diff --git a/devlog/_plan/260905_external_image_roundtrip/000_plan.md b/devlog/_plan/260905_external_image_roundtrip/000_plan.md
new file mode 100644
index 0000000000..8c3e09a673
--- /dev/null
+++ b/devlog/_plan/260905_external_image_roundtrip/000_plan.md
@@ -0,0 +1,68 @@
+# External-client image round trips
+
+## Loop specification
+
+- Class: C3 protocol compatibility repair; spec-satisfaction, no optimization race.
+- Trigger: external clients report missing screenshots through OpenAI routes.
+- Goal: preserve supported image bytes, URLs, ordering and detail across translation.
+- Non-goals: no new uploader, provider settings, auth changes, live-service restart,
+  release, image synthesis, or unrelated adapter refactor.
+- Verifier: standalone converter/parser/adapter body inspection, TypeScript, exact-head
+  GitHub CI. ALL local test suites are forbidden by the user, including focused suites.
+- Stop: reviewed two-layer stack merged bottom-up to dev with green CI and ancestry.
+- Memory: this unit and the session-bound goalplan/ledger.
+- Outcomes: DONE only with proof; external dependencies may be BLOCKED/NEEDS_HUMAN;
+  unsafe expansion is UNSAFE. No implementation-success claim from docs-only work.
+- Scope: this managed checkout, read-only Aside official docs, GitHub stack/CI/admin
+  merge. Maximum four concurrent agents; reassess after 90 minutes; no token cap set.
+- Escalation: reclaim a lane after two distinct failed agents; any delegated writes
+  must be planned with disjoint paths before B. No production credentials in artifacts.
+
+## Measured baseline and hypotheses
+
+H1: normal user images disappear in Responses serialization. Falsifier: compare the
+synthetic URL in final request JSON. REJECTED: direct Chat converter -> parseRequest ->
+canonical forward buildRequest preserves the input_image, as does openai-chat.
+H2: Chat ingress drops image metadata or tool-result images. Falsifier: compare role:user
+and role:tool with identical image_url parts. CONFIRMED: user detail is absent and tool
+output becomes just `Read this`. Source: src/chat/inbound.ts:80 and :284.
+H3: external route/native forwarding or Claude ingress drops otherwise preserved
+images. Independent read-only investigation pending; don't assume a token count alone
+identifies a serializer. Plain Claude image and tool-result paths have dedicated mapping.
+
+Baseline command: standalone `bun -e` importing chat/inbound, responses/parser,
+openai-responses, openai-chat and createTranslatorBudget. Exit 0; direct source imports
+observe the actual owners, no bun:test import and no network. User image retained in
+both wire formats; identical tool image absent from both. Original typecheck could not
+resolve bun-types in this fresh worktree; frozen-lockfile dependency install (scripts
+disabled) completed, with no manifest/lock edits. CI remains the test-suite authority.
+
+No-code options: do nothing leaves demonstrated loss; deletion/configuration cannot
+restore discarded payloads. Reuse userContentToBlocks and existing downstream image
+serialization. Do not add a generic image helper or patch correct Responses code.
+
+## Dependency-ordered roadmap
+
+1. wp0: docs-only roadmap and independent audit (this cycle).
+2. wp1 / 010: preserve Chat image detail and structured tool output; lower PR to dev.
+3. wp2 / 020: cross-protocol wire regressions and public contract; child PR to lower
+   branch, then CI/review/admin-merge bottom-up, retarget child and verify again.
+
+Existing placement is reused: src/chat/, tests/responses/, public reference/proxy-formats,
+structure/04_transports-and-sidecars.md. No new package, runtime module, or config.
+The user explicitly requested stacking; the upper layer consumes the corrected
+converter and protects the integrated contract independently of unit-level assertions.
