# Deterministic \`editToolCall\` JSON parse failure on \`cursor-agent\` when Anthropic tool\_use is served from Bedrock (Vertex path succeeds identically) **URL:** \ **Category:** Bug Reports\ **Tags:** cli, anthropic\ **Created:** [July 6, 2026, 3:00pm UTC](https://forum.cursor.com/t/deterministic-edittoolcall-json-parse-failure-on-cursor-agent-when-anthropic-tool-use-is-served-from-bedrock-vertex-path-succeeds-identically/164927 "2026-07-06T15:00:23Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![dmitry\_afk](https://avatars.discourse-cdn.com/v4/letter/d/f475e1/32.png) [@dmitry\_afk](https://forum.cursor.com/u/dmitry_afk)\ **Post date:** [July 6, 2026, 3:00pm UTC](https://forum.cursor.com/t/deterministic-edittoolcall-json-parse-failure-on-cursor-agent-when-anthropic-tool-use-is-served-from-bedrock-vertex-path-succeeds-identically/164927/1 "2026-07-06T15:00:23Z")
### Where does the bug appear (feature/product)? Cursor CLI ### Describe the Bug Every `edit_file` tool call is unparseable (position 125, missing comma between `path` and `contents`) when the Anthropic model instance is served from AWS Bedrock; identical calls succeed 100 % when routing lands on Google Vertex. - **Product:** Cursor Agent CLI, `2026.05.28-a70ca7c` (running under `--print --output-format stream-json --model claude-opus-4-7`). - **Deployment:** headless, non-interactive, one CLI invocation per microservice. - **Model alias requested:** `claude-opus-4-7` - **Model as reported by CLI on `system` init event:** `Opus 4.7 (Thinking) 1M Extra High` - **Runner OS:** RHEL 8 host, container built from `bitnami/openjdk:17-debian-12` (JVM host launches `cursor-agent`). - **Network:** corporate network with HTTPS\_PROXY to `api2.cursor.sh`; no proxy transformation on the tool call payloads (proxy is TLS pass-through). - **Approx. workload per invocation:** 30-45 minute session, 150-250 tool calls, including 30-60 `edit_file` calls with 20-90 KB `contents`. Every `edit_file` tool call in an affected session fails with the same shape: ```auto JSON.parse error: Expected ',' or '}' after property in object at position 125 ``` The byte 125 sits immediately after the `path` field value in the tool\_use arguments, i.e. the model appears to have emitted: ```auto {"path":"/tmp/.../output/ApiProfile.md""contents": … ^ missing comma ``` The CLI retries via its checkpoint mechanism (rewind to last valid state and re-emit). Because the checkpoint restores the same model state, the same malformed argument is re-emitted and the retry hits the same parse error at the same byte position. After several attempts the CLI aborts with `resource_exhausted` and the process exits non-zero. ## What we can rule out - **Not content-driven.** The identical `ApiProfile.md` content that fails in one session was verified re-writable in a fresh cursor-agent session on a different network path. - **Not path-length-driven.** The absolute path (~120-160 chars) writes cleanly in isolated reproduction with the same tool schema on newer CLI builds. - **Not CLI-version-driven.** The 2026.05.28 CLI ships work when routing lands on Vertex, so the binary itself is capable of parsing valid tool\_use. - **Not model-alias-driven.** Same alias (`claude-opus-4-7`) succeeds in the Vertex-routed sessions. - **Not prompt-driven.** Same prompt template, same repo checkout, same cursor-agent args between failing and succeeding sessions. ## What we CAN correlate — with hard numbers We enumerated the Anthropic `tool_use.id` prefix (`toolu_bdrk_` vs `toolu_vrtx_`) across 6 sessions in the same pipeline for the same microservice.. 