GPT-5.5 xhigh via Amazon Bedrock stops automatically mid-task in Codex CLI, while GPT-5.4 xhigh works with the same setup

[Mhrnqaruni]

What version of Codex CLI is running?

codex-cli 0.137.0 and codex-cli 0.138.0-alpha.6

What subscription do you have?

AWS Bedrock

Which model were you using?

gpt-5.5

What platform is your computer?

on both Windows and Linux is same!

What terminal emulator and version are you using (if applicable)?

All, even codex app have same issue

Codex doctor report

{
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        "daemon state dir": "C:\\Users\\User\\.codex\\app-server-daemon",
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        "pid file": "C:\\Users\\User\\.codex\\app-server-daemon\\app-server.pid (missing)",
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}

What issue are you seeing?

When using Codex CLI with Amazon Bedrock and openai.gpt-5.5 at xhigh reasoning effort, Codex frequently stops automatically in the middle of a task. The session does not complete the requested work, and it looks like the agent simply terminates/halts before finishing the plan, patch, or final response.

The same environment works when I switch to openai.gpt-5.4 with xhigh, so this does not appear to be a general AWS credential, Bedrock access, terminal, or local Codex installation problem.

Observed behavior:

Codex starts the task normally.
It begins reasoning or executing steps.
During a longer coding/editing task, it stops before completion.
Sometimes it stops without a clear final answer or useful error.
The task remains incomplete.
Re-running with openai.gpt-5.4 and xhigh on the same task works much more reliably.
This seems specific to openai.gpt-5.5 + xhigh + Amazon Bedrock provider.

My Codex Bedrock configuration is approximately:

model = "openai.gpt-5.5"
model_provider = "amazon-bedrock"
model_reasoning_effort = "xhigh"

[model_providers.amazon-bedrock]
name = "Amazon Bedrock"
base_url = "https://bedrock-mantle.us-east-2.api.aws/openai/v1"
wire_api = "responses"
requires_openai_auth = false
env_key = "AWS_BEARER_TOKEN_BEDROCK"

[model_providers.amazon-bedrock.aws]
region = "us-east-2"

When I change only the model to GPT-5.4, the same workflow works:

model = "openai.gpt-5.4"
model_provider = "amazon-bedrock"
model_reasoning_effort = "xhigh"

[model_providers.amazon-bedrock]
name = "Amazon Bedrock"
base_url = "https://bedrock-mantle.us-east-2.api.aws/openai/v1"
wire_api = "responses"
requires_openai_auth = false
env_key = "AWS_BEARER_TOKEN_BEDROCK"

[model_providers.amazon-bedrock.aws]
region = "us-east-2"

This suggests the issue may be related to how Codex handles GPT-5.5 xhigh responses through the Bedrock Responses API, possibly involving one or more of:

long-running xhigh reasoning responses being prematurely treated as complete;
streaming/event handling differences for Bedrock Mantle responses;
output truncation or incomplete response lifecycle handling;
Codex not surfacing the underlying Bedrock/API error if the response is interrupted;
tool-call or patch-generation state being lost before the task completes;
an internal timeout or max-output/reasoning-budget interaction specific to GPT-5.5 xhigh.

There is no obvious AWS authentication issue, because GPT-5.4 works through the same Bedrock provider setup.

What steps can reproduce the bug?

Configure Codex CLI to use Amazon Bedrock as the provider.
Set the model to openai.gpt-5.5.
Set reasoning effort to xhigh.
Use region us-east-2.
Start a non-trivial coding task that requires multiple steps and/or file edits.
Observe that Codex starts working but stops automatically before completing the task.
Change only the model to openai.gpt-5.4, keeping xhigh and the same Bedrock configuration.
Run the same or very similar task again.
Observe that GPT-5.4 xhigh completes much more reliably.

What is the expected behavior?

Codex CLI should complete the task when using openai.gpt-5.5 with xhigh through Amazon Bedrock, or it should show a clear actionable error if the Bedrock response is interrupted, truncated, timed out, or rejected.

Expected behavior:

Codex should not silently stop mid-task.
If the model/API response is incomplete, Codex should report that clearly.
If the issue is caused by timeout, token budget, stream interruption, or Bedrock response lifecycle state, Codex should expose that reason.
GPT-5.5 xhigh should behave at least as reliably as GPT-5.4 xhigh for the same Bedrock provider configuration.
For editing tasks, Codex should either complete the patch safely or fail with a clear error before applying partial/incomplete changes.