+
+## Continuity
+
+Roadmap audit: independent gpt-6-astra high reviewer returned GO-WITH-FIXES,
+two medium findings. Both folded: exact no-suite typecheck/push commands and actual
+Claude converter export. Direct node tsc exits 0. Standalone reproduction at
+`.tmp/external-image-probe.ts` exits 1 before production edits with imageRetained=false
+and detailRetained=false. No local suite ran. Aside opened official Chat docs confirming
+image_url.url and nested auto/low/high detail; Anthropic tool-result docs confirm
+nested image content. No upload handler is necessary for data URLs.
+
+Roadmap initially recorded against freshly fetched origin/dev. Never claim the whole
+reported model-specific outage fixed merely because a converter fix lands. Preserve
+the negative result for ordinary user images in the final report.
diff --git a/devlog/_plan/260905_external_image_roundtrip/010_chat_image_parts.md b/devlog/_plan/260905_external_image_roundtrip/010_chat_image_parts.md
new file mode 100644
index 0000000000..64e5db9ff3
--- /dev/null
+++ b/devlog/_plan/260905_external_image_roundtrip/010_chat_image_parts.md
@@ -0,0 +1,55 @@
+# Chat image-part foundation
+
+Depends on wp0. One full PABCD cycle, one lower PR.
+
+## MODIFY src/chat/inbound.ts
+
+Keep imageUrlFromPart's current object/string URL support. In userContentToBlocks,
+extend the input_image push with detail from the nested image_url object, or the part
+for the already-supported string shorthand. Preserve only auto/low/high detail.
+
+```diff
+- blocks.push({ type: "input_image", image_url: imageUrl });
++ const detail = isRec(raw.image_url) ? raw.image_url.detail : raw.detail;
++ blocks.push({ type: "input_image", image_url: imageUrl,
++   ...(detail === "auto" || detail === "low" || detail === "high" ? { detail } : {}) });
+```
+
+For role:tool, reuse the existing content converter, retaining the original text-only
+string behavior when no valid image is present. Responses function_call_output accepts
+input_text/input_image, not input_video; don't newly forward video tool blocks.
+
+```diff
+- const output = typeof msg.content === "string" ? msg.content : contentToText(msg.content);
++ const blocks = userContentToBlocks(msg.content);
++ const output = blocks.some(part => part.type === "input_image")
++   ? blocks.filter(part => part.type === "input_text" || part.type === "input_image")
++   : contentToText(msg.content);
+```
+
+Keep output_text tool parts supported: extend the reusable converter's text recognition
+to output_text (already accepted by contentToText) so mixed arrays lose no old text.
+Field chain: nested Chat detail -> input_image.detail -> parser image.detail -> existing
+Chat image_url.detail; raw Responses preserves detail. No new type/enum/config.
+
+## MODIFY tests/responses/chat-completions-endpoint.test.ts
+
+Add converter-level cases beside the existing conversion tests:
+- user image: remote/data URL, nested detail, no detail, string shorthand;
+- tool image: function_call plus mixed text/image output retains exact order;
+- image-only tool output stays a nonempty array;
+- text-only string/array and invalid image keep existing text behavior;
+- mixed output_text/image preserves text; video does not enter function output.
+Use explicit expected objects, not converter-derived expectations. No removed assertions.
+
+## Acceptance and delivery
+
+Repeat the baseline standalone invocation: tool output must now contain input_image and
+both final wire bodies must contain the synthetic URL; user detail must survive. Run
+`node node_modules/typescript/bin/tsc --noEmit` (not a suite), add tests but execute
+them only in CI. Review source and tests, commit, `git push --no-verify origin
+codex/external-image-parts`, and open templated PR to dev. The user explicitly forbids
+local suites; the installed pre-push hook runs package.json prepush including the full
+suite, so that hook must be bypassed for this authorized push. No persistent hook
+configuration change. Existing large files
+are extended narrowly to avoid an unrelated split. No new exports or upload handler.
diff --git a/devlog/_plan/260905_external_image_roundtrip/020_wire_contract.md b/devlog/_plan/260905_external_image_roundtrip/020_wire_contract.md
new file mode 100644
index 0000000000..7baf039379
--- /dev/null
+++ b/devlog/_plan/260905_external_image_roundtrip/020_wire_contract.md
@@ -0,0 +1,60 @@
+# External wire contract and stack delivery
+
+Depends on wp1 and its corrected Chat converter. One full PABCD cycle.
