforced at dispatch (ADR-0104 D2)', ()
   }, 60_000);
 
   afterAll(async () => {
-    delete process.env.OS_ACTION_PARAMS_STRICT_ENABLED;
+    delete process.env.OS_ALLOW_LAX_ACTION_PARAMS;
     await stack?.stop();
   });
 
@@ -37,33 +44,29 @@ describe('dogfood: action param contract enforced at dispatch (ADR-0104 D2)', ()
   const badBag = { p_priority: 'NOT_AN_OPTION', bogus: 123 };
   const goodBag = { p_text: 'Hello', p_priority: 'high' };
 
-  it('warn-first (default): a malformed param bag still passes and the body runs', async () => {
-    delete process.env.OS_ACTION_PARAMS_STRICT_ENABLED;
+  it('default: a malformed param bag is rejected 400 before the handler runs', async () => {
+    delete process.env.OS_ALLOW_LAX_ACTION_PARAMS;
     const res = await stack.apiAs(token, 'POST', ACTION_PATH, { params: badBag });
-    expect(res.status, `expected pass-through, got ${res.status}: ${await res.clone().text()}`).toBeLessThan(300);
+    expect(res.status).toBe(400);
+    const text = await res.text();
+    expect(text).toMatch(/p_text/);       // required
+    expect(text).toMatch(/p_priority/);   // bad option
+    expect(text).toMatch(/bogus/);        // unknown key
   });
 
-  it('strict: the same malformed bag is rejected 400 before the handler runs', async () => {
-    process.env.OS_ACTION_PARAMS_STRICT_ENABLED = '1';
-    try {
-      const res = await stack.apiAs(token, 'POST', ACTION_PATH, { params: badBag });
-      expect(res.status).toBe(400);
-      const text = await res.text();
-      expect(text).toMatch(/p_text/);       // required
-      expect(text).toMatch(/p_priority/);   // bad option
-      expect(text).toMatch(/bogus/);        // unknown key
-    } finally {
-      delete process.env.OS_ACTION_PARAMS_STRICT_ENABLED;
-    }
+  it('default: a conformant bag passes (dispatcher built-in keys are allowlisted)', async () => {
+    delete process.env.OS_ALLOW_LAX_ACTION_PARAMS;
+    const res = await stack.apiAs(token, 'POST', ACTION_PATH, { params: goodBag });
+    expect(res.status, `expected pass, got ${res.status}: ${await res.clone().text()}`).toBeLessThan(300);
   });
 
-  it('strict: a conformant bag passes (dispatcher built-in keys are allowlisted)', async () => {
-    process.env.OS_ACTION_PARAMS_STRICT_ENABLED = '1';
+  it('escape hatch: OS_ALLOW_LAX_ACTION_PARAMS=1 accepts the malformed bag again', async () => {
+    process.env.OS_ALLOW_LAX_ACTION_PARAMS = '1';
     try {
-      const res = await stack.apiAs(token, 'POST', ACTION_PATH, { params: goodBag });
-      expect(res.status, `expected pass, got ${res.status}: ${await res.clone().text()}`).toBeLessThan(300);
+      const res = await stack.apiAs(token, 'POST', ACTION_PATH, { params: badBag });
+      expect(res.status, `expected pass-through, got ${res.status}: ${await res.clone().text()}`).toBeLessThan(300);
     } finally {
-      delete process.env.OS_ACTION_PARAMS_STRICT_ENABLED;
+      delete process.env.OS_ALLOW_LAX_ACTION_PARAMS;
     }
   });
 });