diff --git a/.changeset/agent-launch-reasoning-transport.md b/.changeset/agent-launch-reasoning-transport.md
new file mode 100644
index 000000000..95bdf4b50
--- /dev/null
+++ b/.changeset/agent-launch-reasoning-transport.md
@@ -0,0 +1,5 @@
+---
+type: Added
+pr: 3474
+---
+**Agent launch model resolution now transports reasoning effort** — `resolve-model` JSON output includes supported runtime `reasoning_effort`, and runtime adapter guidance passes it to child-agent launches only when supported.
diff --git a/docs/CLI-TOOLS.md b/docs/CLI-TOOLS.md
index 505b5807d..c2ac438ba 100644
--- a/docs/CLI-TOOLS.md
+++ b/docs/CLI-TOOLS.md
@@ -207,7 +207,9 @@ node gsd-tools.cjs config-set-model-profile <profile>
 ```bash
 # Get model for agent based on current profile
 node gsd-tools.cjs resolve-model <agent-name>
-# Returns: opus | sonnet | haiku | inherit
+# Raw output returns the selected model ID/tier.
+# JSON output also includes profile and, when the active runtime supports it,
+# reasoning_effort.
 ```
 
 Agent names: `gsd-planner`, `gsd-executor`, `gsd-phase-researcher`, `gsd-project-researcher`, `gsd-research-synthesizer`, `gsd-verifier`, `gsd-plan-checker`, `gsd-integration-checker`, `gsd-roadmapper`, `gsd-debugger`, `gsd-codebase-mapper`, `gsd-nyquist-auditor`
diff --git a/docs/CONFIGURATION.md b/docs/CONFIGURATION.md
index a9354c53a..3480733af 100644
--- a/docs/CONFIGURATION.md
+++ b/docs/CONFIGURATION.md
@@ -980,6 +980,8 @@ The intent is the same as the Claude profile tiers -- use a stronger model for p
 
 When `runtime` is set, profile tiers (`opus`/`sonnet`/`haiku`) resolve to runtime-native model IDs instead of Claude aliases. This lets a single shared `.planning/config.json` work cleanly across Claude and Codex.
 
+`resolve-model` JSON output includes `reasoning_effort` when it is defined by the same runtime tier that selected the model. Runtime adapters may pass that value to child-agent launch calls that support it; runtimes without explicit support omit it.
+
 **Built-in tier maps:**
 
 | Runtime | `opus` | `sonnet` | `haiku` | reasoning_effort |
diff --git a/sdk/src/query/QUERY-HANDLERS.md b/sdk/src/query/QUERY-HANDLERS.md
index b6189e3c6..1d2437ef8 100644
--- a/sdk/src/query/QUERY-HANDLERS.md
+++ b/sdk/src/query/QUERY-HANDLERS.md
@@ -155,7 +155,7 @@ From `read-only-parity.integration.test.ts` (full `toEqual` on this repo):
 
 | SDK dispatch (canonical) | Notes |
 | ------------------------ | ----- |
-| `resolve-model` | Args e.g. `gsd-planner`. |
+| `resolve-model` | Args e.g. `gsd-planner`; returns `reasoning_effort` when the selected runtime tier defines one. |
 | `phase-plan-index` | Phase number arg. |
 | `roadmap.get-phase` | Phase number arg. |
 | `list.todos` | No args. |