+
+## MODIFY tests/responses/openai-responses-passthrough.test.ts
+
+Import real chatCompletionsToResponsesBody, anthropicToResponsesBody,
+parseRequest, and createOpenAIChatAdapter wrapped with the
+existing withTestTranslatorBudget. Add a table-driven regression for each ingress:
+Chat user image, Chat tool screenshot (depends on wp1), Claude user image, Claude
+tool_result image. Use data and HTTPS URL fixtures, two ordered images, and image-only
+tool output. Build each through public API-key Responses, canonical ChatGPT forward,
+and Chat adapter; assert exact image payloads in the actual serialized body, original
+input immutability, and tool call/result adjacency. Add orphan tool-result case using
+the existing repair path; don't modify production adapters unless evidence demands it.
+Do not claim these body tests prove upstream model OCR or live route selection.
+
+## MODIFY docs-site/src/content/docs/reference/proxy-formats.md
+
+After the Chat intro add:
+
+```diff
++ Image URLs and base64 data URLs use Chat `image_url` content parts. Translation
++ preserves supported `detail` values (`auto`, `low`, `high`). OpenCodex also accepts
++ image-bearing tool-result arrays as a compatibility extension: Responses routes
++ retain structured output, while Chat adapters send tool images in a following user
++ message because the upstream Chat tool role is text-only. Plain text results remain
++ strings. Native passthrough follows its upstream contract.
+```
+
+No locale currently contradicts this additive contract; inspect sibling translated
+sections before deciding whether an amendment is needed. Document no model entitlement.
+
+## MODIFY tests/responses/chat-completions-endpoint.test.ts
+
+Reuse mockDualWireUpstream (line 113) and dualWireConfig (line 2764), beside the
+existing Chat-to-Responses HTTP regression (line 2834). POST a user image with high
+detail and a paired tool screenshot to mock/grok-4.5; consume the stream and assert
+one captured /responses body with unchanged ordered image parts. This is real HTTP
+route proof in CI, not real-model OCR or canonical account authentication.
+
+## MODIFY structure/04_transports-and-sidecars.md
+
+Add one short paragraph beside the Chat inbound responsibility: its converter owns
+detail and tool-image preservation; adapters own target-specific image placement.
+Retain all existing transport/security/sidecar policy.
+
+## Acceptance / delivery
+
+Run `node node_modules/typescript/bin/tsc --noEmit`; public documentation build in CI
+or local build (not tests); focused
+regressions and full OS suites in GitHub CI only. A fresh independent patch audit
+checks each wire assertion and absence of secret/logging changes. Publish child branch
+codex/external-image-wire-contract against the open lower branch using `git push
+--no-verify` (same explicit no-local-suite override as 010). Record admin bypass
+authorization in both PR bodies; merge lower only when exact-head full CI is green,
+don't delete parent branch. Prefer merge commits to preserve stack ancestry; retarget
+the child to dev and refresh CI/review. If squash is used, restack and reverify its new
+HEAD before merge. Fetch origin/dev and prove both merge SHAs ancestors. Archive this
+unit only after the completed outcome is public. No restart/deployment is authorized.
diff --git a/docs-site/src/content/docs/reference/proxy-formats.md b/docs-site/src/content/docs/reference/proxy-formats.md
index 754d51a212..39251da8ba 100644
--- a/docs-site/src/content/docs/reference/proxy-formats.md
+++ b/docs-site/src/content/docs/reference/proxy-formats.md
@@ -197,6 +197,14 @@ non-empty `messages` array. It translates system, user, assistant, and tool mess
 Responses items; translates function tools, tool choice, images, reasoning effort, and supported
 response formats; runs the normal Responses routing pipeline; then translates the result back.