100% correlation: `toolu_bdrk_` sessions parse-fail every attempt; `toolu_vrtx_` sessions parse-clean every attempt. No mixed-prefix session was observed — routing is stable per invocation. ### Steps to Reproduce - Reproduction depends on routing choice, which we do not control from the CLI. We have not been able to reproduce on a fresh account (routing there landed on Vertex). - On the affected account, submitting a `edit_file` with any large `contents` (30+ KB) reliably hits the failure while the account is being routed to Bedrock. ### Expected Behavior edit tool call succeeds and not fails on json parse. ### Operating System Linux ### Version Information - **Product:** Cursor Agent CLI, `2026.05.28-a70ca7c` (running under `--print --output-format stream-json --model claude-opus-4-7`). - **Deployment:** headless, non-interactive, one CLI invocation per microservice. ### For AI issues: which model did you use? - **Model alias requested:** `claude-opus-4-7` - **Model as reported by CLI on `system` init event:** `Opus 4.7 (Thinking) 1M Extra High` ### Does this stop you from using Cursor Sometimes - I can sometimes use Cursor ---
**Author:** ![Colin](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/colin/32/90452_2.png) [@Colin](https://forum.cursor.com/u/Colin)\ **Post date:** [July 6, 2026, 4:18pm UTC](https://forum.cursor.com/t/deterministic-edittoolcall-json-parse-failure-on-cursor-agent-when-anthropic-tool-use-is-served-from-bedrock-vertex-path-succeeds-identically/164927/5 "2026-07-06T16:18:46Z")
Hey @dmitry_afk! Thanks for the report. Could you collect [Request IDs](https://cursor.com/help/troubleshooting/reporting-bugs#what-is-a-request-id) – one when the routing goes to Bedrock (where it fails) and one when the routing goes to Vertex, and share them here? You can collect these from the JSON response: ```auto { "type":"result", "subtype":"success", "duration_ms":3425, "duration_api_ms":3425, "is_error":false, "result":"Hi! I received your message but \"test\" is a bit ambiguous. What would you like me to help you with?", "session_id":"20073db4-dd25-4c4f-b67e-6c4fb818631f", "request_id":"5a71cce4-6f36-4b56-841d-e66f35e54d78", <---- "usage":{ "inputTokens":6, "outputTokens":36, "cacheReadTokens":0, "cacheWriteTokens":35829 } ``` ---
**Author:** ![dmitry\_afk](https://avatars.discourse-cdn.com/v4/letter/d/f475e1/32.png) [@dmitry\_afk](https://forum.cursor.com/u/dmitry_afk)\ **Post date:** [July 7, 2026, 6:20am UTC](https://forum.cursor.com/t/deterministic-edittoolcall-json-parse-failure-on-cursor-agent-when-anthropic-tool-use-is-served-from-bedrock-vertex-path-succeeds-identically/164927/7 "2026-07-07T06:20:25Z")
We didn’t keep request ids, I’ll will capture those in future. Below are the details we have (session ids and tool call ids) (FAILED, Bedrock) session\_id: 91548755-4c55-4cce-ab37-d21dac8e56d9 call\_id samples: toolu\_bdrk\_015S1Fx3UvZXbPAJfUf6UJy9 toolu\_bdrk\_01Trzt11A9vWcFiEgyopihHZ toolu\_bdrk\_01JgDkShqpC22k3wMC94j15Y toolu\_bdrk\_01Vh7xSX1Urtc1zqG1bHAWmH toolu\_bdrk\_01KHVJAL4aeXTfWh2SoB9G3Y toolu\_bdrk\_01W74QBw1EpypAQ41iKtKMHk (FAILED, Bedrock) session\_id: 6fac0000-f7fe-414a-9283-470c93330249 call\_id samples: toolu\_bdrk\_01NmMX9AmcQ46czrgrkkQLtY toolu\_bdrk\_0146qL6aktRoDTewLMp9EUHK toolu\_bdrk\_01TwieJ3pcMXc6Jf1XHEUzBu toolu\_bdrk\_016vWfSN5mCWJXHDczCbKxoy toolu\_bdrk\_01SJsJesJV1oKF65hPmJTCLm toolu\_bdrk\_012riUgRhAFMjtjayFr1KmHr (SUCCEEDED, Vertex) session\_id: 2c5e2b00-d6fc-4493-8580-3965fce1c20d call\_id samples: toolu\_vrtx\_01Bk4zYpvYJEbrNSJBfdijgc toolu\_vrtx\_01DttfMaCbfBnAUjAmMFMp9z toolu\_vrtx\_01Vu6KUexzNHycEoEpVs4LFU toolu\_vrtx\_014GG3ekrAof6cEG2QigxPND toolu\_vrtx\_01MBaZ2G393HrsPH3NMsiouF toolu\_vrtx\_01WDwzBQ2oGoV28ffGZNWrxM (SUCCEEDED, Vertex) session\_id: 4a96271f-9ea6-43f7-b398-4d21203f22fa call\_id samples: toolu\_vrtx\_01LD352tJs8vBGuRGfsFxDGx toolu\_vrtx\_01GnkbZRUF5chNhZJZ2pcP5P toolu\_vrtx\_01P4Lnw8w7P1oxFANkWFVSmQ toolu\_vrtx\_01SMRxcrpSPpCVQcpSndGxUS toolu\_vrtx\_01RxD9KSLh5DALD3qqSGubMi toolu\_vrtx\_01XGaoBB3wGzE6DhL1dhPYw5 ---
**Author:** ![system](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/system/32/99069_2.png) [@system](https://forum.cursor.com/u/system)\ **Post date:** [August 13, 2026, 1:39pm UTC](https://forum.cursor.com/t/deterministic-edittoolcall-json-parse-failure-on-cursor-agent-when-anthropic-tool-use-is-served-from-bedrock-vertex-path-succeeds-identically/164927/9 "2026-08-13T13:39:49Z")
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