diff --git a/CHANGELOG.md b/CHANGELOG.md
index f498fd9..dbbbff2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ The project follows Semantic Versioning after the first release.
 
 ### Changed
 
+- Contextual Orchestrator edit-proposal requests now use `mode: "auto"`, leaving model/provider choice, workflow depth, verification, fallback, and known-price optimization to the orchestration plane instead of fixing the consumer to one model call.
 - Hourly development now routes an open same-repository pull request into an
   RCA-driven exact-head remediation session, verifies candidate actions against
   live review and Check evidence, publishes only a normal fast-forward repair
diff --git a/docs/adr/0008-adaptive-contextual-orchestrator-default.md b/docs/adr/0008-adaptive-contextual-orchestrator-default.md
new file mode 100644
index 0000000..ba625f8
--- /dev/null
+++ b/docs/adr/0008-adaptive-contextual-orchestrator-default.md
@@ -0,0 +1,26 @@
+# ADR-0008: Adaptive contextual-orchestrator mode is the proposal default
+
+- Status: Accepted
+- Date: 2026-08-16
+
+## Context
+
+DiagramWeave's adapter sent an OpenAI-compatible request without an explicit orchestration policy. The gateway currently defaults an omitted mode to adaptive behavior, but the consumer contract did not make that requirement reviewable or regression-safe. A consumer-selected single-model route would also prevent the orchestration plane from allocating additional test-time compute when a difficult proposal requires verification.
+
+## Decision
+
+Every edit-proposal request includes `mode: "auto"`.
+
+The orchestration plane owns model and provider selection, workflow depth, verification, fallback, and known-price optimization. Quality sufficiency is the first constraint; cost is minimized among execution paths that satisfy it. Unknown price metadata is not interpreted as zero cost.
+
+DiagramWeave continues to own the source-first prompt, revision binding, strict JSON extraction, scope validation, and Core proposal validation. Explicit route or conduct modes are reserved for controlled ablation or a documented operational override and are not adapter defaults.
+
+## Consequences
+
+Simple proposals may still use one worker when the adaptive policy finds that sufficient. Harder proposals may use deeper orchestration without changing the DiagramWeave API. The adapter remains provider-neutral and sends no tool authority.
+
+## References
+
+Omidvar, H., & Akhlaghi, V. (2026). *A communication-theoretic framework for LLM agents: Cost-aware adaptive reliability* [Preprint]. arXiv. https://doi.org/10.48550/arXiv.2605.09121
+
+Tang, Y., Cetin, E., Xu, J., Sun, Q., Nielsen, S., Richard, V., Goda, H., Tymchenko, I., Nguyen, N., Lee, H., Ashiga, M., Kotyan, S., Kuroki, S., & Clanuwat, T. (2026). *Sakana Fugu technical report* [Technical report]. arXiv. https://doi.org/10.48550/arXiv.2606.21228
diff --git a/packages/contextual-orchestrator/src/client.js b/packages/contextual-orchestrator/src/client.js
index e5aad75..6da47f8 100644
--- a/packages/contextual-orchestrator/src/client.js
+++ b/packages/contextual-orchestrator/src/client.js
@@ -383,6 +383,7 @@ export function createContextualOrchestratorClient(options) {
           headers,
           body: JSON.stringify({
             model: normalized.model,
+            mode: 'auto',
             messages,
             temperature: 0,
             stream: false,
diff --git a/packages/contextual-orchestrator/test/client.test.js b/packages/contextual-orchestrator/test/client.test.js
index ffd0d60..7eca67c 100644
--- a/packages/contextual-orchestrator/test/client.test.js
+++ b/packages/contextual-orchestrator/test/client.test.js
@@ -201,6 +201,7 @@ test('client sends a bounded OpenAI-compatible request and validates the proposa
   assert.equal(observedOptions.headers['content-type'], 'application/json');
   assert.equal(observedOptions.headers.authorization, 'Bearer operator_secret');
   assert.equal(body.model, 'contextual-orchestrator');
+  assert.equal(body.mode, 'auto');
   assert.equal(body.temperature, 0);
   assert.equal(body.stream, false);
   assert.equal(body.messages.length, 2);