 
+Image URLs and base64 data URLs use Chat `image_url` content parts. Translation preserves
+supported `detail` values (`auto`, `low`, `high`). On translated routes, OpenCodex also accepts
+image-bearing tool-result arrays as a compatibility extension: Responses routes retain structured
+output, while the `openai-chat` adapter sends tool images in a following user message because Chat
+tool content is text-only. Other downstream adapters own provider-specific placement. Plain text
+results remain strings. Native passthrough follows its upstream contract; image support still depends
+on the selected model and provider configuration.
+
 Reasoning is part of that translation. `reasoning_effort` (or `reasoning.effort`) becomes
 internal `reasoning.effort`. Because the Responses parser hides thinking unless
 `reasoning.summary` is set and is not `none`, Chat Completions requests that ask for an
diff --git a/src/chat/inbound.ts b/src/chat/inbound.ts
index db3b41d12e..43024ca812 100644
--- a/src/chat/inbound.ts
+++ b/src/chat/inbound.ts
@@ -73,13 +73,18 @@ function userContentToBlocks(content: unknown): Rec[] {
       continue;
     }
     if (!isRec(raw)) continue;
-    if ((raw.type === "text" || raw.type === "input_text") && typeof raw.text === "string") {
+    if ((raw.type === "text" || raw.type === "input_text" || raw.type === "output_text") && typeof raw.text === "string") {
       blocks.push({ type: "input_text", text: raw.text });
       continue;
     }
     const imageUrl = imageUrlFromPart(raw);
     if (imageUrl) {
-      blocks.push({ type: "input_image", image_url: imageUrl });
+      const detail = isRec(raw.image_url) ? raw.image_url.detail : raw.detail;
+      blocks.push({
+        type: "input_image",
+        image_url: imageUrl,
+        ...(detail === "auto" || detail === "low" || detail === "high" ? { detail } : {}),
+      });
       continue;
     }
     const videoUrl = videoUrlFromPart(raw);
@@ -275,7 +280,10 @@ export function chatCompletionsToResponsesBody(raw: unknown): Rec {
           : typeof msg.tool_use_id === "string" ? msg.tool_use_id
           : "";
         if (!callId) throw new ChatCompletionsRequestError("tool messages require tool_call_id");
-        const output = typeof msg.content === "string" ? msg.content : contentToText(msg.content);
+        const blocks = userContentToBlocks(msg.content);
+        const output = blocks.some(part => part.type === "input_image")
+          ? blocks.filter(part => part.type === "input_text" || part.type === "input_image")
+          : contentToText(msg.content);
         input.push({ type: "function_call_output", call_id: callId, output });
         break;
       }
diff --git a/tests/responses/chat-completions-endpoint.test.ts b/tests/responses/chat-completions-endpoint.test.ts
index 7ca64ecdc6..4a4a5a5a12 100644
--- a/tests/responses/chat-completions-endpoint.test.ts
+++ b/tests/responses/chat-completions-endpoint.test.ts
@@ -238,6 +238,82 @@ test("chatCompletionsToResponsesBody maps messages/tools/system", () => {
   expect(input.some(i => i.type === "function_call_output" && i.call_id === "call_1")).toBe(true);
 });
 
+describe("chatCompletionsToResponsesBody image parts", () => {
+  test.each([
+    { part: { type: "image_url", image_url: "https://example.com/image.png" }, expected: { type: "input_image", image_url: "https://example.com/image.png" } },
+    { part: { type: "image_url", image_url: "https://example.com/image.png", detail: "low" }, expected: { type: "input_image", image_url: "https://example.com/image.png", detail: "low" } },
+    { part: { type: "image_url", image_url: { url: "https://example.com/image.png" } }, expected: { type: "input_image", image_url: "https://example.com/image.png" } },