Additional information

This appears to be specific to GPT-5.5 with xhigh reasoning effort through Amazon Bedrock.

Important comparison:

openai.gpt-5.5 + xhigh + Bedrock: stops automatically mid-task / incomplete.
openai.gpt-5.4 + xhigh + Bedrock: works in the same setup.

That comparison makes me think this is not primarily caused by local environment, AWS credentials, Bedrock access, or terminal configuration.

Please let me know if you want logs from a specific Codex debug mode or a specific Bedrock request/response trace format. I can reproduce and provide more details with private information redacted.

[github-actions]

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

• codex is unable to continue after calling any function #26195

Powered by Codex Action

[kivocsa99]

this is the issue that i was talking about , i don't think it is effort related , maybe cause the apply_patch is being executed with empty body as seen in the logs , this happens also in opencode , so i think it is a bedrock / gpt 5.5 issue , don't know what is wrong as everything works perfectly on 5.4

[kivocsa99]

Confirming this is a Bedrock-side gpt-5.5 empty-output issue — with evidence ruling out context/effort/client.

Same setup: openai.gpt-5.5 via Amazon Bedrock (bedrock-mantle.us-east-2), model_reasoning_effort = high, Codex CLI 0.137.0. The turn halts silently mid-task — no error, no final message, task_complete fires with nothing produced.

I captured a halting turn from the rollout. The failing request:

last_token_usage: { input_tokens: 44395, output_tokens: 0, reasoning_output_tokens: 0 }
model_context_window: 258400

The request sent ~44K input tokens and the model returned output_tokens: 0 — a completely empty response (HTTP 200, no error). Codex has no tool call or text to continue with, so the turn ends silently.

/status at the moment of the halt:

Token usage:     164K total (162K input + 1.51K output)
Context window:  87% left (44.4K used / 258K)

This rules out the leading theories:

• Not context exhaustion — 87% of the window was free (44.4K / 258K).
• Not reasoning effort — happens at high here, and OP reports xhigh; the failing request had 0 reasoning tokens too.
• Not Codex-specific — I reproduce the identical empty-output halt in OpenCode with the same Bedrock key/region. Different client, same failure.
• Not credentials/region — other turns in the same session (same key, same region) succeed; it's intermittent.

Control: the exact same tasks on openai.gpt-5.4 (same provider, region, effort) complete reliably — no empty responses observed across extended use.

Conclusion: this looks like an intermittent serving defect for gpt-5.5 on Bedrock Mantle that returns empty completions (output_tokens: 0) mid-session, independent of context size or effort. It's probabilistic and correlates with longer tasks only because more requests = more chances to hit it.

Direct curl to the same endpoint with a minimal prompt usually returns output fine, so it's load/context-shape dependent rather than a hard failure — which makes it hard to reproduce in isolation but very repeatable in real coding sessions.

Workaround for anyone blocked: switch to openai.gpt-5.4.
Please this requires full attention as openai.gpt-5.5 is unusable at all ! .

[celia-oai]

@Mhrnqaruni @kivocsa99 if you are ok sharing the session with us, could you run /feedback and share the thread id with us? this would help us repro the issue

[Mhrnqaruni]

@Mhrnqaruni @kivocsa99 if you are ok sharing the session with us, could you run /feedback and share the thread id with us? this would help us repro the issue

here you are,
btw today I saw new error for using gpt5.5 on Codex CLI using AWS Bedrock API, "stream disconnected before completion: The server had an error while processing your request. Sorry about that!"
and also sadly now gpt5.4 also got issue with AWS bedrock API, now gpt5.4 stop middle of work automatically also

gpt5.5 issue:
https://github.com/openai/codex/issues/new?template=3-cli.yml&steps=Uploaded%20thread:%20019eaa31-6c5f-7db3-9a83-5b0cc9c08751
019eaa31-6c5f-7db3-9a83-5b0cc9c08751

gpt5.4 issue:
https://github.com/openai/codex/issues/new?template=3-cli.yml&steps=Uploaded%20thread:%20019eaa2f-54db-75f1-b4e5-9fcb54a091f6
019eaa2f-54db-75f1-b4e5-9fcb54a091f6