+  ])("preserves user image shorthand and omitted detail: %j", ({ part, expected }) => {
+    const body = chatCompletionsToResponsesBody({ model: "mock/test-model", messages: [{ role: "user", content: [part] }] });
+    expect(body.input).toEqual([{ type: "message", role: "user", content: [expected] }]);
+  });
+
+  test.each(["auto", "low", "high"])("preserves user image detail %s", detail => {
+    const url = "https://example.com/screenshot.png";
+    const body = chatCompletionsToResponsesBody({
+      model: "mock/test-model",
+      messages: [{ role: "user", content: [{ type: "image_url", image_url: { url, detail } }] }],
+    });
+    expect(body.input).toEqual([{ type: "message", role: "user", content: [
+      { type: "input_image", image_url: url, detail },
+    ] }]);
+  });
+
+  test("retains ordered tool screenshots and legacy text without forwarding video", () => {
+    const url = "data:image/png;base64,aGVsbG8=";
+    const body = chatCompletionsToResponsesBody({
+      model: "mock/test-model",
+      messages: [
+        { role: "assistant", tool_calls: [{ id: "call_image", type: "function", function: { name: "screenshot", arguments: "{}" } }] },
+        { role: "tool", tool_call_id: "call_image", content: [
+          { type: "text", text: "before" },
+          { type: "image_url", image_url: { url, detail: "high" } },
+          { type: "output_text", text: "after" },
+          { type: "video_url", video_url: "https://example.com/video.mp4" },
+          { type: "image_url", image_url: "https://example.com/second.png", detail: "low" },
+        ] },
+      ],
+    });
+    expect(body.input).toEqual([
+      { type: "function_call", call_id: "call_image", name: "screenshot", arguments: "{}" },
+      { type: "function_call_output", call_id: "call_image", output: [
+        { type: "input_text", text: "before" },
+        { type: "input_image", image_url: url, detail: "high" },
+        { type: "input_text", text: "after" },
+        { type: "input_image", image_url: "https://example.com/second.png", detail: "low" },
+      ] },
+    ]);
+    expect(() => parseRequest(body)).not.toThrow();
+  });
+
+  test("keeps image-only tool results structured and ignores unsupported detail", () => {
+    const body = chatCompletionsToResponsesBody({
+      model: "mock/test-model",
+      messages: [{ role: "tool", tool_call_id: "call_image", content: [
+        { type: "image_url", image_url: { url: "https://example.com/first.png" } },
+        { type: "image_url", image_url: { url: "https://example.com/second.png", detail: "invalid" } },
+      ] }],
+    });
+    expect(body.input).toEqual([{ type: "function_call_output", call_id: "call_image", output: [
+      { type: "input_image", image_url: "https://example.com/first.png" },
+      { type: "input_image", image_url: "https://example.com/second.png" },
+    ] }]);
+  });
+
+  test.each([
+    { content: "plain", expected: "plain" },
+    { content: [{ type: "text", text: "one" }, { type: "output_text", text: "two" }], expected: "one\ntwo" },
+    { content: [{ type: "image_url", image_url: { url: "" } }, { type: "text", text: "kept" }], expected: "kept" },
+    { content: [], expected: "" },
+  ])("preserves image-free tool output as a string: %j", ({ content, expected }) => {
+    const body = chatCompletionsToResponsesBody({
+      model: "mock/test-model",
+      messages: [{ role: "tool", tool_call_id: "call_text", content }],
+    });
+    expect(body.input).toEqual([{ type: "function_call_output", call_id: "call_text", output: expected }]);
+  });
+});
+
 describe("chatCompletionsToResponsesBody service_tier", () => {
   test("preserves a caller-supplied service_tier", () => {
     const body = chatCompletionsToResponsesBody({